Éditeur(s) : CSIA : Comité de soutien aux Indiens des Amériques
Extrait de : Nitassinan, notre terre
Description : Premier numéro de la revue Nitassinan. Pour les créateurs de cette revue, "à partir de dossiers documentés, Nitassinan a pour objectif d'aider les personnes qui s'intéressent à la cause Indienne à disposer d'une base de réflexion leur permettant de comprendre en profondeur ce qui est en jeu dans les luttes ponctuelles. Plusieurs dossiers sont en préparation traitant du domaine historique, des analyses et des réflexions sur des études concernant les femmes, les enfants, les prisonniers politiques Indiens, le pillage des ressources naturelles sur les territoires réservés, les conséquences des multiples pollutions" ...
Siècle(s) traité(s) : 19
Droits : Ce document est protégé par le droit d'auteur. Il ne peut en aucun cas être utilisé sans l'autorisation de l'auteur et des ayant droits
Permalien : http://www.manioc.org/recherch/T17019
T17019

Éditeur(s) : Yale University
Résumé : Sea-surface temperature images of the coastal upwelling regions off Northwest Africa show that the core of upwelling is sometimes located far from the coast. This has been documented in three regions that share a common feature, namely a wide and shallow continental shelf. This upwelling feature plays a key role in the ecology of the Canary Current System. It creates an innerfront which provides retention for biological material, e.g. fish eggs and larvae, in the highly productive nearshore environment. An analytical model has been developed based on a two dimensional extension of Ekman's solution. The linear and steady response of a homogeneous ocean forced by an upwelling-favorable wind provides a mechanism for the upwelling separation from the coast. The merging of the surface and bottom Ekman layers induces a very weak cross-shore circulation and a "kinematic barrier" for the Ekman transport divergence. In the case of an alongshore wind, the barrier is located near the isobath h ≈ 0.4D, where D is the thickness of Ekman layers. This yields an upwelling cell which is essentially concentrated in the region 0.5D < h < 1.25D, with upwelling occurring preferentially near the isobath h ≈ 0.6D. It turns out that the cross-shore width of upwelling scales with D/S, the ratio of Ekman depth to bottom topographic slope. The application of this solution to real bathymetric profiles rationalizes, not only the offshore upwelling observations in Northwest Africa, but also the influence of topography on the cross-shelf structure of a wind-driven coastal upwelling. The model also quantifies the effect of the cross-shore wind component showing how it drives the nearshore pressure gradient adjustment and how it affects the upwelling. A linear numerical experiment reproduces the theoretical steady solution, thereby allowing investigation of the transient regime. Relaxation of the hypothesis in the numerical model validates the linear assumption of the theory and then allows investigation of the sensitivity to friction parameterizations and the influence of stratification. The latter leads to an "oscillation" of the upwelling cell with seaward migration driven by outcropping and homogeneization of the water column, and, coastal incursion driven by a "boundary layers splitting" process caused by shoreward advection of the isopycnal dome and stratification of the inner shelf.
Journal of Marine Research (Yale University), 2008-09 , Vol. 66 , N. 5 , P. 589-616

Droits : 2008 Yale University
http://archimer.ifremer.fr/doc/2008/publication-6334.pdf
DOI:10.1357/002224008787536790
http://archimer.ifremer.fr/doc/00000/6334/

Résumé : A new strain of L. stylirostris was introduced in New Caledonia. Quarantine facilities were set up inland using RAS and artificial seawater. After 5 months of rearing, all the 16 initial families were still represented with a 50% average survival. Three samplings for known pathogens were made during that period, all of them negative. Half the animals were taken to outdoor ponds for rearing to reproduction size when the rest was used to test different arrangements for a biosecure rearing until reproduction. Numerous spawnings and nauplii were obtained but larval rearings could not be completed. Different options are considered for the set up of a biosecure facility allowing the rearing and the breeding of pathogen free strains of shrimp.
Afin de disposer d’une plus forte diversité génétique exploitable, des producteurs calédoniens ont, en relation avec l’Ifremer, récemment introduit d’Hawaii une autre souche de crevette de l’espèce Litopenaeus stylirostris, domestiquée et garantie exempte de pathogènes. Malgré cette garantie sanitaire, les crevettes ont été maintenues en observation dans une quarantaine tertiaire pendant cinq mois avant la sortie et l’élevage d’une moitié de l’effectif en bassins terre extérieurs. L’autre moitié a été conservée dans les installations de quarantaine comme stock de secours au cas où un problème affecterait les crevettes élevées à l’extérieur. Les installations de quarantaine ont été progressivement transformées, tout en continuant les élevages, afin de réaliser un prototype de conservatoire biosécurisé. Les crevettes ont été élevées jusqu’à la taille de géniteurs en utilisant de l’eau de mer artificielle puis de l’eau de mer naturelle traitée au chlore. Des essais de reproduction et d’élevage larvaire ont été menés et de nombreuses pontes fécondées ont été obtenues mais les élevages larvaires, à une exception, n’ont pas dépassé le stade Zoé 3. Les analyses par PCR réalisées sur les crevettes du conservatoire ont montré que les mesures et précautions sanitaires qui avaient été prises avaient préservé le statut sanitaire “sans pathogènes” initial. Cette expérience a permis de mieux cerner les problèmes qui pouvaient se poser pour la mise en place et le fonctionnement d’installations biosécurisées utilisant des circuits fermés. Ces enseignements ont servi à répertorier les principales contraintes envisageables pour la réalisation d’un futur conservatoire crevette qui viendrait conforter et sécuriser les souches actuellement disponibles en Nouvelle-Calédonie. Plusieurs options sont proposées pour les crevettes devant entrer dans le conservatoire (sans quarantaine, quarantaine tertiaire, quarantaine primaire puis secondaire) et pour le type de fonctionnement du conservatoire. Les principaux critères pour le choix du site, l’utilisation de l’eau de mer et son traitement, les systèmes de recirculation sont abordés; et des schémas d’installations de quarantaine et de conservatoire sont proposés.

Droits : 2007 Ifremer
http://archimer.ifremer.fr/doc/00117/22849/20659.pdf
http://archimer.ifremer.fr/doc/00117/22849/

Éditeur(s) : American Geophysical Union
Résumé : As part of the French CLIPPER project, an eddy permitting model of the Atlantic circulation has been run for 22 years. The domain has open boundaries at Drake passage and at 30 degreesE, from Africa to Antarctica. The simulated mean circulation, as well as the eddy activity, is satisfactory for a 1/3 degrees model resolution, and the meridional heat transport at 30 degreesS is within the range estimated from observations. We use the "mixed" open boundary algorithm of Barnier et al. [1998], which has both a radiation condition and a relaxation to climatology. The climatological boundary forcing strongly constrains the solution in the whole domain. The model heat balance adjusts through the surface (heat flux retroaction term) more than the open boundaries. The radiation phase velocities calculated within the algorithm are analyzed. This shows, quite surprisingly, that both the eastern and western boundaries have a similar behavior, regardless of the preferred directions for advection (mainly eastward) and wave propagation (mainly westward). Our results confirm that open boundary algorithms behave differently according to the dynamics of the region considered. The passive boundary condition that Penduff et al. [2000] applied successfully in the north eastern Atlantic does not work in the present South Atlantic model. We emphasize the need for a careful prescription of the climatology at the open boundary, for which a new approach based on synoptic sections is implemented.
Journal of Geophysical Union - Research C - Oceans (0148-0227) (American Geophysical Union), 2001-10 , Vol. 106 , N. C10 , P. 22115-22129

Droits : 2001 American Geophysical Union
http://archimer.ifremer.fr/doc/2001/publication-454.pdf
DOI:10.1029/2000JC000376
http://archimer.ifremer.fr/doc/00000/454/

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Previous work has demonstrated that geoelectrical measurements, acquired either along the Earth’s surface or in boreholes, can be sensitive to the presence of fractures. However, a lack of numerical approaches that are well suited to modelling electric current flow in fractured media prevents us from systematically exploring the links between geoelectrical measurements and fractured rock properties. To address this issue, we present a highly computationally efficient methodology for the numerical simulation of geoelectrical data in 2.5-D in complex fractured domains. Our approach is based upon a discrete-dual-porosity formulation, whereby the fractures and rock matrix are treated separately and coupled through the exchange of electric current between them. We first validate our methodology against standard analytical and finite-element solutions. Subsequent use of the approach to simulate geoelectrical data for a variety of different fracture configurations demonstrates the sensitivity of these data to important parameters such as the fracture density, depth, and orientation.
ISSN: 0956-540X

hal-01622151
https://hal.archives-ouvertes.fr/hal-01622151
https://hal.archives-ouvertes.fr/hal-01622151/document
https://hal.archives-ouvertes.fr/hal-01622151/file/sanzGJI2017.pdf
DOI : 10.1093/gji/ggx080

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Ce numéro de la Revue Etudes Caribéennes consacré au tourisme vise à poser les bases d’une réflexion sur le fonctionnement des lieux touristiques, les programmes d’aménagement touristique et les différents enjeux pour les territoires. Lieu ouvert ou lieu fermé, flux concentré ou flux diffus, la nature du lieu touristique, avec ses pratiques, classiques ou originales, oriente les types d’impacts potentiels. Les choix opérés en matière d’aménagement touristique sont donc primordiaux : dans quelles conditions opte-t-on pour un tourisme balnéaire classique, massif, ou pour une approche touristique alternative ? Ces différentes déclinaisons sont-elles attachées à des territoires spécifiques ? Faut-il opposer ces deux approches ou les considérer complémentaires dans leurs environnements respectifs, peuvent-elles partager un même espace ? L’objectif de ce numéro thématique est de réunir des approches diverses et renouvelées qui développent des analyses sous l’angle de l’économie, de l’aménagement du territoire, de la sociologie, de la géographie… Les articles pourront proposer une réflexion théorique ou privilégier des études de cas, traitant des relations tourisme de masse – tourisme alternatif ou s’attachant à illustrer l’une de ces deux aspects. Les terrains privilégiés ne seront pas exclusivement caribéens et américains, ils pourront relever de n’importe quelle région du monde et illustrer des situations présentes et/ou passées. Les thématiques privilégiées seront : 1. Les concepts de tourisme de masse et de tourisme alternatif (identification, caractéristiques, logiques spatiales, enjeux économiques, sociaux, environnementaux). 2. Les lieux du tourisme masse (stations balnéaires, villes historiques, formes spécifiques d’aménagement des lieux et les types de structures d’accueil) 3. Alter-tourismes et renouvellement des pratiques touristiques (écotourisme, tourisme communautaire, agrotourisme …) 4. L’aménagement des lieux touristiques et les modalités de gestion des environnements protégés (conservation, protection et pratiques touristiques et récréatives) 5. Les enjeux économiques, sociaux, environnementaux autour de différents types de lieux touristiques. This issue of the Revue Etudes Caribéennes, devoted to tourism, aims to lay the foundations of a reflection on the functioning tourist places, their development programs and the different challenges presented to them. Exposed/Open or closed location, concentrated or diffused flows, the nature of these tourist places with their traditional or original customs, orientate different types of potential impacts. The choices made in tourism development are essential: in which conditions should be opted for the traditional seaside tourism, or for mass tourism, or for alternative tourism? Are certain properties linked to specific territories? Should we oppose these two approaches or consider them as complementary in their environments and can they share the same place? The objective of this thematic issue is to call for various and renewed approaches which develop analysis in terms of the economy, regional planning, sociology, geography etc. Articles may propose a theoretical reflection or focus on case studies, dealing with the relations of mass tourism, alternative tourism, or to illustrate one of these two aspects. Priorities fields will not exclusively be Caribbean and American but can come from any part of the world and can illustrate post and/or present situations. The prioritized analysis will include: 1. The concepts of mass tourism and alternative tourism (identification, characteristics, spatial logics, and economic, social and environmental issues). 2. Places of mass tourism (resorts, historic cities, specific forms of site layout and reception facilities) 3. Alter-tourism and the renewal of tourism practices (ecotourism, community tourism, agrotourism) 4. The development of tourist spots and of management methods concerning protected environments (conservation, protection, tourism practices and recreational practices) 5. Economic, social, and environmental issues surrounding different types of tourist places. Este número de la Revista Estudios Caribeños consagrado al turismo apunta a poner las bases de una reflexión sobre el funcionamiento de los lugares turísticos, los programas de ordenación turística y las diferentes apuestas para los territorios. Lugar abierto o cerrado, flujos concentrados o flujos difusos, la naturaleza del lugar turístico, con sus prácticas, clásicas u originales, orienta los tipos de impactos potenciales. Las elecciones operadas en materia de ordenación turística son primordiales: ¿en qué condiciones se opta por un turismo balneario clásico, masivo, o por un enfoque turístico alternativo? ¿Estas diferentes declinaciones están relacionadas a territorios específicos? ¿Se debe oponer estos dos enfoques o considerarlos complementarios en sus ambientes respectivos, pueden compartir el mismo espacio? El objetivo de este número temático es de reunir los diversos y renovados enfoques que desarrollan los análisis sobre el ángulo de la economía, la ordenación del territorio, la sociología, la geografía… Los artículos podrán proponer una reflexión teórica o privilegiar los estudios prácticos, tratando las relaciones turismo de masa-turismo alternativo o dirigirse a ilustrar uno de estos dos aspectos. Los terrenos privilegiados no serán exclusivamente caribeños y americanos, podrán hacer frente a cualquier región del mundo e ilustrar situaciones presentes y/o pasadas. Los temas privilegiados serán: 1. Los conceptos de turismo de masa y de turismo alternativo (identificación, características, lógicas espaciales, apuestas económicas, sociales, ambientales). 2. Los lugares de turismo de masa (estaciones balnearias, ciudades históricas, formas específicas de ordenación de lugares y de tipos de estructuras de recepción). 3. Alter-turismos y renovación de las prácticas turísticas (ecoturismo, turismo comunitario, agroturismo...). 4. La ordenación de lugares turísticos y las modalidades de gestión de los ambientes protegidos (conservación, protección y prácticas turísticas y recreativas). 5. Las apuestas económicas, sociales, ambientales alrededor de diferentes tipos de lugares turísticos.

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.7521
http://journals.openedition.org/etudescaribeennes/7521

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : Ants have evolved venoms rich in peptides and proteins used for predation, defense, and communication. However, they remain extremely understudied due to the minimal amount of venom secreted by each ant. The present study investigated the differences in the proteome and peptidome of the venom from the bullet ant, Paraponera clavata. Venom samples were collected from a single colony either by manual venom gland dissection or by electrical stimulation and were compared using proteomic methods. Venom proteins were separated by 2D-PAGE and identified by nanoLC-ESI-QTOF MS/MS. Venom peptides were initially separated using C18 reversed-phase high-performance liquid chromatography, then analyzed by MALDI-TOF MS. The proteomic analysis revealed numerous proteins that could be assigned a biological function (total 94), mainly as toxins, or roles in cell regulation and transport. This investigation found that ca. 73% of the proteins were common to venoms collected by the two methods. The peptidomic analysis revealed a large number of peptides (total 309) but with <20% shared by the two collection methods. There was also a marked difference between venoms obtained by venom gland dissection from different ant colonies. These findings demonstrate the rich composition and variability of P. clavata venom.
ISSN: 1535-3893

hal-01603415
https://hal.archives-ouvertes.fr/hal-01603415
DOI : 10.1021/acs.jproteome.6b00948
PRODINRA : 406775
PUBMED : 28118015

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In this paper we present a new local remeshing algorithm that is dedicated to the problem of erosion in finite element models whose grid follows the movement of the free surface. The method, which we name Surface Lagrangian Remeshing (SLR), is adapted to 2D Lagrangian models which couple surface erosion with deformation of Earth materials. The remeshing procedure preserves nodes defining the surface submitted to erosion and removes nodes belonging to surface elements whose internal angles or area is critically low. This algorithm is ideally suited to track long term surface evolution. To validate the method we perform a set of numerical tests, using triangular finite elements, which compare the results obtained with the SLR algorithm with global remeshing and with analytical results. The results show good agreements with analytical solutions. Interpolation errors associated with remeshing are generated locally and numerical diffusion is restricted to the remeshed domain itself. In addition this method is computationally costless compared to classical global remeshing algorithm. We propose to couple the SLR method with the Dynamical Lagrangian Remeshing (DLR) algorithm to enable local remeshing only of Lagrangian models coupling large deformation of Earth materials with large erosion.
ISSN: 0098-3004

hal-00639472
https://hal.archives-ouvertes.fr/hal-00639472
DOI : 10.1016/j.cageo.2010.05.023

Éditeur(s) : HAL CCSD
Résumé : The present PhD thesis is devoted to the numerical simulation and analysis of shear on cohesive granular materials. In the framework of the Contact Dynamics method, we developed a model of cohesive bonding, which mimics cohesion by cementation. This model involves three contact strength parameters (a tensile strength, a coefficient of sliding friction, and a coefficient of rolling friction) as well as a local criterion, which controls the creation and the breaking of cohesive bonds. All contacts are cohesive at the beginning of the numerical simulations, and contact rupture leads to an irreversible loss of tensile strength (debonding). We varied systematically the three contact strength parameters and studied their influence on the shear strength, the dilatancy, and the microstructure of the granular media. Our results show that internal friction and macroscopic tensile strength have different origins at the contact scale. We also find that the microstructure of the granular media, when sheared at the steady state (also known as the `critical state"), is strongly affected by the local coefficients of sliding and rolling friction. In particular, the mechanical role of the weak network changes with these two contact parameters, which results from the formation of a new structure of force transmission. On the other hand, we also applied the same numerical simulation method to the simulation of landslides. We developed a methodology, which takes into account the initial morphology of the hillslope, the strength of geomaterials, and a triggering factor, integrating in the same model the initiation and propagation phases of the landslide. To illustrate this methodology, we applied it to the simulation of a hypothetical example of avalanche triggered by the progressive rise of a water table.
Ce travail de thèse porte sur la modélisation numérique et l'analyse du cisaillement dans les milieux granulaires cohésifs. Dans le cadre de la méthode de la Dynamique des Contacts, nous avons développé un modèle de cohésion qui cherche à imiter la cohésion par cimentation. Ce modèle fait intervenir trois paramètres de résistance au niveau des contacts (une résistance à la traction, un coefficient de frottement de glissement, et un coefficient de frottement de roulement) ainsi qu'un critère de création et de rupture des liens cohésifs. Les contacts sont cohésifs au début des simulations et leur rupture entraîne la perte irréversible de la résistance à la traction. Nous avons fait varier les trois paramètres microscopiques et nous avons étudié leur influence dans la résistance au cisaillement, la dilatance, et la microstructure du milieu. Nos résultats montrent que le frottement interne et l'adhésion macroscopiques ont des origines microscopiques différentes. Nous observons aussi que la microstructure du milieu cisaillé à l'état stationnaire (aussi connu comme ``l'état critique") est fortement affectée par l'angle de frottement et la résistance au roulement au niveau des contacts. En particulier, le rôle mécanique du réseau faible change avec ces deux paramètres microscopiques, ce qui résulte de la formation d'une nouvelle structure de transmission de forces. D'autre part, nous avons appliqué cette méthode de simulation numérique à l'étude d'un processus naturel : les glissements de terrain. Nous avons développé une méthodologie qui tient compte de la morphologie initiale du système, de la résistance des géomatériaux, et d'un mécanisme de déclanchement, ce qui permet d'intégrer dans le même modèle les phases d'initiation et de propagation du glissement. Pour illustrer cette méthodologie, nous l'avons appliquée à la modélisation d'un exemple hypothétique d'avalanche déclenchée par la montée progressive du niveau d'une nappe d'eau.
https://tel.archives-ouvertes.fr/tel-00311303

tel-00311303
https://tel.archives-ouvertes.fr/tel-00311303
https://tel.archives-ouvertes.fr/tel-00311303/document
https://tel.archives-ouvertes.fr/tel-00311303/file/these_estrada.pdf

Éditeur(s) : HAL CCSD
Résumé : Diffusion du document : INRA Documentation de Centre, Domaine de Duclos, 97170 Petitt-Bourg (Guadeloupe, France) 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
Basralocus (Dicorynia guianensis Amshoff, Caesalpiniaceae), first timber exploited species in French Guyana, shows a spatial aggregative distribution. In order to characterize Basralocus clump organisation, many approaches were used : the study of different forest variables (total height, diameter at breast height, .... j, a spatial analysis studied by population splitting in 3 classes according to their diameters at breast height and an architectural analysis. To evaluate the pertinence of different approach, 2 clump structures, located on control and logged plots,are compared. The trees of the logged clump have a smaller height and diameter. a slender habit, a taller crown and a better growth than the control. These 2 clumps stand out by a different number of mature trees and different types of spatial distribution of juvenile trees around them are possible. The opening of the environment by forestry provokes a Jump rejuvenation by the presence of numerous unbranched young trees. The architectural analysis helps to detect a large expression variability in growth strategies which can be reflected by different architectural vigours. The combination between forest variables, spatial and architectural analysis results could suggest a dynamic evolution of these 2 clumps.
L'Angélique (Dicorynia guianensis Amshoff, Caesalpiniaceae), première espèce exploitée Pour le bois d'oeuvre en Guyane française, a une répartition spatiale de type agrégatif. Afin de caractériser la structure d’un agrégat d'Angélique, plusieurs approches sont utilisées: une étude des différents paramètres dendrométriques (hauteur totale, diamètre à 1.30 m....j. une analyse spatiale réalisée en découpant la population des individus en 3 classes de diamètre bien distinctes et une analyse architecturale. Afin de valider la pertinence de ces approches, 2 agrégats, l'un en parcelle témoin et l'autre en parcelle exploitée pour le bois d'oeuvre, sont comparés. Ainsi, les arbres de l'agrégat exploité ont une hauteur et un diamètre plus petit, un port plus élancé, un houppier plus grand et une meilleure croissance. Ces 2 agrégats se distinguent par un nombre variable de semenciers et différents types de répartition spatiale des juvéniles autour de ceux-ci sont possibles. L'ouverture du milieu par l'exploitation forestière provoque un rajeunissement de l'agrégat souligné par la présence de nombreux individus jeunes non ramifiés. L'analyse architecturale permet de déceler une grande variabilité d'expression dans le développement qui se traduit par différentes vigueurs architecturales. En combinant les résultats des analyses dendrométrique, spatiale et architecturale, une évolution dynamique de la structure de ces 2 agrégats est proposée.
https://hal.archives-ouvertes.fr/hal-01189192

hal-01189192
https://hal.archives-ouvertes.fr/hal-01189192
PRODINRA : 13161

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
1] Recent statistical analysis by Lallemand et al. (2008) of subduction zone parameters revealed that the back-arc deformation mode depends on the combination between the subducting (nu(sub)) and upper (nu(up)) plate velocities. No significant strain is recorded in the arc area if plate kinematics verifies nu(up) = 0.5 vsub - 2.3 (cm/a) in the HS3 reference frame. Arc spreading ( shortening) occurs if nu(up) is greater ( lower) than the preceding relationship. We test this statistical law with numerical models of subduction, by applying constant plate velocities far away from the subduction zone. The subducting lithosphere is free to deform at all depths. We quantify the force applied on the two converging plates to sustain constant surface velocities. The simulated rheology combined viscous (non-Newtonian) and brittle behaviors, and depends on water content. The influence of subduction rate vs is first studied for a fixed upper plate. After 950 km of convergence ( steady state slab pull), the transition from extensional to compressive stresses in the upper plate occurs for vs similar to 1.4 cm/a. The effect of upper plate velocity is then tested at constant subduction rate. Upper plate retreat ( advance) with respect to the trench increases extension ( compression) in the arc lithosphere and increases ( decreases) the subducting plate dip. Our modeling confirms the statistical kinematic relationship between vsub and nu(up) that describes the transition from extensional to compressive stresses in the arc lithosphere, even if the modeled law is shifted toward higher rates of upper plate retreat, using our set of physical parameters ( e. g., 100 km thick subducting oceanic plate) and short- term simulations. Our results make valid the choice of the HS3 reference frame for assessing plate velocity influence on arc tectonic regime. The subduction model suggests that friction along the interplate contact and the mantle Stokes reaction could be the two main forces competing against slab pull for upper mantle subductions. Besides, our simulations show that the arc deformation mode is strongly time dependent.
ISSN: 1525-2027

hal-00412328
https://hal.archives-ouvertes.fr/hal-00412328
https://hal.archives-ouvertes.fr/hal-00412328/document
https://hal.archives-ouvertes.fr/hal-00412328/file/arcayG32008.pdf
DOI : 10.1029/2007GC001875

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
This paper presents a synthesis of a multidisciplinary study carried out along the Nîmes Roman aqueduct, located in the southeast part of France. The study was motivated by archaeologists attempting to explain the partial destructions of only one aerial bridge of the aqueduct (Pont de la Lône). Given its close proximity to the Nîmes seismically active fault, a possible seismic origin for the destructions was invoked. Seismologists and structural engineers thus carried out a variety of field and numerical investigations to test the seismic hypothesis. Supporting field evidence was found first along the aerial bridge section of the aqueduct: broken stalactites, arch warping, cracks and destruction of the bridge just above a breast wall shortly after its construction. Secondly, the underground part of the canal was analysed: irregularity in the thickness of calcite deposits of the canal walls, presence of numerous cracks, horizontal shift of the otherwise linear structure of the canal and presence of calcite twins in the deposits, found only where the canal crosses the Nîmes fault system. Numerical modelling and experimental results show that (1) only the Pont de la Lône would have suffered serious damage under seismic solicitation (assuming an M6 earthquake at 10 km distance). The second aerial bridge, the three levels arches Pont du Gard, an historical monument still standing today, would have suffered less damage, due to its very different fundamental frequency of around 0.4 Hz, far from the amplified seismic near-field spectrum; (2) the numerical models also show that a fall of the canal wall would require a higher magnitude event (M > 6); (3) the presence of calcite twinning requires a differential static stress of 4 MPa or greater, which can only be achieved very close to the fault rupture of a M > 6 earthquake; (4) finally, local surface rupturing of such a fault would also corroborate the hypothesis that the observed offset of the canal may be partly seismically induced. Although other possible origins for each individual evidence may not be excluded, the observed spatiotemporal concentration of architectural/geological anomalies together with the numerical results allow us to support a possible co-seismic origin for these disorders, indirectly attesting to the potential seismic activity (M > 6) of the nearby Nîmes fault. Furthermore, following the conclusions of archaeological studies, the disorders occurred between 250 and 350 year AD, thus providing timing for this possible seismic event, an essential parameter in seismic hazard analysis. These results validate the archaeo-seismological approach as a tool that may help improve the knowledge of major infrequent earthquakes in areas of moderate seismic activity.
ISSN: 0921-030X

hal-00379064
https://hal.archives-ouvertes.fr/hal-00379064
DOI : 10.1007/s11069-008-9276-9

Éditeur(s) : Wiley-blackwell
Résumé : The reef fauna connectivity of the West Indian Ocean (WIO) is one of the least studied globally. Here we use genetic analyses of the grouper Epinephelus merra (Bloch 1793) to determine patterns of connectivity and to identify barriers to dispersal in this WIO marine area. Phylogeographic and population-level analyses were conducted on cytochrome b sequences and microsatellites (13 loci) from 557 individuals sampled in 15 localities distributed across the West Indian Ocean. Additional samples from the Pacific Ocean were used to benchmark the WIO population structure. The high level of divergence revealed between Indian and Pacific localities (of about 4.5% in sequences) might be the signature of the major tectonic and climatic changes operating at the Plio-Pleistocene transition, congruently with numerous examples of Indo-Pacific speciation. In comparison, the E. merra sequences from the Indian Ocean constitute a monophyletic clade with a low average genetic distance (d < 0.5%). However both genetic markers indicated some structure within this ocean. The main structure revealed was the isolation of the Maldives from the WIO localities (a different group signature identified by clustering analysis, great values of differentiation). Both marker types reveal further significant structure within the WIO, mainly the isolation of the Mascarene Islands (significant AMOVA and isolation-by-distance patterns) and some patchy structure between the northernmost localities and within the Mozambique Channel. The WIO genetic structure of E. merra appeared congruent with main biogeographic boundaries and oceanographic currents.
Marine Ecology-an Evolutionary Perspective (0173-9565) (Wiley-blackwell), 2015-09 , Vol. 36 , N. 3 , P. 447-461

Droits : 2014 Blackwell Verlag GmbH
http://archimer.ifremer.fr/doc/00189/30046/28566.pdf
DOI:10.1111/maec.12153
http://archimer.ifremer.fr/doc/00189/30046/

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 Elsevier
Résumé : International audience
We investigated the deformation mechanisms and the seismic properties of 10 eclogite samples from different localities (Alps, Norway, Mali and eastern China) through the analysis of their microstructures and lattice-preferred orientations (LPO). These samples are representative of various types and intensity of deformation under eclogitic metamorphic conditions. Omphacite and garnet LPO were determined from electron backscatter diffraction (EBSD) technique. Garnet appears to be almost randomly oriented whereas omphacite develops strong LPO, characterized by the [001]-axes concentrated sub-parallel to the lineation, and the (010)-poles concentrated sub-perpendicular to the foliation. In order to analyze the deformation mechanisms that produced such omphacite LPO, we compare our observations to LPO simulated by viscoplastic self-consistent numerical models. A good fit to the measured LPO is obtained for models in which the dominant slip systems are 1/2h110i{11 ¯ 0}, [001] {110} and [001] (100). Dominant activation of these slip systems is in agreement with TEM studies of naturally deformed omphacite. Seismic properties of eclogite are calculated by combining the measured LPO and the single crystal elastic constants of omphacite and garnet. Although eclogite seismic anisotropies are very weak (less than 3% for both P-and S-wave), they are generally characterized by a maximum P-wave velocity sub-parallel to the lineation and by a minimum velocity approximately normal to foliation. The mean P-and S-wave velocities are high (respectively, 8.6 and 4.9 km/s). The S-wave anisotropy pattern displays complex relationships with the structural frame but the fast polarization plane generally tends to be parallel to the foliation. Calculated reflection coefficients show that an eclogite/crust interface is generally a good reflector (Rc > 0.1), whereas an eclogite body embedded in the upper mantle would be hardly detectable.
ISSN: 0040-1951

hal-01389715
http://hal.univ-reunion.fr/hal-01389715
http://hal.univ-reunion.fr/hal-01389715/document
http://hal.univ-reunion.fr/hal-01389715/file/Bascou_eclo-sismo_tphy2001_hal.pdf
DOI : 10.1016/S0040-1951(01)00156-1

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Le présent article introduit les contributions du numéro de la revue Etudes Caribéennes consacré à la thématique de la mondialisation. L’article passe en revue les différentes théories de la mondialisation, en particulier le courant hyper-globaliste, le courant sceptique et le courant transformationiste. En analysant les différentes contributions du numéro, l’auteur conclut que la majorité des articles se range du côté du transformationisme.
The present article introduces the articles of the issue of the journal Etudes Caribéennes, the theme of which is globalization. The introductory article reviews the theoretical literature on the concept of globalization, particularly the perspectives of the hyper-globalists, the skeptics, and the transformationalists. Analysis of the various articles leads the author to conclude that the majority of them side with transformationalism.

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.6153
http://journals.openedition.org/etudescaribeennes/6153

Éditeur(s) : Université de Bretagne Occidentale
Résumé : Study of mineral suspended particulate matter (SPM) is essential to understand ecosystem dynamics. SPM influences light penetration which is closely related to primary production and carries pollutants and nutrients within the water masses. This work aims to study near-surface mineral SPM dynamics in the English Channel using two complementary methods: remote-sensing by satellites and numerical modelling. Firstly, MODIS and MERIS satellite images processed by the IFREMER semi-analytical algorithm and describing non-algal SPM, are analysed to build three statistical models which are able to estimate near-surface SPM using simple variables, e.g., tidal coefficient, significant wave height and mean chlorophyll-a concentration. Secondly, the three-dimensional hydrosedimentary model ROMS (Regional Ocean Modeling System) is applied in the English Channel. It considers tidal forcing along open boundaries, wind stress at the sea-surface, wave-current interactions in the bottom boundary layer and realistic heterogeneous bottom sediments. Results of the more sophisticated statistical model is also used to impose SPM concentrations at open boundaries. Sensitivity tests on SPM boundary conditions show the importance of prescribing realistic sediment concentrations to improve the model predictions. Biological influences on mineral SPM are also tested using settling velocity and critical shear stress for erosion which vary with seasons. Both statistical and numerical models highlight and locate respective influences of tide, waves and biology on mineral SPM. Numerical predictions indicate that near-surface SPM is mainly composed of silts (>70%). Near-surface suspended silts come largely from seabed resuspension alongshore in the Eastern Channel and from the open boundaries of our limited-area coastal model at the West of Cotentin Peninsula and offshore. Near-surface SPM variations are investigated at semi-diurnal, neap-spring tidal cycle time scales and during a wave event. Finally, dynamics of sediments in the turbidity maximum zone around the Isle of Wight is examined depending on hydrodynamical conditions in order to distinguish the role played by advection and local erosion/settling processes in this area. Keywords: Suspended particulate matter, satellite, remote-sensing, modelling, English Channel, sediments, turbidity, tide, wave
L'étude des matières en suspension (MES) minérales est essentielle pour comprendre le fonctionnement des écosystèmes en Manche : les MES influencent la pénétration de la lumière dans la colonne d'eau, paramètre clé pour la production biologique, et sont susceptibles de transporter des polluants et nutriments. Lors de ce travail, la dynamique des MES minérales de surface en Manche est étudiée à l'aide de deux méthodes complémentaires : l'observation par satellite et la modélisation numérique tridimensionnelle. Dans un premier temps, les images satellite MODIS et MERIS, traitées par l'algorithme semi-analytique développé par l'IFREMER et représentant les MES non-algales de surface, sont analysées afin d'élaborer trois modèles statistiques permettant d'estimer la MES de surface en fonction de variables basiques telles que le coefficient de marée, la hauteur significative des vagues et la concentration moyenne en chlorophylle-a. Dans un deuxième temps, le modèle hydrosédimentaire multiclasse tridimensionnel ROMS (Regional Ocean Modeling System) est implémenté en Manche. Il prend en considération le forçage par la marée aux frontières ouvertes, la contrainte exercée par le vent à la surface de la mer, l'interaction houle-courant en couche limite de fond et l’hétérogénéité spatiale réaliste du lit sédimentaire. Les résultats du modèle statistique le plus sophistiqué sont également utilisés pour forcer la concentration en MES aux frontières ouvertes du domaine de calcul. Des tests de sensibilité sur les conditions limites montrent l'importance de considérer de manière réaliste les sédiments entrant en Manche par les frontières ouvertes lors de la modélisation numérique. L'influence de la biologie sur les MES minérales est testée en utilisant une formulation de la vitesse de chute et de la contrainte critique d'érosion variant saisonnièrement. Grâce à ces deux outils associés, les influences respectives de la marée, de la houle et de la biologie sur les MES minérales sont mises en avant et localisées en Manche. Le modèle numérique prédit que les MES de surface sont composées principalement de silts (>70%). Les silts en suspension en surface proviennent majoritairement du lit sédimentaire près des côtes en Manche orientale et des frontières ouvertes du domaine de calcul à l'ouest de la presqu'île du Cotentin et au large en Manche centrale et orientale. Les variations des MES de surface sont ensuite étudiées aux échelles des cycles de marée semi-diurnes, vive-eau/morte-eau et autour d'un épisode de houles. Enfin, l'évolution de la concentration de sédiments dans la zone de forte turbidité autour de l'île de Wight peut être analysée suivant les conditions hydrodynamiques afin d'évaluer les rôles respectifs des processus locaux d'érosion/dépot et d'advection dans la génération de ces turbidités remarquables. Mots-clés : Matière en suspension, télédétection, satellite, modélisation, Manche, sédiments, turbidité, marée, houle

Droits : 2013 UBO
http://archimer.ifremer.fr/doc/00157/26783/24884.pdf
http://archimer.ifremer.fr/doc/00157/26783/

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) : EDP Sciences
Résumé : Lessons for the future from two development projects in aquaculture in the French overseas territories. Numerous research and development projects have been launched since the seventies in the French overseas territories. Their aim was to foster new activities in agriculture based on local productions for local markets, notably in the French West Indies (FWI). In this paper we analyze two development projects on the rearing of giant freshwater prawn, one in the FWI and the other in French Guyana, over twenty years after their launching. The purpose of these compared studies is twofold: first to try to understand why a set of relevant technical innovations ended in failure 15 years later; second to identify recommendations in terms of methodology in order to diminish risks of mistakes or failure for future projects. To reach this goal we followed two approaches. A first analysis is based on a set of three criteria: social acceptability, legitimacy and time planning. The second analysis, justified by the subjective need for an explanatory tool, is based on the actor-network theory. The results show that beyond the levels of political support and financial investment and support the three key criteria for success are: (i) reactivity of the decision-makers, notably when markets change, (ii) quality of leadership transfer between the launching phase and the stabilized phase, and (iii) capacity of the decision-makers to take into account the concrete consequences of the various scenarios. Regarding this third criterion, our analysis suggests that the scenario of full technical success needs to be explored, notably in terms of economic sustainability. The integration of these two types of analyses into an ex-ante frame should contribute to reducing risks of failure in similar development projects.
De nombreux projets d’aquaculture ont été menés depuis les années 1970 dans les territoires et départements français d’outre-mer. L’objectif était de diversifier l’agriculture avec des productions destinées au marché local comme aux Antilles, ou à l’exportation comme en Guyane. L’étude s’intéresse au bilan de deux projets d’élevage de la crevette tropicale d’eau douce aux Antilles et en Guyane, plus de vingt ans après leur lancement. L’objectif est de comprendre comment des innovations technologiques pertinentes ont conduit à deux échecs sur le moyen terme et de tirer des recommandations de méthode afin de réduire les risques d’erreurs ultérieures. Pour cela, deux cadres d’analyse sont mobilisés : le premier s’appuie sur les concepts de temporalité, légitimité et acceptabilité ; le second, motivé par la recherche subjective de cadres explicatifs, emprunte la vision de la théorie de l’acteur-réseau. Les trois déterminants majeurs du succès ou de l’échec se révèlent être la réactivité des responsables face aux problèmes d’adaptation à l’évolution des marchés, la qualité du transfert du leadership lors du passage de la phase de lancement à la phase de croisière et enfin la capacité de prendre en compte dès le départ les conséquences des scénarios d’évolution du projet, y compris la réussite technique. Une capacité d’intégration de ces types d’analyse, dans un cadre ex ante, devrait permettre de réduire les risques d’échec dans des projets de développement similaires à venir.
Natures Sciences et Sociétés (1240-1307) (EDP Sciences), 2013-12 , Vol. 21 , N. 4 , P. 400-415

Droits : NSS-Dialogues, EDP Sciences 2014
http://archimer.ifremer.fr/doc/00187/29784/28242.pdf
DOI:10.1051/nss/2014004
http://archimer.ifremer.fr/doc/00187/29784/

Éditeur(s) : HAL CCSD Springer Verlag (Germany) Springer Verlag
Résumé : Direct numerical simulations of flow through two millimeter-scale rock samples of limestone and sandstone are performed using three diverse fluid dynamic simulators. The resulting steady-state velocity fields are compared in terms of the associated empirical probability density functions (PDFs) and key statistics of the velocity fields. The pore space geometry of each sample is imaged at 5.06−μm voxel size resolution using X-ray microtomography. The samples offer contrasting characteristics in terms of total connected porosity (about 0.31 for the limestone and 0.07 for the sandstone) and are typical of several applications in hydrogeology and petroleum engineering. The three-dimensional fluid velocity fields within the explicit pore spaces are simulated using ANSYS® FLUENT® ANSYS Inc. (2009), EULAG Prusa et al. (Comput. Fluids 37, 1193–1207 2008), and SSTOKES Sarkar et al. (2002). These computational approaches are highly disperse in terms of algorithmic complexity, differ in terms of their governing equations, the adopted numerical methodologies, the enforcement of internal no-slip boundary conditions at the fluid-solid interface, and the computational mesh structure. As metrics of comparison to probe in a statistical sense the internal similarities/differences across sample populations of velocities obtained through the computational systems, we consider (i) integral quantities, such as the Darcy flux and (ii) main statistical moments of local velocity distributions including local correlations between velocity fields. Comparison of simulation results indicates that mutually consistent estimates of the state of flow are obtained in the analyzed samples of natural pore spaces despite the considerable differences associated with the three computational approaches. We note that in the higher porosity limestone sample, the structures of the velocity fields obtained using ANSYS FLUENT and EULAG are more alike than either compared against the results obtained using SSTOKES. In the low-porosity sample, the structures of the velocity fields obtained by EULAG and SSTOKES are more similar than either is to the fields obtained using ANSYS FLUENT. With respect to macroscopic quantities, ANSYS FLUENT and SSTOKES provide similar results in terms of the average vertical velocity for both of the complex microscale geometries considered, while EULAG tends to render the largest velocity values. The influence of the pore space structure on fluid velocity field characteristics is also discussed.
ISSN: 1420-0597

hal-01174152
https://hal.archives-ouvertes.fr/hal-01174152
DOI : 10.1007/s10596-015-9486-7