On possible reasons of positive near-anode voltage drop in high-current vacuum arc

In this paper we consider some reasons for the occurrence of a positive near-anode potential drop during current constriction in high-current vacuum arc. It is shown that if the radius of constriction is much larger than the electron mean free path, then a positive voltage drop in the near-anode plasma sheath does not occur, but an additional drop may occur in the near-anode plasma layer due to the anomalous resistance. If the current constriction radius is much less than the electron mean free path, then a positive voltage drop in the sheath arises under the usual condition, and the kinetic instabilities in the near-anode plasma do not develop. © 2019 IOP Publishing Ltd. All rights reserved.Russian Foundation for Basic Research, RFBR: 17-02-00346, 18-08-00547Russian Academy of Sciences, RASNational Natural Science Foundation of China, NSFC: 5191153011318-2-2-16This work was supported in part by RFBR(grant Nos. 17-02-00346, 18-08-00547, 19-08-00783, 19-58-53006), by RAS Program (project No. 11) and UB RAS Program (project No. 18-2-2-16), as well as by National Natural Science Foundation of China (project No. 51911530113)

A transverse current rectification in graphene superlattice

A model for energy spectrum of superlattice on the base of graphene placed on the striped dielectric substrate is proposed. A direct current component which appears in that structure perpendicularly to pulling electric field under the influence of elliptically polarized electromagnetic wave was derived. A transverse current density dependence on pulling field magnitude and on magnitude of component of elliptically polarized wave directed along the axis of a superlattice is analyzed.Comment: 12 pages, 6 figure

Результаты длительного лечения бронходилататорами короткого действия больных хронической обструктивной болезнью легких (ХОБЛ) и ХОБЛ в сочетании с бронхиальной астмой

This study was designed to investigate long term treatment effects of short acting bronchodilators on respiratory symptoms, lung function, and the mean pulmonary artery pressure (mPAP) in patients with chronic obstructive pulmonary disease (COPD) and COPD combined with asthma (COPD + BA). The study involved 14 COPD patients and 16 COPD+BA patients, males and females (the average age, 60 yrs) with moderate to severe disease and the mPAP higher than 20 mm Hg. Clinical examination with scoring of cough, sputum, dyspnea, and lung auscultation signs; spirometry, ECG, echocardiography, chest X ray, and blood analysis were used. Clinical status and lung function were evaluated primarily and in 4, 12, and 24 wks; the mPAP was measured initially and in 12 and 24 wks. Before the study no one patient received persistent supporting therapy with bronchodilators, 15 COPD + BA patients and 7 COPD patients were given inhaled steroids. Persistent therapy of all the patients with Berodual 2 doses 4 times daily for 24 wks resulted in improvement in the clinical symptoms and lung function parameters, reduction in mPAP in both the groups but the results were better and they were reached faster in the patients with combined pathology. Thus, the regularly combined therapy with short acting β2 agonists and anticholinergics (Berodual) can be included in the algorithm of therapy of pulmonary hypertension in patients with COPD and COPD + BA.Целью настоящего исследования было изучение влияния бронхорасширяющих препаратов короткого действия на респираторную симптоматику, функцию внешнего дыхания и среднее давление в легочной артерии у больных хронической обструктивной болезнью легких (ХОБЛ) и ХОБЛ в сочетании с бронхиальной астмой (БА) при длительном применении. В исследование были включены 14 больных ХОБЛ и 16 больных ХОБЛ + БА (средний возраст — 60 лет, мужчины и женщины со средней и тяжелой стадиями заболевания и повышением среднего давления в легочной артерии > 20 мм рт. ст.) Применялись клиническое обследование больных, спирометрия, электрокардиография и эхокардиография, рентгенография легких, лабораторные исследования крови. Физикальное обследование и ФВД проводились исходно, через 4, 12 и 24 нед., среднее давление в легочной артерии определялось исходно, через 12 нед. и 24 нед. Клинические признаки (наличие и выраженность кашля, мокроты, одышки, аускультативная легочная симптоматика) оценивались в баллах. До включения в исследование больные не получали постоянной поддерживающей терапии бронходилататорами, 15 больных ХОБЛ + БА и 7 больных ХОБЛ получали ингаляционные кортикостероиды. Пациентам назначалась постоянная поддерживающая терапия Беродуалом по 2 дозы 4 раза в день в течение 24 нед. Результаты показали, что регулярная комбинированная бронходилатационная терапия Беродуалом больных ХОБЛ и ХОБЛ + БА приводит к уменьшению респираторной симптоматики, среднего давления в легочной артерии, улучшению показателей ФВД, однако при сочетанной патологии это происходит быстрее и в большей степени. Регулярная комбинированная бронходилатационная терапия β2 агонистами короткого действия и антихолинергическими препаратами короткого действия (Беродуалом) может быть включена в алгоритм лечения ЛГ у больных ХОБЛ и ХОБЛ + БА

Reorganization of a 2D disordered granular medium due to a small local cyclic perturbation

We measure experimentally the rearrangements due to a small localized cyclic displacement applied to a packing of rigid grains under gravity in a 2D geometry. We analyze the evolution of the response to this perturbation by considering the individual particle displacement and the coarse grained displacement field, as well as the mean packing fraction and coordination number. We find that the displacement response is rather long ranged, and evolves considerably with the number of cycles. We show that a small difference in the preparation method (induced by tapping the container) leads to a significant modification in the response though the packing fraction changes are minute. Not only the initial response but also its further evolution change with preparation, demonstrating that the system still retains a memory of the initial preparation after many cycles. Nevertheless, after a sufficient number of cycles, the displacement response for both preparation methods converges to a nearly radial field with a 1/r decay from the perturbation source. The observed differences between the preparation methods seem to be related to the changes in the coordination number (which is more sensitive to the evolution of the packing than the packing fraction). Specifically, it may be understood as an effect of the breaking of local arches, which affects the lateral transmission of forces.Comment: 13 pages, revised and resubmitted to J. Stat. Mech.: Theory and Exp. (JSTAT

MYCOBACTERIOSIS IN THE PRACTICE OF PULMONOLOGISTS AND PHTHISIOLOGISTS

Goal of the study: to investigate the frequency of mycobacteriosis in the practice of pulmonologists and phthisiologists.Materials and methods. The analysis included medical files of 156 patients with various non-specific respiratory diseases and tuberculosis who were examined in 2011-2014 and non-tuberculous mycobacteria were found in their sputum.Results of the study. pulmonary mycobacteriosis was diagnosed in 93 (59.6%) patients out of 156 who corresponded the criteria of American Thoracic Society and etiotropic treatment was prescribed. While detection of non-tuberculous mycobacteria in the other patients was considered as innidiation of respiratory tract by those mycobacteria in case of chronic non-specific pulmonary disease and/or tuberculosis. Mycobacterioses were treated with the relevance to drug susceptibility of the causative agent and there were numerous obstacles due to high frequency of adverse reactions

Self-induced and induced transparencies of two-dimensional and three- dimensional superlattices

The phenomenon of transparency in two-dimensional and three-dimensional superlattices is analyzed on the basis of the Boltzmann equation with a collision term encompassing three distinct scattering mechanisms (elastic, inelastic and electron-electron) in terms of three corresponding distinct relaxation times. On this basis, we show that electron heating in the plane perpendicular to the current direction drastically changes the conditions for the occurrence of self-induced transparency in the superlattice. In particular, it leads to an additional modulation of the current amplitudes excited by an applied biharmonic electric field with harmonic components polarized in orthogonal directions. Furthermore, we show that self-induced transparency and dynamic localization are different phenomena with different physical origins, displaced in time from each other, and, in general, they arise at different electric fields.Comment: to appear in Physical Review