Éditeur(s) : HAL CCSD American Physical Society
Résumé : We study the equilibrium properties of a liquid phase condensed at the nanoscale between the surfaces of a sharp crack in fused silica in a moist controlled atmosphere. The extension of the condensed phase along the fracture is measured by in situ atomic force microscopy phase imaging and it is shown to be determined by a critical distance between the opposite crack surfaces, which is an increasing function of humidity. The present technique is very promising for measuring the properties of confined liquids at the nanoscale as well as for modeling the physics and chemistry of slow crack propagation in glasses.
ISSN: 0031-9007

hal-00411946
https://hal.archives-ouvertes.fr/hal-00411946
DOI : 10.1103/PhysRevLett.100.165505

Éditeur(s) : HAL CCSD Geological Society of America
Résumé : If the net flux to the island arc crust is primitive arc basalt, the evolved composition of most arc magmas entails the formation of complementary thick ultramafic keels at the root of the island arc crust. Dunite, wehrlite, and Cr-rich pyroxenite from the Jijal complex, constituting the Moho transition zone of the Kohistan paleo–island arc (northern Pakistan), are often mentioned as an example of high-pressure cumulates formed by intracrustal fractionation of mantle-derived melts, which were later extracted to form the overlying mafic crust. Here we show that calculated liquids for Jijal pyroxenites-wehrlites are strongly rare earth element (REE) depleted and display flat or convex-upward REE patterns. These patterns are typical of boninites and are therefore unlike those of the overlying mafic crust that have higher REE concentrations and are derived from light rare earth element (LREE)–enriched melts similar to island arc basalt. This observation, along with the lower 208Pb/204Pb and 206Pb/204Pb ratios of Jijal pyroxenites-wehrlites relative to gabbros, rejects the hypothesis that gabbros and ultramafic rocks derive from a common melt via crystal fractionation. In the 208Pb/204Pb versus 206Pb/204Pb diagram, ultramafic rocks and gabbros lie on the same positive correlation, suggesting that their sources share a common enriched mantle 2 (EM2) signature but with a major depleted component contribution for the ultramafic rocks. These data are consistent with a scenario whereby the Jijal ultramafic section represents a Moho transition zone formed via melt-rock reaction between subarc mantle and incoming melt isotopically akin to Jijal gabbroic rocks. The lack in the Kohistan arc of cogenetic ultramafic cumulates complementary to the evolved mafic plutonic rocks implies either (1) that a substantial volume of such ultramafic cumulates was delaminated or torn out by subcrustal mantle flow from the base of the arc crust in extraordinarily short time scales (0.10–0.35 cm/yr), or (2) that the net flux to the Kohistan arc crust was more evolved than primitive arc basalt.
ISSN: 0091-7613

hal-00406688
https://hal.archives-ouvertes.fr/hal-00406688
DOI : 10.1130/G23675A.1

Éditeur(s) : HAL CCSD Mineralogical Society of America
Résumé : International audience
Pressure-temperature divariant melting phase relations of model carbonated peridotite in the system CaO-MgO-Al2O3-SiO2-CO2 from 8 to 12 GPa are reported. From 8 to 12 GPa, melting temperatures on the studied pressure-temperature divariant surface rise quite rapidly. Liquids, in equilibrium with forsterite, orthopyroxene, clinopyroxene, and garnet, on the low-temperature side of the divariant surface are magnesiocarbonatitic in composition. With increasing temperature along an isobar on the pressure-temperature divariant surface, and with the same crystalline phase assemblage, liquids gradually become kimberlitic in their composition. Given the model system data reported here, Group IB kimberlites and perhaps some kimberlites from Greenland, Canada, and South Africa could be generated from direct melting of carbonated peridotite in the pressure range of approximately 6-8 GPa. Some kimberlites from Canada and Russia could have formed by partial melting of carbonated mantle peridotite at pressures of about 10-12 GPa. From 8 to 12 GPa, liquid compositions on the studied divariant surface show a limited compositional range, which implies that the divariant surface is essentially flat. The implied flatness of the divariant surface, and so long as the liquid is in equilibrium with the crystalline assemblage of forsterite + orthopyroxene + clinopyroxene + garnet on the divariant surface, indicate that kimberlites belonging to Group IA and those more magnesian than Group IA cannot have their origin in only being a melting product of carbonated mantle peridotite. The absence of topography of the studied pressure-temperature divariant surface in all likelihood limits the generation of kimberlites in the Earth's upper mantle only.
ISSN: 0003-004X

hal-01053915
https://hal.archives-ouvertes.fr/hal-01053915
DOI : 10.2138/am.2014.4826

Résumé : Once fished, the shrimps must be cooled quickly in water cooled in order to slow down all chemical and bacteriological activities. In addition, in order to avoid blackening (mélanose) shrimps (céphalothorax and legs) it is necessary to treat those with an antioxydant product. The product currently used to inhibit this enzymatic change is the soda niétabisuifite (Na-> S7 O5), until now, after being fished. the shrimps were directly soaked in a cooled water tank, containing the pesticide. The solution of treatment was progressively prepared needs. The concentration of this one was approximately 2 to 3% of métabisulfite, that is to say 6 to 9 G of SO2 per liter for a starting product containing 320 G of SO2 approximately. In order to preserve a good quality of the liquid of treatment it was essential to often renew it (every 400 to 500 kg) what was not always the case, the métabisulfite being often added progressively with the liking of the appointed person with the treatment of shrimps. In order to cure this delicate problem of renewal of vat and uniformity of the treatment, the SODACAL obtained the system of treatment by sprinkling.
Une fois pêchées, les crevettes doivent être refroidies rapidement dans de l'eau réfrigérée afin de ralentir toutes activités chimiques et bactériologiques. D'autre part, afin d'éviter le noircissement (mélanose) des crevettes (céphalothorax et pattes) il est nécessaire de traiter celles-ci avec un produit anti-oxydant. Le produit actuellement utilisé pour inhiber cette altération enzymatique est le niétabisuifite de soude (Na-> S7 O5), jusqu'à maintenant, après avoir été pêchées. les crevettes étaient directement trempées dans une cuve d'eau réfrigérée, contenant le produit de traitement. La solution de traitement était préparée au fur et à mesure des besoins. La concentration de celle-ci était d'environ 2 à 3 % de métabisulfite, soit 6 à 9 g de SO2 par litre pour un produit de départ contenant 320 g de SO9 environ. Afin de conserver une bonne qualité du liquide de traitement il était indispensable de le renouveler souvent (tous les 400 à 500 kg) ce qui n'était pas toujours le cas, le métabisulfite étant souvent rajouté au fur et à mesure au gré de la personne préposée au traitement des crevettes. Afin de remédier à ce problème délicat de renouvellement de bac et d'uniformité du traitement, la SODACAL s'est dotée du système de traitement par aspersion.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1991/rapport-1648.pdf
http://archimer.ifremer.fr/doc/00000/1648/

Éditeur(s) : HAL CCSD E Schweizerbart Science Publishers
Résumé : Mafic microgranular enclaves produced by co-mingling between minette and syenite magmas are found in the Piquiri Syenite, southern Brazil. These enclaves were crystallized under upper mantle conditions. K-clinopyroxene and pyrope are among the early-crystallized phases, suggesting an initial pressure around 5GPa. The mineralogy of minettes comprises phenocrysts of magnesium biotite and diopside, occasionally apatite, in a groundmass formed by these minerals plus alkali feldspar. Two types of apatites are observed: (i) euhedral grains, as inclusions or groundmass constituents, and (ii) aciculate crystals formed during undercooling of mafic magma. Substitutional schemes suggested for these apatites are Si ⇆ P in the tetrahedral site, and Sr and LREE replacing Ca. La, Ce, Nd, and Sr concentrations reveal that these elements are extremely enriched in apatite. Partition coefficients between early-crystallized apatites and estimated melt compositions are DLa (11.8 - 30.6), DCe (16.1-33), DNd (12-31) and DSr (5.1-8.2). Apatite concentrates the LREE up to 200 times compared to clinopyroxene, even higher values were determined for ap/mica partitioning. The ap/cpx and ap/mica partition coefficients for undercooled minerals are close to the values determined for the near-liquidus phases, which indicates constant behavior of LREE and Sr between apatite-clinopyroxene-mica parageneses and minette liquids. Furthermore, these partitioning data preclude any chemical diffusion of these elements between minette and syenite magmas during co-mingling.
ISSN: 0935-1221

hal-00407602
https://hal.archives-ouvertes.fr/hal-00407602
DOI : 10.1127/0935-1221/2007/0019-0039

Éditeur(s) : Mdpi Ag
Résumé : Marine pelagic diazotrophic cyanobacteria of the genus Trichodesmium (Oscillatoriales) are widespread throughout the tropics and subtropics, and are particularly common in the waters of New Caledonia. Blooms of Trichodesmium are suspected to be a potential source of toxins in the ciguatera food chain and were previously reported to contain several types of paralyzing toxins. The toxicity of water-soluble extracts of Trichodesmium spp. were analyzed by mouse bioassay and Neuroblastoma assay and their toxic compounds characterized using liquid chromatography coupled with tandem mass spectrometry techniques. Here, we report the first identification of palytoxin and one of its derivatives, 42-hydroxy-palytoxin, in field samples of Trichodesmium collected in the New Caledonian lagoon. The possible role played by Trichodesmium blooms in the development of clupeotoxism, this human intoxication following the ingestion of plankton-eating fish and classically associated with Ostreopsis blooms, is also discussed.
Marine Drugs (1660-3397) (Mdpi Ag), 2011-04 , Vol. 9 , N. 4 , P. 543-560

Droits : 2011 MDPI Publishing
http://archimer.ifremer.fr/doc/00040/15143/12576.pdf
DOI:10.3390/md9040543
http://archimer.ifremer.fr/doc/00040/15143/

Résumé : La tribologie est définie comme la science qui étudie les phénomènes de frottement, d’usure et de lubrification. Elle intervient à chaque fois que deux surfaces sont en mouvement relatif l’une par rapport à l’autre. On la rencontre donc principalement dans les moteurs, les instruments de coupe, les assemblages mécaniques etc. Le frottement et l’usure sont les causes principales des pertes de performances et de durabilité des systèmes. L’usure coute 3 % du PIB en France et on estime que 10 % à 30 % de l’énergie produite dans le monde est consommée par frottement, c’est dire l’importance que porte le monde industriel à cette science.C'est la lubrification qui a pour rôle de minimiser le frottement et de protéger les surfaces de l'usure. Il existe différents régimes de lubrification, cependant les travaux effectués au cours de cette thèse de doctorat s’intéressent exclusivement au régime de lubrification limite. Dans ce régime de lubrification, l’épaisseur du film de lubrifiant est du même ordre de grandeur que la hauteur des aspérités des surfaces en contact et le frottement et l'usure des surfaces peuvent être très sévères. La stratégie mise en place pour lutter contre ces phénomènes consiste à ajouter des additifs à l'huile lubrifiante, qui formeront au cours du frottement un film protecteur (le tribofilm). Il apparait donc primordial de bien caractériser ces tribofilms afin de mieux comprendre les mécanismes de réduction de frottement et de l’usure, qui restent encore à ce jour mal connus.Les nanotechnologies permettent aujourd'hui d'apporter un nouvel éclairage sur cette problématique et nous les avons mises à profit pour étudier le comportement mécanique des tribofilms à l’échelle nanométrique.L’objectif de ce travail est de comprendre les processus de réduction de frottement observés à l’échelle macroscopique lorsque des particules de composés lamellaires sont associées à un liquide de faible viscosité. Les tribofilms étudiés sont formés à partir de trois composés lamellaires différents, le graphite, le thiophosphate de nickel NiPS3 et le bisulfure de molybdène MoS2. Pour ces trois composés, deux types de tribofilms ont été étudiés : ceux formés à partir des particules seules (les tribofilms secs) et ceux formés en présence de liquide (les tribofilms éther).L’analyse des propriétés tribologiques mesurées à macro et nano échelle, nous ont permis de mieux comprendre la contribution des effets individuels et collectifs sur les mécanismes réducteurs de frottement. Ces expériences ont permis de mettre en évidence que la réduction du coefficient de frottement observée à macro-échelle n'est pas due à la nanostructuration des tribofilms ni à une baisse des interactions entre les feuillets mais plutôt à un effet collectif des particules et du liquide.
Tribology is the science of friction phenomena, wear and lubrication. It takes part every time two surfaces are in relative motion. It performs meanly in engine and mechanical systems. Friction and wear are the mean reasons of loose of performance and durability of mechanical systems. Wear costs 3% of the GDP in France and about 10% to 30% of the produced energy in the world is consumed by friction.The aim of lubrication is to reduce friction and protect the surface against wear. There are four different types of lubrication regimes but this study is focused on the boundary regime. In this regime, lubricant thickness is of the same order of the magnitude of the sliding surfaces roughness, leading to a high-level of friction and wear. Additives are added to the lubricating base oil, in order to build a protecting tribofilm. Characterization of the tribofilms appears essential to better understand the friction and wear reduction mechanisms.Nanotechnology allows to bring a new insight on this issue through the study of the mechanical behavior of the tribofilms at nanoscale.The aim of this work is to better understand the process of the friction reduction observed at macroscale when lamellar particles are associated to a low viscosity liquid. The tribofilms are formed from three different lamellar compounds, graphite, nickel thiophosphate NiPS3 and molybdenum disulfide MoS2. Two different kinds of tribofilms are studied: those formed with the solids particles only (dry tribofilms) and those formed in presence of liquid (wet tribofilms).The analyses of the tribological properties measured at nanoscale allow us to better understand the contribution of the individual and collective effects on friction reduction mechanims. We show that the reduction of the friction coefficient observed at macroscale is not related to the surface nanostructuration of the tribofilms neither to the decrease of the interaction energy between the sliding surfaces, but rather to collective effects of the liquid and the particles in the contact.

http://www.theses.fr/2014AGUY0706/document

Éditeur(s) : HAL CCSD
Résumé : This thesis compiles two distinct studies that both document the control of microstructures on rock seismic properties. The first part deals with the development of crystallographic preferred orientations (CPO) in the uppermost mantle associated with melt/fluid-rock interactions, recorded in peridotites xenoliths from the Japan sea back-arc basin. The microstructural and geochemical characteristics of the studied samples reveal that active spreading is associated to uppermost mantle deformation similar to that observed in the Oman ophiolite. At the onset of back-arc spreading, there are no strong interactions between melt percolation and deformation in comparison to continental rift zones, probably due to the relatively small size and short duration of the spreading event. The second part presents a unique database of plagioclase CPO from variously deformed mafic rocks. CPO are grouped in three main types; their characteristics as a function of deformation regime (magmatic or crystal-plastic) are outlined and discussed. Calculated seismic properties of gabbroic rocks show that anisotropy tends to increase as a function of fabric strength, although it is generally weak, due to the competing effect of olivine/clinopyroxene and plagioclase.
Cette thèse regroupe deux études distinctes, qui documentent le contrôle des microstructures sur les propriétés sismiques des roches. La première partie traite du développement des orientations préférentielles cristallographiques (OPC) dans le manteau supérieur, associé aux interactions liquide/magma-roche, enregistré dans des xénolites de péridotites du bassin d'arrière-arc de la mer du Japon. Les caractéristiques microstucturales et géochimiques des échantillons étudiés montrent que l'ouverture arrière-arc active est associée à une déformation du manteau supérieure similaire à celle observée dans l'ophiolite d'Oman. L'initiation de l'extension d'arrière-arc n'est pas associée à de fortes interactions entre percolation magmatique et déformation, en comparaison avec les zones de rifting continentales, probablement en raison des taille et durée relativement petites de l'épisode d'ouverture. La seconde partie présente une base de données unique d'OPC de plagioclase de roches mafiques plus ou moins déformées. Les OPC sont classées en 3 types principaux; leurs caractéristiques en fonction du régime de déformation (magmatique ou plastique) sont présentées et discutées. Les propriétés sismiques calculées des roches gabbroiques montrent que l'anisotropie tend à croitre avec l'intensité des fabriques, bien qu'elle soit généralement faible, en raison des effets opposés des olivines/clinopyroxènes et du plagioclase.
https://tel.archives-ouvertes.fr/tel-00795505

tel-00795505
https://tel.archives-ouvertes.fr/tel-00795505
https://tel.archives-ouvertes.fr/tel-00795505/document
https://tel.archives-ouvertes.fr/tel-00795505/file/Satsukawa_thesis_UM2.pdf

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Melting phase relations of model carbonated peridotite in the system CaO-MgO-Al2O3-SiO2-CO2 from 2 to 3 GPa are reported. Experimentally produced melts, which are model carbonatites, with approximately 36-40 wt % CaO, 12-17 wt % MgO, 0.2-1.5 wt % Al2O3, 1-4 wt % SiO2, and 40-42 wt % CO2 (carbon dioxide) are present at all pressures investigated. At 2.8 and 3 GPa, carbonatitic melts are seen experimentally at temperatures that are very close to the vapor-free (CO2) peridotite solidus and are found in equilibrium with forsterite, orthopyroxene, clinopyroxene, and garnet. Solidus phase relations with isobaric and pressure-temperature invariant points, defining the so-called carbonated peridotite solidus ledge, are also reported from 2.1 to 3 GPa. A divariant region exists from 2 to 2.6 GPa wherein two, compositionally different melts are present. In this region, these two melts, carbonatitic and silicate in composition, coexist with crystalline phase assemblage and free vapor. The silicate liquid has approximately 30-48 wt % SiO2 and approximately 6 to 20 wt % of dissolved CO2. The presence of carbonatitic and silicate liquids is interpreted to be due to liquid immiscibility. On the basis of melting phase relations reported here, we conclude that (a) the ledge is a feature along which model carbonatitic liquids are produced by reaction of silicates and CO2 vapor and (b) alkali-free carbonatites and silicate melts can form through melt unmixing at depths of ~60-80 km in the Earth's mantle.
ISSN: 0148-0227

hal-01053913
https://hal.archives-ouvertes.fr/hal-01053913
DOI : 10.1002/2013JB010913

Éditeur(s) : American Geophysical Union
Résumé : [1] Extreme weather events such as tropical cyclones are difficult to observe with conventional means. Satellite-based observations provide essential measurements of key parameters governing tropical cyclones. They are critical for short-term forecasting. Radiometers onboard the Defense Meteorological Satellite Program satellite series, WindSat and Tropical Rainfall Measuring Mission satellites, scatterometers onboard the ERS, ADEOS, and QuikScat satellites offer unprecedented synoptic observations of surface wind and atmospheric liquid water content, revealing the storm structures with good accuracy. However, satellite estimates do not provide direct measurements of geophysical parameters and can suffer from limitations linked to the sensors characteristics, such as the signal wavelength and polarization or the measurement incidence angle. For example, measurements at Ku band are strongly affected by rain. Still, each observing system can offer specific information that can be combined with the others. In particular, we highlight the capabilities of dual-frequency altimeter to provide very high resolution measurements of rain rate, surface wind speed, and wave characteristics. A method is proposed to obtain continuous along-track 5 km resolution measurements of these parameters in the tropical cyclone Isabel. The results shows that dual-frequency altimeters can provide useful information to complement and validate the operational fields provided by the atmospheric numerical models and by NOAA observing systems.
Journal of Geophysical Union - Research C - Oceans (0148-0227) (American Geophysical Union), 2006 , Vol. 111 , N. C1 , P. NIL_38-NIL_50

Droits : 2006 American Geophysical Union
http://archimer.ifremer.fr/doc/2006/publication-1033.pdf
DOI:10.1029/2005JC003068
http://archimer.ifremer.fr/doc/00000/1033/

Éditeur(s) : HAL CCSD
Résumé : International audience
The search for safe antimalarial compounds acting against asexual symptom-responsible stages and sexual transmission-responsible forms of Plasmodium species is one of the major challenges in malaria elimination programs. So far, among current drugs approved for human use, only primaquine has transmission-blocking activity. The discovery of small molecules targeting different Plasmodium falcip-arum life stages remains a priority in antimalarial drug research. In this context, several independent studies have recently reported antiplasmodial and transmission-blocking activities of commonly used stains, dyes and fluorescent probes against P. falciparum including chloroquine-resistant isolates. Herein we have studied the antimalarial activities of dyes with different scaffold and we report that the triar-ylmethane dye (TRAM) Brilliant green inhibits the growth of asexual stages (IC 50 2 mM) and has exflagellation-blocking activity (IC 50 800 nM) against P. falciparum reference strains (3D7, 7G8) and chloroquine-resistant clinical isolate (Q206). In a second step we have investigated the antiplasmodial activities of two polysulfonated triarylmethane food dyes. Green S (E142) is weakly active against P. falciparum asexual stage (IC 50 x 17 mM) whereas Patent Blue V (E131) is inactive in both antimalarial assays. By applying liquid chromatography techniques for the culture supernatant analysis after cell washings and lysis, we report the detection of Brilliant green in erythrocytes, the selective uptake of Green S (E142) by infected erythrocytes, whereas Patent Blue V (E131) could not be detected within non-infected and 3D7-infected erythrocytes. Overall, our results suggest that two polysulfonated food dyes might display different affinity with transporters or channels on infected RBC membrane.
International journal for parasitology. Drugs and drug resistance

Droits : http://creativecommons.org/licenses/by-nc-sa/
pasteur-01614675
https://hal-pasteur.archives-ouvertes.fr/pasteur-01614675
https://hal-pasteur.archives-ouvertes.fr/pasteur-01614675/document
https://hal-pasteur.archives-ouvertes.fr/pasteur-01614675/file/Leba%20LJ-article%20colorant-version%20publiee.pdf
DOI : 10.1016/j.ijpddr.2017.07.002

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Mid-ocean ridge basalts (MORBs) are the most abundant magmas produced on Earth. They are widely studied to infer mantle compositions and melting processes. However, MORB liquids are also the complex end-product of a variety of intra-crustal processes such as partial or fractional crystallization, melt–rock interaction, and contamination. Deciphering the relative contribution of these different processes is of first-order importance. Contamination at ocean crustal levels is likely, and may occur at magma chamber margins where fresh magmas can interact with previously hydrothermally altered rocks. Characterizing the composition of this crustal contaminant component is critical if we are to understand the relative importance of each component in the resulting MORB liquid.Here we present the results of experiments designed to reproduce the processes occurring at oceanic magma chamber roofs, where crustal contamination should be most extensive, by melting a representative sample of the sheeted dike complex. Anatectic melts thus produced are likely to represent the principal crustal contaminant in MORB. These melts were characterized for major and trace elements, showing B, Zr, Hf, and U enrichment, and Sr, Ti, and V depletion relative to original MORB liquids. In comparison to the starting material, relative element fractionations are observed in the anatectic melts, with enrichments of: U relative to Ba, Nb, and Th; LREE and MREE relative to Sr; and Zr–Hf relative to LREE. Bulk partition coefficients for element partitioning during magma chamber roof anatexis are derived and proposed as valuable tools for tracking MORB contamination.Comparison with natural samples from the East Pacific Rise and the Oman ophiolite shows that anatectic melts can crystallize in situ to form oceanic plagiogranite intrusions, and that residual assemblages associated with the hydrous partial melting stage are represented by hornfelsic dikes and enclaves (also named granoblastic basalts). We now recognize these as commonplace at the root of the sheeted dike complex both at present-day and fossil oceanic spreading centers.
ISSN: 0024-4937

hal-01115500
https://hal.archives-ouvertes.fr/hal-01115500
DOI : 10.1016/j.lithos.2014.05.018

Éditeur(s) : HAL CCSD Mineralogical Society of America
Résumé : International audience
To test if hydrogen incorporation by ionic diffusion can occur between a volatile-rich kimberlitic liquid and forsterite, results of high-pressure and high-temperature experiments using a piston-cylinder apparatus at 1200–1300 °C and 1 GPa for durations of 1 min, 5 h, and 23 h, are reported here. Kimberlitic liquid in the system CaO-MgO-Al2O3-SiO2-CO2-H2O and synthetic forsterite single crystals were chosen as a first simplification of the complex natural kimberlite composition. Unpolarized Fourier transform infrared spectroscopy was used to quantify the concentrations of OH in the crystallographically oriented forsterite. Scanning electron microscopy, electron backscattered diffraction, electron microprobe analyses, and transmission electron microscopy were performed to identify the run products. After 5 and 23 h, a forsterite overgrowth crystallized with the same orientation as the initial forsterite single crystal. The kimberlitic liquid has crystallized as micrometer-scale euhedral forsterite neocrystals with random crystallographic orientations, as well as a nanoscale aluminous phase and a calcic phase. Despite theoretical water-saturation of the system and long duration, none of the initial forsterite single crystals display signs of hydration such as hydrogen diffusion profile from the border toward the center of the crystal. Most likely, the presence of CO2 in the system has lowered the H2O fugacity to such an extent that there is no significant hydration of the starting forsterite single crystal or its overgrowth. Also, the presence of CO2 enhances rapid forsterite crystal growth. Forsterite growth rate is around 2 × 108 μm3/h at 1250 °C. These experimental results suggest a deep mantle origin of the high OH content found in natural mantle-derived xenoliths transported in kimberlites, as reported from the Kaapvaal craton. In agreement with previous studies, it also points out to the fact that significant hydration must take place in a CO2-poor environment.
ISSN: 0003-004X

hal-01217157
https://hal.archives-ouvertes.fr/hal-01217157
DOI : 10.2138/am-2015-5200

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Due to shallow penetration of millimeter waves (MMW) and convection in liquid medium surrounding cells, the problem of accurate assessment of local MMW heating in in vitro experiments remains unsolved. Conventional dosimetric MMW techniques, such as infrared imaging or fiber optic (FO) sensors, face several inherent limits. Here we propose a methodology for accurate local temperature measurement and subsequent specific absorption rate (SAR) retrieval using microscale thermocouples (TC). SAR was retrieved by fitting the measured initial temperature rise to the numerical solution of an equivalent thermal model. It was found that the accuracy of temperature measurement depends on thermosensor size, that is, the smaller TC, the more accurate the temperature measurement. SAR determined using TC with lead diameters of 25 and 75m demonstrated 98.5% and 80.4% match with computed SAR, respectively. However, both TC provided the same temperature rises in long run (>10min). FO probe failed to measure adequately local heating both for short and long exposures due to the relatively large size of the probe sensor (400m) and time constant (0.6s). Calculated SAR in the cell monolayer was almost two times lower than that in the surrounding liquid. It was shown that the impact of the cell monolayer on heating due to its small thickness (5 to 10m) can be considered as negligible. Moreover, we demonstrated the possibility of accurate measurement of MMW-induced thermal pulses (up to 10 degrees C) using 25m TC. Bioelectromagnetics. 38:11-21, 2017. (c) 2016 Wiley Periodicals, Inc.
ISSN: 0197-8462

hal-01436768
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01436768
DOI : 10.1002/bem.21999
PUBMED : 27571392

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : National audience
La détection d’Aspergillus dans le liquide bronchiolo-alvéolaire (LBA) est un des critères du diagnostic probable ou prouvé de l’aspergillose invasive (AI). Parallèlement à l’examen mycologique (ED et/ou culture) et à la détection de l’antigène galactomannane (GM) identifiés comme critères EORTC/MSG du diagnostic d’AI probable (de Pauw 2008), la PCR sur prélèvements pulmonaires est devenue un argument majeur du diagnostic de routine. Plusieurs méthodes d’amplification ont été publiées et l’objectif de ce travail était d’évaluer les performances de 2 cibles d’amplification : le gène mitochondrial d’A. fumigatus (AFmito) et l’ARN ribosomal 28S. Entre 01/2012 et 10/2015, 324 LBA ont été prospectivement collectés et analysés sur le plan mycologique (ED et culture) et ont bénéficié d’une détermination du GM (EIA Platelia assay Biorad, seuil à 1,0 si mesure isolée dans le LBA, ou 0,8 si associée à une mesure dans le sérum > 0,5) et d’une PCR AFmito. Puis rétrospectivement, un test PCR 28S a été effectué sur les ADN extraits disponibles (312/324). Selon les critères EORTC/MSG modifiés de 2008, les patients testés étaient classés comme suit : 1 AI prouvée, 47 AI probables et 11 AI possibles. Les autres patients étaient considérés comme 11 colonisés, et 256 non infectés. Les sensibilités du GM dans le LBA, de la PCR 28S et de la PCR AFmito étaient de 58 %, 61 % et 50 %, respectivement. La sensibilité de l’examen mycologique (ED ± culture) était de 33 %. La spécificité du GM dans le LBA, des PCR 28S et AFmito PCR et de la culture étaient de 94 %, 97 %, 97 % et 98 %, respectivement. Les valeurs prédictives négatives étaient de 93 %, 95 %, 92 % et 89 %, respectivement. La concordance entre les 2 PCR était de 97 % (cœfficient kappa 0,84), alors qu’elle était de 88 % (kappa 0,40) entre la PCR 28S et le GM dans le LBA, et de 88 % (kappa 0,43) entre la PCR AFmito PCR et le GM dans le LBA. En conclusion, la PCR 28S a présenté la meilleure performance pour la détection moléculaire d’Aspergillus dans le LBA comparativement à la PCR AFmito. La combinaison de la PCR 28S et de la détection du GM dans le LBA permet d’atteindre une sensibilité de 80 % tout en conservant une excellente spécificité (91 %)
ISSN: 1156-5233

hal-01334068
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01334068
DOI : 10.1016/j.mycmed.2016.04.048

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Heterocyclic aromatic amines (HAA) are formed in cooked meat, poultry and fish but also arise in tobacco smoke and exhaust gases. HAA are potential human carcinogens, which require metabolic activation to exert their genotoxicity. Human tissues can bioactivate HAA to produce reactive intermediates that bind to DNA. HAA DNA adduct formation occurs in human hepatocytes; however, the potential of HAA to form DNA adducts has not been investigated in human T lymphocytes. In this study, we investigated the ability of human T lymphocytes activated with PMA/Ionomycin or CD3/CD28 to express functional CYP1 activity and bioactivate three major HAA: 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-9H-pyrido[2,3-b]indole (AαC) to form DNA adducts. Adducts were measured by ultraperformance liquid chromatography-electrospray ionization/multistage scan mass spectrometry. The highest level of DNA adducts occurred for AαC (16 adducts per 109 nucleotides), followed by PhIP (9 adducts per 109 nucleotides). In contrast, DNA adducts formed from MeIQx and the structurally related aromatic amine 4-aminobiphenyl, a known human carcinogen, were below the limit of detection (< 3 adducts per 109 nucleotides). Moreover, we demonstrate that AαC is a potent inducer of CYP1A1 and CYP1B1 activity through a transcriptional mechanism involving the AhR pathway. Overall, our results highlight the capacity of activated human T lymphocytes to more efficiently bioactivate AαC to form DNA adducts than other prominent HAA or 4-ABP. Environ. Mol. Mutagen. 57:656-667, 2016.
ISSN: 0893-6692

hal-01400486
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01400486
DOI : 10.1002/em.22059
PUBMED : 27801952

Éditeur(s) : HAL CCSD Elsevier
Résumé : Primary arc melts may form through fluxed or adiabatic decompression melting in the mantle wedge, or via a combination of both processes. Major limitations to our understanding of the formation of primary arc melts stem from the fact that most arc lavas are aggregated blends of individual magma batches, further modified by differentiation processes in the sub-arc mantle lithosphere and overlying crust. Primary melt generation is thus masked by these types of second-stage processes. Magma-hosted peridotites sampled as xenoliths in subduction zone magmas are possible remnants of sub-arc mantle and magma generation processes, but are rarely sampled in active arcs. Published studies have emphasised the predominantly harzburgitic lithologies with particularly high modal orthopyroxene in these xenoliths; the former characteristic reflects the refractory nature of these materials consequent to extensive melt depletion of a lherzolitic protolith whereas the latter feature requires additional explanation.Here we present major and minor element data for pristine, mantle-derived, lava-hosted spinel-bearing harzburgite and dunite xenoliths and associated primitive melts from the active Kamchatka and Bismarck arcs. We show that these peridotite suites, and other mantle xenoliths sampled in circum-Pacific arcs, are a distinctive peridotite type not found in other tectonic settings, and are melting residues from hydrous melting of silica-enriched mantle sources. We explore the ability of experimental studies allied with mantle melting parameterisations (pMELTS, Petrolog3) to reproduce the compositions of these arc peridotites, and present a protolith (‘hybrid mantle wedge’) composition that satisfies the available constraints. The composition of peridotite xenoliths recovered from erupted arc magmas plausibly requires their formation initially via interaction of slab-derived components with refractory mantle prior to or during the formation of primary arc melts. The liquid compositions extracted from these hybrid sources are higher in normative quartz and hypersthene (i.e., they have a more silica-saturated character) in comparison with basalts derived from prior melt-depleted asthenospheric mantle beneath ridges. These primary arc melts range from silica-rich picrite to boninite and high-Mg basaltic andesite along a residual spinel harzburgite cotectic. Silica enrichment in the mantle sources of arc-related, subalkaline picrite-boninite-andesite suites coupled with the amount of water and depth of melting, are important for the formation of medium-Fe (‘calc-alkaline’) andesite-dacite-rhyolite suites, key lithologies forming the continental crust.
ISSN: 0016-7037

hal-01553520
https://hal.archives-ouvertes.fr/hal-01553520
DOI : 10.1016/j.gca.2016.09.030

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Meconium is the first fecal excretion of newborns. This complex accumulative matrix allows assessing the exposure of the fetus to xenobiotics during the last 6 months of pregnancy. To determine the eventual effect of fetal exposure to micropollutants in this matrix, robust and sensitive analytical methods must be developed. This article describes the method development of liquid chromatography methods coupled to triple quadrupole mass spectrometry for relevant pollutants. The 28 selected target compounds had different physico-chemical properties from very polar (glyphosate) to non-polar molecules (pyrethroids). Tests were performed with three different types of columns: reversed phase, ion exchange and HILIC. As a unique method could not be determined for the simultaneous analysis of all compounds, three columns were selected and suitable chromatographic methods were optimized. Similar results were noticed for the separation of the target compounds dissolved in either meconium extract or solvent for reversed phase and ion exchange columns. However, for HILIC, the matrix had a significant influence on the peak shape and robustness of the method. Finally, the analytical methods were applied to “real” meconium samples.
ISSN: 0039-9140

hal-01141722
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01141722
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01141722/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01141722/file/Development%20of%20liquid%20chromatography%20%281%29.pdf
PUBMED : 25863396

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Massif du Sud is a large ophiolitic complex that crops out in the southern region of New Caledonia (SW Pacific). It is dominated by harzburgite tectonite that locally shows a transitional gradation to massive dunite up section. Clinopyroxene, orthopyroxene and plagioclase progressively appear in dunite up to the transition to layered wehrlite and orthopyroxene-gabbro. The dunite-wehrlite and wehrlite-gabbro contacts are parallel and the latter defines the paleo-Moho.;Highly depleted modal, mineral and bulk rock compositions indicate that harzburgites are residues after high degrees (20-30%) of partial melting mainly in the spinet-stability field. Their relative enrichment in HFSE, LREE and MREE is due to re-equilibration of melting residues with percolating melts. Dunite formed in the Moho transition zone by reaction between residual mantle harzburgite and olivine-saturated melts that led to pyroxene dissolution and olivine precipitation. Rare clinopyroxene and plagioclase crystallized in interstitial melt pores of dunite from primitive, low-TiO2, ultra-depleted liquids with a geochemical signature transitional between those of island arc tholeiites and boninites.;Ascending batches of relatively high-SiO2, ultra-depleted melts migrated through the Moho transition zone and generated wehrlite by olivine dissolution and crystallization of clinopyroxene, orthopyroxene and plagioclase in variable amounts. These liquids were more evolved and were produced by higher degrees of melting or from a more depleted source compared with melts that locally crystallized clinopyroxene in dunite. Ultra-depleted magmas, non-cogenetic with those that formed the Moho transition zone, ascended to the lower crust and generated gabbroic cumulates with subduction-related affinity. Thus, the ultramafic and mafic rocks in the Moho transition zone and lower crust of the Massif du Sud ophiolite are not products of fractional crystallization from a single magma-type but are the result of migration and accumulation of different melts in a multi-stage evolution. The record of high partial melting in the mantle section, and migration and accumulation of ultra-depleted subduction-related melts in the Moho transition zone and lower crust support that the Massif du Sud ophiolite is a portion of forearc lithosphere generated in an extensional regime during the early phases of the subduction zone evolution. Our results show the existence of different types of ultra-depleted melt compositions arriving at the Moho transition zone and lower crust of an infant intraoceanic paleo-arc. Ultra-depleted melts may thus be a significant component of the melt budget generated in oceanic spreading forearcs prior to aggregation and mixing of a large range of melt compositions in the crust.
ISSN: 0009-2541

hal-00429333
https://hal.archives-ouvertes.fr/hal-00429333
DOI : 10.1016/j.chemgeo.2009.06.004

Éditeur(s) : Gauthier-Villars
Résumé : Preparative pyrolysis followed by liquid chromatographic separation and gas chromatography of hydrocarbons (Pyrolysis-LC-GC) were used to study the participation of terrestrial and/or aquatic compounds in the formation of humic substances in sediments. Analyses performed on humic substances from recent sediments sampled in the Elorn river estuary (France) show that these substances are similar in many respects to other lacustrine or marine humic substances, with regard, for instance, to their high nitrogen and sulphur content and their low aromaticity. Mass balances on pyrolysis products and group composition of the C-14+ fraction of the pyrolysates were performed. The distribution of the total alkane and alkene fraction, isocyclo alkanes and alkenes from these humic acid pyrolysates was compared to that of various reference humic acid pyrolysates. The biomarker study (distribution and hopanes/steranes ratios from humic acid pyrolysates) confirms the participation throughout the estuary of algal precursors in the formation of the studied compounds, irrespective of the location of the sampling zone (upstream, median or downstream part of the estuary).
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1994 , Vol. 17 , N. 1 , P. 43-53

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00099/21029/18655.pdf
http://archimer.ifremer.fr/doc/00099/21029/