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1.
2.
We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux
lines in low T
c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line
lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends
to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the
destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has
employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo
technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing
μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation
of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors. 相似文献
3.
The Milne-Thomson circle theorem is extended to give a simplegeneral expression for the image system in an elliptical cylinderintroduced into an otherwise specified unbounded potential flowwhich contains no singularities in the region to be occupiedby the ellipse. This image system is used to obtain an expressionfor the corresponding source-sink surface singularity distributionon the ellipse, thus providing new benchmark test cases forsource-sink solutions as obtained numerically by a panel method.Several typical examples are given to illustrate the generaltheoretical approach. 相似文献
4.
Constant potential amperometry with Nafion-coated carbon-fiber electrodes has been evaluated as a technique for in vivo detection of the neurotransmitter dopamine. The results of this technique have been compared to results obtained with fast-scan cyclic voltammetry at the same electrode during release of dopamine into the extracellular space of the brain during electrical stimulation of neurons. The data indicate that constant potential amperometry is a viable technique for detecting low concentrations of dopamine. Dopamine permeates the film more quickly with constant-potential amperometry than with repeated fast-scan cyclic voltammetry as predicted by diffusion equations. For the case of cyclic voltammetry, it is demonstrated that the temporal delay caused by diffusion through Nafion film can be removed by deconvolution procedures. Despite the suitability of constant potential amperometry as an in vivo monitoring technique, it does have several disadvantages when compared to fast-scan cyclic voltammetry. The diffusion layer extends outside of the Nafion film making determination of concentration based on in vitro calibrations more difficult to interpret. The reported concentrations are larger than obtained by cyclic voltammetry, a technique with the diffusion layer restricted to the Nafion film, and this result is likely an underestimation of the effect of the catalytic reaction between the o-quinone of dopamine and ascorbate. Amperometry was found to provide only slightly improved signal-to-noise ratios than cyclic voltammetry despite the use of greater filtering. This was because the advantage of dopamine accumulation in the film was lost. In addition, the small magnitude of the amperometric signal makes it more susceptible to electrical interference. 相似文献
5.
The diagonal Padé approximants of the perturbation series for the eigenvalues of the anharmonic oscillator (a βκ1 perturbation of p2 + κ2) converge to the eigenvalues. 相似文献
6.
7.
Lateralization of filtered clicks 总被引:3,自引:0,他引:3
W A Yost F L Wightman D M Green 《The Journal of the Acoustical Society of America》1971,50(6):1526-1531
8.
A reactivity pattern was established for Michael addition of aryl thiolates to 17-acetoxy 5α-androst-1-en-3-one. An abnormal bicyclic bridged adduct was obtained in the reaction of thiourea. 相似文献
9.
Kevin E. Kinzer Douglas R. Lloyd M.S. Gay J.P. Wightman B.C. Johnson J.E. McGrath 《Journal of membrane science》1985,22(1):1-29
The use of two nonsolvents serving as a cosolvent system, replacing the traditional volatile solvent plus less volatile nonsolvent system, in the formation of asymmetric phase inversion membranes was investigated. Specifically, asymmetric membranes of sulfonated polysulfone were cast from a cosolvent system consisting of tetrahydrofuran and formamide. The nonsolvents and the proportions in which they are mixed to produce the cosolvent system, as well as the gelation medium isopropyl alcohol, were selected based on the three-component solubility parameter concept of Hansen. The structure of each membrane was evaluated using scanning electron microscopy; the performance was evaluated for use in pressure-driven membrane separation processes. The membranes were found to be dependent on the composition of the original casting solution and the composition of the nascent membrane at the instant of gelation. These ideas are clearly represented through the use of a triangular polymer solubility diagram. 相似文献
10.
S M Gordon-Salant F L Wightman 《The Journal of the Acoustical Society of America》1983,73(5):1756-1765
A triadic comparisons task and an identification task were used to evaluate normally hearing listeners' and hearing-impaired listeners' perceptions of synthetic CV stimuli in the presence of competition. The competing signals included multitalker babble, continuous speech spectrum noise, a CV masker, and a brief noise masker shaped to resemble the onset spectrum of the CV masker. All signals and maskers were presented monotically. Interference by competition was assessed by comparing Multidimensional Scaling solutions derived from each masking condition to that derived from the baseline (quiet) condition. Analysis of the effects of continuous maskers revealed that multitalker babble and continuous noise caused the same amount of change in performance, as compared to the baseline condition, for all listeners. CV masking changed performance significantly more than did brief noise masking, and the hearing-impaired listeners experienced more degradation in performance than normals. Finally, the velar CV maskers (g epsilon and k epsilon) caused significantly greater masking effects than the bilabial CV maskers (b epsilon and p epsilon), and were most resistant to masking by other competing stimuli. The results suggest that speech intelligibility difficulties in the presence of competing segments of speech are primarily attributable to phonetic interference rather than to spectral masking. Individual differences in hearing-impaired listeners' performances are also discussed. 相似文献