Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Meiotic recombination predominantly occurs at discrete genomic loci called recombination hotspots, but the features defining these areas are still largely unknown (reviewed in refs 1-5). To allow a comprehensive analysis of hotspot-associated DNA and chromatin characteristics, we developed a direct molecular approach for mapping meiotic DNA double-strand breaks that initiate recombination. Here we present the genome-wide distribution of recombination initiation sites in the mouse genome. Hotspot centres are mapped with approximately 200-nucleotide precision, which allows analysis of the fine structural details of the preferred recombination sites. We determine that hotspots share a centrally distributed consensus motif, possess a nucleotide skew that changes polarity at the centres of hotspots and have an intrinsic preference to be occupied by a nucleosome. Furthermore, we find that the vast majority of recombination initiation sites in mouse males are associated with testis-specific trimethylation of lysine 4 on histone H3 that is distinct from histone H3 lysine 4 trimethylation marks associated with transcription. The recombination map presented here has been derived from a homogeneous mouse population with a defined genetic background and therefore lends itself to extensive future experimental exploration. We note that the mapping technique developed here does not depend on the availability of genetic markers and hence can be easily adapted to other species with complex genomes. Our findings uncover several fundamental features of mammalian recombination hotspots and underline the power of the new recombination map for future studies of genetic recombination, genome stability and evolution.
ISSN: 0028-0836

hal-00877681
https://hal.archives-ouvertes.fr/hal-00877681
DOI : 10.1038/nature09869
PUBMED : 21460839

Éditeur(s) : HAL CCSD Walter de Gruyter
Résumé :  
A method for measuring shrinkage resulting from drying in the three anisotropic directions is developed and tested. Measurements are performed on sawn discs, a technique which simplifies preparation and enables large numbers of measurements. Shrinkage values can be represented as a map of the disc surface. The results indicate that comparisons between shrinkage distribution and tension wood distribution on the discs show a clear relationship and can be measured with relatively high accuracy in reference to the "shrinkage map". In the long term, this method could be useful in the timber industry as a means for choosing the direction in which logs are cut depending on their type of wood composition.
Holzforschung

hal-01032055
https://hal.archives-ouvertes.fr/hal-01032055
DOI : 10.1515/HF.2003.100

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
A set of synthetic aggregates, containing mixtures of calcite and muscovite, were compacted with varying uniaxial loads ranging from 20 MPa up to 400 MPa. Their elastic properties have been measured using compressional and shear waves in confining hydrostatic pressures up to 475 MPa. Measured seismic velocities are shown to depend on 1) the ratio of calcite to muscovite, 2) the uniaxial load used during sample manufacturing, and 3) the porosity amount prior to velocity measurements. The matrix framework may also affect the seismic velocities, but this effect is not easily quantifiable. In general, measured seismic velocities decrease with increasing muscovite content and porosity. Elastic properties have been calculated based on texture measurements, which were obtained by neutron diffraction. The calculated velocities are based on the calcite and muscovite single crystal elastic tensors, their orientation distribution functions, and their modal fractions. A large discrepancy is apparent between calculated and measured velocities, where the former always overestimate the actual velocities. Shear waves display less of a difference between calculated and measured values, than do compressional waves, indicating that waves propagating by shearing are less affected by sample porosity and matrix framework. A better agreement between measured and calculated seismic velocities arises when the initial porosity is taken into account, using a differential effective medium model. Seismic anisotropy is evident from both measured and calculated velocities, and is low for samples containing pure calcite, but becomes prominent as the muscovite concentration increases. The intensity of anisotropy further depends on the uniaxial load used during sample compaction and the initial porosity.
ISSN: 0148-0227

hal-00512666
https://hal.archives-ouvertes.fr/hal-00512666
DOI : 10.1029/2009JB006523

Éditeur(s) : HAL CCSD Royal Society of Chemistry
Résumé : International audience
A full equilibrium treatment of molecular aggregation is presented for prototypes of 1D and 3D aggregates, with and without nucleation. By skipping complex kinetic parameters like aggregate size-dependent diffusion, the equilibrium treatment allows to predict directly time-independent quantities such as critical concentrations. The relationships between the macroscopic equilibrium constants for the different paths are first established by statistical corrections and so as to comply with the detailed balance constraints imposed by nucleation, and the composition of the mixture resulting from homogeneous aggregation is then analyzed using the polylogarithm function. Several critical concentrations are distinguished: the residual monomer concentation in equilibrium (RMC) and the critical nucleation concentration (CNC), that is the threshold concentration of total subunits necessary for initiating aggregation. When increasing the concentration of total subunits, the RMC converges more strongly to its asymptotic value, the equilibrium constant of depolymerization, for 3D aggregates and in case of nucleation. The CNC moderately depends on the number of subunits in the nucleus, but sharply increases with the difference between the equilibrium constants of polymerization and nucleation. As the RMC and CNC can be numerically but not analytically determined, ansatz equations connecting them to thermodynamic parameters are proposed
PCCP : Physical chemistry chemical physics

Droits : info:eu-repo/semantics/OpenAccess
hal-01565995
https://hal.archives-ouvertes.fr/hal-01565995
https://hal.archives-ouvertes.fr/hal-01565995/document
https://hal.archives-ouvertes.fr/hal-01565995/file/Aggregates_in_equilibrium.pdf
DOI : 10.1039/c6cp08369b

Éditeur(s) : HAL CCSD Elsevier
Résumé : In this study, I examine the strain modes of the forearc, arc and back-arc domains in arc-continent collisional settings leading to arc material subduction, delamination and/or accretion. The study focusses on two well-documented colliding island arcs: the Izu–Bonin–Mariana (IBM) arc in Japan and the Luzon arc in Taiwan, both carried by the Philippine Sea plate. Firstly, there is a body of evidence that both the IBM and the Luzon arcs were built on the same Late Jurassic to Early Cretaceous “proto-Philippine Sea Plate” crust. Their internal structure is thus more heterogeneous than expected from Paleogene or Neogene supposedly “intra-oceanic” island arcs. Secondly, those arc systems and proximal “back-arcs” have similar seismic characteristics attesting either for the presence of a middle crust with continental velocities and/or serpentinized uppermost mantle that facilitate crustal shortening/slivering and subsequent decoupling from the rest of the subducting plate. It is shown that the proximal back-arc domain (called “rear-arc” in case of paleoarc activity), overlying the mantle wedge and the subducting slab, may lose its strength if slab-derived hydration occur. Decoupling then occurs below the Moho. Arc delamination likely occurs in mid-crustal levels because middle-crust, heated by nearby magmatism, becomes weak. Accretion of arc material onto the upper plate depends on the characteristics of the arc itself and the geodynamic configuration. Most of the accreted material is probably underplated rather than frontally accreted.
ISSN: 0743-9547

hal-01243080
https://hal.archives-ouvertes.fr/hal-01243080
DOI : 10.1016/j.jseaes.2013.07.043

Éditeur(s) : Impr. officielle (Basse-Terre)
Résumé : Variante(s) de titre : Budget des recettes et dépenses _ Guadeloupe
Périodicité : Annuel
Etat de collection : 1858-
Bibliothèque nationale de France, département Philosophie, histoire, sciences de l'homme, FOL-LK19-171

http://gallica.bnf.fr/ark:/12148/cb34437069w/date

Éditeur(s) : HAL CCSD
Résumé : National audience
Objective of the study An estimation of burden of serious fungal diseases in France is essential data to inform public health priorities on the importance of resources and research needed on these infections. In France, precise data are available for invasive fungal diseases but estimates for several other diseases such as chronic and immunoallergic diseases are by contrast less known. Materials and methods A systematic literature search was conducted using the Web of Science Platform. Published epidemiology papers reporting fungal infection rates from France were identified. Where no data existed, we used specific populations at risk and fungal infection frequencies in those populations to estimate national incidence or prevalence, depending on the condition. Results The model predicts high prevalences of severe asthma with fungal sensitization episodes (189 cases/100,000 adults per year), of allergic bronchopulmonary aspergillosis (145/100,000) and of chronic pulmonary aspergillosis (5.24/100,000). Besides, estimated incidence for invasive aspergillosis is 1.8/100,000 annually based on classical high risk factors. Estimates for invasive mucormycosis, pneumocystosis and cryptococcosis are 0.12/100,000, 1/100,000 and 0.2/100,000, respectively. Regarding invasive candidiasis, more than 10,000 cases per year are estimated, and a much higher number of recurrent vaginal candidiasis is probable but must be confirmed. Finally, this survey was an opportunity to report a first picture of the frequency of tinea capitis in France. Conclusion Using local and literature data of the incidence or prevalence of fungal infections, approximately 1,000,000 (1.47%) people in France are estimated to suffer from serious fungal infections each year. © 2016 Elsevier Masson SAS
Journal de Mycologie Medicale

hal-01467554
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01467554
DOI : 10.1016/j.mycmed.2016.11.001
PUBMED : 27887809

Éditeur(s) : Université de Paris 7
Résumé : The Seine estuary and its adjacent region Pays de Caux are two significant sources of mercury for coastal marine environments. It is carried through fluvial means for the Seine bay and through karstic fresh water emergences for Pays de Caux's coastal area. Mercury cycle in the Seine estuary and bay is affected by additional anthropical activities. The estuary's maximal turbidity area acts like a trap and a chemical reactor for fluvial mercury. Within this area, we can confirm: (i) the non conservative behaviour of dissolved mercury; (ii) mercury enrichment of particles when comparing the Seine's and marine environment and we suggest mercury particle redistribution from the organic fraction to the oxyhydroxydes fraction. A large fraction of mercury is exported in this state towards coastal areas. Mercury reduction in surface coastal waters and its atmospherical recycling are major phenomena. Photoreduction and biological reduction play quantitative roles equivalent to total mercury recycling via the atmosphere corresponding approximately to 30 % of fluvial exchanges. We are demonstrating that reactive forms of mercury are supporting photoreduction. Mercury behaviour within Pays de Caux's karst depends of the hydrogeological context of the system (time and flow speed, turbidity, flow); regardless of the speciation and/or partition in underground waters, the total amount of mercury in intertidal areas is quantitatively the same as in the Seine estuary. Mercury brought through intertidal emergences (karstic exudations) is not « filtered » by a maximal turbidity area and is more widely bio-available for mussels than in the Seine estuary. Even being free from growth factor influences through simple models, mussels found in Pays de Caux still show one of the highest mercury contamination on the French coast; for the first time this places the emphasis on how much mercury is brought from underground waters to the coastal environment. Surface complexation modelisation tests are able to reproduce the major part of mercury partition in the Seine estuary and bay if a very low mercury exchangeable fraction and minimum complexation parameters are taken into account; thermodynamic calculations also suggest that a strong or highly concentrated « dissolved » ligand must be present in the water in order to compete with chlorocomplex formations and explain our measures.
L'estuaire de la Seine et la région adjacente du Pays de Caux sont deux sources significatives en mercure pour le milieu marin côtier. Les apports sont d'une part fluviatiles en ce qui concerne la Baie de Seine et karstiques via des émergences d'eau douce pour la zone côtière du Pays de Caux. Le cycle du mercure en estuaire et baie de Seine est perturbé par les apports liés aux activités anthropiques. La zone de turbidité maximum de l'estuaire joue le rôle de piège et de réacteur chimique pour le mercure fluviatile. Au sein de cette zone, nous mettons en évidence : (i) un comportement non-conservatif du mercure dissous; (ii) un enrichissement en mercure des particules par rapport à celles de la Seine et du milieu marin et suggérons une redistribution du mercure particulaire de la fraction organique vers la fraction oxyhydroxydes. C'est sous cette forme qu'une fraction importante du mercure est exportée vers la zone côtière. La réduction du mercure dans les eaux côtières de surface et son recyclage atmosphérique sont des phénomènes majeurs. En effet, la photoréduction et la réduction biologique jouent des rôles quantitativement équivalents avec un recyclage total du mercure via l'atmosphère correspondant à environ 30% des apports fluviatiles. Nous montrons que les formes réactives du mercure constituent le substrat de la photoréduction. Le comportement du mercure au sein du karst du Pays de Caux dépend du contexte hydrogéologiques du système (temps et vitesse de circulation, turbidité, débit) ; quelle que soit la spéciation et/ou la partition dans les eaux souterraines, l'apport en mercure total à la zone intertidale est quantitativement du même ordre de grandeur que les apports de la Seine. Le mercure apporté par les émergences intertidales (exutoires karstiques) n'est pas « filtré » par une zone de turbidité maximale et se trouve plus largement biodisponible pour les moules qu'en estuaire de Seine. En s'affranchissant, par des modèles simples, de l'influences des facteurs de croissance, les moules du Pays de Caux affichent toujours une contamination par le mercure parmi les plus élevées du littoral français; ceci met pour la première fois l'emphase sur l'importance de l'apport en mercure par des eaux souterraines dans un environnement côtier. Les essais de modélisation de complexation de surface reproduisent la majeure partie de la partition du mercure dans l'estuaire et la baie de Seine si l'on tient compte d'une fraction échangeable en mercure très faible et de paramètres de complexation minimums ; les calculs thermodynamiques suggèrent aussi qu'un ligand « dissous » fort ou présent à de fortes concentrations doit être présent dans l'eau afin d'entrer en compétition avec la formation de chlorocomplexes et expliquer nos mesures.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2001/these-1842.pdf
http://archimer.ifremer.fr/doc/00000/1842/

Éditeur(s) : ISTPM
Résumé : Shell is the basis of the distinction between the different species of molluscs. But the elements defining the shape and colour of the shell can vary according to the environmental conditions. So much so that, in numerous cases, a whole range of intermediates can be found between two species. Among molluscs, oysters are considered as a particularly confused group. Their shells are indeed extremely variable. All sorts of intermediates can be found. They usually attach themselves using their bottom valve, and, depending on the shape of the substrate, salinity conditions, temperature, outside environment, they present a wide range of individual variations. I had the opportunity to examine the larval shells of some of our coastal species. I noticed that each species had a specific prodissoconch, with a constant shape and no fundamental individual variations, an understandable fact given their planktonic life. The hinge and the position of the ligament in the hinge enable the definition of their genus. During the study of the collections of oysters from some of the world's most renowned museum (1), I tried to isolate the prodissoconches of the different species. I found them attached to the adult shells, making sure that all the prodissoconches attached to the top of the adult shells showed the same morphological characteristics. (unverified OCR)
LAMARCK, en 1806, dans l'ouverture de son Cours sur les «Animaux sans Vertèbres», s'exprimait ainsi : «En attendant, souvenons-nous que rien de tout cela n'est dans la nature, qu'elle ne connaît ni Classes, ni Ordres, ni Genres, ni Espèces, malgré le fondement que paraissent leur donner les portions de la série naturelle que nous offrent nos collections et que parmi les corps organisés, il n'y a réellement que des individus et des races diverses qui se nuancent dans tous les degrés de l'organisation. » Ainsi, pour LAMARCK, les cadres de la Classification zoologique seraient artificiels, ce seraient des créations de l'esprit, ayant seulement pour but de faciliter l'étude du monde vivant. Effectivement lorsqu'on consulte, comme je l'ai fait, les «Collections Lamarck» des Musées de Paris et de Genève. on s'aperçoit que, pour LAMARCK, le moindre caractère morphologique qui différencie une coquille de Mollusque d'une autre est une entité. Il multipliait le nombre des espèces et créait des variétés. Pour CUVIER (2) : «Le travail des nomenclatures, besogne facile, qui ne demande aucune intelligence a fait négliger la science véritable.» Et dit-il, ailleurs (:1) : «Après tout je n'ai pas jeté cette esquisse de division pour servir aux commençans à trouver les noms des espèces; qu'ils emploient pour cela tel système artificiel qu'ils trouveront le plus facile; cela est juste... » Les systèmes en question ne seraient donc que jeux de l'esprit, pour CUVIER également. Notre pensée a beaucoup évolué depuis cette époque. Nous pouvons dire maintenant que la Vie est la manière d'être des protéines et qu'il existe autant de protéines que d'espèces. Dès 1912, Jacques LOEB disait (4) : «Qu'en toute certitude, chaque animal a des substances germinatives spécifiques et que les substances germinatives diffèrent chimiquement d'un animal à l'autre, Les qualités chimiques d'un oeuf de poulet font qu'il ne peut donner naissance qu'à un poulet.» La notion d'espèce chimique vivante nous entraîne, par ailleurs, vers une nouvelle conception des autres groupes de la classification. L'individu porteur de caractères particuliers par lesquels il peut seulement être défini, est aussi porteur d'un noyau protoplasmique spécifique et enfin d'autres, propres successivement à la famille, à l'ordre, à la classe et à l'embranchement dont il fait partie. Cela est très important, car toutes ces catégories de la classification zoologique ne nous apparaissent plus alors comme de simples entités, subjectives, formelles, mais comme ayant effectivement une réalité précise dans le monde extérieur. La recherche et la définition correcte des espèces apparaissent alors comme un travail de première importance. Lorsqu'on poursuit des recherches embryologiques, physiologiques, biologiques ou autres sur un organisme, il est indispensable de savoir d'une manière précise en présence de quelle espèce on se trouve. Par ailleurs, comment parler de l'évolution des espèces si leur existence objective n'est pas admise et si elles ne sont pas correctement définies? Toute l'histoire de la Zoologie est marquée par l'effort constant de préciser les caractères de l'espèce et d'en faire une réalité objective. Chez les Mollusques, la coquille a servi de base essentielle pour la distinction des espèces. Mais les éléments de la forme et de la couleur de la coquille varient avec les conditions du milieu de telle sorte qu'on trouve dans de nombreux cas, tous les intermédiaires entre deux espèces. Parmi les Mollusques, les Huîtres constituaient un groupe particulièrement confus. En effet, leurs coquilles sont extrêmement variables. On rencontre tous les intermédiaires. Elles se fixent le plus souvent sur un support par la valve inférieure et là selon la forme du support, selon les conditions de la salinité, de la température, du milieu extérieur, elles présentent une immense gamme de variations individuelles. J'ai été amené à examiner les coquilles larvaires de quelques espèces de nos côtes. J'ai constaté que chaque espèce avait une prodissoconque particulière, d'une forme constante et sans variations individuelles fondamentales ce qui se conçoit aisément, étant donné leur vie planctonique. Leur charnière et la position du ligament par rapport à cette dernière, permettent de définir les genres, En étudiant les collections d'Huîtres des grands musées du monde (1), j'ai cherché à isoler les prodissoconques des diverses espèces. Je les ai trouvées sur les coquilles adultes où elles s'étaient fixées. m'assurant chaque fois que les prodissoconques conservées au sommet des coquilles adultes présentaient les mêmes caractéristiques morphologiques. J'ai microphotographié la plupart des coquilles larvaires étudiées. Ce sont les épreuves qui sont reproduites ici. J'en ai fait faire des dessins au trait et pour quelques-unes dont les microphotographies manquent, on trouvera les dessins au trait réalisé à la chambre claire. Chaque espèce est bien définie par sa coquille larvaire. La meilleure démonstration en est fournie par les deux espèces. si voisines par leurs coquilles adultes, Ostrea edulis et Ostrea chilensis; leurs prodissoconques sont spectaculairement différentes. Je remercie Monsieur le Directeur de l'Institut scientifique et technique des Pêches maritimes qui a bien voulu accepter de publier le résultat de ces recherches dans la belle Revue des Travaux de son Institut. (OCR non contrôlé)
Revue des Travaux de l'Institut des Pêches Maritimes (0035-2276) (ISTPM), 1967-06 , Vol. 31 , N. 2 , P. 127-199

Droits : Ifremer
http://archimer.ifremer.fr/doc/1967/publication-3761.pdf
http://archimer.ifremer.fr/doc/00000/3761/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The tg(cyp19a1b-GFP) transgenic zebrafish expresses GFP (green fluorescent protein) under the control of the cyp19a1b gene, encoding brain aromatase. This gene has two major characteristics: (i) it is only expressed in radial glial progenitors in the brain of fish and (ii) it is exquisitely sensitive to estrogens. Based on these properties, we demonstrate that natural or synthetic hormones (alone or in binary mixture), including androgens or progestagens, and industrial chemicals induce a concentration-dependent GFP expression in radial glial progenitors. As GFP expression can be quantified by in vivo imaging, this model presents a very powerful tool to screen and characterize compounds potentially acting as estrogen mimics either directly or after metabolization by the zebrafish embryo. This study also shows that radial glial cells that act as stem cells are direct targets for a large panel of endocrine disruptors, calling for more attention regarding the impact of environmental estrogens and/or certain pharmaceuticals on brain development. Altogether these data identify this in vivo bioassay as an interesting alternative to detect estrogen mimics in hazard and risk assessment perspective.
ISSN: 1932-6203

hal-00877371
https://hal.archives-ouvertes.fr/hal-00877371
https://hal.archives-ouvertes.fr/hal-00877371/document
https://hal.archives-ouvertes.fr/hal-00877371/file/Screening_Estrogenic_Activities-accepted.pdf
DOI : 10.1371/journal.pone.0036069

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
We explored the relationship between soil processes, estimated through soil respiration (Rsoil), and the spatial variation in forest structure, assessed through the distribution of tree size, in order to understand the determinism of spatial variations in Rsoil in a tropical forest. The influence of tree size was examined using an index (Ic) calculated for each tree as a function of (1) the trunk cross section area and (2) the distance from the measurement point. We investigated the relationships between Ic and litterfall,root mass and Rsoil, respectively. Strong significant relationships were found between Ic and both litterfall and root mass. Rsoil showed a large range of variations over the 1-ha experimental plot, from 1.5 to 12.6 gC m−2 d−1. The best relationship between Ic and Rsoil only explained 17% of the spatial variation in Rsoil. These results support the assumption that local spatial patterns in litter production and root mass depend on tree distribution in tropical forests. Our study also emphasizes the modest contribution of tree size distribution-which is mainly influenced by the presence of the biggest trees (among the large range size of the inventoried trees greater than 10 cm diameter at 1.30 m above ground level or at 0.5 m above the buttresses)-in explaining spatial variations in Rsoil.
ISSN: 0032-079X

hal-00797064
https://hal.archives-ouvertes.fr/hal-00797064

Éditeur(s) : Agrocampus Ouest
Résumé : The origin of fish stocks variability is a key question in fisheries science. The exploitation indeed has an important effect in terms of biomass reduction, but environmental forcing is of central interest as it affects numerous key biological processes. Recent theoretical results have shown that the nature of the environmental fluctuations, the environmental noise, has important ecological consequences on populations and particularly on their fluctuations. In addition the effects of exploitation, that are not a simple removal of individuals but also profoundly modifies the demography, the structure and the trophic interactions of fish stocks, can interact with environmental effects. Through an extensive analysis of time series we aim at understanding the effects of environmental noise on fish stocks variability, according to their biological characteristics (life-history traits) and their exploitation. A technique of time series comparison allows to propose that the fluctuations of Atlantic large pelagics are inherited from the interaction between environmental effects, endogenous dynamics and exploitation. We then show that the colour of environmental noise affects the variability of time series, its effects depending on the life-history traits of species. Finally, preliminary results on bentho-demersal and pelagic stocks from the North Atlantic suggest that the exploitation increases the sensitivity of fish stocks to the colour of environmental noise and affects their variability, according to their life-history traits.
L'origine de la variabilité des stocks de pêche est une question centrale en halieutique. Si l'exploitation tient un rôle important dans la réduction de biomasse, le forçage environnemental affecte de nombreux processus biologiques clés. Des résultats théoriques récents ont montré que la nature des fluctuations environnementales, la couleur du bruit environnemental, avait des implications écologiques importantes sur les populations et notamment sur leurs fluctuations. De plus, les effets environnementaux peuvent agir en interaction avec l'exploitation qui ne consiste pas en un simple prélèvement d'individus, mais qui modifie profondément la démographie, la structure et les interactions trophiques des stocks. Au travers de l'analyse extensive de séries temporelles, on essaye ici de comprendre les effets de la couleur du bruit environnemental sur la variabilité des stocks en fonction de leurs caractéristiques biologiques (traits d'histoire de vie) et de leur état d'exploitation. Le développement d'une technique de comparaison des séries temporelles permet de proposer que les fluctuations des grands pélagiques de l'Atlantique sont héritées de l'interaction entre effets environnementaux, dynamique interne et dynamique de l'exploitation. On montre ensuite que la couleur du bruit environnemental affecte la variabilité des séries temporelles, mais que son effet dépend des traits d'histoire de vie des espèces. Enfin, des résultats préliminaires sur les stocks bentho-démersaux et pélagiques de l'Atlantique Nord, suggèrent que l'exploitation augmente la sensibilité des stocks à la couleur du bruit environnemental et affecte leur variabilité en fonction de leurs traits d'histoire de vie.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2008/these-6596.pdf
http://archimer.ifremer.fr/doc/00000/6596/

Éditeur(s) : HAL CCSD MAIK Nauka/Interperiodica
Résumé : Interaction between surface processes and deep tectonic processes plays a key role in the structural evolution, kinematics and exhumation of rocks in orogenic wedges. The deformation patterns observed in analogue models applied to natural cases of present active or ancient mountain belts reflect several first order processes that result of these interactions. Internal strain partitioning due to mechanical behaviour of a thrust wedge has a strong impact on the vertical component of displacement of tectonic units that in return favour erosion in domains of important uplift. Such strain partitioning is first controlled by tectonic processes, but surface processes exert a strong feed back on wedge dynamics. Indeed, material transfer in thrust wedges not only depends on its internal dynamics, it is also influenced by climate controlled surface processes involving erosion and sedimentation. Effects of erosion are multiple: they allow long term localization of deformed domains, they favour important exhumation above areas of deep underplating and combined with sedimentation in the foreland they contribute to maintain the wedge in a critical state for long time periods. The simple models illustrate well how mountain belts structure, kinematics of tectonic units and exhumation are determined by these complex interactions.
ISSN: 0016-8521

hal-00561361
https://hal.archives-ouvertes.fr/hal-00561361
DOI : 10.1134/S0016852110060075

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The IL-33/ST2 axis is known to be involved in liver pathologies. Although, the IL-33 levels increased in sera of viral hepatitis patients in human, the cellular sources of IL-33 in viral hepatitis remained obscure. Therefore, we aimed to investigate the expression of IL-33 in murine fulminant hepatitis induced by a Toll like receptor (TLR3) viral mimetic, poly(I:C) or by pathogenic mouse hepatitis virus (L2-MHV3). The administration of poly(I:C) plus D-galactosamine (D-GalN) in mice led to acute liver injury associated with the induction of IL-33 expression in liver sinusoidal endothelial cells (LSEC) and vascular endothelial cells (VEC), while the administration of poly(I:C) alone led to hepatocyte specific IL-33 expression in addition to vascular IL-33 expression. The hepatocyte-specific IL-33 expression was down-regulated in NK-depleted poly(I:C) treated mice suggesting a partial regulation of IL-33 by NK cells. The CD1d KO (NKT deficient) mice showed hepatoprotection against poly(I:C)-induced hepatitis in association with increased number of IL-33 expressing hepatocytes in CD1d KO mice than WT controls. These results suggest that hepatocyte-specific IL-33 expression in poly(I:C) induced liver injury was partially dependent of NK cells and with limited role of NKT cells. In parallel, the L2-MHV3 infection in mice induced fulminant hepatitis associated with up-regulated IL-33 expression as well as pro-inflammatory cytokine microenvironment in liver. The LSEC and VEC expressed inducible expression of IL-33 following L2-MHV3 infection but the hepatocyte-specific IL-33 expression was only evident between 24 to 32h of post infection. In conclusion, the alarmin cytokine IL-33 was over-expressed during fulminant hepatitis in mice with LSEC, VEC and hepatocytes as potential sources of IL-33.
ISSN: 1932-6203

hal-00874120
https://hal.archives-ouvertes.fr/hal-00874120
https://hal.archives-ouvertes.fr/hal-00874120/document
https://hal.archives-ouvertes.fr/hal-00874120/file/Pathogenic_Mouse_Hepatitis-accepted.pdf
DOI : 10.1371/journal.pone.0074278

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
The variation of elastic- wave velocities as a function of the direction of propagation through the Earth's interior is a widely documented phenomenon called seismic anisotropy. The geometry and amount of seismic anisotropy is generally estimated by measuring shearwave splitting, which consists of determining the polarization direction of the fast shear- wave component and the time delay between the fast and slow, orthogonally polarized, waves. In subduction zones, the teleseismic fast shear- wave component is oriented generally parallel to the strike of the trench(1), although a few exceptions have been reported (Cascadia(2) and restricted areas of South America(3,4)). The interpretation of shear- wave splitting above subduction zones has been controversial and none of the inferred models seems to be sufficiently complete to explain the entire range of anisotropic patterns registered worldwide(1). Here we show that the amount and the geometry of seismic anisotropies measured in the forearc regions of subduction zones strongly depend on the preferred orientation of hydrated faults in the subducting oceanic plate. The anisotropy originates from the crystallographic preferred orientation of highly anisotropic hydrous minerals (serpentine and talc) formed along steeply dipping faults and from the larger- scale vertical layering consisting of dry and hydrated crust - mantle sections whose spacing is several times smaller than teleseismic wavelengths. Fault orientations and estimated delay times are consistent with the observed shear- wave splitting patterns in most subduction zones.
ISSN: 0028-0836

hal-00412016
https://hal.archives-ouvertes.fr/hal-00412016
DOI : 10.1038/nature07376

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) : Pergamon-elsevier Science Ltd
Résumé : Environmental variables affect many processes of fish biology and their fluctuations are thought to be one of the main factors in variability of fish stocks. Recent work has shown that the variability of the environment in the frequency domain (i.e., the environmental noise) can interact with endogenous processes (e.g., density dependence) and affect fluctuations of animal populations. In this study, we investigate whether fluctuations of large pelagics' time series are affected by environmental noise and whether life-history traits of species modulate this response. By analysing several environmental variables and a large dataset of tuna and billfish catch per unit effort (CPUE) time series from the Atlantic, we show that in environments dominated by long-term fluctuations (i.e., red noise) CPUE time series were less variable and displayed smoother fluctuations. Furthermore, larger, slower-growing and later-maturing species were found to be more sensitive to changes of environmental noise than species with a shorter turnover rate. Our results suggest that environmental noise interacts with fish biology; understanding how it is integrated into biological processes might provide important insights to understand the responses of fish stocks dynamics to exploitation and environmental changes. (C) 2010 Elsevier Ltd. All rights reserved.
Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2010-07 , Vol. 86 , N. 1-2 , P. 267-275

Droits : 2010 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00011/12230/9083.pdf
DOI:10.1016/j.pocean.2010.04.025
http://archimer.ifremer.fr/doc/00011/12230/

Éditeur(s) : Edp Sciences S A
Résumé : Moored FADs (MFADs) have been a key area for development in Guadeloupe (Lesser Antilles) since the late 1980's. The main objectives underpinning the development of MFADs were to (i) reduce fishing pressure on coastal fishing resources; (ii) boost fishermen's incomes; and (iii) increase local consumption of locally generated fishery products as a proportion of overall consumption. This paper gives an overview of the current structure of Guadeloupe's fishing fleet and fisheries, with a specific focus on MFAD fleets in a relatively unstructured environment with regard to regulation, and so how these fleets operate in a context of unrestricted development of private MFADs. In addressing the following key issues, this paper aims to: assess the economic performance of fleets operating on MFADs, understand why the MFAD fishing activity has not developed more than it has, and suggest how better MFAD management could improve the situation. Socio-economic information on a trip and fleet level basis were collected and stored on a fisheries information system to analyse the relative attractiveness of MFAD fishing and assess the overall economic performance of MFAD fleets as compared to other non-MFAD fleets. Non-monetary variables were also tested to explain the degree of dependence on MFADs. In 2008, economic returns from FADs were relatively low, both in terms of wages for the crews and in terms of profit for vessel owners. Earnings were higher than coastal fishing activities, but seem to have been very sensitive to the indicators used in our analysis. MFADs are expected to become much more attractive as a result of MFAD regulation, especially through the establishment of collective MFADs.
Aquatic Living Resources (0990-7440) (Edp Sciences S A), 2013-01 , Vol. 26 , N. 1 , P. 97-105

Droits : EDP Sciences, IFREMER, IRD 2013
http://archimer.ifremer.fr/doc/00137/24836/22914.pdf
DOI:10.1051/alr/20013044
http://archimer.ifremer.fr/doc/00137/24836/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Despite many studies, our understanding of silica precipitation from natural waters remains limited, in particular for geothermal waters. Here we present a detailed study on the kinetics of silica polymerization as a function of fluid temperature and pH using high-temperature (250-260 °C) seawater-derived geothermal fluids as those discharged from the Bouillante geothermal site.We monitored the on-site decrease in monomeric silica concentration(initial SiO2 concentration of about 600 mg/l)with time using the molybdenum blue spectrophotometric method on samples of separated water collected from the high-pressure separator at 167 °C and cooled to 25, 50, 75, and 90 °C and for pH values ranging from 5 to 8. During all these experiments, only silica polymerization was observed, with the formation of colloidal particles in suspension in the solutions. No scaling of amorphous silica was formed. The collected data were after modeled in order to determine the useful kinetic parameters for predicting and preventing amorphous silica precipitation in the production wells during fluid exploitation in the specific context of Bouillante. Results under the investigated experimental conditions show that the kinetics of silica precipitation is affected more strongly by pH than by temperature change. The reaction in the acidic Bouillante solution begins with a transition period that significantly decreases the kinetics of silica polymerization. Modeling the experimental data indicates that the silica polymerization up to the state of equilibrium is characterized by a 2nd-order kinetic law relative to dissolved silica; this could indicate that the polymerization is controlled mainly by the formation of dimers. However, the first hour of the experiments is better characterized by a 4th-order kinetic law, suggesting more complex polymerization reactions in the initial stage with the formation of nanocolloidal particles containing 3 to 4 monomers. In both cases, the corresponding kinetics rate constant k is linearly dependent on pH for pH between 5 and 7. The activation energy Ea for the overall reaction, calculated using the Arrhenius equation under the considered pH and temperature conditions, ranges between 41±9.8 and 54±9.6 kJ/mol. To complete this work, the colloid particles formed at the end of the kinetics experiments were extracted and analyzed by SEM and TEM microscopy, X-ray Diffraction and the BET method. Results show that the size of the colloids increase and their specific surface decrease with increasing pH and are thus dependent on pH. Globally, our work provides a reliable database for understanding silica polymerization kinetics in natural geothermal brines or geologic waters characterized by a near neutral pH and moderate dissolved silica concentrations.
ISSN: 0009-2541

hal-01403092
https://hal-brgm.archives-ouvertes.fr/hal-01403092
DOI : 10.1016/j.chemgeo.2016.08.031

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
La lumière est le principal facteur limitant de la croissance en forêt tropicale humide. Malgré 1% du rayonnement incendie disponible en sous-bois, les jeunes arbres doivent rejoindre la canopée pour assurer la régénération du couvert. La compétition pour l'accès à la lumière est forte, et leur stabilité mécanique est souvent perturbée. La gravité étant un facteur omniprésent , tout déséquilibre entraîne des flexions de l'arbre et peut-être dramatique. Les arbres peuvent cependant palier ces déséquilibres en réorientant leurs axes par gravitropisme. Les "moteurs" des réorientations dans les axes lignifiés, sont la croissance radiale, la différentiation de bois de réaction et souvent, une croissance radiale excentrée.La capacité au redressement dépend aussi des dimensions des axes. Ces différents paramètres modulent donc la réponse gravitropique. Les réorientations dépendent de la croissance et donc également des ressources en lumière. Ce travail avait pour buts de quantifier l'impact de la croissance radiale sur le redressement d'une espèce tropicale et de mettre en évidence d'éventuelles différences d'efficience, de réorientation des arbres en fonction de la disponibilité en lumière. La réponse gravitropique de jeunes Symphonia globulifera artificiellement inclinés a été étudiée sous deux niveaux de lumière (1% et 25%°). L'importance de la croissance radiale dans la réaction gravitropique a été quantifiée par une analyse cinématique du redressement et l'utilisation d'un modèle biomécanique simple. Ce travail montre que même à 1% de lumière, les arbres ont une réponse gravitropique. L'efficience de réaction est d'ailleurs plus forte qu'à 25% de lumière. Cette réaction semble donc être une fonction prédominante pour les plantes en sous-bois. Nous avons également montré que le redressement est fortement corrélé à la vitesse de croissance radiale. Les données obtenues complètent celles déjà acquises sur des espèces tempérées. Elles permettront des comparaisons interspécifiques du processus gravitropique et serviront à valider des modèles biomécaniques plus complexes que celui utilisé dans cette étude.
https://hal.archives-ouvertes.fr/hal-01189227

hal-01189227
https://hal.archives-ouvertes.fr/hal-01189227
PRODINRA : 16967