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排序方式: 共有195条查询结果,搜索用时 203 毫秒
91.
Michael North 《Angewandte Chemie (International ed. in English)》2009,48(23):4104-4105
Hidden talent : Often perceived to be too thermodynamically and kinetically inert to be a useful chemical feedstock, carbon dioxide adds to allenes under exceptionally mild reductive conditions in the presence of a palladium pincer complex to give β,γ‐unsaturated carboxylic acids (see scheme). This transformation is discussed in the context of the requirements for CO2 fixation. DMF=N,N‐dimethylformamide, Tf=trifluoromethanesulfonyl.
92.
The mechanism by which four Lewis bases, triethylamine, tetrabutylammonium thiocyanate, tetrabutylammonium azide and tetrabutylammonium cyanide, catalyse the addition of trimethylsilyl cyanide to aldehydes is studied by a combination of kinetic and spectroscopic methods. The reactions can exhibit first or second order kinetics corresponding to three different reaction mechanisms. Spectroscopic evidence for the formation of hypervalent silicon species is obtained for reaction between all of the tetrabutylammonium salts and trimethylsilyl cyanide. The reactions are accelerated by the presence of water in the reaction mixture, an effect which is due to a change in the reaction mechanism from Lewis to Br?nsted base catalysis. Tetrabutylammonium thiocyanate is shown to be an excellent catalyst for the synthesis of cyanohydrin trimethylsilyl ethers on a preparative scale. 相似文献
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94.
Success in isoelectric trapping separations critically depends on the knowledge of the accurate operational pH value of the buffering membranes used. Currently, due to a lack of easy, rapid, accurate methods that can be used for the post-synthesis determination of the operational pH value of a buffering membrane, only nominal pH values calculated from the amounts of the reagents used in the synthesis of the membranes and their acid-base dissociation constants are available. To rectify this problem, UV-absorbing and fluorescent carrier ampholyte mixtures were prepared by alkylating pentaethylenehexamine with a chromophore and a fluorophore, followed by Michael addition of acrylic acid and itaconic acid to the resulting oligoamine. Carrier ampholyte mixtures, with evenly distributed absorbance values across the 3相似文献
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96.
Michael J. North 《Computational & Mathematical Organization Theory》2001,7(4):331-337
Complex Adaptive Systems (CAS) can be applied to investigate large-scale socio-cognitive-technical systems. Viewing such systems from a multi-agent social and organizational perspective allows innovative computational policy analysis. Argonne National Laboratory (ANL) has taken such a perspective to produce an integrated model of the electric power and natural gas markets. This model focuses on the organizational interdependencies between these markets. These organizational interdependencies are being strained by fundamental market transformations. 相似文献
97.
Anton Deitmar School of Mathematical Sciences University of Exeter Laver Building North Park Road Exeter EX QE Devon UK 《数学物理学报(B辑英文版)》2001,(1)
0 IntroductionThe group of norm-1 ideles A1 over a global field lt acts by 1111lltip1ication on t11e additivegroup of adeIes A. Let G = A1 be A be tl1eir semidirect product. Let r be its arithnletic sub-group kx oc k. For the case k = Q Dorian Goldfeld gavc ill [2] a Schwartz kernel on r\G whosegeometrical trace equals the prime 11un1ber side of the explicit fOr1llulas of A. Weil. A spectralillterpretatiou in the seuse of the Selberg trace formula is cal1ed for. In order that a geolllet… 相似文献
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99.
SU XinMing ZHANG JunHui WANG Jing BI YanQiang QIE DianFu XIANG ZhiHai XUE MingDe 《中国科学:物理学 力学 天文学(英文版)》2015,(4):63-71
Thermally induced vibration(TIV)is a typical failure of large-scale space structures.This paper reports a laboratory experiment that aims to investigate this unusual structural behavior of complex engineering structures.With the help of a Fourier finite element program,the fixing of a space boom section is well designed so that the TIV can be successfully observed.Although the observed torsional vibration mode is different from the bending vibration mode predicted by the classic theory based on a simple beam model,it can be successfully explained by the general thermal structural interaction theory.This demonstrates the validity of the theoretical model and the necessity of using finite element program to analyze complex engineering structures. 相似文献
100.
Chidi Amadi-Kamalu Holly Clarke Matthew McRobie James Mortimer Prof. Michael North Yanrui Ran Dr. Anne Routledge Dani Sibbald Matthew Tickias Kai Tse Helen Willway 《ChemistryOpen》2020,9(4):431-441
The influence of various physical and chemical factors on the swelling of polystyrene and PEG based resins in greener organic solvents has been systematically investigated. In general, chemical factors: the nature of the functionality/linker and the degree of loading were found to have a far larger influence on the swelling of the resins than physical parameters such as bead size. The results are interpreted in terms of Hansen solubility parameters for the solvents and there is evidence that some solvents interact with the polymeric core of a resin whilst others interact with the functionality. The results are extended to a study of the changes in resin swelling observed during both deprotection and chain elongation reactions during solid phase peptide synthesis. 相似文献