Solution with an inner transition layer of a two-dimensional boundary value reaction–diffusion–advection problem with discontinuous reaction and advection terms

Theoretical and Mathematical Physics - We study the problem of the existence and asymptotic stability of a stationary solution of an initial boundary value problem for the...     

Synthesis of Ag/ZnO mixture for powdered contact materials

The processes of a ultrafine Ag/ZnO mixture produced by coprecipitation from salt solutions were investigated. The coprecipitation in AgNO₃-ZnNO₃-Na₂CO₃ system was analyzed in the presence of surfactants, considering the pH value and a solution composition contribution. The optimal coprecipitation conditions were Na₂CO₃ precipitating agent excess of ～20%, providing a pH value of ～10, with subsequent thermal decomposition of the mixture at about 700 K. A thermal analysis of the precursor mixtures were carried out. The phase composition, dispersity and morphology of the precipitates were determined before and after a thermal treatment. The size decrease of the precipitated particles, as well as dispersity and distribution uniformity increase of the oxide inclusions in the target composite matrix is due to the presence of surfactants in solutions.     

Quantum-Chemical Study of the Mechanism of Hydrocarbon Oxidation with Molecular Oxygen

The minimal kinetic scheme of the mechanism of hydrocarbon oxidation with molecular oxygen was studied by the PM3 semiempirical quantum-chemical method and also by the B3LYP hybrid density functional method using the 3-21G and 6-21G(d) basis sets and the GAUSSIAN 94 software. The energy characteristics and structural parameters of the reactants, products, and transition states of some elementary stages were determined. The simplest hydrocarbons, methane and ethane, were taken as substrates. For same reactions the effect of substituents, including bulky groups (methylbenzene, ethylbenzene, isopropylbenzene), was considered.     

Synthesis and thermochemical properties of dialkylfuroxans

Conclusions A number of dialkylfuroxans was synthesized and their thermochemical properties, namely the heats of combustion and the enthalpies of formation, were studied.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 842–846, April, 1973.     

Synthesis and studies of new photochromic spiropyrans containing a formylcoumarin fragment

A computer search for new photoactive compounds among indoline spiropyrans of coumarin series was carried out using DFT B3LYP/6-31G(d,p) method. Based on the data obtained, the spiropyrans containing a formylcoumarin fragment annulated to the 2H-pyran ring and possessing photochromic properties were synthesized. The structure and photochromism of these compounds were studied by ¹H NMR, IR, and UV/Vis spectroscopy. The introduction of a formyl group into the coumarin moiety of spiropyrans led to a bathochromic shift of the long wavelength absorption maxima of merocyanine isomers, as well as to a considerable increase in their lifetime.     

Molecular characteristics and surface layer structure of poly(siloxane imides)

The effects of spontaneous ordering of molecular chains of poly(siloxane imide) block copolymers in the surface layers of thin films on glass and gold supports have been studied by the oblique polarized beam and photoelasticity methods. The effective thermodynamic rigidity of molecular chains of the block copolymers (the statistical segment length) has been found to be A = 10.4 × 10^?7 cm. The orientational ordering of molecular chains in poly(siloxane imide) surface layers is characterized by small values of the orientational order parameter (S ₀ ～ 0.007). This finding is explained by the microphase separation of the block copolymers. The evaporated gold layer contributes to the effect of surface birefringence owing to formation of the ordered system composed of islets—clusters of gold atoms.     

Status of the Yakutsk Air Shower Array and Future Plans

Physics of Atomic Nuclei - The Yakutsk Extensive Air Shower Array has been continuously operating for more than 50 years (since 1970) and up until recently it has been one of world’s largest...