Irina N. Zavestovskaya
Achievement of leading positions in the development of technologies of engineering physics for biomedicine and their active employment in the educational process in order to bridge the gap between scientific research, education, device manufacturing and practical medicine.
Development of breakthrough technologies for diagnostics and therapy of cancer and other socially important diseases using unique functional nanomaterials and novel advanced nanoengineering methods based on photonics, radiofrequency, nuclear, ultrasound, magnetic and other modalities:
The uniqueness of our approach is the integrated use of mutually complementary nanoengineering methods (synthesis of nanomaterials, their functionalization and optimization for a specified bioimaging or therapeutic procedure) for early cancer diagnosis, imaging of malignant cells, and their elimination using photonic, ultrasound, radiofrequency, magnetic, and nuclear techniques.
31 educational programs was available in 2016 in PhysBio from which 6 are Bachelor's degree programs, 16 are Master's degree programs, 3 are Specialist's degree programs, and 6 are Postgraduate student’s degree programs. 14 of them are new, the others – modernized.
|Areas of training||Level|
Bachelor's degree programs
03.03.02 – Physics
04.03.02 – Chemistry, Physics and mechanics of materials
06.03.01 – Biology
12.03.04 - Biotechnical Systems and Technologies
18.03.01 - Chemical Technology
Specialist's degree programs
31.05.01 – General Medicine
06.05.01 – Bioengineering and Bioinformatics
14.05.04 – Electronics and automation of physical installations
33.05.01 - Pharmacy
Bachelor's Degree/Specialist's Degree
Master's degree programs
14.04.02 – Nuclear physics and technology
03.04.02 – Physics
06.04.01 – Biology
04.04.02 – Chemistry, Physics and mechanics of materials
12.04.04 - Biotechnical Systems and Technologies
18.04.01 - Chemical Technology
Postgraduate student’s degree
01.06.01 - Mathematics and Mechanics
03.06.01 – Physics and astronomy on speciality
27.06.01 – Management in technical systems
06.06.01 – Biological Sciences
12.06.01 - Photonics, Instrument Engineering, Optical and Bioengineering Communications Systems
04.06.01 - Chemical Sciences
33.06.01 - Pharmacy
Master's Degree/Postgraduate's student'sDegree
Paras Nath Prasad (USA) - SUNY Distinguished Professor, Executive Director, Institute for Lasers, Photonics, and Biophotonics, State University of New York at Buffalo, Head of the PhysBio International Council, H-Index: 105.
Andrei V. Kabashin (France) – Research Director, French National Center for Scientific Research (CNRS), Aix-Marseille University, Laboratory of Lasers, Plasmas and Photonic Processes LP3, H-index: 33.
Vitaly I. Konov (Russia) – Academician of the Russian Academy of Sciences, Professor, Head of Department of Laser Micro- and Nanotechnologies in NRNU MEPhI; Director of the Natural Sciences Center, General Physics Institute of the Russian Academy of Sciences, H-index=35.
Igor R. Nabiev (France) – 1 class Professor, University of Reims Champagne-Ardenne, Director of the European technology platform “Semiconductor Nanocrystals”, Head of the Nano Bioengineering Laboratory in MEPhI, H-index=37.
Giovanni Barbero (Italy) – Professor, Politecnico di Torino, H-index: 29.
Marc Sentis (France) – Research Director, French National Center for Scientific Research (CNRS), Aix-Marseille University, Laboratory of Lasers, Plasmas and Photonic Processes LP3, H-index = 31.
Philippe Delaporte – Research Director, French National Center for Scientific Research (CNRS), Aix-Marseille University, Laboratory of Lasers, Plasmas and Photonic Processes LP3, H-index = 25.
Rudolf Steiner (Germany) – Professor emeritus, Honorary Director of the “Institute for Laser Technologies in Medicine and Metrology (ILM)” at the University of Ulm, H-index: 22.
Alfredo Strigazzi (Italy) – Senior Professor, Department of Applied Science and Technology, Politecnico di Torino, H-index: 18.
Victor Yu. Timoshenko (Russia) – Professor, Moscow State University, H-index: 31.
Valentin A. Orlovitch (Belarus) – Academician of the National Academy of Sciences of Belarus, Professor, Head of the Laboratory of Nonlinear Optics of the Institute of Physics, National Academy of Sciences of Belarus, H-index: 21.
Andrei V. Zvyagin (Australia) – Associate Professor, Department of Physics, Faculty of Sciences, Macquarie University, H-index: 19.
Igor V. Meglinski (Finland) – Professor, Director of the Opto-Electronics and Measurement Techniques Department, Faculty of the Information Technology and Electrical Engineering, University of Oulu, H-index: 26.
Yury P. Rakovich (Spain) – Research Professor, IKERBASQUE, Materials Physics Center in San Sebastián, Professor at Materials Physics Department, University of the Basque Country, H-index: 26.
Gleb B. Sukhorukov (Great Britain) – Professor, Chair in Biopolymers and Bio-organic Interfaces, School of Engineering and Materials Science, Queen Mary University of London, H-index: 81.
Anton Fojtík (Czech Republic) – Assoc. Professor Dr. Ing., Czech Technical University in Prague, Faculty of Biomedical Engeneering, Nanosciences, Nanotechnology and Nanostructures, H-index: 18.
Giovanni Alberto Cesare Ummarino (Italy) – Professor, Politecnico di Torino, H-index: 20.
We have developed a mathematical model able to predict the dependence of the current density, j0, in the dc limit, on the thickness of a photoactive semiconductor layer, d, in contact with an electrolyte. The model considers the application of an external bias. The theoretical analysis has been done by means of a diffusive model, where the excess of charges moves by diffusion in the presence of a generation term, due to the incident light, and a recombination term, proportional to the excess of charge carriers. We show that a non-monotonic dependence of j0 vs. d is expected. For small d, the photocurrent density is proportional to d and the proportionality constant is related to both the attenuation of the light in the photoactive semiconductor layer and to the applied potential. In the opposite limit of large d, the current tends to a constant value that is dependent on both the light intensity and the applied bias. Our theoretical predictions are in qualitative agreement with the experimental data reported in literature for BiVO4 films. © 2017 Elsevier B.V.
A detailed study of pseudorapidity densities and multiplicity distributions of primary charged particles produced in proton–proton collisions, at s= 0.9, 2.36, 2.76, 7 and 8 TeV, in the pseudorapidity range | η| < 2 , was carried out using the ALICE detector. Measurements were obtained for three event classes: inelastic, non-single diffractive and events with at least one charged particle in the pseudorapidity interval | η| < 1. The use of an improved track-counting algorithm combined with ALICE’s measurements of diffractive processes allows a higher precision compared to our previous publications. A KNO scaling study was performed in the pseudorapidity intervals | η| < 0.5, 1.0 and 1.5. The data are compared to other experimental results and to models as implemented in Monte Carlo event generators PHOJET and recent tunes of PYTHIA6, PYTHIA8 and EPOS. © 2017, CERN for the benefit of the ALICE collaboration.
The inclusive J/ψ production has been studied in Pb–Pb and pp collisions at the centre-of-mass energy per nucleon pair sNN=5.02 TeV, using the ALICE detector at the CERN LHC. The J/ψ meson is reconstructed, in the centre-of-mass rapidity interval 2.5>y<4 and in the transverse-momentum range pT<12 GeV/c, via its decay to a muon pair. In this Letter, we present results on the inclusive J/ψ cross section in pp collisions at s=5.02 TeV and on the nuclear modification factor RAA. The latter is presented as a function of the centrality of the collision and, for central collisions, as a function of the transverse momentum pT of the J/ψ. The measured RAA values indicate a suppression of the J/ψ in nuclear collisions and are then compared to our previous results obtained in Pb–Pb collisions at sNN=2.76 TeV. The ratio of the RAA values at the two energies is also computed and compared to calculations of statistical and dynamical models. The numerical value of the ratio for central events (0–10% centrality) is 1.17±0.04(stat)±0.20(syst). In central events, as a function of pT, a slight increase of RAA with collision energy is visible in the region 2-6 GeV/c. Theoretical calculations qualitatively describe the measurements, within uncertainties. © 2017 The Author
Characteristic photoluminescence (PL) of nanodiamonds (ND) of different origin (detonation, HPHT, extracted from meteorite) was studied in situ at high temperatures in the range 20-450 °C. Luminescence was excited using 473 nm laser and recorded in the range 500-800 nm. In contrast to decrease of point defect PL in bulk diamond with temperature, we found that the ND luminescence related to ND surface defects increases almost an order of magnitude upon heating to 200-250 °C. The observed effect reveals that water adsorbed on ND surfaces efficiently quenches PL; water desorption on heating leads to dramatic increase of the radiative de-excitation. © 2017 Astro Ltd.
The effect of volatility of local electronic properties in multilayered (3-6 layers) graphene irradiated by nanosecond laser pulses with a wavelength 532 nm in humid atmosphere was found. The experiments were carried out in situ in a scanning probe microscope (SPM) with Pt/Si tip. It was established that along with local profile transformation of graphene sheet (the formation of "nanocrater" with depth up to 2 urn and 1 pm diameter) in the zone of the laser action (similar to 0,5 mu m) a decrease (similar to 20 meV) of the electrons work function was observed. It takes place in the region larger but comparable with the irradiation spot size. Analysis of the experimental data on local electrical conductivity have shown that the bottom of conduction band for graphene in laser irradiation area was reduced by 50 meV. The observed changes of graphene physical properties were associated with the laser-induced radial displacement of the water layer intercalated between graphene and substrate. In addition, it was experimentally established that the graphene work function was decreased significantly less than can be expected for an "ideal" 3-6 layer graphene. The investigated process of laser induced changes of graphene properties demonstrated the reproducible character and long-term stability. Possibility of laser fabrication of arrays in graphene with periodic modulation of electronic properties was demonstrated.
In any pulsed and repetitive laser process a part of the absorbed laser energy is thermalized and stays in the material as residual heat. This residual heat is accumulating from pulse to pulse, continuously increasing the temperature, if the time between two pulses does not allow the material to sufficiently cool down. Controlling this so-called heat accumulation is one of the major challenges for materials processing with high average power pulsed lasers and repetitive processing. Heat accumulation caused by subsequent pulses (HAP) on the same spot and heat accumulation caused by subsequent scans (HAS) over the same spot can significantly reduce process quality, e.g., when the temperature increase caused by heat accumulation exceeds the melting temperature. In both cases, HAS and HAP, it is of particular interest to know the limiting number of pulses or scans after which the heat accumulation temperature exceeds a critical temperature and a pause has to be introduced. Approximation formulas for the case, where the duration of the heat input is short compared to the time between two subsequent heat inputs are derived in this paper, providing analytical scaling laws for the heat accumulation as a function of the processing parameters. The validity of these approximations is confirmed for HAP with an example of surface ablation of CrNi-steel and for HAS with multi-scan cutting of carbon fiber reinforced plastics (CFRP), both with a picosecond laser at an average power of up to 1.1 kW. It is shown that for the important case of 1-dimensional heat flow the limiting number of heat inputs decreases with the inverse of the square of the average laser power. © 2017 Optical Society of America.
We report on the successful growth of single crystals of Fe2+:CdSe by seeded physical vapor transport (SPVT) technique with doping within the growing process and subsequent annealing in Se vapor. Luminescence lifetime measurements, spectroscopic studies of E-5-T-5(2) transition of Fe2+ in CdSe, and laser experiments were performed. The lifetime of the T-5(2) energy level was measured to be 20 +/- 5 ns at a room temperature (RT) of 290 K. At liquid nitrogen (LN) temperature, luminescence kinetics displayed a non-exponential decay, which can be fitted to a bi-exponential function with time constants tau(1) = 6 mu s and tau(2) = 29 mu s. As much as 3.2 mJ of output energy at 5.2 mu m with 27% absorbed pump energy slope efficiency of an Fe2+:CdSe laser was achieved at RT under 2.94 mu m nanosecond Er:YAG laser pumping. The Fe2+:CdSe laser was tuned from 4.63 to 6.10 mu m. Obtained characteristics of Fe2+: CdSe indicate that the crystal can be considered a promising medium for amplification of femtosecond pulses in the middle infrared range up to 6 mu m.
Purpose: Modular nanotransporters (MNTs) are a polyfunctional platform designed to achieve receptor-specific delivery of short-range therapeutics into the cell nucleus by receptor-mediated endocytosis, endosome escape, and targeted nuclear transport. This study evaluated the potential utility of the MNT platform in tandem with Auger electron emitting In-111 for cancer therapy. Methods: Three MNTs developed to target either melanocortin receptor-1 (MC1R), folate receptor (FR), or epidermal growth factor receptor (EGFR) that are overexpressed on cancer cells were modified with p-SCN-Bn-NOTA and then labeled with In-111 in high specific activity. Cytotoxicity of the In-111-labeled MNTs was evaluated on cancer cell lines bearing the appropriate receptor target (FR: HeLa, SK-OV-3; EGFR: A431, U87MG. wtEGFR; and MC1R: B16-F1). In vivo micro-single-photon emission computed tomography/computed tomography imaging and antitumor efficacy studies were performed with intratumoral injection of MC1R-targeted In-111-labeled MNT in B16-F1 melanoma tumor-bearing mice. Results: The three NOTA-MNT conjugates were labeled with a specific activity of 2.7 GBq/mg with nearly 100% yield, allowing use without subsequent purification. The cytotoxicity of In-111 delivered by these MNTs was greatly enhanced on receptor-expressing cancer cells compared with In-111 nontargeted control. In mice with B16-F1 tumors, prolonged retention of I-111(n) by serial imaging and significant tumor growth delay (82% growth inhibition) were found. Conclusion: The specific in vitro cytotoxicity, prolonged tumor retention, and therapeutic efficacy of MC1R-targeted In-111-NOTA-MNT suggest that this Auger electron emitting conjugate warrants further evaluation as a locally delivered radiotherapeutic, such as for ocular melanoma brachytherapy. Moreover, the high cytotoxicity observed with FR- and EGFR-argeted In-111-NOTA-MNT suggests further applications of the MNT delivery strategy should be explored.
We studied defects and stress distributions in mosaic epitaxial diamond film using a confocal Raman spectroscopy, with a special attention to the junction area between the crystals. The mosaics was grown by microwave plasma CVD on closely arranged (1 0 0)-oriented HPHT type Ib substrates. The width of stress affected and defect enriched region around the junction show a tendency of extending with the film thickness, from ≈40 μm on the film-substrate interface to ≈250 μm in the layer 500 μm above the substrate, as found from the mosaics analysis in cross-section. The stress field around the junction demonstrates a complex pattern, with mixed domains of tensile and compressive stress, with maximum value of σ ≈ 0.6 GPa. A similar non-uniform pattern was observed for defect distribution as well. No sign of amorphous sp2 carbon in the junction zone was revealed. © 2017
The fluorescence kinetics and spectral intensity ratio (FIR) methods for contactless optical temperature measurement in the NIR spectral range with Nd3+ doped YAG micro- and YPO4 nanocrystals are considered and the problems are revealed. The requirements for good temperature RE doped crystalline nanoparticles sensor are formulated. © 2016 Elsevier B.V.
We report the manufacturing of a novel diamond – rare-earth (RE) composite material with EuF3 nanoparticles (NP) embedded in the synthesized microcrystalline diamond films that show strong photoluminescence in the orange part of the visible spectrum. Synthesis of the aforementioned composite includes placement of EuF3 NP on the diamond substrate and subsequent coating of them with an additional polycrystalline diamond layer grown by microwave plasma chemical vapor deposition (CVD). The produced composite films exhibit high intensity localized photoluminescence (PL) at 612 nm with the decay time of 0.34 ms, which is generated by the EuF3 particles buried within a very stable transparent diamond matrix. The proposed synthetic approach is quite versatile, as it allows preparation of the luminescent diamond - RE particles nanocomposites of different sizes and natures which perform well over a broad range of the visible spectrum. © 2017 Elsevier B.V.
We demonstrated a laser beam profiling method based on imaging of the laser induced photoluminescence of a transparent single-crystal diamond plate. The luminescence at 738 nm is caused by silicon-vacancy color centers formed in the epitaxial diamond film by its doping with Si during CVD growth of the film. The on-line beam monitor was tested for a cw laser emitting at 660 nm wavelength.
We investigated emissive properties of CdTe colloidal quantum wells (CQWs) in applied electric fields in the range of 0–90 kV/cm. Photoluminescence spectra and time-resolved intensities of the excitonic peak were studied. The emission was centered at 2.47 eV with a width of 40 meV. No visible broadening or redshifts were detected in the whole range of applied fields. We obtained the dependencies of integrated intensity and maximum intensity of interband luminescence on the magnitude of applied electric field with the decrease of these characteristics by 15–20% at 90 kV/cm due to field-controlled charge carrier separation. Deceleration of the radiative decay rates with increasing electric field provides the evidence of field-controlled temporary exciton storage as two-fold increase of the number of photons registered in the 1–40 ns time range is observed. This assertion is also confirmed by the growth of the luminescence integrated intensity in the electric fields in the range 30–60 kV/cm. These findings are an important step toward understanding of the influence of electric fields on the operation of hybrid organic-inorganic LEDs with CQW-based emissive layers. © 2017 Elsevier B.V.
For the first time, a possibility of diamond synthesis under high pressures was studied in binary systems “rare earth element (REE)-carbon” with refractory carbides. It was found that at pressure 8 GPa in the Eu-C system graphite transforms into diamond at about melting temperature of EuC2 carbide (1900–2200 °C), while in the Er-C and Tm-C systems diamond formation takes place well below melting temperature of carbides ErC2 or TmC2 (1600–1800 °C). Simultaneous crystallization of diamond and carbides ErC2 or TmC2 from vanishing carbon-saturated liquid phase was proposed as a mechanism for the diamond formation in the latter systems. As compared with Eu, more strong catalytic activity of Er and Tm for diamond synthesis was explained by matching their crystal structures to the diamond one. © 2017 Elsevier B.V.
We used a low-coherence interferometry for precise continuous in situ measurements of thickness and growth rate of epitaxial single crystal diamond layers in microwave plasma CVD in H2-CH4 gas mixtures in a broad range of substrate temperatures Ts (750–1150 °C) and CH4 concentrations (1–13%). Rich growth kinetics is collected in a single experiment by depositing about 60 layers on one (100) Ib HPHT diamond substrate in different regimes (the substrate temperature was controlled by the microwave power) at fixed pressure P = 130 Torr, without the plasma switch-off. The growth rate is found to follow Arrhenius dependence with activation energy Ea = 11.1 ± 1.0 kcal/mol. By appropriate choice of the substrate temperature the growth rate can be significantly enhanced. The growth rate as high as 82 μm/h is achieved by optimizing the temperature and gas composition. At low CH4 content (1%) growth competes with etching by atomic hydrogen, the etching dominating at high Ts (> 1000 °C in the present conditions). The etching rate in pure H2 plasma was measured and activation energy Ea = 9.8 ± 0.8 kcal/mol was deduced. Gas temperature Tg in the plasma core evaluated from optical emission spectra for dimer C2 (Swan band), was found to be either constant or slightly and monotonically increasing with absorbed power, whereas the absorbed microwave power density shows a decreasing, although slight, trend. This suggests the temperature depended surface reactions to play a major role in the diamond growth kinetics under variable microwave power. Raman mapping of cross-section of the produced multilayered sample confirmed high quality of diamond structure over all the deposition regimes explored. © 2017 Elsevier B.V.
Samples of 808-nm quasi-cw laser diode arrays (LDAs) with an output power exceeding 300 W, a pulse duration of 200 μs, and a pulse repetition rate of 100 Hz are developed and fabricated. The main output parameters of a set of five LDAs, including light-current characteristics, current-voltage characteristics, and emission spectra are measured. Preliminary life tests show that the LDA power remains stable for 108 pulses. © 2017 Kvantovaya Elektronika and Turpion Ltd.
Elaboration of methods for the control of biochemical reactions with deoxyribonucleic acid (DNA) strands is necessary for the solution of one of the basic problems in the creation of biocomputers - improvement in the reliability of molecular DNA computing. In this paper, the results of the solution of the four-parameter inverse problem of laser Raman spectroscopy - the determination of the type and concentration of each of the DNA nitrogenous bases in multi-component solutions - are presented. © 2017 Astro Ltd.
Cross-sectional spreading resistance microscopy has been used to investigate nanoscale variations in electronic properties of an undoped Al0.75Ga0.25N/Al0.95Ga0.05N multiple quantum well (MQW) heterostructure grown by plasma-assisted molecular beam epitaxy on an AlN/c-sapphire template, prepared by metalorganic vapor phase epitaxy. It is found that a current signal from the MQWs can be detected only at a negative sample bias. Moreover, its value changes periodically from one quantum well (QW) to another. Analysis of the current-voltage characteristics of the contacts of a tip with the structure layers showed that periodic contrast of MQWs is the result of fluctuations of the chemical composition of the QWs and the concentration of electrons accumulated in them. Mathematical simulations indicate that this modulation is associated with the periodic fluctuations of an Al-mole fraction in the barrier layers of the structure due to counter gradients of the intensity of Al and Ga molecular fluxes across the surface of a substrate rotating slowly during growth. The nanoscale fluctuations of the current contrast observed along the QW layers are caused, most likely, by the presence of the areas of lateral carrier localization, which originate during the formation of QWs by sub-monolayer digital alloying technique. © 2017 Author(s).
We present a new concept of a combined scanning probe microscope (SPM)/ultramicrotome apparatus. It enables “slice-and-view” scanning probe nanotomography measurements and 3D reconstruction of the bulk sample nanostructure from series of SPM images after consecutive ultrathin sections. The sample is fixed on a flat XYZ scanning piezostage mounted on the ultramicrotome arm. The SPM measuring head with a cantilever tip and a laser-photodiode tip detection system approaches the sample for SPM measurements of the block-face surface immediately after the ultramicrotome sectioning is performed. The SPM head is moved along guides that are also fixed on the ultramicrotome arm. Thereby, relative dysfunctional displacements of the tip, the sample, and the ultramicrotome knife are minimized. The design of the SPM head enables open frontal optical access to the sample block-face adapted for high-resolution optical lenses for correlative SPM/optical microscopy applications. The new system can be used in a wide range of applications for the study of 3D nanostructures of biological objects, biomaterials, polymer nanocomposites, and nanohybrid materials in various SPM and optical microscopy measuring modes. © 2017 Author(s).
We consider a possibility of application of laser-electron X-ray generators for diagnosing the vessel status of internal organs. It is shown that modern lasers and linear accelerators can be used for the development of angiographic instruments of a new type with an increased spatial and temporal resolution while maintaining or reducing the radiation load on the patient and medical staff. Such improvements in diagnostic and ambient factors cannot be achieved with the use of X-ray tubes. All particular estimates and calculations have been performed for a contrast agent based on iodine compounds. © 2017 Kvantovaya Elektronika and Turpion Ltd.
We have synthesized highly efficient visible range irradiating Yb:Er- and Yb:Tm-doped SrF2-based up-conversion luminophores, prepared mechanical mixtures of those components, evaluated chromaticity coordinates of the aforementioned mixtures, and demonstrated the potential for smooth adjustment of the said coordinates by varying the corresponding mixture compositions. The chromaticity coordinates of 62.5 wt.% Sr0.9475Yb0.0500Er0.0025F2.0525 + 37.5 wt.% Sr0.8985Yb0.1000Tm0.0015F2.1015 mixture were the closest to the white light parameters; its energy yield was 4.14% (pumping power density1 W/cm2). © 2016 Elsevier B.V.
The suitability of scanning near-field optical microscopy (SNOM) to image photoluminescent diamond nanoparticles with nanoscale resolution is demonstrated. Isolated diamond nanocrystals with an average size of 100 nm, containing negatively charged nitrogen-vacancy (NV-) centers, were chosen as tested material. The NV- luminescence was stimulated by continuous 532 nm laser light. Sizes of analyzed crystallites were monitored by an atomic force microscope. The lateral resolution of the order of 100 nm was reached in SNOM imaging of diamond nanoparticles using 150 nm square aperture of the probe.
Results of targeted modification of the structure and properties of ordered arrays of zinc nanotubes (Zn NTs) by accelerated Xe+22 heavy ions with a fluence of 1 × 109 to 5 × 1011 cm–2 in the energy range of 1.0–1.75 MeV/nucleon are reported. Dynamics of changes in the crystallite shape and orientation of Zn NTs before and after irradiation has been studied by X-ray diffraction. It has been shown that irradiation with accelerated ions has a significant effect on the texture coefficients of Zn NTs. In addition, at a fluence of 1 × 1011 m–2 or higher, the formation of loose areas in the structure of Zn NTs as a result of partial degradation of the crystal structure and, consequently, a decline in conductivity are observed. © 2017, Pleiades Publishing, Ltd.
The recently discovered twist-bend nematic phase, Ntb, is a non-uniform equilibrium nematic phase that presents a spontaneous bend with a precession of the nematic director, n, on a conical helix with a tilt angle θ and helical pitch P. The stability of the Ntb phase has been recently demonstrated from the elastic point of view by extending the Frank elastic energy density of the nematic phase to include the symmetry element of the helical axis, t. In the present article, we investigate the influence of an external bulk field (magnetic or electric) on the Ntb phase. Using symmetry arguments we derive the expression for the flexoelectric polarisation in twist-bend nematic phases. We show that, besides the standard contribution related to the spatial variation of the nematic director, two new contributions connected with the existence of the helical axis appear. In the ground state, where the nematic deformation is a pure heliconical deformation, the new contribution vanishes identically, and the total flexoelectric polarisation is perpendicular to the nematic director. Furthermore, as an example, we study the role of an external magnetic field applied parallel to the helical axis for a material with positive magnetic susceptibility anisotropy. We show that the field modifies the range of values of the coupling parameter between the director and the helical axis, thus shifting the interval of values for which this coupling results in the Ntb phase. © 2016 Informa UK Limited, trading as Taylor & Francis Group
This work reports an experimental characterization of the efficiency of energy transmission of porous laser absorbers as a function of their density and thickness. In this campaign the foams were deposited on different metal substrates, which finally absorbed the energy deposited by the laser on the bulk of the porous material. The dimensions of the craters produced on the substrate can be related to the energy transmitted through the foams. © Published under licence by IOP Publishing Ltd.
Nonstationary photovoltage excitation by frequency-modulated light in an adaptive photodetector based on GaAs is studied. To observe the effect, the crystal is exposed to light beams with the relative frequency shift Delta f(t). Linear frequency modulation Delta f(t) = At is used in the experiments. As a result of such illumination, a pulsed electrical signal is induced in the crystal. The pulse appears at the deceleration of the interference pattern motion, and its duration is controlled by the frequency variation rate A and the time of the charge grating formation. The possibility of using the effect in the systems for measuring velocities and accelerations of moving objects is shown.
The possibility of spatial homogenization of the cryogenic hydrogen fuel structure in laser thermonuclear targets is considered. The results of a large cycle of experimental studies on low-temperature (T = 4.2 K) phonon modulation of the structure of solid hydrogen layers with various ortho-para compositions and its effect on the homogenization process rate are presented. © 2016, Allerton Press, Inc.
We demonstrate the generation of stable 127 fs self-similar pulses at a central wavelength of 1560 nm with 7.14 mW average output power. Similariton lasers have low repetition rate deviation in the averaging time interval 1-1·103 s, a low relative intensity noise-125 dBc/Hz, a narrow single comb line width of 32 kHz, and high reliability. Thus, such lasers are highly promising for further development of the stabilized combs. © 2016 IEEE.
There have been done many past surface temperature reconstructions based on the temperature measurements in rock and glacier boreholes. However, the reliability of these reconstructions connected with the uniqueness and stability properties is not studied. We carried out the reconstruction by search of the past surface temperature in form of the finite set of the Fourier series that provides the unique and stable solution. The tree-ring chronologies are used as the high-resolution proxy climate indicator to find out the dominant periods of the Fourier series. The Tikhonov regularization method is applied to solve the inverse problem. © 2016 Author(s).
The class of direct-drive targets for the laser pulse of a megajoule scale is considered in the work. A distinctive feature of the design of these targets is a relatively low aspect ratio (outer DT-shell radius/shell thickness, A ∼ 10) to provide greater compression stability. The irradiation of the target surface is carried out by the shaped laser pulse on 2ω of Nd-laser. The influence of laser energy absorption inhomogeneity on the parameters of compression and burning of thermonuclear fuel on the final stage of implosion is studied in the work based on 1D and 2D numerical calculations. The results of 2D modeling show that in the case of target's offset from the point of beams crossing significantly greater reduction in the neutron yield is observed than in the case when only irregularities caused by the geometry of irradiation by the finite number of beams are taken into account. © Published under licence by IOP Publishing Ltd.
We report the first results of elliptic (v2), triangular (v3), and quadrangular (v4) flow of charged particles in Pb-Pb collisions at a center-of-mass energy per nucleon pair of sNN=5.02 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurements are performed in the central pseudorapidity region |η|<0.8 and for the transverse momentum range 0.2<pT<5 GeV/c. The anisotropic flow is measured using two-particle correlations with a pseudorapidity gap greater than one unit and with the multiparticle cumulant method. Compared to results from Pb-Pb collisions at sNN=2.76 TeV, the anisotropic flow coefficients v2, v3, and v4 are found to increase by (3.0±0.6)%, (4.3±1.4)%, and (10.2±3.8)%, respectively, in the centrality range 0%-50%. This increase can be attributed mostly to an increase of the average transverse momentum between the two energies. The measurements are found to be compatible with hydrodynamic model calculations. This comparison provides a unique opportunity to test the validity of the hydrodynamic picture and the power to further discriminate between various possibilities for the temperature dependence of shear viscosity to entropy density ratio of the produced matter in heavy-ion collisions at the highest energies. © 2016 CERN.
Semiconductor quantum dots (QDs) obtained by means of colloidal synthesis are widely used in fabrication of organic light-emitting devices (OLEDs). We have fabricated QD-OLEDs with an active light-emitting layer formed by novel CdSe/ZnS/CdS/ZnS core-multishell QDs that have luminescence quantum yield of more than 90%. We have compared the performance of QD-OLEDs with different thickness of the active layer and demonstrated that the best performance is achieved at 45-55 nm, probably due to field redistribution inside the device. Optimization of the thicknesses of transport layers of QD-OLED is likely to further improve the performance of such devices. (C) 2016 Elsevier Ltd. All rights reserved.
The application of the textural analysis methods based on computer microscopy in the visible region of electromagnetic radiation to classify blood cells into lymphoblasts and lymphocytes is considered. The model of digital processing of cell images is proposed. To quantitatively describe cells in diagnostics and differential diagnostics of acute lymphoblastic leucoses (ALLs), textural characteristics of nucleus images with estimation of their parameters are used. © 2016, Allerton Press, Inc.
Wavelength modulation of the excitation source combined with the analysis of the differential PL signal have been applied to studying of electronic spectra of acceptors in compensated CdTe:Cl, CdTe:Ag,Cl single crystals. For the Cl-related complex acceptor with an activation energy of ∼121 meV (A-center), the energies of eight excited states are measured. In the case of tetrahedral AgCdacceptor the splitting of 2P3/2 (Γ8) and 2S3/2 (Γ8) states has been revealed for AgCd centres located at a short distances (5-7 nm) from a hydrogen-like donor (ClTe). A method allowing a simple symmetry test for acceptors in a diverse zinc-blende compound semiconductor is proposed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
New spectroscopic knowledge of the ν1+ν4 R(2) E line of methane over the temperature range 77-300K is reported. Theoretical calculations of the absorption coefficient and the amplitudes of saturated dispersion resonances at 4234cmsup-1/sup were derived. The theoretical dependence on the temperature of the amplitudes of the saturated dispersion resonances was obtained. A novel setup based on a Cr2+:ZnSe laser was used for Doppler-free spectroscopy of methane. The amplitudes of the saturated dispersion resonances of the ν1+ν4 R(2) E line of methane were measured experimentally at different temperatures. A comparison with theoretical dependence supports the reliability of the experiment. The obtained results are of immediate interest in applications demanding laser frequency stabilization. © 2016 Elsevier Ltd.
In this paper, we obtain a continuous analytical expressions approximating the Fermi-Dirac integrals of orders j=-1/2, 1/2, 1, 3/2, 2, 5/2, 3 and 7/2 in a convenient form for calculation with reasonable accuracy (1 divided by 3) over a wide range of degeneration. For approximation was used the approach based on the method of least squares. Requirements for the approximation of integrals, the range of variation of order j and eta adduced Fermi level are considered in terms of the use of Fermi-Dirac integrals to determine the properties of metals and semiconductors.
We present measurements of the azimuthal dependence of charged jet production in central and semi-central sNN=2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as v2ch jet. Jet finding is performed employing the anti-kT algorithm with a resolution parameter R=0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero v2ch jet is observed in semi-central collisions (30-50% centrality) for 20pTch jet90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the v2 of single charged particles at high pT. Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. © 2015 CERN for the benefit of the ALICE Collaboration.
In this paper we present the results of band structure computer simulation of GaSe- based nanostructures using the empirical pseudopotential method. Calculations were performed using a specially developed software that allows performing simulations using cluster computing. Application of this method significantly reduces the demands on computing resources compared to traditional approaches based on ab-initio techniques and provides receiving the adequate comparable results. The use of cluster computing allows to obtain information for structures that require an explicit account of a significant number of atoms, such as quantum dots and quantum pillars. © Published under licence by IOP Publishing Ltd.
The derivation of Warburg's impedance presented in several books and scientific papers is reconsidered. In the past it was obtained by assuming that the total electric current across the sample is just due to the diffusion, and that the external potential applied to the electrode is responsible for an increase of the bulk density of charge described by Nernst's model. We show that these assumptions are not correct, and hence the proposed derivations are questionable. When the electrochemical impedance of a cell of an insulating material where external charges are injected of a given sign is correctly determined, in the high frequency region the real and imaginary parts do not follow the trends predicted by Warburg's impedance. The analysis presented in this paper is relevant to a symmetric cell, in the Nernstian approximation. It can be easily generalized to the case of an asymmetric cell, assuming boundary conditions where the conduction current across the electrodes is proportional to the surface electric field. © 2016 the Owner Societies.
Quantum dots (QDs) are highly fluorescent nanocrystals with advanced photophysical and spectral properties: high brightness and stability against photobleaching accompanied by broad excitation and narrow emission spectra. Water-soluble QDs functionalized with biomolecules, such as proteins, peptides, antibodies, and drugs, are used for biomedical applications. The advantages of QD-based approaches to immuno-histochemical analysis, single-molecule tracking, and in vivo imaging (over traditional methods with organic dyes and fluorescent proteins) are explained. The unique spectral properties of QDs offer opportunities for designing systems for multiplexed analysis by multicolor imaging for the simultaneous detection of multiple targets. Conjugation of drug molecules with QDs or their incorporation into QD-based drug-delivery particles makes it possible to monitor real-time drug tracking and carry out image-guided therapy. Because of the tunability of their photophysical properties, QDs emitting in the near-infrared have become an attractive tool for deep-tissue mono- and multiphoton in vivo imaging. We review recent achievements in QD applications for bioimaging, targeting, and drug delivery, as well as challenges related to their toxicity and non-biodegradability. Key and perspectives for further development of advanced QD-based nanotools are addressed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
A non-linear growth of the scattering intensity and the frequency shift of the spectral lines of scattered light close to the half-width of the spontaneous scattering in the back scattering of light in the suspensions of latex nanoparticles in water were found. It proves that we observed a stimulated scattering of light on the particle concentration variations. Influence of convection is taken into account using Doppler measurements of fluid flow. © Published under licence by IOP Publishing Ltd.
Stokes and anti-Stokes shifts of stimulated concentration light scattering (SCLS, stimulated Mie scattering) in suspensions of various-sized latex nanoparticles in water were measured by the light guide scheme, under conditions of backscattering in the presence of convection. © 2016 Elsevier B.V.
Spectral shifts of the stimulated concentration light scattering (SCLS, stimulated Mie scattering) in suspensions of various sized latex nanoparticles in water were measured by the light guide scheme in conditions of the backscattering in the presence of convection. It is shown that the spectral shift can be either negative or positive depending on the particle size.
A nonlinear growth of the light scattering intensity has been observed and the frequency shift of the spectral line of scattered light has been measured in light backscattered in suspensions of diamond and latex nanoparticles in water. The shift corresponds to the HWHM of the line of spontaneous scattering on particles. We may conclude that there exists stimulated concentration (diffusion) light scattering on variations of the particle concentration, which is also called the stimulated Mie scattering. In a fibre probe scheme, the growth of the shift of the scattered spectral line is observed with an increase in the exciting beam power. The variation of the frequency shift with an increase in the exciting power is explained by convection in liquid.
Fluctuations of the supramolecular structure of albumin facies are analyzed. Two stable states of the supramolecular structure of facies are revealed at room temperature. Optical microscopy is used to assess dynamic character of the supramolecular structure of human serum albumin.
Measurements of charged jet production as a function of centrality are presented for p–Pb collisions recorded at √sNN = 5.02 TeV with the ALICE detector. Centrality classes are determined via the energy deposit in neutron calorimeters at zero degree, close to the beam direction, to minimise dynamical biases of the selection. The corresponding number of participants or binary nucleon–nucleon collisions is determined based on the particle production in the Pb-going rapidity region. Jets have been reconstructed in the central rapidity region from charged particles with the anti-kT algorithm for resolution parameters R= 0.2 and R= 0.4 in the transverse momentum range 20 to 120 GeV/c. The reconstructed jet momentum and yields have been corrected for detector effects and underlying-event background. In the five centrality bins considered, the charged jet production in p–Pb collisions is consistent with the production expected from binary scaling from pp collisions. The ratio of jet yields reconstructed with the two different resolution parameters is also independent of the centrality selection, demonstrating the absence of major modifications of the radial jet structure in the reported centrality classes. © 2016, CERN for the benefit of the ALICE collaboration.
We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at root s(NN) = 2.76 TeV as a function of collision centrality and the average transverse momentum of the pair k(T). Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged one-dimensional radii are extracted. The radii decrease with k(T), following a power-law behavior. This is qualitatively consistent with expectations from a collectively expanding system, produced in hydrodynamic calculations. The radii also scale linearly with dN(ch)/d eta (1/3). This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller root s(NN), a decrease in the ratio R-out/R-side is seen, which is in qualitative agreement with a specific prediction from hydrodynamic models: a change from inside-out to outside-in freeze-out configuration. The results provide further evidence for the production of a collective, strongly coupled system in heavy-ion collisions at the CERN Large Hadron Collider.
The pseudorapidity density of charged particles, dNch/dη, at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of sNN=5.02 TeV. For the 5% most central collisions, we measure a value of 1943±54. The rise in dNch/dη as a function of sNN is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of dNch/dη as a function of the average number of participant nucleons, Npart, calculated in a Glauber model, is compared with the previous measurement at sNN=2.76 TeV. A constant factor of about 1.2 describes the increase in dNch/dη from sNN=2.76 to 5.02 TeV for all centrality classes, within the measured range of 0%-80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions. © 2016 CERN. © 2016 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the »http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Transverse momentum (p(T)) spectra of pions, kaons, and protons up to p(T) = 20 GeV/c have been measured in Pb-Pb collisions at root s(NN) = 2.76 TeV using the ALICE detector for six different centrality classes covering 0%-80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at p(T) approximate to 3 GeV/c in central Pb-Pb collisions that decreases for more peripheral collisions. For p(T) 10 GeV/c, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10%-20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For p(T) 10 GeV/c, the data provide important constraints for models aimed at describing the transition from soft to hard physics.
The inclusive production of the ψ(2S) charmonium state was studied as a function of centrality in p-Pb collisions at the nucleon-nucleon center of mass energy √sNN = 5.02 TeV at the CERN LHC. The measurement was performed with the ALICE detector in the center of mass rapidity ranges −4.46 < ycms< −2.96 and 2.03 < ycms< 3.53, down to zero transverse momentum, by reconstructing the ψ(2S) decay to a muon pair. The ψ(2S) production cross section σψ(2S) is presented as a function of the collision centrality, which is estimated through the energy deposited in forward rapidity calorimeters. The relative strength of nuclear effects on the ψ(2S) and on the corresponding 1S charmonium state J/ψ is then studied by means of the double ratio of cross sections [σψ(2S)/σJ/ψ]pPb/[σψ(2S)/σJ/ψ]pp between p-Pb and pp collisions, and by the values of the nuclear modification factors for the two charmonium states. The results show a large suppression of ψ(2S) production relative to the J/ψ at backward (negative) rapidity, corresponding to the flight direction of the Pb-nucleus, while at forward (positive) rapidity the suppressions of the two states are comparable. Finally, comparisons to results from lower energy experiments and to available theoretical models are presented. © 2016, The Author(s).
The centrality dependence of the charged-particle pseudorapidity density measured with ALICE in Pb-Pb collisions at root s(NN) = 2.76 TeV over a broad pseudorapidity range is presented. This Letter extends the previous results reported by ALICE to more peripheral collisions. No strong change of the overall shape of charged-particle pseudorapidity density distributions with centrality is observed, and when normalised to the number of participating nucleons in the collisions, the evolution over pseudorapidity with centrality is likewise small. The broad pseudorapidity range (-3.5 eta 5) allows precise estimates of the total number of produced charged particles which we find to range from 162 +/- 22(syst.) to 17170 +/- 770(syst.) in 80-90% and 0-5% central collisions, respectively. The total charged-particle multiplicity is seen to approximately scale with the number of participating nucleons in the collision. This suggests that hard contributions to the charged-particle multiplicity are limited. The results are compared to models which describe dN(ch)/d(eta) at mid-rapidity in the most central Pb-Pb collisions and it is found that these models do not capture all features of the distributions. (C) 2016 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.
We demonstrate that the localized surface plasmon resonance applied for studying the colloid noble metal particle interactions can be also used for investigation of metal/non-metal nanoparticle interactions. Using the spectral shift of resonance as a criterion of colloid complex formation, the method can be adapted for exploration of bio-modulated self-assembly processes to be used in life science, for development of smart materials, etc.
Silicon-doped microcrystalline diamond films of 1 μm thickness were grown by chemical vapor deposition in microwave plasma from mixtures of methane–hydrogen–silane on substrates of aluminum nitride, tungsten, and silicon. The diamond films were found to contain optically active silicon vacancy (SiV) centers giving rise to the 737-nm band in the photoluminescence spectra. The spectral features of a newly discovered narrow band of comparable intensity at 720–722 nm were studied. It is shown that the band at 720–722 nm occurs in the photoluminescence spectra only in the presence of silica in the diamond, regardless of the substrate material. The temperature dynamics of the photoluminescence spectra in the range of 5–294 K were investigated. The possible nature and mechanisms of formation of the color centers responsible for the 720–722 nm band are discussed. © 2016 Springer Science+Business Media New York
Confocal photoluminescence (PL) microscopy was used to study a distribution of negatively charged nitrogen-vacancy (NV-) defects within a surface and in a cross section of a homoepitaxial chemical vapor deposition (CVD) diamond layer intentionally grown with a nitrogen concentration close to the solubility limit. A variation in the PL intensity within the whole sample was found to exceed no more than 30% of the intensity maximum. The diamond layers with densely packed NV- arrays are a promising material platform for the design of highly sensitive magnetic field and temperature sensors, as well as for using this material in quantum optics and informatics technologies based on NV- spins. © 2016 Astro Ltd.
It has been demonstrated that photo-induced changes in the optical properties of semiconductor quantum dots (QDs) can be controlled by tuning the parameters of their laser irradiation to vary the relative contributions of photo-brightening and photo-darkening of QDs. For this purpose, the effects of the QD size, photon energy, and intensity of irradiation of QDs on the competing processes of photo-darkening and photo-brightening have been investigated. We have found that photo-brightening of QDs is not accompanied by detectable growth of their photoluminescence (PL) decay time, this process being most pronounced for QDs with an originally low PL quantum yield (QY). In this case, an increase in the PL QY is assumed to be caused by transition of some QDs from the dark (non-emissive) state to the bright (emissive) state. On the other hand, the photo-darkening effect, which was observed only under UV irradiation at 266 nm, was accompanied by simultaneous drop of both the QD QY and their PL decay time. We have also found that, at a constant dose of absorbed energy, the photo-brightening and photo-darkening processes do not depend on the excitation intensity. Thus, the photo-induced changes in the optical properties of QDs are one-photon processes. These data may help to optimize the QD operational conditions in practical applications requiring their intense excitation and add to understanding the fundamental mechanisms of the irreversible photo-induced changes that occur in colloidal QDs under illumination.
We report the measurements of correlations between event-by-event fluctuations of amplitudes of anisotropic flow harmonics in nucleus-nucleus collisions, obtained for the first time using a new analysis method based on multiparticle cumulants in mixed harmonics. This novel method is robust against systematic biases originating from nonflow effects and by construction any dependence on symmetry planes is eliminated. We demonstrate that correlations of flow harmonics exhibit a better sensitivity to medium properties than the individual flow harmonics. The new measurements are performed in Pb-Pb collisions at the center-of-mass energy per nucleon pair of sNN=2.76 TeV by the ALICE experiment at the Large Hadron Collider. The centrality dependence of correlation between event-by-event fluctuations of the elliptic v2 and quadrangular v4 flow harmonics, as well as of anticorrelation between v2 and triangular v3 flow harmonics are presented. The results cover two different regimes of the initial state configurations: geometry dominated (in midcentral collisions) and fluctuation dominated (in the most central collisions). Comparisons are made to predictions from Monte Carlo Glauber, viscous hydrodynamics, ampt, and hijing models. Together with the existing measurements of the individual flow harmonics the presented results provide further constraints on the initial conditions and the transport properties of the system produced in heavy-ion collisions. © 2016 CERN.
A central element of an inertial confinement fusion (ICF) power plant is a target with cryogenic hydrogen fuel that must be delivered to the target chamber center with high accuracy and frequency Therefore, the cryogenic target factory (CTF) is of an integral part of any ICF reactor. A promising path to solve the issue is the FST layering method developed at the Lebedev Physical Institute (LPI). This method (rapid fuel layering inside moving free-standing targets) is a unique and has no analogs in the world. Further FST-technologies development is realizing in the scope of LPI program on creation of modular CTF and commercialization of the obtained results. In this report, we discuss our concept of CTF (CTF-LPI), wich has the following distinctive features: using FST-technologies for elaboration of the flow line production of cryogenic targets using quantum levitation of high-temperature superconductors (HTSC) in magnetic field (maglev) for non-contacting manipulation, transport and positioning of the free-standing cryogenic targets, using Fourier holography for on-line characterization and tracking of a flying targets in the reactor chamber. The original experimental and theoretical works gained in LPI are evidence that existing and developing target fabrication capabilities and technologies can be applied to ICF target production. The unique scientific, engineering and technological base developed in Russia allows creating a CTF-LPI prototype for mass targets producing and their delivery at the required rate.
The influence of the electrode properties on the electric response of nematic liquid crystal cell limited by ITO surfaces is investigated. From electrochemical impedance spectroscopy measurements (EIS) of the real and imaginary parts of the electric impedance of the cell it is evident that in the DC limit the cell behaves as a pure resistance, since its reactance tends to zero linearly with the frequency of the applied voltage. The spectrum of the real part of the impedance shows the presence of two plateaux, one related to the bulk properties of the cell, and the other to the electrode properties. The experimental data can be interpreted in terms of Poisson-Nernst-Planck model, assuming that the presence of the non-blocking electrodes is described by a boundary condition according to which the conduction current across the electrode due to the charge exchange between ions and electrons is due to the surface electric field, as in Ohmic electrodes, and to the variation of the bulk density of ions just in front to the electrodes, as in the Chang-Jaffe model. (C 2016 Published by Elsevier B.V.
Purpose: The cannabinoid type 2 receptor (CB2R) is expressed by immune cells such as monocytes and macrophages. In the brain, CB2R is primarily found on microglia. CB2R upregulation has been reported in animal models of Alzheimer’s disease, with a preferential localization near amyloid beta (Aβ) plaques, and in patients post mortem. We performed in vivo brain imaging and kinetic modelling of the CB2R tracer [11C]NE40 in healthy controls (HC) and in patients with Alzheimer’s disease (AD) to investigate whether higher CB2R availability regionally colocalized to Aβ deposits is present in vivo. Methods: Dynamic 90-min [11C]NE40 PET scans were performed in eight HC and nine AD patients with full kinetic modelling using arterial sampling and metabolite correction and partial volume correction. All AD patients received a static [11C]PIB scan 40 min after injection. In four HC, a retest scan with [11C]NE40 PET was performed within 9 weeks to investigate test–retest characteristics. Results: [11C]NE40 was metabolized quickly leading to 50 % of intact tracer 20 min after injection and 20 % at 90 min. A two-tissue kinetic model fitted most of the time–activity curves best; both binding potential (BPND) and distribution volume (VT) parameters could be used. Brain uptake was generally low with an average K1 value of 0.07 ml/min/ml tissue. VT and BPND were in the range of 0.7 – 1.8 and 0.6 – 1.6, respectively. Test values in HC were about 30 % for VT and BPND. AD patients showed overall significantly lower CB2R binding. No relationship was found between regional or global amyloid load and CB2R availability. Conclusion: Kinetic modelling of [11C]NE40 is possible with a two-tissue reversible model. In contrast to preclinical and post-mortem data, [11C]NE40 PET shows lower CB2R availability in vivo in AD patients, with no relationship to Aβ plaques. A possible explanation for these findings is that [11C]NE40 binds to CB2R with lower affinity and/or selectivity than to CB1R. © 2016 Springer-Verlag Berlin Heidelberg
The strong delocalization of the energy of femtosecond pulses in silicon appears to be an essential factor for preventing laser damage inside a crystal and seemingly excludes the possibility of direct laser writing in the bulk, at least in the one- and two-photon absorption (1 PA and 2 PA) wavelength regions. Previously, the prefocal depletion of the pulse energy and laser-induced free-carrier plasma defocusing of the light were considered to be the main causes of the unlocalized dissipation of light energy. Here, we consider whether the delocalization could be significantly reduced by using longer wavelengths, at which the role of 1 PA and 2 PA decreases and higher orders of nonlinearity come into play. We numerically simulate propagation of focused femtosecond pulses at a wavelength of 1.2-5.25 μm. Plasma defocusing was found to be the crucial delocalization mechanism that prevents the enhancement of material excitation, even in the five-photon absorption region. © 2016 Astro Ltd.
The development of chemically designed matrix metalloprotease (MMP) inhibitors has advanced the understanding of the roles of MMPs in different diseases. Most MMP probes designed are fluorogenic substrates, often suffering from photo- and chemical instability and providing a fluorescence signal of moderate intensity, which is difficult to detect and analyze when dealing with crude biological samples. Here, an inhibitor that inhibits MMP-2 more selectively than Galardin has been synthesized and used for enzyme labeling and detection of the MMP-2 activity. A complete MMP-2 recognition complex consisting of a biotinylated MMP inhibitor tagged with the streptavidin-quantum dot (QD) conjugate has been prepared. This recognition complex, which is characterized by a narrow fluorescence emission spectrum, long fluorescence lifetime, and negligible photobleaching, has been demonstrated to specifically detect MMP-2 in in vitro sandwich-type biochemical assays with sensitivities orders of magnitude higher than those of the existing gold standards employing organic dyes. The approach developed can be used for specific in vitro visualization and testing of MMP-2 in cells and tissues with sensitivities significantly exceeding those of the best existing fluorogenic techniques. (Chemical Equation Presented). © 2016 American Chemical Society.
Scanning near-fi eld optical microscopy (SNOM) with an aperture probe has been used to map the luminescence of isolated submicron diamond crystallites. 532-nm laser light was used to excite luminescence of nitrogen-vacancy (NV) centers. The sizes of the analyzed diamond crystallites were determined with an atomic-force microscope. The optical resolution for the lateral dimensions of the luminescing diamond crystallites was doubled on going from confocal luminescence microscopy to scanning near-fi eld optical microscopy with a 290-nm probe aperture diameter.
The gamma-camera is the detector for nuclear medical imaging where the photomultiplier tubes (PMTs) could be replaced by the silicon photomultipliers (SiPMs). Common systems have the energy resolution about 10% and intrinsic spatial resolution about 3 mm (FWHM). In order to achieve the requirement energy and spatial resolution the classical Anger's logic should be modified. In case of a standard monolithic thallium activated sodium iodide scintillator (500x400x10 mm(3)) and SiPM readout it could be done with identification of the clusters. We show that this approach has a good results with the simulated data.
We report on the response of metal-less CVD polycrystalline-diamond pixel sensors under β-particles irradiation. A 21×21 array of 0.18×0.18 mm2 pixels was realized on one side of a 10.0×10.0×0.5 mm3 polycrystalline diamond substrate by means of laser induced surface graphitization. With the same technique, a large graphite contact, used for detector biasing, was fabricated on the opposite side. A coincidence detecting method was used with two other reference polycrystalline diamond detectors for triggering, instead of commonly used scintillators, positioned in the front and on the back of the sensor-array with respect to the impinging particles trajectory. The collected charge distribution at each pixel was analyzed as a function of the applied bias. No change in the pulse height distribution was recorded by inverting the bias voltage polarity, denoting contacts ohmicity and symmetry. A fairly good pixel response uniformity was obtained: the collected charge most probable value saturates for all the pixels at an electric field strength of about ±0.6 V/μm. Under saturation condition, the average collected charge was equal to <Qcoll>=1.64±0.02 fC, implying a charge collection distance of about 285 µm. A similar result, within 2%, was also obtained for 400 MeV electrons at beam test facility at INFN Frascati National Laboratory. Experimental results highlighted that more than 84% of impinging particles involved only one pixel, with no significant observed cross-talk effects. © 2016 Elsevier B.V.
The paper reviews the status of diamond detectors for UV laser monitoring and imaging. Single pixel detectors, position sensitive architectures, optically activated switches and sensor arrays for beam positioning and imaging are analyzed. The performances of natural diamond and synthetic diamond produced by chemical vapor deposition are compared to evaluate the suitability of such an outstanding material for the described applications. © 2016 Astro Ltd Printed in the UK.
Diamond devices have now become ubiquitous in the LHC experiments, finding applications in beam background monitoring and luminosity measuring systems. This sensor material is now maturing to the point that the large pads in existing diamond detectors are being replaced by highly granular tracking devices, in both pixel and strip configurations, for detector systems that will be used in Run II at the LHC and beyond. The RD42 collaboration has continued to seek out additional diamond manufacturers and quantify the limits of the radiation tolerance of this material. The ATLAS experiment has recently installed, and is now commissioning a fully-fledged pixel tracking detector system based on diamond sensors. Finally, RD42 has recently demonstrated the viability of 3D biased diamond sensors that can be operated at very low voltages with full charge collection. These proceedings describe all of these advances. © 2016.
The production of J/psi and psi (2S) was studied with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity (2.5 y 4) down to zero transverse momentum (p(T)) in the dimuon decay channel. Inclusive J/psi yields were extracted in different centrality classes and the centrality dependence of the average p(T) is presented. The J/psi suppression, quantified with the nuclear modification factor (R-AA), was measured as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/psi production is the result of an interplay between color screening and recombination mechanisms in a deconfined partonic medium, or at its hadronization. Results on the psi(2S) suppression are provided via the ratio of psi(2S) over J/psi measured in pp and Pb-Pb collisions.
The operation of a room-temperature, solid-state, Cr-doped CdSe continuous-wave laser is demonstrated. Longitudinal pumping with a continuous-wave diode laser array at 1.94 μm produced a broadband output of 200 mW at 2.6 μm with an incident power slope efficiency of 6.4%.
In this paper we report on the study of the buried laser-modified region produced inside single crystal diamond by femtosecond laser irradiation. The cross-section of the modified region was prepared via precise mechanical polishing to investigate its intrinsic structure with Raman spectroscopy, scanning electron microscopy and scanning spreading resistance microscopy. It is found that the opaque laser-modified region is pierced by 40-100 nm thick sheets of graphenic carbon united into a single conductive network, while the gaps between the sheets are filled by diamond. Only small part of the irradiated diamond volume (∼16 vol. %) is transformed into the spsup2/sup phase. The results obtained are consistent with the model of laser-induced crack-assisted phase transition in diamond bulk proposed earlier. © 2016 Elsevier Ltd. All rights reserved.
Direct photon production at mid-rapidity in Pb-Pb collisions at √sNN=2.76 TeV was studied in the transverse momentum range 0.9<pT<14 GeV/c. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the esup+/supesup-/sup pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0-20%, 20-40%, and 40-80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for pT > 5 GeV/c. Direct photon spectra down to pT≈1 GeV/c could be extracted for the 20-40% and 0-20% centrality classes. The significance of the direct photon signal for 0.9<pT<2.1 GeV/c is 2.6σ for the 0-20% class. The spectrum in this pT range and centrality class can be described by an exponential with an inverse slope parameter of (297±12supstat/sup±41supsyst/sup) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties. © 2016 CERN for the benefit of the ALICE Collaboration.
We report the experimental evidence of directional Fano resonances at the scattering of a linearly polarized electromagnetic plane wave by a homogeneous dielectric sphere with a high refractive index and low losses. We observe a typical asymmetric Fano profile for the intensity scattered in practically any given direction, while the overall extinction cross section remains Lorentzian. The phenomenon originates in the interference of the selectively excited electric dipolar and quadrupolar modes. The selectivity of the excitation is achieved by the proper choice of the frequency of the incident wave. Owing to the scaling invariance of the Maxwell equations, in these experiments we mimic the scattering of the visible and near IR radiation by a nanoparticle made of common semiconductor materials (Si, Ge, GaAs, GaP) by the equivalent scattering of a spherical particle of 18 mm in diameter in the microwave range. The theory developed to explain the experiments extends the conventional Fano approach to the case when both interfering partitions are resonant. A perfect agreement between the experiment and the theory is demonstrated.
Single vs multimode laser beams were compared for double pulse laser ablation, plasma properties and laser induced breakdown spectroscopy (LIBS) analytical capabilities. Laser beams with Gaussian and multimode profiles were generated within the same Nd:YAG laser in single and double pulse regimes. Gaussian beam produced a small and deep crater while multimode beam formed a wide shallow crater. Greater double pulse enhancement of ablated material and plasma volume were observed for Gaussian beam sampling. The higher intensity for atomic/ionic lines in the plasma spectra was observed for multimode beam sampling due to greater laser pulse energy and larger ablated mass. Interestingly, spectra line intensity enhancement for double pulse ablation was 2–3 times greater for Gaussian than for multimode beam ablation. Background emission decreased for plasma induced by multimode beam when using double pulse mode while for Gaussian beam an opposite dependence was observed. Surprisingly, higher peak fluence at sample surface for Gaussian beam didn't provide higher plasma temperature and electron density for double pulse ablation. Analytical capabilities of LIBS method were compared for double pulse plasma induced by Gaussian and multimode beam in terms of precision, sensitivity and linearity of calibration curves. It was observed that Gaussian beam sampling leads to improvement of analysis precision while sensitivity was element dependent. © 2016 Elsevier B.V.
The results of recent studies have provided strong evidence for the transgenerational effects of parental exposure to ionising radiation and chemical mutagens. However, the transgenerational effects of parental exposure on survival and fertility remain poorly understood. To establish whether parental irradiation can affect the survival and fertility of directly exposed organisms and their offspring, crustacean Daphnia magna were given 10, 100, 1000 and 10,000 mGy of acute γ-rays. Exposure to 1000 and 10,000 mGy significantly compromised the viability of irradiated Daphnia and their first-generation progeny, but did not affect the second-generation progeny. The fertility of F0 and F1 Daphnia gradually declined with the dose of parental exposure and significantly decreased at dose of 100 mGy and at higher doses. The effects of parental irradiation on the number of broods were only observed among the F0 Daphnia exposed to 1000 and 10,000 mGy, whereas the brood size was equally affected in the two consecutive generations. In contrast, the F2 total fertility was compromised only among progeny of parents that received the highest dose of 10,000 mGy. We propose that the decreased fertility observed among the F2 progeny of parents exposed to 10,000 mGy is attributed to transgenerational effects of parental irradiation. Our results also indicate a substantial recovery of the F2 progeny of irradiated F0 Daphnia exposed to the lower doses of acute γ-rays. © 2016 Elsevier Inc.
We present the results of experimental studies of internal quantum efficiency of photoluminescence of blue LED heterostructures based on multiple InxGa1–xN/GaN quantum wells with short-period InyGa1–yN/GaN superlattices containing small amounts of In at high levels of optical pumping. Introduction of an InyGa1–yN/GaN superlattice from the side of the n-region of a LED InxGa1–xN/GaN heterostructure allows to increase the value of its internal quantum efficiency presumably by reducing the quantum-confined Stark effect and Auger recombination rate. © 2016 Springer Science+Business Media New York
Doping of pristine materials can change their chemical and electrical properties. Namely nitrogen doping of graphene results in modulation of electronic properties of graphene. In this work we present experimental results on nitrogen doped graphene fabricated in two steps. At first, the graphene samples were synthesized by a chemical vapor deposition method on copper foils. Then they were treated with ammonia radio frequency discharge plasma. The prepared samples were investigated by atomic-force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, optical absorption spectroscopy including Fourier transform infrared spectroscopy (FTIR), X-ray and ultraviolet photoelectron spectroscopy. In doped graphene a dependence of N-atom concentration on the treatment parameters has been revealed. A maximum doping level of 3 atomic % has been obtained and the shift of valence band maximum of 0.2 eV was observed at this concentration of nitrogen. © 2015 Elsevier Ltd.
The effective electric charge of a nanoparticle in an ionic magnetic colloidal system (an ionic ferrofluid) is determined by using the impedance spectroscopy technique. The electric response of the samples to a harmonic external electric field excitation is described by means of the Poisson-Nernst-Planck model. The model proposed for the theoretical interpretation of the impedance spectroscopy data considers that the magnetic particles are electrically charged with H+ and have in their vicinity Cl- counterions, resulting in an effective charge Qeff. In the presence of an harmonic, in time, external field (frequency bigger than 10 4 Hz) particles are assumed to be at rest, due to inertial reason. In this framework, the response of the cell is due to the H+ and Cl- present in the solution. From the spectra of the real and imaginary components of the electric impedance of the cell, by means of a best fit procedure to our model, we derive the effective electric charge of the magnetic particles and the bulk density of ions. From an independent measurement of the ζ-potential of the suspension, it is possible to calculate the hydrodynamic radius of the particle, in good agreement with that independently measured. © 2016 Author(s).
Here, we present investigation of the influence of different gases (carbon dioxide, ammonia, and iodine vapor) on the sensory properties of graphene and single-wall carbon nanotube films. The gas molecules are adsorbed by carbon films (graphene or nanotubes) and change the film's electrical resistance. In the course of this work, the setup for studying the electrophysical properties of carbon nanomaterials has been designed and constructed in the lab. With this home-made equipment, we have demonstrated a high efficiency of graphene and nanotubes as adsorbents of different gases and a possibility to use these materials as gas sensors. We have also performed a chemical modification of graphene and carbon nanotubes by attaching the nanoparticles of calcium carbonate (CaCO3) to improve the sensitivity and selectivity of sensors. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).
Coherent stimulated rotational Raman self-scattering is proposed as the mechanism of electron-free filamentation of the ultra-short KrF laser pulse in air. © 2016 IEEE.
Using measurements of conductivity and low-temperature photoluminescence, we have studied electronic levels in the band gap of CdTe:Bi and CdTe:Bi,Cl single crystals grown by the modified Bridgman technique. Three type of deep levels (EV+0.29 eV, EV+0.4 eV, EV+0.72 eV) and Bi-related shallow acceptor have been observed depending on the doping conditions. Energy spectrum of a shallow Bi-related acceptor has been measured and its low symmetry has been established. The tentative interpretation for all the levels observed has been proposed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity (|y| 0.7) is measured in Pb-Pb collisions at TeV with ALICE at the LHC. The particle azimuthal distribution with respect to the reaction plane can be parametrized with a Fourier expansion, where the second coefficient (v (2)) represents the elliptic flow. The v (2) coefficient of inclusive electrons is measured in three centrality classes (0-10%, 10-20% and 20-40%) with the event plane and the scalar product methods in the transverse momentum (p (T)) intervals 0.5-13 GeV/c and 0.5-8 GeV/c, respectively. After subtracting the background, mainly from photon conversions and Dalitz decays of neutral mesons, a positive v (2) of electrons from heavy-flavour hadron decays is observed in all centrality classes, with a maximum significance of 5.9 sigma in the interval 2 p (T) 2.5 GeV/c in semi-central collisions (20-40%). The value of v (2) decreases towards more central collisions at low and intermediate p (T) (0.5 p (T) 3 GeV/c). The v (2) of electrons from heavy-flavour hadron decays at mid-rapidity is found to be similar to the one of muons from heavy-flavour hadron decays at forward rapidity (2.5 y 4). The results are described within uncertainties by model calculations including substantial elastic interactions of heavy quarks with an expanding strongly-interacting medium.
The elliptic flow, v2, of muons from heavy-flavour hadron decays at forward rapidity (2.5<y<4) is measured in Pb-Pb collisions at sNN=2.76 TeV with the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v2 of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, pT, is studied in the interval 3<pT<10 GeV/c. A positive v2 is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the pT interval from 3 to about 5 GeV/c with a significance larger than 3σ, based on the combination of statistical and systematic uncertainties. The v2 magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6<pT<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. © 2015 CERN for the benefit of the ALICE Collaboration.
Metallic and semiconducting fractions of single-walled carbon nanotubes (SWCNTs) sorted by an aqueous two-phase extraction technique and integrated into thin films were used to produce CuCl@SWCNT hybrid material via a gas phase filling the nanotubes with CuCl. As a result of doping, the SWCNTs in the hybrid material possess a higher optical transparency than the pristine ones. The hybrid material properties strongly depend on the metallic/semiconducting tube ratio in a pristine material. In this work, with UV-vis-NIR optical absorption and Raman techniques we show that upon filling with CuCl the solely metallic nanotubes provide much higher doping efficiency than the solely semiconducting SWCNTs. The CuCl@SWCNT hybrid material based on sorted nanotubes is more competitive as a transparent conductive material for the future photovoltaics. A schematic view of electron transfer between CuCl@s-SWCNT and CuCl@m-SWCNT within a bundle of CuCl@SWCNT. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
We report on results obtained with the event-shape engineering technique applied to Pb-Pb collisions at root s(NN) = 2.76 TeV. By selecting events in the same centrality interval, but with very different average flow, different initial-state conditions can be studied. We find the effect of the event-shape selection on the elliptic flow coefficient v(2) to be almost independent of transverse momentum p(T), which is as expected if this effect is attributable to fluctuations in the initial geometry of the system. Charged-hadron, -pion, -kaon, and -proton transverse momentum distributions are found to be harder in events with higher-than-average elliptic flow, indicating an interplay between radial and elliptic flow.
Routine infertility investigations in the male and female include imaging techniques such as ultrasonography and endoscopy (fertiloscopy). However, these techniques lack the resolution to localize vital sperm or to reveal detailed morphological analysis of the oviduct which is often the cause of infertility in females. Therefore we set out to evaluate the efficiency of optical coherence tomography (OCT) as a diagnostic imaging tool for micron-scale visualization of the male and female genital tract. Using the bovine as a model, the optical features of the TelestoTM, GanymedeTM (both Thorlabs) and NirisTM (Imalux) OCT imaging systems were compared. Comparative visualization of ex vivo bovine testicular tissue by the TelestoTM microscopic optical coherence tomography system (left) and corresponding H&E staining (right). Routine infertility investigations in the male and female include imaging techniques such as ultrasonography and endoscopy (fertiloscopy). However, these techniques lack the resolution to localize vital sperm or to reveal detailed morphological analysis of the oviduct which is often the cause of infertility in females. Here, the efficiency of optical coherence tomography (OCT) as a diagnostic imaging tool for micron-scale visualization of the male and female genital tract is evaluated. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
A technology for the production of fully hybrid microcavities on the basis of Zn(S)Se films and amorphous insulating SiO2/Ta2O5 coatings is proposed. The influence of all stages of the manufacturing cycle on the structure of exciton states in the Zn(S)Se films is demonstrated. This influence is reduced to four main effects: the appearance of a fine structure of emission lines related to free excitons; a decrease in the relative contribution of excitons bound at neutral acceptors to the exciton-emission spectrum; a shift of the emission lines related to exciton–impurity complexes and free excitons to lower frequencies; and a decrease in the splitting between emission lines related to heavy and light excitons. Samples of fully hybrid microcavities, in which the high structural and optical quality of Zn(S)Se films is retained, are fabricated. © 2016, Pleiades Publishing, Ltd.
We succeeded in synthesis of the novel Eu-based luminophore with almost 100% efficiency of energy transfer from ligands to the lanthanide ion. The luminophores with β- diketonate ligands were characterized by means of optical spectroscopy. Impact of different types of β-diketonates on the quantum yield of luminescence was revealed. A β-diketonate complex exhibiting the highest luminescence quantum yield and prospective for OLED applications was determined. The reasons for decreasing quantum efficiencies for other types of investigated ligands are discussed. © Published under licence by IOP Publishing Ltd.
This work demonstrates an integrated approach for studying graphene films with various doping levels of nitrogen. The graphene films grown by a chemical vapor deposition technique were doped by treatment in ammonia radio-frequency plasma discharge. The graphene samples were investigated by x-ray photoelectron spectroscopy with a parallel registration of photoemission angular dependence. The depth-dependent changes in the valence band structure and the nitrogen peak position were recorded. The shift of valence band maximum relative to the initial value (0.13 ± 0.04 eV) was observed using ultraviolet photoelectron spectroscopy. The dispersion and the shift of π-plasmon maximum were registered while the percentage of nitrogen atoms in two-dimensional graphene network increased. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).
To determine the depth of the area of radiopharmaceutical accumulation a method of simultaneous recording of two lines of gamma rays of different energies and quantitative comparison of the intensity of these lines on the surface of the patient's body is provided. Since the coefficient of linear absorption of gamma radiation in the medium depends not only on the characteristics of the medium, but also on the gamma radiation energy, the intensity of gammas of different energies is attenuated differently after passing through the same absorber layer (soft tissues). Thus, the quantitative comparison of the relative intensities of gamma lines on the surface of the patient's body allows to determine the depth of area of the accumulation of the radiopharmaceutical. The result is achieved by analyzing the energy spectrum of the source, obtained with a semiconductor spectrometer, by measuring the ratio of areas of the absorption peaks of the radioisotope and defining the depth of gamma source using the calibration dependence between the areas ratio and the medium layer thickness. The most widely used medical radioisotope technetium-99m has two gamma-lines - 140 keV and 18.5keV, which allows one to apply the proposed method to search for the sentinel lymph nodes and non-palpable malignant tumors in the soft tissues.
We report on an external-cavity diamond Raman laser (DRL) pumped with a Q-switched Nd:YAG and generating at 1st and 2nd Stokes (1240 nm and 1485 nm) with enhanced output energy. The slope efficiency of 54% and output energy as high as 1.2 mJ in single pulse at 1240 nm have been achieved with optimized cavity, while the pulse energy of 0.70 mJ was obtained in the eye-safe spectral region at 1485 nm. Calculations of thermal lensing effect indicate it as a possible reason for the observed decrease in conversion efficiency at the highest pump energies. © 2016 Astro Ltd.
X-ray planar compound refractive lenses were fabricated from a polycrystalline diamond plate grown by chemical vapor deposition, by precise through cutting with femtosecond laser pulses. The lens geometry and the surface morphology were investigated with optical and scanning electron microscopy, while the material structure modification was analyzed by Raman spectroscopy. The results of the preliminary lens test at 9.25-keV X-rays are presented. © 2016, Springer-Verlag Berlin Heidelberg.
This work is about the possibility of fluorescence diagnosis application with the use of aluminum phthalocyanine nanoparticles (nAlPc) in order to detect enamel microdamage. For the investigation, five human teeth samples of various age groups were removed for various reasons. The autofluorescence spectrums of these samples hard tissues and fluorescence spectrums of nAlPc mixed with enamel powder were obtained during the experiment. The research shows that sample pathogenic microflora causes nAlPc fluorescence. This fact will allow detecting enamel microdamage in future studies. © Published under licence by IOP Publishing Ltd.
A new type of ferroelectric liquid crystal (FLC) is considered, where the reorientation of the director (main optical axes) at the interaction of an electric field with the FLC's spontaneous polarization is due to the movement of spatially localized waves with a stationary profile: solitons arise at the transition due to the Maxwellian mechanism of energy dissipation. Under certain conditions, the appearance of such waves leads to the formation of a structure of transient domains, and as a consequence, to the scattering of light. The Maxwellian mechanism of energy dissipation allows one to reduce the electric field strength at which the maximum efficiency of light scattering is achieved down to 2-3 V/μm and to increase the frequency of light modulation up to 3-5 kHz. Intensive bistable light scattering in an electro-optical cell filled with a specially designed helix-free FLC was studied, and a stable scattering state can be switched on and off for a few tens of microseconds and memorized for a few tens of seconds. © 2016 Optical Society of America.
Influence of nanodiamonds (ND) of 35 and 100 nm in size, containing NV centers, on the strength of hydrogen bonds under heating of the ND water suspensions in the range of 5–95 °C was studied by Raman spectroscopy. General tendency of both NDs to weaken hydrogen bonds in water was found. Substantial influence of functional state of ND surface on hydrogen bond strength was revealed. An influence of hydrogen bonds on fluorescence properties of the NDs in water suspensions was studied as well. It was found that fluorescence properties of NV centers of 100-nm NDs are stable with regard to change of their surface state, whereas, a fluorescence intensity of the 35-nm NDs essentially depends on strength of hydrogen bonds in the suspension. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Strained epitaxial ZnSe layers are grown on GaAs substrates by the method of vapor-phase epitaxy from metal-organic compounds. It is found that Se nanoislands with a density of 10(8) to 10(9) cm(-2) are formed at the surface of such layers. It is established that an increase in the size of Se islands and a decrease in their density take place after completion of growth. Annealing in a H-2 atmosphere at a temperature higher than 260A degrees C leads to the disappearance of Se islands and to a decrease in the surface roughness. It is shown that annealing does not lead to deterioration of the structural perfection of the epitaxial ZnSe films; rather, annealing gives rise to a decrease in the intensity of impurity-defect luminescence and to an increase in the intensity of intrinsic radiation near the bottom of the exciton band.
Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 |η| 4.0) and associated particles in the central range (|η| 1.0) are measured with the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The trigger particles are reconstructed using the muon spectrometer, and the associated particles by the central barrel tracking detectors. In high-multiplicity events, the double-ridge structure, previously discovered in two-particle angular correlations at midrapidity, is found to persist to the pseudorapidity ranges studied in this Letter. The second-order Fourier coefficients for muons in high-multiplicity events are extracted after jet-like correlations from low-multiplicity events have been subtracted. The coefficients are found to have a similar transverse momentum (pT) dependence in p-going (p-Pb) and Pb-going (Pb-p) configurations, with the Pb-going coefficients larger by about 16 ± 6%, rather independent of pT within the uncertainties of the measurement. The data are compared with calculations using the AMPT model, which predicts a different pT and η dependence than observed in the data. The results are sensitive to the parent particle v2 and composition of reconstructed muon tracks, where the contribution from heavy flavour decays is expected to dominate at pT2 GeV/c. © 2015 CERN for the benefit of the ALICE Collaboration.
We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium-doped all-fiber ring laser hybridly mode-locked with a coaction of a single-walled carbon nanotube-based saturable absorber and nonlinear polarization evolution that was introduced through the insertion of the short-segment polarizing fiber. Depending on the total intracavity dispersion value, the laser emits conservative solitons, transform-limited Gaussian pulses, or highly chirped stretched pulses with almost 20 nm wide parabolic spectrum in both clockwise (CW) and counterclockwise (CCW) directions of the ring. Owing to the polarizing action in the cavity, we have demonstrated for the first time, to the best of our knowledge, an efficient tuning of soliton pulse characteristics for both CW and CCW channels via an appropriate polarization control. We believe that the bidirectional laser presented may be highly promising for gyroscopic and other dual-channel applications. (C) 2016 Optical Society of America
Basic features and mechanism of femtosecond laser graphitization of diamond surface were studied in the two regimes of irradiation: (1) by an intensive (>10 J/cmsup2/sup) single shot and (2) by a train of pulses with near-threshold intensity (~1–10 J/cmsup2/sup). Special attention was paid to the so-called accumulative regime, when multipulse laser treatment results in prolonged delay of an appearance of crystal modification of the crystal. The light absorption mechanisms dominating in each regime are discussed. The experiments with fundamental (800 nm), second (400 nm) and third (266 nm) harmonics of Ti–sapphire laser (100 fs) have revealed that thermally stimulated processes play an essential role in latent diamond graphitization. © 2016, Springer-Verlag Berlin Heidelberg.
The strong two-photon absorption and induced plasma are well-known factors restricting the penetration of intense focused laser pulses in silicon crystals. In this paper, we demonstrate that the role of plasma is not exhausted by the defocusing effect in a beam waist. We investigated experimentally the propagation of an IR laser pulse focused inside a silicon target and found a complex filament-like transformation of the beam. The results of numerical simulation suggest that this behavior is the result of wavefront distortion induced by the subsurface plasma (Formula presented.). © 2016, Springer-Verlag Berlin Heidelberg.
Background: The new methods of osteoarthritis treatment are in constant demand due to the complexity of the early diagnosis and therapy. Specific features of s(cyrillic)hlorin e6 derivative (Ce6) accumulation in knee joint tissues and the efficiency of photodynamic therapy (PDT) of gonarthritis were studied. Methods: The experimental research was conducted on the model of posttraumatic gonarthritis on rabbits. The analysis of dynamics of change of Ce6 concentration in tissues of a knee joint was carried out by the method of fluorescent diagnostics. The intra-joint PDT was carried out using 662 nm laser with energy density of 120-150 J/cm2 and a sapphire diffuser. An analysis of slices was conducted to confirm the anti-inflammatory effect through apoptosis. Results: The method of fluorescent spectroscopy revealed that the highest amount of Ce6 was accumulated in the synovial membrane of a damaged knee joint 2.5 h after its intravenous introduction. On 14th day after gonarthritis modeling but before PDT the synovial membrane showed signs of synovitis. On 21st day after PDT the synovial membrane possessed noticeable villous structure, and no cells of inflammatory nature were observed. Conclusion: Fluorescent diagnostics in knee joint tissues can be used in clinical practice of gonarthritis before, during and after PDT for monitoring the Ce6 accumulation and for treatment control. Optimal radiation energy density was determined to be 150 J/cm2. In the studied time intervals (5-25 min) no dependency of PDT effect on irradiation time at the same energy density was observed. The analysis of results of clinical and morphological research shows that PDT is a low-invasive method of gonarthritis treatment with a high degree of efficiency and selectivity. © 2016 Elsevier B.V.
Results of studying the formation of InAs quantum dots (QDs) on GaAs(100) substrates by droplet epitaxy using trimethylindium and arsine (AsH3) as precursors are presented. The growth process was carried out at temperatures within 230–400°C in a horizontal reactor for metalorganic vapor phase epitaxy (MOVPE) using high-purity hydrogen as the carrier gas. Data on the influence of process temperature on the QD size and the density of QD array and results of investigation of the low-temperature photoluminescence of obtained samples are presented. © 2016, Pleiades Publishing, Ltd.
Silicon-doped diamond nanopillars have been produced by a microwave plasma chemical vapor deposition (CVD) on a single crystal diamond substrate through holes in a Si mask perforated with a focused ion beam. Arrays of 400 nm diameter pillars with aspect ratio up to 2.8 are grown epitaxially being confined by channels in the mask, the latter serving also as the Si doping source. Strong photoluminescent (PL) emission of the SiV centers at 738.7 nm wavelength, localized within the pillars, has been detected and imaged with a fluorescence microscope. The SiV PL decay time of 1.1 ns has been deduced from PL kinetics measurements. An increase of specific PL intensity (intensity per unit volume of the pillar) with the aspect ratio is noted. © 2016 Elsevier B.V.
The current status of research on generating a powerful shock wave with a pressure of up to several gigabars in a laboratory experiment is reviewed. The focus is on results which give a possibility of shock-wave experiments to study an equation of state of matter (EOS) at the level of gigabar pressure. The proposals are discussed to achieve a plane record-pressure shock wave driven by laser-accelerated fast electrons with respect to EOS-experiment as well as to prospective method of inertial fusion target (ICF) ignition as shock ignition. © 2016 IOP Publishing Ltd and Sissa Medialab srl.
An analytical solution has been obtained for the spherical isothermal expansion of the outer layer of a ball whose mass increases at a constant areal density of the heated layer, which is equal to the product of the initial values of the depth of heating and the density of the layer for the entire time of expansion into vacuum. This solution differs from the known solution for the isothermal spherical expansion of a given mass of a material in a slower decrease in the density and, as a result, in the pressure of the expanding material with the time. In particular, it describes the expansion of the boundary layer of the ball heated by a flow of fast electrons in application to the problem of the ignition of an inertial confinement fusion target by a shock wave induced because of the heating of the target by the flow of laser-accelerated fast electrons (shock ignition).
It has been proposed to use the formation of a magnetized plasma of laser-accelerated ions and electrons at the irradiation of the curved surface of the inner cavity of the target by a petawatt laser pulse to initiate a neutronless nuclear reaction of protons with boron nuclei. The possibility of an additional increase in the intensity of the reaction owing to the compression of the plasma at the irradiation of the outer surface of the target by a second terawatt laser pulse synchronized in time with the plasma-forming pulse has been discussed. The parameters of laser pulses and a target have been determined at which the ignition of a pB plasma occurs; i.e., the energy released in reactions is equal to the energy of the plasma. © 2016, Pleiades Publishing, Inc.
In the framework of classical electrodynamics we have obtained and investigated analytical expressions for the radiation linewidth of forbidden E2 transitions in an atom located near a dimer of spherical particles. It is shown that the material of particles, their location and size have a significant effect on the linewidth of the E2 transition in the atom. It is found that in the gap between metal spherical nanoparticles, the linewidth of E2 transitions in the atom can take on substantially larger values than in the case of an atom near a single metal nanoparticle. © 2016 Kvantovaya Elektronika and Turpion Ltd.
Coronene molecules are used as filler for single-walled carbon nanotubes. Variation of the synthesis temperature regimes leads to formation of different types of carbon nanostructures inside the nanotubes. Accurate determination of the structures by optical spectroscopy methods remains an important issue in composite materials. Clear distinction between adsorbed organic molecules on the surface of the tubes and filled structures may be accessed by Raman and photoluminescence spectroscopies. We perform additional heat treatment after the initial synthesis procedure and show the evolution of the optical spectral features corresponding to the filled structures and adsorbed materials on the surface of single-walled carbon nanotubes. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).
SiO2, ZrO2, B2O3 and MgO oxides and their combinations were used as sintering aids for preparation of yttrium aluminum garnet (YAG) ceramics doped by Nd2O3, Er2O3, Ho2O3, Tm2O3 and Yb2O3. The influence of these additives on optimal sintering temperature, grain growth, volume of residual pores and optical quality of the ceramics were investigated. The best combination of the sintering additives was found and high quality samples of YAG:Nd (1 at.%) ceramics were obtained. The original method of laser optical quality characterization of ceramics was developed and tested. The main laser parameters of YAG:Nd (1 at.%) ceramics samples are measured and compared with the best well known laser ceramics. The samples of YAG:RE (RE- Er2O3, Ho2O3, Tm2O3 and Yb2O3) ceramics are obtained, and their optical transmittance spectra are measured. Composite structures of YAG:Yb (5 at.%) - YAG were obtained by the simplest method of successive joint compaction of different composition layers.
SiO2, ZrO2, B2O3 and MgO oxides and their combinations were used as sintering aids for preparation of yttrium aluminum garnet (YAG) ceramics doped by Nd2O3. The influence of these additives on optimal sintering temperature, grain growth, volume of residual pores and optical quality of the ceramics were investigated. The best combination of the sintering additives was found and high quality samples of YAG:Nd (1 at.%) ceramics were obtained. The original method of laser optical quality characterization of ceramics was developed and tested. The main laser parameters of YAG:Nd (1 at.%) ceramics samples are measured and compared with the best well known laser ceramics. © 2016 Elsevier B.V.
Core/shell quantum dots (QDs) with maximal photoluminescence quantum yields offer much promise for nanotechnological applications in biosensing and multiphoton fluorescent imaging. The best QD shell coating methods are based on layer-by-layer precursor deposition. We have developed a new procedure for the synthesis of highly luminescent CdSe/ZnS/CdS/ZnS core/multishell QDs whose structure is based on charge carrier confinement engineering and which have highly uniform epitaxial shells and photoluminescence quantum yields as high as 100%. We have characterized two-photon properties of these QDs with cores of different sizes. The obtained data demonstrate that the large two-photon excitation action cross section makes synthesized core/multishell QDs a promising photoluminescent material for engineering of bright nanoprobes for multiphoton microscopy. (C) 2016 Elsevier Ltd. All rights reserved.
Concept of a solid-state femtosecond laser system with a multigigawatt power level in the 4–5 μm range has been proposed. The system contains an ultrashort pulse seeder, a two-stage chirped pulse amplifier based on a broadband Fe2+:ZnSe active element with optical pumping by a YSGG:Cr:Er laser, and an output stage that provides additional nonlinear optical compression of an amplified pulse to approximately 30 fs in a dielectric CaF2 medium with anomalous group velocity dispersion in this spectral range. © 2016, Allerton Press, Inc.
The growth of single crystal diamond plates in a microwave plasma using H2-CH4 and H2-CH4-Ar gas mixtures in a broad range of methane concentration (2-15%) is studied. The growth rates up to 60 μm/h in H2-CH4 mixtures and up to 105 μm/h in Ar-H2-CH4 mixtures are achieved at high CH4 content, without adding nitrogen, still obtaining transparent crystals. The thermal conductivity k of the SCs in the temperature range of 220-420 K is measured by a laser flash technique. High thermal conductivity k ≈ 2300 W/m × K at room temperature is found for the sample grown at low growth rate in H2-CH4, this value reducing to k ≈ 2000 W/mK for the material produced in high rate regime at 15% CH4. The spatial profiles of Hα and C2 line intensities in the plasma were determined with optical emission spectroscopy (OES). Soot formation at high CH4 contents is observed at the plasma border both for Ar-free and Ar-containing mixtures, the soot yield being roughly proportional to diamond growth rate. The soot temperature Ts, as measured with OES, is almost constant (3800 ± 300 K) in H2-CH4 mixtures over the all methane concentration range explored, while for Ar-containing plasma the Ts is even higher (4100-4200 K) at [CH4] 10%, reducing, however, below 3800 K in CH4-reach mixtures. Raman spectra of collected soot correspond to crystalline graphite with high density of defects. The estimated carbon conversion efficiency from CH4 precursor to the soot can exceed 10% and should be taken into account in overall carbon balance in the CVD process. © 2015 Elsevier B.V. All rights reserved.
We report on fast polishing of polycrystalline CVD diamond films by ultrasonic machining in a slurry with diamond particles. The material removal mechanism is based on diamond micro-chipping by the bombarding diamond particles subjected to action of an ultrasonic radiator. The treated samples were characterized with optical profilometry, SEM, AFM and micro-Raman spectroscopy. The developed method demonstrates the polishing rate higher than those known for mechanical or thermo-mechanical polishing, particularly, the surface roughness of 0.5 mm thick film can be reduced in a static regime from initial value Ra ≈5 μm to Ra ≈0.5 μm for the processing time as short as 5 min. No appearance of amorphous carbon on the lapped surface was revealed, however, formation of defects in a sub-surface layer of a few microns thickness was deduced using Raman spectroscopy. The polishing of a moving workpiece confirmed the possibility to treat large-area diamond films. © 2016 Elsevier B.V.
The elliptic, triangular, quadrangular and pentagonal anisotropic flow coefficients for π±, K± and p + p ¯ in Pb-Pb collisions at sNN=2.76 TeV were measured with the ALICE detector at the Large Hadron Collider. The results were obtained with the Scalar Product method, correlating the identified hadrons with reference particles from a different pseudorapidity region. Effects not related to the common event symmetry planes (non-flow) were estimated using correlations in pp collisions and were subtracted from the measurement. The obtained flow coefficients exhibit a clear mass ordering for transverse momentum (pT) values below ≈ 3 GeV/c. In the intermediate pT region (3 < pT< 6 GeV/c), particles group at an approximate level according to the number of constituent quarks, suggesting that coalescence might be the relevant particle production mechanism in this region. The results for pT< 3 GeV/c are described fairly well by a hydrodynamical model (iEBE-VISHNU) that uses initial conditions generated by A Multi-Phase Transport model (AMPT) and describes the expansion of the fireball using a value of 0.08 for the ratio of shear viscosity to entropy density (η/s), coupled to a hadronic cascade model (UrQMD). Finally, expectations from AMPT alone fail to quantitatively describe the measurements for all harmonics throughout the measured transverse momentum region. However, the comparison to the AMPT model highlights the importance of the late hadronic rescattering stage to the development of the observed mass ordering at low values of pT and of coalescence as a particle production mechanism for the particle type grouping at intermediate values of pT for all harmonics.[Figure not available: see fulltext.] © 2016, The Author(s).
The production of the hypertriton nuclei HΛ3 and H[U+203E]Λ-3 has been measured for the first time in Pb-Pb collisions at sNN=2.76 TeV with the ALICE experiment at LHC. The pT-integrated HΛ3 yield in one unity of rapidity, dN/dy×B.R.(HΛ3→He3,π-)=(3.86±0.77(stat.)±0.68(syst.))×10-in the 0-10% most central collisions, is consistent with the predictions from a statistical thermal model using the same temperature as for the light hadrons. The coalescence parameter B3 shows a dependence on the transverse momentum, similar to the B2 of deuterons and the B3 of sup3/supHe nuclei. The ratio of yields S3=HΛ3/(He3×Λ/p) was measured to be S3=0.60±0.13(stat.)±0.21(syst.) in 0-10% centrality events; this value is compared to different theoretical models. The measured S3 is compatible with thermal model predictions. The measured HΛ3 lifetime, τ=181-39+54(stat.)±33(syst.)ps is in agreement within 1σ with the world average value. © 2016 CERN for the benefit of the ALICE Collaboration.
Shallow impurity–defect states in undoped Cd1–xZnxTe (x ∼ 3–6%) single crystals have been studied using low-temperature photoluminescence measurements. It has been found that the effect exerted by zinc is mainly reduced to a rigid shift of all the specific features associated with the exciton radiation, which made it possible, with a high (∼0.3 meV) accuracy, to measure the band gap and the zinc concentration in solid solutions. Hydrogen-like donors with the ground-state energy of ∼14 meV and four types of acceptors with average activation energies of 59.3 ± 0.6 meV, 69.6 ± 1.5 meV, 155.8 ± 2.0 meV, and 52.3 ± 0.6 meV have been identified in all the crystals studied. Based on a comparison with the results of the analysis of the impurity background and the data available in the literature on impurity–defect emission in undoped CdTe, the first three acceptors can be assigned to the substitutional impurities NaCd, PTe, and CuCd, respectively. The most shallow acceptor (52.3 ± 0.6 meV) is a complex defect in which there is a nonstandard excited level separated by only 7 meV from the ground level. This level is formed apparently due to the removal of degeneracy, which is characteristic of TD acceptors, by the low-symmetry potential of the complex defect. © 2016, Pleiades Publishing, Ltd.
We report on the inclusive production cross sections of (Formula presented.) , (Formula presented.) , (Formula presented.) (1S), (Formula presented.) (2S) and (Formula presented.) (3S), measured at forward rapidity with the ALICE detector in (Formula presented.) collisions at a center-of-mass energy (Formula presented.) TeV. The analysis is based on data collected at the LHC and corresponds to an integrated luminosity of 1.23 pb (Formula presented.). Quarkonia are reconstructed in the dimuon-decay channel. The differential production cross sections are measured as a function of the transverse momentum (Formula presented.) and rapidity y, over the (Formula presented.) ranges (Formula presented.) GeV/c for (Formula presented.) , (Formula presented.) GeV/c for all other resonances, and for (Formula presented.). The cross sections, integrated over (Formula presented.) and y, and assuming unpolarized quarkonia, are (Formula presented.) (Formula presented.) b, (Formula presented.) (Formula presented.) b, (Formula presented.) nb, (Formula presented.) nb and (Formula presented.) nb, where the first uncertainty is statistical and the second one is systematic. These values agree, within at most (Formula presented.) , with measurements performed by the LHCb collaboration in the same rapidity range. © 2016, CERN for the benefit of the ALICE collaboration.
Today the porous silicon photonic crystals are widely used as components of the optical sensors. The structures with the resonance properties, e.g. a narrow reflection band, which provides high sensitivity of the device, generate considerable interest. One of the most interesting structures of this type are rugate filters. Rugate filter is a photonic crystal with a gradually varying under harmonic law index of refraction and narrow spectral reflection band. In this paper, we present our results of the optimization of silicon electrochemical etching parameters, in order to fabricate filters in a visible spectral range with reflection bandwidth of less than 30 nm and a reflectance higher than 80%. © Published under licence by IOP Publishing Ltd.
A complete phenomenological description of the electrode polarisation and of the non-blocking character of electrodes is theoretically discussed. To do this, the role of the ions on the electrical response of an electrolytic cell submitted to an external field of small amplitude is investigated. We assume that the conduction current across the electrodes is limited by energy barriers which determine the activation energy of the corresponding electrochemical reactions responsible for the processes of charge transfer between the solution containing ions and the external circuit. This assumption implies that the boundary conditions for the conduction current on the electrodes contain two terms: one proportional to the surface electric field, as in the Ohmic model, and the other proportional to the surface variation of the bulk concentration of ions, as in the Chang-Jaffe model. We deduce, in the one-mobile ion approximation, the expression for the electric impedance of the cell, in the shape of a slab, for mixed boundary conditions. Our expression contains, as particular cases, the Ohmic and Chang-Jaffe models. The equivalence between the general case considered in our analysis and previous models is discussed. © 2016 AIP Publishing LLC.
A general concept of a new interdisciplinary glossary, which includes particle accelerator terminology used in medicine, as well as relevant medical concepts, is presented. Its structure and usage rules are described. An example, illustrating the quickly searching technique of relevant information in this Glossary, is considered. A website address, where one can get an access to the Glossary, is specified. Glossary can be refined and supplemented.
We report on the temperature dependence of the Milli-Q water cell response, limited by surgical steel electrodes, to an external periodic excitation. Using the Electrochemical Impedance Spectroscopy technique (EIS), the spectra of the real and imaginary parts of the electrical impedance of the cell are experimentally obtained. Important deviations from the theoretical predictions of the Poisson–Nernst–Planck model, assuming blocking electrodes, are observed. Our experimental results indicate that the properties of the electrodes play an important role in the low frequency part of the spectra. In the absence of a simple physically based theoretical model, we fit our data utilizing three equivalent electric circuits containing a constant phase element (CPE) charged to describe the properties of the electrodes. From our analysis it follows that a “good” equivalent electric circuit for the analysis of the response of an electrolytic cell to an external periodic voltage is formed by a parallel of a bulk capacitance and resistance of ionic origin. The CPE is then charged to mimic the interface effects. From a mathematical point of view this is equivalent to assume that the phenomenological parameters describing the non-ideal blocking properties of the electrode, in the Chang-Jaffe, Ohmic or Langmuir models, are frequency dependent. © 2016
We have performed a study of CVD multiwalled carbon nanotubes (MWCNTs) produced with Fe-Co catalysts with a variable ratio of active metals. The Raman data were considered in combination with the temperature dependence of MWCNT conductivity. The data analysis is based on the point that the value of I2D/ID ratio correlates with the graphene fragment size. The fragments are considered as building blocks of MWCNTs. We showed that MWCNT defectiveness depends on the ratio of bimetallic active components in the Fe-Co catalyst. Thus, the ratio of I2D/ID increases and the D-mode intensity decreases while the Fe content in the catalyst increases. This also points to the reduction of defect number in the bigger graphene fragments. These results correlate with the data on conductivity temperature dependence. Namely, the increase of Fe content in the active component of the Fe-Co catalyst results in the increase of charge carrier concentration, which, in turn, indicates a decrease in MWCNT defectiveness. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).
Time-resolved optical reflection microscopy studies demonstrate spatiotemporal dynamics of melting and ablation of graphite surface molten by single IR femtosecond laser pulses, which are revealed by monitoring picosecond oscillations of the probe reflectivity modulated by transient acoustic reverberations in the surface melt. Temporal periods and amplitudes of the reverberations are affected through transient variations of melt thickness and acoustic impedance by melting, thermal expansion, spallation and fragmentation processes, thus enabling quantitative evaluation of their contributions and basic parameters. © 2016 Pleiades Publishing, Inc.
On the basis of low-temperature (5 K) microphotoluminescence measurements in a wide ZnSe/ZnMgSSe quantum well, the existence of isolated quantum emitters in this heterostructure is demonstrated. Characteristically, the corresponding emission lines experience stepwise spectral shifts by a few meV on a time scale of 1-10 min. The unconventional properties of the observed emitters are explained by considering the picture of a system with a large dipole moment in the ground state, such as a single donor-acceptor pair or a similar system located near an extended defect.
Application of ionizing radiation in oncology (radiation therapy) is a widespread way to eliminate malignant tumors. Normal tissues are inevitable included in any radiation field, and their reliable protection is actual till now. All attempts to solve the problem are based on search of effective radioprotectors, i.e. chemical compounds of various classes, which should be entered into the patient. To date about 50,000 compounds with some radioprotection properties had been tested, but the most effective of them have been simultaneously the most toxic. Here the preliminary results of researches devoted to development of an optical technique on basis of the light-oxygen effect for the protection of women with breast cancer from side effects of the radiation therapy are presented. A low intensity emission of the semiconductor laser in a red spectral interval was used to excite a very small quantity of endogenous molecular oxygen in O2(1Δg) state. It is shown, that application of the method at occurrence of earliest signs of radiation injury allows notably reducing dangerous breaks in radiation therapy course.
We present measurements of two-particle correlations with neutral pion trigger particles of transverse momenta 8>pT suptrig/sup>16 GeV/c and associated charged particles of 0.5>pT supassoc/sup>10 GeV/c versus the azimuthal angle difference Δφ at midrapidity in pp and central Pb–Pb collisions at sNN=2.76 TeV with ALICE. The new measurements exploit associated charged hadrons down to 0.5 GeV/c, which significantly extends our previous measurement that only used charged hadrons above 3 GeV/c. After subtracting the contributions of the flow background, v2 to v5, the per-trigger yields are extracted for |Δφ|>0.7 on the near and for |Δφ−π|>1.1 on the away side. The ratio of per-trigger yields in Pb–Pb to those in pp collisions, IAA, is measured on the near and away side for the 0–10% most central Pb–Pb collisions. On the away side, the per-trigger yields in Pb–Pb are strongly suppressed to the level of IAA≈0.6 for pT supassoc/sup<3 GeV/c, while with decreasing momenta an enhancement develops reaching about 5 at low pT supassoc/sup. On the near side, an enhancement of IAA between 1.2 at the highest to 1.8 at the lowest pT supassoc/sup is observed. The data are compared to parton-energy-loss predictions of the JEWEL and AMPT event generators, as well as to a perturbative QCD calculation with medium-modified fragmentation functions. All calculations qualitatively describe the away-side suppression at high pT supassoc/sup. Only AMPT captures the enhancement at low pT supassoc/sup, both on the near and away side. However, it also underpredicts IAA above 5 GeV/c, in particular on the near-side. © 2016 The Author(s)
An effective suppression of multiple filamentation of the sub-TW peak power supercritical laser beam in xenon gas was demonstrated in direct amplification of subpicosecond UV pulses at Ti:sapphire/KrF laser facility GARPUN-MTW. A large negative nonlinear refractive index due to a two-photon resonance of KrF laser radiation with Xe 6p[1/2]0 state ensured Kerr self-defocusing of a few hundred filaments with a local peak intensity of ∼0.2 TW cmsup-2/sup, 200-fold higher than the average one over the beam cross section, and thus homogenized the laser beam. UV filaments in Xe produced a narrow-angle monochromatic coherent cone emission at 828 nm wavelength due to stimulated hyper-Raman scattering and amplified spontaneous emission at the transition 6p [1/2]0 → 6s[ 3/2]1 sup0/sup . © 2016 Astro Ltd.
The dynamic light scattering (DLS) method allows the determination of the particle size distribution of suspensions. At high dilutions, an artifact peak appears in the size distribution, which does not correspond to actual particles, but is caused by crossing the scattering volume boundaries by individual particles. The parameters of this peak are analyzed, the causes of its appearance and its effect on determined particle sizes are studied. © 2016, Allerton Press, Inc.
This work is devoted to the investigation of sizes and concentrations of particles in blood plasma by dynamic light scattering (DLS). Blood plasma contains many different proteins and their aggregates, microparticles and vesicles. Their sizes, concentrations and shapes can give information about donor's health. Our DLS study of blood plasma reveals unexpected dependence: with increasing of the particle sizes r (from 1 nm up to 1 μm), their concentrations decrease as r-4 (almost by 12 orders). We found also that such dependence was repeated for model solution of fibrinogen and thrombin with power coefficient is -3,6. We believe that this relation is a fundamental law of nature that shows interaction of proteins (and other substances) in biological liquids. © Published under licence by IOP Publishing Ltd.
This article contains the analysis of tube expander dynamics in complex interaction of structural elements of heat-exchange tubes attachment assembly in the process of roll-forming operation, description of dynamic process theoretical aspect. It is shown that torque variations lead to velocity fluctuations and influences the service life of operative parts of tube expander and quality of tube attachment assemblies. © JVE International Ltd.
We report a theoretical and experimental study of the energy profile deformation along the laser beam axis during the fabrication of graphite microstructures inside a diamond crystal. The numerical simulation shows that the use of a focusing lens with a numerical aperture NA < 0.1 at a focusing depth of up to 2 mm makes it possible to avoid a noticeable change in the energy profile of the beam due to the spherical aberration that occurs in the case of refraction of the focused laser beam at the air - diamond interface. The calculation results are confirmed by experimental data on the distribution of the laser intensity along the beam axis in front of its focal plane, derived from observations of graphitisation wave propagation in diamond. The effect of radiation self-focusing on laser-induced graphitisation of diamond is analysed. It is shown that if the wavefront distortion due to self-focusing can be neglected at a minimum pulse energy required for the optical breakdown of diamond, then an increase in the beam distortion with increasing pulse energy has no effect on the graphitisation process. © 2016 Kvantovaya Elektronika and Turpion Ltd.
Certain properties of photons viewed as quanta (particles of an electromagnetic field) are discussed. Specifically, the nature of localization (size) of photons along and across the direction of wave propagation is examined. © 2016, Allerton Press, Inc.
Phase transition induced with infrared (λ = 2920 nm and λ = 2940 nm) nanosecond laser pulses in strongly absorbing liquids (water, ethanol) under transparent solid cover is investigated with the help of acoustical and optical monitoring. LiNbO3 transducer is used for registration of pressure pulses generated in irradiated liquids. Optical signals due to scattering and specular reflection of probing optical beams are explored with the schemes involving total internal reflection and interference effects. Combination of these two optical diagnostic methods permits for the first time to show that irradiation of covered liquids leads to vapor cavity formation which is divided from the cover with thin (submicron) liquid film despite the fact that radiation intensity maximum is located just at the liquid–plate boundary. The cavity formation is due to explosive boiling which occurs when the superheated liquid reaches its superheating limit in near critical region. After the first acoustical signal, the second signal is observed with several hundreds microseconds time delay which is caused by the vapor cavity collapse. Some results of optical and acoustical diagnostics in the case of free liquid surface are also presented. © 2016, Springer-Verlag Berlin Heidelberg.
The possibility of laser induced modification of local mechanical properties of polycrystalline chemical vapor deposition graphene on silicon substrate in air has been demonstrated. Nanosecond laser pulses (wavelength 532 nm) with focal spot diameter similar to 1 mu m were used. Samples were placed and irradiated inside a scanning probe microscope (SPM) that allowed in situ studies of surface morphology and mechanical phase contrast in SPM tapping mode before and after multipulsed laser treatment. It was found that along with local profile transformation of graphene sheet (formation of nanopits and nanobumps), transformation of mechanical properties of graphene on a substrate structure took place. Such laser modified graphene area is larger than (but of the order of) the irradiation spot size. Its appearance is related to laser induced radial extension of an adsorbed water nanolayer intercalated between graphene and substrate. It is shown that the process of water layer lateral migration has a reversible character. This effect is proved by laser spot shift and sequential irradiation.
The chemical etching of the surface of a natural diamond single crystal irradiated by subpicosecond laser pulses with a high repetition rate (f ≤ 500 kHz) in air is experimentally investigated. The irradiation has been performed by the second-harmonic (515 nm) radiation of a disk Yb:YAG laser. Dependences of the diamond surface etch rate on the laser energy density and pulse repetition rate are obtained. © 2016 Kvantovaya Elektronika and Turpion Ltd.
The results on femtosecond laser formation of polyynic linear carbon chains (LCCs) are reported. To reduce the oxidation and degradation of carbon chains, the synthesis of LCCs was performed in liquid media. The flakes of graphite were suspended in water or in hexane and ultrasonicated to obtain a suspension of micron-size graphite particles. This suspension was irradiated by pulses of Ti:sapphire laser. The spectral lines at 189, 199, 215, 225, 262, 276, 284, 299, 323, 342, and 368 nm in the optical absorption spectrum of the irradiated graphite suspension were clearly distinguished. They were attributed to the absorption of polyynic carbon chains CnH2, where n=2 to 20. The stability of the synthesized one-dimensional carbon chains suspended in water and hexane was defined based on the intensity of the optical absorption bands. Its half-life time was estimated to be 20 h at room temperature for water, and 7 and 25 days for hexane at 60°C and 5°C, respectively. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).
Vaporization of absorbing liquid (water) under a transparent solid cover upon exposure to nanosecond pulses of a holmium laser (λ = 2920 nm) is studied using acoustic and optical diagnostics. The features of the optical signal reflected from the liquid–cover interface suggest that a vapor cavity appears at a submicrometer distance from this interface and exists for about one hundred microseconds. An additional acoustic signal appearing after returning the light signal to the initial level is caused by known cavitation effects accompanying vapor cavity fracture and collapse in liquid. © 2016, Allerton Press, Inc.
Crystalline silicon (Si) nanoparticles present an extremely promising object for bioimaging based on photoluminescence (PL) in the visible and near-infrared spectral regions, but their efficient PL emission in aqueous suspension is typically observed after wet chemistry procedures leading to residual toxicity issues. Here, we introduce ultrapure laser-synthesized Si-based quantum dots (QDs), which are water-dispersible and exhibit bright exciton PL in the window of relative tissue transparency near 800 nm. Based on the laser ablation of crystalline Si targets in gaseous helium, followed by ultrasound-assisted dispersion of the deposited films in physiological saline, the proposed method avoids any toxic by-products during the synthesis. We demonstrate efficient contrast of the Si QDs in living cells by following the exciton PL. We also show that the prepared QDs do not provoke any cytoxicity effects while penetrating into the cells and efficiently accumulating near the cell membrane and in the cytoplasm. Combined with the possibility of enabling parallel therapeutic channels, ultrapure laser-synthesized Si nanostructures present unique object for cancer theranostic applications.
The optical properties of two-component films composed of mesotetraphenylporphyrin (TPP) and erbium-doped yttrium vanadate Yt0.95Er0.05VO4 prepared by spincoating have been studied for the first time. A decrease in the TPP content in the films leads to a hypsochromic shift of the Soret band peak by 1–9 nm; this finding suggests that the degree of aggregation of TPP decreases with decreasing TPP content in the film. The fluorescence peak of TPP is located at an emission wavelength of λem = 634 nm and an excitation wavelength of λex = 420 nm. The fluorescence peaks of Y0.95Er0.05VO4 at λem = 526, 546, and 555 nm (λex = 300 nm) correspond to the following transitions of the Er3+ ion: the band at 526 nm, to the 2H11/2 → 4I15/2 transition; the bands at 546 and 555 nm, to the 4S3/2 λ 4I15/2 transition. The fluorescence band peaks preserve their positions with a change in the ratio of components in the film; that is, the fluorescent characteristics of TPP and Y0.95Er0.05VO4 clusters do not depend on their interaction. For both TPP and Y0.95Er0.05VO4, the maximum fluorescence intensity is observed at a TPP content in the film of 40%; the gain with respect to single-component TPP and Y0.95Er0.05VO4 films is 70 and 4–15%, respectively. In this case, a significant effect is exerted not so much by the nature and structure of the components and their interaction as by the topographic features of organization of the photoactive elements in the film, their ratio, and mutual orientation, which determine the energy capture probability. © 2016, Pleiades Publishing, Ltd.
The optical and photovoltaic properties of two-component TPP–Yt0.95Er0.05VO4 films prepared by the spincoating method are for the first time studied. A 30% increase in the photovoltage (PV) of TPP: Yt0.95Er0.05VO4 = 3: 2 films on silicon carbide (SiC) supports as compared to TPP one-component films is observed. In contrast, for films on tin dioxide (SnO2) supports, the PV drops by 35–96% as the TPP content in the film decreases from 80 to 20%. The properties of the films are monitored by atomic force microscopy. The highest roughness of the films corresponds to a 40–60% TPP content. © 2016, Pleiades Publishing, Ltd.
Poly(methyl metacrylate) samples with uniformly dispersed single-wall carbon nanotubes (SWCNTs) were mechanicaly stretched up to 4 times at 150 °C. As a result, SWCNTs were oriented preferentially along the stretch direction. The width of the angular distribution of the SWCNT orientation determined by polarized Raman scattering and THz absorption spectroscopy was 15 and 12°, respectively. Both methods revealed a high anisotropy of optical response of the composite film. Its application as an efficient polarizer in a wide spectral range from visible to THz is promising. © 2016 Astro Ltd.
New approaches for visualisation of silicon nanoparticles (SiNPs) in cancer cells are realised by means of the linear and nonlinear optics in vitro. Aqueous colloidal solutions of SiNPs with sizes of about 10-40 nm obtained by ultrasound grinding of silicon nanowires were introduced into breast cancer cells (MCF-7 cell line). Further, the time-varying nanoparticles enclosed in cell structures were visualised by high-resolution structured illumination microscopy (HR-SIM) and micro-Raman spectroscopy. Additionally, the nonlinear optical methods of two-photon excited fluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS) with infrared laser excitation were applied to study the localisation of SiNPs in cells. Advantages of the nonlinear methods, such as rapid imaging, which prevents cells from overheating and larger penetration depth compared to the single-photon excited HR-SIM, are discussed. The obtained results reveal new perspectives of the multimodal visualisation and precise detection of the uptake of biodegradable non-toxic SiNPs by cancer cells and they are discussed in view of future applications for the optical diagnostics of cancer tumours.
Diamond single crystals implanted with sup7/supLisup+/sup ions within broad range of fluences including those higher graphitization threshold were studied by secondary ion mass spectrometry (SIMS) and optical interference profilometry. It has been shown that sputtering coefficient of diamond does not depend on the level of radiation damage and on the microstructure of the material, which may be due to the formation of an amorphous layer on the surface during the ion bombardment. Graphitization domains were observed immediately after high-fluence ion implantation, prior to annealing. No diffusion of implanted lithium (at any fluences) was observed in diamond both at high-temperature treatment and under strong photothermal excitation near the ablation threshold. SIMS measurements have shown sharp decrease of lithium ion yield in strongly damaged diamond, particularly in graphitized region, which has not yet been satisfactorily explained. © 2016 Elsevier B.V.
Introduction: The limits of tumor detection by means of nuclear medicine do not exceed: 3 mm for X -Ray tomography and MRI; 4 mm for PET; 1.5 in diameter in average by clinical investigation among the USA citizens. Thus at least 3 problems remain unsolved: diagnostics and consequent treatment of the one third of all malignant tumors', i.e. their early states, squamous cell carcinoma of mucous tissue; and the third one problem: 'a long way and expensive'. The limit of tumor detection by methods of optical spectroscopy is around 1-2 mm, although in principle it is possible to reach pathologies 5-10 mu m in diameter. The problem formation: It is possible to diagnose and conduct treatment of those types of pathologies which could be reached by irradiation or could selectively accumulate a Photosensitiser (PS). 
Luminescence properties of water-soluble hybrid associates of semiconductor colloidal CdS quantum dots (QDs) with average size of 2.5 nm, 3.2 nm, 4.2 nm and J-aggregates of 3,3'-di-(gamma-sulfopropyl)-4,4',5,5'-dibenzo-9-ethylthiacarbocyanine betaine pyridinium salt (Dye) in gelatin were investigated using the methods of absorption, steady-state and time-resolved luminescence spectroscopy. The decrease in luminescence intensity of CdS QDs and increase in luminescence intensity of Dye J-aggregates were detected with increasing of Dye concentration. It was shown that curves of luminescence decay of CdS QDs are non-exponential. The decreasing of luminescence lifetime of CdS QDs with increasing of Dye J-aggregates concentration was observed. It was concluded that dynamic quenching due to non-radiative resonance energy transfer takes place. It was shown that overlap integral between luminescence spectra of CdS QDs and absorption spectra of Dye J-aggregates increases with the increase of average diameter of CdS QDs and luminescence decay of CdS QDs is accelerated. Energy transfer efficiency for all three sizes of QDs was more than 31%. (C) 2016 Elsevier B.V. All rights reserved.
We present a composite material based on polymer matrices doped with a new europium(III) complex exhibiting high quantum yield. The Eu(III) complex was introduced into two types of polymer matrices. We investigate the concentration influence of the complex embedded into polymers on luminescent properties of the composite material. This Eu(III) complex proved to be highly dispersible in polymers and compatible with ink-jet technology.
Background: The existence of zones of humoral skin-subskin tissue linkage with internal organs as well as the possibility of targeted administration of preparation into the affected organs were studied. Methods: An experimental study of preparation and distribution in the bodies of mice was held by both intravenous and lymphotropic methods of administration. By means of detection with a photosensitizer (as a marker), the study was conducted on healthy mice and mice with testicle inflammation. Based on the experimental results, the study has been implemented into the clinical practice of treatment of acute inflammatory diseases of testicle and its epididymis. Patients were administered antibiotics either by the lymphotropic method, or by traditional methods. Results: The concentration of the preparation, administered by the lymphotropic method, maintained in target organs (testicles) at a high level for a longer time, while the intravenous injections provided fast achievement of high concentrations. Moreover there was a lower level of accumulation of the photosensitizer in parenchymal organs after subcutaneous (lymphotropic) administration. Conclusions: The presence of humoral connection of certain areas of skin and subcutaneous tissue with testicles and their epididymis was proved. It was found that the lymphotropic administration leads to earlier clinical improvement and normalization of laboratory indices, and, thus, to significant reduction in hospital stay. Such results open the possibility of targeted drug delivery to the diseased organs. In perspective, the method may be used in treating patients not only in urology, but also in surgery, as well as for many acute, chronic or cancer diseases. © 2015 Elsevier B.V.
We evaluate the effect of ions on the electric response of an insulting liquid by means of the total electric polarization induced in a cell by an external field. The limiting surfaces are assumed blocking and identical and the ions pointike nonpolarizable charged particles. The analysis is limited to the case where the selective ionic adsorption is absent, in such a manner that in the absence of external electric field the sample is locally and globally neutral. We obtain formulas for the effective dielectric constant renormalized by the presence of the ions in the absence and presence of adsorption from the surfaces. Our results coincide with those obtained by means of the electric impedance of the cell. From the coincidence of the results relevant to the effective dielectric constant we infer that the ions in an insulating liquid do not have a conductive or dielectric nature. They are just electric charges dissolved in an insulating liquid. © 2016 American Physical Society.
This paper deals with a possibility of new types of photosensitizers application - Aluminum Phthalocyanine nanoparticles (nAlPc) in clinical practice for diagnosis, prevention and therapy of inflammatory diseases in dentistry and traumatology. It was detected that the aluminum phthalocyanine (AlPc) fluoresces in the nanoparticle form in the presence of pathologic microflora or inflammation process. It will make possible to detect the local accumulation of pathological microflora on the enamel surface and also for diagnostics and treatment of inflammatory diseases. Experimental studies of interaction of NP-AlPc with tooth enamel and with biological joint tissue at arthrosis are presented. © Published under licence by IOP Publishing Ltd.
In this study, the fluorescence intensity decay of aluminum phthalocyanine nanoparticles colloidal solutions at different pH was investigated. Hamamatsu Streak-Camera (C10627 - 13 Hamamatsu Photonics) with picosecond temporal resolution (15 ps) was used to carry out the measurements. For excitation we used Hamamatsu Picosecond Light Pulser PLP - 10 with 637 nm wavelength and 65 ps pulse duration. The changes in fluorescence decay kinetics were found during the experiment. The number of fluorescence lifetime components and duration of lifetimes depends on pH. At pH 2 the presence of two fluorescence lifetimes was recorded: the first one was 5 ns, which corresponded to the molecular form in solution, and 1.5 ns, which corresponded to bound state of phthalocyanine molecules. This work is a preparatory step towards a model which describes the interaction of aluminum phthalocyanine nanoparticles with environment in biological tissue. © Published under licence by IOP Publishing Ltd.
Two-dimensional lattices of chiral nanoholes in a plasmonic film with lattice constants being slightly larger than light wavelength are proposed for effective control of polarization and spatial properties of light beams. Effective polarization conversion and strong circular dichroism in non-zero diffraction orders in these chiral metafilms are demonstrated by electromagnetic simulations. These interesting effects are found to result from interplay between radiation pattern of single chiral nanohole and diffraction pattern of the planar lattice, and can be manipulated by varying wavelength and polarization of incoming light as well as period of metastructure and refractive indexes of substrate and overlayer. Therefore, this work offers a novel paradigm for developing planar chiral metafilm-based optical devices with controllable polarization state, spatial orientation and intensity of outgoing light. (C) 2016 Optical Society of America
Were analyzed possibilities of thermodynamic, kinetic and molecular dynamics approaches to the investigation of the kinetic properties moving interfaces in metals with different crystallographic lattices: Al, Cu (fcc) and Fe (bcc) in a wide range of solid phase overheating and overcooling of liquid - (0.4 divided by 0.6)T-m T-sl
We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (pT0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at sNN
The measurement of prompt D-meson production as a function of multiplicity in p-Pb collisions at sNN=5.02 TeV with the ALICE detector at the LHC is reported. D0, D+ and D∗+ mesons are reconstructed via their hadronic decay channels in the centre-of-mass rapidity range −0.96 < ycms< 0.04 and transverse momentum interval 1<pT<24 GeV/c. The multiplicity dependence of D-meson production is examined by either comparing yields in p-Pb collisions in different event classes, selected based on the multiplicity of produced particles or zero-degree energy, with those in pp collisions, scaled by the number of binary nucleon-nucleon collisions (nuclear modification factor); as well as by evaluating the per-event yields in p-Pb collisions in different multiplicity intervals normalised to the multiplicity-integrated ones (relative yields). The nuclear modification factors for D0, D+ and D∗+ are consistent with one another. The D-meson nuclear modification factors as a function of the zero-degree energy are consistent with unity within uncertainties in the measured pT regions and event classes. The relative D-meson yields, calculated in various pT intervals, increase as a function of the charged-particle multiplicity. The results are compared with the equivalent pp measurements at s=7 TeV as well as with EPOS 3 calculations.[Figure not available: see fulltext.] © 2016, The Author(s).
The production of prompt Ds sup+/sup mesons was measured for the first time in collisions of heavy nuclei with the ALICE detector at the LHC. The analysis was performed on a data sample of Pb-Pb collisions at a centre-of-mass energy per nucleon pair, (Formula presented.) , of 2.76 TeV in two different centrality classes, namely 0–10% and 20–50%. Ds sup+/sup mesons and their antiparticles were reconstructed at mid-rapidity from their hadronic decay channel Ds sup+/sup → ϕπsup+/sup, with ϕ → Ksup−/supKsup+/sup, in the transverse momentum intervals 4 < pT < 12GeV/c and 6 < pT < 12 GeV/c for the 0–10% and 20–50% centrality classes, respectively. The nuclear modification factor RAA was computed by comparing the pT-differential production yields in Pb-Pb collisions to those in proton-proton (pp) collisions at the same energy. This pp reference was obtained using the cross section measured at (Formula presented.) TeV and scaled to (Formula presented.) TeV. The RAA of Ds sup+/sup mesons was compared to that of non-strange D mesons in the 10% most central Pb-Pb collisions. At high pT (8 < pT < 12 GeV/c) a suppression of the Ds sup+/sup-meson yield by a factor of about three, compatible within uncertainties with that of non-strange D mesons, is observed. At lower pT (4 < pT < 8 GeV/c) the values of the Ds sup+/sup-meson RAA are larger than those of non-strange D mesons, although compatible within uncertainties. The production ratios Ds sup+/sup/Dsup0/sup and Ds sup+/sup/Dsup+/sup were also measured in Pb-Pb collisions and compared to their values in proton-proton collisions. © 2016, The Author(s).
The production of electrons from heavy-flavour hadron decays was measured as a function of transverse momentum (pT) in minimum-bias p-Pb collisions at sNN=5.02 TeV using the ALICE detector at the LHC. The measurement covers the pT interval 0.5<pT<12 GeV/c and the rapidity range -1.065<ycms<0.135 in the centre-of-mass reference frame. The contribution of electrons from background sources was subtracted using an invariant mass approach. The nuclear modification factor RpPb was calculated by comparing the pT-differential invariant cross section in p-Pb collisions to a pp reference at the same centre-of-mass energy, which was obtained by interpolating measurements at s=2.76 TeV and s=7 TeV. The RpPb is consistent with unity within uncertainties of about 25%, which become larger for pT below 1 GeV/c. The measurement shows that heavy-flavour production is consistent with binary scaling, so that a suppression in the high-pT yield in Pb-Pb collisions has to be attributed to effects induced by the hot medium produced in the final state. The data in p-Pb collisions are described by recent model calculations that include cold nuclear matter effects. © 2015 CERN for the benefit of the ALICE Collaboration.
We report the transverse energy (ET) measured with ALICE at midrapidity in Pb-Pb collisions at root s(NN) = 2.76 TeV as a function of centrality. The transverse energy was measured using identified single-particle tracks. The measurement was cross checked using the electromagnetic calorimeters and the transverse momentum distributions of identified particles previously reported by ALICE. The results are compared to theoretical models as well as to results from other experiments. The mean ET per unit pseudorapidity (eta), dE(T)/d eta , in 0%-5% central collisions is 1737 +/- 6(stat.) +/- 97(sys.) GeV. We find a similar centrality dependence of the shape of dE(T)/d eta as a function of the number of participating nucleons to that seen at lower energies. The growth in dE(T)/d eta at the LHC energies exceeds extrapolations of low-energy data. We observe a nearly linear scaling of dE(T)/d eta with the number of quark participants. With the canonical assumption of a 1 fm/c formation time, we estimate that the energy density in 0%-5% central Pb-Pb collisions at root s(NN) = 2.76 TeV is 12.3 +/- 1.0 GeV/fm(3) and that the energy density at the most central 80 fm(2) of the collision is at least 21.5 +/- 1.7 GeV/fm(3). This is roughly 2.3 times that observed in 0%-5% central Au-Au collisions at root s(NN) = 200 GeV.
We demonstrate a first-of-its-kind efficient amplification of a broadband tunable (from 3.8 to 4.8 μm) mid-IR femtosecond seed pulse generated from a AgGaS2-based optical parametric amplifier pumped by a Cr:forsterite laser in a multi-pass Fesup2+/sup:ZnSe amplifier optically pumped by a solid-state nanosecond Cr:Yb:Ho:YSGG laser. A total gain of 2000 for an input seed energy of 40 nJ has been obtained. The magnitude of the output energy reaches 80 μJ at a pulse duration of 200 fs. © 2016 Astro Ltd.
The output energy of 10.6 and 3.25 J with a pulse duration of ∼1 ms and a crystal temperature of 85 K was achieved in the Fe:ZnSe and Fe:ZnS lasers, respectively. At room temperature, the Fe:ZnSe laser energy was as high as 1.2 J with a pulse duration of 150 ns. A few optical schemas of the Cr:CdSe laser with laser diode pumping were realized.
Results and their visualizations are presented for the case of nanosecond laser ablation of a metal liquid film at different incident laser intensities G = 38.5, 44, 88 and 154 MW/cmsup2/sup. The ablation of an Al film (thickness 430nm, initial particle number 5.10sup5/sup) including subcritical to supercritical states is investigated with the help of the classical molecular dynamic method and continual description of a conduction electron subsystem. Behavior of a thinner metal film (48nm) is also investigated at G = 29 MW/cmsup2/sup and G = 51 MW/cmsup2/sup (5 and 8,8 K/ps). 3D calculation results are given in the form of 2D particle distribution snapshots as well as temperature, density, pressure and particle velocity 1D distributions. As in the previously considered case of dielectric films for metal films four different ablation regimes are observed depending on the laser intensity: quasistationary surface evaporation, explosive (volume) boiling, spinodal decomposition and supercritical fluid expansion. Changes in spacetime behavior of the density fluctuations in these regimes are clearly seen from the presented visualizations. Explosive boiling realization in metal ablation is not evident beforehand because of the high values of the thermal conductivity and absorption coefficients which can impede the manifestation of the process. Recoil pressure pulses that are caused by explosive boiling can be used as experimental markers of getting closer to the critical region while the critical region transition is characterized by the disappearance of the pressure pulsation.
We examine absorption of electromagnetic radio-frequency (RF) radiation in aqueous suspensions of semiconductor (silicon) and metal (gold) nanoparticles (NPs) and theoretically investigate the heat release in these systems. The absorption of RF radiation is considered in both bulk electrolyte and the region around the NPs. Simulations show a strong dependence of the heating rate on electrical conductivity of the electrolyte rather than on that of NPs properties. The obtained results indicate that NPs can act as sensitizers of the RF induced hyperthermia for biomedical applications. © 2016 SPIE.
The work deals with the study of the influence of combined action of thermomechanical and laser treatments of rapidly quenched TiNiCu thin ribbons on the properties of two-way shape memory effect. It was shown that increasing of the energy density of the laser radiation and the external mechanical stress leads to growth of the reversible strain of the received amorphous-crystalline composite in the interval of martensitic transformation. © Published under licence by IOP Publishing Ltd.
Photonic crystals doped with fluorescent nanoparticles offer a plenty of interesting applications in photonics, laser physics, and biosensing. Understanding of the mechanisms and effects of modulation of the photoluminescent properties of photonic crystals by varying the depth of nanoparticle penetration should promote targeted development of nanocrystal-doped photonic crystals with desired optical and morphological properties. Here, we have investigated the penetration of semiconductor quantum dots (QDs) into porous silicon photonic crystals and performed experimental analysis and theoretical modeling of the effects of the depth of nanoparticle penetration on the photoluminescent properties of this photonic system. For this purpose, we fabricated porous silicon microcavities with an eigenmode width not exceeding 10 nm at a wavelength of 620 nm. CdSe/CdS/ZnS QDs fluorescing at 617 nm with a quantum yield of about 70% and a width at half-height of about 40 nm were used in the study. Confocal microscopy and scanning electron microscopy were used to estimate the depth of penetration of QDs into the porous silicon structure; the photoluminescence spectra, kinetics, and angular fluorescence distribution were also analyzed. Enhancement of QD photoluminescence at the microcavity eigenmode wavelength was observed. Theoretical modeling of porous silicon photonic crystals doped with QDs was performed using the finite-difference time-domain (FDTD) approach. Theoretical modeling has predicted, and the experiments have confirmed, that even a very limited depth of nanoparticle penetration into photonic crystals, not exceeding the first Bragg mirror of the microcavity, leads to significant changes in the QD luminescence spectrum determined by the modulation of the local density of photonic states in the microcavity. At the same time, complete and uniform filling of a photonic crystal with nanoparticles does not enhance this effect, which is as strong as in the case of a very limited depth of nanoparticle penetration. Our results will help to choose the best technology for fabrication of efficient sensor systems based on porous silicon photonic crystals doped with fluorescent nanoparticles. © 2016 SPIE.
This paper presents the results of application of the elaborated methods for monitoring of nanodiamonds in human urine using fluorescence spectroscopy. High efficiency of artificial neural networks applied for recognition and estimation of the concentration of nanodiamonds in urine with a strong autofluorescence background is demonstrated. It was found that minimal concentration of nanodiamonds with strong fluorescence containing nitrogen-vacancy (NV) centers can be detected in urine by fluorescence spectroscopy at a level of 3.06 × 10−4 g L−1; while use of artificial neural networks for detection of weakly fluorescent detonation nanodiamonds provides reasonably high accuracy of detection, not worse than 6.8 × 10−3 g L−1. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
The multi-strange baryon yields in PbPb collisions have been shown to exhibit an enhancement relative to pp reactions. In this work, Ξ and Ω production rates have been measured with the ALICE experiment as a function of transverse momentum, pT, in pPb collisions at a centre-of-mass energy of sNN=5.02 TeV. The results cover the kinematic ranges 0.6 GeV/c<pT<7.2 GeV/c and 0.8 GeV/c<pT<5 GeV/c, for Ξ and Ω respectively, in the common rapidity interval -0.5<yCMS<0. Multi-strange baryons have been identified by reconstructing their weak decays into charged particles. The pT spectra are analysed as a function of event charged-particle multiplicity, which in pPb collisions ranges over one order of magnitude and lies between those observed in pp and PbPb collisions. The measured pT distributions are compared to the expectations from a Blast-Wave model. The parameters which describe the production of lighter hadron species also describe the hyperon spectra in high multiplicity pPb collisions. The yield of hyperons relative to charged pions is studied and compared with results from pp and PbPb collisions. A continuous increase in the yield ratios as a function of multiplicity is observed in pPb data, the values of which range from those measured in minimum bias pp to the ones in PbPb collisions. A statistical model qualitatively describes this multiplicity dependence using a canonical suppression mechanism, in which the small volume causes a relative reduction of hadron production dependent on the strangeness content of the hyperon. © 2016 The Author(s).
The use of photoluminescence (PL) probes in immunodiagnostic procedures requires highly specific and precise labeling of biomarkers and he tags whose PL is easily differentiable from that of the autofluorescence of cells in clinical specimens. Nanoprobes consisting of core/shell quantum dots (QDs), notably CdSe/ZnS ones, and single-domain antibodies (sdAbs) with PL excited in the multiphoton mode meet both requirements. These diagnostic nanoprobes are 12 nm in size, and their two-photon absorption cross section exceeds 49,000 GM. Such nanoprobes, upon two-photon excitation (TPE) in near infrared region, provide precise fluorescent microscopic images of deep areas of tissue samples, the QD PL to autofluorescence intensity ratio being more than an order of magnitude higher than that for the one-photon mode of excitation. (C) 2016 Elsevier Ltd. All rights reserved.
Three- and four-pionBose-Einstein correlations are presented in pp, p-Pb, and Pb-Pb collisions at the LHC. We compare our measured four-pion correlations to the expectation derived from two-and three-pion measurements. Such a comparison provides a method to search for coherent pion emission. We also present mixed-charge correlations in order to demonstrate the effectiveness of several analysis procedures such as Coulomb corrections. Same-charge four-pion correlations in pp and p-Pb appear consistent with the expectations from three-pion measurements. However, the presence of non-negligible background correlations in both systems prevent a conclusive statement. In Pb-Pb collisions, we observe a significant suppression of three-and four-pion Bose-Einstein correlations compared to expectations from two-pionmeasurements. There appears to be no centrality dependence of the suppression within the 0%-50% centrality interval. The origin of the suppression is not clear. However, by postulating either coherent pion emission or large multibody Coulomb effects, the suppression may be explained.
We present a multiplex quantitative lateral flow (LF) assay for simultaneous on-site detection of botulinum neurotoxin (BoNT) types A, B, and E in complex matrixes, which is innovative by virtually no sacrifice in performance while transition from the single-plex assays and by characteristics on the level of laboratory quantitative methods. The novel approach to easy multiplexing is realized via joining an on-demand set of single-plex LF strips, which employ magnetic nanolabels, into a miniature cylinder cartridge that mimics LF strip during all assay stages. The cartridge is read out by an original portable multichannel reader based on the magnetic particle quantification technique. The developed reader offers the unmatched 60 zmol detection limit and 7-order linear dynamic range for volumetric registration of magnetic labels inside a cartridge of several millimeters in diameter regardless of its optical transparency. Each of the test strips, developed here as building blocks for the multiplex assay, can be used "as is" for autonomous quantitative single-plex detection with the same measuring setup, exhibiting the limits of detection (LOD) of 0.22, 0.11, and 0.32 ng/mL for BoNT-A, -B, and -E, respectively. The proposed multiplex assay has demonstrated the remarkably similar LOD values of 0.20, 0.12, 0.35 ng/mL under the same conditions. The multiplex assay performance was successfully validated by BoNT detection in milk and apple and orange juices. The developed methods can be extended to other proteins and used for rapid multianalyte tests for point-of-care in vitro diagnostics, food analysis, biosafety and environmental monitoring, forensics, and security, etc. © 2016 American Chemical Society.
We report on two-particle charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions as a function of the pseudorapidity and azimuthal angle difference, Delta eta and Delta phi respectively. These correlations are studied using the balance function that probes the charge creation time and the development of collectivity in the produced system. The dependence of the balance function on the event multiplicity as well as on the trigger and associated particle transversemomentum (p(T)) in pp, p-Pb, and Pb-Pb collisions at root s(NN) = 7, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for 0.2 p(T) 2.0 GeV/c, the balance function becomes narrower in both Delta eta and Delta phi directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mechanisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low pT is a feature of bulk particle production.
The production of charged pions, kaons and (anti)protons has been measured at mid-rapidity (−0.5<y<0) in p–Pb collisions at sNN=5.02 TeV using the ALICE detector at the LHC. Exploiting particle identification capabilities at high transverse momentum (pT), the previously published pT spectra have been extended to include measurements up to 20 GeV/c for seven event multiplicity classes. The pT spectra for pp collisions at s=7 TeV, needed to interpolate a pp reference spectrum, have also been extended up to 20 GeV/c to measure the nuclear modification factor (RpPb) in non-single diffractive p–Pb collisions. At intermediate transverse momentum (2<pT<10 GeV/c) the proton-to-pion ratio increases with multiplicity in p–Pb collisions, a similar effect is not present in the kaon-to-pion ratio. The pT dependent structure of such increase is qualitatively similar to those observed in pp and heavy-ion collisions. At high pT (>10 GeV/c), the particle ratios are consistent with those reported for pp and Pb–Pb collisions at the LHC energies. At intermediate pT the (anti)proton RpPb shows a Cronin-like enhancement, while pions and kaons show little or no nuclear modification. At high pT the charged pion, kaon and (anti)proton RpPb are consistent with unity within statistical and systematic uncertainties. © 2016 The Author
Multimodal nanoand microscale surface textures are produced by scanning the surfaces of various structural materials using IR femtosecond laser radiation. The topographies of the modified surfaces and their wettabilities upon hydrophobization are studied. © 2016, Allerton Press, Inc.
The spectroscopic properties of potentially perspective nanostructure: diamond nanoparticles with a surface layer of IR-photosensitizer, bacteriochlorin, were experimentally investigated in this study. Such specific structure of the object encourages enhancement of the drug tropism to the tumor, as well as increasing of photodynamic penetration depth. The size distribution spectra of diamond nanoparticles; diamond nanoparticles, artificially covered with bacteriochlorin molecules layer, in aqueous solution, were obtained during the study. Based on the absorption and fluorescence spectra analysis, the benefits of functional nanostructure as a drug for deep-lying tumor diagnostics and therapy were reviewed. © Published under licence by IOP Publishing Ltd.
The nonlinear response of metal oxide nanoparticles obtained by the acoustic plasma method is measured in aqueous disperse systems at a wavelength of 532 nm. Induced absorption is detected in the Cu2O, WO3, and ZnO disperse systems, and bleaching is detected in the Fe2O3 system. The real and imaginary parts of nonlinear third-order susceptibilities are determined. © 2016, Allerton Press, Inc.
In state-of-the-art nanoprobes, monoclonal antibodies (mAbs) used as capture molecules are often too large for nanoparticle targeting and are randomly orientated relative to the nanoparticle surface due to the inherent characteristics of the procedure for their fabrication. Here, we are reviewing our recent publications on the smallest known nanoprobes consisting of quantum dots (QDs) and single-domain antibodies (sdAbs), low-molecular-weight fragments of llama immunoglobulins produced in E. coli and attached to the QDs in a strictly specified orientation. The nanoprobe developed has a hydrodynamic diameter smaller than 12 nm and consists of four sdAbs and a QD. They are sensitive and specific enough to accurately estimate even a small number of cells with target biomarkers by means of flow cytometry. The small size of the probes enables immunohistochemical staining much deeper areas of tissue samples as compared to standard probes. Tests with clinical biopsies have shown that sdAb-QD probes provide the same or higher quality of biomarker detection compared to the gold-standard histochemical approach. The nanoprobes developed have many implications for quick multiplexed diagnosis and FRET-based detection platforms. (C) 2016 Elsevier Ltd. All rights reserved.
We performed site-selective spectroscopy and analyzed static (Direct Energy Transfer, DET) Förster kinetics of impurity quenching N(t) in the water-dispersible 0.1% Nd3+: KY3F10 nanoparticles (NPs) synthesized by microwave-hydrothermal treatment (MWHT) to determine the acceptor space dimension D and estimate the concentration of -OH acceptors. As a result we found two types of optical sites for Nd3+ ions and revealed that a moderate amount of -OH quenching acceptors is distributed in the volume of the nanoparticles, rather than on their surface. The result is similar to the one obtained for the previously studied water-dispersible the Nd3+: KYF4 and Nd3+: YPO4 NPs, and thus may be extended to all nanoparticles synthesized by water-based techniques. Therefore, all of the previously obtained results concerning the fluorescence quenching of such NPs should be reviewed in the light of the new data on the actual source of the quenching. Also, we compared quantitatively the near IR fluorescence quenching in the Nd3+: KY3F10 NPs with that in the Nd3+ doped KYF4 and YPO4 nanoparticles with close sizes and size distribution (all the nanoparticles were synthesized by MWHT). We found minimum fluorescence quenching and accordingly maximum fluorescence quantum yield for the Nd3+: KY3F10 nanocrystals, which is in agreement with the relative amount of -OH molecular groups in the volume of the NPs estimated from Förster kinetics and with the results of TG/DTG-DTA data analysis. The analysis of the fluorescence kinetics of the 1% Nd3+: KY3F10 NPs revealed the realization of the late fluctuation stage. The formation of the fluctuation stage confirmed the high concentration of the -OH acceptors in the volume of the NPs compared to the optically active Nd3+ ions. Furthermore, the analysis of the fluctuation stage confirmed the reduced -OH concentration in the Nd3+ doped KY3F10 NPs in comparison with the KYF4 and YPO4 NPs. This makes the Nd3+: KY3F10 NPs especially promising material for near IR imaging. © 2015 Elsevier B.V. All rights reserved.
A second-power yield of resonantly enhanced third harmonic and three-photon luminescence of 744 nm femtosecond laser pump pulses, weakly focused onto a layer of silver nanorolls on a silica substrate, was spectrally detected in the fluence range of 4-20 mJ cm(-2), saturating at higher fluences. The third-harmonic yield and its saturation were explored in terms of ultrafast carrier dynamics, based on direct three-photon or cascade one-and two-photon transitions balanced by Auger recombination (and the final band-filling effect) which limited the radiative recombination output in the form of the third harmonic and three-photon luminescence.
Spatial profiles of single-shot microcraters produced by tightly focused femtosecond laser pulses with variable pulse energies are measured by means of a laser confocal microscope. Dependences of crater depth on laser intensity at different pulse energies appear as overlapping saturating curves with the same threshold, indicating the presence of nonlinear absorption and absence of nonlocal ablation effects. A monotonic twofold increase in absorption nonlinearity is related to the transition from minor defect-band absorption to fundamental band-to-band absorption. © 2016, Pleiades Publishing, Inc.
SiC nanoparticles by carbothermal reduction show promising properties in terms of second harmonic and multiphoton excited luminescence. In particular, we estimate a nonlinear efficiency
The nonlinear optical response of a colloidal solution of planar CdSe semiconductor nanocrystals (nanoplatelets) is studied for the first time. The nonlinear optical response of these nanoparticles is compared to that of spherical CdSe nanocrystals (quantum dots). The photoinduced nonlinearity is attributed to the optical generation of long-lived charge carriers in the nanoobjects under study. It is shown that, upon the exposure of a cell with the solution of nanoparticles to focused continuous-wave (cw) laser radiation with a wavelength of 473 nm, the nonlinear optical responses of CdSe nanoplatelets and quantum dots are somewhat different at identical optical densities at the above-indicated wavelength. The differences are supposedly associated with a higher diffusion rate of spherical nanoparticles in the solution because of their smaller size compared to that of nanoplatelets. © 2016, Pleiades Publishing, Ltd.
A semiempirical model describing how images are formed in a scanning electron microscope operating in the backscattered electron collection mode is discussed. The model involves four imaging mechanisms. The model and the experiment are compared for grooves in silicon with rectangular and trapezoidal relief profiles. © 2016, Pleiades Publishing, Ltd.
The results of investigating the imaging of grooves in silicon with a trapezoidal profile and large side-wall inclination angles, which are obtained using a scanning electron microscope operating in the back-scattered-electron collection mode, are presented. Only two among the four known imaging mechanisms is demonstrated to provide contributions to the image-formation process. The lack of contributions from two other mechanisms is explained. © 2016, Pleiades Publishing, Ltd.
A definition of virtual measuring instruments (MIs) is presented and their operation in measuring the characteristics of the objects under study is described. The objectives and tasks of virtual MIs, as well as their role in proving the correctness of solutions to incorrect inverse problems, are discussed. © 2016, Pleiades Publishing, Ltd.
The variations in the luminescence spectra of detonation nanodiamond (DND) with probe light wavelength are studied and these dependences are compared for water suspensions of DND and graphene oxide (GO). It is found that changing the laser excitation wavelength from 405 to 532 nm shifts the broad-band luminescence peaks of DND and GO from 530 to 615 nm and from 490 to 580 nm. The observed dependences are explained by the luminescence ″red edge″ effect, which shows up when the electrostatic interaction (solvation) times of a luminophore with a polar solvent are comparable to the luminescence lifetime. These data confirm the common origin of luminescence in nanodiamonds and oxidized graphene nanoclusters. © 2016 Springer Science+Business Media New York
It is proposed to use the HTSC quantum levitation phenomenon in magnetic fields of various configurations to develop the systems of contact-free positioning and transport of cryogenic fuel targets (CFTs) to the focus of a high-power laser installation or the IFE reactor. The results are presented of a large cycle of experimental studies using YBa2Cu3O7−x superconducting ceramics and permanent magnet guideways based on various combinations of permanentmagnets to develop “CFT-MAGLEV” delivery systems. © 2016, Allerton Press, Inc.
The rates of multipulse nanoablation of the diamond surface in air by pico-and nanosecond laser pulses that cause single-photon, two-photon, three-photon and four-photon absorption in diamond are measured. In the experiments the radiation of ArF, KrF and Ti : Al2O3 lasers and the second harmonic of the Yb : YAG laser was used. The power dependence of the material etching rate on the fluence of laser pulses was found. The power exponent of this dependence appeared to be twice lower than that found earlier for femtosecond pulses. We discuss the causes of the difference in the nanoablation regularities for 'short' and 'long' laser pulses. © 2016 Kvantovaya Elektronika and Turpion Ltd.
The filling of single-walled carbon nanotube films with 1-adamantanemethanol and 1-bromoadamantane molecules was carried out by a gas-phase procedure. Optical absorption and Raman spectroscopies revealed the effects of charge transfer for samples treated with 1-bromoadamantane. Using density functional simulations we show that the charge transfer takes place when bromine is detached from the carbon cage and accepts electrons as free-standing atoms or as polybromide structures. Transmission electron microscope images confirm the presence of individual bromine atoms inside carbon nanotubes, treated with 1-bromoadamantane molecules. The observed charge transfer is, therefore, a marker of the dehalogenization reaction, a critical step in the synthesis process of narrow 1D sp3 nanostructures. © 2016 Elsevier Ltd
Multiwalled carbon nanotubes (MWCNTs) were successfully incorporated inside silica aerogel matrix. Solid composite materials were investigated by high-resolution transmission microscopy, scanning electron microscopy, optical spectroscopy. MWCNTs in the form of small bundles and individual tubes get locked inside the aerogel between its pores resulting in the local solution-free environment for nanotubes. Optical transmission of the composite material can be modified by the amount of the added MWCNTs. Nonlinear optical properties were studied by a Z-scan technique. Composite materials demonstrate saturable absorption for femtosecond laser pulses at 515nm wavelength that are attributed to the properties of embedded nanotubes. Silica aerogels possess significantly better thermal stability compared to polymer matrices, hosts that are frequently used for saturable absorption applications of carbon nanotubes. Solid and lightweight silica aerogels with embedded nanotubes can be used as optical elements for various photonic devices. Photo of silica aerogel with embedded MWCNTs. Normalized Z-scan transmittance of silica aerogel with nanotubes for two different on-focus intensities. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Silicon nanowires (SiNWs) were fabricated by metal-assisted chemical etching (MACE) where hydrofluoric acid (HF), which is typically used in this method, was changed into ammonium fluoride (NH4F). The structure and optical properties of the obtained SiNWs were investigated in details. The length of the SiNW arrays is about 2 μm for 5 min of etching, and the mean diameter of the SiNWs is between 50 and 200 nm. The formed SiNWs demonstrate a strong decrease of the total reflectance near 5–15 % in the spectral region λ < 1 μm in comparison to crystalline silicon (c-Si) substrate. The interband photoluminescence (PL) and Raman scattering intensities increase strongly for SiNWs in comparison with the corresponding values of the c-Si substrate. These effects can be interpreted as an increase of the excitation intensity of SiNWs due to the strong light scattering and the partial light localization in an inhomogeneous optical medium. Along with the interband PL was also detected the PL of SiNWs in the spectral region of 500–1100 nm with a maximum at 750 nm, which can be explained by the radiative recombination of excitons in small Si nanocrystals at nanowire sidewalls in terms of a quantum confinement model. So SiNWs, which are fabricated by environment-friendly chemistry, have a great potential for use in photovoltaic and photonics applications. © 2016, The Author(s).
To investigate the nature of defects in Galfenols (Fe100-xGax) with content near the local minimum (x=20.5 and x=22.4) and the local maximum of magnetostriction (x=26.3), the positron annihilation lifetime spectroscopy (PALS) and the X-ray diffraction analysis (XRD) are applied. It is found that the behavior of vacancies during ordering processes in the alloy with content higher than in stoichiometric composition of Fe3Ga (x 25) differs significantly from the other two alloys (x 25). All the studied alloys quenched from 1000 degrees C exhibit a positron lifetime of about 175 ps, which corresponds to high concentration of single vacancies ( 2 . 10(-4) at (-1)). The growth of the bcc-born D0(3) ordered phase with relatively low concentration of vacancies in Fe(79 5)Ga20.5 and Fe77.6Ga22.4 samples causes a decrease of the average positron lifetime. The formation of the D0(3) phase in Fe73.7Ga26.3 does not reduce average positron lifetime, which indicates a high concentration of constitutional vacancies in the ordered D0(3) phase of Fe73.7Ga26.3. The D0(3)- L1(2) phase transition is always accompanied by additional vacancy formation. (C) 2016 Elsevier B.V. All rights reserved.
We discuss the novel idea for direct terahertz pulse stimulated emission in the MPO4 (M = Nd3+, Dy3+) rare-earth doped nanocrystals as a result of transitions between crystal -field (Stark) levels of the Nd3+ and Dy3+ manifolds.
We present a Bayesian approach to particle identification (PID) within the ALICE experiment. The aim is to more effectively combine the particle identification capabilities of its various detectors. After a brief explanation of the adopted methodology and formalism, the performance of the Bayesian PID approach for charged pions, kaons and protons in the central barrel of ALICE is studied. PID is performed via measurements of specific energy loss (dE/dx) and time of flight. PID efficiencies and misidentification probabilities are extracted and compared with Monte Carlo simulations using high-purity samples of identified particles in the decay channels K-S(0) - pi(-)pi(+), phi - K-K+, and A - p pi(-) in p-Pb collisions at root sNN = 5.02 TeV. In order to thoroughly assess the validity of the Bayesian approach, this methodology was used to obtain corrected p(T) spectra of pions, kaons, protons, and D-0 mesons in pp collisions at root s = 7TeV. In all cases, the results using Bayesian PID were found to be consistent with previous measurements performed by ALICE using a standard PID approach. For the measurement of D-0 - K-pi(+), it was found that a Bayesian PID approach gave a higher signal-to-background ratio and a similar or larger statistical significance when compared with standard PID selections, despite a reduced identification efficiency. Finally, we present an exploratory study of the measurement of A(c)(+) - pK(-)pi(+) in pp collisions at root s = 7TeV, using the Bayesian approach for the identification of its decay products.
We have studied the saturation behavior of single-walled carbon-nanotube-based saturable absorbers (SWCNT-SAs) at different temperatures and SWCNT concentrations in the polymer matrix and tried to relate it to the mode-locked erbium-doped fiber laser performance. It has been observed that a modulation depth of SWCNT-SA transmission which we relate to the ground state recovery time monotonically decreases upon temperature growth. Comparing laser performance with different SWCNT-SAs, we suppose that the defects in the CNT lattice promote recovery acceleration resulting in shorter pulse generation as obtained for boron-nitride-doped SWCNTs. Moreover, for the first time, to the best of our knowledge, we have observed and studied the long-term relaxation of SWCNT-SA saturated transmission exhibiting temperature-dependent behavior. (C) 2016 Optical Society of America
Photoconductivity of thin layers prepared by spin coating of blends of CdSe quantum dots (QDs) and a low-band-gap polymer PCDTBT or PTB7 has been studied. It has been found that photocurrent in the composites containing QDs of 10-nm in size is significantly higher than in those of containing 5-nm QDs. Analysis of the results showed that the photoresponse of the thin layers is mainly determined by the relative positions of the frontier energy levels of the materials used, organic semiconductors and QDs. Therefore, the ability to tune the relative positions of these levels by varying the QD size is of special importance, thus allowing the optimization of photodetectors and photovoltaic cells. © 2016 Elsevier B.V. All rights reserved.
Recently, photofluidization and mass-transfer effects have gained substantial interest because of their unique abilities of photocontrolled manipulation with material structure and physicochemical properties. In this work, the surface topographies of amorphous, nematic, and crystalline films of an azobenzene-containing bent-core (banana-shaped) compound were studied using a special experimental setup combining polarizing optical microscopy and atomic force microscopy. Spin-coating or rapid cooling of the samples enabled the formation of glassy amorphous or nematic films of the substance. The effects of UV and visible-light irradiation on the surface roughness of the films were investigated. It was found that UV irradiation leads to the fast isothermal transition of nematic and crystalline phases into the isotropic phase. This effect is associated with E-Z photoisomerization of the compound accompanied by a decrease of the anisometry of the bent-core molecules. Focused polarized visible-light irradiation (457.9 nm) results in mass-transfer phenomena and induces the formation of so-called "craters" in amorphous and crystalline films of the substance. The observed photofluidization and mass-transfer processes allow glass-forming bent-core azobenzene-containing substances to be considered for the creation of promising materials with photocontrollable surface topographies. Such compounds are of principal importance for the solution of a broad range of problems related to the investigation of surface phenomena in colloid and physical chemistry, such as surface modification for chemical and catalytic reactions, predetermined morphology of surfaces and interfaces in soft matter, and chemical and biochemical sensing. © 2016 American Chemical Society.
Two new methods for the formation of nanotip arrays under the action of single or double femtosecond laser pulses on a surface of bulk aluminum are presented. It is shown that a key role in the formation of nanotips is played by the excitation of surface electromagnetic waves and their mutual interference, and by their interference with the exciting electromagnetic field of the laser pulse. © 2016, Allerton Press, Inc.
Hybrid systems based on photonic crystals embedded with luminophores are among the most promising materials for the development of sensors and photonic devices, and porous silicon is especially suitable candidate for manufacturing of one-dimensional photonic crystals. The use of a porous silicon microcavity as a matrix for luminophores allows control over the emission of embedded luminophores. We have investigated the photoluminescence modulation of CdSe/ZnS quantum dots (QDs) and poly(phenylevenylene) derivatives (MDMO-PPV and BEHP-co-MEH-PPV). Strong narrowing of luminophore photoluminescence spectral band due to Purcell effect has been observed. (C) 2016 Elsevier Ltd. All rights reserved.
Pathology is one of the most dynamically developed medical specialties. The wide spread of whole-slide imaging systems has leaded to the development of microscopic image analysis software. This review shows the possibilities of these programs and their role in the routine work of a pathologist.
The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented.
Daily inspections of the radiation output of accelerator radiation beams prior to patient treatment are a compulsory component of all international recommendations on quality assurance. In the classic version, such an inspection is performed using standard “wired” (connected by wires) dosimetric equipment, such as calibrated ionization chambers or detector matrices. However, in the case of testing of a large number of accelerators and lack of appropriate radiological equipment and personnel, morning inspections may affect the beginning time of the treatment process. To accelerate this procedure, the N.N. Blokhin Russian Cancer Research Center of the Russian Academy of Medical Sciences developed and implemented a wireless technique of morning inspections using portal imaging devices for testing constancy of the absolute dose of photon radiation and assessing the accuracy of the multileaf collimator. The performance of the system for data transmission between the department server and the accelerator console, as well as the possibility of imaging, is checked simultaneously with the morning inspection. © 2016 Springer Science+Business Media New York
Ability to precisely control the Si-related color center abundance in diamond is important for the use of silicon-vacancy (SiV) defects with bright photoluminescence (PL) in quantum information technologies and optical biomarkers. Here, we evaluated the efficiency of Si incorporation in (100) plane of homoepitaxial diamond layers upon in situ doping by adding silane SiH4 in the course of diamond chemical vapor deposition in microwave plasma using CH4–H2 mixtures. Both the Si concentration in the doped samples, as determined by secondary ion mass spectrometry, and PL intensity of SiV centers at 738 nm wavelength, measured at excitation wavelength of 473 nm, demonstrate a linear increase with silane content in feed gas in the range. The incorporation efficiency f, defined as the ratio of Si concentration in diamond to that in gas, f = [Si/C]dia/[Si/C]gas is found to be (1.1 ± 0.5) × 10−3 for the silane concentrations explored, [SiH4/CH4] < 0.7 %; thus, the Si atoms are accommodated in (100) diamond face easier than nitrogen and phosphorus, but more difficult than boron. This finding allows a tailoring of the Si content and photoluminescence intensity of SiV centers in in situ doped CVD diamond. © Springer-Verlag Berlin Heidelberg 2016.
We have estimated a local heating which takes place owing to the ionization energy losses at the terminal part of a fast positron track and at nano-vicinities of the sup57/supFe Mössbauer nuclei in case of the emission Mössbauer spectroscopy. It is shown that in experiments close to the melting point one may expect local melting near the probe species. © Published under licence by IOP Publishing Ltd.
The production of Ksup∗/sup(892)sup0/sup and ϕ(1020) mesons has been measured in p–Pb collisions at sNN= 5.02 TeV. Ksup∗ 0/sup and ϕ are reconstructed via their decay into charged hadrons with the ALICE detector in the rapidity range - 0.5 < y< 0. The transverse momentum spectra, measured as a function of the multiplicity, have a pT range from 0 to 15 GeV/c for Ksup∗ 0/sup and from 0.3 to 21 GeV/c for ϕ. Integrated yields, mean transverse momenta and particle ratios are reported and compared with results in pp collisions at √s= 7 TeV and Pb–Pb collisions at sNN= 2.76 TeV. In Pb–Pb and p–Pb collisions, Ksup∗ 0/sup and ϕ probe the hadronic phase of the system and contribute to the study of particle formation mechanisms by comparison with other identified hadrons. For this purpose, the mean transverse momenta and the differential proton-to-ϕ ratio are discussed as a function of the multiplicity of the event. The short-lived Ksup∗ 0/sup is measured to investigate re-scattering effects, believed to be related to the size of the system and to the lifetime of the hadronic phase. © 2016, CERN for the benefit of the ALICE collaboration.
The production of (anti-)deuteron and (anti-)He3 nuclei in Pb-Pb collisions at sNN=2.76 TeV has been studied using the ALICE detector at the LHC. The spectra exhibit a significant hardening with increasing centrality. Combined blast-wave fits of several particles support the interpretation that this behavior is caused by an increase of radial flow. The integrated particle yields are discussed in the context of coalescence and thermal-statistical model expectations. The particle ratios, He3/d and He3/p, in Pb-Pb collisions are found to be in agreement with a common chemical freeze-out temperature of Tchem≈156 MeV. These ratios do not vary with centrality which is in agreement with the thermal-statistical model. In a coalescence approach, it excludes models in which nucleus production is proportional to the particle multiplicity and favors those in which it is proportional to the particle density instead. In addition, the observation of 31 anti-tritons in Pb-Pb collisions is reported. For comparison, the deuteron spectrum in pp collisions at s=7 TeV is also presented. While the p/π ratio is similar in pp and Pb-Pb collisions, the d/p ratio in pp collisions is found to be lower by a factor of 2.2 than in Pb-Pb collisions. © 2016 CERN. ©2016 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
The pseudorapidity (η) and transverse-momentum (pT) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy √s=13 TeV. The pseudorapidity distribution in |η|<1.8 is reported for inelastic events and for events with at least one charged particle in |η|<1. The pseudorapidity density of charged particles produced in the pseudorapidity region |η|<0.5 is 5.31±0.18 and 6.46±0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15<pT<20 GeV/c and |η|<0.8 for events with at least one charged particle in |η| < 1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. © 2015 CERN for the benefit of the ALICE Collaboration.
We present measurements of the elliptic (v2), triangular (v3) and quadrangular (v4) anisotropic azimuthal flow over a wide range of pseudorapidities (−3.5<η<5). The measurements are performed with Pb–Pb collisions at sNN=2.76 TeV using the ALICE detector at the Large Hadron Collider (LHC). The flow harmonics are obtained using two- and four-particle correlations from nine different centrality intervals covering central to peripheral collisions. We find that the shape of vn(η) is largely independent of centrality for the flow harmonics n=2–4, however the higher harmonics fall off more steeply with increasing |η|. We assess the validity of extended longitudinal scaling of v2 by comparing to lower energy measurements, and find that the higher harmonic flow coefficients are proportional to the charged particle densities at larger pseudorapidities. Finally, we compare our measurements to both hydrodynamical and transport models, and find they both have challenges when it comes to describing our data. © 2016 The Author
The single-shot spallation thresholds for copper and silver surfaces demonstrate a considerable IR-laser (1030 nm) pulse-width dependent increase over a range of 0.2-12 ps for the former material and a very weak increase for the latter one, while the corresponding thresholds for visible (515 nm) laser pulses remain almost constant. The IR-laser increase of the ablation thresholds is related to two-photon interband (d-s) absorption in copper, contrasting with the linear absorption of visible laser pulses in this material. In silver, common weakly sublinear dependences on the laser pulsewidth were observed, ruling out possible multi-photon-either three(four)-photon in IR, or two-photon in the visible range-interband transitions in this material. Moreover, electron-lattice thermalization times of 1-2 ps were evaluated for these materials in the spallative ablation regime, contrasting strongly with the previously theoretically predicted multi-picosecond thermalization times.
Emission spectral properties and quantum efficiency of upconversion particles NaYF4, SrF2, LaF3, BaF2. CaF2, doped with rare earth ions pair Yb3+-Er3+ were studied using continuous wave (CW) and pulsed periodic excitation modes in the near infrared (NIR) spectral range. Analysis of the obtained results showed that the intensity ratio of upconversion luminescence in green and red spectral ranges depends on excitation pulse duration. Thus, by changing the pulse duration the spectral properties of upconversion luminescence can be controlled. Crystals with higher phonon energy are more sensitive to the change of pumping mode. Interpretation of results was performed on the rate equation model basis. Using numerical methods for all energy levels involved in the upconversion process the population and depopulation dynamics were obtained with respect to the duration of the excitation pulses. It was shown that about 30 ms was required for the complete population of F-4(9/2) state, from which the luminescence in the red spectral range occurs. When the pulse duration was less than 30 ms, the F-4(9/2) population did not reach a steady state and the intensity of the luminescence in the red part of the spectrum was reduced. The theoretical dependence of the upconversion luminescence intensity in the green and red ranges of the excitation pulse duration for NaYF4:Yb-0.2-Er-0.02 composition was obtained and demonstrates good agreement with the experimental results.
A pulsed quantum cascade laser emitting in the wavelength range 9.5-9.7 μm at 77.4 K is developed based on the GaAs/Al0. 45Ga0.55As heteropair. The laser heterostructure was grown by MOCVD. The threshold current density was 1.8 kA cm-2. The maximum output power of the laser with dimensions of 30 μm x 3 mm and with cleaved mirrors exceeded 200 mW. © 2016 Kvantovaya Elektronika and Turpion Ltd.
Hybrid composites of polymers with fluorescent nanoparticles are unique materials combining good mechanical properties of the host polymer matrices and luminescent properties of the embedded nanoparticles. Here, we report on the optical characterization of novel inorganic–organic hybrid composites based on nanoporous polypropylene (PP) as a polymer matrix and quantum dots (QDs) as a fluorescent inorganic component. The first type of the composite films is prepared by absorption of CdSe/ZnS QDs onto the porous structure of the PP films, followed by annealing at 170 °C, i.e., above the melting point of the PP. The second type of the composite films is obtained by filling of porous QD–PP composites with a nematic liquid crystalline (LC) mixture. Both types of composites are characterized by low light scattering, which makes it possible to study their optical properties by absorbance and fluorescence spectroscopies. TEM and confocal fluorescence microscopy have been used to analyze the aggregation of QDs in composites of different types. It has been shown that introduction of QDs into PP with a low draw ratio decreases the degree of alignment of LC molecules embedded into the pores of QD–PP composite films. © 2016 Elsevier Ltd
Enhancing the radiative decay rate of quantum emitters is a fundamental problem for many practical applications. Here we report on the fundamental constraints pertaining to the enhancement of the radiative emission rate achievable with planar lamellar metamaterials of any kind. We show that neither dielectric lamellar structures nor hyperbolic metamaterials are able to provide radiative rate enhancement by more than a factor of 2 in the half-space containing emitter. However, the increase in radiative rate in the opposite half space can be substantial. We show that the origin of this enhancement is in the leakage of the plasmon waves excited on the metal-dielectric interface into the substrate. © 2016 American Physical Society.
Effect of silver nanoparticles (AgNPs) on the D96N mutant form of bacteriorhodopsin (BRh-D96N) contained in fragments of purple membranes (PMs) of bacteria Halobacterium salinarum has been analyzed. It has been found that interaction of AgNPs with BRh-D96N in SERS-active spots leads to "freezing" of the protein photocycle. The AgNPs change and then fix the state of BRh-D96N in SERS-active spots. Outside of SERS-active spots, the effect of AgNPs is weaker and is expressed in deceleration of the M-form decay. Thus, the fundamental difference in the influence of AgNPs on the mutant BRh-D96N in comparison with wild-type BRh was found. (C) 2016 Elsevier Ltd. All rights reserved.
DARPins fused with other proteins are promising non-immunoglobulin scaffolds for specific binding to target cells. In this study HER2-specific DARPin (DARPin-9-29) was used as a tumor-targeting moiety for the delivery of a cytotoxic agent - the fragment of Pseudomonas aeruginosa exotoxin A. It was determined that DARPin-PE40 possesses a considerable cytotoxic activity and induces apoptosis in HER2-positive cells. Cytotoxic effect of DARPin-PE40 strongly correlates with the HER2 expression level. The effect of intravenous administration of DARPin-PE40 was tested in the xenograft model of breast cancer. It was shown that treatment of animals with DARPin-PE40 caused strong and prolonged suppression of xenograft tumor growth. © 2016 Elsevier B.V. All rights reserved.
The use of detonation nanodiamond (DND) slurries in biomedical applications requires the understanding of interactions at the particle/solvent interphase. In this article, interactions of nanodiamond particles with molecules of protic solvents (water and water-ethanol mixture) were studied by the methods of laser Raman and fluorescence spectroscopy. It was found that nanodiamonds modified by carboxyl groups significantly decrease the average hydrogen bonds energy in protic solvents. In turn, the strength of hydrogen bonds at the DND/solvent interphase influences the fluorescent properties of nanodiamonds: the weaker the effect of the hydrogen bonds, the stronger is the fluorescence of DNDs in suspensions. © 2016 American Chemical Society.
Recent experiments on multiple filamentation of sub-picosecond terawatt-level KrF laser pulse in air and multi-photon ionization of air revealed an extremely low electron density in filaments, which is out of the conventional filamentation model considering Kerr self-focusing and plasma de-focusing. We propose here the coherent resonant scattering and ionization processes at the pulse durations significantly less than the polarization relaxation time to be possible explanation of the observed filamentation peculiarities. Namely, we argue that the plasma production results from the resonance enhanced (2+1)-photon ionization of the oxygen molecules through the two-photon excitation of the 3s metastable Rydberg state. Coherent Raman self-scattering at rotational transitions of nitrogen molecules provides self-induced focusing of the ultrashort UV laser pulse and filament formation. © 2015 Elsevier B.V. All rights reserved.
The recent results of molecular-dynamics simulation of nanosecond vaporization of a thin liquid film are analyzed within the continual approach. The analysis shows a significant increase in the thermal conductivity at the film temperature maximum before its explosive decomposition, which indicates the closeness of the achievable limiting overheating temperature to the spinodal. © 2016, Allerton Press, Inc.
We have experimentally studied saturation behavior of Single-Walled Carbon Nanotube-based saturable absorbers at different temperatures and SWCNT concentrations in the carboxymetylcellulose polymer matrix and related it to the mode-locked erbium-doped fiber laser performance. © 2016 IEEE.
A new experimental approach to multiparametric three-dimensional (3D) investigation of a broad class of composite nanostructural materials is developed on the basis of scanning near-field optical nanotomography (SNONT). Using this method, it is possible to simultaneously study the optical properties, 3D morphology, and distribution of the mechanical and electrical properties of the same region of a sample. The proposed method combines features of the confocal and near-field optical microspectroscopy (fluorescence and Raman spectroscopy) with a lateral resolution of up to 50 nm and scanning-probe microscopy. The possibility of studying the volume distribution of optical, morphological, electrical, and mechanical characteristics of a material with nanoscale resolution is related to the probing of sequential layers at a step of up to 20 nm and a total Z-scan depth of up to 3 mm. In particular, the SNONT method has been used to study a liquid-crystalline polymer doped with fluorescent nanocrystals. © 2016, Pleiades Publishing, Ltd.
We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible Λn bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at sNN=2.76 TeV, by invariant mass analysis in the decay modes Λn→dπ+ and H-dibaryon →Λpπ-. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton. © 2015 The Authors.
The degree of influence of radiative processes on the ignition of deuterium–tritium (DT) plasma has been theoretically studied as dependent on the content of inactive impurities in plasma. The analytic criterion of plasma ignition in inertial confinement fusion (ICF) targets is modified taking into account the absorption of intrinsic radiation from plasma in the ignition region. The influence of radiative processes on the DT plasma ignition has been analytically and numerically studied for plasma that contains a significant fraction of inactive impurities either as a result of DT fuel mixing with ICF target ablator material or as a result of using light metal DT-hydrides as solid noncryogenic fuel. It has been shown that the effect of the absorption of intrinsic radiation leads to lower impurity-induced increase in the ignition energy as compared to that calculated in the approximation of optically transparent ignition region. © 2016, Pleiades Publishing, Inc.
We review our recently obtained data on the employment of Si nanoparticles as sensitizers of radiofrequency (RF) - induced hyperthermia for mild cancer therapy tasks. Such an approach makes possible the heating of aqueous suspensions of Si nanoparticles by tens of degrees Celsius under relatively low intensities (1-5 W/cm2) of 27 MHz RF radiation. The heating effect is demonstrated for nanoparticles synthesized by laser ablation in water and mechanical grinding of porous silicon, while laser-ablated nanoparticles demonstrate a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations. The observed RF heating effect can be explained in the frame of a model considering the polarization of Si NPs and electrolyte in the external oscillating electromagnetic field and the corresponding release of heat by electric currents around the nanoparticles. Our tests evidence relative safety of Si nanostructures and their efficient dissolution in physiological solutions, suggesting potential clearance of nanoparticles from a living organism without any side effects. Profiting from Si nanoparticle-based heating, we finally demonstrate an efficient treatment of Lewis Lung carcinoma in vivo. The obtained data promise a breakthrough in the development of mild, non-invasive methods for cancer therapy. © 2016 SPIE.
Interaction of silver nanoparticles (AgNPs) with purple membranes (PM) has been studied using atomic force microscopy and optical spectroscopy. It was shown that AgNPs alter the photocycle of the bacteriorhodopsin (BRh) molecules located in SERS-active spots. AgNPs suppresses the photocycle by "freezing" the state of retinal in which BRh has bound AgNPs. Outside SERS-active spots, BRh molecules retain the capacity for carrying out the photocycle but with shorter lifetimes of its photointermediate states. Thus, the AgNPs may affect the BRh photocycle through its acceleration in the regions of weak AgNPs-PM interaction or by the photocycle freezing in the SERS-active spots. (C) 2016 Elsevier Ltd. All rights reserved.
This work is devoted to the study of a single Staphylococcus aureus bacterium detection using surface-enhanced Raman spectroscopy (SERS) and resonant Raman spectroscopy (RS). It was shown that SERS allows increasing sensitivity of predominantly low frequency lines connected with the vibrations of Amide, Proteins and DNA. At the same time the lines of carotenoids inherent to this kind of bacterium are well-detected due to the resonance Raman scattering mechanism. The reproducibility and stability of Raman spectra strongly depend on the characteristics of nanostructured substrate, and molecular structure and size of the tested biological object. © Published under licence by IOP Publishing Ltd.
The PING-M experiment is designed to investigate solar X-ray activity. The instrument includes a hard X-ray polarimeter (PING-P), a hard X-ray spectrometer (HXRS) and a soft X-ray spectrometer (SXRS). PING-P has the energy range of 20-150keV and an effective area of about 2.5cmsup2/sup. It uses three organic scintillation detectors as active scatterers, which work in coincidence with six absorber detectors, based on CsI(Tl) scintillator. This technique allows us to considerably improve the polarimeter sensitivity. HXRS has the energy range of 20-600keV and an effective area of about 15cmsup2/sup. It is based on a fast inorganic scintillator (LaBr3(Ce) or CeBr3) with a relatively high energy resolution of 3.5-4.5% at 662keV. The SXRS energy range is 1.5-25keV, and its aperture is ø0.1mm, which provides the registration of solar flares in the range from C1 to X20 class of GOES scale. It is based on a SDD semiconductor detector with an energy resolution better than 200eV at 5.9keV line. The experiment will be performed onboard the Russian interplanetary mission Interhelioprobe which is planned for launch after 2025.The instrument will allow us to investigate angular and energy distributions of accelerated electrons, plasma heating processes, etc. Stereoscopic polarimetry and spectrometric observations will be possible if a similar instrument is installed onboard a near Earth satellite, or the second probe of the Interhelioprobe mission. © 2016 COSPAR.
This paper presents a new approach to estimate optical properties (absorption and scattering coefficients mu(a) and mu(s)) of biological tissues from spatially-resolved spectroscopy measurements. A Particle Swarm Optimization (PSO)-based algorithm was implemented and firstly modified to deal with spatial and spectral resolutions of the data, and to solve the corresponding inverse problem. Secondly, the optimization was improved by fitting exponential decays to the two best points among all clusters of the "particles" randomly distributed all over the parameter space (mu(s); mu(a)) of possible solutions. The consequent acceleration of all the groups of particles to the "best" curve leads to significant error decrease in the optical property estimation. The study analyzes the estimated optical property error as a function of the various PSO parameter combinations, and several performance criteria such as the cost-function error and the number of iterations in the algorithms proposed. The final one led to error values between ground truth and estimated values of mu(s) and mu(a) less than 6%. (c) 2016 Optical Society of America
The authors develop an original and promising method of suppressing the speckle- noise in images generated by a laser beam by means of a compact despeckler based on an electro-optical cell with the smectic ferroelectric liquid crystal (FLC), realizing spatially inhomogeneous phase modulation of light. The mechanisms of destruction of the phase relations in the laser beam passing through a cell with helix-free FLC are discussed. The electric field induces the light scattering and small-scale randomly distributed gradients of the refractive index in FLC layer. The features and benefits of a despeckler using helix-free FLC compared to helix FLC are indicated. © Published under licence by IOP Publishing Ltd.
The spectral characteristics of cw laser diodes with a maximum reliable power of 15 W mounted on F-mount heat sinks are studied. It is found that the spectrum envelopes have features at emission powers exceeding 5 - 7 W. A method for determining the maximum of a spectrum envelope under the conditions of its broadening and appearance of features is discussed. The thermal resistance of diodes is determined experimentally at pump currents from threshold to maximum (14 A) and is found to be 2.25 K W-1 at a current of 10 A and 1.5 K W-1 at a current of 4 A. The results obtained are compared with the literature data. The adequacy of using the thermal resistance parameter for comparing and estimating thermal characteristics of laser diodes is considered.
Surface modification of conductive boron-doped diamond has been conducted using the electrical field of the probe of a scanning probe microscope (SPM) at varying relative humidity (RH) of the ambient environment. It has been found that, under the action of positive polarity pulses applied to the sample via a grounded SPM probe, the sample material undergoes modification. The modification pattern depends on atmospheric RH: low (up to 32%) and high humidity values (above 35%) lead to the formation of cavities and protrusions, respectively. It has been found that the resulting protrusions exhibit temporary instability; that is, a protrusion is partially transformed into an array of nanoobjects. The mechanism of modification of boron-doped diamond–local anodic oxidation–has been discussed. © 2016, Pleiades Publishing, Ltd.
Ultrashort pulse lasers constitute an important tool in the emerging field of optical frequency metrology and are enabling unprecedented measurement capabilities and new applications in a wide range of fields, including precision spectroscopy, atomic clocks, ultracold gases, and molecular fingerprinting. We demonstrate the generation of stable 127-fs self-similar pulses at a central wavelength of 1560 nm with 7.14-mW average output power. Similariton lasers have a low repetition rate deviation in the averaging time interval 1-1 10sup3/sup, a low relative intensity noise -120 dBc/Hz (30 Hz to 10 kHz), a narrow single comb line width of 32 kHz, and high reliability. Thus, such lasers are highly promising for further development of the stabilized combs and open up a robust and substantially simplified route to synthesizing low-noise microwaves. © 1986-2012 IEEE.
The application of the STED method (STimulated Emission Depletion) to silver photoreduction and metal and metalorganic nanostructure formation is demonstrated. We study the influence of various factors on the process of STED nanolithography. We investigate the morphology and structural parameters of the hybrid nanostructure arrays produced with the STED method. The influence of silver nanoparticles on the physical properties of photoinitiator molecules (DETC) manifests itself in a lifetime reduction of the excited state with 2.3 to 0.6 ns. A new method of additive nanotechnology is proposed. © 2016, Pleiades Publishing, Ltd.
In this study, the deformation mechanisms operating with stress in bulk nanocrystalline (NC) titanium–nickel with an average grain size below a critical size of 10–20 nm have been investigated. We demonstrate a sequential variation of the deformation mechanism from grain boundary (GB) sliding and grain rotation to grain growth and dislocation activity with the increase of the deformation stress. These deformation mechanisms are different from the previous understanding that below a critical grain size of 10–20 nm, GB sliding and grain rotation govern plastic deformation of NC materials. © 2016 Institute of Materials, Minerals and Mining.
A gold target was ablated by femtosecond laser radiation in aqueous solutions of preliminarily prepared Si nanoparticles. The ablation process led to the formation of Au-based spherical colloids with the mean size around 5-10 nm and a weak abundance of larger species. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray (EDX) analysis revealed the presence of Au and Si in colloid composition, while the stoichiometry of colloids did not depend on laser fluence during the fabrication experiments. The formation of Au-Si nanohybrid structure was explained by an effect of the interaction of laser-ablated Au nanoclusters with water-dispersed Si nanoparticles. The fabricated structures can be of importance for biomedical, catalysis, and photovoltaics applications. © 2016 SPIE.
Submicron dimensions, nanoscale crystalline structure, and fabrication mechanisms of microcones on silver films of variable (50-380 nm) thickness deposited onto glass substrates by single strongly focused femtosecond laser pulses of different fluences are experimentally studied using scanning electron microscopy. Fabrication mechanisms for nanoholes and microcones are discussed for films of the different thickness, as well as the extraordinary shapes of their constituent nanocrystallites, strongly elongated along the melt flow direction in thin films.
Studies of the structure and magnetic properties of layers formed on nonmagnetic substrates by laser powder fusing (LPF) showed that crystalline phases are separated from initial powders of bronze, inconel (IN 625), and PGSR-4with the transformation of nonmagnetic materials to soft ferromagnets. The fused bronze powder layer exhibits soft ferromagnetic properties with two types of magnetic domains with the Curie temperatures of 80 and 300 K and a coercivity to 90 Oe at 300 K; in layers based on In625 and PGSR-4, only one type of magnetic domains with the Curie temperatures of 260-270 K is formed, which provides soft ferromagnetic properties at 4 De and the paramagnetic transition at 300 K.
In-vitro Raman micro-spectroscopy was used for diagnostics of the processes of uptake and biodegradation of porous silicon nanoparticles (SiNPs) in breast cancer cells (MCF-7 cell line). Two types of nanoparticles, with and without photoluminescence in the visible spectral range, were investigated. The spatial distribution of photoluminescent SiNPs within the cells obtained by Raman imaging was verified by high-resolution structured-illumination optical microscopy. Nearly complete biodegradation of SiNPs inside the living cells was observed after 13 days of the incubation. The results reveal new prospects of multi-modal visualization of SiNPs inside cancer cells for theranostic applications. © 2016 Elsevier Inc.
Radial breathing modes (RBMs) are widely used for the atomic structure characterization and index assignment of single-walled carbon nanotubes (SWNTs) from resonant Raman spectroscopy. However, for double-walled carbon nanotubes (DWNTs), the use of conventional ωRBM(d) formulas is complicated due to the van der Waals interaction between the layers, which strongly affects the frequencies of radial modes and leads to new collective vibrations. This paper presents an alternative way to theoretically study the collective radial breathing-like modes (RBLMs) of DWNTs and to account for interlayer interaction, namely the continuous two-dimensional membrane theory. We obtain an analytical ωRBLM(do,di) relation, being the equivalent of the conventional ωRBM(d) expressions, established for SWNTs. We compare our theoretical predictions with Raman data, measured on individual index-identified suspended DWNTs, and find a good agreement between experiment and theory. Moreover, we show that the interlayer coupling in individual DWNTs strongly depends on the interlayer distance, which is manifested in the frequency shifts of the RBLMs with respect to the RBMs of the individual inner and outer tubes. In terms of characterization, this means that the combination of Raman spectroscopy data and predictions of continuous membrane theory may give additional criteria for the index identification of DWNTs, namely the interlayer distance. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).
ALICE is one of four large experiments at the CERN Large Hadron Collider near Geneva, specially designed to study particle production in ultra-relativistic heavy-ion collisions. Located 52 meters underground with 28 meters of overburden rock, it has also been used to detect muons produced by cosmic ray interactions in the upper atmosphere. In this paper, we present the multiplicity distribution of these atmospheric muons and its comparison with Monte Carlo simulations. This analysis exploits the large size and excellent tracking capability of the ALICE Time Projection Chamber. A special emphasis is given to the study of high multiplicity events containing more than 100 reconstructed muons and corresponding to a muon areal density ρμ > 5.9 msup-2/sup. Similar events have been studied in previous underground experiments such as ALEPH and DELPHI at LEP. While these experiments were able to reproduce the measured muon multiplicity distribution with Monte Carlo simulations at low and intermediate multiplicities, their simulations failed to describe the frequency of the highest multiplicity events. In this work we show that the high multiplicity events observed in ALICE stem from primary cosmic rays with energies above 10sup16/sup eV and that the frequency of these events can be successfully described by assuming a heavy mass composition of primary cosmic rays in this energy range. The development of the resulting air showers was simulated using the latest version of QGSJET to model hadronic interactions. This observation places significant constraints on alternative, more exotic, production mechanisms for these events. © 2016 CERN for the benefit of the ALICE Collaboration.
One-dimensional gratings with a period of 0.5 - 2.3 μm are formed on the surfaces of CdSe and ZnSe crystals ablated by two interfering radiation beams of a nanosecond excimer KrF laser. Investigated are the dependences of the shape and depth of gratings on the energy density under irradiation by a single pulse, and on the number of pulses at a given energy density. The maximum grating depth is estimated as ∼0.57 of the period. By forming a one-dimensional grating with a period of 1.5 μm and a depth of 0.53 μm on the CdSe-crystal surface, this surface becomes antireflective at a wavelength of 4 μm. The surface reflectivity is reduced by 88 %. A possibility of forming two-dimensional gratings having periods of 1 and 1.5 μm is demonstrated. © 2016 Kvantovaya Elektronika and Turpion Ltd.
We have developed a facile approach to engineering ratiometric sensors nano-thermosensors (NTSs) with a core/shell structure. A layer of "smart" thermosensitive poly(N-vinylcaprolactam) doped with quantum dots (QDs) with the emission wavelength lambda(em shell) makes it possible to obtain fluorescence emission depending on temperature. QDs with a different emission wavelength lambda(em core) incorporated in the NTS core emit a reference signal which allows ratiometric temperature measurements to be performed within a nanoscale volume. It has been shown that an NTS has a high temperature sensitivity if long-wavelength QDs are located in the core of the sensor, whereas the temperature-sensitive shell contains short-wavelength QDs (lambda(em core) lambda(em shell)). An optimally selected thermosensitive polymer has allowed us to design NTSs operating in the physiological temperature range. (C) 2016 Elsevier Ltd. All rights reserved.
Single-shot thresholds of surface ablation of aluminum and silicon via spallative ablation by infrared (IR) and visible ultrashort laser pulses of variable width τlas (0.2–12 ps) have been measured by optical microscopy. For increasing laser pulse width τlas < 3 ps, a drastic (threefold) drop of the ablation threshold of aluminum has been observed for visible pulses compared to an almost negligible threshold variation for IR pulses. In contrast, the ablation threshold in silicon increases threefold with increasing τlas for IR pulses, while the corresponding thresholds for visible pulses remained almost constant. In aluminum, such a width-dependent decrease in ablation thresholds has been related to strongly diminished temperature gradients for pulse widths exceeding the characteristic electron-phonon thermalization time. In silicon, the observed increase in ablation thresholds has been ascribed to two-photon IR excitation, while in the visible range linear absorption of the material results in almost constant thresholds. © 2016, Pleiades Publishing, Inc.
Photoconductive atomic force microscopy (PC-AFM) allows one to study the influence of illumination on the conductive properties of different samples at the nanoscale. However, for such measurements to be considered reliable, one has to be sure that illumination does not impact the tip-sample contact force. The change of the contact force may be caused by the influence of radiation on the atomic force microscope's position sensitive detector (PSD) as well as the probe and sample. There are certain approaches to reduce this illumination influence; however, they cannot always be implemented. Therefore, it is important to perform a detailed study of the influence of illumination on the PSD, the probe, and the sample during measurements in the PC-AFM mode. In this paper, this was done by studying the mechanism by which elevation is formed in topographic images of the cleaved GaAs substrate surface under lateral continuous wave (CW) laser illumination, with λ = 1064 and 404 nm. It was demonstrated that the illumination results, mainly, in the thermal expansion of the tip and the sample, as well as the generation of a thermal stress in the cantilever. The authors consider the cases in which these effects can increase the tip-sample contact force during PC-AFM measurements and suggest simple approaches by which the increase in force can be minimized. Also, the authors developed the model of thermal expansion of the GaAs sample fixed in the holder under CW laser illumination. Based on this model, the approach was suggested for estimation of the thermal contact conductance value for different solid-solid interfaces. © 2016 American Vacuum Society.
We performed synthesis of single crystal (SC) diamond by microwave plasma chemical vapor deposition in methane-enriched H2-CH4 gas mixtures, and achieved growth rates more than 30 μm/h, without adding nitrogen in reaction mixture. A low-coherence interferometry (LCI) was employed for precise measurements of the thickness and growth rate of the epitaxial diamond layers in the course of the process. The performance of this in situ technique is demonstrated by continuously monitoring the SC diamond thickness in a single growth run upon variation of CH4 percentage in steps, up to 17%, without switching off the plasma, to produce a "multilayer" diamond film. In addition, etching rate of diamond in pure hydrogen plasma has been evaluated with the same method. The LCI technique allows quick collection of growth kinetics data upon systematic variation of a selected process parameter for the growth optimization. © 2016 Elsevier B.V. All rights reserved.
We develop a technique for stochastic prediction of the drift duration of technical parameters of objects within tolerances, using geometric and exponential probability distribution laws. We consider the application of this methodology when estimating the duration of the calibration interval of platinum resistance thermometers. © 2016 Springer Science+Business Media New York
Using the molecular dynamics method, heterogeneous melting–crystallization of aluminum is simulated under conditions when the phase front propagates over the overheated-overcooled phase. The dependence of the phase front velocity on the temperature deviation from the equilibrium melting temperature is determined. The dependence obtained from atomistic simulation is used as an approximating function to obtain the temperature dependence of the kinetic rate in the analytical form. The steady-state temperature dependence of the kinetic rate v(Tsℓ) for extreme values of aluminum overheating-overcooling is constructed for the first time. © 2016, Allerton Press, Inc.
One critical functionality of the carrier system utilized in targeted drug delivery is its ability to trigger the release of the therapeutic cargo once the carrier has reached its target. External triggering is an alluring approach as it can be applied in a precise spatiotemporal manner. In the present study, we achieved external triggering through the porous silicon (PSi) nanoparticles (NPs) by providing a pulse of infrared or radiofrequency radiation. The NPs were grafted with a temperature responsive polymer whose critical temperature was tailored to be slightly above 37°C. The polymer coating improved the biocompatibility of the NPs significantly in comparison with their uncoated counterparts. Radiation induced a rapid temperature rise, which resulted in the collapse of the polymer chains facilitating the cargo release. Both infrared and radiofrequency radiation were able to efficiently trigger the release of the encapsulated drug in vitro and induce significant cell death in comparison to the control groups. Radiofrequency radiation was found to be more efficient in vitro, and the treatment efficacy was verified in vivo in a lung carcinoma (3LL) mice model. After a single intratumoral administration of the carrier system combined with radiofrequency radiation, there was clear suppression of the growth of the carcinoma and a prolongation of the survival time of the animals. TOC image The temperature responsive (TR) polymer grafted on the surface of porous silicon nanoparticles (PSi NPs) changes its conformation in response to the heating induced by infrared or radiofrequency radiation. The conformation change allows the loaded doxorubicin to escape from the pores, achieving controlled drug release from TR PSi NPs, which displayed efficacy against malignant cells both in vitro and in vivo. © 2016 Elsevier B.V.
Evolution of crystalline phases with temperature has been studied in materials produced by high-pressure high-temperature treatment of 9-borabicyclo[3.3.1]nonane dimer (9BBN), triphenylborane and trimesitylborane. The boron-doped diamond nanoparticles with a size below 10nm were obtained at 8-9GPa and temperatures 970-1250°C from 9BBN only. Bridged structure and the presence of boron atom in the carbon cycle of 9BBN were revealed to be a key point for the direct synthesis of doped diamond nanocrystals. The diffusional transformation of the disordered carbon phase is suggested to be the main mechanism of the nanodiamond formation from 9BBN in the temperature range of 970-1400°C. Aqueous suspensions of primary boron-doped diamond nanocrystals were prepared upon removal of non-diamond phases that opens wide opportunities for application of this new nanomaterial in electronics and biotechnologies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The effect of silver nanoparticles (AgNPs) that are adsorbed on the surface of the purple membranes of Halobacterium salinarium bacteria on the optical properties and functional peculiarities of the lightsensitive protein bacteriorhodopsin (BR) has been demonstrated for the first time. Two mechanisms of the effect of AgNPs on the protein photocycle have been demonstrated using Raman scattering, giant Raman scattering, flash photolysis, and atomic force microscopy. It has been shown that the nanoparticles in the immediate spatial vicinity of BR fix its photocycle at the stage where it was at the moment of interaction with the nanoparticles. At greater distances, which reach three radii of an AgNPs, they have a weaker effect on BR, under which it retains the ability to be involved in the photocycle, however, has its parameters significantly changed. Thus, in the case of wild-type BR the photocycle accelerates and for the BR-D96N mutant it becomes slower. The data that are obtained could be of significance for creation of such optoelectronic hybrid systems with BR, where the parameters of its photocycle can be controlled using NPs. The results of the study may also be used in the field of nanobioengineering research, which is directed to creation of unique materials with controlled properties for recording and storage of information, energy transformation, and identification and characterization of trace amounts of analytes. © 2016, Pleiades Publishing, Ltd.
We present the results of optical power, total efficiency and spectra of CW laser diodes emitting at wavelength 970 nm. Total efficiency in maximum 72% was measured and reliable operation at 15 W CW was achieved. At the base of measured CW spectral parameters in wide range of pump currents we discuss the possible reasons of observed features in dependences of spectral envelope, spectral maximum and spectral half-width against pumping current.
Strong shock wave generation by a mono-energetic fast electron beam in a plasma with an increasing density profile is studied theoretically. The proposed analytical model describes the shock wave characteristics for a homogeneous plasma preceded by a low density precursor. The shock pressure and the time of shock formation depend on the ratio of the electron stopping length to the preplasma areal density and on the initial energy of injected electrons. The conclusions of theoretical model are confirmed in numerical simulations. © 2016 Author(s).
It was reliably proved in recent years both theoretically and experimentally that the electrically controlled birefringence (Formula presented.) of chiral smectic C* phase with subwavelength helix pitch is proportional to the square of the electric field E. The goal of the present work is to investigate the restrictions of the quadratic effect imposed by the thickness of the smectic C* layer between two solid substrates, and by the frequency of applied voltage. It is shown that these restrictions are mainly associated with the dielectric dispersion of the Goldstone mode under various boundary conditions. © 2015 Taylor & Francis.
Recently it was shown that in deformed helix ferroelectric (DHF) structure, the electrically controlled birefringence (Formula presented.) of chiral smectic C* phase with subwavelength helix pitch ((Formula presented.) is known to be proportional to the square of the electric field E) depends on the cell thickness and on the frequency of applied voltage, given as a Step function of the time. The purpose of the present work is to investigate whether this quadratic effect depends also on the voltage function shape, comparing the electrically controlled birefringence (Formula presented.) and the Kerr constant in DHF cells with different thickness, driven by STAIR and Step voltage functions. © 2015 Taylor & Francis
The recombination photoluminescence (PL) properties of hydrophilic colloidal CdS quantum dots (QDs) dispersed in gelatin were investigated. The average size of QDs varies from 2.4 to 4.4 nm. The size dependence of the emission peak position is defined in the range from 1.65 to 2.27 eV. The PL decay (0.3–4·10sup3/sup ns) is accompanied by the red shift of its maximum. It is interpreted as the radiative recombination via the donor-acceptor pairs. The analysis of the half-width and shape of the observed PL spectra was performed taking into account the QDs size distribution and the Coulomb interaction of donor and acceptor uniformly distributed in QD volume. The deviation of the theoretical PL spectra from experimental data on the half-width was determined, which amounted of the order 0.4 eV. It is concluded that to describe the PL spectra of CdS QDs it is necessary to consider a different degree of localization of the wave functions and the variation of the binding energy of the donor and acceptor versus their depth in the QD volume. © 2016
Injection lasers were developed on the basis of the solid solution Pb1-xSnxSe for the spectral range of 16 μkm, where the rotational-vibrational absorption lines of heavy molecules are placed. For this purpose, were used, composition the solid solution Pb1-xSnxSe near the inversion point xi = 0.12. Single crystals Pb1-xSnxSe (Eg = 0.077 eV) were grown by directional crystallization from the vapor phase.
We studied the possibility of in vivo tracing of multipotent mesenchymal stromal cells labeled with a radiophermaceutic preparation based on metastable isotope Technetium-99m and injected to rats with modeled traumatic brain injury. Accumulation of labeled cells occurred primarily in the liver and lungs. The cells distribution in internal organs greatly varied depending on the administration route. Cell injection into the carotid artery led to their significant accumulation in the damaged brain hemisphere, while intravenous injection was followed by diffuse cell distribution in all brain structures. Scintigraphy data were confirmed by magnetic resonance imaging and histological staining of cells. Visualization of stem cells labeled with Technetium-99m-based preparation by scintigraphy is an objective and highly informative method allowing real-time in vivo cell tracing in the body. © 2016 Springer Science+Business Media New York
For the first time, an experimentally measured seed pulse gain of about 2 cm-1 allows possibilities in the scaling power of such a femtosecond laser system in terawatts. The concept of a subterawatt power level hybrid femtosecond mid-IR (4-5 μm) laser system, based on a weak pulse from an optical parametric mid-IR seeder that is amplified in chalcogenide monocrystalline Fe2+:ZnSe, to gain medium has been proposed and designed. The method and approach for optimizing the choice of nonlinear medium, its length, and the required light intensity for the efficient non-linear self-compression of an ultrashort pulse has also been proposed and considered. © 2016 Astro Ltd.
Transverse mode locking of the Stokes component generated in the mode of stimulated Raman scattering self-conversion by a pulsed diode end-pumped Nd:YVO4/Cr:YAG laser is implemented for the first time under conditions of frequency degeneracy of cavity modes. © 2016, Allerton Press, Inc.
The production of prompt charmed mesons Dsup0/sup, Dsup+/sup and Dsup∗+/sup, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the centre-of-mass energy per nucleon pair, (Formula presented.) , of 2.76 TeV. The production yields for rapidity |y| < 0.5 are presented as a function of transverse momentum, pT, in the interval 1–36 GeV/c for the centrality class 0–10% and in the interval 1–16 GeV/c for the centrality class 30–50%. The nuclear modification factor RAA was computed using a proton-proton reference at (Formula presented.) TeV, based on measurements at (Formula presented.) TeV and on theoretical calculations. A maximum suppression by a factor of 5-6 with respect to binary-scaled pp yields is observed for the most central collisions at pT of about 10 GeV/c. A suppression by a factor of about 2-3 persists at the highest pT covered by the measurements. At low pT (1-3 GeV/c), the RAA has large uncertainties that span the range 0.35 (factor of about 3 suppression) to 1 (no suppression). In all pT intervals, the RAA is larger in the 30-50% centrality class compared to central collisions. The D-meson RAA is also compared with that of charged pions and, at large pT, charged hadrons, and with model calculations. © 2016, The Author(s).
Two-photon-induced Förster resonance energy transfer from water-solubilized CdSe/ZnS quantum dots (QDs) to the photosensitive protein bacteriorhodopsin (bR) is described. The two-photon absorption cross section (TPACS) of QDs at an excitation wavelength of 790 nm has been found to be about 20000 GM, which is two orders of magnitude larger than the maximal TPACS of bR. Therefore, the two-photon excitation of QDs in QD-bR systems is highly selective. The data obtained demonstrate the possibility to extend the effective spectral range of excitation of bR to the infrared region. This result paves a way to new applications of bR-QD hybrid materials in photovoltaics, biosensing, and optoelectronics. © 2016 Elsevier Ltd.
Electric collector investigations of the singleand multi-shot femtosecond laser ablation of optical-quality surfaces of different materials, including aluminum, copper, titanium, silicon, and graphite, show that the emission of erosion plasma is significantly lower than the energy density of laser ablation of these materials and replaces the dominant electron emission at lower energy densities. I–V characteristics and cumulative dependences of the collector signal are studied in the emission mode. The observed dependences of the electron and plasma emission signals on the laser pulse energy density are discussed. © 2016, Allerton Press, Inc.
Si/SiOx nanoparticles (NPs) produced by laser ablation in deionized water or aqueous biocompatible solutions present a novel extremely promising object for biomedical applications, but the interaction of these NPs with biological systems has not yet been systematically examined. Here, we present the first comprehensive study of biodistribution, biodegradability and toxicity of laser-synthesized Si-SiOx nanoparticles using a small animal model. Despite a relatively high dose of Si-NPs (20 mg/kg) administered intravenously in mice, all controlled parameters (serum, enzymatic, histological etc.) were found to be within safe limits 3 h, 24 h, 48 h and 7 days after the administration. We also determined that the nanoparticles are rapidly sequestered by the liver and spleen, then further biodegraded and directly eliminated in urine without any toxicity effects. Finally, we found that intracellular accumulation of Si-NPs does not induce any oxidative stress damage. Our results evidence a huge potential in using these safe and biodegradable NPs in biomedical applications, in particular as vectors, contrast agents and sensitizers in cancer therapy and diagnostics (theranostics).
Recent angle-resolved photoemission spectroscopy measurements of CaKFe4As4 report the presence of four superconductive gaps on different sheets of Fermi surface. The interesting aspect of this superconductor is that it is stoichiometric and with a high critical temperature. I show that the phenomenology of this superconductor can be explained in the framework of four-band s ± -wave Eliashberg theory choosing antiferromagnetic spin fluctuations as pairing glue. In particular, various experimental data reported in literature: the energy gaps, the critical temperature, the temperature dependence of the upper critical field, the penetration depth and the thermopower can be reproduced by this model in a strong-coupling regime with a small number of free parameters. © 2016 Elsevier B.V.
The great interest in upconversion nanoparticles exists due to their high efficiency under multiphoton excitation. However, when these particles are used in scanning microscopy, the upconversion luminescence causes a streaking effect due to the long lifetime. This article describes a method of upconversion microparticle luminescence lifetime determination with help of modified Lucy-Richardson deconvolution of laser scanning microscope (LSM) image obtained under near-IR excitation using nondescanned detectors. Determination of the upconversion luminescence intensity and the decay time of separate microparticles was done by intensity profile along the image fast scan axis approximation. We studied upconversion submicroparticles based on fluoride hosts doped with Yb3+-Er3+ and Yb3+-Tm3+ rare earth ion pairs, and the characteristic decay times were 0.1 to 1.5 ms. We also compared the results of LSM measurements with the photon counting method results; the spread of values was about 13% and was associated with the approximation error. Data obtained from live cells showed the possibility of distinguishing the position of upconversion submicroparticles inside and outside the cells by the difference of their lifetime. The proposed technique allows using the upconversion microparticles without shells as probes for the presence of OH- ions and CO2 molecules. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).
Morphofunctional disorders in unicellular aquatic protozoa – Spirostomum ambiguum infusorians after 30-, 60-, and 360-min exposure in electromagnetic field at a radiation frequency of 1 GHz and energy flow density of 50 μW/cm2 were analyzed by intravital computer morphometry. Significant disorders in morphometric values correlated with low mobility of the protozoa. The results suggested the use of intravital computer morphometry on the protozoa for early diagnosis of radiation-induced effects of the mobile communication electromagnetic field, for example, low mobility of spermatozoa. © 2016 Springer Science+Business Media New York
Specific features of plane-geometry nanocrystals (CdSe nanoplatelets) functioning in an organic–inorganic light emitting diode are analyzed. © 2016, Allerton Press, Inc.
Colloidal quantum dots (QDs) are semiconductor nanocrystals which exhibit strong photoluminescence and have a variety of applications in modern nanotechnology. Specifically, QDs may serve as source of photoelectrical response to optical excitation, thus paving the way to development of novel optoelectronic and photovoltaic QD-based systems and devices. QD photoexcitation gives rise to excitons, electron-hole pairs which are bound by Coulomb forces and may dissociate in such a way that the charge carriers leave the nanoparticle and interact with the environment. The surface of inorganic QDs is always covered with organic ligands ensuring their colloidal stability during the synthesis and subsequent processing. The possibility to control the composition of the surface ligands is considered a promising way to modulate different parameters of charge formation and separation in nanoparticles, including the secondary pathways of charge transfer, rates of carrier generation, radiative or nonradiative electron-hole recombination, and some others.The rates and directions of these processes strongly affect the fundamental photophysical properties of QDs, such as luminescence quantum yield, quenching, bleaching, blinking, and photostability; they also determine the applicability of nanocrystals to specific areas of photovoltaics, photocatalysis, and bioanalysis, as well as fabrication of light-emitting diodes (LEDs) and QD cellular automata (the transistorless computation paradigm).In this review we analyze recent advances in controlled charge generation, separation, and transfer in QD-based organic and inorganic systems, with a special emphasis on the role of the surface-stabilizing ligands in the transfer and separation of photogenerated charge carriers. The prospects of development of advanced QD-based photovoltaic and optoelectronic devices employing carefully selected surface ligands that improve the nanocrystal photophysical properties are analyzed in the "Summary and outlook" section. © 2016 Elsevier Ltd.
Research on the surface chemistry of quantum dots (QDs) has been rapidly developing in recent years, since the understanding of the processes that occur on their surface is prerequisite for successful exploration of the outstanding fluorescence properties and superior stability of these nanomaterials in numerous applications. The lack of stability during long-term storage under atmospheric conditions restricts QD applications. Here, we have investigated the interaction of QDs with carbon dioxide as a model system for studying their long-term storage or operation in atmospheric environment. Quenching of the photoluminescence of CdSe/ZnS semiconductor QDs continuously treated with CO2 has shown that this process depends on the type of the QD surface ligands. The luminescence of QDs capped with amine ligands is quenched to a higher degree, the quenching being caused by the formation of carbamic acid precipitate. The luminescence of QDs capped with thiols remain absolutely stable upon CO2 treatment due to the chemical resistance of thiol functional groups to CO2, which makes this type of QDs suitable for long-term storage and operation under atmospheric conditions. However, further functionalization of such QDs may be difficult, because the strong bond between thiol ligands and QD surface may limit the efficiency of ligand-exchange procedures. A new ligand system of alkylamine salts of fatty acids has been proposed as an alternative to thiols. It has been shown to be inert to CO2, and also can be easily replaced with functional surface ligands The results are important for development of next generation QDs with superior stability suitable for various applications requiring efficient ligand exchange and operation in the atmospheric environment.
Comparative investigations of homoepitaxial diamond films with natural and modified isotopic compositions, grown by chemical vapor deposition (CVD) on type-Ib diamond substrates, are carried out using double-crystal X-ray diffractometry and topography. The lattice mismatch between the substrate and film is precisely measured. A decrease in the lattice constant on the order of (Δa/a)relax ∼ (1.1–1.2) × 10sup–4/sup is recorded in isotopically modified sup13/supС (99.96%) films. The critical thicknesses of pseudomorphic diamond films is calculated. A significant increase in the dislocation density due to the elastic stress relaxation is revealed by X-ray topography. © 2016, Pleiades Publishing, Inc.
Xenon detector based gamma-ray spectrometer for a radioactive waste sorting complex and its characteristics are described. It has been shown that the "thin-wall" modification of the detector allows better registration of low-energy gamma rays (tens of keV). The spectrometer is capable of operation in unfavorable field conditions and can identify radionuclides of interest in less than 1 second.
In the present study, results towards the development of a 3D diamond sensor are presented. Conductive channels are produced inside the sensor bulk using a femtosecond laser. This electrode geometry allows full charge collection even for low quality diamond sensors. Results from testbeam show that charge is collected by these electrodes. In order to understand the channel growth parameters, with the goal of producing low resistivity channels, the conductive channels produced with a different laser setup are evaluated by Raman spectroscopy. © 2015 Elsevier B.V.
A comprehensive study of the interactions between lectins and glycoproteins possessing different glycosylation profiles in the composition of nanoparticles was carried out in order to find specifically interacting protein pairs for the creation of novel classes of multifunctional nanoagets that based on protein-assisted selfassembly. We obtained information about specific interactions of certain lectins with selected glycoproteins as well as about the ability of certain monosaccharides to competitively inhibit binding of glycoproteins with lectins. These protein-mediated interactions may be involved in the formulation of self-assembled nanoparticles for therapy and diagnostics of various diseases. © 2015, Pleiades Publishing, Ltd.
A method for detecting ultralow quantities of explosives in air with use a state-of-the-art picosecond chip Nd3+:YAG laser has been developed. The method combines field asymmetric ion mobility spectrometry (FAIMS) with laser ionization of examined air samples. Radiation of lambda= 266nm, tau(pulse) = 300ps, E-pulse = 30-150 mu J,. = 20-300Hz was used. Processes in the ion source for the use both picosecond and nanosecond ionization modes were analyzed. Parameters of the laser ion source have been specially optimized. The dependences on frequency, pulse energy, peak intensity, and average power for trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) were obtained. It was shown that the optimal peak intensity should be no less 3.10(6) W/cm(2). The detected ion signals for all explosives were shown to be threefold higher for picosecond excitation in comparison with use a nanosecond laser of the same average power. The estimated detection threshold of the prototype equals 1.10(-15) g/cm(3). The results are promising for the development of a highly sensitive, portable laser explosive detector.
Cytotoxic effects of a new targeted phototoxin DARPin-miniSOG and mechanism of its action were investigated in vitro. It was determined that DARPin-miniSOG causes light-induced death of HER2/neu-positive cancer cells (ICinf50/inf 0.8 μM). Treatment of the cells with DARPin-miniSOG in the presence of ascorbic acid eliminated the light-induced cytotoxic action of the protein. This observation suggests the involvement of oxidative stress in the mechanism of the phototoxin action. DNA fragmentation analysis, caspase-3 activity assay and PI-staining of HER2/neu-positive cancer cells treated with DARPin-miniSOG indicated that phototoxin induces necrotic cell death under blue light illumination. Co-localization analysis showed that DARPin-miniSOG accumulates mostly in endosomes and lysosomes. © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.
A method for quantitative investigation of affinity constants of receptors immobilized on magnetic nanoparticles (MP) is developed based on spectral correlation interferometry (SCI). The SCI records with a picometer resolution the thickness changes of a layer of molecules or nanoparticles due to a biochemical reaction on a cover slip, averaged over the sensing area. The method is compatible with other types of sensing surfaces employed in biosensing. The measured values of kinetic association constants of magnetic nanoparticles are 4 orders of magnitude higher than those of molecular antibody association with antigen. The developed method also suggests highly sensitive detection of antigens in a wide dynamic range. The limit of detection of 92 pg/ml has been demonstrated for prostate-specific antigen (PSA) with 50-nm MP employed as labels, which produce 3-order amplification of the SCI signals. The calibration curve features high sensitivity (slope) of 3-fold signal raise per 10-fold increase of PSA concentration within 4-order dynamic range, which is an attractive compromise for precise quantitative and highly sensitive immunoassay. The proposed biosensing technique offers inexpensive disposable sensor chips of cover slips and represents an economically sound alternative to traditional immunoassays for disease diagnostics, detection of pathogens in food and environmental monitoring.
A combined method of spectroscopic analysis of biochemical and structural markers of tumor changes, including blood volume, hemoglobin oxygen saturation, protoporphyrin IX accumulation, and change in the scattering properties, was developed on the basis of the results of simulation modeling of light propagation in media with optical properties similar to those of biotissues. The method was verified on a series of optical phantoms and applied in a clinical setting for intraoperative navigation with the aim of demarcation of glioblastoma multiforme borders. It was shown that the method developed is superior in sensitivity and specificity to the method of video-fluorescent visualization with a Carl Zeiss OPMI Pentero microscope and can be used for demarcation of the borders of tumors exhibiting infiltrative growth.
Emission spectra of LT-GaAs photoconductive antennas based on epitaxial films of "low-temperature" gallium arsenide (LT-GaAs) are measured in the terahertz frequency region by the Fourier transform spectroscopy. © 2015 The Authors.
A two-phase emission detector containing 5 kg of liquid Xe is installed at the horizontal experimental channel of the research nuclear reactor IRT MEPhI to measure the liquid Xe response to nuclei recoils with kinetic energies below 1 keV. Preliminary tests have demonstrated that ≥ 15 μs electron lifetime in liquid Xe and ~ 10 photoelectrons single ionization electron signal are achieved. These parameters are sufficient to detect and identify events at the single electron level.
A miniature γ probe for nuclear medicine based on a LaBr3:Ce scintillation crystal and a silicon photomultiplier is described. The γ ray detection efficiency is 29% for 137Cs (662 keV) and 70% for 57Co (122 keV). The spatial resolution and selectivity measured with a tungsten collimator for 57Co are 8 mm and 26°, respectively.
The absorption of powerful laser radiation in a porous material is investigated theoretically and numerically. The behavior of the medium during the process of pores filling in the heated region is described by a model of viscous homogenization. The porous material is described as a partially homogenized plasma where the density within the pores increases with time from zero to an average density of the porous substance depending on the ratio of laser pulse duration and homogenization time. An expression describing the time and space dependence of the absorption coefficient of laser radiation in such a material is derived. The initial pore's sizes, the average density of the material and the laser intensity are the parameters of the model. The absorption of a nanosecond laser pulse in totally ionized plasma of porous material of light elements is investigated numerically within the present model. The calculations are performed for porous media with an average density larger or smaller than the critical density of the laser-produced plasma. For the latter, the results are compared with those for a homogeneous plasma with the same density.
We demonstrate new simple methods of all-laser fabrication of nanoantenna (nanojet) with an additional elements for coupling/focusing of surface plasmon-polaritons (SPPs). The first method is realized by using an aluminum (Al) plasmonic lens irradiated by a linearly polarized femtosecond laser pulse at fluences higher than the ablation threshold of aluminum. The resulting plasmonic lenses contain single nanojets in their centers owing to focusing of intense surface plasmon-polaritons and melt expulsion in the locally heated area. Such surface structure resembles a parabolic antenna, which has a receiver and focusing reflector. The second method is based on double-shot femtosecond laser nanoablation of thin supported metallic (Au) film. The first fs-laser pulse produces nanojet, standing on bump of microscale diameter. Irradiation by spatially shifted (on several microns) second laser pulse results in the bump removing, transition of nanojet into nanosphere and formation of concentric periodical semi-rings. Resulted surface structure represents nanoantenna (gold nanospere), surrounded by plasmonic lens, delivering more incident energy to the nanoantenna.
Fluorescence spectra and quantum yield of graphitic (g-Cinf3/infNinf4/inf) and spherical (s-Cinf3/infNinf4/inf) modifications of carbon nitride were measured. It was found that the intensity of the fluorescence at the maximum is more than two orders as high for carbon nitride spheres as for graphitic carbon nitride particles. The high value of the fluorescence quantum yield (QY), up to 32% at excitation 532 nm and 38% at excitation 633 nm, was attributed to the spherical shape of this form of carbon nitride. One of the interesting features of the fluorescence excited in s-Cinf3/infNinf4/inf is the high intensity of the anti-Stokes fluorescence. © 2015 Elsevier B.V. All rights reserved.
In this report the efficacy of extracellular pharmaceutical Gd-DTPA in Binary Radiotherapy was studied. The study was carried out in mice bearing transplantable adenocarcinoma Ca755 using X-ray based contrast enhanced radiotherapy as a practical implementation of Binary Radiotherapy. It was shown that intravenous administration of 0.3. ml of 0.5. M water solution of Gd-DTPA followed by X-irradiation at a dose of 10. Gy provides T/C%=10±3% and leads to complete tumor regression in 25% of mice. © 2015 Elsevier Ltd.
The application of digital methods for spectrometric observations by example of space projects executing at MEPhI is described. Some aspects of using schematic solutions and electronic component base are discussed. The example of realisation of space born spectrometer is presented. © 2015 The Authors.
The influence of transverse mode locking in critical cavity configurations on the threshold pump power of diode end-pumped solid-state lasers was investigated both theoretically and experimentally for the large portion of the cavity stability region. An experimental study was performed for lasers based on Nd:YLF, Nd:YVO4, Nd:GdVO4 and Nd:KGW crystals.
The structure of the shock and thermal waves in the air in the expansion of the plasma is investigated. Simulations have shown that the characteristics of plasma formation, the occurrence of shock and heat waves are dependent on a number of influence parameters and environment properties. The nature of the interaction of thermal and hydrodynamic flow quality varies with the magnitude of the thermal conductivity of the medium. High thermal conductivity leads to thermal waves of two different types subsonic and supersonic. The structure of the solutions of supersonic mode is represented as two consecutive waves thermal and hydrodynamic. The subsonic structure of the solution presented in the form of three waves: the isothermal shock wave located between the two (subsonic and supersonic) thermal waves. To solve nonlinear equations of hydrodynamics with a thermal conductivity we use finitedifference approach, combined with the procedure of dynamic adaptation of the computational grid that allows us to explicitly locate the strong (shock waves) and weak (thermal wave front) discontinuities. Visualization and analysis of the results of calculations on a grid containing 30 nodes are carried out in comparison with selfsimilar solutions found for similar problems. The work was financially supported by the Russian science Foundation (project code 151100032).
Craters on the surface of an yttrium-aluminum garnet crystal plate under irradiation by nanosecond laser pulses with an intensity of 10sup9/sup–10sup10/sup W/cmsup2/sup and a wide (∼500Å) spectrum have been studied. The mechanism of crater formation as a result of plastic deformation of the surface during the laser action has been discussed. The proposed mechanism takes into account specific features of nonlinear effects under the action of a broadband radiation on the medium. In the stimulated Brillouin scattering of pumping radiation, acoustic waves transform into shock waves, on the fronts of which stimulated Raman scattering develops. As a result, crystal lattice defects formed on the shock-wave fronts are dragged in the direction of pumping, which leads to a high-rate deformation of the crystal surface. © 2015, Pleiades Publishing, Ltd.
The nuclear modification factor, R-AA, of the prompt charmed mesons D-0, D+ and D*+, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy root s(NN) = 2 : 76 TeV in two transverse momentum intervals, 5 p(T) 8 GeV/c and 8 p(T) 16 GeV/c, and in six collision centrality classes. The R-AA shows a maximum suppression of a factor of 56 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the R-AA of non-prompt J/psi from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions.
We present a measurement of inclusive J/psi production in p-Pb collisions at root S-NN = 5.02 TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. The measurement is performed with the ALICE detector down to zero transverse momentum, p(T), in the backward (-4.46 y(cms) -2.96) and forward (2.03 y(cms) 3.53) rapidity intervals in the dimuon decay channel and in the mid-rapidity region (-1.37 y(cms) 0.43) in the dielectron decay channel. The backward and forward rapidity intervals correspond to the Pb-going and p-going direction, respectively. The p(T)-differential J/psi production cross section at backward and forward rapidity is measured for several centrality classes, together with the corresponding average p(T) and p(T)(2) values. The nuclear modification factor is presented as a function of centrality for the three rapidity intervals, and as a function of p(T) for several centrality classes at backward and forward rapidity. At mid-and forward rapidity, the J/psi yield is suppressed up to 40% compared to that in pp interactions scaled by the number of binary collisions. The degree of suppression increases towards central p-Pb collisions at forward rapidity, and with decreasing p(T) of the J/psi. At backward rapidity, the nuclear modification factor is compatible with unity within the total uncertainties, with an increasing trend from peripheral to central p-Pb collisions.
We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at root s(NN) = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N-part) or the number of nucleon-nucleon binary collisions (N-coll) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the N-part dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-pT the p-Pb spectra are found to be consistent with the pp spectra scaled by N-coll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.
A novel facile method of non-doped and fluorescent terbium-doped cerium fluoride stable aqueous sols synthesis is proposed. Intense green luminescence of CeF3:Tb nanoparticles can be used to visualize these nanoparticles' accumulation in cells using confocal laser scanning microscopy. Cerium fluoride nanoparticles are shown for the first time to protect both organic molecules and living cells from the oxidative action of hydrogen peroxide. Both non-doped and terbium-doped CeF3 nanoparticles are shown to provide noteworthy protection to cells against the vesicular stomatitis virus.
At the ion accelerator HELIS at LPI, the neutron yield is investigated in DD reactions within a strongly textured polycrystalline deuterium-saturated CVD diamond under irradiation by a deuterium ion beam with the energy of less than 30keV. The measurements of the neutron flux in the beam direction are performed using a multichannel detector based on 3He counters, in dependence on the target angle, ?, with respect to the beam axis. A significant anisotropy in the neutron yield is observed. At ? =0° the yield is higher by a factor of 3 as compared to that at ? =±45°. The possible reasons for the anisotropy, including ion channeling, are discussed.
The differential charged jet cross sections, jet fragmentation distributions, and jet shapes are measured in minimum bias proton-proton collisions at center-of-mass energy root s = 7 TeV using the ALICE detector at the LHC. Jets are reconstructed from charged particle momenta in the midrapidity region using the sequential recombination k(T) and anti-k(T) as well as the SISCone jet finding algorithms with several resolution parameters in the range R = 0.2-0.6. Differential jet production cross sections measured with the three jet finders are in agreement in the transverse momentum (p(T)) interval 20 p(T)(jet,ch) 100 GeV/c. They are also consistent with prior measurements carried out at the LHC by the ATLAS Collaboration. The jet charged particle multiplicity rises monotonically with increasing jet p(T), in qualitative agreement with prior observations at lower energies. The transverse profiles of leading jets are investigated using radial momentum density distributions as well as distributions of the average radius containing 80% ( R-80 ) of the reconstructed jet p(T). The fragmentation of leading jets with R = 0.4 using scaled p(T) spectra of the jet constituents is studied. The measurements are compared to model calculations from event generators (PYTHIA, PHOJET, HERWIG). The measured radial density distributions and R-80 distributions are well described by the PYTHIA model (tune Perugia-2011). The fragmentation distributions are better described by HERWIG.
We present modification of difference frequency generator of coherent THz radiation in a nonlinear GaSe crystal using dual-wavelength diode-pumped solid-state Nd:YLF laser. Generation at the two wavelengths (1.047 and 1.053 μm) was carried out by equalization of the gains at these wavelengths near the frequency degeneracy of the transverse modes in resonator cavity, Q-switched by acousto-optical modulator. The main parameters of the device were measured: angular synchronism (width 0.6 degrees), polarization ratio (1:100), conversion efficiency (10-7), pulse power (0.8 mW), frequency and width (53,8 μm-1, 0,6 μm-1), pulse width and repetition rate (10 ns, 7 kHz). The method is promising for practical purposes. © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.
We report the first measurement at the LHC of coherent photoproduction of ρsup0/sup mesons in ultra-peripheral Pb-Pb collisions. The invariant mass and transverse momentum distributions for ρsup0/sup production are studied in the πsup+/supπsup−/sup decay channel at mid-rapidity. The production cross section in the rapidity range |y| < 0.5 is found to be dσ/dy = 425 ± 10(stat.)inf− 50/inf sup+ 42/sup (sys.) mb. Coherent ρsup0/sup production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. The results are compared with those from lower energies and with model predictions. © 2015, The Author(s).
We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultra-peripheral Pb. Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S)→l+l- and ψ(2S)→J/ψπ+π- decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb-1. The cross section for coherent ψ(2S) production in the rapidity interval -0.9<y<0.9 is dσψ(2S)coh/dy=0.83±0.19(stat+syst) mb. The ψ(2S) to J/ψ coherent cross section ratio is 0.34-0.07+0.08(stat+syst). The obtained results are compared to predictions from theoretical models. © 2015 CERN for the benefit of the ALICE Collaboration.
The time of visualization of proliferation centers of glial tumors in rats by the contrastenhanced magnetic resonance imaging (MRI) has been reduced up to 3 - 4 days since inoculation by consecutive intravenous injections of dextran-ferrite (DF) nanoparticles and gadolinium-based contrast agent Magnevist®. The well controllable conditions for combined photodynamic magnetothermochemotherapy of the revealed tumors have been achieved by MRI and quantified mapping of the DF particles in the rat’s organs and tumors realized by an electronic sensor with inductive coils using non-linear magnetization of the particles. As a result of the proposed therapy, the life span of the rats with glioma (GC6) and glioblastoma (GB 101/8) increased by up to 166% and 74%, respectively. © (2015) Trans Tech Publications, Switzerland.
We demonstrate the operation of a room-temperature, solid-state, broadly tunable Cr-doped CdSe single-crystal continuous-wave laser. Longitudinal pumping with a continuous-wave diode laser array at 1.94 μm produced a broadband output of 280 mW at 2.6 μm with an incident power slope efficiency of 12%. With an intracavity Brewster-cut CaF2 prism, we tuned the Crsup2+/sup:CdSe laser from 2.45 to 3.06 μm with a resolution of 10 nm and an output power up to 55 mW. © 2015 Astro Ltd.
In inertial fusion power research, a considerable attention has recently been focused on the ability to inexpensively fabricate large quantities of targets by developing a specialized layering module of repeatable operation. The targets must be free-standing, or unfixed. Therefore, the development of a target factory for inertial confinement fusion (ICF) is centered at methods that can ensure a cost-effective target production with high-repeatability. Tritium inventory minimization (i.e. minimization of time and space for all production steps) is a necessary condition as well. Additionally, the cryogenic hydrogen fuel inside the targets must have such a structure (ultrafine layers - the grain size should be scaled back into the nanometer range), which supports the fuel layer survivability under target injection and transport through the reactor chamber. To meet the above requirements, at the Lebedev Physical Institute (LPI), significant progress has been made in the technology development based on rapid fuel layering inside moving free-standing targets, which refers to as FST (free-standing target) layering method. As a result of research, the LPI gained a unique experience in the development of the FST-layering module for target fabrication with an ultrafine fuel layer, including a reactor-scaled target design. This experience will be used at the development of the next-generation FSTlayering module for construction of a prototype of the target factory for power laser facilities and inertial fusion power plants.
Long-term research effort of the Lebedev Physical Institute (LPI) results in creation of a unique technology of rapid free-standing target (FST) production for continuous supply with a cryogenic hydrogen fuel of the burn area in the ICF facilities. A fundamental difference of the FST layering method from generally accepted approaches is that it works with moving unmounted targets, which allows one to economically fabricate large quantities of such targets and to continuously (or at a required rate) inject them at the laser focus. For that very reason the FST layering method is a promising candidate for development of ICF transmission line at a high rep-rate capability intended for using in future power plants for process engineering. In this paper, the original results of the theoretical and experimental work in the scope of cryogenic layers formation with an ultrafine structure are presented. Such layers have a potential to advance materials for application to fusion targets fabrication in the form that meets the requirements of implosion physics. They are referred to as layers with self-inherent survival features that is of critical importance for finished target delivery into ICF reaction chamber.
One of the major tasks in controlled inertial confinement fusion (ICF) now is the development of scientific, engineering and technologi-cal basis for mass production of cryogenic hydrogen fuel encapsulated in ICF targets. To demonstrate ICF as a power source, the targets must be accurately delivered to the focus of a power laser facility or ICF reactor at a rate of 1-10 Hz. In this paper, a comparative ana-lysis of state-of-the-Art in the world in the field of target fabrication and transport in the ICF systems is presented. The paper also summa-rizes the results of theoretical and experimental efforts in Russia and describes a unique free-standing (FST) fabrication technology, which can serve as a basis for ICF reactor fueling. Now there is an advanced scientific and technological groundwork for designing and building of the world's first target FST factory for a pilot ICF-plant with continuous delivery of the cryogenic hydrogen fuel into the ICF burn area.
The Lebedev Physical Institute (LPI) has outstanding achievemens in the development of structure-sensitive methods for cryogenic fuel layer formation with a required structure. For the first time, it was demonstrating that cryogenic hydrogen fuel (hydrogen isotopes and their mixtures) can be obtained in the form of ultrafine modifications or nanosystems, which exhibit peculiar and interesting mechanical and physical properties. Comparative investigations of different structural modifications have shown that the fuel layer in an ultrafine state (type of glassy hydrogen) can serve acute problems on survivability of fuel layers within ICF targets during their delivery to the reactor chamber. Among them are minimization of the target injection temperature, reducing the rate of heat-and-mass transfer, minimization of the temperature gradient on the layer surface. Distinctive features of the ultrafine fuel layers allow defining them as a new type of the solid fuel, which has enhanced mechanical strength and thermal stability in the process of target acceleration and injection in the area of a thermonuclear burn.
Stimulated Raman scattering has been discovered in a monoisotopic 13C diamond single crystal grown by chemical vapor deposition. The first results of the experimental study of impulsive χ(3)-nonlinear lasing under femtosecond IR pumping are presented. © 2015, Pleiades Publishing, Ltd.
We show that the phenomenology of the iron chalcogenide superconductor FeTe1-xSex can be explained within an effective three-band s +/--wave Eliashberg model. In particular, various experimental data reported in literature-the critical temperature, the energy gaps, the upper critical field, the superfluid density-can be reproduced by this model in a moderate strong-coupling regime provided that both an intraband phononic term and an interband antiferromagnetic spin-fluctuations term are included in the coupling matrix. The intraband coupling is unusual in Fe-based compounds and is required to explain the somehow anomalous association between gap amplitudes and Fermi surfaces, already evidenced by ARPES.
Single-crystalline diamond plates were implanted by He+ ions with a set of energies and fluences that ensure uniform radiation damage (RD) in a 670-nm-thick layer. Implantation is carried out at a wide range of fluences, which allows one to cover the range of RD levels from very low to complete graphitization of diamond. Using the measurement data on the bending of diamond plates and the surface swelling of the ion-implanted material, we calculate the mechanical stress and the density of diamond for various levels of RD. Diamonds with various levels of RD are investigated by the Raman scattering and optical transmission methods. We establish that, above the graphitization threshold, the diamond phase almost completely disappears as the RD level increases, while the fraction of sp 2 material sharply increases. Such a material is unexpectedly ductile. It cannot be restored to diamond even by annealing under a pressure corresponding to thermodynamic stability of diamond.
Sensing with semiconductor colloidal quantum dots (QDs) is driven by attractive properties of these fluorophores such as spectrally narrow and tunable emission and broad absorption spectra, which enable simultaneous excitation of fluorescence of different colors. The possibility of lasing upon inclusion of QDs into microcavities offers new opportunities for highly sensitive sensing. Here, we discuss the fundamental properties of QDs, the principles of lasing from QDs, and potential applications of the effect of QD lasing to diagnostics and ultrasensitive sensing. © 2015 IEEE.
Hot electrons created in laser plasma interaction at laser intensities 1 - 10 PW cm - 2 in shock ignition scheme can deposit their energy in the shell of the target, augmenting the strength of the ignitor shock. Here, we present a model that describes the effect of the spatial profile of fast electron energy deposition on the dynamics of shock wave formation. A criterion of a strong shock formation is obtained for an arbitrary electron beam distribution function. It is shown that the time and the position of the shock formation are defined by the electron average stopping range, while the strength of the shock decreases as the width of electron energy distribution increases. The latter feature is explained by the fast electron target preheat. The conclusions of theoretical model are confirmed in numerical simulations. The pressure, the strength of the shock, and the efficiency of shock generation are calculated for different electron distributions with the same average stopping range. © 2015 AIP Publishing LLC.
With the use of a novel thermoluminescence technique, a new type of surface traps is observed in colloidal CdSe nanocrystals of planar geometry (nanoplatelets). The emptying of these traps, which cannot be detected by means of the conventional thermally stimulated luminescence scheme, proceeds via a cascade process involving their own excited states. An energy-level diagram of nanoplatelets taking into account the specific characteristics of these traps is proposed and the density of surface states, featuring two peaks at energies of 100 and 280 meV, is determined. © 2015, Pleiades Publishing, Ltd.
Compact single-domain antibodies (sdAbs) are nearly 13 times smaller than full-size monoclonal antibodies (mAbs) and have a number of advantages for biotechnological applications, such as small size, high specificity, solubility, stability, and great refolding capacity. Carcinoembryonic antigen (CEA) is a tumor-associated glycoprotein expressed in a variety of cancers. Detection of CEA on the tumor cell surface may be carried out using anti-CEA antibodies and conventional fluorescent dyes. Semiconductor quantum dots (QDs) are brighter and more photostable than organic dyes; they provide the possibility for labeling of different recognition molecules with QDs of different colors but excitable with the same wavelength of excitation. In this study, the abilities for specific detection of CEA expressed by tumor cells with anti-CEA sdAbs biotinylated in vitro and in vivo, as well as with anti-CEA mAbs biotinylated in vitro, were compared using flow cytometry and the conjugates of streptavidin with QDs (SA-QDs). The results demonstrated that either in vitro or in vivo biotinylated anti-CEA sdAbs are more sensitive for cell staining compared to biotinylated anti-CEA mAbs. The data also show that simultaneous use of biotinylated sdAbs with highly fluorescent SA-QDs can considerably improve the sensitivity of detection of CEA on tumor cell surfaces. (C) 2015 Elsevier Inc. All rights reserved.
The method for experimental determination of the sensitivity and detection threshold of the interferometer phase is proposed. Based on the method the indicated parameters for an adaptive fiber-optic interferometer are estimated using the dynamic hologram formed in the photorefractive CdTe crystal.
Monoclonal antibodies (mAbs) are often too big for the nanoparticle targeting purpose and the conditions used for their conjugation provide nanoprobes with irregular orientation of mAbs on the surface of nanoparticle. Here, we are reviewing our recent publications reporting on ultra-small nanoprobes engineered through oriented conjugation of quantum dots (QDs) with 13-kDa single-domain antibodies (sdAbs) derived from llama and produced in E. coli. Developed nanoprobes with hydrodynamic diameter below 12 nm contain four homogeneously oriented copies of sdAbs on the surface of each QD. They demonstrated excellent specificity and sensitivity for the quantitative detection of rare biomarker-expressing cells using flow cytometry. The higher diffusibility of sdAbs enables immunohistochemical analysis of thick tissues not accessible to mAbs. The data shows that sdAbs-QD conjugates lead to biopsy tissue labelling displaying an equivalent or even better quality than that obtained with gold standard immunohistochemical diagnostics. Developed sdAbs-QD nanoprobes should find numerous applications in multiplexed high-throughput diagnostics and FRET-based detection platforms. © 2015 IEEE.
A 3-channel biosensor based on spectral correlation interferometry (SCI) has been adapted for direct optical detection of antigens by measuring changes in thickness of a biolayer on functionalized glass slips employed as affordable single-use sensor chips. The instrument is insensitive to the bulk refractive index of a solution under test and provides signals in metrological units (pm or nm). Using real-time monitoring with the SCI, protocols for fabrication of sensor chips with different functional (epoxylated, carboxylated, and biotinylated) surfaces for antibody immobilization have been developed and optimized to minimize chip-to-chip variations and achieve better limit of detection (LOD), shorter assay time, and longer shelf life. The optimized coupling surfaces have been compared for detection of human serum albumin (HSA) used as a model agent of medical significance. The dynamic ranges for measuring the HSA concentration were 0.07–20, 0.12–30, and 0.25–10 μg/ml, and the assay durations were less than 20, 15, and 30 min for the epoxylated, carboxylated, and biotinylated chips, respectively. The advantages of each type of sensor chip have been shown, namely, the carboxylated chips feature the shortest assay time, the epoxylated ones demonstrate the best LOD, and the biotinylated chips exhibit the longest shelf life in an unprotected environment. The developed protocols of antibody immobilization can be used in different biosensors and assay techniques including those based on fluorescent, magnetic or plasmonic labels, etc. The SCI is well compatible with various partially transparent layers used in biosensing and with microarrays for multi-analyte detection.
Dissociation of trinitrotoluene (TNT) sorbed on porous silicon (pSi) surface under UV laser irradiation has been studied. A method based on ion mobility spectrometry (IMS) has been used in this study. Excitation and ionization of TNT molecules has been occurred at atmospheric pressure. A dependence of TNT ion spectrum on standing time of TNT molecules on pSi surface has been demonstrated. The ion type has changed from (TNT-H) - to (TNT-NO2) - which indicates a slow chemical reaction between pSi surface and TNT molecules. The first step of (TNT-NO2) - formation has been found to be a result of laser stimulated surface dissociation and subsequent desorption of a neutral TNT-NO2 fragment. The second step of (TNT-NO2) - formation is a capture of an electron emitted from the pSi surface under laser irradiation. The result of this study could be used in the area of explosive detection. © 2015 The Authors.
The work is devoted to the study of sizes and concentrations of proteins, and their aggregates in blood plasma samples, using static and dynamic light scattering methods. A new approach is proposed based on multiple repetition of measurements of intensity size distribution and on counting the number of registrations of different sizes, which made it possible to obtain statistically confident particle sizes and concentrations in the blood plasma. It was revealed that statistically confident particle sizes in the blood plasma were stable during 30 h of observations, whereas the concentrations of particles of different sizes varied as a result of redistribution of material between them owing to the protein degradation processes. © 2014 Society of Photo-Optical Instrumentation Engineers. © 2015 SPIE.
A 60mW output power has been achieved in mid-UV (λ=270nm) spontaneous sources with electron-beam pulse-scanning pumping, fabricated from AlGaN MQW heterostructures grown by PA MBE on c-Al2O3 substrates. Under the CW pumping at much lower excitation power density the mid-UV sources demonstrate a 4.7mW output power. In that regime the power efficiency of the structures is about 0.24%, while their internal quantum efficiency is estimated to be as high as 50%.
The electrooptical characteristics of organic light-emitting diodes with quantum dots passivated with organic ligands of different lengths as emitting centers are investigated. It is established that the thickness of the ligand coating covering the quantum dots has little effect on the Förster energy transfer in the diodes, but significantly affects the direct injection of charge carriers into the quantum-dot layer. It is shown that the thickness of the passivation coating covering the quantum dots in a close-packed nanoparticle layer is deter- mined both by the length of passivating ligands and the degree of quantum-dot coverage with ligands. © 2015, Pleiades Publishing, Ltd.
The organic ligands passivating the surface of semiconductor quantum dots (QDs) and the solvents used strongly determine the photostability of QD solutions. Highly purified QD solutions in chloroform have been shown to photodegrade upon pulsed ultraviolet (UV) irradiation, irrespectively of the type of surface ligand. However, the photostability of QDs dissolved in n-octane, a more photochemically inert solvent, strongly depends on the ligands passivating their surface. In n-octane, hexadecylamine-coated QDs are completely stable and display no photochemical response to pulsed UV laser irradiation. In solutions of octanethiol-capped QDs, the photoluminescence intensity slightly decreases under irradiation. QDs coated with trioctylphosphine oxide exhibit a more complex pattern of photobleaching, which depends on the initial value of fluorescence quantum yield of QDs. This complex pattern may be accounted for by two competing processes: (1) ligand photodesorption accompanied by photobleaching due to specific alignment of the band levels of QDs and highest occupied molecular orbital of the ligand and (2) photoinduced decrease in the population of trapping states. Furthermore, practically no thermodynamic degradation of QD solutions has been observed for the micromolar QD concentration used in the study, in contrast to lower concentrations, thus confirming the photoinduced origin of the changes caused by UV irradiation. Obtained results show that the photostability of QDs may be strongly increased by careful selection of the ligands passivating their surface and the solvents used in the experiments.
Experiments with full-colour mFISH chromosome painting have revealed high yield of radiation-induced complex chromosomal aberrations (CAs). The ratio of complex to simple aberrations is dependent on cell type and linear energy transfer. Theoretical analysis has demonstrated that the mechanism of CA formation as a result of interaction between lesions at a surface of chromosome territories does not explain high complexes-to-simples ratio in human lymphocytes. The possible origin of high yields of γ-induced complex CAs was investigated in the present work by computer simulation. CAs were studied on the basis of chromosome structure and dynamics modelling and the hypothesis of CA formation on nuclear centres. The spatial organisation of all chromosomes in a human interphase nucleus was predicted by simulation of mitosis-to-interphase chromosome structure transition. Two scenarios of CA formation were analysed, 'static' (existing in a nucleus prior to irradiation) centres and 'dynamic' (formed in response to irradiation) centres. The modelling results reveal that under certain conditions, both scenarios explain quantitatively the dose-response relationships for both simple and complex γ-induced interchromosomal exchanges observed by mFISH chromosome painting in the first post-irradiation mitosis in human lymphocytes. © The Author 2015.
We report on the fabrication of a hybrid light-emitting-diode based on colloidal semiconductor CdSe nanoplatelets as emitters and organic TAZ [3-(Biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole] and TPD [N, N?-bis (3-methylphenyl)-N, N?-bis (phenyl)-benzidine] materials as the electron and hole transporting layers. Electroluminescent and current-voltage characteristics of the developed hybrid device with the turn-on voltage of 5.5 V and the radiation wavelength of 515 nm have been obtained. Semiconductor nanoplatelets like CdSe are attractive for the fabrication of hybrid LEDs with low operating voltages, spectrally pure color and short-wavelength electroluminescence, which is required for RGB devices.
We report on the results of studying quasi-two-dimensional nanostructures synthesized here in the form of semiconducting CdSe nanoplatelets with a characteristic longitudinal size of 20–70 nm and a thick-ness of a few atomic layers. Their morphology is studied using TEM and AFM and X-ray diffraction analysis; the crystal structure and sizes are determined. At room and cryogenic temperatures, the spectra and kinetics of the photoluminescence of such structures (quantum wells) are investigated. A hybrid light-emitting diode operating on the basis of CdSe nanoplatelets as a plane active element (emitter) is developed using the organic materials TAZ and TPD to form electron and hole transport layers, respectively. The spectral and current-voltage characteristics of the constructed device with a radiation wavelength λ = 515 nm are obtained. The device triggering voltage is 5.5 V (visible glow). The use of quasi-two-dimensional structures of this type is promising for hybrid light-emitting diodes with pure color and low operating voltages. © 2015, Pleiades Publishing, Inc.
Emission of erosive plasma has been observed during electric probe and optical emission spectral measurements of plumes produced by single-shot femtosecond laser ablation of optical-quality surfaces of various materials—copper, titanium, and silicon—at laser fluences well below the corresponding thermal ablation thresholds, replacing presumably electron emission at lower fluences. The onset of erosive plasma correlates on the fluence scale with saturation of dependences of self-reflectivity of the pumping femtosecond laser pulses, reflecting the “freezing” of electron dynamics (variation of electron density or temperature) during the pumping pulses, despite the monotonically increasing laser fluences. © 2015, Pleiades Publishing, Inc.
The results of the study of laser plasma generated by nanosecond laser radiation with controlled spatial coherence incident on various targets containing gadolinium are presented. X-ray radiation of such plasma is studied using an X-ray diagnostic system developed and fabricated by the authors. Metal gadolinium, gadolinium oxide, gadolinium and aluminum alloy, and aluminum were used as targets. The electron temperature of generated plasma and the efficiency of laser-to-X-ray radiation conversion are estimated; the emitting region sizes are determined. Particular attention is paid to the study of laser plasma spectra in the X-ray region near the wavelength of 6.7 nm. © 2015, Allerton Press, Inc.
In this work we present the results of the resonance energy transfer study in bio-nanohybrid structures, engineered on the basis of semiconductor quantum dots (QD) and photosensitive membrane protein bacteriorhodopsin (bR) in purple membranes (PM) under one- and two-photon excitation. We showed the formation of bio-nanohybrid complexes between QDs and PMs and we also showed the Forster resonance energy transfer (FRET) from QDs to bR under one-photon excitation. The measured two-photon absorption cross-section (TPACS) of QDs was about two orders of magnitude larger than TPACS of bR and consequently the two-photon excitation of QDs in hybrid structure is highly selective. It was found that FRET in bio-nanohybrid system of QDs and bR under two-photon excitation is possible and the FRET efficiency was sufficient to initiation of bR photocycle. Studying of energy transfer between QDs and bR gives the perspective of considerable improvement of bR light absorption and consequently extends the possible applications of this photo-converting material. Additionally we showed that the two-photon excitation of QDs in QD-bR hybrid material makes possible the initiating of bR photocycle in the infrared spectral range. © 2015 The Authors.
The interaction of slighly relativistic femtosecond laser radiation with microstructured Si targets was studied. The microstructuring was performed by nanosecond pulse laser ablation with additional chemical etching of the target material. An analysis was made of the optical damage under the action of femtosecond radiation near the ablation threshold. It was experimentally demonstrated that the hot electron temperature increases appreciably in the laser-driven plasma (from ∼370 to almost 500 keV) as well as radiation yield in the MeV range at the interaction of a high power femtosecond laser pulse with a microstructured surface in comparison with a flat surface. Numerical simulations using 3D3V PIC code Mandor revealed that the charged particle energy growth is caused by the stochastic motion of electrons in the complex field formed by the laser field and the quasistatic field at the sharp tips of micromodifications. © 2015 Astro Ltd.
Hybrid systems with luminophores embedded in a matrix attract much interest in areas of sensors and photonic elements. The use of photonic crystals as the matrices allows controlling the propagation and distribution of light emitted by the luminophore, which could improve the sensitivity of sensors and performance of photonic elements. We have investigated the luminescent properties of CdSe/CdS/Zns quantum dots embedded in a porous silicon Bragg mirror using simple technique based on capillary effect. For the first time an angular dependence of the photoluminescence spectrum has been measured. We have found that luminescence spectrum has been found to depend on the shape of the Bragg mirror reflection spectrum. Enhancement of QD PL at the wavelength corresponding to the edge of the photonic band gap of the photonic crystal has been demonstrated. © 2015 The Authors.
Interactions of oxidized detonation nanodiamond and carbon dots with protic solvent molecules in suspensions of water, methanol, and isopropyl alcohol were studied by Raman and fluorescence spectroscopy. The structure of the solvent at the interface with nanoparticles and the strength of the hydrogen bonds between the functional groups on the surface of the nanoparticles and the solvent molecules depend on the type of solvent. The molecules of the solvent affect the fluorescent properties of the nanoparticles. It was found that the more intense fluorescence of nanoparticles corresponds to weaker hydrogen bonding between the surface of the carbon nanoparticles and the surrounding molecules of the solvent. The mechanism of mutual influence of the carbon nanoparticles and the solvent on the properties of each other has been suggested. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
We have successfully synthesized Eu-based luminophores promising for inkjet printing with almost 100% efficiency of energy transfer from ligands to the lanthanide ion. The luminophores with β-diketonate ligands are characterized by means of optical spectroscopy. We reveal the impact of different types of β-diketonates on the quantum yield of luminescence and determine a β-diketonate complex exhibiting the highest luminescence quantum yield and promising for organic light-emitting diode (OLED) applications. We discuss the reasons for decreasing quantum efficiencies of other types of investigated ligands. © 2015 Springer Science+Business Media New York
In this work the formation of laser-induced periodic surface structures (LIPSS) on a titanium surface upon irradiation by linearly polarized femtosecond (fs) laser pulses with a repetition rate of 1 kHz in air environment was studied experimentally. In particular, the dependence of high-spatial-frequency-LIPSS (HSFL) characteristics on various laser parameters: fluence, pulse number, wavelength (800 nm and 400 nm), pulse duration (10 fs - 550 fs), and polarization was studied in detail. In comparison with low-spatial-frequency-LIPSS (LSFL), the HSFL emerge at a much lower fluence with orientation perpendicular to the ridges of the LSFL. It was observed that these two types of LIPSS demonstrate different fluence, shot number and wavelength dependencies, which suggest their origin is different. Therefore, the HSFL formation mechanism cannot be described by the widely accepted interference model developed for describing LSFL formation. (C) 2015 Optical Society of America
A conceptual model of the expert system (ES) of hemoglobinopathy diagnostics is considered. The ES core is the knowledge base (KB) including grouped data on qualitative and quantitative blood indicators, among which is the amount of membrane-bound hemoglobin, i.e., a new indicator in hematological practice. Quantitative indications are complemented by qualitative ones reflecting morphological changes of pathological erythrocytes. The presented ES is a tool for supporting doctor decision making in hemoglobinopathy diagnostics. © 2015, Allerton Press, Inc.
Results are presented from a series of experimental and theoretical studies on creating weakly ionized extended plasma channels in atmospheric air by 248-nm UV laser radiation and their application to control long high-voltage discharges. The main mechanisms of air ionization by UV laser pulses with durations from 100 fs to 25 ns and intensities in the ranges of 3×1011–1.5×1013 and 3×106–3×1011 W/cm2, respectively, which are below the threshold for optical gas breakdown, as well as the main relaxation processes in plasma with a density of 109–1017 cm−3, are considered. It is shown that plasma channels in air can be efficiently created by amplitude-modulated UV pulses consisting of a train of subpicosecond pulses producing primary photoelectrons and a long UV pulse suppressing electron attachment and sustaining the density of free electrons in plasma. Different modes of the generation and amplification of trains of subterawatt subpicosecond pulses and amplitude-modulated UV pulses with an energy of several tens of joules were implemented on the GARPUN-MTW hybrid Ti:sapphire-KrF laser facility. The filamentation of such UV laser beams during their propagation in air over distances of up to 100 m and the parameters of the corresponding plasma channels were studied experimentally and theoretically. Laser initiation of high-voltage electric discharges and control of their trajectories by means of amplitude-modulated UV pulses, as well as the spatiotemporal structure of breakdowns in air gaps with length of up to 80 cm, were studied.
The possibility of fabricating a silicon diffractive four-level THz Fresnel lens by laser ablation is studied. For a microrelief to be formed on the sample surface, use is made of a femtosecond Yb: YAG laser with a high pulse repetition rate (f = 200 kHz). Characteristics of the diffractive optical element are investigated in the beam of a 141-μm free-electron laser. The measured diffraction efficiency of the lens is in good agreement with the theoretical estimate. © 2015 Kvantovaya Elektronika and Turpion Ltd.
We determine the optimal regime of femtosecond IR laser nano- and micro-texturing of a stainless steel surface for subsequent multimodal surface relief texturing and chemical hydrophobization. We characterize the topological parameters of the modi_ed surface and its wetting parameters after hydrophobization.
The burning efficiency of a preliminarily compressed inertial confinement fusion (ICF) target with a solid noncryogenic fuel (deuterium-tritium beryllium hydride) upon fast central ignition by a fast ion beam is studied. The main aim of the study was to determine the extent to which the spatial temperature distribution formed under the heating of an ICF target by ion beams with different particle energy spectra affects the thermonuclear gain. The study is based on a complex numerical modeling including computer simulations of (i) the heating of a compressed target with a spatially nonuniform density and temperature distributions by a fast ion beam and (ii) the burning of the target with the initial spatial density distribution formed at the instant of maximum compression of the target and the initial spatial temperature distribution formed as a result of heating of the compressed target by the ion beam. The threshold energy of the igniting ion beam and the dependence of the thermonuclear gain on the energy deposited in the target are determined. © 2015, Pleiades Publishing, Ltd.
We report on a ferroelectric chiral smectic C (C*) phase obtained in a mixture of a nematic liquid crystal (NLC) and a chiral nonmesogenic dopant. The existence of C* phase was proven by calorimetric, dielectric and optical measurements, and also by X-rays analysis. The smectic C* which is obtained in such a way can flow, allowing to restore the ferroelectric liquid crystal layer structure in the electro-optical cells after action of the mechanical stress, as it happens with the cells filled with NLC. The proposed method of obtaining smectic C* material allows us to create innovative electro-optical cell combining the advantages of NLC (mechanical resilience) and smectic C* (high switching speed). (C) 2015 AIP Publishing LLC.
In this work, we demonstrate an all-laser method of fabrication of optical nanoantennas (ONAs) with an additional coupling/focusing diffractive element. This method is based on double-shot femtosecond laser nanoablation of a thin supported metallic film, inducing a sequence of electrodynamic (surface plasmon-polariton [SPP] excitation and interference), thermal (melting, ablation and ultrafast cooling), and hydrodynamic processes. In particular, the thermal and hydrodynamic processes are important for ONA formation after the first laser shot, while second spatially shifted laser shot via an induced SPP wave results in a radial surface grating near the nanoantenna. Such gratings provide efficient coupling between incident laser radiation and SPP waves, thus significantly improving the ONA efficiency. (C) 2015 Optical Society of America
Abstract: The strength of forward-backward (FB) multiplicity correlations is measured by the ALICE detector in proton-proton (pp) collisions at s$$ s $$ = 0.9, 2.76 and 7 TeV. The measurement is performed in the central pseudorapidity region (|η| < 0.8) for the transverse momentum pinfT/inf> 0.3 GeV/c. Two separate pseudorapidity windows of width (δη) ranging from 0.2 to 0.8 are chosen symmetrically around η = 0. The multiplicity correlation strength (binfcorr/inf) is studied as a function of the pseudorapidity gap (ηinfgap/inf) between the two windows as well as the width of these windows. The correlation strength is found to decrease with increasing ηinfgap/inf and shows a non-linear increase with δη. A sizable increase of the correlation strength with the collision energy, which cannot be explained exclusively by the increase of the mean multiplicity inside the windows, is observed. The correlation coefficient is also measured for multiplicities in different configurations of two azimuthal sectors selected within the symmetric FB η-windows. Two different contributions, the short-range (SR) and the long-range (LR), are observed. The energy dependence of binfcorr/inf is found to be weak for the SR component while it is strong for the LR component. Moreover, the correlation coefficient is studied for particles belonging to various transverse momentum intervals chosen to have the same mean multiplicity. Both SR and LR contributions to binfcorr/inf are found to increase with pinfT/inf in this case. Results are compared to PYTHIA and PHOJET event generators and to a string-based phenomenological model. The observed dependencies of binfcorr/inf add new constraints on phenomenological models.[Figure not available: see fulltext.] © 2015, The Author(s).
Recently reported photoluminescent nanographene oxides (nGOs), i.e. nanographene oxidised with a sulfuric/nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamonds (NDs), graphene quantum dots (GQDs), all of which demonstrate a variety of properties that are attractive for biomedical imaging such as low toxicity and stable photoluminescence. In this study, the nGOs were organically surface-modified with poly(ethylene glycol)-poly(ethylene imine) (PEG-PEI) copolymers tagged with folic acid as the affinity ligand for cancer cells expressing folate receptors. The functionalization enhanced both the cellular uptake and quantum efficiency of the photoluminescence as compared to non-modified nGOs. The nGOs exhibited an excitation dependent photoluminescence that facilitated their detection with a wide range of microscope configurations. The functionalized nGOs were non-toxic, they were retained in the stained cell population over a period of 8 days and they were distributed equally between daughter cells. We have evaluated their applicability in in vitro and in vivo (chicken embryo CAM) models to visualize and track migratory cancer cells. The good biocompatibility and easy detection of the functionalized nGOs suggest that they could address the limitations faced with quantum dots and organic fluorophores in long-term in vivo biomedical imaging. © 2014 The Royal Society of Chemistry.
Multi-pulse laser irradiation of diamond bulk after the optical breakdown causes extension of continuous graphitized region toward the laser beam that can be described as propagation of a “graphitization wave.” Velocity of the graphitization wave in single-crystal diamond is measured experimentally as a function of local laser fluence for a few numerical apertures (NA = 0.36–0.09), pulsewidths (140 fs–5 ps), and beam orientations (along  or  diamond axes). The experimental results are used to develop the model of the crack-assisted thermal graphitization of diamond at the boundary of the laser-modified region. Velocity of the graphitization wave is determined in general case by diffusion of heat from the light-absorbing modified region. The revealed rise in the graphitization wave velocity for the  beam orientation can be explained by the local electric field enhancement near the crack tip, which facilitates diamond ionization and plasma-assisted energy absorption. The proposed model predicts a specific internal structure of the laser-modified region: the network of graphitic inclusions with diamond-filled gaps between them. © 2015 Springer-Verlag Berlin Heidelberg
Nanocrystalline diamond (NCD) films were produced by microwave plasma enhanced chemical vapor deposition (MPCVD) in methane/hydrogen/air plasma. The thickness of the films was varied from 0.15 to 22 μm. X-ray diffraction (XRD), Raman spectroscopy and atomic force microscopy (AFM) were used to investigate the structure and surface morphology of the films. During a short initial period of the deposition, i.e. from 2.5 min to 60 min, the growth dynamics involve relatively strong non-local effects, followed by a growth stage, which is characterized by a contribution of non-local and non-linear effects to the growth dynamics. The later regime of growth with roughness exponent α ∼ 0.35-0.4 and growth exponent β ∼ 0.25 can be related with the Kardar-Parisi-Zhang (KPZ) scaling regime of growth. The morphological peculiarities observed on the NCD film surface after already 2.5 min of deposition influence the morphology of the films for prolonged deposition time. Therefore, control over the size and distribution of these peculiarities by systematic variation of the deposition parameters allows to optimize the surface morphology for specific applications. The mountain-like patterns observed on the NCD films surface can be related to conformal KPZ growth regime, in contrast to the cusp-like patterns caused by non-local effects and noise. © 2015 Elsevier B.V. All rights reserved.
This review is presented on modern research to achieve in a laboratory experiment the new level of shock-wave pressure of a few hundred or even thousands of Mbar when a substance is exposed to a stream of laser-accelerated fast electrons. The applications associated with the use of ultra-power shock waves as the ignition driver of inertial fusion targets as well as the tool in studying the equation of a state of a matter are discussed.
Using the quasi-static approximation we have found exact analytical solutions to the problem of the field of a point electromagnetic source in the presence of a layer of a bi-isotropic (chiral) metamaterial. At some parameters of the problem, the resulting solution can be represented as a set of several point sources (electric and magnetic), which are images of the original source. If the original source is located near the layer, these images become real sources of the field. This paradoxical solution is then generalised to the case taking into account the retardation effects, which allows one to physically interpret the obtained solutions as a set of sources and 'sinks' of circularly polarised waves.
We have investigated theoretically the spontaneous decay rate of an excited molecule placed near a circular aperture in a perfectly conducting infinitely thin plane screen. A quasistatic analytical solution for a molecule with an arbitrary position near the aperture is found. In a case with a retardation, an exact analytical solution expressed through spheroidal wave functions is obtained. Analytical results are in good agreement with numerical simulations. The results may be useful in the design and development of optical nanodevices based on the control of elementary quantum systems emission.
We have obtained and investigated analytical expressions for the radiative spontaneous decay rate of a chiral (optically active) molecule located near a cluster of two identical chiral (bi-isotropic) spherical particles. It is found that the composition of the particles, their location and size have a significant effect on the spontaneous emission of chiral molecules. In particular, it is shown that in the case of nanoparticles of chiral metamaterials, the radiative spontaneous decay rate for the 'right-' and 'left-handed' enantiomers of chiral molecules located in the gap of the cluster are significantly different.
The formation of a matrix evaporation zone (MEZ) in carbon fiber reinforced plastics during multi-pass laser cutting with picosecond laser pulses is studied for a wide range of pulse frequencies (finfp/inf=10-800kHz) and feed rates (vinff/inf=0.002-10m/s). Three regimes of the formation of the MEZ are found and related with different heat accumulation effects: (i) small MEZ (<2μm) with negligible heat accumulation, (ii) moderate-size MEZ (up to a few hundred microns) determined by heat accumulation between pulses, and (iii) large MEZ (up to a few millimeters) caused by heat accumulation between scans. The dependence of the size of the MEZ on the number of scans and the scan frequency was studied to distinguish the two heat accumulation effects (between pulses and between scans), which occur on different time-scales. A diagram to illustrate the boundaries between the three regimes of the formation of the MEZ as a function of feed rate and pulse frequency is proposed as a promising base for further studies and as a useful tool to optimize the processing parameters in practice. © 2015 AIP Publishing LLC.
An exact analytic solution is found for the steady-state distribution function of fast electrons with an arbitrary initial spectrum irradiating a planar low-Z plasma with an arbitrary density distribution. The solution is applied to study the heating of a material by fast electrons of different spectra such as a monoenergetic spectrum, a step-like distribution in a given energy range, and a Maxwellian spectrum, which is inherent in laser-produced fast electrons. The heating of shock- and fast-ignited precompressed inertial confinement fusion (ICF) targets as well as the heating of a target designed to generate a Gbar shock wave for equation of state (EOS) experiments by laser-produced fast electrons with a Maxwellian spectrum is investigated. A relation is established between the energies of two groups of Maxwellian fast electrons, which are responsible for generation of a shock wave and heating the upstream material (preheating). The minimum energy of the fast and shock igniting beams as well as of the beam for a Gbar shock wave generation increases with the spectral width of the electron distribution. © 2015, Pleiades Publishing, Inc.
ZnSe-based electron-beam pumped vertical-cavity surface-emitting lasers for the green (λ = 530 nm) and blue (λ = 462 nm) spectral region have been realized. Structures with and without epitaxial bottom distributed Bragg reflector have been fabricated and characterized. The samples consist of an active region containing 20 quantum wells with a cavity length varying between an optical thickness of 10 λ to 20 λ. The active material is ZnCdSSe in case of the green devices and ZnSe for the blue ones. Room temperature single mode lasing for structures with and without epitaxial bottom mirror with a maximum output power up to 5.9 W (green) and 3.3 W (blue) is achieved, respectively. © 2015 AIP Publishing LLC.
An instrumental system and the corresponding experimental technique for multiparametric nanoscale 3D characterization of a wide range of composite nanomaterials have been developed. This system makes it possible to obtain 3D data on the chemical composition of a material by optical methods in the confocal and near-field optical microspectroscopy modes (fluorescence and Raman) with a lateral resolution up to 50 nm, as well as data on the 3D morphology and spatial distribution of mechanical, electrical, and other characteristics of the material in the scanning probe microscopy mode with a resolution of about 10 nm on the X and Y axes and several angstroms on the Z axis, for a single area of the sample (100 μm × 100 μm × 3 mm). The nanoscale 3D pattern of the distribution of these characteristics is obtained by sequentially examining nanomaterial layers at a step of 20 nm along the Z axis and a total depth of Z-scanning of 3 mm. © 2015 The Authors.
We report on detailed experimental study of various nanoscale surface hydrodynamic instabilities on thin Au/Pd alloy films induced by tightly focused single femtosecond pulses. Each type of laser-induced hydrodynamic instabilities results in the formation of corresponding resolidified surface relief nanostructure: nanojet, nanocrown or hybrid structure (a nanojet surrounded by a nanocrown), where the hybrid structure is reported for the first time. Thickness of metal films, as well as the laser pulse energy, were found to be the key parameters determining the type of the resulting surface structures. Single nanojets were revealed to appear only on films with sub-100-nm thickness, while irradiation of thicker films (120-240. nm) leads to the formation of nanocrowns at near-threshold energies or hybrid structures at higher energies. The underlying formation mechanisms giving rise to all of these laser-induced nanostructures are also discussed.
The three-step three-color laser population of the I2(beta(1)g, nu(beta), J(beta) and D0(u)(+), v(D), J(D)) rovibronic states via those of the B0(u)(+) and 1(u), 0(g)(+)(bb) states, correlating with the second and third dissociation limits of the valence states, has been used for the study of mechanisms of optical transitions involved in the population of the beta 1(g), v(beta), J(beta) rovibronic states. It has been shown that the 1(u)(bb) - B0(u)(+) transition is allowed due to hyperfine interactions of the 1(u)(bb), nu(1u), J(1u) and 0(g)(+)(bb), v(0), J(0) rovibronic states, though energy gaps between these pairs of the states are huge, greater than 0.7 cm(-1). The Delta J
We present a theoretical study of ignition thresholds and combustion efficiencies of fusion fuels in the form of solid chemical compounds of hydrogen isotopes with light elements that can be used in inertial confinement fusion targets without cryogenic devices required in traditional deuterium–tritium (DT) ice fuel designs. © 2015 Springer Science+Business Media New York
The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities (2.3 < η < 3.9) in proton–proton collisions at three center-of-mass energies, √s = 0.9, 2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2± 0.3% (stat) ± 8.8% (sys) and 61.2 ± 0.3 % (stat) ± 7.6% (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range. © 2015, CERN for the benefit of the ALICE collaboration.
The photophysical properties of colloid semiconductor quantum dots (QDs) and QD-containing composites attract increasing interest. The possibility of tuning of the luminescence wavelength by varying the QD size, their broad absorption spectrum and feasibility of obtaining QD-based thin layers and composites offer great prospects for application in photonics and optoelectronics. Some emerging trends in the development of QD-based light-emitting diodes and solar cells require embedding of QDs into a polymer matrix. Although there is evidence that the photophysical characteristics of QDs in such systems depend on the type of their surface ligands, yet, there are only few studies on this subject. Here, the luminescence characteristics CdSe/ZnS/Cds/ZnS QDs coated with aliphatic or aromatic ligands, embedded in a polymethylmethacrylate (PMMA) matrix, have been studied. The quantum yield (QY) of the QD/PMMA composites containing QDs with aliphatic ligands has been found to be three times higher compared to those containing QDs with aromatic ligands. We assume that this effect is due to hole capture on TP aromatic π-orbital. © 2015 The Authors.
The characteristics of a Fe : ZnSe laser pumped by a single-pulse free-running Er : YAG laser and a repetitively pulsed HF laser are presented. An output energy of 4.9 J is achieved in the case of liquid-nitrogen cooling of the Fe2+ : ZnSe active laser element longitudinally pumped by an Er:YAG laser with a pulse duration of 1 ms and an energy up to 15 J. The laser efficiency with respect to the absorbed energy is 47%. The output pulse energy at room temperature is 53 mJ. The decrease in the output energy is explained by a strong temperature dependence of the upper laser level lifetime and by pulsed heating of the active element. The temperature dependence of the upper laser level lifetime is used to determine the pump parameters needed to achieve high pulse energies at room temperature. Stable repetitively-pulsed operation of the Fe2+ : ZnSe laser at room temperature with an average power of 2.4 W and a maximum pulse energy of 14 mJ is achieved upon pumping by a 1-s train of 100-ns HF laser pulses with a repetition rate of 200 Hz.
Introduction and objective: In Europe, nearly every sixth couple in the reproductive age is involuntarily childless. In about 30%, both male and female reveal fertility problems. In about 10% of infertile men, azoospermia is the underlying cause. As conventional therapeutic options are limited, surgical testicular sperm extraction (TESE) is necessary to obtain sperms for assisted reproductive techniques. Regarding the females, up to 30% of all idiopathic infertilities are due to alterations of the uterine tube So far, no imaging technique, which does not require any labelling, is available to evaluate the male and female genital tract at a microscopic level under in vivo conditions. Thus, the aim of this study was to investigate the potential of optical coherence tomography (OCT) as a non-invasive diagnostic tool in gynaecology and andrology. Material and Methods: Tissues samples from the bovine testis, epididymis, vas deferens, ovary, oviduct (ampulla and isthmus) and uterus were obtained immediately after slaughter (14 cows aged 3 to 8 years and 14 bulls aged 3 to 6 years; breeds: Holstein- Friesian, and Deutsches Fleckvieh). Imaging was done by using the US Food and Drug Administration (FDA) approved probe-based Niris Imaging System (Imalux, Cleveland, Ohio, USA) and the Telesto 1325 nm OCT System and Ganymede 930 nm OCT System (Thorlabs Inc., Dachau, Germany). All images obtained were compared to histological images after paraffin embedding and HE staining. Results: OCT imaging visualized the microarchitecture of the testis, epididymis, spermatic duct and the ovary, oviduct and uterus. Using the Thorlabs systems a axial resolution of approx. 5μm and lateral resolution of 8- 15μm could be achieved. Different optical tissue volumes could be visualized, which depends on the optical penetration depth of the wavelength of the system used. While the tissue volume observed by probe based Imalux-OCT is similar to the used Thorlabs systems, the optical resolution is reduced. By means of the microscopic OCT-system differentiation of testical tissue structures like content and diameter of seminiferous tubules and the epididymal duct was possible. Structures of the female oviduct, like the primary, secondary and tertiary folds including the typical epithelium consisting of secretory and ciliated cells were identified. Ampulla and isthmus were clearly differentiated by the height of the folds and the thickness of the smooth muscle layer. Imaging was successful both from the outside wall and from the inner lumen. After experience with microscopic OCT-structure identification such structures could also be identified by means of probe based OCT. Conclusions: Technical improvement of probe-based OCT up to a high-resolution level of nowadays-available OCT microscopic systems could open up new ways of in vivo imaging in the reproductive tract. Potential applications could be an OCT-guided testicular biopsy for improving sperm retrieval or microscopic evaluation of the oviduct by OCT-assisted fertiloscopy. The latter would provide a valuable tool to facilitate the decision of which type of assisted reproductive techniques might be preferred.
Nowadays surface assisted laser desorption/ionization is widely used in different analytical methods. Some of the most interest methods are based on laser irradiation of nanostructured surfaces, porous silicon (pSi) in particular. This method already proved itself in mass spectrometry due to the combination of high sensitivity and possibility of investigation of small molecules because of the absence of the influence of a substrate on the ion signal. In this work we present summarized results of our investigations dedicated to the use of the surface assisted laser desorption/ionization on pSi in ion mobility spectrometry (IMS), which is one of the most promising analytical methods in the area of fast detection of low concentrations of organic molecules. We use trinitrotoluene (TNT) as a substance to be investigated. Obtained results show that TNT ionization mechanism under laser irradiation is complicated and relates both to the electron emission process from the pSi surface and subsequent ion-molecular reactions in gas phase and to the surface proton transfer as well. © 2015 The Authors.
We have analysed the possibility of appearance of anti-Stokes lines in the spectrum of Raman scattering of a photon by a 'quasi-bound' charged particle in the regime of planar (axial) channelling. It is shown that radiation may emerge at the frequency, which is a combination of the incident photon frequency ?0 and transition frequency ?i in the transverse quantised motion of a channelled particle: ? = ?0 ± 2?;2?i, where ?; is the relativistic (Lorentz) factor of a channelled particle.
The properties of new carbon materials (single-crystal and polycrystalline CVD diamond films and wafers, single-wall carbon nanotubes and graphene) and the prospects of their use as optical elements and devices are discussed.
The results of the theoretical study of damage and nonlinear light absorption mechanisms in transparent materials, i.e., wide band-gap semiconductors and insulators, are presented. It is shown that ablation processes in transparent materials exposed to laser pulses with intensity of the order of tens of TW/cmsup2/sup and pulse duration of the order of hundreds femtoseconds are efficient for various surface treatment technologies. The mechanism of tunneling nonlinear light absorption is studied. Ablation thresholds of GaN and other transparent materials such as sapphire (Alinf2/infOinf3/inf), vitreous SiOinf2/inf, and the same SiOinf2/inf with Ge impurity are determined. It is found that the ablation threshold depends on the band gap (absorption band edge) Einfg/inf as Einfg/inf sup3/sup, which is in good agreement with experiment. © 2015, Allerton Press, Inc.
The observed interference of single photons is explained without contradiction using the indivisibility principle. © 2015 The Authors.
An implementation scheme of the adaptive fiber-optic laser hydrophone with a membrane-type fiber-optic sensor as a sensitive element is proposed and studied. The sensor signal is phase demodulated using an adaptive holographic interferometer whose key element is a dynamic hologram formed in a photorefractive CdTe crystal. The hydrophone is distinguished by high noise immunity and high sensitivity (–117 dB rel. to 1 V/µPa at a frequency of 4.9 kHz) providing stable detection of hydroacoustic signals with an acoustic pressure from 31 dB (rel. to 20 µPa) in the dynamic range to 42 dB (at 9.6 kHz). © 2015, Allerton Press, Inc.
The main objective of the work is to study the conversion of the laser pulse energy into the energy of the hydrodynamic motion of matter in a solid target following the initial absorption of laser radiation in a layer of porous material. Results of experiments on plane massive aluminum targets, coated with a layer of porous plastic with density greater than the critical density of the plasma created, are presented. Experiments were carried out on the laser installation ABC of the Research Center ENEA-Frascati; the targets were irradiated by a beam of the fundamental harmonic of Nd-laser radiation with an energy of about 50 kJ, intensity of 10(13) W/cm(2), and 3 ns duration. The experimental method consisted in measuring the volume of the craters created on the aluminum surface behind various thicknesses and densities of the porous absorber of laser radiation. On the basis of these measurements and of an advanced analytical model, quantitative conclusions are made on how the efficiency of laser energy transfer to the solid part of the target (laser-ablated loading) depends on thickness and density of the porous absorber. (C) 2015 AIP Publishing LLC.
Multi-layered graphene deposited on silicon wafer was irradiated in air by sequences of nanosecond laser pulses. It is shown that ultra-shallow craters (cavities) with depth of ?1 nm and microholes can be formed in graphene sheet on the substrate at laser fluence ?0.04 J/cm2 well below the experimentally known graphene ablation threshold ? 0.25 J/cm2. Influence of intensity and number of laser pulses on the depth and roughness of the cavities are described. We suggest that the observed effects are related to laser heating and boiling of the adsorbate at graphene-silicon interface.
Luminescence properties of single color centers were studied in nanodiamonds of different origin. It was found that single photon emitters could be realized even in molecularsized diamond (less than 2 nm) capable of housing stable luminescent center "silicon-vacancy." First results on incorporation of single-photon emitters based on luminescent nanodiamonds in plasmonic nanoantennas to enhance the photon count rate and directionality, diminish the fluorescence decay time, and provide polarization selectivity are presented. © 2015 Owned by the authors, published by EDP Sciences.
Polyphenylquinolines (PPQs), which are compound donor–acceptor complexes, are studied by luminescence-kinetic spectroscopy. It is shown that, as the π system becomes stronger on passing from (O, C) to (O, IC) and (PhA, C), an increase in the lifetime T of the excited state is first observed, and for the strongest charge-transfer complex PPQ (PhA, IC), whose luminescence kinetics is described by two exponentials, the lifetime decreases to a value equal to T of PPQ (O, C). This indicates that this complex has two emitting centers localized in the arylene moiety and in the phenylquinoline ring and thereby confirms a previously made conclusion that compound donor–acceptor complexes are formed in polyphenylquinolines with a branched π system of compound D–A complexes. © 2015, Pleiades Publishing, Ltd.
Charged jet production cross sections in p-Pb collisions at sNN=5.02 TeV measured with the ALICE detector at the LHC are presented. Using the anti-kinfT/inf algorithm, jets have been reconstructed in the central rapidity region from charged particles with resolution parameters R=0.2 and R=0.4. The reconstructed jets have been corrected for detector effects and the underlying event background. To calculate the nuclear modification factor, RinfpPb/inf, of charged jets in p-Pb collisions, a pp reference was constructed by scaling previously measured charged jet spectra at s=7 TeV. In the transverse momentum range 20≤pinfT,chjet/inf≤120 GeV/c, RinfpPb/inf is found to be consistent with unity, indicating the absence of strong nuclear matter effects on jet production. Major modifications to the radial jet structure are probed via the ratio of jet production cross sections reconstructed with the two different resolution parameters. This ratio is found to be similar to the measurement in pp collisions at s=7 TeV and to the expectations from PYTHIA pp simulations and NLO pQCD calculations at sNN=5.02 TeV. © 2015 CERN for the benefit of the ALICE Collaboration.
Prompt D meson and non-prompt J/ψ yields are studied as a function of the multiplicity of charged particles produced in inelastic proton-proton collisions at a centre-of-mass energy of √ = 7 TeV. The results are reported as a ratio between yields in a given multiplicity interval normalised to the multiplicity-integrated ones (relative yields). They are shown as a function of the multiplicity of charged particles normalised to the average value for inelastic collisions (relative charged-particle multiplicity). Dsup0/sup, Dsup+/sup and Dsup*+/sup mesons are measured in five pinfT/inf intervals from 1 GeV/c to 20 GeV/c and for |y| < 0.5 via their hadronic decays. The D-meson relative yield is found to increase with increasing charged-particle multiplicity. For events with multiplicity six times higher than the average multiplicity of inelastic collisions, a yield enhancement of a factor about 15 relative to the multiplicity-integrated yield in inelastic collisions is observed. The yield enhancement is independent of transverse momentum within the uncertainties of the measurement. The Dsup0/sup-meson relative yield is also measured as a function of the relative multiplicity at forward pseudo-rapidity. The non-prompt J/ψ, i.e. the B hadron, contribution to the inclusive J/ψ production is measured in the di-electron decay channel at central rapidity. It is evaluated for pinfT/inf > 1.3 GeV/c and |y| < 0.9, and extrapolated to pinfT/inf > 0. The fraction of non-prompt J/ψ in the inclusive J/ψ yields shows no dependence on the charged-particle multiplicity at central rapidity. Charm and beauty hadron relative yields exhibit a similar increase with increasing charged-particle multiplicity. The measurements are compared to PYTHIA 8, EPOS 3 and percolation calculations. © 2015, The Author(s).
A measurement of dijet correlations in p-Pb collisions at √sNN=5.02 TeV with the ALICE detector is presented. Jets are reconstructed from charged particles measured in the central tracking detectors and neutral energy deposited in the electromagnetic calorimeter. The transverse momentum of the full jet (clustered from charged and neutral constituents) and charged jet (clustered from charged particles only) is corrected event-by-event for the contribution of the underlying event, while corrections for underlying event fluctuations and finite detector resolution are applied on an inclusive basis. A projection of the dijet transverse momentum, kinfTy/inf=psupch+ne/sup; infT,jet/infsin(δϕinfdijet/inf) with δϕinfdijet/inf the azimuthal angle between a full and charged jet and psupch+ne/sup; infT,jet/inf the transverse momentum of the full jet, is used to study nuclear matter effects in p-Pb collisions. This observable is sensitive to the acoplanarity of dijet production and its potential modification in p-Pb collisions with respect to pp collisions. Measurements of the dijet kinfTy/inf as a function of the transverse momentum of the full and recoil charged jet, and the event multiplicity are presented. No significant modification of kinfTy/inf due to nuclear matter effects in p-Pb collisions with respect to the event multiplicity or a PYTHIA8 reference is observed. © 2015 CERN for the benefit of the ALICE Collaboration.
The pT-differential production cross section of electrons from semileptonic decays of heavy-flavor hadrons has been measured at midrapidity in proton-proton collisions at s=2.76TeV in the transverse momentum range 0.5<pT<12GeV/c with the ALICE detector at the LHC. The analysis was performed using minimum bias events and events triggered by the electromagnetic calorimeter. Predictions from perturbative QCD calculations agree with the data within the theoretical and experimental uncertainties.
We report the measurement of a new observable of jet quenching in central Pb-Pb collisions at vsNN = 2.76 TeV, based on the semi-inclusive rate of charged jets recoiling from a high transverse momentum (high-pinfT/inf) charged hadron trigger. Jets are measured using collinear-safe jet reconstruction with infrared cutoff for jet constituents of 0.15 GeV, for jet resolution parameters R = 0.2, 0.4 and 0.5. Underlying event background is corrected at the event-ensemble level, without imposing bias on the jet population. Recoil jet spectra are reported in the range 20 pinfT,jet/infch 100 GeV. Reference distributions for pp collisions at vs
The transverse momentum (pinfT/inf) spectrum and nuclear modification factor (RinfAA/inf) of reconstructed jets in 0-10% and 10-30% central Pb-Pb collisions at sNN=2.76 TeV were measured. Jets were reconstructed using the anti-kinfT/inf jet algorithm with a resolution parameter of R=0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet pinfT/inf spectra are reported in the pseudorapidity interval of |ηinfjet/inf|<0.5 for 40<pinfT,jet/inf<120 GeV/c in 0-10% and for 30<pinfT,jet/inf<100 GeV/c in 10-30% collisions. Reconstructed jets were required to contain a leading charged particle with pinfT/inf>5 GeV/c to suppress jets constructed from the combinatorial background in Pb-Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb-Pb collisions had a negligible effect on the RinfAA/inf. The nuclear modification factor RinfAA/inf was found to be 0.28±0.04 in 0-10% and 0.35±0.04 in 10-30% collisions, independent of pinfT,jet/inf within the uncertainties of the measurement. The observed suppression is in fair agreement with expectations from two model calculations with different approaches to jet quenching. © 2015.
The measurement of primary $$$$supπ±/sup, $$K$$supK±/sup, $$p$$p and $$p$$p¯ production at mid-rapidity ($$|y| <$$|y|< 0.5) in proton–proton collisions at $$s$$s$$=$$= 7 TeV performed with a large ion collider experiment at the large hadron collider (LHC) is reported. Particle identification is performed using the specific ionisation energy-loss and time-of-flight information, the ring-imaging Cherenkov technique and the kink-topology identification of weak decays of charged kaons. Transverse momentum spectra are measured from 0.1 up to 3 GeV/$$c$$c for pions, from 0.2 up to 6 GeV/$$c$$c for kaons and from 0.3 up to 6 GeV/$$c$$c for protons. The measured spectra and particle ratios are compared with quantum chromodynamics-inspired models, tuned to reproduce also the earlier measurements performed at the LHC. Furthermore, the integrated particle yields and ratios as well as the average transverse momenta are compared with results at lower collision energies. © 2015, CERN for the benefit of the ALICE collaboration.
An improved resonator method is developed, which allows for a change in the resonator coupling coefficient at insertion of the sample during the measurement of the imaginary part of the material permittivity. The method makes it possible to measure small samples. The permittivity at a frequency of 27GHz is measured for rods made of polycrystalline CVD diamond plates of 57 and 100mm in diameter grown in the microwave plasma in methane−hydrogen mixtures, and the loss tangent tan δ is determined at a level of the order of 10sup−3/sup. © 2015, Allerton Press, Inc.
The diagnosis and treatment of cancer have been greatly improved with recent developments in bio-nanotechnology, including engineering of multifunctional probes. One of the promising nanoscale tools for cancer imaging is fluorescent quantum dots (QDs), whose small size and unique optical properties allow them to penetrate into cells and ensure highly sensitive optical diagnosis of cancer at the cellular level. Furthermore, novel multi-functional probes have been developed in which QDs are conjugated with one or several functional molecules, including targeting moieties and therapeutic agents. Here, the strategy for engineering novel nanocarriers for controlled nucleus-targeted antitumor drug delivery and real-time imaging by single- or two-photon microscopy is described. A triple multifunctional nanoprobe is being developed that consists of a nitrogen-based heterocyclic derivative, an anticancer agent interacting with a DNA in living cells; a recognized molecule serving as a vector responsible for targeted delivery of the probe into cancer cells; and photoluminescent QDs providing the imaging capability of the probe. Subsequent optimization of the multifunctional nanoprobe will offer new possibilities for cancer diagnosis and treatment. © 2015 The Authors.
The measured stationary and time-resolved photoluminescence is used to study the properties of the exciton gas in a second-order 5-nm-thick Si0.905Ge0.095/Si quantum well. It is shown that, despite the presence of an electron barrier in the Si0.905Ge0.095 layer, a spatially indirect biexciton is the most favorable energy state of the electron–hole system at low temperatures. This biexciton is characterized by a lifetime of 1100 ns and a binding energy of 2.0–2.5 meV and consists of two holes localized in the SiGe layer and two electrons mainly localized in silicon. The formation of biexcitons is shown to cause low-temperature (5 K) luminescence spectra over a wide excitation density range and to suppress the formation of an exciton gas, in which quantum statistics effects are significant. The Bose statistics can only be experimentally observed for a biexciton gas at a temperature of 1 K or below because of the high degree of degeneracy of biexciton states (28) and a comparatively large effective mass (about 1.3me). The heat energy at such temperatures is much lower than the measured energy of localization at potential fluctuations (about 1 meV). This feature leads to biexciton localization and fundamentally limits the possibility of observation of quantum coherence in the biexciton gas. © 2015, Pleiades Publishing, Inc.
High-quality imaging for immunofluorescence diagnosis in medical practice requires a high sensitivity of labeling and discrimination between the fluorescence of immunostaining probes and tissue autofluorescence. Multiphoton microscopy with excitation in the near-infrared spectral region, far from the region of excitation of tissue autofluorescence, enables deep imaging of biological tissues. CdSe/ZnS quantum dots (QDs) conjugated to single-domain antibodies (sdAbs) are efficient diagnostic nanoprobes with diameters <12 nm and the two-photon absorption cross section exceeding 49,000 GM. Such nanoprobes ensure clear discrimination of tumor areas from normal tissue with the ratio of sdAb-QD emission to the autofluorescence for two-photon excitation >40 times higher than that for one-photon excitation. © 2015 IEEE.
Multiple filamentation of subpicosecond UV pulses with peak power up to 0.2. TW was investigated at the Ti:Sapphire/KrF GARPUN-MTW laser facility in the direct amplification scheme. Filamentation arose in the initial preamplifier stage when peak power exceeded the critical value of 0.1. GW. The filamentation pattern was well reproducible for repetitive pulses in time scales from nanoseconds to several minutes. © 2015.
Multiplexed analysis of cancer markers is crucial for early tumor diagnosis and screening. We have designed lab-on-a-bead microarray for quantitative detection of three breast cancer markers in human serum. Quantum dots were used as bead-bound fluorescent tags for identifying each marker by means of flow cytometry. Antigen-specific beads reliably detected CA 15-3, CEA, and CA 125 in serum samples, providing clear discrimination between the samples with respect to the antigen levels. The novel microarray is advantageous over the routine single-analyte ones due to the simultaneous detection of various markers. Therefore the developed microarray is a promising tool for serum tumor marker profiling. © 2015 The Authors.
Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum range 0.7<pT,assoc<pT,trig<5.0 GeV/c is examined, to include correlations induced by jets originating from low momentum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |?|<0.9. The near-side long-range pseudorapidity correlations observed in high-multiplicity p-Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the non-jet-like components. The yields in the jet-like peaks are found to be invariant with event multiplicity with the exception of events with low multiplicity. This invariance is consistent with the particles being produced via the incoherent fragmentation of multiple parton-parton scatterings, while the yield related to the previously observed ridge structures is not jet-related. The number of uncorrelated sources of particle production is found to increase linearly with multiplicity, suggesting no saturation of the number of multi-parton interactions even in the highest multiplicity p-Pb collisions. Further, the number scales only in the intermediate multiplicity region with the number of binary nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.
Nano-bio hybrid materials obtained by conjugation of capture molecules and plasmonic (metal) or excitonic (semiconductor) nanocrystals or microspheres encoded with fluorescent semiconductor nanocrystals of different colors are the basis for development of a new generation of high-throughput diagnostic systems. Here, the general principles of development of "ideal" diagnostic nanoprobes based on oriented conjugates of capture molecules with the nanoparticles of different chemical compositions or with optically encoded microspheres are summarized and the basic requirements for individual components of the photonic nanoprobes being developed are discussed in the context of ensuring their advantages over the existing photonic diagnostic systems. © 2015 The Authors.
A nanoscale chaotic relief structure appears as a result of subthreshold single-shot femtosecond laser ablation of gold films in the regimes of fabrication of microbumps and nanospikes, but only for a relatively thick film. The observed nanoablation tendency versus film thickness makes it possible to suppose the existence of a sub-surface temperature maximum in thicker gold films and its absence within thinner film, which results from competing evaporative cooling and electronic heat conduction, as demonstrated by numerical simulations of the thermal dynamics.
About 10.7% cases of prostate cancer were registered in Russia in 2011 (40 000 patients). More than half of cancer cases were revealed in advanced (III-IV) stages when metastases inevitably developed quickly. Clinical problem of early diagnostics and treatment of metastatic prostate cancer is still not solved. Anatomical imaging techniques have low sensitivity and specificity for the detection of this disease. Metabolic visualization methods which use prostate specific antigen (PSA) as a marker are also ineffective. This article describes prostate-specific membrane antigens (PSMA) that are proposed as a marker for diagnostics and therapy of prostate cancer. The most promising PSMA-based radiopharmaceutical agent for diagnostics has been developed and clinically tested in the European countries. These pharmaceuticals are based on small peptide molecules modified with urea, and have the highest affinity to PSMA. Favorable pharmacokinetics, rapid accumulation in the tumor and rapid excretion from the body are beneficial features of these pharmaceuticals.
We consider high-technology information-measuring complexes of cancer diagnostics, using one of the basic methods – the histological method. We investigate the main interdisciplinary problems in the development of systems of histological diagnosis (HD). We discuss key points in the construction methodology of such complexes, confirmed by the successful experience of their development and introduction into clinical practice. © 2015 Springer Science+Business Media New York
We consider the architecture of expert systems in software-hardware measuring complexes for oncological (cancer) diagnosis with the use of procedures of image recognition and on the basis of one of the most important methods of oncomorphology – the histological method. We develop a knowledge model and a model (theoretical foundations) for carrying out expert measurements. The adequacy of the models is confirmed by the high efficiency of introduction of the complexes developed into clinical practice. © 2015 Springer Science+Business Media New York
We consider measurement problems in intellectual (based on pattern recognition) systems of histological diagnosis of oncological illnesses. We discuss the principles of investigation for the stage of microanalysis of tumors, based on an estimate for the characteristics of tissue and cell structures with the use of various measurement scales. © 2015 Springer Science+Business Media New York
We consider measurement problems in intellectual (based on pattern recognition) systems of histological diagnosis of oncological illnesses. We discuss the principles of investigation for the stage of microanalysis of tumors, based on an estimate for the characteristics of tissue and cell structures with the use of various measurement scales. © 2015 Springer Science+Business Media New York.
The electromagnetic field interference distribution on the aluminum surface during formation of laser-induced periodic surface structures (ripples) under femtosecond laser irradiation is studied. The nonlinear dependence of optical feedback on the geometric parameters of the ripples is shown to play a key role in nonlinear evolution of the relief with increasing number of pulses. The strongest optical feedback is observed for periods of ripples in the range of Λ = 0.65λ–0.75λ at relief modulation of h = 0.15λ–0.2λ, where λ is the laser wavelength. On the basis of the developed approach, we explain why the frequently observed femtosecond laser-induced ripples have similar periods on materials with a high value of the imaginary part and strongly negative real part of permittivity. © 2015, Pleiades Publishing, Inc.
Non-linear cumulative self-organization dynamics of femtosecond laser-induced surface relief ripples was for the first time experimentally revealed on a silicon surface as their primary appearance, degradation and revival, reflecting ultrafast non-linear dynamics of corresponding optical interference surface patterns. Such dynamics were revealed by electrodynamic modeling to be directly driven by related instantaneous surface optical patterns, which are sensitive not only to cumulative ripple deepening (steady-state feedback factor), but to laser-induced instantaneous variation of surface dielectric function, providing either positive or negative fluence-dependent optical feedbacks.
We present an experimental investigation of photooxidation of a diamond surface exposed to femtosecond laser pulses that induce transient high concentrations of free carriers (>10sup22/supcmsup-3/sup) while the lattice stays cold. Etching rate measurements and a laser-induced plasma study indicated that the rate of desorption of carbon species is proportional to the square of the induced plasma density, which contrasts with previous investigations of diamond etching by nanosecond pulses. We discuss how laser-induced ionization of diamond occurs and how it affects the photoreaction mechanism. © 2015 Astro Ltd.
A video projector with liquid crystal microdisplay based on FLCoS- structure is considered, and the new low-voltage ferroelectric liquid crystal (FLC) with a compensated helix as an electro-optical material providing physically realizable continuous gray scale hysteresis-free modulation characteristic is proposed to use in FLCoS. As light sources in RGB color channels the laser diodes of red, green and blue light are proposed to use. To prevent the interference of light beams resulting in the speckle noise appearance in output images it is proposed to input a despeckler - single FLC cell into an optical unit of information readout, in order this cell implemented fast electrically controlled spatially- inhomogeneous phase light modulation with a depth of ≥π. To form on a screen the large data blocks with information capacity of 108...109 pixels and with different geometric configuration a two-dimensional scanner is proposed to use, which is optically coupled to a screen and optical unit of information readout. Possible technical results - increasing the frame rate up to 600 Hz as a minimum, the color gamut expansion, increasing a brightness of images, suppression of the speckle noise, - can be used not only in new devices of information visualization and displaying, but also in systems of data storage and processing and others. © 2015 The Authors.
The results of investigation into the imaging of grooves in silicon with a trapezoidal profile and small side-wall inclination angles, which are obtained using a scanning electron microscope operating in the backscattered electron recording mode, are presented. It is shown that there exist four imaging mechanisms. The first of them is caused by primary electrons of the probe. The next two are related to the multiple scattering of primary and secondary (ionizing) electrons. The fourth mechanism is associated with the interaction between electrons released into free space and the sample relief. The first three mechanisms provide direct image contrast, and the fourth is characterized by opposite contrast. © 2015, Pleiades Publishing, Ltd.
The principles of the construction of a virtual scanning electron microscope (SEM) are discussed. It is demonstrated that such a microscope cannot be created using a imitator of real SEM operation. It is concluded that a virtual SEM must be developed using a simulator of information similar to that which is obtained by means of a real microscope. The possibilities of reducing the time required to generate micro- and nanostructure images to values comparable with the imaging duration of real SEMs are analyzed. © 2015, Pleiades Publishing, Ltd.
In germanium-doped thin polycrystalline diamond films grown in microwave plasma on Ge substrates, strong photoluminescence in the orange spectral region with a zero-phonon line (ZPL) at a wavelength of 602 nm is detected. The ZPL width is 4-5 nm at room temperature and 1.2 nm at T = 5K. It is assumed that the new optically active defect is a germanium-vacancy (Ge-V) complex similar to the known Si-V color center in diamond.
It is shown that one should take into account rather small radiation penetration length in metal (Al) to describe properly nanosecond laser induced explosive (volume) boiling process. The result is obtained in the framework of molecular dynamic simulations combined with continual description of metal electron subsystem.
The results of experimental studies using SuperOx J-PI-12-20Ag-20Cu tape superconductors in developing capsule carriers for cryogenic systems of noncontact transport of targets for IFE are presented. © 2015, Allerton Press, Inc.
The size of the particle emission region in high-energy collisions can be deduced using the femtoscopic correlations of particle pairs at low relative momentum. Such correlations arise due to quantum statistics and Coulomb and strong final state interactions. In this paper, results are presented from femtoscopic analyses of pi(+/-) pi(+/-), K-+/- K-+/-, K-S(0) K-S(0), pp, and (pp) over bar correlations from Pb-Pb collisions at root s(NN) = 2.76 TeV by the ALICE experiment at the LHC. One-dimensional radii of the system are extracted from correlation functions in terms of the invariant momentum difference of the pair. The comparison of the measured radii with the predictions from a hydrokinetic model is discussed. The pion and kaon source radii display a monotonic decrease with increasing average pair transverse mass m(T) which is consistent with hydrodynamic model predictions for central collisions. The kaon and proton source sizes can be reasonably described by approximate m(T) scaling.
The infrared reflection spectra of PbTe/CdTe multilayer nanostructures grown by molecular-beam epitaxy are measured in the frequency range of 20–5000 cmsup−1/sup at room temperature. The thicknesses and high-frequency dielectric constants of the PbTe and CdTe layers and the frequencies of the transverse optical (TO) phonons in these structures are determined from dispersion analysis of the spectra. It is found that the samples under study are characterized by two TO phonon frequencies, equal to 28 and 47 cmsup−1/sup. The first frequency is close to that of TO phonons in bulk PbTe, and the second is assigned to the optical mode in structurally distorted interface layers. The Raman-scattering spectra upon excitation with the radiation of an Arsup+/sup laser at 514.5 nm are measured at room and liquid-nitrogen temperatures. The weak line at 106 cmsup−1/sup observed in these spectra is attributed to longitudinal optical phonons in the interface layers. © 2015, Pleiades Publishing, Ltd.
We have predicted theoretically and verified experimentally the occurrence of a giant asymmetry of the transmission of arbitrarily polarized light propagating through a linear nonmagnetic optical system that consists of a metal film with a two-dimensional array of nanoholes in it and that is deposited on the surface of a planar dielectric photonic crystal. The asymmetry of the light transmission is caused by two factors: (i) the excitation of an optical Tamm state in the system, and (ii) the existence of many secondary lobes in the diffraction pattern. Our results are of interest for the development of efficient planar optical diodelike systems and related nanophotonic devices. © 2015 American Physical Society.
Experimental samples of organic light-emitting diodes with transport layers based on polythienothiophenes and using CdSe/CdS/ZnS semiconductor quantum dots with an internal quantum efficiency up to 85% in the emitting layer are investigated. It is shown that solubility and film-forming properties are key for using polythienothiophenes in light-emitting diodes. The most promising polythienothiophenes are identified on the basis of the results obtained. © 2016, Pleiades Publishing, Ltd.
Our recent results in the field of engineering and application of highly oriented conjugates of single-domain antibodies and fluorescent quantum dots are summarized. These novel conjugates proved to be excellent nanoprobes for immunolabeling of tumor-associated biomarkers on cells and tissue specimens detectable by means of flow cytometry or one- or two-photon confocal microscopy. The results are discussed in terms of the most promising future applications of these conjugates and further developments in this field. © 2015 The Authors.
A generalization of the phase function method known in quantum mechanics to the problems of acoustic wave scattering on continuous medium inhomogeneities is proposed. The idea of the use of this method in acoustics is based on the fact that the wave equation for the acoustic potential or pressure in an inhomogeneous medium is reduced to the Schrodinger equation with a variable scattered field potential by a special substitution.
The possibility of using iron oxide(III) nanoparticles covered with photoactive derivative of zinc phthalocyanine for diagnostics and treatment of malignant tumors was studied experimentally.
The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. © 2015 Kvantovaya Elektronika and Turpion Ltd.
The processes of the synthesis of silicon-doped microcrystalline diamond films on AlN and Si substrates in microwave plasma in “methane-hydrogen-silane” mixtures were studied. It is shown that the dependence of the photoluminescence (PL) line intensity of silicon-vacancy centers in diamond (? = 738 nm) on the silane concentration in a gas mixture passes through a maximum at SiH4/CH4 concentrations of 0.1% for Si substrates and 0.6% SiH4/CH4 for aluminum nitride substrates. It was found that such nonmonotonic variation of the PL intensity with increasing silane concentration occurs despite the unchanged growth rate of the diamond film, its structure, and phase composition in the studied silane concentration SiH4/CH4 range of 0–0.9%.
Photoluminescence spectra show that silicon impurity is present in lattice of some nanodiamond grains (ND) of various chondrites as a silicon-vacancy (SiV) defect. The relative intensity of the SiV band in the diamond-rich separates depends on chemical composition of meteorites and on size of ND grains. The strongest signal is found for the size separates enriched in small grains; thus, confirming our earlier conclusion that the SiV defects preferentially reside in the smallest (≤2 nm) grains. The difference in relative intensities of the SiV luminescence in the diamond-rich separates of individual meteorites are due to variable conditions of thermal metamorphism of their parent bodies and/or uneven sampling of nanodiamond populations. Annealing of separates in air eliminates surface spsup2/sup-carbon; consequently, the SiV luminescence is enhanced. Strong and well-defined luminescence and absorption of the SiV defect is a promising feature to locate cold (<250 °C) nanodiamonds in space. © The Meteoritical Society, 2015.
Homoepitaxial single crystal diamond layers with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738nm wavelength have been grown on (100) diamond substrates by a microwave plasma CVD using a controlled Si doping via adding silane to CHinf4/inf-Hinf2/inf reaction gas mixture in the course of the deposition process. In the range of the silane concentrations SiHinf4/inf/CHinf4/inf explored, from 0 to 2.4%, the SiV PL intensity shows a nonmonotonic behavior with silane addition, with a maximum at 0.6%SiHinf4/inf/CHinf4/inf, and a rapid PL quenching at higher Si doping. The maximum SiV concentration of ≈450ppb in the samples has been determined from optical absorption spectra. It is found that the SiV PL intensity can strongly, an order of magnitude, increase within non-epitaxial inclusions in single crystal diamond film. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The problems of using physical research methods in diagnostics of oncological diseases of the gastrointestinal tract and constructing a multimedia learning system on their basis for doctors are considered. The system includes: expert systems, a remote learning system, and an electronic textbook. Disease localizations in esophagus, stomach, intestines, pancreas, and liver are considered. Practical application of the system provides an increase in the learning efficiency during postgraduate training of oncologists and their advanced training. © 2015, Allerton Press, Inc.
A simple approach of preparation of advanced fluorescent polyethylene (PE) composites containing the high concentration of CdSe/ZnS quantum dots (QDs) was elaborated. The method is based on the infiltration of concentrated solution of QDs in octadecene into the films of porous stretched PE. A developed technique allowed one to introduce high concentration of QDs (15 wt%) into the polymer films. The composite films possess very bright fluorescence, high thermal stability, flexibility, and good mechanical properties. An annealing of the films enables to collapse porous structure and obtain stable, flexible, highly fluorescent, and transparent composite films. The developed approach enables to prepare materials promising for applications in optoelectronics and photonics.
We propose porous silicon nanoparticles (PSi NPs) with natural oxide coating as biocompatible and bioresorbable contrast agents for magnetic resonant imaging (MRI). A strong shortening of the transversal proton relaxation time (T-2) was observed for aqueous suspensions of PSi NPs, whereas the longitudinal relaxation time (T-1) changed moderately. The longitudinal and transversal relaxivities are estimated to be 0.03 and 0.4 l/(g.s), respectively, which are promising for biomedical studies. The proton relaxation is suggested to undergo via the magnetic dipole-dipole interaction with Si dangling bonds on surfaces of PSi NPs. MRI experiments with phantoms have revealed the remarkable contrasting properties of PSi NPs for medical diagnostics. (C) 2015 AIP Publishing LLC.
This paper reports on properties of a plasma formed by sequential action of two laser beams on a flat target, simulating the conditions of shock-ignited inertial confinement fusion target exposure. The experiments were performed using planar targets consisting of a massive copper (Cu) plate coated with a thin plastic (CH) layer, which was irradiated by the 1 PALS laser beam (=1.315m) at the energy of 250J. The intensity of the fixed-energy laser beam was scaled by varying the focal spot radius. To imitate shock ignition conditions, the lower-intensity auxiliary 1 beam created CH-pre-plasma which was irradiated by the main beam with a delay of 1.2ns, thus generating a shock wave in the massive part of the target. To study the parameters of the plasma treated by the two-beam irradiation of the targets, a set of various diagnostics was applied, namely: (i) Two-channel polaro-interferometric system irradiated by the femtosecond laser (similar to 40fs), (ii) spectroscopic measurements in the X-ray range, (iii) two-dimensional (2D)-resolved imaging of the K line emission from Cu, (iv) measurements of the ion emission by means of ion collectors, and (v) measurements of the volume of craters produced in a massive target providing information on the efficiency of the laser energy transfer to the shock wave. The 2D numerical simulations have been used to support the interpretation of experimental data. The general conclusion is that the fraction of the main laser beam energy deposited into the massive copper at two-beam irradiation decreases in comparison with the case of pre-plasma. The reason is that the pre-formed and expanding plasma deteriorates the efficiency of the energy transfer from the main laser pulse to a solid part of the targets by means of the fast electrons and the wave of an electron thermal conductivity.
The measurement of the mass differences for systems bound by the strong force has reached a very high precision with protons and anti-protons(1,2). The extension of such measurement from (anti-)baryons to (anti-) nuclei allows one to probe any difference in the interactions between nucleons and anti-nucleons encoded in the (anti-) nuclei masses. This force is a remnant of the underlying strong interaction among quarks and gluons and can be described by effective theories(3), but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the difference between the ratios of the mass and charge of deuterons (d) and anti-deuterons ((d) over bar), and He-3 and (3)(He) over bar nuclei carried out with the ALICE (A Large Ion Collider Experiment)(4) detector in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV. Our direct measurement of the mass-over-charge differences confirms CPT invariance to an unprecedented precision in the sector of light nuclei(5,6). This fundamental symmetry of nature, which exchanges particles with anti-particles, implies that all physics laws are the same under the simultaneous reversal of charge(s) (charge conjugation C), reflection of spatial coordinates (parity transformation P) and time inversion (T).
The production of the strange and double-strange baryon resonances (?(1385)±, ?(1530)0) has been measured at mid-rapidity (|y|<0.5) in proton–proton collisions at vs = 7 TeV with the ALICE detector at the LHC. Transverse momentum spectra for inelastic collisions are compared to QCD-inspired models, which in general underpredict the data. A search for the ?(1860) pentaquark, decaying in the ?? channel, has been carried out but no evidence is seen.
We report on the production of inclusive gamma(1S) and gamma(2S) in p-Pb collisions at root S-NN = 5.02 TeV at the LHC. The measurement is performed with the ALICE detector at backward (-4.46 ycms 2.96) and forward (2.03 ycms 3.53) rapidity down to zero transverse momentum. The production cross sections of the gamma(1S) and gamma(2S) are presented, as well as the nuclear modification factor and the ratio of the forward to backward yields of gamma(1S). A suppression of the inclusive gamma(1S) yield in p-Pb collisions with respect to the yield from pp collisions scaled by the number of binary nucleon-nucleon collisions is observed at forward rapidity but not at backward rapidity. The results are compared to theoretical model calculations including nuclear shadowing or partonic energy loss effects. (C) 2014 The Authors. Published by Elsevier B.V.
A method of estimating the components of the error of measurements of the linear dimensions of objects in automatic systems of computer microscopy with the use of an object micrometer and automatic image processing is proposed. © 2015 Springer Science+Business Media New York
The parameters of pulsed blue-violet (λ ≈ 430 nm at T = 300 K) lasers based on an AlGaN/InGaN/GaN structure with five InGaN quantum wells and transverse electron-beam pumping are studied. At room temperature of the active element, the minimum electron energy was 9 keV and the minimum threshold electron beam current density was 8 A cmsup-2/sup at an electron energy of 18 keV. © 2015 Kvantovaya Elektronika and Turpion Ltd.
To evaluate the possibility of using an automated classifying system of experimental scientific association in physics, information science and technology (ACS ESAPST) to identify changes in the osteoarticular system in tuberculous spondylitis. In our study we analyzed the results of radiological studies and the quantitative measurement of homeostasis of 45 patients with tuberculous spondylitis and 36 patients of the comparison group by ACS ESAPST. In assessing homeostasis most (n=41) of the patients had osteoarticular system in the 3rd grade impairment. We found that using system ACS ESAPST may help to detect tuberculous changes in osteo-articular system. The data obtained by system ACS ESAPST can be used for diagnosis of bone tuberculosis at an early stage of disease.
Quantum dots (QDs) are highly fluorescent nanoscale crystals with size-dependent emission spectra. Due to their excellent photophysical properties, QDs are a promising alternative to organic fluorescent dyes and fluorescent proteins for cell targeting, imaging, and drug delivery. For biomedical applications, QDs should be chemically modified to be stable in aqueous solutions and tagged with the recognition molecules or drugs. Here, we review surface modification approaches to, and strategies for, conjugation of bioactive molecules with QDs. There are a variety of methods of QD surface modification and QD incorporation into larger delivery systems that yield fluorescent nanocarriers from 10 nm to several micrometers. Conjugates of QDs with peptides, proteins, antibodies, oligonucleotides, and small molecules have been used for fluorescent targeting, tracking, and imaging both in vitro and in vivo. Due to an extremely high stability to photobleaching, QDs were used for long-term visualization. QD applications pave the way for new generations of ultrasensitive detection, diagnostic systems, as well as drug delivery approaches, combining accurate targeting, delivery, and imaging in a single assay. © 2015 American Chemical Society.
An immunodiagnostic lab-on-a-bead suspension microarray based on microbeads encoded with quantum dots (QDs) has been developed and preclinically validated for multiplexed quantitative detection of prostate cancer markers in human serum samples. The sensitivity and specificity of the microarray are similar to those of "gold-standard" single-analyte ELISA. Moreover, the array has an improved immunoassay capacity, ensures quantitative detection of multiple cancer biomarkers and may be operational in a considerably wider dynamic range of concentrations. The array is characterized by reduced time and cost of analysis and is compatible with classical flow cytometers. Proof-of-concept preclinical tests ensured simultaneous quantitative determination of free and total prostate-specific antigens in human serum, with clear discrimination between the control and clinical samples. The proposed approach is flexible and paves the way to development of a wide variety of immunodiagnostic assays for multiplexed early diagnosis of various diseases. From the Clinical Editor: Early diagnosis of cancer can result in better prognosis for patients. Thus, the use of specific tumor markers is widely employed in clinical practice. Traditional screening methods only employ single markers. The authors here developed a microarray system based on microbeads encoded with quantum dots (QDs), which can be used for multiplexed quantitative detection. The validated results on patient samples should lead to the development of a wider variety of assays for other diseases. © 2015 Elsevier Inc.
We have studied the transverse-momentum (p(T)) dependence of the inclusive J/psi production in p-Pb collisions at root s(NN) = 5.02 TeV, in three center-of-mass rapidity (y(cms)) regions, down to zero p(T). Results in the forward and backward rapidity ranges (2.03 y(cms) 3.53 and -4.46 y(cms) -2.96) are obtained by studying the J/psi decay to mu(+)mu(-), while the mid-rapidity region (-1.37 y(cms) 0.43) is investigated by measuring the e(+)e(-) decay channel. The p(T) dependence of the J/psi production cross section and nuclear modification factor are presented for each of the rapidity intervals, as well as the J/psi mean p(T) values. Forward and mid-rapidity results show a suppression of the J/psi yield, with respect to pp collisions, which decreases with increasing p(T). At backward rapidity no significant J/psi suppression is observed. Theoretical models including a combination of cold nuclear matter effects such as shadowing and partonic energy loss, are in fair agreement with the data, except at forward rapidity and low transverse momentum. The implications of the p-Pb results for the evaluation of cold nuclear matter effects on J/psi production in Pb-Pb collisions are also discussed.
It is shown that an experimental decrease in the reflection of a probe femtosecond pulse from an aluminum film heated by a higher-power femtosecond pulse can be quantitatively described taking into account the inhomogeneous distribution of the laser pulse field in the film and the evolution of the electron and lattice temperature during absorption of the heating inhomogeneous field. Analysis of the electron temperature evolution on the heated film surface combined with modern concepts about the influence of a surface volume charge on thermal emission gave the relation between the amount of emitted electrons and experimental data on the heating of the aluminum film by the femtosecond pulse.
The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E11 M, to the background absorption and to the absorption band of semiconducting nanotubes E11 S, respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E11 M) and 1745 nm (E11 S).
The mechanism of spectral broadening and self-compression of down-chirped femtosecond pulses in the visible range (473 nm) upon nonlinear interaction of a converging Gaussian beam with a 1-mm-thick fused silica plate is experimentally and theoretically investigated. It is found experimentally that when the intensity increases and plasma is formed in the sample, the regime of femtosecond pulse splitting is transformed into the single-pulse generation regime during nonlinear interaction. As a result of self-compression, the duration of the initial transform-limited pulse is reduced by a factor of 3. Based on the numerical solution of the generalised nonlinear Schrödinger equation, with the plasma formation disregarded, it is shown that the profile, spectrum and temporal phase of the pulse transmitted through the sample acquire a stationary shape behind the focal plane of the focusing mirror. The calculation results are in good agreement with experimental data. The possibility of parametric amplification of the pulse spectral components under given experimental conditions is discussed. © 2015 Kvantovaya Elektronika and Turpion Ltd.
The paper is a continuation of research carried out at Prague Asterix Laser System (PALS) related to the shock ignition (SI) approach in inertial fusion, which was carried out with use of 1ω main laser beam as the main beam generating a shock wave. Two-layer targets were used, consisting of Cu massive planar target coated with a thin polyethylene layer, which, in the case of two-beam irradiation geometry, simulate conditions related to the SI scenario. The investigations presented in this paper are related to the use of 3ω to create ablation pressure for high-power shock wave generation. The interferometric studies of the ablative plasma expansion, complemented by measurements of crater volumes and K α emission, clearly demonstrate the effect of changing the incident laser intensity due to changing the focal radius on efficiency of laser energy transfer to a shock wave and fast electron emission. The efficiency of the energy transfer increases with the radius of the focused laser beam. The pre-plasma does not significantly change the character of this effect. However, it unambiguously results in the increasing temperature of fast electrons, the total energy of which remains very small (0.1% of the laser energy). This study shows that the optimal radius from the point of view of 3ω radiation energy transfer to the shock wave is the maximal one used in these experiments and equal to 200 µm that corresponds to the minimal effect of two-dimensional (2D)-expansion. Such a result is typical for the ablation process determined by electron conductivity energy transfer under the conditions of one-dimensional or 2D matter expansion without any appreciable effect due to energy transfer by fast electrons. The 2D simulations based on application of the ALANT-HE code and an analytical model that includes generation and transport of hot electrons has been used to support of experimental data. Copyright © Cambridge University Press 2015
Nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) films with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738 nm have been grown using a microwave plasma CVD technique. The films were doped with Si via adding silane to CH4-H-2 reaction gas mixture in the course of the deposition process. The dependence of SiV PL intensity on silane concentration in gas shows a maximum at SiH4/CH4 ratios of 02% and 0.6% for NCD and MCD films, respectively, the maximum intensity for MCD being an order of magnitude stronger compared with that for NCD. The PL quenching at higher CH4 addition occurs, however, no significant degradation of the film structure, such as Si-induced amorphous carbon formation, was observed within the SiH4 concentration range studied (0%-0.9%). The higher PL efficiency of the MCD films is related to their less defective structure, as deduced from Raman spectroscopy analysis. (C) 2015 Elsevier B.V. All rights reserved.
Ultrafast intense photoexcitation of a silicon surface is complementarily studied experimentally and theoretically, with its prompt optical dielectric function obtained by means of time-resolved optical reflection microscopy and the underlying electron-hole plasma dynamics modeled numerically, using a quantum kinetic approach. The corresponding transient surface plasmon-polariton (SPP) dispersion curves of the photo-excited material were simulated as a function of the electron-hole plasma density, using the derived optical dielectric function model, and directly mapped at several laser photon energies, measuring spatial periods of the corresponding SPP-mediated surface relief nanogratings. The unusual spectral dynamics of the surface plasmon resonance, initially increasing with the increase in the electron-hole plasma density but damped at high interband absorption losses induced by the high-density electron-hole plasma through instantaneous bandgap renormalization, was envisioned through the multi-color mapping.
Three projects has been started in our laboratory as part of megagrant "High energy physics and nuclear medicine with silicon photomultiplier detectors" in NRNU MEPHI. The goal of these projects is development of devices for nuclear medicine in which replacement of photomultiplier tubes (PMT) with solid-state silicon photomultipliers promises various advantages. The first project is full-body SPECT, where replacement of PMT's could reduce size of the detector module and improve spatial resolution while keeping other parameters. The second project is development of a TOF-PET module. Replacement of PMTs with silicon photomultipliers makes it possible to use that detector not only in high magnetic fields but also for Time-of-Flight measurements (higher signal-to-noise ratio on final image) due to very high timing resolution of a SiPM. And the last project is the SiPM-based position-sensitive Gamma-spectrometer for dose monitoring in neutron-capture therapy based on SiPM's. © 2015 The Authors.
Luminescence properties of nitrogen-vacancy (NV) and silicon-vacancy (SiV) centers were investigated for the series of O-terminated composite nanodiamonds consisting of a high-pressure-high-temperature (HPHT) diamond core and a chemical-vapor-deposition (CVD) diamond outer layer of different thickness. It was found that emission of NV and SiV centers cease to "feel" the diamond surface at a distance of 12 and 4nm, respectively, from it. This finding determines minimum sizes of O-terminated nanodiamonds in which stable single photon emitters could be formed based on NV and SiV centers. Suggested composite diamond nanostructure are optimal for design of two-color luminescent markers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
GRIS (Gamma and Roentgen Irradiation of the Sun) is a scientific instrument for detection of hard X-rays and gamma-rays of solar flares with the energies from 50 keV to 200 MeV and for registration of solar neutrons with energies above 30 MeV. The experiment will be performed since 2019 onboard the International Space Station. The instrument includes two spectrometers: the low energy spectrometer based on a fast scintillator with high energy resolution 3.5-4.5% at 662 keV (LaBrinf3/inf(Ce) or CeBrinf3/inf) and dimensions ø7.62 × 7.62 cm, and the high energy spectrometer based on CsI(Tl) scintillator ø12 × 15 cm (which is also intended for neutron registration). The apparatus will be mounted on the oriented platform outside the Zvezda service module in 2019. Simulated response of the detectors to background radiation and to solar flares of different magnitudes and compositions obtained with GEANT4 toolkit confirms the instrument's possibility to measure different components of the solar flares spectra: narrow gamma lines, pion decay component, etc. with a sufficient confidence due to the usage of two types of detectors. © 2015 COSPAR. Published by Elsevier Ltd. All rights reserved.
The first space-time resolved spontaneous magnetic field (SMF) measurements realized on Prague Asterix Laser System are presented. The SMF was generated as a result of single laser beam (1.315 μm) interaction with massive planar targets made of materials with various atomic numbers (plastic and Cu). Measured SMF confirmed azimuthal geometry and their maximum amplitude reached the value of 10 MG at the laser energy of 250 J for both target materials. It was demonstrated that spatial distributions of these fields are associated with the character of the ablative plasma expansion which clearly depends on the target material. To measure the SMF, the Faraday effect was employed causing rotation of the vector of polarization of the linearly polarized diagnostic beam. The rotation angle was determined together with the phase shift using a novel design of a two-channel polaro-interferometer. To obtain sufficiently high temporal resolution, the polaro-interferometer was irradiated by Ti:Sa laser pulse with the wavelength of 808 nm and the pulse duration of 40 fs. The results of measurements were compared with theoretical analysis. © 2015 AIP Publishing LLC.
Specific features of ablation of a thin silver film with a 1-μm-thick layer of a highly transparent photoresist and the same film without a photoresist layer under single tightly focused femtosecond laser pulses in the visible range (515 nm) are experimentally investigated. Interference effects of internal modification of the photoresist layer, its spallation ablation from the film surface and formation of through hollow submicron channels in the resist without its spallation but with ablation of the silver film lying under the resist are found and discussed. © 2015 Kvantovaya Elektronika and Turpion Ltd.
Results of an experimental-theoretical study of spallation in synthetic diamonds are presented. In this study, data were first obtained on dynamic tensile strength of poly- and singlecrystal diamond samples at mechanical loads of up to 0.34 TPa and strain rates of 10–100 µssup−1/sup. Shock-wave loading was performed by 70 ps laser pulses on a Kamerton-T facility using a Nd:glass laser (second harmonics λ = 527 nm, pulse energy of up to ≈3 J) at intensities of ≈8 TW/cmsup2/sup. The obtained maximal value of the spall strength ≈16.4 GPa is 24% of the theoretical ultimate strength of diamond. Raman scattering experiments showed that a small amount of diamond was graphitized in the spall area on the backside of the sample. © 2015, Pleiades Publishing, Ltd.
Saturated dispersion resonances of the methane E(2)-line vinf1/inf+vinf4/inf-band over the temperature range 77-300 K were observed with two-mode Crsup2+/sup:ZnSe laser with intracavity absorption cell. The resonances amplitudes were measured and compared with calculations. © 2015 OSA.
Dynamical mechanical and positron annihilation spectroscopies were applied to study the structure of two Fe-Ga alloys with 18 and 21 at. pct Ga after quenching and subsequent annealing. It was found that the alloy with 18 pct Ga has much better damping capacity (? ? 30 pct) than the alloy with 21 pct Ga (? ? 5 pct). The reason for that is the ordering of the Ga atoms in Fe-21Ga alloy. Ordering processes in both alloys are studied at heating by differential scanning calorimetry, dilatometry, and internal friction or by step-by-step annealing using positron annihilation spectroscopy and hardness tests. Experimental results are explained by sequence of ordering transitions: A2 D03 L12.
We analyze the information content of wavelet features in identification and classification of peripheral blood leukocytes in searching for blast cells, using data-acquisition systems for diagnosis of acute leukemias.
We perform electric double-layer gating experiments on thin films of niobium nitride. Thanks to a cross-linked polymer electrolyte system of improved efficiency, we induce surface charge densities as high as ≈ 2.8 × 1015cm−2 in the active channel of the devices. We report a reversible modulation of the superconducting transition temperature (either positive or negative depending on the sign of the gate voltage) whose magnitude and sign are incompatible with the confinement of the perturbed superconducting state to a thin surface layer, as would be expected within a na¨ıve screening model. © 2015 Springer Science+Business Media New York
The morphology of craters on the YAG crystal surface caused by broadband (≈500) nanosecond laser pulses with intensities 10sup9/sup-10sup10/sup W cmsup-2/sup was studied. A mechanism of structural changes and the appearance of craters due to plastic deformations in the crystal are discussed. © 2015 Astro Ltd.
Desorption/ionization on silicon (DIOS) is widely used in modern mass spectrometry for obtaining ions of various organic substances. The high efficiency of DIOS suggests that it may be a promising method in ion-mobility spectrometry (IMS) using gas-phase ion separation. The influence of laser wavelength and intensity on DIOS of trinitrotoluene (TNT) molecules under ambient conditions has been studied. If laser with a wavelength of 266 or 355 nm is used, TNT molecules predominantly form (TNT - H)- negative ions. Their formation has been found to result from laser-induced proton transfer from TNT molecules to the porous silicon (pSi) surface, rather than gas-phase ion-molecule reactions. The dependence of the yield of (TNT - H)- ions on the laser intensity has been analyzed. The ion yield curve has been demonstrated to fit the Arrhenius function at laser intensity lower than ∼2.5×107 W/cm2. Experiments have shown that the desorption/ionization of TNT molecules is not a purely thermal process. The results demonstrate that DIOS can be widely used in the IMS technology. © 2015 American Chemical Society.
The method of epitaxial growth of localized photoluminescence sources in the form of the ordered microcolumn diamond structures with silicon-vacancy (SiV) color centers is implemented. The process is based on diamond deposition in microwave plasma in CH4-H2 mixtures in microwells in a silicon mask on a diamond single crystal substrate, where the Si mask itself is a silicon doping source. Strong photoluminescence of SiV centers at a wavelength of 738 nm is detected; the spatial distribution of luminescence completely coincides with the synthesized structure arrangement.
This work discusses a system for monitoring cancer patients during comprehensive therapy of lymphatic leukemia. The input parameters of the monitoring system are blood characteristics. The output parameters are classification characteristics. The software system improves the diagnostic capacity of medical personnel.
It was reliably proved in recent years both theoretically and experimentally that the electrically controlled birefringence (Formula presented.) of chiral smectic C* phase with subwavelength helix pitch is proportional to the square of the electric field E. The goal of the present work is to investigate the restrictions of the quadratic effect imposed by the thickness of the smectic C* layer between two solid substrates, and by the frequency of applied voltage. It is shown that these restrictions are mainly associated with the dielectric dispersion of the Goldstone mode under various boundary conditions. © 2015 Taylor & Francis.
Recently it was shown that in deformed helix ferroelectric (DHF) structure, the electrically controlled birefringence (Formula presented.) of chiral smectic C* phase with subwavelength helix pitch ((Formula presented.) is known to be proportional to the square of the electric field E) depends on the cell thickness and on the frequency of applied voltage, given as a Step function of the time. The purpose of the present work is to investigate whether this quadratic effect depends also on the voltage function shape, comparing the electrically controlled birefringence (Formula presented.) and the Kerr constant in DHF cells with different thickness, driven by STAIR and Step voltage functions. © 2015 Taylor & Francis
The source of X-ray radiation with quantum energy in the range hv = 1-0 keV was developed for interaction of x-ray with matter and modification of solid surface. It was based on vacuum spark discharge with laser-triggering. The comprehensive study of X-rays imaging, quantum energy and temporal characteristics was carried out. Correlated estimates of the temperature of the investigated plasma based on moderate powerful vacuum discharge were obtained using the two methods in the case of lowstored energy (E1 J). © 2015 The Authors.
The source of X-ray radiation with the energy of quanta that may vary in the range hν = 1÷12 keV was developed for studies in X-ray interaction with matter and modification of solid surfaces. It was based on a vacuum spark discharge with the laser triggering. It was shown in our experiments that there is a possibility to adjust X-ray radiation spectrum by changing the configuration of the electrode system when the energy stored in the capacitor is varied within the range of 1÷17 J. A comprehensive study of X-ray imaging and quanta energy was carried out. These experiments were carried out for the case of both direct and reverse polarity of the voltage on the electrodes. Additionally, ion composition of plasma created in a laser-triggered vacuum discharge was analyzed. Highly charged ions Znsup(+21)/sup, Cusup(+20)/sup and Fesup(+18)/sup were observed.
The light microscopy method is widely used in the diagnosis of the neoplastic diseases of the blood system. The experience and qualifications of the physician have a significant role in the outcome of microscopy studies of blood cells. But sometimes there is a dispute among experts on the identification of cell types. For this reason, the objectification of the blood cells description is an actual problem. One of the essential features in the classification of immature blood cells (e.g. blast cells) is a type of chromatin structure in the nucleus of these cells. The quantitative description of the blood cells images with using the wavelet analysis is discussed in the article. The description models on the basis of wavelet functions Haar, Daubechies, Cohen-Daubechies-Feauveau were studied. The selection of blood cells with different chromatin structure was formed to assess the effectiveness of the proposed models. The quantitative features were identified for the greatest discernment of the chromatin structure according to the results of the experiments. The proposed approach can be used to automate the diagnosis of hematologic diseases. © 2015 World Scientific and Engineering Academy and Society. All Rights Reserved.
The article considers application of technology of analysis of cytological slides in external quality control of clinical diagnostic laboratories. The advantages of virtual slides are demonstrated against other applied technologies of external evaluation of quality i.e. slide plate and digital micro-photography. The conditions of formation of virtual slides for external evaluation of quality of clinical diagnostic laboratories. The technology of their application is described. The success of practical application of considered technology in the Federal system of external evaluation of quality is emphasized.
A model for melting of a nanoporous material by means of nanosecond laser pulses was developed. In present model the pore size is small in comparison with film thickness and when film temperature reaches the melting temperature there is an instantaneous collapse of pores under the influence of surface tension forces. In numerical solution the temperature dependence of thermophysical quantities of a material and material porosity were taken into account. The melting penetration depth was determined with due regard for the material porosity. © 2015 The Authors.
Light-current and current-voltage characteristics of a set of high-power laser diodes of the spectral region of 980 nm, fabricated by the authors, are experimentally studied. The dependences of their total efficiency and heat load on the pump current are constructed. The latter experimental dependence is used for calculations in the three-dimensional thermal model of the laser diode with a stripe contact width of 100 µm. Thermal fields are studied and isothermal surfaces are constructed for laser diodes fabricated on C-mount heat sink elements under heat loads corresponding to output powers of 10 W and higher in continuous mode. © 2015, Allerton Press, Inc.
We discuss the design and application perspectives of different crystal, ceramic and composite-type submounts with thermo-compensating properties as well as submounts from materials with high thermal conductivity for overcoming thermal problem in high-power laser diodes (LD) and improving thermal management of other high-power optoelectronic and electronic semiconductor devices. Thermal fields in high-power laser diodes were calculated in 3 D thermal model at CW operation for some heatsink designs taking into account the experimental dependence of laser total efficiency against pumping current in order to extend the range of reliable operation up to thermal loads 20-30 W and corresponding output optical power up to 15-20 W for 100 μm stripe laser diodes. © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.
The thermal stabilization system for the RED-100 liquid-xenon two-phase emission detector has been designed and tested. The RED-100 detector is developed by the Russian Emission Detectors (RED) collaboration for the experiment aimed at detecting the effect of coherent neutrino scattering from xenon nuclei. The system is based on thermosyphons (closed two-phase tubular heat pipes) that are filled with nitrogen and use free-boiling liquid nitrogen pool as a cooling machine. The system is capable of condensing 180-kg liquid xenon sample for 24 h and maintaining the temperature of a titanium cryostat in the range of 160-190 K with a precision about 0.1 K.
Central ignition of a thin two-layer-shell fusion target that is directly driven by a 2-MJ profiled pulse of Nd laser second-harmonic radiation has been studied. The parameters of the target were selected so as to provide effective acceleration of the shell toward the center, which was sufficient for the onset of ignition under conditions of increased hydrodynamic stability of the ablator acceleration and compression. The aspect ratio of the inner deuterium-tritium layer of the shell does not exceed 15, provided that a major part (above 75%) of the outer layer (plastic ablator) is evaporated by the instant of maximum compression. The investigation is based on two series of numerical calculations that were performed using one-dimensional (1D) hydrodynamic codes. The first 1D code was used to calculate the absorption of the profiled laser-radiation pulse (including calculation of the total absorption coefficient with allowance for the inverse bremsstrahlung and resonance mechanisms) and the spatial distribution of target heating for a real geometry of irradiation using 192 laser beams in a scheme of focusing with a cubo-octahedral symmetry. The second 1D code was used for simulating the total cycle of target evolution under the action of absorbed laser radiation and for determining the thermonuclear gain that was achieved with a given target.
Micro and nanostructure of scaffolds made from fibroin of Bombyx mori silkworm by salt leaching technique was studied by scanning probe nanotomography. Nanopores with dimensions in range from 30 to 180 nm are observed in the scaffold volume. Three - dimensional analysis of obtained data shows that degree of scaffold nanoporosity is 0.5% and nanopores are not interconnected with each other. Usage of scanning probe nanotomography technique enables to obtain unique nanoscale information of 3D structure of biopolymer nanomaterials. © 2015 The Authors.
The charge collection performance of a three-dimensional diamond-graphite detector is reported. Buried graphite pillars with high aspect ratio were formed inside a single crystal synthetic diamond slab by using a femtosecond IR laser with 200 kHz of repetition rate. Grouped in two series and connected by graphite strips on the surface, eight independent 3D electrodes were used to collect the charge carriers generated by energy deposited in the detector by sup90/supSr,Y β-particles. Different impinging configurations were used to test charge collection and signal dependence on voltage. Reversing the bias polarity the pulse height distribution does not changes and the charge collection saturation of any group of connected pillars was observed around ±80 V (0.53 V/μm). The average charge collected by one pillars row is Qinfav/inf=1.60±0.02 fC, with electrons impinging orthogonally the rows, in such a way demonstrating full charge collection. © 2015 Elsevier B.V.
We demonstrate the first Crsup2+/sup:CdSe single crystal laser with diode laser array pumping. Laser efficiency of 12% with output power of 280 mW was obtained. Tunable CW operation was observed in 2450-3060 nm range. © OSA 2015.
Energy transfer from nanostructures to biological supramolecular photosystems is an important fundamental issue related to the possible influence of nanoobjects on biological functions. We demonstrate here two-photon-induced Forster resonance energy transfer (FRET) from fluorescent CdSe/ZnS quantum dots (QDs) to the photosensitive protein bacteriorhodopsin (bR) in a QD-bR hybrid material. The two-photon absorption cross section of QDs has been found to be about two orders of magnitude larger than that of bR. Therefore, highly selective two-photon excitation of QDs in QD-bR complexes is possible. Moreover, the efficiency of FRET from QDs to bR is sufficient to initiate bR photoconversion through two-photon excitation of QDs in the infrared spectral region. The data demonstrate that the effective spectral range in which the bR biological function is excited can be extended beyond the band where the protein itself utilizes light energy, which could open new ways to use this promising biotechnological material. (C) 2015 Optical Society of America
We report the results of the femtoscopic analysis of pairs of identical pions measured in p-Pb collisions at root(NN)-N-S = 5.02 TeV. Femtoscopic radii are determined as a function of event multiplicity and pair momentum in three spatial dimensions. As in the pp collision system, the analysis is complicated by the presence of sizable background correlation structures in addition to the femtoscopic signal. The radii increase with event multiplicity and decrease with pair transverse momentum. When taken at comparable multiplicity, the radii measured in p-Pb collisions, at high multiplicity and low pair transverse momentum, are 10%-20% higher than those observed in pp collisions but below those observed in A-A collisions. The results are compared to hydrodynamic predictions at large event multiplicity as well as discussed in the context of calculations based on gluon saturation.
We have studied the upper limits for incorporation of nitrogen and formation of arrays of nitrogen-vacancy (NV) color centers in optical-quality single-crystalline diamond synthesized by chemical vapor deposition (CVD). The CVD diamond samples were grown in a microwave plasma in methane-hydrogen mixtures with high content (200-2000 ppm) of the nitrogen dopant in the gas mixture, and were analyzed using Raman and photoluminescence spectroscopy. From the UV absorption spectra, we established that the solubility limit for substitutional nitrogen in the studied material is close to 2 center dot 10(18) cm(-3) (under typical synthesis conditions), which lets us in particular form arrays of NV center with similar concentrations by means of irradiation and annealing.
The possibility of laser induced variation of optical and electrical properties of conductive nanocrystalline diamond (CNCD) films has been demonstrated. The films were produced by microwave plasma chemical vapor deposition (MPCVD) from CH4:H2:N2 gas mixtures. The films were irradiated in air with 20 ns pulses of an ArF excimer laser ( = 193 nm). It was found that low laser pulse intensity (∼0.05 J/cm2), well below film surface graphitization (∼0.3 J/cm2) and nanoablation (∼0.08 J/cm2) thresholds, induces changes of the film properties. The effect requires multiple pulsed irradiation and results in a decrease of the film electrical conductivity, which is accompanied by optical bleaching of the diamond film absorption © 2015 Elsevier B.V. All rights reserved.
We have investigated the role of adsorption water in the local transformation of multilayer graphene deposited on an oxidised silicon substrate, which was exposed to nanosecond low-intensity focused laser radiation with a wavelength of 532 nm in the air. Experimental data obtained for a laser energy density E = 0.04 J cm(-2) suggest that the formation of micropits (craters) is a consequence of the multipulse removal of the layer of a water adsorbate, which is intercalated between graphene and the substrate, from the zone of laser irradiation of the graphene sheet. The energy threshold of graphene damage in the regions devoid of water was found to be higher in comparison with the initial one (0.058 against 0.048 J cm(-2)). According to computer simulations of the heating dynamics of the sample and the heat distribution in the substrate - adsorbate - graphene multilayer system, at energy densities corresponding to the experimental ones the water adsorbate layer heats to a temperature sufficiently high to form an increased-pressure vapour cavity under the graphene film.
The results of measurements of the hypersound velocity and absorbtion by Mandelstam—Brillouin spectra in aqueous solutions of glycerin in a wide temperature (viscosity) range are presented. It is shown that the experimental results are well described by formulas of the Isakovich—Chaban nonlocal theory based on the assumption about the two-component structure of a viscous liquid containing clusters with sharp boundaries, “floating” in a disordered liquid. In the experiment, the viscous component concentration in a low-viscosity medium was varied, which corresponded to cluster concentration variations in it. It was shown that clusters are stable structures. The number of clusters decreases as a low-viscosity solvent is added, while their size remains unchanged. © 2015, Allerton Press, Inc.
Abstract This review discusses recent works on monolayer, multilayer and polymer films of various crown-ether derivatives. Preparation and investigation of such membrane nanostructures based on photosensitive and surface-active crown-ethers is a rapidly growing field at the "junction" of colloids and polymers, materials sciences and nanotechnology. These membranes can serve as convenient models for studying the self-organization and molecular recognition processes at interfaces that are typical for biomembranes. The results obtained for such structures by absorption and fluorescence spectroscopy, atomic force and Brewster-angle microscopy, surface pressure and surface potential isotherm measurements have been described. The possibility of developing multifunctional materials possessing advanced properties has been demonstrated. © 2014 Elsevier B.V.
Design of the nanostructures based on membrane proteins (the key functional elements of biomembranes) and colloid nanoparticles is a fascinating field at the interface of biochemistry and colloids, nanotechnology and biomedicine. The review discusses the main achievements in the field of ultrathin films prepared from bacterial reaction center proteins and light-harvesting complexes, as well as these complexes tagged with quantum dots. The principles of preparation of these thin films and their structure and properties at different interfaces are described; as well as their characteristics estimated using a combination of the modern interfacial techniques (absorption and fluorescence spectroscopy, atomic force and Brewster angle microscopy, etc.) are discussed. Further approaches to develop the nanostructures based on the membrane proteins and quantum dots are suggested. These supramolecular nanostructures are promising prototypes of the materials for photovoltaic, optoelectronic and biosensing applications.