30 research outputs found
Usefulness of two SCAR markers for marker-assisted selection of seedless grapevine cultivars
A PCR-specific marker, SCP18, was developed from a RAPD marker linked to a major locus involved in seedlessness, sdI. A preliminary study of the usefulness of SCP18 and SCC8 (a marker linked to sdI previously developed by LAHOGUE et al. 1998) for the marker assisted selection of seedless varieties was realized using various strategies: a posteriori test in seedless x seedless and seeded x seeded progenies and test of their allelic diversity in a set of 81 seedless and seeded varieties. In contrast to SCP18, SSC8 was found to be a useful marker at least in the seedless x seedless progenies and to show a good linkage disequilibrium with seedlessness in our set of varieties
Iron oxides in fractured quartz : development and evolution of iron sandstone layers in the Kinshasa area, DR Congo
Quartz grains in an iron sandstone layer in near-surface sandy deposits at Kasangulu, south of Kinshasa, DR Congo, are marked by the presence of iron oxides in subparallel horizontal cracks within the sand grains. This exceptional feature was investigated to understand its origin and paleoenvironmental significance. Based on thin section observations, supplemented by Mossbauer spectroscopy results and other data, the occurrence of filled subparallel cracks is attributed to iron oxide remobilisation following crack opening within an iron-oxide-cemented sand intercalation that became exposed through erosion, whereby crack opening is related to surface temperature fluctuations. The development of filled crack occurrences of this type requires a period of surface exposure, implying that their presence is indicative of the position of former surface levels. A macroscopically similar iron sandstone layer at another locality in the Kinshasa area, lacking filled cracks, provides indications for both surface exposure and cement type as factors in their development
Palygorskite-bearing fracture fills in the Kinshasa area, DR Congo - an exceptional mode of palygorskite vein development
Tectonic fractures in Palaeozoic strata of the Kinshasa area, DR Congo, locally host palygorskite-bearing veins and associated calcite occurrences. The palygorskite deposits are typically massive, with a varying degree of alignment of clay particles, a higher quartz content than the arkose substrate, and a variable amount of smectite (montmorillonite). The associated calcite occurrences are macrocrystalline coatings and infillings, and more fine-grained calcite veins with cataclastic texture. The calcite coatings and infillings formed from solution in earth surface conditions, as recorded by their stable isotope signature. The palygorskite-dominated deposits in the fractures formed at a later stage, in a setting without indications of authigenic mineral formation related to hydrothermal activity or to low-temperature interaction of solutions with the local substrate. The veins most likely formed by vertical infiltration of suspended matter in fractures that extended to a post-Palaeozoic palaeosurface, during or after deposition of palygorskite-bearing Upper Jurassic to Early Cretaceous sediments. This represents an exceptional mode of palygorskite vein development, unrelated to any form of mineral authigenesis that is typically invoked to explain vein-type occurrences of palygorskite and related minerals
Réseau d'assainissement de la ville de Rennes
International audienceL'objectif de l'étude est de mettre en évidence l'état du réseau d'assainissement de la ville de Rennes, de manière à pouvoir envisager les opérations de maintenance dans une logique de prévention et non consécutive à un accident. Au cours du temps, les évolutions de la ville ont conduit au déplacement des activités industrielles en périphérie et se sont substituées des zones pavillonnaires. Les effluents circulant dans le réseau d'assainissement ont donc changés de nature. Le but de cette étude est de déterminer l'état actuel des conduites : propriétés des matériaux et des ouvrages sur le plan physique, chimique et mécanique. La passivation des armatures est déterminée, les formations cristallines liées aux différentes attaques sont analysées par MEB, EDX et diffraction X. Les attaques peuvent être au contact du sol, des effluents et des granulats. Ainsi, il est possible d'estimer, la durée de vie de ces conduites, sous réserves que les conditions d'environnement ne varient pas dans le temps
On-going studies at CEA on chromium coated zirconium based nuclear fuel claddings for enhanced accident tolerant LWRS fuel
International audienceChromium coatings aiming to protect the current zirconium alloy nuclear fuel cladding materials from high temperature steam oxidation, especially in accidental conditions, are being developed at CEA in the framework of the French Nuclear Institute in partnership with AREVA and EDF. The present paper focuses on recent results obtained on chromium-coated cladding on Zircaloy-4 and substrate. A complementary paper is presented by AREVA. Typical as-fabricated microstructures of chromium coatings are illustrated. Preliminary autoclave oxidation tests at 415°C (steam, 100 bars) have been performed on both uncoated reference materials and on chromium coated Zircaloy-4 based samples, showing very encouraging results for the last generation of Cr coatings fabricated. Additionally, results obtained after High Temperature (HT) oxidation in steam are presented. It is shown that the chromium coatings developed so far may significantly improve the post-HT oxidation clad mechanical properties (i.e. ductility and strength) compared to conventional uncoated materials. As a consequence, the developed chromium coatings provide significant additional margins for loss-of-coolant accident (LOCA) and, to some extent, for beyond LOCA conditions