Complexation of Fe3+, Cu2+, and Cr3+ β-diketonates with poly(urethane) and poly(methyl methacrylate) in semi-interpenetrating networks: Effect on phase separation

Complexation of iron, copper, and chromium β-diketonates with poly(urethane) and poly(methyl methacrylate) in semi-interpenetrating polymer networks was studied by IR spectroscopy and ESR using various paramagnetic probes. It was shown that types of complexes arising in semi-interpenetrating polymer networks depend on the central metal ion in a chelate. In the networks containing iron and copper β-diketonates, formation of complexes between chelates of these metals and donor groups of PUR and PMMA promotes mutual penetration of poly(urethane) and poly(methyl methacrylate) phases. As a consequence, the degree of their separation decreases and the interphase region widens.     

Fabrication of polytetrafluoroethylene- and graphite-containing oxide layers on aluminum and titanium and their structure

Stable aqueous electrolyte emulsions with negatively charged micelles containing dispersed particles of polytetrafluoroethylene (PTFE) or graphite are obtained using siloxane-acrylate emulsion as an emulsifier. The oxide coatings formed in such electrolytes contain carbon, polytetrafluoroethylene, or graphite. The coatings with PTFE particles are similar to monolithic polytetrafluoroethylene with respect to its hydrophobic characteristics. According to X-ray photoelectron spectroscopy data, the surface of the formed coatings predominantly contains aliphatic carbon (C-C and C-H bonds) and some fraction of oxidized (or, in the case of PTFE-containing electrolytes, fluorinated) carbon.     

Multidimensional Watson lemma and its applications

We prove the multidimensional analog of the well-knownWatson lemma and then apply it to prove a local limit theorem for the transition probabilities of symmetric random walks on the multidimensional lattice with infinite variance of jumps.     

Transformations of 6,7-Epoxy Derivatives of Citral and Citronellal in Various Acidic Media

The transformations of 6,7-epoxy derivatives of widely spread in the nature unsaturated aldehydes, citral and citronellal, in various acidic media both under conditions of homogeneous and heterogeneous catalysis were investigated. A number of previously unknown products belonging to different classes of organic compounds was obtained. Probable mechanisms of the products formation are discussed.     

Reactions of caryophyllene,isocaryophyllene, and their epoxy derivatives with acetonitrile under ritter reaction conditions

Acid-catalyzed reactions between acetonitrile and caryophyllene, isocaryophyllene, caryophyllene 4, 5-epoxide, and isocaryophyllene 4,5-epoxide affording optically active amides with a tricyclic skeleton were investigated.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 11, 2004, pp. 1641–1646.Original Russian Text Copyright © 2004 by Yarovaya, Korchagina, Rybalova, Gatilov, Polovinka, Barkhash.     

Harmonic Vibrations of a Viscoelastoplastic Sandwich Cylindrical Shell

The free and forced harmonic vibrations of viscoelastoplastic sandwich shells are analyzed. An equation for approximate determination of the amplitudes of near-resonance vibrations is derived. As an example, the problem is solved for a sandwich circular cylindrical shell     

Synthesis and colloidochemical properties of cerium dioxide hydrosols stabilized by zirconium polycationic compounds

It is shown that cerium dioxide hydrosols can be stabilized by polycationic compounds of zirconium, and the optimum conditions of the stabilization are determined. Stable CeO₂ hydrosols with concentrations of higher than 20 wt % are prepared; the sizes and electrophoretic mobility of their particles, as well as sol stability in the presence of some electrolytes, are investigated. The nature of the aggregation stability of the stabilized cerium dioxide sols is discussed.     

Large deviations for a symmetric branching random walk on a multidimensional lattice

An important role in the theory of branching random walks is played by the problem of the spectrum of a bounded symmetric operator, the generator of a random walk on a multidimensional integer lattice, with a one-point potential. We consider operators with potentials of a more general form that take nonzero values on a finite set of points of the integer lattice. The resolvent analysis of such operators has allowed us to study branching random walks with large deviations. We prove limit theorems on the asymptotic behavior of the Green function of transition probabilities. Special attention is paid to the case when the spectrum of the evolution operator of the mean numbers of particles contains a single eigenvalue. The results obtained extend the earlier studies in this field in such directions as the concept of a reaction front and the structure of a population inside a front and near its boundary.