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91.
92.
The static polarizabilities and the second-order hyperpolarizabilities of a series of tri-nuclear metal cluster models MS4(M′PPh3)2(M′PPh3)(M=Mo,W;M′=Cu,Ag,Au)have been calculated within the first-principle theoretical framework. The model clusters have two fragments of rhombic units and it is the charge ransfer from one of these moieties to the other that is responsible for nonlinear optical property. This kind of electronic delocaization, differentiated from that of planar π-system, is very interesting and is worthy for further investigation. 相似文献
93.
Summary A
tail-made polymer matrix is proposed to remove strontium ions from aqueous
solutions. The removal behavior of strontium ions on a crosslinked copolymer
containing methacrylic acid as functional groups was investigated as a function
of sorptive concentration, time, temperature and pH. It was observed that an
increase of these parameters enhanced the removal of Sr(II) ions from aqueous
solution. It is found that a maximum adsorption of Sr(II) ions can be obtained
on the crosslinked copolymer after 30 minutes and at pH 8. The increase of
Sr(II) ion concentration in the solution resulted in an increase in the amount
of Sr(II) ions adsorbed on the crosslinked copolymer containing methacrylic
acid as functional groups. However, after a maximum of Sr(II) concentration in
the solution, the percentage of adsorbed Sr(II) ions decreased. The adsorption
data are well represented by the Freundlich, Langmuir and Dubinin-Radushkevich
(D-R) isotherms. The adsorption capacity of the copolymer and the free energy
change were calculated by using the D-R isotherm. For the adsorption of Sr(II)
ions on the crosslinked copolymer the thermodynamic parameters (DH°,DS° andDG°) were
calculated.</p>
</p> 相似文献
94.
An oligosaccharide homologue named SnS-2 was isolated from the root of Scrophularia ningpoensis Hemsl.SnS-2 was purified by means of gel-permeation chromatography and ion-exchange chromatography. Its physicochemical properties, including carbohydrate content and molecular weight were determined. The structure of SnS-2 was elucidated by chemical methods along with ^1H and ^13C NMR spectroscopy, including two-dimensional DQCOSY and H-detected ^1H, ^13C HMQC experiments. These results show that SnS-2 possesses a backbone consisting of terminal α-Galp-(1→, α-Galp-(1→6), α-Glcp-(1→6) and nonreducing end β-Fruf-(2→. The bioactive assay showed that it could inhibit the growth of Lewis pulmonary carcinoma implanted in mice. 相似文献
95.
Feng K De Boni L Misoguti L Mendonca CR Meador M Hsu FL Bu XR 《Chemical communications (Cambridge, England)》2004,(10):1178-1180
Two new classes of two-photon absorbing Y-shaped molecules have been developed to possess an imidazole-thiazole core and a stilbene-type conjugation pathway with either nitro or sulfonyl as terminal electron-accepting group. 相似文献
96.
97.
The monodisperse, macroporous poly(glycidyl methacrylate- co-ethylene dimethacrylate) beads were synthesized by a single-step swelling and polymerization method. Based on this media, a weak cation exchange (WCX) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages for biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery, and good resolution for proteins. The measured bioactivity recovery for lysozyme was 98+/-5%. The dynamic protein loading capacity of the WCX packings was 17.3 mg g(-1). The experimental results show that the synthesized WCX resin has very weak hydrophobicity. 相似文献
98.
针对不确定环境下具有不同供应合约的供应商选择与订单分配问题,本文构建了基于风险-均值分析的模糊两阶段多周期集成优化模型。与传统的该问题研究并未充分考虑供应商选择与订单分配两阶段决策的交互影响不同,在该模型中,第一阶段供应商选择的评价目标依赖于后期实际运营中的订单分配决策;并考虑未来需求和实际运营成本的不确定性,引入在险价值和期望值两种决策准则对供应商选择方案的绩效进行评价。提出了该模型的分析求解方法,在险价值得以精确评估,期望值被控制在确定的误差范围内,并可以达到足够的精度要求。 相似文献
99.
本文在考虑政府奖惩机制下,研究零售商主导的闭环供应链中成员的动态均衡策略,其中制造商负责回收再制造,回收率随时间动态变化。分别构建了三种模式下的Stackelberg微分博弈模型:政府不对制造商和零售商实施奖惩机制、政府只对制造商实施奖惩机制以及政府同时对制造商和零售商实施奖惩机制。运用贝尔曼连续型动态规划理论,求解了三种模式下制造商和零售商的决策均衡结果并进行了对比分析,从消费者剩余价值和成员利润的视角证明了政府实施奖惩机制的有效性。最后通过算例对成员均衡策略进行了稳态分析和非稳态分析。研究结果表明:政府的奖惩机制能够正确引导闭环供应链成员做出最优决策,有利于减缓分散决策所带来的双重边际效应,提高消费者剩余价值。零售商分担回收责任会削减政府对制造商回收的激励作用,降低闭环供应链整体利润。相比之下,政府只对制造商实施奖惩机制是最优模式选择,可以同时提高经济和环保双重效益。 相似文献
100.
J. N. Spencer Jarusha DeGarmo I. M. Paul Qing He Xiaoming Ke Zhenqing Wu C. H. Yoder Shuyun Chen J. E. Mihalick 《Journal of solution chemistry》1995,24(6):601-609
Calorimetric studies of the inclusion complexes of straight and branched alcohols and of diols with alpha-cyclodextrin (-CD) have been carried out in water solvent. The data suggest that straight and branched chain alcohols enter the cavity of -CD alkyl end first. The hydroxyl group hydrogen bonds to the outer oxygen ring of the cyclodextrin. For branched chain alcohols the longer alkyl part of the molecule penetrates the -CD cavity up to the hydroxyl group. Diols form two hydrogen bonds to the outer oxygen ring of the cyclodextrin with some penetration into its interior. 相似文献