排序方式: 共有34条查询结果,搜索用时 15 毫秒
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Gröger H Hummel W Buchholz S Drauz K Nguyen TV Rollmann C Hüsken H Abokitse K 《Organic letters》2003,5(2):173-176
[reaction: see text] An enzyme-compatible biphasic reaction media for the asymmetric biocatalytic reduction of ketones with in situ cofactor regeneration has been developed. In this biphasic reaction media, which is advantageous for reactions at higher substrate concentrations, both enzymes (alcohol dehydrogenase and FDH from Candida boidinii) remain stable. The reductions with poorly water-soluble ketones were carried out at substrate concentrations of 10-200 mM, and the optically active (S)-alcohols were formed with moderate to good conversions and with up to >99% ee. 相似文献
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Jose Castro‐Perez Nathan Hatcher Nana Kofi Karikari Sheng‐Ping Wang Vivienne Mendoza Henry Shion Alan Millar John Shockcor Mark Towers David McLaren Vinit Shah Stephen Previs Karen Akinsanya Michele Cleary Thomas P. Roddy Douglas G. Johns 《Rapid communications in mass spectrometry : RCM》2014,28(22):2471-2479
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Zhicheng Wang Yaw D. Yeboah Tiejun Bai Kofi B. Bota 《Plasma Chemistry and Plasma Processing》2004,24(3):405-420
Given the operational constraints of aerospace ground equipments (AGE), the nonthermal plasma discharge (NTPD) has been identified as a promising technology for their NOx removal. As part of a program to optimize an NTPD system for this particular application, an investigation of the effect of discharge gap spacing on the electrical and chemical processes that occur in NTPDs was initiated. A number of experiments were performed to examine how the gap spacing affects the NO removal efficiency, discharge characteristics, and chemical reactions in a NTPD device. Gap spacings ranging from 0.8 to 4.0 mm were investigated in this study. An optimum gap spacing for NO removal was observed at approximately 2 mm and, based on the experimental data, a physical explanation for the optimum was developed. The experiments, results and conclusions are discusssed in detail in this paper. 相似文献
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This paper presents a model of exchange where a single commodity serves as a means of payment and trade must pass through designated brokers. Broker buy and sell prices, trader allocations, and broker profits depend on the buy and sell decisions of all the market participants, and the exchange problem is described as a noncooperative game. The existence of an equilibrium is established and bounds are placed on the price spread on each commodity. Finally, the properties of the noncooperative equilibria under replication are examined. 相似文献
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Y. Auffret D. C. D. Roux N. El Kissi D. E. Dunstan I. Pignot-Paintrand 《Rheologica Acta》2009,48(4):423-432
We present the results of extensive strain- and stress-controlled rheometry performed on an AOT–water–iso-octane system, which
forms lamellar structures with a high density of topological defects. In spite of different time-scales, both measurement
methods, strain- and stress-controlled, are shown to be controlled by the level of strain experienced by the material. In
both cases, after a complex transition, an apparent steady state is reached. Whereas both apparent steady states are identical
for intermediate shear rate and shear stress following a power law, these are found to differ once the lower values of applied
shear rate and shear stress are considered. The origin of this difference is discussed in terms of supplied energy to the
sheared sample.
I. Pignot-Paintrand is affiliated with The Université Joseph Fourier and member of the Institut de Chimie Moléculaire de Grenoble 相似文献
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M.H. Frommer J. Bostock Kofi Agyeman R.M. Rose M.L.A. MacVicar 《Solid State Communications》1973,13(9):1357-1359
No evidence for a superconducting tunneling s-band energy gap in single crystal Nb has been observed for any of the main symmetry directions investigated in Nb-oxide-Pb0.7Bi0.3 and Nb-oxide-In junctions. 相似文献
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Sulemana?S.?Abukari Kofi?W.?AduEmail author Samuel?Y.?Mensah Natalia?G.?Mensah Kwadwo?A.?Dompreh Anthony?Twum Musah?Rabiu 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(4):182
We investigate theoretically the feasibility of amplification of terahertz radiation in aligned achiral carbon nanotubes, a zigzag (12,0) and an armchair (10,10) in comparison with a superlattice using a combination of a constant direct current (dc) and a high-frequency alternate current (ac) electric fields. The electric current density expression is derived using the semiclassical Boltzmann transport equation with a constant relaxation time. The electric field is applied along the nanotube axis. Analysis of the current density versus electric field characteristics reveals a negative differential conductivity behavior at high frequency, as well as photon assisted peaks. The photon assisted peaks are about an order of magnitude higher in the carbon nanotubes compared to the superlattice. These strong phenomena in carbon nanotubes can be used to obtain domainless amplification of terahertz radiation at room temperature. 相似文献
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Kofi P. Adragni Elias Al-Najjar Sean Martin Sai K. Popuri Andrew M. Raim 《Computational Statistics》2016,31(3):923-941
Sufficient dimension reduction methodologies in regressions of Y on a p-variate X aim at obtaining a reduction \(R(X) \in {\mathbb R}^{d}, d \le p\), that retains all the regression information of Y in X. When the predictors fall naturally into a number of known groups or domains, it has been established that exploiting the grouping information often leads to more effective sufficient dimension reduction of the predictors. In this article, we consider group-wise sufficient dimension reduction based on principal fitted components, when the grouping information is unknown. Principal fitted components methodology is coupled with an agglomerative clustering procedure to identify a suitable grouping structure. Simulations and real data analysis demonstrate that the group-wise principal fitted components sufficient dimension reduction is superior to the standard principal fitted components and to general sufficient dimension reduction methods. 相似文献
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Kissi Benaissa Parron Vera Miguel Angel Rubio Cintas Maria Dlolores Dubujet Philippe Khamlichi Abdellatif Bezzazi Mohammed El Bakkali Larbi 《Applied Mathematical Modelling》2012
CFD simulation with enhanced modeling of turbulence and near-wall treatment is used to model water–clay mixtures flowing through a cylindrical pipe domain. Effects on the wall-shear stress resulting from varying water clay content and applied hydraulic gradient are analyzed. Various parametric studies were performed and had shown that the two-dimensional modelling introduced in the present study does not yield a uniform wall-shear stress along the pipe wall and that clay concentration affects significantly the wall-shear stress value. This is in contrast with the common hypothesis used in one-dimensional modeling approaches where this stress is assumed constant and which gives rise to uniform erosion along the pipe wall. The obtained results had enabled predicting more realistically erosion amount and had allowed for understanding the irregular eroded hole wall shape as observed experimentally after performing the standard hole erosion test. 相似文献