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891.
Intracavity coherent addition of 16 laser distributions 总被引:2,自引:0,他引:2
The efficient intracavity coherent addition of 16 separate laser Gaussian mode distributions is presented. The coherent addition is achieved in a multichannel pulsed Nd:YAG laser resonator by use of four intracavity interferometric beam combiners. The results reveal 88% combining efficiency with a combined output beam of nearly pure Gaussian distribution. 相似文献
892.
We investigated the nature of the ground state and static response properties (mu, alpha, and beta) for a promising class of twisted pi-electron system nonlinear optical chromophores at the HF, B3LYP, MP2, and CASSCF levels. We report results for a substituted twisted ethylene and a larger tictoid analogue. Previous work has reported only a zwitterionic character for such tictoid species, however, (14,13) CASSCF calculations predict a ground-state diradical. At the HF, B3LYP, MP2, and (14,13) CASSCF levels, the values of beta are orders of magnitude smaller than those predicted by semiempirical methods. 相似文献
893.
Pearson AR Marimanikkuppam S Li X Davidson VL Wilmot CM 《Journal of the American Chemical Society》2006,128(38):12416-12417
The bacterial enzyme methylamine dehydrogenase (MADH) contains the protein-derived cofactor tryptophan tryptophylquinone (TTQ). TTQ is generated by the posttranslational modification of two endogenous MADH tryptophans, betaW57 and betaW108. Two oxygens are inserted sequentially into betaW57 to generate the quinone moiety, after which it is cross-linked to betaW108. We have previously shown that the second oxygenation and cross-link formation are catalyzed by the novel di-heme cytochrome MauG. Here we show, using isotopically labeled oxygen and water, that the first addition of oxygen occurs specifically at the C7 position of betaW57 and that MauG then inserts the second oxygen at position C6. 相似文献
894.
Two new group 4 initiators based on N,N′-Bis(2-hydroxybenzyl)ethylenediamine have been prepared and fully characterised via multi-nuclear NMR spectroscopy and single crystal X-ray diffraction studies. The complexes have been tested for the production of polylactide. The phenolate ligand complexes to Ti(IV) to generate the β-cis isomer in the solid-state. Whereas for Zr(IV) the isolated species (regardless of stoichiometery) is a diligated complex. 相似文献
895.
Brigitte Bauer Dr. Max Davidson Dr. Owe Orwar Prof. 《Angewandte Chemie (International ed. in English)》2009,48(9):1656-1659
A simple and scalable method is presented for harvesting, purification, and on‐chip processing of mammalian plasma membrane vesicles (PMVs) optimized for downstream proteome analysis. After immobilization on a microfluidic flowcell of PMVs, the embedded membrane proteins are proteolytically digested, and the peptides harvested and analyzed by LC‐MS/MS. Over 93 % of the detected proteins are plasma‐membrane‐derived.
896.
We experimentally study anomalous diffusion of ultracold atoms in a one dimensional polarization optical lattice. The atomic spatial distribution is recorded at different times and its dynamics and shape are analyzed. We find that the width of the cloud exhibits a power-law time dependence with an exponent that depends on the lattice depth. Moreover, the distribution exhibits fractional self-similarity with the same characteristic exponent. The self-similar shape of the distribution is found to be well fitted by a Lévy distribution, but with a characteristic exponent that differs from the temporal one. Numerical simulations suggest that this is due to long trapping times in the lattice and correlations between the atom's velocity and flight duration. 相似文献
897.
O. Pelletier C. Bourgaux O. Diat P. Davidson J. Livage 《The European physical journal. E, Soft matter》2000,2(2):191-198
We report small-angle X-ray scattering experiments performed in both the isotropic and nematic phases of aqueous V2O5 suspensions. We show that the scattering in the isotropic phase can be well described in the whole accessible q-range by only considering the form factor of non-interacting ribbons. We investigate the influence of concentration and pH on the dimensions of V2O5 ribbons and show that these parameters do not have any significant effect, as long as the system stays well within the chemical
stability domain of the ribbons. We then show that nematic single domains display an anisotropic small-angle scattering pattern,
even at scattering vectors small compared to that at which a characteristic correlation peak is observed. This feature is
expected for a nematic phase, but was rarely observed. We finally try to describe this scattering within the framework of
theories developed for the structure factor of a nematic polymer, and we reach the conclusion that chain ends are certainly
important to understand this pattern.
Received 21 July 1999 and Received in final form 17 December 1999 相似文献
898.
Francisco B. C. Machado Tapan K. Ghanty Subhas Chakravorty Ernest R. Davidson 《International journal of quantum chemistry》2001,81(3):238-245
Ab initio calculations employing relativistic effective core potentials were carried out to investigate the electronic structure of xenon fluoride molecules. The chemical bonds and geometrical stability of some isoelectronic ions, which have the central atom replaced by iodine, cesium, and barium ions, were also investigated. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 238–245, 2001 相似文献
899.
NO2 concentration profiles in shock-heated NO2/Ar mixtures were measured in the temperature range of 1350–2100 K and pressures up to 380 atm using Ar+ laser absorption at 472.7 nm, IR emission at 6.25±0.25 μm, and visible emission at 300–600 nm. In the course of this study, the absorption coefficient of NO2 at 472.7 nm was measured at temperatures from 300 K to 2100 K and pressures up to 75 atm. Rate coefficients for the reactions NO2+M→NO+O+M (1), NO2+NO2→2NO+O2 (2a), and NO2+NO2→NO3+NO (2b) were derived by comparing the measured and calculated NO2 profiles. For reaction (1), the following low- and high-pressure limiting rate coefficients were inferred which describe the measured fall-off curves in Lindemann form within 15% [FORMULA] The inferred rate coefficient at the low- pressure limit, k1o, is in good agreement with previous work at higher temperatures, but the energy of activation is lower by 20 kJ/mol than reported previously. The pressure dependence of k1 observed in the earlier work of Troe [1] was confirmed. The rate coefficient inferred for the high pressure limit, k1∞, is higher by a factor of two than Troe's value, but in agreement with data obtained by measuring specific energy-dependent rate coefficients. For the reactions (2a) and (2b), least-squares fits of the present data lead to the following Arrhenius expressions: [FORMULA] For reaction (2), the new data agree with previously recommended values of k2a and k2b, although the present study suggests a slightly higher preexponential factor for k2a. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 483–493, 1997. 相似文献