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81.
The microwave spectrum of cis-thiopropionic acid in the ground vibrational state has been observed in the frequency range between 10 and 35 GHz. The rotational and centrifugal distortion constants, and the dipole moments have been determined. The conformation of this molecule is discussed on the basis of the observed results. 相似文献
82.
83.
The Mössbauer spectroscopy was applied on a random mixture of two kinds of magnetic ions with competing anisotropies, Fe1?xCoxCl2·2H2O. The Mössbauer spectra observed in the Co(Fe)-rich antiferromagnetic (AF) phase near the tetracritical point show that, although the m2(m1) spin component parallel to the easy axis of pure FeCl2·2H2O(CoCl2·2H2O) has no long-range order in this phase (from the neutron diffraction experiment), the m2(m1) spin component contributes to the magnetic hyperfine field at 57Fe nuclei as well as the m1(m2) spin component (which has a long-range order). This fact indicates that the m2(m1) spin components exists in the Co(Fe)-rich AF phase near the tetra-critical point at least in a time scale of ~ 10?8s. This result predicts that the antiferromagnetic ordering in the Co(Fe)-rich AF phase is a new type one. The new phase observed in the intermediate concentration region is demonstrated as the “mixed ordering” phase. 相似文献
84.
85.
Harada Y Girolami GS Nuzzo RG 《Langmuir : the ACS journal of surfaces and colloids》2004,20(25):10878-10888
The growth kinetics and morphologies of self-assembled monolayers deposited by contact printing 7-octenyltrichlorosilane (OCT) and octadecyltrichlorosilane (OTS) on Si(100) were studied by ellipsometry and atomic force microscopy. We found that, for both OCT and OTS, full monolayers could be obtained at room temperature after printing times of 120-180 s; the printing-based monolayer assembly processes follow apparent Langmuir adsorption kinetics, with the measured film growth rates increasing both with the ambient humidity and with concentration of the ink used to load the stamp. At a dew point of 10 degrees C and an ink concentration (in toluene) of 50 mM, the observed film growth rate constant is 0.05 s(-)(1). When the printing was carried out at a lower ambient humidity (dew points of 1-3 degrees C), the measured rates of assembly were approximately a factor of 2 slower. Increasing the deposition temperature from 25 to 45 degrees C under these conditions increased the film growth rate only slightly. The morphology of the films depends on the identity of the ink. Uniform, high-coverage films could be obtained readily from the eight-carbon chain length adsorbate OCT, provided that the stamp was not overloaded with the ink; for high concentrations outside of the optimal range, the surface presented significant numbers of adsorbed particles ascribed, in part, to siloxane polymers formed by hydrolysis of the ink on the stamp before printing. In marked contrast, for the 18-carbon adsorbate OTS, the printed films always consisted of a mixture of a uniform monolayer plus adsorbed polysiloxane particles. The different film morphologies seen for OCT and OTS are proposed to result from the different transfer efficiencies of the organotrichlorosilane relative to polysiloxane hydrolysis products formed during the printing process. These transfer efficiencies exhibit sensitivities related to the permeation of the poly(dimethylsiloxane) (PDMS) stamp by the silane reagents. Short-chain inks such as OCT evidently permeate the PDMS stamp more deeply than longer-chain inks such as OTS. This difference, and the different diffusion rates of ink vs oligomeric silane hydrolysis products, determines the film morphology obtained by contact printing. The mass transfer dynamics of the process thus yield surface layers derived from varying quantities of siloxane oligomers, which subsequently transfer to the substrate along with unhydrolyzed silane adsorbate during the printing step. The structural evolution of the contact-printed films so obtained is strikingly different from that of SAMs prepared by immersion. 相似文献
86.
Juzo Nakayama Mitsuru Tanuma Yoshiko Honda Masamatsu Hoshino 《Tetrahedron letters》1984,25(40):4553-4556
A series of arylmethanesulfonyl chlorides were treated with triethylamine in THF to give stilbenes in excellent yields. Workup of the mixtures below 10 °C permits isolation of stilbene episulfones which on warming decompose to yield the corresponding stilbenes stereospecifically. Application of the reaction to 9-fluorenylsulfonyl chloride affords bifluorenylidene, while trans-styrylmethanesulfonyl chloride gives 4,5-dihydro- 4,5-diphenylthiepin 1,1-dioxide and 1,6-diphenylhexatriene. 相似文献
87.
88.
The combination of Mo and cationic Au catalysts dramatically accelerated the rearrangement of diverse propargyl alcohols, which includes a short reaction time, mild conditions, and high product yields. A practical application to the highly challenging primary propargyl alcohols and the N-alkynyl amides is achieved. 相似文献
89.
The synthesis of a ring-expanded 4′-thio-apio-nucleoside derivative 4, designed to serve as a potential anti-HIV agent, is described. The epoxy alcohol derivative 10, prepared from 2-butene-1,4-diol, was converted to an allylsulfide derivative 13 in 3 steps. Ring-closing-metathesis of 13 gave the dihydrothiopyran derivative 20, which was further converted into sulphoxide 24. A Pummerer-type thioglycosylation reaction of 24 with a persilylated uracil derivative, followed by conversion to a cytosine derivative and deprotection, gave a racemic mixture of the ring-expanded 4′-thio-apio-nucleoside derivative 4 in good yield. 相似文献
90.
Ikeda K Kubo A Akahoshi N Yamada H Miura N Hishiki T Nagahata Y Matsuura T Suematsu M Taguchi R Ishii I 《Analytical and bioanalytical chemistry》2011,400(7):1853-1863
Fatty liver is one of the typical manifestations in homocysteinemia/homocystinuria patients and their genetic animal model, mice lacking cystathionine ??-synthase (Cbs ?/?). The vast majority of Cbs ?/? die within 4?weeks after birth via yet unknown mechanisms, whereas a small portion survive to adulthood, escaping fatty degeneration of the liver during lactation periods, through regeneration. To investigate the molecular basis of such fatty changes, we analyzed lipid components in fatty livers of 2-week-old Cbs ?/? and regenerated non-fatty livers of 8-week-old Cbs ?/? survivors using a chip-based nanoESI (electrospray ionization)-MS system, which allows quantitative detection of triacylglycerol/phospholipid molecular species. Hepatic levels of all major triacylglycerol species were much higher in Cbs ?/? than in wild-type mice at 2?weeks, although not at 8?weeks. Levels of some phospholipid species were either up- or downregulated in 2-week-old Cbs ?/?; e.g. saturated (16:0 and 18:0) or mono-unsaturated (16:1 and 18:1) fatty acids-containing phosphatidylcholine/phosphatidylethanolamine species were upregulated, while poly-unsaturated fatty acids-containing phosphatidylcholine (18:2?C18:2 and 18:2?C20:5), phosphatidylethanolamine (18:1?C20:4), and phosphatidylinositol (18:0?C20:4) were downregulated. Capillary electrophoresis-MS analysis identified high-level accumulation of S-adenosylmethionine and S-adenosylhomocysteine in fatty livers of 2-week-old Cbs ?/? but much less in non-fatty livers of 8-week-old Cbs ?/?. Although hepatic S-adenosylmethionine/S-adenosylhomocysteine ratios were comparable between 2-week-old Cbs ?/? and wild-type, global protein arginine methylation was disturbed in fatty livers of Cbs ?/?. Our results suggest that cellular signaling mediated by altered phospholipid contents might be involved in pathogenesis of fatty liver in Cbs ?/?C. 相似文献