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221.
W.E. Billups Long-Jin Lin Benny E. Arney Wayne A. Rodin Edward W. Casserly 《Tetrahedron letters》1984,25(36):3935-3938
Treatment of 1-bromo-2,2-dichloro(trimethylsilyl)cyclopropane (2) with tetra--butylammonium fluoride in tetrahydrofuran yields 1-bromo-2-chlorocyclopropene (1). 1H-Cyclopropa[b]phenanthrene (3) can be prepared by aromatization of the Diels-Alder adduct of 1 and 1,2-dimethylene-3,5,6,7,8,9-hexahydronaphthalene (6) using DDQ followed by potassium -butoxide in tetrahydrofuran. 相似文献
222.
Geoffrey H. Campbell Jürgen M. Plitzko Wayne E. King Stephen M. Foiles Christian Kisielowski Gerd J.M. Duscher 《Interface Science》2004,12(2-3):165-174
New insight into the atomic segregation of copper to an aluminum grain boundary has been obtained using multiple, complementary atomic resolution electron microscopy techniques coupled with ab-initio electronic structure calculations. The copper segregation is site specific and changes the structure of the boundary by occupying interstitial sites. Minor elemental constituents in materials can have profound effects on their engineering performance. This change in structure can be associated with these strong effects. The observed structural change will alter the mass transport behavior of the boundary and has implications for the understanding of electromigration mechanisms. 相似文献
223.
James R. Damewood Jr. Wayne P. Anderson Joseph J. Urban 《Journal of computational chemistry》1988,9(2):111-124
Molecular mechanics methods are applied to the study of neutral molecule complexation with crown ethers. Protocols for the development of parameters necessary to describe these molecule-molecule interactions are presented. Application of these methods to the study of 1:1 and 2:1 (guest:host) complexation between acetonitrile (1), nitromethane (2), malononitrile (3) and dimethylsulfone (4) reveals positive cooperativity in formation of the 2:1 complexes in isolation. 相似文献
224.
We provide a simple constructive characterization for trees with equal domination and independent domination numbers, and for trees with equal domination and total domination numbers. We also consider a general framework for constructive characterizations for other equality problems. 相似文献
225.
C. Eugene Wayne 《Communications in Mathematical Physics》1984,96(3):311-329
The existence of quasiperiodic trajectories for Hamiltonian systems consisting of long chains of nearly identical subsystems, with interactions which decay rapidly with increasing distance between the interacting components, is studied. Such models are of interest in statistical mechanics. It is shown that nonergodic motions persist for much larger perturbations than prior work indicated. If the number of degrees of freedom of the system isN, the allowed perturbation decreases only as an inverse power ofN, as the number of degrees of freedom increases, rather than the inverse power ofN! which previous estimates yielded.This work was completed while the author was at the Institute for Mathematics and Its Applictations, University of Minnesota, Minneapolis, MN, 55455, USASupported in part by NSF Grant DMS-8403664 相似文献
226.
Adsorption of CO on a Pd monolayer (ML) supported on Mo(110) has been studied using low energy electron diffraction (LEED), temperature programmed desorption (TPD), and high resolution electron energy loss spectroscopy (HREELS). Three ordered CO substructures denoted as
are observed with LEED. The binding energy of C0 on the 1.0 ML Pd/Mo(110) surface is reduced by 12 kcal/mol relative to the Pd(111) surface, consistent with previous results for supported palladium monolayers on other substrates. Two vibrational states of C0 are observed near 1950 and 2050 cm−1, with the feature at the lower wavenumber having the smaller binding energy. 相似文献
227.
Surface-mediated alignment of nematic liquid crystals with polarized laser light was reported recently [1]. In this communication we describe the alignment of a guest-host liquid crystal medium with polarized laser light. Liquid crystals in the illuminated region orient perpendicular to the direction of the laser polarization and remain aligned in the absence of laser radiation. The liquid crystals can be reoriented again by subsequent illumination. The kinetic feature of this surface-mediated liquid crystal orientation is characterized by the presence of coexisting liquid crystal regions of directors pointing away from the initial alignment. 相似文献
228.
229.
Tom Scarvie Nord Andresen Ken Baptiste John Byrd Mike Chin Michael C. Martin Wayne R. McKinney Christoph Steier 《Infrared Physics & Technology》2004,45(5-6):403-408
The quality of infrared microscopy and spectroscopy data collected at synchrotron based sources is strongly dependent on signal-to-noise. We have successfully identified and suppressed several noise sources affecting beamlines 1.4.2, 1.4.3, and 1.4.4 at the advanced light source (ALS), resulting in a significant increase in the quality of FTIR spectra obtained. In this paper, we present our methods of noise source analysis, the negative effect of noise on the infrared beam quality, and the techniques used to reduce the noise. These include reducing the phase noise in the storage ring radio-frequency (RF) system, installing an active mirror feedback system, analyzing and changing physical mounts to better isolate portions of the beamline optics from low-frequency environmental noise, and modifying the input signals to the main ALS RF system. We also discuss the relationship between electron beam energy oscillations at a point of dispersion and infrared beamline noise. 相似文献
230.
Wayne M. Getz 《Natural Resource Modeling》1994,8(2):195-197
Scaling Fisheries: The Science of Measuring the Effects of Fishing, 1855–1955, (Cambridge studies in applied ecology and resource management), Tim D. Smith, Cambridge University Press, 1994, 392 pp. 相似文献