A Cardiac MicroRNA Governs Systemic Energy Homeostasis by Regulation of MED13

SummaryObesity, type 2 diabetes, and heart failure are associated with aberrant cardiac metabolism. We show that the heart regulates systemic energy homeostasis via MED13, a subunit of the Mediator complex, which controls transcription by thyroid hormone and other nuclear hormone receptors. MED13, in turn, is negatively regulated by a heart-specific microRNA, miR-208a. Cardiac-specific overexpression of MED13 or pharmacologic inhibition of miR-208a in mice confers resistance to high-fat diet-induced obesity and improves systemic insulin sensitivity and glucose tolerance. Conversely, genetic deletion of MED13 specifically in cardiomyocytes enhances obesity in response to high-fat diet and exacerbates metabolic syndrome. The metabolic actions of MED13 result from increased energy expenditure and regulation of numerous genes involved in energy balance in the heart. These findings reveal a role of the heart in systemic metabolic control and point to MED13 and miR-208a as potential therapeutic targets for metabolic disorders.PaperCli

Star formation triggered by non-head-on cloud-cloud collisions, and clouds with pre-collision sub-structure

In an earlier paper, we used smoothed particle hydrodynamics (SPH) simulations to explore star formation triggered by head-on collisions between uniform-density 500 M clouds, and showed that there is a critical collision velocity, vCRIT. At collision velocities below vCRIT, a hub-and-spoke mode operates and delivers a monolithic cluster with a broad mass function, including massive stars (M 10 M) formed by competitive accretion. At collision velocities above vCRIT, a spider’s-web mode operates and delivers a loose distribution of small sub-clusters with a relatively narrow mass function and no massive stars. Here we show that,if the head-on assumption is relaxed, vCRIT is reduced. However, if the uniform-density assumption is also relaxed, the collision velocity becomes somewhat less critical: a low collision velocity is still needed to produce a global hub-and-spoke system and a monolithic cluster, but, even at high velocities, large cores – capable of supporting competitive accretion and thereby producing massive stars – can be produced. We conclude that cloud–cloud collisions may be a viable mechanism for forming massive stars – and we show that this might even be the major channel for forming massive stars in the Galaxy

Caractérisation d’hétérostructures polycristallines par microscopie électronique en transmission : application aux cellules solaires à base de Cu(In,Ga)Se2

The aim of this thesis is the characterization of Cu(In,Ga)Se2 based (CIGSe) thin film solar cells at the nanoscale by transmission electron microscopy (TEM) to better understand some of their macroscopic electrical characteristics. The CIGSe cells electrical back contact is amolybdenum thin layer made of crystalline columns separated by an amorphous phase which allows alkali, necessary to obtain high conversion yields, to diffuse from the glass substrate toward the CIGSe layer. The volume fraction of the amorphous phase can be adjusted by varying the argon pressure during molybdenum deposition by sputtering. Electron energy loss spectroscopy (EELS) allowed the identification of this amorphous phase. MoSe2 layer, which is formed spontaneously at the interface between Mo and CIGSe layers, was characterized by TEM under different deposition conditions. The elemental composition of the CIGSe layer is not homogenous. When the CIGSe layer is deposited by the "3-stage" process, the In/Ga ratio varies throughout the layer. This composition gradient depends on the characteristics of the molybdenum layer and affects the electrical results of the cells. In/Ga gradient was determined from low loss EELS signal and has been evaluated by comparing the profiles with those obtained by other analytical techniques. The potential role of alkali in the amplitude of In/Ga gradient is also discussed.L’objectif de cette thèse est de caractériser les cellules solaires en couches minces à base de Cu(In,Ga)Se2 (CIGSe) à l’échelle nanométrique par microscopie électronique en transmission (MET) afin de mieux comprendre certaines de leurs caractéristiques électriques macroscopiques. Le contact électrique arrière des cellules CIGSe est une couche mince de molybdène constituée de colonnes cristallisées séparées par une phase amorphe qui laisse diffuser les alcalins nécessaires à l’obtention de rendements de conversion élevés depuis le substrat de verre vers la couche de CIGSe. La fraction volumique de la phase amorphe peut être ajustée en faisant varier la pression d’argon lors du dépôt de molybdène. La spectroscopie de perte d’énergie des électrons (EELS) a permis de l’identifier. La couche de MoSe2 qui se forme spontanément à l’interface entre la couche de Mo et celle de CIGSe a été caractérisée par MET en fonction de différentes conditions de dépôt. La composition élémentaire de lacouche de CIGSe n’est pas homogène. Lors du dépôt de la couche de CIGSe par le procédé « 3-stage », le rapport In/Ga varie le long de la couche. Ce gradient de composition dépend des caractéristiques de la couche de molybdène et influence les résultats électriques descellules. La détermination du gradient In/Ga par EELS à partir du signal des pertes faibles a été validée en comparant les profils à ceux obtenus par d’autres techniques d’analyse. Le rôle que peuvent jouer les alcalins dans l’amplitude du gradient In/Ga a également été discuté

Toward the Coordination Fingerprint of the Edge-Sharing BO 4 Tetrahedra

International audienceThe K3Sb4BO13 (KSBO) material undergoes an uncommon symmetry increase upon cooling, from triclinic symmetry at room temperature to monoclinic symmetry at low temperature. The first-order phase transition is accompanied by shrinkage of the unit cell, resulting in the transformation of every pair of head-to-tail triangular BO3 groups into one B2O6 unit featuring unique edge-sharing BO4 tetrahedra. This is the first material with B2O6 units formed through temperature lowering and exhibiting a B–O anionic framework composed uniquely of isolated edge-sharing BO4 tetrahedra. Several techniques including single-crystal X-ray diffraction experiments, Raman and 11B magic-angle-spinning NMR spectroscopies, and, for the first time, B K-edge electron energy loss spectroscopy were used to evidence the rare and discrete B2O6 units. The complete transformation of BO3 units into B2O6 units makes the KSBO compound the perfect candidate to extract information about B2O6 units whose signal can be unambiguously assigned

Synthesis, characterization and catalytic properties of polypyrrole-supported catalysts

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Platinum supported on doped alumina catalysts for propulsion applications. Xerogels versus aerogels.

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Caractérisation par MET de la région proche de la surface de l’absorbeur dans les cellules solaires à base de Cu(In,Ga)Se2

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Low-temperature synthesis and electrophoretic deposition of shape-controlled titanium dioxide nanocrystals

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Aerogel and xerogel catalysts based on theta alumina doped with silicon for high temperature reactions

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Physique-Tout le cours en fiches

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