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991.
The transverse spin asymmetry of a quark in a baryon and the linear polarization of a gluon in a vector meson are studied from thet-channel point of view. Using the Altarelli-Parisi approach, they are shown to obey independent evolution equations and to decrease with increasingQ 2. We investigate the possibility to measure them at leading twist, to leading order in α and αs and without analyzing the final polarizations. This requires simultaneous polarization of the beam and the target; the observable effect is in the azimuthal distribution of the highP T particle or jet. Assuming a simple (quark+scalar diquark) model for the baryon, a large asymmetry is expected inp \(\bar p\) Drell-Yan collisions, a smaller one in highP T pp collisions, from the interference term in the scattering of two identical quarks. 相似文献
992.
J. O. Eeg 《Zeitschrift fur Physik C Particles and Fields》1990,46(4):665-670
I consider some low energy restrictions for a “flipped” left-right symmetric model containing exotic fermions ofE 6 and a right-handedW-boson, all with oddR-parity. The new interactions due toW R-exchange have no significant impact on rare kaon decays, because theW R does not couple tod,s,b quarks. On the other hand,W R exchanges might induce rare processes like \(D - \bar D\) mixing, \(D^0 \to \mu \bar \mu ,D^0 \to \mu \bar e,\mu \to e\gamma ,\mu \to 3e\) , and μN→eN. It turns out that the strongest bound is obtained from \(D - \bar D\) mixing. With reasonable extra assumptions, it is found that the exotic right-handed W-boson is likely to be heavier than 500 to 1500 GeV. 相似文献
993.
J. Baacke 《Zeitschrift fur Physik C Particles and Fields》1990,47(4):619-623
We generalize a new method of calculating the effective action for fields in a spherically symmetric background to the case of a spin 1/2 field whose mass is a function ofr=|x|, as it is the case in the nontopological soliton model of Friedberg and Lee. The quantum corrections to the soliton energy are sizeable, of the same order as the bound state energies that stabilize the soliton. 相似文献
994.
High dose implantations of Fe into metals and semiconductors have been performed with beam energies up to 1 MeV at the UNILAC-injector at GSI. Unusual high concentrations of 70 atomic % for Si and 20 atomic % for Cu have been obtained, with doses of 1018 Fe/cm2 in the case of Si and several 1017 Fe/cm2 in the case of Cu. For Si the thickness of the layers were determined by Rutherford backscattering to be 4500 Å. These results are consistent with calculations, which show that these high concentrations are due to the reduction of the sputter yield at the relative high particle energies. Samples have been characterized using several complementary methods (Mössbauer Spectroscopy (MS), Rutherford Backscattering Spectroscopy (RBS), Auger electron Spectroscopy (AES). Scanning Electron Microscopy (SEM), X-ray diffraction (XRD)). 相似文献
995.
TheN-(2-phenylethyl)amide of-(1, 1-ethylenedioxy)-ethyl--hydroxybutyric acid (II) and theN-(p-methoxybenzyl)amide of-(1, 1-ethylenedioxy)-ethyl--hydroxybutyric acid (III) have been synthesized and the crystal structure ofIII has been solved. CompoundIII, C16H23O5N, crystallizes in the monoclinic space groupP21/c witha=12.572(2),b=11.149(2),c=12.317(2) Å and=106.53(1)°. The structure was solved by direct methods, and refined by full-matrix least squares to giveR=0.040 (R
w
=0.047) for 2004 intensities. The dioxolane ring has a deformed half-chair conformation. 相似文献
996.
Elizabeth M. Holt Balawant S. Joshi Dilip H. Gawad S. William Pelletier 《Journal of chemical crystallography》1990,20(3):261-264
The crystal and molecular structure of 1-ethyl-4-methoxy-9H-pyrido[3,4b]indole (crenatine) carbonate C14H14N2O·H2CO3, (MS, m/z 226)M
R
288.3, a-carboline alkaloid, has been determined from X-ray diffraction data. The compound crystallizes in the space group Pbca with cell parameters:a=11.616(4),b=18.450(8),c=12.992(5)Å,V=2784(2)Å3,Z=8,D
calc=1.375 g cm–3, (MoK)=0.71069Å,(Mo K)=0.94 cm–1,F(000)=1216,R/R
w
=8.2/10.3% for 1099 reflections. The ring system of the-carboline nucleus is planar. The title compound shows a two center hydrogen bond between the indole N-H group and the oxygen atom of a carbonate group. The structure does not display hydrogen bonding between-carboline groups but rather a bonding network involving the carbonate group. 相似文献
997.
J. F. Voloch 《Bulletin of the Brazilian Mathematical Society》1990,21(1):91-94
Letf:CE be a non-constant rational map between curves over a finite field, whereE is elliptic. We estimate the number of rational points ofC whose image underf generate the group of rational points ofE. 相似文献
998.
Basford JR 《Journal of laser applications》1990,2(1):57-63
Low energy laser therapy has gained varying acceptance as a treatment for a broad range of soft tissue, musculoskeletal and neurological conditions. A controversial, but surprisingly large body of research with cell cultures suggests that laser irradiation can nondestructively alter cellular processes. Unfortunately, animal and human studies are often contradictory and difficult to evaluate due to differing study designs. As a result, the clinical effectiveness of low energy laser therapy remains debatable. Nevertheless, the findings are intriguing and deserve further investigation. 相似文献
999.
1000.
We have measured the resistivity of the YBa2Cu3O7–Ag composite system with Ag volume fraction,p
Ag ranging from 0–100%. The percolation behavior and the normal-state resistivity are studied. We find a three-dimensional threshold for the Ag matrix occurring atp
Ag 20% and a threshold for the superconducting matrix occurring at 1–p
Ag30%. The electrical resistivity is interpreted in terms of a resistivity model for granular YBa2Cu3O7 proposed by Halbritter et al. [Z. Phys. B —Condensed Matter71, 411 (1988)]. Based on this model, we show that the resistivities between the YBa2Cu3O7 grains and flaws in the grains are greatly diminished in the samples, indicating significantly improved grain growth behavior of the YBa2Cu3O7 phase resulting from the addition of Ag. With the diminishing of the grain boundary resistivities, an intrinsic value for the temperature coefficient of resistivity, (1/gr)(d/dT), can be inferred, which is 3.3×10–3/K at 300 K. This value is very close to that observed in the Cu–O2 planes in single crystals and epitaxial films of YBa2Cu3O7. 相似文献