International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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Thermal properties measurement of two tropical wood species as a function of their water content using the parallel hot wire method
No full textInternational audienceThe water content of material can affect it thermal properties. The aim of this work was to study the thermal behavior of two tropical wood species namely Ayous and Tali. with their water content. The gravimetric method was used to estimate the water content of these species. The parallel hot-wire method was used as a direct technique to simultaneously measure the thermal properties and water content of the sample at the time of measurement. A comparison between the results obtained by the parallel hot wire method and those obtained by the gravimetric method was carried out. The gap between the water content given by the gravimetric method and that of the parallel hot wire is less than 6% for water conditions above 10% water content. These results testified that parallel hot wire method can be used to estimate water content in hygroscopic materials. A linear increase in thermal conductivity and volumetric heat capacity with water content was observed
Evidence that Pacific tuna mercury levels are driven by marine methylmercury production and anthropogenic inputs
No full textInternational audiencePacific Ocean tuna is among the most-consumed seafood products but contains relatively high levels of the neurotoxin methylmercury. Limited observations suggest tuna mercury levels vary in space and time, yet the drivers are not well understood. Here, we map mercury concentrations in skipjack tuna across the Pacific Ocean and build generalized additive models to quantify the anthropogenic, ecological, and biogeochemical drivers. Skipjack mercury levels display a fivefold spatial gradient, with maximum concentrations in the northwest near Asia, intermediate values in the east, and the lowest levels in the west, southwest, and central Pacific. Large spatial differences can be explained by the depth of the seawater methylmercury peak near low-oxygen zones, leading to enhanced tuna mercury concentrations in regions where oxygen depletion is shallow. Despite this natural biogeochemical control, the mercury hotspot in tuna caught near Asia is explained by elevated atmospheric mercury concentrations and/or mercury river inputs to the coastal shelf. While we cannot ignore the legacy mercury contribution from other regions to the Pacific Ocean (e.g., North America and Europe), our results suggest that recent anthropogenic mercury release, which is currently largest in Asia, contributes directly to present-day human mercury exposure
Estimation et prédiction dans un modèle de régression linéaire semi-fonctionnelle spatiale avec dérivées
No full textEPIsciencesIn this paper, we tackle estimation and prediction at the non-visted sites in a spatial semi-functional linear regression model with derivatives that combines a functional linear model with a nonparametric regression model. The parametric part is estimated by a method of moments and the other one by a local linear estimator. We establish the convergence rate of the resulting estimators and predictor. A simulation study and application to ozone pollution prediction at the non-visted sites are proposed to illustrate our results.Dans cet article, nous abordons l'estimation et la prédiction à des sites non-visités dans un modèle de régression linéaire semi-fonctionnelle avec dérivées, qui combine un modèle linéaire fonctionnel avec celui de la régression non paramétrique. La partie paramétrique est estimée par une méthode des moments et l'autre par un estimateur linéaire local. Nous établissons la vitesse de convergence des estimateurs et prédicteur résultants. Une étude de simulation et une application à la prédiction de la pollution d'ozone à des sites non-visités, sont proposées pour illustrer nos résultats
Synergy between an emerging monopartite begomovirus and a DNA-B component
No full textInternational audienceIn recent decades, a legion of monopartite begomoviruses transmitted by the whitefly Bemisia tabaci has emerged as serious threats to vegetable crops in Africa. Recent studies in Burkina Faso (West Africa) reported the predominance of pepper yellow vein Mali virus (PepYVMLV) and its frequent association with a previously unknown DNA-B component. To understand the role of this DNA-B component in the emergence of PepYVMLV, we assessed biological traits related to virulence, virus accumulation, location in the tissue and transmission. We demonstrate that the DNA-B component is not required for systemic movement and symptom development of PepYVMLV (non-strict association), but that its association produces more severe symptoms including growth arrest and plant death. The increased virulence is associated with a higher viral DNA accumulation in plant tissues, an increase in the number of contaminated nuclei of the phloem parenchyma and in the transmission rate by B. tabaci. Our results suggest that the association of a DNA-B component with the otherwise monopartite PepYVMLV is a key factor of its emergence
Optimisation de la maintenance par la conception robuste de la modularité : Application au torréfacteur de soja
No full textFor a given piece of equipment, knowing its modular architecture has the advantage of facilitating its maintenance. Indeed, during a maintenance problem, we do not act on all the equipment, except on the faulty module and we also gain time to detect the observed fault. However, the definition of a good architecture is conditioned by a judicious choice of the design parameters, more specifically of the disassembly parameters because during the initial design phase, the constraints of disassembly are increasingly integrated to guarantee a good disassembly of equipment for maintenance purposes. Following the major difficulties in maintaining complex topology systems, the modular design is therefore an asset for companies. On the other hand, the modular design although it has advantages of standardization and reconfigurability is enormously expensive, which requires more resources, more time and more work of the designers. This has consequences for the maintenance of the equipment, because the more complex or denser the modules of the equipment, the more expensive the maintenance is. This thesis therefore aims to improve maintenance by designing modularity. Achieving this objective requires a methodology which consists first of evaluating the best design solution to assess the relevance of the design constraints chosen, then developing a tool which is based on the existing clustering algorithm, by having first presented the limits of the existing clustering algorithm and finally validate the proposed tool by observing a reduction in module coupling costs to guarantee good maintenance and deduce reconfiguration of the equipment.Pour un équipement donné, la connaissance de son architecture modulaire présente l’avantage de faciliter sa maintenance. En effet, lors d’un problème relevant de la maintenance, on n’agit pas sur tout l’équipement, sauf sur le module défaillant et on gagne aussi en temps pour détecter le défaut observé. Cependant, la définition d’une bonne architecture est conditionnée par un choix judicieux des paramètres de conceptions, plus spécifiquement des paramètres de désassemblage du fait que lors la phase initiale de conception, on intègre de plus en plus les contraintes de désassemblage pour garantir une bonne désassembilité des équipements pour des fins de maintenance. Suite aux difficultés majeures de maintenance des systèmes de topologies complexes, la conception modulaire est donc un atout pour les entreprises. D’autre part, la conception modulaire bien qu’elle présente des avantages de standardisation et de reconfigurabilité est énormément onéreuse, ce qui nécessite plus de ressources, plus de temps et plus de travail des concepteurs. Cela engendre des conséquences sur la maintenance des équipements, car plus les modules de l’équipement sont complexes ou plus denses, plus la maintenance est couteuse. Il est donc question dans cette thèse d’améliorer la maintenance par la conception de la modularité. L’atteinte de cet objectif passe par une méthodologie qui consiste d’abord à évaluer la meilleure solution de conception pour apprécier la pertinence des contraintes de conceptions choisies, ensuite développer un outil qui s’appuie sur l’algorithme de clustering existant , en ayant au préalable présenté les limites de l’algorithme de clustering existant et enfin valider l’outil proposé en observant une réduction en coûts de couplage des modules pour garantir une bonne maintenance et déduire une reconfiguration de l’équipement
Establishment of five new genera in the family Geminiviridae: Citlodavirus, Maldovirus, Mulcrilevirus, Opunvirus, and Topilevirus
No full textInternational audienceGeminiviruses are plant-infecting, circular single-stranded DNA viruses that have a geminate virion morphology. These viruses infect both cultivated and non-cultivated monocotyledonous and dicotyledonous plants and have a wide geographical distribution. Nine genera had been established within the family Geminiviridae (Becurtovirus, Begomovirus, Capulavirus, Curtovirus, Eragrovirus, Grablovirus, Mastrevirus, Topocuvirus, and Turncurtovirus) as of 2020. In the last decade, metagenomics approaches have facilitated the discovery and identification of many novel viruses, among them numerous highly divergent geminiviruses. Here, we report the establishment of five new genera in the family Geminiviridae (Citlodavirus, Maldovirus, Mulcrilevirus, Opunvirus, and Topilevirus) to formally classify twelve new, divergent geminiviruses
Structure, age, and tectonic evolution of the Gulf of Mexico
No full textInternational audienceThe Gulf of Mexico is an isolated oceanic basin whose nature, structure and age are not fully elucidated, mostly because seafloor spreading isochrons have not been identified in this basin so far. We compiled and processed all publicly available marine magnetic data to produce a new magnetic anomaly map of the Gulf of Mexico. This map reveals a fan-like set of intermediate-wavelength (>100 km) magnetic anomalies related to seafloor spreading. Our magnetic anomaly-based plate reconstructions (1) support a counterclockwise rotation of the Yucatán Block around a pole located NW of Cuba, (2) accommodate the fracture zone trends depicted by the gravity data, and (3) suggest that the Continent-Ocean Boundary lies immediately south of the Houston magnetic anomaly, close to the shoreline, implying that oceanic crust underlies a significant part of the Sigsbee salt province. Our attempt to identify the intermediate wavelength anomalies by comparison with filtered Geomagnetic Polarity Time Scales dates the onset of seafloor spreading before the Tithonian (>150 Ma) and its cessation at the Berriasian (140 Ma)
Influence of aphotic haloclines and euxinia on organic biomarkers and microbial communities in a thalassohaline and alkaline volcanic crater lake
No full textInternational audienceStudies on microbial communities, and their associated organic biomarkers, that are found thriving in the aphotic euxinic waters in modern stratified ecosystems are scarce compared to those undertaken in euxinic photic zones. The Dziani Dzaha (Mayotte,Indian Ocean) is a tropical, saline, alkaline crater lake that has recently been presentedas a modern analog of Proterozoic Oceans due to its thalassohaline classification (having water of marine origin) and specific biogeochemical characteristics. Continuous intense photosynthetic production and microbial mineralization keep most of the water column permanently aphotic and anoxic preventing the development of a euxinic (sulfidic and anoxic) photic zone despite a high sulfide/sulfate ratio and the presence of permanent or seasonal haloclines. In this study, the molecular composition of the organic matter in Lake Dziani Dzaha was investigated and compared to the microbial diversity evaluated through 16S rRNA gene amplicon sequencing, over two contrasting seasons (rainy vs. dry) that influence water column stratification. Depth profiles of organic biomarker concentrations (chlorophyll-a and lipid biomarkers) and bacterial and archaeal OTU abundances appeared to be strongly dependent on the presence of aphotic haloclines and euxinia. OTU abundances revealed theimportance of specific haloalkaliphilic bacterial and archaeal assemblages in phytoplanktonic biomass recycling and the biogeochemical functioning of the lake, suggesting new haloalkaline non-phototrophic anaerobic microbial precursors for some of the lipid biomarkers. Uncultured Firmicutes from the family Syntrophomonadaceae (Clostridiales), and Bacteroidetes from the ML635J-40 aquatic group, emerged as abundant chemotrophic bacterial members in the anoxic or euxinic waters and were probably responsible for the production of short-chain n-alkenes, wax esters, diplopterol, and tetrahymanol. Halocline-dependent euxinia also had a strong impact on the archaeal community which was dominated by Woesearchaeota in the sulfide-free waters. In the euxinic waters, methanogenic Euryarchaeota from the Methanomicrobia, Thermoplasmata, and WSA2 classes dominated and were likely at the origin of common hydrocarbon biomarkers of methanogens (phytane, pentamethyl-eicosenes, and partially hydrogenated squalene)
La relation école-famille à La Réunion
No full textFamily-school relationships are subject to many debates. In our research, we did not run out of resources. We noticed that this topic had an important place among educational issues. We studied how each entity represented itself. Our study led to two observations. First, parents expectations about scholarship for their child depend on their own school experience. Then, maintaining a high quality school-family relationship has a positive impact on student's learning.With the child’s academic success in mind, school and family must overcome the difficulties together to reach an agreement so as to end up with a caring and effective partnership. Coeducation is a principle based on a trustful relationship that values parents, children and teachers.On the one hand, we discovered that the quality of the school-family relationship depended on many aspects such as representations, and on the other hand, we found that quality played a role in student's learning. Our key question is the influence of the school-family relationship, the representations of parents and their involvement on learning. We attempted to tackle the issues by conducting surveys and interviews.In short, the results obtained show the need to create a partnership to improve the school environment.La relation famille-école fait l’objet de nombreuses discussions. Lors de nos recherches, nous n'avons pas manqué de ressources. Nous avons retenu ce thème car il tient une place importante parmi les enjeux éducatifs. Nous avons cherché à savoir comment chaque entité se représentait l’une l’autre. Nos travaux ont abouti à deux constats. D’abord, les attentes des parents envers l’école pour leur enfant dépendent de leur propre vécu scolaire. Ensuite, entretenir une relation école-famille de qualité impacte positivement les apprentissages des élèves.En ayant en tête la réussite scolaire de l’enfant, école et famille doivent surmonter ensemble des difficultés pour aboutir à une entente dans un partenariat bienveillant et efficace. La coéducation est un principe qui repose sur une relation de confiance qui valorise parents, enfants et enseignants.D’une part, nous avons observé que la qualité du lien école-famille dépendait de nombreux paramètres tels que les représentations, d'autre part nous avons constaté que la relation école- famille jouait un rôle dans les apprentissages des élèves. Notre problématique nous pousse à réfléchir sur l’influence de la relation école-famille, des représentations des parents et de leur implication sur les apprentissages. Nous avons tenté d'y répondre en menant des enquêtes grâce à des questionnaires et des entretiens.En somme, les résultats obtenus font état de la nécessité de créer un partenariat autour de l’écoute et de la bienveillance pour aboutir à l’amélioration du climat scolaire de l’établissement
Amniotic fluid peptides predict postnatal kidney survival in developmental kidney disease
No full textInternational audienceAlthough a rare disease, bilateral congenital anomalies of the kidney and urinary tract (CAKUT) are the leading cause of end stage kidney disease in children. Ultrasound-based prenatal prediction of postnatal kidney survival in CAKUT pregnancies is far from accurate. To improve prediction, we conducted a prospective multicenter peptidome analysis of amniotic fluid spanning 140 evaluable fetuses with CAKUT. We identified a signature of 98 endogenous amniotic fluid peptides, mainly composed of fragments from extracellular matrix proteins and from the actin binding protein thymosin-β4. The peptide signature predicted postnatal kidney outcome with an area under the curve of 0.96 in the holdout validation set of patients with CAKUT with definite endpoint data. Additionally, this peptide signature was validated in a geographically independent sub-cohort of 12 patients (area under the curve 1.00) and displayed high specificity in non-CAKUT pregnancies (82 and 94% in 22 healthy fetuses and in 47 fetuses with congenital cytomegalovirus infection respectively). Change in amniotic fluid thymosin-β4 abundance was confirmed with ELISA. Knockout of thymosin-β4 in zebrafish altered proximal and distal tubule pronephros growth suggesting a possible role of thymosin β4 in fetal kidney development. Thus, recognition of the 98-peptide signature in amniotic fluid during diagnostic workup of prenatally detected fetuses with CAKUT can provide a long-sought evidence base for accurate management of the CAKUT disorder that is currently unavailable