Éditeur(s) : HAL CCSD Taylor & Francis (Routledge): STM, Behavioural Science and Public Health Titles
Résumé : International audience
The aim of this study was to determine factors associated with complete satisfaction with the care provided (satisfaction with physicians and satisfaction with services and organization) among HIV-infected patients followed up in the French ANRS CO8 APROCO-COPILOTE cohort. Analyses focused on cross-sectional data collected during the ninth year of cohort follow-up. Satisfaction with care, sociodemographic characteristics, and behavioral data were collected using self-administered questionnaires, while clinical data were derived from medical records. Complete satisfaction with care was defined as being 100% satisfied. Two logistic regression models were used to identify predictors of (1) complete satisfaction with physicians (n=404) and (2) complete satisfaction with services and organization (n=396). Sixteen percent of patients were completely satisfied with physicians, while 15.9% were completely satisfied with services and organization. Being older and reporting fewer discomforting antiretroviral therapy (ART) side effects were factors independently associated with complete satisfaction with both physicians and services and organization. Strong support from friends and absence of hepatitis C (HCV) co-infection were independently associated with complete satisfaction with physicians, while strong support from one's family and comfortable housing conditions were independently associated with complete satisfaction with services and organization. Even after nine years of follow-up, social vulnerabilities still strongly influence HIV-infected patients' interactions with the health care system. Day-to-day experience with the disease, including perceived treatment side effects, appears to play a key role in the quality of these interactions. More attention should be given to patient satisfaction, especially for socially vulnerable patients, in order to avoid potentially detrimental consequences such as poor adherence to ART.
AIDS Care

hal-00875619
https://hal.archives-ouvertes.fr/hal-00875619
DOI : 10.1080/09540121.2011.613909
PUBMED : 21999644

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
In this work, we have studied quenching of the fluorescence of two well-known oxygen probes, 1-pyrene butyric acid (PBA) and tris(2,2'-bipyridine)ruthenium ([Ru(bpy)(3)](2+)) by reactive oxygen species (superoxide anion, nitric oxide derivative, hydrogen peroxide) and by the O(2) molecule. Both, time-resolved and steady state fluorescence measurements were performed in solution (ethanol, dimethyl sufoxide, water) and in micelles of Sodium Dodecyl Sulfate that serve as a model for membrane-containing biological structures. We have found that only the free radicals and O(2) can actively quench for the two probes, but not the diamagnetic H(2)O(2). Our data correspond to the classical Stern-Volmer equation. H(2)O(2) has an effect only at high molar concentrations (>0.1 M). In contrast, effective concentrations of free radicals and O(2) that lead to quenching are in millimolar range. In conclusion, our methods allows for detecting global ROS that are small free radicals without interference from the reactive hydroxyl radical. Our data suggest that the method can be used for the quantification of ROS in individual living cells based on the measurement of fluorescence lifetime of those probes
ISSN: 1053-0509

hal-01326234
https://hal.archives-ouvertes.fr/hal-01326234
DOI : 10.1007/s10895-008-0425-z

Éditeur(s) : HAL CCSD
Résumé : International audience
Filamentous sulfur bacteria of the genus Beggiatoa form large mats covering the sediment in the shallow waters of a Guadeloupean mangrove (French West Indies). The abundance of these bacteria varies over the year and their trophic role may, therefore, also vary. We investigated this variation by conducting a survey examining the stable isotopic compositions of four grazers and four food sources during nine sampling sessions in three different periods of the year. We analyzed bulk isotopic compositions for each component except for the bacterial and diatom communities, for which we carried out a compound-specific 13C analysis of phospholipid-derived fatty acids (PLFAs). Correlations between isotopic compositions revealed a predominance of diatoms in the diet of nematodes and the important role of detritus and bacteria in the diet of the polychaete Ceratocephale sp. None of the grazers had an isotopic composition correlated with that of Beggiatoa suggesting that sulfur bacteria were not a predominant part of the diet of any grazer. Beggiatoa has a large central vacuole, resulting in a very low carbon content-to-volume ratio, potentially accounting for its low level of attractiveness to grazers. Mangrove sediments are habitats rich in organic carbon, in which, the addition of a food source, such as Beggiatoa, would have a limited effect on the structure of the food web over the course of the year.
Food Webs

hal-01545906
https://hal.archives-ouvertes.fr/hal-01545906
DOI : 10.1016/j.fooweb.2016.04.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Over the last decades, numerous studies have emphasized the role of serpentinites in the subduction zone geodynamics. Their presence and role in subduction environments are recognized through geophysical, geochemical and field observations of modern and ancient subduction zones and large amounts of geochemical database of serpentinites have been created. Here, we present a review of the geochemistry of serpentinites, based on the compilation of ~ 900 geochemical data of abyssal, mantle wedge and exhumed serpentinites after subduction. The aim was to better understand the geochemical evolution of these rocks during their subduction as well as their impact in the global geochemical cycle. When studying serpentinites, it is essential to determine their protoliths and their geological history before serpentinization. The geochemical data of serpentinites shows little mobility of compatible and rare earth elements (REE) at the scale of hand-specimen during their serpentinization. Thus, REE abundance can be used to identify the protolith for serpentinites, as well as magmatic processes such as melt/rock interactions before serpentinization. In the case of subducted serpentinites, the interpretation of trace element data is difficult due to the enrichments of light REE, independent of the nature of the protolith. We propose that enrichments are probably not related to serpentinization itself, but mostly due to (sedimentary-derived) fluid/rock interactions within the subduction channel after the serpentinization. It is also possible that the enrichment reflects the geochemical signature of the mantle protolith itself which could derive from the less refractory continental lithosphere exhumed at the ocean-continent transition. Additionally, during the last ten years, numerous analyses have been carried out, notably using in situ approaches, to better constrain the behavior of fluid-mobile elements (FME; e.g. B, Li, Cl, As, Sb, U, Th, Sr) incorporated in serpentine phases. The abundance of these elements provides information related to the fluid/rock interactions during serpentinization and the behavior of FME, from their incorporation to their gradual release during subduction. Serpentinites are considered as a reservoir of the FME in subduction zones and their role, notably on arc magma composition, is underestimated presently in the global geochemical cycle.
ISSN: 0024-4937

hal-00903601
https://hal.archives-ouvertes.fr/hal-00903601
DOI : 10.1016/j.lithos.2013.05.019

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
In the mid-afternoon of 15 July 2007, during the Convective and Orographically induced Precipitation Study (COPS), in a very warm and dry environment, an isolated, short-lived, deep convective system developed over the southern Black Forest. Most of the high-resolution, convection-permitting models involved in COPS were unable to capture this event whereas the Meso-NH forecast was quite skilful. To assess the Meso-NH performance further, the model results were carefully checked against the various and numerous COPS observations. In full agreement with clear-air radar observations, model results underlined the triggering role of a low-level convergence line that developed in the lee of the Feldberg. The main departure from the observations was found to be in the low-level moisture fields, which appeared significantly moister in the model than in the observations and also slightly moister than in the other models. Sensitivity studies showed that this departure from the observations was strongly controlled by the initial surface moisture conditions. When the surface moisture was reduced by 20% or replaced by the value derived from a different analysis, the evolution of the planetary boundary layer was more accurately represented while the storm evolution was still correctly captured. These results demonstrate that the quality of the initial forecast cannot be ascribed to the moist bias of the model. It could therefore be hypothesized that the key parameters for a satisfactory forecast of this event lie more in the ability of the model to reproduce the dynamical forcing accurately than in the characteristics of the air-mass instability.
ISSN: 0035-9009

hal-00554400
https://hal.archives-ouvertes.fr/hal-00554400
DOI : 10.1002/qj.710

Éditeur(s) : HAL CCSD Elsevier
Résumé : Le titre a été changé Ancien titre: Roles for local crowding and pressure in counteracting density fluctuations at equilibrium
International audience
What is the probability that all the gas in a box accumulates in the same half of this box? Though amusing, this question underlies the fundamental problem of density fluctuations at equilibrium, which has profound implementations in many physical fields. The currently accepted solutions are derived from the studies of Brownian motion by Smoluchowski, but they are not appropriate for the directly colliding particles of gases. Two alternative theories are proposed here using self-regulatory Bernoulli distributions. A discretization of space is first introduced to develop a mechanism of matter congestion holding for high densities. In a second mechanism valid in ordinary conditions, the influence of local pressure on the location of every particle is examined using classical laws of ideal gases. This approach reveals that a negative feedback results from the reciprocal influences between individual particles and the population of particles, which strongly reduces the probability of atypical microstates. Finally, a thermodynamic quantum of time is defined to compare the recurrence times of improbable macrostates predicted through these different approaches.
Physica A: Statistical Mechanics and its Applications

hal-00920985
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00920985
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00920985v2/document
ARXIV : 1404.6223
DOI : 10.1016/j.physa.2014.03.067

Éditeur(s) : ICES 2008 Annual Science Conference, 22-26 september 2008, HALIFAX, CANADA
Résumé : While the majority of small-scale coastal fisheries are found in developing nations, a considerable number exist in developed nations as well. Indeed, small-scale fisheries are strongly represented in all European Union (EU) Member States, 81% and 87% of the EU 25 whole fleet is composed of vessels less than 12 and 15 meters long respectively. In 2000, European regulation established a fisheries data collection framework including economic information requirements in order to provide the scientific basis for the implementation of the Common Fisheries Policy. This paper presents the methodology designed to collect the relevant economic data and characterize the status of the French fleets from an economic perspective. Based on stratified sampling plan including the following of small-scale fleets, data collection by field survey is based on a single questionnaire for all the fleets, whatever the size of the vessel, the gear used, the fishing area or the species targeted. It provides a large data set including earnings and costs but also capital, employment, fishing activity figures. Statistical analysis through a revenue model gives the basis for a re-assessing of the small-scale fisheries contribution to national production. Economic indicators such as gross added value, revenues, and direct employment are derived from the data set. The significant role of small scale fisheries in the French fishing sector is established and the impact of the rising fuel costs in fisheries is discussed.

Droits : 2008 ICES
http://archimer.ifremer.fr/doc/00059/16998/14500.pdf
http://archimer.ifremer.fr/doc/00059/16998/

Éditeur(s) : Elsevier
Résumé : The uptake and loss kinetics of Cd were determined in two species of scallops from the European coasts, the variegated scallop Chlamys varia and the king scallop Pecten maximus, following exposures via seawater, phytoplankton and sediment using highly sensitive radiotracer techniques (Cd-109). Results indicate that, for seawater and dietary pathways, C. varia displays higher bioaccumulation capacities in terms of uptake rate from water and fraction absorbed from ingested food (assimilation efficiency) than Pecten maximus. Regarding sediment exposure, P. maximus displayed low steady-state Cd transfer factor (TFSS < 1); however, once incorporated, a very large part of Cd transferred from sediment (92%) was strongly retained within R maximus tissues. Both species showed a high retention capacity for Cd (biological half-life, T-b1/2 > 4 months), suggesting efficient mechanisms of detoxification and storage in both species. The digestive gland was found to be the main storage organ of Cd in the two scallops regardless of the exposure pathway. However, Cd was stored differently within this organ according to the species considered: 40% of the total Cd was found in the soluble cellular fraction in C. varia whereas this soluble fraction reached 80% for P. maximus. This suggests that the two species displayed different Cd detoxification/storage mechanisms. Finally, the present study has determined the relative contribution of the different exposure pathways to global Cd bioaccumulation for the two scallop species. Results clearly show that for both species, food constitutes the major accumulation pathway, contributing for >99% and 84% of the global Cd bioaccumulation in C. varia and R maximus, respectively. This work confirms the previous assumption, derived from a bibliographic overview, that dietary pathway plays a prevalent role in metal bioaccumulation in Pectinidae. (C) 2007 Elsevier B.V. All rights reserved.
Journal of Experimental Marine Biology and Ecology (0022-0981) (Elsevier), 2007-12 , Vol. 353 , N. 1 , P. 58-67

Droits : 2007 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2007/publication-3581.pdf
DOI:10.1016/j.jembe.2007.09.001
http://archimer.ifremer.fr/doc/00000/3581/

Éditeur(s) : Elsevier Science Bv
Résumé : There has been growing interest in the development of mud crab aquaculture in New Caledonia. However, for this to become established at a commercial level, a cost-effective formulated feed based on internationally-available ingredients needs to be developed. We have evaluated the optimal dietary protein content for juvenile crabs, Scylla serrata (Forskål, 1775), using a series of diets with a protein content ranging from 27 to 49% and soy protein concentrate (SPC) as the main protein source. For this purpose, 54 individually housed crabs were allocated to five dietary treatments (n = 10 or 11). The crabs were fed ad libitum, for 81 days with the allocated diets. The apparent digestibilities of dry mater, crude protein and energy were high (96.2-97.3%), irrespective of the diet. The voluntary feed intake (VFI) of crabs widely varied from 46 to 220 g kg- 1of fresh initial body weight per week (iBW week- 1) whatever the diet. However, SPC intake and protein intake increased significantly with dietary protein content up to the diet with 40% crude protein, but did not increase further with diets containing 44% and 49% crude protein. The cumulative molts were strongly affected by the VFI levels or energy intake and also, to a lesser extent, by the levels of SPC or protein in diets. Two phases in tissue gain were observed after ecdysis: an initial deposition phase lasting around 30 days followed by a plateau which lasted until the next molt. The daily tissue growth was 16.5% of dry body weight (dry BW) one day after ecdysis and dramatically decreased to 3.6% of dry BW over the first 10 days, then decreased more slowly to the minimum value of 1.3% of dry BW over the next 70 days. During the course of experiment, the best growth (tissue growth and molt frequency) and the best feed efficiency (FCR, PER, retention of proteins and lipids) were obtained with crabs fed on the diet with 40% crude protein. This result was confirmed by a bioenergetic study which showed significantly higher allocation of the energy intake for growth (RE) of crabs fed on diet 40% crude protein. Finally, under our experimental conditions, 1 kg of juvenile crabs required 6.5 ± 1.1 g of protein per day. This level was obtained with the diet SPC-42 that contained 40% of protein of which almost three quarters were derived from SPC. Two hypotheses are proposed to explain the negative effect of high level of SPC or protein on growth and feed efficiency for crabs fed on in diets containing 52% and 60% SPC.
Aquaculture (0044-8486) (Elsevier Science Bv), 2014-10 , Vol. 434 , P. 499-509

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00211/32196/30630.pdf
http://archimer.ifremer.fr/doc/00211/32196/

Éditeur(s) : Université Paris 7 – Denis Diderot
Résumé : Sea surface salinity (SSS) influences numerous oceanic phenomena, for instance surface water ventilation, deep water formation and thermohaline circulation. SSS also controls some ocean-atmosphere coupled processes, such as the intensity of freshwater flux and the penetration of heat flux and turbulence. Salinity is more difficult to measure than temperature from in situ surveys, which results in 20 times less data being currently available. Moreover, sea surface temperature (SST) is routinely estimated from satellites, which is not possible yet for SSS. Two space missions will fill this gap soon: SMOS from the European Space Agency and Aquarius/SAC-D from NASA and CONAE. To contribute to the SMOS project, we propose a method for estimating SSS from current satellite observations and for studying the mechanisms governing its variability. We developed a simplified model of the ocean mixed layer, based on the "slab mixed layer" formulation (Frankignoul et Hasselmann, 1977). This 2D horizontal model is implemented over the global ocean, using a near 100 km resolution, and integrated during a climatological year. Air-sea fluxes are taken from the ECMWF meteorological model (ERA40 reanalysis) and the surface currents are provided by altimeter data (SSALTO-DUACS analysis). The mixed layer depth (MLD) is derived from SST observations, using an original inversion technique. The MLD fields obtained from this inversion are well correlated to in situ estimates. This effective depth represents the air-sea fluxes penetration and ensures consistency between fluxes, les currents and SST. We first validate the simulation through examination of the heat balance in north-eastern Atlantic, by comparing to measurements and models from the POMME experiment. Then we study the salinity balance in the global domain, in terms of its geographical distribution and seasonal evolution. Equilibrium between the various processes appears generally more complex than for temperature. Noteworthy, the role of atmospheric flux is less predominant (22%), while geostrophic advection (33%) and diapycnal mixing (22%) contribute more strongly. Our results indicate this model succeeds in reconstructing SSS variability over most of the oceans. Daily SSS variations are also simulated, whereas they are not represented in current observed data at a global scale. Owing to its simplicity and fast computation, the model will be useful to the SMOS mission. It can help for the measurement calibration/validation and provide a first guess estimate to the sophisticated algorithm required for SSS restitution.
La salinité de surface des océans (SSS) influence de nombreux phénomènes océaniques, parmi lesquels la ventilation des eaux de surface, la formation d'eaux profondes et la circulation thermohaline. Elle détermine aussi certains processus couplés océan-atmosphère, notamment l'intensité du flux d'eau douce, la pénétration du flux de chaleur et de la turbulence. La mesure in situ de salinité est plus compliquée que celle de température, si bien qu'on dispose actuellement de 20 fois moins de données pour cette propriété. De plus, la température de surface (SST) est couramment estimée par satellite, ce qui n'est pas encore le cas de la SSS. Deux missions spatiales vont prochainement combler cette lacune : le satellite SMOS de l'Agence Spatiale Européenne et le satellite Aquarius/SAC-D de la NASA et de la CONAE. En préparation du projet SMOS, nous proposons une méthode pour estimer la SSS à partir des observations satellitaires actuelles et étudier les mécanismes de sa variabilité. Nous avons développé un modèle simplifié de couche mélangée océanique, basé sur la formulation "slab mixed layer" (Frankignoul et Hasselmann, 1977). Ce modèle 2D horizontal est implémenté sur l'océan global, avec une résolution proche de 100 km, et intégré au cours d'une année climatologique. Les flux air-mer proviennent du modèle météorologique ECMWF (réanalyse ERA40) et les courants de surface sont issus de l'altimétrie (analyse SSALTO-DUACS). La profondeur de la couche mélangée (MLD) est dérivée des observations de SST, grâce à une technique d'inversion originale. La MLD obtenue par inversion est bien corrélée aux estimations basées sur des données in situ. Cette profondeur effective représente la pénétration des flux air-mer et assure la cohérence entre les flux, les courants et la SST. La simulation est d'abord validée en examinant le bilan de chaleur dans l'Atlantique Nord-Est, par comparaison aux mesures et aux modèles de l'expérience POMME. Puis le bilan de salinité est étudié dans le domaine global, en termes de distribution géographique et d'évolution saisonnière. L'équilibre entre les différents processus est généralement plus complexe que pour la température. Notamment, le rôle du flux atmosphérique est moins prépondérant (22%), tandis que l'advection géostrophique (33%) et le mélange diapycnal (22%) contribuent fortement. Nos résultats montrent que ce modèle parvient à restituer la variabilité de la SSS sur la majeure partie des océans. Le modèle simule aussi les variations journalières de SSS, qui ne sont pas représentées à l'échelle globale dans les observations actuelles. Grâce à sa simplicité et à sa rapidité, le modèle pourra être utile dans le cadre de SMOS. Il pourra aider à la calibration/validation de la mesure et fournir une estimation a priori pour l'algorithme complexe nécessaire à la restitution de la SSS.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/these-2302.pdf
http://archimer.ifremer.fr/doc/00000/2302/

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: Myosin II (or Myosin Heavy Chain II, MHCII) is a family of molecular motors involved in the contractile activity of animal muscle cells but also in various other cellular processes in non-muscle cells. Previous phylogenetic analyses of bilaterian MHCII genes identified two main clades associated respectively with smooth/non-muscle cells (MHCIIa) and striated muscle cells (MHCIIb). Muscle cells are generally thought to have originated only once in ancient animal history, and decisive insights about their early evolution are expected to come from expression studies of Myosin II genes in the two non-bilaterian phyla that possess muscles, the Cnidaria and Ctenophora. Results: We have uncovered three MHCII paralogues in the ctenophore species Pleurobrachia pileus. Phylogenetic analyses indicate that the MHCIIa /MHCIIb duplication is more ancient than the divergence between extant metazoan lineages. The ctenophore MHCIIa gene (PpiMHCIIa) has an expression pattern akin to that of ``stem cell markers'' (Piwi, Vasa...) and is expressed in proliferating cells. We identified two MHCIIb genes that originated from a ctenophore-specific duplication. PpiMHCIIb1 represents the exclusively muscular form of myosin II in ctenophore, while PpiMHCIIb2 is expressed in non-muscle cells of various types. In parallel, our phalloidin staining and TEM observations highlight the structural complexity of ctenophore musculature and emphasize the experimental interest of the ctenophore tentacle root, in which myogenesis is spatially ordered and strikingly similar to striated muscle formation in vertebrates. Conclusion: MHCIIa expression in putative stem cells/proliferating cells probably represents an ancestral trait, while specific involvement of some MHCIIa genes in smooth muscle fibres is a uniquely derived feature of the vertebrates. That one ctenophore MHCIIb paralogue (PpiMHCIIb2) has retained MHCIIa-like expression features furthermore suggests that muscular expression of the other paralogue, PpiMHCIIb1, was the result of neofunctionalisation within the ctenophore lineage, making independent origin of ctenophore muscle cells a likely option.
ISSN: 1471-2148

hal-01544486
https://hal.archives-ouvertes.fr/hal-01544486
DOI : 10.1186/1471-2148-12-107

Éditeur(s) : HAL CCSD National Academy of Sciences
Résumé : International audience
Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of similar to 12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 size-fractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.
ISSN: 0027-8424

hal-01545320
https://hal.archives-ouvertes.fr/hal-01545320
DOI : 10.1073/pnas.1509523113

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : Modern geochronology has moved beyond the acquisition of dates: the goal is to understand the significance of these numbers for the geodynamic evolution of Earth at all scales. The coupling of the laser-ablation microprobe (LAM) to inductively coupled plasma mass spectrometers (ICPMS, multicollector (MC)-ICPMS) has revolutionised geochronology and geochemistry over the last 10 years. These systems enable the rapid and precise in situ analysis of trace-element patterns and isotopic systems, while adding information related to microstructural context and major-element composition. The integration of these multiple sources of data is crucial in constraining the origin of the sample and the processes leading to its formation, so that we can understand the meaning of a date in terms of geological events. LAM-ICPMS measurement of U-Pb ages and trace-element patterns in zircon, coupled with LAM-MC-ICPMS analysis of Hf isotopes in the same grains, gives new insights into the processes of magma genesis. Applied to detrital zircons from modern drainages or sedimentary rocks (the TerraneChron approach), it becomes a powerful tool to investigate problems of crustal evolution on scales ranging from single terranes to continents. The in situ analysis (LAM-MC-ICPMS) of Re-Os systematics in single grains of sulfides in mantle-derived peridotites has demonstrated that most mantle rocks contain several generations of Os-bearing sulfides; whole-rock analyses are mixtures reflecting multiple melting and metasomatic events in the lithospheric mantle. These deep-seated events are commonly mirrored in the crust; Os model-age spectra from xenolith suites show age 'peaks' that correspond to the ages of thermal/tectonic events in the overlying crust, suggesting strong linkages between crust and mantle. Integrated studies of the timing and nature of crustal and mantle events, using these techniques, will be important for understanding the large-scale dynamics of the Earth.
ISSN: 0812-0099

hal-00411328
https://hal.archives-ouvertes.fr/hal-00411328
DOI : 10.1080/08120090802097450

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
We investigate the deformation induced by water pressure variations in hydrologically active natural fractures, and recorded by tiltmeters and strainmeters. The deformation associated with a single fracture is derived using finite-element modelling (FEM). A range in fracture geometries is explored, first to highlight the sensitivity of each geometrical parameter to the deformation, and secondly to allow transfer to observation sites. Water level variations in the fracture are then derived from a hydrological model, driven by observed rainfall, and calibrated on fracture water flow measurements. The modelling results are explicitly applied to constrain the local hydrological contribution to observations with the 100-m-long hydrostatic tiltmeter installed at Sainte-Croix-aux-Mines (France). Our study shows that well-founded physical modelling of local hydrological effect allows a substantial correction of records in observatories.
ISSN: 0956-540X

hal-00708093
https://hal.archives-ouvertes.fr/hal-00708093
https://hal.archives-ouvertes.fr/hal-00708093/document
https://hal.archives-ouvertes.fr/hal-00708093/file/fracture_v72.pdf
BIBCODE : 2009GeoJI.178..667L

Éditeur(s) : HAL CCSD Copernicus Publications
Résumé : International audience
During Ocean Drilling Program Leg 134, a mixed sequence of volcaniclastic and carbonate sediments was cored together with basaltic breccias and a single basalt sill in Hole 833B. In this study, data from Schlumberger's Geochemical Logging Tool, together with physical property logs, characterise part of the section and establish a complete log-derived lithostratigraphy. The major transition between the sedimentary rocks and a basaltic sill at 830 mbsf (metres below sea floor) is clearly seen as well as the distinction between the silicate-rich sediments and the carbonate-rich part of the section. The transition between the volcanic sandstone interbedded with basaltic and sed-lithic breccia of Unit III, and the volcanic sandstone of Unit IV is clearly marked by the physical property logs. The accuracy of the logging data was evaluated and discussed with an improved log versus core correlation. The cluster analysis of the complete data set shows a correlation with the data provided by the mechanical caliper device, which in turn indicates the quality of the borehole.
ISSN: 1816-8957

hal-00642165
http://hal.upmc.fr/hal-00642165
http://hal.upmc.fr/hal-00642165/document
http://hal.upmc.fr/hal-00642165/file/Rabaute_et_al-SciDrilling-1997.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The aim of this study is to assess the availability and quality of data from the International GNSS Service (IGS) Global Positioning System (GPS) network in Africa, especially for retrieving zenith tropospheric delay (ZTD), from which precipitable water vapour (PWV) can be derived, in view of application to the African Monsoon Multidisciplinary Analysis (AMMA) project. Three major error sources for the GPS data analysis evaluating PWV in Africa are the accuracy of the satellite orbits, the correction for the radio delay induced by the ionosphere and the vertical site displacements due to ocean loading. The first part of this study examines these error sources and the validity of GPS data for meteorological applications in Africa in dedicated analyses spanning the year 2001. These analyses were performed using the IGS precise orbits. Weak degradation of baseline precision with increasing baseline lengths suggests that the average orbital error is not limiting the GPS analysis in Africa. The impact of the ionosphere has been evaluated during a maximum of solar activity in 2001. The loss of L2 data has actually been observed. It amounts to 2% on average for 2001, with maxima of 8% during magnetic storm events. A slight decrease in formal accuracy of ZTD seems to be related to the loss of L2 data at the end of the day. This indicates that scintillation effects are present in the GPS observations but however are not a major limitation. The impact of ocean loading is found to be significant on ZTD estimates (up to ±2 mm in equivalent PWV). The use of a proper ocean loading model eliminates this effect. The second aspect of this study concerns the IGS analysis quality for the African stations. The accuracy has been assessed through position dispersion between individual solutions and the most recent version of the IGS combined solution IGb00, and residuals from the transformation of the IGS combined solution into the International Terrestrial Reference Frame 2005. The positioning performance of the IGS analysis is consistent with an accuracy in ZTD of ±6 mm (±1 mm in PWV), as requested for meteorological applications such as planned in AMMA.
ISSN: 1364-6826

insu-00347961
https://hal-insu.archives-ouvertes.fr/insu-00347961
DOI : 10.1016/j.jastp.2007.04.008

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Deformation of the continental lithosphere is traditionally modeled assuming that heat production in the subcontinental lithospheric mantle is negligible. Although this may be appropriate for highly depleted Archean lithosphere, studies of mantle xenoliths and lithospheric-derived mafic rocks suggest that heat productions of up to 0.4 ;μW/m3 may be attained in the mantle of Phanerozoic and Neoproterozoic regions due to modal metasomatism. To investigate the effect of a local enrichment in heat-producing elements within the lithospheric mantle on the continental deformation, we performed a series of 2D thermo-mechanical models simulating the deformation of a lithospheric plate 1000 km long, which contains in its central part a 200 km wide and 20 km-thick mantle layer with a heat production of 0.05;–0.25 ;μW/m3 between 40 and 80 km depth, leading to a local enhancement of the surface heat flow by 1;–5 mW/m2. Compression models show that a 20 km-thick layer with a heat production as low as 0.05 ;μW/m3 within the shallow lithospheric mantle leads to strain localization in both the enriched mantle and the overlying crust. Strain localization depends exponentially on the temperature increase in the lithosphere section, which is controlled by the volume of metasomatized mantle and the intensity of the metasomatic enrichment in heat-producing elements. A heat production of 0.25 μW/m3 between 60 and 80 km depth results, for instance, in strains within and above the metasomatized mantle 5 times higher than in the surrounding lithosphere. Strain localization also depends on the location of the heat-producing domain and on the plate rheological structure; deeper heat-producing domains and weaker plates leading to stronger localization. These results provide an explanation for strain localization in intraplate environments, leading to the formation of orogenic belts situated hundreds to thousands of kilometers away from known plate boundaries, as observed in the Neoproterozoic belts of Gondwana and in the present-day deformation of the Asian plate.
ISSN: 0012-821X

hal-00411386
https://hal.archives-ouvertes.fr/hal-00411386
DOI : 10.1016/j.epsl.2008.07.040

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
An analytical solution in the Laplace domain is derived for modeling anomalous pressure diffusion during pumping tests in aquifer displaying hierarchical fractal fracture networks. The proposed solution generalizes all of the analytical models for fractal flow published previously by combining multifractal diffusion and nested multiporosity with transient exchanges, interface skin effects, and well storage effect. Solutions are derived for fracture-delimited blocks with planar, cylindrical, and spherical shapes, as well as with any fractional dimensional shapes. Any combinations of these shapes can be defined in order to model a large range of situations. Within each permeability level, the fractal properties of the fracture network can be specified and the fractal dimension can be distinct from the shape dimension of the block.
ISSN: 0043-1397

hal-00411549
https://hal.archives-ouvertes.fr/hal-00411549
DOI : 10.1029/2008WR007125

Éditeur(s) : HAL CCSD
Résumé : We study various proofs of the caracterization of constant functions, more precisely of the theorem: a derivable function, defined on a real interval, is constant if, and only if, its derivative is null. Our aim is to study the relationships of these proofs with the mathematical curriculum of secondary schools and the begining of undergraduate studies in France, from various point of views (epistemological, historical, didactical).
https://hal.archives-ouvertes.fr/hal-00318449

hal-00318449
https://hal.archives-ouvertes.fr/hal-00318449
https://hal.archives-ouvertes.fr/hal-00318449v2/document
https://hal.archives-ouvertes.fr/hal-00318449/file/CroissanceSansTAF10HALV2.pdf
ARXIV : 0809.0965

Éditeur(s) : EDP Sciences
Résumé : Daily growth increments measured in the otolith of Thunnus atlanticus were used to estimate the age and growth of individuals. which were sampled from an artisanal fishery operating around fish aggregating devices (FADs) moored off Martinique Island. In this study, 76 otoliths were analysed for fish ranging from 20 to 68 cm fork lengths (FL). The fish were caught using trolling lines at depths ranging from 0 to 10 m. Counts were made, under a light microscope, on the external part of the transverse section of the sagittae, from the primordium to the ventral edge. The mean coefficient of variation of the age reading was 2.4%. To validate readings, the number of increments for 11 individuals was counted using both optic and scanning electron microscopes. The calculated relationship between readings of both methods was found to be linear, with a slope of 1.03 and R-2 = 0.99. Frequency of growth increment formation could not be validated. Growth rates derived from otolith readings were, however, compared to those obtained using a modal progression analysis, which was performed on the length-frequency distributions of the landings over a period of two months. The corroboration between the growth rates was good. One increment was assumed to represent one day. The parameters of the von Bertalanffy growth curve for both sexes were L-infinity = 71.4 cm FL, k = 0.002 day(-1) and tau(0) = -80 days. According to our results, there is no evidence that Martinican moored FADs act as ecological traps for blackfin tuna. Instead, young blackfin tuna probably leave the vicinity of Martinican moored FADs to undergo a trophic migration at 7 to 8 month-old, and then come back about 8 months later to breed in the Lesser Antilles area.
Les microstructures présentes dans les otolithes de Thunnus atlanticus ont été utilisées pour estimer l'âge et la croissance des thons capturés par la pêcherie artisanale exploitant les dispositifs de concentrations de poissons (DCP) mouillés autour de la Martinique. Des thons de 20 à 68 cm de longueur à la fourche (LF) ont été capturés à la ligne de traîne de surface entre 0 et 10 m de profondeur. Les stries d'accroissement ont été comptées sur 76 otolithes en microscopie optique sur la partie externe des coupes transversales de la sagitta, du nucléus jusqu'à l'extrémité verticale de la coupe (coefficient de variations 2,4 %). Afin de vérifier qu'il n'y avait pas de sous-estimation du nombre de stries, nous avons effectué un comptage, en microscopie électronique à balayage, pour 11 individus. La relation établie entre ces deux méthodes de comptage est linéaire avec un pente égale à 1,03 et R2 = 0,99. La vitesse de croissance issue de l'analyse des otolithes a été comparée à celle estimée à partir de l'analyse en progression modale des distributions en fréquence de taille des débarquements sur une période de 2 mois. La corroboration entre les deux méthodes était bonne. Nous avons supposé que la formation des stries de croissance suivait un rythme journalier. Les paramètres de l'équation de croissance de von Bertalanffy pour les 2 sexes confondus sont: L-infinity = 71.4 cm FL, k = 0.002 day(-1) and tau(0) = -80 days. Les résultats de cette étude n'indiquent pas que les DCP ancrés martiniquais puissent agir comme des pièges écologiques pour les thons noirs. Les jeunes thons noirs semblent au contraire quitter la proximité des DCP et entreprendre une migration trophique lorsqu'ils atteignent 7 à 8 mois. Ils ne reviendraient ensuite dans la zone des Petites Antilles qu'environ 8 mois plus tard, manifestement pour se reproduire.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2004 , Vol. 17 , N. 1 , P. 13-18

Droits : EDP Sciences, IFREMER, IRD 2004
http://archimer.ifremer.fr/doc/2004/publication-396.pdf
DOI:10.1051/alr:2004009
http://archimer.ifremer.fr/doc/00000/396/