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Application of high pres sure at 250 degrees C irreversibly dehydrated five inorganic compounds containing molecular water to lower hydrates or to anhydrous forms. Compression at 250 degrees C also lead to ten new reversible phase transformations in another group of nine hydrates. Maximum pressure applied was 22.6 kilobars. 相似文献
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Fine structure constant defines visual transparency of graphene 总被引:1,自引:0,他引:1
Nair RR Blake P Grigorenko AN Novoselov KS Booth TJ Stauber T Peres NM Geim AK 《Science (New York, N.Y.)》2008,320(5881):1308
There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc feminine 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure. 相似文献
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Field studies have indicated that bolas spiders attract male moth prey, apparently by mimicking the odor of female moth sex pheromones. Three moth sex pheromone compounds, (Z)-9-tetradecenyl acetate, (Z)-9-tetradecenal, and (Z)-11-hexadecenal, were identified in volatile substances emitted by hunting adult female Mastophora cornigera spiders. These compounds are components of pheromone blends that attract some of this spider's moth prey species. 相似文献
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Williams RR 《Science (New York, N.Y.)》1938,87(2269):559-563
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An ultrafast optical shutter was used to image ultrasmall objects hidden behind scattering walls by a procedure that selects in time the ballistic component and rejects the scattered diffusive light. Scattering walls used in this experiment included human breast tissue, chicken breast tissue, and a water suspension of polystyrene particles with scattering coefficients up to 21.7. Submillimeter resolution was achieved for two-dimensional ballistic images of a single point, a double-point fluorescence source, and a bar test chart in or behind these different turbid media. 相似文献