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Redox variations in glass manufacturing: effects of oxygen fugacity and temperature on glass and melt properties
No full textInternational audienceAt the time of the energy transition, it is important to modify the manufacturing conditions of glasses, in particular by reducing the CO 2 footprint. How do changes in the oxygen fugacity of a furnace affect the redox and properties of glass and melts? In this short article, we present redox calculations for some glass compositions and property measurements on a simplified low-iron glass composition. The increase in glass transition temperature by 10°C when the redox ratio Fe 3+ /(Fe 2+ +Fe 3+ ) changes from 0.4 to 0.73 highlights the role of iron as a network-former in glass.</div
Intense and localized export of selected marine snow types at eddy edges in the South Atlantic Ocean
No full textInternational audienceAbstract. The biological carbon pump (BCP) comprises a wide variety of processes involved in transferring organic carbon from the surface to the deep ocean. This results in long-term carbon sequestration. Without the BCP, atmospheric CO2 concentrations would be around 200 ppm higher. This study reveals that ocean dynamics at the mesoscale and submesoscale could have a major impact on particulate organic matter (POM) vertical distribution. Our results indicate that intense submesoscale frontal regions, such as those between mesoscale eddies, could lead to an important accumulation and transport of POM from the mixed-layer depth (MLD) down to the mesopelagic zone. To reach these conclusions, a multifaceted approach was applied. It included in situ measurements and marine snow images from a BGC-Argo float equipped with an Underwater Vision Profiler (UVP6), satellite altimetry data, and Lagrangian diagnostics. We focused our study on three intense features in marine snow distribution, observed during the 17-month-long float mission in the Cape Basin in the southwest of Africa. These features were located in the frontal region between mesoscale eddies. Our study suggests that a particle injection pump induced by a frontogenesis-driven mechanism has the potential to enhance the effectiveness of the biological pump by increasing the depth at which carbon is injected into the water column. This work also emphasizes the importance of establishing repeated sampling campaigns targeting the interface zones between eddies. This could improve our understanding of the mechanisms involved in the deep accumulation of marine snow observed at eddy interfaces
LA MONNAIE ET ATTRAIT TOURISTIQUE EN REPUBLIQUE DEMOCRATIQUE DU CONGO Présenté par : LUNDA NGANDU Jacques Directeur : TSHITUNGU KONGOLO Antoine Professeur Ordinaire Co-promoteur : KEBA GUMBA Guy
No full textGeochemical signatures of forearc serpentinites from oceanic to continental subduction
No full textInternational audienceIn subduction systems, the forearc (FA) serpentinized mantle plays a key role as a reservoir for fluid-mobile elements, especially those prone to early mobilisation from the slab. FA serpentinites therefore provide an indication of the fluid characteristics that have been steamed out of the slab, and allow better quantification of elemental recycling and fluid flow. FA serpentinites outcropping along the Indus Suture Zone are formed by hydration of mantle peridotites by fluids derived from the Indian slab, providing a geochemical record of fluidrock interactions during the India-Eurasia convergence. Systematic trace and multi-isotope (Sr and Pb) analyses of serpentinites from three major sites, namely Shergol-Tingdo, Kargil and Tso Morari, along the Indus Suture Zone in Ladakh (NW Himalaya) show that these rocks record a major change in the origin of metasomatic agents, from oceanic to continental subduction. The Shergol-Tingdo and Kargil FA serpentinites, formed under low temperature and pressure conditions, are characterised by high B enrichment and As and Sb depletion, high alkali/U ratios and relatively unradiogenic Sr and Pb isotope ratios. These geochemical characteristics are identical to those reported for modern oceanic subduction zones (e.g., Mariana forearc) and are consistent with input by fluids derived from subducted oceanic crust. In contrast, FA serpentinites from the Tso Morari ultra-high pressure unit show enrichment in fluid mobile elements such as As, Sb and U, low alkali/U ratios and radiogenic Sr and Pb isotopic compositions. These features suggest a change in the metasomatizing agent with a strong influence from subducted continental material. Consistent with this scenario, the Sr-Pb isotopic composition of the Kargil FA serpentinites can be reproduced by mixing between an Indian MORB-depleted mantle source and fluids derived from dewatering of blueschist facies oceanic metasediments, whereas in the case of Tso Morari a fluid end-member derived from various eclogitic continental metasediments is required. We propose that the observed geochemical signature of the Indus Suture Zone FA serpentinites can be used to reconstruct the geochemical exchanges between the slab and the overlying mantle from intra-oceanic to continental subduction. This successful systematic approach could be applied to other collisional contexts.</div
Tourisme noir ou religieux à Lubumbashi ? Cas du prison KASOMBO
No full textLa ville de Lubumbashi connut sous le nom de la ville cuprifère suite à son activité minière reconnue mondialement depuis l’époque coloniale cache beaucoup d’autres richesses à présenter au monde entier. Cette destination reçoit de plus en plus de visiteurs attirés autant par les minerais que par le tourisme. Ainsi les hôtels naissent du jour au lendemain prouvant la forte demande touristique. Au-delà des autres formes de tourisme existant, on retrouve dans cette ville le« tourisme noir » (John Lennon et Malcolm foley,1996) qui prend de l’ampleur. Ce phénomène consiste à visiter les lieux liés à la mort, à la souffrance, à la visite des prisons, des champs des batailles, des bidonvilles, etc. la ville de Lubumbashi à participer à la disparition tragique du héros national Patrice Emery Lumumba et du prisonnier qui a passé plus de temps d’incarcération d’Afrique soit 30 ans à la personne de Simon Kibangu dans la prison Kasombo recevant un mauvais traitement des coups des fouets chaque matin1. Cet endroit à l’image de la souffrance endurée par le prophète attire des foules des visiteurs de différents horizons. Cette étude vise à répondre aux interrogations suivante : s’agit-il du tourisme religieux ou noir à la prison Kasombo ? tous les visiteurs viennent-t-il pour la prière personnelle ? Pour y arriver, nous allons recourir à la méthode descriptive suivis des interviews et entretien avec le personnel du site
Are LSTM and conceptual rainfall-runoff models able to cope with limited training datasets under diverse hydrometeorological conditions?
No full textInternational audienceAs climate change exacerbates variability and non-stationarity in rainfall patterns, it is crucial to assess the predictive capabilities of forecasting models. Previous researches on rainfall-runoff modeling have focused on the impact of training dataset size on Artificial Neural Networks (ANNs) results, with limited consideration of hydrometeorological diversity. This study first evaluates the influence of the training dataset length (1 to 15 years) on performance of a Long Short-Term Memory (LSTM) and a traditional conceptual model, Superflex, across 10 validation years. Next, training years are categorized based on hydrometeorological diversity (wetter, standard, drier). This clustering allows for experiments where models are trained on data from similar or different clusters, enhancing understanding of how data diversity, and therefore climate change, can affect model performance. Results indicate that the LSTM model is highly sensitive to training length, showing poor performance with short datasets (below three years), reaches similar performance to Superflex around six training years on average, and overperforms with 15 years of training. Conversely, Superflex maintains rather constant performance levels regardless of the dataset length. LSTM model benefits from diverse 1 training data, achieving higher accuracy and reliability when trained on years with diverse hydrological typology. Despite their potential to outperform traditional models (with six or more training years on average), LSTM models are highly dependent on the quality and diversity of training data. In climate change scenarios, caution is needed when applying LSTM models to unfamiliar conditions, as their predictive accuracy may decline more rapidly than that of more traditional hydrological models
E-mail Overload: Exploring Employees’ Experiences using E-mail during Worktime and Leisure Time and Consequences for their Subjective Well-being
No full textInternational audienc
Teachers and didactics of plurilingualism – attitudes, practices and digital perspectives
No full textInternational audienceEuropäische Sprachenpolitik, sei es auf der Ebene des Europarats oder der Europäischen Union, fördert seit Jahren mehrsprachige Bildung durch Referenzrahmen, Zielsetzungen und Empfehlungen. Vor kurzem noch (2022) veröffentlichte der Europarat eine Empfehlung «zur Bedeutung der plurilingualen und interkulturellen Bildung für die demokratische Kultur». Trotz allem setzt sich in der Praxis mehrsprachige Bildung (insbesondere im Sekundarbereich) noch schwer durch und die Ergebnisse dieser Politik bleiben unzureichend. Die Empfehlung des Rates der europäischen Union aus dem Jahr 2019 «zu einem umfassenden Ansatz für das Lehren und Lernen von Sprachen» betont explizit die «fehlende Mehrsprachenkompetenz» der Bevölkerung in der EU. Auf der Basis einer europaweiten Umfrage, die 2024 im Rahmen des ERASMUS+ Projekts PEP (Promouvoir l’éducation plurilingue / Förderung der mehrsprachigen Bildung) durchgeführt wurde, soll gezeigt werden, was Sprachlehrende von Mehrsprachigkeit und mehrsprachiger Bildung halten und was sie in diesem Bereich konkret mit den Lernenden unternehmen. Es sollen ebenfalls Möglichkeiten aufgezeigt werden, wie digitale Aufgabentypen und die Nutzung digitaler Ressourcen mehrsprachige Sprachnutzung in den Vordergrund stellen können
Social-ecological system approach relevant for modelling the ecological niche of a mangrove gastropod at small regional scale
No full textInternational audienceThe gastropod Terebralia palustris is found in mangroves from the Indo-Pacific, where it plays important ecological roles and is fished by humans. As such, it reflects interactions occurring within the socio-ecosystem, although information regarding its regional distribution and ecological niche is uneven. The present study aimed at defining the relative importance of factors of the mangrove socio-ecological system (MSES) on the realized niche of T. palustris at the regional scale. We studied its distribution at the scale of Mayotte Island (France, Indian Ocean), including local ecological knowledge and environmental memory held by population. To this end, a survey campaign of the 29 mangroves of Mayotte allowed mapping its occurrence and correlating the spatial pattern to factors of the MSES related to three dimensions of the niche (accessibility, abiotic, and biotic) pertaining to both societal and ecological components. Questionnaire interviews revealed both past presence and current presence undetected by the survey campaign. At the scale of Mayotte, the gastropod is found on large and deep mangroves, distant from the sea by a deep central and external mangrove, where Avicennia marina is not the only mangrove tree species and the canopy is relatively opened, at the bottom of watersheds holding large urban areas. Our study showed that dealing with both ecosystemic and societal subsystems and their involvement in each dimension of the niche concept is a promising way of understanding the drivers of species distribution in anthropized system
Construction et (dé)légitimation des savoirs et des représentations dans la gouvernance évolutive du “risque requin” (La Réunion)
No full textThis interdisciplinary study explores humanities and social sciences expertise commissionedand later contested by the State regarding shark risk in Réunion Island. The appointed expertimplemented a participatory framework with transformative aims and authored a novel toexpose power dynamics while circumventing institutional pressures. The dual communicationapproach (scientific expertise and literary narrative) is discussed with both the expert-authorand the state commissioning authority. Referring to the theory of evolutionary governance,this study illustrates how power-knowledge forms related to risk management are contestedand reconfigured in a context of public controversy.Cette étude interdisciplinaire porte sur une expertise en sciences humaines et socialescommanditée puis contestée par l’État, sur le risque requin à La Réunion. L’expert mandaté adéployé un dispositif participatif à visée transformative et rédigé un roman pour y révéler desrapports de pouvoir en contournant les pressions institutionnelles. Le double dispositifcommunicationnel (expertise scientifique et récit littéraire) est discuté avec l’expert-auteur etle commanditaire étatique. Se référant à la théorie de la gouvernance évolutive, cette étudeillustre comment des formes de pouvoir-savoir sur la gestion des risques sont contestées etreconfigurées dans un contexte de controverse publique