How to Increase Water Resistance of Adhesive Wood Compounds Formed by Adhesives Based on Polyvinyl-Acetate Dispersion

The influence of glyoxal on the water resistance of pine–pine and beech–beech wood compounds formed by adhesives on the basis of polyvinyl acetate dispersion is studied. A noticeable increase in water resistance is observed for pine–pine compounds if the adhesive composite contains not only glyoxal, but also aluminum chloride and “chymol” additives. However, in the case of beech–beech compounds, the effect of this composition becomes less pronounced.     

Crystal structure and thermodynamic properties of dipotassium diiron(III) hexatitanium oxide

In the present work, the temperature dependence of heat capacity of dipotassium diiron(III) hexatitanium oxide has been measured for the first time in the range from 10 to 300 K by means of precision adiabatic vacuum calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity $ C_{p}^{ \circ } (T) $ , enthalpy $ H^{ \circ } (T) - H^{ \circ } (0) $ , entropy $ S^{ \circ } (T) - S^{ \circ } (0), $ and Gibbs function $ G^{ \circ } (T) - H^{ \circ } (0) $ for the range from T → 0 to 300 K. The structure of K₂Fe₂Ti₆O₁₆ is refined by the Rietveld method: space group I4/m, Z = 1, a = 10.1344(2) Å, c = 2.97567(4) Å, V = 305.618(7) Å³. The high-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion.     

Comparative nonempirical study and isodesmic calculations of heats of formation of HNCO and HPCO isomers

The structural, electronic, and energetic characteristics of CHNO and CHOP isomers, and also of several related compounds, were calculated by a nonempirical method. Enthalpies of these isomers, obtained using the method of isodesmic reactions, are given.V. I. Lenin Moscow Pedagogical State University, 117913 Moscow. Institute of Physiologically Active Compounds, Russian Academy of Sciences, 142432 Chernogolovka. Institute of New Chemical Problems, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1585–1590, July, 1992.     

Acid-catalyzed acylation of 4-alkyl-3-azapyrylium salts and the synthesis of 4-acylaminopyrylium salts

4-Alkyl-3-azapyrylium salts undergo acylation at the alkyl group under acid-catalyzed conditions to give 4-acylmethyl-3-azapyrylium derivatives, which upon heating in proton-donating solvents recyclize to give 4-acylaminopyrylium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 265–269, February, 1991.     

Convergence Theory for Preconditioned Eigenvalue Solvers in a Nutshell

Preconditioned iterative methods for numerical solution of large matrix eigenvalue problems are increasingly gaining importance in various application areas, ranging from material sciences to data mining. Some of them, e.g., those using multilevel preconditioning for elliptic differential operators or graph Laplacian eigenvalue problems, exhibit almost optimal complexity in practice; i.e., their computational costs to calculate a fixed number of eigenvalues and eigenvectors grow linearly with the matrix problem size. Theoretical justification of their optimality requires convergence rate bounds that do not deteriorate with the increase of the problem size. Such bounds were pioneered by E. D’yakonov over three decades ago, but to date only a handful have been derived, mostly for symmetric eigenvalue problems. Just a few of known bounds are sharp. One of them is proved in doi: 10.1016/S0024-3795(01)00461-X for the simplest preconditioned eigensolver with a fixed step size. The original proof has been greatly simplified and shortened in doi: 10.1137/080727567 by using a gradient flow integration approach. In the present work, we give an even more succinct proof, using novel ideas based on Karush–Kuhn–Tucker theory and nonlinear programming.     

Stabilization of unstable stationary points in equations with delayed argument

We solve the problem of localization and stabilization of an unstable stationary point of a nonlinear system of ordinary differential equations (ODE) with a delayed argument for parameter values when the ODE system has chaotic dynamics. Translated from Nelineinaya Dinamika i Upravlenie, pp. 133–141, 1999.     

Role of Fe and Co in optical conductivity and electronic structure of TbNi4Fe and TbNi4Co

Optical properties of two intermetallic compounds TbNi₄Fe and TbNi₄Co have been studied employing ellipsometry in a spectral range 0.22–15 μm to reveal their characteristic features in comparison with the parent compound TbNi₅. The electronic structure of TbNi₄Fe and TbNi₄Co was calculated within the LSDA + U method (local spin density approximation with Hubbard U-correction). Based on the calculated electronic structure results, the theoretical optical conductivity was calculated and used to interpret experimental conductivity in the range of interband optical absorption.     

Synthesis and Crystal Structure of Rubidium Uranyltricarbonate

A procedure for the synthesis of uranyltricarbonatetetrarubidium Rb₄UO₂(CO₃)₃ was developed. Its crystal structure was determined by X-ray diffraction analysis: space group C2/c; a=10.778(5) , b=9.381(2) , c=12.509(3) . =94.42(3)°, Z=4; 1178 independent reflections, R=0.0662.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 387–390.Original Russian Text Copyright © 2005 by Chernorukov, Mikhailov, Knyazev, Kanishcheva, Zamkovaya.     

Effect of iodine-containing promoter on the catalytic activity of silver in the course of ethylene glycol oxidation

Surface morphology and catalytic properties of electrolytic silver crystals in partial oxidation of ethylene glycol into glyoxal were studied.     

Effects of chain length on the rates of C-C bond dissociation in linear alkanes and polyethylene

Molecular dynamics modeling of C-C bond dissociation is performed for a series of linear alkanes and polyethylene macromolecules with the chain lengths ranging from one to a thousand constituent ethylene monomers (PE-1-PE-1000). The rate constants obtained in molecular dynamics calculations are compared with those determined using variational transition state theory with the same potential energy surface. The results of simulations demonstrate a significant accelerating effect of chain length on the rates of C-C bond scission. Per-bond rate constant values increase with the increasing chain length, up to an order of magnitude, in the sequence of linear alkanes from PE-1 (ethane) to PE-5 (decane); this dependence becomes saturated for longer chain lengths. Stiffening the potentials of bending and especially the torsional degrees of freedom diminishes the accelerating effect of chain length, while constraining the bond distances for all C-C bonds except the one undergoing dissociation has no effect. The results of the calculations are compared with existing experimental data on the dependences of the rates of thermal decomposition of linear alkanes on the alkane chain length.