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31.
具有优良NLO性质的芪唑盐(记为S)已被用于制备LB薄膜,但其成膜性不好,稳定性差;S和花生酸镉(记为A)的混合系虽可改善成膜性,但在此混合膜系中,S相的稳定性仍然不佳。应用SAXS和微机模型拟合(MCMI)研究了上述两类LB薄膜的凝聚态结构,结果指出:在LB薄膜的二维类晶系结构中,S分子中呈哑铃形的芪唑基倾向于作倾斜状的密堆砌,S分子中的丙条脂肪链则倾向于采取全反式燕尾式构象,而且脂肪链只占S分子长的2/3,这就导致了S分子在二维类晶系结构中凝聚力的下降,以及造成LB薄膜层状超分子结构的破坏和崩塌。 相似文献
32.
Maria?NowakowskaEmail author Krzysztof?Szczubia?ka Miros?aw?Gr?bosz 《Colloid and polymer science》2004,283(3):291-298
The interactions between copolymers of sodium styrene sulfonate (SSS) and N-isopropylacrylamide (NIPAM), anionic polyelectrolytes, and dodecyltrimethylammonium chloride (DTAC), a cationic surfactant, were studied in aqueous solutions of various ionic strengths. The copolymers were found to be thermoresponsive, showing a lower critical solution temperature (LCST). The influence of the polymer composition, the surfactant concentration, and the ionic strength on the LCST was studied. The surfactant was found to interact strongly with the polymer, forming mixed polymer-surfactant micelles. The critical aggregation concentration (cac) of the polymer-surfactant system was found from fluorescence spectroscopy using pyrene as a fluorescent probe. A strong dependence of the anionic polyelectrolyte-cationic surfactant interactions on the structure of the ionic comonomer was observed. 相似文献
33.
Hong JW Benmansour H Bazan GC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(14):3186-3192
Conjugated polymers and oligomers can serve as highly responsive fluorescent reporters for biosensor applications. However, their optical properties in aqueous media are highly dependent upon environmental conditions. The structure of the paracyclophane framework provides a platform for designing optical reporters that show little sensitivity to surfactants, and thus is well-suited for fluorescent assays. The permanent intramolecular delocalization through the paracyclophane core dominates intermolecular perturbations in spontaneously formed aggregates. 相似文献
34.
本文从商品化的间溴苯甲醚和对甲氧基苯甲醛出发,通过傅-克酰基化反应、串联的羟醛缩合及1,4-迈克尔加成反应,得到三芳基取代的1,5-二酮,然后用查尔酮(Chalcone)作氧化剂,二酮与BF3.Et2O 反应形成吡喃鎓盐,再与苯基乙酸钠盐缩合得到芳香二溴代衍生物,产物的DMA溶液在DBU和钯催化剂的作用下,160°C 加热12 h进行脱卤化氢环化反应, 生成四甲氧基取代的二苯并并四苯(DBN)类衍生物。并报道了产物的晶体结构和在溶液中的聚集效应。 相似文献
35.
Pierre Parisot 《商业与工业应用随机模型》1985,1(1):35-54
We studied a population of paraplegic patients in order to give prominence to a possible relationship between the topography of their spinal lesion and the occurrence of special articular diseases (P.O.A.). According to the motor and sensory state of their spinal cord, we first tried to obtain a classification of these lesions (the usual one schematically separates ‘flaccid’ and ‘rigid’ paraplegics). We mainly put the emphasis on this clustering step of the study:
- 相似文献
36.
搅拌釜中制备草酸铈的团聚尺寸模型研究 总被引:6,自引:0,他引:6
以硝酸铈和草酸铵反应生成草酸铈沉淀为研究对象,探讨了搅拌釜中输入功率、溶液过饱和度与产物团聚尺寸之间的变化关系并在团聚和破碎动力学的基础上建立了团聚尺寸模型。根据草酸铈沉淀实验中得到的实验结果求得了一定反应体系浓度下的模型K1,K2和K3值,最后通过-↑LtE,max的模型计算值与实验值,ε--↑LtE的模型曲线与实验曲线的比较初步证明了该模型的实际适用性。 相似文献
37.
38.
Natural products of the medicinal fungus Ganoderma lucidum: occurrence,biological activities,and pharmacological functions 总被引:1,自引:0,他引:1
Shiao MS 《Chemical record (New York, N.Y.)》2003,3(3):172-180
Ganoderma lucidum, a fungus used in traditional Chinese medicine, produces polysaccharides and oxygenated triterpenoids with a very broad spectrum of biological activities and pharmacological functions. Among the Ganoderma triterpenoids, many pairs of C-3 alpha/beta stereoisomers and C-3/C-15 positional isomers have been identified. Biosynthetic study has indicated that the C-3alpha series of oxygenated triterpenoids is derived from the C-3beta series via an oxidation-reduction pathway. The interaction of Ganoderma triterpenoids with human platelets in the induction of aggregation and inhibition of agonist-induced aggregation and signal transduction has been elucidated. Reduction of cellular mevalonate content to a stage in which cholesterol synthesis is strongly inhibited and cell growth is marginally arrested sensitizes hepatoma cells to the oxygenated triterpenoids. A combination treatment of lovastatin and Ganoderma triterpenoids in animal studies has exhibited a potential anticancer effect. 相似文献
39.
We present a series of conformational search calculations on the aggregation of short peptide fragments that form fibrils similar to those seen in many protein mis-folding diseases. The proteins were represented by a face-centered cubic lattice model with the conformational energies calculated using the Miyazawa-Jernigan potential. The searches were performed using algorithms based on the Metropolis Monte Carlo method, including simulated annealing and replica exchange. We also present the results of searches using the tabu search method, an algorithm that has been used for many optimization problems, but has rarely been used in protein conformational searches. The replica exchange algorithm consistently found more stable structures then the other algorithms, and was particularly effective for the octamers and larger systems. 相似文献
40.
J. P. Dassaud B. Gallot A. Guyot R. Spitz J. P. Beautemps C. Williams C. Bourgaux A. Eisenberg 《先进技术聚合物》1994,5(2):79-89
Polypropylene ionomers have been prepared by sulfonation of copolymers of propene and 7 methyl, 1-6 octadiene, followed by neutralization to cesium salts. Both WAXS and SAXS were used to study the morphology of the samples, while their thermal properties were studied by DSC and their mechanical properties by DMTA. The sulfonation process is shown to cause a further drop in crystallinity in addition to the effect of comonomer incorporation. Ion clustering is observed when the extent of sulfonation is high enough, the limit being dependent on the copolymer composition. The ion pairs which are not incorporated into the cluster cause a small-angle upturn in the WAXS pattern. The mechanical properties are strongly affected by the drop in crystallinity, but may be partly recovered due to ion clustering. No disruption of the ion clusters is observed before thermal decomposition of the polymer. 相似文献