Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During the early years of the Iceland Deep Drilling Project (IDDP), development of three distinctive technological and scientific approaches were formalised and then carried out until 2010 within a European funded project called HiTI (high temperature instruments for supercritical geothermal reservoir characterisation and exploitation). These approaches were: (1) development of several downhole instruments allowing them to function up to 300 ◦C and 400 ◦C, (2) identification of two new Na/Li cation ratio geothermometric relationships valid at very high temperature, (3) tracer testing with high temperature tolerant organic isomers and finally and (4) basalt rock deformation and petrophysical properties laboratory investigations at high temperature and pressure conditions.
ISSN: 0375-6505

hal-00921127
https://hal-brgm.archives-ouvertes.fr/hal-00921127
DOI : 10.1016/j.geothermics.2013.07.008

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
The elucidation of relationships between biodiversity and ecosystem processes has been limited by the definition of metrics of biodiversity and their integration into experimental design. Functional trait screening can strengthen the performance of these designs.* We suggest the use of Rao's quadratic entropy to measure both functional diversity and phylogenetic diversity of species mixtures proposed for an experimental design, and demonstrate how they can provide complementary information.* We also present an index assessing the statistical performance of these independent variables in different experimental designs. Measurement of independent variables as continuous vs. discrete variables reduces statistical performance, but improves the model by quantifying species differences masked by group assignments.* To illustrate these advances, we present an example from a tropical forest tree community in which we screened 38 species for nine functional traits. The proposed TropiDEP design is based on the relative orthogonality of two multivariate trait axes defined using principal component analysis.* We propose that independent variables describing functional diversity might be grouped to calculate independent variables describing suites of different traits with potentially different effects on particular ecosystem processes. In other systems these axes may differ from those reported here, yet the methods of analysis integrating functional and phylogenetic diversity into experimental design could be universal.
La compréhension des relations pouvant exister entre biodiversité et fonctionnement des écosystèmes a été longtemps limitée par la définition de méthodes de quantification de la diversité biologique et la mise en œuvre de dispositifs expérimentaux permettant sa mesure. L'identification de syndromes de traits fonctionnels clefs influençant des fonctions écosystémiques particulières peut renforcer la performance de ces dispositifs.* Nous suggérons l'utilisation de l'entropie quadratique de Rao pour mesurer la diversité fonctionnelle et phylogénétique dans des assemblages synthétiques d'espèces, et montrons comment ces mesures de diversité sont complémentaires.* Nous présentons également un indice permettant de tester la performance statistique de ces variables indépendantes dans différents modèles expérimentaux. L'utilisation de variables indépendantes continues plutôt que discrètes réduit la performance statistique mais améliore le modèle en quantifiant les différences fonctionnelles entre espèces; différences généralement masquées lors de leur assignation en groupes fonctionnels.* Pour illustrer ces avancées, nous présentons un exemple d'assemblages synthétiques à partir de 38 espèces d'arbres de forêt tropicale sélectionnées pour 9 traits fonctionnels (TropiDEP). Le plan d'expérience de TropiDEP est basé sur l'orthogonalité relative de deux axes multivariés de traits fonctionnels définis par analyse en composantes principales.* Nous proposons que les variables décrivant la diversité fonctionnelle soient groupées pour calculer des variables indépendantes, divisées en plusieurs axes décrivant des combinaisons de différents traits pouvant influencer des processus différents de l'écosystème (e.g. processus du N et du C). Dans d'autres systèmes, ces axes peuvent différer de ceux présentés ici, mais les méthodes d'analyse peuvent être universelles.
ISSN: 1286-4560

Droits : info:eu-repo/semantics/OpenAccess
hal-00883621
https://hal.archives-ouvertes.fr/hal-00883621
https://hal.archives-ouvertes.fr/hal-00883621/document
https://hal.archives-ouvertes.fr/hal-00883621/file/hal-00883621.pdf
DOI : 10.1051/forest/2009110

Éditeur(s) : Elsevier
Résumé : In biological modelling of the coastal phytoplankton dynamics, the light attenuation coefficient is often expressed as a function of the concentrations of chlorophyll and mineral suspended particulate matter (SPM). In order to estimate the relationship between these parameters over the continental shelf of the northern Bay of Biscay, a set of in situ data has been gathered for the period 1998-2003 when SeaWiFS imagery is available. These data comprise surface measurements of the concentrations of total SPM, chlorophyll, and irradiance profiles from which is derived the attenuation coefficient of the photosynthetically available radiation, K-PAR. The performance of the IFREMER look-up table used to retrieve the chlorophyll concentration from the SeaWiFS radiance is evaluated on this new set of data. The quality of the estimated chlorophyll concentration is assessed from a comparison of the variograms of the in situ and satellite-derived chlorophyll concentrations. Once the chlorophyll concentration is determined, the non living SPM, which is defined as the SPM not related to the dead or alive endogenous phytoplankton, is estimated from the radiance at 555 nm by inverting a semi-analytic model. This method provides realistic estimations of concentrations of chlorophyll and SPM over the continental shelf all over the year. Finally, a relationship, based on non living SPM and chlorophyll, is proposed to estimate K-PAR on the continental shelf of the Bay of Biscay. The same formula is applied to non living SPM and chlorophyll concentrations, observed in situ or derived from SeaWiFS radiance.
Remote Sensing of Environment (0034-4257) (Elsevier), 2005-03 , Vol. 95 , N. 1 , P. 29-46

Droits : 2004 Elsevier Inc. All rights reserved
http://archimer.ifremer.fr/doc/2005/publication-1172.pdf
DOI:10.1016/j.rse.2004.11.007
http://archimer.ifremer.fr/doc/00000/1172/

Éditeur(s) : HAL CCSD
Résumé : National audience
We study various proofs of the characterization 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 beginning of undergraduate studies in France, from various points of views (epistemological, historical, and didactical). This study leads to the construction of the mathematical site of the studied theorem and can serve as a basis for training activities around the fundamental theorems of elementary analysis.
Nous étudions plusieurs démonstrations de la caractérisation suivante des fonctions constantes : une fonction, définie sur un intervalle, dérivable est constante si, et seulement si, sa dérivée est nulle. Le but est d'étudier les relations entre ces démonstrations et le curriculum en France à la jonction entre la fin des études secondaires et le début des études supérieures, avec des apports venant de différents points de vue (épistémologique, historique, didactique). Cette étude mène à la construction du site mathématique local du théorème étudié et peut servir de base à des activités de formation autour des théorèmes fondamentaux de l'analyse élémentaire.
Recherches et Ressources en Éducation et Formation

hal-01529547
https://hal.univ-antilles.fr/hal-01529547
https://hal.univ-antilles.fr/hal-01529547/document
https://hal.univ-antilles.fr/hal-01529547/file/8_Delcroix-et-Silvy-2009.pdf

Éditeur(s) : HAL CCSD Institute of Mathematics Polish Academy of Sciences
Résumé : International audience
In analogy to the classical isomorphism between L(D(Rn);D0(Rm)) and D0(Rm+n) (resp. L(S(Rn); S0(Rm)) and S0(Rm+n)), we show that a large class of moderate linear mappings acting between the space GC(Rn) of compactly supported generalized functions and G(Rn) of generalized functions (resp. the space GS(Rn) of Colombeau rapidly decreasing generalized functions and the space G (Rn) of temperate ones) admits generalized integral representations, with kernels belonging to specic regular subspaces of G(Rm+n) (resp. G (Rm+n)). The main novelty is to use accelerated -nets, which are unit elements for the convolution product in these regular subspaces, to construct the kernels. Finally, we establish a strong relationship between these results and the classical ones.
ISSN: 0137-6934

hal-01529541
https://hal.univ-antilles.fr/hal-01529541
https://hal.univ-antilles.fr/hal-01529541/document
https://hal.univ-antilles.fr/hal-01529541/file/delcroix.pdf
DOI : 10.4064/bc88-0-7

Éditeur(s) : HAL CCSD Ecological Society of America
Résumé : We investigated the relationship between habitat association and physiological performance in four congeneric species pairs exhibiting contrasting distributions between seasonally flooded and terra firme habitats in lowland tropical rain forests of French Guiana, including Virola and Iryanthera (Myristicaceae), Symphonia (Clusiaceae), and Eperua (Caesalpiniaceae). We analyzed 10-year data sets of mapped and measured saplings (stems 150 cm in height and <10 cm diameter at breast height [dbh]) and trees (stems 10 cm dbh) across 37.5 ha of permanent plots covering a 300-ha zone, within which seasonally flooded areas (where the water table never descends below 1 m) have been mapped. Additionally, we tested the response of growth, survival, and leaf functional traits of these species to drought and flood stress in a controlled experiment. We tested for habitat preference using a modification of the torus translation method. Strong contrasting associations of the species pairs of Iryanthera, Virola, and Symphonia were observed at the sapling stage, and these associations strengthened for the tree stage. Neither species of Eperua was significantly associated with flooded habitats at the sapling stage, but E. falcata was significantly and positively associated with flooded forests at the tree stage, and trees of E. grandiflora were found almost exclusively in nonflooded habitats. Differential performance provided limited explanatory support for the observed habitat associations, with only congeners of Iryanthera exhibiting divergent sapling survival and tree growth. Seedlings of species associated with flooded forest tended to have higher photosynthetic capacity than their congeners at field capacity. In addition, they tended to have the largest reductions in leaf gas exchange and growth rate in response to experimental drought stress and the least reductions in response to experimental inundation. The corroboration of habitat association with differences in functional traits and, to a lesser extent, measures of performance provides an explanation for the regional coexistence of these species pairs. We suggest that specialization to seasonally flooded habitats may explain patterns of adaptive radiation in many tropical tree genera and thereby provide a substantial contribution to regional tree diversity.
ISSN: 0012-9658

hal-01031746
https://hal.archives-ouvertes.fr/hal-01031746

Éditeur(s) : HAL CCSD PeerJ
Résumé : International audience
Coral reefs are in decline across the globe as a result of overexploitation, pollution, disease and, more recently, climate change. The impacts of changes in coral cover on associated fish communities can be difficult to predict because of the uneven dependence of reef fish species on corals for food, shelter or the three-dimensional structure they provide. We compared live coral cover, reef fish community metrics, and their associations in two surveys of the lagoon of the remote atoll of Mataiva (French Polynesia) carried out 31 years apart. In contrast to the general pattern of decreasing coral cover reported for many parts of the Indo-Pacific region, live coral cover increased 6–7 fold at Mataiva between 1981 and 2012, and fish density nearly doubled. The stable overall reef fish species richness belied a significant shift in community structure. There was little overlap in community composition across years, and fish assemblages in 2012 were more homogeneous in composition than they were in 1981. Changes in species abundance were not clearly related to species-specific reliance on corals. The strong positive relationships between live coral cover and fish diversity and abundance noted in 1981, when coral cover rarely exceeded 10%, were no longer present in 2012, when coral cover rarely fell below this value. The most parsimonious explanation for these contrasting relationships is that, over the combined range of coral cover observed in the 1981 and 2012 snapshots, there is a rapidly asymptotic relationship between coral and fish. Our results, and other data from the south and west Pacific, suggest that fish diversity and abundance might accumulate rapidly up to a threshold of approximately 10% live coral cover. Such a relationship would have implications for our expectations of resistance and recovery of reef fish communities facing an increasingly severe regime of coral reef disturbances.
ISSN: 2167-8359

Droits : http://creativecommons.org/licenses/by/
hal-01135589
https://hal.archives-ouvertes.fr/hal-01135589
https://hal.archives-ouvertes.fr/hal-01135589/document
https://hal.archives-ouvertes.fr/hal-01135589/file/2015_02_26_more_coral_more_fish.pdf
DOI : 10.7717/peerj.745

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) : Université de Bretagne Occidentale
Résumé : The major objectives of this thesis were to study the structure, functioning and dynamics of different faunal assemblages associated with cold seep ecosystems in the eastern Mediterranean Sea. We focused our study on three main sites: the Marmara Sea, the Mediterranean ridge and the Nile deep sea fan. This thesis aims at determining the environmental signature of Mediterranean sites and the characteristics of the associated fauna at European and global scales. The specific objectives were to (1) determine the composition, diversity, density, biomass of invertebrate assemblages, (2) characterize biogeochemical conditions within different microhabitats in the vicinity of organisms, (3) to define the trophic relationships amongst seep fauna using stable isotope analyses (collaboration) and lastly, (4) to compare the spatial distribution and assemblage characteristics at different spatial scales (local, structure-scale, regional). The results show that (1) the Napoli mud volcano is the richest structure in terms of numbers of taxa while the Nile deep-sea fan sites need additional sampling, (2) a high variability is observed both between the different microhabitats but also within a single microhabitat, (3) the methane and oxygen gradients as well as substratum type are the main structuring factors explaining the distribution of the fauna and (4) the characteristics of the microhabitats, rather than the study area, influence the structure of benthic communities associated with Mediterranean cold seeps.
Les objectifs principaux de cette thèse sont d’étudier la structure, le fonctionnement et la dynamique de différents assemblages de faune associée aux émissions de fluides froids de Méditerranée orientale. Trois principaux sites ont été étudiés : la mer de Marmara, la ride méditerranéenne et le delta profond du Nil. Cette thèse tente de déterminer la « signature environnementale » des sites méditerranéens et les caractéristiques de la faune qui y est associée dans un contexte de marges européennes et mondiale. Les objectifs spécifiques sont (1) de déterminer la composition, la diversité, la densité et la biomasse des assemblages d'invertébrés ; (2) de caractériser les conditions biogéochimiques au sein des différents microhabitats à proximité des organismes; (3) de caractériser les relations trophiques sur les différents assemblages de faune par une approche isotopique (en collaboration) et finalement, (4) de comparer la distribution spatiale et les caractéristiques des assemblages à différentes échelles spatiales (locale, à l’échelle d’une structure géologique, régionale). Les résultats montrent que : (1) le volcan de boue Napoli est le site le plus riche en taxons alors que les sites du delta du Nil nécessiteraient un échantillonnage plus approfondi ; (2) il existe une grande variabilité entre les microhabitats ainsi qu’au sein d’un même microhabitat ; (3) les gradients en méthane, en oxygène ainsi que la nature du substrat sont les principaux facteurs abiotiques expliquant la distribution de la faune, (4) les caractéristiques des microhabitats, plutôt que la zone d’étude, influencent la structure des communautés benthiques associées aux écosystèmes de fluides froids méditerranéens.

Droits : 2010 The Author, UBO
http://archimer.ifremer.fr/doc/00020/13138/10178.pdf
http://archimer.ifremer.fr/doc/00020/13138/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Dans la mémoire collective des Antilles, les moulins ne semblent être qu’une image isolée, sans contexte ni humain ni historique, une machine veuve de son travail et de sa fonction, une réalité déjà morte, puisque dénuée de sens et donc ignorée des regards. L’objectif de l’article est de redonner aux moulins l’importance qu’ils ont perdue dans la mémoire collective, de réintroduire la conscience de la nature même des machines, de leurs relations mutuelles, mais aussi de leurs relations avec l’homme et des valeurs impliquées dans ces relations. Étudier les machines, c’est comprendre les évènements passés, interpréter les paysages et surtout rendre hommage aux Hommes.
In the collective memory of the West Indies, mills seem to be an image without human or historical context i.e. a machine deprived of its former significance it had for production of a commodity. Mills are not viewed in their former context as an important relict of the past. The purpose of the article is to give back to mills the importance that they have lost in the collective memory by reintroducing their relationship with man and the values involved in these relationships. Studying the function of machines leads to an understanding of past events, helps to interpret landscapes and especially pays tribute to the role of man.
Martinique

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.461
http://journals.openedition.org/etudescaribeennes/461

Éditeur(s) : HAL CCSD Elsevier
Résumé : Rh (Rhesus) is a major blood group system in man, which is clinically significant in transfusion medicine. Rh antigens are carried by an oligomer of two major erythroid specific polypeptides, the Rh (D and CcEe) proteins and the RhAG glycoprotein, that shared a common predicted structure with 12 transmembrane a-helices (M0 to M11). Non erythroid homologues of these proteins have been identified (RhBG and RhCG), notably in diverse organs specialized in ammonia production and excretion, such as kidney, liver and intestine. Phylogenetic studies and experimental evidence have shown that these proteins belong to the Amt/Mep/Rh protein superfamily of ammonium/methylammonium permease, but another view suggests that Rh proteins might function as CO2 gas channels. Until recently no information on the structure of these proteins were available. However, in the last two years, new insight has been gained into the structural features of Rh proteins (through the determination of the crystal structures of bacterial AmtB and archeaebacterial Amt-1. Here, models of the subunit and oligomeric architecture of human Rh proteins are proposed, based on a refined alignment with and crystal structure of the bacterial ammonia transporter AmtB, a member of the Amt/ Mep/Rh superfamily. This alignment was performed considering invariant structural features, which were revealed through Hydrophobic Cluster Analysis, and led to propose alternative predictions for the less conserved regions, particularly in the N-terminal sequences. The Rh models, on which an additional Rh-specific, N-terminal helix M0 was tentatively positioned, were further assessed through the consideration of biochemical and immunochemical data, as well as of stereochemical and topological constraints. These models highlighted some Rh specific features that have not yet been reported. Among these, are the prediction of some critical residues, which may play a role in the channel function, but also in the stability of the subunit structure and oligomeric assembly. These results provide a basis to further understand the structure/function relationships of Rh proteins, and the alterations occurring in variant phenotypes.
ISSN: 1246-7820

hal-00068842
https://hal.archives-ouvertes.fr/hal-00068842

Éditeur(s) : CNRS Programme Environnement : Colloque Recherche et Environnement Strasbourg, 24-25 Septembre 1990
Résumé : As the third millennium draws near, industrial societies are becoming aware of the limits of what they can do to constrain the biosphere, ending up where "primitive" societies left off. If the perverse effects of a century of technical revolution and economic expansion are above all perceptible in the area of multiple contaminations that put in danger the well-being of people, environments and in a general way the biosphere's functioning, they also concern the standardisation of products and landscapes and overinvestment in the means of exploiting resources (inputs increasing more rapidly than outputs, when they are not bringing about their decrease). The search for solutions to the growing imbalance of the relationships Man – Nature – Resources cannot reside in a partial approach or a technical resolution of the problems posed by using renewable resources.
(OCR non controlé) A l'approche du troisième millénaire, les sociétés industrielles prennent la mesure des limites de leurs possibilités de contraindre la biosphère, aboutissant là d'où partaient les sociétés "primitives". Si les effets pervers d'un siècle de révolution technique et d'expansion économique sont surtout perceptibles dans le domaine des pollutions multiples qui mettent en péril le bien-être des personnes, les milieux et d'une manière générale le fonctionnement de la biosphère, ils concernent également l'uniformisation des produits et des paysages et le surinvestissement dans les moyens d'exploitation des ressources (les intrants croissant plus vite que les rendements, quand ils n'entraînent pas leur baisse). La recherche de solutions au déséquilibre croissant des relations Hommes - Nature - Ressources ne peut résider dans une approche partielle ou une résolution technique des problèmes posés par l'utilisation des ressources renouvelables.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1990/acte-2416.pdf
http://archimer.ifremer.fr/doc/00000/2416/

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks, predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tanδ) and in specific modulus of elasticity (E′/ρ) allow reconstructing the general tanδ-E′/ρ statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide with observations on chemically modified woods, either “artificially”, or by natural extractives.
Wood Science and Technology

hal-01096868
https://hal-agroparistech.archives-ouvertes.fr/hal-01096868
DOI : 10.1007/S00226-010-0393-8

Éditeur(s) : Elsevier
Résumé : We investigated the influence of bioturbation by macrofauna on the vertical distribution of living (stained) benthic foraminifera in marine intertidal sediments. We investigated the links between macrofaunal bioturbation and foraminiferal distribution, by sampling from stations situated on a gradient of perturbation by oyster-farming, which has a major effect on benthic faunal assemblages. Sediment cores were collected on the French Atlantic coast, from three intertidal stations: an oyster farm, an area without oysters but affected by oyster biodeposits, and a control station. Axial tomodensitometry (CT-scan) was used for three-dimensional visualization and two-dimensional analysis of the cores. Biogenic structure volumes were quantified and compared between cores. We collected the macrofauna, living foraminifera, shells and gravel from the cores after scanning, to validate image analysis. We did not investigate differences in the biogenic structure volume between cores. However, biogenic structure volume is not necessarily proportional to the extent of bioturbation in a core, given that many biodiffusive activities cannot be detected on CT-scans. Biodiffusors and larger gallery-diffusors were abundant in macrofaunal assemblage at the control station. By contrast, macrofaunal assemblages consisted principally of downward-conveyors at the two stations affected by oyster farming. At the control station, the vertical distribution of biogenic structures mainly built by the biodiffusor Scorbicularia plana and the large gallery-diffusor Hediste diversicolor was significantly correlated with the vertical profiles of living foraminifera in the sediment, whereas vertical distributions of foraminifera and downward-conveyors were not correlated at the station affected by oyster farming. This relationship was probably responsible for the collection of foraminifera in deep sediment layers (> 6 cm below the sediment surface) at the control station. As previously suggested for other species, oxygen diffusion may occur via the burrows built by S. plana and H. diversicolor, potentially increasing oxygen penetration and providing a favorable microhabitat for foraminifera in terms of oxygen levels. By contrast, the absence of living foraminifera below 6 cm at the stations affected by oyster farming was probably associated with a lack of biodiffusor and large gallery-diffusor bioturbation. Our findings suggest that the effect of macrofaunal bioturbation on the vertical distribution of foraminiferal assemblages in sediments depends on the effects of the macrofauna on bioirrigation and sediment oxidation, as deduced by Eh values, rather than on the biogenic structure volume produced by macrofauna. The loss of bioturbator functional diversity due to oyster farming may thus indirectly affect infaunal communities by suppressing favorable microhabitats produced by bioturbation.
Journal of Experimental Marine Biology and Ecology (0022-0981) (Elsevier), 2009-03 , Vol. 371 , N. 1 , P. 20-33

Droits : 2009 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2009/publication-6146.pdf
DOI:10.1016/j.jembe.2008.12.012
http://archimer.ifremer.fr/doc/00000/6146/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We discuss various methods of regularization of singular differential problems. Their common point is that we use the flexibility of the theories of nonlinear generalized functions for adapting the regularization to the singularity of the problem. We particularly underline the relationship between the generalized solutions and those classical or distribution, when they exist, giving a general result for the case of the regularization of data.
Journal of Mathematical Analysis and applications

hal-01529550
https://hal.univ-antilles.fr/hal-01529550
DOI : 10.1016/j.jmaa.2008.11.077

Éditeur(s) : HAL CCSD
Résumé : contient des versions PDF d'articles scientifiques (versions éditeur)
Spectrins are actin binding proteins that constitute the main components of membrane skeletons, the protein network located under the plasma membrane. Erythroid or non erythroid (in this case, they are called fodrins), spectrins play an important structural function in the membrane as demonstrated in the red blood cell. Spectrins are composed of two long α and β chains, associated in tetramers (αβ)2, forming the long flexible filaments of the network. Both chains are composed of repeating units which are folded in a triple helical arrangement (A, B and C helices), except for segment α10 which corresponds to a Src Homology 3 domain (SH3). The head-to-head interaction between dimers implies the N-terminal end of α chain and the C-terminal end of β chain. A model was proposed for the tetramerization site of spectrin : the two A and B helices of the last repeat of α chain interact with the C helix of the β chain in order to constitute a triple-helical structure similar to the repeats along the remainder of spectrin molecule. This model was first inferred from the relationship between the severity of the spectrin self-association defect and the location of the underlying mutations found in hereditary elliptocytosis (HE). Using recombinant peptides we defined the region, on both chains, which was sufficient and necessary to generate a fully functional tetramerization site. Producing peptides carrying a βHE mutation, we reproduced the tetramerization defect as observed in red blood cells of patients.
Finally, the presence of an SH3 domain probably gives to spectrins new functions which are different from the stability of the membrane. After contesting the existence of interaction between the fodrin SH3 domain and the α subunit of epithelial sodium channel sensitive to amiloride, we searched for partners of this domain, by screening a rat kidney library with the yeast two-hybrid system. We identified severals proteins implicated in the actin polymerization asoociated with motility or cell differenciation, suggesting that SH3 domain could play a part in this process.
Les spectrines, protéines liant l'actine, sont des constituants majeurs du squelette membranaire, réseau multiprotéique localisé sous la membrane plasmique. Érythroïdes ou non érythroïdes (dans ce cas, on les appelle fodrines), les spectrines ont un rôle structural important dans la membrane comme cela a déjà été démontré, pour la spectrine, dans le globule rouge. Elles sont constituées de deux longues chaînes a et ß associées côte à côte en tétramères (aß)2 qui forment les longs filaments du réseau. Chacune des chaînes est composée par la répétition de segments homologues, 22 pour a et 17 pour ß. Ces segments sont constitués de trois hélices a (hélices A, B et C) repliées sur elles-mêmes. Cette succession de structures trihélicoïdales est parfois interrompue par un domaine particulier comme le domaine SH3 (Src Homology 3) présent au milieu de la chaîne a. Les tétramères (aß)2 de spectrine constituent les filaments du squelette membranaire. L'interaction tête-à-tête de deux dimères aß implique les extrémités NH2 de la chaîne a et COOH de la chaîne ß. D'une part la sévérité du défaut d'auto-association et la localisation des mutations associées à celui-ci et d'autre part, les séquences en acides aminés des extrémités impliquées dans le site d'auto-association ont permis de proposer un modèle : la première hélice C isolée de la chaîne a pourrait s'associer aux deux dernières hélices A et B de la chaîne ß pour reconstituer une unité conformationnelle trihélicoïdale semblable à celles observées le long de la molécule. Un défaut dans la formation du tétramère est le support moléculaire le plus fréquemment observé dans les elliptocytoses héréditaires (HE). À l'aide de peptides recombinants, nous avons défini, sur les deux chaînes, les régions nécessaires et suffisantes possédant les caractéristiques pleinement fonctionnelles du site de tétramérisation. Nous avons ensuite, par mutagenèse dirigée, reproduit le lien entre la présence de mutations HE localisées dans les hélices A ou B et le défaut d'auto-association observé dans les globules rouges de patients HE. La présence d'un domaine SH3 localisé au milieu de la chaîne a confère probablement aux spectrine des fonctions autres que le maintien et la stabilité de la membrane. Les SH3, petits domaines protéiques, participent aux interactions protéine/protéine. Le seul partenaire connu du domaine SH3 de la fodrine était la sous-unité a du canal sodium sensible à l'amiloride (ENaC) mais la fonction de ce complexe n'était pas encore caractérisée. À l'aide de différentes méthodes, nous avons remis en cause l'interaction directe entre ENaC et le SH3 de la fodrine. La fonction de ce domaine SH3 étant liée à la nature de son ligand, nous avons donc recherché les partenaires putatifs du domaine SH3 de la fodrine par la technique du double-hybride. 29 partenaires ont été identifiés, regroupés en 19 familles et 10 clones isolés. La spécificité des interactions a été étudiée à la fois par double-hybride, à l'aide de mutants du domaine SH3 de la fodrine produits par mutagenèse dirigée. Les interactions vis-à-vis d'autres domaines SH3 (spectrine ou une protéine de levure non relatée Scd2) ont été également analysées. Enfin, la spécificité de certains partenaires a été confirmée par des études d'interactions in vitro. Deux des protéines les plus spécifiques du domaine SH3 de la fodrine sont des protéines tyrosine-phosphatase PTP. La première est l'isoforme A de PTP de faible poids moléculaire (LMPTPA) mais l'interaction n'a pas été confirmée in vitro. La deuxième, TD14, est une nouvelle PTP dont la seule fonction connue est d'inhiber la formation des foyers tumoraux des cellules surexprimant l'oncogène Ha-ras. Ces PTP pourraient soit déphosphoryler la fodrine, soit être recrutées sous la membrane pour déphosphoryler une autre cible. Nous avons également identifié trois partenaires (N-WASP, Evl et une protéine de la famille des formines) suggérant que les domaines SH3 des spectrines pourraient être impliqués dans les processus de polymérisation de l'actine liés à la mobilité ou la différenciation cellulaire. Mot clés : spectrine, fodrine, tétramérisation, SH3, double-hybride, polymérisation de l'actine
https://tel.archives-ouvertes.fr/tel-00284819

Droits : info:eu-repo/semantics/OpenAccess
tel-00284819
https://tel.archives-ouvertes.fr/tel-00284819
https://tel.archives-ouvertes.fr/tel-00284819/document
https://tel.archives-ouvertes.fr/tel-00284819/file/Nicolas_1999_-_These.pdf

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 Royal Society, The
Résumé : Plant leaf litter generally decomposes faster as a group of different species than when individual species decompose alone, but underlyingmechanisms of these diversity effects remain poorly understood. Because resource C : N: P stoichiometry (i.e. the ratios of these key elements) exhibits strong control on consumers, we supposed that stoichiometric dissimilarity of litter mixtures (i.e. the divergence in C : N: P ratios among species) improves resource complementarity to decomposers leading to faster mixture decomposition. We tested this hypothesis with: (i) a wide range of leaf litter mixtures of neotropical tree species varying in C : N: P dissimilarity, and (ii) a nutrient addition experiment (C, N and P) to create stoichiometric similarity. Litter mixtures decomposed in the field using two different types of litterbags allowing or preventing access to soil fauna. Litter mixture mass loss was higher than expected from species decomposing singly, especially in presence of soil fauna. With fauna, synergistic litter mixture effects increased with increasing stoichiometric dissimilarity of litter mixtures and this positive relationship disappeared with fertilizer addition. Our results indicate that litter stoichiometric dissimilarity drives mixture effects via the nutritional requirements of soil fauna. Incorporating ecological stoichiometry in biodiversity research allows refinement of the underlying mechanisms of how changing biodiversity affects ecosystem functioning.
ISSN: 0962-8452

hal-01204222
https://hal.archives-ouvertes.fr/hal-01204222
DOI : 10.1098/rspb.2014.1682
PRODINRA : 289918

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
The diffusion of titanium along with Ni, Co and Mn in pure synthetic forsterite has been studied as a function of temperature, oxygen fugacity, crystallographic orientation and chemical potentials in the four-component system MgO–SiO2–TiO2–TiO1·5. In over 100 different experimental conditions, no Ti diffusion profiles with the classical shape of the error function were observed. Instead, the profiles vary between ‘stepped’ at high fO2 (probably owing to diffusion on octahedral sites and trapping in tetrahedral sites), to hockey-stick shapes at low fO2 owing to concentration-dependent diffusion. The profile shapes vary systematically between these end-members according to oxygen fugacity. These profile shapes are also reproduced in experiments using natural San Carlos olivine. The change in profile shape is interpreted to be a function of valence-state change from Ti4+ to Ti3+, shown by a sigmoidal log fO2–diffusivity relationship. To distinguish between Ti4+ and Ti3+ in forsterite, a diffusion profile was also investigated using ‘hydroxylation spectroscopy’ whereby a crystal from a diffusion experiment was hydroxylated by annealing in an H2O-rich fluid at moderate pressure and temperature. The point defects associated with the added structural OH were then determined by infrared spectroscopy, providing evidence for the presence of Ti4+ and Ti3+ at intermediate oxygen fugacity. The transition from Ti4+ to Ti3+ occurs at considerably higher fO2 in these diffusion experiments than in equilibrium experiments in similar systems. Titanium diffusion, qualified using a mobility parameter (M), is fastest along the c-axis, at high activity of silica, low oxygen fugacity and high temperature. The rate of Ti diffusion is broadly similar to those of Mn, Ni and Co, and closer to published rates of Mg self-diffusion in olivine than Si self-diffusion. The observed Ti3+ and Ti4+ diffusion occurs on the M-sites. From statistical examination of the large Mn, Ni and Co diffusivity dataset, we determine that there is a 102/3 dependence of diffusion on aSiO2; the cations diffuse more rapidly at high aSiO2. In addition, diffusivity has a 10–1/8 dependence on fO2, suggested to be the result of increased concentration of loosely bound Ti3+–vacancy pairs, which enhance the mobility of other cations. This behaviour is likely to be present in natural systems where trivalent (e.g. Fe3+, Al3+, Cr3+) and divalent cations diffuse together. Consideration should be given to diffusive interference by highly charged, fast-moving cations when extracting time scales from frozen diffusion profiles.
ISSN: 0022-3530

hal-01531344
https://hal.archives-ouvertes.fr/hal-01531344
DOI : 10.1093/petrology/egw067

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Implication of immune processes in bipolar disorder (BD) has recently gained increasing attention. Tolerogenic molecules, among which HLA-G plays a prominent role, mediate the modulation of such processes. The HLA-G locus is characterized by a high number of polymorphisms including a functionally relevant 14 base pair (bp) insertion/deletion (Ins/Del) allele affecting the HLA-G expression. Here, we analyzed the distribution of this polymorphism in 561 BD patients and 161 healthy and found that the HLA-G 14bp Ins/Ins genotype was significantly more prevalent in healthy controls than in patients (corrected p; pc=0.032) and that the prevalence of such protective genotype is lower among patients born during the winter season as compared to those born in other periods (pc=0.006). Possible mechanisms between low HLA G expression and resistance to infections as well as potential relationships between infections in early life and susceptibility to BD are discussed.
ISSN: 0198-8859

inserm-00864639
http://www.hal.inserm.fr/inserm-00864639
http://www.hal.inserm.fr/inserm-00864639/document
http://www.hal.inserm.fr/inserm-00864639/file/HLA-G_and_BD_manuscript_-1.pdf
DOI : 10.1016/j.humimm.2012.11.032