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Highly dispersed molybdena-titania catalyst can be prepared by an equilibrium adsorption method. In this method, molybdate
anions adsorb onto the positively charged titania surfaces via electrostatic attraction by controlling the pH of the impregnating
solution and they increase as an inverse function of the pH. 95Mo-NMR and UV spectroscopic studies of impregnating solution show that the polymeric species like Mo7O24
6-ions are adsorbed on titania in the acidic impregnating solution. XRD, Raman, and XPS data of the calcined samples show that
mono-layer coverage of molybdenum oxide over-layer possesses a highly distorted MoO6 group with a molecular geometry resembling the distorted square pyramid.
The catalytic oxidation of methanol over the surface molybdate species on titania possesses higher turnover numbers and higher
selectivities of partial oxidation products than the catalysts supported on alumina, silica, zirconia, or magnesia. Changes
of the surface properties either after reduction and sulfiding treatment over monolayer catalyst on titania have also been
investigated. The NO chemisorption and XPS studies show that two types of active sites appeared after reduction treatment:
one site is active for hydrogenation of 1,3-butadiene and the other site is active for metathesis of propene. A higher degree
coordinative unsaturations of MO is required for hydrogenation than metathesis. After sulfiding treatments of the catalyst,
hydrogenation of 1,3-butadiene also requires triply coordinative unsaturation, and hydrogenolysis of thiophene requires the
ensemble of doubly or triply coordinative unsaturations. 相似文献
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Ichikawa H Yoshie S Shirasawa S Yokoyama T Yue F Tomotsune D Sasaki K 《Cryo letters》2011,32(6):516-524
Poor adhesion of single human embryonic stem (hES) cells after freeze-thawing causes death. To investigate mechanisms responsible for this, Rho-dependent protein kinase (ROCK) inhibitor Y-27632-treated and untreated single hES cells were analyzed for E-cadherin and F-actin distribution by immunostaining and phalloidin staining respectively and for G13 signaling pathway components by DNA microarray and quantitative polymerase chain reaction (PCR). Y-27632-treated cells clustered rapidly and maintained E-cadherin and F-actin distribution without losing Oct-3/4. Immediately after thawing, E-cadherin in untreated hES cells dotted along the membrane and then displayed eccentric cytoplasmic localization. Bleb formation and early Oct-3/4 loss occurred after F-actin network condensation in the cytoplasm. Microarray analyses and quantitative PCR indicated upregulation of two actin reorganization-associated components of the G13 signaling pathway, Arhgdib and Cdc42, in untreated cells. Considering these findings and that cell death was partly interrupted by Y-27632, E-cadherin and actin cytoskeleton network disruption through the G13 signaling pathway may cause hES cell death after freeze-thawing. 相似文献
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The relationship between scattering and the acoustic characteristics of urban streets is examined by computer simulation. The simulation method is a combination of the image method for specular reflection and the radiosity method for scattering reflection. The findings are as follows: (1) the effect of scattering on the SPL appears as an increase at short distances and as a decrease at great distances. The range of the increase in SPL is larger in high-facade streets. In low-facade streets, the primary effect of scattering on SPL is a decrease in SPL. (2) In low-facade streets the reverberation time is determined by the sum of absorption coefficient and scattering coefficient. In contrast, in high-facade streets, the reverberation time is determined by the absorption coefficient. (3) The simulated result for the reverberation time shows good agreement with measured value in actual streets. (4) The estimated values for the sum of absorption coefficient and scattering coefficient of facades of actual urban streets range from 0.1 to 0.25. 相似文献
4.
Lúcia H. B. Baptistella Alana Z. Neto Helena Onaga Eduardo A. M. Godoi 《Tetrahedron letters》1993,34(52):8407-8410
Tipson-Cohen reactions of sugar derivatives containing contiguous sulfonyloxy groups have been studied in a microwave oven. Considerable rate increases and high yields of the unsaturated products have been observed. 相似文献
5.
Koji Matsuoka Tomotsune Onaga Jun-Ichi Sakamoto Nobuo Sakairi Daiyo Terunuma 《Tetrahedron letters》2004,45(51):9383-9386
An efficient synthesis of a useful thioglycosyl donor 2 was accomplished directly from known peracetylated sialic acid methyl ester and 1-dodecanethiol (lauryl mercaptan) in the presence of BF3-OEt2. The reactivities of the lauryl glycosides for glycosidation by means of TMSOTf as a convenient promoter were investigated, and the lauryl thioglycoside showed satisfactory activities. Further transformation of the lauryl glycoside was also attempted to give a 5-azide analogue 14 of the sialic acid, which was also reacted with a secondary alcohol in the presence of TMSOTf to give known glycoside 15 in high yield. 相似文献
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