International Journal of Agricultural Research, Innovation and Technology (IJARIT)
International Journal of Agricultural Research, Innovation and Technology (IJARIT)Not a member yet
12720 research outputs found
Sort by
Médiatisations d'une question de santé publique et journalisme scientifique face à l’épreuve des faits. Cas du traitement de la Covid-19 dans les médias audiovisuels au Cameroun
No full textInternational audienc
Towards a holistic sulfate-water-O2 triple oxygen isotope systematics.
No full text13 pagesInternational audienceTriple oxygen isotope (∆17O with δ18O) signals of H2O and O2 found in sulfate of oxidative weathering origin offer promising constraints on modern and ancient weathering, hydrology, atmospheric gas concentrations, and bioproductivity. However, interpretations of the sulfate-water-O2 system rely on assuming fixed oxygen-isotope fractionations between sulfate and water, which, contrastingly, are shown to vary widely in sign and amplitude. Instead, here we anchor sulfate-water-O2 triple oxygen isotope systematics on the homogeneous composition of atmospheric O2 with empirical constraints and modeling. Our resulting framework does not require a priori assumptions of the O2- versus H2O‑oxygen ratio in sulfate and accounts for the signals of mass-dependent and mass-independent fractionation in the ∆17O and δ18O of sulfate's O2‑oxygen source. Within this framework, new ∆17O measurements of sulfate constrain ~2.3 Ga Paleoproterozoic gross primary productivity to between 6 and 160 times present-day levels, with important implications for the biological carbon cycle response to high CO2 concentrations prevalent on the early Earth
Conception optimisée d’un microgrid isolé à forte intégration renouvelable avec objectif de fiabilité
No full textOff-grid electrical systems are a promising solution to power remote areas, where the lack of electricity access represents a barrier to development. This thesis focuses on isolated microgrids, which are small electrical systems designed to power regions that lack a connection to the main electricity grid. These microgrids, comprising photovoltaic arrays, diesel generators and storage systems are more fragile, and users can experience frequent interruptions if the system is not designed properly. Reliability is thus a critical criterion to ensure viable microgrid projects with a real impact on living conditions for the concerned populations. A multi-objective optimisation method is therefore proposed to design these microgrids considering three objectives: economical, environmental and reliability. The method uses a genetic algorithm to make the configuration of the microgrid evolve towards and optimum and enables visualising trade-offs between all design objectives. All microgrid components including generators, power converters, storage systems and control units are modelled on an energetic scale. The results have shown that reliability can be optimised with a high level of renewable integration with little extra cost. The consideration for component failure has been seen to be beneficial as they impact overall reliability. Reliability is often evaluated in the literature solely regarding power adequacy. The method was then adapted to enable evolutive sizing of microgrids, which has been observed to improve the overall performance. By enabling smaller initial sizing with progressive repowering, the overall long-term cost can be reduced while optimising solicitation on system components. A sensibility analysis has enabled identifying the parameters with high impact on optimisation results. Load consumption evolution is a main uncertainty, whose impact can be reduced with the proposed evolutive sizing.Les solutions d’électrification hors-réseaux sont en pleine expansion dans les zones isolées de la planète où l'absence d'accès à l'électricité représente un frein principal au développement. Cette thèse se concentre sur les microgrids isolés qui sont des petits réseaux électriques destinés à alimenter des zones n’ayant pas de raccordement possible au réseau de distribution principal. Ces microgrids isolés, fonctionnant à base de production solaire, de groupes électrogènes et de stockage par batteries, sont cependant plus fragiles et les utilisateurs peuvent subir des interruptions fréquentes si le réseau n'est pas conçu avec précaution. La fiabilité est donc un critère important pour assurer d’une part la viabilité de ces projets et d’autre part pour permettre l’amélioration des conditions de vie des populations. Ainsi, il est proposé une méthode de conception multi-objective de ces microgrids isolés sur les critères économique, environnemental, et de fiabilité. La méthode utilise un algorithme génétique pour faire évoluer la configuration du microgrid vers un optimum et permet de visualiser les compromis entre les trois objectifs. Une modélisation énergétique du système est utilisée pour l’ensemble des composants du microgrid et des différentes briques de contrôle. Les résultats ont montré que la fiabilité peut être optimisée avec un taux d’intégration renouvelable très important et un coût maîtrisé. Il y a un intérêt à prendre en compte les pannes des composants qui ont un impact sur l’indisponibilité globale subie par les microgrids, les méthodes retrouvées dans la littérature se focalisant généralement seulement sur un critère d’adéquation production-consommation. L’adaptation de la méthode pour permettre un dimensionnement évolutif des microgrids a permis d’optimiser davantage la performance en permettant un dimensionnement initial plus faible et des renforcements possibles au fur et à mesure de la vie du projet. L’impact sur le coût long-terme est important tout en optimisant les sollicitations des composants aux différents stades d’évolution du système. Une analyse de sensibilité a permis de mettre en avant les facteurs d’impact les plus importants. L’évolution de la consommation est une forte incertitude, donc l’impact peut être réduit par le dimensionnement évolutif proposé dans cette thèse
Case study of a mesospheric inversion over Maïdo observatory through a multi-instrumental observation
No full textInternational audienceMesospheric temperature inversions are subject to investigations due to the links with multiscale dynamics such as planetary wave and gravity waves. Knowing the impact on climatological inversions also requires understanding the phenomena occurring before, through, and after a mesospheric inversion. We use data obtained during a measurement campaign over Maïdo observatory in La Réunion Island and focus on a specific event occurring in the night between the 9th and the 10th of October 2017. Among the several observations available, LIDAR measurements provided vertical profiles of temperature and gravity waves potential energy completed by high vertical resolution radiosoundings. The airglow layer observed by an InGaAs camera shows the evolution of gravity wave structures at about 87 km between 0.9 and 1.7 km. Gravity wave parameters such as horizontal wavelengths or intensity emission variations are extracted, along with potential energy compared with LIDAR data. We use atmospheric models (ERA5, WACCM, WRF) and specific tools (NEMO, GROGRAT) to add supplementary information about the night selected. We present here the first results related to the gravity waves and energy exchanges in the frame of the temperature inversion
Destructive outbreaks of the corallivorous starfish Acanthaster cf. solaris spare coral assemblages in the shallowest reef flat areas in New Caledonia
No full textInternational audienceAbstract Outbreaks of the corallivorous starfish Acanthaster cf. solaris (COTS) are not fully understood, especially in the shallowest areas behind the reef crests where limited COTS impacts are often reported. Here, we investigated the outbreak occurrence and compared post-outbreak habitat impacts in reef flats vs. upper fore reefs at 13 sites in New Caledonia. In this Pacific territory so far considered marginally affected by COTS, we documented wide occurrences of aggregations, combining massive population increases (maximum 605 COTS per swim, abundances >100 COTS recorded in 46% of the sites) with limited spatiotemporal boundaries. Abundance levels met the highest values in the literature, but were restricted to relatively small, isolated mid-shelf reefs. Typical residence time was short (< two years), with at least one site where COTS seemingly disappeared within seven months. The spread of COTS population and subsequent impacts appeared self-contained, and never affected the reef flats (0.5–1.5 m). The transition to severely affected fore reefs was abrupt, with live coral cover divided by nine and morphological diversity halved within a very few meters (3–5 m). We suggest that these differential impacts likely result from harsh environmental conditions making shallow, coral-rich areas less suitable for COTS, thereby pushing predation pressure further downwards
The Nurse Plant Acacia spirorbis Enriches Ectomycorrhizal Community Composition of a Target Species: Tristaniopsis calobuxus
No full textInternational audienceWe investigated the suitability of Acacia spirorbis Labill., a tropical ectomycorrhizal (ECM) tree, as a nurse plant to improve the growth of Tristaniopsis calobuxus Brongn. & Gris seedlings for the restoration of nickel mines in New Caledonia. Rehabilitation of nickel mines in New Caledonia is a major concern. In such harsh soil conditions, ectomycorrhizal (ECM) symbiosis is important for tree growth, survival, and resistance. To improve ecological restoration in New Caledonia, new technical itineraries have undergone experimentation using ECM as a plant nurse, allowing ECM saplings to rapidly acquire a wide range of ECM fungi. We transplanted ECM seedlings of Tristaniopsis calobuxus from the nursery to bare ferralitic soils harbouring some scattered 12-year-old Acacia spirorbis to be used as ECM nurse plants. Using molecular characterisation of ITS rDNA, we characterised ECM fungal communities of A. spirorbis and of T. calobuxus saplings at transplanting time and 13 months later. We observed changes in the composition of fungal communities of T. calobuxus with an increase in diversity, notably the appearance of operational taxonomic units (OTUs) affiliated with /russula, /boletus and /pisolithus-scleroderma and a decrease in ubiquitous nursery order such as /sebacina. We also observed a higher number of shared OTUs between T. calobuxus and A. spirorbis. The vicinity of A. spirorbis enabled diversification and adaptation of the T. calobuxus ECM fungal community. These results led us to recommend A. spirorbis as a good nurse tree candidate in the framework of ecological restoration of mine sites
La zone de libre-échange continentale Africaine (ZLECAF) nécessite une politique d'intelligence économique
No full textAvec la création de la zone de libre-échange continentale Africaine (ZLECAF), les Etats membres se sont fixé comme objectif entre autres : le renforcement de la compétitivité de leurs économies aux niveaux continental et mondial.Dans cet article, l’auteur met en lumière la nécessité d’une politique d’intelligence économique adaptée aux réalités du continent, la présentant comme un levier pouvant permettre aux pays Africains d’atteindre cet objectif
Metallome deregulation and health-related impacts due to long-term exposure to recent volcanic ash deposits: New chemical and isotopic insights
No full textInternational audienceVolcanic ash exposure can lead to significant health risks. Damage to the respiratory and pulmonary systems are the most evident toxic side effects although the causes of these symptoms remain unclear. Conversely, the effects on other organs remain largely under-explored, limiting our understanding of the long-term volcanic ash-related risk at the whole-body scale. The metallome i.e. metal concentrations and isotopic compositions within the body, is suspected to be affected by volcanic ash exposure, having thus the potential for capturing some specificities of ash toxicity. However, the means by and extent to which the metallome is affected at the entire body scale and how the consequent chemical and isotopic deregulations correlate with pathophysiological dysfunctions are currently poorly understood. Here, we adopt a transdisciplinary approach combining high precision chemical analyses (major and trace element concentrations) and Cusingle bondZn isotope measurements in seven organs and two biological fluids of isogenic mice (C57BL/6) exposed to eruption products from La Soufrière de Guadeloupe (Eastern Carribean), in tandem with biological parameters including physiological and morphological data. Based on principal component analysis, we show that after one month of exposure to volcanic ash deposits, the mice metallome; originally organ-specific and isotopically-typified, is highly disrupted as shown for example by heavy metal accumulation in testis (e.g., Fe, Zn) and Cu, Zn isotopic divergence in liver, intestine and blood. These metallomic variations are correlated with early testicular defects and might reflect the warning signs of premature (entero)hepatic impairments that may seriously affect fertility and favor the emergence of liver diseases after prolonged exposure. Monitoring the temporal evolution of the Cu and Zn isotope compositions seems to be a promising technique to identify the main biological processes and vital functions that are vulnerable to environmental volcanogenic pollutants although this will require further validation on human subjects
Decoupling of inorganic and organic carbon during slab mantle devolatilisation
No full textInternational audienceSerpentinites are an important sink for both inorganic and organic carbon, and their behavior during subduction is thought to play a fundamental role in the global cycling of carbon. Here we show that fluid-derived veins are preserved within the Zermatt-Saas ultra-high pressure serpentinites providing key evidence for carbonate mobility during serpentinite devolatilisation. We show through the O, C, and Sr isotope analyses of vein minerals and the host serpentinites that about 90% of the meta-serpentinite inorganic carbon is remobilized during slab devolatilisation. In contrast, graphite-like carbonaceous compounds remain trapped within the host rock as inclusions within metamorphic olivine while the bulk elemental and isotope composition of organic carbon remains relatively unchanged during the subduction process. This shows a decoupling behavior of carbon during serpentinite dehydration in subduction zones. This process will therefore facilitate the transfer of inorganic carbon to the mantle wedge and the preferential slab sequestration of organic carbon en route to the deep mantle
: Voir la pandémie comme une période de subjectivation des troubles autistiques
No full textIl semble assez vain désormais, au bout d’un an et demie de pandémie mondiale, et de passages de confinements-dé/re-confinements variés, locaux, académiques ou nationaux, de ne plus considérer ce phénomène comme un fait social total. La réponse médicale pour gérer cette crise se heurte aux représentations sociales qui font obstacles aux attentes médicales (Rousselon, 2012), aux préconisations et aux protocoles sociétaux pour se soigner (Keck, Kelly et Lynteris, 2019). Les risques de mises à distance de certaines populations et l'identification d’un “bouc émissaire” (Sidéris, 2020) et l’accentuation de clivages sociétaux sont réels. Ainsi, la maladie est vécue dans sa dimension anthropologique et culturelle comme une rupture identitaire et sociale avec la communauté, aboutissant à un isolement mortifère et à la perte de signification du lien social. Lefer Sauvage et Mercier (2021) mentionnent d'ailleurs un glissement sémantique intéressant dans le discours des enseignants pour tenter de s’approprier le protocole sanitaire en vigueur dans les écoles, en mentionnant désormais une « distance sociale » plutôt qu’une « distance physique », et en oubliant les indicateurs métriques de référence (une distance d’un mètre devient « La Distance »). Nous adoptons donc ici une posture pragmatique (Auray, 2016) qui consiste à penser que « toute redescription prend la forme d'une recontextualisation, dont l'objectif est de connecter l'objet redécrit avec une nouvelle théorie explicative, une nouvelle classe de comparaison, un nouveau vocabulaire descriptif » (Michel, 2011, p. 66). En tant que psychologues, nous tentons de poser un diagnostique de cet état de fait qu’est la pandémie et considérons que cette pandémie traumatisante peut-être vue (au sens de Wittgenstein, 2004) comme mettant la société dans le quotidien d'enfants présentant des troubles autistiques. Alors que les institutions, les professionnels, les associations et les familles sont dans « l’attente » d’un potentiel Plan Autisme V, nous inventons ici, au regard du phénomène pandémique, les grandes lignes de ce que ce plan pourrait devenir, toujours dans une articulation subtile entre le phénomène social de la pandémie et celui de l’autisme, considérant qu’une dialectique est possible. C'est à travers un ensemble d'enquêtes (Genevois et al., 2020 ; Mercier, 2020 ; Lefer Sauvage et al., 2020) et de témoignages que nous constituons les grandes lignes de ce Cinquième Plan autisme