Mechanism of olefin epoxidation in the presence of a titanium-containing zeolite

The effect of the nature of a solvent on the liquid-phase epoxidation of olefins with an aqueous solution of hydrogen peroxide over a titanium-containing zeolite is studied. Butanol-1, butanol-2, propanol-1, isopropanol, methanol, ethanol, water, acetone, methyl ethyl ketone, isobutanol, and tert-butanol are examined as solvents. A mechanism of olefin epoxidation with hydrogen peroxide in an alcohol medium over a titanium-containing zeolite is proposed. Epoxidation reactions involving hydrogen peroxide and different olefins are studied experimentally.     

Albanese homomorphism of the Chow group of 0-cycles of a real Algebraic variety

We study a certain homomorphism of the Chow group of 0-cycles of degree zero of a real algebraic variety into the group of real points of the Albanese variety; this homomorphism is obtained from the Albanese mapping for the corresponding variety. The kernel of this homomorphism is calculated and estimates for the kernel of the mapping of the torsion groups are obtained. Translated fromMatematicheskie Zametki, Vol. 65, No. 1, pp. 76–83, January, 1999.     

Flow effects in high-energy nucleus collisions with Ag(Br) in emulsion

Various flow phenomena observed by a unique emulsion method are reviewed. The experimental data of the emission of projectile and target fragments and relativistic particles in collisions of 1–160 A GeV/c ¹⁶O, ²²Ne, ²⁸Si, ³²S, ⁸⁴Kr, ¹⁹⁷Au, and ²⁰⁸Pb nuclei with ¹⁰⁸Ag (⁸⁰Br) targets are investigated. The transverse-momentum approach, the flow-angle analysis using principal vectors, the azimuthal correlation functions, the method of azimuthal correlations between charged secondaries, and the method of Fourier expansion of the azimuthal angle distributions are applied. Evidence of the directed flow of spectators has been obtained in the medium-impact nuclear interactions. In azimuthal distributions, with respect to the reaction plane, the signal of the elliptic flow of participants has been observed.     

Transport properties of Nb/Cu multilayers in 2D and 3D state

Transport properties of Nb/Cu multilayers were measured along and across layers. 3D-2D crossover occurs both when the temperature is belowT _2D and when the magnetic field parallel to layers exceeds the ‘breaking field’,H _br.     

Chemical Modification of Plant Alkaloids. III. X-Ray Diffraction and NMR Studies of the Structure of 1,3-Dimethyl-5-arylmethyl-5-cytisylmethylbarbituric Acids

The three-dimensional structure of 1,3-dimethyl-5-(4-allyloxybenzyl)-5-cytisylmethylbarbituric acid was found by x-ray structure analysis. A conformation with proximal cytisine and 2,4,6-trioxopyrimidine moieties was observed. Analogous structures for other synthesized 1,3-dimethyl-5-arylmethyl-5-cytisylmethylbarbituric acids and their 2-thio analogs were proved and the intramolecular effects caused by mutual magnetic shielding of spatially proximal groups were studied using PMR.