1,531 research outputs found
Superconducting magnesium diboride films on Silicon with Tc0 about 24K grown via vacuum annealing from stoichiometric precursors
Superconducting magnesium diboride films with Tc0 ~ 24 K and sharp transition
\~ 1 K were successfully prepared on silicon substrates by pulsed laser
deposition from a stoichiometric MgB2 target. Contrary to previous reports,
anneals at 630 degree and a background of 2x10^(-4) torr Ar/4%H2 were performed
without the requirement of Mg vapor or an Mg cap layer. This integration of
superconducting MgB2 films on silicon may thus prove enabling in
superconductor-semiconductor device applications. Images of surface morphology
and cross-section profiles by scanning electron microscopy (SEM) show that the
films have a uniform surface morphology and thickness. Energy dispersive
spectroscopy (EDS) reveals these films were contaminated with oxygen,
originating either from the growth environment or from sample exposure to air.
The oxygen contamination may account for the low Tc for those in-situ annealed
films, while the use of Si as the substrate does not result in a decrease in Tc
as compared to other substrates.Comment: 5 pages, 4 figures, 15 references; due to file size limit, images
were blure
Phylogenetic characterization and promoter expression analysis of a novel hybrid protein disulfide isomerase/cargo receptor subfamily unique to plants and chromalveolates
Low Frequency Quantum Transport in a Three-probe Mesoscopic Conductor
The low frequency quantum transport properties of a three-probe mesoscopic
conductor are studied using B\"uttiker's AC transport formalism. The static
transmission coefficients and emittance matrix of the system were computed by
explicitly evaluating the various partial density of states (PDOS). We have
investigated the finite size effect of the scattering volume on the global
PDOS. By increasing the scattering volume we observed a gradual improvement in
the agreement of the total DOS as computed externally or locally. Our numerical
data permits a particular fitting form of the finite size effect.Comment: 13 pages, LaTeX, submitted to Phys. Rev.
Low frequency admittance of a quantum point contact
We present a current and charge conserving theory for the low frequency
admittance of a quantum point contact. We derive expressions for the
electrochemical capacitance and the displacement current. The latter is
determined by the {\em emittance} which equals the capacitance only in the
limit of vanishing transmission. With the opening of channels the capacitance
and the emittance decrease in a step-like manner in synchronism with the
conductance steps. For vanishing reflection, the capacitance vanishes and the
emittance is negative.Comment: 11 pages, revtex file, 2 ps figure
Estereotipos relativos a la edad y el sexo aplicados a la comunicación mediada por intérpretes de conferencias
Estudios previos concluyen que la combinación del sexo y la edad de los intérpretes puede condicionar la percepción de la interpretación simultánea. En este estudio, 156 participantes contestaron un cuestionario para evaluar diversos factores no verbales de las interpretaciones realizadas por ocho intérpretes, cuatro hombres y cuatro mujeres, grabadas en un estudio de grabación. Las grabaciones se controlaron para lograr una producción homogénea de los factores verbales que no interfiriera en la evaluación de los factores no verbales. Los resultados muestran que las características relacionadas con el sexo y la edad de los intérpretes pueden sesgar la percepción de la interpretación simultánea por parte de los oyentes
An improved continuous compositional-spread technique based on pulsed-laser deposition and applicable to large substrate areas
A new method for continuous compositional-spread (CCS) thin-film fabrication
based on pulsed-laser deposition (PLD) is introduced. This approach is based on
a translation of the substrate heater and the synchronized firing of the
excimer laser, with the deposition occurring through a slit-shaped aperture.
Alloying is achieved during film growth (possible at elevated temperature) by
the repeated sequential deposition of sub-monolayer amounts. Our approach
overcomes serious shortcomings in previous in-situ implementations of CCS based
on sputtering or PLD, in particular the variations of thickness across the
compositional spread and the differing deposition energetics as function of
position. While moving-shutter techniques are appropriate for PLD-approaches
yielding complete spreads on small substrates (i.e. small as compared to
distances over which the deposition parameters in PLD vary, typically about 1
cm), our method can be used to fabricate samples that are large enough for
individual compositions to be analyzed by conventional techniques, including
temperature-dependent measurements of resistivity and dielectric and magnetic
and properties (i.e. SQUID magnetometry). Initial results are shown for spreads
of (Sr,Ca)RuO.Comment: 6 pages, 8 figures, accepted for publication in Rev. Sci. Instru
Dose-Response Relationships Following Oral Administration of DuP 753 to Normal Humans
We assessed the inhibitory effect of DuP 753, an orally active angiotensin II receptor antagonist, on the pressor action of exogenous angiotensin I and II in healthy volunteers. In a single dose study, doses of 2.5, 5, 10, 20, and 40 mg of DuP 753 or placebo were tested serially at one week intervals. In the multiple dose study, the administration of placebo or DuP 753 (5, 10, 20, or 40 mg, per os once daily) for eight consecutive days was evaluated. The blood pressure response to angiotensin I and II was inhibited in a dose-dependent fashion with a blocking effect still present 24 h post drug. DuP 753 also induced a dose-dependent compensatory rise in plasma renin. This new compound was well tolerated by these normal volunteers. Thus, DuP 753 appears to be a well tolerated, orally active, potent and long-lasting antagonist of angiotensin II in humans. Am J Hypertens 1991;4:350S-354
Partial Densities of States, Scattering Matrices, and Green's Functions
The response of an arbitrary scattering problem to quasi-static perturbations
in the scattering potential is naturally expressed in terms of a set of local
partial densities of states and a set of sensitivities each associated with one
element of the scattering matrix. We define the local partial densities of
states and the sensitivities in terms of functional derivatives of the
scattering matrix and discuss their relation to the Green's function. Certain
combinations of the local partial densities of states represent the injectivity
of a scattering channel into the system and the emissivity into a scattering
channel. It is shown that the injectivities and emissivities are simply related
to the absolute square of the scattering wave-function. We discuss also the
connection of the partial densities of states and the sensitivities to
characteristic times. We apply these concepts to a delta-barrier and to the
local Larmor clock.Comment: 13 pages (revtex), 4 figure
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