The possibility of emersion of the outer layers in a massive star simultaneously with iron-core collapse: A hydrodynamic model

We analyze the behavior of the outer envelope in a massive star during and after the collapse of its iron core into a protoneutron star (PNS) in terms of the equations of one-dimensional spherically symmetric ideal hydrodynamics. The profiles obtained in the studies of the evolution of massive stars up to the final stages of their existence, immediately before a supernova explosion (Boyes et al. 1999), are used as the initial data for the distribution of thermodynamic quantities in the envelope. We use a complex equation of state for matter with allowances made for arbitrary electron degeneracy and relativity, the appearance of electron-positron pairs, the presence of radiation, and the possibility of iron nuclei dissociating into free nucleons and helium nuclei. We performed calculations with the help of a numerical scheme based on Godunov's method. These calculations allowed us to ascertain whether the emersion of the outer envelope in a massive star is possible through the following two mechanisms: first, the decrease in the gravitational mass of the central PNS through neutrino-signal emission and, second, the effect of hot nucleon bubbles, which are most likely formed in the PNS corona, on the envelope emersion. We show that the second mechanism is highly efficient in the range of acceptable masses of the nucleon bubbles (≤0.01M _⊙) simulated in our hydrodynamic calculations in a rough, spherically symmetric approximation.     

Observations of neutral hydrogen in the corona

Measurements of the linear polarization degree (p) of the emission in the inner corona (<1.5 R _⊙) in the green and red continuum ranges are discussed. “Excess p” (Δp = pgreen — pred), which reaches its maximum at 1.2–1.3 R _⊙ (<5%) in the polar regions and 20% within large-scale streamers, is present everywhere in the corona. It has been mentioned that excess p can be explained by the presence of neutral hydrogen in the corona.     

Kuranakh complex diabases in the western part of the Aldan-Stanovoi Shield: Age and tectonic setting

The age of Kuranakh Complex diabases in the western part of the Aldan-Stanovoi Shield determined by the zircon U-Pb method is virtually identical to that of basic rocks in the Chinei stratified pluton and granites in the Kodar Complex. Thus, it is possible to suggest that they form a unified bimodal magmatic association and belong to the South Siberian postcollision magmatic belt, which extends along the southwestern framing of the Siberian Craton for more than 2500 km from the Yenisei mountain range to the Aldan-Stanovoi Shield. The occurrence of the diabase dike swarms in magmatic associations of this belt testifies to formation under lithospheric extension conditions.     

Middle-Upper Miocene stratigraphy of the Taman Peninsula, Eastern Paratethys

The stratigraphy of the Taman Peninsula is defined using the sections at Zelensky Hill ?? Panagia, Popov Kamen, Taman and Zheleznyi Rog. The stratigraphy is constructed from distribution of mollusks, foraminifers, nannofossils, diatoms, and organic-walled phytoplankton, as well as incorporating paleomagnetic data. The occurrence of oceanic diatom species in the Middle-Upper Sarmatian, Maeotian and Lower Pontian makes a direct correlation possible between the sections studied, the Mediterranean basin and oceanic zonation. The new data on planktonic and benthic biotic groups suggests a pulsating connection of the Eastern Paratethys with the open marine basins, especially during transitional intervals within constant environments. Comprehensive studies of the Chokrakian-Kimmerian microbiota provide evidence for several levels of marine microbiotic associations that are related to short-term marine invasions. The biotic and paleomagnetic data of the Taman Peninsula sections give a more comprehensive, but sometimes a controversial picture on the Eastern Paratethys history and the nature of its relationship with the adjacent marine basins.     

The MASTER-II network of robotic optical telescopes. First results

The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gammaray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was observed for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars. Sixty-nine optical transients have been discovered.     

Mariinskite, BeCr2O4, a new mineral, chromium analog of chrysoberyl

A new mineral, mariinskite, BeCr₂O₄, the chromium analog of chrysoberyl, has been found at the Mariinsky (Malyshevo) deposit, the Ural Emerald Mines, the Central Urals, Russia. The mineral is named after its type locality. It was discovered in chromitite in association with fluorphlogopite, Cr-bearing muscovite, eskolaite, and tourmaline. Mariinskite occurs as anhedral grains ranging from 0.01 to 0.3 mm in size; in some cases it forms pseudohexagonal chrysoberyl-type twins. The mineral is dark-green, with a pale green streak; the Mohs’ hardness is 8.5, microhardness VHN = 1725 kg/mm². D _meas = 4.25(2) g/cm³, D _calc = 4.25 g/cm³. Microscopically, it is emerald-green, pleochroic from emerald-green (γ) to yellow-green (β) and greenish yellow (α). The new mineral is biaxial (+), γ = 2.15(1), β = 2.09(3), and α = 2.05(1), 2V _meas = 80 ± (10)°, 2V _calc = 80.5°. In reflected light, it is gray with green reflections; R _max (589) = 12.9%; R _min (589) = 12.3%, and there are strong, internal green reflections. The strongest absorption bands in the IR spectrum are as follows (cm^?1): 935, 700, 614, 534. Space group Pnma, a = 9.727(3), b = 5.619(1), c = 4.499(1) Å, V = 245.9(3) ų, Z = 4. The strongest reflections in the X-ray powder diffraction pattern are as follows (d Å, I, hkl): 4.08(40)(101), 3.31(90)(111), 2.629(50)(301), 2.434(50)(220), 2.381(40)(311), 2.139(60)(221), 1.651(100)(222). The average chemical composition of mariinskite (electron microprobe, wt %) is as follows: BeO 16.3, Al₂O₃ 23.89, Cr₂O₃ 58.67, Fe₂O₃ 0.26, V₂O₃ 0.26, TiO₂ 0.61, total is 99.98. The empirical formula, calculated on the basis of four O atoms is Be_1.03(Cr_1.22Al_0.74Ti_0.01Fe_0.01V_0.01)_1.99O₄. The compatibility index 1 ? (K_p/K_c), 0.019, is excellent. The type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, and the Ural Geological Museum, Yekaterinburg, Russia.     

Climatic Reasons for the Current Expansion of the Range of the Italian Locust in Russia and Neighboring Countries

Doklady Earth Sciences - The species climatic range of a dangerous locust pest, called the Italian locust, was modelled for the territories of Russia and neighboring countries over two time periods...     

Early Ordovician brachiopods from south-west Wales

The Early Ordovician brachiopods of south-west Wales (Pembrokeshire and Carmarthenshire) are identified, in most cases for the first time. That period is termed the local Arenig Stage in Britain, but it is now correlated with the Floian, Dapingian, and earlier half of the Darriwilian, which are more recently established international stages in the system of stratigraphical nomenclature. The rocks in south-west Wales were laid down as turbidites in a backarc basin which formed part of the margin of the relatively small independent microcontinent of Avalonia at that time. However, since the Rheic Ocean between Avalonia and the immense Gondwana continent was relatively narrow in the Arenig, the brachiopods reviewed here can be established to be part of the Mediterranean Province, which was also extensive in the higher-latitude sectors in and around Gondwana in the Early Ordovician. The 17 brachiopod species identified within the Arenig brachiopod faunas of south-west Wales are described, including the new species Aporthophyla prisca, Tritoechia bolohaulensis, Skenidoides pontyfennensis and Paurorthis? llangynogensis.     

Studying characteristics of a fine layered structure of the lower troposphere on the basis of acoustic pulse sounding

Results of acoustic sounding of the lower troposphere with the aid of detonation generators of acoustic pulses are given. This sounding method is based on a partial reflection of acoustic pulses with shock fronts from vertical wind-velocity and temperature gradients continuously varying with height in the troposphere and on the penetration of reflected signals into the region of acoustic shadow. Experiments on tropospheric sounding were carried out on the ground of the Barva Innovation Scientific and Technical Center (Talin, Armenia) in September 2015. In these experiments, an antihail acoustic system was first used as a generator of acoustic pulses. Experimental results have been compared with data obtained earlier in similar experiments carried out in the vicinity of Zvenigorod with the use of a special detonation generator of acoustic pulses. Due to the high resolution (in height) of the sounding method, which reaches 1 m in the stably stratified lower troposphere within a height range of 250–600 m, the vertical profiles of layered effective sound speed inhomogeneities with vertical scales from a few to a few tens of meters have been retrieved. The influence of these fluctuations on the form and amplitude of acoustic signals at a long distance from their pulsed source has been studied.