Éditeur(s) : Elsevier Science Bv
Résumé : The biodynamic and saturation models offer promising lines of enquiry to predict the bioaccumulation of metals by aquatic organisms. However, in order to construct these models, the accumulation strategies have to be defined for each metal/organism couple in controlled conditions. This study aims at modelling the waterborne bioaccumulation of Ni and the influence of the water's geochemical properties on this process in a crustacean that is widely distributed in Europe, Gammarus pulex. In the laboratory, G. pulex was exposed to several Ni concentrations (from 0.001 to 100 mg L(-1)) in aquatic microcosms. Our results show that G. pulex is very tolerant to Ni (LC50(48 h) = 477 mg L(-1) Ni). Time course experiments enabled the construction of a biodynamic model by determining the uptake (k(u)) and elimination (k(e)) rate constants. When the exposure concentration exceeded 1 mg L(-1) Ni, the metal uptake reached a maximum due to a limited number of binding sites for Ni. Therefore, the organism's maximal capacity to accumulate the metal (B(max)) and the half-saturation constant (K) were determined to establish the saturation model. We showed that the two models are comparable for the lowest exposure concentrations (<1 mg L(-1) Ni), with k(u)/k(e) = B(max)/K. Then, the bioaccumulation of Ni was recorded in waters exhibiting various concentrations of three major ions (Na(+), Mg(2+) and Ca(2+)). Only Ca had an inhibitory effect on the Ni uptake. This study reports for the first time the bioaccumulation of Ni in G. pulex. Because of its high tolerance to Ni and its high capacity to accumulate this metal, this crustacean could be used as an indicator of Ni bioavailability in freshwaters. (C) 2011 Elsevier B.V. All rights reserved.
Aquatic Toxicology (0166-445X) (Elsevier Science Bv), 2011-08 , Vol. 104 , N. 3-4 , P. 161-167

Droits : 2011 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00041/15217/18005.pdf
DOI:10.1016/j.aquatox.2011.04.011
http://archimer.ifremer.fr/doc/00041/15217/

Éditeur(s) : Montpellier 1
Résumé : Understanding bioaccumulation mechanisms of persistent organic pollutants (POPs) is a major issue for environmental risk assessment. In this work, polychlorinated biphenyls (PCBs), a model contaminant family, has been studied in the European hake (Merluccius merluccius), a high trophic level species from the Gulf of Lions. High concentrations of PCBs were measured in hake from this area compared to those encountered in the population of the Bay of Biscay. PCB biomagnification was highlighted along its food web from marine phytoplankton, suggesting a strong influence of diet on contamination levels. The role of other biological processes was also apprehended in order to understand the high variability of observed levels. Thus, growth, sex, and also the degree of sexual maturity appear as major factors explaining the measured concentrations in fish. A PCB bioaccumulation model in the hake, based on the Dynamic Energy Budget theory (DEB), was developed. This approach is based on a bioenergetic model, reproducing the main physiological functions of an organism (feeding, growth and reproduction), coupled with a kinetic model of contaminants. The growth and evolution of contamination levels of several PCB congeners during the life of male and female hakes is satisfactorily simulated, both in the Gulf of Lions and in the Bay of Biscay, validating the processes taken into account. This combined modelling approach appears well adapted to study the fate of contaminants in fish, and paves the way for a realistic understanding of their effects on major biological functions of fish.
La compréhension des mécanismes de bioaccumulation des contaminants organiques persistants (POP) est un enjeu majeur pour l'évaluation des risques environnementaux. Lors de ce travail, le devenir d'une famille de contaminants modèles, les polychlorobiphényles (PCB), a été étudié chez une espèce de rang trophique élevé du golfe du Lion, le merlu Européen (Merluccius merluccius). Des concentrations élevées en PCB ont été mesurées dans les merlus de ce secteur en comparaison à celles rencontrées dans la population du golfe de Gascogne. La mise en évidence d'une bioamplification des PCB le long de son réseau trophique, depuis le phytoplancton marin, suggère une influence importante de l'alimentation sur les niveaux de contamination. Le rôle d'autres processus biologiques a également été appréhendé afin de comprendre la forte variabilité des niveaux observés. Ainsi, la croissance, le sexe, mais également le degré de maturité sexuel apparaissent comme des facteurs explicatifs majeurs des concentrations en PCB mesurées dans les poissons. Un modèle de bioaccumulation des PCB chez le merlu, basé sur la théorie de Budget d'Energie Dynamique (DEB), a été développé. Il s'agit d'une approche basée sur le couplage d'un modèle bioénergétique, reproduisant les principales fonctions physiologiques de l'organisme (nutrition, croissance et reproduction), avec un modèle de cinétique des contaminants. La croissance et l'évolution des niveaux de contamination de plusieurs congénères de PCB au cours de la vie des merlus mâles et femelles est simulée de manière satisfaisante, tant dans le golfe de Gascogne que dans le golfe du Lion, validant ainsi les processus pris en compte. Cette approche combinée de modélisation apparaît tout à fait adaptée à l'étude du devenir des contaminants chez les poissons, et ouvre la voie à une compréhension réaliste de leurs effets sur les grandes fonctions biologiques de ces organismes.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2008/these-6490.pdf
http://archimer.ifremer.fr/doc/00000/6490/

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy B - Oxford Open Option A Oxford University Press (OUP)
Résumé : International audience
Peridotite xenoliths exhumed by Quaternary alkaline magmatism in the Tahalgha district, southern Hoggar, represent fragments of the subcontinental lithospheric mantle beneath the boundary between the two major structural domains of the Tuareg Shield: the ‘Polycyclic Central Hoggar’ to the east and the ‘Western Hoggar’, or ‘Pharusian Belt’, to the west. Samples were collected from volcanic centres located on both sides of a major lithospheric shear zone at 4°35' separating these two domains. Although showing substantial variations in their deformation microstructures, equilibrium temperatures and modal and chemical compositions, the studied samples do not display any systematic changes of these features across the 4°35' fault. The observed variations rather record small-scale heterogeneities distributed throughout the study area and reflecting the widespread occurrence of vein conduits and metasomatized wall-rocks related to trans-lithospheric melt circulation during the Cenozoic. These features include partial annealing of pre-existing deformation microstructures, post-deformation metasomatic reactions, and trace-element enrichment, coupled with heating from 750–900°C (low-temperature lherzolites) to 900–1150°C (intermediate-T lherzolites and high-T harzburgites and wehrlites). Trace-element modelling confirms that the range of rare earth element (REE) variations observed in the Tahalgha clinopyroxenes may be accounted for by reactive porous flow involving a single stage of basaltic melt infiltration into a light REE (LREE)-depleted protolith. Whole-rock compositions record the final entrapment of disequilibrium metasomatic melts upon thermal relaxation of the veins–wall-rock system. The striking correlations between equilibrium temperatures and trace-element enrichment favor a scenario in which the high-temperature peridotites record advective heat transport along melt conduits, whereas the intermediate- and low-temperature lherzolites reflect conductive heating of the host Mechanical Boundary Layer. This indicates that the lithosphere did not reach thermal equilibrium, suggesting that the inferred heating event was transient and was rapidly erased by thermal relaxation down to the relatively low-temperature present-day geotherm. The low-T (<900°C) deformed lherzolites (porphyroclastic to equigranular) are characterized by only incipient annealing and LREE-depleted clinopyroxene compositions. They were only weakly affected by the Cenozoic events and could represent relatively well-preserved samples from rejuvenated Pan-African lithosphere. Extensive lithospheric rejuvenation occurred either regionally during the Pan-African orogeny, as a result of lithospheric delamination or thermomechanical erosion after thickening, or more locally along the meridional shear zones. The low-T Tahalgha lherzolites are comparable with lherzolites from Etang de Lherz, southern France, interpreted as lithospheric mantle rejuvenated by melt-induced refertilization during a late stage of the Variscan orogeny.
ISSN: 0022-3530

hal-01107410
https://hal.archives-ouvertes.fr/hal-01107410
DOI : 10.1093/petrology/egu056

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The paper is motivated by the long term safety analysis of the CO 2 geological storage. We present a methodology for the assessment of the ge-omechanical impact of progressive rock dissolution. The method is based on the use of X-ray tomography and the numerical dissolution technique. The influence of evolution of the microstructure on the macroscopic properties of the rock is analysed by using periodic homogenization method. The numerical computations show progressive degradation of all components of the stiffness (orthotropic) tensor. Moreover, the evolution of associated mass transfer properties (as tortuosity and conductivity tensors), by using the periodic homogenization method, is also calculated. The correlation between the mechanical parameters and the transfer properties during the dissolution pro-cess is presented. The results show that the highest increase of the hydraulic conductivity (in direction Y) is not associated with the highest decrease of Young modulus in this direction. Moreover, the highest decrease of Young modulus (in the direction X) is not associated with percolation in this direction. Finally, an incremental law to calculate settlement, in case of a rock with evolving microstructure, is proposed. The solution of the macroscopic settlement problem under constant stress and drained conditions showed that the geomechanical effects of the rock dissolution are rather limited.
ISSN: 0363-9061

hal-01104204
https://hal.archives-ouvertes.fr/hal-01104204
https://hal.archives-ouvertes.fr/hal-01104204/document
https://hal.archives-ouvertes.fr/hal-01104204/file/Numerical_computations_rock_dissolution_Wojtacki_al_2014.pdf
DOI : 10.1002/nag.2316

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
We herein focus on understanding what controls the detachment and migration of oceanic crustal slices along subduction zones. We provide evidence for the coeval Middle to Late Cretaceous exhumation of oceanic blueschists in the same Neotethyan subduction zone, across more than 3000 km, from depths around 30-40 km, over a short time interval (similar to 25 Ma) compared to the duration of subduction (>100 Ma). We stress the importance of such a geodynamic process and suggest that this exhumation was promoted by a regional-scale change in the long-term interplate mechanical coupling. On the basis of geological and geophysical evidence, we propose that the upward migration of oceanic fragments in subduction zones is normally inhibited and only occurs discontinuously, as the subduction channel opens up in response to a major change in plate geodynamics, slab geometry and dynamics, mantle wedge and slab hydration, or a combination of these.
ISSN: 1525-2027

hal-00420898
https://hal.archives-ouvertes.fr/hal-00420898
DOI : 10.1029/2009GC002428

Éditeur(s) : HAL CCSD
Résumé : The geological storage of CO 2 is considered as one of the solutions to the problem of global warming. The most possible scenarios of geological behavior of soil in the long term conditions has to be precisely defined to avoid catastrophic damages in the future. Chemical properties of saline water in the aquifer after the CO 2 injection becomes more acidic with time. Therefore, chemical degradation of rock occurs, which leads to modifications of its mechanical properties (chemo-mechanical coupling) [1]. In this paper an incremental model of chemo-mechanical coupling using homogenization approach (asymptotic expansion method [2,3]) is proposed. The paper is focused on the numerical computations for the X-ray tomography image of carbonate rock microstructure [4]. The chemical degradation of the microstructure is obtained as a homogeneous dissolution in each direction (Fig.1. – Fig.2.) For every porosity state numerical computations to obtain full, orthotropic elasticity tensor are performed. Therefore, the degradations functions for all components of the rigidity tensor were defined (Fig.3.). Moreover, results of numerical calculations of diffusion, tortuosity and permeability tensors are presented [5,6]. The link between geometrical properties and mechanical and transport parameters are discussed. The numerical analysis of the carbonate rock sample in long term conditions shows the increase of porosity and associated mechanical weakening of the rock. Moreover, the increase of diffusion, tortuosity and permeability tensors elements with time were observed. Finally, the solution of the one-dimensional macroscopic problem of soil settlement due to chemical dissolution of rock at constant load is presented. The method is universal, in the sense that the non-dimensional time scale is used.
ALERT Workshop 2013
Aussois, France

hal-01103175
https://hal.archives-ouvertes.fr/hal-01103175

Éditeur(s) : Inter-research
Résumé : Environmental conditions experienced by aquatic organisms are archived in biogenic carbonates such as fish otoliths, bivalve shells and coral skeletons. These calcified structures present an accretionary growth and variations in optical properties - color or opacity - that are used to reconstruct time. Full and reliable exploitation of the information extracted from these structures is, however, often limited as the metabolic processes that control their growth and their optical properties are poorly understood. Here, we propose a new modeling framework that couples both the growth of a biogenic carbonate and its optical properties with the metabolism of the organism. The model relies on well-tested properties of Dynamic Energy Budget (DEB) theory. It is applied to otoliths of the Bay of Biscay anchovy (Engraulis encrasicolus) for which a DEB model has been previously developed. The model reproduces well-known otolith patterns and thus provides us with mechanisms for the metabolic control of otolith size and opacity at the scale of an individual lifespan. Two original contributions using this framework are demonstrated. First, the model can be used to reconstruct the temporal variations in the food assimilated by an individual fish. Reconstructing food conditions of past and present aquatic species in their natural environment is key ecological information to better understand population dynamics. Second, we show that non-seasonal checks can be discriminated from seasonal checks, which is a well-recognized problem when interpreting fish otoliths. We discuss further developments of the model and the experimental settings required to test this new promising framework.
Marine Ecology-progress Series (0171-8630) (Inter-research), 2012 , Vol. 447 , P. 151-164

Droits : 2012 Inter-Research
http://archimer.ifremer.fr/doc/00060/17082/14593.pdf
DOI:10.3354/meps09492
http://archimer.ifremer.fr/doc/00060/17082/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This paper aims to present an overview on the influence of rheological heterogeneity and mechanical anisotropy on the deformation of continents. After briefly recapping the concept of rheological stratification of the lithosphere, we discuss two specific issues: (1) as supported by a growing body of geophysical and geological observations, crust=mantle mechanical coupling is usually efficient, especially beneath major transcurrent faults which probably crosscut the lithosphere and root within the sublithospheric mantle; and (2) in most geodynamic environments, mechanical properties of the mantle govern the tectonic behaviour of the lithosphere. Lateral rheological heterogeneity of the continental lithosphere may result from various sources, with variations in geothermal gradient being the principal one. The oldest domains of continents, the cratonic nuclei, are characterized by a relatively cold, thick, and consequently stiff lithosphere. On the other hand, rifting may also modify the thermal structure of the lithosphere. Depending on the relative stretching of the crust and upper mantle, a stiff or a weak heterogeneity may develop. Observations from rift domains suggest that rifting usually results in a larger thinning of the lithospheric mantle than of the crust, and therefore tends to generate a weak heterogeneity. Numerical models show that during continental collision, the presence of both stiff and weak rheological heterogeneities significantly influences the large-scale deformation of the continental lithosphere. They especially favour the development of lithospheric-scale strike-slip faults, which allow strain to be transferred between the heterogeneities. An heterogeneous strain partition occurs: cratons largely escape deformation, and strain tends to localize within or at the boundary of the rift basins provided compressional deformation starts before the thermal heterogeneity induced by rifting are compensated. Seismic and electrical conductivity anisotropies consistently point towards the existence of a coherent fabric in the lithospheric mantle beneath continental domains. Analysis of naturally deformed peridotites, experimental deformations and numerical simulations suggest that this fabric is developed during orogenic events and subsequently frozen in the lithospheric mantle. Because the mechanical properties of single-crystal olivine are anisotropic, i.e. dependent on the orientation of the applied forces relative to the dominant slip systems, a pervasive fabric frozen in the mantle may induce a significant mechanical anisotropy of the whole lithospheric mantle. It is suggested that this mechanical anisotropy is the source of the so-called tectonic inheritance, i.e. the systematic reactivation of ancient tectonic directions; it may especially explain preferential rift propagation and continental break-up along pre-existing orogenic belts. Thus, the deformation of continents during orogenic events results from a trade-off between tectonic forces applied at plate boundaries, plate geometry, and the intrinsic properties (rheological heterogeneity and mechanical anisotropy) of the continental plates.
ISSN: 0040-1951

hal-01389719
http://hal.univ-reunion.fr/hal-01389719
http://hal.univ-reunion.fr/hal-01389719/document
http://hal.univ-reunion.fr/hal-01389719/file/vauchez_etal_rheology_1998_hal.pdf
DOI : 10.1016/S0040-1951(98)00137-1

Éditeur(s) : HAL CCSD Geological Society of London
Résumé : We have applied transmission electron microscopy (TEM) analyses coupled with viscoplastic self-consistent (VPSC) numerical modelling to identify the active slip systems and to better understand the crystal preferred orientation (CPO) development of the Torridon quartz mylonite (NW Scotland). TEM analyses showed evidence of activation of 1/3〈a〉{π′}, 1/3〈a〉{z} and possible 〈a〉(c) slip systems, as well as dislocation climb and dynamic recrystallization. All the CPOs generated by VPSC models share common characteristics with the Torridon quartz mylonite, but only Models 2 and 3 reproduce the [c]-axes maxima at low angle (<20°) to the foliation pole along the YZ plane, as observed in the mylonite. In Model 2, this concentration only occurs at γ≥2.6, whereas in Model 3 this maxima occurs at lower shear strains. The models that start with a previous preferred orientation acquire very strong CPOs after small-imposed strains, followed by the rapid rotation of the fabric in relation to the new imposed finite strain axes. The combined activation of 〈a〉{π′}, 〈a〉{z} and possibly 〈a〉(c) slip systems, as demonstrated by TEM analyses, suggests that the VPSC model that best predicts CPO development in the Torridon quartz mylonite is Model 2, where the critical resolved shear stress (CRSS) of 〈a〉{π/π′} is assumed to be slightly stronger than 〈a〉(c).
Deformation Mechanisms, Rheology and Tectonics: Microstructures, Mechanics and Anisotropy

hal-00688840
https://hal.archives-ouvertes.fr/hal-00688840

Éditeur(s) : Université Paul Sabatier, Toulouse III
Résumé : The marine phytoplankton in the ocean represents only less than 1% of global biomass. Phytoplankton performs half of all photosynthesis. This autotrophic biomass in ocean is then an essential element in the climate regulation through processes as carbon dioxide absorption during the photosynthesis. Therefore, we need to estimate precisely this biomass as well as the processes which affect it. Using remotely sensed data (altimetry and ocean colour) and a coupled physical/biogeochemical model (MERCATOR-OPA/NPZDDON), Rossby waves and their influence on phytoplankton biomass are specifically studied in the North Atlantic Ocean. Their features and their influences on surface chlorophyll concentrations were analysed. Through the different mechanisms identified, we estimated that these waves can induce local increases from 60% to 150% of the estimated primary production.
Même si l'océan ne représente que moins de 1% de la biomasse liée aux plantes sur la terre, il est responsable de près de la moitié de la photosynthèse nette de la biosphère. Cette biomasse est par conséquent un élément essentiel dans la régulation du climat à travers par exemple le cycle océanique du carbone. Il est donc nécessaire d'estimer correctement cette biomasse ainsi que les processus qui l'affectent. A l'aide de données satellites altimétriques et couleur de l'eau et d'un modèle couplé physique/biogéochimie (MERCATOR-OPA / NPZDDON), les ondes de Rossby et leur influence sur cette biomasse sont spécifiquement étudiées dans l'océan Atlantique Nord. Leurs propriétés et leur influence sur les concentrations en chlorophylle de surface sont analysées. Au travers des mécanismes mis en jeu identifiés, nous estimons que ces ondes peuvent entraîner une augmentation locale comprise entre 60% et 150% de la production primaire estimée.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2005/these-2454.pdf
http://archimer.ifremer.fr/doc/00000/2454/

Éditeur(s) : HAL CCSD
Résumé : The presence of biological matter (biofilms) in deep geological sites for storage of, for instance, toxic elements or groundwater in aquifers was clearly proved. That biomass triggers physical and chemical processes which greatly modify the durability and the sustainability of the sites. These processes, mainly from oxidative/reductive reactions, are poorly understood. This is mainly due to the fact that former studies were done at the macroscopic level far away from the micrometric scale where relevant processes induced by bacteria take place. Investigations at microscopic level are needed. Thus, we developed an experimental set-up based on the combined use of optical microscopy (transmission), atomic force microscopy (AFM) and electrical and electro-chemical AFM microscopy (EC_AFM) in order to get simultaneous information on topographic and electro-chemical processes. The first highly sensitive step was to use AFM with biological samples in liquid environment: wepresent here a study about AFM imaging of living, moving or self-immobilized bacteria, in their genuine physiological liquid medium and in true in vivo conditions. No external immobilization protocol, neither chemical nor mechanical was needed. For the first time, the native gliding movements of Gram negative Nostoc cyanobacteria upon the surface were studied by AFM. AFM height and mechanical stiffness data were simultaneously acquired. From these, mechanical parameters, inner turgor pressure and Young modulus, were derived for different bacterial species (Anabaenopsis circularis, Rhodococcus wratislaviensis). Our study revealed that AFM imaging is thus possible on moving living species. These results open a large window on new studies of both dynamical phenomena of practical and fundamental interests such as the formation of biofilms and dynamic properties of bacteria in real physiological conditions. The second delicate step was to combine AFM and optical measurements with electrical ones. We mounted a new experimental set-up coupling real-time (i) monitoring of optical properties as the optical density (OD) evolution related to bulk bacterial growth in liquid or as the counting of number of bacteria adhering on the surface of the sample as well and (ii) electrical and electrochemical measurements. Furthermore, these results will shortly be applied to the optimized monitoring of the in-situ activity of bacteria consuming oil pollutants, following this way, in real-time, the bioremediation of an oilcontaminated soil (ANR ECOTECH_BIOPHY program).
La présence de matière biologique (biofilms) dans les sites de stockage géologique profond, d'éléments toxiques ou encore de l'eau potable des aquifères est maintenant clairement démontrée. Cette biomasse est à l'origine de processus physiques et chimiques qui modifient considérablement la durabilité et la pérennité des sites concernés. Ces processus, principalement de type oxydo-réductif, sont encore mal compris. Ceci est principalement dû aux méthodes d'investigation, principalement macroscopiques, loin de l'échelle micrométrique caractéristique des bactéries. Seules des études, basées sur des méthodes d'investigation locale, peuvent apporter les informations requises. Ainsi, nous avons développé un dispositif expérimental basé sur l'utilisation combinée de la microscopie optique (en transmission), la microscopie à force atomique (AFM) et la microscopie AFM en mode électrique et électrochimique (EC_AFM) afin d'obtenir des informations simultanées sur la topographie de l'échantillon et sur les processus électrochimiques à l'échelle des bactéries. La première étape sensible consistait à utiliser l'AFM sur des échantillons biologiques en milieu liquide: nous présentons ici les résultats de l'imagerie AFM en milieu liquide de plusieurs types de bactéries dans leurs conditions physiologiques naturelles (conditions in vivo). Aucun protocole d'immobilisation, ni chimique ni mécanique, n'a été nécessaire; et pour la première fois, les mouvements de reptation de cyanobactéries Nostoc ont été étudiés par l'AFM. Les études AFM ont permis d'acquérir des données topographiques mais aussi mécaniques : nous avons pu ainsi mesurer le module d'Young, la pression de turgescence de différentes souches bactériennes (Anabaenopsis circularis, Rhodococcus wratislaviensis). Cette étude complète, a révélé que l'imagerie AFM est donc possible sur des espèces vivantes en mouvement. Ces résultats ouvrent une grande fenêtre sur de nouvelles études d'intérêts tels que la formation de biofilms et les propriétés dynamiques de bactéries dans des conditions physiologiques réelles. La deuxième étape délicate était de combiner l'AFM aux mesures optiques et électriques. Nous avons développé un nouveau dispositif expérimental permettant (i) le suivi de l'évolution de la croissance bactérienne par la mesure des propriétés optiques comme la densité optique DO (pour le développement bactérien en volume - milieu planctonique) , ou l'analyse de l'image du substrat par comptage du nombre de bactéries sur la surface de l'échantillon (biofilm), et (ii) les mesures électriques et électrochimiques. L'ensemble de ces résultats sera prochainement appliqué au développement de nouveaux outils de surveillance d'une biodépollution de terrain contaminé par les hydrocarbures, par le suivi in situ et en temps réel de l'activité de bactéries dépolluantes (ECOTECH_BIOPHY ANR).
https://tel.archives-ouvertes.fr/tel-01044714

tel-01044714
https://tel.archives-ouvertes.fr/tel-01044714
https://tel.archives-ouvertes.fr/tel-01044714/document
https://tel.archives-ouvertes.fr/tel-01044714/file/theseDhahri2013.pdf

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Les « printemps » arabo-africains se suivent et ne se ressemblent pas, aux  « printemps » doux et pacifiques succèdent des « printemps » chauds et sanguinaires. Un « printemps » en chasse un autre, mais le bilan est mitigé, l’avenir encore incertain et les acquis réversibles. Indéniablement, ils n’ont pas encore dit leur dernier mot. De nouvelles raisons de préoccupations voient le jour, de nature différente ; elles ont pour nom : instabilité, intolérance, chaos, paralysie de l’État et ses institutions, menace qui plane sur le droit des femmes, des minorités de tous ordres, sur la liberté de conscience et le droit à la différence. Mais aussi de nouvelles raisons d’espérer des lendemains meilleurs.L'Afrique n’en est pas à un « printemps » près, mais les retombées sont toujours restées en deçà des attentes. La mise en place laborieuse d'un système panafricain des droits de l’homme et des peuples fut saluée, à juste titre, comme un évènement majeur et un « printemps » avant  la  lettre.L'article retrace toutes les étapes et péripéties de cette mise en place, le contexte, les tenants  et  les aboutissants de l'élaboration de la Charte africaine des droits de l'homme et des peuples qui en constitue le substratum. Il met en exergue ses spécificités, ses originalités, les mécanismes prévus et les organes érigés (Commission et Cour Africaine des Droits de l'Homme et des Peuples) pour assurer l'application et la promotion des  droits de l'homme et des peuples. À beaucoup d’égards, la Charte innove courageusement et originalement par  rapport à ses illustres devancières.Dans son intitulé d'abord : il s'agit d'une Charte et non d’une Déclaration. Ensuite, les droits de l’homme sont couplés aux droits des peuples et hissés au même niveau d'importance et d'impérativité, sinon plus. Enfin, la Charte ne reconnait pas seulement des droits mais elle édicte des devoirs (envers la famille, la communauté, l'État, l'Afrique, l’environnement, etc.) et fait de l'accomplissement de ceux-ci une condition de la jouissance de ceux-là. Deux décennies de recul et seulement 12 affaires traitées (sur seulement 24 qui lui sont parvenus), on peut dire que cette dernière est loin d'avoir atteint sa vitesse de croisière et mérité tant d'espoir placé en elle. De là à jeter le bébé avec l'eau du  bain, occulter tous les bienfaits d'un système qui est loin d'avoir démérité, il n'y a qu'un pas que ne franchirons guère.
The Arab-African springs follow one after the other but are not alike, soft and peaceful springs are succeeded by hot and bloodthirsty springs. One spring expels another one, but the situation s balance sheet is mixed, the future is still uncertain and the experiences are reversible. Undeniably, they didn't say their last word. New reasons of preoccupation are born, made of different nature : they are named : instability, intolerance, chaos, paralysis of the state and its institutions, threat to the women rights, minorities of all kinds, the conscience freedom and the rights to difference ; but also new reasons to hope for a better tomorrow. Africa is not at its last "spring" but the rewards remained always below expectations.The laborious Implementation of a Pan-African system of human rights and peoples was hailed, deservedly, as a major event and a "spring" far ahead of its time. The article in attached outlines all the steps and vicissitudes of this implementation rerelease the context, the end and results of the elaboration of human and people’s rights African charter which constitutes the substratum. It highlights its specificities, its originalities, the planed mechanisms and high instruments (Commission and the African Court of Human and Peoples' Rights) to ensure the application and the promotion of human and people’s rights.In many respects, the Charter innovates bravely and originally compared to its illustrious predecessors.At first in its title: it is matter of a charter and not a declaration. Then, human rights are closely connected to the people’s rights and hoisted at the same level of importance and imperativeness or more. Finally, the Charter does not only recognizes rights but it promulgates duties (to family, community, the state, Africa, the environment, etc.) and makes of the fulfillment of these a condition of enjoyment of those. Two decades backout, and only 12 cases treated (from only 24 have reached) later, in front of the Court, we can say that it is far from having reached its cruising speed and deserved so much hope placed in it.From there to throw the baby out with the bath water, hide all the benefits of a system which is far from being unworthy, there is only one step which shall exceed hardly.
Afrique

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.6735
http://journals.openedition.org/etudescaribeennes/6735

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Longmen Shan range is one of the major topographic and structural features of the easternmargin of the Tibetan Plateau. With an impressive topographic gradient and low convergence rates across the range this region has raised important questions concerning the dynamics of plateaumargin settings, such as the long-term mechanisms of topographic evolution. The investigation of the distribution in space and time of denudation can provide critical insight into such dynamics and shed light on still unresolved controversies. For that purpose, we present a new dataset that documents the intensity and distribution of denudation processes across this plateaumargin through field survey of fluvial incision markers, quantitative geomorphology and cosmogenic nuclide derived basin-wide erosion rates. Erosion is < 0.5 mm/year in the frontal region of the Longmen Shan and between 0.5 and 1 mm/year further west, with a gradual decrease when reaching the northern headwaters of the Min Jiang watershed, adjacent to the beginning of the Tibetan Plateau. The spatialdistribution of denudation inferred from the various methods we use suggests that most of the differential uplift in the Central Longmen Shan is accommodated by the Beichuan Fault and frontal structures located in the foothills. The denudation pattern seems also to reflect the large-scale propagation of erosion from the Sichuan Basin toward the Plateau. This suggests that the Longmen Shan range is submitted to the combined influences of slow thrusting activity on the frontal structures and progressive westward regressiveerosion as a probable response to a pulse of uplift of the Tibetan PlateauEasternmargin, that started 10 Ma ago.
ISSN: 0040-1951

hal-01564192
https://hal.archives-ouvertes.fr/hal-01564192
DOI : 10.1016/j.tecto.2009.10.026

Éditeur(s) : HAL CCSD
Résumé : To understand the effect of inherited lithospheric structures on the continental plates deformation process, we have developed a multi scale model that explicitly takes into account an anisotropic viscosity due to the Crystal Preferred Orientation (CPO) of olivine in the mantle by coupling a viscoplastic self-consistent simulation of the deformation at the polycrystalline aggregate to a 3D Finite Element code. Using this tool, we calculate the mechanical behavior of a continental lithosphere submitted to extension for various initial structures. The first set of experiments investigates the deformation of a plate with a homogeneous initial olivine CPO. Results show that the macroscopic anisotropy is strongly dependent on the initial orientation of the olivine CPO relative to the solicitation and to its evolution. The second set of experiments aims to analyze the deformation of a continental plate containing pre-existing lithospheric scale shear zones. These multi-domain models show that the olivine mechanical anisotropy may induce the reactivation of pre-existing lithospheric scale shear zones in a plate submitted to rifting. In both cases, the results shows that the macroscopic mechanic anisotropy induced by the evolution of olivine CPO in the upper mantle is a key parameter to understand the deformation of the continental plates and to explain the observed reactivation of inherited structure from past tectonics events
Afin de comprendre l'effet des structures préexistantes sur la déformation des plaques continentales, nous avons développé une méthode de modélisation mécanique multi-échelle utilisant une viscosité anisotrope induite par les Orientations Préférentielles du Réseau (OPR) des cristaux d'olivine présents dans le manteau. Cette méthode en couple le calcul viscoplastique autocohérent de la déformation d'un agrégat d'olivine à un code éléments finis 3D. Elle a été utilisée pour le calcul du comportement mécanique d'une plaque continentale soumise à une extension. Une première série d'expériences numériques sur l'extension de plaque lithosphérique présentant des OPR initiales d'olivine homogènes a permis de montrer que l'anisotropie mécanique macroscopique est fortement dépendante de l'orientation initiale de l'OPR. La seconde série de simulations analyse l'extension d'une plaque continentale présentant une zone présentant des OPR d'olivine héritées d'un événement tectonique précédant. Les résultats de ces calculs multi-domaines que l'anisotropie mécanique de l'olivine peut expliquer la réactivation des zones de cisaillement héritées lors du rifting. Les résultats obtenus dans les deux séries de modèles montrent que l'anisotropie mécanique macroscopique induite par l'évolution des OPR d'olivine dans le manteau supérieur est un paramètre clé pour la compréhension de la déformation des plaques continentales et pour expliquer la réactivation observée de structures tectoniques, tels que les grands décrochements, lors des épisodes tectoniques ultérieurs.
https://tel.archives-ouvertes.fr/tel-00369463

tel-00369463
https://tel.archives-ouvertes.fr/tel-00369463
https://tel.archives-ouvertes.fr/tel-00369463/document
https://tel.archives-ouvertes.fr/tel-00369463/file/KnollThese09.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The kinetics of hydrogenation of dry iron-bearing olivine single crystals was determined by performing hydration experiments under hydrothermal conditions at high pressure. The experiments were performed in a multi-anvil press at 3 GPa, for a temperature range between 900 and 1200 °C and for various durations. The oxygen fugacity was buffered along Ni-NiO joint. Polarized Fourier transform infrared spectroscopy and recent empirical calibration were used to quantify the hydroxyl distributions in the samples along crystallographic axes after the experiments. The chemical diffusion coefficients are similar (barely slower) than in olivine hydrated at lower pressure (0.2 and 0.3 GPa) for the same diffusion mechanism. Under the given experimental conditions, the anisotropy of diffusion is the same as for proton-vacancy mechanism, with diffusion along the [0 0 1] axis faster than along the [1 0 0]. However, the anisotropy at 3 GPa is weaker compared to measurements at lower pressures and the analysis of concentration profiles using 3D models shows that an isotropic solution could also be relevant. Fits of the diffusion data to an Arrhenius law yield activation energies for the slightly faster [0 0 1] axis of the crystallographic axes around 198 ± 5 kJ mol−1, a value only slightly lower than the results from previous experimental studies for natural iron-bearing olivine hydrogenated at lower confining pressure. At 3 GPa, hydrogenation can be well approximated by a single mechanism controlled by coupled diffusion of protons and octahedral vacancies (di- and tri-valent ions). The diffusion rates are fast enough to alter hydrogen concentration within olivine in xenoliths ascending from the mantle or experiencing hydrogen-rich metasomatism events, but too slow to permit complete homogenization of hydrogen in olivine-rich rocks at kilometer scale in less than one My.
ISSN: 0031-9201

hal-01412663
https://hal.archives-ouvertes.fr/hal-01412663
DOI : 10.1016/j.pepi.2016.08.005

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
Nowadays, technological advances in satellite imagery measurements as well as the development of dense geodetic and seismologic networks allow for a detailed analysis of surface deformation associated with active fault seismic cycle. However, the study of earthquake dynamics faces several limiting factors related to the difficulty to access the deep source of earthquake and to integrate the characteristic time scales of deformation processes that extend from seconds to thousands of years. To overcome part of these limitations and better constrain the role and couplings between kinematic and mechanical parameters, we have developed a new experimental approach allowing for the simulation of strike-slip fault earthquakes and analyze in detail hundreds of successive seismic cycle. Model rheology is made of multilayered visco-elasto-plastic analog materials to account for the mechanical behavior of the upper and lower crust and to allow simulating brittle/ductile coupling, postseismic deformation phase and far-field stress transfers. The kinematic evolution of the model surface is monitored using an optical system, based on subpixel spectral correlation of high-resolution digital images. First, results show that the model succeed in reproducing the deformation mechanisms and surface kinematics associated to the main phases of the seismic cycle indicating that model scaling is satisfactory. These results are comforted by using numerical algorithms to study the strain and stress distribution at the surface and at depth, along the fault plane. Our analog modeling approach appears, then, as an efficient complementary approach to investigate earthquake dynamics.
ISSN: 0278-7407

hal-01174176
https://hal.archives-ouvertes.fr/hal-01174176
DOI : 10.1002/2014TC003701

Éditeur(s) : HAL CCSD
Résumé : Spermatogenesis in mammals is a complex biological function including cellular processes such as proliferation, meiosis and differentiation, aiming to the production of male gametes in the testis. If the seminiferous epithelium is well described in terms of organization and cellular morphology of cells that compose it, the processes by which undifferentiated diploid germ cells enter meiosis and give haploid cells that undergo many morphological transformations, are not fully decrypted. These processes rely on the coordinated and sequential expression of genes, including specific products for each stage of germ cell development These gene products are essential at each key stage of spermatogenesis. Transcriptomics since the 1990s, and proteomics since the 2000s have contributed to the improved. understanding of these mechanisms. A long term proteomic study aiming at characterizing the proteomes of Sertoli cells and germ cells, and a recent study that characterized and quantified the transcriptome of isolated rat testicular cells at high resolution using de novo sequencing of transcripts (RNA-Seq), have been the basis of my thesis work. The latter study showed the accumulation of long non-Coding RNAs (lncRNAs) and testicular unannotated transcripts (TUTs) at meiotic and post-Meiotic stages of spermatogenesis in the rat. In this context, my thesis work aimed at validating the coding potential of many genes expressed in germ cells using RNA-Seq combined with shotgun proteomics, a so-Called PIT (Proteomics Informed by transcriptomics) approach. In this approach, the protein sequences translated from the transcripts assembled by RNA-Seq in the different testicular cell types are integrated into a custom database of protein sequences used to query mass spectrometry data obtained from proteins of meiotic and post-Meiotic cells. The PIT approach showed that 69 TUTs or lncRNA (corresponding to 44 loci) code for proteins in meiotic cells and post meiotic cells, and we confirmed experimentally the meiotic and post-Meiotic expression for two new transcripts encoding for VAMP9, a protein of the SNARE family, and a new testicular enolase T-ENOL. The post-Meiotic expression of T-ENOL protein was confirmed by immunohistochemistry using a polyclonal antibody raised against the recombinant protein. This approach also allowed us to identify new isoforms of known proteins, specific to each stage of spermatogenesis. Germ cells and Sertoli cells maintain a dialogue which is necessary to the success of spermatogenesis and spermiogenesis. Another part of my work aimed at identifying membrane proteins, in germ cells and residual bodies, that may be involved in the dialogue between Sertoli cells and germ cells, using a ICPL relative quantification proteomic approach. The ICPL analysis enabled us to establish a list of 166 proteins whose expression is differential between pachytene spermatocytes, round spermatids and residual bodies. Their differential expression suggests that these proteins may play a role in spermiogenesis. Thanks to the Gene Ontology annotations, a list of 8 proteins with a putative role in signal transduction, cell recognition or differentiation, thus potentially involved in the dialogue between Sertoli and germ cells was drawn. In addition, I provided a first proteome of rat Sertoli cells, germ cells and residual bodies obtained by shotgun proteomics.
La spermatogenèse chez les mammifères est une fonction biologique complexe incluant des processus de prolifération cellulaire, de méiose et de différenciation uniques visant à la production des gamètes mâles au sein du testicule. Si l’épithélium séminifère est bien décrit sur le plan de son organisation et de la morphologie des cellules qui le composent, les processus par lesquels les cellules germinales diploïdes indifférenciées entrent en méiose pour donner ensuite des cellules haploïdes subissant par la suite de nombreuses transformations morphologiques, ne sont pas totalement décryptés. Ils reposent sur l’expression coordonnée et séquentielle de gènes dont les produits spécifiques de chaque stade de développement des cellules germinales sont essentiels aux étapes clés de la spermatogenèse. La transcriptomique depuis les années 1990 et la protéomique depuis les années 2000 ont contribué à l’amélioration de la connaissance de ces mécanismes. Une étude protéomique visant à caractériser par des approches systématiques et différentielles les protéomes des cellules de Sertoli et de la lignée germinale, et d’autre part une étude récente, réalisée dans notre unité, qui a permis de caractériser et de quantifier le transcriptome des cellules testiculaires isolées de rat en utilisant le séquençage de novo des transcrits (RNA-Seq), ont été à la base de mes travaux de thèse. Cette dernière étude a mis en évidence l’accumulation de longs ARNs non codants (lncRNAs) et de transcrits testiculaires non annotés (TUTs) aux stades méiotique et post- méiotique de la spermatogenèse chez le rat. Dans ce contexte, mon travail a consisté à valider le potentiel codant de nombreux gènes exprimés dans les cellules germinales par une approche dite PIT (Proteomics Informed by Transcriptomics) couplant protéomique Shotgun et RNA-Seq. Dans ce type d’approche, les séquences protéiques déduites des transcrits des différents types cellulaires, assemblés par RNA-Seq, sont intégrées dans une base personnalisée de séquences protéiques utilisée pour interroger les données de spectrométrie de masse obtenues à partir de protéines de cellules méiotiques et post-Méiotiques. L’approche PIT a permis de montrer que 69 TUTs ou lncRNA (correspondant à 44 loci) codent pour des protéines dans les cellules méiotiques et post méiotiques. L’expression post-Méiotique de deux nouveaux transcrits, l’un codant pour la protéine VAMP9, une protéine de la famille SNARE, et l’autre pour une nouvelle énolase T-ENOL a pu être confirmée. L’expression post-Méiotique de T-ENOL a été confirmée par immunohistochimie à l’aide d’un anticorps polyclonal produit contre la protéine recombinante. Cette approche nous a également permis d’identifier de nouvelles isoformes de protéines connues spécifiques de chaque stade de la spermatogenèse. Les cellules germinales et les cellules de Sertoli entretiennent le dialogue nécessaire au bon déroulement de la spermatogenèse. Une autre partie de mon travail a consisté à identifier des protéines membranaires des cellules germinales et des corps résiduels, susceptibles d’intervenir dans le dialogue entre les cellules de Sertoli et les cellules germinales, par une approche protéomique de quantification relative ICPL. Cette approche a permis d’établir une liste de 166 protéines différentiellement exprimées entre les spermatocytes pachytène, les spermatides rondes et les corps résiduels, qui sont susceptibles de jouer un rôle dans la spermiogénèse. Grâce aux annotations de le Gene Ontology, j’ai pu établir une liste de 8 protéines ayant un rôle supposé dans la transduction du signal, la reconnaissance cellulaire ou bien la différenciation. Par ailleurs, j’ai pu établir par protéomique Shotgun un premier protéome des cellules de Sertoli, des cellules germinales et des corps résiduels chez le rat.
https://tel.archives-ouvertes.fr/tel-01127389

Droits : info:eu-repo/semantics/OpenAccess
NNT : 2014REN1S064
tel-01127389
https://tel.archives-ouvertes.fr/tel-01127389
https://tel.archives-ouvertes.fr/tel-01127389/document
https://tel.archives-ouvertes.fr/tel-01127389/file/2014REN1S064.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During the last decade, the interaction of deep processes in the lithosphere and mantle with surface processes (erosion, climate, sea-level, subsidence, glacio-isostatic readjustment) has been the subject of heated discussion. The use of a multidisciplinary approach linking geology, geophysics, geodesy, modelling, and geotechnology has led to the awareness of coupled deep and surface processes. Deep earth dynamics (topography, erosion, tectonics) are strongly connected to natural hazards such as earthquakes, landslides, and tsunamis; sedimentary mass transfers have important consequences on isostatic movements and on georesources, geothermal energy repartitions. The ability to read and understand the link between deep Earth dynamics and surface processes has therefore important societal impacts. Ground-truthing at carefully-selected sites of investigation is imperative to better understand these connections.Due to its youth (<30 Ma) and its subsidence history, the almost land-locked Gulf of Lion–Sardinia continental margins system provides a unique record of sedimentary deposition from the Miocene to present. Due to its high subsidence rate, palaeoclimatic variations, tectonic events and vertical evolution are all recorded here at very high resolution. The late Miocene isolation and desiccation of the Mediterranean, the youngest and most catastrophic event, the Messinian Salinity Crisis (MSC), induced drastic changes in marine environments: widespread deposition of evaporite (gypsum, anhydrite and halite) in the central basin, and intense subaerial erosion along its periphery. These extraordinary mass transfers from land to sea induced strong isostatic re-adjustments that are archived in the sedimentary record and represent a window to the lithospheric rheology and the deep processes.The GOLD (Gulf of Lion Drilling) project, proposes to explore this unique sedimentary record as well as the nature of the deep crustal structure, providing valuable information about the mechanisms underlying vertical motions in basins and their margins.
ISSN: 0264-8172

insu-01197393
https://hal-insu.archives-ouvertes.fr/insu-01197393
https://hal-insu.archives-ouvertes.fr/insu-01197393/document
https://hal-insu.archives-ouvertes.fr/insu-01197393/file/Rabineau%20et%20al.-final-MPG2014_REVISED-FINAL-No-Marked_FINAL%2BFigures.pdf
DOI : 10.1016/j.marpetgeo.2015.03.018

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Acquiring information is indisputably energy-consuming and conversely, the availability of information permits greater efficiency. Strangely, the scientific community long remained reluctant to establish a physical equivalence between the abstract notion of information and sensible thermodynamics. However, certain physicists such as Szilard and Brillouin proposed: (i) to give to information the status of a genuine thermodynamic entity (k B T ln2 joules/bit) and (ii) to link the capacity of storing information inferred from correlated systems, to that of indefinitely increasing organization. This positive feedback coupled to the self-templating molecular potential could provide a universal basis for the spontaneous rise of highly organized structures, typified by the emergence of life from a prebiotic chemical soup. Once established, this mechanism ensures the longevity and robustness of life envisioned as a general system, by allowing it to accumulate and optimize microstate-reducing recipes, thereby giving rise to strong nonlinearity, decisional capacity and multistability. Mechanisms possibly involved in priming this cycle are proposed.
ISSN: 0169-6149

inserm-00826658
http://www.hal.inserm.fr/inserm-00826658
http://www.hal.inserm.fr/inserm-00826658/document
http://www.hal.inserm.fr/inserm-00826658/file/OLEB-2013.pdf
DOI : 10.1007/s11084-013-9329-2

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Strain and strain rate partitioning in partially molten rocks are two of the important mechanisms that govern the process of coupling and/or decoupling of the partially molten lithosphere. Consequently, the proportion of partial melt and crystals and their network in partially molten rocks influence the degree of the partitioning along with the bulk rheology of the system. This study explores the possible role of finite strain and strain rate on the rate and volume of partial melting and crystallization in a metapelitic system undergoing deformation. Cylinders of synthetic quartz-muscovite aggregate (7: 3 volume ratio) were deformed in torsion at 750 C, 300 MPa and constant shear strain rate ((gamma) over dot = 3 x 10(-4) s(-1)) for finite shear strains (gamma) 1-15. The deformed samples were studied along the longitudinal tangential ( LT) and axial ( LA) sections to obtain the data along a range of strain rates for a given finite strain and vice versa. The results showed that deformation plays an important role on the kinetics of partial melting and crystallization. With increasing strain rate, amount and rate of crystallization comprise the volumetrically dominant process compared to partial melting at a given finite strain. In contrast, when the strain rate is constant, partial melting is the dominant process over crystallization up to moderate strain (gamma < 5). The dominant process reverses at higher strain, and the system shows more crystallization than partial melting. Application of the experimental data to geological systems implies that for metapelites a significant amount (similar to 20%) of partial melt can generate at high strain rate and moderate strain (gamma similar to 7), but at high strain (gamma = 15) the system is melt depleted. Under such conditions, decoupling should take place in brittle-ductile mode. On the other hand, rocks undergoing deformation with low strain rates and strain (gamma < 3) contain more than 25% partial melt, which can act as a major decoupling agent by localizing ductile shear zones.
ISSN: 0148-0227

hal-00617714
https://hal.archives-ouvertes.fr/hal-00617714
DOI : 10.1029/2010JB007865