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61.
62.
G. M. Luke L. P. Le B. J. Sternlieb Y. J. Uemura J. H. Brewer R. Kadono R. F. Kiefl S. R. Kreitzman T. M. Riseman C. L. Seaman Y. Dalichaouch M. B. Maple J. D. Garrett 《Hyperfine Interactions》1991,64(1-4):517-522
We have performed both zero field and high transverse field measurements at dilution refrigerator temperatures on a number of heavy electron systems, examining the superconducting and magnetic properties of these interesting materials. Among the materials studied to date are UBe13, URu2Si2 and U6Fe. The magnetic field penetration depth in the superconducting state of UBe13 is greater than 10000 Å, as no increase in the transverse field relaxation rate is observed belowT c . A sharp increase in the precession frequency is seen, starting atT c . This frequency shift shows little temperature dependence at low temperature; we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu2Si2 show the weak antiferromagnetic transition at 17.5 K. Finally, we we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu2Si2 show the weak antiferromagnetic transition at 17.5 K. Finally, we have observed relaxation in high transverse field due to the formation of a flux lattice in U6Fe, a material where the electron effective mass is rather lighter than in other heavy fermion systems. The relaxation exhibits a sharp onset atT c=3.9 K, and is flat at low temperatures as expected for a conventional superconductor. 相似文献
63.
F. Cannata J. P. Dedonder L. Le?niak 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(4):451-460
We investigate the origin of the attraction in theK¯K channel around the threshold by introducing an additional channel to theππ andK¯K channels in a separable potential formalism assuming, in general, no direct interaction in theK¯K channel. To reproduce the features of the data, we find that the threshold of the additional channel is much above thef 0(975) meson position. We show that this three-channel problem can be reduced to an effective two-channel problem where thef 0(975) behaves as if it were aK¯K molecule bound by the coupling to the exotic channel. This picture is also supported by the fact that a single pole only, in the complexK¯K momentum plane, is associated to thef 0(975) meson. Various physical observables, like the decay branching ratio and theK¯K scattering length, are then discussed in an effective two-channel framework. 相似文献
64.
Summary. In the context of the generalized ADI method, we are concerned with the problem of finding in the set of rational functions
r with numerator degree m and denominator degree n an element that minimizes where E,F are disjoint real intervals. By extending a recent analysis by Levin and Saff, we present an explicit formula for choosing
the pair (m,n) for given m +n. Furthermore, we provide a characterization of and a Remes type algorithm for its determination. Extensive numerical computations furnish some comparison of with asymptotically optimal solutions based on Fejér-Walsh and Leja-Bagby points.
Received September 6, 1996 / revised version received June 30, 1997 相似文献
65.
66.
R W Milne R L Nation G D Reynolds A A Somogyi J T Van Crugten 《Journal of chromatography. A》1991,565(1-2):457-464
Improvements to previously reported methods for the determination of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) in human plasma are described. The improved methods involve the use of a solid-phase extraction cartridge and a chromatographic system which uses paired-ion reversed-phase high-performance liquid chromatography with a radially compressed column. Only one cartridge is used to prepare each sample for chromatography and each cartridge may be used for at least fourteen 1-ml plasma samples. The recovery is greater than 85%. The improvements to the method of sample pretreatment and in the chromatographic conditions have allowed determination of morphine, M3G and M6G in human plasma down to 13.3 nmol/l (coefficient of variation = 9.3%), 108 nmol/l (6.6%) and 41 nmol/l (6.7%), respectively, using ultraviolet detection alone. It was shown that all three compounds were stable in plasma for up to 101 weeks when stored at -20 degrees C. 相似文献
67.
M. H. Gehlen M. Van der Auweraer F. C. De Schrwer 《Photochemistry and photobiology》1991,54(4):613-618
The luminescence decay of excited probes in micelles in the presence of a Poisson distribution of quenchers is considered under conditions where both probe and quencher within the lifetime of the excited probe may exchange between the micelles. Analytical and numerical results show that the luminescence decay can be expressed by a generalized self convolution product of a multiexponential decay function. 相似文献
68.
C. Bréchignac Ph. Cahuzac F. Carlier C. Colliex M. de Frutos N. Kébaïli J. Le Roux A. Masson B. Yoon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):265-268
We studied shape relaxation of nano-fractal islands,
during annealing, after their growth from antimony cluster
deposition on graphite surface. Annealing at
180°C shows evidence of an increase
of the fractal branch width with time followed by branch
fragmentation, without changing the fractal dimension. The time
evolution of the width of the arm suggests the surface
self-diffusion mechanism as the main relaxation process. With
Monte Carlo simulations, we confirmed the observed behavior.
Comparison is done with our previous results on fragmentation of
nano-fractal silver islands when impurity added to the incident
cluster promotes rapid fragmentation by surface self-diffusion
enhancement [1]. 相似文献
69.
T. Van Cauteren J. Ryckebusch B. Metsch H. -R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):613-615
We present some of our results for the electromagnetic properties of excited Σ hyperons, computed within the framework of the Bonn constituent-quark model, which is based on the Bethe-Salpeter approach.
The seven parameters entering the model are fitted against the best-known baryon masses. Accordingly, the results for the
form factors and helicity amplitudes are genuine predictions. We compare with the scarce experimental data available and discuss
the processes in which Σ
*'s may play an important role. 相似文献
70.
Khanh Le Chau Pham Duc Chinh 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1991,42(4):614-622
In this paper inequalities for the effective conductivity of isotropic composite materials are derived. These inequalities depend on several coefficients characterizing the microstructure of composites. The obtained coefficients can be exactly calculated for models of a two-component aggregate of multisized, coated ellipsoidal inclusions, packed to fill all space. As a result, new bounds for effective conductivity, considerably narrower than those of Hashin-Shtrikman, are established for such models of composite materials. 相似文献