Competitive 0 and {\pi} states in S/F multilayers: multimode approach

We have investigated the critical temperature behavior in periodic superconductor/ ferromagnet (S/F) multilayers as a function of the ferromagnetic layer thickness $d_f$ and the interface transparency. The critical temperature $T_c(d_f)$ exhibits a damped oscillatory behavior in these systems due to an exchange field in the ferromagnetic material. In this work we have performed $T_c$ calculations using the self-consistent multimode approach, which is considered to be exact solving method. Using this approach we have derived the conditions of 0 or $\pi$ state realization in periodic S/F multilayers. Moreover, we have presented the comparison between the single-mode and multimode approaches and established the limits of applicability of the single-mode approximation, frequently used by experimentalists

A New Numerical Procedure for Determination of Effective Elastic Constants in Unidirectional Composite Plates

In this paper a composite plate with similar unidirectional fibers is considered. Assuming orthotropic structure, theory of elasticity is used for investigating the stress concentration. Also, complex variable functions are utilized for solving the plane stress problems. Then the effective characteristics of this plate are studied numerically by using ANSYS software. In this research a volume element of fibers in square array is considered. In order to investigate the numerical finite element modeling, the modeling of a quarter unit cell is considered. For determining the elasticity coefficients, stress analysis is performed for considered volume with noting to boundary conditions. Effective elasticity and mechanical properties of composite which polymer epoxy is considered as its matrix, are determined theoretically and also by the proposed method in this paper with finite element method. Finally, the variations of mechanical properties with respect to fiber-volume fraction are studied

Differential approximation for Kelvin-wave turbulence

I present a nonlinear differential equation model (DAM) for the spectrum of Kelvin waves on a thin vortex filament. This model preserves the original scaling of the six-wave kinetic equation, its direct and inverse cascade solutions, as well as the thermodynamic equilibrium spectra. Further, I extend DAM to include the effect of sound radiation by Kelvin waves. I show that, because of the phonon radiation, the turbulence spectrum ends at a maximum frequency $\omega^* \sim (\epsilon^3 c_s^{20} / \kappa^{16})^{1/13}$ where $\epsilon$ is the total energy injection rate, $c_s$ is the speed of sound and $\kappa$ is the quantum of circulation.Comment: Prepared of publication in JETP Letter

Does nitrate reductase play a key role in photoinduction of carotenoid synthesis in Neurospora crassa?

Does nitrate reductase play a key role in photoinduction of caroteniod synthesis in Neurospora crassa

Biexciton oscillator strength

Our goal is to provide a physical understanding of the elementary coupling between photon and biexciton and to derive the physical characteristics of the biexciton oscillator strength, following the procedure we used for trion. Instead of the more standard two-photon absorption, this work concentrates on molecular biexciton created by photon absorption in an exciton gas. We first determine the appropriate set of coordinates in real and momentum spaces to describe one biexciton as two interacting excitons. We then turn to second quantization and introduce the "Fourier transform in the exciton sense" of the biexciton wave function which is the relevant quantity for oscillator strength. We find that, like for trion, the oscillator strength for the formation of one biexciton out of one photon plus a \emph{single} exciton is extremely small: it is one biexciton volume divided by one sample volume smaller than the exciton oscillator strength. However, due to their quantum nature, trion and biexciton have absorption lines which behave quite differently. Electrons and trions are fermionic particles impossible to pile up all at the same energy. This would make the weak trion line spread with electron density, the peak structure only coming from singular many-body effects. By contrast, the bosonic nature of exciton and biexciton makes the biexciton peak mainly rise with exciton density, this rise being simply linear if we forget many-body effects between the photocreated exciton and the excitons present in the sample

Features of Mathematical Training of Programmers to Kherson State University

Вопросу подготовки программистов посвящены многочисленные научные дискуссии и исследования, так как на эту проблему существуют диаметрально противоположные точки зрения. В статье анализируются учебные планы подготовки программистов в Украине. Рассматриваются основные стандарты математической подготовки по специальностям «Компьютерные науки и информационные технологии» и «Инженерия программного обеспечения». Исследуется мотивация студентов к обучению математике. Программист по роду своей деятельности должен уметь строить модель программного продукта, для чего ему необходимы знания, умения, навыки анализа и синтеза широкого диапазона алгоритмов, структур и математических методов, а также выбора адекватных исследованиям методов, средств и технологий. Подготовка программистов в ХГУ ориентирована не только на решение задач определенной предметной области, но и на готовность к самостоятельному приобретению новых знаний и опыта в разных сферах человеческой деятельности, где внедрены информационные технологии.Question of programmers dedicated to numerous scientific debate and research, as this problem there are diametrically opposing views. The article analyzes the educational programmers training plans in Ukraine. The basic standards for mathematical training in the field of "Computer Science and Information Technology" and "Software Engineering". We investigate the motivation of students to learn mathematics. Programmer course of their work should be able to build a model of a software product for which it requires the knowledge, skills, skills of analysis and synthesis of a wide range of algorithms, mathematical methods and structures, as well as the choice of adequate research methods, tools and technologies. Training of KSU is focused not only on the tasks a particular subject area, but also on the willingness of independent acquisition of new knowledge and experience in different spheres of human activity, where information technologies are introduced

Phase diagrams of the diode effect in superconducting heterostructures

At present the superconducting diode effect (SDE) attracts a lot of attention due to new possibilities in the superconducting electronics. One of the possible realizations of the SDE is the implementation in superconducting hybrid structures. In this case the SDE is achieved by means of the proximity effect. However, the optimal conditions for the SDE quality factor in hybrid devices remain unclear. In this study we consider the Superconductor/Ferromagnet/Topological insulator (S/F/TI) hybrid device and investigate the diode quality factor at different parameters of the hybrid structure. Consequently, we reveal important parameters that have crucial impact on the magnitude of the SDE quality factor.</p