Crazing of polymers in the presence of hyperbranched poly(ethoxysiloxane)

The crazing of various polymers (PET, isotactic PP, and HDPE) in the presence of branched poly(ethoxysiloxane) and its low-molecular-mass analog—tetraethoxysilane—has been studied. The hyperbranched poly(ethoxysiloxane) is shown to be an effective adsorptionally active medium for crazing of various solid polymers and development of nanoporous structures with a volume porosity of up to 60%. Depending on the nature of polymers, two mechanisms of crazing (either classical or delocalized crazing) can take place. The reactions of hydrolysis (basic and acidic) within the pores leading to formation of solid silica have been performed. Electron microscopic observations provide evidence that the transformation of a viscous adsorptionally active liquid into a solid compound directly within the volume of a polymer matrix leads to the stabilization of a highly dispersed polymer structure that arises in the course of crazing.     

Invasion zone modeling using water- and oil-based muds

The hydrodynamic processes of displacement of reservoir fluids in an oil-saturated reservoir in vertical well drilling are studied by numerical simulation accounting for the drilling conditions and the type of mud (water-clay or oil-based). The influence of the hydrodynamic characteristics of the invasion zone on the specific electrical resistance depending on the type of mud is studied. The results of numerical simulations for the interpretation of high-frequency electromagnetic logs were used to construct geoelectric and hydrodynamic models in the reservoirs with different fluid saturations.     

The possibility of using specific markers of certain types of medicinal plant raw material for the analysis of multicomponent plant teas and phytoteas

Thirteen multicomponent plant teas and phytoteas are studied to determine specific components in the given product. The validity of the chromato-mass-spectrometry method based on markers contained in the plant raw material for the external control of the composition of plant teas, phytoteas, and other phytopreparations is shown.     

Structure and isomerization of heterapentalene compounds containing hypervalent bonds with central nitrogen,phosphorus, or arsenic atom

The possibility for a specific type of isomerization (electromorphism) to occur in conjugated bicyclic organic compounds containing Group V elements was studied by the ab initio (RHF/6-31G**, MP2(full)/6-31G**), and DFT (B3LYP/6-31G**) methods. Compounds 2 (X = N, P, As) were found to exist in a monocyclic planar form with intramolecular donor-acceptor N...O coordination (X = N) and as aromatic heterapentalene structures with hypervalent O--X--O bonds (X = P, As). According to calculations, no isomerization of planar heteroaromatic structures into pyramidal ones occurs. The strength of the O--X--O hypervalent bond and the aromaticity of heterapentalene structures 2 with ten -electrons increase on going from X = N to X = P. Correct estimation of these effects requires the inclusion of electron correlation.     

Catalytic effect of alcohols on ligand substitution in tris (acetylacetonato) iron (III) by trifluoroacetylacetone

We have examined the effect of alcohols and chloroform on the substitution of ligands by trifluoroacetylacetone in tris(acetylacetonato) Fe(III). Alcohols appear to increase the reaction rate considerably, while chloroform catalyzes the reaction only slightly. Alcohols and chloroform enter the outersphere of tris(acetylacetonato) iron(III) via hydrogen bonds, thus weakening the Fe–O bond and promote the substitution of one ligand by another.     

Diffraction of pulse shear waves in a tunnel cavity of curvilinear section in an anisotropic massif

The problem of diffraction of longitudinal shear waves in the form of periodic triangular pulses by a cylindrical tunnel cavity in a rectilinearly orthotropic unbounded massif is reduced to a number of problems on the diffraction of harmonic shear waves of different relative length. Each of the problems on stationary diffraction is solved in series in the basis solutions of shear vibrations equations by using an affine coordinate transformation of the original domain. It is proposed to use a point method of least squares to seek the coefficients of the series. The influence of the degree of anisotropy of the elastic properties of the massif on the shear stress concentration at the boundary of a circular section is analyzed for a different position of the incident triangular pulse front relative to center of the cavity.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 20, pp. 70–76, 1989.