Kinetic characteristics of the reaction of resveratrol with peroxyl radicals and natural thiols in aqueous medium

Russian Chemical Bulletin - The method of competing reactions was used to determine the rate constants of the reaction of resveratrol (RVT) with peroxyl radicals formed on decomposition of the...     

Discovery of the classical Bose-Einstein condensation of magnons in solid antiferromagnets

Results of experiments in which the Bose-Einstein condensate of magnons is created in the CsMnF₃ easy-plane antiferromagnet in a system with coupled nuclear-electron precession with dynamical frequency shift are presented. This condensate is similar to the Bose-Einstein condensate of magnons in superfluid ³He-A in aerogel.     

Application of Fourier analysis of scanning electron microscopy images for studying variation features of reservoir properties of carbonate rocks at stages of catagenetic transformations

The applicability of the fast Fourier transform method to studying carbonate rocks using a scanning electron microscope is experimentally studied. The method was used to find an integral estimate of sizes of carbonate matrix crystals formed during recrystallization at catagenesis stages.     

Gradient‐based nodal limiters for artificial diffusion operators in finite element schemes for transport equations

This paper presents new linearity‐preserving nodal limiters for enforcing discrete maximum principles in continuous (linear or bilinear) finite element approximations to transport problems with steep fronts. In the process of algebraic flux correction, the oscillatory antidiffusive part of a high‐order base discretization is decomposed into a set of internodal fluxes and constrained to be local extremum dim inishing. The proposed nodal limiter functions are designed to be continuous and satisfy the principle of linearity preservation that implies the preservation of second‐order accuracy in smooth regions. The use of limited nodal gradients makes it possible to circumvent angle conditions and guarantee that the discrete maximum principle holds on arbitrary meshes. A numerical study is performed for linear convection and anisotropic diffusion problems on uniform and distorted meshes in two space dimensions. Copyright © 2017 John Wiley & Sons, Ltd.     

Anisotropic slope limiting for discontinuous Galerkin methods

In this paper, we present an anisotropic version of a vertex‐based slope limiter for discontinuous Galerkin methods. The limiting procedure is carried out locally on each mesh element utilizing the bounds defined at each vertex by the largest and smallest mean value from all elements containing the vertex. The application of this slope limiter guarantees the preservation of monotonicity. Unnecessary limiting of smooth directional derivatives is prevented by constraining the x and y components of the gradient separately. As an inexpensive alternative to optimization‐based methods based on solving small linear programming problems, we propose a simple operator splitting technique for calculating the correction factors for the x and y derivatives. We also provide the necessary generalizations for using the anisotropic limiting strategy in an arbitrary rotated frame of reference and in the vicinity of exterior boundaries with no Dirichlet information. The limiting procedure can be extended to elements of arbitrary polygonal shape and three dimensions in a straightforward fashion. The performance of the new anisotropic slope limiter is illustrated by two‐dimensional numerical examples that employ piecewise linear discontinuous Galerkin approximations. Copyright © 2017 John Wiley & Sons, Ltd.     

Pro- and antioxidant characteristics of natural thiols

In aqueous solutions at physiological temperature, the mechanism of antioxidative action of natural thiols (glutathione, cysteine, and homocysteine) mainly involves reactions with reactive oxygen species (ROS), peroxyl radicals and hydrogen peroxide. Reduction of hydrogen peroxide by thiols is accompanied by radical generation. The kinetic characteristics of these processes, including those for the reactions of hydrogen peroxide and glutathione immobilized on solid supports such as sodium montmorillonite (clay) and cellulose were determined. Prooxidative effects of thiols are related with the reactions of thiyl radicals formed in the exchange reactions of thiols with other radicals and in the reactions between thiols and hydroperoxides. Thiyl radicals are known to react easily with double bonds. Resveratrol and caffeic acid, phenolic antioxidants containing double bond in their molecules, were shown to be consumed when reacted with glutathione and the process accelerated in the presence of hydrogen peroxide.     

Coupled spin, elastic, and electromagnetic waves in the magnetic of a ferromagnetic spiral phase

The spectrum of coupled spin, elastic, and electromagnetic waves in the magnetic of a ferromagnetic spiral phase is investigated. The frequency dependences of the reflection coefficient of electromagnetic waves from the surface of a semi-infinite magnet for different angles of the spiral are obtained. An acoustic analog of the Faraday effect in the magnetics of a ferromagnetic spiral phase is considered.     

Measurement of neutral-meson masses in meson-nucleus interactions at a momentum of 7 GeV/c at the Hyperon-M setup

The π ⁰, η, K ⁰, ω, and f ₂(1270) masses were measured at the HYPERON-Msetup in meson-nucleus interactions at a momentum of 7 GeV/c by using six nuclear targets: Be, C, Al, Cu, Sn, and Pb. The experiment in question proved to be insensitive to the expected effects of a modification to the omega-meson mass in nuclear matter. As for the f ₂(1270) meson, its mass and width values averaged over all experimental data, $m_{f_2 }$ = 1275.8 ± 1.0(stat.) ± 0.4(syst.) MeV/c ² and $\Gamma _{f_2 }$ = 190.3 ± 1.9(stat.) ± 1.8(syst.) MeV/c ², agree well with the world-average values. At the same time, our experimental data do not rule out the possible effect of an in-medium modification to the f ₂(1270)-meson mass for heavy nuclei at a level better than 0.4%.     

Temperature effect on the competition between the processes of 9-cyanophenanthrene exciplex decay

The activation parameters of internal conversion, intersystem crossing, and dissociation into radical ions were determined for the exciplexes of 9-cyanophenanthrene with 1,3,5- and 1,2,3-trimethoxybenzene. The activation enthalpies for the different processes of exciplex decay were found to be close for a given exciplex in a given solvent, thus allowing a linear approximation for the temperature dependence of the logarithm of the exciplex lifetime.Translated from Khimiya Vysokikh Energii, Vol. 39, No. 1, 2005, pp. 26–31.Original Russian Text Copyright © 2005 by Dogadkin, Dolotova, Soboleva, Kuzmin, Plyusnin, Pozdnyakov, Grivin.