Global Spiral Modes in NGC 1566: Observations and Theory

We present an observational and theoretical study of the spiral structure in galaxy NGC 1566. A digitized image of NGC 1566 in I-band was used for measurements of the radial dependence of amplitude variations in the spiral arms. We use the known velocity dispersion in the disk of NGC 1566, together with its rotation curve, to construct linear and 2D nonlinear simulations which are then compared with observations. A two-armed spiral is the most unstable linear global mode in the disk of NGC 1566. The nonlinear simulations are in agreement with the results of the linear modal analysis, and the theoretical surface amplitude and the velocity residual variations across the spiral arms are in qualitative agreement with the observations. The spiral arms found in the linear and nonlinear simulations are considerably shorter than those observed in the disk of NGC 1566. We argue therefore, that the surface density distribution in the disk of the galaxy NGC 1566 was different in the past, when spiral structure in NGC 1566 was linearly growing.Comment: 41 pages, 20 figures, to be published in the Astrophysical Journa

Formation of Plumes in Head-on Collisions of Galaxies

Using N-body and SPH modeling we perform 3D numerical simulations of head-on collisions between gas rich disk galaxies, including collisions between counter-rotating disks and off-center collisions. Pure stellar intruders do not produce gaseous plumes similar to those seen in the Cartwheel and VII Zw466 complexes of interacting galaxies; the presence of gas in an intruder galaxy and radiative cooling are important for the formation of a gaseous plume extending from the disk of a target galaxy. A noticeable plume structure can be formed if the mass of an intruder is a few percent of the mass of the primary. The halo of the intruder is stripped in the collision, and dispersed particles form a broad stellar bridge connecting the two galaxies. The fraction of the intruder's halo dispersed in the collision depends on the total mass of the intruder, and low-mass intruders lose most of their mass.Comment: 15 pages, 14 figures in GIF. To appear ApJ. Vol. 505 #

The mechanism of industrial educational clusters creation as managerial entities of vocational education

© 2016, Econjournals. All rights reserved.The relevance of the paper is conditioned by the increasing role of vocational education in the regional economy. In modern conditions vocational education is regarded as a system of integrative interaction of education, science and industry, aimed at the development of a specialist ready for the life-long learning, capable to a certain type of professional activities, self-organization and competitiveness on the labor market. The aim of the paper is to develop the mechanism of branch educational clusters’ creation as the entities of vocational education’s management. The leading method is the method of action research, allowing to obtain new knowledge about vocational education’s management and to propose mechanisms for its optimization to obtain qualitatively new results of vocational training process. The article defines the essence of an industrial educational cluster as a set of vocational educational institutions, united by industrial features and partnerships with industrial enterprises; presents the mechanisms of interaction between labor market and vocational education; describes the mechanism of educational clusters’ formation on the basis of vertical integration of educational institutions; reveals the mechanism of industrial educational clusters’ formation on the basis of social partnership of the manufacture and vocational educational institutions. The paper submissions can be useful for scientific and pedagogical staff of vocational educational system, specialists of educational managerial bodies and regional authorities

Dynamics of Gaseous Disks in a Non-axisymmetric Dark Halo

The dynamics of a galactic disk in a non-axisymmetric (triaxial) dark halo is studied in detail using high-resolution, numerical, hydrodynamical models. A long-lived, two-armed spiral pattern is generated for a wide range of parameters. The spiral structure is global, and the number of turns can be two or three, depending on the model parameters. The morphology and kinematics of the spiral pattern are studied as functions of the halo and disk parameters. The spiral structure rotates slowly, and its angular velocity varies quasi-periodically. Models with differing relative halo masses, halo semi-axis ratios, distributions of matter in the disk, Mach numbers in the gaseous component, and angular rotational velocities of their halos are considered.Comment: 22 pages, 11 figure

Gravitational stability and dynamical overheating of stellar disks of galaxies

We use the marginal stability condition for galactic disks and the stellar velocity dispersion data published by different authors to place upper limits on the disk local surface density at two radial scalelengths $R=2h$. Extrapolating these estimates, we constrain the total mass of the disks and compare these estimates to those based on the photometry and color of stellar populations. The comparison reveals that the stellar disks of most of spiral galaxies in our sample cannot be substantially overheated and are therefore unlikely to have experienced a significant merging event in their history. The same conclusion applies to some, but not all of the S0 galaxies we consider. However, a substantial part of the early type galaxies do show the stellar velocity dispersion well in excess of the gravitational stability threshold suggesting a major merger event in the past. We find dynamically overheated disks among both seemingly isolated galaxies and those forming pairs. The ratio of the marginal stability disk mass estimate to the total galaxy mass within four radial scalelengths remains within a range of 0.4---0.8. We see no evidence for a noticeable running of this ratio with either the morphological type or color index.Comment: 25 pages, 5 figures, accepted to Astronomy Letter

K^+ production in the reaction 58Ni+58Ni^{58}Ni+^{58}Ni at incident energies from 1 to 2 AGeV

Semi-inclusive triple differential multiplicity distributions of positively charged kaons have been measured over a wide range in rapidity and transverse mass for central collisions of $^{58}$Ni with $^{58}$Ni nuclei. The transverse mass ($m_t$) spectra have been studied as a function of rapidity at a beam energy 1.93 AGeV. The $m_t$ distributions of K^+ mesons are well described by a single Boltzmann-type function. The spectral slopes are similar to that of the protons indicating that rescattering plays a significant role in the propagation of the kaon. Multiplicity densities have been obtained as a function of rapidity by extrapolating the Boltzmann-type fits to the measured distributions over the remaining phase space. The total K^+ meson yield has been determined at beam energies of 1.06, 1.45, and 1.93 AGeV, and is presented in comparison to existing data. The low total yield indicates that the K^+ meson can not be explained within a hadro-chemical equilibrium scenario, therefore indicating that the yield does remain sensitive to effects related to its production processes such as the equation of state of nuclear matter and/or modifications to the K^+ dispersion relation.Comment: 24 pages Latex (elsart) 7 PS figures to be submitted to Nucl. Phys

Сравнительная оценка удлинения длинных костей нижних конечностей по Илизарову и «поверх» интрамедуллярного стержня

Introduction. Lengthening over the nail (LON) combines the advantages of external and internal fixations.The objective was to compare the effectiveness of the application, to assess the structure and frequency of complications in patients treated with lengthening by Ilizarov technique and lengthening over the nail.Methods and materials. We analyzed 55 LON cases and 64 cases lengthening by Ilizarov technique. The duration of the external fixation period, complications and quality of the patient life were compared.Results. The external fixation period in LON group was 4 times less than in the Ilizarov technique group. There were 25 complications (45.5 %) in LON group and 54 complications (84.4 %) in the Ilizarov technique group. Femur lengthening was associated with a greater number of complications in both groups. Pin infections were 2.5 times less frequently in the femur LON group. Knee contractures were only in Ilizarov technique group (11.4 %). Ankle joint contracture was noted with the same frequency during tibial lengthening in both groups. Disorders of the consolidation were 2 times more often in the femur LON group and 5 times more often in the tibial lengthening with Ilizarov technique. Premature fusion was observed only in the LON group. There were 2 times less fractures of the half-pins and wires in the LON group.Conclusions. A reduction of external fixation period in LON group correlates with the 2-fold decrease of complications and an increase of the treatment comfort. LON is promising for wider clinical applications.Введение. Методика удлинения костей поверх гвоздя (УПГ) сочетает преимущества чрескостного остеосинтеза и внутренней фиксации.Цель исследования — сравнить эффективность применения, оценить структуру и частоту осложнений у пациентов, пролеченных по методике УПГ и при удлинении по Илизарову.Методы и материалы. Проанализированы 55 случаев УПГ бедра и голени и 64 случая удлинения по Илизарову (чрескостный остеосинтез, ЧО). Сравнивали длительность периода внешней фиксации, осложнения и качество жизни пациентов.Результаты. Период чрескостного остеосинтеза при УПГ был в 4 раза меньше, чем в группе ЧО. При УПГ отмечено 25 (45,5 %) осложнений, в группе ЧО — 54 (84,4 %) осложнения. В обеих группах при удлинении бедренной кости отмечено большее число осложнений. Воспаления в области чрескостных элементов при УПГ бедра отмечались в 2,5 раза реже, чем в группе ЧО. Контрактуры коленного сустава встречались только при ЧО в 11,4 %. Контрактура голеностопного сустава при удлинении голени отмечена с одинаковой частотой. Нарушения процессов консолидации при удлинении бедра отмечены в 2 раза чаще в группе УПГ, при удлинении голени — в 5 раз чаще в группе ЧО. Преждевременное сращение отмечено только при УПГ. Переломов чрескостных элементов было в 2 раза меньше в группе УПГ.Заключение. Сокращение периода чрескостного остеосинтеза при УПГ коррелирует со снижением осложнений в 2 раза и повышением комфортности лечения. УПГ перспективно для более широкого клинического применения

Control of star formation by supersonic turbulence

Understanding the formation of stars in galaxies is central to much of modern astrophysics. For several decades it has been thought that stellar birth is primarily controlled by the interplay between gravity and magnetostatic support, modulated by ambipolar diffusion. Recently, however, both observational and numerical work has begun to suggest that support by supersonic turbulence rather than magnetic fields controls star formation. In this review we outline a new theory of star formation relying on the control by turbulence. We demonstrate that although supersonic turbulence can provide global support, it nevertheless produces density enhancements that allow local collapse. Inefficient, isolated star formation is a hallmark of turbulent support, while efficient, clustered star formation occurs in its absence. The consequences of this theory are then explored for both local star formation and galactic scale star formation. (ABSTRACT ABBREVIATED)Comment: Invited review for "Reviews of Modern Physics", 87 pages including 28 figures, in pres

Central Collisions of Au on Au at 150, 250 and 400 A MeV

Collisions of Au on Au at incident energies of 150, 250 and 400 A MeV were studied with the FOPI-facility at GSI Darmstadt. Nuclear charge (Z < 16) and velocity of the products were detected with full azimuthal acceptance at laboratory angles of 1-30 degrees. Isotope separated light charged particles were measured with movable multiple telescopes in an angular range of 6-90 degrees. Central collisions representing about 1 % of the reaction cross section were selected by requiring high total transverse energy, but vanishing sideflow. The velocity space distributions and yields of the emitted fragments are reported. The data are analysed in terms of a thermal model including radial flow. A comparison with predictions of the Quantum Molecular Model is presented.Comment: LateX text 62 pages, plus six Postscript files with a total of 34 figures, accepted by Nucl.Phys.

Entropy production in the Au + Au reaction between 150 and 800 A MeV

The entropy per nucleon (S/A) has been extracted for the Au [(150—800)A MeV] + Au reaction by using the phase I setup of the 4 pi facility at GSI, Darmstadt. The entropy has been obtained from the comparison of various observables characterizing the dM/dZ fragment multiplicity distributions, extending up to Z~15, with those calculated with the quantum statistical model. It is the first time that S/A values are determined by considering the full ensemble of charged products detected in the reaction. Consistent values of S/A are found from different methods. These entropy values are shown to be fairly independent of the volume of the ``participant'' region considered. They are somewhat lower than those extracted in earlier works but are in good agreement with hydrodynamic calculations and suggest a low viscosity for the hot and dense nuclear matter