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31.
[formula: see text] The generation of (2-PyMe2Si)2CHLi was easily accomplished by the deprotonation of (2-PyMe2Si)2CH2 using n-BuLi in Et2O. Thus generated (2-PyMe2Si)2CHLi was found to react with a variety of aldehydes and ketones to give the corresponding vinylsilanes in extremely high yields with complete stereoselectivities. 相似文献
32.
An attempt to estimate the thermal decomposition mechanism of polymers using the simultaneous TG-DTA/FT-IR system was summarized. The library search of FT-IR spectra at various temperatures and of the subtraction spectrum obtained by subtracting the spectra at different temperatures were used to determine the types of evolved gases from poly(ethylene terephthalate) and poly(butylene terephthalate) at given stages of decomposition. The quantitative analysis of evolved gases was carried out using the specific gas profiles at the specific absorption band. The kinetic parameters were estimated from both TG and spectroscopic curves measured at various heating rates. 相似文献
33.
34.
H. Yoshida 《Israel Journal of Mathematics》1986,54(3):366-380
Given two kinds of functionsf(X) andh(y) defined on them-dimensional Euclidean spaceR m (m≧1) and the set of positive real numbers respectively, we give an estimation of growth of subharmonic functionsu(P) defined onR m+n (n≧1) such that $$u(P) \leqq f\left( X \right)h\left( {\left\| Y \right\|} \right)$$ for anyP=(X, Y),X ∈R m, Y ∈R n, where ‖Y ‖ denotes the usual norm ofY. Using an obtained result, we give a sharpened form of an ordinary Phragmén-Lindelöf theorem with respect to the generalized cylinderD ×R n, with a bounded domainD inR m. 相似文献
35.
Antioxidant activity of a series of hydroxybenzalacetones was determined against peroxynitrite-induced lipid peroxidation in red blood cell membrane and SOS response through DNA damage in bacterial cells. Hydroxybenzalacetone derivatives with hydroxy, methoxy, ethoxy or methyl substitution were analyzed and found to be more effective than the water-soluble vitamin E analogue Trolox. The inhibitory effect against lipid peroxidation correlated well to that against the SOS response, which is dependent on decomposition of peroxynitrite by hydroxybenzalacetones outside of the cell membrane. The antioxidant activity was shown to correlate well with the electric parameter sigma+. Electron-donating substituents with more negative sigma+ values increased the potencies. The result suggests that hydroxybenzalacetones with more electron-donating substituents will protect tissue more effectively against oxidative stress. 相似文献
36.
Flameless atomic absorption spectrometry (flameless a.a.s.) was applied to study the state of mercury deposited on a gold plate electrode from very dilute mercury(II) solution by controlled-potential electrolysis. A stable monolayer is formed on the gold electrode by the electrolysis at a potential about 200 mV more positive than the reversible Nernst potential for the reduction of mercury(II) to mercury(0). After the monolayer formation, bulk mercury is deposited on the monolayer at the reversible potential and an adatom layer is also found. The difference of activation free energies between the evaporation of mercury from the monolayer and that from bulk mercury corresponds to the underpotential shift for the electrodeposition of mercury on the gold electrode. 相似文献
37.
Liu J Raveendran P Shervani Z Ikushima Y 《Chemical communications (Cambridge, England)》2004,(22):2582-2583
Ag2S nanocrystals with a mean diameter of 5.9 nm (sigma= 1.65 nm) and characteristic surface plasmon resonance absorption at 330 nm have been synthesized in water-in-supercritical CO2 reverse microemulsion using the commonly used AOT surfactant with 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (F-pentanol) as cosurfactant. 相似文献
38.
Tsuguo Yamaoka Nobuko Nakajima Ken'ichi Koseki Yutaka Maruyama 《Journal of polymer science. Part A, Polymer chemistry》1990,28(9):2517-2532
A series of novel photosensitive polybenzoxazole precursors were prepared from polycondensation of 2,2-bis(3,3′-amino-4,4′-hydroxyphenyl)hexafluoropropane with photosensitive dicarboxylic acid chlorides such as p-phenylenediacryloyl chloride and benzophenone-4,4′-dicarboxylic chloride. The precursors are soluble in common organic solvents owing to the presence of perfluoromethyl groups in the chain structure, and insolubilized in the solvents on irradiation with the light. Polybenzoxazole patterns with high resolution as well as high aspect ratio were reproduced by baking the precursor patterns at 300°C. The pattern shrinkage on the conversion to polybenzoxazole was slight. The polybenzoxazole films offered good heat-resistance up to 400°C in addition to good electrical properties. 相似文献
39.
Structure-activity relationships of a new antifungal imidazole, AFK-108, and related compounds 总被引:1,自引:0,他引:1
Hori K Sakaguchi A Kudoh M Ishida K Aoyama Y Yoshida Y 《Chemical & pharmaceutical bulletin》2000,48(1):60-64
Fungicidal activity of widely used imidazole antifungal drugs in topical applications is not so strong in spite of their fungistatic activities against dermatophytes and pathogenic yeasts. In order to improve fungicidal activity of imidazole antifungal agents, a series of novel imidazole derivatives having a hydrophobic substituent derived from isoprenoid were synthesized. The efficacy of these compounds was evaluated with respect to direct cell-membrane damaging activity, ergosterol biosynthesis inhibition, minimum growth-inhibitory concentration (MIC) and therapeutic effect for experimental dermatophytosis of guinea pigs. Among the newly synthesized compounds, the geranyl derivative named AFK-108 (2a) showed the highest in vivo fungicidal activity with both cell membrane damaging activity and ergosterol biosynthesis inhibition in vitro. 相似文献
40.
Chesney A Bryce MR Yoshida S Perepichka IF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(7):1153-1159
Two conceptually different routes to transient 1,2-diselones are reported: 1) via ring fragmentation of the 1,4,2-diselenazine system 6, and 2) by the tributylphosphane-induced depolymerisation of the shelf-stable organoselenium polymer 15. Evidence for the intermediacy of 1,2-diselone species 7 and 16 is provided in both cases by in situ trapping with dimethyl acetylenedicarboxylate (DMAD) to yield 1,4-diselenin derivatives. The route via 15 is especially expedient and trapping of 16 is efficient. Subsequent reactions of adduct 17 afford [1,2-ethanediylbis(diphenylphosphane)] [5,6-bis(methoxycarbonyl)-1,4-diselenin-2,3-dithiolato]nickel(IV) (20). Theoretical calculations at Hartree-Fock (HF) and Moller-Plesset electron-correlated levels (MP2) suggest that the cyclic 1,2-diselenete structure 7c is significantly more stable than the acyclic 1,2-diselone structure 7a. For the bicyclic system 16, the difference in energy between the cyclic and acyclic structures is considerably reduced due to the conformational rigidity imposed by the fused 1,3-dithiole ring. In contrast, the acyclic structures of the 1,2-dithione analogues 13a and 25a are computed to be more stable than their corresponding cyclic 1,2-dithiete structures 13c and 25c. 相似文献