Numerical simulation of three-dimensional cavitation bubble oscillations by boundary element method

This work is devoted to a numerical investigation of threedimensional cavitation bubble. Bubble oscillations in ambient unbounded fluid are investigated numerically. The fluid is assumed inviscid, incompressible and unbounded and the flow is irrotational. The boundary integral method is used as an instrument of numerical investigation. Much attention is paid to the description of a numerical algorithm.http://deepblue.lib.umich.edu/bitstream/2027.42/84303/1/CAV2009-final127.pd

Structural transformations in heat resistant coatings containing rare earth elements

Degradation of two-layered coatings and ZhS6U alloy microstructure were studied during long-term processes of high temperature annealing and creeping. It was shown that yttrium and zirconium oxides are promising as protective coatings for heat resistant nickel based alloy

A new method for reconstructing the density distribution of matter in the disks of spiral galaxies from the rotation velocity curve in it

In this paper we propose a new method for reconstructing the surface density of matter in flat disks of spiral galaxies. The surface density is expressed through observational rotation velocity curves of visible matter in the disks of spiral galaxies. The new method is not based on quadrature of special functions. The found solution is used for processing and analysis of observational data from several spiral galaxies. The new method can be used to more accurately estimate the amount of dark matter in spiral galaxies.Comment: 18 pages, 6 figure

Features of ultrasound and dopplerometric endometry examination in autoimmune thyroiditis patients with abnormal uterine bleeding

Abnormal uterine bleeding  occurs in 10–30% of reproductive age women. Ultrasound examination is one of the most effective methods of diagnosing lesions of the pelvic organs while it has high sensitivity (96%), but low specificity (13.8%) in relation to endometrial lesions, the informativeness of ultrasound in the diagnosis of abnormal uterine bleeding ranges from 60 to 93.3%. It had been revealed revealed that the imbalance of thyroid hormones can have a direct effect on the endometrium. Thus, the analysis of ultrasound examinations data  together with dopplerometric assessment of the blood flow of the internal genital organs in autoimmune thyroiditis patients with abnormal uterine bleeding is an urgent task of modern gynecology. The purpose is to determine the features of ultrasound exanimation with Doppler assessment of the endometrium  in autoimmune thyroiditis patients with abnormal uterine bleeding. Materials and methods.  The patients’ examinations were carried out from 2019 to 2022 We examined 120 patients, of whom 90 (75%) suffered from abnormal uterine bleeding and 30 (25%) did not have signs of gynecological and somatic pathology (control group). Abnormal bleeding patients average age was 36.3±3.2 years. The average age of bleeding and thyroid pathology women was 34.8±2.6 years, the control group average age was 30.7±2.9 years. Results. Echographic signs of endometrium structural changes were detected in 83 (92.2%) of abnormal nautoimmune bleeding women and in 7 (7.8%) women ultrasound signs of pathology were not detected. Significant differences were found when analyzing the results of ultrasonographic examination of patients with bleeding and bleeding + thyroid pathology. Conclusion. Ultrasound is an important method that contributes to a significant improvement in the diagnosis of isolated or combined benign uterine diseases in women with abnormal autoimmune bleeding at the background of thyroid pathology, and in most cases corresponds to the histological diagnosis

Anomalous optical phonons in FeTe pnictides: spin state, magnetic order, and lattice anharmonicity

Polarized Raman-scattering spectra of non-superconducting, single-crystalline FeTe are investigated as function of temperature. We have found a relation between the magnitude of ordered magnetic moments and the linewidth of A1g phonons at low temperatures. This relation is attributed to the intermediate spin state (S=1) and the orbital degeneracy of the Fe ions. Spin-phonon coupling constants have been estimated based on microscopic modeling using density-functional theory and analysis of the local spin density. Our observations show the importance of orbital degrees of freedom for the Fe-based superconductors with large ordered magnetic moments, while small magnetic moment of Fe ions in some iron pnictides reflects the low spin state of Fe ions in those systems.Comment: 17 pages, 3 figure

The Hitting Times with Taboo for a Random Walk on an Integer Lattice

For a symmetric, homogeneous and irreducible random walk on d-dimensional integer lattice Z^d, having zero mean and a finite variance of jumps, we study the passage times (with possible infinite values) determined by the starting point x, the hitting state y and the taboo state z. We find the probability that these passages times are finite and analyze the tails of their cumulative distribution functions. In particular, it turns out that for the random walk on Z^d, except for a simple (nearest neighbor) random walk on Z, the order of the tail decrease is specified by dimension d only. In contrast, for a simple random walk on Z, the asymptotic properties of hitting times with taboo essentially depend on the mutual location of the points x, y and z. These problems originated in our recent study of branching random walk on Z^d with a single source of branching

Study of the structure and kinematics of the NGC 7465/64/63 triplet galaxies

This paper is devoted to the analysis of new observational data for the group of galaxies NGC 7465/64/63, which were obtained at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) with the multimode instrument SCORPIO and the Multi Pupil Fiber Spectrograph. For one of group members (NGC 7465) the presence of a polar ring was suspected. Large-scale brightness distributions, velocity and velocity dispersion fields of the ionized gas for all three galaxies as well as line-of-sight velocity curves on the basis of emission and absorption lines and a stellar velocity field in the central region for NGC 7465 were constructed. As a result of the analysis of the obtained information, we revealed an inner stellar disk (r ~ 0.5 kpc) and a warped gaseous disk in addition to the main stellar disk, in NGC 7465. On the basis of the joint study of photometric and spectral data it was ascertained that NGC 7464 is the irregular galaxy of the IrrI type, whose structural and kinematic peculiarities resulted most likely from the gravitational interaction with NGC 7465. The velocity field of the ionized gas of NGC 7463 turned out typical for spiral galaxies with a bar, and the bending of outer parts of its disk could arise owing to the close encounter with one of galaxies of the environment.Comment: 20 pages, 6 figure

Amplification of spin-filtering effect by magnetic field in GaAsN alloys

We have found that intensity $I$ and circular polarization degree $\rho$ of the edge photoluminescence, excited in GaAsN alloys by circularly polarized light at room temperature, grow substantially in the longitudinal magnetic field $B$ of the order of 1\,kG. This increase depends on the intensity of pumping and, in the region of weak or moderate intensities, may reach a twofold value. In two-charge-state model, which considers spin-dependent recombination of spin-oriented free electrons on deep paramagnetic centers, we included the magnetic-field suppression of spin relaxation of the electrons bound on centers. The model describes qualitatively the rise of $\rho$ and $I$ in a magnetic field under different pump intensities. Experimental dependences $\rho(B)$ and $I(B)$ are shifted with respect to zero of the magnetic field by a value of $\sim$170\,Gauss, while the direction of the shift reverses with change of the sign of circular polarization of pumping. As a possible cause of the discovered shift we consider the Overhauser field, arising due to the hyperfine interaction of an electron bound on a center with nuclei of the crystal lattice in the vicinity of the center.Comment: 8 pages, 6 figures, Submitted to Physical Review