International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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Effects of sexual dimorphism on pollinator behaviour in a dioecious species
No full textData are available from the Dryad Digital Repository: (Moquet et al. 2021).International audienceFloral traits often display sexual dimorphism in insect-pollinated dioecious plant species, with male individuals typically being showier than females. While this strategy is theorized to be optimal when pollinators are abundant, it might represent a risk when they become scarce, because the disproportionately high number of visits on the most attractive sex, males, might preclude efficient pollen transfer from males to females. Here, the effect of sexual dimorphism on pollination efficiency was assessed in experimental arrays of dioecious Silene dioica that were exposed to one frequent visitor of the species, Bombus terrestris, and that differed in the magnitude of sexual dimorphism for either flower number or flower size. We found that flower number dimorphism negatively affected the number of visits on female plants, on female flowers and on the number of female flowers visited after a male flower. However, flower number dimorphism had no effect on the number of pollen grains deposited per stigma, presumably because the decrease in the number of visits to female flowers was compensated by a higher number of pollen grains deposited per visit. Flower size dimorphism did not affect visitation patterns and pollen transfer in our experimental arrays. These results highlight the need to jointly study visitation patterns and pollen receipt on stigmas when exploring the effect on floral phenotypes on pollination efficiency
A class of dynamic unilateral contact problems with sub-differential friction law
No full textInternational audienceWe study a class of dynamic unilateral contact problems with subdifferential friction law, and thermal effects, for time depending long memory viscoelastic materials, with or without the clamped condition. We describe the mechanical problem, derive its variational formulation, and after specifying the assumptions on the data and operators, we prove an existence and uniqueness of weak solution on displacement and temperature fields
Analyse de la croissance inclusive dans quelques pays du Maghreb
No full textInternational audienceCe papier analyse la croissance inclusive au sein de quelques Pays du Maghreb (Egypte, Tunisie, Maroc), de la période allant de 1980 jusqu'en 2019. Les données sont en Panel provenant de différentes bases de données (WDI, BAD, FMI,). Après estimation d'un modèle homogène, les résultats montrent que la croissance a été tout de même inclusive durant la période choisie
Forest Fragments, Lemur Communities and Local Perception of Nature in a Protected Area of Northwestern Madagascar
No full textInternational audienceBiological conservation projects conducted in inhabited areas are often based on the combination of ecological diagnostics and study of practices and use of the environment by local communities. They less frequently integrate the influence of the perception and representation of nature on these practices, while these should also be taken into account in the initiation of sustainable conservation actions. We carried out a long-term study combining biological and social science approaches in North-western Madagascar in the Antrema protected area (with dry forest/savannah/coastal ecosystems), including an analysis of the use and perception of nature by its inhabitants. Together with the study of tree diversity, forest structure and biomass in 7 forest fragments, we estimated population densities of whole communities of diurnal and nocturnal lemurs, one of which is considered sacred. We interviewed local resource users from several villages using classical methods of social anthropology supplemented with perception tests derived from sensory evaluation methods. The structure of forest fragments as well as their basal area and richness in tree species varied with human pressure on specific plants (timber extraction) or with historical changes in pasture management (forest regrowth). Lemurs were generally abundant, with a high total biomass compared to other dry forests. Although the inhabitants of Antrema (Sakalava, Tsimihety, and Betsileo) still strongly adhered to local use rights and shared deeply rooted knowledge about the forest, the use and perception of nature (e.g., regarding the sacred lemur Propithecus coronatus) have changed since the Antrema protection project in 2000. The results suggest that local communities tend to integrate traditional rules about nature with international environmental regulation, perhaps a sign of a new ecological awareness. However, in the new management mode accompanying this transition, it can also be a means of local empowerment that takes advantage of a program supporting pro-environmental management of the Antrema area
Apoptosis during ZIKA Virus Infection: Too Soon or Too Late?
No full textInternational audienceCell death by apoptosis is a major cellular response in the control of tissue homeostasis and as a defense mechanism in the case of cellular aggression such as an infection. Cell self-destruction is part of antiviral responses, aimed at limiting the spread of a virus. Although it may contribute to the deleterious effects in infectious pathology, apoptosis remains a key mechanism for viral clearance and the resolution of infection. The control mechanisms of cell death processes by viruses have been extensively studied. Apoptosis can be triggered by different viral determinants through different pathways as a result of virally induced cell stresses and innate immune responses. Zika virus (ZIKV) induces Zika disease in humans, which has caused severe neurological forms, birth defects, and microcephaly in newborns during the last epidemics. ZIKV also surprised by revealing an ability to persist in the genital tract and in semen, thus being sexually transmitted. Mechanisms of diverting antiviral responses such as the interferon response, the role of cytopathic effects and apoptosis in the etiology of the disease have been widely studied and debated. In this review, we examined the interplay between ZIKV infection of different cell types and apoptosis and how the virus deals with this cellular response. We illustrate a duality in the effects of ZIKV-controlled apoptosis, depending on whether it occurs too early or too late, respectively, in neuropathogenesis, or in long-term viral persistence. We further discuss a prospective role for apoptosis in ZIKV-related therapies, and the use of ZIKV as an oncolytic agent
Mechanical behavior of tropical Glued Laminated Timber beams with fingers joints
No full textInternational audienceThis paper presents an experimental investigation on Glued Laminated Timber (GLT) beams made with two tropical woods species, for structural purposes. Two tropical wood species with different density and under-exploited were chosen. These are Dacryodes buettneri (Ozigo) and Pterocarpus osun (Padouk), Ozigo species was taken as a reference species. A Phenol Resorcinol Formaldehyde (PRF) adhesive resistant to harsh tropical environments was used for bonding. The static bending tests were conducted on beams compound of two and three lamellas with fingers joints. The aims of these tests were to determine the key mechanical parameters such as Module of Rupture (MOR) and the Module of Elasticity (MOE). Influence of the finger’s joints on the bending strength of the GLT beams is also investigated in this work. The results show that the position of lamella and finger joint has an impact on the loss of bending strength of the specimens tested, but they have no influence on their stiffness properties
Les séries congruo-harmoniques alternées - Partie 1 - Somme et restes partiels
No full textInternational audienceFor every fixed couple (p;q) of strictly positive integers, the « alternate congruo-harmonic series » parameterized by (p;q) is the convergent series whose general term is (-1)^k/(pk+q). The paper first exposes the general and explicit calculation of the sum S_(p,q) of such a series by means of elementary transcendant functions. It then points the relationships between the family of sums (S_(p,1) )_(p∈N^* ) and the digamma function as well as the more general relationships between the family of sums (S_(p,q) )_((p;q)∈(N^* )^2 ) with the Hurwitz-Lerch function. Finally, an expansion of every partial rest of the series in generalized continued fractions is demonstrated.Pour tout couple fixé (p;q) d’entiers naturels non nuls, on appelle série « congruo-harmonique alternée » de paramètres (p;q) la série convergente de terme général (-1)^k/(pk+q) . L’article expose d’abord le calcul général et explicite de la somme S_(p,q) d’une telle série au moyen de fonctions transcendantes élémentaires. Il met ensuite en évidence le lien entre la sous-famille (S_(p,1) )_(p∈N^* ) et la fonction digamma, ainsi que celui plus général entre la famille de sommes (S_(p,q) )_((p;q)∈(N^* )^2 ) et la fonction d’Hurwitz-Lerch. Est enfin établi un développement en fraction continue généralisée de chaque reste partiel de toute série congruo-harmonique alternée
Analyser la réception sociale du recul stratégique face au risque de submersion marine en Camargue et en Normandie à travers une expérience simulée
No full textInternational audienceÀ travers un dispositif de jeu et de simulation mobilisé lors d’ateliers participatifs, cet article étudie les conditions de réception sociale du recul stratégique face à la submersion marine, par des gestionnaires du risque (élus et agents) de Camargue et Normandie. Après avoir défini la notion de réception sociale, l’article décrit le processus de réception via les actions de jeu des participants. La variété des formes de compréhension que les gestionnaires ont du recul stratégique et la dimension temporelle sont mises en avant. D’autres facteurs de réception sont ensuite mis en exergue (contexte politique, représentations sociales, perception des échelles de gestion), à partir cette fois-ci de l’analyse des discours territorialement ancrés qu’ont les participants durant les ateliers. À travers les parallèles opérés entre jeu et réalité, l’étude met en évidence les facteurs qui déterminent la réception sociale des politiques publiques de gestion des risques côtiers sur chaque territoire étudié
La protection juridique des baleines dans le sud-ouest de l'océan Indien
No full textEvery southern winter, humpback whales, coming from Antarctica, cross waters under the jurisdiction or sovereignty of several states and territories in the South West Indian Ocean. Faced with multiple threats linked to different sectors of activity (fishing, shipping, whale watching, etc.), whale protection requires a holistic approach which has not yet been thought of in the region, unlike to other parts of the world. Tourism and economic challenges have pushed for the adoption of specific rules at the domestic or local level, but without real cooperation between the states concerned. Furthermore, various universal and regional organizations have competences that could favor a protection of whales more adapted to the migratory character of this species, but they also act in isolation or in a segmented way. The legal protection of whales in the South West Indian Ocean must take into account this complex but enabling normative and institutional environment. Consequently, it is necessary to use current legal frameworks, but above all, to reveal the links between them. These ones may be considered from a top down approach, through the implementation of international agreements in domestic legal order, but also from a bottom up dynamic, through the regional consistency of existing protection tools designed at locally. The global perspective, necessary for cetacean protection finally suppose emphasizing the normative production of various subsidiary stakeholders of international relations. NGOs, infra-state actors, experts, or companies, sometimes formed in transnational networks, contribute indeed to “defragment” the regional governance to protect whales at the regional level in the southwestern Indian Ocean.Chaque hiver austral, les baleines à bosse, provenant de l’Antarctique, traversent les eaux sous juridiction ou souveraineté de plusieurs États et territoires du sud-ouest de l’océan Indien. Confrontées à de multiples menaces liées à différents secteurs d’activités (pêche, navigation, whale watching, etc.), les baleines requièrent une protection selon une approche holistique qui n’est pas encore pensée dans la région, contrairement à d’autres parties du monde. Les enjeux touristiques et économiques ont poussé à l’adoption de règles spécifiques au niveau national ou local, mais sans réelle coopération entre les États concernés. Par ailleurs, diverses organisations universelles et régionales sont dotées de compétences qui peuvent favoriser une protection plus adaptée au caractère migratoire de cette espèce, mais elles agissent également de façon cloisonnée ou segmentée. La protection juridique des baleines à l’échelle du sud-ouest de l’océan Indien doit prendre en compte cet environnement normatif et institutionnel complexe mais prometteur. Il est ainsi nécessaire d'utiliser les cadres juridiques existant dans cette région du monde, et surtout de révéler les liens les unissant. Ces derniers peuvent être envisagés selon une approche descendante, par la mise en œuvre dans les ordres juridiques internes d’accords internationaux, mais aussi dans une dynamique ascendante, à travers la mise en cohérence régionale d’outils de protection élaborés localement. La perspective globale, nécessaire à la protection des cétacés, suppose enfin de mettre l'accent sur la production normative de divers acteurs subsidiaires des relations internationales. Les ONG, collectivités infra-étatiques, experts, ou encore les entreprises, parfois constitués en réseaux transnationaux, contribuent, en effet, à « défragmenter » la gouvernance régionale afin de protéger les baleines à l’échelle du sud-ouest de l’océan Indien
Modélisation, analyse et contrôle du scolyte des baies du caféier
No full textCoffee production is an important agricultural activity, in particular in several developing countries. For decades in Cameroon, coffee has been a proven cash crop and continues to be grown despite the fact that production basins have been reduced to make way for food crops. A major threats on coffee production is the serious damage caused by a small insect, Hypothenemus hampei called coffee berry borer (CBB). This insect is very difficult to control as it reproduces and spends most of its life cycle inside the coffee berry. It hence causes severe crop losses. The objective of this thesis is to develop mathematical models for the study, understanding and control of the dynamics of CBB in its ecosystem through theoretical and numerical developments. After a brief presentation of the biology of the interaction between coffee berries and CBB, a basic model is proposed. This model is governed by a non-linear system of ordinary differential equations that describes the infestation dynamics of coffee berries by CBB over a cropping season, taking into account berries availability. Based on the knowledge that berry preference is age-dependent during the selection and infestation process of colonising CBB, our basic model is then extended into a system of partial differential equations with an age structure of the coffee berries. Since the ultimate goal of coffee producers is to produce high quality coffee at the best market price and at the lowest cost, we design optimal control strategies based on the use of environmentally friendly methods such as trapping and release of phytopathogenic fungi. The objective of these control strategies is to maximise yield while minimising control costs and the CBB population for the next cropping season. An extended modelling approach based on the basic model taking into account the fruiting period of coffee berries and multiple cropping seasons is then proposed and studied. By using cultural control, which consists of a thorough harvesting of berries at the end of each production period and a cleaning of the plantation during the intercropping, we determine the criteria for extinction of the CBB population over several seasons. On the agronomical front, the main outputs of this thesis consists in the analysis of the dynamics of CBB-berries interaction over several seasons, but also the emphasis on the advantage of using more than one economically friendly CBB control methods simultaneously.La production du café est une activité agricole importante, notamment dans de nombreux pays en voie développement. Depuis des décennies au Cameroun, le Café est une culture de rente qui a fait ses preuves et continu malgré les bassins de production qui ont diminué pour laisser la place aux cultures vivrières. L'une des principales menaces à la production du café est le grave dommage causé par un petit insecte, Hypothemus hampei encore appelé scolyte des baies du caféier. Cet insecte est très difficile à contrôler car il se reproduit et passe la majeure partie de son cycle de vie à l'intérieur de la baie du caféier. Il génère ainsi des pertes de récolte importantes. L’objectif de cette thèse est de développer des modèles mathématiques pour l’étude, la compréhension et le contrôle de la dynamique des scolytes dans son écosystème via des approches numériques et analytiques. Après une présentation succincte des préalables biologique sur l’interaction entre baies du caféier et scolytes, un modèle de base est proposé. Ce modèle est régi par un système d’équations différentielles ordinaire non linéaire qui décrit la dynamique d’infestation des baies du caféier par les scolytes au cours d’une saison culturale en tenant compte de la disponibilité des baies. Comme la préférence des baies est fonction de l’âge lors du processus de sélection et d'infestation par les scolytes colonisantes, notre modèle de base est ensuite étendu en un système d'équations aux dérivées partielles avec une structure en âge des baies du caféier. L'objectif ultime des producteurs de café étant de produire un café de haute qualité au meilleur prix du marché et au coût le plus bas, nous concevons ensuite des stratégies optimales de lutte basées sur l’utilisation de méthodes respectueuses de l’environnement telles les pièges et l'introduction de champignons phytopathogènes. Le but de ces stratégies de contrôle étant de maximiser le rendement tout en minimisant les coûts de contrôles et la population des scolytes pour la prochaine saison de culture. Une approche étendue de modélisation basée sur le modèle de base en prenant en compte la période de fructification des baies du caféier et les saisons de culture multiples est ensuite proposée et étudiée. En utilisant la lutte culturale qui consiste à faire une bonne récolte des baies à la fin de chaque période de production et un nettoyage de la plantation pendant l’intersaison, nous déterminons les critères d’extinction de la population des scolytes sur plusieurs saisons. Du point de vue agronomique, les résultats principaux de cette thèse sont l'analyse de la dynamique d'interaction baies-scolytes sur plusieurs saisons, ainsi que la mise en évidence des bénéfices à utiliser plusieurs méthodes de lutte simultanément