Acid-Catalyzed Reactions of 2,3-Epoxy Derivatives of Citral with Alcohols

Acid-catalyzed reactions of 2,3-epoxy derivatives of citral (which is a widely spread naturally occurring unsaturated aldehyde) with alcohols were studied under conditions of heterogeneous catalysis and in fluorosulfonic acid. A number of new products were obtained, and possible mechanisms of their formation were proposed.     

The monotonicity of the probability of return into the source in models of branching random walks

The paper discusses two models of a branching random walk on a many-dimensional lattice with birth and death of particles at a single node being the source of branching. The random walk in the first model is assumed to be symmetric. In the second model an additional parameter is introduced which enables “artificial” intensification of the prevalence of branching or walk at the source and, as the result, violating the symmetry of the random walk. The monotonicity of the return probability into the source is proved for the second model, which is a key property in the analysis of branching random walks.     

Plasma electrolytic synthesis and characterization of pH-sensitive TiO2-ZrO2-ZrTiO4-CeOx films on titanium

Journal of Solid State Electrochemistry - The Ti/TiO2 + ZrO2, Ti/TiO2 + CeOx, and Ti/TiO2 + CeOx + ZrO2 composites, including Y-doped ones, have been...     

Sequential semi-interpenetrating polymer networks based on polyurethane and polystyrene

The formation of microheterogeneous sequential semi-interpenetrating polymer networks based on network polyurethanes with different molecular masses of chain segments between crosslinks and a linear polystyrene has been studied by DSC and small-angle X-ray scattering. It has been shown that variation in the molecular mass of polymer segments between polyurethane network junctions affects the formation of the linear component of semi-interpenetrating polymer networks. As a result, the material structure may change in a wide range from a nearly single-phase system to a two-phase one. SAXS measurements indicate that there is a cymbate dependence between the degree of segregation of components of sequential semi-interpenetrating polymer networks and their microheterogeneous structure on the internetwork space. Two hierarchical heterogeneity levels are found to exist in polymer networks, and the features of each of these levels are analyzed.     

Spectral properties of evolutionary operators in branching random walk models

We introduce a model of continuous-time branching random walk on a finite-dimensional integer lattice with finitely many branching sources of three types and study the spectral properties of the operator describing the evolution of the mean numbers of particles both at an arbitrary source and on the entire lattice. For the leading positive eigenvalue of the operator, we obtain existence conditions determining exponential growth in the number of particles in this model.     

Formation of oxide layers modified with polytetrafluoroethylene or graphite on aluminum and titanium alloys by plasma electrolytic oxidation

For one-stage formation of coatings containing polytetrafluoroethylene or graphite, it was proposed to use Na₂SiO₃ + NaOH aqueous electrolyte containing siloxane-acrylate emulsion and dispersed powders of polytetrafluoroethylene or graphite. The phase and elemental composition and surface morphology of the formed coatings were determined. It was shown that the introduction of polytetrafluoroethylene markedly increases the hydrophobic and wear-resistant properties of coatings.     

Calcium and strontium phosphates coatings on titanium formed by the plasma electrolytic oxidation

Oxide-phosphate coatings were formed in electrolytes with Ca(II) and Sr(II) polyphosphate complexes. The data on an effect of a ratio of metal polyphosphate complexes in the electrolyte, treatment time on an elemental and phase compositions, thickness and morphology of coatings were obtained. The approach is promising for application of the coatings containing calcium phosphate with additives of phosphates of other metals to titanium implants.