The Proto-neutron Star Phase of the Collapsar Model and the Route to Long-soft Gamma-ray Bursts and Hypernovae

Recent stellar evolutionary calculations of low-metallicity massive fast-rotating main-sequence stars yield iron cores at collapse endowed with high angular momentum. It is thought that high angular momentum and black hole formation are critical ingredients of the collapsar model of long-soft gamma-ray bursts (GRBs). Here, we present 2D multi-group, flux-limited-diffusion MHD simulations of the collapse, bounce, and immediate post-bounce phases of a 35-Msun collapsar-candidate model of Woosley & Heger. We find that, provided the magneto-rotational instability (MRI) operates in the differentially-rotating surface layers of the millisecond-period neutron star, a magnetically-driven explosion ensues during the proto-neutron star phase, in the form of a baryon-loaded non-relativistic jet, and that a black hole, central to the collapsar model, does not form. Paradoxically, and although much uncertainty surrounds stellar mass loss, angular momentum transport, magnetic fields, and the MRI, current models of chemically homogeneous evolution at low metallicity yield massive stars with iron cores that may have too much angular momentum to avoid a magnetically-driven, hypernova-like, explosion in the immediate post-bounce phase. We surmise that fast rotation in the iron core may inhibit, rather than enable, collapsar formation, which requires a large angular momentum not in the core but above it. Variations in the angular momentum distribution of massive stars at core collapse might explain both the diversity of Type Ic supernovae/hypernovae and their possible association with a GRB. A corollary might be that, rather than the progenitor mass, the angular momentum distribution, through its effect on magnetic field amplification, distinguishes these outcomes.Comment: 5 pages, 1 table, 2 figures, accepted to ApJ

Innovations in foreign (chinese) students’ grammar competence formation while training them russian as a foreign language: network technology and the module approach

The article deals with the researches in the field of finding new methods of teaching Russian to foreign (Chinese) students and its Grammar aspect, in particular. In this connection the authors share the results of the investigation dealt with the development of one of the most future-oriented approaches in methods of training the Russian Grammar standards which may be called the Module Approach realized by means of Network Technologie

Features of the Acoustic Mechanism of Core-Collapse Supernova Explosions

In the context of 2D, axisymmetric, multi-group, radiation/hydrodynamic simulations of core-collapse supernovae over the full 180$^{\circ}$ domain, we present an exploration of the progenitor dependence of the acoustic mechanism of explosion. All progenitor models we have tested with our Newtonian code explode. We investigate the roles of the Standing-Accretion-Shock-Instability (SASI), the excitation of core g-modes, the generation of core acoustic power, the ejection of matter with r-process potential, the wind-like character of the explosion, and the fundamental anisotropy of the blasts. We find that the breaking of spherical symmetry is central to the supernova phenomenon and the blasts, when top-bottom asymmetric, are self-collimating. We see indications that the initial explosion energies are larger for the more massive progenitors, and smaller for the less massive progenitors, and that the neutrino contribution to the explosion energy may be an increasing function of progenitor mass. The degree of explosion asymmetry we obtain is completely consistent with that inferred from the polarization measurements of Type Ic supernovae. Furthermore, we calculate for the first time the magnitude and sign of the net impulse on the core due to anisotropic neutrino emission and suggest that hydrodynamic and neutrino recoils in the context of our asymmetric explosions afford a natural mechanism for observed pulsar proper motions. [abridged]Comment: Accepted to the Astrophysical Journal, 23 pages in emulateapj format, including 12 figure

A supersymmetric model for triggering Supernova Ia in isolated white dwarfs

We propose a model for supernovae Ia explosions based on a phase transition to a supersymmetric state which becomes the active trigger for the deflagration starting the explosion in an isolated sub-Chandrasekhar white dwarf star. With two free parameters we fit the rate and several properties of type Ia supernovae and address the gap in the supermassive black hole mass distribution. One parameter is a critical density fit to about $3 \cdot 10^7$ g/cc while the other has the units of a space time volume and is found to be of order $0.05\,$ Gyr $R_E^3$ where $R_E$ is the earth radius. The model involves a phase transition to an exact supersymmetry in a small core of a dense star.Comment: 20 pages, 5 figures, expanded version to be published in Physical Review

Effect of prolonging radiation delivery time on retention of gammaH2AX

<p>Abstract</p> <p>Background and purpose</p> <p>Compared to conventional external beam radiotherapy, IMRT requires significantly more time to deliver the dose. Prolonging dose delivery potentially increases DNA repair which would reduce the biological effect. We questioned whether retention of γH2AX, a measure of lack of repair of DNA damage, would decrease when dose delivery was protracted.</p> <p>Materials and methods</p> <p>Exponentially growing SiHa cervical carinoma cells were irradiated with 6 MV photons in a water tank using a VarianEX linear accelerator. Cells held at 37°C received 2 Gy in 0.5 min and 4 Gy in 1 min. To evaluate effect of dose delivery prolongation, 2 and 4 Gy were delivered in 30 and 60 min. After 24 h recovery, cells were analyzed for clonogenic survival and for residual γH2AX as measured using flow cytometry.</p> <p>Results</p> <p>Increasing the dose delivery time from 0.5 or 1 min to 30 or 60 min produced a signficant increase in cell survival from 0.45 to 0.48 after 2 Gy, and from 0.17 to 0.20 after 4 Gy. Expression of residual γH2AX decreased from 1.27 to 1.22 relative to background after 2 Gy and 1.46 to 1.39 relative to background after 4 Gy, but differences were not statistically significant. The relative differences in the slopes of residual γH2AX versus dose for acute versus prolonged irradiation bordered on significant (p = 0.055), and the magnitude of the change was consistent with the observed increase in surviving fraction.</p> <p>Conclusion</p> <p>These results support the concept that DNA repair underlies the increase in survival observed when dose delivery is prolonged. They also help to establish the limits of sensitivity of residual γH2AX, as measured using flow cytometry, for detecting differences in response to irradiation.</p

Cosmic Rays from PeV to ZeV, Stellar Evolution, Supernova Physics and Gamma Ray Bursts

The recent success of a proposal from some time ago to explain the spectrum of cosmic rays allows some strong conclusions to be made on the physics of supernovae: In the context of this specific proposal to explain the origin of cosmic rays, the mechanism for exploding supernovae of high mass has to be the one proposed by Bisnovatyi-Kogan more than 30 years ago, which was then based on a broader suggestion by Kardashev: A combination of the effects of rotation and magnetic fields explodes the star. Interestingly, this step then leads inevitably to some further suggestions, useful perhaps for the study of gamma ray bursts and the search of a bright standard candle in cosmology

Structure of Contextual Synonymic Rows in Russian and English Newspapers: Ecolinguistic and Contrastive Aspects

The article deals with the aspects of contextual synonyms functioning in Russian and English newspaper texts united by the theme of refugee migration in Europe. The relevance of the work is determined by its interdisciplinarity and combination of contrastive and ecolinguistic approaches. Contrastive approach consists in identification of common and distinctive features of the synonymic rows in English and Russian newspapers. Ecolinguistic approach involves determining the intensity of use of substandard tokens in the contextual synonymic rows. The research material are 18 contextual synonymic rows, formed by 4 newspapers - “Kommersant,” “Komsomolskaya Pravda,” “The Guardian Weekly,” “The Daily Mail.” The paper discusses the concept of contextual synonym and contextual synonymic row. There are 3 models of synonymic row including: (1) only literary units; (2) literary and colloquial lexemes; (3) literary, colloquial and substandard units. It was revealed that news texts in Russian and English high-quality publications characterized by the presence of expert assessments and targeted at the educated reader, differ by homogeneous material flow and primarily using standard tokens. Tabloid edition aimed at a wide readership often use colloquial synonyms. It is determined that Russian-language rows have a higher coefficient of colloquialisms (17.2 %) than the English (4.8 %)

Equilibrium Configurations of Strongly Magnetized Neutron Stars with Realistic Equations of State

We investigate equilibrium sequences of magnetized rotating stars with four kinds of realistic equations of state (EOSs) of SLy (Douchin et al.), FPS (Pandharipande et al.), Shen (Shen et al.), and LS (Lattimer & Swesty). Employing the Tomimura-Eriguchi scheme to construct the equilibrium configurations. we study the basic physical properties of the sequences in the framework of Newton gravity. In addition we newly take into account a general relativistic effect to the magnetized rotating configurations. With these computations, we find that the properties of the Newtonian magnetized stars, e.g., structure of magnetic field, highly depends on the EOSs. The toroidal magnetic fields concentrate rather near the surface for Shen and LS EOSs than those for SLy and FPS EOSs. The poloidal fields are also affected by the toroidal configurations. Paying attention to the stiffness of the EOSs, we analyze this tendency in detail. In the general relativistic stars, we find that the difference due to the EOSs becomes small because all the employed EOSs become sufficiently stiff for the large maximum density, typically greater than $10^{15}\rm{g} \rm{cm}^{-3}$. The maximum baryon mass of the magnetized stars with axis ratio $q\sim 0.7$ increases about up to twenty percents for that of spherical stars. We furthermore compute equilibrium sequences at finite temperature, which should serve as an initial condition for the hydrodynamic study of newly-born magnetars. Our results suggest that we may obtain information about the EOSs from the observation of the masses of magnetars.Comment: submitted to MNRA

Analysis of change management experience in organizations

The article considers the issues of change management taking into account the Russian and American experience. Change management has been reviewed as an integral part of the management theory. It has been proposed to consider the process of change management as primarily the management of phenomena that accompany the process of change.The concept of “change” has been reflected as a process of transformation and as the transformation of an object into new legal forms through reorganization. The presented experience of managing American companies shows, first of all, the situation in which economic growth is carried out and all transformations are aimed at integration processes.The analysis of modern experience of change management has been made in the context of crisis situations that require flexibility in managing all processes in the organization. The article presents a division of changes into groups, allowing you to identify areas that require timely management influence when developing an organization’s development program. The analysis examines the most popular change management models and the actions of companies to manage changes during the coronavirus pandemic.In conclusion, it has been concluded that for modern companies, change management requires not only constant analysis of internal organizational processes, but also the application of specific knowledge to solve  problematic management tasks