Table of contents

The International Conference PhysicA. SPb was held 18-22 October 2021 in Saint Petersburg, Russia. The Conference continues the tradition of St.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 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/2021 has brought together over 400 academics from many universities and research institutes across whole Russia as well as from USA, UK, South Africa, Poland, Ukraine, Kazakhstan, Belarus, Azerbaijan, and Australia. 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, Multilayered structures, Spectroscopy of atoms and molecules and Physics of quantum structures.

This issue of the Journal of Physics: Conference Series presents the extended contributions from participants of PhysicA.SPb/2021 that were peer-reviewed by expert referees through processes administered by the Presiders of the Organising and Program Committees to the best professional and scientific standards. This was made possible by the efforts of the Sectional and Technical 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), Prof. Mikhail Nestoklon (Ioffe Institute), Dr. Andrey Dunaev (Orel State University), Prof. Anton Vershovskii (Ioffe Institute), Dr. Vadim Evtikhiev (Ioffe Institute), Prof. Alexey Ustinov (St.Petersburg Electrotechnical University "LETI"), Dr. Alexandra Kalashnikova (Ioffe Institute), Prof. Ivan Mitropolsky (NRC Kurchatov Institute - PNPI), Dr. Evgenia Cherotchenko (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 Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

• Type of peer review: Single-blind

• Conference submission management system: IOPP ReView

• Number of submissions received: 472

• Number of submissions sent for review: 260

• Number of submissions accepted: 236

• Acceptance Rate (Number of Submissions Accepted/Number of Submissions Received X 100): 50%

• Average number of reviews per paper: 2

• Total number of reviewers involved: 966

• Contact person for queries: Grigorii S. Sokolovskii, Ioffe Institute (gs@mail.ioffe.ru)

The Tunka-Grande array is part of a single experimental complex, which also includes the Tunka-133 and TAIGA-HiScORE (High Sensitivity COsmic Rays and gamma Explorer) wide-angle Cherenkov arrays, TAIGA-IACT array (Imaging Atmospheric Cherenkov Telescope) and TAGA-MUON scintillation array. This complex is located in the Tunka Valley (Buryatia Republic, Russia), 50 km from Lake Baikal. It is designed to study the energy spectrum and the mass composition of charged cosmic rays in the energy range 100 TeV - 1000 PeV, to search for diffuse gamma rays above 100 TeV and to study local sources of gamma rays with energies above 30 TeV.

This report outlines 3 key points. The first is the description of the Tunka-Grande scintillation array. The second one presents the computer simulation strategy of the Tunka Grande array based on the Geant4 software. The third one is devoted to the prospects for future research in the field of cosmic ray physics and gamma-ray astronomy using simulation results.

It is generally accepted that the Coulomb crystal model can be used to describe matter in the neutron star crust. In [1] we study the properties of deformed Coulomb crystals and how their stability depends on the polarization of the electron background. The breaking stress in the crust σ_max at zero temperature was calculated based on the analysis of the electrostatic energy and the phonon spectrum of the Coulomb crystal. In this paper, I briefly discuss the influence of zero-point, thermal contributions and the internal magnetic field on σ_max.

Faddeev variant of embedding theory is an example of using the embedding approach for the description of gravity. In the original form of the embedding approach, the gravity is described by an embedding function of a four-dimensional surface representing our spacetime. In Faddeev variant, the independent variable is a non-square vielbein, which is a derivative of embedding function in embedding theory. We study the possibility of the existence of extra solutions in Faddeev variant, which makes this theory non-equivalent to GR. To separate the degrees of freedom corresponding to extra matter, we propose a formulation of this theory as GR with an additional contribution to the action. We analyze the equations of motion for a specific class of solutions corresponding to a weak gravitational field. We construct a simple exact solution corresponding to arbitrary matter and nontrivial torsion, which is an extra solution in Faddeev variant in the absence of real matter.

Neutron stars are superdense compact astrophysical objects. The central region of the neuron star (the core) consists of locally homogeneous nuclear matter, while in the outer region (the crust) nucleons are clustered. In the outer crust these nuclear clusters represent neutron-rich atomic nuclei and all nucleons are bound within them. Whereas in the inner crust some neutrons are unbound, but nuclear clusters still keeps generally spherical shape. Here we consider the region between the crust and the core of the star, so-called mantle, where non-spherical nuclear clusters may exist. We apply compressible liquid drop model to calculate the energy density for several shape types of nuclear clusters. It allows us to identify the most energetically favorable configuration as function of baryon number density. Employing four Skyrme-type forces (SLy4 and BSk24, BSk25, BSk26), which are widely used in the neutron star physics, we faced with strong model dependence of the ground state composition. In particular, in agreement with previous works within liquid drop model, mantle is absent for SLy4 (nuclear spheres directly transit into homogeneous nuclear matter; exotic nuclear shapes do not appear).

The spectral lags of gamma ray bursts are defined as the difference in the registration time of the same radiation pulse in different energy channels of the recording device. This parameter can characterize both the mechanism of radiation generation by the source and the physical conditions of radiation propagation from the source to the observer. In this paper, the dependence of the arrival time of photons on their energy for the gamma ray burst GRB 190114C is obtained from the data of the Gamma ray Burst Monitor (NaI detectors) of the Fermi Gamma ray Space Telescope. It is shown that this dependence is mainly due to the back edges of the light curve pulses. The spectral lags of the leading edges of the pulses are small and comparable in magnitude to the measurement errors. The observed anomaly in the energy range from 5 to 20 keV is probably related to the quasi-thermal radiation of the source.

Observations of hard X-ray emission from the Vela pulsar wind nebula (PWN) with the ISGRI camera aboard INTEGRAL gamma-ray observatory have been analysed with the aim to search for possible flux variability on scales from weeks to years, which could be caused by short-term evolution of pulsar wind structures similar to those governing sharp flares and flux depressions observed in the sub-GeV emission of the Crab PWN. No statistically significant flux depressions or flares have been found in none of the considered energy ranges: 20-50 keV, 50-100 keV, and 100-200 keV, however some hints of flux instability can be seen in the former two bands. If the variability of the pulsar wind termination surface or instabilities of turbulent magnetic field in the nebula predicted by a number of PWN models indeed influence the synchrotron spectrum of such objects, the variability of the 1-30 MeV emission from the Vela PWN could be checked with the next generation of gamma-ray facilities, like eASTROGAM or HERMES.

The Moon might be considered as an integral detector of Galactic Cosmic Rays (GCR) as it contains on its surface cosmogenic isotopes produced by nuclear reactions. Since the retrieval of lunar regolith cores by Apollo missions, there were numerous attempts to measure concentrations and depth profiles of those isotopes and reconstruct the level of cosmic radiation at 1AU at various time scales, ranging from thousands to millions of years. The data also contains encoded levels of solar activity, as the Sun affects the differential flux of GCRs in a well-known manner. All those attempts showed that our nuclear interaction codes, GEANT4 for example, need corrections to describe the lunar data, be it tweaking of cross-sections or any other methods. There are also such archives on Earth: ice cores and trees. Based on terrestrial modulation potential reconstruction we try to calibrate GEANT4 code in a transparent manner, and also present our estimates on the solar activity on time scales of 0.02 and 3 Myrs. The estimates made using our calibration procedure show values consistent with modern understanding of history of solar modulation potential, and demonstrate the necessity to establish an agreed correction method for the analysis of lunar data. We also compare our results and method with another estimation of solar modulation potential during the last 1 Myr.

²²Ne/²⁰Ne isotopic ratio is found to be about 5 times higher in Galactic cosmic rays (GCRs) than in the solar wind. In this paper we develop the hypothesis that the ²²Ne overabundance in CRs is generated in compact massive star clusters which contain populations of Wolf-Rayet stars. Winds of Wolf-Rayet stars are considered to have high content of ²²Ne. We assume that particle acceleration occurs on the ensemble of strong shocks from the massive stars' winds. We present a model of cosmic ray enrichment with ²²Ne, adding isotopic yields from supernovae and taking into account the acceleration efficiency during the lifetime of the stars. The impact of the parameters (the initial mass function in the cluster, rotation velocity, black hole cut-off mass) is discussed. The energy balance for our model is calculated.

Radio observations revealed a presence of relativistic supernovae - a class of objects intermediate between the regular supernovae and gamma-ray bursts. The typical Lorentz-factors of plasma flows in relativistic radio-bright supernovae were estimated to be about 1.5. Mildly relativistic shocks in electron-ion plasmas are known to efficiently accelerate radio-emitting electrons if the shock is subluminous. The inclination angle of the velocity of subluminous shock to the ambient magnetic field should be below a critical angle which depends on the Mach number and the plasma magnetization parameter. In this paper we present particle-in-cell modeling of electron acceleration by mildly-relativistic collisionless shock of different obliquity in a plasma with ratio of the magnetic energy to the bulk kinetic energy σ ≈ 0.004 which is of interest for the relativistic supernovae modeling. It was shown earlier that a development of the ion scale Bell-type instability in electron-ion relativistic shock may have a strong influence on the electron injection and acceleration. In the time period of about $1500\omega _{_{pi}}^{ - 1}$ (ω_pi is the ion plasma frequency) after the shock initialization the magnetic field fluctuations generated by Bell's instability may significantly decreases number of accelerated electrons even in a sub-luminous shock. We study here the evolution of the electron spectra of subluminous shocks of different obliquity. This is important to for modeling of synchrothron spectra from relativistic supernovae.

Gamma-ray quanta, which occur during solar flares due to the interaction of accelerated protons with the photosphere and deeper layers of the sun, enter interplanetary space from a thickness of several tens of g/cm². In the presented work, gamma quanta with energies of more than 511 keV are considered. This makes it possible to exclude from consideration the dependence of the probability of ortho- and parapositronium formation on the temperature and density of the solar matter. And also do not consider the probability of annihilation by two or 3 gamma quanta. Thus, the reactions of thermal neutrons remain dependent on the temperature. As the ambient temperature increases, the average number of elastic neutron scattering before capture increases. This leads to a more likely penetration of neutrons to a greater depth or their departure into the interplanetary space. The high temperature of the Sun below the photosphere may be one of the reasons for the absence of the 2.223 MeV line in solar flares with registered protons in the PAMELA and AMS2 experiments. Using the GEANT4 package, the spectra of gamma-quanta arising in nuclear interactions are calculated. The temperature-dependent features of the gamma-ray spectra are discussed.

Analysis of the isotopic composition of nuclei in galactic cosmic rays (GCR) in the orbital experiment of the PAMELA collaboration makes it possible to study the problems of the origin and propagation of cosmic rays in the Galaxy. The data of the PAMELA magnetic spectrometer, due to their high statistical and methodological accuracy, ensured significant progress in the study of the isotopic composition of light nuclei from H to Be in GCR in the energy range ~ 0.1-1 GeV/nucleon and for the first time made it possible to estimate the contribution to GCR of Local Interstellar Sources (LIS) from close (∼ 100 pc) of recent (~ million years) supernova explosions. To date, the isotopic composition of beryllium nuclei in GCR has been measured only for ⁷Be./⁹Be, ¹⁰Be/⁹Be ratios in the energy range of ∼ 100 MeV/nucleon in the space experiments IMP 7/8, Voyager, Ulysses, ACE/CRIS and for ¹⁰Be/⁹Be in balloon experiment with a superconducting magnet ISOMAX-98 for energies 0.2-1.0 and 1.1-2.0 GeV/nucleon. In this work, using flight data PAMELA 2006-2014, on the rigidity of the detected nuclei and their velocity (time-of-flight analysis and ionization losses in the multilayer calorimeter of the instrument), a new analysis of the isotopic composition of beryllium nuclei in the energy range of ~ 0.1-1.4 GeV/nucleon has been carried out. The results of isotopic analysis of beryllium nuclei in GCR (spectra ⁷Be, ⁹Be, ¹⁰Be and ⁷Be/⁹Be, ¹⁰Be/⁹Be - ratio depending on the rigidity and energy of nuclei) in comparison with the existing measurement and calculation data will be presented.

The collisional excitation of methanol molecule in non-dissociative magnetohydro-dynamic shock waves is considered. All essential chemical processes that determine methanol abundance in the gas are taken into account in the shock model. The large velocity gradient approximation is used in the calculations of energy level populations of the molecule. We calculate the optical depth for inverted methanol transitions, and present the list of candidates for Class I methanol masers that have collisional pumping mechanism.

The fast stellar winds of massive stars, along with supernovae, determine the dynamics within the star-forming regions. Within a compact star cluster, counterpropagating supersonic MHD shock flows associated with winds and supernova remnants can provide favorable conditions for efficient Fermi I particle acceleration up to energies > 10 PeV over a short timescale of several hundred years. To model the nonthermal spectra of such systems it is necessary to know the complex structure of colliding supersonic flows. In this paper using the PLUTO code we study on a subparsec scale a 2D MHD model of the collision of a core-collapse supernova remnant with a magnetized wind of a hot rotating O-star. As a result the detailed high resolution (~ 10⁻⁴ pc) maps of density, magnetic field, and temperature during the the wind - supernova shell interaction are presented.

We present a self-consistent Monte Carlo model of particle acceleration by relativistic shock waves. The model includes the magnetic field amplification in the shock upstream by cosmic ray driven plasma instabilities. The parameters of the Monte Carlo model are obtained based on PIC calculations. We present the spectra of accelerated particles simulated in the frame of the model.

We combined in-situ solar wind observations by ARTEMIS and MMS missions with kinetic hybrid simulations to study the interaction of solar wind rotational discontinuities (RDs) with the foreshock of the Earth's bow shock. We found that whistler modes excited by diffuse energetic particles were strongly coupled with RDs and lead to their temporary dissociation. At the same time, RDs trigger the steepening of whistler waves and the generation of 'shocklets' - small localised shock-like structures, capable of trapping energetic particles and growing up by absorbing the particles energy.

Supernova remnants (SNRs) are well known sources of the non-thermal radiation, particle acceleration and magnetic field generation and amplification. Synchrotron radiation of the accelerated electrons in the magnetic field is an important emission mechanism in SNRs that can dominate in radio and X-ray energy bands. Turbulent magnetic field yields to formation of the special inhomogeneous (clumpy) structure in the SNR synchrotron X-ray images. This structure could differ significantly on the SNR polarization maps for different types of the magnetic turbulence. A new family of the gas pixel detector X-ray polarimeters that are supposed to have good sensitivity and angular resolution should be well suited for SNR polarimetry. IXPE (NASA) will be the first polarimeter of this kind. Lately a model IXPE synchrotron polarization images of Tycho SNR were simulated in the 3 — 8 keV energy band. It was shown that IXPE observation time of ~ 1 Ms should be enough to distinguish characteristic features that are specific for some types of the magnetic turbulence. We perform simulations of Tycho SNR polarization maps for a wider set of energy bands in order to determine the most suitable energy range for study of the SNR turbulent magnetic field using IXPE. The dependence of the polarization degree on the photon energy is accurately considered in the simulations. IXPE background influence on the observations of Tycho SNR is also discussed here together with possible ways of data processing and interpretation reducing this effect.

Titan makes up 95% of the mass of all 82 satellites of Saturn. Titan's diameter is 5152 km, which means that it is larger than the Moon by 50%, and it is also significantly larger than Mercury. On the satellite, a subsurface ocean is possible, the theory of the presence of which has already been advanced earlier by some scientists. It is located under a layer of ice and consists of 10% ammonia, which is a natural antifreeze for it and does not allow the ocean to freeze. On the one hand, the ocean contains a huge amount of salt, which makes the likelihood of life in it hardly possible. But on the other hand, since chemical processes constantly occur on Titan, forming molecules of complex hydrocarbon substances, this can lead to the emergence of the simplest forms of life. There are limitations on the probabilistic and statistical approaches, since not every process and not every result (form and structure of the system) is probabilistic in nature. In contrast to this, fractal analysis allows one to study the structure of complex objects, taking into account their qualitative specifics, for example, the relationship between the structure and the processes of its formation. When constructing a harmonic model of Titan, the method of decomposition of topographic information into spherical functions was used. As a result, based on the harmonic analysis of the Cassini mission data, a topographic model of Titan was created. In the final form, the model describing Titan's surface includes the expansion of the height parameter depending on the spherical coordinates into a slowly converging regression series of spherical harmonics. For modeling surface details of the surface on a scale of 1 degree requires analysis of the (180 + 1)² harmonic expansion coefficients. An over determined topographic information system was solved to meet the regression modelling conditions. In this case, a number of qualitative stochastic data, such as external measures, were used together with the standard postulation of the harmonic system of the Titan model. As a result of a sampling of self-similar regions (with close values of the self-similarity coefficients) on the surface of Titan, coinciding with the SRGB parameter (characterizes the color fractal dimension), the elements of the satellite's surface were determined, which with a high degree of probability were evolutionarily formed under the action of the same selenochemical processes.

Natural processes existing in complex objects of inanimate and living matter are of a stochastic and non-equilibrium nature. The main problem in the study of such systems is to determine the value of entropy as a quantitative measure of the uncertainty and systematicity of states of dynamical systems in different phase spaces. This paper presents a new method for analyzing active processes of solar dynamics using the theory of non-Markov random discrete processes (NMRDP). The NMRDP theory is based on the Zwanzig-Mori kinetic equations in a finite-difference discrete interpretation. This is consistent with the concept of non-equilibrium statistical condensed matter physics. Qualitative information about the set of behavioral patterns, relaxation processes, dynamic characteristics and internal properties of solar activity can be obtained using NMRDP modeling by the author's methodological approach developed in this work. This approach is focused on the analysis of spectral frequency memory functions, dynamic orthogonal parameters, phase transformations, relaxation and kinetic processes and self-organization in complex physical systems. In this work, for modeling NMRDP, the author's software package APSASA (automated program for solar activity stochastic analysis) was used, which also allows predicting the trend of solar activity for a limited period of time. Modeling NMRDP associated with active processes occurring on the Sun made it possible to build a mathematical model with whose help it is possible to study the regularities and randomness of stochastic processes, as well as to reveal the patterns arising from the recurrence and periodicity of solar activity.

The powerful flow of highly accurate and multiparameter information produced by spacecrafts has caused a surge interest in the industrial robotic exploration of the Moon and manned flight to Mars after the creation of long-term lunar bases. The modern level of both ongoing and planned lunar studies is characterized by a high level of observation accuracy and a large variety of observation methods. The study of the Moon's rotational parameters (MRP) is of important value. For this reason, new methods for analyzing big data sets on observation of MRP and extracting the highest possible amount of scientific information from them are needed. Such space technologies require the creation of in-situ telescopes on the Moon. The long-term laser measurements have supplied comprehensive observational information about the Moon. This allows for a description of the Moon's dynamics with the accuracy required at the current stage - the error of determining the distance to the Moon should be less than a meter, while the one of establishing rotational parameters - arc milliseconds. Nevertheless, there is a necessity to obtain observation data independent of laser measurements. One of the ways to do it is to place on the lunar surface one or several optical telescopes, that will allow determining lunar rotational parameters by measuring the trajectories of the stars and will also be used to solve astrophysical and astrometric problems in the future. This work considers the results of computer modeling of observations taken by lunar in-situ telescopes located at various selenographic latitudes. The sensitivity of MRP to the observed selenographic coordinates of the stars is assessed. Based on the analysis of the simulation results, the optimum location of the telescope is concluded to be at a latitude of 30–45°. The constructive suggestions on the described experiment's implementation are presented in the paper. The details that will allow implementing or declining the practical implementation of the in-situ telescope are discussed.

We show that even the slow (subsonic) motion of pulsar wind nebulae (PWNe) relative to an ambient matter has a significant impact on their observables. The motion changes the appearance of nebulae on X-ray images, comparing to what would be observed for a nebula at rest. Accounting for the relative motion is necessary to avoid misinterpretation of the structure of the nebulae when analyzing their X-ray morphology. The motion also introduces some extra time scales in variability of non-thermal high-energy emission of PWNe and allows to reproduce a number of their structures that are not explained by stationary nebula models.

X-ray observations show that a jet and a counter-jet in pulsar wind nebulae often differ one from another. Sometimes one of the jets is not observed at all. We show that the most likely reason for this difference is the relative motion of a pulsar and an ambient matter. Even the slow (subsonic or transonic) ambient matter stream in the pulsar rest frame strongly affects the jets, making the windward jet bright and dynamic, and the leeward jet dim and diffuse. The effect is illustrated using a relativistic MHD model of a double-torus pulsar wind nebula. The model is shown to explain reasonably well the observational appearance of the jets in the Vela nebula - a double-torus object which evolves in a transonic stream initiated by the passage of the reverse shock of the parent supernova.

The work focuses on using the isophote method to construct a 45P/Honda comet model. At the same time, important problems were solved for modeling the physical surface of a comet and studying the structure of the cometary nucleus. This is due to the fact that, on the basis of modern studies of meteoroids, complex internal processes and dynamic phenomena on their surface have been discovered. The study of comet nuclei is of great importance, since, according to the theory of their formation, they were formed from the matter of the protoplanetary disk. Thus, modeling and analysis of the structure of various comets make it possible to create a more accurate theory of their evolution. This made it possible to evaluate the structural parameters more accurately and reliably. This allowed for the evaluation of the structural parameters more accurately and reliably. Isophotes of the nucleus, coma and tail of comet 45P/Honda were determined. Depending on the point where the comet is located on the trajectory of its orbit, one can see structural changes in the comet's brightness from the nucleus to the peripheral region. Near the cometary nucleus, the isophotes are circular in shape. If in the center of the model the isophotes have a shape close to narrow rings, then elongations in the direction of the cometary tail and thickening of their structure appear towards the peripheral regions. Large and small tail rays can be distinguished, and the nucleus is well marked. In the future, the author's method for modeling isophotes, developed in this work, will allow studying the structure of various cometary objects, and, based on the results, determine the degree of comet activity. On the other hand, about the development of the theory of dynamic processes and the evolution of the Solar system, one can use the data on changes in cometary activity in the process of its movement around the Sun.

Three proxy records of Southern Fennoscandia climate variability were analyzed. It was found that their decadal variations correlate significantly (p=0.961-0.993) with a quasi 11-year solar cycle of Schwabe during AD 1706-1990. But two proxy records have significant decadal correlation with the index of summer North-Atlantic Oscillation (SNAO) as well. Taking into account that decadal periodicity in the SNAO index also has some correlation with the solar cycle of Schwabe, the revealed relations could be a result of influence of solar activity on the Southern Fennoscandian climate realizing by the complicated way. Possible causes of such complexity are discussed.

The work is focused on the analysis of modern observations of meteoroids included in the data bank formed by both professional researchers and amateur astronomers. Based on the modern physical theory of meteoroids (PTM), a new method for analyzing measurements developed, which provides the accuracy comparable with the results of radar observations. Due to the fact that the accuracy of the new method for analyzing meteoroids observations has increased significantly, it became possible to process observations of the Perseid and Leonid showers over a period of 120 years. The use of PTM made it possible for the first time to explain the distribution of meteor echo signals observed at an altitude of 2 MHz, at which the upper part of this distribution refers to an altitude of 140 km. In the process of work, a database of orbital characteristics of meteoroids was created. A method has been developed for modeling the probability of hitting a certain area of a meteor particle with a mass greater than a certain specified value and determining the density of a meteor shower from radio observations as well as a new "tomography" method for calculating the density distribution of sporadic meteors in the sky using radar observations of meteors at the same station with a goniometer. The method allows calculating the density of a meteor shower on the celestial sphere with an angular resolution of 2°. The use of these methods served as a proof that the distribution density of meteoroid showers on the celestial sphere has two planes of symmetry: the first coincides with the plane of the ecliptic, passing through the poles of the Earth, the other one is perpendicular to the plane of the ecliptic.

This work examines the change in the activity of the Sun based on the reconstruction of the heliospheric modulation potential in the time interval 8000 - 1000 BC. Reconstructions of this potential were obtained using radiocarbon data, taking into account the influence of changes in the Earth's climate. A comparison is made of the variations in the activity of the Sun with the global surface temperature. It is shown that variations in global temperature during this period could be the result of changes in solar activity. So high solar activity could lead to recorded temperature maximums around 7000 and 5300 BC. The drop in temperature in the range 3000-1000BC could be the result of low solar activity.

The design and scheme of signal readout from silicon photomultipliers OnSemi MicroFJ-60035 used as sensitive elements (pixels) of a new detector cluster for the camera of the Cherenkov gamma-ray telescope TAIGA-IACT are developed. The design of the developed pixel follows the shape of the photomultiplier tube XP1911 using in the first generation clusters, and that provides compatibility of the new cluster with the telescope camera. Due to the adjustable gain, the developed scheme allows one to detect and digitize signals in a wide dynamic range from several to 10 000 photons.

In the frame of this study astrometric observations of an unusual object 2020 SO - a newly discovered asteroid that turned out to be a Centaur upper-stage booster from 1960s - during its two close approaches to the Earth in December, 2020 and February, 2021 were carried out using two telescopes of Pulkovo observatory. The orbit of the object in question was determined and its future orbital evolution was modelled.

We investigate evolution of physical parameters of the intergalactic medium using an analysis of Lya forest lines detected towards distant quasars. We used the enlarged sample of 98 quasars obtained with Keck/HIRES and VLT/UVES. We show that taking into account a finite spatial size of absorbers, regulated by pressure smoothing, significantly affects the inferred thermal parameters of the intergalactic gas, such as the hydrogen photoionization rate and parameters of the temperature-density relation. Using Bayesian framework we constrained for the first time the scale parameter between the Jeans length and characteristic size of the absorbers. We also discuss limitations of the method based on the analysis of the minimal broadending of Lya lines, which stem from the patchy nature of He II reionization.

A small near-Earth asteroid, discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) on September 17, 2020, turned out to be a part of the Centaur upper stage of the Surveyor 2 spacecraft launched by NASA on September 20, 1966 and subsequently crashed. This object had moved in a heliocentric orbit until it was under the influence of Earth's gravitational field. As a result, a close approach to the Earth took place at a distance of about 50000 km on December 1, 2020. Despite the fact that the Centaur escaped back into a new orbit around the Sun in March 2021, it is of special interest for research, in particular, to consider the impact of non-gravitational effects on its orbital characteristics. Thus, it was calculated that the maximum displacement of the object trajectory due to the influence of solar radiation pressure over 15 years (the next close approach will take place in 2036) can be about 10.3-13.5 km, depending on the albedo. Estimations of the Yarkovsky effect showed that the magnitude of the expected change in the semi-major axis of Centaur's orbit is from -8.1 • 10⁻¹³ to 1.6 10⁻¹³, depending on the angle of its rotation.

Magnetar atmospheres can contain a substantial fraction of once-ionized helium. At the magnetic fields about 10¹⁴ −10¹⁵ G, typical of magnetars, Landau quantization is important not only for the electrons, but also for the centre-of-mass (CM) motion of the He+ ion. The CM and internal motions are mutually dependent, which complicates theoretical studies of the He+ characteristics. We present asymptotic analytic expressions for the binding energies, oscillator strengths, and photoionization cross sections of the moving hydrogenlike ions in an ultra-strong magnetic field, which can be used to construct approximate models of magnetar atmospheres.

Currently, for the world's space agencies, the robotic exploration of Mars is one of the most important tasks. One of the necessary stages for the implementation of this mission is the development and addition of new information to the State standard "Meteoric substance, spatial distribution model". Until now, the State Standard has been more detailed in comparison with the American analogue (developed by NASA) and the European one. The standard is a mandatory document in the design of spacecraft. It should be noted that modeling of meteor hazard at a distance from Earth to Mars is a complex problem, since the analysis of the meteor population in near-Earth space does not give a complete picture of the propagation of meteoroids along the Earth-Mars route. Moreover, the further the trajectory of the spacecraft from the Earth's orbit is, the less the number of near-Earth meteorites becomes. That is, objects that have the same orbital parameters with small bodies crossing the Earth's orbit. The only way to solve this problem is to build an interpolation regression model, which is based on measurements from the Earth's surface and observations of space missions. For this purpose, the density of sporadic meteoroids was transformed from the space mission coordinate system to the ground one. This was done in order to analyze meteorite observations by the Mariner 4 and Pioneer 10 spacecrafts. The results of the work made it possible to obtain new data for the spatial distribution of meteoroids on the Earth-Mars path. According to a comparison of our data with the data on the density of space debris in the previous works the most safe for space flights are normalization conditions of distributions of the elements of the orbits of meteoric bodies P(Z, e, i) < 60.

We investigated models of the internal structure of initially homogeneous Moon differentiated as a result of partial melting, using data on seismic velocities according to the seismic models assume the zonal structure of the lunar mantle is a model of the Moon which was obtained with using the array processing methods of high velocities in the lower mantle. As a result of inversion of gravity (mass, moment of inertia), seismic (P- and S-waves velocities) and petrological (balance ratios) data, the Monte Carlo method was used to reconstruct the chemical composition and internal structure of the Moon. The phase composition and physical properties of the mantle were obtained with Gibbs free energy minimization method and equations of state in the five-component system CaO-FeO-MgO-Al2O3-SiO2. For all models, possible values of seismic velocities and concentrations of the main oxides in three zones of the mantle were obtained, satisfying the geochemical and geophysical constraints and the possible sizes of the Fe-10%S core were determined. It was found that the lunar mantle chemical composition (concentration of FeO, Al2O3 and CaO) differs depending on the mantle zone. Constraints on the values of seismic velocities in the lower mantle and the most probable size of the lunar core were determined: VP ≤ 8.45 km/s; Fe-10%S core radius is ∼360 km.

The features of 3D printing method for rapid prototyping and manufacturing of models for a pulsed high-speed gas-dynamic experiment are considered. Modern additive technologies allow the production of models. The basic properties of the materials and the advantages of 3D printing methods are described. The structure and properties of the obtained models can be unattainable using traditional manufacturing techniques. The design of the wind tunnel nozzle block is considered, which provides for the production of profiled contours using 3D printing. The advantages and disadvantages of use of such units on the shock tube are considered.

The influence of surface small-scale magnetic field on the heating of PSR J0250+5854 polar cap is considered. It is assumed that the polar cap is heated only by reverse positrons accelerated in pulsar diode. It is supposed that pulsar diode is located near the star surface (polar cap model) and operates in the steady state space charge-limited flow regime. The reverse positron current is calculated in the framework of two models: rapid and gradually screening. To calculate the production rate of electron-positron pairs we take into account only the curvature radiation of primary electrons and its absorption in magnetic field. It is assumed that some fraction of electron-positron pairs may be created in bound state that can later be photoionized by thermal photons from star surface.

Currently, the asteroid Ceres belongs to small celestial bodies with the most well-known physical parameters. The study of the structural and real properties of Ceres is an urgent and modern task, the solution of which will make it possible to develop the evolutionary theory of a minor planet. In this work, the fractal properties of the dwarf planet Ceres were analyzed using data from the Dawn space mission. Using the expansion in a harmonic series in spherical functions the height parameters of the structural model of Ceres, a 3D model of Ceres was constructed. The analysis showed that the resulting system has a complex multiparameter fractal configuration. The study of such objects requires the use of harmonic multiparameter methods. Multivariate fractal analysis allows to represent systems similar to the Ceres model in the form of a spectrum of fractal dimensions. The advantage of fractal analysis is the ability to explore local areas of the physical surface. In this work, the Minkowski algorithm was used for this purpose. At the final stage, an overdetermined system was solved for various local areas of topocentric information in order to postulate a model that takes into account external measures. Fractal dimensions D are determined for local regions and the entire model of the planet. Fractal dimensions vary from 1.37 to 1.92 depending on the longitude and latitude of Ceres. The main results are as follows: 1) the structure of the Ceres surface varies more strongly in longitude; 2) the structure of Ceres is smoother in latitude; 3) the coefficient of self-similarity changes rather quickly in longitude, which indicates that different local regions of the minor planet were formed under the influence of various physical processes. It is necessary to emphasize that the resulting fractal dimensions are significantly scattered both in longitude and latitude of Ceres. This fact confirms the presence of a complex structure in the spatial model of a minor planet. This also applies to the actual physical surface of Ceres. The results of the work allow us to conclude that fractal modeling can give independent values of the fractal dimension both for the entire model of Ceres and for its local macrostructural regions.

This study was devoted to measurements of the UV-range photon detection efficiency (PDE) of OnSemi MicroFJ SiPM detectors use together with custom UV filters and of the transmission coefficient of these filters at 277 nm. The final goal of these measurements was to determine feasibility of the filters for the new detector cluster of the TAIGA-IACT telescope. PicoQuant PLS-270 UV source emitting pulses at 277 nm was calibrated. The obtained dependences of the registered radiation power on the distance between the emission source and the reference detector are well approximated by the inverse square function, hence no significant scattering or absorption influenced the PDE measurements. The dependences of the number of detected photons on the distance between the source and the detector were obtained. These dependencies are also well approximated by the inverse square function. The PDE of SiPM MicroFJ-60035 detector was measured at the level of 10.0 ± 0.7%. The transmission coefficients of the considered set of filters at the wavelength of 277 nm were also obtained. The SL 240-300 filter has a sufficiently high transmission coefficient and it is advisable to use it as a bandpass ultraviolet filter in the new detector cluster of the TAIGA-IACT telescope; the SL 290-590 filter absorbs ultraviolet light quite well and is applicable in the visible range.

Asteroids and comets are the oldest objects in the Solar System and contain the initial matter that existed at the moment of its formation. By studying those small celestial bodies one may describe the processes taking place at the early stages and conditions of the formation of the Solar System. The study of the genetic relationships (using metrics based on orbital elements) of meteor showers with parent bodies (asteroids and comets) can be used to develop the theory of evolutionary processes that took place at the time of the formation of the solar system. In this work, we have studied the genetic relationships of the small meteor shower of the h-Virginids (HVI) with the near-Earth asteroids of the Apollo group. An author's multi-factor method is applied, which implies the use of D-criterion by Drummond, metric by Kholshevnikov, Tisserand's parameter, μ and ν quasi-stationary parameters of the restricted three-body problem, and the analysis of the orbit's perihelion longitude π. The observational base includes television catalogues meteor orbits that are in the public domain: Meteoroid Orbit Database v2.0 (2010–2012) (CAMS) and the European meteor network EDMOND (2001–2016) catalogues. As a result of this study, the orbit of the h-Virginids (HVI), according to the values of Tisserand's parameter, was found to be transitional, and thus, it was impossible to identify whether it was of cometary or of asteroid type. Using the author's method, the asteroids 2001SZ269 and 2014HD19 were distinguished. The 2001SZ269 asteroid was distinguished as a candidate having a possible connection with the h-Virginids' parent body.

Long-term evolution of areas with open configuration of magnetic field (coronal holes) on the Sun reconstructed on the basis of H-alpha synoptic charts for the period 1887-2016 was studied and compared with annual occurrence frequencies of magnetic storms with gradual (GC) commencements. It was found that correlation between yearly values of coronal hole (CH) areas and sunspot numbers with no time shift is negative and not strong, but increases up to ∼0.6-0.7 when CH areas are delayed by 4-5 years relative to sunspot numbers. Temporal variations of CH areas in the Northern and Southern hemispheres are characterized by dominant ∼11-year periodicities; however, they differ significantly on the multidecadal time scale. The wavelet spectra of CH areas in the Southern hemisphere, unlike those in the Northern one, reveal persistent periodicities of ∼30-35 years on the studied time interval. Similar periodicities of ∼30-35 years are observed in annual occurrences of GC magnetic storms which are caused by high-speed streams of solar wind from coronal holes. The results of cross wavelet analysis of annual occurrence frequencies of GC magnetic storms and areas of coronal holes revealed common periodicities ∼11, ∼35 and ∼60 years which confirmed a close link of these storms with the evolution of large-scale magnetic fields on the Sun.

The extreme acceleration of the Earth rotation observed in the summer of 2020 is considered. It is concluded that this phenomenon is a consequence of two factors: the longterm acceleration of the Earth rotation, which has been observed since the 1970s, and the extremely strong meteorological excitation of the LOD, which took place in the summer of 2020. The coincidence of the anomaly of the AAM and the geomagnetic Dst index, as well as the correlation between the LOD on the one hand and the solar wind speed and the Gaussian coefficients of the expansion of the Earth's magnetic field, on the other, are noted. The problem of negative leap second is considered. Preliminary estimates have been made of introduction of a negative leap second, if the current trends in the behavior of UT1-UTC continue. The conclusion is made about the low probability of such an event.

Using the developed method of combining numerous scattered time series of the same type of measurements into a single weighted average series, according to the data of the GOES series satellites, a single series of daily data was synthesized during the 22^nd, 23^rd and 24^th solar cycles (1986 – 2019 years). The flare and background components were distinguished from this data series, which were investigated by means the method of constructing a composite spectral periodogram for the presence of quasiperiodic oscillations at various solar cycles. Some of these found quasiperiods may be explained by both synodic and sidereal rotation of the Sun, while others coincide with the average lifetime of the solar atmosphere active formations such as the sunspot groups and the facular plages. Special attention was paid to the study of the change over time the revealed quasiperiodic values over the course of solar cycles by calculating the sample normalized spectral density of the analyzed data in a sliding time window with a value of up to two years. Based on the revealed quasiperiodic value changes presented on the dynamic diagrams, it can be concluded that the differential rotation of the solar corona is unstable and manifests itself only at certain stages of the development and existence of solar activity cycles.

The process of collision of two multicomponent galaxies is considered in detail based on numerical simulations of the dynamics of gravitating gas, stars and dark mass. To solve the equations of motion of the gas component, we use the Smoothed Particle Hydrodynamics method. Modeling of collisionless components is based on the N-body model. The computations of gravitational forces are carried out using both the approximate hierarchical TreeCode algorithm and the direct method of summing the gravitational contribution from all particles, which provides an accurate solution. This approach allows testing various models and evaluating the resulting errors associated with the calculation of gravitational forces and a finite number of particles in each of the components. Both methods for calculating gravity are software implemented as parallel codes for Nvidia Tesla GPUs. The estimates of the lost mass and the efficiency of matter exchange between galaxies are discussed depending on the model parameters.

The interaction of gamma quantum from distant sources with thermal bremsstrahlung photons of hot intracluster gas with producing electron-positron pair in case of 10 galaxy clusters is considered. It is supposed that intracluster gas in considered clusters is isothermal and electron number density may be described by β distribution with β = 2/3. It is presented that the optical depth due to considered interaction is about 10⁻⁸ — 10⁻.

The temporal evolution of Langmuir waves due to induced scattering on thermal electrons of solar plasma for a case of anisotropic distribution of waves is considered. The results of calculations are submitted. It is shown that the induced scattering of waves on thermal electrons does not lead to isotropization of Langmuir waves. But effective transition of energy from waves with the large wave vectors to waves with smaller wave vectors occurs similar to the isotropic case.

Modern data science faces a lot of challenges, one of which is the search for diagnostic criteria for neurological diseases. New methods of statistical analysis are actively applied in the field of biophysics to solve this issue. In this paper we apply the Memory Functions Formalism to analyze electroencephalogram signal recordings in the sleeping state of 8 healthy subjects and 19 patients with nocturnal lobe epilepsy. We observe the considerable difference of statistical memory effects and fractal properties at the pathology in comparison with the control group. Furthermore, we reveal significant alterations in brain rhythms at power spectra of statistical memory functions for two groups of subjects. As a result, we show that the application of the statistical analysis methodology of bioelectrical brain cortex activity recordings, after appropriate verification, can be useful in the search for diagnostic criteria of nocturnal frontal lobe epilepsy.

In this work, the results of spectral and optical studies of the grey matter tissues of the brain by a laser hyperthermia action are presented. The coefficients of optical absorption and transport scattering in the spectral range of 250-1500 nm are determined, and the features of the spatial distribution of the laser radiation intensity in the studied objects are identified. It is shown that the coagulation effects lead to compaction and an increase in the concentration of endogenous chromophores and structural elements, which is reflected in the optical properties of biological objects.

This work presents the results of parameterization of magnetoencephalogram signals from healthy subjects and a patient with photosensitive epilepsy. Diagnostic criteria were established during the extraction of resonant and high-frequency (chaotic) components of the initial time signals. It is shown that an increase in the intensity of the chaotic components of the studied signals in the high-frequency region leads to a violation of cross-correlation relationships and a decrease in the level of manifestation of frequency-phase synchronization. The discovered signs of photosensitive epilepsy will contribute to the development of new methods for the diagnosis and medical control of this disease based on Flicker-Noise Spectroscopy.

The article discusses the use of the formalism of a complex electrical module to determine the relaxation parameters α, β, τ of blood serum. Approximating formulas for the real and imaginary components of the electrical modulus, obtained from the Havrilyak-Negami equation, are given. The assumption is made that for healthy organisms the parameters α, β, τ are constant (or change insignificantly), and for cancer patients they change, and the more the disease develops, the more these parameters change. It is also assumed that the activation energies E_a of macromolecules in the composition of blood serum are different for healthy and diseased organisms. Thus, the study of the dynamics of changes in the parameters α, β, τ, E_a can be used in the monitoring of oncological diseases.

Interaction of iohexol (Omnipaque), an X-Ray contrast agent, with a mimetic peptide of collagen (GPH)₃ as one of the main components of biological tissues has been studied with the use of methods of classical molecular dynamics (GROMACS). Complex molecular modeling of the post-diffusion stage of optical clearing allowed to evaluate such parameters as the average number of hydrogen bonds, formed between the clearing agent and collagen per unit time, and the immersion agent's effect on changes in the collagen peptide volume. The obtained results are compared with similar results for glycerol, a polyatomic alcohol, and with the existing experimental data on the efficiency of optical clearing of these immersion agents.

The article presents the results of a study of low-temperature exposure on animal biological tissue using the novel prototype of a liquid nitrogen cryoapplicator. The data obtained are compared with the cryoapplicator characteristics cooled by nitrogen dioxide that are currently used for the atrial fibrillation treatment. Data analysis confirmed the liquid nitrogen cryoapplicators effectiveness and made it possible to highlight their advantages.

The non-histone chromosomal proteins HMGB1 and HMGB2 were found in the cells of all studied eukaryotes. They are involved in cell decision and many biological processes such as replication, transcription, repair, etc. In this work, the secondary structure of the HMGB1 and HMGB2 proteins was studied by the circular dichroism method. It was shown that, despite the high homology between them, the secondary structure of these proteins is different. The revealed structural features, most likely, should influence their functions in the cell nucleus, in particular, the interaction with DNA and other proteins.

In this work, the surface of polyimide films of PMDA-ODA was modified using a barrier discharge in order to optimize their biological properties when interacting with a culture of human dermal fibroblasts. The optimal modes of processing films in a gas discharge, which allows to increase the proliferative activity of cells, are found.

Multiple myeloma (MM) is a serious disease that is difficult to diagnose especially at early stage. Infrared spectroscopy is a promising approach for diagnosing MM. The principal component analysis (PCA) allows us to reduce the dimension of the data and keep only the important variables. In this study, we apply principal components analysis to infrared (IR) spectra of blood serum from healthy donors and multiple myeloma patients. As a result of the analysis by PCA, it was possible to visualize the separation of patient's and donor's samples into two clusters. The result indicates that this method is potentially applicable for diagnosis of multiple myeloma.

One of the promising approaches for diagnosing oncohematological diseases is infrared spectroscopy of blood serum. In this work secondary structure of blood serum proteins of patients with multiple myeloma, chronic lymphocytic leukemia and healthy donors was studied using IR spectroscopy. As a result of the study, it was found that the secondary structure of blood serum proteins in patients with chronic lymphocytic leukemia does not change in comparison with healthy donors. In contrast, patients with multiple myeloma have significant differences in the secondary structure composition of serum proteins compared to healthy donors. We conclude, that IR spectroscopy makes it possible to distinguish serum of healthy donors and patients with multiple myeloma, leading to the potential applicability of this approach to the diagnosis of multiple myeloma.

In this work we observed three different elastomeric materials with different Young's modulus: Silastic T-4, Plat Set 30, and Lasil-C. Their usage makes it possible to overlap the range of rigidity obtained for Silgard under different curing conditions, without high temperatures and long curing time. The results obtained during the replicas formation using a brass master mold with micro-sized structures for these elastomers were presented. The quality of the replication in materials with low Young's modulus turned out to be better than for Silgard, and for the hard Silastic T-4 – it is comparable to it.

The results of the research of enamel of periodontitis-affected teeth before and after open curettage are presented in the work. The Raman spectroscopy method was used as an evaluation method of curettage influence on tooth enamel. Chemometric analysis of the Raman spectra of tooth enamel before and after curettage was made. Spectral changes of tooth enamel were detected. It was found that after the procedure of open curettage spectral changes occur in tooth enamel related to the changes in mineral composition and organic matrix forming.

The effect of static and alternating magnetic fields on the conformation of nucleoids in cells of different types is considered. The model of slow and nonuniform rotation of the charged DNA domain is used. An equation is obtained for the resonance frequencies of the alternating magnetic field.

The article describes a new technique for determining two main parameters of DNA melting: the melting temperature T_m and the temperature melting range ΔT, based on the plotting of an approximating polynomial function for the DNA melting curve. An algorithm is proposed for reducing the melting curve to approximation by the fourth degree polynomial function in accordance with the physical aspect of the DNA melting process. The correctness of the optimal degree choice from the condition of minimizing the value of the Akaike's information criterion corrected has been confirmed. Analytical expressions for calculating the values of T_m and ΔT are given oriented to a polynomial function of the fourth degree. Results comparison of applying the proposed and well-known techniques based on the experimental data is performed. The advantages of the new technique are revealed.

The results of modeling a collector with 4-stage recovery of residual electron energy for the SPbPU gyrotron with a frequency of 74.2 GHz and an output power of 100 kW are presented. For spatial separation of electrons with different energies, an azimuthal magnetic field created by a toroidal solenoid is used. An increase of the recovery efficiency and a decrease of the current of electrons reflected from the collector is achieved by reducing the spread of the radial position of the leading centers of electron trajectories at optimal parameters of the toroidal solenoid, as well as by using a sectioned electron beam. The trajectory analysis of the spent electron beam in the collector region showed the possibility of achieving the total efficiency of the gyrotron, close to 80%.

A bistability phenomenon in a ring resonator consisting of a delay line on surface spin waves and a microwave amplifier has been experimentally investigated. It is shown that an enhancement of the gain coefficient above a specified value provides an appearance of a hysteresis at the resonator transmission characteristic. A frequency range of the bistability broadens due to an increase of the gain coefficient as well as the external magnetic field. While the value of the gain is limited from above by a transition of the ring into a self-oscillating regime, an increase in the magnetic field from 1150 Oe up to 3150 Oe provides an expansion of the frequency range of the hysteresis from 77 kHz to 185 kHz.

If the group velocity of the wave is close to the bunch velocity, the bunch placed in the maximumum of the radiated pulse. It provides high effeciency of the electron-wave interaction. However, there are other factors related to particle dynamics, which have strong influence on the radiation process. In this paper the regime with three resonance frequencies is discussed. By varying the phase size of the electron bunch, the generation conditions at each of the frequencies can be changed. There are results for the spontaneous coherent super-radiative undulator emission in the terahertz frequency range from a short (as compared to the wavelength of the radiated wave) dense electron bunch. As a result, an electron bunch radiates two pulses with amplitudes of the radiated fields ∼ 10-70 MV/m.

There are results for the spontaneous coherent super-radiative undulator emission in the terahertz frequency range from a short (as compared to the wavelength of the radiated wave) dense electron bunch. If the group velocity of the wave is close to the bunch velocity, this is a process of spontaneous radiation followed by amplification of a single wave cycle. Despite the Coulomb repulsion of electrons inside the bunch, its compactness is provided by the compression of the bunch under the action of its own radiation fields. As a result, formation of an ultra-short (several cycles long) powerful wave packet occurs when the bunch moves through several undulator periods with high (∼20% in optimized systems) efficiency of extraction of the electron energy and high intensity (∼ 100 MV/m) of the peak wave field.

Synthesis and modification of gallium oxide as a wide-bandgap semiconductor is a topical task in the fields of power electronics, UV detectors, gas sensors, telecommunication. In the present work, the Ga2O3 films deposited on sapphire substrates by magnetron sputtering have been studied. The influence of deposition parameters and subsequent annealing on the structure and optical properties of the synthesized films is analyzed. Ion doping of magnetron-deposited films with silicon is carried out by the ion implantation method. It is shown by the Raman scattering and optical transmission spectroscopy that ion irradiation leads to the disordering of the crystal structure, but subsequent annealing results in a partial recovery of the structure. Hall-effect measurements for irradiated and then annealed films do not reveal the formation of a conducting layer. Apparently, this is due to the fact that the main contribution to the resistance is made by grain boundaries in the magnetron-deposited films.

The study is devoted to the treatment of in situ radiation tests results for silicon p-i-n detectors of relativistic protons, which showed the two-stage process of charge transport with avalanche multiplication at a temperature of 1.9 K. The goal of the work is to extract the carrier transport parameters from the experimental data obtained by transient current technique. For that, the impact of a spatial nonuniformity of carrier generation by the laser and spreading of the drifting carrier cloud due to diffusion on the current pulse response formation were considered. The mathematical procedure proposed for the current pulse simulation showed a key contribution of avalanche multiplication in the signal formation and allowed direct estimation of the multiplication factor from the experimental pulses. It is found that this factor only slightly depends on the bias voltage, which suggests the electric field inside the detector to be affected by the space-charge-limited current.

Based on the Zhurkov's kinetic concept of solids' fracture a local internal stress estimation method is introduced. Stress field is computed from the time series of acoustic emission intervals between successive signals. For the case of two structurally different materials the time evolution of these stresses is examined. It is shown that temporal changes of these stresses' accumulation law may serve as a precursor of incoming macroscopic fracture.

Hexagonal boron nitride is a wide band gap semiconductor exhibiting various luminescence bands in visible and near ultraviolet range, which can be used as single photon source. The luminescence band with zero phonon line at 4.1 eV is commonly ascribed to the carbon impurity introduced during crystal growth. In this paper we provide experimental evidence that carbon-related luminescent centers can be introduced in hBN by local electron irradiation in the chamber of scanning electron microscope at room temperature that can be used as a technique for the nanofabrication of single photon source devices with desired pattern.

By using two methods of nondestructive testing, i.e., acoustic emission (AE) measurements and X-ray computed microtomography (CT), an experimental study of defect accumulation during a uniaxial compression of a natural heterogeneous material was carried out. A joint analysis of the AE and CT data revealed a correspondence between energy characteristics of the acoustic emission accompanying defect formation and volume of defects. It is shown that the dependence of the total energy of AE signals on the defect volume is linear, which is consistent with the phenomenological dependences for earthquake focuses obtained earlier. The linear dependence was used to estimate the average defect size. It is shown that, regardless of the assumed defect shape, its average linear size does not exceed 100 μm.

In this work, a method for estimating the saturation time of traps in dielectric layers based on the KPM is proposed. Using hafnium oxide layers as an example, it is shown that when charging with a series of points with different durations, a different dependence of the residual potential on time is observed. It is assumed that this technique makes it possible to evaluate the performance of devices based on dielectric layers.

The presented paper is focused around radiation damage of silicon material under the different ions irradiation. The ion total energy range is 0.7 GeV for ⁷Li to 208 GeV for ²⁰⁸Pb. The results of TRIM modeling for the set of six ions are presented. The extracted information about vacancy production allows making first assumptions of the Si degradation dependence on mass and energy of the incident ion.

Fe_1-xMe_xBO₃ (Me = Al, Sc) single crystals have been synthesized by flux growth technique using B₂O₃-PbO-PbF₂ solvent and approach of identical synthesis conditions. The contents of the diamagnetic ions Me in the initial charge of both compositions were equal, xcharge=0.05. The exact contents and crystal lattice parameters of the synthesized crystals were determined by X-ray fluorescence analysis and X-ray diffraction, respectively.

Single crystals of the amino acid glycine (Gly) C2H5NO2 doped with croconic acid (CA) C5H2O5 were synthesized by evaporation from an aqueous solution. The crystals grow in the form of hexagonal pyramids or thin plates. Analysis of polarized Raman scattering spectra (excitation wavelength of 532 nm) measured at room temperatures showed that crystals in the form of pyramids corresponded to γ-polymorph (γ-Gly), and crystals in the form of plates to α-polymorph of glycine (α - Gly). The presence of croconic acid molecules in the crystals is confirmed by the change in their color from white in pure Gly crystals to light or dark yellow, characteristic of CA crystals, as well as the presence of weak lines corresponding to CA in the Raman spectra. In single crystals of both Gly:CA polymorphs, strong green luminescence significantly exceeding the intensity of Raman scattering is observed in the range 400 - 700 nm with a maximum at 510 nm (2.44 eV) upon excitation at λ= 325 nm.

In this work, the modeling of the sulfur interaction with substitutional impurities (Mn, P) and interstitial (C) has been carried out. All calculations were performed using the density functional theory in the WIEN2k software package. For the first two coordination spheres, there is a strong repulsion between carbon and sulfur, but in the third relative position, a slight attraction arises between the atoms. When sulfur interacts with manganese, attraction occurs only for the first coordination sphere, while the dissolution energy of both manganese and sulfur decreases. In the case of the S-P interaction, the binding energy is negative, and the dissolution energy of both sulfur and phosphorus decreases for all configurations, although the distance between phosphorus and sulfur increases. It can be assumed that the presence of phosphorus leads to the accumulation of sulfur in the material.

Crystals of xenotime-structured phosphates doped with erbium had been grown from molybdate flux at a temperature 1220 ° C followed by slow cooling. The crystals synthesized had been studied using X-ray diffraction and electron probe microanalysis in combination with optical microscopy and luminescence studies.

Materials based on the Sm₂Fe₁₇ compound with nitrogen have great potential for the manufacture of highly efficient permanent magnets. The initial, nitrided, and hydrogenated alloys based on the Sm2Fe17 intermetallic compound with partial substitution of erbium atoms for samarium atoms Sm_1.2Er_0.8Fe₁₇(H, N)_x have been studied by X-ray phase analysis and scanning electron microscopy. Nanopowders of Sm_1.2Er_0.8Fe₁₇N₂ were obtained by mechanical grinding. The grinding time was varied from 0 to 60 minutes. The magnetic hysteresis properties of all powder samples were studied in static magnetic fields up to 7 T, as well as in pulsed magnetic fields up to 60 T. The strength of the intersublattice exchange interaction was estimated. The obtained values λ are valid only for the explored concentration of Sm/Er ions.

The features of the photo-e.m.f. are experimentally studied on the metal/n-InSe contact under conditions of heating the current carriers by an electric field in the temperature range of T₀ =77÷350 K. The dependences of the photo-e.m.f. (U_ph) value have been measured in the absence of $({U}_{ph}^{0})$ and under the condition of heating the current carriers $({U}_{ph}^{\hat{E}})$, as well as the value of $\Delta {U}_{ph}=({U}_{ph}^{\hat{E}}{\text{-U}}_{ph}^{0})$ from the wavelength (λ) and light intensity (I), heating electric field strength (Ê), time (τ), temperature (T₀), the initial value of the dark resistivity (ρD0 at 77K) n-InSe. It has been established that the heating of current carriers by an electric field significantly affects the magnitude and behavior of the photo-e.m.f. characteristics on the metal/n-InSe contact. The nature of this effect depends on T₀,_ρD0, I. The value of ${U}_{ph}^{\hat{E}}$ significantly exceeds the value of ${U}_{ph}^{0}$. With an increase in Ê, the value of AUph increases linearly (ΔU_ph~Ê) at relatively small Ê, and the dependence of ΔU_ph(Ê) reaches saturation at higher Ê. The value of ΔU_ph decreases with increasing _ρD0, at relatively small Ê. With an increase in _ρD0, the relaxation time of the photo-e.m.f. also increases when turned off the pulse of the electric field. The obtained experimental results are explained on the basis of the dependence of the photo-e.m.f. on the metal/n-InSe contact on the effective temperature of heated current carriers (T_e), considering the effect of the spatial inhomogeneity of n-InSe crystals on the photo-e.m.f. and on the process of heating the current carriers.

In this work, the phase composition (relative fractions of monoclinic m-ZrO₂, tetragonal t-ZrO₂, and cubic c-ZrO₂ phases) and mechanical properties (hardness, fracture toughness, compressive strength) of alumina toughened zirconia (ATZ) ceramics, with an addition of silica were investigated. Calcium oxide was used as a stabilizer for the zirconia tetragonal phase. It was shown that CaO-ATZ+SiO₂ ceramics demonstrate increased resistance to low-temperature degradation. The plasticity signs at room temperature were found due to the SiO2 addition to CaO-ATZ ceramics. A yield plateau appears in the uniaxial compression diagram at 5 mol. % SiO₂ concentration. It is hypothesized that discovered plasticity is due to the increased t→m transformability.

Chemical vapor deposited (CVD) diamonds have been irradiated with fast reactor neutrons at fluencies F = 1·10¹⁸ and 3 · 10¹⁸ cm^-2 and then heated at temperatures up to 1600 °C. The processes of annealing in and annealing out of various complexes of intrinsic defects responsible for vibrational and electron-vibrational bands in the IR absorption spectra have been studied in detail. Some tens of local vibrational modes and zero-phonon lines with rather small width caused by numerous complexes of intrinsic defects were observed in the 400-11000 cm^-1 range.

Nonstationary Schroedinger equation (NSE) is solved analytically and numerically to study a phenomenon of dynamical stabilization of the inverted oscillator driven by polyharmonic in time and spatially uniform force with specially chosen phase shifts. It is shown that for Gaussian wave packet asymptotically fitting the initial condition (IC) it occurs temporary delay of the packet center about top of the parabolic potential for about 2 fundamental time periods followed by the center bifurcation.

We present a brief review of the basic properties of regular electrically charged black holes and electromagnetic solitons, predicted by analysis of regular solutions to dynamical equations of Nonlinear Electrodynamics minimally coupled to Gravity (NED-GR). The fundamental generic feature of regular NED-GR objects is the de Sitter vacuum interiors and the relation of their masses to spacetime symmetry breaking from the de Sitter group. Regular spinning NED-GR objects have interior de Sitter vacuum disk with the properties of a perfect conductor and ideal diamagnetic. The disk is confined by the ring with the superconducting current which provides the non-dissipative source of the electromagnetic fields and of the intrinsic magnetic momentum.

Supratransmission waves are stable objects that can exist in different discrete environments. In this paper, we consider the interaction of such waves with single edge dislocations of various configurations in a crystal with A3B stoichiometry. The model was a Pt3Al crystal, the potential obtained by the embedded atom method was used to describe the interaction of its atoms. Quantitative characteristics of the wave were obtained before and after the interaction. It is found that the degree of energy dissipation by dislocations depends on the mutual orientation of the wave front and the extra plane of the dislocation. Numerical estimates are made for four different configurations. The results obtained can be useful in studying the propagation of soliton-type waves in defect crystals of various compositions.

A vertical liquid bridge of small volume between a conical shaper and a convex crystallization front was investigated. Two variants of the front crystallization shape selection are considered: a conical and a spherical fronts. A variational statement of the original problem is given. As the boundary conditions we used the condition of engagement at the edge of the shaper and a given growth angle at the crystallization front. The Bond number was assumed to be small, and to find a solution of the problem the asymptotic approach was applied. The calculations are carried out for small diameter cylindrical sapphire crystals, grown from the melt by the Stepanov method. The results of the menisci shapes calculations are presented. The comparison of the results of calculations for conical and spherical crystallization fronts is carried out.

The models of hemodynamics, corresponding to the inviscid, Newtonian, and non-Newtonian models, are compared. The models are constructed by the averaging of the hydrodynamic system on the vessel cross-section. For the inviscid case, the analytical solution of the problem for pulse propagation is obtained. As the result of the comparison, the deviations of the solutions for non-Newtonian models from the Newtonian and inviscid cases are demonstrated.

A model of a micro-/nanomotor with a hydrodynamic mechanism of motion due to the action of a rotating uniform external magnetic field is proposed. Micro-/nanomotor - is a chain of three charged particles, one of which has a magnetic moment. The total charge of the system is zero. In the absence of an external field, the particles are in equilibrium due to the action of the forces of attraction and repulsion, which corresponds to the minimum interaction energy. After applying a rotating magnetic field, a particle with a magnetic moment begins to rotate, forming a flow in the surrounding viscous fluid. The flow induces a hydrodynamic force that moves the chain in a specific direction. The forces of hydrodynamic interaction of particles with each other are taken into account, as well as internal forces holding the particles together. The dynamics of six model aggregates with one rotating particle is simulated numerically. The proposed mechanism for moving the chain can be used in the design of micro-/nanomotors and control them to deliver the payload.

Long crystals of NiFeGaCo alloy with shape memory effect, including magnetically controlled ones, were obtained by the methods of Czochralski and Stepanov. A strong influence on the properties of crystals of dendritic formations, especially noticeable in the initial part of the crystal, has been revealed. In order to optimize the growth experiments, the heat transfer process in the thermal growth zone was simulated. It is shown that the formation of dendrites is due to a change in heat transfer during growth, which leads to an increase in the axial temperature gradient near the crystallization front as the crystal grows. This fits into the framework of the classical concepts of the transition from dendritic growth to normal growth.

The purpose of this work is to create a method for determining the aerodynamic characteristics of fine particles in a highly rarefied plasma. The created method is based on the theorem on the change in momentum imparted to the body. The "body+surrounding plasma" system was considered to be closed; therefore, the change in the momentum of the body is equal in the impulse of the incident flow and is opposite to it in direction. The change in the pulse flux is calculated using the statistical method. To compare the results and approbation of the calculation method, the deceleration forces of a spherical body in a flow of neutral gas were determined. Next, we calculated the drag coefficient from the side of the charged plasma component. The calculation results are presented in the graphs.

In the work, the field and temperature dependencies on the pyroelectric coefficients of ceramic capacitor structures were measured. Barium titanate (BT) and solid solutions of barium-strontium titanate (BST) were investigate. At temperatures range from 20 °C to 30 °C, the values of the pyroelectric coefficients of the BST ceramics (p) 10^-5 - 10^-4 C/m² K exceeded p for the BT ceramics by an order. The developed measurement technique made it possible to carry out direct pyroelectric coefficients measurements and determine the polarization initial state of the samples, regardless of their phase state.

The possibility of epitaxial growth of Pb_0.7Sn_0.3Te crystalline topological insulator films on the Si(111) surface was shown and epitaxial relations were found. It was shown that, depending on the growth temperature, it is possible to control not only the character of the morphology, but also, to a significant extent, the smoothness of the epitaxial layer surface, which is extremely important for further transport measurements of the films. Analysis of the grown films surface morphology made it possible to establish the average value of the height and lateral size of the terraces and islands forming Pb_0.7Sn_0.3Te surface.

The current-voltage characteristics of Ge₂Sb₂Te₅ thin films were measured by a sequence of triangular current pulses with an increasing maximum current. Each current pulse forms in the sample a conducting filament with an area proportional to the maximum current in the recording pulse.

In this work the properties of the BP/Si heterojunction interface were investigated by capacitance methods, the deep levels transient spectroscopy method and admittance spectroscopy. Admittance spectroscopy did not detect any defects, but the deep level transient spectroscopy showed response with activation energy of 0.33 eV and capture cross-section σ_n=(1-10)·10^-19 cm² and defect concentration (NT) is in the order of 10¹³ cm^-3. This defect level is a trap for electron with position of 0.33 eV below the conduction band in region near the BP/Si interface.

In this paper, we investigate the behavior of a ferromagnetic (FM) film on a nonmagnetic substrate near the Curie point by the computer simulation. The influence of the substrate is specified using the two-dimensional Frenkel-Kontorova (FK) potential. The study is carried out for a two-dimensional film described by the Ising model. At the first step, we calculate the positions of the substrate's atoms in the ground state depending on the parameters. The parameters are (i) the ratio of the substrate periods and the crystal lattice of the film; and (ii) the ratio of the substrate potential amplitude to the elasticity coefficient of interatomic interaction. The period ratio determines the system coverage ratio. Minimization of the system's total energy determines the ground state. Calculations show that the ground state has a periodic structure that differs from a square lattice with a coverage coefficient not equal to unity. We calculate the displacements of atoms from the equilibrium position for systems with a different linear scale.

In this work, we investigate mechanical scanning probe lithography (SPL) of thick MoSe2 flakes. The conventional technique faces difficulties in processing the thick samples due to cantilever twisting that leads to the growth of a number of defects and artifacts that decrease spatial resolution. In course of this work, we proposed the approach of frictional-SPL based on small pressure force and many repetitions of lithographic patterns. This approach allows to avoid the formation of remarkable defects and maintain high spatial resolution. By frictional-SPL, we processed thick MoSe2 flakes (up to 40 nm thick) with the highest resolution down to 20 nm. The results of this work show that frictional-SPL is an effective method of resistless lithography suitable for fabricating nanodevices based on transition metal dichalcogenides (TMDC) materials.

The kinetics of the first-order solid-state structural transition in monodisperse n-alkanes samples of even tetracosane C₂₄H₅₀ was studied by FTIR spectroscopy. The existence of many irregular conformers in solid phases of tetracosane, the concentration of which reaches a maximum when approaching the melting temperature, has been demonstrated. The existence of these defective molecules promotes transitions between different rotator phases in the solid state.

Growth of Ga₂O₃ by metalorganic chemical vapour deposition in horizontal flow reactor from trimethylgallium (TMG) and oxygen is studied in a wide temperature range. The growth rate is directly proportional to TMG flow, weakly affected by O₂ flow and non-monotonically depends on temperature. Growth rate over 3 μm/h is demonstrated, indicating that TMG can be used for growth of β-Ga₂O₃ thick layers for device applications.

The structural properties of amorphous nanocarbon films fabricated by laser sputtering of a graphite target are investigated by means of Raman spectroscopy. Analysis of the spectral features in the region of 100–3600 cm^-1 allowed us to determine the allotrope composition of the films and the degree of disorder in terms of average crystallite size. The results obtained are important for application of such films in the field of electrode coatings.

Composites based on n-alkane and nanoscale additives were investigated to determine the efficiency of heat transfer during phase transitions in phase change materials. It was found that the thermal conductivity of composite materials is several times higher than the thermal conductivity of the initial n-alkane. The observed effect is due to the specificity of the supramolecular nanostructure of the composite, which differs from the supramolecular structure of the nonadecane.

The ultra-high-molecular-weight polyethylene reactor powders are widely used for the actively developing solvent-free method for producing high-strength high-modulus PE filaments, which includes the compaction and sintering of a powder followed by orientational hardening. To find an appropriate regime of the technological process, it is important to know how the nanostructure changes when transforming from a powder to a precursor for hardening. Nanocrystalline lamellae are characteristics of the powder structure. For the first time, the DSC technique was used to follow changes in the thickness distribution of lamellae in ultra-high-molecular-weight polyethylene reactor powder on its way to a precursor for orientation hardening. It was found that the percentage of thick (>15 nm) and thin (10 nm) lamellae in compacted samples and those sintered at temperatures lower than the melting temperature of PE (140°C) remains nearly the same. However, significant changes in the content of lamellae of different thicknesses were observed in the samples sintered at 145°C with subsequent cooling under different conditions. The influence of the lamellae thickness distribution in precursors on the mechanical characteristics of oriented filaments was discussed.

Various applications of superconducting materials require accounting of the critical current anisotropy relative to magnetic field direction - I_c7(θ). However, today there is no sufficiently comprehensive model that takes into account the anisotropy, therefore the angular dependences are usually not analysed, but only described using various mathematical formulas. As a result, the fitting parameters have no physical meaning and it is difficult to correlate the picture with the features of the microstructure. In this paper, we propose a method for analysing the critical current angular dependences based on the anisotropic pinning model. The applicability of this model for conventional superconducting Nb-Ti tapes with one peak in the I_c7(θ) dependence is shown. The possibility of extending this model to analyse the angular dependences of HTS materials is discussed.

In this study, two empirical models for the growth of millimetre–thick GaN material with either highly ordered textured or polycrystalline structure on a ceramic substrate by Hydride Vapour Phase Epitaxy (HVPE) are considered. It is suggested that the specific type of the structure of GaN is determined at the nucleation stage and depends on the character of the wetting of the surface of the substrate by the liquid gallium melt.

The possibility of the controlled removal of GaN nanowires (NWs) from an SiO_x inhibitor layer of patterned SiO_x/Si substrates has been demonstrated. It has been found that the wet KOH etching preserves the selectively grown GaN NWs on Si surface, whereas the GaN NWs grown on inhibitor SiOx layer are removing. The effect is described by the difference in polarity between GaN NWs grown on a Si surface and NWs grown on a SiO_x inhibitor layer.

Within the framework of experimental investigations and computer modeling using the viscoplastic self-consistent (VPSC) model of a material plastic flow, the regularities of preferential orientations formation were established, the proportion of certain texture components was estimated, and existing slip systems (SS) and twinning systems (TS) were identified for equal-channel angular pressing (ECAP) of copper alloys depending on the stacking fault energy (SFE).

The study of nanostructure, thermal and relaxation properties (by HAADF-STEM, EDXS, DMA and DSC), combined with the calculations of interparticle distances and interfacial areas, has been performed for a series of the hybrid Cyanate Ester Resin (CER)/Si0₂ polymer composites with 0.01 to 10 wt.% Si0₂ units introduced via a sol-gel process. The absence of clusterization, arising only subnanometric Si0₂ nodes and their quasi-regular distribution within the amorphous matrix, with the shortest distances between nodes, provided their exceptional positive impact on the matrix properties at ultra-low Si0₂ contents of 0.03-0.1 wt.%. The superiority of these subnanocomposites over the nanocomposites was determined by the role of constrained interfacial dynamics over the whole matrix.

In this work, the calculation of the values of elastic deformations and stresses arising in tapered nanowires is carried out. It was found that in tapered nanowires the magnitude of deformations changes from the base of the nanowire to its tip not linearly (as would be the case in cylindrical nanowires), but in a more complex manner. The ranges of conicity angles at which an extended region of increased stresses can appear in tapered nanowires have been determined.

The photoluminescence (PL) spectra of CdTe/ZnTe double quantum wells (QWs) are studied on a series of samples containing two CdTe layers with nominal thicknesses of 2 and 4 monolayers (ML) in the ZnTe matrix. The QWs were grown in atomic-layer epitaxy and separated by ZnTe spacers with the thicknesses d_sp=40−160 ML. The dependences of the relative intensity of shallow QW₁ and deep QW₂ PL bands (I₁ and I₂, respectively) on the pump intensity (J) when excited by the lasers with different radiation wavelengths are investigated. It is found that in the sample with d_sp=40 ML, the ratio Y(J)=I₁/I₂ depends on J and the shape of the Y(J) dependency changes with the excitation wavelength. In the samples with d_sp > 70 ML Y(J) also changes with the excitation intensity J, but the shape of this dependence is the same for various excitation wavelengths. It is concluded that the energy relaxation in these samples is influenced not only by the tunneling of charge carriers from QW₁ to QW2, but also by carrier relaxation at the nonradiative centers, for which the recombination rate is different for shallow and deep QWs.

In this work, the modification of the surface parameters of graphene chips after electrolysis treatment in a NaClO₄ aqueous solution has been studied. Two electrolysis modes have been analysed. In the first one, a negative potential (-0.2 V) is applied to the graphene chips, while in the second one the potential is positive (0.8 V). Investigation using a number of techniques including atomic force microscopy, Kelvin probe force microscopy, Raman spectroscopy, measurements of current-voltage characteristics and low-frequency noise has shown that the electrolysis mode with application of a positive potential on graphene chips decreases the 1/f noise and allows one to obtain a uniform surface potential distribution while leaving the graphene structure undamaged. The results of this study help to understand the efficiency and reproducibility of the procedure for electrolysis treatment of graphene chips.

The work focuses on the study of the charge relaxation kinetics in composite materials based on polyethylene. Time dependences of the electretic potential differences for samples with different mass values of the filler, as well as dependences of conductivity from the mass percentage of the filler, were achieved. The conductivity curves were analyzed according to the modern theory of intrinsic conductivity.

The effect of solar cell fragment annealing on its noise characteristics is shown. The calculated difference in relaxation times arising from the change in noise after annealing was 30%. Measurements of noise characteristics in the dark and under illumination with a red laser with different radiation power were carried out. Close to linear dependences of noise power reduction with increasing radiation power were obtained.

In this work a technique for optically active nanocomposite structures consisting of an oxide matrix with plasmonic NPs were demonstrated. A nanocomposite film was formed on a silicon substrate by NiO oxide matrix sputtering and gold nanoparticles dewetting. Studies of the morphology, elemental composition, and structure of the nanocomposite using SEM, EDS, XRD methods are presented. The transfer of the film onto a polymer substrate made it possible to study the optical characteristics of the obtained structures. It is shown that formed nanocomposite coatings on a polymer substrate are highly flexible and exhibit excellent mechanical properties.

The paper presents the results of studies of the conditions for the formation of A3B5 compound semiconductors heterointerfaces including InP, InGaAsP and GaAs layers. The heterostructures were grown by molecular-beam epitaxy and were fused by wafer fusion technique. Improvement of planarity and homogeneity over the thickness of heterointerface due to using optimized preliminary preparation of semiconductor wafer surfaces was demonstrated. No additional extended defects such as dislocations were found.

The effect of a magnetic field on the polymerization process and the electrophysical characteristics of polyvinyl alcohol (PVA) films with the inclusion of multiwalled carbon nanotubes (MWCNTs) was studied. Using SEM micrographs, it was shown that the films obtained under the action of a magnetic field have a more homogeneous structure, while a significant number of MCNT agglomerations are present in the control samples. In the study of the conductivity at direct and alternating current, it was found that the films obtained in a magnetic field have a conductivity that significantly exceeds the conductivity of the control samples. It has been shown that the use of a magnetic field during polymerization has a noticeable effect on the properties and characteristics of nanocomposite films based on PVA and MWCNTs.

The kinetics of the formation of silver clusters Ag from nanoscale continuous films of Ag on the surface of silicate glass and composite structures from films of Ag with carbon in the form of a continuous film and individual nanoparticles upon annealing in air at temperatures up to 670K is investigated. In the course of the work, the dependences of the surface morphology of silver clusters and absorption spectra in the visible wavelength range were obtained by the methods of atomic force microscopy and optical spectrophotometry.

This paper presents a study of large area field emitter based on carbon nanotubes grown by PECVD method on Si/SiO2 substrate with Fe catalyst. The catalyst was deposited by CVD on the substrate from ferrocene in the form of islands. The sample creation technology was described and results of the emission properties study were presented. Current-voltage characteristics were registered and tested for compliance with the cold field emission regime. The fluctuation statistic of effective microscopic parameters was constructed. Using data from a computerized field projector, the emission profile of the sample was calculated.

This paper presents the results of using hybrid-organic zinc complex C₂₄H₂₄N₆O₃Zn as a component for creating fullerene C₆₀-based heterostructures. The synthesis technique of the complex compound, the microscopy of the film surfaces obtained, their optical and luminescence properties are described in the paper. The introduction of zinc complex to fullerene shows that there occurs a potential barrier at the active layer interface. The obtained thin-film structures have rectifying light volt-ampere characteristics.

We developed a technique for fabrication microfluidic silicon-glass chips with a system of nanochannels connecting two microchannel using traditional optical lithography and a focused ion beam. To investigate the transport phenomena in the nanochannels we experimentally studied their ion conductivity and using optical microscopy confirmed the existence of the diffusion flow through them. The developed method allows us to create systems of nanochannels with on-purpose geometry and controlled sizes. Devices with such nanochannels can be applied in the creation of biosensor devices and for genetic studies.

A series of the hybrid Bisphenol A based Phthalonitrile (BAPhN)/amino-Montmorillonite (amino-MMT) polymer nanocomposites with the complex heterocyclic matrix network and 0.03–5.0 wt.% amino-MMT were synthesized and studied. Their molecular structure, nanostructure, molecular dynamics, thermal, relaxation and elastic properties were characterized using TEM, EDXS, DMA, TGA, FTIR and Far-IR spectroscopies including also the experiments in flowing nitrogen medium. Depending on nanofiller content, different extents of MMT stacks exfoliation, from a single nanolayer to stacks with tens nanolayers-thickness, were registered in these nanocomposites. The exceptional combining of high temperature properties was revealed for these nanocomposites.

Ce-doped (Pb, Gd)₃(Al, Ga)₅O₁₂ and Ce-doped (Bi, Gd)3(Al, Ga)₅O₁₂ single crystalline garnet films were grown using liquid-phase epitaxy method from supercooled PbO–B₂O₃- and Bi₂O₃–B₂O₃-based melt solutions on substrates from Gd₃Ga₅O₁₂, Gd₃(Al, Ga)₅O₁₂ and Y₃Ga₅O₁₂ single crystals. Optical absorption, photo- and cathodoluminescent and scintillation properties of the films were studied. Ce-doped (Pb,Gd)₃(Al, Ga)₅O₁₂ and Ce-doped (Bi, Gd)₃(Al, Ga)₅O₁₂ garnet films can be used as a fast phosphor and scintillation screens.

This article considers the results of the study of the titanium VT1-0 surface degradation (Grade-4 equivalent) for recrystallized- and ultrafine-grained states after fatigue testing. Comparative analysis of peculiarities of the titanium samples degradation was performed after coating formation by Micro-Arc Oxidation. It was found, that the coating formed by Micro-Arc Oxidation shows different degradation behaviors for recrystallized and ultrafine-grained states

The work is aimed at obtaining microscopic emission characteristics of individual emission sites of a multi-tip field cathode or large-area emitter (LAFE) based on processing the current-voltage characteristics and emission glow patterns. Processing was carried out on a hardware-software complex for the study of field emission characteristics in real time. The calculation of the microscopic characteristics of the local emission sites — the field enhancement factor and emission area — was carried out by several different algorithms. A comparison of the results showed that the algorithms gave close values of the characteristics, which increases the reliability of the estimates made.

The Cahn-Hilliard concepts are generalized and used to the description of the spinodal decomposition of A³B⁵ quaternary semiconductor solid solutions, when the mixing of components occurs simultaneously in the metallic and metalloid sublattices of the sphalerite structure. The resulting system of differential equations for material decomposition was used to describe the effect of composition modulation observed in the synthesis of Ga_xIn_1-xP_yAs_1-y - InP heterostructures. Numerical simulation of the spinodal decomposition of the GaxIm-xPyAsuy solid solution is carried out. The intervals of the thermodynamic parameters of the technological process of the synthesis of structures, in which the effect of modulation of the composition should be manifested, are found.

Extruded bulk nanostructured samples of Bi₈₅Sb₁₅ solid solution from particles with average sizes ∼ 2.10⁵; 950; 650; 380; 30 and 15 nm were obtained and investigated their galvanomagnetic properties in the range of ∼ 77-300 K. Were investigated samples that have not passed heat treatment, and the same samples that have passed heat treatment. It was found that the electrical and thermal properties of Bi₈₅Sb₁₅ solid solution samples significantly depend on the size of nanoparticles and post-extrusion heat treatment. Heat treatment leads to a decrease in the concentration of current carriers and to an increase in the mobility of current carriers and the total thermal conductivity of the samples under study, which is mainly due to the electronic component of thermal conductivity. The change in thermal parameters is satisfactorily explained by changes in occurring in the structure of samples during extrusion and heat treatment and correlates well with changes in the electrical parameters of these processes.

Infrared converters to visible range are in demand for creation of optoelectronic devices, infrared visualizers and other non-linear optical devices. In this work we study nonlinear optical properties of monodisperse SiO₂ and Si/SiO₂ spheres encapsulated into silicone films. The fabricated silicone films containing SiO₂ spheres demonstrated a bright third harmonic generation signal, and films with Si/SiO₂ spheres demonstrated a significant second harmonic generation signal in the whole visible range. The developed materials and methods provide a platform for future infrared to visible converters based on silicon.

This work shows the possibility of forming a planar diode structure based on carbon nanotubes formed on a catalytic alloy film Co-Nb-N-(O). The paper presents a technological route for the formation of a planar diode structure Si/SiO₂/Si₃N₄/Co-Nb-N-(O)/SiO₂ and studies the emission characteristics. The current-voltage characteristic of the obtained diode structure in the Fowler-Nordheim coordinates is close to linear in the range from 15 to 22 V, which confirms the phenomenon of electron emission.

The possibility of AlGaAs nanowires with GaAs quantum dots and InP nanowires with InAsP quantum dots growth by molecular-beam epitaxy on silicon substrates has been demonstrated. Results of GaAs quantum dots optical properties studies have shown that these objects are sources of single photons. In case of InP nanowires with InAsP quantum dots, the results we obtained indicate that nearly 100% of coherent nanowires can be formed with high optical quality of this system on a silicon surface. The presence of a band with maximum emission intensity near 1.3 μm makes it possible to consider the given system promising for further integration of optical elements on silicon platform with fiber-optic systems. Our work, therefore, opens new prospects for integration of direct bandgap semiconductors and singlephoton sources on silicon platform for various applications in the fields of silicon photonics and quantum information technology.

This article is devoted to the formation and study of the properties of amorphous gallium phosphide layers obtained by plasma-chemical deposition at a temperature of 250 °C. The optical and structural properties of the obtained layers on fused silica and silicon substrates were investigated. The possibility of the formation of a homogeneous amorphous gallium phosphide with a smooth surface at a low temperature and low power of RF plasma was shown.

Diffusion of aluminum in amorphous silicon films during crystallization through infrared laser irradiation was studied. Diffusion regime was found to change from limited source to abundant source diffusion at higher laser source power. At the same time, crystalline structure of the obtained samples becomes more perfect, which is more characteristic to limited source diffusion mode.

Oligomeric diisocyanate based coatings with different contents of barium titanate (BaTiO₃) submicron sized particles as a ferroelectric filler are synthesized on poly(dimethylsiloxane) (PDMS) supports. The study of thus obtained coatings using confocal scanning electron microscopy allowed the characterization of their morphology and features of BaTiO₃ particles distribution in the polymer binder, including the determination of threshold filler contents corresponding to the formation of an infinite cluster, matrix-island and chain-like structures as well as the percolation. Dielectric permittivity and dielectric losses of the composites are measured and studied depending on BaTiO₃ filler content and relating structural features.

Studied are the films of variously doped polycrystalline n-semiconductors (ZnO, SnO₂) as selective sensitive elements (SE) of chemical sensors for various gases and vapours (ammonia, acetone, propane, ethanol, hexane, solvent, turpentine etc.) in artificial air. It has been revealed that their conductivity changes under temperature modulation makes possible data processing which identifies the impurities above. This processing is based on nonlinear regression estimation of so called principal parameters which set is unique for every concentration of every of the gases/vapours.

In this work the study of the optical properties of europium doped titanium dioxide thin films (TiO₂:Eu) enhanced by gold plasmonic nanostructures are presented. Plasmonic platforms were manufactured by thermal annealing of thin film of Au, deposited on a Corning glass substrate. As a result of thermal treatment, gold spherical nanostructures with average dimensions of 50 nm were obtained. Luminescent TiO₂:Eu film was deposited by RF magnetron sputtering method, from mosaic target. Morphology of gold nanostructures was investigated by SEM and TEM microscopes, while composition of oxides film was analysed by XPS methods. Luminescence properties were studied on the basis of excitation and emission spectra. Experiments have shown that such structures exhibit interesting luminescent properties and could be potential candidates for optoelectronics applications.

This study is devoted to the investigation of the effect of growth conditions (growth temperature, values of molecular beam fluxes) on the formation of self-catalytic GaP NW on Si(111), namely surface density, orientation and NW morphology. Nanowire arrays were grown on Si (111) by the plasma-assisted molecular beam epitaxy. It was determined that an increase of the temperature and a decrease of the Ga flux, while maintaining the V/III ratio, reduces the inclined NWs and parasitic islands nucleation probability.

This work demonstrates the possibility of using a combination of zinc oxide nanorods with silver nanoparticles as a self-cleaning SERS substrate. In addition to Raman scattering enhancement such structures demonstrate the self-cleaning effect during UV treatment. The ZnO nanorods (NRs) array was synthesized on a ZnO seed layer by the hydrothermal method. The Ag nanoparticles (NPs) array was formed by vacuum thermal evaporation over the ZnO NRs. Rhodamine-B 230 μM solution has been detected using the formed SERS-substrates without additional mathematical processing of the Raman spectra. Subsequent UV radiation treatment showed a 3-fold decrease in the intensity of the spectral peaks of the analyte.

Currently, the study of the electric parameters of porous anodic alumina (PAA) layers is of interest for sensor applications (humidity, DNA, etc.). PAA layers are synthesized using electrochemical anodizing of aluminum foil in potentiostatic mode with an aqueous solution of sulfuric acid and glycerin as an electrolyte. The surface morphology of the layers was studied by atomic force microscopy. The electric characteristics were studied using impedance spectroscopy at room temperature and under heating. An increase in the impedance of the heat-treated PAA sample was found, as well as an increase in the impedance with an increase in the measurement temperature. The results are explained by the influence of adsorbed water molecules on the electric characteristics of porous layers.

We present an analytical approach to the problem of the interband transitions in an armchair graphene nanoribbon (AGNR), exposed to the time-periodic electric field of strong light wave, polarized parallel to the ribbon axis. The two-dimensional Dirac equation for the massless electron subject to the ribbon confinement is employed. In the resonant approximation the probability of the transitions between the valence and conduction size-quantized subbands are calculated in an explicit form. We trace the dependencies of the Rabi frequency for these transitions on the ribbon width and electric field strength for both the multiphoton-assisted and tunneling regimes relevant to the fast oscillating and practically constant electric field, respectively. Estimates of the expected experimental values for the typically employed AGNR and laser technique facilities show that the Rabi oscillations can be observed under laboratory conditions. The data, corresponding to the intersubband tunneling, makes the AGNR a 1D condensed matter analog, in which the quantum electrodynamic vacuum decay can be detected by the employment of the attainable electric fields.

The length of single-walled carbon nanotubes (SWCNTs) affects the optoelectronic and mechanical properties of macroscopic SWCNT layers. Modern methods are capable to measure the length of short nanotubes, and also require complex sample preparation procedures. In this work we show that the average length of SWCNTs can be estimated by measuring the resistance of randomly oriented SWCNTs array. We observe the change in the slope of the resistance dependence on the distance between the contacts with the interval between 100 and 200 μm. The change of resistance slope indicates a change in the path of current flow through the SWCNT. The change in the conduction path can be associated with the "effective bundle length", which should be related to the average nanotube length. Thus, we have demonstrated a simple and quick technique to measure SWCNT bundle length, which can be used in-situ and does not require special sample preparation.

Thin films of ZnO-SnO₂, with a molar ratio of Zn: Sn = 0:100, 1:99, and 5:95, were synthesized by the sol-gel method. As a result of a study of the electrophysical and gas-sensitive properties of thin ZnO-SnO₂ films, the effect of a decrease in the working temperature at low concentrations of zinc oxide was found. The value of the coefficient of gas sensitivity of ZnO-SnO₂ films correlates with the activation energy of conduction. For sensor structures based on films with a composition of: 5:95 at a working temperature of 200 °C, a higher gas sensitivity coefficient and the fastest response among all the samples under study are observed.

An important goal of current ultra-relativistic heavy ion research is the investigation of the quark-gluon plasma (QGP). Measurements of elliptic flow lend insight on reaction dynamics and are important for defining parameters of viscous hydrodynamic, which can describe QGP behavior. In this paper elliptic flow for φ-mesons in Cu+Au collisions at $\sqrt{{s}_{NN}}=200\text{GeV}$ and in U+U collisions at $\sqrt{{s}_{NN}}=193\text{GeV}$ GeV is studied as a function of kinetic properties and centrality. The obtained results are compared to hydrodynamic model predictions. New FVTX detector and combinations of different approaches of flow measurements provide a possibility to measure the elliptic flow for the φ-mesons for the first time as a function of centrality at PHENIX. The elliptic flow for φ-mesons in Cu+Au and U+U collisions as function of transverse kinetic energy per one quark follows the trend for other hadrons with respect to the number of quarks in hadrons, regardless of centrality. This result along with agreement of obtained data to hydrodynamic model iEBE-VISHNU predictions suggests that QGP can be described with viscous hydrodynamic with specific viscosity η/s = 1/(4π).

The study of deconfinement state of nuclear matter called quark-gluon plasma (QGP) and phase transition of QGP to hadronic gas is the main goal of high energy physics. Some of the important signatures of QGP formation in heavy-ion collisions include strangeness enhancement at intermediate values of the transverse momentum (ρ_T) and a jet quenching effect at high ρ_T values. Nuclear modification factors (R_AB) for light hadrons are used to quantify these effects. The K^*0 and φ mesons can serve as a good probes to investigate QGP properties, because these mesons contain (anti)strange quark and its yields can be measured in a wide ρ_T range. Comparison of experimental data with theoretical model calculations is important for understanding the evolution of heavy-ion collision. One of the most commonly used event generators to describe experimental results of collider experiments is Pythia8. This paper shows, that Pythia8 predicts R_AB values of K^*0 and φ less than R_AB values in experimental data. Consequently, additional (hidden)strange particle production mechanisms are involved.

Ultrarelativistic ion collisions provide the unique possibility to study the quark-gluon plasma, a state of matter formed in the universe at the very first moments after the Big Bang. The minimal temperature and baryon density for the quark-gluon plasma formation requires scrutiny, since the signatures of the quark-gluon plasma formation are observed in large systems (such as Au+Au) at $\sqrt{{s}_{NN}}=200\text{GeV}$, whereas collective effects in p+p collisions are not revealed. The φ-meson production measurements are considered to be a convenient tool to investigate the collision dynamics, as it is sensitive to the quark-gluon plasma effects. To interpret the nuclear modification effects and to study the process of the possible QGP formation the comparison with different theoretical models predictions is needed. This paper presents the comparison of the obtained experimental results on φ-meson production in small collision systems (p+Al, p+Au) at $\sqrt{{s}_{NN}}=200\text{GeV}$ to default and string melting versions of the AMPT model and PYTHIA model predictions. The results indicate that the minimal conditions (temperature and baryon density) for a QGP formation may lie in between in p+Al and p+Au collisions.

The main goal of PHENIX expirement, located at Relativistic Heavy-ion collider, is the investigation of quark-gluon plasma (QGP). One of the aspects of the QGP study is describing the process of its hadronization. Very important contribution to understanding of hadronization process was given by discovering of anomaly large ratio of protons production to pions production (ρ/π) in Au+Au collisions in comparison to the same ratio in proton-proton collisions. This effect was called baryon puzzle and was explained in a frame of recombination model of hadronization.

Although charged hadrons production has been previously studied in elementary proton-proton collisions and symmetric Au+Au collisions, it has never been investigated before in the large asymmetric collisions systems (such as Cu+Au) or the collisions of large deformed nuclei (U+U). The study of such large collisions systems allows to study features of baryon and meson production versus collision geometry and system size.

The paper proposes a method and its realization for stabilizing the characteristics of a multichannel position-sensitive spectrometer. The device uses a new design of the semiconductor strip detector, which allows a simultaneous injection of stable in time electric charges on all strips. This solution enables the electronics to track changes in the conversion characteristics of all electronic channels including detectors strips, and correct them during the spectrometer operation. In addition, the proposed detector design makes it possible to control the signal propagation along the strips, thus providing an on-line check of the integrity of strips metallization and the quality of their connection with the readout electronics.

The response function of the recoil nuclei in detectors designed for detection of neutrinos or dark matter particles can be determined only through usage of a neutron source with a known energy spectrum. A possible solution for a compact neutron calibration source is a combination of a ²⁵²Cf neutron source and a semiconductor detector that detects fission fragments, and thus records the neutron emission moment. This work is devoted to the degradation study of the operating parameters for silicon semiconductor detectors irradiated by fission fragments of the nuclide of ²⁵² Cf. Two types of Si detectors were under investigations - silicon-lithium Si(Li) p-i-n detectors and silicon surface barrier detectors. As a result of the measurements, the maximum permissible radiation doses for the correct operation of both types of detectors and the relation of the received radiation dose to the spectroscopic characteristics of the detectors were determined.

Deterioration of the operation parameters of p-type Si surface-barrier detector and Si(Li) p-i-n detector upon irradiation by alpha-particles was investigated. The detectors were irradiated at room temperature up to a total number of the registered α-particles N_α equal to 6 × 10⁹. Prolonged irradiation has resulted in a deterioration of the detectors energy resolution ability and it was found that the increase of α-peaks broadening can be described by a linear function of N_α with a slope Δσ/ΔN_α ∼ (1.4–1.8) × 10^–9 keV/α for both detectors. Resolution deterioration was associated with the increase of the detectors leakage current, which proceeds linearly with the number of absorbed α-particles with the slope ΔI/ΔNα ∼ (7-17) × 10^-17 A/α. The increase of the detectors reverse current was related with appearance of radiation-induced defect level at 0.56 eV above the valence band.

The short-lived hadronic resonances are used to study properties of the hot and dense medium produced in relativistic heavy-ion collisions. Due to their short lifetimes, the resonance yields and masses measured in the hadronic channels are sensitive to rescattering and regeneration effects in the hadronic phase. The measurement of resonances is foreseen in the physical program of the MPD experiment at NICA in heavy-ion collisions at $\sqrt{{S}_{NN}}=4\text{-}11\text{GeV}$, in the range of energies where extensive measurements of resonances are not experimentally available. In this contribution, we explore the sensitivity of the ρ(770)⁰, K*(892), ϕ(1020), ∑(1385)^±, Λ(1520) and Ξ(1530)⁰ resonances measured in the hadronic decay channels to different stages of the heavy-ion collisions at NICA energies and report the feasibility studies for the reconstruction of resonances in the MPD setup

Precision β-spectra measurement always had a great importance in some fundamental physics problems including neutrino physics. Magnetic and electrostatic spectrometers have high resolution, but at the same time usage of such kinds of equipment involves the size and cost issues. Since electron mean free path at the energy of 3 MeV (which is basically the maximum energy of a β-transition for the long-lived nuclei) does not exceed 2 g/crn², electron registration could be effectively performed with the solid state scintillators and semiconductors. A strong probability of backscattering from detector surface is present in case of semiconductor detectors and is dependent upon the detector material. Such problem can be solved with 4π geometry detector development, which fully covers the radioactive source and is able to register the backscattered electrons. In this work we present the newly developed technology of 4π geometry β-spectrometer based on two semiconductor detectors. This spectrometer was used for measurement of the ¹⁴⁴Ce - ¹⁴⁴Pr spectrum, that is the perspective anti-neutrino source due to endpoint energy at 3 MeV and can be used for the sterile neutrino search experiments. The form-factor parameters that were obtained are: C(W) = 1 + (-0.02877 ± 0.00028)W + (-0.11722 ± 0.00297)W^-1. The measurement accuracy was sufficiently enhanced with respect to the previous results.

A newly developed experimental technique based on ¹⁶⁹Tm-containing cryogenic bolometer detector was employed in order to perform the search for solar axions. The inclusion of target material into the active detector volume allowed for significant increase in sensitivity to axion parameters. A short 6.6 days measurement campaign with 8.18 g detector crystal yielded the following limits on axion couplings: $|g{}_{A\gamma }({g}_{{}_{AN}^{0}}+{g}_{AN}^{3})\le 1.44\times {10}^{-14}{\text{GeV}}^{-1}$ and $|g{}_{Ae}({g}_{{}_{AN}^{0}}+{g}_{AN}^{3})\le 2.81\times {10}^{-16}$. The achieved results demonstrate high scalability potential of presented experimental approach.

A calculation method is developed for production of the copper-64 isotope from the ⁶⁴Ni(p, n)⁶⁴Cu nuclear reaction. The ⁶⁴Cu radioisotope used in nuclear medicine is produced by irradiating a natural nickel target with a proton beam produced on a cyclotron. The conditions of the production were dictated by the capabilities of the cyclotron. The energy of the protons was 17 MeV (the beam current is 10 μॅ). As a result, the activity of copper-64 isotope for various irradiation times were obtained. The depth of proton penetration into the target material was studied.

The shape of ²¹⁰Bi β-spectrum was measured using a spectrometer based on Si(Li) detectors with a 4π geometry. Full absorption spectrometer allows for a direct measurement of the β-spectra without using the electron backscattering corrections for the response function. The measured value of nuclear shape factor C(W)=1+(-0.4378±0.0072)W+ (0.0526±0.0021) W² is in agreement with the results of previous studies.

Laue diffraction theory of X-ray microbeams in multilayers (MLs) is developed. The solution for calculating X-ray reciprocal space maps is obtained. The pendulum (Pendellösung) effect for perfect and imperfect MLs is shown. The numerical simulation of Laue diffraction in Mo/Si multilayers with boundary conditions in the case of geometrical optics and the Fresnel approximation is carried out. It is shown that for X-ray microbeams one should to take into account the diffraction of X-ray waves at the edges of slits (collimators) of the diffraction scheme.

Thermal stable solid solutions of titanates, niobates, and tantalates of bismuth with a pyrochlore structure doped with 3d-metal atoms were studied using XPS and NEXAFS spectroscopy. Based on spectral studies, it was shown that the manganese, cobalt, nickel and copper atoms in these solid solutions have mainly charge state +2 and iron atoms – charge state +3.

The results of joint theoretical and experimental studies aimed at revealing features in the Raman spectra, which can be used for evaluation of the interface quality between GaN and AlN layers in short-period GaN/AlN superlattices (SLs) are presented. The Raman spectra for SLs with sharp interface and with different degree of interface diffusion are simulated by ab initio calculations and within the framework of random-element isodisplacement model, respectively. The comparison of the results of theoretical calculations and experimental data obtained on PA MBE and MOVPE grown SLs, leads to conclusion that the spectral region of the A₁(LO) confined phonons is very sensitive to the degree of interface sharpness. As a result of comprehensive studies, the correlations between the parameters of the A₁(LO) confined phonons and the structure of SLs are obtained. The results of the complex studies can be used to optimize the parameters of the growth process in order to form structurally perfect short-period GaN/AlN SLs.

Photoluminescence and X-ray diffraction (XRD) were used for the studies of the properties of HgCdTe samples with CdTe molar fraction x=0.3 grown by various methods. According to the results of photoluminescence studies, all samples possessed a considerable degree of alloy disorder, yet the scale of the disorder seemed not to be directly related to the structural quality of the material as revealed using XRD. Prospects of using HgCdTe material grown by various methods in optoelectronic devices are discussed.

In this paper we have studied influence of attenuation on conversion processes of the fundamental mode (FM) in multihelicoidal optical fibers (MHF) in the vicinity of the point of accidental spectrum degeneracy within the framework of the scalar approximation. To this end, we have obtained expressions for modes of the MHF, which consist of the FM and an optical vortex (OV), and shown that conversion of the FM into the OV takes place. The difference in the attenuation coefficients for the partial fields of MHF's modes leads to deterioration in the conversion process even with an ideal system's tuning. At sufficiently large values of attenuation coefficients the conversion of the incoming FM into the vortex vanishes. Also we have shown the presence of exceptional point (EP) in the spectra of modes of the MHF and demonstrated enhanced sensitivity of the fiber in the vicinity of the EP to perturbations.

We present a theoretical investigation of effect of quantum fluctuations on laser solitons. Derivation of the stochastic equation, linearized with respect to quantum perturbations is carried out and the solutions are found. Explicit expressions are obtained for the time dependence of the soliton coordinates and momentum dispersion (variance) for perturbations averaged over the reservoir. It is shown that the dispersion of the soliton momentum becomes constant. It is shown that the dispersion of quantum perturbations tends to infinity near the Andronov-Hopf bifurcation threshold. The magnitude of quantum perturbations near the threshold of the appearance of hysteresis is estimated. It is shown that quantum perturbations do not significantly noise the soliton profile even with a very low intensity tending to zero. The number of photons in such solitons without supporting radiation, can reach unity.

We investigate, analytically and numerically, tubular topological laser solitons, which serve as intermediate link between 2D- and 3D-dissipative optical solitons in media with nonlinear amplification and absorption of light or in large-size laser with such a medium. Features of both 3D-dark solitons (with nonvanishing intensity at periphery for all spatial dimensions) and bright-dark solitons (vanishing in two of three dimensions) are studied, including their stability.

Advanced for the infrared region of the spectrum chalcogenide glass composition As_30.5S_44.5I₂₅ with small germanium additives were investigated. The concentration dependences of some physical and chemical properties indicate an increase in the performance of glasses due to the modification of the glass network. The character of the change in the short-wavelength absorption edge with an increase in the content of germanium atoms had an exponential character, shifting from 597 to 582 nm. A non-monotonic dependences were also found for the values of density, refractive index, and glass transition temperature. A joint analysis of the results obtained and structural studies described in the literature for similar glass systems made it possible to propose possible structural groups of glass compositions under investigation.

The investigation of unique carbonate substituted bioapatite of Champsocephalus gunnari icefish jaw and skull bones was carried out using NEXAFS spectroscopy. It has been established that these bones contain the B-type carbonate substituted hydroxyapatit with a content [CO₃]^2- anion of about 0.79-3.07 wt.%.

The dependences of the reflection coefficients at a wavelength of λ = 355 nm for germanium and silicon single crystals on the energy density of impacting laser radiation in the range 0.01 - 0.1 J/cm2 have been measured. Analytical expressions were obtained. It is assumed, that they are also valid in the range 0.1 - 1.0 J/cm². With a further increase in the energy density, the dependence should acquire a more complex character due to the resulting optical breakdown.

The influence of pollutants on the spectral properties of common buckwheat (Fagopyrum esculentum) has been investigated insufficiently, compared to the cereals from the Poaceae family. A two-stage spectral survey has been carried out, growing common buckwheat in containers with set concentrations of copper(II) sulfate in soil both in laboratory conditions and in the open air. Spectral distributions of diffuse reflectance of the plants were registered in the range of 400 – 1100 nm, and spectral indices were calculated, using wavelengths corresponding to spectral features of plant pigments. Simultaneously, digital photos were taken to account for projective cover of the plants. Four spectral indices were found to depend quantitatively on pollutant concentration, three of them taking extreme values at the time of maximal projective cover. When growing buckwheat in the open air, lower temperatures and higher irradiation lead to closer values of spectral indices corresponding to different copper concentration, than in laboratory conditions. The results show the usability of common buckwheat as an indicator of soil pollution by copper.

The coefficients of reflection, transmission and absorption are calculated in the framework of the kinetic approach, when an electromagnetic E-wave interacts with a thin conducting film located between two dielectric media. To account for the surface scattering of charge carriers is used a model of mirror-diffuse boundary conditions, assuming that the specularity coefficients of the upper and lower surfaces of the film differ from each other. The electromagnetic wave falls on the upper surface of the film at an arbitrary angle. The case of an anisotropic isoenergetic surface of a conductor having the form of a three-axis ellipsoid, one of the main axes of which is parallel to the magnetic field strength of the wave, and the other is perpendicular to the film surfaces, is considered. The impurity scattering of electrons (holes) is dominated in the volume of the conductor. The dependence of the absorption coefficient on the parameters of the isoenergetic surface of the conductor is analyzed.

The problem of the surface acoustic Rayleigh wave scattering on a deterministic three-dimensional roughness, occupying a finite size rectangular region of an isotropic solid free surface, is solved in the Rayleigh-Born approximation of the perturbation theory in a roughness amplitude. Formula for the displacement field in the scattered Rayleigh wave at a big distance from the roughness, as compared to rough region sizes L₁,₂ along the x_1,2- axes respectively, and asymptotic formulas for this displacement field in the Bragg, i.e. short-wavelength λ≪ L_1,2 limit, where λ is the wavelength, are derived. The new laws of scattering are obtained. They are caused by a strong modulation of scattering by the roughness form. They exceed the fundamental physical conception, that a wave scattering in the short-wavelength limit takes place on a medium discontinuities, by the statement, that a wave strongly senses the structure of a medium in the near vicinity of discontinuities as well as the form-factor of the discontinuities lattice. This form-factor is a dependence of the discontinuity amplitude, i.e. of a difference of the left and right limit values of a roughness non-zero derivative, including one of zero order, in coordinate at a point of discontinuity, on a number of this discontinuity in a lattice. This exceeded physical conception violates the classical Laue-Bragg-Wulff laws of scattering.

The model of a single-emitter laser generating in the regime of small number of photons in the cavity mode is theoretically investigated. Based on a system of equations for different moments of the field operators the analytical expressions for mean photon number and photon number variance are obtained. Using the master equation approach the differential equation for the phase-averaged quasi-probability Q is derived. For some limiting cases the exact solutions of this equation are found.

This work is devoted to the development of a method for the quantitative comparison of the luminosity of weakly luminous samples, such as self-glowing crystals. A self-glowing crystal is an efficient scintillator, whose self-luminescence is due to the decay of a radioactive isotope introduced into the crystal matrix during its growth. Such crystals can be used as low current sources with a service life of 50 years or more. This technique takes into account the luminescence spectra of the samples under study, the spectral functions of the spectrometer and photodetector. Information on the luminescence spectra of samples can be obtained based on their cathodoluminescence spectra. Thanks to the calculations performed according to this technique, it becomes possible to estimate the optical radiation power of a self-glowing crystal, which can be converted into an electric current using a photodiode. Also, the proposed technique can be applied to assess the luminosities of any materials under the influence of radioactive radiation.

The experiments in optical evaluation of biomaterials taken from juvenile dentin have been made using the Raman spectroscopy method. It was shown that juvenile teeth lose their mineral components and preserve organic components in the process of demineralization with the use of hydrochloric acid.

Start The experiments in evaluation of hard tissues using the Raman spectroscopy method have been made. Spectral differences between the tooth enamel and dentin before and after the in-office whitening procedure were found as a result of the work. It was shown with the use of the Raman spectroscopy method that the whitening process causes changes of tooth enamel and dentin related to the changes of organic and mineral components.

In this paper we investigated tight focusing of optical vortex with topological charge m = 2 and left circular polarization. The simulation was based on Richards-Wolf equation. Light with wavelength 532 nm was focused by aplanatic lens with numerical aperture NA=0.95. It was shown that the longitudinal component of Poynting vector has negative values on the optical axis. The reason of the energy backflow is due to the fact that the projection of the spin flow onto the optical axis is negative and exceeds in absolute value the projection of the orbital energy flow, which is always positive.

We report the excitation of nonstationary holographic currents in a monoclinic gallium oxide crystal. Although the crystal is almost transparent and insulating for a visible light, the dynamic space-charge gratings are recorded and holographic currents are observed for both the diffusion and drift modes. The anisotropy along the [100] and [010] directions is revealed, namely, there is a small difference in the transport parameters and a pronounced polarization dependence of the signal. The crystal's photoconductivity, responsivity and diffusion length of electrons are estimated for the light wavelength λ = 457 nm.

In this work, the focusing of a circularly polarized plane wave (wavelength 532 nm) was simulated by a lens with a numerical aperture NA = 0.95. The wave front was considered flat. When integrating according to the Richards-Wolf formulas, the semicircular aperture was set by limiting the azimuthal angle from 0 to π. It was shown that when focusing light with right and left circular polarization, the focal spot turns out to be elliptical - elongated along the y axis, and, depending on the direction of polarization, its center shifts by about 0.05 μm in different directions along the x axis. It was also shown that the reverse flow region is located near the focal spot (at a distance of 0.25 μm from the center). Depending on the direction of polarization, it is located either to the right or to the left of the focal spot. Thus, the polarization state of the incident radiation can be determined from the displacement of the spot in focus.

The results of the research of bone mineral component (BMC) composition using the Raman spectroscopy method are presented in the work. The subjects of the research were the groups of BMC samples made of compact bone tissue of cows using "Lyoplast"® technology where vacuum delipidation of initial material was replaced by the flow one by washing it out in hydrogen peroxide and ether. The solution filtration after bone tissue demineralization was used as additional treatment. The results of the experiment show that the flow delipidation can be used for preparing this biomaterial (BMC), which is cost-effective compared to standard vacuum cleaning and additional filtration stage can be rejected.

In this paper, we present the results of the propagational dynamics of vortex beams in the scope of their possible applications for interferometric non-contact robust and precision optical surface profilometry with nanoscale longitudinal resolution. The result of coaxial superposition of the reference plane wave with singly charged vortex beams represents a dynamically changing intensity distribution. The nature of this changes, namely, rotational effects of intensity zeros, allows to determine directly the optical path difference which is introduced by the surfaces and internal structure of test object. We have proposed the experimental setup for examination of reflecting and transmitting objects.

In this work, we investigated bulk β-Ga₂O₃ samples grown by the Czochralski method on Al₂O₃ and β-Ga₂O₃ seeds. The elemental composition of the samples and its effect on the luminescent and electrophysical properties of the samples were determined. The Kelvin probe microscopy was used to study the processes of localization and dissipation of charges in the samples. It was shown that in a β-Ga₂O₃ sample grown on an Al₂O₃ seed, the characteristic charge dissipation time is 10 times longer.

Using data on the absorption cross sections the refraction coefficient spectral dependence n(E) and the spectra of the remaining optical coefficients (reflection coefficient, phase shift, and atomic form factor) in the fullerite C₆₀ C 1s near edge X-ray absorption fine structure (NEXAFS) region (280–350 eV) were determined. For the n(E) calculations the Kramers-Kronig integral relations (KKRs) were used. The KKR computations were performed using data on atomic carbon absorption cross sections in the 10–30000 eV range and on solid and gaseous C₆₀ – in the 0–120 eV. Absorption cross section spectrum in the fullerite C₆₀ C 1s NEXAFS region were measured.

The aim of the paper is to describe a well-known quantum key distribution GG02 protocol using multimode coherent states generated on subcarrier frequencies of the optical spectrum. In order to detect signal states, we use a method of coherent detection without the participation of a local oscillator directly but where power from a carrier wave is used as such. Within the framework of the modern GG02 protocol description and the secutity proof against collective attacks, we introduce the necessary amendments to reduce our model to a model of the common system.

Silver nanoparticles have unique optical properties due to resonance effects that arise due to the presence of conduction electrons in them. When these electrons interacte with photons, they can create localization of electric fields at the interfaces with the environment. Silver nanoparticles deposited on a transparent substrate are often used for research, while Ag nanostructures on Si are studied in this work. They have great potential for practical applications. The interaction of light with nanostructures can be described using various models (pseudo-dielectric functions, effective medium, thin-layer structures, etc.) and optical methods for the experimental determination of their parameters (refractometry, spectrophotometry). Bulk plasmon resonance is considered in this work, which is excited when plasmons are excited at their resonant frequency by an external electromagnetic wave. Calculations were performed for different diameters of silver nanoparticles on a silicon substrate with different structure periods. The calculated spectra are in good agreement with the experimental data of the obtained samples. As a result of the plasmon resonance modeling, the position of the plasmon resonance depends on the density of the arrangement of silver nanoparticles, with an increase in the displacement resonance towards the long-wavelength region.

The article describes the behaviour of the Zn ions in aqueous subphase in presence of arachidic acid films at the air/liquid interface first studied by XANES spectroscopy in the fluorescent mode under total external reflection conditions. Fingerprint analysis of experimental spectra was carried out to determine the local structure of zinc ions in arachidic acid. It showed that zinc is surrounded by oxygen atoms, which may correspond to the interaction of zinc ions with polar groups of arachidic acid.

Heat treatment conditions effect on the characteristics of exciton absorption and luminescence of CuCl and CuBr nanocrystals in potassium-aluminaborate glass is studied. The size effect of the band edge absorption and luminescence energy is confirmed. The simultaneous presence of copper halide nanocrystals and free monovalent copper ions in the glass matrix is shown. Possible conditions for the formation of mixed CuCl-CuBr crystals are considered.

The method of spectral Fourier microscopy was used to study the reflection spectra with an angular resolution of submicron periodic gratings based on amorphous and crystalline Ge₂Sb₂Te₅. The form of the dispersion curves of quasi-waveguide modes in the structures under study was established. The experimental data were compared with the calculations of dispersion curves in synthesized diffraction gratings. Reasonable agreement between theoretical and experimental data was obtained.

In this paper, the design of a plasmonic lens in gold and silver thin films for focusing the light with radial polarization is presented. Using the finite difference time domain method the optimal parameters of the plasmonic lens design are found. It was shown that the silver plasmonic lens produces a tight focal spot with a full width at half maximum of 0.38 of the incident light wavelength.

Using the FDTD simulation, sharp focusing of a linearly polarized Gaussian beam with an embedded topological charge m = 3 by a phase zone plate and focusing of a Gaussian beam by a phase spiral zone plate with topological charge m = 3 were studied. The obtained results showed that proposed elements formed different patterns of intensity at a focal plane. The spiral zone plate forms a focal spot with three petals. At a distance of 13.5 μm from the focus, the lobe structure of the intensity (and energy flux) is replaced by an annular distribution.

Vertical-cavity surface-emitting lasers of 1.3 μm spectral range with the active region based on the InGaAs/InGaAlAs superlattice were studied. VCSEL heterostructure was formed by a wafer-fusion of the heterostructure with an active region and two DBRs grown by molecular-beam epitaxy on InP and GaAs substrates respectively. Fabricated VCSELs have shown threshold current below 1.6 mA and frequency of small signal modulation near 9 GHz at 20°C.

A model of the optical power degradation of an InGaN/GaN LED during testing under direct current, which takes into account the inhomogeneous distribution of the defects density in the heterostructure, is presented. According to the simulation results, the rate of degradation of the LED optical power significantly depends on the degree of inhomogeneity of the defects density distribution profile. Experimental testing of the model has been carried out. The proposed model makes it possible to predict the rate of degradation of InGaN-based LEDs with varying degrees of inhomogeneity of the defects density distribution profile and can be used to develop a technique for rejecting defective and potentially unreliable LEDs.

Our work is aimed at the method of fabricating arrays of semiconductor III-V NWs transferred into a flexible polymer membrane made of polydimethylsiloxane. GaP/GaPAs NWs with an axial p-i-n structure were synthesized by molecular beam epitaxy. The synthesized NW arrays on substrates were encapsulated into a silicone membrane by the G-coating method in a swinging-bucket centrifuge. After membranes were treated in a plasma mixture of O₂/CF₂ gases to open the NWs tops, which ensured the application of conductive transparent contacts - single-walled carbon nanotubes obtained by aerosol chemical method. At the last technological stage, the membranes were separated from substrates by peeling with a razor blade and the second carbon nanotubes contact was formed. The obtained LED NW/silicone membranes were characterized by I-V and the electroluminescence spectroscopy measurements.

An induced impurity photoconductivity by the electric field, thermally stimulated conductivity and spontaneous pulsations of the dark current were found in the undoped (with a dark resistivity P77≈3•10⁴÷10⁸ Ω-cm at T≈77 K) and erbium doped (N_Er=10^–5÷10^–1 at.%) p-GaSe crystals in the temperature range of T≤240÷250 K at electric field strengths (E) creating a noticeable injection. It was found that the value of the observed impurity photoconductivity (M) monotonically increase at low illumination in undoped crystals with increasing P77 and its spectrum smoothly expands towards longer waves. The value of ∆i_i and the width of its spectrum change non-monotonically with increasing N_Er in doped crystal and it gets its maximum value at N_Er≈5•10^-4 at.%. The intensity of spontaneous pulsations increases with increasing E at the higher electric field strengths. However, the impurity photoconductivity and the peak of thermally stimulated conductivity gradually disappeared. The amplitude and frequency of the observed spontaneous pulsations of the dark current is increased with increasing in the injection ability of the contacts. Moreover, the pulsations of the dark current gradually disappeared with increasing T. It was shown that all these three phenomena are directly caused by the recharge of sticking levels with a depth _Er≈+0.42 eV and a density N_t≈ 10¹⁵ cm^-3 by injected holes. However, in high-resistance undoped and doped _Er≤10^-2 at.% crystals, it is also necessary to consider the presence of random macroscopic defects in the samples to explain their features. A qualitative explanation is proposed based on the obtained results.

This paper discusses multijunction solar cells with optically coupled p-n junctions under radiation exposure photosensitivity spectral response study. It is shown that if the measurement technique does not consider the luminescent coupling and does not track the optical coupling degradation, then instead of a decrease (which is a natural response of a photoconverter to radiation damage), an abnormal increase in the narrow-bandgap photoresponse (receiving luminescent radiation) subcell due to radiation damage can be observed. Accordingly, with an increase in the irradiation dose, an increase in the subcell photocurrent forming a "negative" degradation dependence of MJ SC being used in space applications is recorded.

We propose a hybrid microcavity design of a 1.3 μm range electrically driven single-photon source (SPS) consisting of two high-contrast dielectric distributed Bragg reflectors which surround a 3λ-thick semiconductor cavity with two intra-cavity contact layers and four 40-nm-thick oxide-confined apertures. According to 3D finite-difference time-domain modelling, the overall photon-extraction efficiency of ~74% and the Purcell factor of ~13 can be obtained by properly adjusting the position of oxide-confined apertures relative to the electric field of the fundamental optical mode. The studied SPS design also demonstrates a coupling efficiency of up to 13% within numerical aperture 0.12 in contrast to ~5% reached for a conventional semiconductor micropillar.

We demonstrate noise characterization of novel 894.4 nm vertical-cavity surface emitting lasers with intracavity contacts and a rhomboidal oxide current aperture (IC-VCSELs), dedicated to ¹³³Cs D1 line compact optically pumped atomic magnetometers (OPM). The laser relative intensity noise, measured to be -139 dB/Hz at 10 kHz frequency in 1 Hz bandwidth for a laser optical power of 0.8 mW, is decreased with optical power growth. The IC-VCSELs polarization-resolved relative intensity noise is 143 dB/Hz at 10 kHz frequency in 1 Hz bandwidth for 0.8 mW. The emission linewidth of the VCSEL is about 55 MHz. The IC-VCSEL parameters are determined, such as emission linewidth ~ 50-60 MHz, optical power ~ 0.5-1.0 mW, at which the polarization-resolved RIN becomes close to the RIN, which makes it possible to use these lasers in various OPM Mz and Mx schemes. The ultimate sensitivity of OPM was estimated by the ratio of the magnetic resonance to the signal to noise level. It is shown that a OPM based on the IC-VCSELs, assuming magnetic resonance FWHM ~ 1 kHz, can achieve a shot noise-limited sensitivity around 20 fT in 1 Hz bandwidth without any polarization improvements by polarizer or polarization beam splitter cube (PBC). Developed IC-VCSELs is acceptable for use in compact OPM for magnetoencephalography.

The present research focuses on the study of the phase-sensitive amplification based on periodically poled lithium niobate (PPLN) made from gradient Er doped lithium niobate. It is shown that the presence of a growing Er gradient increases the gain while maintaining phase sensitivity to the input signal.

This paper presents a study of Zn diffusion process into InP and InGaAs/InP epitaxial heterostructures grown by molecular beam epitaxy. It was found that both diffusion systems: a resistively heated quartz reactor with a solid-state Zn vapor source placed inside and hydrogen or nitrogen as the carrier gas and MOCVD reactor with hydrogen as the carrier gas allow achieving similar dopant concentration above 2*10e18 cm^-3. The depth of the diffusion front in the InP layer is located from 2 to 3.5 μm depending on the temperature and time of the diffusion process. The diffusion of Zn into InP through the intermediate InGaAs layer provides better surface quality comparing with direct zinc diffusion into InP surface.

The article considers the formation of titanium channel optical waveguides in LiTaO₃ substrates. These structures were obtained by dry etching of grooves in SF₆ plasma and magnetron sputtering of titanium film. After that, waveguides were formed by plasma etching using photoresist as mask. Technological features and modes of microstructure production are described. Al contact pads were produced by magnetron sputtering thin metal films on LiTaO₃. Aluminum wires were ultrasonically bonded to Al contact pads using Delvotec 5630. The developed technology of formation of contact pads and bonding modes made it possible to obtain a bonded joint with a bond strength of 23-25 Gs.

LEDs operating under high pulsed current are of a great interest for different applications, in particular, for VLC (LiFi) systems and laser pumping. Current dependences of the efficiency and emission spectra as well as the rise and fall times of high-power blue LEDs were investigated under extremely high pulse current density up to 7 kA/cm² and pulse duration from 100 ns to 3 μs. Analysis of the pulse behaviour of the LEDs reveals that the main droop in the efficiency and change in spectra occur up to the current densities ~ 1 kA/cm² and seems to be non-thermal.

The purposes of this work was to study the possibility of using photoconductive semiconductor antenna based on Ge or GaAs for receiving information signals in the frequency communications and satellite navigation bands and to study a scattering parameter S11 – a return loss (a reflection coefficient) of configurable loop antennas with laser-plasma control based on semiconductor photoresistor. It is shown that the addition of semiconductor photoresistor element in the loop antenna makes it possible to significantly expand its functionality and control its characteristics using an external laser source.

The technology of MEMS atomic cells containing rubidium or caesium vapors in an atmosphere of neon buffer gas has been developed. Two-chamber silicon cells containing an optical cavity, shallow filtration channels and a technical container for a solid-state alkali source have been implemented in a single-step process of anisotropic wet chemical etching. To prevent significant undercutting of the filtration channels during etching of the through silicon cavities, the shapes of the compensating elements at the convex corners of the silicon nitride mask have been calculated and the composition of the silicon etchant has been experimentally found. The sealing of the cells has been carried out by silicon-glass anodic bonding at a temperature of 250 °C. For this purpose the LK5 glass which has an increased ionic conductivity in comparison with the conventional glass Borofloat 33 was used. The best microfabricated cells allowed us to obtain estimates of the relative instability of the coherent population trapping resonance frequency at the level of 5 · 10^-11 at 1 s.

Results are presented of a study of commercial blue and UV light-emitting diodes based on structures with InGaN/GaN quantum wells. An accelerated aging was provided by currents of 80 – 190 mA under a forward bias with duration not exceeding 3 h. The study demonstrated the possible rise in the external quantum efficiency by 20% relative to that in the starting samples. The possible physical mechanisms responsible for the rise in the quantum efficiency and for the formation of a low-frequency current noise are presented.

Deformable mirror (DM) is an active element that can change the shape of the surface to compensate for wavefront aberrations. Historically, the development of DMs started from piezostack deformable mirrors (PDM) due to their large stroke, flexibility in actuators geometry, high resonant frequency. However, the cost of PDMs is comparatively high because of their labor-intensive process of manufacturing. In the article innovative design of PDM is presented. The assembling of unconventional PDMs was carried out using piezoceramic combs. This step should allow to decrease number of technological steps, increase spatial resolution of the mirror and thereby reduce the cost of final product.

Here novel high efficient semi-transparent perovskite solar cells (PSCs) based on ZrO₂ photoelectrodes were fabricated and were used as top elements in tandem systems with crystalline silicon (c-Si) solar cells in four-terminal configuration. The comparative analysis of photovoltaic parameters measured for PSCs, c-Si solar cells and PSC/c-Si tandem solar cells demonstrated that the use of ZrO₂ photoelectrodes allows to improve the PSC performance and to achieve efficiencies for PSC/c-Si tandem solar cell higher than for a standalone c-Si solar cell under varying illumination conditions.

In the work, the effect of In_0.8Ga_0.2As quantum dots position in the i-region of a GaAs solar cell on its spectral and photoelectric characteristics has been investigated. Three solar cell structures were obtained by metal-organic vapor-phase epitaxy, in which layers of quantum dots were placed in the middle of the i-region and also have been shifted to the base and the emitter. As a result, it has been shown that the solar cell with a quantum dot array shifted to the base demonstrates the smallest open-circuit voltage drop and, accordingly, a higher efficiency value.

In this work, titanate Cs₂Fe₂Ti₆O₁₆ with a hollandite-type structure was synthesized by solid-phase synthesis. The electrical conductivity of the obtained ceramics was investigated in the temperature range from 25 to 800 °C in air and in the presence of an argon-hydrogen mixture (3% H₂). It was found that the electrical conductivity of the compound under consideration depends on the composition of the atmosphere — the activation energy of conduction changes (0.57 eV in air and 0.91 eV in the presence of hydrogen). The volumetric and grain-boundary contributions to the total resistance of the sample in the gases under consideration are separated by impedance spectroscopy at a temperature of 800 °C.

Investigations of the temperature stability of the peak tunneling current density of connecting tunneling diodes, which are necessary for the creation on their basis of multijunction photoconverters of powerful optical radiation, have been carried out. The structures of n++-GaAs/i-GaAs/i-AlGaAs/p⁺⁺-AlGaAs of connecting TD with an intermediate undoped layer thickness of 7.5 nm and a growth temperature of 500 °C (structure "A") and with a thickness of 10 nm and a temperature of 450 °C (structure "B") were investigated. When heated to 80 °C, an increase in the peak tunneling current density of the TD structure "B" by 4% is observed. However, for structure "A", a decrease in the peak tunneling current density by 5% with heating is observed. The factors leading to the appearance of a negative or positive temperature coefficient of the peak tunneling current density are determined using mathematical modeling of tunneling diodes based on GaAs/AlGaAs materials. By reducing the epitaxial growth temperature of n⁺⁺–GaAs/i-GaAs/i-AlGaAs/p⁺⁺–AlGaAs tunnel diode structure to 450 °C and including an undoped i-layer 10 nm thick between the degenerate layers ensure the temperature stability of peak current density when heated to 80 °C.

The possibility of creating of a radioisotope source of energy based on a radio-luminescent crystal of YPO₄:Eu/(²³⁸Pu) and Al_xGa_1-xAs/GaAs photovoltaic converter is demonstrated and its characteristics are analyzed. A prototype of an ecologically safe radioisotope source with low content (< 0.1%) of the ²³⁸Pu isotope, efficiency of ~1.4%, and long service life has been developed.

Polycrystalline Tb_xDy_1-xR_0.1Fe_2-zCo_z (R = Nd, Pr, x = 0.2, 0.3; z = 0, 1.3) cubic Laves phase alloys with MgCu2-type structure were prepared by arc melting followed by homogenizing annealing. The crystal structure, magnetic properties, and magnetostriction have been investigated. Compounds with high values of magnetostrictive susceptibility were found in the temperature range 150-300 K. Compounds with partial substitution of cobalt for iron demonstrate a change in the sign of anisotropic magnetostriction. This work continues the search for magnetostrictive materials with inexpensive neodymium and praseodymium.

We present a new parametrization of the d + ³He → p + ⁴He fusion reaction astrophysical factor based on the effective range approximation, which is an effective theoretical method for describing near-threshold, including resonance, nuclear reactions. In the framework of this approximation we describe experimental data on the energy dependence of the cross section and the astrophysical factor within the experimental uncertainties in the energy range of 0-800 keV. On this basis we calculate the temperature dependence of the Maxwellian-averaged reaction rate in the range of 0-400 keV. In conclusion, we discuss the effect of the calculated reaction rates on the Lawson criterion for thermonuclear reactors based on d-³He fuel.

The results of studies of the dielectric constant ε' and the DTA signal of a new organic ferroelectric (R)-3-quinuclidinol (C₇H₁₃NO), embedded in porous glasses with an average pore size of 100 nm, are presented. The phase transition was found to shift to low temperatures by 3 K upon heating and 6 K upon cooling, in comparison with bulk (R)-3-quinuclidinol. A decrease in the phase transition temperature in composites with (R)-3-quinuclidinol nanoparticles is consistent with theoretical models of the influence of size effects on the structural phase transition.

The magnetostatic and magnetic resonance properties of the Y_0.5Sr_0.5Cr_0.5Mn_0.5O₃ polycrystalline system have been experimentally studied. The intracrystalline ferromagnetic interaction turned out to be prevalent while the intercrystalline interaction appears to have antiferromagnetic character. We found that two absorption lines are observed in the spectrum in the magnetic ordering region at T < 80 K. The high-field line corresponds to the interacting parts of polycrystal related to the disordered shells and the low-field peak is system of ferromagnetic particles.

We recall the experimental data of one-dimensional axial propagation of sound near the center of the Bose-Einstein condensate cloud, which used the optical dipole force method of a focused laser beam and rapid sequencing of nondestructive phase-contrast images. We reanalyze these data within the general quantum fluid framework but without model-specific theoretical assumptions; using the standard best fit techniques. We demonstrate that some of their features cannot be explained by means of the perturbative two-body approximation and Gross-Pitaevskii model, and conjecture possible solutions.

A model of quasistationary states is constructed for the one-dimensional edge states propagating along the edge of a two-dimensional topological insulator based on HgTe/CdTe quantum well in the presence of magnetic barriers with finite transparency. The lifetimes of these quasistationary states are found analytically and numerically via different approaches including the solution of the stationary Schrödinger equation with complex energy and the solution of the transmission problem for a double barrier structure. The results can serve as a guide for determining the parameters of magnetic barriers creating the quantum dots where the lifetimes for the broadened discrete levels are long enough for manipulation with their occupation numbers by external fields.

The influence of two types of AlN/GaN interfacial non-idealities, namely unintentional Ga incorporation into AlN spacer and blurring of the spacer due to Al and/or Ga atomic diffusion on the mobility and density of two-dimensional electron gas in AlGaN/AlN/GaN heterostructure was studied theoretically. It was found that moderate amount of GaN in the nominal AlN spacer does not affect much the mobility and density of 2DEG as long as the interface is abrupt. In contrast, the blurring of AlN/GaN interface was found to have a significant impact on the mobility and sheet resistance of the structure since the GaN channel actually becomes AlGaN and alloy-disorder scattering takes place.

Results are presented of a series of RANS computations aimed at creating a new experimental flow model of a curved turbulent wake evolving under adverse pressure gradient. In the course of the computations, key geometric parameters of the model (the angle of attack of a flat plate generating the wake and the shape and the angles of attack of liner foils creating the pressure gradient) were varied in a wide range. The purpose was to find the parameters ensuring desirable features of the flow, namely, a considerable wake curvature and its strong deceleration leading to formation of a large stagnation or even a reversal flow region, on the one hand, and no flow separation either from the flat plate or from the surfaces of the liner foils, on the other hand. As a result, the design satisfying all these demands has been found. This design will be implemented and studied in the framework of recently launched joint German-Russian project "Complex Wake Flows" which presents a continuation of an earlier similar project devoted to symmetric wakes.

Stability features of steady-state solutions for a diode with counter-streaming electron and ion flows are studied. For this purpose, the time-dependent problem for an exponential potential perturbation with complex frequency is considered. By linearization of the Poisson equation and electron and ion densities integrodifferential equation for the potential perturbation amplitude is derived. In the case of uniform unperturbed potential distribution an explicit solution of this equation is obtained. Eigen modes of the perturbation are studied. The limiting value of the diode length above which steady state solutions in question are unstable is found. The obtained analytical Eigen modes coincide with the result of numerical simulation of the potential perturbation evolution.

Stability features of steady-state solutions for a vacuum diode with complete deceleration of electron beam is studied. A boundary line on the (inter-electrode gap, external voltage)-plane separating stable solutions from unstable ones is built up. An instability development is shown to end in a state with non-linear oscillations of the electric field but with no virtual cathode in a plasma. Existence of non-linear oscillations of the electric field in a vacuum diode with total reflection of an electron beam points out that such a diode can be a basis to create microwave generator.

This paper presents the experiment results of modelling the one engine failure at the landing mode on a model of a light transport airplane in the T-102 TsAGI low speed wind tunnel. The effect of starboard and port engines failure on the aerodynamic characteristics and stability of the model is researched. The model maximum lift coefficient is reduced about ≈8% and there are the same moments in roll and yaw for starboard and port engines failure case. It was found that the failure of any engine has little impact on the efficiency of control surfaces. Approaches of compensation of forces and moments arising in the engine failure case were investigated.

The present study aimed to modeling of surgically corrected venous valve. The Arbitrary Lagrangian-Eulerian (ALE) method was used to model the blood–leaflet interactions. The contact process between leaflets was evaluated using a frictionless contact method. The results of the numerical study of the flow in the venous valve after extravasal correction was compared with the results for the normal venous valve.

The two-dimensional turbulent transonic flow over a symmetric flat-sided airfoil with a blunt trailing edge is studied numerically. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver on a fine computational mesh. The non-uniqueness of flow field in certain bands of the given free-stream Mach number and angle of attack is demonstrated. Intricate dependence of the lift coefficient on the free-stream parameters is discussed. Adverse free-stream parameters, which admit abrupt changes of the flow structure and lift, are identified.

The paper presents a comparative numerical study of pulsatory blood flow in five patient-specific models of femoral-popliteal artery anastomosis. Three-dimensional geometric models of a proximal junction of the common femoral artery/graft were constructed on the bases of CT angiography. The influence of junction geometry on the blood flow and wall shear stress is analyzed. The ratio of the measured CFA and graft diameters and the junction angle are considered as the major geometrical parameters. Numerically calculated velocity fields are analyzed, and stagnant zones in the anastomoses flow are identified. Time-averaged distributions of wall shear stress and oscillatory shear index obtained for five patient-specific model are compared.

Results of the studies on turbulences carried out on the Globus-M2 and Globus-M tokamaks are presented. The main focus was on the analysis of the data obtained using Doppler backscattering method (DBS). The developed codes for the analysis of DBS signals allowed to study the effects of turbulences on the operational mode of the tokamak. A description of the data processing codes is also included. The analysis performed indicates the suppression of turbulence and the formation of a velocity shear during the L-H transition. It was also successfully used to study density fluctuations during and between edge localized modes (ELMs). Spectral and correlation analysis also led to the discovery of limit-cycle oscillations (LCO) and quasi coherent fluctuations (QCFs) during the I-phase.

The discharge propagation velocity towards electromagnetic radiation of sub-THz and THz bands was measured in various noble gases (argon, krypton) mixtures with nitrogen in the wide pressure range (0.1 – 2 atm) for various field intensities into the focal spot (from dozen of kW/cm² to several MW/cm²). In the experimental setups two different gyrotrons were used. In case of 263 GHz it was CW gyrotron with power up 1 kW, in case of 670 GHz – pulsed gyrotron (20 μs) with power up to 40 kW. In both cases the focusing system provided the size of the focal spot of (2–3)·λ, which ensured the investigation of discharge phenomena in a wide pressure range (0.1 – 2 atm). In both cases discharge appeared in the focal spot spread towards heating radiation into the area with the field intensity much less than one in the focal spot. Velocity of the discharge propagation was measured by using photos from speed camera with small exposure (down to 20 ns) and streak camera. It was demonstrated that discharge velocity increase along with pressure decrease and drops with electric field decrease as it moves away from the focal spot.

The results of using Large Eddy Simulation with Wall Functions (WFLES) in application to basic wall-bounded flows, such as turbulent boundary layer and channel flow cases are presented. In particular, it is shown that WFLES is suitable for predicting wall bounded flows and provides reasonable accuracy when using appropriate grids. The grid for WFLES should have isotropic cells with size smaller than 10% of the boundary layer thickness. Using coarser grids or anisotropic cells leads to significant reduction of accuracy.

Large Eddy Simulation with Wall Function (WFLES) is known to be a cheap alternative to classical LES methods for simulation of flow where large and complex computational meshes are typically required. This makes it attractive for engineering applications. However experience of applying such methods to complex turbulent flows with flow separation and reattachment is still little-known in literature. In this work WFLES of flow around simplified car body with slant angle equal to 25 degrees and Re_L = 2.8 · 10⁶ is carried out on Octree mesh to demonstrate the capabilities and limitations of the method in such type of the flow. The results on a series of meshes show that even though the general flow topology is well captured, the critical part of the flow on the slant is hardly predicted even on 100 mln mesh. It is concluded that the prediction of separation above the slant requires significant mesh refinement even in the frame of WFLES.

Direct numerical simulation (DNS) of the separated flow in axisymmetric CS0 diffuser is conducted. The obtained results are in a good agreement with experimental data of Driver and substantially supplement them. Along with other data, eddy viscosity extracted from performed DNS could be used for RANS turbulence model improvement.

The results of the temperature and electric potential numerical simulation in the model of an anisotropic thermoelement under thermal action typical for the experimental conditions on shock tubes are presented. The influence of the thermal conductivity anisotropy on the temperature distribution and the generated thermoelectric power is analysed. The results of solving the inverse problem - determining the heat flux from the calculated thermoelectric power are presented. The errors in calculating the heat flux on the basis of the one-dimensional model have been determined.

A new point of view on the appearance of S-, P- and R-striations in a positive column of inert gases is proposed, based on a dynamic analysis of the resonance properties of electron phase trajectories in spatially periodic fields. The positive column may be considered as a resonator containing a set of resonant modes. Like a tuning fork, being disturbed, it responds with one of the modes, in particular with of S-, P-, or R-modes or striations, depending on the discharge conditions. The dynamic approach eliminates the difficulties of the kinetic theory associated with the long length of the solution of Boltzmann equation, which is much greater than the length of the positive column.

Dynamics of low-intensity air shock waves in the shock tube containing an aqueous foam layer is theoretically investigated. Modeling of studied process is carried out using two-phase model of aqueous foam developed by the authors in single-pressure, single-speed and two-temperature approximations. The model takes into account the Ranz-Marshall interphase contact heat transfer, effective Herschel-Bulkley viscosity, which describes foam behavior as a non-Newtonian fluid, and elastic properties of aqueous foam under a weak shock impaction without destruction of foam structure. Properties of air and water as the foam components are described by realistic equations of state. Computer implementation of the aqueous foam model is carried out in the solver, developed by the authors in OpenFOAM software. The influence of aqueous foam viscoelastic properties on the intensity and structure of a shock wave has been investigated. When analyzing the obtained solutions, reliability of the proposed model and method of numerical modeling is estimated by comparative analysis of the found solutions and literature experimental data.

The study is devoted to assessing the applicability of the manufactured thermoelectric sensor to measure pulsed heat fluxes in shock-wave processes. It is shown that the created thermoelectric sensor has fast response time and sufficient level of electric signal and can be successfully used in short duration high speed gas dynamic experiments.

The dynamics formation of a vapor jet with near-critical state parameters outflowing from a high-pressure vessel through a thin nozzle is studied. The numerical modeling of this process, by using a system of model equations for gas-vapor-liquid mixture, which include conservation laws of mass, momentum, and energy of phases in accordance with one-pressure, one-velocity and two-temperature approximations, was conducted, taking into account heat and mass transfer processes of evaporation and condensation under conditions of equilibrium state with modified reactingTwoPhaseEulerFoam solver of open package OpenFOAM. The process of barrel shock formation in supersonic boiling jet with shaping Mach disk is shown. It was found that the process of boiling fluid outflow is accompanied by formation of vortex zones near axis of symmetry and leads to generation of acoustic wave pulses series preceding the main jet flow, which are the source of pulsations, observed in experiments. The justification of applied numerical method reliability is shown by comparing the computational and analytical solutions for Sedov's problem of a point explosion in gas-water mixture at the plane case.

The paper presents the results of a study of pulse-periodic discharge cesium lighting lamps with discharge tubes 5 mm in diameter and an interelectrode distance of 55 and 22 mm. The cesium pressure varied from 10 to 750 Torr at a constant triangular current pulse with an amplitude of 80 A. It is shown that the maximum of the luminous efficacy (~ 65 lm/W) corresponds to a pressure of ~ 130 Torr. It was found that a discharge column in the long tube at a pressure of ~ 300 Torr contracted into a bright pinch with a diameter close to that of the electrodes (2 mm). The pinch was localized along the surface of the tube and moves randomly on it. Contraction leads to a repeated increase in the luminous efficacy with pressure up to ~ 70 lm/W. Wall stabilization limits the plasma temperature on the axis of the pinch (it was found from the recombination continuum) to the level of 6000 – 6500 K. The column in short tube is localized along the axis of the tube over the entire power range. The temperature in it quickly rises to 13000-– 14000 K after the maximum of the luminous efficacy.

This paper reflected preliminary results of physical modeling of pulsating flow in a model of abdominal aortic bifurcation with taking into account the physiological elasticity of the vessel walls. Elastic vessel models were made via molding from a silicone mixture based on Lasil-T4 silicone rubber. The auxiliary study was performed to assess the elastic properties of the silicone mixture and select a necessary composition. The experiment on the pulsating flow in the rigid and elastic models of the abdominal aortic bifurcation was carried out using a blood flow simulator with circulation of blood-emulating fluid. It was revealed that interaction between the elastic model and closed rigid circuit of the blood flow simulator resulted in generation of intense parasite flow oscillations and prevented from getting similar flow conditions for rigid and elastic models. A way to solve the problem is to include dampers with liquid in the hydraulic circuit of the blood flow simulator at the inlet and the outlets of the elastic model.

We propose a double-well linear Paul trap for particle's spatial selection according to the charge-to-mass ratio. To perform spatial selection we implemented an experimental setup that permits to detect particles' positions in the double-well trap from three different view-points: top, front left, and front right. The setup gives an opportunity to monitor the particles' axial density distribution in real-time. We have shown a strong correlation between axial position of separated localization areas and the DC voltages applied to the rod and end-cap electrodes. We have experimentally determined the critical localization parameters where double-well mode acquires for all the trapped charged microparticles. According to the experimental data and a numerical simulation a upper value of charge-to-mass ratio of the trapped microparticles was estimated.

We report on the optical properties of He-related color centers created by He-ion implantation and subsequent thermal annealing in natural diamonds, including the temperature (300–700 K) and excitation power (1–1800 kW/cm²)-dependent photoluminescence (PL) measurements. The prospects for the use of He-implanted diamonds for temperature sensing are discussed. The effect of fast neutron irradiation on the optical properties of Si-V color centers in CVD diamonds were also examined.

Consideration of nonlinear spin-exchange equations showed that, in addition to the well-known suppression of the relaxation of the transverse orientation of atoms in a low magnetic field, relaxation of higher polarization moments (alignment, octupole, hexadecapole, etc) are also suppressed. Such suppression of relaxation is caused by the conservation of the transverse angular momentum of atoms in collisions.

We study theoretically the nonlinear optical response of a super-lattice of regularly arranged three-level identical quantum emitters with a doublet in the excited state to the action of a monochromatic electromagnetic field quasi-resonant to optical transitions in the emitter, using into account the dephasing of the system. The total retarded dipole-dipole interaction of the emitters is accounted for in the mean-field approximation. This interaction plays the role of positive feedback, which (in combination with the immanent nonlinearity of emitters themselves) leads to multistability of the super-lattice response. The stability of different response branches is analyzed using the Lyapunov exponents' method. Another important property of the super-lattice is its high reflectance in a certain frequency range; i.e., within this range, the super-lattice operates as a perfect nanometer mirror; moreover, reflection can be switched to transmission changing slightly the incident field amplitude (bistability). The possibility of the application of the above-mentioned super-lattice optical properties in nanophotonics is discussed.

We study theoretically the optical response of a 2D super-crystal of quantum Λ-emitters which are coupled by their secondary dipole field. The latter introduces a feedback into the system, the interplay of which with the intrinsic nonlinearity of emitters results in an exotic behavior of the system's optical response, such as periodic or quasi-periodic self-oscillations and chaotic dynamics. We argue therefore that these predicted features can be promising for various nanophotonic applications.