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981.
L. Cianchi F. Del Giallo F. Pieralli M. Mancini S. Sciortino G. Spina 《Hyperfine Interactions》1991,66(1-4):387-391
Mössbauer parameters of151Eu in Eu1+x Ba2?x Cu3O7+δ have been studied as a function of temperature, forx=0.15 andx=0.25. The areas of the absorption spectra for the two samples are almost equal. This could mean that thef-Mössbauer factor for151Eu at the barium sites is much smaller than that for151Eu at the rare earth sites, i.e. we only observe the spectra of the latter sites. According to this, the fits of the spectra with a single quadrupolar pattern and with two quadrupolar patterns have given equivalent χ2 values. 相似文献
982.
983.
Manfred F. Gz 《Mathematical Methods in the Applied Sciences》1994,17(10):787-805
Wave-hierarchy problems appear in a variety of applications such as traffic flows, roll waves down an open inclined channel and multiphase flows. Usually, these are described by the compressible Navier-Stokes equations with specific non-linearities; in a fluidized bed model they contain an additional pressure gradient term and are supplemented by an elliptic equation for this unknown pressure. These equations admit solutions periodic in space as well as in time, i.e. periodic travelling waves. Therefore, the corresponding initial value problem with periodic boundary conditions is solved locally in time in appropriate Sobolev spaces. Some remarks are made concerning global solutions, the occurrence of clusters or voids and the bifurcation of time periodic solutions, respectively. 相似文献
984.
The liquid chromatographic analysis of drugs in urine through direct injection without any sample pretreatment was extended to micellar chromatography with nonionic surfactants, the Pinkerton ISRP column and the shielded hydrophobic phase (Hisep) column. The feasibility of using each was demonstrated through the determination of the diuretic, hydrochlorothiazide, in urine. Good separation, recovery, precision and linearity, and adequate limits of detection were obtained for this analysis with all three techniques. The advantages and limitations of the mobile phase approach of micellar chromatography and the two stationary phase approaches are discussed for the direct injection of urine as well as other biological fluids. 相似文献
985.
V. Vittoria R. Russo F. De Candia P. L. Magagnini B. Bresci 《Journal of Polymer Science.Polymer Physics》1991,29(9):1163-1168
The transport properties of a side-chain liquid-crystalline polymer forming a smectic A phase have been investigated using dichloromethane as a permeant. Samples differing in the isotropization enthaoly were analyzed. A. Correlation between this thermal parameter and sorption has been found, while the diffusion coefficient is substantially the same in all samples. The results obtained can be explained in terms of a biphasis model in which a disordered permeable phase is present within the liquid-crystalline phase, which is impermeable to the diffusant molecules. 相似文献
986.
In this paper we define the vertex-cover polynomial Ψ(G,τ) for a graph G. The coefficient of τr in this polynomial is the number of vertex covers V′ of G with |V′|=r. We develop a method to calculate Ψ(G,τ). Motivated by a problem in biological systematics, we also consider the mappings f from {1, 2,…,m} into the vertex set V(G) of a graph G, subject to f−1(x)f−1(y)≠ for every edge xy in G. Let F(G,m) be the number of such mappings f. We show that F(G,m) can be determined from Ψ(G,τ). 相似文献
987.
M. M. J. F. Janssen 《Zeitschrift fur Physik C Particles and Fields》1991,52(1):165-174
For theep collider at HERA, we study processes with neutrinos in the final state. Furthermore, we discuss the production ofW andZ bosons. Because of the very small lifetimes of theW andZ, we consider the production of their leptonic decay products rather than the bosons themselves. All the results are based on exact calculations of the matrix element at the tree level. Total cross sections and various kinematical distributions are presented. 相似文献
988.
S. Coffa D. C. Jacobson J. M. Poate F. Priolo 《Applied Physics A: Materials Science & Processing》1992,54(6):481-484
We have investigated ion-beam-enhanced diffusion of Au in undoped and B doped amorphous Si. The diffusion coefficients depend linearly on ion flux and exibit an Arrhenius-like temperature dependence with an activation energy of 0.37 eV in the temperature range 200–350° C. Moreover the diffusivity is enhanced by a factor of 5 by B-doping at a concentration of 1×1020 atoms/cm3. A similar enhancement is observed in thermal diffusion of Au which has an activation energy of 1.5 eV. On the basis of these results a model for the ion-beam-enhanced diffusion of Au is proposed where the high density of defects present in amorphous Si act as traps for the fast moving interstitial Au atoms. The effectiveness of this trapping process can be changed by the high concentration of mobile defects generated by the beam and also by a change in the charge state of the traps induced by the presence of B. 相似文献
989.
Akhmetvaleev R. R. Bikbulatov R. V. Belogaeva T. A. Akbutina F. A. Miftakhov M. S. 《Russian Journal of Organic Chemistry》2002,38(8):1226-1227
Russian Journal of Organic Chemistry - 相似文献
990.
H. Leutwyler 《Czechoslovak Journal of Physics》2002,52(2):B9-B27
The lectures review some of the basic concepts relevant for an understanding of the low energy properties of the strong interactions: chiral symmetry, spontaneous symmetry breakdown, Goldstone bosons, quark condensate. The effective field theory used to analyze the low energy structure is briefly sketched. As an illustration, I discuss the implications of the recent data on the decay K→ππeν for the magnitude of the quark condensate. 相似文献