Oblique rifting at oceanic ridges: Relationship between spreading and stretching directions from earthquake focal mechanisms

International audienceThe relationship between spreading and stretching directions is investigated at oblique-spreading oceanic ridges using earthquake focal mechanisms. The stretching direction at ridge axes corresponds to the direction of the greatest principal strain epsilon1 taken as the mean trend of the seismic T-axes of extensional earthquake focal mechanisms. It is compared with the spreading direction provided by global plate-motion models. We find that the stretching direction trends approximately halfway between the spreading direction and the normal to the ridge trend, a result in line with analogue experiments of oblique rifting. This result is satisfactorily accounted for with an analytical model of oblique rifting, for which the direction of epsilon1 is calculated with respect to rifting obliquity for different amounts of stretching using continuum mechanics. For low stretching factors, typical of incremental seismic deformations, epsilon1 obliquity is two times lower than rifting obliquity. For higher stretching factors, the stretching and spreading directions become parallel

Micro-tectonic constraints on the evolution of the Barles half-window (Digne Nappe, southern Alps). Implications for the timing of folding in the Valensole foreland basin

International audienceThe "Vélodrome" overturned syncline, at the northern margin of the Cenozoic foreland basin of Valensole in SE France, was formed during the Late Cenozoic at the front of the Digne nappe. Microstructural analyses reveal that mesoscale faulting in the molassic series, from the Oligocene "Molasse Rouge" at the base to the middle to late Miocene "Valensole Conglomerates" at the top, partly occurred before the folding, as layer-parallel shortening: the NNE-SSW-directed compression is recorded by two systems of reverse and strike-slip faults, which formed when the strata were still horizontal and were passively tilted as folding occurred. These data suggest that the Vélodrome folding postdates the deposition of the Valensole Conglomerates and occurred in late Miocene-Pliocene times during the emplacement of the Digne nappe. These results are difficult to reconcile with the interpretation of the Vélodrome as a growth fold progressively formed in 10-15 m.y. during the deposition of the Miocene molasses. Structural data collected in the Barles tectonic half-window enable to reconstruct the evolution of the deformation since the Jurassic. The two main phases of shortening, the pre-Oligocene Pyrenean-Provençal and the Mio-Pliocene Alpine phases, are almost homoaxial with a direction of compression trending N-S for the former and NNE-SSW for the later. A late Eocene-basal Oligocene N-S extensional episode is documented between these two phases, probably in relation with the formation of the western European rift system. The direction of extension of the Liassic rifting of the Alpine Tethys is roughly constrained in the NW-SE quadrant. Paleo-stress field reconstruction brings consistent results at the regional scale and proves to be a powerful tool to decipher the evolution of the deformation in a remarkably complicated tectonic setting

Représentations sociales de citoyens de Saint-Léonard à l'égard de l'immigration

L'immigration demeure un phénomène fortement répandu dans les communautés rurales francophones qui veulent contrecarrer les conséquences démographiques, économiques, sociales et politiques de la dépopulation progressive. Les collectivités se voient ainsi de plus en plus touchées par ce phénomène qui apporte certes plusieurs avantages, mais aussi une quantité innombrable de défis à relever. L'intégration des immigrants au sein de ces collectivités rurales, dont les collectivités du nord-ouest du Nouveau-Brunswick, comporte des difficultés. L'insertion professionnelle et sociale dépend de divers facteurs que ce soit la connaissance et la maitrise de la langue, la capacité à établir et maintenir des liens sociaux, la capacité de s'approprier un ensemble de valeurs ; de normes et de rôles, etc. Parmi les facteurs qui sont susceptibles de nuire ou de faciliter le processus d'intégration, les représentations que se font les citoyens du phénomène de l'immigration pourraient occuper une place substantielle. Dans cette recherche exploratoire, on rend compte des représentations sociales dans un lieu géographiquement déterminé. La conceptualisation des représentations s'inspire en partie des travaux de Serge Moscovici et de certains auteurs plus contemporains, tels que Jodelet, qui s'inscrivent dans son prolongement. Plus précisément, nous étudions les représentations de l'immigration chez les citoyens de la municipalité de Saint-Léonard, au Nouveau-Brunswick. Ce terrain semblait particulièrement riche pour étudier ce concept étant donnée sa récente histoire et expérience avec le phénomène de l'immigration. À cet égard, ont été identifiées et décrites : les valeurs, les sentiments, les émotions, les idéologies, les concepts, les opinions, les orientations de comportements, etc. de treize personnes rencontrées dans le cadre d'entrevues semi-dirigées individuelles. Les entretiens ont permis de colliger les éléments de définition ou des caractéristiques de l'immigration dans la région du nord-ouest du Nouveau-Brunswick. Les travaux de Milton Bennett qui portent sur les stades de développement de l'ouverture interculturelle ont servi d'inspiration et ont permis d'analyser les discours des citoyens. Cette théorie a permis de mettre en relief le positionnement des citoyens face à l'immigration et à la présence de personnes immigrantes dans leur communauté. De l'analyse des données recueillies (transcription des verbatims, puis identification et regroupement des segments pertinents), il ressort que les acteurs locaux se représentent l'immigration et les immigrants avec une certaine crainte et méfiance. Cette thèse se veut une première étape permettant une compréhension de la perception des locaux face aux immigrants. Toutefois, d'un point de vue pratique et dans le but de mieux cibler les actions pertinentes à mener au sein de la communauté, le modèle du champ de forces de Kurt Lewin a permis de représenter la situation actuelle et souhaitée de façon à ce que l'immigration et l'intégration des immigrants soient vécues positivement de part et d'autre

ECHAP « L’architecture des couverts végétaux : un levier pour réduire l’utilisation des fongicides ? »

L’objectif du projet ECHAP est d’identifier les possibilités de réduction de traitements fongicides via l’utilisation de l’architecture des couverts. Le projet a tout d’abord apporté des connaissances qui ont levé des verrous sur les mécanismes d’interaction. Il combine également 3 expérimentations opérationnelles au champ et un travail de modélisation du système. Les expérimentations au champ confirment l’effet de l’architecture sur le développement épidémique ainsi que l’effet marqué sur l’interception des fongicides et qui s’exprime clairement entre les variétés. Un modèle innovant et original simulant le système « architecture–épidémie-fongicide », septo3dfongi, a été développé. Il est opérationnel et permet de simuler et de raisonner des stratégies de traitements. Des critères d’évaluation multicritères des stratégies ont été également proposés

Stratégie industrielle pour un écosystème en émergence : le cas de la mobilité 2.0, décarbonée, intermodale et collaborative

L’industrie automobile traditionnelle subit la triple pression de l’évolution géographique des zones de marchés, des changements socio-culturels des consommateurs et des politiques publiques en faveur du développement durable. Les demandes ne s’orientent plus uniquement vers l’achat particulier d’un produit automobile, mais vers l’usage d’une mobilité moins coûteuse, 2.0, décarbonée, intermodale et collaborative. Dans ce contexte en rupture, nous nous interrogeons sur la capacité d’adaptation organisationnelle et stratégique des entreprises qui constituent l’industrie automobile actuelle. En référence à d’autres secteurs qui ont connu des évolutions radicales de leurs business modèles, nous proposons une approche organisationnelle basée sur l’identification d’écosystèmes d’affaires et la mise en œuvre de stratégies de façonnage.The traditional automotive industry is under a triple pressure due to the geographical evolution of different world markets and the consumers sociocultural changes as well as the public policies which are supporting sustainable development. The demands are not solely directed towards the purchase of a particular automobile product any more but towards the use of a cheaper, 2.0, low-carbon, intermodal and collaborative mobility. Within this disruptive context, we question the organizational and strategic adaptation ability of companies in the actual automotive industry. In reference to other sectors that experienced comparable radical changes in their business models, we propose an organizational approach based on business ecosystems and an implementation of shaping strategies

Mutation of exposed hydrophobic amino acids to arginine to increase protein stability

BACKGROUND: One strategy to increase the stability of proteins is to reduce the area of water-accessible hydrophobic surface. RESULTS: In order to test it, we replaced 14 solvent-exposed hydrophobic residues of acetylcholinesterase by arginine. The stabilities of the resulting proteins were tested using denaturation by high temperature, organic solvents, urea and by proteolytic digestion. CONCLUSION: Altough the mutational effects were rather small, this strategy proved to be successful since half of the mutants showed an increased stability. This stability may originate from the suppression of unfavorable interactions of nonpolar residues with water or from addition of new hydrogen bonds with the solvent. Other mechanisms may also contribute to the increased stability observed with some mutants. For example, introduction of a charge at the surface of the protein may provide a new coulombic interaction on the protein surface

Acetylcholinesterase alterations reveal the fitness cost of mutations conferring insecticide resistance

BACKGROUND: Insecticide resistance is now common in insects due to the frequent use of chemicals to control them, which provides a useful tool to study the adaptation of eukaryotic genome to new environments. Although numerous potential mutations may provide high level of resistance, only few alleles are found in insect natural populations. Then, we hypothesized that only alleles linked to the highest fitness in the absence of insecticide are selected. RESULTS: To obtain information on the origin of the fitness of resistant alleles, we studied Drosophila melanogaster acetylcholinesterase, the target of organophosphate and carbamate insecticides. We produced in vitro 15 possible proteins resulting from the combination of the four most frequent mutations and we tested their catalytic activity and enzymatic stability. Mutations affected deacetylation of the enzyme, decreasing or increasing its catalytic efficiency and all mutations diminished the stability of the enzyme. Combination of mutations result to an additive alteration. CONCLUSION: Our findings suggest that the alteration of activity and stability of acetylcholinesterase are at the origin of the fitness cost associated with mutations providing resistance. Magnitude of the alterations was related to the allelic frequency in Drosophila populations suggesting that the fitness cost is the main driving force for the maintenance of resistant alleles in insecticide free conditions

Enhanced anti-HCV activity of interferon alpha 17 subtype

<p>Abstract</p> <p>Background</p> <p>Pegylated interferon alpha 2 (a or b) plus ribavirin is the most effective treatment of chronic hepatitis C but a large proportion of patients do not respond to therapy. So, it is interesting to improve the treatment efficacy. Interferon alpha is a type I interferon composed of 12 different subtypes. Each subtype signals by the Jak-Stat pathway but modulations in the antiviral activity was previously described.</p> <p>Methods</p> <p>Using the hepatitis C virus (HCV) culture system, we have tested the anti-HCV activity of each interferon alpha subtypes. We have analyzed the effect of each subtype on the HCV multiplication and the cell-signaling pathway for some subtypes.</p> <p>Results</p> <p>There were divergent effects of IFN alpha subtypes against HCV. We have found that IFN alpha 17 was three times more efficient than IFN alpha 2a on HCV. This efficiency was related to a stronger stimulation of the Jak-Stat pathway.</p> <p>Conclusion</p> <p>We suggest that IFN α17 should be tested therapeutically with a view to improving treatment efficacy.</p

Regulation by protein kinase-C of putative P-type Ca channels expressed in Xenopus oocytes from cerebellar mRNA

AbstractXenopus oocytes injected with rat cerebellar mRNA expressed functional voltage-dependent Ca channels detected as an inward Ba current (IBa). The pharmacological resistance to dihydropyridines and ω-conotoxin together with the blockade obtained with Agelenopsis aperta venom suggest that these channels could be somehow assimilated to P-type Ca channels. The precise nature of the transplanted Ca channels was assessed by hybrid-arrest experiments using a specific oligonucleotide antisense-derivated from the recently cloned α1-subunit of P channels (BI-1 clone). In addition, we demonstrate that exogenous Ca channel activity was enhanced by two different PKC activators (a phorbol ester and a structural analog to diacylglycerol). The general electrophysiological and pharmacological properties of the stimulated Ca channels remain unchanged. This potentiation induced by PKC activators is antagonized by a PKC inhibitor (staurosporine) and by a monoclonal antibody directed against PKC. It is concluded that P-type Ca channels are potentially regulated by PKC phosphorylation and the functional relevance of this intracellular pathway is discussed

A focus reduction neutralization assay for hepatitis C virus neutralizing antibodies

BACKGROUND/AIM: The role of humoral immunity in hepatitis C virus (HCV) infection is poorly understood. Nevertheless, there is increasing interest in characterizing the neutralizing antibodies in the serum of HCV-infected patients. Focus reduction assays have been widely used to evaluate neutralizing antibody responses against a range of non-cytopathic viruses. Based on the recent development of a HCV cell culture system using the genotype 2 JFH-1-strain, we developed a focus reduction assay for HCV-neutralizing antibodies. METHODS: The focus reduction assay was based on a standard microneutralization assay in which immunostained foci on tissue culture plates are counted. The neutralizing anti-HCV antibodies titers of purified serum immunoglobulin samples from seventy-seven individuals were determined using a 50% focus reduction neutralization assay. Each titer was determined as the log value of the reciprocal antibody dilution that reduced the number of viral foci by 50%. IgG antibodies were first purified from each serum in order to avoid the facilitating effect of HDL on HCV entry. RESULTS: The assay's cut-off using an ELISA and RNA HCV-negative samples was found to be 1.25 log, corresponding to a dilution of 1:18. The assay was compared with a commercial HCV ELISA and exhibited specificity and sensitivity values of 100% and 96.5%, respectively, and good reproducibility (with intra-assay and inter-assay coefficients of variation of 6.7% and 12.6%, respectively). The assay did not show any cross-reactivity with anti-HIV, anti-HBs or heterophile antibody-positive samples. The neutralizing antibodies titers were 2.13 log (1:134) for homologous samples from HCV genotype 2 infected patients harboring the same genotype as JFH-1 and 1.93 log (1:85) for heterologous samples from patients infected by genotypes other than type 2. These results confirm the presence of broadly cross-neutralizing antibodies already reported using the HCV pseudoparticles system. CONCLUSION: This study presents a simple, specific and reproducible cell culture-based assay for determination of HCV-neutralizing antibodies in human sera. The assay should be an important tool for gauging the relationship between the neutralizing antibodies response and viral load kinetics in acutely or chronically infected patients and for investigating the possible eradication or prevention of HCV infection by neutralizing antibodies