31 research outputs found
El cĂłmic es cosa seria. El cĂłmic como mediaciĂłn para la enseñanza en la educaciĂłn superior Caso Universidad Nacional, Universidad de MedellĂn y Universidad Pontificia Bolivariana
El problema planteado en esta investigaciĂłn es estudiar el posible uso del cĂłmiccomo mediaciĂłn para la enseñanza en la educaciĂłn superior. Su objetivo es establecerlas condiciones y caracterĂsticas que debe tener el cĂłmic para enseñar. El trabajoconsidera una muestra referenciada de informantes, y se desarrolla por medio deobservaciones, entrevistas en profundidad, redacciĂłn de diarios de campo y estudio defuentes documentales. Las principales conclusiones son que el cĂłmic tiene potencialdidĂĄctico, que ha sido poco utilizado para enseñar, y que las instituciones de educaciĂłnsuperior deben propiciar su uso, e investigar para validar este potencial. Se plantea unapropuesta didĂĄctica para fomentar la utilizaciĂłn del cĂłmic en la educaciĂłn superior.Los tres proponentes de esta investigaciĂłn son docentes y utilizan la imagen en suslabores educativas
Dynamique des flux sĂ©dimentaires et des Ă©lĂ©ments mĂ©talliques en lien avec lâexploitation courante et exceptionnelle dâun barrage hydroĂ©lectrique
Dam reservoir contexts concentrate social, economic and environmental issues. Their presence modifies both natural water and sediments continuity. Water level can be stable or fluctuate according to hydrological cycles and exploitation, leading to more or less pronounced sediments and associated contaminants remobilization. In such context, this work aims at studying spatio-temporal changes in concentrations, fluxes as well as speciation of metallic elements during natural and anthropologically-driven sediments accumulation and resuspension phases. For this purpose, a 19 months field survey was performed upstream and downstream from the dam during both routine and exceptional exploitation. The water and sediments quality during two sluicing events, performed in order to re-erode deposited reservoir sediments and flush them downstream through the bottom valves of the dam during high flows, were notably monitored. As for the influence of the main physicochemical parameters (i.e., solid/liquid ratio, pH, redox potential, drying) on metallic elements fate and speciation as well as the different processes involved, they were studied through laboratory experiments, statistical analyses and modeling. Results highlighted that during routine exploitation, dam presence leads to a significant discontinuity in metallic element dissolved concentrations, fluxes and speciation, mainly through pH changes magnified by water flow artificial lowering. During sluicing management, the high local pH, redox and S/L changes of the downstream water, mainly following maximum sediments release, enhance As, Fe and Mn solubilization through desorption or metallic oxydes dissolution. Nevertheless, given the overall low mobility of the metallic elements and bearing phases stability, dissolved fluxes remain far lower than particular ones. Recurrent sluicing management permits to minimize sediments and metallic fluxes, limiting toxicity towards aquatic biota.Les retenues de barrage sont lâobjet dâenjeux sociĂ©taux, Ă©conomiques et environnementaux. Leur prĂ©sence affecte le transit naturel de lâeau et de la charge sĂ©dimentaire associĂ©e. Selon les cycles hydrologiques et leur exploitation, la remobilisation des sĂ©diments accumulĂ©s et des contaminants associĂ©s est plus ou moins marquĂ©e. Dans ce contexte, cette Ă©tude a pour principal objectif de dĂ©terminer lâĂ©volution des teneurs, flux et spĂ©ciation des Ă©lĂ©ments mĂ©talliques au cours des phases dâaccumulation et de remobilisation sĂ©dimentaire naturelles et influencĂ©es. Pour ce faire, une Ă©tude de terrain de 19 mois Ă lâamont et Ă lâaval de lâouvrage a Ă©tĂ© effectuĂ©e en conditions courantes et Ă©vĂ©nementielles dâexploitation. Le suivi de deux opĂ©rations de chasses dâhydrocurage, destinĂ©es Ă lâĂ©vacuation des sĂ©diments de la retenue par ouverture des vannes de fond du barrage en pĂ©riode de hautes eaux, a notamment Ă©tĂ© rĂ©alisĂ©. Lâimpact des diffĂ©rents paramĂštres physicochimiques (ratio solide/liquide, pH, potentiel redox, sĂ©chage) sur le devenir et la spĂ©ciation des Ă©lĂ©ments mĂ©talliques ainsi que les diffĂ©rents mĂ©canismes associĂ©s ont quant Ă eux Ă©tĂ© Ă©valuĂ©s Ă lâaide dâexpĂ©riences de laboratoire, dâĂ©tudes statistiques et de modĂ©lisation. Les rĂ©sultats ont montrĂ© quâen pĂ©riode dâexploitation courante, la prĂ©sence de lâouvrage induit une discontinuitĂ© amont/aval des teneurs, flux et partition des Ă©lĂ©ments mĂ©talliques, amplifiant notamment lâinfluence du pH sur leur spĂ©ciation et mobilitĂ© du fait de lâartificialisation des conditions dâĂ©coulement. Lors des opĂ©rations dâexploitation Ă©vĂ©nementielle par chasse dâhydrocurage, la modification des conditions de pH, dâoxydorĂ©duction et de ratio S/L au sein du cours dâeau aval lors du passage de la charge sĂ©dimentaire augmente les teneurs en As, Fe et Mn solubilisĂ©s via des phĂ©nomĂšnes de dĂ©sorption et de dissolution des oxydes mĂ©talliques. NĂ©anmoins, Ă©tant donnĂ© la faible mobilitĂ© des Ă©lĂ©ments mĂ©talliques et la stabilitĂ© des phases porteuses, les flux dissous restent minoritaires par rapport aux flux particulaires. La rĂ©alisation frĂ©quente des opĂ©rations de chasse permet de minimiser les flux sĂ©dimentaire et mĂ©tallique mis en jeu au cours du temps, limitant par consĂ©quent son impact sur le cours dâeau aval
Influence of routine and exceptional exploitation of a hydroelectric dam on sediments and metallic elements dynamics
Les retenues de barrage sont lâobjet dâenjeux sociĂ©taux, Ă©conomiques et environnementaux. Leur prĂ©sence affecte le transit naturel de lâeau et de la charge sĂ©dimentaire associĂ©e. Selon les cycles hydrologiques et leur exploitation, la remobilisation des sĂ©diments accumulĂ©s et des contaminants associĂ©s est plus ou moins marquĂ©e. Dans ce contexte, cette Ă©tude a pour principal objectif de dĂ©terminer lâĂ©volution des teneurs, flux et spĂ©ciation des Ă©lĂ©ments mĂ©talliques au cours des phases dâaccumulation et de remobilisation sĂ©dimentaire naturelles et influencĂ©es. Pour ce faire, une Ă©tude de terrain de 19 mois Ă lâamont et Ă lâaval de lâouvrage a Ă©tĂ© effectuĂ©e en conditions courantes et Ă©vĂ©nementielles dâexploitation. Le suivi de deux opĂ©rations de chasses dâhydrocurage, destinĂ©es Ă lâĂ©vacuation des sĂ©diments de la retenue par ouverture des vannes de fond du barrage en pĂ©riode de hautes eaux, a notamment Ă©tĂ© rĂ©alisĂ©. Lâimpact des diffĂ©rents paramĂštres physicochimiques (ratio solide/liquide, pH, potentiel redox, sĂ©chage) sur le devenir et la spĂ©ciation des Ă©lĂ©ments mĂ©talliques ainsi que les diffĂ©rents mĂ©canismes associĂ©s ont quant Ă eux Ă©tĂ© Ă©valuĂ©s Ă lâaide dâexpĂ©riences de laboratoire, dâĂ©tudes statistiques et de modĂ©lisation. Les rĂ©sultats ont montrĂ© quâen pĂ©riode dâexploitation courante, la prĂ©sence de lâouvrage induit une discontinuitĂ© amont/aval des teneurs, flux et partition des Ă©lĂ©ments mĂ©talliques, amplifiant notamment lâinfluence du pH sur leur spĂ©ciation et mobilitĂ© du fait de lâartificialisation des conditions dâĂ©coulement. Lors des opĂ©rations dâexploitation Ă©vĂ©nementielle par chasse dâhydrocurage, la modification des conditions de pH, dâoxydorĂ©duction et de ratio S/L au sein du cours dâeau aval lors du passage de la charge sĂ©dimentaire augmente les teneurs en As, Fe et Mn solubilisĂ©s via des phĂ©nomĂšnes de dĂ©sorption et de dissolution des oxydes mĂ©talliques. NĂ©anmoins, Ă©tant donnĂ© la faible mobilitĂ© des Ă©lĂ©ments mĂ©talliques et la stabilitĂ© des phases porteuses, les flux dissous restent minoritaires par rapport aux flux particulaires. La rĂ©alisation frĂ©quente des opĂ©rations de chasse permet de minimiser les flux sĂ©dimentaire et mĂ©tallique mis en jeu au cours du temps, limitant par consĂ©quent son impact sur le cours dâeau aval.Dam reservoir contexts concentrate social, economic and environmental issues. Their presence modifies both natural water and sediments continuity. Water level can be stable or fluctuate according to hydrological cycles and exploitation, leading to more or less pronounced sediments and associated contaminants remobilization. In such context, this work aims at studying spatio-temporal changes in concentrations, fluxes as well as speciation of metallic elements during natural and anthropologically-driven sediments accumulation and resuspension phases. For this purpose, a 19 months field survey was performed upstream and downstream from the dam during both routine and exceptional exploitation. The water and sediments quality during two sluicing events, performed in order to re-erode deposited reservoir sediments and flush them downstream through the bottom valves of the dam during high flows, were notably monitored. As for the influence of the main physicochemical parameters (i.e., solid/liquid ratio, pH, redox potential, drying) on metallic elements fate and speciation as well as the different processes involved, they were studied through laboratory experiments, statistical analyses and modeling. Results highlighted that during routine exploitation, dam presence leads to a significant discontinuity in metallic element dissolved concentrations, fluxes and speciation, mainly through pH changes magnified by water flow artificial lowering. During sluicing management, the high local pH, redox and S/L changes of the downstream water, mainly following maximum sediments release, enhance As, Fe and Mn solubilization through desorption or metallic oxydes dissolution. Nevertheless, given the overall low mobility of the metallic elements and bearing phases stability, dissolved fluxes remain far lower than particular ones. Recurrent sluicing management permits to minimize sediments and metallic fluxes, limiting toxicity towards aquatic biota
Le fluor dans les roches métamorphiques du Massif Central français
Roques Maurice, Tempier Paul, FrĂ©mion Monique, Aubert Daniel. Le fluor dans les roches mĂ©tamorphiques du Massif Central français. In: PhĂ©nomĂšnes de transport de matiĂšre dans l'Ă©corce terrestre. ATP - CNRS. Action thĂ©matique ProgrammĂ©e du Centre National de la Recherche Scientifique. RĂ©sultats scientifiques. Strasbourg : Institut de GĂ©ologie â UniversitĂ© Louis-Pasteur, 1979. pp. 95-100. (Sciences GĂ©ologiques. MĂ©moire, 53
Le fluor dans les roches métamorphiques du Massif Central français
Roques Maurice, Tempier Paul, FrĂ©mion Monique, Aubert Daniel. Le fluor dans les roches mĂ©tamorphiques du Massif Central français. In: PhĂ©nomĂšnes de transport de matiĂšre dans l'Ă©corce terrestre. ATP - CNRS. Action thĂ©matique ProgrammĂ©e du Centre National de la Recherche Scientifique. RĂ©sultats scientifiques. Strasbourg : Institut de GĂ©ologie â UniversitĂ© Louis-Pasteur, 1979. pp. 95-100. (Sciences GĂ©ologiques. MĂ©moire, 53
Amalgam is a ligand for the transmembrane receptor neurotactin and is required for neurotactin-mediated cell adhesion and axon fasciculation in Drosophila
Neurotactin (NRT), a member of the cholinesterase-homologous protein family, is a heterophilic cell adhesion molecule that is required for proper axon guidance during Drosophila development. In this study, we identify amalgam (AMA), a member of the immunoglobulin superfamily, as a ligand for the NRT receptor. Using transfected Schneider 2 cells and embryonic primary cultures, we demonstrate that AMA is a secreted protein. Furthermore, AMA is necessary for NRT-expressing cells both to aggregate with themselves and to associate with embryonic primary culture cells. Aggregation assays performed with truncated NRT molecules reveal that the integrity of the cholinesterase-like extracellular domain was not required either for AMA binding or for adhesion, with only amino acids 347â482 of the extracellular domain being necessary for both activities. Moreover, the NRT cytoplasmic domain is required for NRT-mediated adhesion, although not for AMA binding. Using an ama-deficient stock, we find that ama function is not essential for viability. Pupae deficient for ama do exhibit defasciculation defects of the ocellar nerves similar to those found in nrt mutants
NiCo Buster: Engineering E. coli for fast and efficient capture of cobalt and nickel
cited By 11International audienceBackground: Metal contamination is widespread and results from natural geogenic and constantly increasing anthropogenic sources (mainly mining and extraction activities, electroplating, battery and steel manufacturing or metal finishing). Consequently, there is a growing need for methods to detoxify polluted ecosystems. Industrial wastewater, surface water and ground water need to be decontaminated to alleviate the contamination of soils and sediments and, ultimately, the human food chain. In nuclear power plants, radioactive metals are produced; these metals need to be removed from effluents before they are released into the environment, not only for pollution prevention but also for waste minimization. Many physicochemical methods have been developed for metal removal from aqueous solutions, including chemical coagulation, adsorption, extraction, ion exchange and membrane separation; however, these methods are generally not metal selective. Bacteria, because they contain metal transporters, provide a potentially competitive alternative to the current use of expensive and high-volume ion-exchange resins.Results: The feasibility of using bacterial biofilters as efficient tools for nickel and cobalt ions specific remediation was investigated. Among the factors susceptible to genetic modification in Escherichia coli, specific efflux and sequestration systems were engineered to improve its metal sequestration abilities. Genomic suppression of the RcnA nickel (Ni) and cobalt (Co) efflux system was combined with the plasmid-controlled expression of a genetically improved version of a specific metallic transporter, NiCoT, which originates from Novosphingobium aromaticivorans. The resulting strain exhibited enhanced nickel (II) and cobalt (II) uptake, with a maximum metal ion accumulation of 6 mg/g bacterial dry weight during 10 min of treatment. A synthetic adherence operon was successfully introduced into the plasmid carrying the improved NiCoT transporter, conferring the ability to form thick biofilm structures, especially when exposed to nickel and cobalt metallic compounds.Conclusions: This study demonstrates the efficient use of genetic engineering to increase metal sequestration and biofilm formation by E. coli. This method allows Co and Ni contaminants to be sequestered while spatially confining the bacteria to an abiotic support. Biofiltration of nickel (II) and cobalt (II) by immobilized cells is therefore a promising option for treating these contaminants at an industrial scale
âNiCo Busterâ: engineering E. coli for fast and efficient capture of cobalt and nickel
BACKGROUND: Metal contamination is widespread and results from natural geogenic and constantly increasing anthropogenic sources (mainly mining and extraction activities, electroplating, battery and steel manufacturing or metal finishing). Consequently, there is a growing need for methods to detoxify polluted ecosystems. Industrial wastewater, surface water and ground water need to be decontaminated to alleviate the contamination of soils and sediments and, ultimately, the human food chain. In nuclear power plants, radioactive metals are produced; these metals need to be removed from effluents before they are released into the environment, not only for pollution prevention but also for waste minimization. Many physicochemical methods have been developed for metal removal from aqueous solutions, including chemical coagulation, adsorption, extraction, ion exchange and membrane separation; however, these methods are generally not metal selective. Bacteria, because they contain metal transporters, provide a potentially competitive alternative to the current use of expensive and high-volume ion-exchange resins. RESULTS: The feasibility of using bacterial biofilters as efficient tools for nickel and cobalt ions specific remediation was investigated. Among the factors susceptible to genetic modification in Escherichia coli, specific efflux and sequestration systems were engineered to improve its metal sequestration abilities. Genomic suppression of the RcnA nickel (Ni) and cobalt (Co) efflux system was combined with the plasmid-controlled expression of a genetically improved version of a specific metallic transporter, NiCoT, which originates from Novosphingobium aromaticivorans. The resulting strain exhibited enhanced nickel (II) and cobalt (II) uptake, with a maximum metal ion accumulation of 6Â mg/g bacterial dry weight during 10Â min of treatment. A synthetic adherence operon was successfully introduced into the plasmid carrying the improved NiCoT transporter, conferring the ability to form thick biofilm structures, especially when exposed to nickel and cobalt metallic compounds. CONCLUSIONS: This study demonstrates the efficient use of genetic engineering to increase metal sequestration and biofilm formation by E. coli. This method allows Co and Ni contaminants to be sequestered while spatially confining the bacteria to an abiotic support. Biofiltration of nickel (II) and cobalt (II) by immobilized cells is therefore a promising option for treating these contaminants at an industrial scale