排序方式: 共有40条查询结果,搜索用时 15 毫秒
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CLAUDIA L. PARKER OSCAR N. VENTURA STAN K. BURT RAÚL E. CACHAU 《Molecular physics》2013,111(17):2659-2668
We present a general purpose QM-MM-MD engine (DYNGA) designed to test alternative hybrid Hamiltonians geared towards the treatment of problems of interest in structural biology including the use of experimental data constraints. In this first presentation we use DYNGA to explore the behaviour of a traditional QM-MM approach in the treatment of the water—water interaction. We find the potential energy hypersurface for the water dimer computed with the HF 4–31G*/TIP3P hybrid Hamiltonian tends to be too flat. We also explore the effect of using traditional QM-MM techniques on proton wires and conclude there is a need for improvement, possibly addressed by using polarizable force fields. 相似文献
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Bosch R.A. Bidwell S.W. Gilgenbach R.M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(4):428-432
Current clamping (constant current behavior) was observed in measurements of the current drawn by a metal plate acting as a beam collector for long-pulse (300 ns) electron beam, propagating a short distance through low-pressure gas (40-1000 mtorr). When the clamping occurs, oscillations in the beam collector current are reduced, resulting in a flat current pulse. Good agreement is found with a model which considers the impedance of the plasma produced by the electron beam in parallel with the inductance of the beam-collector current path. The current clamping occurs when the plasma impedance is smaller than the inductive impedance of the beam-collector current path 相似文献
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Abstract We analyze the efficiency of the international management of the Bay of Biscay anchovy. While a sharing agreement between France and Spain has been in place since 1992, the fish stock collapsed in 2005 and the fishery closed from 2005 to spring 2010. We consider differences in production technologies between both countries and calibrate our model using data from 1987 to 2009. Our results suggest two sources of rent dissipation under the existing sharing agreement: inefficient quota allocation and production inefficiencies due to inflexible national regulations. We discuss several alternatives to improve management. 相似文献
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A newly developed interface coupling a CHN combustion device (elemental analyser 'EA') to an isotope ratio mass spectrometer is described and evaluated. The purpose of the device is to extend the dynamic range of delta(13)C and delta(15)N analysis from less than 2 orders of magnitude to more than 3 orders of magnitude. Carbon isotope ratio measurements of atropine as a model compound have been performed analysing between 1 μg to 5 mg C with acceptable to excellent precision (0.6 to 0.06 per thousand, delta-notation). The correction due to the blank signal is critical for sample amounts smaller than 4 μg C. The maximum sample weight is determined by the combustion capacity of the EA. Larger sample amounts are measured using dilution of a small part of the EA effluent with helium. The dilution mechanism works virtually free of isotope fractionation. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Enloe C.L. Gilgenbach R.M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(3):379-389
Flashover of electrically stressed polymeric insulators in vacuum has been induced by ultraviolet radiation from an excimer laser (KrF). The authors present the results of an experiment which (1) quantifies the effects of ultraviolet illumination on polymeric insulators; (2) characterizes ultraviolet-induced flashover over insulators at positive and negative angles, and (3) correlates microscopic and macroscopic material properties to flashover behavior. A theory of ultraviolet-induced insulator flashover is developed, which explains the unexpected variation of flashover strength with geometry in view of the current understanding of flashover in vacuum 相似文献
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