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121.
We develop a (classical) local field theory which contains as a special solution the (classical) dual string recently discussed by Goddard, Goldstone, Rebbi and Thorn. The basic field is a gauge field Fμν(x), and the Lagrangian is given by . We treat the case of closed strings (corresponding to the Shapiro-Virasoro model) where Fμν can be expressed in terms of potentials Aμ. Quantization of Fμν is briefly discussed, but a more thorough discussion is postponed. 相似文献
122.
W. Semmler K. Bonde Nielsen J. C. Sindholt G. Weyer F. Abildskov 《Hyperfine Interactions》1979,7(1):71-80
Differential perturbed angular-distribution measurements have been performed for107Cd and109Cd in silver hosts. The data have been obtained at various target temperatures with and wthout applied magnetic fields. The theory of static, combined electric and magnetic hyperfine interaction has been applied for comparison of the zero-field quadrupole data and the external field Larmor-precession data.It is concluded that this combined interaction of the external magnetic field and the damage-induced, electric field gradients quantitatively accounts for the observed dependence of Larmor-precession amplitudes on time, temperature and field strength. The significance of the experimental time range for the appearance and thus for the interpretation of this dependence is demonstrated. 相似文献
123.
We draw some conclusions from the saturation of QED2 correlation functions by non-quasiclassical instantons. 相似文献
124.
The parallel band ν6(A″2) of C3D6 near 2336 cm?1 has been studied with high resolution (Δν = 0.020 – 0.024 cm?1) in the infrared. The band has been analyzed using standard techniques and the following parameters have been determined: B″ = 0.461388(20) cm?1, D″J = 3.83(17) × 10?7 cm?1, ν0 = 2336.764(2) cm?1, αB = (B″ ? B′) = 8.823(12) × 10?4 cm?1, βJ = (D″J ? D′J) = 0, and αC = (C″ ? C′) = 4.5(5) × 10?4 cm?1. 相似文献
125.
Mean field calculations of the Peierls instability have been carried out for arbitrary bandfilling both in the case of free electrons as well as for the tightbinding approximation. New expressions for Δ(0) and Tp are derived which change the experimentally derived λ to a more reasonable value. Δ(0)/kBTp may differ significantly from the BCS value 1.76 in the tightbinding approximation. 相似文献
126.
127.
Refection electron microscopy has been applied for studying single crystal surfaces of noble metals in a conventional electron microscope using diffracted electrons for the imaging. This is equivalent to dark field imaging in transmission electron microscopy. The image contains far more contrast due to deviation from the ideal surface structure than any other surface imaging technique. A resolution of the order of 20 Å has been achieved for directions perpendicular to the incident beam. In directions parallel to the incident beam the resolution is much worse and the magnification is reduced with a factor 15 to 100 because the surface is viewed at the angle of the diffracted beam used for imaging (foreshortening). Nevertheless the achieved resolution is one to two orders of magnitude better than for other surface imaging methods. Since a correspondence can be established between image and diffraction pattern by means of selected area diffraction, the present technique should be very useful in structure analysis of surfaces. 相似文献
128.
We argue that the starting point of Kaluzas idea of unifying electrodynamics and gravity was the analogy between gravitation and electromagnetism which was pointed out by Einstein and Thirring. It seems that Kaluzas attention was turned to this point by the three papers on the Lense–Thirring effect and the analogy between gravitation and electromagnetism which were published a short time before Kaluzas paper was submitted. We provide here also an English translation of the third of these papers (Phys. Zeits. 19: 204, 1918). 相似文献
129.
It is proposed that dark matter could consist of compressed collections of atoms (or metallic matter) encapsulated into, for example, 20 cm big pieces of a different phase. The idea is based on the assumption that there exists at least one other phase of the vacuum degenerate with the usual one. Apart from the degeneracy of the phases we only assume standard model physics. The other phase has a Higgs vacuum expectation value appreciably smaller than in the usual electroweak vacuum. The balls making up the dark matter are very difficult to observe directly, but inside dense stars may expand absorbing the star and causing huge explosions (gamma ray bursts). The ratio of dark matter to ordinary matter is expressed as a ratio of nuclear binding energies and predicted to be about 5. 相似文献
130.
Nielsen M Thomsen AH Cló E Kirpekar F Gothelf KV 《The Journal of organic chemistry》2004,69(7):2240-2250
Rigid linear and tripoidal organic modules based on the oligo(phenylene ethynylene) backbone having salicylaldehyde-derived termini are synthesized. A highly functionalized 5-iodosalicyl aldehyde was prepared and coupled to each ethynyl group of 1,4-diethynylbenzene or 1,3,5-triethynylbenzene in Sonogashira couplings. The two or three termini of the compounds are functionalized for incorporation in linear and branched oligonucleotide strands. For the linear module (LM), the two termini are equipped with amide spacers, and one of these was functionalized with a DMTr (dimethoxytrityl)-protected hydroxy group and the other with a phosphoramidite. One of the tripoidal modules is prepared with DMTr groups in two of its three termini. A tripoidal module is also synthesized with three different groups on its hydroxy termini: a phosphoramidite, a DMTr group, and an Fmoc group. Extended studies have shown that these rigid linear and tripoidal organic modules can be incorporated into short oligonucleotides. Several of these modules can be applied for DNA-directed assembly and covalent coupling into structures of predetermined connectivity. Such structures have potential application for molecular electronics and nanotechnology. 相似文献