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851.
852.
853.
For a connected graph G we denote by d(G,k) the number of vertex pairs at distance k. The Hosoya polynomial of G is H(G,x) = ∑k≥0 d(G,k)xk. In this paper, analytical formulae for calculating the polynomials of armchair open‐ended nanotubes are given. Furthermore, the Wiener index, derived from the first derivative of the Hosoya polynomial in x = 1, and the hyper‐Wiener index, from one‐half of the second derivative of the Hosoya polynomial multiplied by x in x = 1, can be calculated. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
854.
Ge-132对小鼠H22肝癌移植瘤的实验研究证明:1.Ge-132对H22肝癌移植瘤有一定的抑制作用,300mg/kg体重剂量抑瘤率达到36.19%;2.增强机体的抗氧化作用,抑制脂质的过氧化物水平;3.促进免疫功能,当Ge-132和环磷酰胺联合使用时,可抵抗环磷酰胺的免疫抑制作用,而且并不减弱其抑制瘤作用。 相似文献
855.
856.
我们用Fe_2(SO_4)_3·xH_2O为催化剂,对2-甲基-2-已醇脱水生成烯烃反应的溶剂化能力及其动力学做了研究,测定了20种不同溶剂中的反应速率常数和以丙至辛6种直链醇为溶剂于不同温度下反应的速率常数,确定了溶剂化能力与溶剂介电常数之间的线性关系。这方面工作尚未见报道。 相似文献
857.
Highly ordered rod-like large-pore periodic mesoporous organosilica (PMO) was successfully synthesized at low acid concentration with the assistance of inorganic salt using triblock copolymer P123 as a template. The roles of inorganic salt and acidity in the production of highly ordered mesostructure and the morphology control of PMOs were investigated. It was found that the inorganic salt can significantly widen the range of the synthesis parameters to produce highly ordered 2D hexagonal pore structure of p6mm symmetry. However, the uniform rod-like PMOs can only be synthesized in a narrow range of acid and salt concentrations, which were sensitive to induction time. The adsorption of lysozyme on PMO was studied at different pH values in comparison with adsorption on pure silica material under controlled morphology and pore structure. It was found that the adsorption capacity of lysozyme on the PMO was lower than that on pure SBA-15 silica material and the adsorption amounts are larger at pH 9.6 than at 7.0 for both materials. The results show that the electrostatic interaction between lysozyme and PMO/SBA-15 surface is more dominant than the hydrophobic forces and the interaction of neighboring lysozyme molecules also plays an important role. 相似文献
858.
Zhang WW Ren XM Li H Xie JL Lu CS Zou Y Ni ZP Meng QJ 《Journal of colloid and interface science》2003,268(1):173-180
Self-assembled monolayers (SAMs) of functionalized azobenzene thiols (RAzoCnSH, n=3-6 for R=H, abbreviated as AzoCnSH; and n=4 for R=CH(3)CONH, abbreviated as aaAzoC4SH) on different substrates RAzoCnSz.sbnd;z.sfnc;S (S represents substrates of vacuum-deposited gold (Au), silver foil (Ag), HNO(3) etched silver foil (EAg), and silver mirror (mAg)) have been studied by SERS in the near-infrared region. SERS of the SAMs on EAg and/or mAg exhibit SERS effects that vary with etching time and/or deposition time. The most appropriate time is 5 s for etching in 1:1 HNO(3) and 40 s for deposition in 0.1 M Ag(NH(3))(2)NO(3). Further, a layer of Ag mirror was conveniently deposited on the top of the SAMs on different substrates, yielding a more efficient SERS-active system possessing a "sandwiched" structure of mAgz.sfnc;RAzoCnS-z.sfnc;S. An appropriate surface roughness is required for the strongest SERS effect. Scanning electron microscopy (SEM) indicates that there exist a large number of projects around 100 nm on the surface showing the strongest SERS effect. When the surface roughness is decreased or increased, the SERS effect decreases sharply. The relationship between the SERS effect and the structural nature was investigated and showed that the enhancement factor decays exponentially with increasing in distances of the azobenzene group from the underlying substrate or the overlying silver mirror. This result reveals that the SERS effect may be the result of the electromagnetic coupling effect between two metal layers. 相似文献
859.
860.
Xing Yong Wang Jing Nan Cui Wei Min Ren Feng Li Chun Liang Lu Xu Hong Qian State Key Laboratory of Fine Chemicals Dalian University of Technology Dalian China School of Chemical Engineering Technology China University of Mining & Technology Xuzhou China Shanghai Key Laboratory of Chemical Biology East China University of Science Technology Shanghai China 《中国化学快报》2007,18(6):681-684
Baker's yeast mediated reduction of acenaphthenequinone within 4-10 h afforded mono-hydroxyacenaphthenone mainly with low enantioselectivity, the substrate and mono-hydroxyacenaphthenone product almost converted to dihydroxyacenaphthene after 48 h. By control of the reaction time and in the presence of DMF as co-solvent, the reduction of 6-substituted acenaphthenequinones under vigorous agitation afforded the corresponding 2-hydroxyacenaphthenones in 24-84% yields with 10-93% ee. 相似文献