110 research outputs found
Dynamiques des paysages de la vallée du Yamé depuis 4000 ans. Contribution à la compréhension d'un géosystÚme soudano-sahélien. (Ounjougou, Pays dogon, Mali).
The main of objectives study of the landscape dynamic of the YamĂ© valley since 4000 years is to understand the genesis of landscapes and their changes since the societies are beginning to manage intensively the environment. Through this research, we contribute to the knowledge of African cultural landscapes taking into account anthropic and bioclimatic actions. The Yame Valley is located in the Sudano-Sahelian zone in central Mali. It is the main rivers of the Dogon Country. In order to respond to our problem, we choose for a thematic plan. In the first section, we present the framework and contexts of study. The second part consists of a chronostratigraphic presentation at high resolution. The third part is the analysis of fluvial system and hydro-sedimentary analyses thanks to (from grain-size distributions and micromorphology). The fourth part is a presentation of vegetation cover and their evolution (palynological, anthracological, carpological methods and analysis of signal fire). The fifth part is a synthesis of results, with a spatial and temporal interpretation of the valley Yame landscapes changes during four thousand years the past. This study reveals a progressive opening of landscapes associated with a change of appearance of vegetal species in relation with an aridification at the climate and the establishment agrosystems in the area. The vegetation has changed in the valley between different mosaics of savannas and woodlands which are gradually of Sudano-Sahelian character. Pyrophiles species are progressly more while farming emergence millet by the archaeobotanical data and seasonal anthropogenic fires. These analyses it is suggest landscapes scenarii that synthesize Dogon Country landscapes developments and the anthropic roles importance. Thus highlighted the growing the influence of societies in their environment during the past four millennia in West Africa leading to the buiding of cultural landscapes.Etudier les dynamiques des paysages de la vallĂ©e du YamĂ© depuis quatre milles ans consiste Ă comprendre la genĂšse des paysages et les changements qu'ils connaissent depuis que les sociĂ©tĂ©s commencent Ă intervenir de façon intensive sur le milieu. Nous souhaitons Ă travers cette recherche contribuer Ă la connaissance des paysages africains en tant qu'entitĂ© culturelle en tenant compte des actions anthropiques et bioclimatiques. La vallĂ©e du YamĂ© est localisĂ©e dans la zone soudano-sahĂ©lienne au centre du Mali. Elle est le principal cours d'eau du Pays dogon. Afin de rĂ©pondre Ă notre problĂ©matique, nous avons optĂ© pour un plan thĂ©matique. Dans une premiĂšre partie, nous prĂ©sentons le cadre et les contextes d'Ă©tudes. La deuxiĂšme partie consiste en une prĂ©sentation du cadre chronostratigraphique rĂ©alisĂ© Ă haute rĂ©solution. La troisiĂšme partie correspond Ă l'analyse des formations fluvio-palustres et des fonctionnements hydro-sĂ©dimentaires (Ă partir d'analyses granulomĂ©triques et micromorphologiques). La quatriĂšme partie est une prĂ©sentation des paysages vĂ©gĂ©taux et de leur Ă©volution, Ă partir des mĂ©thodes palynologiques, anthracologiques, carpologiques et de l'analyse du signal incendie. La cinquiĂšme partie repose sur une synthĂšse des rĂ©sultats, avec une interprĂ©tation spatio-temporelle des paysages de la vallĂ©e du YamĂ© depuis quatre mille ans. Cette recherche permet d'observer une ouverture progressive des paysages associĂ©e Ă un changement de physionomie des espĂšces qui doit ĂȘtre reliĂ©e Ă une aridification du climat et Ă la mise en place d'agrosystĂšmes dans la rĂ©gion. La vĂ©gĂ©tation a Ă©voluĂ© dans la vallĂ©e entre diffĂ©rentes mosaĂŻques de savanes et forĂȘts claires et/ou denses sĂšches qui sont progressivement Ă caractĂšre soudano-sahĂ©lien. Les espĂšces pyrophiles se dĂ©veloppent progressivement, en relation avec l'Ă©mergence d'une agriculture basĂ©e sur la culture du mil, attestĂ©e par l'archĂ©obotanique avec des feux saisonniers d'origine anthropique. Ces diffĂ©rentes analyses permettent de proposer des scenarii paysagers, qui synthĂ©tisent les Ă©volutions des paysages au Pays dogon et met en Ă©vidence le rĂŽle crucial des sociĂ©tĂ©s. Ainsi est mise en Ă©vidence l'influence croissante des hommes sur leur environnement en Afrique de l'Ouest, au cours de ces quatre derniers millĂ©naires qui aboutit Ă la construction de vĂ©ritables paysages culturels
A volcaniclastic deep-sea fan off La RĂ©union Island (Indian Ocean): Gradualism versus catastrophism
International audienceA new geophysical data set off La RĂ©union Island (western Indian Ocean) reveals a large volcaniclastic submarine fan developing in an open-ocean setting. The fan is connected to a torrential river that floods during tropical cyclones. Sediment storage at the coast is limited, suggesting that the sediments are carried directly to the basin. The fan morphology and turbidites in cores lead us to classify it as a sand-rich system mainly fed by hyperpycnal flows. In the ancient geological record, there are many examples of thick volcaniclastic successions, but studies of modern analogues have emphasized mechanisms such as debris avalanches or direct pyroclastic flow into the sea. Because the Cilaos deep-sea fan is isolated from any continental source, it provides information on architecture and noncatastrophic processes in a volcaniclastic deep-sea fan
Studying Past Deep-ocean Circulation and the Paleoclimate Record in the Gulf of Cadiz
Deep marine currents are strongly influenced by climatic changes. They also deposit, rework, and sort sediment, and can generate kilometer-scale sedimentary bodies (drifts). These drifts are made of thoroughly bioturbated, stacked sedimentary sequences called contourites [Gonthier et al., 1984]. As a consequence, change in the direction or intensity of currents can be recorded in the sediment
Developing a Chronology Integrating Archaeological and Environmental Data from Different Contexts: The Late Holocene Sequence of Ounjougou (Mali)
Premiers résultats d'une étude géophysique sur le flanc nord des glissements de Storegga (NorvÚge)
Metatranscriptomics and Pyrosequencing Facilitate Discovery of Potential Viral Natural Enemies of the Invasive Caribbean Crazy Ant, Nylanderia pubens
BACKGROUND: Nylanderia pubens (Forel) is an invasive ant species that in recent years has developed into a serious nuisance problem in the Caribbean and United States. A rapidly expanding range, explosive localized population growth, and control difficulties have elevated this ant to pest status. Professional entomologists and the pest control industry in the United States are urgently trying to understand its biology and develop effective control methods. Currently, no known biological-based control agents are available for use in controlling N. pubens. METHODOLOGY AND PRINCIPAL FINDINGS: Metagenomics and pyrosequencing techniques were employed to examine the transcriptome of field-collected N. pubens colonies in an effort to identify virus infections with potential to serve as control agents against this pest ant. Pyrosequencing (454-platform) of a non-normalized N. pubens expression library generated 1,306,177 raw sequence reads comprising 450 Mbp. Assembly resulted in generation of 59,017 non-redundant sequences, including 27,348 contigs and 31,669 singlets. BLAST analysis of these non-redundant sequences identified 51 of potential viral origin. Additional analyses winnowed this list of potential viruses to three that appear to replicate in N. pubens. CONCLUSIONS: Pyrosequencing the transcriptome of field-collected samples of N. pubens has identified at least three sequences that are likely of viral origin and, in which, N. pubens serves as host. In addition, the N. pubens transcriptome provides a genetic resource for the scientific community which is especially important at this early stage of developing a knowledgebase for this new pest
Altimetry for the future: Building on 25 years of progress
In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ââGreenâ Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instrumentsâ development and satellite missionsâ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion
Altimetry for the future: building on 25 years of progress
In 2018 we celebrated 25âŻyears of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology.
The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the âGreenâ Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instrumentsâ development and satellite missionsâ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion
Contribution à la commande stochastique d'un robot redondant sous contraintes d'environnement : application à l'assistance aux handicapés physiques
The work described in this thesis relates to the development of a manipulator mounted on an electric wheelchair. This document presents the different aspects studied during the achievement of teletheses, and more broadly during the achievement of cooperative robots. Avery special care is brought to problems relating to the operator's safety. This problem is divided into two sub-problems : the overahh reliability of the system and the collision avoidance. From this last point a new approach to collision avoidances is proposed/ "the randomized generation of trajectory in real time with restraining environment", which allows the operator to work in a non structured world. This method gives satisfaying results with some reservations and is compatible with an on line generation of trajectoriesaLes travaux proposés dans ce mémoire sont relatifs au développement d'un bras manipulateur embarqué sur fauteuil roulant électrique. Ce document présente les différents aspects abordés lors de la conception de téléthÚses et plus généralement de robots de coopération. Une attention particuliÚre est accordée aux problÚmes liés à la sécurité de l'opérateur. Ce problÚme est divisé en deux sous-problÚmes qui sont la fiabilisation générale du systÚme et l'évitement de collision. A partir de ce dernier point nous proposons une méthode innovante: la génération stochastique de trajectoires en temps réel avec contraintes d'environnement, qui permet à l'opérateur de man?uvrer dans un univers non structuré. Cette méthode donne des résultats satisfaisants sous certaines restrictions et est compatible avec une génération en ligne de trajectoir
Parlementarisme, Ă©loquence parlementaire et violence sous la DeuxiĂšme RĂ©publique
La rĂ©volution de fĂ©vrier 1848 sâest voulue, au prix dâun paradoxe fĂ©cond, la rĂ©volution de la concorde, prĂ©lude Ă lâĂ©tablissement de la « dĂ©mocratie pacifique ». Or, sâagissant de la violence et de la rĂ©solution des conflits socio-politiques, lâhistoire de la pĂ©riode 1848-1851 est celle dâun Ă©chec Ă©vident. TrĂšs rapidement, la jeune rĂ©publique est rattrapĂ©e par la violence. Celle, dâabord, des souvenirs invoquĂ©s par les acteurs eux-mĂȘmes : 93 et la Terreur supplantent vite 89 dans les harangue..
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