2,946 research outputs found
Proximity effect in granular superconductor-normal metal structures
We fabricated three-dimensional disordered Pb-Cu granular structures, with
various metal compositions. The typical grain size of both metals is smaller
than the superconductor and normal metal coherence lengths, thus satisfying the
Cooper limit. The critical temperature of the samples was measured and compared
with the critical temperature of bilayers. We show how the proximity effect
theories, developed for bilayers, can be modified for random mixtures and we
demonstrate that our experimental data fit well the de Gennes weak coupling
limit theory in the Cooper limit. Our results indicate that, in granular
structures, the Cooper limit can be satisfied over a wide range of
concentrations.Comment: 15 pages, 4 figure
Passive Tracking System and Method
System and methods are disclosed for passively determining the location of a moveable transmitter utilizing a pair of phase shifts at a receiver for extracting a direction vector from a receiver to the transmitter. In a preferred embodiment, a phase difference between the transmitter and receiver is extracted utilizing a noncoherent demodulator in the receiver. The receiver includes antenna array with three antenna elements, which preferably are patch antenna elements placed apart by one-half wavelength. Three receiver channels are preferably utilized for simultaneously processing the received signal from each of the three antenna elements. Multipath transmission paths for each of the three receiver channels are indexed so that comparisons of the same multipath component are made for each of the three receiver channels. The phase difference for each received signal is determined by comparing only the magnitudes of received and stored modulation signals to determine a winning modulation symbol
Measuring patient-perceived quality of care in US hospitals using Twitter
BACKGROUND: Patients routinely use Twitter to share feedback about their experience receiving healthcare. Identifying and analysing the content of posts sent to hospitals may provide a novel real-time measure of quality, supplementing traditional, survey-based approaches. OBJECTIVE: To assess the use of Twitter as a supplemental data stream for measuring patient-perceived quality of care in US hospitals and compare patient sentiments about hospitals with established quality measures. DESIGN: 404 065 tweets directed to 2349 US hospitals over a 1-year period were classified as having to do with patient experience using a machine learning approach. Sentiment was calculated for these tweets using natural language processing. 11 602 tweets were manually categorised into patient experience topics. Finally, hospitals with ≥50 patient experience tweets were surveyed to understand how they use Twitter to interact with patients. KEY RESULTS: Roughly half of the hospitals in the US have a presence on Twitter. Of the tweets directed toward these hospitals, 34 725 (9.4%) were related to patient experience and covered diverse topics. Analyses limited to hospitals with ≥50 patient experience tweets revealed that they were more active on Twitter, more likely to be below the national median of Medicare patients (p<0.001) and above the national median for nurse/patient ratio (p=0.006), and to be a non-profit hospital (p<0.001). After adjusting for hospital characteristics, we found that Twitter sentiment was not associated with Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) ratings (but having a Twitter account was), although there was a weak association with 30-day hospital readmission rates (p=0.003). CONCLUSIONS: Tweets describing patient experiences in hospitals cover a wide range of patient care aspects and can be identified using automated approaches. These tweets represent a potentially untapped indicator of quality and may be valuable to patients, researchers, policy makers and hospital administrators
Creating traveling waves from standing waves from the gyrotropic paramagnetic properties of Fe ions in a high-Q whispering gallery mode sapphire resonator
We report observations of the gyrotropic change in magnetic susceptibility of
the Fe electron paramagnetic resonance at 12.037GHz (between spin states
and ) in sapphire with respect to applied magnetic field.
Measurements were made by observing the response of the high-Q Whispering
Gallery doublet (WGH) in a Hemex sapphire resonator cooled to 5
K. The doublets initially existed as standing waves at zero field and were
transformed to traveling waves due to the gyrotropic response.Comment: Accepted for publication in Phys. Rev.
Application of mixed formulations of quasi-reversibility to solve ill-posed problems for heat and wave equations: the 1d case
International audienceIn this paper we address some ill-posed problems involving the heat or the wave equation in one dimension, in particular the backward heat equation and the heat/wave equation with lateral Cauchy data. The main objective is to introduce some variational mixed formulations of quasi-reversibility which enable us to solve these ill-posed problems by using some classical La-grange finite elements. The inverse obstacle problems with initial condition and lateral Cauchy data for heat/wave equation are also considered, by using an elementary level set method combined with the quasi-reversibility method. Some numerical experiments are presented to illustrate the feasibility for our strategy in all those situations. 1. Introduction. The method of quasi-reversibility has now a quite long history since the pioneering book of Latt es and Lions in 1967 [1]. The original idea of these authors was, starting from an ill-posed problem which satisfies the uniqueness property, to introduce a perturbation of such problem involving a small positive parameter ε. This perturbation has essentially two effects. Firstly the perturbation transforms the initial ill-posed problem into a well-posed one for any ε, secondly the solution to such problem converges to the solution (if it exists) to the initial ill-posed problem when ε tends to 0. Generally, the ill-posedness in the initial problem is due to unsuitable boundary conditions. As typical examples of linear ill-posed problems one may think of the backward heat equation, that is the initial condition is replaced by a final condition, or the heat or wave equations with lateral Cauchy data, that is the usual Dirichlet or Neumann boundary condition on the boundary of the domain is replaced by a pair of Dirichlet and Neumann boundary conditions on the same subpart of the boundary, no data being prescribed on the complementary part of the boundary
ITERATED QUASI-REVERSIBILITY METHOD APPLIED TO ELLIPTIC AND PARABOLIC DATA COMPLETION PROBLEMS
International audienceWe study the iterated quasi-reversibility method to regularize ill-posed elliptic and parabolic problems: data completion problems for Poisson's and heat equations. We define an abstract setting to treat both equations at once. We demonstrate the convergence of the regularized solution to the exact one, and propose a strategy to deal with noise on the data. We present numerical experiments for both problems: a two-dimensional corrosion detection problem and the one-dimensional heat equation with lateral data. In both cases, the method prove to be efficient even with highly corrupted data
ArDM: first results from underground commissioning
The Argon Dark Matter experiment is a ton-scale double phase argon Time
Projection Chamber designed for direct Dark Matter searches. It combines the
detection of scintillation light together with the ionisation charge in order
to discriminate the background (electron recoils) from the WIMP signals
(nuclear recoils). After a successful operation on surface at CERN, the
detector was recently installed in the underground Laboratorio Subterr\'aneo de
Canfranc, and the commissioning phase is ongoing. We describe the status of the
installation and present first results from data collected underground with the
detector filled with gas argon at room temperature.Comment: 6 pages, 3 figures, Light Detection In Noble Elements (LIDINE 2013
Elaboration et évaluation d'algorithmes de dépistage des MST chez la femme enceinte à Libreville, Gabon
La lutte contre les MST constitue une priorité de santé publique des pays en développement de par leurs complications propres, en particulier chez la femme, et de par leur rôle facilitant la transmission du VIH. Une des stratégies de lutte contre les MST est le diagnostic et le traitement précoces de ces infections. Les MST, en particulier les infections à gonocoques et à #Chlamydiae trachomatis). L'évaluation de différentes stratégies diagnostiques et d'algorithmes montre que, quel que soit le niveau d'examen (données d'interrogatoire, examen clinique simple, examen au spéculum), l'utilisation de scores intégrant des facteurs de risque, des symptômes et des signes cliniques est plus performante que les algorithmes hiérarchiques. Ces scores présentent des sensibilités et des spécificités élevées et sont d'une mise en oeuvre facile. Leur application pourrait donc permettre le dépistage efficace des MST et éviter, ainsi, une grande partie des complications maternelles et infantiles. (Résumé d'auteur
Status of the ArDM Experiment: First results from gaseous argon operation in deep underground environment
The Argon Dark Matter (ArDM-1t) experiment is a ton-scale liquid argon (LAr)
double-phase time projection chamber designed for direct Dark Matter searches.
Such a device allows to explore the low energy frontier in LAr. After
successful operation on surface at CERN, the detector has been deployed
underground and is presently commissioned at the Canfranc Underground
Laboratory (LSC). In this paper, we describe the status of the installation and
present first results on data collected in gas phase.Comment: 21 pages, 20 figure
- …