Study of the polymorphic hexagonal-face-centered-cubic transformation in Cu2S

The results of a dynamic high-temperature x-ray diffraction investigation into the special characteristics of the hexagonal-fcc polymorphic transformation in Cu₂S are presented. Close to the phase-transformation temperature, two groups of superstructural reflections appear on the x-ray diffraction patterns, some of these being indexed in the 12H hexagonal lattice (Ramsdel) and others in the 14H lattice. The mechanism of the hexagonal — fcc phase transition in Cu₂S is considered as passing through the intermediate 12H and 14H polytypic structures by way of the successive accumulation of periodically disposed stacking faults. The effect of thermal cycling within the phase-transformation temperature range on the course of the actual transformation is verified.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 100–103, May, 1976.     

Convection and heat transfer near the critical point of carbon dioxide

A study has been made of convective heat transfer between carbon dioxide and electrically heated wires in horizontal and vertical channels. The heat-transfer and convection coefficients have been and a dimensionless correlation determining the onset of convection verified.     

Polymer–Colloid Complexes Based on Cationic Imidazolium Amphiphile,Polyacrylic Acid and DNA Decamer

The solution behavior and physicochemical characteristics of polymer–colloid complexes based on cationic imidazolium amphiphile with a dodecyl tail (IA-12) and polyacrylic acid (PAA) or DNA decamer (oligonucleotide) were evaluated using tensiometry, conductometry, dynamic and electrophoretic light scattering and fluorescent spectroscopy and microscopy. It has been established that PAA addition to the surfactant system resulted in a ca. 200-fold decrease in the aggregation threshold of IA-12, with the hydrodynamic diameter of complexes ranging within 100–150 nm. Electrostatic forces are assumed to be the main driving force in the formation of IA-12/PAA complexes. Factors influencing the efficacy of the complexation of IA-12 with oligonucleotide were determined. The nonconventional mode of binding with the involvement of hydrophobic interactions and the intercalation mechanism is probably responsible for the IA-12/oligonucleotide complexation, and a minor contribution of electrostatic forces occurred. The latter was supported by zeta potential measurements and the gel electrophoresis technique, which demonstrated the low degree of charge neutralization of the complexes. Importantly, cellular uptake of the IA-12/oligonucleotide complex was confirmed by fluorescence microscopy and flow cytometry data on the example of M-HeLa cells. While single IA-12 samples exhibit roughly similar cytotoxicity, IA-12–oligonucleotide complexes show a selective effect toward M-HeLa cells (IC₅₀ 1.1 µM) compared to Chang liver cells (IC₅₀ 23.1 µM).     

Kinetics of hydrogen oxidation near the lower explosion limit

Kinetics of hydrogen oxidation near the lower explosion limit in the kinetic region of chain termination has been studied. Major effects, causing deviations of the reaction kinetics from calculations by the linear theory of branched chain processes, are shown to be (1) the inhibition of the reacting mixture by the products of interaction of active centers with vacuum grease or with impurities contained in it and (2) the heterogeneous negative interaction of reaction active centers. The kinetics of hydrogen oxidation in this region has been calculated with consideration of the heterogeneous negative chain interaction. A set of parameters has been obtained that make it possible to determine by the shape of the kinetic curves the sign and the value of nonlinear interaction of chains near the lower explosion limit. It has been shown that the experimental data are in good agreement with the calculations, provided the heterogeneous negative chain interaction is taken into consideration and the inhibiting effect of impurities is eliminated. The rate of heterogeneous generation of chains on a quartz surface treated with hydrofluoric or boric acid has been determined.     

Hierarchical Framework for Shape Correspondence

Detecting similarity between non-rigid shapes is one of the fundamental problems in computer vision. In order to measure the similarity the shapes must first be aligned. As opposite to rigid alignment that can be parameterized using a small number of unknowns representing rotations, reflections and translations, non-rigid alignment is not easily parameterized. Majority of the methods addressing this problem boil down to a minimization of a certain distortion measure. The complexity of a matching process is exponential by nature, but it can be heuristically reduced to a quadratic or even linear for shapes which are smooth two-manifolds. Here we model the shapes using both local and global structures, employ these to construct a quadratic dissimilarity measure, and provide a hierarchical framework for minimizing it to obtain sparse set of corresponding points. These correspondences may serve as an initialization for dense linear correspondence search.     

Conformational Analysis of N-Alkyl-N-[2-(diphenylphosphoryl)ethyl]amides of Diphenylphosphorylacetic Acid: Dipole Moments,IR Spectroscopy,DFT Study

Experimental and theoretical conformational analysis of N-methyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, N-butyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, and N-octyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide was carried out by the methods of dipole moments, IR spectroscopy, and Density Functional Theory (DFT) B3PW91/6-311++G(df,p) calculations. In solution, these N,N-dialkyl substituted bisphosphorylated acetamides exist as a conformational equilibrium of several forms divided into two groups—with Z- or E-configuration of the carbonyl group and alkyl substituent, and syn or anti arrangement of the phosphoryl-containing fragments relative to the amide plane. The substituents at the phosphorus atoms have eclipsed cis- or staggered gauche-orientation relative to the P=O groups, and cis orientation of the substituents is due to the presence of intramolecular H-contacts P=O...H−C_phenyl or p,π conjugation between the phosphoryl group and the phenyl ring. Preferred conformers of acetamides molecules are additionally stabilized by various intramolecular hydrogen contacts with the participation of oxygen atoms of the P=O or C=O groups and hydrogen atoms of the methylene and ethylene bridges, alkyl substituents, and phenyl rings. However, steric factors, such as a flat amide fragment, the bulky phenyl groups, and the configuration of alkyl bridges, make a significant contribution to the realization of preferred conformers.