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91.
92.
A new pyromeconic acid derivative,pyromeconic acid-3-O-β-D-glucopyranoside-3′-(O-β-D-glucopyranoside)-6′-(O-4″-hydroxybenzoate) (1),along with two known ones,were isolated from the whole plants of Conyza canadensis.Their structures were elucidated based on the analysis of their spectroscopic data.The in vitro antibacterial testing results showed that all of these three compounds were inactive towards two bacterial strains,Escherichia coli and Staphyloccocus aureus. 相似文献
93.
WANG Ying FU Ai-ping LI Hong-liang TIAN Feng-hui YUAN Shu-ping SI Hong-zong DUAN Yun-bo WANG Zong-hua Institute for Computational Science Engineering Laboratory of New Fiber Materials Modern Textile Growing Base for State Key Laboratory College of Chemical Environmental Engineering Qingdao University Qingdao P.R.China 《高等学校化学研究》2011,(4):673-677
The effects of two different amino acid catalysts on the stereoselectivities in the direct Mannich reactions of cyclohexanone,p-anisidine and p-nitrobenzaldehyde were studied with the aid of density functional theory.Transition states of the stereo-determining C C bond-forming step with the addition of enamine intermediate to the imine for the L-proline(·-amino acid) and (R)-3-pyrrolidinecarboxylic acid(·-amino acid)-catalyzed processes were reported.B3LYP/6-31G calculations provide a good explanation for t... 相似文献
94.
本文结合第二届国际非均质材料力学会议 (ICHMM2008,黄山)专题讨论会和部分特邀报告的情况, 以及2011年5月22$\sim$26日在上海崇明岛举行的ICHMM2011国际会议的内容, 对该领域的研究进展及其热点、焦点和生长点进行了综合性的评述. 重点讨论了多物理场与多尺度模拟、材料结构与力学行为从原子到连续介质的分析、随机微结构演化与退化、真实材料微结构的模拟、生物材料力学与仿生设计、在位实验和模型验证、功能梯度材料结构力学、微纳米功能器件开发等前沿性课题. 其中特别用较多的篇幅讨论了多物理场与多尺度模拟的背景、目标、必要性、现有方法的优缺点、障碍、应用例子与其他前沿研究领域的联系及其发展态势, 并阐述其研究焦点与值得注意的进展. 相似文献
95.
Tang Y Ross IN Hernandez-Gomez C New GH Musgrave I Chekhlov OV Matousek P Collier JL 《Optics letters》2008,33(20):2386-2388
A short-pulse source based on optical parametric chirped-pulse amplification (OPCPA) technology has been developed with properties that make it a suitable seed for a high-energy OPCPA system. This source generated a diffraction-limited pulse at 910 nm with a full bandwidth of > 165 nm and a spectrum having a transform-limited pulse duration of less than 15 fs. The technique has potential for generating bandwidths > 200 nm and pulse durations < 10 fs. 相似文献
96.
The 9 and 12MeV proton irradiations of the Chinese CMOS Image Sensor in the fluence range from 1×109 to 4×10×10cm-2 and 1×109 to 2×1012cm-2 have been carried out respectively. The color pictures and dark output images are captured, and the average brightness of dark output images is calculated. The anti-irradiation fluence thresholds for 9 and 12~MeV protons are about 4×1010 and 2×1012 cm-2, respectively. These can be explained by the change of the concentrations of irradiation-induced electron-hole pairs and vacancies in the various layers of CMOS image sensor calculated by the TRIM simulation program. 相似文献
97.
A general formalism suitable for the semiclassical treatment of many two-photon resonant problems is presented, and the method demonstrated for the specific examples of two-photon self-induced transparency, and third harmonic generation in the cw case. 相似文献
98.
New theoretical results connected with the stability of multiple pulsing in a passively mode-locked quasicontinuous laser in the rate equation approximation are presented. Together with earlier results, these allow the number of pulses per cavity transit to be predicted and a qualitative estimate made of the pulse duration for any combination of parameters. The results are illustrated by computer evolutions. 相似文献
99.
S. GustafsonRID=""ID=""Present address: Courant Institute Mercer St. New York NY USA.¶E-mail: gustaf@cims.nyu.edu I. M. Sigal 《Communications in Mathematical Physics》2000,212(2):257-275
We study the linearized stability of n-vortex (n∈ℤ) solutions of the magnetic Ginzburg–Landau (or Abelian Higgs) equations. We prove that the fundamental vortices (n = ± 1) are stable for all values of the coupling constant, λ, and we prove that the higher-degree vortices (|n|≥ 2) are stable for λ < 1, and unstable for λ > 1. This resolves a long-standing conjecture (see, eg, [JT]).
Received: 16 November 1998 / Accepted: 3 January 2000
RID="*"
ID="*"Research on this paper was supported by NSERC under grant N7901
RID="**"
ID="**"Present address: Courant Institute, 251 Mercer St., New York, NY 10012, USA.¶E-mail: gustaf@cims.nyu.edu 相似文献
100.
The digital particle image velocimetry (DPIV) technique has been used to investigate the flow fields of an elliptic jet in cross flow (EJICF). Two different jet orientations are considered; one with the major axis of the ellipse aligned with the cross flow (henceforth referred to as a low aspect ratio (AR) jet), and the other with the major axis normal to the cross flow (henceforth referred to as a high aspect ratio jet). Results show that the vortex-pairing phenomenon is prevalent in the low aspect ratio jet when the velocity ratio (VR)3, and is absent in the high aspect ratio jet regardless of the velocity ratio. The presence of vortex pairing leads to a substantial increase in the leading-edge peak vorticity compared to the lee-side vorticity, which suggests that vortex pairing may play an important role in the entrainment of ambient fluid into the jet body, at least in the near-field region. In the absence of vortex pairing, both the leading-edge and the lee-side peak vorticity increase monotonically with velocity ratio regardless of the aspect ratio. Moreover, time-averaged velocity fields for both AR=0.5 and AR=2 jets reveal the existence of an unstable focus (UF) downstream of the jet, at least for VR2. The strength and the location of this focus is a function of both the velocity ratio and aspect ratio. In addition, time-averaged vorticity fields show a consistently higher peak-averaged vorticity in the low aspect ratio jet than in the high aspect ratio jet. This behavior could be due to a higher curvature of the vortex filament facing the cross flow in the low aspect ratio jet, which through mutual interaction may lead to higher vortex stretching, and therefore higher peak-averaged vorticity.Nomenclature A nozzle or jet cross-sectional area - AR aspect ratio, defined as the ratio of the nozzle cross-stream dimension to its streamwise dimension, =H/L - D characteristic jet diameter (for circular jet only) - Dh hydraulic diameter, =4A/P - Dmajor major axis of an elliptic nozzle - Dminor minor axis of an elliptic nozzle - H cross-stream dimension of the nozzle - L streamwise dimension of the nozzle - P perimeter of the nozzle - Rej jet Reynolds number, =VjD/ - VR velocity ratio, =Vj/V - Vj mean jet velocity - V mean cross-flow velocity - x downstream distance from jet center - X cross-plane vorticity - kinematic viscosity 相似文献