Moscow State University

About: Moscow State University is a education organization based out in Moscow, Russia. It is known for research contribution in the topics: Catalysis & Laser. The organization has 66747 authors who have published 123358 publications receiving 1753995 citations. The organization is also known as: MSU & Lomonosov Moscow State University.

Gamma-Ray Emission Concurrent with the Nova in the Symbiotic Binary V407 Cygni

Abstract: Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable γ-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce π0 decay γ-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.

Estimating the Contribution of Dynamical Ejecta in the Kilonova Associated with GW170817

Abstract: The source of the gravitational-wave (GW) signal GW170817, very likely a binary neutron star merger, was also observed electromagnetically, providing the first multi-messenger observations of this type. The two-week-long electromagnetic (EM) counterpart had a signature indicative of an r-process-induced optical transient known as a kilonova. This Letter examines how the mass of the dynamical ejecta can be estimated without a direct electromagnetic observation of the kilonova, using GW measurements and a phenomenological model calibrated to numerical simulations of mergers with dynamical ejecta. Specifically, we apply the model to the binary masses inferred from the GW measurements, and use the resulting mass of the dynamical ejecta to estimate its contribution (without the effects of wind ejecta) to the corresponding kilonova light curves from various models. The distributions of dynamical ejecta mass range between = - - - M M ej 10 10  3 2 for various equations of state, assuming that the neutron stars are rotating slowly. In addition, we use our estimates of the dynamical ejecta mass and the neutron star merger rates inferred from GW170817 to constrain the contribution of events like this to the r-process element abundance in the Galaxy when ejecta mass from post-merger winds is neglected. We find that if 10% of the matter dynamically ejected from binary neutron star (BNS) mergers is converted to r-process elements, GW170817-like BNS mergers could fully account for the amount of r-process material observed in the Milky Way.

Soluble complexes from poly(ethylene oxide)-block-polymethacrylate anions and N-alkylpyridinium cations

Abstract: Complexes from poly(ethylene oxide)-b-poly(sodium methacrylate) (PEO-b-PMANa) and N-alkylpyridinium bromides are water soluble, in marked contrast to those from poly(sodium methacrylate). These systems are studied using potentiometric titration, microcalorimetry, ζ-potential measurement, light scattering and electron microscopy. Three regions (A−C) are observed with a complex from PEO-b-PMANa and cetylpyridinuim bromide (C16PyBr) when the composition of the mixture (Z = [C16PyBr]/[COO-]) is varied. (A) At Z 0). The particles formed at saturating concentrations ...

Effect of structural and physico-chemical features of cellulosic substrates on the efficiency of enzymatic hydrolysis

Abstract: Effects of major physicochemical and structural parameters of cellulose on the rate and degree of its enzymatic hydrolysis were tested with cellulosic materials from various sources Some different pretreatments were: mechanical (milling), physical (X-ray irradiation), and chemical (cadoxen, H3PO4, H2SO4, NaOH, Fe2+/H2O2) The average size of cellulose particles and its degree of polymerization had little effect on the efficiency of enzymatic hydrolysis For samples of pure cellulose (cotton linter, microcrystalline cellulose, α-cellulose), increase in the specific surface area accessible to protein molecules and decrease in the crystallinity index accelerated the enzymatic hydrolysis (the correlation coefficients were 089 and 092, respectively) In the case of lignocellulose (bagasse), a quantitative linear relationship only between specific surface area and reactivity was observed

Cavitation Bubble Cluster Activity in the Breakage of Kidney Stones by Lithotripter Shockwaves

Abstract: High-speed photography was used to analyze cavitation bubble activity at the surface of artificial and natural kidney stones during exposure to lithotripter shock waves in vitro. Numerous individual bubbles formed at the surface of stones, but these bubbles did not remain independent and combined with one another to form bubble clusters. Bubble clusters formed at the proximal end, the distal end, and at the sides of stones. Each cluster collapsed to a narrow point of impact. Collapse of the proximal cluster caused erosion at the leading face of the stone and the collapse of clusters at the sides of stones appeared to contribute to the growth of cracks. Collapse of the distal cluster caused minimal damage. We conclude that cavitation-mediated damage to stones was due not to the action of solitary bubbles, but to the growth and collapse of bubble clusters.