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61.
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Chun-Yang Jina Dao-Dao Zhang Tetsuya Oguma Shi-Xiong Qian 《Journal of inclusion phenomena and macrocyclic chemistry》1996,24(4):301-310
Cycloisomalto-heptaose (CI-7) and cycloisomalto-octaose (CI-8) are two novel cyclodextrans. Treatment with C60 or C70 by kneading leads to the formation of four distinct water-soluble inclusion complexes: CI-7/C60 (2: 1), CI-8/C60 (2: 1), CI-7/C70 (2: 1) and CI-8/C70 (2: 1). Their formation and structures have been examined by UV vis spectroscopy, X-ray powder diffraction and fluorescence spectral studies. The reaction is a reversible process. 相似文献
63.
Ethyl pentafluoropropanethioate, prepared by treating ethanethiol with hexafluoro-1, 2-epoxypropane in the presence of triethylamine, was found to be a convenient pentafluoropropionylating agent for amines and alcohols. 相似文献
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A carrier transport model to explain the high-frequency response in high-speed MQW lasers is described. The ambipolar approximation, which is unsuitable for dealing with the high-speed carrier dynamics in MQW structures, was not adopted for small-signal analysis. The carrier transport effect can be characterized by four time constants: the electron transport time, bmn; the hole transport time, bmp; the electron escape time, wbn; and the hole escape time, wbp. The frequency response was interpreted as the sum of the constant response term due to the fast electron current and the roll-off term due to the slow hole transport time. The ratio of the electron contribution to the total response was proportional to the ratio of electron contribution to the total differential gain, , and reciprocally proportional to n0 = 1 + bmn/wbn. The value of was calculated to be about 0.5 for typical MQW lasers. The roll-off frequency is mainly determined by . The ratio p0 = 1 + bmp/wbp affects the resonant frequency and the damping rate in the high-bias condition. 相似文献
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We investigate the Ward identities of theW
symmetry in the super-Liouville theory coupled to the super-conformal matter of central charge
. The theory is classified into two chiralities. For the positive chirality, all gravitationally dressed scaling operators are generated from theq–1 gravitational primaries by one of the ring generators in the R-sector acting on them repeatedly. After fixing the normalizations of the dressed scaling operators, we find that the Ward identities are expressed in the form of theusual
W
q
algebra constraints as in the bosonic case:W
n
(k+1)
,=0, (k=1,...,q–1;nZ1–k), where the equations for even and oddn come from the currents in the NS- and the R-sector respectively. The non-linear terms come from the anomalous contributions at the boundaries of moduli space. The negative chirality is defined by interchanging the roles ofp andq. Then we get theW
p
algebra constraints. 相似文献
69.
Ishikawa T Watanabe T Tanigawa H Saito T Kotake KI Ohashi Y Ishii H 《The Journal of organic chemistry》1996,61(8):2774-2779
Nitrosation of 3-methoxyphenol and 1-naphthol were examined under both acidic (NaNO(2)-EtCO(2)H-H(2)O) and basic (i-AmNO(2)-K(2)CO(3)-DMF) conditions. Acidic nitrosations afforded ortho-directed products, whereas para-directed nitrosations were observed under basic conditions to yield p-quinone monooximes. The basic para-directed nitrosation was further examined using 15 phenols, two naphthols, and four phenolic heterocyclics. A one-pot operation of the basic nitrosation followed by methylation with dimethyl sulfate gave the corresponding methyl ethers in high yield. Two p-quinone monooximes derived from 3-methoxyphenol and 8-hydroxyquinoline showed a moderate activity against HSV-1, and the latter oxime was also effective against HSV-2. On the other hand, p-quinone monooximes derived from methyl salicylate, 1-naphthol, 7-hydroxy-2-methylbenzo[b]furan, and 8-hydroxycoumarin showed the comparable activity to that of DDI against HIV-1. 相似文献
70.