INTEGRAL and Swift observations of the hard X-ray transient MAXI J1828-249

In this paper we report on the observations performed with INTEGRAL and Swift of the first outburst detected from the hard X-ray transient MAXI J1828-249. During the first about two days of the outburst, the source was observed by MAXI to undergo a very rapid transition from a hard to a softer spectral state. While the hard state was not efficiently monitored because the transition occurred so rapidly, the evolution of the source outburst in the softer state was covered quasi-simultaneously in a broad energy range (0.6-150 keV) by the instruments on-board INTEGRAL and Swift. During these observations, the spectra measured from the source displayed both a prominent thermal emission with temperature kT 0.7 keV and a power-law hard component with a photon index gamma 2.2 extending to 200 keV. The properties of the source in the X-ray domain are reminiscent of those displayed by black hole transients during the soft intermediate state, which supports the association of MAXI J1828-249 with this class of objects.Comment: 5 pages, 5 figures, 2 tables. Accepter for publication in A&

Short-Range Order in Fe-Rich Fe-Cr Alloys as Revealed by M\"ossbauer Spectroscopy

Distribution of Cr atoms in Fe_{100-x}Cr_x alloys with x \le 25 within the first two coordination shells, 1NN-2NN, around probe 57Fe atoms was studied by means of the M\"ossbauer Spectroscopy. Clear evidence was found that the distribution is characteristic of a given atomic configuration. Only the configurations with Cr atoms situated in 2NN exhibit a quiasi-random distribution, while those with Cr atoms present in 1NN shell and those with Cr atoms in both shells is evidently not random showing clastering or anticlastering features. These findings are novel and much more complete than the up-to-date knowledge according to which there is an inversion of the short-range order parameter at x = 11. The inversion in the present study was found only for the configuration with one Cr atom in 1NN. On average, Cr atoms are distributed almost randomly within the 1NN-2NN volume for x \eq ~10, and do cluster for larger x.Comment: 4 pages and 4 figure

Relation between the X-ray and Optical Luminosities in Binary Systems with Accreting Nonmagnetic White Dwarfs

We investigate the relation between the optical (g-band) and X-ray (0.5-10 keV) luminosities of accreting nonmagnetic white dwarfs. According to the present-day counts of the populations of star systems in our Galaxy, these systems have the highest space density among the close binary systems with white dwarfs. We show that the dependence of the optical luminosity of accreting white dwarfs on their X-ray luminosity forms a fairly narrow one-parameter curve. The typical half-width of this curve does not exceed 0.2-0.3 dex in optical and X-ray luminosities, which is essentially consistent with the amplitude of the aperiodic flux variability for these objects. At X-ray luminosities Lx~1e32 erg/sec or lower, the optical g-band luminosity of the accretion flow is shown to be related to its X-ray luminosity by a factor ~2-3. At even lower X-ray luminosities (Lx~1e30 erg/sec), the contribution from the photosphere of the white dwarf begins to dominate in the optical spectrum of the binary system and its optical brightness does not drop below Mg~13-14. Using the latter fact, we show that in current and planned X-ray sky surveys, the family of accreting nonmagnetic white dwarfs can be completely identified to the distance determined by the sensitivity of an optical sky survey in this region. For the Sloan Digital Sky Survey (SDSS) with a limiting sensitivity m_g~22.5, this distance is ~400-600 pcComment: 7 pages, 3 figures, published in Astronomy Letter

On the Modified maximum Principle in Estimation Problems for Uncertain Systems

The present report is devoted to the problems of estimating the state of a linear dynamic system on the basis of on-line observation. It is assumed that the disturbances in the system inputs and in the current measurements are uncertain, a set-membership description of their values being only given in advance. A considerable number of problems concerning systems of the above type are covered by the theory of control and observation under uncertainty conditions. The main problems of this paper deal with the description of certain informational domains that are consistent with the results of available measurements of the state space variables. Here we consider the case when the disturbances in the system dynamics and in the observation equation are subjected to instantaneous (or "geometric") constraints. One approach to the problem based on an imbedding procedure of the primary problem into an auxiliary one of linear-quadratic estimation theory is given in the paper. The proposed procedure involves certain quadratic forms to bound the uncertainties in the modified problem. This method allows one to derive an appropriate maximum principle that is satisfied by system trajectories leading to boundary points of the informational domain

A Note on the Evolution Property of the Assembly of Viable Solutions to a Differential Inclusion

The paper deals with the description of the bundle of viable trajectories for a differential inclusion with phase constraints. The graph of the right-hand side of the differential inclusion is assumed to be star-shaped and characterizes the reachable set multifunction in terms of set-valued solutions to an evolution equation of special type. The author thus characterizes an important class of nonlinear systems

Exponentially convergent data assimilation algorithm for Navier-Stokes equations

The paper presents a new state estimation algorithm for a bilinear equation representing the Fourier- Galerkin (FG) approximation of the Navier-Stokes (NS) equations on a torus in R2. This state equation is subject to uncertain but bounded noise in the input (Kolmogorov forcing) and initial conditions, and its output is incomplete and contains bounded noise. The algorithm designs a time-dependent gain such that the estimation error converges to zero exponentially. The sufficient condition for the existence of the gain are formulated in the form of algebraic Riccati equations. To demonstrate the results we apply the proposed algorithm to the reconstruction a chaotic fluid flow from incomplete and noisy data

Imbalance of the Humoral Component of the Immune System as a Basis for the Progression of Non-Alcoholic Fatty Liver Disease in Patients with Obesity and Concomitant Biliary Tract Pathology

The objective of the research was to study the features of the indicators of the humoral component of the immune system depending on the body mass index in patients with non-alcoholic hepatic steatosis, non-alcoholic steatohepatitis, concomitant obesity and biliary tract pathology.Material and methods. 200 patients with non-alcoholic fatty liver disease, concomitant obesity and biliary tract pathology including 100 patients with non-alcoholic hepatic steatosis and 100 with non-alcoholic steatohepatitis were examined. 70 out of 100 patients with non-alcoholic steatohepatitis had the minimum level of alanine transaminase activity and 30 patients had a moderate alanine transaminase activity. The control group included 30 apparently healthy persons. The body mass index was determined using the Quetelet formula. All the patients with non-alcoholic hepatic steatosis and non-alcoholic steatohepatitis were divided into three groups depending on the increase in the body mass index and the presence of biliary tract pathology. The humoral immune system state was evaluated by the levels of immunoglobulins A, M and G and the content of circulating immune complexes. Results. In patients with non-alcoholic hepatic steatosis and non-alcoholic steatohepatitis, concomitant obesity and biliary tract pathology, there were observed abnormalities in the humoral component of the immune system with possible increase in the levels of major immunoglobulin classes as well as in the content of circulating immune complexes being more pronounced in patients with non-alcoholic steatohepatitis compared to patients with non-alcoholic hepatic steatosis (p<0.05) and apparently healthy persons (p<0.001). The increase in the body mass index led to a significant increase in the levels of Ig A, M, G and the activation of circulating immune complexes.More significant changes in humoral indices were observed in patients with chronic non-calculous and calculous cholecystitis in the presence of inflammatory biliary tract changes during the exacerbation of the pathology compared to patients who underwent cholecystectomy on the background of the aggravation of postcholecystectomy syndrome.Conclusions. The obtained data indicated that one of the elements in the pathogenesis of non-alcoholic fatty liver disease with concomitant obesity and biliary tract pathology is a significant change in the indicators of humoral immunity, namely the increase in the levels of Ig (A, M, G) and circulating immune complexes which depend on the clinical form (non-alcoholic hepatic steatosis or non-alcoholic steatohepatitis), increase in the body mass index and the presence of biliary tract comorbidity