Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The objectives are to study and model the aggregate wind power fluctuations dynamics in the multifractal framework. We present here the analysis of aggregate power output sampled at 1 Hz during three years. We decompose the data into several Intrinsic Mode Functions (IMF) using Empirical Mode Decomposition (EMD). We use a new approach, arbitrary order Hilbert spectral analysis, a combination of EMD approach with Hilbert spectral analysis (or Hilbert Huang Transform) and the classical structure function analysis to extract the scaling exponents or multifractal spectrum $zeta(q)$: this function provides a full characterization of a process at all intensities and all scales. The application of both methods, i.e. structure function and arbitrary-order Hilbert spectral analyses, give similar results indicating that the aggregate power output from a wind farm, possesses intermittent and multifractal properties. In order to check this result, we generate stochastic simulations of a Multifractal Random Walk (MRW) using a log-normal stochastic equation. We show that the simulation results are fully compatible with the experimental results.
Physica A

hal-01527887
https://hal.archives-ouvertes.fr/hal-01527887
DOI : 10.1016/j.physa.2013.04.038

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Thermal diffusivity of synthetic quartz single-crystals and natural polycrystalline aggregates were measured using a modified Angstrom method at ambient pressure and up to 800 degrees C in order to investigate the effect of crystal preferred orientation on thermal diffusivity of quartz rich rocks. The thermal diffusivity tensor of quartz was determined by measuring the thermal diffusivity of an oriented synthetic quartz single-crystal along the [100] and [001] directions. A naturally deformed, fine-grained quartzite mylonite, was used to compare the single crystal properties with aggregate properties. Using the crystal preferred orientations (CPO) measured by the Electron Back Scattered Diffraction (EBSD) method and the measured thermal diffusivity tensor of quartz, the three-dimensional aggregate thermal diffusivity was modelled using volume averaging models. In order to test the validity of these models that are only based on the properties of the constituent minerals, the thermal diffusivity was then measured on oriented cores as a function of temperature, along three orthogonal directions, parallel to the (X-lineation, Y, Z-pole to foliation) structural frame. Both modelled and direct measurement of thermal diffusivity show an anisotropy of thermal diffusivity, heat transport being more effective parallel to Y-direction and less effective parallel to the lineation X-direction. Thermal diffusivities measured in a given direction on the natural rock are lower by less than 10% than the modelled thermal diffusivity in the same direction, showing that rock imperfections have a weak effect on heat transport. In addition, the modelled thermal diffusivity anisotropy based on the characterization of crystal orientations and thermal diffusivity tensor shows a good agreement with measurements in both alpha and beta stability field. This validation of the petrophysical simulation allows for evaluating the 3D thermal diffusivity of quartz rich rocks in different crustal conditions. The 3D thermal diffusivity of five naturally deformed quartzites displaying quartz fabrics expected in different crustal pressure and temperature ranges were simulated. The resulting thermal diffusivity anisotropies of quartzites range between 40% and 10%, depending on temperature, crystallographic fabric patterns and fabric strength. Under crustal conditions, quartzites deformed in the granulite facies display a high thermal diffusivity in the (XZ) foliation plane, whereas quartzites deformed in greenschist facies have highest thermal diffusivity in the (Z) direction normal to the foliation plane.
ISSN: 0040-1951

hal-00413568
https://hal.archives-ouvertes.fr/hal-00413568
DOI : 10.1016/j.tecto.2008.11.006

Éditeur(s) : HAL CCSD Springer-Verlag Berlin Heidelberg
Résumé : International audience
The main biological function of reaction wood is to act as " muscle " for trees, enabling them to control their posture. The key property to achieve this function is the development of high mechanical stress during the formation of reaction wood cells, called " maturation strains ". Actually, reaction wood formation is basically the asymmetric formation of wood around the tree circumference, with higher maturation strains on the side where reaction wood is formed than on the opposite side. This asymmetry enables stems to bend upward or to compensate for the downward bending induced by gravity. At the cross section level, the performance in this biological function is linked not only to the magnitude of this asymmetry but also to an effect of the cross-sectional size (diameter) of the stem. Eccentric growth and variations in wood mechanical stiffness are second order effects that can modify this performance. Differences in maturation strains between reaction and non-reaction woods are related to their specific cell wall structure and composition. The swelling of the cell wall matrix during maturation and the effect of microfibril angle explain the differences in maturation strains between normal and compression wood. However, this mechanism fails in explaining the high maturation shrinkage of tension wood, and several hypotheses at the molecular levels are still under debate. How trees perceive their gravitational disequilibrium is also an open question for physiologists. Integrative biomechanical modelling (from the polymer level to the cell wall, cross section and whole tree levels) enables defining key variables that explain the performance of reaction wood as a system that insures the stem motricity. Maturation strains can be precisely measured only in recently formed wood at the tree surface, but their changes during the whole tree life can also be estimated by retrospective dendrochronological analysis through structural markers of reaction wood. Lastly, wood in living trees ensures general storage, defence, vascular and skeletal functions, that ask general questions about synergies and trade-offs as the structural characteristics of reaction wood can affect all these functions.
The Biology of Reaction Wood

ISBN : 978-3-642-10813-6
hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085/document
https://hal.archives-ouvertes.fr/hal-01452085/file/Chap_Gril_al_Biomechanical_action_biological_functions_2014.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : The Duffy antigen/receptor for chemokine (DARC) is an erythrocyte receptor for malaria parasites (Plasmodium vivax and Plasmodium knowlesi) and for chemokines. In contrast to other chemokine receptors, DARC is a promiscuous receptor that binds chemokines of both CC and CXC classes. The four extracellular domains (ECDs) of DARC are essential for its interaction with chemokines, whilst the first (ECD1) is sufficient for the interaction with malaria erythrocyte-binding protein. In this study, we elaborate and analyze structural models of the DARC. The construction of the 3D models is based on a comparative modeling process and on the use of many procedures to predict transmembrane segments and to detect far homologous proteins with known structures. Threading, ab initio, secondary structure and Protein Blocks approaches are used to build a very large number of models. The conformational exploration of the ECDs is performed with simulated annealing. The second and fourth ECDs are strongly constrained. On the contrary, the ECD1 is highly flexible, but seems composed of three consecutive regions: a small beta-sheet, a linker region and a structured loop. The chosen structural models encompass most of the biochemical features and reflect the known experimental data. They may be used to analyze functional interaction properties.
ISSN: 0006-3002

inserm-00143373
http://www.hal.inserm.fr/inserm-00143373
http://www.hal.inserm.fr/inserm-00143373/document
http://www.hal.inserm.fr/inserm-00143373/file/de_Brevern_BBA_2005.pdf
DOI : 10.1016/j.bbagen.2005.05.016

Éditeur(s) : HAL CCSD
Résumé : Joint inversions are now commonly used in Earth Sciences. They have been developed to better understand Earth structure since they provide more constraints on the inverted parameters. We propose a new process to simultaneously invert several data sets in order to better image 3-D crustal and upper mantle structures. Our inversion uses 3 kind of data which present a good complementarity : (1) P receiver functions to provide Moho depth variations, (2) teleseismic delay times of P waves to retrieve velocity anomalies in the crust and upper mantle, (3) gravity anomalies to image density variations at lithospheric scale. In our scheme, receiver functions are first inverted. The resulting Moho depths are then interpolated and incorporated as a priori information into the joint inversion of teleseismic delay times and gravity anomalies process. In our new approach, we perform a model space search for Moho variations, P-velocity and density structure to find acceptable fit to the three data sets. In order to preferentially sample the good data fit region, we chose the Neighborhood algorithm of Sambridge to optimistically survey the model space. We model the delay times with a 3-D raytracing using velocity nodes evenly spaced and linked with density nodes via a linear relationship. This relationship can evolve through depth, simulating its pressure dependance. We test our scheme on synthetic examples, and apply the method in a continental rifting region where deformation processes are complex and badly known. This joint inversion thus provides more constraints on the inverted parameters, and allows us to better image crust - mantle interactions in the case of the Hangai dome (Central Mongolia). Indeed, in this area, we expect an asthenospheric upwelling to dynamically support the topography, but we image a density - velocity anomaly in the lower crust. The effects on topography and the origin (composition vs. thermal) of this anomaly are still under debate.
Les inversions conjointes sont maintenant communément utilisées en Sciences de la Terre. Elles ont été développées afin d'améliorer notre connaissance et compréhension de la structure interne de la Terre puisqu'elles apportent de plus en plus de contraintes sur les paramètres inversés. Dans cette thèse, nous proposons un nouveau processus d'inversion conjointe qui prend en compte trois paramètres différents et qui mène à l'obtention d'un modèle lithosphérique tridimensionnel. Notre méthode utilise trois types de données gravimétriques et sismologiques qui présentent une bonne complémentarité : (1) Les fonctions récepteur P afin d'obtenir les variations de profondeur du Moho, (2) les délais de temps d'arrivées P des téléséismes pour retrouver les anomalies de vitesse dans la croûte et le manteau supérieur, (3) les anomalies gravimétriques qui donnent accès aux variations de densité à l'échelle lithosphérique. Dans le schéma d'inversion proposé, nous inversons d'abord les fonctions récepteur. Les variations de profondeur du Moho qui en résultent sont alors interpolées puis incorporées comme information a priori dans le processus d'inversion conjointe gravimétrie - tomographie télésismique. Que ce soit pour les fonctions récepteur ou pour la partie conjointe, notre méthode d'inversion se base sur un algorithme de recherche afin de trouver la structure qui minimise l'écart aux trois types de données. Nous avons opté pour l'algorithme de voisinage qui présente l'avantage de concentrer sa recherche dans les régions qui minimisent l'écart aux données sans toutefois abandonner les autres régions afin de limiter les risques de convergence vers un minimum local. Nous utilisons un modèle 3-D constitué de noeuds de vitesse afin de modéliser les délais de temps. Ces noeuds de vitesse sont liés aux noeuds de densité grâce à une relation linéaire entre vitesse et densité. Cette relation peut évoluer avec la profondeur de manière à simuler les effets dus aux variations de pression. Nous avons réalisé plusieurs tests synthétiques afin d'évaluer le comportement de notre nouvelle méthode. Ils ont permis de montrer que les variations du Moho ainsi que les anomalies de vitesse et densité sont bien retrouvées. Ils ont également montré l'importance de la prise en compte de ces trois types de données dans un même schéma d'inversion, notamment en ce qui concerne la faculté de discerner les variations d'interfaces des anomalies volumiques. Nous avons ensuite appliqué la méthode dans une région continentale en phase de rifting où les processus de déformation sont complexes et mal connus. Notre nouvelle méthode a apporté davantage de contraintes sur les paramètres inversés et a permis d'obtenir un modèle correctement résolu de la croûte et du manteau supérieur sous le dôme de Hangai (Mongolie Centrale). Une anomalie asthénosphérique sous le dôme est souvent invoquée pour expliquer sa topographie élevée mais c'est une anomalie (en vitesse et densité) crustale (croûte inférieure) qui s'exprime dans nos modèles. Ses effets sur la topographie et son origine (compositionnelle et/ou thermique) sont encore débattus et nécessiteraient des études plus poussées (paramétriques, VP =VS, ...).
https://tel.archives-ouvertes.fr/tel-00783524

tel-00783524
https://tel.archives-ouvertes.fr/tel-00783524
https://tel.archives-ouvertes.fr/tel-00783524/document
https://tel.archives-ouvertes.fr/tel-00783524/file/Basuyau2011.pdf

Éditeur(s) : HAL CCSD Lippincott, Williams & Wilkins
Résumé : International audience
BACKGROUND: People in developed countries are widely exposed to low levels of organochlorine pesticides, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Seafood is a major contributor to PCB exposure. Toxicity of those various pollutants to reproductive and endocrine functions raises questions about possible effects on fertility. We explored whether serum levels of these pollutants and seafood consumption were associated with the fertility of couples enrolled in a French birth cohort (PELAGIE). METHODS: Time-to-pregnancy was investigated in 3,421 pregnant women by asking how many months they had taken to conceive. Levels of 14 organochlorine pesticides, 12 PCBs, and 10 PBDE compounds were measured in cord blood serum from a random subcohort (n = 394). Mercury concentrations measured in maternal hair were considered as a potential coexposure. Fecundability odds ratios (ORs) were estimated from multivariate discrete-time Cox proportional hazard models. RESULTS: Shellfish consumption was associated with longer time-to-pregnancy (fecundability OR ≥twice/week vs. 0.410 µg/L vs. <0.266 µg/L, fecundability OR = 0.46 [0.32-0.66]). In multiple sensitivity analyses, reduced fecundability was most consistently associated with shellfish consumption, p,p'-DDE, total PCBs, PCB153, and PCB187. Models that simultaneously included multiple coexposure factors led to similar conclusions. CONCLUSIONS: Our findings were robust in sensitivity analyses, including analysis restricted to primiparous women. These results suggest that PCBs, p,p'-DDE, and other shellfish contaminants may impair human fertility.
ISSN: 1044-3983

inserm-00826533
http://www.hal.inserm.fr/inserm-00826533
DOI : 10.1097/EDE.0b013e31827f53ec
PUBMED : 23348067

Éditeur(s) : Ecole Nationale Supérieure Agronomique de Rennes (ENSAR)
Résumé : Artificial Fish Aggregating Devices (FADs) are known to concentrate tropical tunas. This aggregative behaviour drastically increases the vulnerability of these species to fishing. Alternatively, FADs can be used as oceanic observatories to study the aggregative behaviour of large pelagic fish. We conducted sea surveys in Martinique (Lesser Antilles) to i) establish a typology of the pelagic fish aggregations found around moored FADs ii) study their relations with their biotic and abiotic environment and the local fishery. The mean biomass of large pelagic fish aggregations was also estimated to provide scientific inputs to achieve a sustainable management of the moored FAD fishery. The first part presents the background of the study. We introduce the regional pelagic ecosystem, the aggregative behaviour of pelagic fish around FADs and the Martinican moored FAD fishery. The second part begins with a presentation of the conceptual framework of the study: the hierarchy theory. Observation scales and survey methodology are therefore described. Repeated echosounder surveys run in a star pattern were conducted around 2 moored FADs, in combination with underwater video observations, classical fishing experiments and CTD profiles. In the third part, the elements of the [moored FAD ¿ pelagic fish - environment - fishing] system and their interactions are numerically characterised in the vertical plane. The main type of pelagic fish aggregation was a large aggregation distributed in sub-surface (40-100 m) within a radius of 400 m of the FAD. This aggregation was mostly made of 60 cm FL blackfin tunas (Thunnus atlanticus). It appeared at sunrise and mostly spread away in the late afternoon. It was observed during all daytime surveys. The average density and the vertical structure of the micronektonic sound scattering layers (SSLs) were assessed locally around a FAD for 48h cycles. These SSLs descriptors showed positive correlation with the size and the abundance of the sub-surface tuna aggregation. Whereas this aggregation accounted for about 95% of the total biomass aggregated around a moored FAD, it was nearly unexploited by the local commercial fishermen. The fourth part focuses on the sub-surface tuna aggregation. A high variability of the spatial distribution of the aggregation was evidenced in the horizontal plane at daily, day to day and monthly temporal scales. These variations were related to fluctuations of the global abundance of the aggregation. The daytime average density of sub-surface tuna was modelled as a function of the distance to FAD, within an advection-diffusion framework. Based on these results, a universal kriging model was designed to assess the mean maximum daily biomass of the sub-surface tuna aggregation. This mean biomass estimate yielded 11 tons with an estimation error of 26%. To conclude, we present a hierarchical organization in space and time of a sub-surface tuna population distributed within a network of moored FADs, from micro to meso-scale. We suggest that the spatial distribution of tunas can be explained from fine to coarse-scales by behavioural processes (self-organization, feeding, aggregative behaviour) whereas their spatial distribution is mainly forced by environmental processes at broader scales.
L'utilisation de Dispositifs de Concentration de Poissons permet de provoquer la formation de larges agrégations de thonidés autour de dispositifs artificiels, ce qui augmente considérablement la vulnérabilité de ces ressources vis-à-vis de l'exploitation halieutique. Les DCP peuvent également être utilisés en tant qu'observatoires océaniques, afin d'étudier le comportement agrégatif du macronecton pélagique. Nous avons ainsi réalisé des observations autour de DCP ancrés en Martinique, afin de définir une typologie des agrégations de macronecton et de étudier leurs relations avec leur environnement biotique, abiotique et l'exploitation halieutique locale. Nous avons ensuite estimé la biomasse moyenne de macronecton agrégé autour d'un DCP ancré, afin de fournir des éléments scientifiques nécessaires à une gestion durable de ces ressources. La première partie présente le contexte de l'étude i.e. l'écosystème pélagique régional, le phénomène d'agrégation du macronecton autour des DCP et la pêche associée aux DCP ancrés en Martinique. La deuxième partie introduit la théorie de la hiérarchie qui a fourni le cadre conceptuel de l'étude et présente les échelles et méthodes d'observation. Le principal outil d'observation est un échosondeur scientifique, mis en oeuvre le long de parcours en étoile autour du DCP. Les prospections acoustiques ont été combinées à des observations vidéo sous marines, des pêches expérimentales et un suivi in-situ de l'environnement abiotique. La troisième partie présente une typologie des éléments constituant le système [DCP ancré - macronecton - environnement - pêche] dans le plan vertical et précise leurs interactions. Le type d'agrégation de macronecton dominant est une grande agrégation composée d'une majorité de thons noirs (Thunnus atlanticus) de taille moyenne (60 cm) distribuée en sub-surface (40-100 m), dans un rayon de 300 m autour de la tête des DCP. Cette agrégation se forme au lever du soleil et se disperse presque totalement dans l'après midi. Elle a été observée de jour lors de toutes les campagnes. Une corrélation positive entre la densité et la structure moyenne des couches micronectoniques diurnes évaluée localement autour du DCP au cours de 48 h et les dimensions et l'énergie acoustique de l'agrégation de thons de subs-surface a été mise en évidence. Malgré le fait que cette agrégation représente en moyenne 95 % de l'énergie acoustique du macronecton autour des DCP, elle est presque inexploitée par les pêcheurs artisans locaux. La quatrième partie met en évidence les fortes variations conjointes de la distribution spatiale dans le plan horizontal de la densité de l'agrégation de thons de sub-surface et de son abondance globale. Ces variations ont été observées au cours du cycle nycthéméral et aux échelles inter-journalières et mensuelles. La distribution spatiale moyenne de la densité diurne de l'agrégation en fonction de la distance au centre de gravité de l'agrégation est cependant très stable et peut être modélisée au moyen d'une équation d'advection-diffusion. Un modèle de krigeage universel, utilisant les résultats du modèle d'advection-diffusion, a permis d'évaluer la biomasse maximale journalière moyenne de l'agrégation de thons de sub-surface à une dizaine de tonnes, avec un coefficient de variation d'estimation de 26%. Nous proposons une représentation hiérarchique synthétique de la distribution spatiale d'une sous-population de thons dans un réseau de DCP ancrés de la micro à la méso-échelle. Nous suggérons que la distribution spatiale des thons est déterminée principalement à l'échelle fine (100m-1km) et à l'échelle grossière (1-10 km) par des processus comportementaux (auto-organisation, agrégation, nutrition) et par des processus environnementaux à échelle plus large.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/these-1735.pdf
http://archimer.ifremer.fr/doc/2006/sup-1735.pdf
http://archimer.ifremer.fr/doc/00000/1735/

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Rifting in a cratonic lithosphere is strongly controlled by several interacting processes including crust/mantle rheology, magmatism, inherited structure and stress regime. In order to better understand how these physical parameters interact, a 2 yr long seismological experiment has been carried out in the North Tanzanian Divergence (NTD), at the southern tip of the eastern magmatic branch of the East African rift, where the southward-propagating continental rift is at its earliest stage. We analyse teleseismic data from 38 broad-band stations ca. 25 km spaced and present here results from their receiver function (RF) analysis. The crustal thickness and Vp/Vs ratio are retrieved over a ca. 200 × 200 km2 area encompassing the South Kenya magmatic rift, the NTD and the Ngorongoro-Kilimanjaro transverse volcanic chain. Cratonic nature of the lithosphere is clearly evinced through thick (up to ca. 40 km) homogeneous crust beneath the rift shoulders. Where rifting is present, Moho rises up to 27 km depth and the crust is strongly layered with clear velocity contrasts in the RF signal. The Vp/Vs ratio reaches its highest values (ca. 1.9) beneath volcanic edifices location and thinner crust, advocating for melting within the crust. We also clearly identify two major low-velocity zones (LVZs) within the NTD, one in the lower crust and the second in the upper part of the mantle. The first one starts at 15–18 km depth and correlates well with recent tomographic models. This LVZ does not always coexist with high Vp/Vs ratio, pleading for a supplementary source of velocity decrease, such as temperature or composition. At a greater depth of ca. 60 km, a mid-lithospheric discontinuity roughly mimics the step-like and symmetrically outward-dipping geometry of the Moho but with a more slanting direction (NE–SW) compared to the NS rift. By comparison with synthetic RF, we estimate the associated velocity reduction to be 8–9 per cent. We relate this interface to melt ponding, possibly favouring here deformation process such as grain-boundary sliding (EAGBS) due to lithospheric strain. Its geometry might have been controlled by inherited lithospheric fabrics and heterogeneous upper mantle structure. We evidence that crustal and mantle magmatic processes represent first order mechanisms to ease and locate the deformation during the first stage of a cratonic lithospheric breakup.
ISSN: 0956-540X

hal-01622078
https://hal.archives-ouvertes.fr/hal-01622078
https://hal.archives-ouvertes.fr/hal-01622078/document
https://hal.archives-ouvertes.fr/hal-01622078/file/plasmanGJI2017.pdf
DOI : 10.1093/gji/ggx177

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : We designed a thermo-mechanical numerical model for fast-spreading mid-ocean ridge with variable viscosity, hydrothermal cooling, latent heat release, sheeted dyke layer, and variable melt intrusion possibilities. The model allows for modulating several accretion possibilities such as the "gabbro glacier" (G), the "sheeted sills" (S) or the "mixed shallow and MTZ lenses" (M). These three crustal accretion modes have been explored assuming viscosity contrasts of 2 to 3 orders of magnitude between strong and weak phases and various hydrothermal cooling conditions depending on the cracking temperatures value. Mass conservation (stream-function), momentum (vorticity) and temperature equations are solved in 2-D cartesian geometry using 2-D, alternate direction, implicit and semi-implicit finite-difference scheme. In a first step, an Eulerian approach is used solving iteratively the motion and temperature equations until reaching steady states. With this procedure, the temperature patterns and motions that are obtained for the various crustal intrusion modes and hydrothermal cooling hypotheses display significant differences near the mid-ocean ridge axis. In a second step, a Lagrangian approach is used, recording the thermal histories and cooling rates of tracers travelling from the ridge axis to their final emplacements in the crust far from the mid-ocean ridge axis. The results show that the tracer's thermal histories are depending on the temperature patterns and the crustal accretion modes near the mid-ocean ridge axis. The instantaneous cooling rates obtained from these thermal histories betray these discrepancies and might therefore be used to characterize the crustal accretion mode at the ridge axis. These deciphering effects are even more pronounced if we consider the average cooling rates occurring over a prescribed temperature range. Two situations were tested at 1275-1125 °C and 1050-850 °C. The first temperature range covers mainly the crystallization range that is characteristic of the high temperature areas in the model (i.e. the near-mid-oceanic-ridge axis). The second temperature range corresponds to areas in the model where the motion is mainly laminar and the vertical temperature profiles are closer to conductive. Thus, this situation results in less discriminating efficiency among the crustal accretion modes since the thermal and dynamic properties that are described are common to all the crustal accretion modes far from the ridge axis. The results show that numerical modeling of thermo-mechanical properties of the lower crusts may bring useful information to characterize the ridge accretion structure, hydrothermal cooling and thermal state at the fast-spreading ridges and may open discussions with petrological cooling rate results.
ISSN: 1991-959X

hal-00907012
https://hal.archives-ouvertes.fr/hal-00907012
DOI : 10.5194/gmd-6-1659-2013

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
We image the lithospheric and upper asthenospheric structure of western continental Yemen with 24 broadband stations to evaluate the role of the Afar plume on the evolution of the continental margin and its extent eastwards along the Gulf of Aden. We use teleseismic tomography to compute relative P-wave velocity variations in southwestern Yemen down to 300 km depth. Published receiver function analysis suggest a dramatic and localized thinning of the crust in the vicinity of the Red Sea and the Gulf of Aden, consistent with the velocity structure that we retrieve in our model. The mantle part of the model is dominated by the presence of a low velocity anomaly in which we infer partial melting just below thick Oligocene flood basalts and recent off-axis volcanic events (from 15 Ma to present). This low velocity anomaly could correspond to an abnormally hot mantle and could be responsible for dynamic topography and recent magmatism in western Yemen. Our new P-wave velocity model beneath western Yemen suggests the young rift flank volcanoes beneath margins and on the flanks of the Red Sea rift are caused by focused small-scale diapiric upwelling from a broad region of hot mantle beneath the area. Our work shows that relatively hot mantle, along with partial melting of the mantle, can persist beneath rifted margins after breakup has occurred.
ISSN: 1525-2027

hal-01015496
https://hal.archives-ouvertes.fr/hal-01015496
https://hal.archives-ouvertes.fr/hal-01015496/document
https://hal.archives-ouvertes.fr/hal-01015496/file/Korostelev_etal_GGG_2014.pdf
DOI : 10.1002/2014GC005316

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Binding of ligand FasL to its receptor Fas triggers apoptosis via the caspase cascade. FasL itself is homotrimeric, and a productive apoptotic signal requires that FasL be oligomerized beyond the homotrimeric state. We generated a series of FasL chimeras by fusing FasL to domains of the Leukemia Inhibitory Factor receptor gp190 which confer homotypic oligomerization, and analyzed the capacity of these soluble chimeras to trigger cell death. We observed that the most efficient FasL chimera, called pFasL, was also the most polymeric, as it reached the size of a dodecamer. Using a cellular model, we investigated the structure-function relationships of the FasL/Fas interactions for our chimeras, and we demonstrated that the Fas-mediated apoptotic signal did not solely rely on ligand-mediated receptor aggregation, but also required a conformational adaptation of the Fas receptor. When injected into mice, pFasL did not trigger liver injury at a dose which displayed anti-tumor activity in a model of human tumor transplanted to immunodeficient animals, suggesting a potential therapeutic use. Therefore, the optimization of the FasL conformation has to be considered for the development of efficient FasL-derived anti-cancer drugs targeting Fas.
ISSN: 1932-6203

hal-00873684
https://hal.archives-ouvertes.fr/hal-00873684
https://hal.archives-ouvertes.fr/hal-00873684/document
https://hal.archives-ouvertes.fr/hal-00873684/file/Functional_Characterization-accepted.pdf
DOI : 10.1371/journal.pone.0054000

Éditeur(s) : HAL CCSD
Résumé : International audience
In all vertebrate species, estrogens play a crucial role in the development, growth, and function of reproductive and nonreproductive tissues. A large number of natural or synthetic chemicals present in the environment and diet can interfere with estrogen signaling; these chemicals are called endocrine disrupting chemicals (EDCs) or xenoestrogens. Some of these compounds have been shown to induce adverse effects on human and animal health, and some compounds are suspected to contribute to diverse disease development. Because xenoestrogens have varying sources and structures and could act in additive or synergistic effects when combined, they have multiple mechanisms of action. Consequently, an important panel of in vivo and in vitro bioassays and chemical analytical tools was used to screen, evaluate, and characterize the potential impacts of these compounds on humans and animals. In this paper, we discuss different molecular actions of some of the major xenoestrogens found in food or the environment, and we summarize the current models used to evaluate environmental estrogens.
Int J Endocrinol

Droits : info:eu-repo/semantics/OpenAccess
inserm-00863365
http://www.hal.inserm.fr/inserm-00863365
http://www.hal.inserm.fr/inserm-00863365/document
http://www.hal.inserm.fr/inserm-00863365/file/501851.pdf
PUBMED : 23737774

Éditeur(s) : HAL CCSD
Résumé :   Diplôme : DEA
il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATION
Links between architectural stages of development (ASD), photosynthetic capacities and leaf characteristics in Tachigali melinonii (Caesalpiniaceae) were investigated in the tropical forest of French Guiana. Three ASD were sampled under three light conditions to elucidate the impact of ASD- and light-related changes on photosynthetic functional traits. Photosynthetic parameters (maximum rate in RubisCO carboxylation (Vcmax) and maximum rate of electron transport (Jmax) were estimated by adjusting a biochemical model (Farquhar et al., 1980) to response curves of CO2 assimilation rate to intercellular CO2 concentration, under saturated light. In addition, N and C foliar concentrations were analysed and N allocations to the carboxylation and bioenergetic processus of photosynthesis were calculated using the model of Niinemets and Tenhunen (1997). The variations in ecophysiological parameters observed were due to leaf anatomical and structural changes instead of changes in photosynthetic components, suggesting adjustments to light conditions. Tachigali melinonii thus appears to display morphological and anatomical plasticity at different ASDs and under different light conditions.
Une espèce forestière de Guyane Française, Tachigali melinonii (Caesalipiniaceae), a été choisie afin de regarder la variation des traits fonctionnels relatifs à la photosynthèse en fonction de la disponibilité en lumière et en fonction de son stade de développement architectural. Du fait du tempérament de l'espèce vis-à-vis de la lumière de type «struggling gambler» (ombrage nécessaire aux jeunes stades puis développement en pleine lumière), trois stades clefs de développement parmi la séquence de différenciation de l'espèce ainsi que trois environnements lumineux ont été choisis. Les capacités photosynthétiques foliaires ont été estimées à partir de l'ajustement de paramètres du modèle biochimique de photosynthèse foliaire (Farquhar et al. 1980) sur des courbes de réponses de l'assimilation de CO² (A) à des concentrations intracellulaires en CO² (Ci) croissantes, en condition de lumière saturante. La vitesse maximale de carboxylation Vcmax et le flux maximal d'électrons photosynthétiques Jmax ont ainsi été estimés et ensuite reliés aux caractéristiques structurales foliaires, notamment la concentration en azote, en carbone ainsi qu'avec la densité et l’épaisseur. Les fractions d'azote allouées aux processus photosynthétiques de carboxylation et de bioénergétique ont été calculées. Des variations, dues à un effet du stade de développement sur les paramètres étudiés ainsi qu’à un effet de la quantité de lumière disponible, ont été constatées. Ces variations sont surtout liées à des ajustements anatomiques et structuraux foliaires et non à des modifications de l’appareil photosynthétique. Tachigali melinonii semble donc modifier ses caractéristiques structurales foliaires en fonction de son stade de développement, ce qui suppose un contrôle ontogénique partiel, et en fonction de la disponibilité en lumière.
https://hal.archives-ouvertes.fr/hal-01189520

hal-01189520
https://hal.archives-ouvertes.fr/hal-01189520
PRODINRA : 44951

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Cross-species analyses of plant functional traits have shed light on factors contributing to differences in performance and distribution, but to date most studies have focused on either leaves or stems. We extend these tissue-specific analyses of functional strategy towards a whole-plant approach by integrating data on functional traits for 13 448 leaves and wood tissues from 4672 trees representing 668 species of Neotropical trees. Strong correlations amongst traits previously defined as the leaf economics spectrum reflect a tradeoff between investments in productive leaves with rapid turnover vs. costly physical leaf structure with a long revenue stream. A second axis of variation, the 'stem economics spectrum', defines a similar tradeoff at the stem level: dense wood vs. high wood water content and thick bark. Most importantly, these two axes are orthogonal, suggesting that tradeoffs operate independently at the leaf and at the stem levels. By simplifying the multivariate ecological strategies of tropical trees into positions along these two spectra, our results provide a basis to improve global vegetation models predicting responses of tropical forests to global change.
ISSN: 1461-023X

hal-00594040
https://hal.archives-ouvertes.fr/hal-00594040

Éditeur(s) : HAL CCSD American Physiological Society
Résumé : International audience
Zidi-Yahiaoui N, Callebaut I, Genetet S, Le Van Kim C, Cartron JP, Colin Y, Ripoche P, Mouro-Chanteloup I. Functional analysis of human RhCG: comparison with E. coli ammonium transporter reveals similarities in the pore and differences in the vestibule. Am J Physiol Cell Physiol 297: C537–C547, 2009. First published June 24, 2009; doi:10.1152/ajpcell.00137.2009.—Rh glycoproteins are members of the ammonium transporter (Amt)/methylamine permease (Mep)/Rh family facilitating movement of NH3 across plasma membranes. Homology models constructed on the basis of the experimental structures of Escherichia coli AmtB and Nitrosomonas europaea Rh50 indicated a channel structure for human RhA (RhAG), RhB (RhBG), and RhC (RhCG) glycoproteins in which external and internal vestibules are linked by a pore containing two strictly conserved histidines. The pore entry is constricted by two highly conserved phenylalanines, “twin-Phe.” In this study, RhCG function was investigated by stopped-flow spectrofluorometry measuring kinetic pH variations in HEK293E cells in the presence of an ammonium gradient. The apparent unitary NH3 permeability of RhCG was determined and was found to be close to that of AmtB. With a site-directed mutagenesis approach, critical residues involved in Rh NH3 channel activity were highlighted. In the external vestibule, the importance of both the charge and the conformation of the conserved aspartic acid was shown. In contrast to AmtB, individual mutations of each phenylalanine of the twin-Phe impaired the function while the removal of both resulted in recovery of the transport activity. The impact of the mutations suggests that, although having a common function and a similar channel structure, bacterial AmtB and human Rh vary in several aspects of the NH3 transport mechanisms.
ISSN: 0363-6143

hal-00417492
https://hal.archives-ouvertes.fr/hal-00417492
DOI : 10.1152/ajpcell.00137.2009.

Éditeur(s) : HAL CCSD
Résumé : The main objective of this thesis was to study the influence of Guianan terra firme rainforests types on medium- and large-sized vertebrates community organization. First, we choose a model species which permitted to develop an appropriate abundance estimation method which take into account the imperfect detection and temporary immigration of mobile species, and to test environmental conditions effects at different spatial scales of analysis. Second, given that bias due to animal detection can be important in the abundance estimation, we determinated the relative role of environmental conditions and species biological traits on detection probability. From this methodological framework, we studied then processes of community organization, by identifying the main determinants involved in community organization, using composition and alpha and beta diversities, and, in a complementary manner, three metrics (taxonomic, functional, and phylogenetic). We sought from these general framework to determinate the relative role of environmental conditions and historical contingency, responsible for the current community organization, and to test the forest refugia hypothesis. Finally, we downscaled the analysis to determinate, and tried to disentangle the effects of environmental conditions and interspecific interactions on species co-occurrence. We used then functional traits to test the relationship between species co-occurrence and similarities.This thesis highlights the important role of historical contingency and facilitation in the structure of regional diversity and the local assembly processes of medium- and large-sized vertebrates, respectively, in French Guiana.
Cette thèse a pour but d’étudier l'influence de l'hétérogénéité des forêts de terre ferme en Guyane sur l'organisation des communautés de moyens et grands vertébrés. Nous avons, d'abord, choisi une espèce modèle afin de déterminer une méthode adéquate d'estimation d'abondance prenant en compte la détection imparfaite et l'immigration temporaire des espèces, et de tester l'effet des conditions environnementales à différentes échelles d'analyse. Puis, partant du constat que les biais dus à la détection dans l'estimation d'abondance pouvaient être importants, nous avons déterminé l'importance relative des conditions environnementales et des traits biologiques des espèces sur la probabilité de détection. A partir de ce cadre d'étude, nous avons étudié la composition et les diversités alpha et beta en utilisant de façon complémentaire les métriques taxonomique, fonctionnelle, et phylogénétique pour déterminer le rôle relatif de l'environnement et de la contingence historique dans l'organisation des communautés, et de tester l’hypothèse des refuges forestiers. Enfin, en descendant dans l'échelle d'analyse, nous avons tenté de démêler l'effet de l'environnement et des interactions interspécifiques sur la cooccurrence des espèces, et utilisé les traits fonctionnels des espèces pour tester le lien entre cooccurrence et similitude fonctionnelle. Cette thèse met en avant les rôles prépondérants de la contingence historique et de la facilitation dans, respectivement, la structuration de la diversité régionale et les processus d’assemblages locaux des communautés de moyens et grands vertébrés en Guyane.
https://tel.archives-ouvertes.fr/tel-01537779

NNT : 2017YANE0004
tel-01537779
https://tel.archives-ouvertes.fr/tel-01537779
https://tel.archives-ouvertes.fr/tel-01537779/document
https://tel.archives-ouvertes.fr/tel-01537779/file/these_thomas_denis.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The 12 May 2008 the Sichuan earthquake was one of the worst natural disasters in China. Here, we present a detailed picture of the epicentral area inferred geophysical data. Based on the analysis of teleseismic data acquired by a dense seismic network, we highlight an abrupt 20 km Moho offset between the Sichuan Basin and the Tibetan plateau and a horizontal discontinuity at similar to 15 km depth, which may connect with the ruptured zone of the 2008 event. We obtain low mean crustal velocity ratios, which suggest the absence of a thick and extensive zone of partial melt within the crust beneath the eastern part of the Songpan-Garze Terrane. All our data support the idea that the Longmen Shan range mark a zone of active strain localization due to the rigid Yangtze craton resisting eastward displacement of the Tibetan Plateau.
ISSN: 0040-1951

hal-00534471
https://hal.archives-ouvertes.fr/hal-00534471
DOI : 10.1016/j.tecto.2009.11.010

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
The dynamic model of plant growth GreenLab describes plant architecture and functional growth at the level of individual organs. Structural development is controlled by formal grammars and empirical equations compute the amount of biomass produced by the plant, and its partitioning among the growing organs, such as leaves, stems and fruits. The number of organs initiated at each time step depends on the trophic state of the plant, which is evaluated by the ratio of biomass available in plant to the demand of all the organs. The control of the plant organogenesis by this variable induces oscillations in the simulated plant behaviour. The mathematical framework of the GreenLab model allows to compute the conditions for the generation of oscillations and the value of the period according to the set of parameters. Two case-studies are presented, corresponding to emergence of oscillations associated to fructification and branching. Similar alternating patterns are commonly reported by botanists. In this article, two examples were selected: alternate patterns of fruits in cucumber plants and alternate appearances of branches in Cecropia trees. The model was calibrated from experimental data collected on these plants. It shows that a simple feedback hypothesis of trophic control on plant structure allows the emergence of cyclic patterns corresponding to the observed ones.
ISSN: 0973-5348

hal-00780592
https://hal-ecp.archives-ouvertes.fr/hal-00780592
https://hal-ecp.archives-ouvertes.fr/hal-00780592/document
https://hal-ecp.archives-ouvertes.fr/hal-00780592/file/Mathieu_2012_Published_mmnp201276p47.pdf
DOI : 10.1051/mmnp/20127603

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Our knowledge and understanding of the 3-D lithospheric structure of the Himalayas and the Tibetan Plateau is still challenging although numerous geophysical studies have been performed in the region. The GOCE satellite mission has the ambitious goal of mapping Earth's gravity field with unprecedented precision (i.e. an accuracy of 1-2 mGal for a spatial resolution of 100 km) to observe the lithosphere and upper-mantle structure. Consequently, it gives new insights in the lithospheric structure beneath the Himalayas and the Tibetan Plateau. Indeed, the GOCE gravity data now allow us to develop a new strategy for joint gravimetry-seismology inversion. Combined with teleseismic data over a large region in a joint inversion scheme, they will lead to lithospheric velocity-density models constrained in two complementary ways. We apply this joint inversion scheme to the Hi-CLIMB (Himalayan-Tibetan Continental Lithosphere during Mountain Building) seismological network which was deployed in South Tibet and the Himalayas for a 3-yr period. The large size of the network, the high quality of the seismological data and the new GOCE gravity data set allow us to image the entire lithosphere of this active area in an innovative way. We image 3-D low velocity and density structures in the middle crust that fit the location of discontinuous low S-velocity zones revealed by receiver functions in previous geophysical studies. In the deeper parts of our velocity model we image a positive anomaly interpreted to be the heterogenous Indian lithosphere vertically descending beneath the centre of the Tibetan Plateau.
ISSN: 0956-540X

hal-00858024
https://hal.archives-ouvertes.fr/hal-00858024
DOI : 10.1093/gji/ggs110

Éditeur(s) : HAL CCSD Wiley
Résumé : Negative density dependence (NDD) and environmental filtering (EF) shape community assembly, but their relative importance is poorly understood. Recent studies have shown that seedlings mortality risk is positively related to the phylogenetic relatedness of neighbours. However, natural enemies, whose depredations often cause NDD, respond to functional traits of hosts rather than phylogenetic relatedness per se. To understand the roles of NDD and EF in community assembly, we assessed the effects on seedling mortality of functional similarity, phylogenetic relatedness and stem density of neighbouring seedlings and adults in a species-rich tropical forest. Mortality risks increased for common species when their functional traits departed substantially from the neighbourhood mean, and for all species when surrounded by close relatives. This indicates that NDD affects community assembly more broadly than does EF, and leads to the tentative conclusion that natural enemies respond to phylogenetically correlated traits. Our results affirm the prominence of NDD in structuring species-rich communities.
ISSN: 1461-023X

hal-01032429
https://hal.archives-ouvertes.fr/hal-01032429
DOI : 10.1111/j.1461-0248.2011.01705.x