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961.
Sott R Granander J Williamson C Hilmersson G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(16):4785-4792
The mixed-metal complex formed from n-butylsodium, n-butyllithium, and a chiral amino ether has been studied by NMR spectroscopy. Three different mixed-metal amides were used as chiral bases for the deprotonation of cyclohexene oxide. The selectivity and initial rate of reaction were compared for sodium-amido ethers, lithium-amido ethers, and mixtures of sodium and lithiumamido ethers in diethyl ether and tetrahydrofuran, respectively. The mixed sodium/lithium amides are more reactive than the single sodium and lithium amides, whereas the stereoselectivities are higher when lithium amides are used. The alkali-metal/gamma-amido ethers exhibit both higher initial reaction rates and stereoselectivities than their beta-amido ether analogues. NMR spectroscopic studies of mixtures of n-butylsodium (nBuNa), n-butyllithium (nBuLi), and the gamma-amino ethers in diethyl ether show the exclusive formation of dimeric mixed-metal amides. In diethyl ether, the lithium atom of the mixed-metal amide is internally coordinated and the sodium atom is exposed to solvent; however, in tetrahydrofuran, both metals are internally coordinated. 相似文献
962.
Rare-earth oxide nanopolyhedra, nanoplates, and nanodisks 总被引:2,自引:0,他引:2
963.
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968.
Recursive equations for compound distribution with the severity distribution of the mixed type 总被引:1,自引:0,他引:1
YANG Jingping CHENG Shihong & WU Qin LMAM Department of Financial Mathematics Peking University Beijing China 《中国科学A辑(英文版)》2005,48(5):594-609
In this paper, recursive equations are obtained for compound distribution with the number of claims belonging to (a, b)-family and the severity distribution of the mixed type. Numerical methods to solve these equations are presented, and some numerical results are given. 相似文献
969.
WU Mixia & WANG Songgui College of Applied Sciences Beijing University of Technology Beijing China 《中国科学A辑(英文版)》2005,48(11):1451-1464
For the mixed effects models with balanced data, a new ordering of design matrices of random effects is defined, and then a simple formula of the spectral decomposition of covariance matrix is obtained. To compare with the two methods in literature, the decomposition can not only give the actual number of all distinct eigenvalues and their expression, but also show clearly the relationship between the design matrices of random effects and the decomposition. These results can be applied to the problems for testifying the analysis of the variance estimate being a minimum variance unbiased under all random effects models and some mixed effects models with balanced data, for finding the explicit solution of maximum likelihood equations for the general mixed effects model and for showing the relationship between the spectral decomposition estimate and the analysis of variance estimate. 相似文献
970.
We prove existence and uniqueness results for non-linear elliptic equations with lower order terms, L1 data, and mixed boundary conditions that include as particular cases the Dirichlet and the Neumann problems.
Mathematics Subject Classification (2000) 35J25, 35D05, 35J70, 35J60 相似文献