排序方式: 共有38条查询结果,搜索用时 15 毫秒
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Arena DA Bartynski RA Nayak RA Weiss AH Hulbert SL Weinert M 《Physical review letters》2003,91(17):176403
The Pd M4VV and M5VV Auger spectra of the 0.1 ML Pd/Ag(100) dilute surface alloy have been measured using Auger-photoelectron coincidence spectroscopy. The M4VV spectrum indicates that Pd 3d(3/2) core holes have a Coster-Kronig decay rate that is approximately 10 times that of Pd metal. Our calculations show that this giant enhancement arises from the local electronic structure of excited Pd atoms at the surface. Anomalous features in the Auger line shape are similar to those seen in dilute bulk PdAg alloys, and these features in the M5VV and M4VV lines are in good agreement with theoretical predictions. 相似文献
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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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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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Wenhua Chen Alan L. Stottlemyer Payam Kaghazchi Theodore E. Madey Robert A. Bartynski 《Surface science》2009,603(20):3136-16391
We report on the adsorption and decomposition of NO on O-covered planar Ir(2 1 0) and nanofaceted Ir(2 1 0) with variable facet sizes investigated using temperature programmed desorption (TPD), high-resolution electron energy loss spectroscopy (HREELS), and density functional theory (DFT). When pre-covered with up to 0.5 ML O, both planar and faceted Ir(2 1 0) exhibit unexpectedly high reactivity for NO decomposition. Upon increasing the oxygen coverage to 0.7 ML O, planar Ir(2 1 0) has little activity while faceted Ir(2 1 0) still remains active toward NO decomposition, although NO decomposition is completely inhibited when both surfaces are pre-covered by 1 ML O. NO molecularly adsorbs on O-covered Ir at 300 K. At low NO and oxygen coverage, NO adsorbs on the atop sites of planar Ir(2 1 0) while on the bridge and atop sites of faceted Ir(2 1 0) composed of (1 1 0) and {3 1 1} faces. No evidence for size effects in the decomposition of NO on O-covered faceted Ir(2 1 0) is observed for average facet size in the range 5-14 nm. Our findings should be of importance for development of Ir-based catalysts for NO decomposition under oxygen-rich conditions. 相似文献
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