Journal of Next-Generation Research 5.0
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CHAPITRE 3. L'efficacité de la « politique » maritime africaine dans le contexte de l'économie bleue
No full textInternational audienceAbstract: The appropriation of the concept of the «blue economy» by African states has radically change their perception of the sea. Today, the sea is considered as a pillar of sustainable economic growth and of the well-being of African populations. The ambitions of developing the blue economy and building continental maritime integration expressed in the 2050 African Integrated Maritime Strategy (AIM 2050) and the Lomé charter, the foundations of what is referred to here as African maritime «policy», are a mark of this new era of the continent's maritime history. The key to achieving the goals is the full commitment of African states to promoting the blue economy. The purpose of this reflection is to show that the effectiveness of the African maritime «policy» depends on the degree of African states' individual, collective and concrete commitment to enhancing the sea. They are then the masters of success or the causes of failure
Textural, thermal, and topographic constraints on lava flow system structure: the December 2010 eruption of Piton de la Fournaise
No full textco-auteur étrangerInternational audienceIn this study, we examine the channel-fed ‘a‘ā lava flow system that was emplaced during a very short (less than 15 h long) eruptionat Piton de la Fournaise (La Réunion) in December 2010. The system had four branches, the longest of which was 1100 m long.Three brancheswere emplaced over a smooth-surfaced pāhoehoe flow fieldwith a vertical relief of 1–2mand did not undergo burialby subsequent events. The fourth branch erupted from the same vent as the 1957 eruption and re-used the pre-existing channels ofthat eruption. In the proximal–medial sections of the three systems that were unconfined, we identified channelized flow sectionsthat were characterized by the presence of either a single channel or multiple braided channels. These fed short (30–260 m long)zones of dispersed flow in the distal sections. We subsequently investigated the role of lava rheology (as controlled by downflowvariations in crystal and bubble content) and pre-existing topography in triggering the transitions between single-channel andbraided channel flow sections. Crystal content was 10 to 70 vol% and vesicle content was 18 to 55 vol%; cooling rates overdistance (derived from glass chemistry) were 11 °C/km to 27 °C/km. However, downflow textural and thermal evolution appearedto neither affect, nor be affected by, whether the channel was single or braided. Instead, the channel network architecture could berelated to even modest underlying slope variations. Here, a slope increase resulted in channel confluence, and a slope decreaseresulted in channel bifurcation. This process was reversible, in that downflow slope variation could drive the channel networkarchitecture to switch back and forth between a single channel and multiple braided channels several times along its length.Dispersed flow is always present immediately behind the flow front, irrespective of underlying topography. Three previous studiesof basaltic lava flows found that steeper slopes favored braided channels, the opposite of what was observed here.We suggest thatthe underlying substrate and lava type may exert a control on this behavior, but further studies remain necessary
Benthic nitrite exchanges in the Seine River (France) An early diagenetic modeling analysis
No full textInternational audienceNitrite is a toxic intermediate compound in the nitrogen (N) cycle. Elevated concentrations of nitrite have been observed in the Seine River, raising questions about its sources and fate. Here, we assess the role of bottom sediments as potential sources or sinks of nitrite along the river continuum. Sediment cores were collected from two depocenters, one located upstream, the other downstream, from the largest wastewater treatment plant (WWTP) servicing the conurbation of Paris. Pore water profiles of oxygen, nitrate, nitrite and ammonium were measured. Ammonium, nitrate and nitrite fluxes across the sediment-water interface (SWI) were determined in separate core incubation experiments. The data were interpreted with a one-dimensional, multi-component reactive transport model, which accounts for the production and consumption of nitrite through nitrification, denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA). In all core incubation experiments, nitrate uptake by the sediments was observed, indicative of high rates of denitrification. In contrast, for both sampling locations, the sediments in cores collected in August 2012 acted as sinks for nitrite, but those collected in October 2013 released nitrite to the overlying water. The model results suggest that the first step of nitrification generated most pore water nitrite at the two locations. While nitrification was also the main pathway consuming nitrite in the sediments upstream of the WWTP, anammox dominated nitrite removal at the downstream site. Sensitivity analyses indicated that the magnitude and direction of the benthic nitrite fluxes most strongly depend on bottom water oxygenation and the deposition flux of labile organic matter
Augmenter les synergies opérationnelles entre les réseaux d'observation de la Terre: opportunités pour faire progresser la modélisation de la dynamique du système terrestre
No full text[Departement_IRSTEA]Eaux [ADD1_IRSTEA]Hydrosystèmes et risques naturelsInternational audienceAdvancing our understanding of Earth system dynamics (ESD) depends on the development of models and other analytical tools that apply physical, biological, and chemical data. This ambition to increase understanding and develop models of ESD based on site observations was the stimulus for creating the networks of Long-Term Ecological Research (LTER), Critical Zone Observatories (CZOs), and others. We organized a survey, the results of which identified pressing gaps in data availability from these networks, in particular for the future development and evaluation of models that represent ESD processes, and provide insights for improvement in both data collection and model integration. From this survey overview of data applications in the context of LTER and CZO research, we identified three challenges: (1) widen application of terrestrial observation network data in Earth system modelling, (2) develop integrated Earth system models that incorporate process representation and data of multiple disciplines, and (3) identify complementarity in measured variables and spatial extent, and promoting synergies in the existing observational networks. These challenges lead to perspectives and recommendations for an improved dialogue between the observation networks and the ESD modelling community, including co-location of sites in the existing networks and further formalizing these recommendations among these communities. Developing these synergies will enable cross-site and cross-network comparison and synthesis studies, which will help produce insights around organizing principles, classifications, and general rules of coupling processes with environmental conditions
Using Boolean factors for the construction of an artificial neural networks
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Das lastentragen im heutigen Afrika- vom weltlichen zum heiligen Tragen. Ainige persönliche Beobachtungen
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Long-Range Transport of Water Channelized through the Southern Subtropical Jet
No full textInternational audienceIn this study, an air mass (containing a cirrus cloud) was detected by light detection and ranging (lidar) above São Paulo (Brazil) in June 2007 and tracked around the globe, thanks to Lagrangian calculations as well as ground-based and satellite observations. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data were also used to provide locations of occurrence of cirrus around the globe and extract their respective macro physical parameters (altitude and temperature). An analysis of the air mass history based on Lagrangian trajectories reveals that water coming from the Equator is channelized through the southern subtropical jet for weeks. In this case, the back-trajectories showed that the cirrus cloud detected at São Paulo was a mixture of air masses from two different locations: (1) the active convective area located around theEquator, with transport into the upper troposphere that promotes cirrus cloud formation; and (2) the South Pacific Ocean, with transport that follows the subtropical jet stream (STJ). Air masses coming from equatorial convective regions are trapped by the jet, which contributes to maintaining the lifetime of the cirrus cloud for a few days. The cloud disappears near the African continent, due to a southern excursion and warmer temperatures, then reappears and is detected again by the lidar system in São Paulo after 12 days. The observed cloud is located at a similar altitude, revealing that sedimentation is small or compensated by radiative uplift
Diversity and assemblage structure of tropical marine flora on lava flows of different ages
No full textInternational audienceRecent volcanic lava flows extending into the ocean represent an ideal opportunity to study the long-term successional development of marine floral assemblages on the bare new substratum. We describe the floral assemblages of nine lava flows of different ages (prehistoric to 2007) at Piton de la Fournaise (Reunion Island, Indian Ocean) based on a survey of 37 stations. We identified 159 species including 148 macroalgae, 1 seagrass, and 10 cyanobacteria. Fifty-one of those represent new records for Reunion Island, and at least 9 taxa were identified as new to science. Recent lava flows were characterized by the dominance of ephemeral, opportunistic species, such as Pseudobryopsis hainanensis and Acrocladus dotyanus, while prehistoric lava flows were mainly characterized by perennial species, particularly Sargassum portiericuzum and Turbinaria ornata. A canonical correspondence analysis revealed that the environmental factor that most significantly correlated to the variation in floral assemblages was the distance to the most recent lava flow (2007). This factor was also highly correlated to coral cover. The composition of the different floral assemblages is discussed in relation to abiotic and biotic factors to explain ecological succession in a tropical environment
Lire des vies. L’approche biographique en lettres et en sciences humaines et sociales
No full textInternational audienceCet ouvrage collectif constitue les actes d’un colloque qui a réuni autour de la question biographique des chercheurs de diverses disciplines, à Saint-Denis de La Réunion, du 22 au 24 février 2017. Le genre biographique y apparaît comme un objet d’enquêtes de terrain tout autant que d’investigations littéraires, artistiques, historiques, communicationnelles, etc. Il est également un support de réflexions épistémologique, théorique et méthodologique, riche d’apport pour la recherche. À partir de singularités diverses, ces quinze contributions, recueillies et introduites par B. Idelson et I. Babou, donnent à voir des parcours de vie « ordinaire » et révèlent des manières de les appréhender au sein de tensions contemporaines qui traversent l’ensemble des sciences humaines et sociales et des lettres : individu vs collectif, sujet vs structure, biographique vs contextualisation, etc. En retraçant l’histoire de ces vies, en les replaçant dans les mondes sociaux qu’elles révèlent, en observant les ressorts et les ressources de l’énonciation de tels récits, les auteur.es suggèrent une approche, plutôt pragmatique, pour lire des vies