Développements de composants millimétriques pour la caractérisation de la polarisation du fond diffus cosmologique

The Cosmic Microwave Background (CMB), the first light emitted by the Universe is a radiation observed today in the millimeter wave range. One of the major challenges of modern cosmology is the detection of the B-mode polarization anisotropies in the CMB. Their precise characterization constitutes a major step towards to constrain models of inflation, a very fast phase of expansion during the first moments of the Universe. This very weak signal requires a new generation of instruments combining a high sensitivity and a very good control of systematics. This manuscript describes the developments of millimeter wave range components made during my thesis. For the project QUBIC, a telescope based on the bolometric interferometry, I contributed to the study of large horn array made with a fabrication technique called platelets. I'm also involved in the development of an original solution for waveguide switches working in a cryogenic environment at 4K, essential components for the calibration of the instrument. With the project BSD funded by CNES, I contributed to the characterization of a diplexer of polarization and to the development of a switch and a phase shifter using the superconducting planar technology. These components are very interesting to develop an integrated detection architecture for the next generation of instruments dedicated to the characterization of CMB B-modes.Le fond diffus cosmologique (CMB), première lumière émise par l'Univers est un rayonnement observable aujourd'hui dans le domaine de longueur d'onde millimétrique. L'un des défis de la cosmologie observationnelle est la détection des modes B de polarisation du CMB. Leur caractérisation précise constitue une étape majeure pour contraindre les modèles d'inflation, phase d'expansion très rapide durant les premiers instants de l'Univers. Ce signal très faible nécessite une nouvelle génération d'instruments combinant une très grande sensibilité et un très bon contrôle des bruits instrumentaux. Ce manuscrit décrit les développements de composants millimétriques réalisés durant ma thèse. Pour le projet QUBIC, télescope basé sur le concept de l'interférométrie bolométrique, j'ai contribué à l'étude de grandes matrices de cornets réalisées à partir d'une technique d'assemblage appelée platelets. J'ai également participé au développement d'une solution originale pour des commutateurs en guide d'onde, éléments essentiels pour l'étalonnage de l'instrument et fonctionnant dans un environnement cryogénique à 4K. Dans le cadre du projet BSD financé par le CNES, j'ai contribué à la caractérisation d'un diplexeur de polarisation et au développement d'un commutateur et d'un déphaseur utilisant la technologie planaire supraconductrice. Ces composants sont très intéressants pour le développement d'une architecture de détection intégrée au plan focal pour les futurs instruments dédiés à la caractérisation des modes B

Le buis, Buxus sempervirens L., dans le nord de la France (phytogéograhie, socio-écologie, aspects ethnobotaniques et historiques)

AMIENS-BU Santé (800212102) / SudocSudocFranceF

The Nuclear Hormone Receptor Peroxisome Proliferator-Activated Receptor β/δ Potentiates Cell Chemotactism, Polarization, and Migration▿ †

After an injury, keratinocytes acquire the plasticity necessary for the reepithelialization of the wound. Here, we identify a novel pathway by which a nuclear hormone receptor, until now better known for its metabolic functions, potentiates cell migration. We show that peroxisome proliferator-activated receptor β/δ (PPARβ/δ) enhances two phosphatidylinositol 3-kinase-dependent pathways, namely, the Akt and the Rho-GTPase pathways. This PPARβ/δ activity amplifies the response of keratinocytes to a chemotactic signal, promotes integrin recycling and remodeling of the actin cytoskeleton, and thereby favors cell migration. Using three-dimensional wound reconstructions, we demonstrate that these defects have a strong impact on in vivo skin healing, since PPARβ/δ−/− mice show an unexpected and rare epithelialization phenotype. Our findings demonstrate that nuclear hormone receptors not only regulate intercellular communication at the organism level but also participate in cell responses to a chemotactic signal. The implications of our findings may be far-reaching, considering that the mechanisms described here are important in many physiological and pathological situations

Dual-Color Antenna-Coupled LEKID for Next-Generation Multi-chroic CMB Focal Planes

International audienceWe present an antenna-coupled Kinetic Inductance Detector for millimeter wave astronomy. Next-generation telescopes for observing the cosmic microwave background are demanding in terms of number of detectors and focal plane area filling efficiency. Moreover, foreground reduction in B-Mode polarimetry requires sky observation with multiple frequency bands. In this context, KIDs are a promising technology because of their large multiplexing rate, while antenna coupling can provide multi-band and dual-polarization solutions in compact design. We have developed polarization-sensitive dual-band pixel at 140 and 160 GHz with a bandwidth of almost 8% for each sub-band. The design involves a microstrip-excited slot antenna and two open-stub band-pass filters to direct the signal toward two resonators. These are lumped elements capacitively coupled to the antenna and include an aluminum strip as absorber. The architecture proposed is particularly simple to fabricate, via-less and only involves two metallization levels. The transition does not require any dielectric deposition above the resonator, thus preventing limitations from any source of noise due to a non-monocrystalline substrate. Furthermore, the same coupling technique can be applied to many types of microstrip-excited antennas, which allow to accommodate band-pass filters

Viability limits of the renewable source in an electricity mix: The MIXOPTIM analysis methodology

International audienceIn this article, we use a spectral and statistical analysis of load fluctuations to calculate plausible conditions that an electricity mix of power sources must satisfy to fulfill a variable power demand on a territory. These criteria can be applied to electricity mixes with a variable composition in controlled (dispatchable) and mandatory (non-dispatchable) sources in order to derive the maximum amount of mandatory fluctuating sources that can be tolerated in the mix if frequent power cuts are to be avoided. These criteria take into account the intermittent nature of the production of the mandatory renewable sources. Incorporated in the MIXOPTIM software, the three criteria can be used to assess the respective merits of the controllable power sources (e.g., coal, gas, nuclear, ... according to their agility, and what would be gained if this agility could be improved. These criteria take into account the influence of interconnection between the considered territory and its neighbors, and allows one to calculate to what extent an increase of the interconnection capacity increases the physically allowable proportion of renewable power sources in the mix. They also make it possible to evaluate the beneficial influence of demand smoothing, and of electricity storage facilities, and to calculate to what extent the introduction of demand smoothing or storage facilities move the physical limits of introduction of renewable mandatory fluctuating sources in the mix. We also investigate how these physical limits evolve if the renewable fluctuating sources are no longer considered as mandatory, and become controlled sources, with curtailment of their excess output when this excess power is not needed. This paper is devoted to the description of this methodological toolbox, a separate paper is devoted to its application to the French mix

Viability limits of the renewable source in an electricity mix: Application to the French mix with anamorphic evolutions

International audienceThis article is the second part of a work devoted to the study of the physical and economic limits of the addition of renewable power sources to an electricity mix on a territory. In the first part of the work, devoted to methodology, we discuss three criteria of viability of the electricity mix, based on the spectral and statistical analysis of the load fluctuations, taking into account the intermittent nature of the production of the mandatory renewable sources. The present paper is devoted to the application of the MIXOPTIM software, which includes this methodological toolbox, to the metropolitan French mix. Starting from the French mix 2015, we change its composition in controlled and mandatory power sources by anamorphic deformations, and analyze, with the MIXOPTIM toolbox, the viability and performance indicators of the modified mix. The viability criteria determine the maximum amount of mandatory fluctuating sources that can be tolerated in the mix if frequent power cuts are to be avoided. They provide a tool to assess the respective merits of the controllable (e.g., coal, gas, nuclear, ... sources according to their agility and what would be gained if this agility could be improved. The study takes into account the influence of interconnection between the considered territory and its neighbors, and evaluates to what extent an increase of the interconnection capacity increases the physically allowable proportion of renewable power sources in the mix. We also evaluate the beneficial influence of demand smoothing, and of electricity storage facilities, and calculate to what extent the introduction of demand smoothing or storage facilities move the physical limits of the introduction of renewable mandatory fluctuating sources in the metropolitan French mix. In the last part of the article, we investigate the conditions under which a 100% renewable electricity mix might be viable in France

Conception of a 90-GHz metamaterial-based coupler for astrophysical applications

International audienceDesigned for astrophysical applications, this coupler must be as small as possible to be integrated in a low temperature superconducting detection chain. By using metamaterials, dimensions can be reduced and performances enhanced compared with a conventional coupler. The novelty of the work presented in this paper is a coupler that operates at millimeter waves (W band) and cryogenic temperatures (4 K) for astrophysics applications and more precisely for the detection of the cosmological microwave background radiation

Co-Administration of Simvastatin Does Not Potentiate the Benefit of Gene Therapy in the mdx Mouse Model for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is the most common and cureless muscle pediatric genetic disease, which is caused by the lack or the drastically reduced expression of dystrophin. Experimental therapeutic approaches for DMD have been mainly focused in recent years on attempts to restore the expression of dystrophin. While significant progress was achieved, the therapeutic benefit of treated patients is still unsatisfactory. Efficiency in gene therapy for DMD is hampered not only by incompletely resolved technical issues, but likely also due to the progressive nature of DMD. It is indeed suspected that some of the secondary pathologies, which are evolving over time in DMD patients, are not fully corrected by the restoration of dystrophin expression. We recently identified perturbations of the mevalonate pathway and of cholesterol metabolism in DMD patients. Taking advantage of the mdx model for DMD, we then demonstrated that some of these perturbations are improved by treatment with the cholesterol-lowering drug, simvastatin. In the present investigation, we tested whether the combination of the restoration of dystrophin expression with simvastatin treatment could have an additive beneficial effect in the mdx model. We confirmed the positive effects of microdystrophin, and of simvastatin, when administrated separately, but detected no additive effect by their combination. Thus, the present study does not support an additive beneficial effect by combining dystrophin restoration with a metabolic normalization by simvastatin

Les frontières de la politique

Cette nouvelle livraison de Variations s’offre aux lecteurs alors que les frontières de la politique ont été malmenées et dérangées par les principaux candidats à la présidentielle, et qu’un homme a pu prendre le pouvoir grâce à un discours de rejet, celui de Mai 68, mais aussi celui de l’Autre et de la différence. Cette édition de printemps propose de revenir sur une série de thèmes de lutte et de révolte devant ce type de discours idéologique régressif