Electronic structure, magnetic and optical properties of intermetallic compounds R2Fe17 (R=Pr,Gd)

In this paper we report comprehensive experimental and theoretical investigation of magnetic and electronic properties of the intermetallic compounds Pr2Fe17 and Gd2Fe17. For the first time electronic structure of these two systems was probed by optical measurements in the spectral range of 0.22-15 micrometers. On top of that charge carriers parameters (plasma frequency and relaxation frequency) and optical conductivity s(w) were determined. Self-consistent spin-resolved bandstructure calculations within the conventional LSDA+U method were performed. Theoretical interpetation of the experimental s(w) dispersions indicates transitions between 3d and 4p states of Fe ions to be the biggest ones. Qualitatively the line shape of the theoretical optical conductivity coincides well with our experimental data. Calculated by LSDA+U method magnetic moments per formula unit are found to be in good agreement with observed experimental values of saturation magnetization.Comment: 16 pages, 5 figures, 1 tabl

Observation of Néel-type skyrmions in acentric self-intercalated Cr_1+δTe₂

Transition-metal dichalcogenides intercalated with 3d-transition metals within the van der Waals (vdW) gaps have been the focus of intense investigations owing to their fascinating structural and magnetic properties. At certain concentrations the intercalated atoms form ordered superstructures that exhibit ferromagnetic or anti-ferromagnetic ordering. Here we show that the self-intercalated compound Cr1+δTe2 with δ ≈ 0.3 exhibits a new, so far unseen, three-dimensionally ordered (2×2×2) superstructure. Furthermore, high resolution X-ray diffraction reveals that there is an asymmetric occupation of the two inequivalent vdW gaps in the unit cell. The structure thus lacks inversion symmetry, which, thereby, allows for chiral non-collinear magnetic nanostructures. Indeed, Néel-type skyrmions are directly observed using Lorentz transmission electron microscopy. The skyrmions are stable within the accessible temperature range (100–200 K) as well as in zero magnetic field. The diameter of the Néel skyrmions increases with lamella thickness and varies with applied magnetic field, indicating the role of long-range dipole fields. Our studies show that self-intercalation in vdW materials is a novel route to the formation of synthetic non-collinear spin textures

First-principles study of orthorhombic CdTiO3 perovskite

In this work we perform an ab-initio study of CdTiO3 perovskite in its orthorhombic phase using FLAPW method. Our calculations help to decide between the different cristallographic structures proposed for this perovskite from X-Ray measurements. We compute the electric field gradient tensor (EFG) at Cd site and obtain excellent agreement with available experimental information from a perturbed angular correlation (PAC) experiment. We study EFG under an isotropic change of volume and show that in this case the widely used "point charge model approximation" to determine EFG works quite well.Comment: 4 pages, 1 figure. Accepted in Physical Review

Determination of the copy numbers of type A porcine endogenous retroviruses in domestic pigs and wild boars

Modern transplantology is in need of transplants. To solve this problem, the use of animal organs and tissues for grafting to humans (xenografts) has been proposed. However, the progress in this direction is hampered by the risk of zoogenous infection of recipients. With regard to economic and ethical criteria and to the anatomical and physiological similarity to humans, the pig is the best source of xenografts. The pig genome harbors type A porcine endogenous retroviruses (PERV), which can infect human cell lines in vitro. A population of Siberian minipigs was raised at the Institute of Cytology and Genetics just for xenografting. The goal of the present study is to analyze the copy numbers of PERV A in Siberian minipigs, their founder breeds Landrace and Large White, and wild boars. The copy numbers of PERVs have been determined by absolute measurement with SYBR Green dye. End-point dilutions of a sample with a known copy number have been used for reference. The PERV A copy numbers in standard samples of Siberian minipig DNA are 2.4, 3.6, and 4.9 per cell, which is consistent with data obtained by other scientists. Minipigs and wild boars show a significant difference in retrovirus copy numbers. Thus, the Siberian minipig genome has a considerable number of type A PERVs, conceivably pathogenic to humans. It is necessary to select animals with minimum PERV numbers in the genome for xenografting. The method of PERV A quantitation with SYBR Green allows detection of such animals and selection of Siberian minipigs for reduction of this index

Risk factors for orthorexia nervosa in health professionals

The purpose of the study is to identify the prevalence and additional risk factors for ON in healthcare professionals.Цель исследования – выявить распространенность и дополнительные факторы риска НО у медицинских работников

Theory and computation of covariant Lyapunov vectors

Lyapunov exponents are well-known characteristic numbers that describe growth rates of perturbations applied to a trajectory of a dynamical system in different state space directions. Covariant (or characteristic) Lyapunov vectors indicate these directions. Though the concept of these vectors has been known for a long time, they became practically computable only recently due to algorithms suggested by Ginelli et al. [Phys. Rev. Lett. 99, 2007, 130601] and by Wolfe and Samelson [Tellus 59A, 2007, 355]. In view of the great interest in covariant Lyapunov vectors and their wide range of potential applications, in this article we summarize the available information related to Lyapunov vectors and provide a detailed explanation of both the theoretical basics and numerical algorithms. We introduce the notion of adjoint covariant Lyapunov vectors. The angles between these vectors and the original covariant vectors are norm-independent and can be considered as characteristic numbers. Moreover, we present and study in detail an improved approach for computing covariant Lyapunov vectors. Also we describe, how one can test for hyperbolicity of chaotic dynamics without explicitly computing covariant vectors.Comment: 21 pages, 5 figure

Влияние Кортизола в комплексе с липопротеинами очень низкой плотности на развитие гепатомы на-1 и карциномы Эрлиха

Studies were conducted using ascetic HA-1 hepatomas and ascitic Ehrlich’s carcinoma cells. After passage of cells in mice, cell culture containing tumor-associated macrophages was studied. It was shown that the very low-density lipoprotein (VLDL)-cortisol complex significantly inhibited proliferative activity of tumor cells. The obtained constant of cortisol binding to VLDL indicated that the protein component of lipoproteins participated in the complex formation. Tumor-associated macrophages were suggested to play an important role in the formation of this complex. It was found that inhibition of tumor cell growth was related to apoptosis.Исследования проводились на клетках асцитной НА-1 гепатомы и асцитной карциномы Эрлиха. После пассажа клеток на мышах выделяли смешанную культуру клеток, содержащую опухоль-ассоциированные макрофаги. Показано, что в сокультуре комплекс ЛПОНП–кортизол значительно подавлял пролиферативную активность опухолевых клеток. Полученная константа связы- вания кортизола с ЛПОНП указывает на то, что в комплексообразовании принимает участие белковый компонент липопротеинов. Предполагается, что в образовании такого комплекса важную роль играют опухоль-ассоциированные макрофаги. Обнаружено, что механизм подавления роста опухолевых клеток связан с апоптозо

A Grassmann integral equation

The present study introduces and investigates a new type of equation which is called Grassmann integral equation in analogy to integral equations studied in real analysis. A Grassmann integral equation is an equation which involves Grassmann integrations and which is to be obeyed by an unknown function over a (finite-dimensional) Grassmann algebra G_m. A particular type of Grassmann integral equations is explicitly studied for certain low-dimensional Grassmann algebras. The choice of the equation under investigation is motivated by the effective action formalism of (lattice) quantum field theory. In a very general setting, for the Grassmann algebras G_2n, n = 2,3,4, the finite-dimensional analogues of the generating functionals of the Green functions are worked out explicitly by solving a coupled system of nonlinear matrix equations. Finally, by imposing the condition G[{\bar\Psi},{\Psi}] = G_0[{\lambda\bar\Psi}, {\lambda\Psi}] + const., 0<\lambda\in R (\bar\Psi_k, \Psi_k, k=1,...,n, are the generators of the Grassmann algebra G_2n), between the finite-dimensional analogues G_0 and G of the (``classical'') action and effective action functionals, respectively, a special Grassmann integral equation is being established and solved which also is equivalent to a coupled system of nonlinear matrix equations. If \lambda \not= 1, solutions to this Grassmann integral equation exist for n=2 (and consequently, also for any even value of n, specifically, for n=4) but not for n=3. If \lambda=1, the considered Grassmann integral equation has always a solution which corresponds to a Gaussian integral, but remarkably in the case n=4 a further solution is found which corresponds to a non-Gaussian integral. The investigation sheds light on the structures to be met for Grassmann algebras G_2n with arbitrarily chosen n.Comment: 58 pages LaTeX (v2: mainly, minor updates and corrections to the reference section; v3: references [4], [17]-[21], [39], [46], [49]-[54], [61], [64], [139] added

Search for 2p Decay of the First Excited State of 17 Ne

Structure of nuclei located near and beyond the drip-lines plays important role in the explosive astrophysical processes. The problem of two-proton decay of the 17Ne first excited state is a good example of such situation. The two-proton radiative capture is a possible bypass of the 15O waiting point in the rp-process. The rate of this process drastically depends on the value of the weak