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231.
232.
233.
J. Fröhlich 《Zeitschrift für Physik A Hadrons and Nuclei》1982,307(3):275-278
A proper treatment of various electromagnetic contributions toN-4He scattering enables one to determinen(p)-4He observables fromp(n)-4He data. Several calculations ofn-4He observables considering different electromagnetic effects are presented. It is shown that the contribution of thep-4He Coulomb corrections ton-4He polarizations and differential cross sections dominates over other electromagnetic effects forθ c.m.≧30°. For smaller scattering angles, neutron magnetic scattering is important and produces a divergingn-4He differential cross section atθ=0° and a large peak (Mott-Schwinger effect) in the polarization. The influence of thep- andn-4He vacuum polarizations on then-4He observables is found to be small. 相似文献
234.
Le Foulon FX Braud E Fabis F Lancelot JC Rault S 《Journal of combinatorial chemistry》2005,7(2):253-257
A 1140-library of thiophene ureidoacids was synthesized by the reaction of a set of 60 primary or secondary amines with a number of 19 thieno[3,2-d]- or thieno[2,3-d][1,3]oxazine-2,4-diones. All compounds were obtained by a simple solution-phase combinatorial strategy on a 200-400-mg scale with over 70% yields and purities over 80%. Sixty library members chosen at random were successfully characterized by standard 1H NMR, HPLC/MS, and IR studies. Analgesic, antalgic, and antiinflammatory potential were investigated. The 1140-member ureidothiophene carboxylic acid library will be used in high-throughput screening assays. 相似文献
235.
Grosshans F 《Physical review letters》2005,94(2):020504
We present here an information theoretic study of Gaussian collective attacks on the continuous variable key distribution protocols based on Gaussian modulation of coherent states. These attacks, overlooked in previous security studies, give a finite advantage to the eavesdropper in the experimentally relevant lossy channel, but are not powerful enough to reduce the range of the reverse reconciliation protocols. Secret key rates are given for the ideal case where Bob performs optimal collective measurements, as well as for the realistic cases where he performs homodyne or heterodyne measurements. We also apply the generic security proof of Christiandl et al. to obtain unconditionally secure rates for these protocols. 相似文献
236.
We study tight-binding models of itinerant electrons in two different bands, with effective on-site interactions expressing Coulomb repulsion and Hunds rule. We prove that, for sufficiently large on-site exchange anisotropy, all ground states show metallic ferromagnetism: They exhibit a macroscopic magnetization, a macroscopic fraction of the electrons is spatially delocalized, and there is no energy gap for kinetic excitations. 相似文献
237.
When a plate falls on the ground, it breaks. We study this phenomenon at the macroscopic level. We restrict ourselves to 1-D problems and illustrate the theory with a chandelier to which a falling stone is tied. The collisions are assumed instantaneous. Percussions are introduced at the unknown fracture points. Equations of motion and constitutive laws give a set of differential equations, whose corresponding variational problem may be solved in SBV (special functions of bounded variation). The example shows how the theory applies and gives realistic results. 相似文献
238.
In this paper are presented some properties of smooth cocycles over irrational rotations on the circle with values in the
groupSU(2). It is proved that the degree of anyC
2-cocycle (the notion of degree was introduced in [2]) belongs to 2πℕ (ℕ={0, 1, 2,...}). It is also shown that if the rotation
satisfies a Diophantine condition, then everyC
∞-cocycle with nonzero degree isC
∞-cohomologous to a cocycle of the form
, where 2πr is the degree of the cocycle andw is a real number. The above statement is false in the case of cocycles with zero degree. The proofs are based on ideas presented
by R. Krikorian in [6].
Research partly supported by KBN grant 2 P03A 027 21(2001), by FWF grant P12250-MAT and by the Foundation for Polish Science. 相似文献
239.
Couturier M Ménard F Ragan JA Riou M Dauphin E Andresen BM Ghosh A Dupont-Gaudet K Girardin M 《Organic letters》2004,6(11):1857-1860
Lewis-base-catalyzed cycloisomerization of bis(enones) to decalins has been demonstrated as an alternative to the traditional Lewis acid catalyzed Diels-Alder cycloaddition. In this process, a trialkylphosphine mediates both bond formation steps in two distinct catalytic cycles. The single-pot operation generates two carbon-carbon bonds and up to five contiguous stereocenters in one step, starting from achiral, aliphatic substrates; eight examples are provided. [reaction: see text] 相似文献
240.
Frédéric?Faure Stéphane?NonnenmacherEmail author 《Communications in Mathematical Physics》2004,245(1):201-214
We consider the quantized hyperbolic automorphisms on the 2-dimensional torus (or generalized quantum cat maps), and study the localization properties of their eigenstates in phase space, in the semiclassical limit. We prove that if the semiclassical measure corresponding to a sequence of normalized eigenstates has a pure point component (phenomenon of strong scarring), then the weight of this component cannot be larger than the weight of the Lebesgue component, and therefore admits the sharp upper bound 1/2. 相似文献