Fine frequency shift of sigle vortex entrance and exit in superconducting loops

The heat capacity $C_{p}$ of an array of independent aluminum rings has been measured under an external magnetic field $\vec{H}$ using highly sensitive ac-calorimetry based on a silicon membrane sensor. Each superconducting vortex entrance induces a phase transition and a heat capacity jump and hence $C_{p}$ oscillates with $\vec{H}$. This oscillatory and non-stationary behaviour measured versus the magnetic field has been studied using the Wigner-Ville distribution (a time-frequency representation). It is found that the periodicity of the heat capacity oscillations varies significantly with the magnetic field; the evolution of the period also depends on the sweeping direction of the field. This can be attributed to a different behavior between expulsion and penetration of vortices into the rings. A variation of more than 15% of the periodicity of the heat capacity jumps is observed as the magnetic field is varied. A description of this phenomenon is given using an analytical solution of the Ginzburg-Landau equations of superconductivity

Localization of sources with estimation of the antenna shape

This paper deals with the problem of detecting multiple narrow-band sources and estimating their angles of arrivai using the signais received on a large moving array in underwater acoustic passive listening . We describe a preliminary process leading to estimate the array deformation during the experiment, in the case where a dominant known source is available. This result provides the antenna with its maximum gain and permits to reconstruct the line-array antenna underlying most array processing methods . Afterwards we can estimate the number of secondary sources and their location . After recalling the AIC and MDL detection criteria, we briefly describe the MUSIC algorithm that we use te, identify the sources supposed narrow-band and far from the réception array . Finally, we apply this processing to experiment data. The results are compared with those, provided by the two-dimensional- Fourier Transform . This spatio-temporal representation points out that knowledge of the geometry of the receving antenna is very important.Détection et localisation de sources en acoustique sous-marine à l'aide d'une antenne longue tractée. Nous présentons tout d'abord un traitement permettant d'estimer la surface d'onde du signal reçu sur le réseau. Si au cours de l'expérimentation on utilise une source forte connue, on peut en déduire la forme d'antenne. Cette phase d'apprentissage effectuée, il est alors possible de détecter et de localiser des sources secondaires. Pour cela, nous rappelons les critères de détection AIC et MDL. Nous appliquons cette suite de traitements sur des signaux expérimentaux. Les résultats obtenus sont comparés à ceux provenant de la transformée de Fourier bidimensionnell

Immunological Tolerance to Muscle Autoantigens Involves Peripheral Deletion of Autoreactive CD8+ T Cells

Muscle potentially represents the most abundant source of autoantigens of the body and can be targeted by a variety of severe autoimmune diseases. Yet, the mechanisms of immunological tolerance toward muscle autoantigens remain mostly unknown. We investigated this issue in transgenic SM-Ova mice that express an ovalbumin (Ova) neo-autoantigen specifically in skeletal muscle. We previously reported that antigen specific CD4+ T cell are immunologically ignorant to endogenous Ova in this model but can be stimulated upon immunization. In contrast, Ova-specific CD8+ T cells were suspected to be either unresponsive to Ova challenge or functionally defective. We now extend our investigations on the mechanisms governing CD8+ tolerance in SM-Ova mice. We show herein that Ova-specific CD8+ T cells are not detected upon challenge with strongly immunogenic Ova vaccines even after depletion of regulatory T cells. Ova-specific CD8+ T cells from OT-I mice adoptively transferred to SM-Ova mice started to proliferate in vivo, acquired CD69 and PD-1 but subsequently down-regulated Bcl-2 and disappeared from the periphery, suggesting a mechanism of peripheral deletion. Peripheral deletion of endogenous Ova-specific cells was formally demonstrated in chimeric SM-Ova mice engrafted with bone marrow cells containing T cell precursors from OT-I TCR-transgenic mice. Thus, the present findings demonstrate that immunological tolerance to muscle autoantigens involves peripheral deletion of autoreactive CD8+ T cells

Etude du comportement alimentaire d'un parasitoïde de pucerons : Aphidius ervi (Hymenoptera : Braconoidae)

* Inra Poitou-Charentes, ERIST, Route de Saintes BP 6, 86600 Lusignan (FRA) Diffusion du document : Inra Poitou-Charentes, ERIST, Route de Saintes BP 6, 86600 Lusignan (FRA) Diplôme : Maîtris

Temporal and spatial analysis of the wave surface received on a large array in the sea

We study the signais received on a large array far away in the sea for transmitted signais low frequency wave . The amplitude and phase analysis of the Fourier Transform, at the signal frequency on every receiver, points out the characteristics of the wave surface. We describe here the experiment and present some resuits for various distances and analysis durations. In the case of multifrequencies emission, we use a spatial Wiener filtering to greatly improve the results . Theoretical developments and expérimental results of the proccessing are given in this paper .L'analyse des modules et des phases de la transformée de Fourier donne une information sur la nature de la surface d'onde. Présentation de la méthode de traitement ainsi que des résultats expérimentaux obtenus dans le cas d'une émission monochromatiqu

Utilisation du sous-espace signal cohérent pour la localisation de sources bande large

Depuis quelques années on s'intéresse à l'étude de signaux de type bande large. On s'intéresse à la détection et à la localisation de sources émettant de tels signaux. Plusieurs méthodes ont été proposées qui utilisent soit le sous-espace signal incohérent (S.E.S.I), soit le sous-espace signal cohérent (S.E.S.C.). Dans cette étude nous nous proposons d'analyser le S.E.S.C. en définissant un opérateur de focalisation. Cet opérateur a pour objectif de rendre cohérentes les différentes matrices interspectrales de façon à pouvoir les moyenner, afin d'estimer par la suite le S.E.S.C.. Ce dernier sera utilisé pour localiser les différentes sources rayonnantes