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991.
Karl S. Minsker Vadim P. Zakharov Alexander Al. Berlin Gennadi E. Zaikov 《应用聚合物科学杂志》2004,94(2):613-624
Investigations on development of a macrokinetics approach were generalized to the analysis of fast chemical reactions, mainly using cationic polymerization of isobutylene as an example, which is a new class of liquid‐phase processes. The removal of diffusional constraints on polymer synthesis, by intensification of turbulent mixing in the reaction zone, makes it possible to calculate the kinetic parameters of polymerization and polymer‐analogous reactions, to optimize the molecular characteristics of polymeric products obtained, and to control the character of the process as a whole. The laws pertaining to the progression of fast processes are considered for the synthesis of separate polymers, in particular stereoregular polydienes, ethylene–propylene copolymers, and chlorobutyl rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 613–624, 2004 相似文献
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993.
The nature of the authors' observational coding, both as a process and as a strategy, represents one of the clearest expressions of their philosophy of science and approach to clinical model building. They believe that there is no support for prioritizing one vs another observational coding approach. More important, they assert that a dialogue among various perspectives is essential for the knowledge base to expand and for clinical models to develop. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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995.
Alexander E.Braun 《集成电路应用》2006,(5):25-25
涉足尖端技术研究工作的芯片制造商正在把无数新材料和奇特的器件结构结合起来,用于65nm及更低节点的量产。同时他们发现,在这些研究上的努力生产的结果还包括目前必须着手解决各器件各个层上出现的 相似文献
996.
Eugne T. W. M. Schipper Alexander H. C. Roelofs Pieter Piet Anton L. German 《Polymer International》1994,33(1):79-86
In order to study the promoting effect of polycations on the cobalt(II)phthalocyanine-tetrasodiumsulphonate (CoPc(NaSO3)4)-catalysed autoxidation of thiols, it is imperative to know the molecular weight dependence of the polymer. Monodisperse oligomers can often supply a lot of information. To elecidate the mechanism of the promoting effect of 2,4-ionene, a poly(quaternary ammonium)salt, on the CoPc(NaSO3)4-catalysed autoxidation of 2-mercaptoethanol, a series of monodisperse 2,4-ionene oligomers were prepared. Trimeric 2,4-ionenes, containing two quaternary ammonium groups separated by four methylene groups, showed a high co-catalytic activity, and active Co-aggregates were detected with visible light spectroscopy. The spectroscopic behaviour was in close agreement with that of high molecular 2,4-ionene/CoPc(NaSO3)4 complexes. In order to achieve this aggregation several oligomeric ionenes have to act concertedly. If the distance between the ionic sites is short the trimer acts as a simple salt in stablizing the aggregates. With respect to the catalytic activity the optimum polycation/catalyst ratio, expressed as the N+/Co ratio, decreased with increasing chain lenght and reached a constant level of 50 at a 2,4-ionene nonamer. For the trimers and pentamers this ratio is affected by the type of end-group. All synthesized 2,4-ionene oligomers exhibited excellent co-catalytic properties at the optimum N+/Co ratio, with maximum turnover frequencies of 4600 mol thiol/(mol Co s), i.e. 50 times higher than those obtained for the polymer-free system. In the case of monodisperse 2,4-ionene pentamer with bromo end-groups, double Michaelis–Menten kinetics were observed, as also was exhibited by high molecular weight ionene. 相似文献
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998.
Alexander Silverman 《Journal of the American Ceramic Society》1924,7(11):795-802
A discussion of the various elements and compounds found in a colloidal state in glass. Attention is called to the similarity of colloidal behavior in vitreous and aqueous media. Theories and experimental evidence are furnished to account for the formation and destruction of the colloidal state. 相似文献
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