368 research outputs found
ContrÎle et lutte contre la fraude du patient européen
Il est des chiffres qui donnent le vertige. Incontestablement, ceux concernant les pertes dues à la fraude et la corruption en matiÚre de soins en font partie. Certaines estimations font en effet état de 56 milliards d'euros perdus annuellement en Europe, ce qui représente prÚs de 80 millions de perte chaque jour et plus de 5% de l'ensemble des budgets nationaux consacrés à la santé (Gee et alii, 2010)
Continuous non-perturbative regularization of QED
We regularize in a continuous manner the path integral of QED by construction
of a non-local version of its action by means of a regularized form of Dirac's
functions. Since the action and the measure are both invariant under
the gauge group, this regularization scheme is intrinsically non-perturbative.
Despite the fact that the non-local action converges formally to the local one
as the cutoff goes to infinity, the regularized theory keeps trace of the
non-locality through the appearance of a quadratic divergence in the transverse
part of the polarization operator. This term which is uniquely defined by the
choice of the cutoff functions can be removed by a redefinition of the
regularized action. We notice that as for chiral fermions on the lattice, there
is an obstruction to construct a continuous and non ambiguous regularization in
four dimensions. With the help of the regularized equations of motion, we
calculate the one particle irreducible functions which are known to be
divergent by naive power counting at the one loop order.Comment: 23 pages, LaTeX, 5 Encapsulated Postscript figures. Improved and
revised version, to appear in Phys. Rev.
Time-resolved diffuse optical tomography for non-invasive flap viability assessment: Pre-clinical tests on rats
We present a new setup for time-resolved diffuse optical tomography based on multiple source-detector acquisitions analysed by means of the Mellin-Laplace transform. The proposed setup has been used to perform pre-clinical measurements on rats in order to show its suitability for non-invasive assessment of flap viability
Trends in Metal Oxide Stability for Nanorods, Nanotubes, and Surfaces
The formation energies of nanostructures play an important role in
determining their properties, including the catalytic activity. For the case of
15 different rutile and 8 different perovskite metal oxides, we find that the
density functional theory (DFT) calculated formation energies of (2,2)
nanorods, (3,3) nanotubes, and the (110) and (100) surfaces may be described
semi-quantitatively by the fraction of metal--oxygen bonds broken and the
bonding band centers in the bulk metal oxide
A Mouse Model for Chikungunya: Young Age and Inefficient Type-I Interferon Signaling Are Risk Factors for Severe Disease
Chikungunya virus (CHIKV) is a re-emerging arbovirus responsible for a massive outbreak currently afflicting the Indian Ocean region and India. Infection from CHIKV typically induces a mild disease in humans, characterized by fever, myalgia, arthralgia, and rash. Cases of severe CHIKV infection involving the central nervous system (CNS) have recently been described in neonates as well as in adults with underlying conditions. The pathophysiology of CHIKV infection and the basis for disease severity are unknown. To address these critical issues, we have developed an animal model of CHIKV infection. We show here that whereas wild type (WT) adult mice are resistant to CHIKV infection, WT mouse neonates are susceptible and neonatal disease severity is age-dependent. Adult mice with a partially (IFN-α/ÎČR+/â) or totally (IFN-α/ÎČRâ/â) abrogated type-I IFN pathway develop a mild or severe infection, respectively. In mice with a mild infection, after a burst of viral replication in the liver, CHIKV primarily targets muscle, joint, and skin fibroblasts, a cell and tissue tropism similar to that observed in biopsy samples of CHIKV-infected humans. In case of severe infections, CHIKV also disseminates to other tissues including the CNS, where it specifically targets the choroid plexuses and the leptomeninges. Together, these data indicate that CHIKV-associated symptoms match viral tissue and cell tropisms, and demonstrate that the fibroblast is a predominant target cell of CHIKV. These data also identify the neonatal phase and inefficient type-I IFN signaling as risk factors for severe CHIKV-associated disease. The development of a permissive small animal model will expedite the testing of future vaccines and therapeutic candidates
The exceptionally powerful TeV gamma-ray emitters in the Large Magellanic Cloud
The Large Magellanic Cloud, a satellite galaxy of the Milky Way, has been
observed with the High Energy Stereoscopic System (H.E.S.S.) above an energy of
100 billion electron volts for a deep exposure of 210 hours. Three sources of
different types were detected: the pulsar wind nebula of the most energetic
pulsar known N 157B, the radio-loud supernova remnant N 132D and the largest
non-thermal X-ray shell - the superbubble 30 Dor C. The unique object SN 1987A
is, surprisingly, not detected, which constrains the theoretical framework of
particle acceleration in very young supernova remnants. These detections reveal
the most energetic tip of a gamma-ray source population in an external galaxy,
and provide via 30 Dor C the unambiguous detection of gamma-ray emission from a
superbubble.Comment: Published in Science Magazine (Jan. 23, 2015). This ArXiv version has
the supplementary online material incorporated as an appendix to the main
pape
Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination
Direct observation shows superposition and large scale flexibility within cytoplasmic dynein motors moving along microtubules
Cytoplasmic dynein is a dimeric AAA+ motor protein that performs critical roles in eukaryotic cells by moving along microtubules using ATP. Here using cryo-electron microscopy we directly observe the structure of Dictyostelium discoideum dynein dimers on microtubules at near-physiological ATP concentrations. They display remarkable flexibility at a hinge close to the microtubule binding domain (the stalkhead) producing a wide range of head positions. About half the molecules have the two heads separated from one another, with both leading and trailing motors attached to the microtubule. The other half have the two heads and stalks closely superposed in a front-to-back arrangement of the AAA+ rings, suggesting specific contact between the heads. All stalks point towards the microtubule minus end. Mean stalk angles depend on the separation between their stalkheads, which allows estimation of inter-head tension. These findings provide a structural framework for understanding dyneinâs directionality and unusual stepping behaviour
Mechanochemical modeling of dynamic microtubule growth involving sheet-to-tube transition
Microtubule dynamics is largely influenced by nucleotide hydrolysis and the
resultant tubulin configuration changes. The GTP cap model has been proposed to
interpret the stabilizing mechanism of microtubule growth from the view of
hydrolysis effects. Besides, the microtubule growth involves the closure of a
curved sheet at its growing end. The curvature conversion also helps to
stabilize the successive growth, and the curved sheet is referred to as the
conformational cap. However, there still lacks theoretical investigation on the
mechanical-chemical coupling growth process of microtubules. In this paper, we
study the growth mechanisms of microtubules by using a coarse-grained molecular
method. Firstly, the closure process involving a sheet-to-tube transition is
simulated. The results verify the stabilizing effect of the sheet structure,
and the minimum conformational cap length that can stabilize the growth is
demonstrated to be two dimers. Then, we show that the conformational cap can
function independently of the GTP cap, signifying the pivotal role of
mechanical factors. Furthermore, based on our theoretical results, we describe
a Tetris-like growth style of microtubules: the stochastic tubulin assembly is
regulated by energy and harmonized with the seam zipping such that the sheet
keeps a practically constant length during growth.Comment: 23 pages, 7 figures. 2 supporting movies have not been uploaded due
to the file type restriction
- âŠ