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991.
William A. Boulanger 《合成通讯》2013,43(12):2201-2210
We report novel procedures for the efficient resolution of (±)-cis-2 -hydroxy-5, 9-dimethyl-6, 7-benzomorphan via the (-)-N-acetyl-L-glutamate and (+)-α-bromocamphor-φ-sulfonate salts, the direct N-substitution of the (+)-α-bromocamphor-φ-sulfonate salts, and the use of these methods for the synthesis of racemic, (+)-, and (-)-cyclazocine. 相似文献
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993.
William Slofstra 《Advances in Mathematics》2012,229(2):968-983
Braverman and Finkelberg have recently proposed a conjectural analogue of the geometric Satake isomorphism for untwisted affine Kac–Moody groups. As part of their model, they conjecture that (at dominant weights) Lusztig's q-analog of weight multiplicity is equal to the Poincare series of the principal nilpotent filtration of the weight space, as occurs in the finite-dimensional case. We show that the conjectured equality holds for all affine Kac–Moody algebras if the principal nilpotent filtration is replaced by the principal Heisenberg filtration. The main body of the proof is a Lie algebra cohomology vanishing result. We also give an example to show that the Poincare series of the principal nilpotent filtration is not always equal to the q-analog of weight multiplicity. Finally, we give some partial results for indefinite Kac–Moody algebras. 相似文献
994.
Experimental Techniques - The time-of-flight method has been used to measure the longitudinal and shear wave speeds in six polymers (polyether ether ketone [PEEK], PEEK with 10% carbon fibers,... 相似文献
995.
J. William Helton J. E. Pascoe Ryan Tully-Doyle Victor Vinnikov 《Integral Equations and Operator Theory》2016,84(2):151-181
We establish several new relations between the discrete transition operator, the continuous Laplacian and the averaging operator associated with combinatorial and metric graphs. It is shown that these operators can be expressed through each other in a very explicit way. In particular, the averaging operator appears to be closely related to the solutions of the associated wave equation. The machinery used allows one to study a class of infinite graphs without assumption on the local finiteness. 相似文献
996.
Tony Brown 《Research in Mathematics Education》2013,15(1):11-22
Abstract Derrida's revolutionary work in the study of language has seriously challenged the way in which we see words being attached to meanings. This paper makes tentative steps towards examining how his work might assist us in understanding the way in which our attempts to describe or capture our mathematical experiences modify the experience itself. In doing this we draw on the work of Jacques Derrida and John Mason in locating possible frameworks through which to conceptualise the relationship between language and mathematical cognition. It concludes that mathematical meaning never stabilises since it is caught between the individual's ongoing experience and society's ongoing renewal of its conventions. That is, mathematics, language and the human performing them are always evolving in relation to each other. 相似文献
997.
Ross F. Koby Alicia M. Doerr Nicholas R. Rightmire Nathan D. Schley Dr. William W. Brennessel Prof. Brian K. Long Prof. Timothy P. Hanusa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(31):8195-8202
Without solvents present, the often far-from-equilibrium environment in a mechanochemically driven synthesis can generate high-energy, non-stoichiometric products not observed from the same ratio of reagents used in solution. Ball milling 2 equiv. K[A’] (A’=[1,3-(SiMe3)2C3H3]−) with CaI2 yields a non-stoichiometric calciate, K[CaA’3], which initially forms a structure ( 1 ) likely containing a mixture of pi- and sigma-bound allyl ligands. Dissolved in arenes, the compound rearranges over the course of several days to a structure ( 2 ) with only η3-bound allyl ligands, and that can be crystallized as a coordination polymer. If dissolved in alkanes, however, the rearrangement of 1 to 2 occurs within minutes. The structures of 1 and 2 have been modeled with DFT calculations, and 2 initiates the anionic polymerization of methyl methacrylate and isoprene; for the latter, under the mildest conditions yet reported for a heavy Group 2 species (one-atm pressure and room temperature). 相似文献
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