Polarization Analysis to Separate the Resonance Contribution to the Allowed X-Ray Reflections

JETP Letters - It has been shown that channels of resonant X-ray scattering with a change in polarization can be present in allowed Bragg reflections. The measurement of the energy and azimuthal...     

The globulins of cotton seeds XI. The structure of the chymotryptic peptides of the 7S globulin

Summary The amino-acid sequences of the chymotryptic peptides of the 7S globulin of cotton seeds have been determined.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 682–687, September–October, 1977.     

Kinetics of oxidation of β-picoline to nicotinic acid over vanadia-titania catalyst. 4. Kinetic model

A kinetic model for the β-picoline oxidation over vanadia-titania catalyst is presented. The model covers the reaction mechanism, temperature dependences and a system of kinetic equations. The activation energies and constants in these equations are calculated.     

Sonochemical synthesis of Biginelli compounds

The ultrasound effect accelerates the Biginelli reaction 40 and more times. A sonochemical method for the synthesis of ethyl 4-R-6-methyl-2-oxo- and 4-R-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates was developed. The target products were obtained within 2 to 5 min in 90—95% yields.     

Transformations of pyridine bases on a nickel-aluminum catalyst

The electronic structures of some pyridine bases are analyzed by means of ¹H and ¹³C NMR spectroscopic data for substituted pyridines and the calculated bond orders in the pyridine ring. The differences in the chemical bonds in the pyridine ring of isomeric methylpyridines and the carbon—carbon bonds between the ring and the methyl groups in these compounds are in agreement with the experimental data on the thermal stability of the simplest pyridine bases and the gas-phase transformation of the isomeric methylpyridines on an industrial nickel—aluminum catalyst. The possibility of obtaining mono- or dialkylpyridines under these conditions, depending on the structure of the starting pyridine bases, is demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 371–374, March, 1982.     

Multicomponent sonochemical synthesis of podands

An efficient sonochemical methodology is described for the synthesis of new podands containing substituted dihydropyrimidines.     

Mutual Influence of Electrode Processes during Electrodeposition of Layered Structures by the Single-Bath Method: The Effect of Nickel Deposition and Hydrogen Evolution on the Transport of Copper Ions in Acetate and Sulfamate Electrolytes

The effect of nickel deposition and hydrogen evolution on the transport of copper-containing ions is studied by numerically solving an electrodiffusion problem with use made of variational values of the formation constants of nickel and copper complexes in acetate and sulfamate electrolytes and thicknesses of the diffusion layer. It is concluded that the major contribution to the mass transfer is made by the effects of exaltation of the migration current and by the agitation of the near-electrode layer of electrolyte by evolving hydrogen. The possibility of employing migration effects in order to reduce the limiting current of copper in the region of nickel deposition and hydrogen evolution is substantiated. This will decrease the copper content in a layer of alloy during electrodeposition of layered structures.     

Methods for calculating the resonant part of the atomic factor in crystals with partial filling of the crystallographic position

The resonant part of the tensor atomic factor, which is important for incident radiation energies close to the atom absorption edges, is sensitive to the local environment of a scattering atom (near-range order). In this paper, a method for mathematical modeling of the resonant part of the atomic factor is developed by taking into account crystal-lattice relaxation caused by the partial filling of a crystallographic position. It is shown that an additional contribution leading to the appearance of purely resonance “forbidden” reflections can exist in the resonant atomic factor. As examples, crystals of potassium dihydrophosphate (KDP) and rubidium dihydrophosphate (RDP) are used to calculate such a contribution to the atomic factor of potassium and rubidium, and the last is compared to the thermally induced and dipole-quadrupole contributions to the atomic factor.     

Gold distribution in pyrrhotite crystals grown under hydrothermal conditions

The distribution of gold between pyrrhotite and greenockite was studied by the method of hydrothermal thermal-gradient cocrystallization of the components at a temperature of 450°C, a pressure of 1 kbar, and different activities of sulfur in the presence of As and Se impurities. The structural component of Au impurity in these minerals was selected by studying statistical samplings of the analytical data for single crystals. Ferrous greenockite incorporates a maximum of 10 ± 2 ppm Au in solid solution. The incorporation limit of Au in stoichiometric pyrrhotite was estimated to be 25 ± 9 ppm; for nonstoichiometric pyrrhotites, it is lower. The As and Se impurities barely affect the concentration of structural gold in the minerals. It was shown that constitutional vacancies in pyrrhotite do not capture Au impurity. The observed phenomenon may be the growth effect related to the surface properties of nonstoichiometric pyrrhotite crystals grown under hydrothermal conditions. Differences in the surface structure of pyrrhotites of different composition and the products of their sorption of gold were revealed by X-ray photoelectron spectroscopy.