31,000 research outputs found
Quasi-particle dephasing time in disordered d-wave superconductors
We evaluate the low-temperature cutoff for quantum interference 1/tf induced
in a d-wave superconductor by the diffusion enhanced quasiparticle interactions
in the presence of disorder. We carry out our analysis in the framework of the
non-linear sigma-model which allows a direct calculation of 1/tf, as the mass
of the transverse modes of the theory. Only the triplet amplitude in the
particle-hole channel and the Cooper amplitude with is pairing symmetry
contribute to 1/tf. We discuss the possible relevance of our results to the
present disagreement between thermal transport data in cuprates and the
localization theory for d-wave quasiparticles
COMPARISONS OF HISPANIC HOUSEHOLDS' DEMAND FOR MEATS WITH OTHER ETHNIC GROUPS
The objective of this research was to analyze the demand patterns of Hispanic households for meats in comparison with other ethnic groups using data from the 1998 Consumer Expenditure Survey. A system of demand equations of the LinQuad form were estimated for ten meat products using an incomplete system of censored equations. Hispanic households showed a clear preference for beef. Price, income, and household-size elasticities were estimated for each meat product by ethnic group. The demand for ground beef was the most income-inelastic product regardless of ethnicity. Household size had a positive effect on the probability of consuming a particular meat product but a negative effect on actual item expenditures.Consumer/Household Economics, Demand and Price Analysis,
A CENSORED SYSTEM ESTIMATION OF HISPANIC HOUSEHOLD FOOD CONSUMPTION PATTERNS
A system of nine censored Engel curve equations was estimated for Hispanic households in the U.S.: grains, vegetables, fruits, milk, meat, legumes, fats, sugar, and beverages. Income and household size elasticities, with their respective confidence intervals, are reported and the results compared with other ethnic groups in the U.S.Food Consumption/Nutrition/Food Safety,
Geometrically constrained magnetic wall
The structure and properties of a geometrically constrained magnetic wall in
a constriction separating two wider regions are investigated theoretically.
They are shown to differconsiderably from those of an unconstrained wall, so
that the geometrically constrained magnetic wall truly constitutes a new kind
of magnetic wall, besides the well known Bloch and Neel walls. In particular,
the width of a constrained wall cann become very small if the characteristic
length of the constriction is small, as is actually the case in an atomic point
contact. This provides a simple, natural explanation for the large
magnetoresistance observed in ferromagnetic atomic point contacts.Comment: RevTeX, 4 pages, 4 eps figures; v2: revised version; v3: ref. adde
Quantum size effects in the low temperature layer-by-layer growth of Pb on Ge(001)
The electronic properties of thin metallic films deviate from the
corresponding bulk ones when the film thickness is comparable with the
wavelength of the electrons at the Fermi level due to quantum size effects
(QSE). QSE are expected to affect the film morphology and structure leading to
the low temperature (LT) ``electronic growth'' of metals on semiconductors. In
particular, layer-by-layer growth of Pb(111) films has been reported for
deposition on Ge(001) below 130 K. An extremely flat morphology is preserved
throughout deposition from four up to a dozen of monolayers. These flat films
are shown to be metastable and to reorganize into large clusters uncovering the
first Pb layer, pseudomorphic to the substrate, already at room temperature.
Indications of QSE induced structural variations of the growing films have been
reported for Pb growth on Ge(001), where the apparent height of the Pb(111)
monatomic step was shown to change in an oscillatory fashion by He atom
scattering (HAS) during layer-by-layer growth. The extent of the structural QSE
has been obtained by a comparison of the HAS data with X-ray diffraction (XRD)
and reflectivity experiments. Whereas step height variations as large as 20 %
have been measured by HAS reflectivity, the displacement of the atomic planes
from their bulk position, as measured by XRD, has been found to mainly affect
the topmost Pb layer, but with a lower extent, i.e. the QSE observed by HAS are
mainly due to a perpendicular displacement of the topmost layer charge density.
The effect of the variable surface relaxation on the surface vibration has been
studied by inelastic HAS to measure the acoustic dispersion of the low energy
phonons.Comment: 28 pages (laTex,elsart) and 13 figures (eps); updated reference
Outcomes in the emergency endovascular repair of blunt thoracic aortic injuries
Abstract
Thoracic aorta blunt injury (BAI) is a highly lethal lesion. A large number of victims die before obtaining emergency care. Thoracic endovascular aneurysm repair (TEVAR) is a less invasive method compared with open surgery and may change protocols for BAI treatment. This retrospective study was developed to evaluate the potential issues about thoracic endografting in the management of these patients. Twenty-seven patients with a BAI underwent aortic stent grafting. Intervention was preceded by the treatment of more urgent associated lesions in nine cases. In-hospital mortality was 7.4%. No paraplegia or ischemic complications developed because of the coverage of the left subclavian artery. In one case (3.2%), a type I endoleak was detected, proximal endograft infolding in two cases (7.4%) and endograft distal migration in further two cases were detected during follow-up (6-110 months). Thoracic endovascular aneurysm repair of BAI showed encouraging results in terms of perioperative mortality and morbidity. Concerns still remain about the potential mid- and long-term complications in younger patients
Observation of inertial energy cascade in interplanetary space plasma
We show in this article direct evidence for the presence of an inertial
energy cascade, the most characteristic signature of hydromagnetic turbulence
(MHD), in the solar wind as observed by the Ulysses spacecraft. After a brief
rederivation of the equivalent of Yaglom's law for MHD turbulence, we show that
a linear relation is indeed observed for the scaling of mixed third order
structure functions involving Els\"asser variables. This experimental result,
confirming the prescription stemming from a theorem for MHD turbulence, firmly
establishes the turbulent character of low-frequency velocity and magnetic
field fluctuations in the solar wind plasma
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