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991.
Carlo F. Barenghi Gregory H. Bauer David C. Samuels Russ J. Donnelly 《Czechoslovak Journal of Physics》1996,46(1):29-30
We have performed numerical simulations of quantized vortex lines in a model of normal fluid turbulence. The results are used to discuss the idea, put forward to explain some recent experiments, that in isothermal turbulent helium flow the high density of vortex lines locks the two fluid components together. 相似文献
992.
F. Bridges C.H. Booth G.G. Li E.D. Bauer J. Boyce T. Claeson 《Superlattices and Microstructures》1996,19(4):313-325
Many highTcsystems exhibit structural distortions or anomalies, some of which correlate withTc. We present our results for three such systems and discuss them in the context of providing any evidence for coupling of the lattice to the superconducting pairs. We then propose a modulation type of experiment that should provide unambiguous results if a significant lattice-pair coupling does exist. 相似文献
993.
Using a 90mm-bore, 3.15 m long detonation tube, experimental detonation characteristics (detonability limits, detonation
velocities and peak pressures) of stoichiometric methane-oxygen-diluent mixtures at an initial pressure up to 3.5 MPa have
been experimentally investigated. A parametric study has been carried out as a function of both amount and nature of diluent,
namely carbon dioxide, nitrogen and helium. The experimental results allowed the adjustment and validation of computations
of the Chapman-Jouguet characteristics by means of a thermochemical code. These experimental data associated with validated
computations provide a valuable tool, among others, for the choice of the most appropriate mixture composition in the superdetonative
combustion mode for ram accelerator (ramac) experiments. The investigations were organized to determine the upper detonable
areas of dense ternary mixtures, and to provide detonation velocity data in order to adjust a series of intermolecular parameters
involved in the thermochemical code.
Received 8 May 1997 / Accepted 15 December 1997 相似文献
994.
Emmanuelle Canet Didier Revel Rmy Forrat Claire Baldy-Porcher Michel de Lorgeril Laurent Sebbag Jean-Paul Vallee Dominique Didier Michel Amiel 《Magnetic resonance imaging》1993,11(8):1139-1145
Superparamagnetic iron oxide particles (SPIOs) are usually referred to as T2 MR contrast agents, reducing signal intensity (SI) on T2-weighted MR images (negative enhancement). This study reports the original use of SPIOs as T1-enhancing contrast agents, primarily assessed in vitro, and then applied to an in vivo investigation of a myocardial perfusion defect. Using a strongly T1-weighted subsecond MR sequence with SPIOs intravenous (IV) bolus injection, MR imaging of myocardial vascularization after reperfusion was performed, on a dog model of coronary occlusion followed by reperfusion. Immediately after the intravenous bolus injection of 20 μmol/kg of SPIOs, a positive signal intensity enhancement was observed respectively, in the right and left ventricular cavity and in the nonischemic left myocardium. Moreover, compared to normal myocardium, the remaining ischemic myocardial region (anterior wall of the left ventricle) appeared as a lower and delayed SI enhancing area (cold spot). Mean peak SIE in the nonischemic myocardium (posterior wall) was significantly higher than in the ischemic myocardium (anterior wall) (110 ± 23% vs. 74 ± 22%, Mann-Whitney test < 1%, n1 = 6, n2 − n1 = 0, U > 2). In conclusion, the T1 effect of SPIOs at low dose, during their first intravascular distribution, suggests their potential use as positive markers to investigate the regional myocardial blood flow and some perfusion defects such as the “no-reflow phenomenon”. 相似文献
995.
996.
997.
Michel Poirier 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,25(2):117-125
An easily tractable model is proposed to compute radial matrix elements between discrete states of one-electron atoms or ions. Assuming a closed-shell core, polarization effects are included in the model, and core penetration is accounted for empirically. The required inputs for this algorithm are the energies of the involved levels, and the core size and polarisabilities. Ignoring core polarization, the derived Coulomb matrix elements (possibly between levels with non-zero quantum defects) agree with those tabulated elsewhere in the literature. The method is then applied to dipolar and quadrupolar transitions in alkali atoms and singly-ionized alkaline-earth elements; it proves to be in fair agreement with available experimental data. An accuracy test of the method is proposed. 相似文献
998.
We give the explicit analytic development of Macdonald polynomials in terms of “modified complete” and elementary symmetric functions. These expansions are obtained by inverting the Pieri formula. Specialization yields similar developments for monomial, Jack and Hall-Littlewood symmetric functions. 相似文献
999.
Jeroen van den Brink Michel van Veenendaal 《Journal of Physics and Chemistry of Solids》2005,66(12):2145-2149
We express the cross section for indirect resonant inelastic X-ray scattering in terms of an intrinsic dynamic correlation function of the system that is studied with this technique. The cross section is a linear combination of the charge response function and the dynamic longitudinal spin density correlation function. This result is asymptotically exact for both strong and weak local core-hole potentials. We show that one can change the relative charge and spin contribution to the inelastic spectral weight by varying the incident photon energy. 相似文献
1000.
Summary The ultra trace element bismuth is regulary found in wine on an average of about 0.1 ppb. Very low bismuth contents were also determined in soil and different biomaterials. In spite of those very low quantities even speciation experiments show results, so far that about 90% of the bismuth in the grapes is water-soluble, resumably as saccharic acids. For detecting such low quantities a very sensitive method of differential pulse anodic stripping voltammetry was developped. The speciation experiments were carried out by fractional extraction.
Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet 相似文献