Influence de la cristallochimie des smectites sur la structuration de l’eau et des cations interfoliaires.

Swelling clay minerals such as smectites are ubiquitous at the Earth surface and possess major hydration ability and contaminant uptake/retention capacity. As a consequence smectites exert a pivotal influence on elemental transfers in surficial environments. These properties are especially relevant also when smectites are used as sealant in engineered or geological barriers for waste disposal facilities. As interlayer H2O molecules account for more than 80% of smectite water in undersaturated conditions, characterization of H2O organization and dynamics in smectites interlayers is essential to determining the geometrical and dynamical properties of clay barriers for waste disposal and to predicting the mobility of contaminant whose principal vector is water. Within this general framework, the present works describe, in a first time, the structuration of interlayer water/cations in saturated conditions. Then, in a second time, review the influence of structural parameters such as the amount and location of layer charge deficit and the chemical composition (and more especially the presence of structural fluorine/hydroxyl) on smectite hydration properties. A set of samples covering the whole compositional range of swelling phyllosilicates has thus been synthesized and characterized chemically and structurally.Special attention was paid to determining the amount (water vapor sorption isotherms) and the distribution (X-ray diffraction) of interlayer water. Molecular modeling allowed unraveling the origin of the contrasting behaviors observed experimentally and to determine the influence of the different crystal-chemical parameters on smectite hydration. This step is essential for the prediction of smectite reactivity in the environment from a limited number of crystal-chemical parameters. Molecular modeling allowed unraveling the origin of the contrasting behaviors observed experimentally and to determine the influence of the different crystal-chemical parameters on smectite hydration. This step is essential for the prediction of smectite reactivity in the environment from a limited number of crystal-chemical parameters.Les minéraux argileux gonflants tels que les smectites sont omniprésents à la surface de la Terre et possèdent d’importantes capacités d'hydratation et d’absorption/rétention de contaminants.Ainsi, ces dernières exercent une influence clé sur les transferts d’éléments dans les environnements de surface. Ces propriétés sont particulièrement importantes quand les smectites sont utilisées comme barrières ouvragées ou géologiques pour les installations de contrôle des déchets. Les molécules d’eau dans l’interfoliaire représentent plus de 80% de l'eau en contact avec les smectites, dans des conditions non saturées. La caractérisation de l'organisation et de la dynamique de l’eau dans les smectites est donc essentielle pour prédire la mobilité des contaminants, dont le principal vecteur est l'eau. Dans ce cadre général, les présents travaux décrivent, dans un premier temps, la structuration interfoliaire eau/cations dans des conditions saturées, jusqu’alors méconnue. Puis, dans un second temps, nous avons examiné l'influence des paramètres structuraux (tels que la quantité et l'emplacement des charges, la composition chimique et plus particulièrement la présence de groupements fluors/hydroxyles) sur les propriétés d'hydratation des smectites. Une série d'échantillons couvrant toute la gamme de composition des smectites a donc été synthétisée et caractérisée structurellement. Une attention particulière a été accordée à la détermination du montant (isothermes vapeur d'eau de sorption) et la distribution (de diffraction des rayons X) de l'eau dans l’espace interfoliaire. La modélisation moléculaire a permis d’aller plus loin dans la compréhension de l'origine des comportements contrastés observés expérimentalement, et de déterminer l'influence des différents paramètres cristallochimiques sur l'hydratation de la smectite. Cette étape est essentielle pour la prédiction de la réactivité des smectites dans l'environnement sur la base d'un nombre limité de paramètres cristallochimiques

Population genomics and antimicrobial resistance in Corynebacterium diphtheriae

Background: Corynebacterium diphtheriae, the agent of diphtheria, is a genetically diverse bacterial species. Although antimicrobial resistance has emerged against several drugs including first-line penicillin, the genomic determinants and population dynamics of resistance are largely unknown for this neglected human pathogen. Methods: Here, we analyzed the associations of antimicrobial susceptibility phenotypes, diphtheria toxin production, and genomic features in C. diphtheriae. We used 247 strains collected over several decades in multiple world regions, including the 163 clinical isolates collected prospectively from 2008 to 2017 in France mainland and overseas territories. Results: Phylogenetic analysis revealed multiple deep-branching sublineages, grouped into a Mitis lineage strongly associated with diphtheria toxin production and a largely toxin gene-negative Gravis lineage with few toxin-producing isolates including the 1990s ex-Soviet Union outbreak strain. The distribution of susceptibility phenotypes allowed proposing ecological cutoffs for most of the 19 agents tested, thereby defining acquired antimicrobial resistance. Penicillin resistance was found in 17.2% of prospective isolates. Seventeen (10.4%) prospective isolates were multidrug-resistant (≥ 3 antimicrobial categories), including four isolates resistant to penicillin and macrolides. Homologous recombination was frequent (r/m = 5), and horizontal gene transfer contributed to the emergence of antimicrobial resistance in multiple sublineages. Genome-wide association mapping uncovered genetic factors of resistance, including an accessory penicillin-binding protein (PBP2m) located in diverse genomic contexts. Gene pbp2m is widespread in other Corynebacterium species, and its expression in C. glutamicum demonstrated its effect against several beta-lactams. A novel 73-kb C. diphtheriae multiresistance plasmid was discovered. Conclusions: This work uncovers the dynamics of antimicrobial resistance in C. diphtheriae in the context of phylogenetic structure, biovar, and diphtheria toxin production and provides a blueprint to analyze re-emerging diphtheria

Influence of smectites crystal chemistry on the structure of water and interlayer cations

Les minéraux argileux gonflants tels que les smectites sont omniprésents à la surface de la Terre et possèdent d'importantes capacités d'hydratation et d'absorption/rétention de contaminants. Ainsi, ces dernières exercent une influence clé sur les transferts d'éléments dans les environnements de surface. Ces propriétés sont particulièrement importantes quand les smectites sont utilisées comme barrières ouvragées ou géologiques pour les installations de contrôle des déchets. Les molécules d'eau dans l'interfoliaire représentent plus de 80% de l'eau en contact avec les smectites, dans des conditions non saturées. La caractérisation de l'organisation et de la dynamique de l'eau dans les smectites est donc essentielle pour prédire la mobilité des contaminants, dont le principal vecteur est l'eau. Dans ce cadre général, les présents travaux décrivent, dans un premier temps, la structuration interfoliaire eau/cations dans des conditions saturées, jusqu'alors méconnue. Puis, dans un second temps, nous avons examiné l'influence des paramètres structuraux (tels que la quantité et l'emplacement des charges, la composition chimique et plus particulièrement la présence de groupements fluors/hydroxyles) sur les propriétés d'hydratation des smectites. Une série d'échantillons couvrant toute la gamme de composition des smectites a donc été synthétisée et caractérisée structurellement. Une attention particulière a été accordée à la détermination du montant (isothermes vapeur d'eau de sorption) et la distribution (de diffraction des rayons X) de l'eau dans l'espace interfoliaire. La modélisation moléculaire a permis d'aller plus loin dans la compréhension de l'origine des comportements contrastés observés expérimentalement, et de déterminer l'influence des différents paramètres cristallochimiques sur l'hydratation de la smectite. Cette étape est essentielle pour la prédiction de la réactivité des smectites dans l'environnement sur la base d'un nombre limité de paramètres cristallochimiques.Swelling clay minerals such as smectites are ubiquitous at the Earth surface and possess major hydration ability and contaminant uptake/retention capacity. As a consequence smectites exert a pivotal influence on elemental transfers in surficial environments. These properties are especially relevant also when smectites are used as sealant in engineered or geological barriers for waste disposal facilities. As interlayer H2O molecules account for more than 80% of smectite water in undersaturated conditions, characterization of H2O organization and dynamics in smectites interlayers is essential to determining the geometrical and dynamical properties of clay barriers for waste disposal and to predicting the mobility of contaminant whose principal vector is water. Within this general framework, the present works describe, in a first time, the structuration of interlayer water/cations in saturated conditions. Then, in a second time, review the influence of structural parameters such as the amount and location of layer charge deficit and the chemical composition (and more especially the presence of structural fluorine/hydroxyl) on smectite hydration properties. A set of samples covering the whole compositional range of swelling phyllosilicates has thus been synthesized and characterized chemically and structurally. Special attention was paid to determining the amount (water vapor sorption isotherms) and the distribution (X-ray diffraction) of interlayer water. Molecular modeling allowed unraveling the origin of the contrasting behaviors observed experimentally and to determine the influence of the different crystal-chemical parameters on smectite hydration. This step is essential for the prediction of smectite reactivity in the environment from a limited number of crystal-chemical parameters. Molecular modeling allowed unraveling the origin of the contrasting behaviors observed experimentally and to determine the influence of the different crystal-chemical parameters on smectite hydration. This step is essential for the prediction of smectite reactivity in the environment from a limited number of crystal-chemical parameters

Scientific bulletin

Swelling clay minerals such as smectites are ubiquitous at the Earth surface and possess major hydration ability and contaminant uptake/retention capacity. As a consequence smectites exert a pivotal influence on elemental transfers in surficial environments. These properties are especially relevant also when smectites are used as sealant in engineered or geological barriers for waste disposal facilities. As interlayer H2O molecules account for more than 80% of smectite water in undersaturated conditions, characterization of H2O organization and dynamics in smectites interlayers is essential to determining the geometrical and dynamical properties of clay barriers for waste disposal and to predicting the mobility of contaminant whose principal vector is water. Within this general framework, the present works describe, in a first time, the structuration of interlayer water/cations in saturated conditions. Then, in a second time, review the influence of structural parameters such as the amount and location of layer charge deficit and the chemical composition (and more especially the presence of structural fluorine/hydroxyl) on smectite hydration properties. A set of samples covering the whole compositional range of swelling phyllosilicates has thus been synthesized and characterized chemically and structurally. Special attention was paid to determining the amount (water vapor sorption isotherms) and the distribution (X-ray diffraction) of interlayer water. Molecular modeling allowed unraveling the origin of the contrasting behaviors observed experimentally and to determine the influence of the different crystal-chemical parameters on smectite hydration. This step is essential for the prediction of smectite reactivity in the environment from a limited number of crystal-chemical parameters. Molecular modeling allowed unraveling the origin of the contrasting behaviors observed experimentally and to determine the influence of the different crystal-chemical parameters on smectite hydration. This step is essential for the prediction of smectite reactivity in the environment from a limited number of crystal-chemical parameters.Les minéraux argileux gonflants tels que les smectites sont omniprésents à la surface de la Terre et possèdent d'importantes capacités d'hydratation et d'absorption/rétention de contaminants. Ainsi, ces dernières exercent une influence clé sur les transferts d'éléments dans les environnements de surface. Ces propriétés sont particulièrement importantes quand les smectites sont utilisées comme barrières ouvragées ou géologiques pour les installations de contrôle des déchets. Les molécules d'eau dans l'interfoliaire représentent plus de 80% de l'eau en contact avec les smectites, dans des conditions non saturées. La caractérisation de l'organisation et de la dynamique de l'eau dans les smectites est donc essentielle pour prédire la mobilité des contaminants, dont le principal vecteur est l'eau. Dans ce cadre général, les présents travaux décrivent, dans un premier temps, la structuration interfoliaire eau/cations dans des conditions saturées, jusqu'alors méconnue. Puis, dans un second temps, nous avons examiné l'influence des paramètres structuraux (tels que la quantité et l'emplacement des charges, la composition chimique et plus particulièrement la présence de groupements fluors/hydroxyles) sur les propriétés d'hydratation des smectites. Une série d'échantillons couvrant toute la gamme de composition des smectites a donc été synthétisée et caractérisée structurellement. Une attention particulière a été accordée à la détermination du montant (isothermes vapeur d'eau de sorption) et la distribution (de diffraction des rayons X) de l'eau dans l'espace interfoliaire. La modélisation moléculaire a permis d'aller plus loin dans la compréhension de l'origine des comportements contrastés observés expérimentalement, et de déterminer l'influence des différents paramètres cristallochimiques sur l'hydratation de la smectite. Cette étape est essentielle pour la prédiction de la réactivité des smectites dans l'environnement sur la base d'un nombre limité de paramètres cristallochimiques

Développement d'une méthode de mesure de l'expression génique utilisant des plasmides rapporteurs luciférase: Application à l'expression des gènes d'antibiorésistance chez Salmonella

Licenc

Polygenic Risk Score in complex diseases

Curs 2017-2018Motivation: Plenty genome-wide datasets are produced from complex diseases by traditional GWAS studies, but they are limited. A new approach has emerged in the last decade, the Polygenic Risk Scores (PRS), to combine several SNP into a single predictor to try to explain the complex genetic behind diseases like Asthma or Autism Spectrum Disorders. Results: Here we analyse genome-wide data from these two diseases a compute PRS with three different approaches, PLINK’s method, a machine learning approach (biglasso) and a targeted-based method using SFARI database. We find that this kind of analysis are quite complex like the diseases they try to predict, and PRS only explain a very low percentage of the variance of the disease. The validation analysis we performed show us that the parameters used to compute the PRS have to be optimize using bigger datasets. We also used a machine learning approach (XGBoost) to impute the data in certain analysis.Supervisor/a: Juan R GonzálezDirector/a: M. Luz Call

Place de l'anorexie mentale masculine dans une pathologie à prédominance féminine (comparaisons avec la jeune fille, prise en charge et témoignages)

POITIERS-BU Médecine pharmacie (861942103) / SudocSudocFranceF

Interlayer structure model of tri-hydrated low-charge smectite by X-ray diffraction and Monte Carlo modeling in the Grand Canonical ensemble

International audienceThe present study aims primarily at refining a structure model for interlayer cations and H2O molecules in tri-hydrated (3W) smectite (d(001) = 18-19 angstrom). The <2 mu m fraction of the SWy-2 source clay (low-charge montmorillonite) was saturated by Mg2+, Ca2+, Ba2+, or Na cations, before collection of X-ray diffraction (XRD) patterns at 98% relative humidity. Experimental d(001) values derived for the essentially homogeneous 3W hydrates provided volume constraints for Grand Canonical Monte Carlo (GCMC) simulations. Computed atomic density distribution of interlayer species were used in turn to calculate XRD intensities of 00l reflections. The agreement between calculated and experimental 00l intensities allowed validating the GCMC results of both interlayer H2O content and distribution of interlayer species (cations and H2O molecules). Computed atomic density profiles do not correspond to the usual model of three discrete planes of H2O molecules but rather exhibit two sharp planes of H2O molecules wetting the clay surfaces (at similar to 2.7 angstrom from the clay layer surface). Additional H2O molecules belong to cation hydration shells or define a poorly organized ensemble filling internal voids. This alternative model suggests that the stability of the 3W hydrate results from the dual interaction of some H2O molecules with interlayer cation, through their second hydration shell; and with the 2:1 clay surface. Computed atomic density profiles were approximated to propose an interlayer structure model for 3W smectite. This simplified model includes two sets of two planes (symmetrical relative to the interlayer mid-plane) for H2O molecules and one set for interlayer cations. This model allows reproducing experimental XRD patterns for the different samples investigated and thus represents a valid set of parameters for routine quantitative analysis of XRD profiles in an effort to determine smectite reactivity close to water-saturated conditions. Implications of such studies are crucial to provide experimental constraints on the behavior of the main vector of element transfer under conditions common in surficial environments and prevailing in waste repositories. In addition, the present study provides an experimental validation of structure models derived from the widely used ClayFF model, and thus allows its use to predict the fate of water in clayey systems close to water-saturated conditions

Sulfur and lead isotopic evidence of relic Archean sediments in the Pitcairn mantle plume

The isotopic diversity of oceanic island basalts (OIB) is usually attributed to the influence, in their sources, of ancient material recycled into the mantle, although the nature, age, and quantities of this material remain controversial. The unradiogenic Pb isotope signature of the enriched mantle I (EM I) source of basalts from, for example, Pitcairn or Walvis Ridge has been variously attributed to recycled pelagic sediments, lower continental crust, or recycled subcontinental lithosphere. Our study helps resolve this debate by showing that Pitcairn lavas contain sulfides whose sulfur isotopic compositions are affected by mass-independent fractionation (S-MIF down to Δ33S = −0.8), something which is thought to have occurred on Earth only before 2.45 Ga, constraining the youngest possible age of the EM I source component. With this independent age constraint and a Monte Carlo refinement modeling of lead isotopes, we place the likely Pitcairn source age at 2.5 Ga to 2.6 Ga. The Pb, Sr, Nd, and Hf isotopic mixing arrays show that the Archean EM I material was poor in trace elements, resembling Archean sediment. After subduction, this Archean sediment apparently remained stored in the deep Earth for billions of years before returning to the surface as Pitcairn´s characteristic EM I signature. The presence of negative S-MIF in the deep mantle may also help resolve the problem of an apparent deficit of negative Δ33S anomalies so far found in surface reservoirs