bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics and 2D temperature distribution of plasma obtained by femtosecond laser-induced breakdown
Authors: Hossain Afaque M , Ehrhardt Martin , Rudolph Martin , Kalanov Dmitry , Lorenz Pierre , Zimmer Klaus , Anders André
Published: December 2021

Recently, plasma produced by focusing femtosecond laser in gases has been introduced as an etching tool in materials processing. Proper control of the plasma in this application necessitates the apt understanding of the different morphological features of the plasma. In this contribution we show that, the plasma produced in air goes through several stages of morphological development–from ellipsoidal to spherical to toroidal plasma, whereas in argon, axial compression of an ellipsoidal plasma is observed. To explain this dissimilarity, we have quantified the temperature by emission spectroscopy (Planck analysis with Wien’s approximation). The evolution of temperature shows a triple exponential dependence in time which can be correlated with different stages of morphological changes of the plasma. Open Source Field Operation and Manipulation simulations using experimentally determined temperature values show that—(i) the reverse pressure gradient propagates radially inwards and compresses the plasma in both air and argon and forms a localized high pressure zone at the center that generates a secondary pressure wave in air, but not in argon, and (ii) the baroclinic torque that is generated because of the Richtmyer–Meshkov instability, dominates the rate of vorticity in air, whereas effects of flow compressibility and velocity gradients dominate the vortices in argon. Knowledge of the initial state and the dynamics of the subsequent stages of the plasma formation can be utilized for control and optimization of laser-induced plasma applications.
A nonlinear magneto-elastoplastic coupling model based on Jiles–Atherton theory of ferromagnetic materials
Authors: Hu Xiangyi , Bu Yang , Zhang Jianhua
Published: December 2021

As seen in the Jiles–Atherton (J–A) model and its modified form, the linear relationship between the magnetization coefficient and the stress deviates significantly from the experimental results. It is necessary to introduce many parameters that are difficult to obtain or unknown to describe the effect of elastoplastic deformation on magnetization or hysteresis, such as shape coefficient, pinning coefficient, and molecular field coefficient. In this paper, a new nonlinear magneto-elastoplastic model for ferromagnetic materials is established based on the magneto-mechanical coupling effect, and both the sixth-order term of magnetization and the nonlinear equation of the magnetization coefficient are introduced into the magnetostriction equation. In the models established in this paper, the elastoplastic deformation equivalent magnetic field is introduced into the effective magnetic field, and the Frohlich–Kennelly equation is used to describe the anhysteretic magnetization. After comparing the prediction results of different models with the available experimental results, it is observed that the proposed model in this paper exhibits superior prediction ability for magnetostrictive strain, magnetization, and hysteresis phenomena under different stresses. This paper has also analyzed the mechanism of the effect of elasto-plastic loading and residual stress on the hysteresis in different models as well as the differences between them. The determination coefficient of the proposed model in this paper is closer to 1, which is better than the existing models, indicating that it has a better fitting effect and is of great significance to the development of quantitative non-destructive testing technology.
Continuous and discrete symmetries of renormalization group equations for neutrino oscillations in matter
Authors: Zhou Shun
Published: December 2021

Three-flavor neutrino oscillations in matter can be described by three effective neutrino masses

m

~

i

(for i = 1, 2, 3) and the effective mixing matrix V

αi
(for α = e,μ, τ and i = 1, 2, 3). When the matter parameter

a
≡
2

2

G

F

N

e

E

is taken as an independent variable, a complete set of first-order ordinary differential equations for

m

~

i

2

and |V

αi
|2 have been derived in the previous works. In the present paper, we point out that such a system of differential equations possesses both the continuous symmetries characterized by one-parameter Lie groups and the discrete symmetry associated with the permutations of three neutrino mass eigenstates. The implications of these symmetries for solving the differential equations and looking for differential invariants are discussed.
Assessment of secondary neutrons in particle therapy by Monte Carlo simulations
Authors: Vedelago José , Geser Federico A , Muñoz Iván D , Stabilini Alberto , Yukihara Eduardo G , Jäkel Oliver
Published: December 2021

Objective. The purpose of this study is to estimate the energy and angular distribution of secondary neutrons inside a phantom in hadron therapy, which will support decisions on detector choice and experimental setup design for in-phantom secondary neutron measurements. Approach. Dedicated Monte Carlo simulations were implemented, considering clinically relevant energies of protons, helium and carbon ions. Since scored quantities can vary from different radiation transport models, the codes FLUKA, TOPAS and MCNP were used. The geometry of an active scanning beam delivery system for heavy ion treatment was implemented, and simulations of pristine and spread-out Bragg peaks were carried out. Previous studies, focused on specific ion types or single energies, are qualitatively in agreement with the obtained results. Main results. The secondary neutrons energy distributions present a continuous spectrum with two peaks, one centred on the thermal/epithermal region, and one on the high-energy region, with the most probable energy ranging from 19 up to 240 MeV, depending on the ion type and its initial energy. The simulations show that the secondary neutron energies may exceed 400 MeV and, therefore, suitable neutron detectors for this energy range shall be needed. Additionally, the angular distribution of the low energy neutrons is quite isotropic, whereas the fast/relativistic neutrons are mainly scattered in the down-stream direction. Significance. It would be possible to minimize the influence of the heavy ions when measuring the neutron-generated recoil protons by selecting appropriate measurement positions within the phantom. Although there are discrepancies among the three Monte Carlo codes, the results agree qualitatively and in order of magnitude, being sufficient to support further investigations with the ultimate goal of mapping the secondary neutron doses both in- and out-of-field in hadrontherapy. The obtained secondary neutron spectra are available as supplementary material.
Dynamics of ultrafast heated radiative plasmas driven by petawatt laser light
Authors: Sugimoto K , Iwata N , Sunahara A , Sano T , Sentoku Y
Published: December 2021

A relativistic petawatt laser light can heat a high Z metal above keV temperatures isochorically and ionize it almost fully. Copious hard x-rays are emitted from a high-Z hot plasma, which acts as an x-ray source, while x-ray emissions serve as an energy sink for the plasma. The isochoric heating of a solid silver foil irradiated by a relativistic laser light is studied with the help of 1D and 2D particle-in-cell simulations including Coulomb collisions, ionizations, and radiation processes. We find that the radiation power from the keV silver plasma is comparable to the incident laser power when the laser intensity is less than 1019 W cm−2. Thus, the plasma formation and particle acceleration are affected by the radiation, e.g. a highly compressed shock formation. Once the laser heating is over, the silver plasma loses its energy on a timescale of picoseconds, during which hard x-rays flash. The radiation spectra of the keV silver plasma are also presented.
The physics of empty liquids: from patchy particles to water
Authors: Russo John , Leoni Fabio , Martelli Fausto , Sciortino Francesco
Published: December 2021

Empty liquids represent a wide class of materials whose constituents arrange in a random network through reversible bonds. Many key insights on the physical properties of empty liquids have originated almost independently from the study of colloidal patchy particles on one side, and a large body of theoretical and experimental research on water on the other side. Patchy particles represent a family of coarse-grained potentials that allows for a precise control of both the geometric and the energetic aspects of bonding, while water has arguably the most complex phase diagram of any pure substance, and a puzzling amorphous phase behavior. It was only recently that the exchange of ideas from both fields has made it possible to solve long-standing problems and shed new light on the behavior of empty liquids. Here we highlight the connections between patchy particles and water, focusing on the modelling principles that make an empty liquid behave like water, including the factors that control the appearance of thermodynamic and dynamic anomalies, the possibility of liquid–liquid phase transitions, and the crystallization of open crystalline structures.
Theoretical study of highly efficient CH3NH3SnI3 based perovskite solar cell with CuInS2 quantum dot
Authors: Gagandeep  , Singh Mukhtiyar , Kumar Ramesh , Singh Vinamrita , Srivastava Sunita
Published: December 2021

Simulation studies have been carried out for the n–i–p perovskite solar cell (PSC) structure i.e. ITO/SnO2/CH3NH3PbI3/CuInS2/Au. We have considered this cell as our primary structure and is simulated using solar cell capacitance simulator-1D software. Here, the CuInS2 quantum dot (CIS QD) acts as an inorganic hole transporting layer. Further, the use of the CIS QD in PSCs has been explored by simulating 20 different cell structures. These PSCs are based on recently used absorber layers, i.e. MASnI3, FAPbI3, and (FAPbI3)0.97 (MAPbBr1.5Cl1.5)0.03, and electron transporting layers, i.e. SnO2, TiO2, ZnO, C60, and IGZO. The performance of all structures has been optimized by varying the thickness of the absorber layers and electron transporting layers. The cell structure, ITO/SnO2/CH3NH3SnI3/CuInS2/Au, has been found to exhibit the highest power conversion efficiency of 21.79% as compared to other cells. Investigations have also been carried out to analyze the effect of defect density in the absorber layer and the interface of the cell structure. In addition, the cell performance has been ascertained by examining the impact of operating temperature, metal contact work function and that of resistance in series as well as in parallel. The simulation results of our primary cell structure are found to be in good agreement with the recent experimental study.
On the shear test of a MR elastomer under magnetic field applied at various angles
Authors: Dohmen Eike , Borin Dmitry
Published: December 2021

In this paper the influence of the angle between the applied external magnetic field and the mechanical shear direction on the measured elasticity of a magnetorheological (MR) elastomer is addressed. The whole range of magnetic field angles from 0∘ to 90∘ is analyzed in steps of 5∘. Though this dependence is of highest importance for practical applications this issue is rather neglected in previous studies. The work uses MR elastomer specimens based on a silicone rubber matrix containing iron powder in weight fractions of 82 and 89 wt.%. It has been shown that the measured modulus of elasticity of such composites decreases as the angle between an external magnetic field and applied shear deformation increases. As the framework for the discussion of the findings a macroscopic explanation associated with the magneto-deformation effect as well as an influence of the demagnetizing factor are considered.
Characterization of slide ring materials for dielectric elastomer actuators
Authors: Shintake Jun , Matsuno Koya , Kumegawa Shohei , Baba Kazumasa , Takeuchi Hiromitsu
Published: December 2021

This paper investigates the characteristics of sliding ring materials (SRMs), which are promising elastomeric materials for dielectric elastomer actuators (DEAs). Two different types of SRMs with Young’s modulus of 0.8 MPa and 3.3 MPa, respectively, are prepared, and their material and mechanical properties and electro-mechanical performances at electric fields of up to 30 V µm−1 are characterized. For comparison, the same tests are also performed on several commercially available elastomers: Elastosil 2030, Ecoflex 00-30, CF19-2186, and VHB 4905. The results reveal that SRMs demonstrate negligible Mullins effect and hysteresis, while their dielectric strength (62.4–112.4 V µm−1) and viscoelasticity (

tan
δ

0.07–0.24 at 10 Hz) are comparable or even superior to those of other elastomers. In addition, elongation at break is found to be 163.8%–172.1%. SRMs exhibit excellent electro-mechanical performance; for instance, one of the two types has an actuation force 293.2 mN at 24.9 V µm−1 and a strain of 5.2% at 22.3 V µm−1. These values are the largest or larger than most of the tested elastomers. The high performance of SRMs results from their dielectric constant, which ranges from 10.3 to 13.4, leading to an electro-mechanical sensitivity of up to 15.3 MPa−1. These results illustrate SRMs as attractive material options for DEAs.
Field-induced tricritical phenomenon and magnetic structures in magnetic Weyl semimetal candidate NdAlGe
Authors: Zhao Jun , Liu Wei , Rahman Azizur , Meng Fanying , Ling Langsheng , Xi Chuanying , Tong Wei , Bai Yuming , Tian Zhaoming , Zhong Yunbo , Hu Ying , Pi Li , Zhang Lei , Zhang Yuheng
Published: December 2021

Non-centrosymmetric NdAlGe is considered to be a candidate for magnetic Weyl semimetal in which the Weyl nodes can be moved by magnetization. Clarification of the magnetic structures and couplings in this system is thus crucial to understand its magnetic topological properties. In this work, we conduct a systematical study of magnetic properties and critical behaviors of single-crystal NdAlGe. Angle-dependent magnetization exhibits strong magnetic anisotropy along the c-axis and absolute isotropy in the ab-plane. The study of critical behavior with H∥c gives critical exponents β = 0.236(2), γ = 0.920(1), and δ = 4.966(1) at critical temperature T
C = 5.2(2) K. Under the framework of the universality principle, M(T, H) curves are scaled into universality curves using these critical exponents, demonstrating reliability and self-consistency of the obtained exponents. The critical exponents of NdAlGe are close to the theoretical prediction of a tricritical mean-field model, indicating a field-induced tricritical behavior. Based on the scaling analysis, a H–T phase diagram for NdAlGe with H∥c is constructed, revealing a ground state with an up-up-down spin configuration. The phase diagram unveils multiple phases including up-up-down domains, up-up-down ordering state, polarized ferromagnetic (PFM), and paramagnetic (PM) phases, with a tricritical point (TCP) located at the intersection [T
TCP = 5.27(1) K, H
TCP = 30.1(3) kOe] of up-up-down, PFM, and PM phases. The multiple phases and magnetic structures imply a delicate competition and balance between variable interactions and couplings, laying a solid foundation for unveiling topological properties and critical phenomena in this system.
Nonlinear dynamics in the jupiter magnetosphere: implications of dust-acoustic cnoidal mode
Authors: Tolba R E , Yahia M E , Moslem W M
Published: December 2021

Different types of waves and their nature in the Jovian middle magnetosphere are still not clear or specified. For this purpose, a generalized hydrodynamic model for an arbitrary amplitude dust-acoustic waves is built for true Jovian magnetosphere. The plasma system consists of positive dust grains, Maxwellian ions and electrons. An evolution equation containing a Sagdeev potential is derived, and its numerical analysis is presented. Unexpectedly, the given data yielded cnoidal waves only with positive potential. The effect of the external magnetic field, Mach number, and directional cosine parameters are studied and manipulated. We think that the present results are important in realizing the main waves in the Jovian magnetosphere, and the possible correlation to its particles’ stability and pole acoustic waves.
Electron Bernstein wave aided heating of collisional nanocluster plasma by nonlinear interactions of two super-Gaussian laser beams
Authors: Varma Ashish , Kumar Asheel
Published: December 2021

In this present theoretical study, we investigate electron Bernstein wave (EBW) aided collisional nanocluster plasma heating by nonlinear interaction of two super-Gaussian laser beams. The interactions of laser beams electric field profiles with electronic clouds of nanoclusters cause the beat wave. The nonlinear ponderomotive force is generated through the beat wave. There may be good potential to excite the EBW aiding cluster plasma to lead electron heating via cyclotron damping of the Bernstein wave. An analytical scheme is proposed for the anomalous heating and evolution of electron temperature by using this mechanism. Graphical discussions were promised to achieve extreme heating rate via the spatial shape of super-Gaussian laser beams and the resonance condition of beat wave to surface plasmon frequency. The heating is controlled by tuning the laser beam width, mode index, collisional frequency, clustered radius, and density.
Cross-code comparison of the edge codes SOLPS-ITER, SOLEDGE2D and UEDGE in modelling a low-power scenario in the DTT
Authors: Moscheni M. , Meineri C. , Wigram M. , Carati C. , De Marchi E. , Greenwald M. , Innocente P. , LaBombard B. , Subba F. , Wu H. , Zanino R.
Published: December 2021

As reactor-level nuclear fusion experiments are approaching, a solution to the power exhaust issue in future fusion reactors is still missing. The maximum steady-state heat load that can be exhausted by the present technology is around 10 MW m−2. Different promising strategies aiming at successfully managing the power exhaust in reactor-relevant conditions such that the limit is not exceeded are under investigation, and will be tested in the Divertor Tokamak Test (DTT) experiment. Meanwhile, the design of tokamaks beyond the DTT, e.g. EU-DEMO/ARC, is progressing at a high pace. A strategy to work around the present lack of reactor-relevant data consists of exploiting modelling to reduce the uncertainty in the extrapolation in the design phase. Different simulation tools, with their own capabilities and limitations, can be employed for this purpose. In this work, we compare SOLPS-ITER, SOLEDGE2D and UEDGE, three state-of-the-art edge codes heavily used in power exhaust studies, in modelling the same DTT low-power, pure-deuterium, narrow heat-flux-width scenario. This simplified, although still reactor-relevant, testbed eases the cross-comparison and the interpretation of the code predictions, to identify areas where results differ and develop understanding of the underlying causes. Under the conditions investigated, the codes show encouraging agreement in terms of key parameters at both targets, including peak parallel heat flux (1%–45%), ion temperature (2%–19%), and inner target plasma density (1%–23%) when run with similar input. However, strong disagreement is observed for the remaining quantities, from 30% at outer mid-plane up to a factor 4–5 at the targets. The results primarily reflect limitations of the codes: the SOLPS-ITER plasma mesh not reaching the first wall, SOLEDGE2D not including ion-neutral temperature equilibration, and UEDGE enforcing a common ion-neutral temperature. Potential improvements that could help enhance the accuracy of the code models for future applications are also discussed.
Analysis of hypervelocity impacts: the tungsten case
Authors: Fraile Alberto , Dwivedi Prashant , Bonny Giovanni , Polcar Tomas
Published: December 2021

The atomistic mechanisms of damage initiation during high velocity (v up to 9 km s−1, kinetic energies up to 200 keV) impacts of W projectiles on a W surface have been investigated using parallel molecular-dynamics simulations involving large samples (up to 40 million atoms). Various aspects of the high velocity impacts, where the projectile and part of the target material undergo massive plastic deformation, breakup, melting, and vaporization, are analyzed. Different stages of the penetration process have been identified through a detailed examination of implantation, crater size and volume, sputtered atoms, and dislocations created by the impacts. The crater volume increases linearly with the kinetic energy for a given impactor; and the total dislocation length (TDL) increases with the kinetic energy but depends on the size of the impactor. We found that the TDL does not depend on the used interatomic potential. The results are rationalized based on the physical properties of bcc W.
Corrigendum: Non-collinear ground state and stable bimerons from four-spin chiral interactions in D3h magnet (2021 J. Phys.: Conf. Ser
2015 012118)
Authors: Rakhmanova G R , Osipov A N , Ilin D I , Shushakova I V , Iorsh I V
Published: December 2021

Please see Article PDF for corrigendum text.
Non-spherical nucleon clusters in the mantle of a neutron star: CLDM based on Skyrme-type forces
Authors: Zemlyakov N A , Chugunov A I , Shchechilin N N
Published: December 2021

Neutron stars are superdense compact astrophysical objects. The central region of the neuron star (the core) consists of locally homogeneous nuclear matter, while in the outer region (the crust) nucleons are clustered. In the outer crust these nuclear clusters represent neutron-rich atomic nuclei and all nucleons are bound within them. Whereas in the inner crust some neutrons are unbound, but nuclear clusters still keeps generally spherical shape. Here we consider the region between the crust and the core of the star, so-called mantle, where non-spherical nuclear clusters may exist. We apply compressible liquid drop model to calculate the energy density for several shape types of nuclear clusters. It allows us to identify the most energetically favorable configuration as function of baryon number density. Employing four Skyrme-type forces (SLy4 and BSk24, BSk25, BSk26), which are widely used in the neutron star physics, we faced with strong model dependence of the ground state composition. In particular, in agreement with previous works within liquid drop model, mantle is absent for SLy4 (nuclear spheres directly transit into homogeneous nuclear matter; exotic nuclear shapes do not appear).
Wind of a young massive star colliding with a supernova remnant shell
Authors: Badmaev D V , Bykov A M
Published: December 2021

The fast stellar winds of massive stars, along with supernovae, determine the dynamics within the star-forming regions. Within a compact star cluster, counterpropagating supersonic MHD shock flows associated with winds and supernova remnants can provide favorable conditions for efficient Fermi I particle acceleration up to energies > 10 PeV over a short timescale of several hundred years. To model the nonthermal spectra of such systems it is necessary to know the complex structure of colliding supersonic flows. In this paper using the PLUTO code we study on a subparsec scale a 2D MHD model of the collision of a core-collapse supernova remnant with a magnetized wind of a hot rotating O-star. As a result the detailed high resolution (~ 10−4 pc) maps of density, magnetic field, and temperature during the the wind - supernova shell interaction are presented.
Magnetic turbulence in supernova remnants: perspective for IXPE polarimeter
Authors: Bykov A M , Uvarov Y A
Published: December 2021

Supernova remnants (SNRs) are well known sources of the non-thermal radiation, particle acceleration and magnetic field generation and amplification. Synchrotron radiation of the accelerated electrons in the magnetic field is an important emission mechanism in SNRs that can dominate in radio and X-ray energy bands. Turbulent magnetic field yields to formation of the special inhomogeneous (clumpy) structure in the SNR synchrotron X-ray images. This structure could differ significantly on the SNR polarization maps for different types of the magnetic turbulence. A new family of the gas pixel detector X-ray polarimeters that are supposed to have good sensitivity and angular resolution should be well suited for SNR polarimetry. IXPE (NASA) will be the first polarimeter of this kind. Lately a model IXPE synchrotron polarization images of Tycho SNR were simulated in the 3 — 8 keV energy band. It was shown that IXPE observation time of ~ 1 Ms should be enough to distinguish characteristic features that are specific for some types of the magnetic turbulence. We perform simulations of Tycho SNR polarization maps for a wider set of energy bands in order to determine the most suitable energy range for study of the SNR turbulent magnetic field using IXPE. The dependence of the polarization degree on the photon energy is accurately considered in the simulations. IXPE background influence on the observations of Tycho SNR is also discussed here together with possible ways of data processing and interpretation reducing this effect.
Jet and counter-jet in transonic pulsar wind nebulae
Authors: Ponomaryov G A , Levenfish K P , Petrov A E
Published: December 2021

X-ray observations show that a jet and a counter-jet in pulsar wind nebulae often differ one from another. Sometimes one of the jets is not observed at all. We show that the most likely reason for this difference is the relative motion of a pulsar and an ambient matter. Even the slow (subsonic or transonic) ambient matter stream in the pulsar rest frame strongly affects the jets, making the windward jet bright and dynamic, and the leeward jet dim and diffuse. The effect is illustrated using a relativistic MHD model of a double-torus pulsar wind nebula. The model is shown to explain reasonably well the observational appearance of the jets in the Vela nebula - a double-torus object which evolves in a transonic stream initiated by the passage of the reverse shock of the parent supernova.
Analytic approximations to photoabsorption cross sections of once-ionized helium in magnetar atmospheres
Authors: Demidov I V , Potekhin A Y
Published: December 2021

Magnetar atmospheres can contain a substantial fraction of once-ionized helium. At the magnetic fields about 1014 −1015 G, typical of magnetars, Landau quantization is important not only for the electrons, but also for the centre-of-mass (CM) motion of the He+ ion. The CM and internal motions are mutually dependent, which complicates theoretical studies of the He+ characteristics. We present asymptotic analytic expressions for the binding energies, oscillator strengths, and photoionization cross sections of the moving hydrogenlike ions in an ultra-strong magnetic field, which can be used to construct approximate models of magnetar atmospheres.
Recent acceleration of the Earth rotation in the summer of 2020: possible causes and effects
Authors: Trofimov D A , Petrov S D , Movsesyan P V , Zheltova K V , Kiyaev V I
Published: December 2021

The extreme acceleration of the Earth rotation observed in the summer of 2020 is considered. It is concluded that this phenomenon is a consequence of two factors: the longterm acceleration of the Earth rotation, which has been observed since the 1970s, and the extremely strong meteorological excitation of the LOD, which took place in the summer of 2020. The coincidence of the anomaly of the AAM and the geomagnetic Dst index, as well as the correlation between the LOD on the one hand and the solar wind speed and the Gaussian coefficients of the expansion of the Earth’s magnetic field, on the other, are noted. The problem of negative leap second is considered. Preliminary estimates have been made of introduction of a negative leap second, if the current trends in the behavior of UT1-UTC continue. The conclusion is made about the low probability of such an event.
Major merging of galaxies in multicomponent numerical models: mass loss and exchange
Authors: Titov Alexander , Khoperskov Alexander , Khrapov Sergey
Published: December 2021

The process of collision of two multicomponent galaxies is considered in detail based on numerical simulations of the dynamics of gravitating gas, stars and dark mass. To solve the equations of motion of the gas component, we use the Smoothed Particle Hydrodynamics method. Modeling of collisionless components is based on the N-body model. The computations of gravitational forces are carried out using both the approximate hierarchical TreeCode algorithm and the direct method of summing the gravitational contribution from all particles, which provides an accurate solution. This approach allows testing various models and evaluating the resulting errors associated with the calculation of gravitational forces and a finite number of particles in each of the components. Both methods for calculating gravity are software implemented as parallel codes for Nvidia Tesla GPUs. The estimates of the lost mass and the efficiency of matter exchange between galaxies are discussed depending on the model parameters.
The search for statistical patterns of pathological activity in human EEG signals in focal epilepsy
Authors: Yunusov V A , Demin S A , Panischev O Y , Demina N Y
Published: December 2021

Modern data science faces a lot of challenges, one of which is the search for diagnostic criteria for neurological diseases. New methods of statistical analysis are actively applied in the field of biophysics to solve this issue. In this paper we apply the Memory Functions Formalism to analyze electroencephalogram signal recordings in the sleeping state of 8 healthy subjects and 19 patients with nocturnal lobe epilepsy. We observe the considerable difference of statistical memory effects and fractal properties at the pathology in comparison with the control group. Furthermore, we reveal significant alterations in brain rhythms at power spectra of statistical memory functions for two groups of subjects. As a result, we show that the application of the statistical analysis methodology of bioelectrical brain cortex activity recordings, after appropriate verification, can be useful in the search for diagnostic criteria of nocturnal frontal lobe epilepsy.
Research of replication accuracy in some elastomer materials with different Young’s modulus
Authors: Germash N N , Esikova N A , Afonicheva P K , Evstrapov A A
Published: December 2021

In this work we observed three different elastomeric materials with different Young’s modulus: Silastic T-4, Plat Set 30, and Lasil-C. Their usage makes it possible to overlap the range of rigidity obtained for Silgard under different curing conditions, without high temperatures and long curing time. The results obtained during the replicas formation using a brass master mold with micro-sized structures for these elastomers were presented. The quality of the replication in materials with low Young’s modulus turned out to be better than for Silgard, and for the hard Silastic T-4 – it is comparable to it.
New possibilities of collectors with azimuthal magnetic field for multistage energy recovery in gyrotrons
Authors: Louksha O I , Trofimov P A , Usherenko B D
Published: December 2021

The results of modeling a collector with 4-stage recovery of residual electron energy for the SPbPU gyrotron with a frequency of 74.2 GHz and an output power of 100 kW are presented. For spatial separation of electrons with different energies, an azimuthal magnetic field created by a toroidal solenoid is used. An increase of the recovery efficiency and a decrease of the current of electrons reflected from the collector is achieved by reducing the spread of the radial position of the leading centers of electron trajectories at optimal parameters of the toroidal solenoid, as well as by using a sectioned electron beam. The trajectory analysis of the spent electron beam in the collector region showed the possibility of achieving the total efficiency of the gyrotron, close to 80%.
Parameterization of charge transport process with avalanche multiplication in irradiated Si p-i-n structures at T = 1.9 K
Authors: Shepelev A S , Eremin V K , Verbitskaya E M
Published: December 2021

The study is devoted to the treatment of in situ radiation tests results for silicon p-i-n detectors of relativistic protons, which showed the two-stage process of charge transport with avalanche multiplication at a temperature of 1.9 K. The goal of the work is to extract the carrier transport parameters from the experimental data obtained by transient current technique. For that, the impact of a spatial nonuniformity of carrier generation by the laser and spreading of the drifting carrier cloud due to diffusion on the current pulse response formation were considered. The mathematical procedure proposed for the current pulse simulation showed a key contribution of avalanche multiplication in the signal formation and allowed direct estimation of the multiplication factor from the experimental pulses. It is found that this factor only slightly depends on the bias voltage, which suggests the electric field inside the detector to be affected by the space-charge-limited current.
Low-temperature degradation resistance and plastic deformation of ATZ ceramics stabilized by CaO
Authors: Dmitrievskiy AA , Zhigacheva DG , Vasyukov VM , Ovchinnikov PN
Published: December 2021

In this work, the phase composition (relative fractions of monoclinic m-ZrO2, tetragonal t-ZrO2, and cubic c-ZrO2 phases) and mechanical properties (hardness, fracture toughness, compressive strength) of alumina toughened zirconia (ATZ) ceramics, with an addition of silica were investigated. Calcium oxide was used as a stabilizer for the zirconia tetragonal phase. It was shown that CaO-ATZ+SiO2 ceramics demonstrate increased resistance to low-temperature degradation. The plasticity signs at room temperature were found due to the SiO2 addition to CaO-ATZ ceramics. A yield plateau appears in the uniaxial compression diagram at 5 mol. % SiO2 concentration. It is hypothesized that discovered plasticity is due to the increased t→m transformability.
Stability of supratransmission waves in a crystal of A3B stoichiometry upon interaction with single dislocations
Authors: Lutsenko I S , Zakharov P V , Starostenkov M D , Dmitriev S V , Korznikova E A
Published: December 2021

Supratransmission waves are stable objects that can exist in different discrete environments. In this paper, we consider the interaction of such waves with single edge dislocations of various configurations in a crystal with A3B stoichiometry. The model was a Pt3Al crystal, the potential obtained by the embedded atom method was used to describe the interaction of its atoms. Quantitative characteristics of the wave were obtained before and after the interaction. It is found that the degree of energy dissipation by dislocations depends on the mutual orientation of the wave front and the extra plane of the dislocation. Numerical estimates are made for four different configurations. The results obtained can be useful in studying the propagation of soliton-type waves in defect crystals of various compositions.
Magnetic drive micro/nanomotor model
Authors: Martynov S I , Tkach L Y
Published: December 2021

A model of a micro-/nanomotor with a hydrodynamic mechanism of motion due to the action of a rotating uniform external magnetic field is proposed. Micro-/nanomotor - is a chain of three charged particles, one of which has a magnetic moment. The total charge of the system is zero. In the absence of an external field, the particles are in equilibrium due to the action of the forces of attraction and repulsion, which corresponds to the minimum interaction energy. After applying a rotating magnetic field, a particle with a magnetic moment begins to rotate, forming a flow in the surrounding viscous fluid. The flow induces a hydrodynamic force that moves the chain in a specific direction. The forces of hydrodynamic interaction of particles with each other are taken into account, as well as internal forces holding the particles together. The dynamics of six model aggregates with one rotating particle is simulated numerically. The proposed mechanism for moving the chain can be used in the design of micro-/nanomotors and control them to deliver the payload.
The deceleration of small charged bodies in a rarefied plasma
Authors: Gunko Yu F , Gunko N A
Published: December 2021

The purpose of this work is to create a method for determining the aerodynamic characteristics of fine particles in a highly rarefied plasma. The created method is based on the theorem on the change in momentum imparted to the body. The “body+surrounding plasma” system was considered to be closed; therefore, the change in the momentum of the body is equal in the impulse of the incident flow and is opposite to it in direction. The change in the pulse flux is calculated using the statistical method. To compare the results and approbation of the calculation method, the deceleration forces of a spherical body in a flow of neutral gas were determined. Next, we calculated the drag coefficient from the side of the charged plasma component. The calculation results are presented in the graphs.
Study of Ga2O3 deposition by MOCVD
Authors: Lundin W V , Rodin S N , Sakharov A V , Yagovkina M A , Smirnov A N , Eliseyev I A , Davydov V Yu , Tsatsulnikov A F
Published: December 2021

Growth of Ga2O3 by metalorganic chemical vapour deposition in horizontal flow reactor from trimethylgallium (TMG) and oxygen is studied in a wide temperature range. The growth rate is directly proportional to TMG flow, weakly affected by O2 flow and non-monotonically depends on temperature. Growth rate over 3 μm/h is demonstrated, indicating that TMG can be used for growth of β-Ga2O3 thick layers for device applications.
Structure of GaN grown from vapour phase on a seeded layer of gallium melt formed on a boron nitride ceramic substrate
Authors: Mynbaeva M G
Published: December 2021

In this study, two empirical models for the growth of millimetre–thick GaN material with either highly ordered textured or polycrystalline structure on a ceramic substrate by Hydride Vapour Phase Epitaxy (HVPE) are considered. It is suggested that the specific type of the structure of GaN is determined at the nucleation stage and depends on the character of the wetting of the surface of the substrate by the liquid gallium melt.
Cyanate Ester Resin/Silica subnanocomposites and their superiority over nanocomposites due to fundamental role of constrained interfacial dynamics
Authors: Bershtein V A , Fainleib A M , Kirilenko D A , Yakushev P N
Published: December 2021

The study of nanostructure, thermal and relaxation properties (by HAADF-STEM, EDXS, DMA and DSC), combined with the calculations of interparticle distances and interfacial areas, has been performed for a series of the hybrid Cyanate Ester Resin (CER)/Si02 polymer composites with 0.01 to 10 wt.% Si02 units introduced via a sol-gel process. The absence of clusterization, arising only subnanometric Si02 nodes and their quasi-regular distribution within the amorphous matrix, with the shortest distances between nodes, provided their exceptional positive impact on the matrix properties at ultra-low Si02 contents of 0.03-0.1 wt.%. The superiority of these subnanocomposites over the nanocomposites was determined by the role of constrained interfacial dynamics over the whole matrix.
The study of the charge relaxation kinetics in polyethylene with nanofillers
Authors: Pavlov A A , Kamalov A M , Borisova M E , Greshnyakov G V , Vaganov G V
Published: December 2021

The work focuses on the study of the charge relaxation kinetics in composite materials based on polyethylene. Time dependences of the electretic potential differences for samples with different mass values of the filler, as well as dependences of conductivity from the mass percentage of the filler, were achieved. The conductivity curves were analyzed according to the modern theory of intrinsic conductivity.
Study of optical and luminescent properties of the epitaxial garnet films doped with Ce3+
Authors: Vasil’eva N V , Spassky D A , Kurosawa Sh , Omelkov S I , Kochurikhin V V , Vasil’ev D A
Published: December 2021

Ce-doped (Pb, Gd)3(Al, Ga)5O12 and Ce-doped (Bi, Gd)3(Al, Ga)5O12 single crystalline garnet films were grown using liquid-phase epitaxy method from supercooled PbO–B2O3- and Bi2O3–B2O3-based melt solutions on substrates from Gd3Ga5O12, Gd3(Al, Ga)5O12 and Y3Ga5O12 single crystals. Optical absorption, photo- and cathodoluminescent and scintillation properties of the films were studied. Ce-doped (Pb,Gd)3(Al, Ga)5O12 and Ce-doped (Bi, Gd)3(Al, Ga)5O12 garnet films can be used as a fast phosphor and scintillation screens.
Composition modulation in the GaxIni-xPyAs1-y - InP heterostructure during spinodal decomposition under the conditions of internal energy resonance
Authors: Kuznetsov V V , Moskvin P P , Skurativskyi S I
Published: December 2021

The Cahn-Hilliard concepts are generalized and used to the description of the spinodal decomposition of A3B5 quaternary semiconductor solid solutions, when the mixing of components occurs simultaneously in the metallic and metalloid sublattices of the sphalerite structure. The resulting system of differential equations for material decomposition was used to describe the effect of composition modulation observed in the synthesis of GaxIn1-xPyAs1-y - InP heterostructures. Numerical simulation of the spinodal decomposition of the GaxIm-xPyAsuy solid solution is carried out. The intervals of the thermodynamic parameters of the technological process of the synthesis of structures, in which the effect of modulation of the composition should be manifested, are found.
Study of nonlinear optical phenomena in silicone films encapsulated with SiO2 and Si/SiO2 spherical particles
Authors: Mastalieva V , Nikolaeva A , Neplokh V , Eurov D , Makarov S , Kurdyukov D , Stovpiaga E , Golubev V , Mukhin I
Published: December 2021

Infrared converters to visible range are in demand for creation of optoelectronic devices, infrared visualizers and other non-linear optical devices. In this work we study nonlinear optical properties of monodisperse SiO2 and Si/SiO2 spheres encapsulated into silicone films. The fabricated silicone films containing SiO2 spheres demonstrated a bright third harmonic generation signal, and films with Si/SiO2 spheres demonstrated a significant second harmonic generation signal in the whole visible range. The developed materials and methods provide a platform for future infrared to visible converters based on silicon.
Aluminum diffusion during laser-stimulated crystallization of thin silicon films
Authors: Solodovnikova S O , Volkovoynova L D , Serdobintsev A A , Starodubov A V , Kozhevnikov I O , Pavlov AM
Published: December 2021

Diffusion of aluminum in amorphous silicon films during crystallization through infrared laser irradiation was studied. Diffusion regime was found to change from limited source to abundant source diffusion at higher laser source power. At the same time, crystalline structure of the obtained samples becomes more perfect, which is more characteristic to limited source diffusion mode.
New sorbents for electrochromatography based on polymer-inorganic dielectric composites
Authors: Shmykov A Y , Mjakin S V , Bubis N A , Kuztetzov L M , Esikova N A , Fedorov A A , Kurochkin V E
Published: December 2021

Oligomeric diisocyanate based coatings with different contents of barium titanate (BaTiO3) submicron sized particles as a ferroelectric filler are synthesized on poly(dimethylsiloxane) (PDMS) supports. The study of thus obtained coatings using confocal scanning electron microscopy allowed the characterization of their morphology and features of BaTiO3 particles distribution in the polymer binder, including the determination of threshold filler contents corresponding to the formation of an infinite cluster, matrix-island and chain-like structures as well as the percolation. Dielectric permittivity and dielectric losses of the composites are measured and studied depending on BaTiO3 filler content and relating structural features.
Charged pion, kaon, proton and antiproton production in large collision systems
Authors: Larionova D M , Berdnikov A Ya , Berdnikov Ya A , Kotov D O , Mitrankov Iu M
Published: December 2021

The main goal of PHENIX expirement, located at Relativistic Heavy-ion collider, is the investigation of quark-gluon plasma (QGP). One of the aspects of the QGP study is describing the process of its hadronization. Very important contribution to understanding of hadronization process was given by discovering of anomaly large ratio of protons production to pions production (ρ/π) in Au+Au collisions in comparison to the same ratio in proton-proton collisions. This effect was called baryon puzzle and was explained in a frame of recombination model of hadronization.

Although charged hadrons production has been previously studied in elementary proton-proton collisions and symmetric Au+Au collisions, it has never been investigated before in the large asymmetric collisions systems (such as Cu+Au) or the collisions of large deformed nuclei (U+U). The study of such large collisions systems allows to study features of baryon and meson production versus collision geometry and system size.
Production of the isotope copper-64 by using natural nickel target with proton energy 17 MeV and beam current 10 μA at cyclotron
Authors: Tiba A , Berdnikov Ya A , Egorov Yu A
Published: December 2021

A calculation method is developed for production of the copper-64 isotope from the 64Ni(p, n)64Cu nuclear reaction. The 64Cu radioisotope used in nuclear medicine is produced by irradiating a natural nickel target with a proton beam produced on a cyclotron. The conditions of the production were dictated by the capabilities of the cyclotron. The energy of the protons was 17 MeV (the beam current is 10 μॅ). As a result, the activity of copper-64 isotope for various irradiation times were obtained. The depth of proton penetration into the target material was studied.
Laue diffraction of X-ray microbeams by multilayers
Authors: Punegov V I
Published: December 2021

Laue diffraction theory of X-ray microbeams in multilayers (MLs) is developed. The solution for calculating X-ray reciprocal space maps is obtained. The pendulum (Pendellösung) effect for perfect and imperfect MLs is shown. The numerical simulation of Laue diffraction in Mo/Si multilayers with boundary conditions in the case of geometrical optics and the Fresnel approximation is carried out. It is shown that for X-ray microbeams one should to take into account the diffraction of X-ray waves at the edges of slits (collimators) of the diffraction scheme.
Analysis of the sharpness of interfaces in short-period GaN/AlN superlattices using Raman spectroscopy data
Authors: Davydov Yu V , Roginskii E M , Kitaev Yu E , Smirnov A N , Eliseyev I A , Rodin S N , Zavarin E E , Lundin W V , Nechaev D V , Jmerik V N , Smirnov M B
Published: December 2021

The results of joint theoretical and experimental studies aimed at revealing features in the Raman spectra, which can be used for evaluation of the interface quality between GaN and AlN layers in short-period GaN/AlN superlattices (SLs) are presented. The Raman spectra for SLs with sharp interface and with different degree of interface diffusion are simulated by ab initio calculations and within the framework of random-element isodisplacement model, respectively. The comparison of the results of theoretical calculations and experimental data obtained on PA MBE and MOVPE grown SLs, leads to conclusion that the spectral region of the A1(LO) confined phonons is very sensitive to the degree of interface sharpness. As a result of comprehensive studies, the correlations between the parameters of the A1(LO) confined phonons and the structure of SLs are obtained. The results of the complex studies can be used to optimize the parameters of the growth process in order to form structurally perfect short-period GaN/AlN SLs.