Induced magnetic field in accretion disks around neutron stars

There are X-ray pulsating sources that are explained by accretion from disks around neutron stars. Such disks deserve a detailed analysis. In particular, the dipole magnetic field of the central star may penetrate the disk, giving rise to an induced magnetic field inside the disk due to the frozen-in condition. The growth of the induced field can be limited by the turbulent diffusion. In the present work, I calculate the induced field in this case. The problem is reduced to the induction equation to which I have found an analytical solution describing radial and vertical structures of the induced field. The radial structure is close to the earlier predicted dependence on the difference in angular velocities between the magnetosphere and disk, $b \propto \Omega_{\rm s} - \Omega_{\rm k}$, while the vertical structure of an induced field is close to the linear dependence on the altitude above the equator, $b \propto z$. The possibility of the existence of non-stationary quasi-periodic components of the induced field is discussed.Comment: 8 pages, 3 figures, accepted to Astronomy Letters, proceedings of Physics of Neutron Stars conference (10-14 July 2023, Saint Petersburg, Russia), translation by the autho

Effective lining of tunnel kiln cars made of aluminosilicate ceramoconcrete

Aluminosilicate ceramoconcrete lining for cars used in ceramic plant firing kilns was developed and introduced. The first cars with this lining have already operated for more than 50 cyclesyesBelgorod State Universit

Nonlinear evolution of short-wavelength torsional Alfvén waves

We analyze nonlinear evolution of torsional Alfvén waves in a straight magnetic flux tube filled in with a low-β plasma, and surrounded with a plasma of lower density. Such magnetic tubes model, in particular, a segment of a coronal loop or a polar plume. The wavelength is taken comparable to the tube radius. We perform a numerical simulation of the wave propagation using ideal magnetohydrodynamics. We find that a torsional wave nonlinearly induces three kinds of compressive flows: the parallel flow at the Alfvén speed, which constitutes a bulk plasma motion along the magnetic field, the tube wave, and also transverse flows in the radial direction, associated with sausage fast magnetoacoustic modes. In addition, the nonlinear torsional wave steepens and its propagation speed increases. The latter effect leads to the progressive distortion of the torsional wave front, i.e., nonlinear phase mixing. Because of the intrinsic non-uniformity of the torsional wave amplitude across the tube radius, the nonlinear effects are more pronounced in regions with higher wave amplitudes. They are always absent at the axes of the flux tube. In the case of a linear radial profile of the wave amplitude, the nonlinear effects are localized in an annulus region near the tube boundary. Thus, the parallel compressive flows driven by torsional Alfvén waves in the solar and stellar coronae, are essentially non-uniform in the perpendicular direction. The presence of additional sinks for the wave energy reduces the efficiency of the nonlinear parallel cascade in torsional Alfvén waves

Off-limb EUV observations of the solar corona and transients with the CORONAS-F/SPIRIT telescope-coronagraph

The SPIRIT telescope aboard the CORONAS-F satellite (in orbit from 26 July 2001 to 5 December 2005), observed the off-limb solar corona in the 175 Å (Fe IX, X and XI lines) and 304 Å (He II and Si XI lines) bands. In the coronagraphic mode the mirror was tilted to image the corona at the distance of 1.1...5 <I>R</I><sub>sun</sub> from the solar center, the outer occulter blocked the disk radiation and the detector sensitivity was enhanced. This intermediate region between the fields of view of ordinary extreme-ultraviolet (EUV) telescopes and most of the white-light (WL) coronagraphs is responsible for forming the streamer belt, acceleration of ejected matter and emergence of slow and fast solar wind. We present here the results of continuous coronagraphic EUV observations of the solar corona carried out during two weeks in June and December 2002. The images showed a "diffuse" (unresolved) component of the corona seen in both bands, and non-radial, ray-like structures seen only in the 175 Å band, which can be associated with a streamer base. The correlations between latitudinal distributions of the EUV brightness in the corona and at the limb were found to be high in 304 Å at all distances and in 175 Å only below 1.5 <I>R</I><sub>sun</sub>. The temporal correlation of the coronal brightness along the west radial line, with the brightness at the underlying limb region was significant in both bands, independent of the distance. On 2 February 2003 SPIRIT observed an expansion of a transient associated with a prominence eruption seen only in the 304 Å band. The SPIRIT data have been compared with the corresponding data of the SOHO LASCO, EIT and UVCS instruments

Поражение суставов и позвоночника у б ольных с воспалительными заболеваниями кишечника

The paper reviews literature on locomotor apparatus injury in inflammatory bowel disease (IBD). It describes the types of joint and spinal column involvement in ulcerative colitis (UC) and Crohn’s disease (CD). The ratio of onset to the activity of IBD and articular syndrome is estimated. The most common type of articular syndrome is peripheral arthritis that involves mainly the knee and ankle joints and that is associated with IBD activity in most cases. Unlike peripheral arthritis, the course of axial spondyloarthritis manifesting as isolated sacroiliitis and ankylosing spondylitis (AS) is unrelated to IBD activity. There is evidence on isolated sacroiliitis that is rather common asymptomatic, that is diagnosed late, and that is a finding in a number of patients during examination. The paper provides the clinical and instrumental characteristics of AS in IBDand points to the similarity of their clinical manifestations and radiographic changes with those in idiopathic AS. It also describes the picture of enthesitis with emphasis on the systemic extra-articular manifestations of IBD, which are associated with articular syndrome (erythema nodosum and uveitis) in a number of cases. Radiographic changes in peripheral joints and spinal column are characterized in different types of locomotor apparatus injury in patients with IBD. There are data available in the literature on the treatment of articular syndrome in patients with UC and CD. It is noted that there is a need for a differentiated approach to treating peripheral arthritis and axial skeleton involvement; the role of nonsteroidal anti-inflammatory drugs, sulfasalazine, and biological agents in the treatment of articular syndrome in IBD is assessed. It is indicated that IBD patients having rheumatic manifestations should be followed up jointly by a gastroenterologist and a rheumatologist.Представлен обзор литературы, посвященной поражению опорно-двигательного аппарата при воспалительных заболеваниях кишечника (ВЗК). Описаны варианты поражения суставов и позвоночника при язвенном колите (ЯК) и болезни Крона (БК). Дана оценка соотношения дебюта и активности ВЗК и суставного синдрома. Наиболее частым вариантом суставного синдрома оказался периферический артрит, протекавший с вовлечением преимущественно коленных и голеностопных суставов, в большинстве случаев связанный с активностью ВЗК. В отличие от периферического артрита течение аксиального спондилоартрита, представленного изолированным сакроилиитом и анкилозирующим спондилитом (АС), не зависело от активности ВЗК. Приведены данные об изолированном сакроилиите, который нередко протекает бессимптомно, поздно диагностируется и у ряда больных является находкой при обследовании. Дана клинико-инструментальная характеристика АС при ВЗК, отмечена схожесть клинических проявлений и рентгенологических изменений с таковыми при идиопатическом АС. Описана картина энтезита, уделено внимание системным внесуставным проявлениям ВЗК, в ряде случаев ассоциированным с суставным синдромом (узловатая эритема и увеит). Охарактеризованы рентгенологические изменения периферических суставов и позвоночника при различных вариантах поражения опорно-двигательного аппарата у больных с ВЗК. Приведены данные литературы, касающиеся лечения суставного синдрома у больных ЯК и БК. Отмечена необходимость дифференцированного подхода к лечению периферического артрита и поражения аксиального скелета, оценена роль нестероидных противовоспалительных препаратов, сульфасалазина, генно-инженерных биологических препаратов в лечении суставного синдрома при ВЗК. Указано, что пациентов с ВЗК, имеющих ревматологические проявления, должны наблюдать совместно гастроэнтеролог и ревматолог

Low-cement refractory concretes of aluminum silicate composition based on submicron aluminum oxide grade NK-Alumina 14

Properties are provided for submicron aluminum oxide developed in SAO PKF NK for low-cement refractory concretes, and also for the LCRC of aluminosilicate composition obtained. It is demonstrated that the properties of concretes prepared on the basis of the alumina developed are no worse than domestic and imported analog

Production of fine-ground NK-alumina 11 and NK-alumina 14 for low-cement refractory castables

This article characterizes fine-ground NK-Alumina 11 and NK-Alumina 14 developed in PKF "NK" for low-cement refractory castables. The quality indicators of the developed aluminas are not inferior to international analog

APPLICATION FEATURES OF FUZZY CONTROLLERS ON EXAMPLE OF DC MOTOR SPEED CONTROL

A prerequisite for the use of intelligent control methods, including algorithms of fuzzy logic, is increasing complexity in all industries, especially when parameters of technical systems while in operation vary in wide range. The paper provides comparative analysis of the basic types of common fuzzy direct action controllers on the example of speed control system in the DC motor drive. Design features of these types of fuzzy controllers are shown. Their comparison with traditional PI controller is carried out through the use of simulation, including the conditions of uncertainty expressed in changing of equivalent moment of inertia of the motor shaft. As a result, the conclusion about the feasibility of fuzzy PID-type controller application is made. The features of fuzzy controllers outlined in the paper can be summarized to more complex motor drive systems and to other non-linear systems that require the maintenance of any parameter within a given range

Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT

This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. Since 1998, digital receivers performing on-the-fly dynamic spectrum calculations or waveform data recording without data loss have been used at the UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio telescope. Here we detail these receivers developed for operation in the strong interference environment that prevails in the decameter wavelength range. Data collected with these receivers allowed us to discover numerous radio astronomical objects and phenomena at low frequencies, a summary of which is also presented.Comment: 24 pages, 15 figure