Manifolds with invariant semi-Riemannian almost product structure

A manifold M with semi-Riemannian almost product structure invariant relative to a transformation group G is considered. A connection with special G-invariance property is constructed in the corresponding bundle of frames.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 44, No. 7, pp. 926–931, July, 1992.     

Structure of polynuclear palladium(ii) hydroxocomplexes formed upon alkaline hydrolysis of palladium(ii) chloride complexes

The structure of polynuclear Pd^II hydroxocomplexes (PHC) formed as a result of alkaline hydrolysis of Pd^II chloride complexes was studied by EXAFS, SAXS, and TEM methods. It is established that in aqueous solutions a hydroxocomplex particle is a filament curled into a ball containing about 100 Pd atoms. The filament consists of planar coordination squares of PdO₄ units linkedvia one or two oxygen bridges of different geometry. Aging of samples results in an increase in the number of single bridging ligands and a decrease in the diameter of particles. Interatomic distances around palladium atoms were determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimlcheskaya, No. 10, pp. 1901–1905, October, 1995.     

New palladium nanoclusters. Synthesis,structure, and catalytic properties

The reduction of palladium(ii) carboxylates Pd₃(OCOR)₆ (R = Me, Et, CHMe₂, CMe₃) with hydrogen in alcohol solutions containing 1,10-phenanthroline (phen) and subsequent oxidation with oxygen gave new palladium nanoclusters, mainly particles with a nearly spherical metal core and an average size of 18 . Based on elemental analysis, NMR, X-ray photoelectron spectroscopy, and EXAFS, nanoclusters were described by the idealized formula Pd₁₄₇phen₃₂O₆₀(OCOR)₃₀. The specimens contained up to 25% smaller 55-atomic Pd clusters with a 10 metal core. New nanoclusters catalyze hydrogenation of alkynes and alkenes, reduction of nitriles with formic acid, oxidation of aliphatic and benzylic alcohols, oxidative esterification of ethylene and propylene, and disproportionation of benzyl alcohol into toluene and benzaldehyde.     

Sulfide Catalysts Supported on Al2O3: VI. Synthesis of Catalysts with the Use of Binuclear Molybdenum(V) Complexes with Sulfur-Containing Ligands

A new method was developed for the preparation of sulfide catalysts supported on aluminum oxide. The surface assembling of a direct precursor of the active component was used in this method. The method consists in the sequential immobilization of binuclear molybdenum complexes with S-containing ligands on the support surface followed by the immobilization of nickel (cobalt) compounds at the surface molybdenum complexes. The complexation and structure of the resulting complexes in solution and the structure of surface complexes were studied by ⁹⁵Mo and ¹⁷O NMR, IR, and EXAFS spectroscopy. The surface assembling of a direct precursor of the active component of sulfide hydrodesulfurization catalysts was demonstrated using IR and EXAFS spectroscopy. The activity of the resulting catalysts in a model reaction of thiophene hydrogenolysis was comparable to the activity of sulfide catalysts of the metal complex origin and was much higher than the activity of commercial catalysts and catalysts prepared by impregnation.     

Crystal and molecular structure of 6b,7,8,8a-tetramethyl-6b,8a-dihydrocyclobut[a]acenaphthylene and 1,2,2a,10b-tetramethyl-2a,10b-dihydrocyclobuta[l]phenanthrene

The crystal and molecular structure of 6b,7,8,8a-tetramethyl-6b,8a-dihydrocyclobut[a]acenaphthylene (I) and 1,2,2a,10b-tetramethyl-2a,10b-dihydrocyclobuta[l]phenanthrene (II) is established by XRD analysis. The C(6b)-C(8a) bond in I is lengthened to 1.603(3) ∢, and the C(2a)-C(10b) bond in II is prolonged to 1.589(6) ∢. The acenaphthene and dihydrophenanthrene frameworks are planar; the rms deviations of atoms from the plane are 0.011 and 0.032 ∢, respectively. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1140–1145, November–December, 1997.     

(CuO-CeO2)/glass cloth catalysts for selective CO oxidation in the presence of H2: The effect of the nature of the fuel component used in their surface self-propagating high-temperature synthesis on their properties

The potential of surface self-propagating high-temperature synthesis (SSHS) for obtaining (CuO-CeO₂)/glass cloth catalysts is demonstrated. The dependence of the structural and catalytic properties of the catalysts on their preparation conditions (nature of the fuel component) is considered. X-ray diffraction, electron microscopy, and EXAFS data suggest that the short-term action of high temperature in the SSHS leads to the complete decomposition of the precursors and has an effect on the distribution of the resulting phases. According to H₂ TPR and XPS data, the degree of dispersion of CuO and the electronic state of the reacting CuO and CeO₂ phases depend on the choice of fuel. This is likely due to fuels varying in the amount of heat released in their combustion. The degree of dispersion of CuO and the total contribution from Cu¹⁺ and Ce⁴⁺ to the electronic state of the active component increase as the standard enthalpy of combustion increases in the urea < glycerol < citric acid order. This leads to an increase in the catalytic activity of the (CuO-CeO₂)/glass cloth system in selective CO oxidation.     

Comparison of the efficiency of titanium(IV) and iron(III) oxide nanoparticles as mediators in suppression of bacterial growth by radiation of a blue (405 nm) light-emitting diode

The effect of blue (405 nm) radiation of a light-emitting diode in combination with titanium(IV) and iron(III) oxide nanoparticles on S. aureus 209 P, S. simulans, and D. hominis bacteria is studied. It is shown that, upon irradiation of bacteria by blue (405 nm) light, Fe₂O₃ nanoparticles have a stronger (by 5–30%) antibacterial effect than TiO₂ nanoparticles.     

Synthesis of new aminocyclitols by selective epoxidation of N-benzyl-N-methyl-2-cyclohepten-1-amine and tert-butyl 4-[benzyl(methyl)amino]-2,3,4,7-tetrahydro-1H-azepine-1-carboxylate

Synthesis of N-benzyl-N-methyl-2-cyclohepten-1-amine and tert-butyl 4-[benzyl(methyl)amino]-2,3,4,7-tetrahydro-1H-azepine-1-carboxylate from cyclic allyl acetates was performed. The features of stereoselective epoxidation of these substrates were investigated. The subsequent epoxide opening with water led to the formation of new pseudosaccharides, (1RS,2RS,3RS)-3-[benzyl(methyl)amino]-1,2-cycloheptanediol, (1RS,2RS,3SR)-3-[benzyl(methyl)amino]-1,2-cycloheptanediol, and (3RS,4RS,5RS)-3-[benzyl(methyl)amino]-4,5-azepanediol.     

Luminescent Method of Measuring the EXAFS Spectra of Structural Defects of Alkali‐Halide Crystals

It is shown that xray spectral methods — those of EXAFS and XEOL spectroscopy — allow determination both of the structure of inherent or impurity centers of luminescence in alkalihalide crystals and investigation of the dynamics of their change under the action of ionizing radiation. The methods are noted for high sensitivity. The possibilities of the methods are demonstrated for KBr, NaCl:Ni, and NaCl:Ni,Cu crystals taken as an example. New data on the structures of different luminescence centers investigated and dynamics of their change are obtained.