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.     

Influence of solid surface on the compatibility in polymer blends produced in situ

Blends of linear polyurethane and poly(methyl methacrylate) were obtained in situ in the course of simultaneously proceeding reactions of polymerization and polyaddition. The effect of filler nanoparticles on the thermodynamic properties of the systems was investigated. Introduction of filler into the monomer mixture before curing increases the compatibility of final systems, as follows from diminishing thermodynamic interaction parameters. The reverse correlation has been established between the interaction parameter and the fraction of an interfacial region between two phases, its origin being the result of incomplete phase separation. Introducing filler into the reaction system determines simultaneously the increasing compatibility and increasing fraction of an interfacial region, i.e., prevents phase separation. Both effects are due to increasing of the interaction between two polymeric components at the interface with solid and changing conditions of incomplete phase separation in the course of reaction.     

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.     

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.     

Synthesis and Antiviral Properties of Camphor-Derived Iminothiazolidine-4-Ones and 2,3-Dihydrothiazoles

A set of heterocyclic products was synthesized from natural (+)-camphor and semi-synthetic (−)-camphor. Then, 2-Imino-4-thiazolidinones and 2,3-dihydrothiazoles were obtained using a three-step procedure. For the synthesized compounds, their antiviral activity against the vaccinia virus and Marburg virus was studied. New promising agents active against both viruses were found among the tested compounds.     

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     

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.     

Circular Sandwich Plates under Local Impulsive Loads

The axisymmetric transverse vibrations of a circular elastic sandwich plate under impulsive surface and linear loads are studied. To describe the kinematics of the asymmetric plate, the hypotheses of broken normal are adopted. The core is a lightweight material. Analytical solutions are obtained using Heaviside functions and Dirac delta-function. The solutions are analyzed numerically     

Positive Discrete Spectrum of the Evolutionary Operator of Supercritical Branching Walks with Heavy Tails

We consider a continuous-time symmetric supercritical branching random walk on a multidimensional lattice with a finite set of the particle generation centres, i.e. branching sources. The main object of study is the evolutionary operator for the mean number of particles both at an arbitrary point and on the entire lattice. The existence of positive eigenvalues in the spectrum of an evolutionary operator results in an exponential growth of the number of particles in branching random walks, called supercritical in the such case. For supercritical branching random walks, it is shown that the amount of positive eigenvalues of the evolutionary operator, counting their multiplicity, does not exceed the amount of branching sources on the lattice, while the maximal of these eigenvalues is always simple. We demonstrate that the appearance of multiple lower eigenvalues in the spectrum of the evolutionary operator can be caused by a kind of ‘symmetry’ in the spatial configuration of branching sources. The presented results are based on Green’s function representation of transition probabilities of an underlying random walk and cover not only the case of the finite variance of jumps but also a less studied case of infinite variance of jumps.