Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Mass tourism is a historically significant phenomenon. For decades, it has been a source for stereotypes within academic research and in public discussions. This study addresses stereotypes of mass tourism by giving voice to travel agents and tourist guides working for mass package tour operators. They were asked to comment and reflect on the statements about phenomenon in which they are working. The Finnish socio-cultural context is discussed as well as the positionality and contextuality of the interviewees. In total, 20 interviews were conducted. The results show that there is no one way to understand these stereotypes: Both professional groups contextualized and scaled the universalist statements in multiple ways. In tourism research, more attention should be directed at how the categorization of mass tourism is done as a discursive practice and what kinds of effects it has to the theory and practice.
Le tourisme de masse est un phénomène historiquement significatif. Pendant des décennies, il a été une source de stéréotypes dans la recherche universitaire et dans les débats publics. Cette étude porte sur les stéréotypes du tourisme de masse et donne la parole à des agents et des guides touristiques travaillant pour les tour-opérateurs qui vendent des produits de masse. Ils ont été invités à commenter et réfléchir sur les déclarations sur le tourisme de masse. Le contexte socio-culturel finlandais est discuté ainsi que le positionnement et la contextualité des personnes interrogées. Au total, 20 interviews ont été menées. Les résultats montrent qu'il n'y a pas une façon de comprendre ces stéréotypes: les professionnels contextualisent et appréhendent le phénomène de plusieurs manières. Les recherches sur le tourisme mériteraient d’accorder plus d’attention sur les processus de catégorisation du tourisme de masse, la construction de la pratique discursive et leurs effets sur les théories et les pratiques.
Finlande
Crète

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.7609
http://journals.openedition.org/etudescaribeennes/7609

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Le débat théorique sur les migrations et la famille connait une ambivalence allant du postulat de la migration comme une logique « individualiste » et de distanciation de la famille à celui de la migration vue comme une stratégie de survie portée par le réseau familial. C’est dans le but de contribuer à ce débat que le présent texte aborde l’analyse du processus migratoire sous l’angle des stratégies déployées par les migrants « Hloua » de la côte béninoise. Quatre dimensions ont particulièrement retenu notre attention : la prise de décision, le financement et l’organisation du voyage, l'intégration dans le milieu d’accueil, et les rapports maintenus avec le milieu d'origine.L’analyse s’appuie sur les récits de migration collectés auprès de migrants de retour ou de membres de familles restés au village, ceci dans le cadre d’une enquête plus large sur la pauvreté et les stratégies de survie dans le milieu de la pêche artisanale (Avloh, Ayiguinnou et Agoué) au Bénin. Cette analyse de récit a été complétée par des analyses de type quantitatif sur la fréquence des recours pour l’organisation et la prise de décision, la fréquence de recours pour l’insertion résidentielle et professionnelle, et le montant des envois de fonds. Les résultats montrent la place centrale du réseau familial le long du processus migratoire depuis la prise de décision, l’organisation du voyage, le « confiage » de la femme et des enfants du migrant, à l’établissement résidentiel et l’insertion professionnelle dans le milieu d’accueil. Ce réseau organise et structure efficacement le phénomène migratoire en intervenant lors des étapes décisives. Cependant, une fois insérés, les rapports maintenus avec le réseau familial se limitent pour la plupart à une solidarité affective, caractérisée par des contacts téléphoniques ou transferts de message et quelques envois de fonds largement en deçà des attentes. Ce qui fait dire de plus en plus que le migrant diminue le capital social de la famille sans pour autant y contribuer de façon substantielle sur le plan financier : Un paradoxe qui pourrait bien trouver son explication dans les recherches futures sous une perspective dynamique des migrations.
The theoretical debate on migration and family is ambivalent. Migration can be seen from an “individualist’’ and distant logic of the family or, on the other hand, migration can be viewed as a strategy of survival for the family network. It is in the objective of contributing to this debate, the present article will analyze the migration process from a migrant strategy perspective, more specifically from the perspective of the “Hloua” migrants off the Benin coast. Four dimensions are of particular interest: the decision making process, the cost and organization of the trip, integration in the host community and the maintenance of relations with the host community. Within a large scale research on poverty and the strategies of survival of artisan fishing (Avloh, Ayiguinnou et Agoué) in Bénin, the present analysis is based on migration stories collected from returning migrants or from family members still living in the village. This story analysis has been completed with quantitative analyses on the frequency of the use of organization and decision making, the frequency of the use of residential and professional insertion, and the amount of remittances. The results show the central place of family ties during the migratory process from the start of the decision making process, the travel planning, the entrusting of the women and children of the migrant, to the residential establishment and the professional insertion in the host society. This network organizes and structures efficiently the migratory phenomenon by intervening during the decisive steps. However, once inserted, the connections maintained with the family network are limited for the majority to an affective solidarity characterized by telephone contacts or message transfers, and sometimes remittances sent back largely lower to the family’s expectations. This results more and more in the migrant diminishing the social capital of the family without always contributing in some substantially way on the financial side. A paradox which could find its explanation in future researches under a perspective of migrations’ dynamics.
Bénin

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.5785
http://journals.openedition.org/etudescaribeennes/5785

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Experimental studies have demonstrated that the antileukemic trivalent inorganic arsenic prevents the development of severe pro-inflammatory diseases mediated by excessive Th1 and Th17 cell responses. Differentiation of Th1 and Th17 subsets is mainly regulated by interleukins (ILs) secreted from dendritic cells (DCs) and the ability of inorganic arsenic to impair interferon-γ and IL-17 secretion by interfering with the physiology of DCs is unknown. In the present study, we demonstrate that high concentrations of sodium arsenite (As(III), 1-2 μM) clinically achievable in plasma of arsenic-treated patients, block differentiation of human peripheral blood monocytes into immature DCs (iDCs) by inducing their necrosis. Differentiation of monocytes in the presence of non-cytotoxic concentrations of As(III) (0.1 to 0.5 μM) only slightly impacts endocytotic activity of iDCs or expression of co-stimulatory molecules in cells activated with lipopolysaccharide. However, this differentiation in the presence of As(III) strongly represses secretion of IL-12p70 and IL-23, two major regulators of Th1 and Th17 activities, from iDCs stimulated with different toll-like receptor (TLR) agonists in metalloid-free medium. Such As(III)-exposed DCs also exhibit reduced mRNA levels of IL12A and/or IL12B genes when activated with TLR agonists. Finally, differentiation of monocytes with non-cytotoxic concentrations of As(III) subsequently reduces the ability of activated DCs to stimulate the release of interferon-γ and IL-17 from Th cells. In conclusion, our results demonstrate that clinically relevant concentrations of inorganic arsenic markedly impair in vitro differentiation and functions of DCs, which may contribute to the putative beneficial effects of the metalloid towards inflammatory autoimmune diseases.
ISSN: 0041-008X

inserm-00813758
http://www.hal.inserm.fr/inserm-00813758
DOI : 10.1016/j.taap.2012.11.008
PUBMED : 23164666

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : Installation and maintenance of FADs by the Government of Guam began in 1979, initially with funding from the Salstonstall-Kennedy Act through the Pacific Tuna Development Foundation. Current funding for the Guam FAD project is provided through the Dingell-Johnson/Wallop-Breaux Sport Fish Restoration programme, a Federal Aid Project funded by taxes collected on the purchase of fishing equipment and motorboat fuels nationwide. There are now sixteen operational FAD sites in Guam's waters. At a cost of approximately US$10,000 per system, concern for the rising costs of replacing and maintaining FAD systems has prompted the Department of Agriculture's Division of Aquatic and Wildlife Resources (DAWR) to investigate alternative FAD maintenance strategies and system design. Several cost-cutting measures being considered include the use of reliable solar-powered navigation lights to reduce the number of maintenance trips required, and switching to a newer generation of lighter, more durable buoys and mooring systems. Average time on station for a dawr fad system is nearing two years. Interestingly, in most cases where an errant system is recovered, the failure in the mooring system was observed to occur at a depth from 35 to 500 metres. These observations have led to speculation that additional protection of the mooring line down to 500 m may result in doubling the average time on station of most FAD systems.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15324/12650.pdf
http://archimer.ifremer.fr/doc/00042/15324/

Éditeur(s) : HAL CCSD
Résumé : National audience
La Zone Nord-Pyrénéenne (ZNP) résulte de l’inversion debassins albo-cénomaniens ouverts entre les plaques Europe etIbérie. Le manteau subcontinental a été exhumé dans le fond decertains de ces bassins et la couverture sédimentaire mésozoïquepré-rift, désolidarisée du soubassement paléozoïque, est venue localementen contact tectonique avec les péridotites. Ceci faitde la ZNP un analogue pour l’étude des marges continentalespassives à manteau exhumé. L’extension crustale s’est produiteen régime thermique chaud comme le montre le métamorphismecrétacé des sédiments pré-rift. Les Chaînons Béarnais (PyrénéesOccidentales) représentent un témoin peu inversé de ce type demarge chaude et sont donc propices à l’étude des modalités del’amincissement crustal dans un tel système. Les analyses detempératures par spectrométrie Raman réalisées sur la couverturesédimentaire aux abords du manteau (Saraillé, Urdach, Turon dela Técouère), montrent que la totalité du système a été soumis àdes températures maximales variant de 253C à 482C. Le contacttectonique majeur entre les sédiments pré-rift décollés et lemanteau est une zone d’intense circulation de fluides avec formationde roches métasomatiques à talc+chlorite+pyrite dans lesconditions du faciès schistes verts. La géochimie isotopique (O, C,Sr) et les inclusions fluides triphasées montrent une circulation desaumures chaudes (~200C), à travers toute la couverture sédimentairedans les derniers stades de l’exhumation du manteau.Nous montrons pour la première fois que pendant l’exhumationdes péridotites : (1) les sédiments pré-rift ont subi un amincissementsyn-métamorphique avec génèse d’une foliation S0/S1 et,(2) le socle paléozoïque a été réduit à de fines lentilles tectoniquesdéformées ductilement et restées adhérentes au manteau. Ainsi, larhéologie de la croûte supérieure durant l’amincissement est contrôléeen grande partie par la présence d’une couverture sédimentairepré- et syn-rift épaisse décollée jouant le rôle d’un couverclethermique efficace. Ces nouvelles données mettent en avant le caractèrede marge passive distale chaude de la ZNP. Cela constitueun élément important pour la compréhension des mécanismes del’amincissement crustal en contexte d’exhumation du manteau etses conséquences comme héritage structural lors de l’inversion tectoniquedes bassins.
RST 2016, livre des résumés
Caen, France

insu-01387892
https://hal-insu.archives-ouvertes.fr/insu-01387892

Éditeur(s) : HAL CCSD
Résumé : International audience
Continental erosion and weathering destroy parts of the stratigraphic record. Analyses of the sedimentary filling of paleokarsts help completing the geological record of regions that have been submitted to post-depositional, long-term, continental evolution. Jurassic carbonate platform of Languedoc (South of France) has undergone several karstification phases from Cretaceous to Neogene. Later incision of canyons through the carbonate massifs allows to observe paleokarsts over 400m depth, within the massifs. Paleokarsts are partly filled with sediments. Some have yielded marine bioclasts (echinoderms, radiolars), foraminifera and nannofossils; others are composed of polygenic detrital sediments, including sources from the upstream Paleozoic basement (Cevennes). The age of the filling of successive paleokarsts can be constrained by structural relationships and by biostratigraphy. These findings suggests 1) the marine elements of the karstic filling relate to a Late Cretaceous to Early Paleocene interval, while 2) the Paleozoic basement-sourced-sediments were trapped in the karst during Miocene to Present. Karstic sediment containing Early Paleocene foraminifera and nannofossils are found in paleokarsts cavities distributed across the entire thickness of the carbonate massif (≥350m). This requires base-level lowering and associated karstification, followed by base-level rise and karst filling of at least 350 m amplitude, respectively. The time interval corresponding to the occurrence of foraminifera and nannofossils in karsts covers 10 Myrs ; surprisingly, no equivalent marine sediments are preserved on the surface. In addition, analyses of the different forams species suggests several (up to 3) distinct karstification and marine filling cycles. Finally, sedimentological facies analysis of the karst filling reveals the following succession of processes: low energy settling of mudstone, high energy reworking, transport and deposition of silts and sandstones within the karst system. Integration of geological, paleontological and sedimentological data, leads to a polyphase scenario in response to repeated base-level variations, more than 350m amplitude. Such an amplitude excludes eustacy, and the improbable repeated sequence of uplift and subsidence rules out tectonics, as driving forces for base-level change, respectively. We propose that the high-amplitude base-level changes results from a succession of desiccation-flooding events of an endorheic, silled, basin during Early Paleogene. The later detrital assemblage sourced in the Cevennes occurs on perched paleosurfaces and in karst cavities across the whole 350m-deep canyon walls. When found on paleosurfaces, they correspond to the south-flowing Early Miocene fluvial drainage, and can be correlated downstream with the marine, well dated, Early Miocene, sediments. When found within the karst cavities, they correspond to successive base-level surfaces connected to the progressive incision of the canyon. This canyon incision is coeval with a Late Miocene uplift of the hinterland.
24th International Karstological School "Classical karst" : Paleokarst
Postojna, Slovenia

hal-01306683
https://hal-brgm.archives-ouvertes.fr/hal-01306683
https://hal-brgm.archives-ouvertes.fr/hal-01306683/document
https://hal-brgm.archives-ouvertes.fr/hal-01306683/file/Abstract_IKS.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This paper discusses and analyses the productivity of solar home systems in isolated areas in French Guiana, a region characterized by specific human and environmental conditions.Its aim is a better understanding of the attitudes, expectations, and relationship of the users towards the solar home system. The data collected made it possible to make suggestions for adapting the photovoltaic systems to their environment by taking into account social, cultural, and geoclimatic specificities. Analysis of on-site productivity provides valuable information on energy profiles and types of use. Field surveys made it possible to associate users’ perception of the energy production equipment and their degree of satisfaction with operating efficiency and on-site maintenance. This aspect is essential for analyzing the actual rate of use of the energy that is theoretically available.Parallel to these surveys, the results of the study carried out on the performance of the solar home systems made it possible to learn the quantitative aspects of the energy produced and consumed as well as the qualitative aspects of the parameters that condition the performance of the photovoltaic systems.After keyboarding, the subjective, qualitative as well as the quantitative variables were processed using a statistical analysis program in order to determine the correlations between them and to prepare the final conclusions.
ISSN: 1364-0321

hal-01304585
https://hal.archives-ouvertes.fr/hal-01304585
https://hal.archives-ouvertes.fr/hal-01304585/document
https://hal.archives-ouvertes.fr/hal-01304585/file/article%20RSER%20Hal.pdf
DOI : 10.1016/j.rser.2009.06.015

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We report microstructural evidence for fluid-assisted ductile strain localization in a ≤ 50 m-wide mylonitic–ultramylonitic shear zone in the Ronda Peridotite massif, Southern Spain. Strain localization occurred at relatively low pressure (< 0.8 GPa) and moderate temperature (750–1000 °C). Initial deformation by dislocation creep resulted in formation of mylonites. Focusing of aqueous fluids in the shear zone favored the activation of dissolution–precipitation creep, resulting in further strain localization. This process is recorded by two generations of ultramylonitic bands composed of fine-grained, well-mixed olivine–orthopyroxene aggregates. Microstructural observations in the ultramylonites suggest alternating dissolution and precipitation of olivine and orthopyroxene, which may be explained by local changes in silica molality of the percolating fluid (disequilibrium and mass transfer at scales > mm). In the mylonites, olivine shows a crystal preferred orientation (CPO) coherent with dominant (001)[100] glide, probably due to the presence of interstitial fluids during deformation. In the ultramylonites, olivine CPO is weak to very weak, consistently with a decreasing contribution of dislocation creep to deformation. In contrast, fine-grained orthopyroxene in both mylonites and ultramylonites displays a clear CPO characterized by a [001] maximum normal to the foliation, which is not consistent with dislocation glide in any known slip system for orthopyroxene. We interpret this CPO as formed by oriented crystallization during dissolution–precipitation. In the present study, dissolution–precipitation creep predominates only in small-scale ultramylonite bands due to limited fluid availability and localized dynamic permeability. However, this process may be important in intermediate temperature domains of subduction zones, where it may lead to a feedback between strain localization and fluid transport.
ISSN: 0024-4937

hal-01395122
https://hal.archives-ouvertes.fr/hal-01395122
DOI : 10.1016/j.lithos.2016.07.038

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : The properties of the subduction interplate domain are likely to affect not only the seismogenic potential of the subduction area but also the overall subduction process, as it influences its viability. Numerical simulations are performed to model the long-term equilibrium state of the subduction interplate when the diving lithosphere interacts with both the overriding plate and the surrounding convective mantle. The thermomechanical model combines a non-Newtonian viscous rheology and a pseudo-brittle rheology. Rock strength here depends on depth, temperature and stress, for both oceanic crust and mantle rocks. I study the evolution through time of, on one hand, the brittle-ductile transition (BDT) depth, zBDT, and, on the other hand, of the kinematic decoupling depth, zdec, simulated along the subduction interplate. The results show that both a high friction and a low ductile strength at the asthenospheric wedge tip shallow zBDT. The influence of the weak material activation energy is of second order but not negligible. zBDT becomes dependent on the ductile strength increase with depth (activation volume) if the BDT occurs at the interplate decoupling depth. Regarding the interplate decoupling depth, it is shallowed (1) significantly if mantle viscosity at asthenospheric wedge tip is low, (2) if the difference in mantle and interplate activation energy is weak, and (3) if the activation volume is increased. Very low friction coefficients and/or low asthenospheric viscosities promote zBDT = zdec. I then present how the subducting lithosphere age affects the brittle-ductile transition depth and the kinematic decoupling depth in this model. Simulations show that a rheological model in which the respective activation energies of mantle and interplate material are too close hinders the mechanical decoupling at the down-dip extent of the interplate, and eventually jams the subduction process during incipient subduction of a young (20-Myr-old) and soft lithosphere under a thick upper plate. Finally, both the BDT depth and the decoupling depth are a function of the subducting plate age, but are not influenced in the same fashion: cool and old subducting plates deepen the BDT but shallow the interplate decoupling depth. Even if BDT and kinematic decoupling are intrinsically related to different mechanisms of deformation, this work shows that they are able to interact closely. Comparison between modelling results and observations suggests a minimum friction coefficient of 0.045 for the interplate plane, even 0.069 in some cases, to model realistic BDT depths. The modelled zdec is a bit deeper than suggested by geophysical observations. Eventually, the better way to improve the adjustment to observations may rely on a moderate to strong asthenosphere viscosity reduction in the metasomatised mantle wedge.
ISSN: 1869-9510

hal-00795559
https://hal.archives-ouvertes.fr/hal-00795559
DOI : 10.5194/se-3-467-2012, 2012

Résumé : SODACAL prawn farm which was set up as a pilot farm for the development of a prawn industry in New Caledonia, saw its production exponentially rise from 1984 to 1992 (to 400 t/year, then experienced a sharp drop in 1993 (250 t/year) which carried on until 1997, and finally rose back to a stabilizing level around 400 t/year until 1999. The study analyses the difficulties observed before and during the drop of production. Among them, mortality outbreaks, other biological perturbations (benthic mat clearing and crab and fish mortality) and focus on the noxious state of the bottom (reduced and smelling sulfide hydrogen). It particularly shows that Syndrome 93 outbreaks could be observed on this farm from 1990. The analysis highlights the particular climatic conditions in New Caledonia from 1990 to 1995 (drought) and their potential impact on the production. The development of this very particular process of physical and topographic differential evolution of the pond bottom under wind action (accumulation and digging) and its consequences on pond preparation is explained. This work takes a close look at the grow-out management : age and quality of post larvae, pond stocking with pre-grown animals, feed characteristics and management, water exchange management and pumping capacity, strategy on density and size of harvested animals. The results have been assessed using a distinctive tool, the "survival differential", allowing inter-pond comparisons within a site, inter-farms comparisons over pluri-annual periods of time. >From the commented farm results over a 20 year period, we could distinguish the principal factors responsible for the drop of grow-out capacity of some ponds. We have outlined a conceptual description of the different parameters leading to the decrease of survival, an epidemiological scenario and a synoptic table of the history of events and their relative severity. The study draws the hypothesis of a cumulative effect of positive factors, which could have led back to satisfying production results: a physical and biochemical restoration of pond bottoms, a modified and standardized grow-out management, an appropriate pumping capacity and the come back of adequate climatic conditions. This case study illustrates the concept of « flexibility » of the farming capacity and the sustainability of prawn farming in New Caledonia. The clear objective of this 20 year historic investigation was to get relevant information, in order to improve the understanding on the "summer syndrome" which hits two farms at the moment, and to participate in the hypothesis under study by the DAC (2005). We also tried to make the new farmers aware of the fragility of the pond ecosystem, and give some common-sense advices in the hope that such problems will not happen again in other places.
La ferme de SODACAL, conçue à l'origine comme une ferme de démonstration pour le développement d'une filière d'aquaculture exportatrice de crevettes en Nouvelle-Calédonie a connu une phase de croissance exponentielle de sa production de 1984 à 1992 (jusqu'à 400 t/an), puis une chute brutale en 1993 (250 t/an) qui s'est prolongée jusqu'en 1997 et enfin une reprise à partir de 1998 pour arriver à une stabilisation autour de 420 t/an depuis 1999. L'étude inventorie les dysfonctionnements observés avant et pendant la crise de production. Parmi ceux-ci sont évoqués les épisodes de mortalité de crevettes, d'autres désordres biologiques (décollements de tapis benthique et « hécatombes » de crabes et de poissons), l'état délétère des fonds (sédiments réduits et odeur d'hydrogène sulfuré). Elle permet notamment de montrer que des épisodes de mortalité typiques du Syndrome 93 pouvaient être observés sur cette ferme dès 1990. L'étude met en évidence les conditions climatiques remarquables qui ont sévi en Nouvelle-Calédonie de 1990 à 1995 (sécheresse) et leur impact probable sur les élevages. La genèse du phénomène très particulier d'évolution physique et topographique des fonds des bassins par l'effet du vent (accumulation et creusement) et des conséquences sur la préparation des bassins est explicitée. Ce travail aborde la gestion zootechnique : l'âge et la « qualité » des post larves, la pratique des ensemencements à partir d'animaux pré grossis, la gestion de l'alimentation et la nature de la provende, le contrôle du renouvellement d'eau et la capacité de pompage, le choix des densités et du calibre des animaux récoltés. Les résultats ont pu être évalués à travers un outil original «le différentiel de survie », permettant des comparaisons inter-bassins au sein du site, inter-fermes à des périodes pluri annuelles distinctes. A partir des résultats commentés de la ferme obtenus sur 20 années, on a pu distinguer les principaux facteurs qui ont provoqué cette chute d'aptitude culturale de certains bassins. Un schéma conceptuel des différents paramètres ayant conduit à la baisse des survies, un scénario épidémiologique ainsi qu'un tableau synoptique de la chronologie des évènements et de leur relative sévérité sont esquissés. Le rapport ébauche l'hypothèse d'un cumul de causes favorables qui ont permis le retour à des résultats zootechniques satisfaisants : une réhabilitation physique et biochimique des fonds de bassins, une zootechnie modifiée et standardisée, une capacité de pompage adéquate et une climatologie de nouveau favorable. Cette étude de cas permet ainsi d'illustrer les notions d « élasticité » de l'aptitude culturale et de durabilité de la crevetticulture en Nouvelle-Calédonie. Le but de cette enquête historique sur 20 ans est l'acquisition d'informations pertinentes permettant d'améliorer la compréhension du « Syndrome d'été » qui affecte actuellement deux fermes de production et ainsi aider à compléter le scénario hypothétique avancé par le Dac (2005). Enfin, au travers de cet historique, on a cherché également à sensibiliser les nouveaux opérateurs de la filière sur la fragilité de l'écosystème-bassin et présenter quelques conseils de bon sens pour éviter que de tels phénomènes ne se reproduisent ailleurs.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2005/rapport-718.pdf
http://archimer.ifremer.fr/doc/00000/718/

Éditeur(s) : HAL CCSD IOP Publishing
Résumé : We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non-metrological institutes are compared. For the first time, corrections for the laser beam diffraction and the self-attraction of the gravimeters are implemented. The gravity observations are also corrected for geophysical gravity changes that occurred during the comparison using the observations of a superconducting gravimeter. We show that these corrections improve the degree of equivalence between the gravimeters. We present the results for two different combinations of data. In the first one, we use only the observations from the metrological institutes. In the second solution, we include all the data from both metrological and non-metrological institutes. Those solutions are then compared with the official result of the comparison published previously and based on the observations of the metrological institutes and the gravity differences at the different sites as measured by non-metrological institutes. Overall, the absolute gravity meters agree with one another with a standard deviation of 3.1 µGal. Finally, the results of this comparison are linked to previous ones. We conclude with some important recommendations for future comparisons.
ISSN: 0026-1394

hal-00853755
https://hal.archives-ouvertes.fr/hal-00853755
DOI : 10.1088/0026-1394/50/3/257

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Brecciated and fractured peridotites with a carbonate matrix, referred to as ophicalcites, are common features of mantle rocks exhumed in passive margins and mid-oceanic ridges. Ophicalcites have been found in close association with massive peridotites, which form the numerous ultramafic bodies scattered along the North Pyrenean Zone (NPZ), on the northern flank of the Pyrenean belt. We present the first field, textural and stable isotopic characterization of these rocks. Our observations show that Pyrenean ophicalcites belong to three main types: (1) a wide variety of breccias composed of sorted or unsorted millimeter- to meter-sized clasts of fresh or oxidized ultramafic material, in a fine-grained calcitic matrix; (2) calcitic veins penetrating into fractured serpentine and fresh peridotite; and (3) pervasive substitution of serpentine minerals by calcite. Stable isotopic analyses (O, C) have been conducted on the carbonate matrix, veins and clasts of samples from 12 Pyrenean ultramafic bodies. We show that the Pyrenean ophicalcites are the product of three distinct genetic processes: (1) pervasive ophicalcite resulting from relatively deep and hot hydrothermal activity; (2) ophicalcites in veins resulting from tectonic fracturing and cooler hydrothermal activity; and (3) polymictic breccias resulting from sedimentary processes occurring after the exposure of subcontinental mantle as portions of the floor of basins which opened during the mid-Cretaceous. We highlight a major difference between the eastern and western Pyrenean ophicalcites belonging, respectively, to the sedimentary and to the hydrothermal types. Our data set points to a possible origin of the sedimentary ophicalcites in continental endorheic basins, but a post-depositional evolution by circulation of metamorphic fluids or an origin from relatively warm marine waters cannot be ruled out. Finally, we discuss the significance of such discrepancy in the characteristics of the NPZ ophicalcites in the frame of the variable exhumation history of the peridotites all along the Pyrenean realm.
ISSN: 1437-3254

insu-00944405
https://hal-insu.archives-ouvertes.fr/insu-00944405
https://hal-insu.archives-ouvertes.fr/insu-00944405/document
https://hal-insu.archives-ouvertes.fr/insu-00944405/file/clerc-etal-IJES-Review.pdf
DOI : 10.1007/s00531-013-0927-z

Éditeur(s) : HAL CCSD Elsevier
Résumé :  
Previous studies in lowland tropical rainforests of French Guiana showed that, among non-N2-fixing trees, two groups of late successional species contrasting in their leaf 15N natural abundance coexist, suggesting two different main ways of nitrogen acquisition. Two abundant late-successional species typically co-occurring in rainforests in French Guiana, namely Eperua falcata and Dicorynia guianensis, were chosen as representative of each group. Stable isotope techniques and measurements of potentials of microbial N transformation were performed to assess to what extent leaf 15N natural abundance of these species could be related to (i) d15N signatures of soil mineral N sources and (ii) the capacity of soil to express nitrification and denitrification (both processes being directly involved in the balance between NH4 + and NO3 - ). Soil d15N-NH4 + was roughly similar to leaf d15N of D. guianensis (around 3.5%), suggesting a preferential use of NH4 +, whereas in E. falcata, leaf d15N values were closer to root d15N-NO3 _ values (0.2 and _2.0%, respectively), suggesting a preferential use of NO3 _. These differences in N source utilization were not accompanied by differences in availability in soil NO3 _ or in intensity of microbial functions responsible for soil N mineral evolution. However, (i) under both tree species, these functions showed clear spatial partitioning, with denitrification occurring potentially in soil and nitrification in the litter layer, and (ii) E. falcata fine roots colonized the litter layer much more strongly than D. guianensis fine roots. This strongly suggests that (i) the contrasted leaf d15N values found in the two late-successional species reveal distinct N acquisition strategies and (ii) the ability of roots to predominantly exploit the litter layer (E. falcata) or the soil (D. guianensis) may constitute an important explanation of the observed differences. A complementarity between tree species, based on mineral N resource partitioning (itself resulting from a spatially structured location of the microbial functions responsible for the balance between NH4 + and NO3 - ), can thus be supposed.
ISSN: 0038-0717

hal-01032035
https://hal.archives-ouvertes.fr/hal-01032035
DOI : 10.1016/j.soilbio.2007.09.011

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé :  
1. Despite considerable interest in the application of plant functional traits to questions of community assembly and ecosystem structure and function, there is no consensus on the appropriateness of sampling designs to obtain plot-level estimates in diverse plant communities. 2. We measured 10 plant functional traits describing leaf and stem morphology and ecophysiology for all trees in nine 1-ha plots in terra firme lowland tropical rain forests of French Guiana (N = 4709). 3.We calculated, by simulation, the mean and variance in trait values for each plot and each trait expected under seven sampling methods and a range of sampling intensities. Simulated sampling methods included a variety of spatial designs, as well as the application of existing data base values to all individuals of a given species. 4. For each trait in each plot, we defined a performance index for each sampling design as the proportion of resampling events that resulted in observed means within 5% of the true plot mean, and observed variance within 20%of the true plot variance. 5. The relative performance of sampling designs was consistent for estimations of means and variances. Data base use had consistently poor performance for most traits across all plots, whereas sampling one individual per species per plot resulted in relatively high performance. We found few differences among different spatial sampling strategies; however, for a given strategy, increased intensity of sampling resulted in markedly improved accuracy in estimates of trait mean and variance. 6. We also calculated the financial cost of each sampling design based on data from our 'every individual per plot' strategy and estimated the sampling and botanical effort required. The relative performance of designs was strongly positively correlated with relative financial cost, suggesting that sampling investment returns are relatively constant. 7. Our results suggest that trait sampling for many objectives in species-rich plant communities may require the considerable effort of sampling at least one individual of each species in each plot, and that investment in complete sampling, though great, may be worthwhile for at least some traits.
Functional Ecology

hal-01032175
https://hal.archives-ouvertes.fr/hal-01032175
DOI : 10.1111/j.1365-2435.2009.01600.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
3D seismic data located in the Gjallar Ridge (Vøring Basin, offshore Norway) reveals a closely-spaced polygonal fault system affecting more than 800 m of homogeneous mud-dominated Quaternary and Tertiary sequences. As some faults reach the modern seafloor, they represent an active polygonal fault system at present day. Even if the processes remain unclear and are still under debate, it is generally agreed that the initiation of polygonal faults is the result of shallow burial dewatering of fine-grained unconsolidated sediments by volumetric compaction. 3D seismic data are commonly interpreted by propagating horizons automatically and by picking faults manually. However, in the case of polygonal fault intervals, this approach is time consuming due to the huge number of faults and because automatic propagation can be misleading. In this study, we applied a new technique of 3D seismic interpretation based on a sequential stratigraphy analysis, using the new PaleoScan© software (Eliis Company). It allowed us to build a 3D geological model computing more than 300 horizons within the faulted intervals. We then used the coherency attribute, depicting anomalies in the shape of seismic waveform like faults, in order to constrain a possible link between fault distribution and stratigraphic levels. Our approach allows fault throws to be calculated in milliseconds on any polygonal fault plane. The result shows that fault segments have been reactivated by dip-linkage. Distribution of faults depends on mechanical units, intervals characterized by different petrophysical properties, which are independent from lithological and diagenetic changes. According to these results, we propose a model showing the evolution of polygonal fault intervals in which faulting stages are separated by a quiescence phase during burial. A first tier of polygonal faults is initiated at a specific depth, according to the Cam-clay model. Then, following a period of quiescence during which mud-rich sediments continued to accumulate, new fault segments are initiated above the first mechanical unit and within this undeformed interval. New nucleated faults then connect downward to pre-existing underlying polygonal fault system, thus progressively increasing the thickness of the faulted interval.
ISSN: 0025-3227

hal-00772470
https://hal.archives-ouvertes.fr/hal-00772470
DOI : 10.1016/j.margeo.2012.07.016

Éditeur(s) : HAL CCSD
Résumé : Transposable elements play a major role in the evolution of eukaryotic genomes. Knowing the distribution of transposable elements between different species within the same taxon is essential to study their dynamics and to better understand their role in the evolution of species. Given their abundance, species diversity and living environment, crustaceans are an excellent model for studying comparative genomics of retrotransposons. It is notably in the squat lobsters that the GalEa clade of Superfamily Copia was defined. We studied the distribution of two well-known LTR retrotransposons superfamilies: Gypsy and Copia, in crustaceans. By combining PCRs with degenerate primers and in silico analysis, we identified 35 families of Copia retrotransposons and 46 families of Gypsy retrotransposons in 15 and 18 species of crustaceans (mainly Malacostraca: crabs, shrimp, krill ...). These elements have different distribution and diversity in crustaceans. Gypsy elements appear relatively commonly and diverse in all species. Conversely, the Copia elements seem rare, and consequently more difficult to detect, and are largely dominated by the elements of the clade GalEa. These results suggest two different dynamic strategies for retrotransposons Gypsy (the Red Queen theory) and retrotransposons GalEa (‘domino days spreading’ branching process). In addition, GalEa elements present a great evolutionary success being widely distributed in many branches of metazoans. They are also present in certain red algae and we have also detected them in Fungi. Taking advantage of the large amount of available genomic data, we have studied the distribution of GalEa elements of Fungi, in order to compare it with the results obtained in crustaceans. In fact, they appear only in a large phylum of Ascomycetes, in Pezizomycotina, and they form a monophyletic group within the GalEa. Finally, in the Fungi, the GalEa elements are not majority among Copia retrotransposons. We have therefore initiated a new study in molluscs, to define if the results obtained in crustaceans are a feature of GalEa elements, Malacostraca or metazoans.
Les éléments transposables jouent un rôle majeur dans l’évolution des génomes eucaryotes. La connaissance de la distribution des éléments transposables entre différentes espèces au sein d’un même taxon est une condition essentielle pour étudier leur dynamique et mieux comprendre leur rôle dans l'évolution des espèces. Compte tenu de leur abondance, de leur diversité spécifique et de milieu de vie, les crustacés sont un excellent modèle pour étudier la génomique comparative des rétrotransposons. C’est notamment chez les Galathées qu’a été défini le clade GalEa des éléments de la superfamille des Copia. Nous avons étudié la distribution de deux superfamilles de rétrotransposons à LTR bien connus: les Gypsy et les Copia, au sein des crustacés. En combinant des PCRs avec amorces dégénérées et des analyses in silico, nous avons identifié 35 familles de rétrotransposons Copia et 46 familles de rétrotransposons Gypsy dans respectivement 15 et 18 espèces de crustacés (principalement des malacostracés : crabes, crevettes, krill...). Ces éléments présentent une distribution et une diversité différentes au sein des crustacés. Les éléments Gypsy apparaissent relativement fréquents et diversifiés dans toutes les espèces. A l’inverse, les éléments Copia semblent rares, donc difficilement détectables, et sont largement dominés par les éléments du clade GalEa. Ces résultats suggèrent deux stratégies différentes de dynamique pour les rétrotransposons Gypsy (théorie de la Reine Rouge) et les rétrotransposons GalEa (‘domino days spreading’ branching process). De plus, les éléments GalEa présentent un grand succès évolutif en étant largement distribués dans de nombreuses branches de métazoaires. Ils sont aussi présents chez quelques algues rouges et nous en avons également détecté chez des Fungi. Profitant des nombreuses données génomiques disponibles, nous avons donc étudié la distribution des éléments GalEa de Fungi, dans le but de comparer celle-ci aux résultats obtenus chez les crustacés. En fait, ils n’apparaissent qu’au sein d’un grand embranchement d’ascomycètes, les Pezizomycotina, et ils forment un groupe monophylétique au sein des GalEa. Enfin, chez les Fungi, les éléments GalEa ne sont pas majoritaire parmi les rétrotransposons Copia. Nous avons donc initié une nouvelle étude chez les mollusques, afin de définir si les résultats obtenus chez les crustacés sont une caractéristique des éléments GalEa, des malacostracés ou des métazoaires.
https://tel.archives-ouvertes.fr/tel-01132413

NNT : 2015PA066017
tel-01132413
https://tel.archives-ouvertes.fr/tel-01132413
https://tel.archives-ouvertes.fr/tel-01132413/document
https://tel.archives-ouvertes.fr/tel-01132413/file/these_archivage_2600252o.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Long-term exposure to air pollution (AP) has been shown to have an impact on mortality in numerous countries, but since 2005 no data exists for France. We analyzed the association between long-term exposure to air pollution and mortality at the individual level in a large French cohort followed from 1989 to 2013. The study sample consisted of 20,327 adults working at the French national electricity and gas company EDF-GDF. Annual exposure to PM10, PM10–2.5, PM2.5, NO2, O3, SO2, and benzene was assessed for the place of residence of participants using a chemistry-transport model and taking residential history into account. Hazard ratios were estimated using a Cox proportional-hazards regression model, adjusted for selected individual and contextual risk factors. Hazard ratios were computed for an interquartile range (IQR) increase in air pollutant concentrations. The cohort recorded 1967 non-accidental deaths. Long-term exposures to baseline PM2.5, PM10-25, NO2 and benzene were associated with an increase in non-accidental mortality (Hazard Ratio, HR = 1.09; 95% CI: 0.99, 1.20 per 5.9 μg/m3, PM10-25; HR = 1.09; 95% CI: 1.04, 1.15 per 2.2 μg/m3, NO2: HR = 1.14; 95% CI: 0.99, 1.31 per 19.3 μg/m3 and benzene: HR = 1.10; 95% CI: 1.00, 1.22 per 1.7 μg/m3).The strongest association was found for PM10: HR = 1.14; 95% CI: 1.05, 1.25 per 7.8 μg/m3. PM10, PM10-25 and SO2 were associated with non-accidental mortality when using time varying exposure. No significant associations were observed between air pollution and cardiovascular and respiratory mortality. Long-term exposure to fine particles, nitrogen dioxide, sulfur dioxide and benzene is associated with an increased risk of non-accidental mortality in France. Our results strengthen existing evidence that outdoor air pollution is a significant environmental risk factor for mortality. Due to the limited sample size and the nature of our study (occupational), further investigations are needed in France with a larger representative population sample.
ISSN: 0160-4120

hal-01187145
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01187145
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01187145/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01187145/file/Association%20between%20long-term%20exposure%20to%20air%20pollution%20and%20mortality_accepted.pdf
DOI : 10.1016/j.envint.2015.08.006

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We have performed tri-axial compression experiments on olivine aggregates at 900 °C and at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus. Deformation at two different constant strain rates (1.1 × 10− 5 s− 1 and 3.4 × 10− 4 s− 1) yields continuous hardening, reaching maximal differential stresses of 930 and 1076 MPa, respectively, before sample failure at ca. 10% strain. The deformed samples were characterized by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Crystallographic preferred orientations (CPO) are weak but reveal an alignment of the [010] axes around the compression direction and some concentration of [001] and [100] axes normal to it. TEM observations confirm plastic deformation by dislocation glide, with both [001] and [100] Burgers vectors. Electron tomography, performed for the first time on deformed fined-grained olivine, shows that [001] dislocations glide extensively on {110} and {130} planes, in complement to the (010) and (100) glide planes often reported at high temperatures. [100] dislocations glide mostly on (010), but {011} and {041} planes are also activated. The experimental CPO and relative activity of slip systems are well reproduced by viscoplastic self-consistent simulations in which all [100] and [001] slip systems have similar strengths. They are also consistent with olivine CPO from natural samples deformed at low temperature. Comparison of the present mechanical results to those obtained for olivine single-crystals at similar conditions shows that at low temperature (below 1100 °C) and high stress (> 300 MPa) polycrystalline olivine has a more complex mechanical behavior than single crystals. However, both datasets advocate for a much weaker dry mantle lithosphere than previously thought.
ISSN: 0040-1951

hal-01053513
https://hal.archives-ouvertes.fr/hal-01053513
DOI : 10.1016/j.tecto.2014.03.022

Éditeur(s) : HAL CCSD
Résumé : Among erosion processes, river incision is classicaly described as a key process controlling erosion of landscapes. Incision efficiency is mainly influenced by climate and erodibility. This latter is not only dependent on the nature of the bedrock, but also on its past deformation, which affects its rheological effective properties, such as fracture density. The main objectives of this thesis are: (1) to better constrain the relationship between effective properties and erodibility, and (2) to quantify the influence of erodibility and erosion on both the temporal and spatial building or decay of the topography. Several numerical tools are developed. A 1D formalism of landscape evolution is introduced, including river incision with stochastic distribution of water discharge and hillslope landsliding. A new remeshing algorithm called Surface Lagrangian Remeshing (SLR) is developed as a complement to remeshing algorithms dealing with internal elements. It allows one to take into account long-term erosion into 2D Lagrangian numerical codes based on triangular finite elements. Then the potentiality of measuring erodibility in-situ using a Schmidt hammer (R) is assessed for the active orogen of Taiwan, the diagenetic Annot sandstones and St Clement fault zone. Results suggest a strong control of R by effective properties. A linear model based on effective medium theory is applied to a fault zone with an unmacthed resolution (750 measures, 25 measures per square meter). The model successfully correlates R to fracture density. These results demonstrate that effective elasticity as well as erodibility are sensitive to the density and type of fractures. Finally I focus on the erosional and rheological conditions that allows reproducing post-orogenic evolution of mountain belts. A model coupling surface erosion and regional isostatic uplift is consistent with observations. The topographic decay and decrease of the ratio of surface elevation over crustal root thickness is at first order controlled by the initial geometry of the mountain belt and erosion efficiency. This new model highlights the control ofclimate and erodibility on the topographic decay and of lithospheric rheology on the perseverance of crustal roots.
Parmi les processus d'érosion, l'incision des rivières est classiquement décrit comme un processus clé contrôlant l'érosion des paysages. L'efficacité de l'incision est principalement influencée par le climat et par l'érodabilité. Ce dernier paramètre ne dépend pas seulement de la nature du substratum rocheux, mais aussi de sa déformation passée qui affecte ses propriétés rhéologiques équivalentes. Les principaux objectifs de cette thèse sont: (1) de mieux contraindre les relations entre propriétés équivalentes et érodabilité, et (2) de quantifier l'influence de l'érosion et de l'érodabilité sur la formation ou la décadence, spatiale et temporelle, de la topographie. Plusieurs outils numériques sont développés. Un formalisme 1D d'évolution des paysages est proposé, prenant en compte simultanément l'incision des rivières avec une distribution stochastique des débits en eau et l'érosion des versants par glissements de terrain. Un nouvel algorithme de remaillage appelé Surface Lagrangian Remeshing (SLR) est développé. Il permet de prendre en compte l'érosion à long terme dans les codes numériques 2D Lagrangiens basés sur des éléments finis triangulaires. Ensuite, la possibilité de mesurer in-situ l'érodabilité avec un marteau de Schmidt (R) est évaluée pour: l'orogène actif de Taiwan, les grès diagénétiques d'Annot et la zone de faille de St Clément. Les résultats suggèrent un fort contrôle de R par les propriétés équivalentes des roches testées. Un modèle linéaire, basé sur la théorie des milieux équivalents, est appliqué à une zone de faille avec une résolution inégalée (750 mesures, 25 mesures par mètre carré). Le modèle permet de corréler avec succès la densité de fracture et R. Ces résultats démontrent empiriquement que l'élasticité équivalente ainsi que l'érodabilité sont sensibles à la densité et à la nature des fractures. Enfin j'étudie les conditions d'érosion et de rhéologie qui permettent de reproduire l'évolution des chaînes de montagnes post-orogéniques. Un modèle couplant érosion en surface et soulèvement isostatique régional est compatible avec les observations. Les taux de décroissance topographique et de diminution du rapport de l'élévation de surface sur l'épaisseur de racine crustale sont contrôlés au premier ordre par la géométrie initiale de la chaîne de montagne et par l'efficacité de l'érosion. Ce nouveau modèle met en évidence le contrôle du climat et de l'érodabilité sur la décroissance topographique et de la rhéologie lithosphérique sur la persévérance des racines crustales.
https://tel.archives-ouvertes.fr/tel-00602341

tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341/document
https://tel.archives-ouvertes.fr/tel-00602341/file/thesephilippesteer.pdf

Éditeur(s) : HAL CCSD
Résumé : This paper presents the experimental results obtained for an automatic detection of ships in High Resolution optical satellite images. Our images are panchromatic SPOT 5 images, whose resolution is 5m per pixel. Our detection method is part of an industrial project of maritime surveillance. It is based on the Bayesian decision theory and does not need any preprocessing.The detection is composed of three stages. The first one is a pre-detection of targets that gives us candidates. The second one is a precise segmentation of each candidate. The third one is a classification of candidates into three classes : real small targets, real big targets and false alarms. The two first stages are based on the bayesian theory, using a very simple image model that leads to very fast algorithms. For now, the classification is based on multivariate decision tree. Finally, the overall results of the method are given for a set of images, as close as possible to the operational conditions and show the performances of the proposed method (detection of almost all the ships, false alarms due to crests of waves and an acceptable computing time).
Journée Nationale de Photogrammétrie et Télédétection

hal-00601854
https://hal.archives-ouvertes.fr/hal-00601854