Radio emission of extensive air shower at CODALEMA: Polarization of the radio emission along the v*B vector

Cosmic rays extensive air showers (EAS) are associated with transient radio emission, which could provide an efficient new detection method of high energy cosmic rays, combining a calorimetric measurement with a high duty cycle. The CODALEMA experiment, installed at the Radio Observatory in Nancay, France, is investigating this phenomenon in the 10^17 eV region. One challenging point is the understanding of the radio emission mechanism. A first observation indicating a linear relation between the electric field produced and the cross product of the shower axis with the geomagnetic field direction has been presented (B. Revenu, this conference). We will present here other strong evidences for this linear relationship, and some hints on its physical origin.Comment: Contribution to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009. 4 pages, 8 figures. v2: Typo fixed, arxiv references adde

Geomagnetic origin of the radio emission from cosmic ray induced air showers observed by CODALEMA

The new setup of the CODALEMA experiment installed at the Radio Observatory in Nancay, France, is described. It includes broadband active dipole antennas and an extended and upgraded particle detector array. The latter gives access to the air shower energy, allowing us to compute the efficiency of the radio array as a function of energy. We also observe a large asymmetry in counting rates between showers coming from the North and the South in spite of the symmetry of the detector. The observed asymmetry can be interpreted as a signature of the geomagnetic origin of the air shower radio emission. A simple linear dependence of the electric field with respect to vxB is used which reproduces the angular dependencies of the number of radio events and their electric polarity.Comment: 9 pages, 15 figures, 1 tabl

The role of canalicular ABC transporters in cholestasis

Item does not contain fulltextCholestasis, a hallmark feature of hepatobiliary disease, is characterized by the retention of biliary constituents. Some of these constituents, such as bile acids, inflict damage to hepatocytes and bile duct cells. This damage may lead to inflammation, fibrosis, cirrhosis, and eventually carcinogenesis, sequelae that aggravate the underlying disease and deteriorate clinical outcome. Canalicular ATP-binding cassette (ABC) transporters, which mediate the excretion of individual bile constituents, play a key role in bile formation and cholestasis. The study of these transporters and their regulatory nuclear receptors has revolutionized our understanding of cholestatic disease. This knowledge has served as a template to develop novel treatment strategies, some of which are currently already undergoing phase III clinical trials. In this review we aim to provide an overview of the structure, function, and regulation of canalicular ABC transporters. In addition, we will focus on the role of these transporters in the pathogenesis and treatment of cholestatic bile duct and liver diseases

A study of switching time and light emission on carbon contact

International audienc

Etude expérimentale des arcs de coupures dans les relais de puissance en courant continu: effet de la double coupure, de l'atmosphère et du champ magnétique.

National audienc

Contact behavior of electrical vehicle-battery junction box under high shortening and breaking current

International audienc

A Study of arc duration on supple carbon contact in automotive field

International audienceMembrane switching technology is commonly used to operate electrical apparatus such as remote controls, automotive switches, mobile phones, etc. This technology is based on a movable contact, mounted in a supple elastomer frame which allows the contact to be pressed against a stationary contact, mounted on a Printed Circuit Board (PCB). The material of the movable contact is typically a carbon-loaded polymer or a metal whereas the PCB electrode structure is copper, coated with a layer of gold. The current trend is to use this technology for power applications such as operating a coil or a direct actuator control. As reported in the literature, for such currents <;1A and inductive loads, microarcs occur between rigid, metallic contacts, during break and make. Their duration and subsequent damage depend highly on the material and the mechanical separation. On the other hand, the high contact resistance of a flexible carbon-loaded polymer and the progressive separation due to its flexibility are expected to modify arc ignition and persistence characteristics. In this paper, we present experimental measurements of the electrical characteristics of such contacts and the consequences of arcing on contact reliability. Long contact rise times of the voltage are found compared to common metallic contacts. These complex voltage characteristics have been analyzed to extract arc voltage and duration. It was found that this supple and resistive contact allows an inductive load to be switched with a minor over-voltage and self-protection against arcing compared to common rigid metallic contacts

Influence of Contact Resistance in Carbon-Gold Contacts in Automotive Keypad Switches

International audienceIn membrane switching technology, a mobile contact, mounted on supple elastomeric parts is pressed onto a static part of the PCB by means of a knob. This technology is commonly used for keyboards in stationary applications where the contact material is made of carbon film while the PCB is coated with a gold layer. For automotive applications that require high reliability and low cost switches, further developments have been made. These are discussed in this paper that concerns the study of contact resistance under low and medium force indentation either in an industrial switch or in a specific sample. A preliminary study on a keypad has shown that the standard power law of contact resistance versus force Rc = Kc Fc-n does not reflect the real contact resistance regarding the complexity of the technologies (multi contact points, path conduction, etc.). Fortunately, the direct indentation of the carbon pill with a reference probe and two secondary probes for current and contact voltage measurement allows us to study the mechanism of conduction of the carbon pill and to perform a parametric study of materials and kinematical closure. As in previous work with metallic materials, we have obtained a similar power law which expresses the contact resistance versus contact force in the domain lcN-10 N. Polymers doped with carbon give a contact resistance value three orders of magnitude higher than in the metallic case. The power n is found to be dependent on mechanical parameters such as roughness and closing speed while the constant Kc reflects the resistivity of the carbon pill i.e. the carbon particle doping level in the polymer. Finally the main results are that the Young's modulus value of 10 MPa is four orders of magnitude lower than in metals (100 GPa for copper material) while the resistivity is five orders of magnitude higher than for common metallic contacts. In addition, an aging test carried out on the switc- - hes has demonstrated the stability of the contact properties