Table of contents

International Conference PhysicA.SPb/2017

The International Conference PhysicA.SPb was held 24-26 October 2017 in Saint-Petersburg, Russia. The Conference continues the tradition of Saint-Petersburg Seminars on Physics and Astronomy originating from mid-90s. Since then PhysicA.SPb maintains both scientific and educational quality of contributions delivered to the young audience. This is the main feature of the Conference that makes it possible to combine the whole spectrum of modern Physics and Astronomy within one event.

PhysicA.SPb/2017 has brought together over 300 young scientists and their colleague professors from many universities and research institutes across whole Russia as well as from Australia, Belarus, Germany, Finland, Ireland, Netherlands, United Kingdom, and France. Oral and poster presentations were combined into well-defined sections among which one should name Astronomy and Astrophysics, Optics and spectroscopy, Physics of ferroics, Nanostructured and thin-film materials, Mathematical physics and numerical methods, Devices and materials for the THz and microwave ranges, Biophysics, Optoelectronic devices, Surface phenomena, Physics and technology of energy conversion, Plasma physics, hydrodynamics and aerodynamics, Nuclear and elementary particle physics, Impurities and defects in solids, and Physics of quantum structures.

This issue of the Journal of Physics: Conference Series presents the extended contributions from participants of PhysicA.SPb/2017 that were peer-reviewed by expert referees through processes administered by the Presiders of the Organising and Programme Committees to the best professional and scientific standards. This was made possible by the efforts of the Sectional Editors of this Issue: Prof. Petr Arseev (Lebedev Physical Institute), Prof. Alexander Ivanchik (Ioffe Institute), Prof. Polina Ryabochkina (Ogarev Mordova State University), Prof. Yuri Kusraev (Ioffe Institute), Dr. Sergey Nekrasov (Ioffe Institute), Dr. Nikolay Bert (Ioffe Institute), Dr. Nikita Gordeev (Ioffe Institute), Dr. Alexey Popov (Ioffe Institute), Dr. Prokhor Alekseev (Ioffe Institute), Dr. Mikhail Dunaevskii (Ioffe Institute), Dr. Alexandra Kalashnikova (Ioffe Institute) and Prof. Dmitry Khokhlov (Moscow State University).

The Editors: Nikita S. Averkiev, Sergey A. Poniaev and Grigorii S. Sokolovskii

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Pulsar wind nebulae with bow shocks (BSPWNe) can efficiently accelerate electrons and positrons of the pulsar wind (PW). The particles injected into such nebulae at the PW termination shock can gain energy due to the Fermi acceleration in the colliding shock flow between the two shocks. Monte-Carlo modeling of the PW particle transport through the nebula reveals a significant deformation of their spectrum between the shocks in comparison with the injected spectrum. The maximal energies achieved by the hard component of the spectrum (f (E) ∝E^−p with p ˂ 2) depend on the flow velocities. Comparison of the obtained spectra of the accelerated PW particles in BSPWNe and their synchrotron emission maps with the observational data obtained in the optical, far-UV and X-ray bands allows one to constrain global parameters of particular BSPWNe such as Lorentz-factors of their PWs.

The interaction of high energy gamma quantum to thermal bremsstrahlung photons of hot intracluster gas with producing electron-positron pair is considered. It is supposed that galaxy cluster is relaxed and electron number density and temperature profiles are spherical symmetric. The dependence of optical depth on gamma quantum energy and distance to cluster center is considered. It is shown that the optical depth due to considered interaction is about 10⁻⁸ − 10⁻⁵ at gamma quantum energy 100 MeV - 1 TeV.

On the basis of satellite observations taken during "Apollo", "Clementine", "Kaguya", "LRO", "GRAIL", and "SMART-1" space missions a model of lunar physical surface of 18th order of expansion into a series of harmonic coefficients was constructed. In order to expand the data on relief into spherical functions a step-by-step regression was applied. All the constructed models included only significant elements. The regression analysis of the models of lunar relief for various expansion orders was carried out; as a result, it was determined that increase in order of expansion did not play a prominent role from a certain stage. The influence of model's overdetermined structure on values of the parameters determined was also investigated.

When using the numerical approach to construct the theory of physical libration of the Moon, it is necessary to solve the problem of comparing the numerical and analytical theories of lunar orbital motion. During these studies, the impact on the parameters of physical libration from the Moon's center of mass motion is determined. The paper contains the results of determining the effects caused by distinction in the position of lunar center of mass whose location is obtained according to two various lunar orbital theories. The analytical theory by Gutzwiller and Schmidt [1] constructed within the main problem of the Moon's motion and DE432 numerical theory taking into account a large number of factors, that extend beyond the main issue and that would be complicated or even impossible to consider when obtaining the analytical solution, are compared. Some reductions had been carried out in order to bring both theories to a unified reference system. Then the positions of the Moon's center of mass obtained in those theories were compared at an interval of 800 years. As a result, it was established that the amplitude of residual differences at the interval did not exceed 80 arc seconds in longitude and 10 arc seconds in latitude. The main reason for the obtained differences is neglecting planetary perturbations in the analytical theory. Other effects to distinguish the numerical theory from the analytical one are: motion of plane of the ecliptic, the Earth's and Moon's flattening, tidal effects etc. Those effects also cause the difference between the theories but slightly.

This paper presents the results of reconstruction of the heliospheric modulation potential based on the content of ¹⁴C cosmogenic isotope in natural archives from the beginning of 11-th to mid 19th century. This time period includes a number of grand minima of solar activity such as Oort, Wolf, Spoerer, Maunder, Dalton and climatic Little Ice Age. Medieval maximum of solar activity has happened during this time interval as well during this period there were variations both in the atmospheric carbon dioxide concentration and in the global temperatures, which were taken into account in the reconstruction of the ¹⁴C production rate in the terrestrial atmosphere. As a result, values of the modulation potential were reconstructed using different temperature proxies.

We present an approach to finding distances to young supernova remnants. Our method is based on hydrodynamical simulations of Tycho's SNR using the SUPREMNA code. For the explosion models, we use the classical W7 deflagration model and the delayed detonation model that was previously shown to provide good fits to the X-ray emission of Tycho's SNR. Combining our hydrodynamical simulations with the Chandra high-resolution images of the remnant obtained in 2015, we derive a distance estimate to Tycho's SNR of 2.8 ± 0.4 kpc.

We study the definitions of energy, naturally arising in the splitting theory, which is the field theoretic formulation of the Regge-Teitelboim gravity. The latter regards our spacetime as a surface embedded in a flat bulk. The splitting theory describes embedded spacetime in the language of the some field theory in a flat bulk. We consider the Noether energy-momentum tensor (EMT) and the metric EMT defined by the variation with respect to the metric of a flat bulk. We discuss a localizability of energy. Then using these EMTs we calculate the full energy of an isolated massive body. We compare the results with the standard general relativity results obtained from the Einstein energy-momentum pseudotensor (pEMT) and from the M0ller pEMT. Finally, we propose the several ways of correction of the definitions of the energy in the splitting theory.

The extreme cosmic event that occurred in AD 775 was detected using ¹⁴C measurements in tree rings and ¹⁰Be, ³⁶Cl abundances in polar ice cores. Perhaps it is the most powerful solar proton event in the past several thousands of years. Simulation of isotope production with the spectra of solar flares observed in the modern era (23.02.56, 04.08.72 etc.) showed that to produce the measured amount of radionuclides, the particle fluence in the AD 775 event has to be by tens - hundreds times greater than the modern powerful solar events. The results of calculations of long-lived cosmogenic radionuclides (¹⁴C, ¹⁰Be, ³⁶Cl) production in the Earth's atmosphere are presented.

In the recent work by Gusakov, Kantor & Ofengeim [Phys. Rev. D 96, 103012 (2017)] a new method to calculate the quasistationary evolution of magnetic field in the core of a neutron star was proposed. Here we further develop it, focusing on a simple case of neutron-proton-electron (npe) core composition with purely poloidal magnetic field B. We find that the meridional flow of the npe-fluid can be unexpectedly large. We estimate the typical timescale τ of the field evolution due to dragging of the magnetic field lines by this flow and show that τ can be as small as ∼ (100 — 1000) yr for magnetars with B ∼ 10¹⁶ G.

The report gives a broad outline of deep, down to a 28 magnitude limit, optical observations of the γ-ray pulsar J2055+2539 (total exposure time ≈ 7.9 ks), which were obtained with the Gran Telescopio Canarias in the g'-band. To derive the most precise pulsar position we utilized recent Chandra observations, where the pulsar X-ray counterpart is detected with high significance. Using two reference stars detected both in the optical and X-rays we improved the absolute astrometry accuracy for the Chandra image of the PSR J2055+2539 field. The resulting Chandra pulsar position error circle of about 0''.2 is compatible with the 1σ Fermi position of the pulsar (0''.5), obtained from timing analysis.

No optical counterpart was detected within the refined pulsar error circle. However, we managed to correct a shallow upper limit on the optical flux of the pulsar, which had been derived from preliminary observations. The new value g' = 26.6. It is brighter than the limit stated above due to the presence of a nearby star, 0''.8 from the pulsar, with g' = 20.3. The inspection of the pulsar multiwavelength spectrum suggests a break between the optical and X-rays.

An epoch before first stars and galaxies formation, so-called cosmic Dark Ages, still remains unobserved. One of the possibilities for observation phenomena took place during Dark Ages is studying hyperfine transition of such elements as hydrogen and deuterium. In this article there were examined physical processes in the Universe after recombination and evolution of 21 and 92 cm brightness temperature and studied influence of baryon-photon ratio on this radiation.

The z_abs = 2.504 Lyman Limit absorption system (LLS) towards Q1009+2956 has previously been used to estimate the primordial deuterium abundance. Since the initial measurement by Burles & Tytler [1], this quasar has been observed extensively with the Keck telescope, providing a substantial increase in signal-to-noise (from 60 to 147 at continuum level of Ly-α at z_abs = 2.504). We explore a set of different models for the absorption system and find that the deuterium feature is contaminated by Ly-α absorption from a low column density HI cloud. This significantly limits precision to which one can estimate the D/H ratio in this LLS. Our final result for this system $\text{D/H}=2.48_{-0.35}^{+0.41}\times {{10}^{-5}}$ has the same relative uncertainty of 17% as the previous estimate by [1] despite the far higher signal-to-noise of our dataset. A weighted mean of 13 D/H measurements available in the literature (including our result) gives the primordial deuterium abundance of (D/H)_p = (2.545 ± 0.025) × 10⁻⁵ and the corresponding baryon density of the Universe of Ω_bh² = 0.02174 ± 0.00025 marginally inconsistent with the 2015 Planck CMB data. More measurements of the deuterium abundance in quasar spectra are needed to check this tension.

Evolution of X-ray surface brightness and spectra of fine spatial structures in the Vela pulsar wind nebula (PWN) are studied. Variability of morphology and the spectrum of a small-scale structure at the base of the southern jet of the nebula – a bright transverse bar is investigated for the first time. The size of the bar located within 4''–5'' from the Vela pulsar is ∼ 4.5'' × 1.5''. It is shown that brightness, shapes, and positions of the bar and the southern jet base vary on the timescale of 1–2 weeks, the bar can disappear and emerge again within 10 days. The power-law photon index of the jet base is much harder than that of the bar, 1.20 ± 0.12 vs 1.65 ± 0.15. The latter index is close to 1.6, a typical value for synchrotron emission of electrons accelerated at an ultrarelativistic shock. We speculate that bright blobs seen on both sides of the southern jet base may have the same nature as the bright blobs in the Crab PWN, which are believed to mark the position of the termination shock of the pulsar wind.

Hybrid simulations of quasiperpendicular collisionless shocks (QRCS) in multicomponent plasmas have revealed that weakly charged ions can keep anisotropic nonequilibrium distributions at relatively long distances downstream the shock front. However, analytic considerations suggest that such distributions lead to growth of the Alfven ion cyclotron (AIC) instability, which in turn governs isotropisation. Hence, we have conducted targeted hybrid simulations of QRCS with increased accuracy, which appeared to agree with the analytical predictions and suggest that the nonequilibrium distributions eventually relax due to the AIC instability. On another hand, downstream electromagnetic instabilities generated by anisotropic particle distributions may affect the energy balance, therefore influencing macroscopic shock parameters, such as the compression ratio. Simulations of QRCS with parameters close to those of the heliospheric termination shock measured by the Voyager mission, showed that an admixture of just 0.7% (by mass) of oxygen decreases the compression ratio by 3-4%. Thus, one might conclude that along with the effect of the pickup ions, the multi-species composition of the interplanetary plasma can add to the observed decrease of the shock compression.

Spectroscopy of the Lya forest in quasar spectra proved to be a useful tool for probing the intergalactic gas. We developed the automatic program for Voigt profile fitting of Lya forest lines. We run this code on 9 high resolution (∼ 50000) quasars spectra with a high signal-to-noise ratio (∼ 50 — 100) from the Keck telescope archive and obtained the sample of single well-fitted Lya lines. Fitting the joint 2d distribution of column density and Doppler parameter from this sample by physically reasonable model we estimate a power law index, γ, of the equation of state of the intergalactic medium in the redshift range z ∼ 2 — 3. We found that our measurement is in an agreement with measurements by other groups obtained with Voigt profile fitting technique.

We recalculated the distance to 554 galactic Planetary Nebulae (PNe) using the relation between the ionized mass of the nebula μ and the optical thickness parameter τ obtained by Akimkin et al. [1]. We classified these nebulae according to the Peimbert [9] types modified by Quireza et al. [11]. The obtained by us distances to galactic PNe were used to obtain the scale heights h for different subsystem of the Milky Way. Next values if h were estimated: h = 208 ± 10 pc for thin disk objects, h = 600 ± 54 pc for thick disk ones, and h = 1378 ± 180 pc for halo PNe.

High-resolution Chandra X-ray observations of Tycho's supernova remnant (SNR 1572) have revealed several series of bright, nearly parallel stripes in some regions of the SNR clearly seen in 4-6 keV band images. The observed radiation of Tycho's SNR is most likely the synchrotron radiation of electrons with energies well above TeV. In this paper we present the modeling of synchrotron X-ray images of Tycho's SNR in order to reveal the physical mechanism of the observed coherent structures formation. It is shown that the mirror instability, which evolves in plasma near SNR shock as a result of anisotropic distribution function of accelerated particles, can be the reason of the bright stripes.

The nature of dark matter in modern physics is an important problem. Therefore, in this paper we consider a quantum system consisting of two identical particles. These particles are candidates for the role of dark matter. We will call them graviatoms and they could be formed in the early Universe. In this paper we have found the energy spectrum of the gravitatom from particles of dark matter, the Bohr radius, the intensity of gravitational radiation, the frequency of radiation, and the lifetime of a state. This lifetime is great for superheavy particles. Estimates of these values for different values of the masses of particles of dark matter are given.

In this paper, the possibility of multiparametric analysis application for studying genetic connections between meteor showers and their parental bodies is considered. The modern methods of determining such connections take into account some parameters of parental bodies, such as size, orbital elements, and chemical composition. Obviously, all of these parameters refer to different physical substances. In this regard, simultaneous estimation of the impact of those parameters may be carried out with a given probability using regression analysis. The aim of this work is to develop a method of robust estimation of genetic parameters and use it for asteroid and meteor genetic connections analysis.

The purpose of this paper is to present the results of structural analysis of gravitational and topographic parameters of Venus using the data from space missions, including "Magellan". The model gravitational potentials are presented as analytical functions of coordinates. The model is constructed on the basis of variations of Venus' artificial satellites orbits. As a result, fractal correlations of Venus' geoid anomalies and gravitational potential in both longitude and latitude as well as the mean value of fractal dimensions are calculated. The mean fractal dimension of Venus topographic model in latitude is $\overline{D}=1.061$, in longitude is $\overline{D}=1.037$; the mean fractal dimension of Venus gravitational potential model in latitude is $\overline{D}=0.96$, in longitude is $\overline{D}=1.053$.

Ground-based baseline observations of the potentially hazardous asteroid 2014 JO25 were made. The data were processed and the accuracy of the orbital elements of the asteroid was estimated on the basis of the obtained observations and the data from the Minor Planet Center. Also, the estimation of BVRI color indices of the asteroid was made.

The problem of particle acceleration by collisionless astrophysical shocks is of fundamental importance for the cosmic ray origin problem and for the high energy astrophysics as a whole. Fast magnetohydrodynamical shocks produced by relativistic jets are considered as very likely sites of cosmic ray acceleration. While cosmic ray acceleration by both non-relativistic and ultra relativistic shocks was studied in some details, the shocks of moderate Lorentz factors have attracted much less attention so far, while they are important for modeling gamma-ray burst afterglows and a number of other interesting objects. In this paper we present simulations of relativistic shock waves in electron-proton plasmas obtained with an implicit particle-in-cell code for the initial study the particle injection efficiencies.

Specialized Pt/C single nanowhisker probes for atomic force microscopy have been used to study the native cellular bio-objects (fibroblasts) in PBS liquid. Optimal parameters of nanowhisker fabrication were found such as accelerating voltage 5 kV, exposure time 5-10 sec, aperture of electron microscope 20 μm. The preliminary results of our study showed an improvement of image contrast and adhesion forces when using nanowhisker probes compared to the standard Si probes.

In paper the Memory functions formalism (MFF) is used to analyze the dynamics of walking stride interval of healthy young adults, healthy old adults and Parkinson's disease. Using the non-Markovian parameter, we determine the degree of manifesting the statistical memory effects in dynamics of the walking stride interval for the considered volunteers. The stride dynamics of the first two volunteer groups demonstrates the low memory effects reflected in high values of non-Markovian parameter.The Parkinsonian patients demonstrate the non- Markovian behavior of stride dynamics with strong memory effects. The method can be used to study the signal dynamics of the different nature.

In this paper we use the Memory function formalism to study the collective phenomena in EEG signals from subjects with musical abilities ("musicians") and from subjects with a low level of these abilities ("non-musicians") at solving the three cognitive tasks. We have revealed the spectral features in the EEG collective dynamics of these groups, as well as sensor pairs, which have the a different interaction of signals.

DNA interaction with disulfophthalocyanine of cobalt (CodSPC) was studied by UVVIS spectrophotometry and low gradient viscometry. The thermal denaturation of DNA in complexes with CodSPC was compared with free DNA denaturation. The small increase in melting temperature indicates that the secondary structure of DNA in complexes is stable. As a results of experimental research the external binding of CodSPC to DNA was determined. The only one type of binding is accompanied by stacking of heterocycles at high concentrations of CodSPC. An increase in viscosity of DNA solutions with the growth of CodSPC concentration can be explained by intermolecular DNA contacts via CodSPC.

DNA damages are the main cause of radiation-induced cell death, mutations and carcinogenesis. The study of influence of environmental conditions on the radiation damage of DNA structure is important for the wide range of medical problems. The present work is devoted to the study of alterations in DNA structure caused by γ-irradiation at the variation of counterions concentration and dose rate.The DNA solutions of the ionic strengths 0.005M and 0.15M NaCl were exposed to γ-radiation with the doses of 0-100 Gy, dose rates2.3Gy/s and 0.3 Gy/s. The lesions in DNA structure (base damages, partial denaturation) were studied by the methods of UV absorption spectroscopy and DNA melting.Radiation-induced base damages decrease at the rise of NaCl concentration in the solution and at the lowering of the dose rate. The stability of DNA secondary structure increase at the rise of ionic strength of irradiated solution. The influence of radiation dose rate on the DNA helicity reveals definitely only at the dose of 100 Gy. The relative fall of the DNA melting temperatureafter the irradiation slightly depends on the dose rate and NaCl concentration.

Complications in designing of one-lead electroencephalographs (EEG) monitor for tracking the deepness of narcosis are discoursed. Connection between the level of narcosis and statistical attributes of the bioelectric signal is disclosed. Electric circuit of the developed EEG monitor is discussed. Obtained recordings of the EEG and ECG signals are shown.

Super-resolution microscopy is especially useful for visualization of structures in small cells which sizes are comparable to the diffraction limit, for instance, in Mollicutes species. In this work we obtained super-resolution images of FtsZ and IbpA protein structures in fixed Acholeplasma laidlawii & Mycoplasma gallisepticum cells using immunofluorescence staining.

The presented work demonstrates new results of studying the photoluminescence kinetics of green leaves of Brassica rapa L. that were separated from the parent plant and in fact is the logical development of our studies. We found that the time dependence of its intensity includes 2 stages characterized by the fact that in the first one there is an increase in intensity, reaching a maximum and then decrease, but with long drying times in conditions of constant room temperature, it does not fall below its characteristic value for a living plant.

The goal of this study was to assess the ability of singlet oxygen generated at PDT to inhibit the activity of the model enzyme - Taq polymerase. Experimentally were determined the laser irradiation dose and the singlet oxygen concentration (over 300 μM) that results to complete inhibition of Taq polymerase activity. The results show that enzymatic proteins have an order of magnitude higher susceptibility than DNA molecules to damage by singlet oxygen.

In this paper one of several directions of caesium atomic clock modernisation is presented. This paper deals with theoretical model which takes into account features of the development of magnetic field stabilization system for caesium atomic clock and describes the affect of this stabilization system on frequency stability of caesium atomic clock. New magnetic field stabilization system allows eliminating one of the most important perturbing factors affecting on long-term frequency stability. Experimental research of the caesium atomic clock's metrological characteristics with magnetic field stabilization system showed improvement long-term frequency stability on 10%.

Experimental investigation of the optoelectronic oscillator constructed with a spin-wave bandpass filter was carried out. A phase noise of -140 dBc/Hz at the frequency offset of 10 kHz was obtained in the frequency range 3-12 GHz.

AlGaAs/InGaAs/GaAs pHEMT heterostructures were investigated by means of electrochemical capacitance-voltage (ECV) and photoluminescence (PL) techniques coupled with a numerical simulation. A set of GaAs pHEMT structures was fabricated using various doping techniques: modulated and δ-doping. The results of the PL spectra simulation and ECV free charge carrier distributions for investigated structures are presented. The analysis and comparison of QW filling in case of different doping mechanism of donor layer was done. Based on obtained results, we suggest optimized heterostructures in order to obtain higher electron localization and occupation of the quantum states.

The purpose of this paper was to develop and research the fiber optical simulators of false target with direct and external modulation for testing radar station for the X-range. The modes of testing radar station by simulator depending on external conditions were studied. Temporal and spectral responses have been received. The optimum modes of simulators depending on external conditions have been defined.

The results of a theoretical and experimental study of temperature effect on a switching process of a 4H-SiC drift step recovery diode are presented. The effect of the injected charge losses lowering at high temperatures is demonstrated.

The results of the research of the developed fiber-optic transmission systems for analog high frequency signal are represented. On its basis, a new method to identify various structural defects in the active phased antenna arrays is elaborated.

In this study we propose a home-made setup based on MP3 Player for producing high quality noise-like shape voltage with 45-kHz frequency band. The proposed generator's output signal is investigated both theoretically and experimentally.

In this paper the transformation of Hermite-Gauss beams with embedded vortex phase by lens system is investigated theoretically and numerically. A particular attention is devoted to the formation of vortex phase singularities in focal area. It is shown, that under appointed relations between HG mode indices and the number of embedded optical vortex the vortex phase singularity in a focal plane centre may disappear.

Stability analysis of lattice Boltzmann equations for the case of body force action is realized. The analysis is performed by von Neumann method and is based on the linearized equations. The stability is estimated by the values of the areas of the stability domains in parametric space. As the results of the analysis, the recommendation on the use of the models in practical simulations may be performed. The proposed approach to the analysis may be extended to the investigation of the other cases of body force actions, especially in the cases of multiphase and multicomponent flows.

The approach to parallel realization of the computational algorithm based on the implicit lattice Boltzmann equations is proposed and discussed. Program realization is performed in C++ language using the OpenMP technology. The program is tested on the lid-driven cavity flow problem. The obtained speedup for the cases of the computations with various processes numbers demonstrate the perspectives for realization of the algorithm on systems based on graphics processing units and systems with hybrid architecture.

High-purity hydrogen is required for clean energy and a variety of chemical technology processes. Different alloys, which may be well-suited for use in gas-separation plants, were investigated by measuring specific hydrogen permeability. One had to estimate the parameters of diffusion and sorption to numerically model the different scenarios and experimental conditions of the material usage (including extreme ones), and identify the limiting factors. This paper presents a nonlinear model of fast hydrogen permeability in accordance with the specifics of the experiment and the parametric identification algorithm.

This article describes algorithms for localizing sources of electromagnetic radiation from a printed circuit board in the near field. The sources of radiation are represented in the form of a set of the simplest oscillators - Hertz dipoles. Comparison of the two methods of localization of radiation sources is carried out using the Tikhonov regularization and the LASSO regression. The model examples show that the application of LASSO regression gives better results.

Zinc oxide piezoelectric nanorstructured coatings were formed on tantalum and aluminum substrates by the chemical solution methods. The methods mentioned above are suitable for formation of active parts of inertial mass based piezoelectric nanogenerator (PENG). This PENGs design using leads to an enhanced output due to the increased effective active parts area. Obtained nanostructured ZnO coatings were investigated by scanning electron microscopy and atomic force microscopy.

With the use of atomic-force microscopy (AFM) technique and X-ray photoelectron spectroscopy (XPS) morphology and composition of the surface in SnO₂-SiO₂ nanocomposites were investigated. The samples were obtained by sol-gel method for their use as sensor agents. It was found that the obtained nanocomposites differ from each other as by the distribution of cluster sizes at the surface layer as by the pores size in a dependence on the composition and preparation technique. The study by X-ray photoelectron microscopy demonstrated that in the composites obtained with the use of the above-named technique tin was present mainly in the form of dioxide with a little admixture of non-oxidized metallic tin. This fact can have a certain impact on the functional characteristics of the sensor structures.

The paper investigates endometallofullerene impact on conductive characteristics of poly(phenyleneoxide) within a wide range of frequencies and temperatures. It is revealed that the introduction of iron into the polymer matrix leads to an increase in the specific conductivity of the material and changes the parametres of its temperature dependence. The revealed regularities can be accounted for electro-donor properties of iron embedded in fullerene molecules.

In this work gas sensitivity of zinc oxide nanostructures to reducing gases (acetone and isopropyl alcohol) was investigated; impedance spectroscopy method was used for resistance measurements in a wide range of frequencies. Special attention is payed to the idea that increasing surface area of the samples leads to a corresponding increase in sensitivity. In order to check it, gas sensitivity of ZnO – SiO₂ nanocomposites was measured first; after that the samples were used to form ZnO nanowires on their surface, and the comparison of gas sensitivity of samples with and without nanowires is presented.

The article considers the information about optical properties of porous silicon layers. Samples were obtained using electrochemical and photoelectrochemical anodic etching methods. The monocrystalline n-type (phosphorus doping) silicon was used as the initial material for preparation. It is shown, that the photoluminescence intensity and wavelength, surface morphology of porous silicon samples are hinge on many technological conditions. The results can be used to estimate an advisability of porous silicon particles application as biomarkers; LED and other optical devices creation.

Segmented capillaries comprising two segments with different surface charges of polymer layers are prepared. One segment with a neutral surface charge is responsible for separation and another one with negatively charged surface provides the electro-osmotic flow adjustment. The average electro-osmotic flow rate is found to correlate with the length of negatively charged segment. A mathematical model is suggested to describe electromigration performances of segmented capillaries depending on the segments length ratio also taking into account the stationary phase/coating with definite surface properties (ξ—potential) or electroosmotic flow rate.

Colloidal nanocrystals of AgInS₂, Zn-Ag-In-S were synthesized directly in an aqueous medium by injection method. Two ligands, L-Glutathione and sodium citrate, were used for preparation of precursor solutions to achieve a balance of the reactivity of the two types of cations. Obtained samples are characterized by asymmetric photoluminescence band, tunable depending on the conditions of the synthesis.

The linearized Poisson-Boltzmann equation is used to estimate the radial distribution of potentials in a coaxial capillary and confirmed by experimental data. ξ-potentials are estimated for a capillary column with a sorbent containing magnetic nanoparticles. The thermal power in the column is calculated on the basis of the strength of an electric field with a certain electric conductivity. The column heating is calculated taking into account a thermal effect of the electric field for two estimates of the thermal diffusivity coefficient in the radial cross-section of a column comprising two layers of compounds with different physical properties.

The article is concerned with the investigation of nanomaterials based on SiO₂ and SnO₂ obtained with the use of sol-gel technology. The specifics of applying the comparative adsorption methods for studying such porous structure parameters of nanomaterials as micropores volume are discussed.

The goal of this work is to study the morphology and crytal structure of novel GaN epitaxial nanostructures (Y-shape nanotripods) grown on silicon (111) by plasma assisted molecular beam epitaxy (PA-MBE). Prior to the nanowire synthesis epitaxial GaN nanoparticles were formed on the Si(111) via nitridation of Ga nanodroplets on Si substrate surface (droplet epitaxy technique). Effect of the seeding layer on futher nanostructure growth, GaN/Si heterointerface formation, crystal structure and morphology is studied by use of different microscopic techniques.

In this paper, we have studied the fractal microstructures that form within conducting layers of oxide compositions and the effects that happen during electrical breakdown. We have determined that application of additional polymer films on top of the layers of oxide compositions allows one to visualize the breakdown processes taking place in the structure. The enlarged "polymer photography" that results in this makes it possible to assess the quality of contact layers without using high-resolution optical equipment.

The paper describes simulation of planar field emission nanostructures on the basis of graphene on a semiinsulating silicon carbide. The effect of arrangement of the electrode planes on the field strength and field gain is shown. The model is considered with a nanoscale interelectrode distance and a potential difference of 10 V.

This study is dedicated to the development of the technology of InAs/GaSb superlattice by MOCVD. There was obtained an InAs/GaSb superlattice consisting of 10 pairs of alternating layers of InAs and GaSb grown at the temperature of 500°C. The obtained structures were studied by transmission electron microscopy (TEM) and photoluminescence (PL). Also, a light-emitting structure with quantum well was obtained to substantiate the developed technology.

The influence of electromagnetic radiation with maxima wavelengths of 455, 520 and 630 nm on silver nanoparticles growth was investigated. The corresponding possibility of the plasmon resonance spectrum reconstruction in the visible range is shown. Investigations of the radiation frequency influence on the shape and size of the particles both at the stages of growth and at post-synthetic processing have been carried out. The possibility of transformation of spherical particles with a diameter of 20 nm into triangular shaped objects with a triangle edge length of 60–90 nm is shown. To study the optical characteristics of silver particles transmission spectroscopy was used as the primary diagnostic technique. The results of photometric measurements are in agreement with the data of scanning electron microscopy, which shows the transformation of the particles shape as a result of electromagnetic radiation.

X-ray diffraction analysis of solid-state compaction/sintering-induced changes in crystalline structure of lab-scale (M332) and commercial UHMWPE (X600) reactor powders has been carried out. The profile fitting programs TOPAS-5 and Peakfit 4.1 have been used to deconvolute the overlapping peaks. The linear FWHM of (110) and (002) X-ray peaks have been taken for calculation of the transverse (D₁₁₀) and longitudinal (D₀₀₂) crystallite sizes with the help of Sherrer method. The growth of crystallite sizes in cold compacted powders with sintering has been detected in both directions. Besides, the sintering has resulted in the generation of the planar a-texture, more pronounced in the lab-scale UHMWPE samples. As known, orientation hardening of the sintered reactor powders is an alternative route to UHMWPE high performance fibers distinct from the common gel-technology. It has been found that the highly oriented thin film threads produced from highly textured sintered material demonstrated the extremely high tensile strength up to 3.0 GPa, close to that of gel-fibers (3.5GPa) [1] while X600 less textured powders has shown low compactability and drawability.

The main purpose of this work was to investigate the structure of short-range order of microcrystalline cellulose (MCC) milled for one hour. Usually mechanical milling produces amorphous segments of crystalline cellulose. Investigation of short-range order was conducted by Debay's method to get X-ray diffraction (XRD) pattern when the coordinates of atoms in a cluster are known. The samples were studied by XRD. Crystallinity degree was measured using Segal's method. Cellulose Iα and Iβ were used as the initial structures to form clusters. The profile factor (R_p) was used, as the evaluation factor. The results showed that the cluster based on cellulose Iβ insufficiently characterized the short-range order of crystalline-amorphous cellulose (R_p>18%). Consequently, we examined a unit cell consisting of one cellobiose fragment. The final modeling cluster had the size of 35Å×22Å×29Å. The cluster consisted of 3 layers orientated randomly in relation to one another. The result of comparison of theoretical and experimental XRD patterns revealed that R_p was 11.4%. Therefore, the structure of short-range order of one-hour ground cellulose can be characterized by disordered cellulose chains with the length of 21 Å.

CuI/porAl₂O₃ nanocomposite was prepared by synthesis of copper iodide (CuI) nanoparticles within porous alumina (porAl₂O₃) matrix. Electrical conductivity and Seebeck coefficient of bulk copper iodide and those of CuI/porAl₂O₃ samples were measured at different temperatures. Optical characteristics of the samples were obtained by spectral ellipsometry. Type and the temperature dependence of electrical conductivity of the materials under study are discussed.

The paper describes experimental study of stress relaxation and generation in (1-2)-μm-thick GaN and AlGaN layers grown on AlN/c-Al₂O₃ buffer layers by low temperature (<720 °C) metal-rich plasma-assisted molecular beam epitaxy (PA MBE). The atomically smooth undoped GaN layers demonstrate only gradual relaxation of the compressive stress, which is probably related to thermodynamically driven inclination of threading dislocations (TDs).The slower stress relaxation at the lower growth temperature is explained by kinetic limitation of this process. The switch of compressive to tensile stress in the less-strained undoped Al_0.7Ga_0.3N layers, attributed mostly to the same effect of TD inclination, occurs in the low-temperature PA MBE conditions at much larger thickness (∼0.6 with) as compared to MOVPE ones. Introduction of high Si doping (n∼10¹⁹cm^-3) reduces noticeably the initial compressive stress in the AlGaN film due to substitution of small Si atoms in the group-III sublattice. At larger thickness, Si atoms seem to effect the TD propagation and suppress generation of tensile stress related to TD inclination, which makes possible to grow ∼1μm-thick Al_0.7Ga_0.3N: Si films without cracking.

We studied the influence of the activation time on the phase composition and geometric parameters of catalytic centers (CC). We found, that the treatment of substrate in an ammonia atmosphere allows to restore oxidized nickel. The activation time and the presence of ammonia plasma do not affect the phase composition of catalyst, but has a significant effect on the geometric dimensions of catalytic centers. Also we studied the influence of growth time on the geometry and structure of vertically aligned carbon nanotubes (VACNT). When the growth time ranged from 5 to 15 min we observed the formation of new walls, which resulted in an increase of the outer diameter. Within the range of 15 to 30 minutes, however, there was a decrease in the diameter of carbon nanotubes, which is associated with the disturbance of structural perfection and disorientation of carbon nanotubes caused by wall undercutting in the plasma.

The possibility of AlGaAs nanowires MBE growth on a silicon substrate with a nanometer silicon carbide buffer layer was demonstrated for the first time. Under the same experimental conditions (including the same composition), the diameter of the AlGaAs/SiC/Si nanowires are smaller than nanowires diameter grown on a silicon substrate. Based on the photoluminescence analysis suggests that when AlGaAs/SiC/Si NWs are grown, a physical complex structure appears due to the self-organized formation of regions with different molar fractions of aluminum in the solid solution.

The investigation of porous silicon/silver nanostructured composite layers (PS/Ag) via Raman spectroscopy technique has been carried out. Interpretation of PS/Ag Raman spectra has been proposed. Data from films acquired by varying anodization time showed a significant shift of a Raman peak primarily located at the frequency expected for monocrystalline silicon towards lower energy. In addition to the single peak a number of low-frequency bands emerged in the Raman spectra of silver-functionalised porous silicon. These effects have been interpreted as due to the influence of functionalizing silver nanoparticles and synthesis parameters on the structure and properties of composite material.

Cd-containing PAN films with modifying additive CdCl₂ have been fabricated by pyrolysis under the influence of incoherent infrared radiation under low vacuum conditions using different temperature and time of heat treatment. The influence of modifying additive concentration and of technological conditions on the films electrical and gas sensitive properties have been investigated. AFM-investigation of the films surface morphology has been fulfilled. The technological conditions for the formation process of the sensitive layer material for hydrogen sulphide sensor have been revealed experimentally.

Becker-Kersten method, which involves observing hysteresis M-H loops under mechanical stress, was applied to measure magnetostriction properties in amorphous rapid quenched ribbons Fe_80-xCo_xP₁₄B₆. It is shown that magnetostriction constant increases with the growth of cobalt atomic content from (1.75 ± 0.13)×10^-6 for x = 25 to (1.60 ± 0.05)×10^-5 for x = 40.

To study properties of quark-gluon plasma(QGP) is one of the main tasks of modern High Energy Physics. One of the signatures of QGP formation is jet quenching, which was observed as a suppression of particle yields (compared to the yield of the same particles in proton-proton collisions) at high transverse momentum region in central collisions of ultra-relativistic heavy nuclei. Jet quenching is the effect of the final state of heavy nuclei collision which is usually explained through parton energy loss in hot and dense medium. Experimentally the jet quenching is studied with nuclear modification factor. This paper presents invariant transverse momentum spectra and nuclear modification factors for π⁰ mesons in different classes of centrality in U+U collisions at √SNN=192GeV. Spectra and factors are measured in a wide p_T range up to 18 GeV/c for different classes of centrality. In central U+U collisions suppression of neutral π-mesons is the same as the suppression of neutral π-mesons in Au+Au collisions at the similar collision energy and similar numbers of participants.

Strongly interacting quark-gluon plasma (sQGP) is a state of nuclear matter at extremely high values of temperature with quarks and gluons as degrees of freedom. Jet-quenching is one of the evidences for sQGP formation in relativistic heavy ion collisions (A+A) and is manifested by suppression of particle yields at high transverse momentum relative to yields of the same particles measured at elementary proton-proton collisions at the same collision energy. Systematic experimental research of jet-quenching is provided by the measurement of nuclear modification factors of light mesons (π⁰, η, $K_{s}^{0}$, ω etc.) in different A+A systems. Asymmetric system of Cu+Au collisions at $\sqrt{{{s}_{NN}}}=200$ GeV is characterised by similar energy density but different collision geometry when compared to symmetric systems (Au+Au or Cu+Cu). This paper presents measurements of π⁰ and η mesons nuclear modification factors in Cu+Au collisions. Results are compared with ones measured in Au+Au and Cu+Cu collisions at the same collision energy.

In this work the features of measuring color characteristics of light-emitting diodes are described. Methods allowing increasing the accuracy of measurements in the laboratory conditions are shown. The results of determination of the color characteristics of white light-emitting diodes using the described technique are analyzed.

In this paper, the passage of individual and combined Laguerre-Gauss modes through the random medium with the given correlation function in the form of the Gaussian function is numerically investigated. The passage of the beams is described with the help of the extended Huygens-Fresnel principle, and the numerical calculation of the propagation operator is realized, using the fast Fourier transform. It is established, that the stability of the state of the orbital angular momentum of single modes, shown earlier is also observed for their superposition, while an increase in the degrees of freedom is provided, which can be used to encode the transmitted information.

It is known that ultrashort pulse coherent propagation through the resonant absorbing medium leads to the pulse splitting and pulse train generation. First of these pulses is the input pulse and the following pulses are resonant medium response. It is also known that such a propagation mode leads to the «spectrum condensation» effect, at which broad-band input femtosecond laser emission, as it leaves opically-dense medium, centralized in the vicinity of the resonance absorption lines. It's interesting to clear up the dependence of a condensation effect on an input femtosecond pulse phase modulation value (chirp).

A theoretical model of the holographic formation of diffractive optical elements for the Gaussian light beams conversion into Bessel-like ones in polymer-dispersed liquid crystals (PDLCs) is developed. The model is based on the solution of the kinetic equations of photopolymerization-diffusion processes of holograms recording in PDLCs by light beams with inhomogeneous amplitude and phase spatial distributions. The model additionally takes into account the photo-induced changings in the absorption coefficient of the PDLC. It is shown that the absorption changings decreases the rate of the refractive index's spatial profile decline over the thickness of the material. In this case, when the characteristic time of the absorption changing is much less than the characteristic polymerization time (the absorption changes more rapidly than the photopolymerization takes place), the diffractive element can be characterized by a homogeneous distribution of the refractive index over the thickness.

Measurements of the mass distribution of xenon clusters in a pulsed supersonic beam during ionization by electrons and photons are carried out. For ionization by electron impact, an electron gun was used. The energy of the electron beam varied in the range 15 – 70 eV. Third harmonic of a titanium-sapphire femtosecond laser with a wavelength of 263 nm was used for multiphoton optical ionization. Clusters of xenon Xe_N with N < 1000 were observed in a supersonic beam,. It is shown that the shape of the mass spectrum in multiphoton optical and electronic ionizations coincide at the electron energy near the ionization threshold (15 – 20 eV). At the electron energy of 30 – 70 eV the shape of the mass spectrum is substantially distorted in the region N ∼ 2 – 150. The change in the shape of the mass spectrum is mainly due to the large fragmentation of multiply ionized xenon clusters due to Coulomb decay.

The work is aimed for analytical approach to maximize ridge laser modal gain at a given beam divergence in a vertical direction. When the gain/loss profile of planar waveguide is known the equation for optimum near-field profile was obtained. Surprisingly, it is appeared to be Schrödinger type equation where normalized gain/loss profile plays role of potential energy. The developed approach was applied to a few examples widely met in practice. Also it was checked whether usage of leaky waveguides is justified or not.

The investigations of the generation of evanescent beams by means of binary diffraction axicon with a numerical aperture (NA) were more than one. It is shown that it is possible to generate evanescent beams using axicons. Numeric simulation of radiation passing through the axicon was investigated by the finite difference time domain method (FDTD).

The paper is devoted to the investigation of mutual influence of low-frequency and microwave resonances in ⁸⁷Rb vapor cell magnetometers system with laser pumping. One of the magnetometers was based on a low-frequency spin generator principle, while the second one was built as passive microwave spectrometer with a resonance frequency lock loop. The paper analyzes the frequency shifts in the low-frequency and microwave channels of the tandem of magnetometers associated with the simultaneous action of the resonant radio fields on the alkali atoms. Such effect is manifested in the frequency shifts of the spin generator for fixed changes in the amplitude of the microwave field.

In this work the inscription and investigation of tilted fiber Bragg gratings induced in a single-mode isotropic optical fiber with increased photorefractivity are demonstrated. Using the Talbot interferometer and the KrF excimer laser system, tilted fiber Bragg gratings with different angles were fabricated, the spectra of the formed diffraction structures were analyzed, and their photographic images were taken with a confocal laser scanning fluorescence microscope in transmitted light. The calculated dependence of the tilt angle of tilted fiber Bragg gratings fabricated in the Talbot interferometer on the angle between the interference fringes created in the interferometer and the cross section of the optical fiber is experimentally verified.

The formation of a narrow nanojet by polyester microcylinder with metall shell was presented by using the finite element method implemented in COMSOL Myltiphysics. Linear polarized light at a wavelength of 532 nm was used as incident light. The presence of a metal layer allows to increase the focal depth.

There are presented the results of the application of Raman-scattering spectroscopy method (RS) for the qualitative analysis of rams' heart valves surfaces before and during their decellularization. While analyzing RS spectra, it was found that basic differences appear at wave numbers 812 cm^-1, 1062 cm^-1, 1340 cm^-1 and 1440 cm^-1, corresponding to phosphodiester linkage of RNA; OSO-3 corresponds to symmetrical stretching of glycosaminoglycans and chondroitin-6-sulfate; corresponds to deformation mode of proteins and nucleic acids (DNA); proteins, lipids. Optical analysis has shown that while analyzing decellularization on the valves surfaces, the content of glycosaminoglycans, proteins and lipids decreases; retains a high DNA content. It was found that with the aid of entered optical numbers it is possible to control the process efficiency of decellularization of the heart valves.

The effect of focused ion beam (FIB) etching by 30 keV Ga⁺ on photoluminescence of AlGaAs/GaAs heterostructure is studied. During etching process, high-energy ions induce radiation defects that lead to a decrease of heterostructure internal quantum efficiency of luminescence. We used the SRIM software to simulate the radiation defects penetration depths in AlGaAs/GaAs heterostructure, then carried out FIB etching guided by received information. Annealing of the structure at 300 °C showed partial recovery of the internal quantum efficiency. Subsequent annealing at 620 °C showed almost full recovery of quantum efficiency depending on the etching depth. Experimental findings allowed us to affirm that FIB etching with subsequent annealing is a potential tool for making photonic nanodevices.

The authors propose to implement a multi-channel continuous scan Fourier spectrometer for simultaneous recording and analysis of the spectral characteristics of several objects. To implement such a scheme is used multiprobe fiber in which several optical fibers, at one end, are connected in one optical connector and fixed in the output of interferometer. In this scheme, the Fourier spectrometer is used as a modulator. On the other hand, each fiber individually mated with the test sample and its own radiation detector. The spectral resolution of the proposed system is 1 cm-1. For the system the aperture of the spectrometer from the condition of minimum spectral resolution and optical fibers parameters is calculated. Using the proposed scheme emission spectra of helium neon lamp have been registered for each single fiber with diameter of 1 mm and a numerical aperture NA = 0,22.

Self-assembled InGaAs quantum dots with In content 80% grown on vicinal GaAs substrates by MOVPE method have been investigated by photoluminescence technique in a wide range of temperatures and excitation densities. Multimodality of distribution of size and (or) shape in array of vertically stacked quantum dots synthesized under different growth conditions as well as in a single layer structure was found on the ground of appearance of a set of peaks in photoluminescence spectra at lowered temperatures. Influence of growth conditions on density and radiation wavelength of quantum dot modes has been analyzed. Investigation of photoluminescence of samples as a function of temperatures has allowed determining activation energies of three channels of the losses that were attributed to different modes of quantum dots.

It was analyzed the self-focusing regime of the Gaussian beam in transparent nanosuspension with electrostrictive nonlinearity. The theoretical analysis of the light-induced mass transfer in the nanosuspension was carried out for large intensities of the Gaussian beam radiation, when the concentration change is comparable to the primary value. The nonlinear lens in this mode is the nonlinear function of the incident light intensity. It is shown that the critical power value decreases significantly for high intensity beam. The results are relevant to the study of the radiation self-action in the nanosuspension and optical diagnostics of such materials.

In this paper, we present the results of experimental studies by using Raman-scattering spectroscopy method of synovial fluid that was obtained from the joint cavity during the surgery. Analyzing the composition of synovial fluid, it was identified that with the progress of degenerative-dystrophic process in synovial fluid of the affected joint, the gross amount of components increases at wave numbers: 1155 cm^-1 (hyaluronic acid (C-O, C-C )) and 1250cm^-1(Amide III). The entered optical numbers allow us to characterize synovial fluid (SF) in osteoarthrosis (OA). This specific Raman-scattering spectroscopy method may become a new diagnostic screening in order to educe the synovial joint pathology.

In this paper, the limited optical two-lens system, which describes the transmission of light beams in the parabolic profile fiber is considered. Vortex eigenfunctions, calculated for the given system form the set of the orthogonal functions, through which another optical field can be represented. Numerical simulation of the passage of the eigenfunctions through the system of the multiple lenses is carried out. It is shown, that eigenfunctions, whose eigenvalues are close to unity by absolute value, can pass through a large number of consecutive two-lens systems with practically no distortion.

We consider the theoretical model of the resonant signals formation in cesium atomic-beam QFS depending on input parameters, such as the number of atoms, the power and the linewidth of the laser radiation in detection area. On the basis of the model calculations were made and the values of fluorescence signal, which are specific for compact cesium QFS, were obtained. The influence of fundamentally irremovable noise sources on the characteristics of atomic-beam frequency standards was considered. On the basis of theoretical expressions, the values of the spectral power density of the noises were calculated and the signal-to-noise ratio was obtained. It was shown that the signal-to-noise ratio for compact cesium atomic-beam QFS does not exceed the value 5×10⁴, which leads to an estimation of the best achievable value of the short-term frequency instability by the quantity 7×10^-13 for 1 second.

The influence of non-uniform distribution of spin density in the temperature range from 5 to 80 K under the conditions of optical orientation of electrons in semiconductors is analyzed. Possibility to determine the kinetic parameters of carriers by depolarization of recombination radiation in a magnetic field is shown. Electron diffusion length and mobility is defined for materials with a hole conductivity. An estimated value of the rate of recombination on a free surface and its influence on the distribution of the concentration of non-equilibrium electrons from the excitation surface into the bulk is presented.

The new magnetic system construction and the registration circuit of the nuclear magnetic resonance signal in the weak magnetic field are considered. The new elaborated construction of the small nuclear magnetic spectrometer gives a possibility to register signals from different nuclei of investigated medium, having magnetic moment. That expands greatly the functional possibilities of the nuclear magnetic resonance in the investigation of media in the express-mode. The experiment investigation results for different media are represented.

In the article peculiarities of determination of dissolved substances concentration change in flowing liquid medium by measuring its refractive index with refractometer are considered. The measuring results of different media refractive indices are presented. The investigations of their refractive index dependencies on different factors (temperature, concentration, etc.) are carried out. The capabilities of refractometer applications for flowing medium state control at light-shadow borders displacement from refracted laser radiation are showed.

The results of application of the Raman spectroscopy method for estimating alternative sources for the production of bone spongy implants using the "Lioplast" technology, namely, the femoral head heads resected in the operation of hip replacement surgery, are presented. It is shown that Raman spectroscopy can be used to assess the component composition of the bone implants surface during their processing. Comparing different sources of sponge bone production before and after demineralization, no significant differences were found, but there are differences in the ratio of the Raman peaks intensities at wave numbers 1555 cm^-1 and 1665 cm^-1 corresponding to amide II and amide I, and also in the intensity of Raman peaks at the wave numbers 429 cm^-1 (PO₄^3- (v₂) (PO symmetric vibrational)), 1068 cm^-1 (CO₃^2- (v₁) B-type substitution (C-O planar valence)), 850 cm^-1 (benzene ring proline), 1000 cm^-1, (aromatic phenylalanine ring).

In two-component fluid (binary mixture) the heat flow can cause concentration stream arising from occurrence of thermodiffusion phenomenon (Soret effect). As a result these phenomenon changes the magnitude of the transport coefficients of the mixture. In this paper the theoretical analysis of the light-induced thermodiffusion mass transfer in two- components liquid in a field of Gaussian beam was carried out. It was calculated a concentration contribution to the thermal lens response. The results are relevant to the study of the radiation self-action in the nanosuspension and optical diagnostics of such materials.

In this paper, the formation of diffraction patterns for regular and random fractals of Cantor is numerically studied. The calculation of diffraction on one-dimensional, two-dimensional and radial fractal structures is performed using a fractional Fourier transform. This propagation operator makes it possible to obtain a field distribution (with the accuracy of scale) in any paraxial region, both in the Fresnel diffraction zone and in the far field.

A new method for constructing an optical image of the configuration of magnetic field lines using a ferrofluid cell with a magnetic fluid is considered. The carried out experimental researches have shown that the proposed method allows to determine the volumetric inhomogeneity of the field in the magnetic system. It is shown that the optical image can be used in real time to adjust the magnetic system to the minimum induction values ΔB in three planes.

We show the possibility of transmission and subsequent decoding of an ultra-wideband signal in an optical communication channel using a noise-like carrier. For an example, the simulation of the transmission of word encoded with Baudot telegraph code was realized. The necessary sequence of symbols was introduced into the noise-like carrier represented by a pseudo-random sequence of ultra short pulses. The possibility of the transmitted word decoding to a high degree of reliability was shown by calculation of auto- and cross-correlation functions. To some extent, the method can be treated as an analog of pulse-position modulation.

In this paper, we showed a technique for the formation of phase-shifted fiber Bragg gratings. The analysis of the efficiency of the obtained structures was carried out with the help of an optical spectrum analyzer with the subsequent calculation of the full width at half maximum of a bandpass in reflection spectrum. Fiber Bragg gratings inscription was performed on the Talbot interferometer, the KrF excimer laser system was used as a UV radiation source, and a phase shift was introduced by the electrical discharge of an arc fusion splicer. The experimental dependence between the length of the obtained structure and the full width at half maximum of a bandpass in reflection spectrum of a phase-shifted grating was presented, the value of the last parameter varies in the range from 24 pm to 96 pm.

The results of studies of the efficacy of treatment of staphylococcal infection in palatine tonsils using «Amoxiclav» by a method of Raman spectroscopy. Spectral changes in the treatment of palatine tonsils with the antibiotic «Amoxiclav» are revealed. The coefficients allowing to estimate the effectiveness of treatment of staphylococcal infection with antibiotics «Amoxiclav» are introduced. It is established that the antibiotic «Amoxiclav» is more effective when exposed to a strain of staphylococcus culture (I).

Carrier lifetime limited by radiative and most probable non-radiative recombination processes was calculated for InAs(Ga,Sb,P) heterostructures under injection. At low temperatures (T<130 K), the carrier lifetime was mostly determined by radiative recombination. With temperature increasing, influence of Auger processes became crucial. Among these processes, the dominating role of CHHS process, in which the energy of a recombining electron-hole pair is transferred to a heavy hole transitioning to the spin-orbit-splitted band, was established at low temperatures.

In this work the reasons leading to the occurrence of interference in the internal structure of the common CCD photodetectors are discussed, that result in degradation of the metrological characteristics of the spectrometers based on them. Methods of removing a protective glass of the photodetector are shown. Possibility of modification of the CCD photodetectors for suppressing the interference by applying the surface phosphor layer is analyzed. It is experimentally confirmed that the proposed method allows achieving almost complete suppression of interference and also increasing the sensitivity of the detector to the radiation in the UV part of the spectral range.

A method for calculation of the resonant frequencies as well as free spectral range was developed for the high-Q whispering gallery mode disk dielectric resonators. The method is based on application of the size quantization to the dispersion equation derived for an infinite dielectric cylinder. The size quantization is caused by the requirement of the phase balance for standing waves in the resonator.

Monocrystals of ternary compounds of A^IIB^III₂C^VI₄ semiconductors (HgGa₂S₄ and CdGa₂S₄) and various photosensitive structures based on them were investigated. The photoelectric properties of the structure obtained were studied using natural and linearly polarized light at 300 K. The results show that the structures created can find application as no polarized radiation photodetectors, and with allowance for high-tetragonal compression of the crystal lattice and linearly polarized radiation.

A^IIIB^V laser-modulator is an advanced optoelectronic device offering new possibilities in the field of on-chip optical interconnecting. To realize the laser-modulator-based interconnections, high-performance integrated photodetectors are required. In this paper, we researched uni-travelling-carrier photodiodes (UTC-PDs). We proposed the extended driftdiffusion model taking into account the effects of carrier drift velocity saturation and electron inter-valley transition. For the implementation of the model, we developed the finite difference numerical simulation technique and dedicated software. These aids were applied for the simulation of InP/InGaAs UTC-PD. According to the simulation results, the device response time is about 3 ps. Thus, it is reasonable to consider the methods of UTC-PD performance improvement.

Results of indium phosphide structures research, showing the possibility of using in the near infrared range photocathodes of InP/InGaAs, are represented. An optimal method of obtaining the atomically clean indium phosphide surface was suggested. The spectral characteristics of InP/InGaAs heterostructure were given. The results of an experimental study of pin-diode, which was used as the receiver of photoelectrons, are presented.

During the work organic light-emitting structures FTO/PEDOT:PSS//TPD/TPD+CQD CdSe(650)/Alq3/Al with an efficiency value of about 2% were created. The technique for introducing CdSe CQD (650) into the structure of OLED was developed. The change in the electroluminescence spectra in structures with colloidal quantum dots is demonstrated. The decrease in OLED switching on voltage in structures with the PEDOT: PSS layer is demonstrated.

During the work, organic photosensitive structures were created. The photosensitivity spectra of the samples were analyzed. According to the spectrum of photosensitivity, were made assumptions about possible transitions that take place in structures.

The series resistance of concentrator solar cells is determined by the processes of current spreading under the contact grid. The influence of the number of subcells in multi-junction solar cells on these processes is considered in the paper. Using the tube model of current spreading, it is shown that with the increase in the number of subcells, the current distribution of tubes becomes more uniform. This affects the shape of the IV-curve of the spreading resistance in such a way that the magnitude of the resistive losses at the maximum power point decreases.

A theoretical model of an electronically tunable multi-loop optoelectronic oscillator (OEO) based on photonic and microwave multiferroic delay lines has been developed. The theory takes into account a dispersion of electromagnetic waves in optical fibers and a dispersion of spin-electromagnetic waves in ferrite-ferroelectric structures. An expression for transfer function of the OEO circuitry was derived. The theory enables one to calculate transmission characteristics and suppression of spurious harmonics of the multi-loop OEOs. The features of both magnetic and electric tunabilities are investigated.

In this paper, we report on the initial studies of cascade photodetectors. The heterostructures used in this work are based on InP. InP is the most suitable material for converting the solar spectrum in the range from 0.95 to 1.2 μm. It is proposed to use nanocrystalline inclusions as a connecting element. For this, nanocrystals GaP are best suitable. Because this material (GaP) does not create an absorption of the incident radiation.

The capability of optical emission spectroscopy for in situ study and control of plasma-enhanced atomic-layer deposition (PE-ALD) of gallium phosphide from phosphine and trimethylgallium carried by hydrogen was explored. The gas composition changing during the PE-ALD process was monitored by in situ measurements of optical emission intensity for phosphine and hydrogen lines. For PE-ALD process where phosphorus and gallium deposition steps are separated in time a negative influence of excess phosphorus accumulation on the chamber walls was observed. Indeed, the phosphorus deposited on the walls during PH₃ decomposition step is etched by hydrogen plasma during the next trimethylgallium decomposition step leading to uncontrollable and unwanted conventional plasma-enhanced chemical vapor deposition. To reduce this effect, it has been proposed to introduce a step of hydrogen plasma etching, which allows one to etch excess phosphorus before the beginning of gallium deposition step and achieve atomic-layer deposition growth mode.

The results of an experimental study of the sensitivity and directivity pattern of the ultrasonic transducers are presented. Data was obtained for transducers with central frequency at 2.5 and 5 MHz with protective matching layers, in comparison with transducers without matching layers. Increase of transducer sensitivity is shown. In addition, it is shown that the directivity patterns for transducers with the matching layer and without it are practically identical. Also was observed that the directivity pattern gets sharper as the frequency of the transducer increases.

In this work the growth peculiarities of InGaAs quantum dots (QDs) on GaAs surface have been investigated by metal-organic vapor-phase epitaxy (MOVPE). The influence of the main structural parameters, such as the amount of deposited InGaAs material and the thickness of the GaAs cap layer, on the optical properties of QDs has been considered. For these parameters the optimal values at which achieved the best photoluminescence intensity of QDs embedded into the matrix of the GaAs-based light-emitting structure have been established. The possibility of using several layers of QDs with the preservation of the optical properties of the investigated structures has been demonstrated. The design of solar cell (SC) based on GaAs with QD arrays in the active area has been proposed. It was shown that 20 layers of QDs embedded into the proposed SC structure contribute to the photogenerated current up to 0.97 mA/cm² for AM0 spectra and up to 0.77 mA/cm² for AM1.5D spectra, while maintaining the high quality of the p-n junction.

The article emphasizes the mechanism of the thermovoltaic effect in the rare-earth semiconductor material of samarium sulfide (SmS). The maximum achieved parameters of the SmS based thermal energy converters are given. Comparison of them with the parameters of classical thermoelements proves the practicability of further developments in this field.

In the work, optical coupling arising in a multijunction solar cell under powerful laser radiation is investigated. To describe the cascade of interconnected luminescent processes in a structure with optical coupling, the photon-coupled characteristic is used. Investigation for two specimens with different effeciency of luminescent interaction was carried out.

A plant, developed with the use of ferro-piezoelectric ceramics for generation of electric power, is studied in the article. The use of electrochemical generator in the plant makes it possible to increase the efficiency of electric power generation by means of polarization of ferro-piezoelectric ceramics control. Polarization control is proved by a mathematical model. Consumption of 1 joule electric power, using mechanical power, generates 3,5...5 joule of electric power output. Efficiency factor of the power plant is about 50....55 percent and depends on ceramics modification and electric circuit.

It was described the thermoelectric effect in thin sandwich metal-ferroelectric-metal system. The effect was observed in doped lithium niobate crystals with two electrodes of different metals. The effect is observed only in doped lithium niobate crystals and has a maximum for concentrations of impurities of iron around 0.3 % weight. It was proposed the electrets model of the investigated phenomena resulting from field contact potential difference on the borders of section of metal-ferroelectric material.

In ceramics, based on a solid solution of strontium barium niobate (0.7SBN) doped with cerium and gadolinium in various concentrations, an investigation was made of dielectric constant, electrical polarization, and the electrocaloric effect. For 0.7SBN ceramics, it was found that the addition of cerium (0.2%) leads to a decrease in the electrocaloric effect compared to pure 0.7SBN, and the addition of gadolinium (˂1%) to an increase in the electrocaloric effect.

The paper is devoted to the study of the formation and propagation features of terahertz bright envelope solitons of dipole-exchange spin waves in thin ferrite and hexaferrite films. The influence of the exchange interaction and the uniaxial anisotropy field on the soliton formation threshold is studied.

The polarization switching was studied in single crystals and thin films of 2- methylbenzimidazole (MBI) obtained by evaporation method from an MBI ethanol solution. Dielectric hysteresis loops were measured in the temperature interval 290-390 K and frequency range 20-1000 Hz for different amplitudes of the electric field. The Kolmogorov β-model with account of Mertz law is used for simulation of hysteresis loops. The temperature dependence of domain wall motion activation field E_a has been obtained. Mechanisms of polarization switching in single crystals and films of MBI are discussed. In MBI films, a comparison of polarization switching for in-plane and out-of-plane electric field orientation is presented.

The results of studies of the current-voltage characteristics of ceramic structures based on manganese doped barium titanate were presented. It was found that the electrical conductivity of ceramic samples based on barium titanate at high field strengths is determined by the Schottky emission. Moreover, the addition of manganese increases the resistance of the samples.

Optical properties of the resonant Bragg heterostructures with 10 and 30 GaN/AlGaN quantum wells were studied. The increasing of reflectivity at the resonance wavelength under condition of the Bragg wavelength and optical transition wavelength matching was observed experimentally at room temperature. The computer simulation of the optical transition wavelength in quantum wells and the optical reflectivity spectra at different reverse bias was implemented to evaluate radiative and non-radiative broadening parameters of the exciton in GaN/AlGaN quantum wells.

We report on fabrication by molecular beam epitaxy and optical studies of hybrid semiconductor-dielectric micropillar structures with distributed Brag reflectors and a microcavity containing InAs/AlGaAs quantum dots. The single photon emission in the visible spectral range with the autocorrelation function g⁽²⁾(0)˂0.2 is detected in such structures with a photon count rate above 1 MHz.

In this paper, the computer simulation methods were used to study the effect of the mutual shielding in the multi-point system of a nanoscale field cathode on its current-voltage characteristics and the characteristic parameter of the field emission area. Modeling is carried out in the COMSOL Multiphysics software package. Geometric parameters of the model correspond to the parameters of carbon nanotubes. As a result of the simulation, the dependence on the distance between the emission centers of the shape of the current-voltage characteristic of the central emitter, the effective current density of the entire emission system, and the size of the field emission area were constructed.

A microscopic analysis of the radiation intraband absorption mechanism by holes with their transition to a spin-split band for quantum wells based on InGaAsP/InP solid solutions is performed within the framework of the four-band Kane model. The calculation is made for two polarizations of the incident radiation: along the crystal growth axis and in the plane of the quantum well. It is shown that this process can be the main mechanism of internal radiation losses for quantum well lasers. It is also shown that the dependence of the absorption coefficient on the width of the quantum well has a maximum at a well width from 40 to 60 A.

We investigate the mutual influence of angular (AMRO) and quantum oscillations (MQO) of interlayer magnetoresistance R_zz (θ) in quasi-two-dimensional (quasi-2D) layered metals. The MQO and the shape of Landau levels (LL) affects the AMRO amplitude. The influence of AMRO on MQO leads to the new qualitative effect: the angular oscillations of the amplitude of MQO, called "false spin zeros", that could lead to a wrong determination of electron g-factor from experiment.

The GaAs/AlGaAs superlattice grown by metal-organic chemical vapour deposition (MOCVD) was investigated by photoreflectance (PR) spectroscopy. Optical transitions over the whole band structure were measured at room temperature. Different laser pump beams (632 and 532 nm) were used to clarify the nature of the PR signal formation. Charge carriers transport over minibands was revealed by using long-wave modulation. An acceptable correlation of theoretical and experimental results was achieved for low-energy transitions. Optical transitions relating to the edges of the first and the second minibands for electrons, heavy and light holes were clearly observed experimentally.

The experiments with auxiliary heating by neutral beam injection (NBI) were carried out before the spherical tokamak Globus-M was upgraded to Globus-M2. The aim of the experiments was to determine the dependence of the confinement time on toroidal magnetic field. The total stored energy was obtained by diamagnetic loops, and verified with ASTRA modelling based on kinetic measurements. The absorbed heating power was estimated using 3D fast ion tracking modeling. The obtained dependence of the energy confinement time is similar to the MAST and NSTX results but contradicts the conventional IPB98(y,2) scaling. The toroidal Alfvén eigenmodes study was performed in a set of discharges with NBI at the early stage of the discharge. The experiments have shown that fast particle losses decrease with the increase of the toroidal magnetic field and plasma current.

The paper presents latest results of constricted glow discharge simulations. Detailed self-consistent plasma model includes a large set of plasma chemical reactions, considering inhomogeneous gas heating and accurate solution of radiation transport equation. Results of the computer simulations were compared with an experimental data of positive column constriction in neon and argon. Experimental plasma diagnostics was performed using classic methods of emission and absorption spectroscopy and a line ratios method. Comparison of the obtained results allows to reveal the influence of resonance radiation trapping on the plasma parameters of a constricted discharge.

It was found out that a reactive load presence in the external circuit of a diode with an electron beam can crucial change its operation modes. Using a non-relativistic Bursian diode with a decelerating electron beam as the example, it was demonstrated that the presence of inductance in the external circuit leads to the development of instability in the diode-external circuit system. Values of the parameters for which the diode can generate oscillations are determined. The instability growth rates and frequencies are calculated.

Cavitation is a phenomenon of formation of bubbles (cavities) in liquid as a result of pressure drop. Cavitation plays an important role in a wide range of applications. For example, cavitation is one of the key problems of design and manufacturing of pumps, hydraulic turbines, ship's propellers, etc. Special attention is paid to cavitation erosion and to performance degradation of hydraulic devices (noise, fluctuation of the mass flow rate, etc.) caused by formation of a two phase system with an increased compressibility. One more important problem accompanying cavitation is liquid degassing due to diffusion of the dissolved gas into the cavities. Determination of the degassed air content is important for the performance forecast of devices. Mathematical models of the degassing in cavitating flows are not yet developed and presented in the literature satisfactorily. Therefore, development of a model for simultaneous cavitation and liquid degassing is an important fundamental and applied task. To validate the algorithm simulations of unsteady flow of a cavitating liquid in a channel have been conducted. The obtained results are in satisfactory agreement with the experimental data and demonstrate the efficiency and robustness of the formulated model and the algorithm.

In this paper we consider one of the most effective ways to improve the performance properties of metals – their treatment by intense flows of metal plasma generated by a vacuum-arc discharge. The change in the thermal regime and the duration of the plasma treatment allows controlling both the thickness of a modified layer and the distribution of implanted ions into its depth. At the first stage of part processing the preliminary cleaning of the surface is carried out using a glow discharge in argon. In the second stage, vacuum-arc plasma sources are used, that provide surface treatment with ions of the sprayed material. To weaken and purify the plasma flow special separation systems were used to ensure the creation of an impassable barrier for the droplet fraction. Modification of the treated surface layer is achieved either due to the high energy of the deposited particles, or due to the implementation of the diffusion processes deep into the substrate. The presence of a modified surface layer allows improving the quality of the working coating that is deposited further.

Comparative analysis of several semi-empirical turbulence models taking into account laminar-turbulent transition (γ-Re_θt SST, γ-SST, γ-SA and e^N-SA) was carried out for flow around an airfoil in the wake generated by another upstream airfoil for different Reynolds numbers and distances between airfoils. Two dimensional Reynolds-averaged Navier Stokes equations were solved in different CFD codes on unstructured and chimera-type structured grids. Results of the considered transition models are virtually independent of the computational code. Results of the SST-based transition models are in reasonable agreement with experimental data while SA-based models predict too early transition.

Depending on the plasma-forming mixture, various types of electrode materials are used. If air, carbon dioxide and steam are used, it is optimal to use copper electrodes, since copper has a high thermal conductivity. Copper rod electrodes of an air AC plasma torch are considered. In the binding zone of the electric arc, the electrode material melts and boils, which leads to physical erosion of the electrode. Scanning electron microscopy with elemental analysis, X-ray phase analysis and IR Fourier spectroscopy were used to analyze the products of electrode erosion. The erosion products content copper, iron, nitrogen, oxygen, and other metals from the plasma torch case.

The paper presents the results of an experimental and numerical study of the structure of a plume formed over a heated disk under conditions of conjugate heat transfer in a range of small and average Grashof numbers. Numerical simulation was performed using the Ansys Fluent code, where the problem of the flow of a compressible gas in conditions of conjugate heat transfer in an unsteady formulation was solved under the assumption of laminar flow regime. One of the main goal of this paper is to compare results of modelling of the plume in assumption of axisymmetric and three-dimensional flow regime. As a result of a comparison of the results of physical and numerical experiments, there is a conclusion about a good qualitative concurrence of the flow structure in a range of a small Grashof numbers.

On the example of the supersonic inviscid flow in a duct with a central wedge, the problem of increased errors of the solution arising in the vicinity of the fractures of a streamlined surface is investigated. The effectiveness of various ways to improve the solution quality is evaluated. Calculations based on the MUSCL approach for increasing the approximation order are performed using the finite-volume unstructured SINF/Flag-S code developed at the Peter the Great St. Petersburg Polytechnic University. The data obtained with this code are compared with the results of calculations performed using the ANSYS Fluent.

An assessment of two approaches aimed at acceleration of the RANS-LES transition in separated flows has been performed in the framework of Delayed Detached Eddy Simulation (DDES). The former approach is based on the use of the shear-layer adapted subgrid scale (DDES Δ_SLA) and the latter involves an alternative subgrid model (σ-DDES). Simulations of two separated flows, namely the backward-facing step flow and flow over a wall-mounted hump have been performed with the use of ANSYS-FLUENT. The results were compared with those obtained with the use of the in-house NTS code and with experimental data. It is shown that both RANS-LES acceleration techniques implemented in ANSYS-FLUENT allow more accurate and less code-sensitive results to be obtained in comparison to the original DDES formulation.

A noise-free volumetric synthetic turbulence generator has been applied for Embedded LES of the flow over the wing-flap configuration experimentally studied by Lemonie et al. Good agreement of CFD results with experimental data provides some evidence for the correctness of the chosen computational strategy, which includes a noise-free volumetric synthetic turbulence generator to create turbulent content, "sponge layers" to avoid the reflection of pressure waves from the external boundaries and the Ffowcs Williams, Hawkings acoustic model for calculating far-field noise.

The goal of the study is the validation of Wall-Modeled Large Eddy Simulation (WMLES) of ventilation in an isothermal room at conditions of experiments by Nielsen et al. Two values of the inlet slot width were considered. Calculations were carried out using the ANSYS Fluent 16.2 software with an algebraic WMLES subgrid-scale model. The uniform computational meshes up to 58 million cells were used. The focus in the results discussion is on the accuracy of mean and rms velocity fields prediction both in the jet zone and the low-velocity occupied zone. It is concluded that to predict the jet spread the meshes used are sufficient. However, there is visible difference between the computed and measured data in the occupied zone especially in the essentially 3D case with narrow inlet slot.

For the thermophysical calculation of the reactor, a mathematical model was developed in Comsol Multiphysics, describing physical processes in the plasma-chemical reactor at a stationary mode. To simplify the calculation at this stage, it was carried out for an air plasma torch. The model includes two processes: fluid dynamic and heat transfer ones. As a result of the mathematical modelling the following parameters were obtained: temperature distribution in the reactor at steady state, average mass temperature in the reaction volume, velocity field and others.

In the present work, numerical simulation was conducted for a typical connection of a vascular graft (prosthesis) and an artery to assess the effect of inducing swirling flow, which is believed to remove unfavourable flow environment. A parametric study on the spiral ridge geometrical features that was conducted showed that the ridge height and pitch have significant effects on inducing swirling flow, and revealed the potential of improving the efficiency of such design. Simulations were carried out for two models – a standard graft and the one with an optimal spiral ridge. Hemodynamic parameters were compared and the results showed that the graft with a spiral ridge is more effective. The induced swirling flow was generally found to be decreasing particle residence time within the connection of the graft and artery region and the host artery, which may be beneficial to the graft patency rates.

The purpose of the studies was to evaluate the possibility of using mechanically activated saponite-containing material (SCM) as an additional binder in cementitious binders of hydration type of hardening. According to the working hypothesis, the activated SCM is able to show the binding properties. To confirm this fact, the phase-structural heterogeneity investigation of the material was made. As a result, after mechanical dispersion the content of the amorphous phase increases by 2 times. Investigations of the microstructure of the binder samples with and without saponite showed that: in the first case, there are two types of crystals: spongy and needle. The SEM and IR spectroscopy data showed that when the additive is introduced, the formation of hydrolides of the tobermorite group is observed, which play the role of an additional binder in the cement hardening process.

The paper presents a procedure for the preparation of sodium polysilicate from silica hydrosol for use as an additional binding agent in the production of composite materials based on wood matrix. It is proved that 3-stages mechanical activation of low quality sand makes it possible to obtain silica particles with sizes on the upper boundary of the ultradispersed range (100 nm). The effect of dimensional characteristics, the zeta potential of the surface of silica particles, and the protolytic properties of the dispersion medium on the gel formation process is studied. The obtained dependence of the zeta potential of particles from the pH of diluent has shown that in acidic region have equivalence point and a low zeta-potential area in which the colloidal particles become unstable (which may lead to rapid gelification in the system). It is proposed to accelerate the process of depolarization of silica particles by maintain the pH value of the dispersion medium equal to 2-4, this will quickly produce a large yield of gel-like sodium polysilicate.

Preliminary studies have shown the possibility of using glyoxal-silica dispersed system for soil stabilization in groundwork base and utility systems. However, the problem associated with optimizing the composition can be solved by measuring energy characteristics. Since the interaction in glyoxal-silica system takes place at the interphase the surface tension was chosen as an energy parameter. The aim of research was to compare calculated by Zisman's and Owens-Wendt-Rabel-Kaelble (OWRK) methods surface tension values of glyoxal-silica composition. Polymineral sand was used as the silica model. The surface tension value calculated by Zisman's method is σ_c=27.47 mN/m. According to the OWRK method, the polar component of surface tension for test material is σ_S^P=12.61 mN/m, dispersion component is σ_S^D=13.50 mN/m, and the total value of surface tension is σ_S=26.11 mN/m. Comparison of surface tension values calculated by different methods has shown good repeatability. However, the OWRK method provides a more detailed overview of interaction in the glyoxal-silica system and makes it possible to estimate the contribution of polar and dispersion components to the total value of a surface energy characteristic. Therefore, the OWRK method can be recommended for characterizing the structure formation process when optimizing the organomineral compound composition.