The paper presents a method for separating the contribution of pair and single top quark production in tWb-associated final state using a neural network. The proposed method makes possible to calculate such processes in a gauge-invariant way with fully taking into account interference contributions and dividing the phase space into single-resonant and double-resonant regions, which is necessary to increase the accuracy of the search for possible deviations from the predictions of the Standard Model in these processes. To train the neural network, the optimized set of observables is used to separate single-resonance and double-resonance contributions to the overall process. The use of this method allows us to avoid the disadvantages inherent in the schemes used in collider physics for calculating the processes of tWb-associated top quark production with the removal of Feynman diagrams, which leads to violation of gauge invariance, or the addition of a subtraction scheme, which leads to the appearance of negative weights for the part of simulated events. The proposed method can be used to increase the efficiency of searching for deviations from the predictions of the Standard Model in the interaction of the top quark with the W boson and b quark.
Show AbstractVarious models of tetraquark generation in the reaction K + p → T (us; s̄s̄)X are considered. The predictions for corresponding inclusive spectra were evaluated at the energy 32 and 250 GeV.
Show AbstractStudying single cells opens up the possibility of understanding the fundamental mechanisms that hold the secrets of life's activity, greatly complementing classical research methods and providing new insights into cell biology. Research techniques such as Atomic Force Microscopy (AFM), scanning ion conductance microscopy (SICM), Nanopipette Analysis Systems, etc. provide a powerful tool to investigate morphological, mechanical and biochemical features of living cells with nanometer spatial resolution under near-native conditions. Over the past decades, SICM has made great strides in the observation and manipulation of single cells, and the non-contact nature of the system, together with the unique features of nanopipette used as probes, has opened up new possibilities for the use of such systems in biomedical applications. In this review, we aim to highlight the latest trends and directions in the development of SICM's sphere and nanopipette systems for single cell analysis.
Show AbstractThe present survey, timed to a century and a half anniversary of practical laboratory works in Physics being introduced in the curriculum of The Imperial University of Moscow for the students of the Faculty of Physics, provides a broad coverage of its functioning in the period from 1873 to 1917. The author gives a brief overview of the history of its founding, includes the data concerning the development of its equipment infrastructure, stuffing and figures about the number of students who took physics labs in those years. The contents of practical laboratory works are being analysed. The author vividly shows that professor A.\,P.~Sokolov’s “Guide to exercises in general physics labs of Physical Institute of The Imperial University of Moscow” relies heavily on “Guide to Practical Classes in Physics” by F.~Kohlrausch. The author familiarizes the readers with some historical references, which enable to better enhance the readers’ understanding of the details of practical training of physics students in The Imperial University of Moscow at the end of the 19th and the beginning of the 20th century. The article also contains rare historical pictures, some of which are published for the first time.
Show AbstractThe goal of this study is to investigate the effect and influence of cross-sections data, implemented in DOSXYZnrc Monte Carlo code, on the dose distribution data such as beam dose profiles and percentage depth dose, and its influences on the efficiency. A SATURNE 43 linear accelerator head’s has been modeled with BEAMnrc Monte Carlo code to simulate a 12 MV photon beam on a square field size of 10 × 10 cm2. The calculated results established that the percentage depth dose curves, beam profiles dose, and efficiency are less sensitive to the photon, pair, and Bremsstrahlung cross-sections data available in DOSXYZnrc code.
Show AbstractIn the present work, for the first time, the generalized Guggenheim equation for a system of hard spheres is obtained based on the use of the Euler accelerated convergence method. This equation allows taking into account an arbitrary number of known virial coefficients. For a metastable region, this equation is generalized to the case of taking into account the asymptotic behavior of the free energy at high densities. The resulting expression for the compressibility of the homogeneous phase of a system of hard spheres describes the data of a numerical experiment within their accuracy.
Show AbstractWe consider a boundary value problem for a singularly perturbed system of two second-order ordinary differential equations with different powers of a small parameter at the second derivatives without requiring the right-hand sides to be quasimonotonic. The specific feature of the problem is that one of the two equations in the degenerate system has a double root. It is proved that for sufficiently small values of a small parameter, the problem has a solution of the boundary layer type. A condition is obtained that replaces the quasimonotonicity condition and expands the class of problems to which the results of the work are applicable.
Show AbstractIt is a brief exposition of results of the investigation of Cauchy problem for some nonlinear equation of pseudoparabolic type that is a generalisation of some model of semiconductor theory.
Show AbstractUsing an analytical description of the evolution of the power of harmonics in free electron laser (FEL) undulators, we study the effect of electron beam parameters on the main characteristics of FEL radiation: the gain length, spectrum, and harmonic power. The possibility of suppressing even harmonics of the FEL as a light source in the study of materials and surfaces by analyzing the second harmonic nonlinear response (SHG) is being studied. The main factors influencing the radiation of even FEL harmonics are revealed; the influence of the beam cross section and the spread of electron energies on their radiation is analyzed. An example of a LEUTL FEL with visible light emission, which is used in studies of the optical properties of materials and the chemical state of molecules on surfaces and interfaces between media, is considered. In this context, the possibility of suppressing the second FEL harmonic is analyzed.
Show AbstractTheoretical results are formulated to assess the strength of the effect of self-compensation of errors in the thicknesses of layers of multilayer optical coatings. They are applicable to any method of optical monitoring of the deposition process. It is shown that considering a possible presence of a strong error self-compensation effect is of great importance for choosing a monitoring method. A comparative analysis of the results obtained to date to assess the strength of the error self-compensation effect for various types of coatings has been carried out. Moreover, a number of results were obtained for the first time directly in this work. The results obtained can be used to select the optimal method for monitoring the deposition process depending on the type of coating.
Show AbstractThis paper studies the three phases of RDX using the first-principles, and calculates electronic properties of RDX. At the same time, the properties of the three phases near the phase transition pressure are calculated. Under normal pressure, the lattice parameters of α-RDX are in good agreement with the experimental values. The lattice parameters of γ-RDX are in good agreement with the experimental values. The theoretical value of the unit cell volume of β-RDX is smaller than the experimental value, because β-RDX will expand in volume at high temperature. Under normal pressure and pressure of 2.8GPa, there is no virtual frequency in phonon spectrum of α-RDX. The appearance of virtual frequency under the pressure of 4 GPa indicates that the structure is unstable under this pressure and phase transition has occurred. Under the action of pressure, the peak values of conduction band and valence band decrease slightly, which is more obvious near the Fermi level, indicating that the electrons around the Fermi level are more sensitive to pressure. According to the calculation of Gibbs free energy, under the pressure of 2.8GPa, α-RDX will change into γ-RDX, which is in good agreement with the experimental value. The result is consistent with the previous phonon spectrum calculation. At the same time, under this pressure, when the temperature rises to 467K, α-RDX transforms into high-temperature phase β-RDX. Finally, the phase transition temperature of α-RDX and β-RDX at 2.7GPa was calculated. And the phase transition temperatures of γ-RDX and β-RDX at 2.9GPa determine the phase boundary of the three phase of RDX.
Show AbstractIn this study, the magnetic, structural, and electronic properties of Pt/[Pt/Co]4/Pt thin film was investigated both experimentally and theoretically. The effects of crystal orientation on magnetic behavior in the primitive cell were investigated via the first-principles methods. Band structures, total and partial density of states was calculated as the electronic properties. Magneto-optical Kerr effect and ferromagnetic resonance techniques were carried out to determine magnetic properties. The magnetic behavior of Pt/[Pt/Co]4/Pt in microscopic framework is revealed by the spin asymmetry in the density of states around the Fermi level. The perpendicular magnetic anisotropy is found to be more favorable for the Pt/[Pt/Co]4/Pt with (111) orientation. It was seen that the crystal orientation of Pt/[Pt/Co]4/Pt has a critical role on the magnetic properties according to the band magnetism calculations.
Show AbstractX-ray diffraction analysis, scanning electron microscopy and Mössbauer spectroscopy have been applied to the study of Fe-xTi (x=20-40 wt.%), Fe/xTi-diamond and Fe-TiC powders structure formation under the conditions of an AGO-2 planetary ball mill. It has been shown that metals with high melting points and limited solubility under high-energy mechanical action for 20 minutes interact to form an alloy of nanostructured iron and grain-boundary phases similar to solid solutions of Fe(Ti), Ti(Fe) and FeTi with a total content of 22-24 %. In the Fe-20wt.%Ti composition, titanium reaches an X-ray amorphous state, and when the titanium content is above 20 wt. % α-Ti crystalline phase remains in an amount of 5-10 wt.%. When the Fe/xTi-diamond mixture is mechanically activated, composite particles with a metal matrix structure with a diamond size of 0.3–1.5 μm are formed. It has been established titanium accelerates the process of grain-boundary and volumetric interaction of iron with diamond and titanium carbide. In the powder compositions under study, a solid solution is formed based on iron and TiC, Fe3C compounds with their total content: Fe/40wt.%Ti-diamond up to 62%; Fe/TiC up to 34%. Under similar conditions in a diamond-iron mixture, the grain-boundary phases of the solid solution do not exceed 26%. The formation of graphite has not detected by X-ray diffraction.
Show AbstractHadron therapy (HT) is a technique that uses accelerated ions, notably protons, and carbon ions, to destroy tumors. It has demonstrated high success rates in the treatment of certain cancers resistant to irradiation. In HT, the majority of the dose is delivered to the tumor volume by electromagnetic interactions with atomic electrons. However, it is important to note that the primary particles used in HT can induce nuclear reactions, generating undesirable secondary radiation, certainly neutrons. As a result, a significant portion of the patient’s body may be exposed to the secondary background radiation field. Thus, these unwanted secondary neutrons should be evaluated. The purpose of this research first is to characterize the secondary neutron production (SNP) during the administration of Hadrons with energies 140 MeV proton, and 264 MeV/u carbon ions 12C in a soft tissue phantom. Second, comparing the neutron spectrum for different angles for protons and carbon ions for carbon targets to experimental data. Our results show that the neutron spectra (thick target neutron yields TTNYs ) at energies less than ≤20 MeV, using the INCL4.6/GEM models and JQMD/GEM across a wide range would be suitable for the Monte Carlo transport simulation.
Show AbstractIn recent times, Monte Carlo simulations are gaining widespread recognition as the most precise tool for calculating particle interactions with matter. In this study, we investigated two primary aspects. Firstly, we examined how the average excitation energy of water (IW ) influences the location of the Bragg Peak (BP). Secondly, we used the Particle and Heavy Ion Transport Code System (PHITS) to study the Bragg curve of 12C ion beam having an energy of 200 MeV/u in three different mediums: water, soft tissue, and bone. Lastly, we examined the impact of secondary particles on the overall dose. Our findings indicate that the average excitation energy of water strongly influences the position of the BP. The tail dose beyond the BP primarily results from secondary fragments of the primary carbon ion beams. Furthermore, the PHITS code accurately reproduces the measured Bragg curves.
Show AbstractWe study the electromagnetic contribution to elastic neutrino-nucleon scattering processes. The neutrino electromagnetic charge, magnetic, electric, and anapole form factors of both diagonal and transition types in the mass basis are taken into account in the present formalism. When treating the nucleon electromagnetic vertex, we take into account not only the charge and magnetic form factors of a nucleon, but also its electric and anapole form factors. We examine the effects of the neutrino magnetic moment on elastic neutrino-nucleon scattering and how they can be disentangled from those of the strange form factors contributions to the nucleon’s weak neutral current.
Show AbstractIn this work, numerical simulations are used to study ambipolar organic field-effect phototransistors, in which a spatially localized photoelectric effect can take place. This effect consists in the fact that there is a small spatially localized photosensitive region in the transistor channel, the position of which can be controlled by changing the gate voltage. The purpose of this work is to analyze the relationship between the form of the field dependence of the bound electron-hole pairs (e/h pairs) dissociation probability and characteristics of the studied ambipolar phototransistors such as normalized photocurrent, spatial resolution, and response time. It is shown that the optimal form of the field dependence of e/h pairs dissociation probability is stepwise-like form, which can provide a high spatial resolution at high values of the normalized photocurrent without degrading the response time of the phototransistor. This shape can be achieved when the organic semiconductor has an extremely narrow distribution of e/h pairs by size, described by the delta function.Also, on the example of several distributions of various shapes, it is shown that a decrease in the width of the distribution leads to an increase in the spatial resolution.Approaches to the selection and modification of organic semiconductor materials that would provide the most pronounced spatially localized photoelectric effect in ambipolar field-effect transistors are discussed.
Show AbstractThe results of modeling the dependence of the “red leak” of photometric filters on various factors (color index V-R, luminosity class, interstellar reddening, air mass and PWV) during observations of stars are presented. The error arising from not taking into account the “red leak” in the case of filters used on the 0.6-m telescope of the CMO SAI can amount to 0.6 mag - 0.8 mag for late stars. Algorithms for reducing observational data are presented for filters U and B. The results of observations of the rapid variability of two symbiotic stars CH Cyg and SU Lyn with cold components of very late spectral types are presented. For CH Cyg, rapid variability was detected on both observation dates. Taking into account the “red leak” effect, the amplitude in the B band was 0.10 mag on November 6, 2019 and 0.19 mag on December 15, 2022, with a characteristic variability time of about 20 minutes. For SU Lyn, no rapid brightness variability was detected in the B band on February 2, 2023 (with an accuracy of 0.003 mag)
Show AbstractThe paper considers the foci of the most severe earthquakes in the Russian segment of the Arctic that occurred during the entire observation period, from 1976 to the present. The stress and strain fields were studied by analyzing the tensor of the seismic moment of registered earthquakes. This analysis is being conducted for the first time. Spatial distributions of the Lode-Nadai coefficient and the rate of seismotectonic deformation are obtained.
Show AbstractAn experimental study of the effect of wind blowing a wave induced by a wave generator in a direct channel has been carried out. It is shown that at low wave steepness ak < 0.1 and wind speed W < 2.3 m/s, a drift current occurs on the water surface due to the influence of viscous forces. A formula for calculating its velocity is proposed. It is found that the phase velocity of the wave increases with the appearance of a drift flow and can be calculated using the formula obtained for linear waves on a flow with a constant velocity shift. With an increase in the steepness of the wave ak > 0.19 and an increase in wind W > 2.3 m/s, the formation of a vortex deforming the water surface was detected in the air flow above the top of the wave crest. The vortex destroys the viscous layer, reducing the drift velocity. At the same time, the phase velocity and wavelength decrease. A mechanism explaining this process is proposed.
Show AbstractThere is growing interest in the oil and gas industry in using the PC-SAFT equation of state to predict phase behavior and physical properties of hydrocarbons. This paper shows how this equation of state can be used in combination with the direct energy minimization algorithm for an isochoric-isothermal system to calculate the vapor-liquid equilibrium parameters of hydrocarbons. The proposed approach is tested for four substances: methane, ethane, propane and n-butane.
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