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71.
Ohne Zusammenfassung 相似文献
72.
73.
Ralf D. Hecht 《General Relativity and Gravitation》1995,27(5):537-554
We discuss two expressions for the conserved quantities (energy momentum and angular momentum) of the Poincaré Gauge Theory. We show, that the variations of the Hamiltonians, of which the expressions are the respective boundary terms, are well defined, if we choose an appropriate phase space for asymptotic flat gravitating systems. Furthermore, we compare the expressions with others, known from the literature. 相似文献
74.
Elmar Hecht 《应用有机金属化学》2005,19(3):390-390
Dimeric and centrosymmetric [MeEtN(CH2)3AlH2]2 comprises aluminum centers, coordinated in a distorted trigonal bipyramidal fashion by three hydrogen atoms, one nitrogen atom and one carbon atom. The aluminum atoms are bridged by hydrogen atoms, creating a planar, four‐membered Al2H2 ring. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
75.
76.
AM Jayannavar 《Pramana》2002,58(2):173-181
We present a simple model of transmission across a metallic mesoscopic ring. In one of its arm an electron interacts with
a single magnetic impurity via an exchange coupling. We show that entanglement between electron and spin impurity states leads
to reduction of Aharonov-Bohm oscillations in the transmission coefficient. The spin-conductance is asymmetric in the flux
reversal as opposed to the two-probe electrical conductance which is symmetric. In the same model, in contradiction to the
naive expectation of a current magnification effect, we observe enhancement as well as suppression of this effect depending
on the system parameters. The limitations of this model to the general notion of dephasing or decoherence in quantum systems
are pointed out. 相似文献
77.
An x-ray analysis of two natural compounds isolated fromPiper sanctum confirmed thetrans configuration for 5-(8-methoxy)cinnamyliden-4-methoxy-but-3-enolide [piperolide (I)] and for 5-[trans-(z)-,-epoxy--methoxycinnamyliden]-4-methoxy-2(5H)-furanon [epoxypiperolide (II)]. The space groups arePbca [a = 44.174(3),b = 8.056(3),c = 7.515(4) Å] for (I) andP21/c [a = 11.351(4),b = 8.292(5),c = 14.292(2) Å, = 96.28(2) °] for (II). The structures were solved by direct methods and refined by least-squares techniques toR = 4.8% (I) andR = 7.5% (II). The stereochemistry of the semicyclic double bond is in favor of theZ-isomers. 相似文献
78.
79.
A theoretical interpretation of the reduction in E2 strengths in 126Ba prior to backbending is presented. A shell model basis is built from normal parity orbilals organized into multiplets of a pseudo SU(3) symmetry coupled to configurations restricted to states of seniority zero and two. Within the framework of the model the scattering of a pair of protons from normal parity to the orbital produces band crossing and a corresponding reduction in E2 transition strengths prior to pair alignment which is the principal mechanism of the backbending. 相似文献
80.
M.H. Hecht A.J. Viescas I. Lindau J.W. Allen L.I. Johansson 《Journal of Electron Spectroscopy and Related Phenomena》1984,34(4):343-353
We report on the four-peak structure observed in the region of 4f photoemission in Yb metal, using synchrotron radiation in the energy range 70–200 eV. We conclude, contrary to previous reports, that the doublet associated with surface emissions results from an intrinsic surface shift on clean regions of the surface. We also demonstrate that the observed structure is consistent with earlier XPS measurements, and we set an upper limit on the width of the bulk peaks. 相似文献