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排序方式: 共有137条查询结果,搜索用时 15 毫秒
21.
Planar chiral arenetricarbonylchromium complexes have been intensively investigated and they have been applied as valuable building blocks for asymmetric synthesis and as ligands for asymmetric catalysis. In contrast, in the field of the isoelectronic cationic [(η(6)-arene)Mn(CO)(3)](+) complexes, until these last 10 years, very few studies were published involving nonracemic planar chiral cationic complexes and their potential applications, certainly because of the difficult access to enantiopure starting material. In 2009, however, the discovery of the first resolution of such compounds opened a new area for their application in the field of organic as well as of organometallic enantioselective syntheses. We felt it important to write a review on this subject to give an up-to-date summary of the methodologies used to prepare enantiomerically pure planar chiral neutral [(η(5)-cyclohexadienyl)Mn(CO)(3)] and cationic [(η(6)-arene)Mn(CO)(3)](+) complexes as well as their potential in enantioselective synthesis. 相似文献
22.
Enantiomeric Sesquiterpene Lactones from Senecio tsoongianus 总被引:2,自引:0,他引:2
From Senecio tsoongianus,two pairs of enantiomeric isomers,tsoongianolides A(1) and B(2),tsoongianolides C (3) and D(4) were isolated. Their structures were elucidated by 1D and 2D-NMR techniques and X-ray diffractions. The cytotoxicity to KB cell of 1 and 2 is also reported. 相似文献
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Julien Gautier Franck Delmotte Arnaud Jérome Francoise Varnière 《Optics Communications》2008,281(11):3032-3035
A two-channel mirror reflecting both Fe-IX/X (λ = 17.1 nm) and He-II (30.4 nm) resonance lines at near normal incidence has been designed, fabricated and characterized. These two passbands are often chosen in space instruments designed for the observation of the solar corona. The mirror structure used for optimization is a superposition of two periodic multilayers with three components per period. It has been designed by using optimization software with an appropriate merit function. The theoretical reflectivity for both resonance lines can reach 0.25. It is shown that, by using a set of filters, one can select either the Fe-IX/X or the He-II channel. The spectral response of the two-channel mirror has been measured on synchrotron radiation source on a large wavelength range, from 12 nm to 35 nm. Experimental reflectivity reaches 0.32 for the Fe-IX/X line and 0.19 for the He-II line. 相似文献
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Michael Klein Gabriel P. Lansbergen Jan A. Mol Sven Rogge Prof. Raphael D. Levine Prof. Francoise Remacle Prof. 《Chemphyschem》2009,10(1):162-173
A silicon field‐effect transistor is operated as a logic circuit by electrically addressing the ground and excited electronic states of an embedded single dopant atom. Experimental results—complemented by analytical and computational calculations—are presented. First, we show how a complete set of binary logic gates can be realized on the same hardware. Then, we show that these gates can be operated in parallel on the very same dopant up to the logic level of a full adder. To use the device not as a switch but as a full logic circuit, we make essential use of the excited electronic states of the dopant and of the ability to shift their energy by gating. The experimental ability to use two channels to measure the current flowing through the device and the conductance (dI/dV) allows for a robust reading of the output of the logic operations. 相似文献
27.
San-jun ZHANG Lotfi BERGUIGA Nicolas HUGO Thibault ROLAND Francoise ARGOUL Juan ELEZGARAY Wen-xueLI He-ping ZENG 《Frontiers of Physics》2009,4(4):469
This article reviews our recent advances in surface plasmon resonance (SPR) based biochips. It includes four issues, which are the preparation and characterization of high quality gold film, the preparation and characterization of self-assembled monolayer (SAM), dynamics of DNA adsorption on SAMs, and SPRbased microscopies. Numerous topics related to SPR, such as, the modeling of SPR by transmission matrix, effective medium theory, applications of SPR in biology, and SPR-based novel microscopies, are discussed. A novel electrochemical technique, which is extremely useful for the preparation and characterization of high quality SAMs, is also discussed. 相似文献
28.
Polina Novoseltseva Dr. Haijun Li Dr. Xiang Wang Dr. Francoise Sauriol Prof. Dr. Suning Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(10):2276-2284
New chiral N,C-chelate organoboron compounds based on benzylideneamines (bza) with the general formula of B(bza-R)Mes2 (R=H or Me; Mes=mesityl) are reported. A chiral substituent group R- or S-CH(CH3)Ph (Ph=phenyl) was introduced to the imine center, which imposed a previously unobserved pseudo- or axial-chirality on the BMes2, creating distinct diastereomers. NMR spectroscopic studies established that the diastereomers undergo slow exchange in solution at ambient temperature. The chiral N,C-chelate B(bza-R)Mes2 molecules undergo photoisomerization in the same manner as their non-chiral analogues, generating chiral BN-cyclooctatriene (BN-COT) derivatives. Most significantly, by tracking the photoisomerization with circular dichroism (CD) and 1H NMR spectra along with time-dependent density functional theory (TD-DFT) computational studies, the photoisomerization was established to proceed in a highly stereoselective manner, that is, one diastereomer converts exclusively to the corresponding diastereomer product in the photoreaction. 相似文献
29.
J. P. Francoise 《Communications in Mathematical Physics》1988,117(1):37-47
We show that there is a Symplectic Action of a Torus associated to Harmonic flows on the Cotangent Bundle of a semi-simple Lie Algebra. This allows to obtain a completely classical proof of the Gallavotti-Marchioro Formula by the method of the Stationary Phase. 相似文献
30.