Within the TANGRA project framework, a new experimental setup has been constructed for the measurement of reaction cross sections (n,Xγ) in the interaction of 14.1 MeV neutrons with nuclei. The facility has a special feature: the use of the tagged neutron method. This method enables efficient separation of background and useful events, as well as accurate tracking of neutron flux. Test measurements were performed on 28Si, 12C, and 16O nuclei, and the results showed satisfactory agreement with available experimental data. This paper presents the features of the setup design and the methodology for processing the obtained experimental data.
Show AbstractThe paper investigates the existence of a stable stationary solution in a system of reaction-diffusion equations with slow and fast components in a two-dimensional spatial variable case. The theorem of the existence of a stationary solution with boundary layers in the case of Dirichlet boundary conditions is proved, its asymptotic approximation is constructed, and the Lyapunov asymptotic stability conditions of this solution are obtained. The research is based on the asymptotic method of differential inequalities applied to a new class of problems. This result is practically important both for various applications described by similar systems and for the application of numerical stationing methods in solving elliptic boundary value problems.
Show AbstractWe propose a modified machine learning technique utilizing ensemble of artificial neural networks for extrapolating energies obtained in variational calculations, in particular, in the No-core Shell Model (NCSM), to the case of infinite basis. We suggest an extended neural network topology and methods for selection of data used for the machine learning as well as for selection of obtained neural networks for the statistical analysis of the results. We test our approach by extrapolating deuteron binding energy in calculations with the Nijmegen II NN interaction and demonstrate that it provides statistically significant stable results. We apply this technique to obtain extrapolated ground state energies of 6Li and 6He nuclei based on the NCSM calculations with Daejeon16 NN interaction.
Show AbstractThe surface treatment of single-crystal germanium with an argon cluster ion beam has been investigated. The initial surface of germanium wafers was bombarded with argon cluster ions with high (105 eV/atom) and low (10 eV/atom) specific energy. Using an atomic force microscope, images were obtained and the surface topography was compared before and after cluster ion bombardment. Using the power spectral density function of roughness, surface smoothing is demonstrated in the range of spatial frequencies: 1) ν = 1−8 μm^−1 – for the high-energy mode; 2) ν = 0.7−2.5 μm^−1 – for low-energy mode.
Show AbstractIn this work, radiation transfer in media with refractive index gradients is studied. The asymptotics of intensity distributions in the vicinity of singular directions are derived. Critical conditions for the appearance of singular intensity distributions in fields of scattered radiation in a medium are formulated. It is shown that singular radiation fields in such media can be generated, among other things, by nonsingular configurations of radiation sources. The results obtained are verified by direct comparison with the results of numerical calculations using the Monte Carlo statistical modeling method.
Show AbstractSimulations were carried out using the VASP software package based on density functional theory. The model system consisted of a metal alloy surface with dimensions of 3x3 cells and a vacuum. During the work, surface binding energies were calculated for pure Ni and Pd metals. The values obtained were 5,32 eV and 4,65 eV, respectively, which is a good accuracy for ab initio calculations. The work also included calculations of the surface binding energy for different configurations of NiPd alloys with nickel and palladium concentrations of 66%, 50%, 33%. For each lattice type, calculations were made for both the surface binding energies of Ni and Pd. Several types of lattices were simulated, and it was found that the average values of the surface binding energy of Ni and Pd are: 5.02 eV and 4.36 eV respectively in an alloy with a concentration of Ni equal to 50%; 4.89 eV and 4.22 eV respectively in an alloy with a concentration of Ni equal to 66%; 5.12 eV and 4.40 eV respectively in an alloy with a concentration of Ni equal to 33%.
Show AbstractA universal technique is developed for the detection of high harmonics generated by relativistic and subrelativistic laser pulses irradiating a solid target. The characteristic features typical of two different generation methods are analyzed: parametric generation in the mid-IR range and amplification of chirped pulses in the near-IR range. Experimental spectra of harmonics in the range up to 35 nm were recorded. They can be used as a source of coherent radiation in the extreme UV region.
Show AbstractMany literature sources discuss diseases associated with the protein of hemoglobin [1], [2]. In the modern world, more than 800 million people suffer from anemia [3]. Assessing hemoglobin level of in the circulatory system is one of the ways to diagnose anemia. Hemoglobin protein is also a promising source of bioactive peptides [4]. The aim of the work was to identify the reasons leading to conformation changes of this protein. It still remains unclear what exactly causes disruption of its functionality. Human hemoglobin from Sigma H7379 was studied in that work; all experiments were carried out on a dynamic light scattering spectrometer - Photocor Complex. Experimental data were obtained using optical methods of static and dynamic light scattering. The analysis of the hemoglobin protein molecules behavior in aqueous and water-salt solutions when changing solution parameters (pH, addition of iron III chloride) was carried out in that work. At pH<(3.56±0.15) and pH>(10.4±0.2) values, the hemoglobin molecule underwent conformational changes, as a result of which the quaternary structure decomposed into alpha\beta -dimers and individual alpha- and beta- globules. As a result of the work, it was found that the addition of FeCl_{3} in aqueous solutions of hemoglobin increases the size and mass of scattering particles, which can be explained by the adsorption of Fe^{3+} ions on the surface of the protein. But when a certain concentration of FeCl_{3} was reached, the $ pH $ of the solution decreased so much that conformational changes in hemoglobin occurred, which led to the disintegration of its quaternary structure. These results can be taken into account when creating drugs for the treatment of anemia and other diseases associated with the hemoglobin protein.
Show AbstractPhenomenological models of phase transitions for two interacting order parameters - one–component and two-component are constructed. The construction was carried out based on the number of control parameters depending on external thermodynamic conditions by methods of the equivariant catastrophe theory of (singularitys theory), taking into account the symmetry of the order parameters. The classification of phenomenological models according to the number of control parameters is carried out. Phase diagrams of the models were constructed and the theoretical temperature dependence of the heat capacity was calculated, which showed a satisfactory qualitative correspondence with the experimental dependence in the the Rb2KInF6 elpasolite crystal.
Show AbstractThe work is devoted to the study of the magnetic response of a metasurface made of split ring resonators (metaatoms) in the MHz and GHz ranges. A new method for calculating the local permeability of a metasurface in the MHz frequency range is proposed, taking into account the finite sizes of elements, and for the first time a result of such a degree of agreement with experimental values has been obtained. In the GHz range, additional factors are also taken into account, such as the delay effect, non-uniform current distribution in the metaatom and the complication of the nature of the interaction of metaatoms compared to the MHz range, in particular, the occurrence of electrical interaction between them.
Show AbstractThis paper presents a catalog of the energy distribution in the spectra of 263 stars in the wavelength range 0.4~- 100~$\mu$m, which are at late stages of evolution and have been observed by the ISO space observatory. For each object in the catalog, estimates of the observed bolometric fluxes are derived from smoothed energy distribution curves. The catalog is available at https://infra.sai.msu.ru/sai_lss_sed both as a table and in machine-readable format. It is shown that for the specified sample of objects their ISO SWS spectra in the range 2.4~- 45~$\mu$m only in 60\% of cases correspond to the general shape of the continuum, and can be used without recalibration. A selection of carbon stars accessible to infrared observations from the MSU observatories was made. For some of them, the first brightness estimates in the $K, L$, and $M$ bands were obtained with the new IR camera of the 2.5-m telescope of CMO.
Show AbstractThe results of a comparative analysis of various characteristics of the temperature conditions of the planetary atmospheres in the Solar System and their dependence on orbital parameters, in particular on the length and angular frequency of the annual cycle, are presented. In particular, the root dependence on the angular frequency of the dry adiabatic lapse rate was noted. The dependence of the planetary equilibrium temperature in the cubic root form of the angular frequency of the annual cycle is associated with Kepler's third law. For Venus, Earth, Mars, Jupiter, Saturn, the root dependence of the scale height and tropospheric height on the length of the annual cycle is manifested, and the atmospheric features of the planets most distant from the Sun - Uranus and Neptune - are noted.
Show AbstractObservation of waves (sea level oscillations) in the coastal water area of the southeastern coast of the Sakhalin Island from November 2021 to May 2022 using bottom high-precision devices ARV-14K with one second discreteness was carried out. Analysis of the obtained time series revealed the presence of abnormal waves in the range of tsunami waves in January 2022. It is shown that the waves detected on 15 January 2022 with periods of 15 min - 4 hours, which stand out significantly above the background, are associated with volcanogenic tsunami waves. Spectral analysis of time series showed that the maximum in the spectra of sea level oscillations which detected after the volcanic eruption is close to the period of the first mode of the shelf seiches, indicating that incoming tsunami waves excite shelf seiches in the coastal zone, and also contribute to the generation of longitudinal and transverse seiches in the Mordvinova Bay. Time series analysis allowed to establish that the spectral density of sea level fluctuations for the time interval of the beginning of the eruption of the Hunga Tonga-Hunga Ha'apai volcano from 21 December 2021 until 11 January 2022, significantly differs from the spectral density for the Plinian time of the volcanic eruption. An analysis of the statistical characteristics of sea level oscillations performed using two-day time series in the period range of 1 min - 4 hours for background waves and tsunamis, showed an increase in the rms by 3.5 times for a time series containing tsunami waves. It has been established that for background time series containing tsunami waves, the coefficients of asymmetry and kurtosis differ little from "Gaussian" values. This indicates that the arrival of tsunami waves from distant sources does not significantly disturb the stationarity of the wave field in the observation area.
Show AbstractThe paper experimentally investigates the effect of natural dust deposited from the air on the evaporation rate from the water surface. The experiments were carried out for a stationary liquid without blowing the surface with wind and a weak wind that does not deform the surface, at a constant particle deposition rate. It is shown that the evaporation rate is a linear function of the difference between the saturated vapor pressure at the water surface and the partial pressure of the air mixture at temperature and relative humidity in the laboratory at the beginning of the deposition process, when the proportion of the water surface covered with dust is small. As the deposition time increases, hydrophobic particles gather into conglomerates, reducing the proportion of the exposed surface and the evaporation rate.
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