Transitions sol-gel de colloïdes anisotropes sous champs de cisaillement, pression et ondes ultrasonores, caractérisées par diffusion de rayons x aux petits angles in-situ

L'objectif de ce travail est de caractériser aux échelles mésoscopiques, l'effet combiné des champs de pression, hydrodynamiques et ultrasonores sur les mécanismes de transition sol-gel de colloïdes anisotropes d'argiles lors de l'ultrafiltration tangentielle. Pour cela, des cellules de filtration ont été développées en intégrant une lame vibrante sollicitée à 20kHz par un générateur ultrasonore. Ces cellules de filtration permettent l'observation in-situ aux échelles nanométriques par diffusion de rayons X aux petits angles (SAXS). Différentes suspensions aqueuses d'argiles ont été étudiées : des argiles naturelles de montmorillonite Wyoming-Na et des argiles synthétiques de Laponite en présence ou non d'un peptisant le tetrasodium diphosphate (Na4P2O7). Par ailleurs l'effet des ultrasons sur le comportement rhéologique de suspensions a aussi été étudié.  L'effet du pré-cisaillement induit par la pompe du circuit de filtration et l'effet des ultrasons, sur les contraintes de cisaillement des suspensions de Laponite ont été mises en évidence. Les deux sollicitations réduisent les niveaux de contrainte et l'effet est plus marqué sur les suspensions avec peptisant (à interaction répulsive dominante) que sur les suspensions sans peptisant (à interaction attractive dominante). Les évolutions temporelles de la structure et de la concentration en colloïdes en fonction de la distance à la membrane ont ainsi été caractérisées sous différentes conditions de filtration et de sollicitations ultrasonores. Deux mécanismes principaux ont été mis en évidence lors de l'application des ultrasons : soit un mécanisme de fracturation ou d'intensification locale de l'écoulement lorsque les colloïdes forment un réseau dense très anisotrope (cas des suspensions de Montmorillonite et de Laponite sans peptisant), soit un mécanisme d'érosion des couches concentrées pour les colloïdes assemblés en structures ouvertes (cas des suspensions de Laponite avec peptisant)

Interaction Testing and Polygenic Risk Scoring to Estimate the Association of Common Genetic Variants with Treatment Resistance in Schizophrenia

Importance: About 20% to 30% of people with schizophrenia have psychotic symptoms that do not respond adequately to first-line antipsychotic treatment. This clinical presentation, chronic and highly disabling, is known as treatment-resistant schizophrenia (TRS). The causes of treatment resistance and their relationships with causes underlying schizophrenia are largely unknown. Adequately powered genetic studies of TRS are scarce because of the difficulty in collecting data from well-characterized TRS cohorts. Objective: To examine the genetic architecture of TRS through the reassessment of genetic data from schizophrenia studies and its validation in carefully ascertained clinical samples. Design, Setting, and Participants: Two case-control genome-wide association studies (GWASs) of schizophrenia were performed in which the case samples were defined as individuals with TRS (n = 10501) and individuals with non-TRS (n = 20325). The differences in effect sizes for allelic associations were then determined between both studies, the reasoning being such differences reflect treatment resistance instead of schizophrenia. Genotype data were retrieved from the CLOZUK and Psychiatric Genomics Consortium (PGC) schizophrenia studies. The output was validated using polygenic risk score (PRS) profiling of 2 independent schizophrenia cohorts with TRS and non-TRS: a prevalence sample with 817 individuals (Cardiff Cognition in Schizophrenia [CardiffCOGS]) and an incidence sample with 563 individuals (Genetics Workstream of the Schizophrenia Treatment Resistance and Therapeutic Advances [STRATA-G]). Main Outcomes and Measures: GWAS of treatment resistance in schizophrenia. The results of the GWAS were compared with complex polygenic traits through a genetic correlation approach and were used for PRS analysis on the independent validation cohorts using the same TRS definition. Results: The study included a total of 85490 participants (48635 [56.9%] male) in its GWAS stage and 1380 participants (859 [62.2%] male) in its PRS validation stage. Treatment resistance in schizophrenia emerged as a polygenic trait with detectable heritability (1% to 4%), and several traits related to intelligence and cognition were found to be genetically correlated with it (genetic correlation, 0.41-0.69). PRS analysis in the CardiffCOGS prevalence sample showed a positive association between TRS and a history of taking clozapine (r2 = 2.03%; P =.001), which was replicated in the STRATA-G incidence sample (r2 = 1.09%; P =.04). Conclusions and Relevance: In this GWAS, common genetic variants were differentially associated with TRS, and these associations may have been obscured through the amalgamation of large GWAS samples in previous studies of broadly defined schizophrenia. Findings of this study suggest the validity of meta-analytic approaches for studies on patient outcomes, including treatment resistance

Conditionnement des greffes autologues de cellules souches hématopoïétiques chez l'adulte. A propos de 102 greffes réalisées au CHU de Reims entre 2005 et 2007

REIMS-BU Santé (514542104) / SudocSudocFranceF

Les sentiers de la mémoire. Paroles de jeunes

À l’initiative de la plateforme « Mémoire & Politique » (Département de science politique, ULg), des élèves de l’Athénée Royal de Vielsalm-Manhay ont réalisé un projet relatif à la transmission de la mémoire des faits génocidaires dans le cadre du « décret mémoire ». Différentes activités ont été réalisées : conférences, rencontres avec des rescapés et visites de lieux de mémoire dont les camps de concentration et d’extermination d’Auschwitz-Birkenau. Ce livre retrace la recherche et l’ensemble du chemin parcouru, il donne la parole aux jeunes qui ne manquent pas de nous interpeller et de nous éclairer sur la manière dont certains faits passés sont transmis.1ère éd

Les seuils du gigantesque

Burgelin Olivier, Morin Edgar, Paillard Bernard, Pignon Dominique. Les seuils du gigantesque. In: Communications, 42, 1985. Le gigantesque, sous la direction de Bernard Paillard. pp. 245-263

Interactions Interparticulaires et Thixotropie des Gels d'Argile

International audienc

Compressive rheology of colloidal gels of anisotropic caly particles

The mechanisms whereby Laponite, a synthetic clay of the hectorite type, is consolidated, have been identified. This relatively monodisperse clay consists of disc-like anisotropic particles of nanometric size which have strongly anisotropic surface charges as the edges have a positive charge and the faces a negative one. These colloidal particles aggregate to form, depending on the physicochemical parameters, an isotropic gel. In this study, the inter-particle interactions may be modified by adding a peptizer, tetrasodium diphosphate. This peptizer consists of anions that attach themselves to the edges of the clay particles and tend to give them a negative surface charge. A large amount of literature is available on this clay, concerning restricted ranges of volume fractions in the dilute to semi-dilute domains, i.e., less than 3%. These studies was concerned by the influence of inter-particles interactions via the aqueous media on the physicochemical properties, on the structure of the dispersions and at larger length scales on their macroscopic behaviour. Other scarcer studies have considered consolidation as a way to concentrate the dispersions because they cannot be concentrated further using normal mixing techniques. These studies do not try to rely the structure and the macroscopic behaviour of the dispersions during and after consolidation

Dissociation of Thixotropic Clay Gels

International audienceLaponite dispersions in water, at moderate ionic strength and high pH, are thixotropic: depending on previous history, they can be fluids or gels. The mechanisms of the fluid-gel and gel-fluid transitions have been examined through ionic analysis of the aqueous phase, static light, and small-angle neutron scattering, rheological experiments, and centrifugation. The results indicate that the particles attract each other in edge-to-face configurations. These attractions cause the particles to gather in microdomains, which subsequently associate to form very large fractal superaggregates, containing all the particles in the dispersion. A gel state is obtained when the network of connections is macroscopic. This network is destroyed by the application of sufficient strain, but it heals at rest. The addition of peptizers weakens the edge-to-face attractions, and makes the healing times much slower