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The structures and stability of the designed PNP pincer amido M(NO)2(PNP) and amino HM(NO)2(PNHP) complexes [M = V, Nb, and Ta, PNP = N(CH2CH2P(isopropyl)2)2, PNHP = HN(CH2CH2P(isopropyl)2)2] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H2 environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-CN, Ph-CHNH, Ph-CHNH-Ph, Ph-CHNCH2Ph, Ph-CCH, Ph-CHCH2, Ph-CHO, and Ph-COCH3, the reaction prefers either a two-step or one-step mechanism for the hydridic MH and protonic NH transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges. 相似文献
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Although proteases are capable of synthesizing peptide bonds, they are not proficient at peptide fragment ligation. Further manipulations are needed to shift the native enzyme activity from the cleavage to the synthesis of peptides. This account reports on the synthetic potential of nonactivatable trypsinogen and zymogen-like enzymes designed to minimize proteolytic side reactions during peptide synthesis. 相似文献
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We study two types of crank moments and two types of rank moments for overpartitions. We show that the crank moments and their derivatives, along with certain linear combinations of the rank moments and their derivatives, can be written in terms of quasimodular forms. We then use this fact to prove exact relations involving the moments as well as congruence properties modulo 3, 5, and 7 for some combinatorial functions which may be expressed in terms of the second moments. Finally, we establish a congruence modulo 3 involving one such combinatorial function and the Hurwitz class number H(n). 相似文献
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Stephan Pannier Kathrin Grossenbacher Martin Liebscher Wolfgang Graf Michael Kaliske 《PAMM》2011,11(1):731-732
In many engineering applications, a structural design is determined by way of a multi-stage design process. Thereby, the information of previous simulations, e.g. sensitivity analysis, should be used for further investigations. In special, the aim is to improve the reliability as early as possible. Therefore, an approach is presented to determine alternative permissible design spaces on the basis of arbitrary point sets. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献