This review focuses on the history of medical physics in Russia and at Moscow University, highlightingkeydevelopmentalmilestones.AspecialemphasisisplacedonMoscowUniversity’s historical role in advancing physical methods and technologies in medicine. The paper notes significant ideas from Russian scientists that formed the basis for high-tech medical devices and systems, as well as crucial moments in the development of nuclear-physical technologies for these purposes. The review describes the stages of creation and improvement of high-tech radiation physics installations, methods, and technologies in domestic medicine. It traces the development trends of radiation technologies in medicine in Russia and globally, along with the needs of Russian healthcare for its sustainable development under current conditions. The paper also outlines the state of staffing in this area of medicine and presents the principles for building a system of personnel training and retraining at Moscow University to facilitate the development and implementation of radiation technologies in medical practice. Finally, it analyzes trends in the application of nuclear-physical methods in Russian medicine and proposes effective approaches to ensure the technological independence of our country’s economy.
Show AbstractA phenomenon of the forming of a guiding topology in energy development of an open thermodynamic system (OTS) through the establishing of energy infrastructure shaped due to confinement of the parameters of energy exchange is considered. The infrastructure consists of two interconnected energy spectra intrinsically stemming from the suggested model of OTS. These spectra are based on innate limitation imposed on the efficiency of energy exchange (primary spectrum) and the net passing energy (secondary spectrum). In this context, the primary spectrum creates the quantitative basis for realization of solution in the points of equilibrium, whereas the secondary spectrum forms the grounds for bidirectional transfer between the evolutionary-spaced points.
Show AbstractAn analytical method has been developed for optimizing the orbital parameters of a space constellation for measuring the Earth’s gravitational field (EGF). The method is based on identifying the repeatability cycles of sub-satellite tracks under unperturbed Keplerian motion, subject to the condition that an integer number of satellite revolutions occurs over an integer number of nodal days. By comparing analytical and numerical approaches, a functional relationship was derived that allows determining the spacecraft orbital altitude for perturbed motion with an accuracy of up to 30 meters. The paper considers two time scales for orbit integration: a full coverage cycle (30 days) and a subcycle (7 days). For the obtained optimal configurations, full-scale integration of the orbital motion and subsequent recovery of the Earth’s gravitational field (EGF) were performed, enabling an assessment of the influence of orbital parameters on the accuracy of the recovered field.
Show AbstractAn analysis of the contemporary geodynamic situation in the Vladikavkaz area is presented, based on long-term GNSS (Global Navigation Satellite System) observations at continuous stations and field sites at the Ossetian geodynamic testing ground. Velocity estimates are made in two reference frames: the global International Terrestrial Reference Frame (ITRF) and the local, relatively fixed Eurasia. In ITRF, the movement of the region is consistent with the overall movement of the Greater Caucasus region in a northeasterly direction at a rate of 27–30 mm/year. The results of velocity profiling in the local reference frame showed a number of opposite-directional kinematic features that define the contemporary geodynamic regime of this area. These results, as well as those from seismological studies, testify that the city of Vladikavkaz is located in a region with relatively active geodynamic processes.
Show AbstractThe static part of the axion-like field created by a rotating neutron star, such as a pulsar or magnetar, has been calculated. It has been shown that this static field is distributed anisotropically around the star, forming a dilaton halo. Therefore, this halo will act as an anisotropic lens for electromagnetic waves.
Show AbstractA novel method to solve a relativistic wave equation for spin-1/2 massive particle is considered. Relativistic wave functions are obtained using neutral networks. Unlike the four-component Dirac bispinor, this approach uses two-component wave functions. The method has been valuated through application to two well-known physical system, namely: a hydrogen-like atom and a charged particle in a uniform magnetic field. The method can be applied to more complex problem in quantum physics and chemistry.
Show AbstractThe influence of quantum effects on the absorption cross section of gold nanoparticles with a polymer coating is considered. Such layered structures are used as photothermal agents in the treatment of oncological formations. A modification of the discrete source method is used for the study. Modeling of quantum effects in the plasmonic core is carried out based on mesoscopic boundary conditions with Feibelman parameters, which allow taking into account such quantum effects as spatial nonlocality, displacement of the electron cloud with respect to the metal surface, and Landau attenuation. As a result of the studies, it was found that by changing the geometry of the plasmonic core, it is possible to control the position of the absorption cross section maximum in the transparency window of biomaterials, while variation of its volume affects only the cross section amplitude. It is shown that taking into account the quantum effect leads to a shift in the absorption cross section maximum to the short-wave region by 10-15 nm, as well as a slight decrease in its amplitude within 5%.
Show AbstractWe present non-perturbative computation of renormalized Green function of the massless real-valued scalar field propagated on the background generated by two-dimensional zero-range potential localized on an infinite straight line. Such a potential corresponds to exotic limit $\xi\to\infty$, $\beta'\sim 1/\xi $ of the vacuum polarization problem near cosmic string. The approach implies renormalization of the delta-coupling~$\lambda$. Renormalized Green and Hadamard functions are presented in several forms as single-variable integrals with integrands being transcendent functions. With usage of the renormalized Hadamard function, we compute renormalized vacuum averages of the field-squared and the energy-momentum tensor operator. Asymptotic cases are analyzed in detail.
Show AbstractThe problem of reconstructing an unknown time-dependent Hamiltonian of a two-level quantum system from its observed dynamics is considered. A method based on a neural network in the Neural ODE framework is proposed, where the continuous evolution of the quantum state is modeled by integrating the Schr¨odinger equation with a parametric Hamiltonian model implemented by the network. The input data consist of measured time series of the expectation values of Pauli operators for a qubit. The network is trained by minimizing the difference between the experimentally observed and simulated trajectories of quantum observables. Using the example of spin dynamics in a time-varying magnetic field, it is shown that the proposed approach allows accurate reconstruction of the parameters of the time-dependent Hamiltonian without interrupting the quantum evolution. The results demonstrate that the Neural ODE model provides continuous handling of the time parameter and robust reconstruction of system dynamics under conditions of limited data and noise.
Show AbstractMagnetic atomic chains have potential applications across various fields, including spintronics, quantum communication, and quantum computing. The kinetic Monte Carlo method is a powerful tool for investigating the magnetic properties of atomic chains over long time scales. In this paper, we extend the simple kMC model proposed by Li and Liu. The primary improvement involves accounting for the dependence of the frequency prefactors on the model parameters. Our results demonstrate that the Meyer-Neldel empirical rule applies to magnetic systems: higher energy barriers are correspond to with higher frequency prefactors. Using numerical approaches such as the geodesic nudged elastic band method and the harmonic approximation within transition state theory, we have calculated the corrections due to the non-collinearity of the magnetic moments of atoms in the transition state. The limitations of the applicability of the presented model are found and discussed. We have demonstrated that, in general, the dependence of frequency prefactors on model parameters cannot be neglected.
Show AbstractA method for determining the matrix elements of a three-body Hamiltonian on a multidimensional Gaussian basis for use in nuclear and atomic physics as well as nuclear astrophysics is discussed in detail. Cental as well as non-cental (spin-orbit and tensor) interactions between particles is considered. It is shown that the proposed method makes it possible to reduce the matrix elements to fairly simple analytical expressions capable of providing high accuracy in determining the Hamiltonian eigenvalues.
Show AbstractIt was shown that in many cases that is possible to obtain new unknown before data on photodisintegration of atomic nuclei, primarily on photoneutron reaction cross sections basing on published data of experiments carried out using Bremsstrahlung. Such type possibilities were realized for 52Cr and 68Zn. At the first time such unpublished data on the reactions σ(γ, 2n) и σ(γ, xn) = σ(γ, 1n) + 2σ(γ, 2n) in the case of 52Cr and σ(γ, 1n), σ(γ, 2n) and σ(γ, sn) = σ(γ, 1n) + σ(γ, 2n) in the case of 68Zn were determined using experimental published data. It was found that experimental partial reaction cross sections on 52Cr do not meet objective physical criteria of data reliability. New cross sections of the reactions 52Cr(γ, 1n), 52Cr(γ, 2n)50Cr meeting those criteria were evaluated using the experimental-theoretical method and used for determination of total photoneutron reaction 52Cr(γ, sn) cross-section. Using this method, new unknown before cross sections of partial reactions 68Zn(γ, 1n)67Zn and 68Zn(γ, 2n)66Zn and total photoneutron reaction cross-section 68Zn(γ, sn) were determined at the first time using the unique only one published neutron yield cross-section 68Zn (γ, xn).
Show AbstractThis paper discusses models and methods for calculating the radiation of laser-electron generators producing X-rays or gamma radiation based on a classical interaction model. The proposed model calculates the total flux, spectral radiance, and polarization of the radiation, taking into account nonlinear effects. The latter inevitably arise when using high-power laser pulses. For a set of model source parameters it is shown that nonlinear effects lead to significant spectral broadening of both the fundamental and higher harmonics. This leads to significant degradation of the source's spectral characteristics and may require additional monochromatization of the working radiation spectrum. Modeling of the X-ray and gamma radiation parameters of a laser-electron source using collimator beam forming lines is conducted.
Show AbstractProcesses of single and double meson photo- and electroproduction provide the largest body of information on the spectrum and structure of nucleon resonances ($N^*$). The electromagnetic transitions from the ground state of the nucleon to the $N^*$ can shed light on fundamental questions like emergence of visible mass in the Universe. Experiments conducted with the CLAS detector (Jefferson Lab, USA) essentialy enlarged our understanding of nucleon resonance electroexcitation, measuring more than $150000$ data points on differential cross sections and various polarization observables. The selected results from the $N^*$ program in Jefferson Lab as well as future directions using data from ongoing experiments with the upgraded CLAS12 detector in Hall B at JLAB will be outlined with specific focus on MSU/JLAB collaboration.
Show AbstractThis work investigates the interaction of a focused electron beam with a short laser pulse in the nonlinear regime. Using numerical modeling, we calculate the spectral–angular characteristics of the emitted radiation for electron beam parameters corresponding to the first station of the Compton Radiation Source at the National Center for Physics and Mathematics (CRS NCPM). The influence of the laser pulse polarization and focusing parameters, as well as the electron beam energy spread and normalized transverse emittance, on the spectral–angular, angular, and spectral distributions of the emitted energy is analyzed. It is shown that employing shorter and more intense laser pulses enables a transition beyond the linear interaction regime and leads to the formation of spectra containing higher harmonics.
Show AbstractThe energy density functional (EDF) theory has been applied to the study of the influence of velocity terms in the Skyrme EDF on the height and position of the Coulomb barrier in the fusion reactions $^{40}$Ca+$^{36-62}$Ca. The nucleus-nucleus interaction potentials are calculated in a double-folding form. It has been shown that the amplification of velocity-dependent terms leads to a noticeable improvement in the description of the Coulomb barrier in the reactions under consideration. A linear correlation between the position and height of the barrier was studied. The impact of shell effects on the properties of the Coulomb barrier in reactions $^{40}$Ca+$^{36-62}$Ca has been identified.
Show AbstractThis work examines the possibilities for the population and induced decay of nuclear isomers using the promising quasi-monochromatic inverse Compton source ICS under development at the National Center of Physics and Mathematics. Experimentally confirmed cases of photo-induced deexcitation of isomers, such as ${}^{180m}$Ta, ${}^{108m}$Ag, and ${}^{68m}$Cu, are discussed, and the obtained quantitative estimates for future photonuclear experiments, in particular on the isotopes ${}^{165}$Ho and ${}^{199}$Hg, are presented. It is shown that the planned parameters of the inverse Compton source, such as beam intensity and monochromaticity, will enable future high-precision measurements with an excellent signal-to-noise ratio. The obtained estimates of the count rate and the number of registered $\gamma$-quanta using an HPGe detector confirm the feasibility of performing activation experiments, as well as demonstrate the potential of the developed complex for addressing a broad range of problems in nuclear photonics, including studies of nuclear structure and isomer decay mechanisms.
Show AbstractThe compaction of biomolecules largely determines their functionality. It has previously been shown that the compaction of DNA and RNA can be estimated from the relative intensity of the low-frequency (LF) region of the Raman scattering spectra, but the applicability of this approach to complexes and mixtures of DNA with other biomolecules remained uncertain due to the unknown relative contribution of these molecules to the LF Raman spectrum. In this work, the experimental Raman spectra of DNA, protein, and fatty acid are compared, and it is shown that the intensity of the LF region is significantly higher for native DNA than for the other two types of biomolecules. Additionally, it is demonstrated that when a complex is formed between DNA and protein, the shape of the Raman spectrum of the complex is similar to that of the DNA spectrum, and the relative intensity of the LF region of the spectrum decreases. This indicates that the Raman signal from DNA dominates and that DNA becomes more compact during complex formation. The obtained results contribute to the development of a method for assessing the compaction of various biomolecules based on the analysis of LF Raman spectra and its application to complex biomolecular systems, such as cell nuclei.
Show AbstractThis paper considers the inverse problem of reconstructing a multichannel image distorted by defocusing and associated chromatic aberration. This problem arises in applied ophthalmology problems related to in vivo diagnostics of living human eye structures using optical methods. A mathematical model describing the formation of a multichannel image is proposed, based on a system of integral equations of the convolution type. To solve the ill-posed inverse problem of multichannel image reconstruction, an algorithm is developed based on a modified iterative implicit Tikhonov regularization method in combination with a frequency-localized regularization parameter selection rule and a stopping criterion. The results of the software implementation of the proposed method allow us to evaluate its effectiveness in the inverse problem of multichannel image reconstruction, including for high-resolution images typical for medical applications.
Show AbstractIn this study, the effect of the concentrations of ytterbium and thulium ions on the dependence of the intensity of luminescence of NaYF4:Yb/Tm nanoparticles on the optical excitation mode and intensity. Two modes of luminescence excitation are analyzed: continuous and pulsed. It has been found that changes in the concentrations of ytterbium and thulium do not change the course of the curve of dependence of the intensity of luminescence of nanoparticles on the intensity of optical excitation under both pulsed and continuous excitation.
Show AbstractThe efficiency and stability of liquid--liquid extraction processes used in hydrometallurgy and nuclear fuel reprocessing are strongly dependent on the acidity of the aqueous phase. Variations in nitric acid concentration affect distribution coefficients, phase stability, and process selectivity, while deviations beyond allowable limits may lead to third-phase formation, precipitation, and operational shutdowns. These considerations make real-time monitoring of nitric acid concentration a critical technological task. In this work, a flow-through Raman spectroscopic setup is developed and experimentally tested for online determination of nitric acid concentration in aqueous solutions over a wide concentration range from 0.01 to 10 M. The method is based on the analysis of systematic changes in the shape and intensity of the broad OH stretching band of water in the 3000--3700~cm$^{-1}$ region. Raman spectra were parameterized using a sum of Gaussian components associated with different hydrogen-bonding environments, and ratiometric spectral indicators based on their amplitudes were employed for calibration. Both linear and third-order polynomial calibration models were considered. Cross-validation using a leave-one-group-out scheme demonstrated that, for metal-free nitric acid solutions, the median absolute deviation of the predicted concentration is 0.14 M for the linear model and decreases to 0.07 M for the nonlinear model. The influence of matrix effects was studied by introducing uranyl ions at concentrations typical for extraction systems. In the presence of uranyl, the median deviation increases to approximately 0.35 M, remaining below 10% for nitric acid concentrations above 3 M. The obtained results demonstrate that Raman spectroscopy with analysis of the OH stretching band provides a robust basis for online monitoring of nitric acid concentration in extraction-related aqueous streams and can be further extended to more complex technological media.
Show AbstractThe paper presents a comparative study of the effect of partial iron substitution with cobalt, as well as the effect of various surface treatment methods on the properties of the magnetostrictive alloy Tb0.3Dy0.7Fe2 (terphenol-D) with the Laves phase structure. The structural features of the surface after mechanical polishing, chemical etching, and ion etching have been studied using atomic force, magnetic force, and scanning electron microscopy. It is shown that the substitution of Fe atoms for Co atoms has a significant effect on the domain structure of the samples. The analysis of the results made it possible to determine the optimal surface preparation methods for studying the properties of the high-friction alloy Tb0.3Dy0.7Fe2 and the substituted composition Tb0.3Dy0.7Fe1.8Co0.2.
Show AbstractThis paper presents a Ti/HfOx/TiN structure capable of switching between both resistive and capacitive states. Impedance spectroscopy data suggest an equivalent electrical circuit that increases the resistive switching of a hafnium oxide filament and suggests the presence of a TiON layer in the HfOx/TiN contact region, which may explain the ferroelectric potential switching. The capacitive switching window is 185 pF, resulting in a 75% increase in capacitance, while the resistance during resistive switching increases tenfold. These features represent an example of a versatile structure that can function as both a capacitor and a multi-state resistor. This enables encoding more information in a single cell and the creation of more complex logic elements. The problem of parasitic currents can also be solved, dramatically improving the energy efficiency and reliability of scalable memory arrays.
Show AbstractSecretion of von Willebrand factor by inflamed endothelium is considered one of the biophysical pathways initiating microvascular thrombosis in infectious diseases. At the initial stage of this process, the attachment of the first layer of platelets to von Willebrand factor is fundamental, while mechanical and hydrodynamic phenomena significantly influence the dynamics of thrombosis. In this study, computer modeling methods were used to investigate the biomechanics of platelet adhesion to inflamed endothelium in a microvessel. Calculations were performed over a range of hemodynamic parameters characteristic of small arterioles. The results demonstrate that platelet adhesion becomes more intense with increasing blood flow velocity due to the synchronous manifestation of two physical mechanism
Show AbstractBased on analytical solutions to the problem of the generation of gravity surface waves when moving along the bottom of a rectangular body, a comparative analysis of wave disturbances calculated within the framework of linear long-wave and potential theories was performed. It is shown that for conditions typical of real underwater landslides, the long-wave theory significantly (up to several orders of magnitude) overestimates the wave energy if the horizontal dimensions of the landslide body are comparable to the depth or less than the depth. In this regard, the application of the equations of the long wave theory to describe landslide tsunamis should be limited to cases of extremely extended landslide bodies.
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