4,714 research outputs found
Magnetization Losses in Multifilament Coated Superconductors
We report the results of a study of the magnetization losses in experimental
multifilament, as well as control (uniform), coated superconductors exposed to
time-varying magnetic field of various frequencies. Both the hysteresis loss,
proportional to the sweep rate of the applied magnetic field, and the coupling
loss, proportional to the square of the sweep rate, have been observed. A
scaling is found that allows us to quantify each of these contributions and
extrapolate the results of the experiment beyond the envelope of accessible
field amplitude and frequency. The combined loss in the multifilament conductor
is reduced by about 90% in comparison with the uniform conductor at full field
penetration at sweep rate as high as 3T/s
Propagation of a magnetic domain wall in magnetic wires with asymmetric notches
The propagation of a magnetic domain wall (DW) in a submicron magnetic wire
consisting of a magnetic/nonmagnetic/magnetic trilayered structure with
asymmetric notches was investigated by utilizing the giant magnetoresistance
effect. The propagation direction of a DW was controlled by a pulsed local
magnetic field, which nucleates the DW at one of the two ends of the wire. It
was found that the depinning field of the DW from the notch depends on the
propagation direction of the DW.Comment: 12 pages, 3 figure
Ultra-low threshold CW Triply Resonant OPO in the near infrared using Periodically Poled Lithium Niobate
We have operated a CW triply resonant OPO using a PPLN crystal pumped by a
Nd:YAG laser at 1.06 micron and generating signal and idler modes in the 2-2.3
micron range. The OPO was operated stably in single mode operation over large
periods of time with a pump threshold as low as 500 microwatts.Comment: 7 pages, 5 figures, submitted to JEOS
Age of the Universe: Influence of the Inhomogeneities on the global Expansion-Factor
For the first time we calculate quantitatively the influence of
inhomogeneities on the global expansion factor by averaging the Friedmann
equation. In the framework of the relativistic second-order
Zel'dovich-approximation scheme for irrotational dust we use observational
results in form of the normalisation constant fixed by the COBE results and we
check different power spectra, namely for adiabatic CDM, isocurvature CDM, HDM,
WDM, Strings and Textures. We find that the influence of the inhomogeneities on
the global expansion factor is very small. So the error in determining the age
of the universe using the Hubble constant in the usual way is negligible. This
does not imply that the effect is negligible for local astronomical
measurements of the Hubble constant. Locally the determination of the
redshift-distance relation can be strongly influenced by the peculiar velocity
fields due to inhomogeneities. Our calculation does not consider such effects,
but is contrained to comparing globally homogeneous and averaged inhomogeneous
matter distributions. In addition we relate our work to previous treatments.Comment: 10 pages, version accepted by Phys. Rev.
Severe myoclonic epilepsy in infancy: evolution of seizures
Changes in seizure type of severe myoclonic epilepsy (SME) in infancy were reviewed retrospectively in 14 patients (11 males and 3 females) who were followed-up to the age of 7 years or more. The observation period ranged from 5 to 16 years with a mean of 10 years. During the follow-up, three or four types of seizures were seen per patient, but the pattern of appearance and disappearance of each seizure type varied considerably among the patients. Tonic-clonic convulsion, either generalized or unilateral, was seen most consistently through the entire course, and it continued to the end of follow-up in 11 patients (79%). On the contrary, myoclonic seizure, complex partial seizure, and atypical absence often disappeared and reappeared repeatedly during the course. In SME, seizure symptoms varied widely among patients in comparison with other neurological symptoms, and the most consistent core seizure type was tonic-clonic convulsions
Domain walls in (Ga,Mn)As diluted magnetic semiconductor
We report experimental and theoretical studies of magnetic domain walls in an
in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our
high-resolution electron holography technique provides direct images of domain
wall magnetization profiles. The experiments are interpreted based on
microscopic calculations of the micromagnetic parameters and
Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial
and biaxial magnetocrystalline anisotropies in the film is directly reflected
in orientation dependent wall widths, ranging from approximately 40 nm to 120
nm. The domain walls are of the N\'eel type and evolve from near-
walls at low-temperatures to large angle [10]-oriented walls and small
angle [110]-oriented walls at higher temperatures.Comment: 5 pages, 4 figure
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