Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
BackgroundSince the discovery of thioautotrophic bacterial symbiosis in the giant tubeworm Riftia pachyptila, there has been great impetus to investigate such partnerships in other invertebrates. In this study, we present the occurrence of a sulphur-oxidizing symbiosis in a metazoan belonging to the phylum Cnidaria in which this event has never been described previously.Methodology/Principal FindingsScanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) observations and Energy-dispersive X-ray spectroscopy (EDXs) analysis, were employed to unveil the presence of prokaryotes population bearing elemental sulphur granules, growing on the body surface of the metazoan. Phylogenetic assessments were also undertaken to identify this invertebrate and microorganisms in thiotrophic symbiosis. Our results showed the occurrence of a thiotrophic symbiosis in a cnidarian identified as Cladonema sp.Conclusions/SignificanceThis is the first report describing the occurrence of a sulphur-oxidizing symbiosis in a cnidarian. Furthermore, of the two adult morphologies, the polyp and medusa, this mutualistic association was found restricted to the polyp form of Cladonema sp.
ISSN: 1932-6203

hal-01203244
https://hal.univ-antilles.fr/hal-01203244
https://hal.univ-antilles.fr/hal-01203244/document
https://hal.univ-antilles.fr/hal-01203244/file/Plos%20Cladonema%20%281%29.pdf
https://hal.univ-antilles.fr/hal-01203244/file/Plos%20Cladonema.pdf

Éditeur(s) : HAL CCSD
Résumé : The use of Xylopia frutescens extract as a C38 steel corrosion inhibitor in 1 M HCl solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. Potentiodynamic polarization curves indicated that Xylopia frutescens extract behaves as mixed-type inhibitor. Graphical methods are illustrated by synthetic data to determine the parameter of CPE (α, Q). The adsorption of the extract constituents was further discussed in view of Langmuir adsorption isotherm. The effect of temperature on the inhibition efficiency was investigated using EIS and potentiodynamic polarization. SEM and EDX observations confirmed the existence of protective inhibitor film on metal surface.
ISSN: 1938-6737

hal-01304527
https://hal.archives-ouvertes.fr/hal-01304527
DOI : 10.1149/06426.0001ecst
PRODINRA : 351608

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
Although they are famous among Earth scientists, the Lherz peridotites are exposed within geological formations of the North Pyrenean Zone (NPZ) still lacking detailed investigations. Our study focuses on the metasediments of the Aulus basin hosting the Lherz peridotite body and associated ultramafic fragments of smaller size. The new data set comprises of structural analysis and detailed geological mapping of the massive Mesozoic marbles that form the prerift sequence typical of the NPZ and of the ultramafic-rich clastic breccia formations surrounding the peridotite bodies. The massive marbles display an evolution from hot and ductile to cold and brittle deformation, indicative of an exhumation process ending with the sedimentary reworking of both the deformed Mesozoic metasediments and the exhumed ultramafic rocks. Crystal Preferred Orientations (CPO) measured in the marbles support a deformation mechanism by dislocation creep of calcite, which is dominant between 400 8C and 600 8C; these deformation temperatures are within the range determined earlier by Clerc et al. (2015), using RSCM (Raman Spectroscopy of Carbonaceous Material) geothermometry. As a consequence, we better describe the transition from ductile to brittle deformation in the prerift marbles and clarify the origin of the syn-rift breccias. Due to continuous exhumation along detachments' faults, the brecciated metamorphic carbonates of the prerift NPZ sedimentary cover were passively uplifted towards shallower levels and progressively unroofed, while transported passively on the back of the exhumed ultramafic footwall. These results are consistent with the recent interpretations of the North Pyrenean peridotites as remnants of subcontinental mantle rocks exhumed within the pre-Pyrenean rift system. We emphasize the importance of tectonic decoupling between the Mesozoic sedimentary cover and the Palaeozoic basement, which leads to the juxtaposition of metamorphosed and deformed Mesozoic Please cite this article in press as: Lagabrielle Y, et al. Very high geothermal gradient during mantle exhumation recorded in mylonitic marbles and carbonate breccias from a Mesozoic Pyrenean palaeomargin (Lherz area, North Pyrenean Zone, France). C. R. Geoscience (2016), http://dx.
ISSN: 1631-0713

Droits : http://creativecommons.org/licenses/by-nc-nd/
insu-01285079
https://hal-insu.archives-ouvertes.fr/insu-01285079
https://hal-insu.archives-ouvertes.fr/insu-01285079/document
https://hal-insu.archives-ouvertes.fr/insu-01285079/file/1-s2.0-S1631071315002060-main.pdf
DOI : 10.1016/j.crte.2015.11.004

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We present archeointensity data carried out on pieces of incense burners from the ancient Maya city of Palenque, Chiapas, Mexico, covering much of the Mesoamerican Classic period, from A.D. 400 to A.D. 850. We worked on pieces from 24 incense burners encompassing the five Classic ceramic phases of Palenque: Motiepa (A.D. 400-500), Cascadas (A.D. 500-600), Otulum (A.D. 600-700), Murcielagos (A.D. 700-770), and Balunté (A.D. 770-850). All the samples come from highly elaborate, flanged pedestal of incense burners that are undoubtedly assigned to a ceramic phase by means of their iconographic, morphological and stylistic analyses. Archeointensity measurements were performed with the Thellier-Thellier's method on pre-selected samples by means of their magnetic properties. We obtained archeointensities of very good technical quality from 19 of 24 pieces, allowing the determination of a precise mean value for each ceramic phase, between View the MathML source29.1±0.9μT and View the MathML source32.5±1.2μT. The firing temperatures of ceramics were estimated with Mössbauer spectroscopy between 700 °C and 1000 °C. These values ensure that a full thermo-remanent magnetization was acquired during the original heating. Our results suggest a relative stability of the field intensity during more than 400 years in this area. The abundance of archeological material in Mesoamerica contrasts with the small amount of archeomagnetic data available that are, in addition, of uneven quality. Thus, it is not possible to establish a trend of intensity variations in Mesoamerica, even using the global databases and secular variation predictions from global models. In this context, our high technical quality data represent a strong constraint for the Mesoamerican secular variation curve during the first millennium AD. The corresponding Virtual Axial Dipole Moments (VADM) are substantially smaller than the ones predicted by the last global geomagnetic models CALS3k.4, suggesting the need for additional data to develop a regional model and a reference curve for Mesoamerica.
ISSN: 0012-821X

hal-00828696
https://hal.archives-ouvertes.fr/hal-00828696
DOI : 10.1016/j.epsl.2012.12.035

Résumé : Ce travail porte sur l'inhibition de l'acier C38 en milieu acide HC1 1M par les extraits alcaloïdes issus de 2 plantes : aspidosperma album et geissospermum laeve. Biodégradables et respectueux de l'environnement, les alcaloïdes pourraient être utilisés temporairement pour prévenir la corrosion de l'acier C39 avec des taux d'inhibition supérieurs à ceux décrits dans la littérature. Dans la première partie du travail, l'influence de la concentration, du temps d'immersion et de la température sur le processus de corrosion de l'acier C38 en milieu HC1 1M en absence de polarisation et spectroscopie d'impédance électrochimique. Les analyses de surface effectuées par microscopie électronique a balayage montrent la présence d'une couche constituée d'un mélange d'oxyde de fer incorporant les alcaloïdes et qui conduit à la diminution de la vitesse de corrosion. La deuxième partie de ce travail a été consacrée à l'isolement des alcaloïdes des deux extraits afin de déterminer le ou les alcaloïdes responsables de l'activité inhibitrice et ainsi remonter aux mécanismes d’adsorption. Il a été montré que l'alcaloïde majoritaire des extraits est responsable de l'inhibition
This work is devoted to the corrosion inhibition of C38 steel in 1M HCL acid medium by alkaloids extracts from two plants : aspidosperma album and geissospermum laeve. Biodegradable and environmentally friendly, alkaloids could be used temporarily to prevent the corrosion of C38 steel with inhibition rates higher than those described in the literature. The first part of this work studies the influence of concentration, immersion time and temperature on the corrosion inhibitor by electrochemical measurements : polarization curves and electrochemical impedance spectroscopy. The surface analyses conducted by scanning electron microscopy showed the presence of a layer composed of an iron oxide mixture incorporating alkaloids extracts and which leads to the decrease of the corrosion rate. The second part of this work was devoted to the isolation of alkaloids of two extracts in order to determine the alkaloids responsible of the inhibitory activity and thus to determine the adsorption mechanisms. It was showed that the major alkaloids of two extracts is responsible of the inhibition activity

http://www.theses.fr/2013AGUY0578/document

Éditeur(s) : HAL CCSD
Résumé : International audience
International journal of electrochemical science

hal-01109736
https://hal-agroparistech.archives-ouvertes.fr/hal-01109736

Éditeur(s) : HAL CCSD Mineralogical Society of America
Résumé : International audience
Crystallization experiments were conducted at 200 MPa to determine the effect of small amounts of H2O on the liquidus temperature of basaltic melts in which plagioclase is the liquidus phase. The H2O concentrations in the quenched glasses, determined by infrared spectroscopy and Karl-Fischer titration, ranged from 0.02 to 4.2 wt% H2O. The dry liquidus temperature at 200 MPa was estimated from experiments at 1 atm (H2O-free) and from the known pressure dependence of plagioclase crystallization temperature. The effect of water (expressed as wt% H2O) on the plagioclase liquidus temperature is nonlinear and diminishing with increasing melt H2O concentrations. According to our new experimental data, it can be empirically predicted with following equation: Formula where CH2O is the water concentration in the melt (wt%), TDRY, and TWET are plagioclase crystallization temperatures in water-free and water-bearing systems, respectively. The relationship between CH2O and liquidus temperature worked out in this study is valid for a range of basaltic compositions, ranging from high-alumina basalts to basaltic andesites. The combination of the empirical equation predicting the liquidus depression of plagioclase with previous models predicting the olivine liquidus curve is useful to determine the liquidus temperature in various H2O-bearing basaltic systems in which either plagioclase or olivine is the liquidus phase.
ISSN: 0003-004X

hal-00757600
https://hal.archives-ouvertes.fr/hal-00757600
DOI : 10.2138/am.2012.4100

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : Four new sesquiterpene alkaloids (1-4) with a β-dihydroagrofuran skeleton and a new triterpenoid (5) were isolated from an ethyl acetate extract of Maytenus oblongata stems. Their structures were elucidated using 1D and 2D NMR spectroscopy as well as MS and ECD experiments. The M. oblongata stem EtOAc extract and the pure compounds isolated were tested for larvicidal activity against Aedes aegypti under laboratory conditions, and compounds 2 and 3 were found to be active.
ISSN: 0163-3864

hal-01603411
https://hal.archives-ouvertes.fr/hal-01603411
DOI : 10.1021/acs.jnatprod.6b00850
PUBMED : 28186749
PRODINRA : 406747