Simulation of Thermal Surface Waves in a Protoplanetary Disk in a Two-Dimensional Approximation

Astronomy Reports - Theoretical models predict that the obscuration of stellar radiation by irregularities on the surface of a protoplanetary disk can cause self-generating waves traveling towards...     

Comparative Assessment of Global Models of the Earth’s Gravity Field

Izvestiya, Physics of the Solid Earth - Abstract—Empirical comparative study of the modern global models of the Earth’s gravity field (EGF) in the form of geopotential spherical...     

Biogeochemical characteristics of dominant gastropod species from the stony littoral of southern Baikal

The trace element composition of dominant gastropod species from the littoral of southern Baikal was investigated. Both different mollusk species and their parts (shells and soft tissues) show specific trace element characteristics. The highest Sr and Ba contents were observed in Maackia herderiana. The highest Zn, Cu, and Cd and lowest Pb contents were detected in Megalovalvata baicalensis. Choanomphalus sp. shows high Mn and Ti and very low Sr, Cu, and Cd contents. Most of Cu, Zn, and Cd and a considerable fraction of Rb, Pb, Mo, Sc, Ce, W, Ga, Y, and Th are incorporated in the gastropod bodies. The maximum concentration of U is also characteristic of the body tissues. The foot tissues of Maackia herderiana and Megalovalvata baicalensis are depleted in the majority of elements compared with their bodies. Sr and Ba are prevalent in the mollusk shells, where high Mn contents were also detected. A close relationship was observed between the chemical compositions of the gastropods, stony substrate, and bottom water. Group concentration of trace elements is common in the species investigated. Relative to the bottom water layer, the gastropod species concentrate Ti, Mn, La, Co, Y, and V and show similarly low extraction of U, W, Mo, and Cs. Compared with the bottom sediments, the mollusks accumulate Sr. In addition, Maackia herderiana and Megalovalvata baicalensis accumulate Cd and Zn. Megalovalvata baicalensis is distinguished by the ability to concentrate Cu. The following sequence is formed by the gastropods with respect to their capacity to accumulate Cd, Zn, and Cu: Megalovalvata baicalensis > Maackia herderiana > Choanomphalus sp.     

Simulation of Thermal Surface Waves in a Protoplanetary Disk in 1+1D Approximation

Astronomy Reports - Heating by the central star is one of the key factors determining the physical structure of protoplanetary disks. Due to a large radial optical thickness, the equatorial regions...     

Characterization of the matrix and fusion crust of the recent meteorite fall Ozerki L6

We studied the interior and the fusion crust of the recently recovered Ozerki L6 meteorite using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy, X‐ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. The phase composition of the interior and of the fusion crust was determined by means of SEM, XRD, and Mössbauer spectroscopy. The unit cell parameters for silicate crystals were evaluated from the X‐ray diffractograms and were found the same for the interior and the fusion crust. Magnetization measurements revealed a decrease of the saturation magnetic moment in the fusion crust due to a decrease of Fe‐Ni‐Co alloy content. Both XRD and Mössbauer spectroscopy show the presence of magnesioferrite in the fusion crust. The temperatures of cation equilibrium distribution between the M1 and M2 sites in silicates calculated using the data obtained from XRD and Mössbauer spectroscopy appeared to be in a good consistency: 553 and 479 K for olivine and 1213 and 1202 K for orthopyroxene.     

Annama H chondrite—Mineralogy,physical properties,cosmic ray exposure,and parent body history

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar‐Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short‐lived radionuclides are compatible with an atmospheric pre‐entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The ¹⁰Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre‐entry radius.     

Evolution of a Viscous Protoplanetary Disk with Convectively Unstable Regions. II. Accretion Regimes and Long-Term Dynamics

Astronomy Reports - In this article, we proceed to study convection as a possible factor of episodic accretion in protoplanetary disks. Within the model presented in Article I, the accretion...     

Temperature Dependence of the Processes of Acrylamide Biodegradation in River Silt Suspensions at Their Inoculation by Selected Bacterial Strains

Water Resources - The temperature dependence of the rate of acrylamide biodegradation by silt microorganisms of small rivers in the Perm krai is studied in the antropogenically polluted Danilikha...     

Assessing the state of water masses of the Southern Baikal in the zone of influence of Baikal PPM by many-year microbiological characteristics

Results of many-year (1990–2009) microbiological studies of waters in different parts of Southern Baikal subject to different anthropogenic load are presented. Long-term observation series made it possible to establish tendencies in variations of the structure and functional activity of microbiocenoses as the result of natural evolution and anthropogenic impact. The obtained microbiological data characterizes water quality and the level of technogenic disturbances near Baikal Pulp-and-Paper Mill. Water quality assessment by sanitary-bacteriological characteristics suggests that the water area near the discharge site of effluents from Baikal PPM chronically experiences bacterial pollution. No significant changes in the technogenic stress on Southern Baikal ecosystem have taken place since the 1990s.