Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The interplay between fault zone cataclasis and cementation is important since both processes can drastically reduce the permeability of faults in porous sandstones. Yet the prediction of fault cementation in high-porosity sandstone reservoirs remains elusive. Nevertheless, this process has rarely been investigated in shallowly buried faults (<2 km; T°<80 °C) where its sealing capacity could be acquired early in the geological history of a reservoir. In this paper, the macro- and microscopic analysis of a fault zone in the porous Cenomanian quartz arenite sands of Provence (France) shows that silica diagenesis occurs in the most intensely-deformed cataclastic parts of the fault zone. This fault zone shows 19–48% of its total thickness occupied by low-porosity quartz-cemented cataclastic shear bands whose porosities range from 0 – ca. 5%. The analysis of the weathering profile around the fault zone reveals the presence of groundwater silcretes in the form of tabular, tightly silicified concretions cross-cut by the fault. Detailed transmitted light, cold-cathodoluminescence and scanning electron microscopy analyses of the silica cements (from the fault and the silcrete) reveal that all the silica cements originate from groundwater diagenetic processes. This study therefore shows that silica cementation can occur specifically in fault zones and as groundwater silcrete in the shallow context of a groundwater system, generated at the vicinity of an erosional unconformity.
ISSN: 0191-8141

hal-01278286
https://hal.archives-ouvertes.fr/hal-01278286
DOI : 10.1016/j.jsg.2015.10.001

Éditeur(s) : HAL CCSD IOP Publishing
Résumé : We present the results of an inter-laboratory comparison of EPMA analysis at low voltage (5-6 kV) of three monophasic alloy steel samples. The aim of the work was to obtain an estimate of the present situation of low-voltage analysis of steel and identify needs for improvement. EPMA analyses of the samples were conducted by seven participant groups using electron microprobes and scanning electron microscopes of different kind, equipped with wavelength- and/or energy-dispersive X-ray spectrometers, and employing their own methodology of analysis. The results using WDS showed essentially an underestimation of the Cr contents, with relative deviations from the reference values ranging from -0.7 % to -17 %, and an overestimation of Fe and Ni, with relative deviations from the reference composition ranging from -4 % to +30 %, and from +14 % to +42 %, respectively. The relative deviations obtained by using EDS showed larger scatter, ranging from -16 % to +54 % for Cr, -0.4 % to +66 % for Fe and from +13 % to +90 % for Ni. Reasons for the differences observed and the scatter of results are discussed.
ISSN: 1757-8981

hal-00813999
https://hal.archives-ouvertes.fr/hal-00813999
DOI : 10.1088/1757-899X/32/1/012014

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Anisotropy of low-field magnetic susceptibility (AMS) of basaltic lava flows can give some clues about post-emplacement tilting occurring in volcanic sequences. Such a study has been carried out on a sequence of 19 successive lava flows from Kerguelen Archipelago. Surprisingly, two different patterns were observed. The first one - herein called normal fabric - is consistent with the lava-flow direction inferred from geological observations, whereas the second one observed for about 70 per cent of the analysed samples - herein called abnormal fabric - appears to be unrelated to the shear history of the lava flows during their emplacements. These abnormal fabrics are not strictly inverse fabric but seem to have a more complex origin. The unusual nature of these abnormal fabrics has been confirmed by lattice preferred orientation of plagioclases obtained from high-resolution electron backscattered diffraction measurements. The aim of this study is to propose a physical interpretation of these fabrics. A first step in our understanding was to clearly identify the nature and the magnetic properties of the Fe-Ti oxides assemblage. Thus, we present a comprehensive rock magnetic analysis relying on low- and high-temperature thermomagnetic curves (K-T), crossover diagrams, first-order reversal curves, ore-microscopy, Mössbauer measurements and electron backscattered images. We found that in the present case the abnormal fabrics are probably linked to a mixture of prevailing single domain (SD) strongly interacting grains population and a subsidiary multidomain grains population. SD grains are identified as small magnetite crystallized within the interstitial glass in globular aggregates along the silicate framework. Then a question arises: to what extent such SD interacting grains in globular aggregates can affect the magnetic susceptibility and its anisotropy? To answer this question, we developed a physical model in which the total energy density of an SD grain with an uniaxial anisotropy is minimized. In this model, the distribution function of the direction of the magnetic interaction field is comprised between two boundary states. It is either isotropic, which formally corresponds to the thermal demagnetized state, or it is ordered, which formally corresponds to the Alternative Field demagnetized state. We show that in both cases the degree of anisotropy decreases as the interaction field increases. Thus, we conclude that the abnormal fabric encountered in this study can be simply explained by strong magnetostatic interactions that would explain the large scattering of AMS often observed in basaltic lava flows.
ISSN: 0956-540X

hal-00716449
https://hal.archives-ouvertes.fr/hal-00716449
https://hal.archives-ouvertes.fr/hal-00716449/document
https://hal.archives-ouvertes.fr/hal-00716449/file/gji-S-12-HAL.pdf
DOI : 10.1111/J.1365-246X.2012.05421.X

Éditeur(s) : HAL CCSD American Institute of Physics
Résumé : International audience
Laser-induced periodic surface structures (LIPSS) were formed on Cu/Si or Cu/glass thin films using Nd:YAG laser beam (40 ps, 10Hz, and 30mJ/cm2). The study of ablation threshold is always achieved over melting when the variation of the number of pulses increases from 1 to 1000. But the incubation effect is leading to reduce the threshold of melting as increasing the number of laser pulse. Also, real time reflectivity signals exhibit typical behavior to stress the formation of a liquid phase during the laser-processing regime and helps to determine the threshold of soft ablation.Atomic Force Microscopy (AFM) analyses have shown the topology of the micro-crater containing regular spikes with different height. Transmission Electron Microscopy (TEM) allows finally to show three distinguished zones in the close region of isolated protrusions. The central zone is a typical crystallized area of few nanometers surrounded by a mixed poly-crystalline and amorphous area. Finally, in the region far from the protrusion zone, Cu film shows an amorphous structure. The real time reflectivity, AFM, and HR-TEM analyses evidence the formation of a liquid phaseduring the LIPSS formation in the picosecond regime. VC 2015 AIP Publishing LLC
ISSN: 0003-6951

hal-01226065
https://hal.archives-ouvertes.fr/hal-01226065
DOI : 10.1063/1.4935413

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Beggiatoaceae, giant sulphur-oxidizing bacteria, are well known to occur in cold and temperatewaters, as well as hydrothermal vents, where they form dense mats on the floor.However, they have never been described in tropical marine mangroves. Here, we describetwo new species of benthic Beggiatoaceae colonizing a marine mangrove adjacent to mangroveroots. We combined phylogenetic and lipid analysis with electron microscopy in orderto describe these organisms. Furthermore, oxygen and sulphide measurements in and exsitu were performed in a mesocosm to characterize their environment. Based on this, two new species, Candidatus Maribeggiatoa sp. and Candidatus Isobeggiatoa sp. inhabiting tropical marine mangroves in Guadeloupe were identified. The species identified as CandidatusMaribeggiatoa group suggests that this genus could harbour a third cluster with organisms ranging from 60 to 120 μm in diameter. This is also the first description of an Isobeggiatoa species outside of Arctic and temperate waters. The multiphasic approach also gives information about the environment and indications for the metabolism of these bacteria. Our study shows the widespread occurrence of members of Beggiatoaceae family and provides new insight in their potential role in shallow-water marine sulphide-rich environments such as mangroves.
ISSN: 1932-6203

hal-01205641
https://hal.univ-antilles.fr/hal-01205641
https://hal.univ-antilles.fr/hal-01205641/document
https://hal.univ-antilles.fr/hal-01205641/file/Beggiatoa%20Plosone2015.pdf
DOI : 10.1371/journal.pone.0117832

Éditeur(s) : HAL CCSD Mineralogical Society of America
Résumé : International audience
In situ mineralization of CO2 in ultramafic rock-hosted aquifers is one of the promising solutions for decreasing CO2 concentrations in the atmosphere. Naturally altered ultramafic rocks suggest that carbonation processes are controlled by local heterogeneities in the structure of the rock and fluid transport at the water-rock interfaces. We studied the role of rock crystallographic anisotropy relative to the global fluid flow direction on the mineralization of CO2 by means of electron microscope analyses from the macro- to the micrometer scale (EBSD-FIB). The sample used for the measurements was a hot pressed olivine core percolated by water enriched in CO2 (pCO2 = 10 MPa) at 180 °C. During the percolation experiment, olivine was dissolved and two types of carbonates, dolomite, and magnesite, were precipitated on olivine surfaces. The results showed that the dissolution of olivine is controlled by its crystallographic properties as shown by the development of etch-pits only on the (010)ol planes and with elongated shapes parallel to the [010]ol axes. In contrast, the precipitation of carbonates is governed by hydrodynamic properties. Carbonates are heterogeneously distributed in the percolated rock. They are mainly located along the moderate (for dolomite) and the minor (for magnesite) flow paths, both oriented parallel to the principal fluid flow direction, which allow carbonates to be supplied with divalent cations (e.g., Ca2+, Mg2+, and Fe2+). In these flow paths, carbonate growth is systematically oriented normal to the flow that facilitates the development of chemical gradients with cationic supersaturation conditions for carbonate precipitation near the walls.In natural systems, the (010)ol planes are parallel to the Moho and the (100)ol planes are vertical; our study suggests that flow of CO2-rich fluids will induce precipitation of carbonates localized along, and preferentially clogging, vertical flow paths while favoring olivine dissolution along horizontal fluid pathways. This dual control of structure and fluid flow on carbonation mechanisms could be an important parameter allowing sustainable CO2 storage in peridotites, while limiting the risks of leakage toward the surface.
ISSN: 0003-004X

hal-01143393
https://hal.archives-ouvertes.fr/hal-01143393
DOI : 10.2138/am-2015-4913

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Carbonation of peridotite is a widespread process in nature, with emerging societal and environmental implications through geological storage of CO2. We studied the micro- and nano-scale structures associated with the carbonation of peridotite pervaded by a CO2-rich water and the induced changes of its hydrodynamic properties. Focused ion beam (FIB) nanotomography was coupled with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. An experimental sample of dunite core percolated by a CO2-rich fluid (pCO2 = 11 MPa) at 160 °C was compared with a naturally carbonated sample from the Atlantic Ridge (Exp. IODP 304). Results of the 8-days percolation experiment show continuous alteration of olivine into magnesite locally associated with a poorly crystalline serpentine-type mineral referred to as proto-serpentine. The experiment is also characterized by an overall decrease in rock porosity (from 7.7 to 6.4%) and permeability (from 8.5 × 10− 16 to 1.7 × 10− 16 m2). The primary inter-granular porosity (1 to 10 μm) is progressively filled with magnesite, leading to the overall decrease of permeability. At the same time, a secondary small-scale porosity (10 nm to 1 μm) is created at the tip of the dissolution features along the (010) cleavage planes of olivine grains. Carbonate crystals grow within these etch-pit structures behind the dissolution front. Dissolution and precipitation occur at a relative rate that maintains the secondary porosity over the timescale of the experiment (i.e. carbonate growth has to be the slowest one). This process is interpreted as an interface coupled dissolution-precipitation mechanism of olivine carbonation. Proto-serpentine is only formed in highly reduced flow areas, such as small olivine etch-pits (10 to 500 nm wide), which are more isolated from CO2 input. SEM-FIB analyses show the 3D preferential orientation of the dissolution-precipitation planes within a given olivine grain. It suggests the formation of lateral connections between the etch-pits (infra-micrometric “channels”) providing access to reactants and removing reaction products at the reaction sites. The experimental results show that olivine dissolution and magnesite precipitation converge to a quasi-steady state resulting in a constant carbonation rate controlled by reaction kinetics and not by mass transfer for this flow regime. The system self-regulates, independently of the porosity change at least during this incipient stage of olivine carbonation. Similar textures are observed in natural samples collected at 170 m-depth in the vicinity of veinlets driving late fluids down into the cooling oceanic lithosphere. This suggests that similar mechanisms are active in nature and can play an important role in the late, low temperature alteration stages of fractured peridotite. These results also highlight the critical role of nm-scale spatial arrangement of dissolution and precipitation features on mass transfers and on the sustainability of olivine carbonation through coupled dissolution-precipitation processes.
ISSN: 0009-2541

hal-01684733
https://hal.archives-ouvertes.fr/hal-01684733
DOI : 10.1016/j.chemgeo.2017.11.013

Éditeur(s) : HAL CCSD Geological Society of London
Résumé : This paper presents the background for the calculation of physical properties of an aggregate from constituent crystal properties and the texture of the aggregate in a coherent manner. Emphasis is placed on the important tensor properties of 2nd and 4th rank with applications in rock deformation, structural geology, geodynamics and geophysics. We cover texture information that comes from pole figure diffraction and single orientation measurements (electron backscattered diffraction or EBSD, electron channelling pattern, Laue pattern, optical microscope universal-stage). In particular, we provide explicit formulae for the calculation of the averaged tensor from individual orientations or from an orientation distribution function (ODF). For the latter we consider numerical integration and an approach based on the expansion into spherical harmonics. This paper also serves as a reference paper for the mathematical tensor capabilities of the texture analysis software MTEX, which is a comprehensive, freely available MatLab toolbox that covers a wide range of problems in quantitative texture analysis, for example, ODF modelling, pole figure to ODF inversion, EBSD data analysis and grain detection. MTEX offers a programming interface which allows the processing of involved research problems as well as highly customizable visualization capabilities; MTEX is therefore ideal for presentations, publications and teaching demonstrations.
Deformation Mechanisms, Rheology and Tectonics: Microstructures, Mechanics and Anisotropy

hal-00688833
https://hal.archives-ouvertes.fr/hal-00688833

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Prediction of ice mass flow and associated dynamics is pivotal at a time of climate change. Ice flow is dominantly accommodated by the motion of crystal defects – the dislocations. In the specific case of ice, their observation is not always accessible by means of the classical tools such as X-ray diffraction or transmission electron microscopy (TEM). Part of the dislocation population, the geometrically necessary dislocations (GNDs) can nevertheless be constrained using crystal orientation measurements via electron backscattering diffraction (EBSD) associated with appropriate analyses based on the Nye (1950) approach. The present study uses the Weighted Burgers Vectors, a reduced formulation of the Nye theory that enables the characterization of GNDs. Applied to ice, this method documents, for the first time, the presence of dislocations with non-basal or Burgers vectors. These or dislocations represent up to of the GNDs observed in laboratory-deformed ice samples. Our findings offer a more complex and comprehensive picture of the key plasticity processes responsible for polycrystalline ice creep and provide better constraints on the constitutive mechanical laws implemented in ice sheet flow models used to predict the response of Earth ice masses to climate change.
ISSN: 0012-821X

hal-01685565
https://hal.archives-ouvertes.fr/hal-01685565
DOI : 10.1016/j.epsl.2017.06.020

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The New Jersey continental shelf extends 150 km off the shoreline. During IODP Expedition 313, siliciclastic deposits of late Eocene to late Pleistocene age were drilled down to 631, 669 and 755 m below seafloor at sites 27A, 28A and 29A respectively in very shallow waters (33.5 to 36 m depth). Pore water salinities display multilayered brackish-salty-brine units 10 to 170 m thick, where low-salinity water is preferentially stored in fine-grained sediments. The sharp boundaries of these buried aquifers are often marked by cemented layers a few centimetres thick. The mineralogy and scanning electron microscope observations of these layers show two phases of cementation by authigenic minerals: (1) the early carbonate cement is frequently associated with pyrite, and (2) the late silicate cement infills the residual porosity. The isotopic compositions of the carbonate cements vary widely: −2.4 < δ¹⁸O ‰ VPDB < +2.8; −15.1 < δ¹³C ‰ VPDB < +15.6. The δ¹⁸O values indicate that the carbonate cements precipitated with pore waters comprising variable mixtures of seawater and ¹⁸O-depleted fresh water originating from submarine groundwater discharge. The δ¹³C values of the carbonate cements are related to organic matter diagenesis, providing ¹³C-depleted dissolved inorganic carbon during bacterial sulphate reduction and anaerobic oxidation of methane, and ¹³C-rich dissolved inorganic carbon during methanogenesis. The diagenetic cementation processes included chemical weathering of reactive silicate minerals by the CO²-rich pore waters issued from organic matter diagenesis that released bicarbonate, cations and dissolved silica, which were further precipitated as carbonate and silicate cements. The estimated range of temperature (18±4 °C) during carbonate precipitation is consistent with carbonate cementation at moderate burial depths; however, silicate cementation occurred later during diagenesis at deeper burial depths.
ISSN: 0276-0460

hal-01559985
https://hal.archives-ouvertes.fr/hal-01559985
DOI : 10.1007/s00367-017-0506-6

Éditeur(s) : HAL CCSD
Résumé : International audience
Millimeter waves (MMW) will be increasingly used for future wireless telecommunications. Previous studies on skin keratinocytes showed that MMW could impact the mRNA expression of Transient Receptor Potential cation channel subfamily Vanilloid, member 2 (TRPV2). Here, we investigated the effect of MMW exposure on this marker, as well as on other membrane receptors such as Transient Receptor Potential cation channel subfamily Vanilloid, member 1 (TRPV1) and purinergic receptor P2X, ligand-gated ion channel, 3 (P2 × 3). We exposed the Neuroscreen-1 cell line (a PC12 subclone), in order to evaluate if acute MMW exposures could impact expression of these membrane receptors at the protein level. Proteotoxic stress-related chaperone protein Heat Shock Protein 70 (HSP70) expression level was also assessed. We used an original high-content screening approach, based on fluorescence microscopy, to allow cell-by-cell analysis and to detect any cell sub-population responding to exposure. Immunocytochemistry was done after 24 h MMW exposure of cells at 60.4 GHz, with an incident power density of 10 mW/cm2. Our results showed no impact of MMW exposure on protein expressions of HSP70, TRPV1, TRPV2, and P2 × 3. Moreover, no specific cell sub-populations were found to express one of the studied markers at a different level, compared to the rest of the cell populations. However, a slight insignificant increase in HSP70 expression and an increase in protein expression variability within cell population were observed in exposed cells, but controls showed that this was related to thermal effect. Bioelectromagnetics. 37:444–454, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
Bioelectromagnetics

hal-01371963
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01371963
DOI : 10.1002/bem.21995
PUBMED : 27483046

Éditeur(s) : HAL CCSD Paris : Muséum national d'histoire naturelle
Résumé : International audience
En prenant comme exemple le gobie à crête Lophogobius cyprinoides (Pallas, 1770), les éléments (canaux et pores et canaux sensoriels muqueux, et papilles sensorielles) composant le système latéral (SL) ont été observés selon plusieurs méthodes de préparation. Des échantillons ont été préparés soit pour observation en microscopie électronique à balayage (MEB), soit pour observation en microscopie photonique après immersion dans du liquide de fixation "Bouin Hollande" ou dans du formol à 4% en eau de mer avant coloration au KMnO4 (technique traditionnelle). Les résultats obtenus avec le MEB et le Bouin Hollande sont meilleurs qu'avec la méthode traditionnelle et présentent une plus grande reproductibilité. Bien que moins rapide et plus onéreuse, la méthode d'évaluation au MEB offre une finesse d'observation qui n'est pas obtenue au Bouin Hollande en raison de la limite du grandissement en microscopie optique. Si l'ultrastructure des papilles sensorielles ne peut être observable qu'au MEB, le SL des poissons Gobiidae peut être facilement étudié de manière approfondie avec les deux méthodologies proposées dans ce travail. Elles sont à préconiser car plus fiables que la technique traditionnelle consistant en une immersion dans une solution de permanganate de potassium et d'acide sulfurique. Celle-ci détériore partiellement les papilles sensorielles du SL rendant son analyse plus délicate.
ISSN: 0399-0974

hal-00749624
https://hal.univ-antilles.fr/hal-00749624

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
In marine invertebrates that acquire their symbionts from the environment, these are generally only taken up during early developmental stages. In the symbiosis between lucinid clams and their intracellular sulfur-oxidizing bacteria, it has been shown that the juveniles acquire their symbionts from an environmental stock of free-living symbiont forms, but it is not known if adult clams are still competent to take up symbiotic bacteria from the environment. In this study, we investigated symbiont acquisition in adult specimens of the lucinid clam Codakia orbiculata, using transmission electron microscopy, fluorescence in situ hybridization, immunohistochemistry and PCR. We show here that adults that had no detectable symbionts after starvation in aquaria for 6 months, rapidly reacquired symbionts within days after being returned to their natural environments in the field. Control specimens that were starved and then exposed to seawater aquaria with sulfide did not reacquire symbionts. This indicates that the reacquisition of symbionts in the starved clams returned to the field was not caused by high division rates of a small pool of remaining symbionts that we were not able to detect with the methods used here. Immunohistochemistry with an antibody against actin, a protein involved in the phagocytosis of intracellular bacteria, showed that actin was expressed at the apical ends of the gill cells that took up symbionts, providing further evidence that the symbionts were acquired from the environment. Interestingly, actin expression was also observed in symbiontcontaining cells of untreated lucinids freshly collected from the environment, indicating that symbiont acquisition from the environment occurs continuously in these clams throughout their lifetime.
ISSN: 1462-2912

hal-00743019
https://hal.univ-antilles.fr/hal-00743019
DOI : 10.1111/j.1462-2920.2012.02748.x

Éditeur(s) : HAL CCSD ACS American Chemical Society - Publications
Résumé : International audience
ABSTRACT: In this paper, the structural, optical and thermal properties of n-type (100),p-type (100) and (111) mesoporous silicon (MePSi) are reported. The mesoporous silicon wasprepared by an electrochemical process from bulk silicon wafer. Depending on the etchingdepth, analyses show that the porosity of p-type (111) increased by 32 to 40% compared to p(100) which, in turn, increased by 22 to 48% compared to n-type (100). The structuremorphology and the abundance of Si-Ox and Si-Hy also depended heavily on the type andcrystal orientation of MePSi. The thermal properties of the MePSi layers such as thermalconductivity (κ), volumetric heat capacity (ρCp) and thermal contact resistance (Rth) weredetermined using the pulsed photothermal method. The thermal conductivity of bulk silicondropped sharply after etching, decreasing by more than twenty-fold in the case of n-type (100)and by over forty-five fold for p-type (100) and (111). According to the percolation modeldepending on both porosity and phonon confinement, the drop in thermal conductivity wasmainly due to the nanostructure formation after etching. Thermal investigations showed thatthe volumetric heat capacity (ρCp) followed the barycentric model which depends mainly onthe porosity. The thermal contact resistances of MePSi layers were estimated to be in therange of 1x10-8 to 1x10-7 K⋅m2⋅W-1.
The Journal of Physical Chemistry C

hal-01495490
https://hal.archives-ouvertes.fr/hal-01495490
DOI : 10.1021/acs.jpcc.6b13101

Éditeur(s) : HAL CCSD
Résumé :  
The gelatinous layer (G-layer) of tension wood fibres in hardwood contributes to the mechanical function of the living tree and has significant consequences on properties of solid wood. Its size, shape and structure observed by optical or electron microscopy exhibits characteristic anatomical features. However, we found that sectioning of non-embedded wood samples results in an uncontrolled swelling of the G-layer was monitored by serial sections, from an embedded wood sample, from its trimmed transverse face to that located several hundreds of micrometers deep. The results revealed that the initial cutting before embedding produced a border effect responsible for the swollen nature, which is similar to sections from non-embedded material. After a conventional embedding technique was applied, a section of at least 30 micrometres below the trimming surface is required to observe an un-swollen G-layer.
IAWA Journal

hal-01032054
https://hal.archives-ouvertes.fr/hal-01032054

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The present study aims to apply the AMS method (Anisotropy of Magnetic Susceptibility) at a regional scale to track the fluid circulation direction that has produced an iron metasomatism within pre-existing dolomite host rock. The Urgonian formations hosting the Zn-Pb mineralizations in La Florida (Cantabria, northern Spain) have been taken as target for this purpose. Sampling was carried out, in addition to ferroan dolomite host rock enclosing the Zn-Pb mineralizations, in dolomite host rock and limestone to make the comparison possible between magnetic signals from mineralized rocks, where fluid circulation occurred, and their surrounding formations. AMS study was coupled with petrofabric analysis carried out by texture goniometry, Scanning Electron Microscopy (SEM) observations and also Shape Preferred Orientation (SPO) statistics. SEM observations of ferroan dolomite host rock illustrate both bright and dark grey ribbons corresponding respectively to Fe enriched and pure dolomites. SPO statistics applied on four images from ferroan dolomite host rock give a well defined orientation of ribbons related to the intermediate axis of magnetic susceptibility K2. For AMS data, two magnetic fabrics are observed. The first one is observed in ferroan dolomite host rock and characterised by a prolate ellipsoid of magnetic susceptibility with a vertical magnetic lineation. The magnetic susceptibility carrier is Fe-rich dolomite. These features are probably acquired during metasomatic fluid circulations. In Fe-rich dolomite host rock, ‹c› axes are vertical. As a rule, (0001) planes (i.e. planes perpendicular to ‹c› axes) are isotropic with respect to crystallographic properties. So, the magnetic anisotropy measured in this plane should reflect crystallographic modification due to fluid circulation. This is confirmed by the texture observed using the SEM. Consequently, AMS results show a dominant NE-SW elongation interpreted as the global circulation direction and a NW-SE secondary elongation that we have considered as sinuosities of the fluid trajectory. The second type of magnetic fabric is essentially observed in the limestone and characterised by an oblate form of the ellipsoid of magnetic susceptibility, a horizontal magnetic foliation and mixed magnetic susceptibility carriers. It is interpreted as a sedimentary fabric.
ISSN: 0012-821X

insu-00342499
https://hal-insu.archives-ouvertes.fr/insu-00342499
https://hal-insu.archives-ouvertes.fr/insu-00342499/document
https://hal-insu.archives-ouvertes.fr/insu-00342499/file/Essalhi-EPSL-2008.pdf
DOI : 10.1016/j.epsl.2008.11.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Ciliates represent a diversified group of protists known to establish symbioses with prokaryotic microorganisms. They are mainly phagotrophs and symbiotic relationships with bacteria can give them an important advantage in chemosynthetic environments. The aim of this study is to describe the thiotrophic association that occurs between the peritrich ciliate Pseudovorticella sp. and potential sulfur-oxidizing bacteria. Investigations at microscopic scale (LM, SEM, TEM) showed ectosymbiotic bacteria covering the surface of the body of Pseudovorticella sp. According to 16S rDNA phylogenetic analysis, these ectosymbiotic bacteria belong to-proteobacteria and are phylogenetically close to the symbiont of the recently described Zoothamnium ignavum, which inhabits shallow-water wood falls. FISH experiments, using symbiont specific probes, clearly indicate that these ectosymbiotic bacteria are also ingested into food vacuoles. Electron lucent granules observed in TEM in the cytoplasm of the ectosymbiotic bacteria have been identified as sulfur granules by Raman microspectrometry analyses. Raman microspec-trometry analyses confirmed the thiotrophic nature of this relationship already suggested by the results obtained by TEM and phylogeny. A complete sulfur map was then performed to investigate the sulfur distribution in the zooid. Results show that the relationship between this protist and its bacterial partner is a thiotrophic ectosymbiosis.
ISSN: 0932-4739

hal-01655933
http://hal.upmc.fr/hal-01655933
http://hal.upmc.fr/hal-01655933/document
http://hal.upmc.fr/hal-01655933/file/GRIMONPREZ_Adrien_sans%20marque.pdf
DOI : 10.1016/j.ejop.2017.11.002

Éditeur(s) : HAL CCSD
Résumé : We present an experimental study of relations between hydraulic properties of clayey rocks and their deformation at bulk and micro scale. The experimentation is based on triaxial deformation of kaolinitic core samples, on permeability measurements, and on several methods of analysis of the microstructure. To produce the samples, remoulded kaolinite material is consolidated by axial loading up to 20 MPa in an oedometric cell. Then, in a triaxial cell, an undrained stress path is applied in order to induce shearing damage in the sample. The permeability of the sample is measured by fluid flow across the sample. Before and after these hydro-mechanical tests, the evolution and the homogeneity of the pore space and moreover the texture of the material are analysed by X-ray tomography, environmental scanning electron microscopy and thermic neutron diffraction. Contrary to expectations, the permeability at the sample scale does not vary significantly, although quite large deformation is reached. The final deformation is heterogeneous, with well-developed shear bands. It appears that the development of compacting and dilating zones generates a heterogeneous permeability field, which results in a negligible variation of the bulk permeability at the sample scale.
International Journal of Rock Mechanics and Mining Science

hal-00496407
https://hal.archives-ouvertes.fr/hal-00496407
DOI : 10.1016/j.ijrmms.2010.04.007

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Four fibers from banana-trees (leaf, trunk) and coconut-tree (husk, fabric) were examined before their incorporation in cementitious matrices, in order to prepare insulating material for construction. Their botanical compositions have been determined following a method described previously. Thermal degradation of these fibers were studied between 200 and 700 °C under nitrogen gas flow. Temperature of pyrolysis was the experimental parameter investigated. The solid residues obtained were analyzed by classical elemental analysis, Fourier Transform Infra Red (FTIR) spectroscopy and were observed by Scanning Electron Microscopy (SEM). This study has shown (1) the relation between botanical, chemical composition with both localization of fibers in the tree and type of tree; (2) the rapid and preferential decomposition of banana fibers with increasing temperature of pyrolysis and (3) the rough samples are made of hollow fibers.
ISSN: 0960-8524

hal-00809780
https://hal.univ-antilles.fr/hal-00809780
DOI : 10.1016/j.biortech.2005.11.030

Éditeur(s) : Gauthier-villars
Résumé : Until recently, the study of the pathology of oysters concerned some bacterial and a large number of parsitic diseases. Among the latter, diseases caused by fungi such as Labyrinthomyxa marina or by sporozoa such as Minchinia nelsoni in the American oyster have had very important econimic repercussions in the affected areas. The causes of some severe epizooties, such as the "Malpecue Bay disease" in Canada, have never been determined; in other cases, including the mass mortality of the Portuguese oyster in Fance, several years of investigations have been required before the first results of an etiologic nature were obtained. The use of electron microscopy has permitted great strides in the pathology of oysters. Thus, virus diseases have been found to be associated with the diseases of the Portuguse oyster, with gill disease and with the mass mortality of 1970. New and important data have also been obtained with regard to the structure and development of Marteilia refringens a parasite of the flat oyster which has been recognized as belonging to the haplosporidan species. Recently, Mycoplasma-like and Rickettsia-like organisms have been detected in several oyster species and oyster viruses have been isolated on cell cultures. Such results confirm the evolution of research in this field.
Les résultats acquis en matière de pathologie des huîtres concernaient jusqu'à une date récente quelques maladies bactériennes et surtout de nombreuses parasitoses. Pour certaines épizooties graves, comme la maladie de l'huître américaine de Malpèque au Canada, les causes n'ont jamais été déterminées et pour d'autres, comme la mortalité massive de l'huître portugaise en France, les premiers résultats d'ordre étiologique n'ont été obtenus que tardivement avec la mise en évidence d'une infection virale. L'étude ultra-structurale de Marteilia refringens, parasite de l'huître plate, la mise en évidence d'une virose associées à la maladie des branchies de l'huître portugaise, puis la découverte récente de nouveaux germes pathogènes tels que mycoplasmes et rickettsies et l'isolement de virus sur cultures cellulaires chez plusieurs espèces d'huîtres devaient confirmer l'évolution des recherches dans ce domaine.
Oceanologica Acta (0399-1784) (Gauthier-villars), 1978 , Vol. 1 , N. 2 , P. 255-262

Droits : 1978 Elsevier
http://archimer.ifremer.fr/doc/00015/12631/9520.pdf
http://archimer.ifremer.fr/doc/00015/12631/