Issue 5, 2024

E. V. Okulich$^1$, V. I. Okulich$^2$, I. G. Kamilevich$^3$, D. I. Tetelbaum$^1$, A. N. Mikhaylov$^1$

The molecular dynamics method was used to simulate the processes of structural changes occurring over a time of about 100 ns in the region of the memristor filament formed in non-stoichiometric silicon oxides, including those subjected to ion implantation, during forming and/or switching. At the same time, the influence of the high temperature at which the filament region is located at certain stages of memristor operation was studied. It is shown that during the indicated periods of time, significant structural rearrangements occur, consisting in the formation and disintegration of various complexes, which is confirmed by calculations of radial distribution functions of distances between atoms in various combinations.

Spacelike motion inside a closed null surface generated by Abelian electromagnetic gauge transformations

A. Garat

It has been proven previously that Abelian electromagnetic gauge transformations can create a region in spacetime surrounded by a null surface such that inside the surface spacetime undergoes a timelike-spacelike reflection. Therefore, timelike intervals will turn into spacelike intervals inside the null surface and vice-versa. We will use this property in order to prove that such a closed region will be able to undergo faster than the speed of light motion in a four-dimensional Einstein-Maxwell or Maxwell-Minkowski spacetimes.

A. A. Borzunov$^1$, E. I. Rau$^2$, S. V. Zaitsev$^2$, N. A. Koshev$^{3,4}$, D. V. Lukyanenko$^{1,5}$, A. G. Yagola$^1$

The paper proposes a method for solving a three-dimensional tomography problem using data from a scanning electron microscope in the backscattered electrons detection mode. Based on the assumption that the sample has a three-layer structure, analytical expressions were constructed for the dependence of the intensity of the detected signal on the chemical composition of the sample, the thickness of the layers and the energy of the primary electrons. Based on the obtained analytical expressions, using the example of a three-layer (aluminium-gold-silicon) structure, the inverse problem of reconstructing the thicknesses of the aluminum and gold layers is solved in two different formulations, depending on the type of a priori information available about the structure of the sample.

A. A. Vikulovskaia$^{1,2}$, D. A. Konyaev$^{1,2}$

One of the methods for solving diffraction problem of electromagnetic waves on perfectly conducting bodies and screens is considered — the method of moments. The basic principles of this method are presented, including the reduction of the problem to an integro-differential equation of electric type and the use of Rao-Wilton-Glisson functions as basic functions, emphasis is placed on the approximation of integrals along triangles of the grid on the surface of a conductor. Based on the considered method of approximating integrals by triangles, an improvement of the previously developed software package has been made, which allows solving diffraction problems on perfectly conducting bodies of complex shape in the vector case. It is demonstrated that the changes reduced the error of the approximate solution. The results obtained using the developed complex are in good agreement with similar calculations on the FEKO software package.

E. I. Nikulin, A. V. Karamyshev

The present work is devoted to the study of a one-dimensional <<reaction-advection-diffusion>> equation with weak smooth advection and a discontinuous reaction in the spatial coordinate. In the work, the construction of asymptotics, proof of existence and study of stability of stationary solutions with the constructed asymptotics, possessing a weak internal layer, which is formed near the discontinuity point, are carried out. To construct the asymptotics, the method of Vasilyeva A.B. was used, to justify the existence of the solution -- the asymptotic method of differential inequalities, to study the stability -- the method of contracting barriers. It is shown that such a solution as a solution of the corresponding initial-boundary value problem is asymptotically stable in the sense of Lyapunov. A stability region of finite (not asymptotically small) width for such a solution is indicated and it is established that the solution to the stationary problem is unique in this region.

V. V. Tarasov$^1$, I. F. Larin$^{1,2}$

Polarizability is a fundamental particle property. Measurement of pion polarizability values allows checking strict ChPT prediction. Charged and neutral pi-mesons polarizability will be extracted from the CPP and NPP experimental data using Primakoff pair production cross-section on nuclear target. The CPP/NPP experiment run at TJNAF Hall-D was conducted in the summer of 2022 and utilized a polarized photon beam with an energy range of 4.5-6.0 GeV and the lead-208 target on the upgraded GlueX experimental setup. The report reviews existing experiments measuring pion polarizability, theoretical predictions of polarizabilities, CPP/NPP experiments setup at the GlueX facility, expectation of these experiments, and preliminary checks of the collected data.

Yu. V. Ryzhikova, S. B. Ryzhikov

General approaches to solving the fundamental scientific problem associated with establishing quantitative relationships between the structural features of biomorphs and their spectral characteristics are considered. The scaling features of fractal biomorphs are determined based on theoretical analysis. The shape features of the Fourier spectra and their connection with the self-similarity elements of the illuminated biosystems are identified. The calculation of light diffraction on bioobjects indicates the possibility of using pattern and scaling analysis for their identification. The obtained modeling results make it possible to improve fractal methods of optical diagnostics of the analyzed biomorphs.

A. M. Chernyak$^{1,2}$, A. I. Musorin$^{1,2}$, A. A. Fedyanin$^2$

The behavior of Faraday rotation on the femtosecond timescale in Mie-resonant magnetophotonic metasurfaces formed by a two-dimensional array of silicon nanodisks coated with a thin nickel film is studied. It is shown that in the static case the maximum of polarization plane rotation is 14◦ at the resonant wavelength for spectrally overlapped electric and magnetic dipole modes. When a single femtosecond laser pulse passes through the designed metasurface, it splits into two, the durations of which are half as long as the initial one, and the polarization planes are rotated in opposite directions, forming almost orthogonal replicas.

I. V. Savitsky$^1$, P. B. Glek$^1$, R. M. Aliev$^1$, E. A. Stepanov$^{1,2}$, A. A. Voronin$^{1,2}$, A. A. Lanin$^{1,2}$, A. B. Fedotov$^{1,2}$

A method for measuring the group refractive index and dispersion in a ZnSe crystal in a pump-probe scheme is demonstrated. A pump-probe scheme with a powerful ionizing pump pulse and a dispersive probe pulse has been implemented. Varying the delay between pulses allows you to control the spectrum passed through the crystal, as well as restore the group refractive index and dispersion of the crystal.

V. A. Kulbachinskii$^1$, A. S. Apreleva$^1$, V. G. Kytin$^1$, A. V. Koshelev$^1$

In this work, we have studied the temperature dependences of resistance ro(temperature range 4.2<T<330 K) of single crystals Bi2-xAsxTe3 (0<x<0.034), Sb2-xCuxTe3 (0<x<0.1) and Sb2-xSnxTe3 (0 <x<0.0075), as well as thermopower and thermal conductivity of Bi2-хAsxTe3 solid solutions in the temperature range 77<T<330 K. In the temperature range 100–320 K, the dependence ro(T) obeys a power law with an exponent m = 2 (Bi2- xAsxTe3), m = 1.2-1.1 (Sb2-xCuxTe3) and m = 1.2-0.6 (Sb2-xSnxTe3). For Bi2-xAsxTe3, it has been established that the conductivity decreases, and the Seebeck coefficient initially increases significantly and then decreases as x increases. The thermal conductivity of samples with As decreases compared to the original bismuth telluride at T<250K. As a result, the maximum thermoelectric efficiency ZT shifts from 300 K to 250 K with increasing As content.

S. E. Kirgizov, O. K. Kuvandikov, D. H. Imamnazarov

Magnetic nanoparticles Co$_x$Ni$_{1−x}$Fe$_2$O$_4$ with x = 0, 0.25, 0.5, 0.75 were synthesized by using chemical coprecipitation method and magnetic fluids based on them were prepared. A structural and phase analysis of the obtained nanoparticles was performed, the characteristic sizes of nanoparticles and size dispersion, the magnetization of magnetic fluids containing 0.5 % volume concentration of magnetic nanoparticles were determined. Diffraction patterns of all compositions confirm the formation of a single-phase structure of cubic spinel NiFe$_2$O$_{4}$ and CoFe$_2$O$_4$. The average particle diameters determined using a transmission electron microscope are 17.22, 15.04, 14.69, 11.18 nm at x = 0, 0.25, 0.5, 0.75, respectively. The saturation magnetization of Co$_x$Ni$_{1−x}$Fe$_2$O$_4$ nanoparticles based magnetic fluids decreases from 38.25 emu/kg to 5.33 emu/kg as the cobalt concentration decreases from x=0.75 to x=0. If at x = 0, 0.25 and 0.5 magnetic fluids are characterized by superparamagnetic properties, then for Co$_{0.75}$Ni$_{0.25}$Fe$_2$O$_4$ based fluids a wide hysteresis loop with a coercive force HC = 612 Oe was discovered, which is associated with the single-domain state of Co$_{0.75}$Ni$_{0.25}$Fe$_2$O$_4$ particles despite their small size.

N. N. Perova$^1$, E. A. Gan'shina$^1$, P. I. Mikhailovich$^1$, D. M. Gridin$^1$, E. V. Harin$^2$, V. A. Tejetov$^2$, E. N. Sheftel$^2$, A. B. Granovsky$^{1,3}$

The results of a study of the magnetic properties of Fe$_{72.4}$Ti$_{5.4}$B$_{19.2}$O$_{3.0}$ nanocrystalline films subjected to annealing in vacuum at 200°, 300° and 400°C are presented. Films with a mixed (nanocrystalline + amorphous) structure with a thickness of 0.52 μm were obtained by magnetron deposition on glass substrates. Hysteresis loops were measured on a vibrating magnetometer, field and spectral dependences of the transverse Kerr effect (TKE), and magnetization reversal processes were visualized on a magneto-optical Kerr magnetometer. It is shown that the processes of partial crystallization of the initially amorphous phase and the redistribution of Ti and B, respectively, within crystal grains and grain boundaries, resulting in the formation of new phases, which occur as a result of annealing, manifest themselves in a two-stage process of magnetization reversal and in modification of the TKE spectra.

I. V. Grigoryan$^1$, A. M. Adelyanov$^1$, G. B. Khomutov$^1$, A. P. Parkhaeva$^3$, E. Yu. Simonenko$^1$, A. G. Mironova$^5$, V. A. Pigareva$^2$, A. V. Sybachin$^2$

In this work, the interaction of β-carboxymethyl cyclodextrins (CMCD) with monomolecular layers of a mixture of electroneutral and cationic lipids on the surface of an aqueous subphase was studied.Monolayers were transferred to mica substrates using the Langmuir-Blodgett method and studied by atomic force microscopy. Analysis of monolayer compression isotherms and AFM images showed that CMC adsorption on the cationic Langmuir lipid monolayer is accompanied by the formation of supramolecular ensembles of similar morphology, regardless of the concentration of added oligosaccharides.

B. P. Kondratyev, K. A. Klyuchinsky

The dynamics of two interacting concentric stellar rings located in the central parsec of the Galaxy is investigated. A massive wide ring with retrograde motion of stars (the "clockwise" disk) is modeled by a disk with a small cutout in the center. The other ring (the "counter-clockwise" disk) is represented by a thin circular ring inclined to the plane of the disk. The masses of the rings, their geometric parameters and spatial orientation are known from observa-tions. The mutual gravitational energy and torque between these rings are found, graphs of these quantities are constructed depending on the angle of inclination. The angular momenta of the rings and their ratio are calculated. The Laplace plane and the angles of its orientation are determined for the system of rings. It is established that mutual perturbation of the rotating rings leads to precession of the nodes with a period The lines of nodes of both rings in the Laplace plane move with the same angular velocity, but in opposite directions. This explains the large angle of divergence of the lines of nodes, known from observations.

I. I. Mokhov$^1$, V. I. Perminov$^2$, I. A. Fomina$^4$

The results of an analysis of temperature variations in the mesopause region based on long-term measurements of hydroxyl airglow at the Zvenigorod Scientific Station of the A.M. Obukhov Institute of Atmospheric Physics RAS (ZSS IAP RAS) in 1960–2024 in comparison with variations of surface temperature characterizing global-scale climate changes are presented. Along with temperature variations in the mesopause region, two versions of temperature variations in the mesopause region, normalized to the same level of solar activity, were analyzed. Quantitative estimates of a strong decrease of temperature in the mesopause region over the past decades in winter against the background of a global increase of surface temperature have been obtained. It was noted that significant coherence of long-term variations of the mesopause region temperature with the surface temperature in the Northern Hemisphere with the use of cross-wavelet analysis, which was not previously evident in data for a shorter time interval. The possibility of such coherence was predicted in (Mokhov et al., 2017) under the continuation of global warming based on the results of model simulations for the 20−21st centuries, taking into account anthropogenic forcing. It was not previously manifested from observational data for a shorter time interval. Along with long-term trends, features of a sharp decrease of temperature in the mesopause region for the 1970s with its synchronicity with the known shift in surface climate regimes associated with El Niño events were analyzed. The results of cross-wavelet analysis using data obtained at the ZSS IAP RAS for the time interval 1960−2024 indicate a more significant connection between temperature variations in the mesopause region and El Niño indices in recent decades.

D. S. Yurov$^{1,2}$, M. A. Borisov$^{2,3}$, A. S. Alimov$^{1,2}$, A. N. Ermakov$^{1,2}$, A. N. Kamanin$^{1,2}$, N. I. Pakhomov$^{1,2}$, A. S. Simonov$^2$, Y. Yu. Filippov$^4$, V. V. Khankin$^{1,2}$, V. I. Shvedunov$^{1,2}$, I. V. Shvedunov$^2$, N. V. Shvedunov$^{1,2}$

The article is devoted to the development of a linear electron accelerator for the radiation therapy complex “Onyx”. A brief overview of the accelerator is given, and the main problems that arose during the development process are indicated. The main part of the article contains a solution to the most critical of them, associated with the back bombardment of the electron gun cathode, which led to instability of the gun current and bremsstrahlung radiation dose rate over time. Changes in the design of the accelerating structure and electron gun are described, which made it possible to eliminate the problem of back-bombardment and achieve the required stability of bremsstrahlung parameters.

D. S. Yurov$^{1,2}$, M. A. Borisov$^{2,3}$, A. S. Alimov$^{1,2}$, S. Z. Bagova$^4$, A. N. Ermakov$^{1,2}$, A. N. Kamanin$^{1,2}$, T. K. Lobzhanidze$^4$, N. I. Pakhomov$^{1,2}$, A. S. Simonov$^2$, V. V. Khankin$^{1,2}$, V. I. Shvedunov$^{1,2}$, I. V. Shvedunov$^2$, N. V. Shvedunov$^{1,2}$

The second part of the article on the development of a linear electron accelerator for the “Onyx” radiation therapy complex is devoted to solving problems associated with high electric field strength in the accelerating structure, which include high dark currents, a long training process, high pulsed RF power losses in the accelerating structure, its low efficiency. The article describes the steps we took to reduce the electric field and increase the efficiency of the accelerating structure. The main results of testing the bremsstrahlung characteristics for the final version of the accelerating structure are shown.