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991.
Nils Andersson 《General Relativity and Gravitation》1996,28(12):1433-1445
Two simple model problems relevant for the gravitational-wave modes of relativistic stars are discussed. It is shown that the entire mode-spectrum can be obtained if one considers the modes as arising because of the trapping of gravitational waves by the spacetime curvature. The stellar fluid need play no dynamic role. Furthermore, it is shown that two distinct families of gravitational-wave modes exist. The first corresponds to waves trapped inside the star, while the second is similar to acoustic waves scattered off a hard sphere. An infinite number of the first kind of modes exist, but the latter family will only have a few members. 相似文献
992.
Electronic excitations in a K layer adsorbed on Ni(100) have been observed by means of electron energy loss spectroscopy. The observed excitation energy depends on the density of K atoms in the layer. In the low density range the loss energy decreases from 3.5 to 1.5 eV as the density increases from 6.1013 to 3.1014 K atoms per cm2. This loss is interpreted to be due to an excitation from below the Fermi level to the shifted K valence level Increasing the density further from 3.1014 to 6.1014 K atoms per cm2 yields a loss peak that increases in energy from 1.5 to 2.3 eV. This loss peak merges into the surface-bulk plasmon complex for a thick K film and the energy vs density dependence is compatible with a plasmon excitation in the K layer. 相似文献
993.
Lars Andersson Piotr T. Chruściel Helmut Friedrich 《Communications in Mathematical Physics》1992,149(3):587-612
The regularity of the solutions to the Yamabe Problem is considered in the case of conformally compact manifolds and negative scalar curvature. The existence of smooth hyperboloidal initial data for Einstein's field equations is demonstrated.Supported in part by NFR, the Swedish Academy of Sciences and the Gustavsson Foundation 相似文献
994.
Two enzymes, phosphoglycerate mutase and peroxidase, were purified by using an immobilized metal ion adsorbent for the removal of unwanted proteins. The mutase was obtained pure from a single column, whereas the purification of peroxidase required the use of a thiophilic adsorbent in a tandem. The capacity was 2.5 mg pure peroxidase per mL gel. 相似文献
995.
B K?gedal T Andersson M Carlsson T Denneberg A Hoppe 《Journal of chromatography. A》1987,417(2):261-267
2-Mercaptopropionic acid has been identified as a normal metabolite of 2-mercaptopropionylglycine (thiopronine) when this drug was given to humans and dogs. A high-performance liquid chromatographic method was developed to resolve the derivatives of these two thiols and thus enable simultaneous determination of the two compounds in plasma and urine. 相似文献
996.
997.
P. O. Holtz B. Sernelius A. V. Buyanov G. Pozina L. D. Madsen H. H. Radamson J. Thordson T. G. Andersson J. P. McCaffrey B. Monemar 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
An ultrathin, a few monolayers (MLs) thick Si δ-layer, has been embedded in GaAs. The Si δ-layer properties have been electrically and structurally characterized. A conductivity transition has been observed, when going from free carrier transport in thin (1 ML) ordered δ-layers to the disordered conditions for Si δ-layers thicker than 4 MLs. Two novel emission bands are observed in photoluminescence (PL) for Si δ-layers in the width range 1–4 MLs, but solely at below bandgap excitation. The pronounced 2D properties of these δ-layers have been clearly demonstrated by an observed blue shift of the PL characterization as the thickness of the Si δ-layer is reduced. The so-derived results on the transition energies and the electronic structure are in good agreement with theoretical predictions obtained by a self-consistent approach. 相似文献
998.
The spectral emittance of polycrystalline beryllium oxide has been measured at four different angles from 0° to 75°, at a temperature of 150°C. From the spectral measurements the average band emittance in the 8–13 μm window has been calculated. The results show that the band emittance decreases from 0.44 at the angle of 0°, down to 0.23 at an angle 75° off the normal. The low band emittance is caused by a strong reststrahlen band in the wavelength region 9.2–14 μm. This reststrahlen band has been modelled by a Lorentz one-oscillator model. Experiment and calculations show that this band of low emittance increases its width towards shorter wavelengths at inclined angles and covers almost the entire upper atmospheric window 8–13 μm at the angle of 75°. 相似文献
999.
B. Andersson G. Gustafson G. Ingelman T. Sjöstrand 《Zeitschrift fur Physik C Particles and Fields》1982,13(4):361-367
We study baryon production in deep inelastic scattering using an extended version of the Lund jet model. There are two contributing sources. The first is baryon production in the target fragmentation. In a scheme related to our earlier work on lowp hu baryon fragmentation we present some details of the fragmentation of a diquark into baryons and mesons. A non-negligible baryon-antibaryon production is observed ine + e ? annihilation. In a previous paper we developed a model for this production, and the same mechanism should also give fast baryons in leptoproduction. In this paper we discuss those features of baryon production which can be more easily studied in a leptoproduction experiment. 相似文献
1000.
A picosecond variable pulse width method has been found to be very useful in the bandwidth determination of Gbit/s photodetectors and fibers. Bandwidths up to 5 GHz have been measured with this technique using picosecond pulses generated from a semiconductor laser. 相似文献