6,597 research outputs found
Focused-ion-beam-induced deposition of superconducting nanowires
Superconducting nanowires, with a critical temperature of 5.2 K, have been
synthesized using an ion-beam-induced deposition, with a Gallium focused ion
beam and Tungsten Carboxyl, W(CO)6, as precursor. The films are amorphous, with
atomic concentrations of about 40, 40, and 20 % for W, C, and Ga, respectively.
Zero Kelvin values of the upper critical field and coherence length of 9.5 T
and 5.9 nm, respectively, are deduced from the resistivity data at different
applied magnetic fields. The critical current density is Jc= 1.5 10^5 A/cm2 at
3 K. This technique can be used as a template-free fabrication method for
superconducting devices.Comment: Accepted for publication in Applied Physics Letter
Superconductivity in metal rich Li-Pd-B ternary Boride
8K superconductivity was observed in the metal rich Li-Pd-B ternary system.
Structural, microstructural, electrical and magnetic investigations for various
compositions proved that Li2Pd3B compound, which has a cubic structure composed
of distorted Pd6B octahedrons, is responsible for the superconductivity. This
is the first observation of superconductivity in metal rich ternary borides
containing alkaline metal and Pd as a late transition metal. The compound
prepared by arc melting has high density, is stable in the air and has an upper
critical field, Hc2(0), of 6T.Comment: 4 pages, 5 figur
Calculated Electron Fluxes at Airplane Altitudes
A precision measurement of atmospheric electron fluxes has been performed on
a Japanese commercial airliner (Enomoto, {\it et al.}, 1991). We have performed
a monte carlo calculation of the cosmic ray secondary electron fluxes expected
in this experiment. The monte carlo uses the hadronic portion of our neutrino
flux cascade program combined with the electromagnetic cascade portion of the
CERN library program GEANT. Our results give good agreement with the data,
provided we boost the overall normalization of the primary cosmic ray flux by
12\% over the normalization used in the neutrino flux calculation.Comment: in REVTEX, 12 pages + 4 figures available upon reques
Standard Model Contributions to the Neutrino Index of Refraction in the Early Universe
With the standard electroweak interactions, the lowest-order coherent forward
scattering amplitudes of neutrinos in a CP symmetric medium (such as the early
universe) are zero, and the index of refraction of a propagating neutrino can
only arise from the expansion of gauge boson propagators, from radiative
corrections, and from new physics interactions. Motivated by nucleosynthesis
constraints on a possible sterile neutrino (suggested by the solar neutrino
deficit and a possible neutrino), we calculate the standard model
contributions to the neutrino index of refraction in the early universe,
focusing on the period when the temperature was of the order of a few . We
find sizable radiative corrections to the tree level result obtained by the
expansion of the gauge boson propagator. For the leading log correction is about , while for
the correction is about
. Depending on the family mixing (if any), effects from different family
scattering can be dominated by radiative corrections. The result for
is zero at one-loop level, even if neutrinos are
massive. The cancellation of infrared divergence in a coherent process is also
discussed.Comment: 46pp, 13 figures (not included), UPR-0495
The Earth Effect in the MSW Analysis of the Solar Neutrino Experiments
We consider the Earth effect in the MSW analysis of the Homestake,
Kamiokande, GALLEX, and SAGE solar neutrino experiments. Using the
time-averaged data and assuming two-flavor oscillations, the large-angle region
of the combined fit extends to much smaller angles (to ) than when the Earth effect is ignored. However, the additional constraint
from the Kamiokande II day-night data excludes most of the parameter space
sensitive to the Earth effect independent of astrophysical uncertainties, and
leaves only a small large-angle region close to maximal mixing at 90\% C.L. The
nonadiabatic solution remains unaffected by the Earth effect and is still
preferred. Both theoretical and experimental uncertainties are included in the
analysis.Comment: (11 pages, Revtex 3.0 (can be changed to Latex), 3 postscript figures
included, UPR-0570T
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