Mössbauer spectroscopic investigations on the pressure (shock wave) dependence of phase generation and carbide precipitation in C80W2 steel

Results of phase generation and carbide formation after a shock wave treatment of the C80W2 steel are reported. It is shown that the reactions follow the energy supply to the steel by shock wave treatment.     

Solid-state thermal polymerization of the heterocyclic HC7N7 acid

The preparation of a new type of thermally stable (up to 385°C) heterocyclic polymer, containing a five-membered fused ring system, is described. The ultraviolet, visible, and infrared spectra indicate that this solid-state polymerization probably proceeds via formation of an azomethine-type intermolecular crosslink, rather than via opening of the C₄N₄ ring system. The reaction is facilitated by the presence of reactive protons, which act as an efficient catalyst for this nucleophilic addition to the nitrile group. It is suggested that this type of solid-state polymerization may possibly be carried out on a single HC₇N₇ crystal resulting in a fully ordered macroscopic polymer single crystal.     

Polysaccharides from the wastes of vegetable and melon-type crops

The water-soluble polysaccharides and pectin substances from the wastes of vegetable and melon-type crops have been studied and their monosaccharide compositions have been determined. High- and low-methoxyl pectins have been isolated, and the physicochemical characteristics are given. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 597–600, September–October, 1994.     

Cycloalkene budding: mass spectrometric studies of competitive and dual cycloalkene extrusion reactions from doubly unsaturated aldehyde N,N-dimethylhydrazones

Mass spectral fragmentation pathways of four doubly unsaturated aldehyde N,N-dimethylhydrazones were investigated using EI-MS and tandem mass spectrometry (MS/MS) under electron ionization and collisionally activated decomposition (CAD) conditions. Cyclopentene extrusion was found to be slightly favored over cyclohexene loss in a hydrazone capable of losing either cycloalkene. Evidence for the regeneration of a chain-shortened iminium radical cation as a result of cycloalkene extrusion was provided by studying substrates capable of undergoing successive cycloalkene budding sequences. EI-MS of these compounds shows sequential loss of both cyclopentene and cyclohexene, in accord with expectations for a cascade mechanism. Although these MS/MS experimental results are also compatible with alternative mechanisms which would entail the simultaneous loss of both neutral cycloalkenes or of a macrocyclic diene, a rapid cascade of cycloalkene budding accounts best for the experimental observations.     

Chiral and Achiral Crystal Structures

An extensive study and analysis of the concepts, classification, presentation, and nomenclature of chirality and lack of chirality in crystal structures and their constituents is presented. Oriented crystal structures are classified. The chirality rules for existence of molecular crystal structures are examined and the relation to segmentation and latent symmetry highlighted. The nomenclature of chirality and related terms, and the relationship of chirality to optical activity is covered. The uses and limitations of the Euclidean normalizer are treated. An improved glossary of terms is included.     

Investigation of adsorption purification of the effluences containing heavy metal ions

Kinetics of adsorption purification of effluences containing heavy metal ions and adsorption of the metal ions under dynamic conditions using various adsorbents, including the products from industrial wastes are studied.     

Concentration dependence of the surface tension of ternary systems

A surface tension isotherm equation for ternary systems was derived based on general thermodynamic expressions with consideration for the concentration dependence of the molar surface area. Within the experimental errors, the equation describes the properties of ternary systems with smooth surface tension isotherms.     

Electrodeposition of fluorine-doped lead dioxide

The electrocatalytic properties of PbO₂ may be increased by incorporation of some ions such as F⁻. In this review, the preparation of fluorine-doped PbO₂ in the presence of some additives of fluorine-containing compounds (F⁻, potassium salt of nonafluoro-1-butanesulfonic acid C₄F₉O₃SK and Nafion^®) is reported. The mechanism of electrodeposition is discussed. The amount of additives in the deposit depends on the experimental conditions: potential, current density and charge of additive species in the plating solution. The physicochemical properties of doped oxide are very different from those of undoped oxide, accounting for the different electrocatalytic activity of the materials.     

Influence of pore diffusion on the kinetics of catalytic oxidation of ethylene

Internal diffusion influences the kinetics of ethylene oxidation on an industrial silver catalyst at temperatures higher than 240°C. This influence is completely eliminated when the diameter of the catalyst grains is decreased by a factor of 1/2.

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, 240°C. .