International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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Source-To-Sink Aeolian Fluxes From Arid Landscape Dynamics in the Lut Desert
No full textInternational audienceWe analyze major landforms of the Lut Desert in Iran to provide a comprehensive source-to-sink picture of aeolian systems on time scales from decades to millions of years. We map the modern sandflows, along which we evaluate the volume and chronology associated with the excavation of mega-yardangs upwind and the formation of giant dunes downwind. Sediment discharges deduced from long-term erosion and deposition are of the same order of magnitude (105-106 m3 yr−1) as short-term and medium-term sand discharges derived from wind data and dune morphodynamics. At the scale of the internal aeolian sediment-routing system of the Lut, we establish an overall sediment budget constrained by the joint development of the erosional and depositional landforms. Our findings thus quantify the geomorphic controls of aeolian processes on arid landscapes at multiple length and time scales, while providing information on mass exchanges between continents and atmosphere
Modélisation et Analyse Mathématique de la Transmission de la Grippe Aviaire par des Bioaérosols
No full textThis thesis aims at modelling and mathematically analysing the environmental transmission of avian influenza and at finding the best policies for the prevention and control of the transmission of this epizootic.We propose non-linear differential systems that take into account five pathways: poultry to poultry, environment to poultry, poultry to human, environment to human and poultry to environment. The mathematical theoretical framework on which we rely to give a complete analysis of our models is that of triangular dynamical systems, Volterra-Lyapunov stable matrices, Poincar\'e-Bendixson and Lyapunov-LaSalle techniques, comparison theorem for parabolic equations, linearization methods and spectral analysis, variational methods, semi-group techniques, the residue theorem and the Pontryagin maximum principle.Numerical simulations are performed to show the impact of the environment, non-local delay, vaccination and education campaigns on the spread of the epizootic. The study suggests that in the event of an avian influenza outbreak, farmers should first reduce their contacts with anything from the farm. Then, the government should launch a program to educate humans to limit their contacts with the poultry environment and a poultry vaccination program.L'objectif des travaux de cette thèse est d'une part la modélisation et l'analyse mathématique de la transmission environnementale de la grippe aviaire et d'autre part la recherche des meilleures politiques pour la prévention et le contrôle de la transmission de cette épizootie. Nous proposons des systèmes différentiels non linéaire qui prennent en compte cinq voies de propagation: de la volaille à la volaille, de l'environnement à la volaille, de la volaille à l'homme, de l'environnement à l'homme et de la volaille à l'environnement. Le cadre théorique mathématique sur lequel nous nous appuyons pour donner une analyse complète de nos modèles est celui des systèmes dynamiques triangulaires, des matrices de Volterra stables au sens de Lyapunov, des techniques de Poincaré-Bendixson et de Lyapunov-LaSalle, du théorème de comparaison pour les équations paraboliques, des méthodes de linéarisation et de l'analyse spectrale, de la méthode variationnelle, des techniques de semi-groupe, du théorème des résidus et enfin du principe du maximum de Pontryagin.Des simulations numériques sont effectuées pour montrer l'impact de l'environnement, du retard non local, de la vaccination et des campagnes d'éducation sur la propagation de cette épizootie. Il ressort donc de cette étude qu'en cas d'épizootie de grippe aviaire, les fermiers devraient dans un premier temps réduire leurs contacts avec tout ce qui provient de la ferme. Ensuite, le gouvernement devrait lancer un programme d'éducation des humains à la limitation de leurs contacts avec l'environnement des volailles et un programme de vaccination des volailles
Properties of beeswax antifungal coatings obtained by high‐pressure homogenisation and their application for preserving bananas during storage
No full textInternational audienceBananas are tropical fruits that are perishable and susceptible to fungal diseases, mainly caused by Colletotrichum musae. Antimicrobial emulsion-based coating materials have been used extensively to inhibit the growth of these fungi and extend the shelf life of bananas. Targeted emulsion-based film functionalities offer excellent mechanical, physicochemical and barrier properties and limit fungal growth kinetics. Antifungal compounds, such as essential oils or phenolic compounds, are added to emulsion-based (wax/ biopolymer) coatings to enhance their antimicrobial properties. This study set out to formulate a beeswax-based emulsion for banana coatings using high-pressure homogenisation (HPH) and hydrophilic food-grade/organic coating materials. The particle size distribution, stability and mechanical properties of the film-forming emulsions, water vapour and the oxygen permeabilities of the resulting coating were investigated. The most promising sucrose emulsions were tested as coatings on banana fruits to assess their efficacy against moisture and firmness loss during storage. Adding thymol (0.5% w/w) to the sucrose emulsions further enhanced the inhibition of Colletotrichum musae growth to its barest minimum of <20%. Emulsion stability was clearly enhanced using HPH while the best inhibition was obtained with a 20% diluted sucrose emulsion containing 0.5% thymol, with or without HPH
Estimating forest above‐ground biomass with terrestrial laser scanning: Current status and future directions
No full textInternational audienceImproving the global monitoring of above-ground biomass (AGB) is crucial for forest management to be effective in climate mitigation. In the last decade, methods have been developed for estimating AGB from terrestrial laser scanning (TLS) data. TLS-derived AGB estimates can address current uncertainties in allometric and Earth observation (EO) methods that quantify AGB. We assembled a global dataset of TLS scanned and consecutively destructively measured trees from a variety of forest conditions and reconstruction pipelines. The dataset comprised 391 trees from 111 species with stem diameter ranging 8.5 to 180.3 cm and AGB ranging 13.5–43,950 kg. TLS-derived AGB closely agreed with destructive values (bias 1,000 kg). More effort should go to further understanding and constraining several TLS error sources. We currently lack an objective method of evaluating point cloud quality for tree volume reconstruction, hindering the development of reconstruction algorithms and presenting a bottleneck for tracking down the error sources identified in our synthesis. Since quantifying AGB with TLS requires only a fraction of the efforts as compared to destructive harvesting, TLS-calibrated ASMs can become a powerful tool in AGB upscaling. TLS will be critical for calibrating/validating scheduled and launched remote sensing initiatives aiming at global AGB mapping
Intégration régionale : un levier pour une insertion réussie de l’Afrique centrale dans les chaînes de valeur mondiales
No full textRésumé de la présentation faite à la Conférence Internationale sur « Les enjeux et instruments de l’intégration régionale en Afrique Centrale », organisée conjointement par la Ferdi et la Commission de la CEMAC à Libreville les 28 et 29 avril 2022International audienceLa Communauté Economique et Monétaire de l’Afrique Centrale (CEMAC), née en 1994 des cendres de l’Union Douanière et Economique de l’Afrique Centrale (UDEAC) créée en 1964, est engagée depuis le début des années 1990 dans un vaste et ambitieux Programme Economique Régional (PER). L’objectif du PER est de faire de la CEMAC un espace démocratique, émergent et prospère à l’horizon 2025. Mais, sa réalisation est fortement contrariée
A cost-effective device and methodology to compute aquifer transmissivity and piezometry from free-flowing artesian wells
No full textInternational audienceArtesian aquifers offer interesting opportunities for water supply by providing a low-vulnerability groundwater resource that is easily abstracted without any installation of pumps or power supply costs. However, hydraulic tests are challenging to perform, notably where the piezometric head is above ground level with free-flowing wells not equipped with valves and open for years. This paper describes a low-cost, easy to reproduce and adaptable device, the free-flowing artesian well device (FFAWD), which is mainly designed with a set of PVC tubes equipped with a pressure probe and a valve. This device is used to perform hydraulic tests on free-flowing artesian wells, to measure the piezometric head of the aquifer and to compute its transmissivity. The practical use of the FFAWD is described and a method is proposed to compute the piezometric head and the transmissivity of the aquifer from this data set (free-flowing well discharge and pressure increase measurements) with any adapted analytical solution, using the Houpeurt-Pouchan method. Artefacts such as post-production effects, surge effects, and the impact of a leaky well are identified to avoid any misinterpretation. The FFAWD was applied to the volcano-sedimentary artesian plain of Pasuruan (Indonesia). The advantages and limitations of using the device, along with the interpretation methodology, are also discussed
NESEPRIN: A new scheme for energy-efficient permutation routing in IoT networks
No full textInternational audienceInternet of Things (IoT) consists of a variety of heterogeneous interconnected devices called objects or things. These objects are generally equipped with sensing, processing and wireless communication capabilities. Unfortunately, these capabilities are not enough compared to those of devices in traditional networks. For example, objects have low battery power, limited memory storage, and less processing power. There are some cases where objects have to communicate with each other. In an Autonomous Vehicular Network for example, when a vehicle needs to change its direction, it has to alert other vehicles in the same network. This is known as the permutation routing problem. More precisely, the permutation routing problem in IoT occurs when some things of the network possess items that belong to others. The goal is to send items to their respective owners. A number of solutions to the problem have been proposed in literature which focus mainly on Wireless Sensor Networks (where the memory size of objects are the same). In this paper, we propose an efficient permutation routing scheme for a single-hop IoT network (the memory size differs from one object to another). The proposed NESEPRIN protocol consists of two phases: In the first phase, we solve the permutation routing problem in a single-hop environment with a single channel, and secondly we generalize the previous solution to a network with multiple channels. Our solution makes use of the wake and sleep technique to improve the energy conservation of objects. The simulation results show that our protocol outperforms the existing protocols designed to solve the permutation routing problem in terms of energy saving when the volume of data to route is large. NESEPRIN is the better candidate to solve the permutation routing problem in a single-hop multi-channels IoT environment where the volume of data to route is huge
HIGH-PRECISION SR AND ND ISOTOPE MEASUREMENTS USING A DYNAMIC ZOOM LENS-EQUIPPED THERMAL IONISATION MASS SPECTROMETER
No full textInternational audienceHigh precision Sr and Nd isotopic measurements are of key importance in the field of Earth Sciences because they are powerful tools to trace sources of materials and to date them. Here, we report the first high-precision data for 87 Sr/ 86 Sr and 143 Nd/ 144 Nd (external error of 5-6 ppm for Sr and 4-5 ppm for Nd) measured using a Nu Instruments TIMS. Such precisions will open new opportunities in fields such as geochemistry, geochronology, cosmochemistry, archaeology or forensics
Spatio-Temporal Dynamics of a Dieldrin Resistance Gene in Aedes albopictus and Culex quinquefasciatus Populations From Reunion Island
No full textInternational audienceThe control of mosquito populations using insecticides is increasingly threatened by the spread of resistance mechanisms. Dieldrin resistance, conferred by point mutations in the Rdl gene encoding the γ-aminobutyric acid receptor, has been reported at high prevalence in mosquito populations in response to selective pressures. In this study, we monitored spatio-temporal dynamics of the resistance-conferring RdlR allele in Aedes (Stegomyia) albopictus (Skuse, 1895) and Culex (Culex) quinquefasciatus (Say, 1823) populations from Reunion Island. Specimens of both mosquito species were sampled over a 12-month period in three cities and in sites located at lower (<61 m) and higher (between 503 and 564 m) altitudes. Mosquitoes were genotyped using a molecular test detecting the alanine to serine substitution (A302S) in the Rdl gene. Overall, the RdlR frequencies were higher in Cx. quinquefasciatus than Ae. albopictus. For both mosquito species, the RdlR frequencies were significantly influenced by location and altitude with higher RdlR frequencies in the most urbanized areas and at lower altitudes. This study highlights environmental factors that influence the dynamics of insecticide resistance genes, which is critical for the management of insecticide resistance and the implementation of alternative and efficient vector control strategies