Microemulsion nanocomposites: phase diagram, rheology and structure using a combined small angle neutron scattering and reverse Monte Carlo approach

The effect of silica nanoparticles on transient microemulsion networks made of microemulsion droplets and telechelic copolymer molecules in water is studied, as a function of droplet size and concentration, amount of copolymer, and nanoparticle volume fraction. The phase diagram is found to be affected, and in particular the percolation threshold characterized by rheology is shifted upon addition of nanoparticles, suggesting participation of the particles in the network. This leads to a peculiar reinforcement behaviour of such microemulsion nanocomposites, the silica influencing both the modulus and the relaxation time. The reinforcement is modelled based on nanoparticles connected to the network via droplet adsorption. Contrast-variation Small Angle Neutron Scattering coupled to a reverse Monte Carlo approach is used to analyse the microstructure. The rather surprising intensity curves are shown to be in good agreement with the adsorption of droplets on the nanoparticle surface

Direct small angle neutron scattering observation of stretched chain conformation in nanocomposites: more insight of polymer contributions in mechanical reinforcement

International audienceIn this paper we present a direct measurement of stretched chain conformation in polymer nanocomposites in a large range of deformation using a specific contrast-matched SANS method. Whatever the filler structure and the chain length the results show a clear identity of chain deformation in pure and reinforced polymer and offer a new insight of the polymer chain contribution in the mechanical reinforcement. It suggests that glassy layer or glassy paths, recently proposed, should involve only a small fraction of chains. As a result, the remaining filler contribution appears strikingly constant with deformation as explained by continuous locking-unlocking rearrangement process of the particles

The identification of a new genotype of avian paramyxoviruses type I in West-Africa provides new outcomes for phylogeny reconstruction

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New avian paramyxoviruses type I strains identified in Africa provide new outcomes for phylogeny reconstruction and genotype classification

Newcastle disease (ND) is one of the most lethal diseases of poultry worldwide. It is caused by an avian paramyxovirus 1 that has high genomic diversity. In the framework of an international surveillance program launched in 2007, several thousand samples from domestic and wild birds in Africa were collected and analyzed. ND viruses (NDV) were detected and isolated in apparently healthy fowls and wild birds. However, two thirds of the isolates collected in this study were classified as virulent strains of NDV based on the molecular analysis of the fusion protein and experimental in vivo challenges with two representative isolates. Phylogenetic analysis based on the F and HN genes showed that isolates recovered from poultry in Mali and Ethiopia form new groups, herein proposed as genotypes XIV and sub-genotype VIf with reference to the new nomenclature described by Diel's group. In Madagascar, the circulation of NDV strains of genotype XI, originally reported elsewhere, is also confirmed. Full genome sequencing of five African isolates was generated and an extensive phylogeny reconstruction was carried out based on the nucleotide sequences. The evolutionary distances between groups and the specific amino acid signatures of each cluster allowed us to refine the genotype nomenclature. (Résumé d'auteur

Oblique rifting and segmentation of the NE Gulf of Aden passive margin

The Gulf of Aden is a young, obliquely opening, oceanic basin where tectonic structures can easily be followed and correlated from the passive margins to the active mid-oceanic ridge. It is an ideal laboratory for studies of continental lithosphere breakup from rifting to spreading. The northeastern margin of the Gulf of Aden offers the opportunity to study on land the deformation associated with oblique rifting over a wide area encompassing two segments of the passive margin, on either side of the Socotra fracture zone, exhibiting distinct morphologic, stratigraphic, and structural features. The western segment is characterized by an elevated rift shoulder and large grabens filled with thick synrift series, whereas the eastern segment exhibits low elevation and is devoid of major extensional structures and typical synrift deposits. Though the morphostructural features of the margin segments are different, the stress field analysis provides coherent results all along the margin. Four directions of extension have been recognized and are considered to be representative of two tensional stress fields with permutations of the horizontal principal stresses s2 and s3. The two dominant directions of extension, N150 E and N20 E, are perpendicular to the mean trend of the Gulf of Aden (N75 E) and parallel to its opening direction (N20 E-N30 E), respectively. Unlike another study in the western part of the gulf, our data suggest that the N150 E extension stage is older than the N20 E extension stage. These conflicting chronologies, which are nowhere unambiguously established, suggest that the two extensions coexisted during the rifting. On-land data are compared with offshore data and are interpreted with reference to oblique rifting. The passive margin segmentation represents a local accommodation of the extensional deformation in a homogeneous regional stress field, which reveals the asymmetry of the rifting process. The first-order segmentation of the Sheba Ridge is inherited from the prior segmentation of the passive margin

Intra- and Interchain Correlations in Polymer Nanocomposites: A Small-Angle Neutron Scattering Extrapolation Method

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L'hépatite B chez les migrants originaires d'Afrique subsaharienne vivant en France (état des lieux et étude de leur perception de la maladie)

Les personnes originaires d Afrique subsaharienne présentent une prévalence élevée de portage de l antigène HBs (5,3%). Seules 17,4% des porteurs en auraient connaissance. Une étude qualitative a été réalisée auprès d elles pour évaluer les connaissances, perceptions et attitudes vis-à-vis de l hépatite B et de sa prévention. Des entretiens individuels semi-directifs et des groupes focus ont été réalisés en 2008 auprès de 41 personnes originaires d Afrique subsaharienne en Ile de France. Bien que l hépatite B fasse partie des préoccupations de santé des migrants, la plupart d entre eux ne se sent pas personnellement exposé. S ils savent que l hépatite B est une maladie virale qui touche le foie, ils ignorent qu elle peut entraîner une cirrhose et un cancer du foie. La transmission sanguine est connue et la transmission salivaire évoquée. Les voies sexuelles, de la mère à l enfant et suite à un contact avec une personne infectée sont rarement connues. Une minorité connaît l existence d une vaccination contre le VHB et la plupart ignore son statut vaccinal. Si peu de participants ont déjà réalisé un dépistage de l hépatite B par manque d information, ils seraient favorables à sa réalisation par l intermédiaire de leur médecin traitant. Les femmes ignorent que le dépistage de l hépatite B est obligatoire pendant la grossesse. Les participants sont plutôt réceptifs aux messages d informations qui leur ont été présentés et apprécient les supports de communication communautaires. Des actions spécifiques d information des migrants et des professionnels devraient être mises en œuvre pour encourager le recours au dépistage et à la vaccination.PARIS6-Bibl.Pitié-Salpêtrie (751132101) / SudocSudocFranceF

Dispositifs hyperfréquences à faible impact environnemental

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