High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)

(abridged) A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs would be a major milestone in extrasolar planets astrophysics. This fundamental goal can be achieved with a mission concept such as NEAT - the Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne extremely-high-precision astrometric measurements sufficient to detect dynamical effects due to orbiting planets of mass even lower than Earth's around the nearest stars. Such a survey mission would provide the actual planetary masses and the full orbital geometry for all the components of the detected planetary systems down to the Earth-mass limit. The NEAT performance limits can be achieved by carrying out differential astrometry between the targets and a set of suitable reference stars in the field. The NEAT instrument design consists of an off-axis parabola single-mirror telescope, a detector with a large field of view made of small movable CCDs located around a fixed central CCD, and an interferometric calibration system originating from metrology fibers located at the primary mirror. The proposed mission architecture relies on the use of two satellites operating at L2 for 5 years, flying in formation and offering a capability of more than 20,000 reconfigurations (alternative option uses deployable boom). The NEAT primary science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits. The remaining time might be allocated to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys.Comment: Accepted for publication in Experimental Astronomy. The full member list of the NEAT proposal and the news about the project are available at http://neat.obs.ujf-grenoble.fr. The final publication is available at http://www.springerlink.co

Immunoenzymatic study of the protein pathway through the glomerular barrier in rat glomerulonephritides

Immunoenzymatic study of the protein pathway through the glomerular barrier in rat glomerulonephritides. Circulating anti-horseradish peroxidase (HRP) IgG antibodies were used in the rat to study the glomerular leakage of proteins in glomerulonephritis (GN) induced by aminonucleoside (AN) and in glomerulonephritis induced by mercuric chloride to produce anti-glomerular basement membrane (GBM) antibodies. In ANGN, autologous albumin and fibrinogen were also detected by immunoperoxidase techniques. In both types of GN, the proteins studied were observed in the glomerular urinary space and proximal tubular cells. No channels were visible in the lamina densa. No accumulation of proteins was seen under the epithelial slits that were not closed. In ANGN, accumulation of proteins was observed in the subepithelial space where the podocytes act as a barrier (closed slits, subepithelial blind pockets, areas covered by broad sheets of cytoplasm), but no accumulation was seen in the lamina rara externa under normal or enlarged slits and areas of large epithelial cytoplasm detachment. Statistical analysis showed that in ANGN, at the time of maximal proteinuria, the number of “micropinocytotic” vesicles in the GBM-embedded part of podocytes was not increased as compared with controls. Such vesicles were not labeled. We conclude that in both types of GN, the permeability of the GBM is diffusely increased and that the plasma proteins pass into the urinary space via an extracellular pathway.Etude immunoenzymatique du passage de protéines à travers la barrière glomérulaire au cours de glomérulonéphrites du rat. La détection d'IgG circulantes anti-peroxydase (PO) a été employée chez le rat pour étudier la fuite glomérulaire des protéines dans la glomérulonéphrite (GN) par aminonucléoside (AN) et la GN par anticorps anti-membrane basale glomérulaire (MBG) induite par le chlorure de mercure. Dans la GNAN, l'albumine et le fibrinogène autologues ont aussi été détectés par les techniques d'immunoperoxydase. Dans les deux GN, les protéines étudiées ont été mises en évidence dans l'espace urinaire glomérulaire et dans les cellules tubulaires proximales. Il n'a pas été vu d'accumulation de protéines sous les fentes épithéliales, ni de passage privilégié de celles-ci à travers certains segments de la lamina densa. Dans la GNAN, une accumulation de protéines a été observée sous les podocytes là où ceux-ci jouaient un rôle de barrière (jonctions étroites, poches aveugles sous épithéliales, zones de “fusion” des pédicelles). En revanche, aucune accumulation n'a été vue dans la lamina rara externa là où existaient des fentes épithéliales normales ou élargies, ou bien des zones de détachement épithélial. L'analyse statistique a montré que le nombre des vésicules de “micropinocytose” a l'insertion des podocytes sur la MBG n'était pas supérieur dans la GNAN à celui observé chez les rats contrôles. Ces vésicules étaient négatives. Ces faits montrent que la perméabilité de la MBG est augmentée de façon diffuse dans les deux GN et que les protéines plasmatiques passent dans l'espace urinaire par voie extracellulaire

The 2010 European Venus Explorer (EVE) mission proposal

International audienceThe European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an 'M-class' mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55 km, where temperatures and pressures are benign (∼25°C and ∼0.5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond