Greenhouse effect on planets and moons of the Solar System
Greenhouse effect on planets and moons of the Solar System
A. V. Aliakin$^{1,2}$, A. V. Karnaukhov$^3$, M. E. Prokhorov$^2$
The article provides an overview of the greenhouse effect on Earth, as well as on various planets and moons in the Solar System. The history of the study of this phenomenon is described. Various types of greenhouse effect are considered. References to key scientific works on all the listed topics are given. The comparative analysis provided may give an idea of possible atmospheric processes and conditions on the surface of Earth-like exoplanets.
Show AbstractThe fast method of bolus shape calculation in the ion beam therapy planning system
The fast method of bolus shape calculation in the ion beam therapy planning system
A. A. Larionov$^1$, F. R. Studenikin$^2$, O. P. Yushchenko$^1$
The method for calculating bolus shape in radiation therapy for wide ions list and different bolus material types is presented. Currently any ion in the range H-Ca can be used as well as materials list consists of polistirol, PLA and aluminium. The lists of ions and materials can be extended. This method is implemented as a component of a planning system for the ion beam therapy center being developed at the NRC “Kurchatov Institute” – IHEP. An example of bolus calculation for a real patient and verification results using detailed modeling in GEANT4 are presented.
Show AbstractPhotonuclear Reactions with Charged Particle Emission: Prospects for Medical Isotope Production
Photonuclear Reactions with Charged Particle Emission: Prospects for Medical Isotope Production
M. V. Zheltonozhskaya, P. D. Remizov, A. P. Chernyaev, K. A. Andrei, V. V. Varlamov, V. I. Shvedunov
Thisreviewfocusesonmethodsforproducingpromisingmedicalradionuclidesusingphotoproton nuclearreactions.Primaryattentionisgiventotheranosticisotopes,suchaslutetiumisotopes 177Lu and rhenium isotopes 186,188,189Re, which can be obtained with high radionuclidic purity. Of particular note is an innovative scheme for producing the diagnostic positronemitting radioisotope zirconium 89Zr via photoproton reactions on molybdenum, which ensures high radionuclidic purity of the preparation and enables production organized on the principle of a generator system. The leading role of the D.V. Skobeltsyn Institute of Nuclear Physics at Lomonosov Moscow State University in the development of this field in Russia is highlighted. This work encompasses fundamental research on photonuclear fission, obtaining reliable cross-sections for photonuclear reactions, and their subsequent application in medical technologies and clinical practice.
Show AbstractRecovering of gaps in multivariate time series using methods of mathematical statistics and machine learning
Recovering of gaps in multivariate time series using methods of mathematical statistics and machine learning
V. S. Aleshnovskii$^1$, V. K. Avilov$^2$, P. V. Golubtsov$^1$, J. A. Kurbatova$^2$, O. A. Kuricheva$^2$, D. A. Makeev$^1$, P. A. Fadeeva$^1$, A. I. Chulichkov$^{1,3}$, N. E. Shapkina$^1$
The research focuses on multivariate time series of geophysical parameters. During the study, statistical and machine learning methods were employed to recover missing data. The following results were achieved: for the $CO_2$ concentration series at a height of 30 meters, the ARIMAX model demonstrated the lowest RMSE and MAE metrics, taking only 2.3 seconds for recovery, which is significantly faster compared to the LSTM (251 sec.) and GRU (160 sec.) neural network models. The air temperature data were most effectively recovered using the recurrent neural network model GRU. The results indicate that ARIMA family models are more suitable for data recovery when correlated parameters are present, whereas GRU-based neural networks are preferable in other cases. These conclusions can be utilized to enhance data recovery methods in multivariate time series analysis.
Show AbstractOn Planar Perturbations in Vertically Stratified Keplerian Disks in a Uniform Magnetic Field
On Planar Perturbations in Vertically Stratified Keplerian Disks in a Uniform Magnetic Field
K. Yu. Parusov
We perform a local modal analysis of the magnetorotational instability (MRI) in the midplane of a thin Keplerian accretion disc with a polytropic vertical density stratification. To obtain an analytic solution, we adopt the approximation $\partial/\partial r=0$ for all perturbations and consider planar adiabatic perturbations of an incompressible fluid with $u_z=0$. We derive an analytic closed-form dimensionless dispersion relation, determine the unstable intervals of the vertical wavenumber $k_z$, and identify the MRI-unstable branch. We show how the unstable wavenumber ranges and the extremal values of the dispersion curve depend on the strength of the background magnetic field.
Show AbstractHelmholtz Free Energy in the Two-Dimensional Ising Model with Defects
Helmholtz Free Energy in the Two-Dimensional Ising Model with Defects
V. V. Binkovskii, S. D. Mostovoy
In this paper, the influence of point defects such as vacancies on the thermodynamic properties of the two-dimensional Ising model is investigated. The main attention is paid to comparing two approaches to describing the system: the traditional analysis of internal energy E and a more complete analysis of the Helmholtz free energy F and entropy S. Using Monte Carlo methods - the Metropolis algorithm and the Wang - Landau algorithm - the temperature dependences of the changes in these quantities upon the introduction of defects are calculated. It is established that the interaction between defects is attractive with a effective radius of d ~ 3. It is shown that in the phase transition region, the free energy behaves as a continuous monotonically decreasing function of temperature, while the internal energy exhibits a singularity caused by the behavior of entropy. The possible dynamics of defects is investigated by comparing the energy of different configurations; a tendency towards defect clustering at temperatures above the critical one is observed. A comparative analysis of the accuracy and computational efficiency of both approaches is carried out.
Show AbstractTemporal analysis of the SOL2015-08-21 flare radiation, theoretical calculation of observed fluxes in the calcium, hydrogen, and helium lines. Inhomogeneity of the flare structure and the role of plasmoids
Temporal analysis of the SOL2015-08-21 flare radiation, theoretical calculation of observed fluxes in the calcium, hydrogen, and helium lines. Inhomogeneity of the flare structure and the role of plasmoids
Yu. A. Kupryakov$^{1,3}$, K. V. Bychkov$^1$, V. A. Maliytin$^1$, A. B. Gorshkov$^1$, O. M. Belova$^2$, M. -. Barta$^3$
We observed a M1.4 class flare in the active region NOAA 12403 using the Horizontal Solar Array for Solar Surveys (HSFA-2) at the Ond\v{r}ejov Observatory in the spectral lines of calcium, helium, and hydrogen, as well as using two radio telescopes. The active region remained unchanged for several days, located in a region of a strong magnetic field. It was a typical bipolar region consisting of a group of spots, pores, and bright flocculi. After processing the spectra, we determined the integrated radiation fluxes in the H$\alpha$, H$\beta$, H$\varepsilon$, H~CaII and IR CaII (8542 \AA{}), HeI D3 lines. Then, using a model of heated homogeneous gas layers, we calculated theoretical fluxes taking into account the physical conditions in the chromosphere, including self-absorption in the spectral lines. To explain the observed fluxes, we had to consider three gas layers oriented perpendicular to the line of sight, each with its own individual parameters. One of them is very extended, while the other two are thin, indicating that the flare plasma is highly inhomogeneous.
Show AbstractPath integral for a charged quantum particle in a magnetic field
Path integral for a charged quantum particle in a magnetic field
K. A. Lursmanashvili$^1$, V. V. Chistiakov$^2$
The quantum-mechanical problem of a charged particle in a magnetic field is considered. Transformations of the functional integration variable of a specific type are analyzed with respect to their action on the Wiener measure. It is shown that the functional integrals for a particle in a uniform magnetic field are equivalent to those for a free particle.
Show AbstractFeatures of fission fragment spin formation in complete fusion reactions of deformed nuclei
Features of fission fragment spin formation in complete fusion reactions of deformed nuclei
V. A. Drozdov$^2$, D. O. Eremenko$^{1,2}$, O. A. Yuminov$^2$
Within the framework of a dynamic model, an analysis of the energy dependencies of the average spins of fission fragments formed in complete fusion reactions of deformed nuclei has been performed. The parameters of the dynamic model were determined based on the conditions for the best description of experimental data on average fission fragment spins for the reactions $^{12}$C$+$$^{232}$Th, $^{16}$O$+$$^{209}$Bi, $^{12}$C$+$$^{209}$Bi and $^{16}$O$+$$^{232}$Th. Special attention is given to the influence of the initial distributions for the components of the total angular momentum of the compound nucleus formed in the entrance channel of the reaction on the spin formation process of the fission fragments. The entrance channel effect is considered using the example of the ${12}$C $+$ $^{236}$U and $^{13}$C $+$ $^{235}$U reactions, , which lead to the formation of the same compound nucleus, $^{248}$Cf. It is shown that at sub-barrier collision energies, noticeable differences in the behavior of the average fission fragment spins should be observed for different entrance channels of the fusion reaction
Show AbstractStudy of the subsurface temperature maximum in meromictic reservoirs of the Kandalaksha Bay based on mathematical modeling
Study of the subsurface temperature maximum in meromictic reservoirs of the Kandalaksha Bay based on mathematical modeling
I. N. Ivanova$^1$, A. V. Klenin$^2$, V. M. Stepanenko$^3$, E. D. Krasnova$^4$, D. A. Voronov$^5$
In the coastal meromictic lakes Kislo-Sladkoe and Trekhtsvetnoe (the White Sea, the Kandalaksha Bay), the temperature regime was studied using the generalized one-dimensional model of thermodynamic, hydrodynamic, and biogeochemical processes, LAKE. Special attention was paid to the process of formation of the Mid-depth temperature maximum (TeM). The model demonstrated its ability to realistically reproduce various physical phenomena in the annual cycle of the water body's life, including the TeM, autumn cooling, and winter temperature maximum. For the first time, the following factors have been suggested to have a key influence on the characteristics of the TeM and its presence: the salinity of the lake's layers relative to each other, the salinity gradient exceeding 10-13 PPT/m, and the location of the maximum salinity gradient relative to the surface of the water body. The data obtained from the modeling have been compared with field measurements.
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