Bloch-Wall Phase Transition in the Spherical Model

The temperature-induced second-order phase transition from Bloch to linear (Ising-like) domain walls in uniaxial ferromagnets is investigated for the model of D-component classical spin vectors in the limit D \to \infty. This exactly soluble model is equivalent to the standard spherical model in the homogeneous case, but deviates from it and is free from unphysical behavior in a general inhomogeneous situation. It is shown that the thermal fluctuations of the transverse magnetization in the wall (the Bloch-wall order parameter) result in the diminishing of the wall transition temperature T_B in comparison to its mean-field value, thus favouring the existence of linear walls. For finite values of T_B an additional anisotropy in the basis plane x,y is required; in purely uniaxial ferromagnets a domain wall behaves like a 2-dimensional system with a continuous spin symmetry and does not order into the Bloch one.Comment: 16 pages, 2 figure

Field Dependence of the Electron Spin Relaxation in Quantum Dots

Interaction of the electron spin with local elastic twists due to transverse phonons has been studied. Universal dependence of the spin relaxation rate on the strength and direction of the magnetic field has been obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid. The theory contains no unknown parameters and it can be easily tested in experiment. At high magnetic field it provides parameter-free lower bound on the electron spin relaxation in quantum dots.Comment: 4 PR pages, no figure

Thermal history of diamond from Arkhangelskaya and Karpinsky-I kimberlite pipes

This work studies and compares the main morphological, structural, and mineralogical features of 350 diamond crystals from the Karpinsky-I and 300 crystals of the Arkhangelskaya kimberlite pipes. The share of crystals of octahedral habit together with individual crystals of transitional forms with sheaf-like and splintery striation is higher in the Arkhangelskaya pipe and makes 15 %. The share of cuboids and tetrahexahedroids is higher in the Karpinsky-I pipe and stands at 14 %. The share of dodecahedroids in the Arkhangelskaya and Karpinsky-I pipes are 60 % and 50 %, respectively. The indicator role of the nitrogen-vacancy N3 center active in absorption and luminescence is shown. Crystals with the N3 absorption system have predominantly octahedral habit or dissolution forms derived from the octahedra. Their thermal history is the most complex. Absorption bands of the lowest-temperature hydrogen-containing defects (3050, 3144, 3154, 3188, 3310 cm−1, 1388, 1407, 1432, 1456, 1465, 1503, 1551, 1563 cm−1), are typical for crystals without N3 system, where in the absorption spectra nitrogen is in the form of low-temperature A and C defects. The above mentioned bands are registered in the spectra of 16 % and 42 % of crystals from the Arkhangelskaya and Karpinsky-I pipes, respectively. The diamond of the studied deposits is unique in the minimum temperature (duration) of natural annealing. Based on a set of features, three populations of crystals were distinguished, differing in growth conditions, post-growth, and thermal histories. The established regularities prove the multi-stage formation of diamond deposits in the north of the East European Platform and significant differences from the diamonds of the Western Cisurals. The results suggest the possibility of the existence of primary deposits dominated by diamonds from one of the identified populations

Magnetic relaxation in finite two-dimensional nanoparticle ensembles

We study the slow phase of thermally activated magnetic relaxation in finite two-dimensional ensembles of dipolar interacting ferromagnetic nanoparticles whose easy axes of magnetization are perpendicular to the distribution plane. We develop a method to numerically simulate the magnetic relaxation for the case that the smallest heights of the potential barriers between the equilibrium directions of the nanoparticle magnetic moments are much larger than the thermal energy. Within this framework, we analyze in detail the role that the correlations of the nanoparticle magnetic moments and the finite size of the nanoparticle ensemble play in magnetic relaxation.Comment: 21 pages, 4 figure

Fast noise in the Landau-Zener theory

We study the influence of a fast noise on Landau-Zener transitions. We demonstrate that a fast colored noise much weaker than the conventional white noise can produce transitions itself or can change substantially the Landau-Zener transition probabilities. In the limit of fast colored or strong white noise we derive asymptotically exact formulae for transition probabilities and study the time evolution of a spin coupled to the noise and a sweeping magnetic field.Comment: 28 pages, 5 figure

СПЕКТР МУТАЦИЙ ГЕНА BRCA1 У БОЛЬНЫХ РАКОМ МОЛОЧНОЙ ЖЕЛЕЗЫ В МОЛОДОМ ВОЗРАСТЕ В РОССИИ

Aim of the study. Aim of the study was to estimate the occurrence of pathogenic mutations in the BRCA1 gene in Russian breast cancer patients.Material and methods. Complete coding sequence of the BRCA1 gene of 445 early onset  breast cancer patients (under 40 years) from Novosibirsk region (Russia) were analyzed by  targeted Next Generation Sequencing (NGS) using Ion Torrent platform. Results. Forty (9%) carriers of various pathogenic mutations were revealed. Thirty five (7,9%) patients  carried 5382insC mutation, described earlier as a founder mutation for Slavic population.  Five (1.1%) patients carried various pathogenic mutations, namely C61G, 462delCC, E143X,  4153delA, and IVS18+1G>T. Besides, 29 genetic variants with no clinical significance or with  unknown clinical significance were detected in BRCA1 gene among 445 early onset breast  cancer patients. Conclusions. Data on the frequency of genetic variations in the BRCA1 gene among early onset breast cancer patients in the Novosibirsk Region (Russia) were  obtained. Proportion of the 5382insC mutation is 87.5% of all pathogenic mutations in the BRCA1 gene found in patients.Цель исследования – оценить частоту встречаемости патогенных мутаций в BRCA1 гене у женщин с раком молочной железы, проживающих в России.Материал и методы. Проведён анализ полной кодирующей части гена BRCA1 у 445 больных раком молочной  железы на ранней стадии (возраст больных до 40 лет), проживающих в Новосибирской области (Россия), с  помощью метода таргетного секвенирования на платформе Ion Torrent. Результаты. Выявлено 40 (9 %)  носительниц различных патогенных мутаций. У 35 (7,9 %) пациенток обнаружена мутация 5382insC, описанная  ранее как «мутация-основателя» в славянской популяции. У 5 (1,1 %) пациенток были выявлены  другие различные патогенные мутации, а именно C61G, 462delCC, E143X, 4153delA и IVS18 + 1G> T. Кроме  того, 29 генетических вариантов с отсутствующей или неясной клинической значимостью были обнаружены в  гене BRCA1 у 445 больных раком молочной железы на ранней стадии. Выводы. Получены данные о частоте  генетических вариаций гена BRCA1 у больных раком молочной железы на ранней стадии, проживающих в  Новосибирской области (Россия). Доля мутации 5382insC составляет 87,5 % от всех патогенных мутаций в гене BRCA1, обнаруженных у пациенток

The ART-XC telescope on board the SRG observatory

ART-XC (Astronomical Roentgen Telescope - X-ray Concentrator) is the hard X-ray instrument with grazing incidence imaging optics on board the Spektr-Roentgen-Gamma (SRG) observatory. The SRG observatory is the flagship astrophysical mission of the Russian Federal Space Program, which was successively launched into orbit around the second Lagrangian point (L2) of the Earth-Sun system with a Proton rocket from the Baikonur cosmodrome on 13 July 2019. The ART-XC telescope will provide the first ever true imaging all-sky survey performed with grazing incidence optics in the 4-30 keV energy band and will obtain the deepest and sharpest map of the sky in the energy range of 4-12 keV. Observations performed during the early calibration and performance verification phase as well as during the on-going all-sky survey that started on 12 Dec. 2019 have demonstrated that the in-flight characteristics of the ART-XC telescope are very close to expectations based on the results of ground calibrations. Upon completion of its 4-year all-sky survey, ART-XC is expected to detect ~5000 sources (~3000 active galactic nuclei, including heavily obscured ones, several hundred clusters of galaxies, ~1000 cataclysmic variables and other Galactic sources), and to provide a high-quality map of the Galactic background emission in the 4-12 keV energy band. ART-XC is also well suited for discovering transient X-ray sources. In this paper, we describe the telescope, results of its ground calibrations, major aspects of the mission, the in-flight performance of ART-XC and first scientific results.Comment: 19 pages, 30 figures, accepted for publication in Astronomy and Astrophysic

SIRT1 Allele Frequencies in Depressed Patients of European Descent in Russia

Depressive disorder (DD) is a widespread mental disorder. Although DD is to some extent inherited, the genes contributing to the risk of this disorder and its genetic mechanisms remain poorly understood. A recent large-scale genome-wide association Chinese study revealed a strong association between the SIRT1 gene variants and DD. The aim of this study was to analyze the occurrence of heterozygote carriers and search for rare SNP variants of the SIRT1 gene in a cohort of DD patients as compared with a cohort of randomly selected members of the Russian population. The complete coding sequences of the SIRT1 gene from 1024 DNA samples from the general Russian population and from 244 samples from patients with DD were analyzed using targeted sequencing. Four new genetic variants of the SIRT1 were discovered. While no significant differences in the allele frequencies were found between the DD patients and the general population, differences between the frequencies of homozygote carriers of specific alleles and occurrences of heterozygous were found to be significant for rs2236318 (P < 0.0001), and putatively, rs7896005 (P < 0.05), and rs36107781 (P < 0.05). The study found for the first time that two new SNPs (i.e., 10:69665829 and 10:69665971) along with recently reported ones (rs773025707 and rs34701705), are putatively associated with DD. The revealed DD-associated SIRT1 SNPs might confer susceptibility to this disorder in Russian population of European descent