Electron microscopic study of the structure of nickel catalysts modified with heteropoly compounds

The state of the active phase on the surface of low-percentage nickel catalysts on carbon supports in the presence of new modifiers, mixed series 12 heteropoly compounds (HPC), was investigated. The presence of a modifier causes an increase in the dispersion of the nickel, formation of nickel-HPC associates on the surface of the support, and determines the high dispersion and thermal stability of the Ni particles in reducing medium. Modified nickel catalysts have higher selectivity for coal oils during liquid-phase hydrogenation of coal, and the process takes place with less gas formation.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2705–2711, December, 1990.     

Isoflavonoids from Heartwood of Maackia amurensis Rupr. et Maxim.

Orobol, tektorigenin, (-)-medicarpin, (±)-vestitol, and a new isoflavanone, the structure of which was established by chemical transformations and spectral data, were isolated from heartwood ofMaackia amurensis     

Pyridyl-substituted porphyrins: II. Synthesis and basic properties of dipyridylporphyrins

5,15-Bis(pyridin-2-yl)-, 5,15-bis(pyridin-3-yl)-, and 5,15-bis(pyridin-4-yl)-substituted 3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphyrins were synthesized, and their acid-base properties in ethanol-sulfuric acid were studied by spectrophotometric titration. Concentration ranges for the existence of mono- and dicationic forms of 5,15-dipyridylporphyrins and the corresponding ionization constants were determined. The effect of pyridine fragments on the basic properties of alkyl-substituted porphyrins was discussed.     

On Moduli Spaces,Equidistribution, Estimates,and Rational Points of Algebraic Curves

We consider the moduli spaces of hyperelliptic curves, Artin–Schreier coverings, and some other families of curves of this type over fields of characteristic p. By using the Postnikov method, we obtain expressions for the Kloosterman sums. The distribution of angles of the Kloosterman sums was investigated on a computer. For small prime p, we study rational points on curves y ² = f(x). We consider the problem of the accuracy of estimates of the number of rational points of hyperelliptic curves and the existence of rational points of curves of the indicated type on the moduli spaces of these curves over a prime finite field.     

Waveguide technique for measuring thin film parameters

A waveguide technique for measuring the absorption coefficient, refractive index, and thickness of thin films is suggested. It is based on taking the angular dependence of the light beam reflection coefficient in an optical scheme involving a prism coupler. Application of the technique to determining the parameters of thin-film waveguides, insulating coatings, and metal films is considered.