The Karoo triple junction questioned : evidence from Jurassic and Proterozoc 40Ar/39Ar ages and geochemistry of the giant Okavango dyke swarm (Botswana).

The lower Jurassic Karoo-Ferrar magmatism represents one of the most important Phanerozoic continental flood basalt (CFB) provinces. The Karoo CFB province is dominated by tholeiitic traps and apparently radiating giant dyke swarms covering altogether ca. 3 106 km2. This study focuses on the giant N110j-trending Okavango dyke swarm (ODS) stretching over 1500 km across Botswana. This dyke swarm represents the main (failed) arm of the so-called Karoo triple junction that is generally considered as a key marker of the impingement of the Karoo starting mantle plume head. ODS dolerites yield six new plagioclase 40Ar/39Ar plateau (and miniplateau) ages ranging from 178.7F0.7 and 180.9F1.3 Ma. The distribution of the ages along a narrow Gaussian curve suggests a short period of magmatic activity centered around 179 Ma, i.e., f5 Ma younger than the emplacement age of Karoo mafic magmas in the southern part of the Karoo CFB province (f184). This age difference indicates that Karoo magmatism does not represent a short-lived event as is generally the case for most CFB but lasted at least 5Ma over the whole province. In addition, small clusters of plagioclase separated from 28 other dykes and measured by "speedy" step-heating experiments (with mostly two to three steps), gave either "Karoo" or Proterozoic ages.Integrated ages of the Proterozoic rocks range from 851 6 to 1672 7 Ma, and one plateau age (959.1 4.6 Ma) and one possibly geologically significant weighted mean age (982.7 4.0 Ma) were obtained. Proterozoic and Karoo mafic rocks are petrographically similar, but Proterozoic dykes display clear geochemical differences (e.g., TiO 22.1%). Geochemical data combined with available Ar/Ar dates allow the identification of the two groups within a total set of 77 dykes investigated: f10% of the bulk ODS dykes are Proterozoic. Thus, the Jurassic Karoo ODS dykes were emplaced along reactivated Proterozoic structures and there is no pristine Jurassic Nuanetsi triple junction as commonly proposed. This throws into doubt the validity of the "active plume head" Karoo CFB rift models as being responsible for the observed "triple junction" dyke geometr

ENDOGLIN is dispensable for vasculogenesis, but required for vascular endothelial growth factor-induced angiogenesis

ENDOGLIN (ENG) is a co-receptor for transforming growth factor-β (TGF-β) family members that is highly expressed in endothelial cells and has a critical function in the development of the vascular system. Mutations in Eng are associated with the vascular disease known as hereditary hemorrhagic telangiectasia type l. Using mouse embryonic stem cells we observed that angiogenic factors, including vascular endothelial growth factor (VEGF), induce vasculogenesis in embryoid bodies even when Eng deficient cells or cells depleted of Eng using shRNA are used. However, ENG is required for the stem cell-derived endothelial cells to organize effectively into tubular structures. Consistent with this finding, fetal metatarsals isolated from E17.5 Eng heterozygous mouse embryos showed reduced VEGF-induced vascular network formation. Moreover, shRNA-mediated depletion and pharmacological inhibition of ENG in human umbilical vein cells mitigated VEGF-induced angiogenesis. In summary, we demonstrate that ENG is required for efficient VEGF-induced angiogenesis

Filterability device, designed for high radioactive product studied in glove box

International audienceIn the Generation IV reactor framework, the fuel reprocessing involves a solid / liquid separation step to recover minor and major actinides solid compounds before oxide conversion at high temperature. Here, the industrial separator choice is based on technical aspect as criticality and reliability. But, it must also takes into account the actinides filterability behavior to obtain a good solid dewatering. This last performance is a mix between the more efficient separator device and the slurry filterability. Previous studies showed the interest of using a small filter cartridge with 1cm inner diameter with a specific laboratory filterability test cell. This significant reduction in the size of this experimental device does not alter the consistency of filtration data. This is an advantage for investigating toxic and hazardous products such as actinides precipitates. A modification of the lab filterability test was undertaken to study plutonium precipitate in a glove box of Atalante nuclear facility, at the CEA Marcoule. This specific design allows filterability test from 1 to 6 bar. It gives compressibility results on high radioactive and harmful products. This is the very first filterability results obtained on plutonium oxalate product. It will give keys on the choice of future solid/liquid separator equipment for Gen. IV reprocessing plant

Filtration performance test, an innovative lab scale device for industrial needs

National audienceMonitoring cake behavior for filterability and compressibility is a useful way to follow a solid precipitation process and anticipate solid/liquid issues in the separation stage. In many cases, experimental results have to be obtained in a few minutes with very small samples (just a few grams) of the suspension. Clearly, a need existed for a Filtration Performance Test (FPT) at a very compact scale. Such a tool could find applications in investigating toxic hazardous products such as radioactive materials or pharmaceutical compounds. Filterability and compressibility values can also be very helpful in choosing the best separator device when moving from pilot to industrial scale. The FPT presented here can meet a wide range of these needs. It will be shown that the technology enables cake specific resistance measurement in accordance with a modified Darcy's law at a constant pressure drop. A statistical approach on 1, 1.8 and 3 cm inner diameter test cells showed that wall effects can be ignored with even the smallest test cell. A high level of confidence is ensured for the filterability data obtained. Hydrodynamic modeling of tank, pipe and test cell situations with Openfoam CFD software led to an optimized design for the filtration tests. Settling zones are avoided and homogeneous cake construction is guaranteed inside the cell. Moreover, a user friendly tactile graphic display for the FPT enables online control of the suspension behavior, which helps ensure the ideal conditions of the industrial solid-liquid separation step. This development, presented in WFC12, concerns the very first commercial apparatus for the Filterability Pressure Test. The model was designed by FlowerSep company after some years of research and development in the CEA. With the Filtration Performance Test, researchers have obtained suspension behavior results contributing to quality control or to the choice of the most appropriate device for the solid/liquid separation stage (centrifugation, filtration)

New 40ar/39ar, stratigraphic and palaeoclimatic data on the Isernia La Pineta Lower Palaeolithic site, Molise, Italy

The archaeological deposits of Isernia la Pineta are a milestone in the European context, being composed of very rich and large-sized occupation layers. The archaeological remains are characterised by the use of anvil in a framework of a very opportunistic and rapid way to produce a large number of flakes and residual cores, usually of very small size. The lithic instruments are associated with remains of large mammals which give a clear indication of the diet. They are represented by Bison schoetensacki Freudenberg, Stephanorhinus hundsheimensis Toula, Elephas (Palaeoloxodon) namadicus Falconer e Cautley, Ursus deningeri von Reichenau, Hippopotamus cf. antiquus Desmarest, Sus scrofa L., Hemitragus cf. bonali Harlè e Stehlin, Megaceroides solilhacus Robert, Cervus elaphus cf. acoronatus Beninde, Dama dama cf. clactoniana Falconer, Capreolus sp., Panthera leo fossilis von Reichenau. The rodent fauna is represented by Clethrionomys sp., Pliomys episcopalis Mèhely, Pliomys lenki Heller, Microtus aff. arvalis Pallas, Microtus brecciensis Gieber, Microtus (Terricola) gr. multiplex-subterraneus, Arvicola cantiana Hinton. The insectivores are Talpa sp., Sorex cf. runtonensis Hinton, Crocidura sp. Two main archaeological layers have been identified. The lower one (sector I, lay.3c) rests on a phytoclastic travertine passing laterally to a phytohermal travertine which generated a small step in the watercourse. A sandy silt layer of lacustrine environment (lay.3b) deposited inside travertine pools and very limited phytostromatolitic travertine sediments cover this layer. The second occupation layer (Lay.3a) rests on these sediments as well as on the travertines. Cross bedded fine gravelly sands cover the deposits and are interlayered with tuffs very rich in pyroxene and sanidine. The latter gave 40Ar/39Ar ages of 610 ± 10 and 606 ± 2 ka (2 error), in two laboratories. This layer is covered by cross bedded gravels weathered by a thick Alfisols with a well expressed Bt horizon. The uppermost part of the series is composed of gravels and colluvia containing another pyroclastic layer. Sanidines of this layer yield scattered Ar/Ar ages, with a main population at about 504 ± 14 ka. A maximum age of 474 ± 3 ka is inferred for this layer. The Isernia travertines are not associated with hot water springs and indicate that the area was frequented at the end of an Interglacial period. The new ages demonstrate that the human frequentation occurred at the beginning of the Middle Pleistocen

New 40Ar/39Ar, stratigraphic and palaeoclimatic data on the Isernia la Pineta lower palaeolithic site, Molise, Italy.

The archaeological deposits of Isernia la Pineta are a milestone in the European context, being composed of very rich and largesized occupation layers. The archaeological remains are characterised by the use of anvils in a very opportunistic and rapid way to produce a large number of flakes and residual cores, usually of very small size. The lithic instruments are associated with remains of large mammals, which give a clear indication of the diet. They are represented by Bison schoetensacki Freudenberg, Stephanorhinus hundsheimensis Toula, Elephas (Palaeoloxodon) namadicus Falconer e Cautley, Ursus deningeri von Reichenau, Hippopotamus cf. antiquus Desmarest, Sus scrofa L., Hemitragus cf. bonali Harle` e Stehlin, Megaceroides solilhacus Robert, Cervus elaphus cf. acoronatus Beninde, Dama dama cf. clactoniana Falconer, Capreolus sp., and Panthera leo fossilis von Reichenau. The rodent fauna is represented by Clethrionomys sp., Pliomys episcopalis Mèhely, Pliomys lenki Heller, Microtus aff. arvalis Pallas, Microtus brecciensis Gieber, Microtus (Terricola) gr. multiplex-subterraneus, and Arvicola cantiana Hinton. The insectivores are Talpa sp., Sorex cf. runtonensis Hinton, and Crocidura sp. Two main archaeological layers have been identified. The lower one (Sector I, layer 3C) rests on a phytoclastic travertine passing laterally to a phytohermal travertine, which generated a small step in the watercourse. A sandy silt layer of lacustrine environment (layer 3b) deposited inside travertine pools and very limited phytostromatolitic travertine sediments cover this layer. The second occupation layer (layer 3a) rests on these sediments as well as on the travertines. Cross-bedded fine gravelly sands cover the deposits and are interlayered with tuffs very rich in pyroxene and sanidine. The latter gave 40Ar/39Ar ages of 610710 and 60672ka (2s error). This layer is covered by cross-bedded gravels weathered by a thick Alfisols with a well-expressed Bt horizon. The uppermost part of the series is composed of gravels and colluvia containing another pyroclastic layer. Sanidines of this layer yield scattered Ar/Ar ages, with a main population at about 504714 ka. A maximum age of 47473 ka is inferred for this layer. The Isernia travertines are not associated with hot water springs and indicate that the area was frequented at the end of an Interglacial period. The new ages demonstrate that the human frequentation occurred at the beginning of the Middle Pleistocene. © 2004 Elsevier Ltd and INQUA. All rights reserved

The influence of cosmic rays on the 3.4 microns interstellar absorption band

IAU Symposium 280, Poster 37, Session 3.International audienceA 3.4 μm absorption band, assigned to aliphatic C-H stretching modes of hydrogenated amorphous carbons (a-C:H), is widely observed in diffuse interstellar medium (ISM), but the only absorption occurring in this wavelength range in dense clouds is a large featureless band at 3.47 μm whose origin and attribution is still debated. Cosmic ray bombardment is one of the interstellar processes destroying the 3.4 μm feature. With the present work, we aim at carefully experimentally investigating the effects of such cosmic rays on the interstellar 3.4 μm absorption band carriers. Samples of carbonaceous interstellar analogs (a-C:H and soot) have been irradiated by swift ions in the MeV range, and monitored by infrared spectroscopy. These ion irradiations result in an effective dehydrogenation and chemical bonding modification of the samples, seen in particular through the decreasing absorbance of the 3.4 μm feature with the fluence (cf. figure). These experimental results allow a proper destruction cross-section determination over a large range of energies. Combined to an ISM cosmic ray distribution, we discuss the implications in different astrophysical environments