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排序方式: 共有146条查询结果,搜索用时 62 毫秒
91.
92.
Reed MW Cullen IJ Walker PM Litvinov YA Blaum K Bosch F Brandau C Carroll JJ Cullen DM Deo AY Detwiller B Dimopoulou C Dracoulis GD Farinon F Geissel H Haettner E Heil M Kempley RS Knöbel R Kozhuharov C Kurcewicz J Kuzminchuk N Litvinov S Liu Z Mao R Nociforo C Nolden F Plass WR Prochazka A Scheidenberger C Steck M Stöhlker T Sun B Swan TP Trees G Weick H Winckler N Winkler M Woods PJ Yamaguchi T 《Physical review letters》2010,105(17):172501
A study of cooled 1??Au projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides 1?3(,)1??(,)1??Hf and 1??(,)1??Ta. The results support the prediction of a strongly favored isomer region near neutron number 116. 相似文献
93.
Typical disturbances of biological environment such as background scatter and refractive index variations have little effect on the size-dependent scattering property of highly refractive nanocrystals, which are potentially attractive optical labels. We report on what is to our knowledge the first investigation of these scattering optical labels, and their sizing, in particular, by imaging at subvideo frame rates and analyzing samples of diamond nanocrystals deposited on a glass substrate in air and in a matrix of weakly scattering polymer. The brightness of a diffraction-limited spot appears to serve as a reliable measure of the particle size in the Rayleigh scattering limit. 相似文献
94.
Cronin SB Yin Y Walsh A Capaz RB Stolyarov A Tangney P Cohen ML Louie SG Swan AK Unlü MS Goldberg BB Tinkham M 《Physical review letters》2006,96(12):127403
Tunable Raman spectroscopy is used to measure the optical transition energies Eii of individual single wall carbon nanotubes. Eii is observed to shift down in energy by as much as 50 meV, from -160 to 300 degrees C, in contrast with previous measurements performed on nanotubes in alternate environments, which show upshifts and downshifts in Eii with temperature. We determine that electron-phonon coupling explains our experimental observations of nanotubes suspended in air, neglecting thermal expansion. In contrast, for nanotubes in surfactant or in bundles, thermal expansion of the nanotubes' environment exerts a nonisotropic pressure on the nanotube that dominates over the effect of electron-phonon coupling. 相似文献
95.
A kinetic study is reported for the reaction of the anionic nucleophiles OH-, CN-, and N 3 - with aryl benzoates containing substituents on the benzoyl as well as the aryloxy moiety, in 80 mol % H2O - 20 mol % dimethyl sulfoxide at 25.0 degrees C. Hammett log k vs sigma plots for these systems are consistently nonlinear. However, a possible traditional explanation in terms of a mechanism involving a tetrahedral intermediate with curvature resulting from a change in rate-determining step is considered but rejected. The proposed explanation involves ground-state stabilization through resonance interaction between the benzoyl substituent and the electrophilic carbonyl center in the two-stage mechanism. Accordingly, the data are nicely accommodated on the basis of the Yukawa-Tsuno equation, which gives linear plots for all three nuceophiles. Literature reports of the mechanism of acyl transfer processes are reconsidered in this light. 相似文献
96.
Richard G. Swan 《Mathematische Zeitschrift》1967,102(4):318-322
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The basic mathematical consequences which follow from the laws of thermodynamics are explored in a systematic new treatment for establishing fluid thermodynamic systems for a number of materials under conditions where they behave as fluids. For metals and many other solids, but less so for liquids, the specific heat at constant volume cν is sensibly constant at all temperatures above room temperature. The partial differential equation of thermodynamics which expresses the constancy of cν is easily solved, the solution involving two arbitrary functions of the specific volume. Various approaches are presented to illustrate how one may choose these functions to accord with experimental observations over large thermodynamic ranges, and so produce practical thermodynamic systems. Two complementary thermodynamic systems are presented, which embody significant experimental results; the first is based on linear shock velocity/particle velocity (U, u) relations; the second on the limiting value of the specific heat ratio at high temperatures. They are complementary in the sense that the first has analytically complicated non-Hugoniot properties which differ insignificantly from the comparatively simple non-Hugoniot properties of the second; whilst the second has analytically complicated Hugoniot properties which differ insignificantly from the simple Hugoniot properties of the first. Together, then, the two systems may be combined to give comprehensive practical simplicity. The main interest in these thermodynamic systems lies in the study of the behaviour of liquids, metals and other solids in shock transitions and under extreme conditions such as occur in high velocity impact or in explosion phenomena; but they are also of importance in stress-wave analysis, where complete thermodynamic systems are required in order to derive stress-strain relationships which do not neglect the effects of temperature changes. 相似文献
100.