2,605 research outputs found
Subtleties on energy calculations in the image method
In this pedagogical work we point out a subtle mistake that can be done by
undergraduate or graduate students in the computation of the electrostatic
energy of a system containing charges and perfect conductors if they naively
use the image method. Specifically, we show that the naive expressions for the
electrostatic energy for these systems obtained directly from the image method
are wrong by a factor 1/2. We start our discussion with well known examples,
namely, point charge-perfectly conducting wall and point charge-perfectly
conducting sphere and then proceed to the demonstration of general results,
valid for conductors of arbitrary shapes.Comment: 9 pages, 2 figures; Major change in this version: subsection added to
Sect.4 (theorem generalization). Minor changes: title replaced; corrections
to the English; some explanatory comments adde
Local density of states in metal - topological superconductor hybrid systems
We study by means of the recursive Green's function technique the local
density-of-states of (finite and semi-infinite) multi-band spin-orbit coupled
semiconducting nanowires in proximity to an s-wave superconductor and attached
to normal-metal electrodes. When the nanowire is coupled to a normal electrode,
the zero-energy peak, corresponding to the Majorana state in the topological
phase, broadens with increasing transmission between the wire and the leads,
eventually disappearing for ideal interfaces. Interestingly, for a finite
transmission a peak is present also in the normal electrode, even though it has
a smaller amplitude and broadens more rapidly with the strength of the
coupling. Unpaired Majorana states can survive close to a topological phase
transition even when the number of open channels (defined in the absence of
superconductivity) is even. We finally study the Andreev-bound-state spectrum
in superconductor-normal metal-superconductor junctions and find that in
multi-band nanowires the distinction between topologically trivial and
non-trivial systems based on the number of zero-energy crossings is preserved.Comment: 11 pages, 12 figures, published versio
Perceptions of an Electronic Medical Record (EMR): Lessons from a French Longitudinal Survey
AbstractThe goal of this longitudinal study is to examine the evolution of the perceptions, namely anxiety, ease of use, usefulness, misfit (not customization), trust and usefulness, related to an Electronic Medical Record (EMR) for the clinical staff in a French Teaching hospital. Two surveys were conducted first in September 2013 and second in December 2015, based on a questionnaire consisting of items on the Likert scale. As results, the correlation of all the variables between the two surveys is very significant (except for usefulness, for which the relationship is significant). This is not surprising, given previous studied focused on habits and learning related to technology adoption. Nevertheless, the increase is not spectacular and it makes necessary to evaluate EMR satisfaction and perceptions in order to elaborate a measure standard enabling comparisons and benchmarking among hospitals
Adiabatic pumping in a Superconductor-Normal-Superconductor weak link
We present a formalism to study adiabatic pumping through a superconductor -
normal - superconductor weak link. At zero temperature, the pumped charge is
related to the Berry phase accumulated, in a pumping cycle, by the Andreev
bound states. We analyze in detail the case when the normal region is short
compared to the superconducting coherence length. The pumped charge turns out
to be an even function of the superconducting phase difference. Hence, it can
be distinguished from the charge transferred due to the standard Josephson
effect.Comment: 4 pages, 2 figures; Fig. 2 replaced, minor changes in the tex
Edge channel mixing induced by potential steps in an integer quantum Hall system
We investigate the coherent mixing of co-propagating edge channels in a
quantum Hall bar produced by step potentials. In the case of two edge channels
it is found that, although a single step induces only a few percent mixing, a
series of steps could yield 50% mixing. In addition, a strong mixing is found
when the potential height of a single step allows a different number of edge
channels on the two sides of the step. Charge density probability has been also
calculated even for the case where the step is smoothened.Comment: final version: 7 pages, 6 figure
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