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721.
Recent theories predict dissipationless spin current induced by an electric field in doped semiconductors. Nevertheless, the charge current is still dissipative in these systems. In this work, we theoretically predict the dissipationless spin-Hall effect, without any accompanying charge current, in some classes of band insulators, including zero-gap semiconductors such as HgTe and narrow-gap semiconductors such as PbTe. This effect is similar to the quantum-Hall effect in that all the states below the gap contribute and there occurs no dissipation. However, the spin-Hall conductance is not quantized even in two dimensions. This is the first example of a nontrivial topological structure in a band insulator without any magnetic field. 相似文献
722.
723.
Tamamura H Hiramatsu K Mizumoto M Ueda S Kusano S Terakubo S Akamatsu M Yamamoto N Trent JO Wang Z Peiper SC Nakashima H Otaka A Fujii N 《Organic & biomolecular chemistry》2003,1(21):3663-3669
A CXCR4 antagonistic peptide, T140, and its bio-stable analogs, such as Ac-TE14011, were previously developed. These peptides inhibit the entry of T cell line-tropic strains of HIV-1 (X4-HIV-1) into T cells. Herein, a series of TE14011 analogs having modifications in the N-terminal region were synthesized to develop effective compounds with increased biostability. Among these analogs, 4F-benzoyl-TE14011 (TF14013) showed the strongest anti-HIV activity derived from CXCR4-antagonism, suggesting that a 4-fluorobenzoyl moiety at the N-terminus of T140 analogs constitutes a novel T140-based pharmacophore for CXCR4 antagonists. Structure-activity relationship (SAR) studies on TE14011 analogs with N(alpha)-acylation by several benzoic acid derivatives have disclosed a significant relationship between the anti-HIV activity and the Hammett constant (sigma) of substituted benzoic acids. TF14013 was found to be stable in mouse serum, but not completely stable in rat liver homogenate due to deletion of the C-terminal Arg14-NH2 from the parent peptide. This biodegradation was completely suppressed by N-alkyl-amidation at the C-terminus. Taken together, the enhancement of the T140-based pharmacophores led to development of a novel CXCR4 antagonist, 4F-benzoyl-TE14011-Me (TF14013-Me), which has very high anti-HIV activity and increased biostability. 相似文献
724.
725.
A six-term auxiliary integral expression for the two-electron Gaussian integral is derived on the basis of the Chebyshev polynomial approximation instead of the seven-term Taylor expansion. This expression and the related recurrence formula enable us to perform a high-speed calculation on a vector processing computer. 相似文献
726.
Fuji Funabiki Tetsuji Yano Shuichi Shibata Masayuki Yamane 《Solid State Ionics》2003,160(3-4):281-288
The Ag2O–TiO2–SiO2 glasses were prepared by Ag+/Na+ ion-exchange method from Na2O–TiO2–SiO2 glasses at 380–450 °C below their glass transition temperatures (Tg), and their electrical conductivities were investigated as functions of TiO2 content and the ion-exchange ratio (Ag/(Ag+Na)). In a series of glasses 20R2O·xTiO2·(80−x)SiO2 with x=10, 20, 30 and 40 in mol%, the electrical conductivities at 200 °C of the fully ion-exchanged glasses of R=Ag were in the order of 10−5 or 10−4 S cm−1 and were 1 or 2 orders of magnitude higher than those of the initial glasses of R=Na. The glass of x=30 exhibited the highest increase of conductivity from 3.8×10−7 to 1.3×10−4 S cm−1 at 200 °C by Ag+/Na+ ion exchange among them. When the ion-exchange ratio was changed in 20R2O·30TiO2·50SiO2 system, the electrical conductivity at 200 °C exhibited a minimum value of 7.6×10−8 S cm−1 around Ag/(Ag+Na)=0.3 and increased steeply in the region of Ag/(Ag+Na)=0.5–1.0. When the ion-exchange temperature was changed from 450 to 400 °C, the conductivity of the ion-exchanged glass of x=30 decreased. The infrared spectroscopy measurement revealed that the ion-exchange temperature of 450 °C induced a structural change in the glass of x=30. The Tg of the fully ion-exchanged glass of x=30 was 498 °C. It was suggested that the incorporated silver ions changed the average coordination number of titanium ions to form higher ion-conducting pathway and resulted in high conductivity in the titanosilicate glasses. 相似文献
727.
The states of chlorophyll a (Chl a) incorporated in a liquid crystal membrane were investigated by spectrophotometry in the
visible and IR regions.N-(p-methoxybenzylidene)-p′-butylaniline (MBBA) was used as the liquid crystal. The Chl a-MBBA (1∶3 in molar ratio) showed the dihydrate-Chl a aggregate
peak at 743 nm under excess water conditions. IR spectroscopic evidence indicated that the Chl a-MBBA membrane was hydrated
in the dihydrate stoichiometry [Chl a-3MBBA-2H2O], via the C-10 ester OC…H(H)O…Mg and the C-9 keto OC…H(H)O…Mg bondings. 相似文献
728.
729.
This paper presents a theorem concerning a matroid with the parity condition. The theorem provides matroid generalizations of graph-theoretic results of Lewin and Gallai. 相似文献
730.
2-Trifluoromethyl-3,3,3-trifluoropropanol gave 2-trifluoromethyl -3,3,3-trifluoroprop-l-ene in good yield by the action of base under mild conditions. 相似文献