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International audience; En comparant avec les résultats d'une thèse soutenue par F Jarrige en 1994 "La dynamique d'offre de cacao entre marché, conditions naturelles et institutions : interprétation à partir d'une comparaison Côte-d'Ivoire-Malaisie", l'auteur étudie l'impact de la politique ivoirienne des prix sur le riz. La production de cacao est très sensible aux variations des rapports de prix dans le contexte de deux politiques agricoles radicalement différentes. A l'inverse, pour le riz, il y a résistance d'un système de production vivrière aux variations de la politique agricole.

International audience; Coffee production is an important agriculture activity which contributes significantly to the economic growth of many countries in the world. One of the major constraints to coffee production throughout the world is the damage caused by the coffee berry borer (CBB), Hypothenemus hampei (Coleoptera: Scolytidae). It is the most damaging insect pest to coffee production in the world. These insects infest coffee berries, preferably mature berries, and spend most of their life cycle inside the berries, which make them quite difficult to control. In this work, we introduce and analyse a berry age-structured model describing the infestation dynamics of coffee berries by CBB. Using the semigroup theory in the case of Lipschitz perturbation, we show that the model has a unique nonnegative and bounded solution. We derive an explicit formula of the basic reproduction number, R0, using the next generation approach and the biological interpretation of this threshold in a specific case. Numerical simulations are carried out to illustrate the theoretical results.

International audience; The coffee berry borer (CBB) Hypothenemus hampei (Coleoptera: Scolytidae) is the most important insect pest affecting coffee production worldwide and generating huge economic losses. As most of its life cycle occurs inside the coffee berry, its control is extremely difficult. To tackle this issue, we solve an optimal control problem based on a berry age-structured dynamical model that describes the infestation dynamics of coffee berries by CBB during a cropping season. This problem consists in applying a bio-insecticide at discrete times in order to maximise the economic profit of healthy coffee berries while minimising the CBB population for the next cropping season. We derive analytically the first-order necessary optimality conditions of the control problem. Numerical simulations are provided to illustrate the effectiveness of the optimal control strategy.

International audience; One of the biggest challenges for the farmer is to increase the incomes generated by his farm. This is not always easy because of pests and the scarcity of nutrients in the soil. In this work, we model, analyze and simulate a self-financing nonlinear mathematical model for cabbage crops. The model takes into account the young biomass, the adult biomass, the main cabbage pest (Plutella Xylostella) in its most devastating developmental state (larvae), the concentration of biopesticides in the culture, the external efforts and the incomes generated by the crop. We assume that the budget is allocated for purchasing new plants, biopesticides, and increasing the growth rate of crops (external efforts). This budget increases only through the sale of adult biomass. We study several variants of the main model. In these different cases, the condition in which the budget must be spent to keep the system alive is obtained. The model analysis reveals that prophylaxis can eradicate larvae in a cabbage crop. In addition, the impact of the delay in the supply of fertilizers and biopesticides to the culture is studied.

Bacteriophages or phages (viruses of bacteria) play numerous roles in shaping the diversity of bacterial communities within the human gut. Either a phage-infected bacterial cell immediately starts a lysis mechanisms (virulent/lytic infection), or it enters a stable state within the host as a prophage (lysogeny), until a trigger event, called Spontaneous Prophage Induction (SPI), allows the lysis phenomenon. We develop an approach to address the role of SPI within phage-bacteria interactions and the influence of lysogeny on the success of phage therapy. This is based on a model structure in terms of time since infection. Our analysis suggests that SPI allows lysogen bacteria to have a competitive advantage over their non-lysogenic counterparts. Moreover, the model exhibits the bistability phenomenon such that, depending on the initial conditions, the dynamic can either converge towards a purely temperate state (only lysogens and temperate phages persist) or a purely lytic state (only nonlysogens and virulent phages persist). We also highlight the existence of SPI's critical values leading to the coexistence of all states through periodic oscillations. Finally, the model suggests that efficient bacteria control through phage therapy can be achieved by minimizing lysogens' offspring.

International audience; The coffee berry borer (CBB), Hypothenemus hampei, is the most destructive insect pest affecting coffee plantations in most coffee-producing countries, hence causing major economic losses worldwide. The cryptic life cycle of CBB inside coffee berries makes their control extremely difficult. To tackle this problem, we use a dynamical model describing the plant–pest interactions during a cropping season, which includes a berry age structure to account for CBB preference for mature berries. We introduce two environmentally friendly control methods, consisting in applying a bio-insecticide to reduce berry infestation and in trapping the colonising CBB. Our objective is to maximise the profit generated by the harvest of healthy coffee berries, while minimising the CBB population for the next cropping season. The existence of an optimal control strategy is provided, and necessary optimality conditions are established. Finally, the optimal control problem is solved numerically and simulations are provided. They show that combining the two control methods is a cost-effective strategy to protect coffee berries from CBB infestation.

The treatment of infectious diseases with antimicrobial agents continues to present problems in modern-day medicine with many studies showing significant increase in the incidence of bacterial resistance to several antibiotics. The screening of antimicrobial activity of plant extracts and natural products has shown that medicinal plants are made up of a potential source of new anti-infective agents. The aim of this study was to evaluate the antimicrobial and antioxidant activities of extracts and compounds from the whole plant Trifolium baccarinii Chiov. and to determine their modes of antibacterial action. The plant extracts were prepared by maceration in organic solvents. The antimicrobial activities were evaluated using the broth microdilution method. The antioxidant activity was evaluated using the 2,2 ′ -diphenyl-1-picrylhydrazyl radical (DPPH) and 2,2 ′ -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) assays. The mechanisms of antibacterial action were determined by lysis, salt tolerance assays, and antioxidant enzyme activities. The cytotoxic effect on the erythrocytes was determined by a spectrophotometric method. Biochanin A, formononetin, luteolin, luteolin-4 ′ -O-β-D-glucopyranoside, 4,7,2 ′ -trihydroxy-4 ′ -methoxyisoflavanol, sissotrin, 1-methyl-β-D-glucopyranoside, ononin, D-mannitol, and 3-O-β-D-glucuronopyranosylsoyasapogenol B were isolated from Trifolium baccarinii. The MeOH, EtOAc, and n-BuOH extracts as well as biochanin A, formononetin, luteolin, luteolin-4 ′ -O-β-D-glucopyranoside, 4,7,2 ′ -trihydroxy-4 ′ -methoxyisoflavanol, and sissotrin from Trifolium baccarinii displayed the highest antimicrobial and antioxidant activities. The MeOH extract and 4,7,2 ′ -trihydroxy-4 ′ -methoxyisoflavanol exhibited antibacterial activity through the bacteriolytic effect and reduction of the antioxidant defenses in the bacterial cells. The present study portrays Trifolium baccarinii as a potential natural source of antibacterial, antifungal, and antioxidant agents.

This paper discusses a novel three field formulation for the Darcy-Forchheimer flow with a nonlinear viscosity depending on the temperature coupled with the heat equation. We show unique solvability of the variational problem by using; Galerkin method, Brouwer's fixed point and some compactness properties. We propose and study in detail a finite element approximation. A priori error estimate is then derived and convergence is obtained. A solution technique is formulated to solve the nonlinear problem and numerical experiments that validate the theoretical findings are presented.

International audience

The chemical study of Rumex abyssinicus Jacp (Polygonaceae) led to the isolation of a new ceramide named (R)-2'-hydroxy-N-[(2S,3S,4R,16E)-1,3,4-trihydroxyhexacos-16-en-2-yl]hexadecanamide (rumexamide) (1) together with sixteen known compounds: bis-(2-ethylhexyl) phthalate (2), chrysophanol (3), physcion (4), citreorosein (5), emodin (6), chrysophanein (7), physcionin (8), lupeol (9), 3β,28-dihydroxylup-20(29)-ene (10), 3β-dihydroxylup-20(29)-en-28-oic acid (11), oleanolic acid (12), ergosta-6,22-diene-3,5,8-triol (13), stigmastane-3,6-dione (14), a mixture of β-sitosterol (15) and stigmasterol (16), and stigmasterol 3-O-β-D-glucoside (17). Their structures were determined by interpretation of their spectroscopic 1D NMR (1H and 13C NMR), 2D NMR (COSY 1H-1H, HSQC and HMBC) data in conjunction with mass spectrometry (TOFESIMS and HR-TOFESIMS) and by comparison with those reported in the literature. Among all the known compounds, twelve (2, 5, 8-17) were firstly isolated from Rumex abyssinicus, seven (2, 10-14 and 17) from the genus Rumex and three (13, 14, 17) from family Polygonaceae. The in vitro antibacterial activities of extracts (MeOH, n-BuOH and EtOAc), as well as compounds 9, 11, 12, 15 + 16 and 17 against pathogenic bacteria (Staphylococcus aureus ATCC 43300, Shigella flexneri NR 518, Klebsiella pneumoniae ATCC 700603, Escherichia coli ATCC 25922), were performed using the broth microdilution method and the results show that, extracts were not active (MIC > 1000 μg/mL) while compounds were weakly or not active (MIC ≥ 500 μg/mL) against all bacteria strains. Furthermore, the chemophenetic relationships of the isolated compounds and their significances were discussed.

Coffee 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.

International audience; The coffee berry borer (CBB), Hypothenemus hampei (Coleoptera: Scolytidae) is the most devastating insect pest of coffee throughout the world, causing a lot of economic damage in all regions where commercial coffee is grown. In this work, we formulate and study a model describing multi-seasonal infestation dynamics of coffee berries by CBB in a rainy/dry season regime, with the aim of identifying how sanitation measures can be applied to ensure CBB eradication. We employ a semi-discrete formalism to describe these dynamics as the epidemiological dynamics are best represented by a continuous model in ODE, while the remaining dynamics, that connect one season to the next, are better or more simply described by discrete-time events: berry harvest and plantation sanitation. During the rainy season, the infestation dynamics of coffee berries by CBB are described as proposed in Fotso Fotso et al (2021) with the coffee berry production rate depending on time. During the dry season, the dynamics are very similar , except that no berry growth takes place and mortality rates are higher as the environment is less favorable. The model is then completed by the discrete events that take place at the end of the rainy season and at the end of the dry season, that correspond to harvesting and plantation cleaning respectively. Based on that model, we first obtain a periodic CBB-free solution, that will be the desirable behaviour of the system. Linearising the dynamics around that solution and applying Floquet theory, we obtain stability conditions for this solution, that give threshold values for the harvesting and cleaning parameters below which asymptotic stability is ensured, hence CBB eradication. Note however that, even with perfect harvesting and cleaning, CBB could still persist through the survival of the colonising forms over the dry season.Finally, with perfect harvesting of the healthy berries at the end of the cropping season, we obtain conditions on harvesting and cleaning of the infested berries, that ensures CBB eradication at the minimum cost, for two versions of the cost.

Background Antibiotic resistance has contributed to the burden of infectious diseases both in the hospital and community setting, and represents a great threat to public health. Previous studies have revealed the role of reactive oxygen species as intermediate mediators of tissue damage, following antibiotherapies, indicating the need of associating antioxidants to these treatments. Therefore, the present work was designed to study the antibacterial, antifungal and antioxidant activities of extracts and compounds from Rumex abyssinicus Jacq. (Polygonaceae), as well as to investigate the antibacterial mechanisms of action of the most effective agents. Methods The plant extracts were prepared by maceration in organic solvents followed by column chromatography of the EtOAc fraction and purification of different fractions which led to the isolation and characterization of pure compounds. The antimicrobial activities of the extracts/compounds and their combinations with ciprofloxacin and fluconazole were evaluated using the broth microdilution method by determining the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC). The effects of the extracts on the bacterial cell membrane and microbial respiratory chain dehydrogenase enzyme activity were determined by spectrophotometric methods. Antioxidant activity was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and gallic acid equivalent antioxidant capacity (GAEAC) assays. Results Chrysophanol (1), physcion (2), Ergosta-6,22-diene-3,5,8-triol (3), emodin (4), 6-hydroxyemodin (citreorosein) (5), chrysophanein (6) and physcionin (7) were isolated from EtOAc fraction of R. abyssinicus and displayed different degrees of antimicrobial activities (MIC = 8–256 μg/mL). The MeOH extract and compounds 2 and 4 exhibited synergistic effects with ciprofloxacin and fluconazole. Compounds 1, 2 and the combined mixture of 6 + 7 displayed the highest antioxidant activity (GAEAC = 83.38–106.03 μg/mL). Conclusion R. abyssinicus is a potential source of antibacterial, antifungal and antioxidant agents. The antibacterial mechanisms of action of the MeOH extract and compound 2 are due to disruption of the cytoplasmic membrane and inhibition of the microbial respiratory chain dehydrogenase enzyme activity. To the best of our knowledge, this is the first report of test samples and ciprofloxacin / fluconazole association against MDR strains. The observed activity of the isolated compounds against bacteria and fungi including MDR strains deserves further exploration.

Existence and uniqueness of strong solutions for three dimensional system of globally modified magnetohydrodynamics equations containing infinite delays terms are established together with some qualitative properties of the solution in this work. The existence is proved by making use of; Galerkin's method, Cauchy-Lipshitz's theorem, a priori estimates, the Aubin-Lions compactness theorem. Moreover, we study the asymptotic behavior of the solution.

This research work focuses on mathematical modeling of the Ebola virus disease, while placing a particular emphasis on control strategies. The models that we propose are carefully analysed thanks to the combined method of Lyapunov and LaSalle, and/or graph therory. Firstly, we focus on an Ebola human-reservoir model with both direct and indirect transmission. Numerically, we show the impact of the manipulation/consumption of bats on the endemicity of the disease in the human population. Furthermore, we dwell on a model of Ebola with contact tracing and isolation. This model is mathematically analysed in the case where any of these control measures is perfect, and in the case where these control measures are imperfect. The numerical analysis of the model shows that a well-designed contact tracing (90% of cases), combined to a perfect isolation is better than any of these measures taken separetely. Afterwards, we pay attention to an Ebola model with vaccination, isolation and education of people to safe burial of the Ebola-deseased individuals. In the case where that pathology is endemic, we address the vaccination and the isolation-safe burial, optimally to reduce its level. Finally, we focus on the dynamics of Ebola in a metapopulation model with the exit screening at the exit-borders of patches. Numerically, we prove that, screening at the exit is less sensitive and can be unfavourable to the patches that implement it. Thus, we suggest screening at the entrance or the combination vaccination-screening at the exit, only implemented in the patch where the disease originated. These problems of optimal controls are resolved mathematically and numerically through the Forward backward sweep method.; Dans cette thèse, nous nous intéressons à la modélisation mathématique de la maladie à virus Ebola en portant un accent particulier sur les stratégies de contrôle. Les modèles que nous proposons sont rigoureusement analysés grâce à la méthode combinée de Lyapunov et LaSalle, et/ou la théorie des graphes. Dans un premier temps, on s'intéresse à un modèle réservoir-humain d'Ebola avec transmission directe et indirecte. Numériquement, nous montrons l'impact de la manipulation /consommation des chauves-souris infectées sur l'endémicité de la maladie dans la population humaine. Dans un deuxième temps, nous nous appesantissons sur un modèle d'Ebola avec recherche des contacts et isolement. Ce modèle est analysé mathématiquement dans le cas où l'une ou l'autre de ces mesures de contrôle est parfaite, et dans le cas où ces stratégies de contrôle sont imparfaites. L'analyse numérique du modèle nous montre que la recherche des contacts bien menée (à 90% des cas), combinée à un isolement parfait est meilleure que chacune de ces mesures prises séparement. Ensuite, nous nous intéressons à un modèle d'Ebola avec vaccination, isolement et éducation des populations à l'inhumation sans risque des décédés d'Ebola. Dans le cas où cette stratégie de contrôle est endémique, nous adressons la vaccination et l'isolement -inhumation sans risque des décédés de manière optimale, afin de réduire son degré. Enfin, nous nous appesantissons sur la dynamique d'Ebola dans un modèle de métapopulations avec dépistage à la sortie des patchs. Numériquement, nous prouvons que le dépistage à la sortie est peu sensible et peut être défavorable aux patchs qui l'implémentent. Ainsi, nous suggérons un dépistage à l'entrée des patchs ou la combinaison vaccination-dépistage à la sortie, implémentée uniquement dans le patch où la maladie a pris naissance. Ces problèmes optimaux sont résolus mathématiquement et numériquement grâce à la méthode de balayage progressif-retroprogressif.

International audience; Diclofenac (DCF) is a common anti-inflammatory drug. In this work, we have developed two new modified electrodes based on attapulgite clay mineral for the determination of DCF. The first one is made of an amino-functionalized attapulgite modified glassy carbon electrode (GCE/Amino-AT) issued from the grafting of attapulgite particles with [3-(2aminoethylamino)propyl]trimethoxysilane. Voltammetric data indicate slightly easier oxidation of DCF on such modified electrode (irreversible anodic peak at +0.750 V vs. Ag/AgCl i.e., about 85 mV lower than on bare GCE), and pH-dependent response resulting from interactions between the probe and the electrode material. The second one is an aminoattapulgite-mesoporous silica composite film generated by electro-assisted self-assembly of a surfactant-templated silica layer entrapping the amino-functionalized attapulgite particles on GCE pretreated by electrografting of [3-aminopropyl]triethoxysilane (GCE/APTES-Amino-AT-Silica), which was designed in order to avoid the loss of clay particles in solution over prolonged use of the modified electrode. After characterization of the film morphology, composition and permeability, respectively by scanning electron microscopy (SEM), energydispersive X-ray spectroscopy (EDX) and cyclic voltammetry (CV), the modified electrodes were applied to the detection of DCF by square wave voltammetry (SWV). Both electrodes gave rise to SWV peak currents varying linearly with DCF concentration in the range of 0.3-20 µΜ (in phosphate buffer at pH 5.7). The detection limits were 0.204 μM on GCE/Amino-AT and 0.053 μM on GCE/APTES-Amino-AT-Silica. The proposed method was successfully applied to the determination of DCF in pharmaceuticals and water samples.

A new crystallographic method is proposed in order to refine a spin-resolved atomic orbital model against X-ray and polarized neutron diffraction data. This atomic orbital model is applied to the YTiO3 perovskite crystal, where orbital ordering has previously been observed by several techniques: X-ray diffraction, polarized neutron diffraction and nuclear magnetic resonance. This method gives the radial extension, orientation and population of outer atomic orbitals for each atom. The interaction term between Ti3+, Y3+ cations and O2− ligands has been estimated. The refinement statistics obtained by means of the orbital method are compared with those obtained by the multipole model previously published.

International audience; Ethnopharmacological relevance. Imperata cylindrica (L.) Raeusch (Gramineae) is a medicinal spice traditionally used in the treatment of hypertension and cancer. Aim of the study: To assess the anti-metastatic potential of the methanol extract of I. cylindrica roots and determined its mechanisms of action. Material and methods. the growth inhibition activity of I. cylindrica root extract in vitro and in vivo in human cervical cancer. The scratch assay and Boyden Chamber assay were used to determine the anti-migrative and anti-invasion actions of the plant extract. The wholegenome gene expression profiling using RNA-Seq was performed to determine the differentially expressed genes in CaSki cells after exposure to I. cylindrica to identify its targeted genes related to metastasis. Using protein analysis (western blotting) and gene expression analysis (RTqPCR), the targeted pathways of the key genes that were initially identified with RNA-Seq, were evaluated. Results. I. cylindrica extract showed dose-dependent cytotoxicity in vitro and in vivo in mice bearing tumors. Furthermore, I. cylindrica root extract significantly inhibited cell migration and cell invasion. After the genome-wide transcriptome analysis, we found that important genes involved in cancer progression and metastasis of cervical cancer, that is, CD24 and TIMP-4 were significantly downregulated and upregulated, respectively. Moreover, I. cylindrica root extract significantly inhibited the PI3/AKT/Snail signalling pathway and blocked the EMT of CaSki cells. Conclusion. These findings provide an anti-metastatic mechanism of action of I. cylindrica root extract toward the human cervical cancer suggesting that this plant maybe developed into selective chemotherapy.

In this thesis, we focus on the proposal of distributed workflow systems dedicated to the automation of administrative business processes. We propose an approach to build such systems by relying on the concepts of multiagent systems, Peer to Peer (P2P) architecture, Service-Oriented Architecture (SOA) and structured documents (artifacts) cooperative edition. Indeed, we develop mathematical tools that allow any workflow systems designer, to express each administrative process in the form of an attributed grammar whose symbols represent tasks to be executed, productions specify a scheduling of these tasks, and instances (the derivation trees that conform to it) represent the different execution scenarios leading to business goal states. The obtained grammatical model is then introduced into a proposed P2P system which is in charge of carrying out the completely decentralised execution of the underlying process's instances. The said system orchestrates a process's instance execution as a choreography during which, various software agents driven by human agents (actors), coordinate themselves through artifacts that they collectively edit. The exchanged artifacts represent the system's memory: they provide information on already executed tasks, on those ready to be executed and on their executors. The software agents are autonomous and identical: they execute the same unique protocol each time they receive an artifact. This protocol allows them to identify the tasks they must immediately execute, to execute them, to update the artifact and to disseminate it if necessary, for the continuation of the execution. Moreover, actors potentially have only a partial perception of processes in which they are involved. In practice, this means that certain tasks can be carried out confidentially: this property makes it possible to offer automatic management of administrative processes that is a little closer to their non-computerised management., Dans cette thèse, nous nous intéressons à la mise en œuvre de systèmes workflows distribués, dédiés à l'automatisation des processus opérationnels dits administratifs. Nous proposons une approche de mise en œuvre de tels systèmes en nous appuyant sur les concepts de systèmes multi-agents, d'architecture Pair à Pair (P2P, égal à égal), d'architecture orientée service et d'édition coopérative de documents structurés (artefacts). En effet, nous développons des outils mathématiques permettant à tout concepteur de systèmes workflows, d'exprimer chaque processus administratif qu'il désire automatiser, sous forme d'une grammaire attribuée dont les symboles représentent les tâches à exécuter, les productions spécifient un ordonnancement de celles-ci, et les instances (les arbres de dérivation qui lui sont conformes) représentent les différents scénarii d'exécution menant aux différents états qui matérialisent l'accomplissement des objectifs de l'entreprise. Le modèle grammatical obtenu est ensuite introduit dans un système P2P que nous proposons, et qui est chargé d'assurer l'exécution complètement décentralisée d'instances du processus sous-jacent. Ledit système orchestre l'exécution d'une instance de processus sous forme d'une chorégraphie durant laquelle, divers agents logiciels pilotés par des agents humains (acteurs), se coordonnent à l'aide d'artefacts qu'ils éditent collégialement. Les artefacts échangés représentent la mémoire du système: ils donnent des informations sur les tâches déjà exécutées, sur celles prêtes à l'être et sur leurs exécutants. Les agents logiciels sont autonomes et identiques: ils exécutent le même et unique protocole à chaque fois qu'ils reçoivent un artefact. Ce protocole leur permet d'identifier les tâches qu'ils doivent exécuter dans l'immédiat, de les exécuter, de mettre à jour l'artefact et de le diffuser si nécessaire, pour la continuation du processus d'exécution. En outre, les acteurs n'ont potentiellement qu'une perception partielle des processus dans lesquels ils sont impliqués. Ce qui autorise donc une possible exécution confidentielle de certaines tâches en pratique: cette propriété permet d'offrir une gestion automatique des processus administratifs se rapprochant un peu plus, de leur gestion non informatisée.

International audience; Coffee berry borer Hypothenemus hampei (Coleoptera: Scolytidae), denoted CBB, is the most important insect pest of coffee worldwide, with a high impact on the economy of coffee producing countries. The insect spends a great part of its life cycle inside the coffee berry and causes severe crop losses. Biological control based on the use of an entomopathogenic fungus is a major alternative to chemical pesticides in order to control CBB. The fungus is sprayed on the coffee berries to kill CBB when the insects drill holes to penetrate inside the berries. Our aim in this work is to optimise the fungus application, using a modelling approach. We first formulate a mathematical model describing the infestation dynamics of coffee berries by CBB. We analyse the model and show that the stability of the pest-free and coexistence equilibria depends on the basic reproduction number. To introduce a control variable corresponding to the application of an entomopathogenic fungus, we then extend the model and include the fungus dynamics. We formulate an optimal problem which consists in maximising the coffee yield, while minimising the control cost, as well as the CBB population for the next cropping season. The existence of the optimal control and the necessary optimality condition are established using Pontryagin's Maximum Principle. The optimal control problem is solved numerically using the BOCOP software and simulations are provided, showing that the use of entomopathogenic fungus effectively controls CBB.

A bacteriophage or phage is a virus that infects bacteria. This infection can either purifies a bacterial polluted environment as well as human small intestine or triggers virulent pathogenic bacterial disease outbreaks such as cholera. The aim of this dissertation is to study the impact of phages–bacteria infection on the transmission dynamics of cholera and assess on the use of phages to control the spread of disease and for therapeutic purpose.To this end, (i) we formulate a predator–prey model to describe and study the phages–bacteria interaction by taking into account both lytic and lysogenic life cycles of phages. A threshold called basic offspring number is computed. We derive using this ecological threshold conditions under which phages purify a bacterial polluted environment and the situations that phages trigger virulent pathogenic bacterial diseases outbreak. (ii) The coupled models of cholera dynamics and phages–bacteria interaction are used to study the influence of phages and bacteria on the spatiotemporal transmission of cholera. The epidemiological threshold called basic reproduction number which is actually the average number of secondary human infections by infectious vibrio cholerae in their entire lifespan is computed. It is shown through these models that whenever the phages–bacteria interaction is considered, the classical condition which consists to drop the basic reproduction number under unity even though necessary is not sufficient to eliminate cholera. We derive an ecological threshold needed for possible elimination of the disease. Our results predict that efforts should be made to drop both epidemiological and ecological thresholds under unity in order to stop the spread of cholera.For the control strategies that should be used to reduce the number of infected human population, we first propose the release of selected lytic/virulent phages into contaminated environment in order to infect and eliminate the population of vibrio cholerae. The second strategy is the ingestion of these selected phages to purify a polluted human small intestine. The latter is known as phage therapy. Using phages for therapeutic purpose has many potential applications in human medicine as well as veterinary science and agriculture., Une phage est un virus qui infecte les bactéries. Cette infection peut d’une part purifier un environnement ou l’organisme d’un individu infecté de bactéries, et d’autre part déclencher la propagation des maladies bactériennes. L’objectif de cette thèse est d’étudier l’impact de l’interaction phage–bactérie sur la transmission du choléra et investiguer sur les possibilités d’utiliser les phages pour un but thérapeutique.Pour ce faire, (i) nous formulons un modèle de proie–prédateur pour décrire et étudier l’interaction phage–bactérie prenant en compte les cycles lytique et lysogénique d’une phage. En utilisant le seuil écologique du modèle, nous déterminons les conditions sous lesquelles la présence des phages peut détruire la population des bactéries et les situations où elle déclenche les maladies bactériennes. Les modèles couplés de choléra et phage–bactérie sont utilisés pour étudier l’influence des phages et bactéries sur la transmission spatiotemporelle du choléra. Le taux de reproduction de base qui représente le nombre moyen d’infectés humains produits par les bactéries infectieuses au cours de leur vie est calculé. Nous montrons à travers ces modèles que lorsque l’infection phage–bactérie est prise en compte dans un modèle de transmission du choléra, la condition classique qui consiste à baisser le seuil épidémiologique en dessous de un n’est pas suffisante pour éradiquer la maladie. Nous déterminons le seuil écologique nécessaire pour l’éradication du choléra. En effet nos résultats prédisent que les efforts doivent être faits pour baisser les deux seuils écologique et épidémiologique en dessous de un.Pour réduire le nombre d’infectés humains de choléra, nous proposons deux moyens de contrôle. La première stratégie consiste à introduire les phages virulents sélectionnées pour infecter et détruire la population de vibrions cholériques dans l’environnement. La deuxième stratégie consiste à consommer ces phages sélectionnées pour éliminer les vibrions cholériques de l’organisme humain. Ce dernier moyen de contrôle est la phagothérapie. Utiliser les phages pour un but thérapeutique a plusieurs applications en médecine humaine, médecine vétérinaire et en agriculture.

International audience; 2-Hydroxy-4-(1’-hydroxy-2’,6’,6’-triméthyl-4-oxo-cyclohex-2’-enyl)-but-3-enoic acid, a new megastigmane derivative, trivially named monanthosin (1), together with eight known compounds (chrysin (2), quercitrin (3), astilbin (4), heptulose (5), allantoin (6), heptitol (7), cis-N-p-coumaroyl tyramin (8) and trans-N-p-coumaroyl tyramin (9)) were isolated from the leaves of Monanthotaxis littoralis (Annonaceae). Structures were assigned by direct interpretation of their spectral data, mainly HR-TOFESIMS, 1D NMR (1H and 13C) and 2D NMR (1H-1H COSY, HSQC, HMBC and NOESY) and by comparison with reported values. The MeOH, EtOAc and n-BuOH extracts as well as compounds 1, 2, 4 and 8 exhibited variable antimicrobial and antioxidant activities. The ethyl acetate extract and compound 4 were the most active samples among extracts and compounds, respectively. The ethyl acetate extract and antibiotics (vancomycin and fluconazole) demonstrated synergistic effect against Escherichia coli, Pseudomonas aeruginosa, Candida albicans, Candida tropicalis and Cryptococcus neoformans and additive effect against Staphylococcus aureus.

Le Rapport général comporte une Introduction et Deux Parties. La I° Partie fonde la nécessité de la Décentralisation partant de la réflexion de Daron ACEMOGLU et James ROBINSON sur "Why Nations Fail", constituant un portrait de nombreux pays africains. La I° Partie aborde "La Décentralisation en Afrique, Ou la Marche vers le Développement local", alors que la II° Partie aborde "La Décentralisation en Afrique, Un Itinéraire difficile vers la Démocratie participative". La Conclusion générale revient sur 4 propositions principales ayant émergé du Symposium, dont la nécessité de la création à brève échéance d'une Banque des Communes et des Régions.

International audience; Background: In Sub-Saharan Africa, chronic hepatitis C (CHC) is a major public health issue. We estimated the long-term clinical benefits of treating CHC with sofosbuvir-based regimens in Cameroon, Côte d'Ivoire and Senegal using Markov model combining data from the literature with estimates of direct-acting antiviral (DAAs) effectiveness in West and Central Africa.Methods: Disease progression was simulated with and without treatment in fictive cohorts of patients "diagnosed" with CHC in Cameroon (n = 3224), Côte d'Ivoire (n = 9748) and Senegal (n = 6358). Lifetime treatment benefits were assessed using (a) life-years saved (LYS); (b) life-years (LY) avoided in compensated cirrhosis (CC), decompensated cirrhosis (DC) and hepatocellular carcinoma; and (c) comparison of the proportions of patients at each disease stage with and without treatment. Probabilistic and determinist sensitivity analyses were performed to address uncertainty.Results: Sofosbuvir-based treatment would save [mean, 95% confidence intervals] 3.3 (2.5; 5.7) LY per patient in Cameroon, 2.7 (2.1; 4.8) in Côte d'Ivoire and 3.6 (2.8; 6.3) in Senegal. With treatment, approximately 6% (1%) of the patients still alive in each of the study countries would be in the CC (DC) health state 11 (15) years after CHC diagnosis, vs 15% (5%) without treatment. Scenario analysis showed earlier diagnosis and treatment initiation would dramatically improve LYS and morbidity.Conclusion: Sofosbuvir-based treatment could significantly reduce CHC-related mortality and help control CHC-related liver disease progression in West and Central Africa. However, the goal of disease elimination necessitates a substantial decrease in DAAs prices, greater political commitment and increases in both national and external health expenditures.

International audience; Les Fondements économiques et institutionnels de la Décentralisation:- Examen du modèle de développement par pôles de développement qui est arrivé à bout de souffle au Cameroun en particulier, et en Afrique subsaharienne en général;- Hypertrophie de la centralisation budgétaire- Nécessité de lever l'unicité du compte des administrations publiques;- Stratégie de développement régional

International audience; In Business Process Management (BPM), process modelling has been solved in various ways. However, there are no commonly accepted modelling tools (languages). Some of them are criticized for their inability to capture both the lifecycle, informational and organizational models of processes. For some others, process modelling is generally done using a single graph; this does not facilitate modularity, maintenance and scalability. In addition, some of these languages are very general; hence, their application to specific domain processes (such as administrative processes) is very complex. In this paper, we present a new language and a new methodology, dedicated to administrative process modelling. This language is based on a variant of attributed grammars and is able to capture the lifecycle, informational and organizational models of such processes. Also, it proposes a simple graphical formalism allowing to model each process's execution scenario as an annotated tree (modularity). In the new language, a particular emphasis is put on modelling (using "views") the perceptions that actors have on processes and their data.

International audience; With the ever-increasing development of the Internet and the diversification of communication media, there is a growing interest in distributed business process models that focus on exchanged data (or artifact) to control and pilot processes. The Guarded Attribute Grammars (GAG) is one such model; it stands out from the others by the fact that it emphasizes the central place occupied by user decisions during the process execution: it is both data-driven and user-centric. In this paper we present an approach to implementing distributed collaborative business processes modeled using GAG in which communications are done by publish/subscribe with redirection of subscriptions (pub/sub-RS). Pub/sub-RS-which we propose-guarantees high data availability during the process execution, by ensuring that an actor, perceived as a subscriber, will always receive a data he needs to perform a task as soon as it is produced. Moreover, if the data is semi-structured, and is produced collaboratively and incrementally by several actors, its subscribers will be notified as soon as one of its components (a prefix) is produced at the same time they will be subscribed in a transparent way to the remaining components (the suffix).; Avec le développement toujours croissant d'internet et la diversification des moyens de communication il est un intérêt croissant pour les modèles de processus métiers distribués qui mettent l'accent sur les données échangées (ou artefacts) pour contrôler et piloter les processus. Les grammaires attribuées avec gardes (GAG) est l'un de ces modèles; il se démarque des autres par le fait qu'il met l'emphase sur la place centrale qu'occupe les décisions des utilisateurs lors de l'exécution d'un processus: il est à la fois centré sur les données et sur l'utilisateur. Dans ce papier, nous présentons une approche de mise en œuvre de processus métiers collaboratifs distribués modélisés à l'aide des GAG dans lesquels les communications se font par publish/subscribe avec redirection de souscriptions (pub/sub-RS). Le pub/sub-RS (que nous proposons), garantit une haute disponibilité des données pendant l'exécution des processus en assurant qu'un acteur (vu comme un abonné), recevra toujours une donnée dont il a besoin pour effectuer une tâche dès qu'elle est produite. De plus, si la donnée est semi-structurée, et produite collaborativement et incrémentalement par plusieurs acteurs, les abonnés seront notifiés dès qu'une de ses composantes (un préfixe) est produite en même temps qu'ils seront abonnés de manière transparente à ses composantes résiduelles (le suffixe).

With the ever-increasing development of the Internet and the diversification of communication media , business processes of companies are increasingly collaborative and distributed. This contrasts with traditional solutions deployed for their management which are usually centralized, based on the activity flow or on the exchanged documents. Moreover, the users who are usually the main actors in collaborations are often relegated to second place. Recently, a distributed, data-driven and user-centric approach called Guarded Attributed Grammar (GAG) has been proposed for the modeling of such processes; it thus provides an answer to most of these limitations. In this paper, we present an approach for implementing business processes modeled using GAG in which communications are done by publish/subscribe with redirection of subscription (pub/sub-RS). The pub/sub-RS-which we propose-guarantees high data availability during the process execution by ensuring that an actor, perceived as a subscriber, will always receive a data he needs to perform a task as soon as it is produced. Moreover, if the data is semi-stuctured, and produced collaboratively and incrementally by several actors, its subscribers will be notified as soon as one of its components (a prefix) is produced simultaneously, as they will be subscribed in a transparent way to the remaining components (the suffix).; Avec le développement toujours croissant de l'Internet et la diversification des moyens de communication, les processus métiers sont de plus en plus collaboratifs et distribués. Ceci contraste avec les solutions traditionnelles déployées pour leur gestion qui sont habituellement centralisées, basées sur le flux d'activités ou sur les documents échangés. Bien plus, les utilisateurs qui sont généralement les acteurs principaux dans la collaboration y sont souvent relégués au second rang. Récemment, une approche distribuée, centrée sur l'utilisateur et pilotée par les données appelée Grammaires Attribuées Gardées (GAG), a été proposée pour la modélisation de tels processus; elle fournit donc une réponse à la plupart de ces limitations. Dans ce papier, nous présentons une approche de mise en œuvre de processus métiers modélisés à l'aide des GAG dans laquelle les communications se font par publish/subscribe avec redirection de souscriptions (pub/sub-RS). Le pub/sub-RS (que nous proposons) garantit une haute disponibilité des données pendant l'exécution d'un processus en assurant qu'un acteur (perçu comme un abonné) recevra toujours une donnée dont il a besoin pour effectuer une tâche dès qu'elle est produite. De plus, si la donnée est semi-structurée et produite collaborativement et incrémentalement par plusieurs acteurs, ses abonnés seront notifiés dès qu'une de ses composantes (un préfixe) est produite en même temps qu'ils seront abonnés de manière transparente aux composantes résiduelles (le suffixe).

International audience; The use of social networks is still confined to infrastructure-based networks such as the Internet. However, many situations (conferences, fairs, etc.) may require the implementation and rapid deployment of an ad-hoc application for disseminating information: we call this type of application, Ad-hoc Social Network. These applications are necessarily distributed, deployable on mobile units, etc. They therefore inevitably share the same characteristics as those inherent in ad-hoc mobile networks and make them good candidates for their deployment. In this paper, by using techniques from the field of generative programming, we propose an approach to produce environments for generating such applications from their specifications in a domain-specific language. By applying this approach, we have developed SMGenerator, an environment for generating mobile ad-hoc social network applications for Android devices. Moreover by using SMGenerator, we easily generated the ConfInfo application: an ad-hoc social network application for disseminating information to participants in a scientific manifestation.

International audience; Administrative workflows refer to variable business processes in which all cases are known; tasks are predictable and their sequencing rules are simple and clearly defined. When such processes are collaboratively executed by several actors, it may be desirable, for security reasons (confidentiality), that each of them has at all times, only a partial perception (this is what we call "actor's view") of the current process state. This concern seems sufficiently important to be considered when specifying such workflows. However, traditional workflow specification languages (BPMN, BPEL, YAWL) only partially address it. This is why we present in this paper, a new language for specifying administrative workflows that allows us not only to simply model all of the processes tasks and their sequence, but also and especially to explicitly express the rights of the various actors with respect to each of them, in order to guarantee a certain degree of security. The proposed model is an executable grammatical specification that allows to express using decorated productions, the different types of basic flows (sequential, parallel, alternative and iterative) that are found in workflow specification languages; moreover, it also allows to specify the rights of each actor in each process and on its data in a formalism similar to that used in UNIX-like operating systems.

Diese Arbeit analysiert das Wachstum der landwirtschaftlichen Produktivität durch Innovationen in der Landwirtschaft und schätzt seine uswirkungen auf die nichtlandwirtschaftliche Beschäftigung in Afrika Subsahara. Anwendung der SFA-Methode Die durchschnittliche jährliche Wachstumsrate wird über den gesamten Zeitraum auf 1,9% geschätzt; und 3,13% im letzten Jahrzehnt hauptsächlich angetrieben durch technische Veränderungen. Unter den zunehmenden Innovationen Einfluss von Ertrag, Kali, Harnstoff und Bewässerungssystemen positive und signifikante Steigerung der landwirtschaftlichen Produktivität. Diversifikation Kulturen als gewinnbringende Innovationen wirken sich positiv aus und signifikant für die Produktivität. Die Ergebnisse unseres Panel-VAR-Modells ermöglichen Gewährleistung eines einseitigen Kausalzusammenhangs mit der landwirtschaftlichen Produktivität in Richtung nichtlandwirtschaftliche Beschäftigung. Und Kausalität funktioniert nur aus Produktivität in Richtung Ungleichheit. Die gesteigerte landwirtschaftliche Produktivität führt daher zu einer Steigerung von nichtlandwirtschaftliche Beschäftigung und erhebliche Ungleichheiten bei der Einkommensverteilung, aber notwendig für das Wachstum von Investitionen. GMM führt zum System Mit der FOD-Transformation können wir die Verteilung von identifizieren Umsatz und Produktpreis ändern sich als Hauptkanäle durch die das Wachstum des Agrarsektors das Beschäftigungsniveau in diesem Sektor beeinflusst nichtlandwirtschaftlich. Für ein nachhaltiges Produktivitätswachstum undAbbau entlassener Arbeitsplätze im afrikanischen Agrarsektor, die Auswirkungen von Fokus auf Verbesserung des Produktionssystems und Spezialisierung Arbeit., This thesis aims at analyzing agricultural productivity growth through innovations in agriculture and estimate its impact on off-farm employment in Sub-Saharan Africa. Applying the Stochastic Frontier Analysis (SFA) on historical crop production data, we find the average growth rate of agricultural productivity estimated at 1.9% per year for the entire period ; and at 3.13% this last decade mainly led by technical change. Scale efficiency change has been the major barrier to TFP growth in the African agriculture. Potash fertilizer, urea, and irrigation systems have a positive and significant influence on agricultural productivity growth as far as yield-increasing innovations are concerned. Crop diversification, as profit-enhancing innovations, has a positive and significant effect on agricutural productivity growth. The results of the panel VAR model depict a causal relationship with single direction from agricultural productivity to off-farm employment. Between agricultural productivity and inequalities, causality functions from productivity to inequalities. Therefore, productivity growth generates an increase of off-farm employment and significant inequalities in the distribution of income, but necessary to investments growth in agricultural sector. The results of GMM system with the FOD transformationallow us to identify, income distribution and product price change as the main channels through which agricultural growth affects the off-farm employment level. To address slow productivity growth and redundant jobs in the African agriculture, policies implications are oriented towards improvement of agricultural production system and labor specialization., Cette thèse analyse la croissance de la productivité agricole à travers les innovations en agriculture et estime son impact sur l’emploi non-agricole en Afrique Sub-Saharienne. Appliquant la méthode SFA, Le taux de croissance annuel moyen est estimé à 1,9% sur toute la période ; et de 3,13% cette dernière décennie principalement conduit par le changement technique. Parmi les innovations augmentant le rendement, l’engrais potasse, l’urée, et les systèmes d’irrigation ont une influence positive et significative sur l’accroissement de la productivité agricole. La diversificationdes cultures, comme innovations augmentant le profit, a un effet positif et significatif sur la productivité. Les résultats de notre modèle VAR en panel permettent de s’assurer d’une relation causale à sens unique de la productivité agricole vers l’emploi non-agricole. Et la causalité fonctionne uniquement de la productivité vers les inégalités. D’où, le surcroit de productivité agricole engendre une hausse de l’emploi non-agricole et des inégalités importantes dans la répartition des revenus, mais nécessaire à la croissance des investissements. Les résultats des GMM en systèmeavec la transformation FOD nous permettent d’identifier, la distribution des revenus et le changement des prix des produits comme étant les principaux canaux par lesquels la croissance du secteur agricole affecte le niveau de l’emploi du secteur non-agricole. En faveur d’une croissance soutenue de la productivité et d’une réduction de l’emploi superflu dans le secteur agricole africain, les implications de politique sont axées sur l’amélioration du système de production et la spécialisation du travail.

More than 22,500 tons per year of waste lubricating oil are non-regulatory managed in Cameroon. They are burned in very dangerous conditions when they are not simply dumped in nature. Yet, these wastes are classified as very dangerous for human-beings. The aim of this work is to promote safer methods of disposal of waste lubricating oil in Cameroon by stressing on materials recovery and energetic valorisation in a steam boiler. A combined method of action of melted salt, distillation under low pressure and treatment on activated adsorbed earth (ASFDPRTTA) is efficacious for the task. The oil, treated by this method strips it of polluting chemical in order to obtain a fuel (ecofuel) meeting up the energetic and environmental expectations as required by standards. On the other hand, the fuel presents physicochemical features nearest to the ones of gasoil so that it has been used in a gasoil steam boiler without risk. Also, the fuel served as a base for the regeneration of a new lubricant (envilub) by adding additives in suitably chosen proportions. Our method is using a low cost investment, simple equipment at the point where inexperienced staff with a minimum of training can master it. It also permits job employment opportunities as well as environmental preservation., Au Cameroun, plus de 25 200 tonnes d’huiles de vidange sont gérées annuellement par des méthodes non réglementaires comme par exemple la combustion en foyers non adaptés, voire le rejet direct dans le milieu naturel. Or, ces huiles sont classées parmi les déchets dangereux tant pour l’homme que pour tous les compartiments de l’environnement. Ce travail a pour objectif la valorisation matière et énergie en chaudière de ces huiles par une méthode combinant l’action des sels fondus, distillation sous pression réduite et traitement sur terre absorbante activée (ASFDPRTTA). Il s’agit d’un enchainement de techniques chimiques simples dans des conditions opératoires particulières pour un résultat tout aussi particulier. L’huile usée, traitée par cette méthode, fournit un combustible (écofuel) avec des taux de polluants extrêmement réduits respectant les normes en vigueur. D’autre part, ce combustible présente des caractéristiques physico-chimiques très proches de celles du gazole, permettant son utilisation directe sans restriction dans une chaudière à gazole. Ce combustible a également été utilisé comme base pour la régénération d’un lubrifiant nouveau (envilub) moyennant l’ajout d’additifs dans des proportions convenablement choisies. Notre méthode à moindre coût, utilisant des équipements simples, peut être mise en œuvre par des personnes sans qualification spécifique, associant ainsi la création d’emploi et la préservation de l’environnement.

Urban growth in Southern cities strengthens the mechanisms of production of natural risks. Bafoussam has seen its population double in the space of 15 years, from 293,000 in 2005 to 600,000 inhabitants in 2020. This spectacular urban growth is above all anarchic and produces natural disasters like the deadly landslide of October 29, 2019, in the Gouache IV district. The level of susceptibility of sites exposed to landslides can be modelled by observing and representing predisposing factors such as soil morphology, land use, geology, climate and hydrology. This study aims to develop an approach to modelling the level of susceptibility to landslides in urban areas by using analytical hierachic process of the various predisposing factors coupled with GIS. The hazard map identified five (5) levels of landslide susceptibility from which a summary assessment and recommendations are made. The insignificant hazard, 35.3% of the total urbanized area (403 km²), requires no recommendation for human settlements, the weak hazard requiring recommendations only for large-scale works (44.1%). From moderate hazard, human settlements are possible, but vigilance is recommended for medium-scale work (16.1%). For the strong hazard (2.9%), human settlements are weakly discouraged and vigilance is recommended in the rainy season while the very strong hazards (1.6%) are strongly discouraged for human settlements., La croissance urbaine des villes du Sud renforce les mécanismes de production des risques naturels. La population de Bafoussam a doublé en espace de 15 ans, de 293.000 en 2005 à 600.000 habitants en 2020. Cette croissance spectaculaire est surtout anarchique et produit des catastrophes naturelles comme le glissement de terrain meurtrier du 29 octobre 2019 au quartier Gouache IV. Le niveau de susceptibilité des sites exposés au glissement de terrain peut être modélisé en observant et en représentant les facteurs de prédisposition comme la morphologie des sols, lutilisation du sol, la géologie, le climat et lhydrologie. Cette étude vise à développer une approche de modélisation du niveau de susceptibilité au glissement de terrain en milieu urbanisé à partir dune analyse multicritère hiérarchique des facteurs de prédisposition couplée aux SIG. La carte de risque a permis de distinguer cinq (5) niveaux de susceptibilité au glissement de terrain à partir desquels une évaluation sommaire et des recommandations sont faites. Le risque non significatif, 35,3% de la superficie totale urbanisée (403 km²), ne nécessite aucune recommandation pour les établissements humains, le risque faible nexigeant de recommandations que pour des travaux de grande envergure (44,1%). À partir du risque modéré, les établissements humains sont possibles, mais de la vigilance est préconisée pour les travaux de moyennes envergures (16,1%). Pour le risque fort (2,9%), létablissement humain est faiblement déconseillé et une vigilance est recommandée en saison de pluie tandis que le risque très fort (1,6%) est fortement déconseillé pour les établissements humains.

International audience; Process modelling is a crucial phase of Business Process Management (BPM). Despite the many efforts made in producing process modelling tools, existing tools (languages) are not commonly accepted. They are mainly criticised for their inability to specify both the tasks making up the processes and their scheduling (their lifecycle models), the data they manipulate (their information models) and their organizational models. Process modelling in these languages often results in a single task graph; such a graph can quickly become difficult to read and maintain. Moreover, these languages are often too general (they have a very high expressiveness); this makes their application to specific types of processes complex: especially for administrative processes. In this paper, we present a new language for administrative processes modelling that allows designers to specify the lifecycle, information and organizational models of such processes using a mathematical tool based on a variant of attributed grammars. The approach imposed by the new language requires the designer to subdivide his process into scenarios, then to model each scenario individually using a simple task graph (an annotated tree) from which a grammatical model is further derived. At each moment then, the designer manipulates only a scenario of the studied process: this approach is more intuitive and modular; it allows to produce task graphs that are more refined and therefore, more readable and easier to maintain.

Urban growth in Southern cities strengthens the mechanisms of production of natural risks. Bafoussam has seen its population double in the space of 15 years, from 293,000 in 2005 to 600,000 inhabitants in 2020. This spectacular urban growth is above all anarchic and produces natural disasters like the deadly landslide of October 29, 2019, in the Gouache IV district. The level of susceptibility of sites exposed to landslides can be modelled by observing and representing predisposing factors such as soil morphology, land use, geology, climate and hydrology. This study aims to develop an approach to modelling the level of susceptibility to landslides in urban areas by using analytical hierachic process of the various predisposing factors coupled with GIS. The hazard map identified five (5) levels of landslide susceptibility from which a summary assessment and recommendations are made. The insignificant hazard, 35.3% of the total urbanized area (403 km²), requires no recommendation for human settlements, the weak hazard requiring recommendations only for large-scale works (44.1%). From moderate hazard, human settlements are possible, but vigilance is recommended for medium-scale work (16.1%). For the strong hazard (2.9%), human settlements are weakly discouraged and vigilance is recommended in the rainy season while the very strong hazards (1.6%) are strongly discouraged for human settlements., La croissance urbaine des villes du Sud renforce les mécanismes de production des risques naturels. La population de Bafoussam a doublé en espace de 15 ans, de 293.000 en 2005 à 600.000 habitants en 2020. Cette croissance spectaculaire est surtout anarchique et produit des catastrophes naturelles comme le glissement de terrain meurtrier du 29 octobre 2019 au quartier Gouache IV. Le niveau de susceptibilité des sites exposés au glissement de terrain peut être modélisé en observant et en représentant les facteurs de prédisposition comme la morphologie des sols, l’utilisation du sol, la géologie, le climat et l’hydrologie. Cette étude vise à développer une approche de modélisation du niveau de susceptibilité au glissement de terrain en milieu urbanisé à partir d’une analyse multicritère hiérarchique des facteurs de prédisposition couplée aux SIG. La carte de risque a permis de distinguer cinq (5) niveaux de susceptibilité au glissement de terrain à partir desquels une évaluation sommaire et des recommandations sont faites. Le risque non significatif, 35,3% de la superficie totale urbanisée (403 km²), ne nécessite aucune recommandation pour les établissements humains, le risque faible n’exigeant de recommandations que pour des travaux de grande envergure (44,1%). À partir du risque modéré, les établissements humains sont possibles, mais de la vigilance est préconisée pour les travaux de moyennes envergures (16,1%). Pour le risque fort (2,9%), l’établissement humain est faiblement déconseillé et une vigilance est recommandée en saison de pluie tandis que le risque très fort (1,6%) est fortement déconseillé pour les établissements humains.

International audience; In this manuscript, we are interested in the specification and decentralized execution of administrative workflows. We present a grammatical model to specify such processes by indicating, in addition to their fundamental elements, the permissions (reading, writing and execution) of each actor in relation to each of the tasks that compose them. We then present a decentralized and artifact-centric execution model of these processes, on a Peer to Peer (P2P) Workflow Management System (WfMS). Our execution model allows the confidential execution of certain tasks by ensuring that, each actor potentially has only a partial perception of the overall process execution status. In our approach, we propose various stable projection algorithms, making it possible to obtain, to verify the coherence and to guarantee the convergence of the various potentially partial perceptions. Our algorithms are then coded and tested using a graphical tool to simulate the decentralized execution of administrative processes.; Dans ce manuscrit, nous nous intéressons à la spécification et à l'exécution décentralisée des processus workflows administratifs. Nous présentons un modèle grammatical permettant de spécifier de tels processus en précisant en plus de leurs éléments fondamentaux, les permissions (lecture, écriture et exécution) de chaque acteur relativement à chacune des tâches qui les composent. Nous présentons ensuite un modèle d'exécution décentralisée et centré-artefact de ces processus, sur un Système de Gestion de Workflows (SGWf) Pair à Pair (P2P). Notre modèle d'exécution autorise l'exécution confidentielle de certaines tâches en permettant à chaque acteur, de n'avoir potentiellement qu'une perception partielle de l'état d'exécution global du processus. Dans notre démarche, nous proposons divers algorithmes de projection stables, permettant d'obtenir, de vérifier la cohérence et de garantir la convergence des diverses perceptions potentiellement partielles. Nos algorithmes sont ensuite codés et expérimentés à l'aide d'un outil graphique de simulation d'exécution décentralisée des processus administratifs.

International audience; In this manuscript, we are interested in the specification and decentralized execution of administrative workflows. We present a grammatical model to specify such processes by indicating, in addition to their fundamental elements, the permissions (reading, writing and execution) of each actor in relation to each of the tasks that compose them. We then present a decentralized and artifact-centric execution model of these processes, on a Peer to Peer (P2P) Workflow Management System (WfMS). Our execution model allows the confidential execution of certain tasks by ensuring that, each actor potentially has only a partial perception of the overall process execution status. In our approach, we propose various stable projection algorithms, making it possible to obtain, to verify the coherence and to guarantee the convergence of the various potentially partial perceptions. Our algorithms are then coded and tested using a graphical tool to simulate the decentralized execution of administrative processes.; Dans ce manuscrit, nous nous intéressons à la spécification et à l'exécution décentralisée des processus workflows administratifs. Nous présentons un modèle grammatical permettant de spécifier de tels processus en précisant en plus de leurs éléments fondamentaux, les permissions (lecture, écriture et exécution) de chaque acteur relativement à chacune des tâches qui les composent. Nous présentons ensuite un modèle d'exécution décentralisée et centré-artefact de ces processus, sur un Système de Gestion de Workflows (SGWf) Pair à Pair (P2P). Notre modèle d'exécution autorise l'exécution confidentielle de certaines tâches en permettant à chaque acteur, de n'avoir potentiellement qu'une perception partielle de l'état d'exécution global du processus. Dans notre démarche, nous proposons divers algorithmes de projection stables, permettant d'obtenir, de vérifier la cohérence et de garantir la convergence des diverses perceptions potentiellement partielles. Nos algorithmes sont ensuite codés et expérimentés à l'aide d'un outil graphique de simulation d'exécution décentralisée des processus administratifs.

International audience; Coffee is an important cash crop for many developing countries. Coffee production is affected by many pests. We are particularly interested in the coffee berry borer(CBB) Hypothenemus Hampei, which is considered as the most important pesteconomically. The CBB is a small insect that feeds and reproduces inside the coffee berries, causing considerable damages resulting in a deterioration of the berry quality and reduced yields. Mature females are responsible for the dispersal of the population: they emerge from the berries to colonise and lay their eggs in new berries, while males and juvenile stages remain inside the berries. The main control methods to decrease CBB infestation are pesticides, but also cultural practices, biological control and trapping. Our global aim is to design and assess the efficiency of control strategies, with a focus on alternatives to pesticides.To tackle this issue, we formulated a control problem, based on a dynamicalmodel that describes the CBB infestation of coffee berries and the berry availability during a cropping season. We aim at maximising the yield at the end of the cropping season, while minimising the control costs as well as the CBB population at the end of the season. The first two terms aim at maximising the grower’s profit. The last term is introduced to reduce the CBB infestation for the next season. We give necessary optimality conditions and numerical simulations are provided to illustrate our results.

International audience; Agriculture plays a major role in the economy of many developing countries, providing export revenues, food and employment. As pests are responsible for severe crop losses every year, their control is a major issue. It often relies on chemical pesticides, which are often costly and detrimental to the environment, so alternative solutions are sought. In this talk, we tackle this issue by designing ecologically friendly controls for two pathosystems: the phytophagous plantain nematode, which attacks plant roots, and the coffee berry borer, which feeds and reproduce in the berries. In both cases, the yield is maximized in order to be economically viable. An efficient method to reduce the nematode population in the soil consists in having fallow periods between cropping seasons. We developed an ODE/hybrid seasonal model for the nematode--root dynamics [1] and we exploit it in the present work to globally optimize the duration of the fallow periods, which potentially vary from one year to the other. For the coffee berry borer, we study how the persistent effect of entomopathogenic fungi can impact the optimal yield, compared to non-persistent controls obtained on a single season ODE model of the berry--borer dynamics [2]. Moreover, we extend our results to a seasonal framework, as for the plantain--nematode pathosystem.[1] I. Tankam Chedjou, S. Touzeau, F. Grognard, L. Mailleret, J.-J. Tewa. An agricultural control of Radopholus similis in banana plantations, 11th ECMTB, Lisbon, Portugal, 2018.[2] Y. Fotso Fotso, S. Touzeau, S. Bowong, F. Grognard, L. Mailleret, B. Tsanou. Modelling and control of coffee berry borer infestation, 11th ECMTB, Lisbon, Portugal, 2018.

International audience; With the emergence of XML as de facto format for storing and exchanging information over the Internet, the search for ever more innovative and effective techniques for their querying is a major and current concern of the XML database community. Several studies carried out to help solve this problem are mostly oriented towards the evaluation of so-called exact queries which, unfortunately, are likely (especially in the case of semi-structured documents) to yield abundant results (in the case of vague queries) or empty results (in the case of very precise queries). From the observation that users who make requests are not necessarily interested in all possible solutions, but rather in those that are closest to their needs, an important field of research has been opened on the evaluation of preferences queries. In this paper, we propose an approach for the evaluation of such queries, in case the preferences concern the structure of the document. The solution investigated revolves around the proposal of an evaluation plan in three phases: rewriting-evaluation-merge. The rewriting phase makes it possible to obtain, from a partitioning-transformation operation of the initial query, a hierarchical set of preferences path queries which are holistically evaluated in the second phase by an instrumented version of the algorithm TwigStack. The merge phase is the synthesis of the best results.; Avec l’émergence du XML comme format de facto de stockage et d’échange d’information à travers internet, la recherche des techniques toujours plus innovantes et efficaces pour leur interrogation est une préoccupation majeure et actuelle de la communauté des bases de données XML. Plusieurs travaux contribuant à solutionner ce problème sont orientés pour la plupart vers l’évaluation des requêtes dites exactes, qui, malheureusement, sont susceptibles (surtout pour le cas des documents semi-structurés) de renvoyer des résultats abondants (cas des requêtes vagues) ou vide (cas des requêtes très précises). Du constat suivant lequel les utilisateurs émettant des requêtes ne sont pas nécessairement intéressés par toutes les solutions possibles mais, plutôt par celles qui se rapprochent le plus de leurs besoins, un champ de recherche important s’est ouvert sur l’évaluation des requêtes dites avec préférences. Nous proposons dans ce papier, une approche d’évaluation de telles requêtes, pour le cas où les préférences portent sur la structure du document. La solution étudiée s’articule autour de la proposition d’un plan d’évaluation en trois phases: réécriture-évaluation-fusion. La phase de réécriture permet d’obtenir à partir d’une opération de partitionnement-transformation de la requête initiale, un ensemble hiérarchique de requêtes de chemins avec préférences, qui sont holistiquement évaluées dans la seconde phase par une version instrumentalisée de l’algorithme TwigStack. La phase de fusion quand à elle consiste en la synthétisation des meilleurs résultats.

International audience; Cet article a pour objectif d'analyser les « brain drain effect » dans un contexte spécifique qui est celui du Cameroun. Territoire au paysage de développement parfois répulsif, le Cameroun souffre ainsi d'une « crise de développement » généralisée. Cette situation favorise une économie au large réservoir de chômeurs très qualifiés et/ou peu qualifiés. Depuis les années 1990, aucune évolution majeure n'est observée dans la dynamique de développement du Cameroun. En plus, son indice de développement humain le range dans la catégorie des pays moyens ou moins avancés.Le Cameroun fait ainsi, partie des pays qui peine à absorber son capital humain formé sur place. Dans cette perspective, pour fuir le déterminisme contextuel, les cadres qualifiés migrent vers des zones plus attractives et/ou moins répulsives. En 1990, le Cameroun avait plus de 1434 des 9515 immigrants nantis d'une formation universitaire résidant aux Etats-Unis. En 2000, le taux d'émigration des diplômés de l'enseignement supérieur était estimé à 17,2%. Ce phénomène prive le pays des ressources humaines susceptibles de favoriser son développement. Le secteur de la santé semble le plus touché. D'après l'Ordre des médecins, 4200 médecins camerounais, en majorité des spécialistes, exercent à l'étranger. Au Cameroun, il en reste seulement 800, ce qui fait un médecin pour 10.000 à 20.000 habitants dans les villes et un médecin pour 40.000 à 50.000 dans les zones périphériques. Ceci entraine le déclin progressif du pays. Cependant, une lecture transnationalisteet interprétative de ce phénomène permet d'observer que cette migration de personnels qualifiés constitue en même temps une fuite de cerveaux, une stratégie de gestion d'excédents en ressources humaines et un potentiel facteur de développement à long terme. Abstract This article aims to analyze "brain drain"effectsin the specific context of Cameroon. As a

This article presents the mechanisms to create a generic platform for decision makers to implement rapid management models, with a multi-scale and multi-level stratification of education, including basic education, secondary and higher education, while minimizing the risk of errors, so as to increase their efficiency in the governance field. We will identify beforehand the various active and passive element involved in an education system, considered here as the model input parameters and the various interactions between them. Then we list the specific objectives and outputs considered in the model. We will build on the analysis and knowledge management techniques to develop a multi-level decision model incorporating input parameters and expected or desired outputs for better decision making. The developed model will be based on a formal language that we define. This work will help to solve the difficulties that governments sometimes face in optimizing and taking decision regarding construction of schools or universities in various localities, assignment of teachers or non-teaching staff in an institution, training of these as needed, allocation of teaching materials, benches and laboratory equipment. It is for us to truly put technology at the service of governance in education, and development in general., Cet article présente les mécanismes de création d'une plateforme générique permettant aux décideurs de mettre en oeuvre des modèles de pilotage rapide, avec une stratification multi-échelle et multi-degré du secteur de l'éducation, couvrant l'éducation de base, le secondaire et le supérieur, tout en minimisant les risques d'erreurs, de manière à accroitre leur efficacité en matière de gouvernance dans le domaine. Nous allons préalablement recenser les différents éléments actifs intervenant dans un système éducatif, considérés ici comme les différents niveaux du modèle, ainsi que les différentes interactions entre ces derniers. Ensuite, nous répertorierons les objectifs spécifiques à atteindre. Nous nous appuierons sur les Techniques d'analyse et de gestion des connaissances, pour développer un modèle décisionnel multi-niveaux intégrant les niveaux et les objectifs à atteindre, pour une meilleure prise de décision. Ce travail contribuera à résoudre les difficultés que les gouvernements rencontrent parfois dans l'optimisation de la prise de décision en matière de construction des établissements scolaires ou d'Universités dans diverses localités, d'affectation des enseignants ou du personnel non enseignant dans un établissement, de formation de ces derniers en fonction des besoins, etc…. Il s'agit pour nous de mettre véritablement la technologie au service de la gouvernance en matière d'éducation, et du développement en général.

The main objective of this research is to show how the abundance of natural re-sources creates economic and political dysfunctions as ilustrated by African countries. This study is based on four essays. The first essay examines empirically about 36 African countries, the determinants of longevity in power. The second essay analyzes the effect of fragmentation in 45 African countries, with particular emphasis on political stability. The third essay deals with the effect of border disputes by conducting an empirical study of the DRC and its nine neigh-boring countries. Finally, the fourth essay focuses on the macroeconomic effects of the type of political regime in the DRC. We use several types of econometrics and data sources adapted to each of the situations mentioned. We achieve the following key results: (1) dependence on oil and minerals positively impacts longevity in power in Africa, and human capital reduces the chances for an African head of state to stay long in power. (2) fragmentation negatively impacts political stability. (3) the mining resource rents increase border conflicts in the DRC (4) The consequences of the type of political regime and the abundance of natural resources increase the macroeconomic instability in the DRC.We suggest that the promotion of the education sec-tor should be at the heart of government strategies and therefore a priority and the strengthe-ning of constitutional rules regarding elections., L’objectif principal de cette recherche est de montrer comment l’abondance des ressources naturelles crée des dysfonctionnements économique et politique à partir de quelques exemples de pays africains. Cette étude s’articule autour de quatre essais. Le premier essai examine em-piriquement sur 36 pays africains, les déterminants de la longévité au pouvoir. Le deuxième essai analyse l’effet de la fragmentation dans 45 pays africains, en mettant un accent particu-lier sur la stabilité politique. Le troisième essai traite l’effet des conflits frontaliers en menant une étude empirique sur la RDC et ses neufs pays voisins. Finalement, le quatrième essai porte sur les effets macroéconomiques du type de régime politique en RDC. Nous mobilisons plu-sieurs types d’économétrie et sources de données adaptés à chacune des situations évoquées. Nous parvenons aux principaux résultats suivants : (1) la dépendance vis-à-vis du pétrole et de minerais impacte positivement la longévité au pouvoir en Afrique, et le capital humain réduit la chance d’un chef d’Etat africain de rester longtemps au pouvoir. (2) la fragmentation impacte négativement la stabilité politique. (3) la rente issue des ressources minières accroît les conflits frontaliers en RDC (4) Les conséquences du type de régime politique et l’abondance des res-sources naturelles augmentent l’instabilité macroéconomique en RDC. Nous suggérons que la promotion du secteur éducatif doit être au cœur des stratégies des pouvoirs publics et donc en faire une priorité et le renforcement des règles constitutionnelles concernant les élections.

In this paper, we developed a mathematical model that describes the infestation dynamics of coffee berry by Hypothenemus hampei (CBB). This model takes into account control some integrated pest management strategies which are used by coffee growers to eradicate CBB in plantations, represented by two functions depending on time. We design these functional controls to maximize the yield of healthy berries at the end of the cropping season, while minimizing the CBB population for the next season. By using optimal control theory, we show that an optimal control exists for this problem and Pontryagin’s maximum principle is used to characterize an optimal control. Numerical simulations are provided to illustrate our results., Dans ce papier, nous developpons un modèle mathématique qui décrit la dynamique d’infestation des baies du caféier par les scolytes (CBB). Ce modèle prend en compte certaines stratégies de lutte intégrée utilisées par les caféiculteurs pour éradiquer les CBB dans les plantations, représentées par deux fonctions dépendant du temps. Nous concevons ces contrôles fonctionnels pour maximiser le rendement des baies saines à la fin de la saison, tout en minimisant la population de CBB pour la prochaine saison. En utilisant la théorie du contrôle optimal, nous montrons qu’un contrôle optimal existe pour ce problème et le principe du maximun de Pontryagin est utilisé pour caractériser ce contrôle optimal. Des simulations numériques sont faites pour illustrer nos résultats.

Human parasites are a real public health problem in tropical countries, especially in underdeveloped countries. Usually, the medical diagnosis of intestinal parasites is carried out in the laboratory by visual analysis of stools samples using the optical microscope. The parasite recognition is realized by comparing its shape with the known forms. We offer a solution to automate the diagnosis of intestinal parasites through their images obtained from a microscope connected directly to a computer. Our approach exploits the contour detection based on the multi-scale wavelet transform for detecting the parasite. Active contours are combined with the Hough transform to perform image segmentation and extraction of the parasite. We used the principal component analysis for the extraction and reduction of features obtained directly from pixels of the extracted parasite image. Our classification tool is based on the probabilistic neural network. The obtained algorithms were tested on 900 samples of microscopic images of 15 different species of intestinal parasites. The result shows a 100% recognition rate of success. Keywords: Intestinal parasites, Wavelet edge detector, Hough transform, Active contours, Probabilistic neural network

In this work, a natural sodium-montmorillonite clay mineral (Mt-Na) was functionalized with aminegroups, either by direct grafting (Mt-NH2) or via acid activation followed by grafting (MtH-NH2) of [3(2-aminoethyl)amino)]propyltrimethoxysilane (AEP-TMS). The morphology and structure of the resulting composite materials were characterizedby scanning electron microscopy, X-ray diffraction, N2 adsorption-desorption isotherms (BET method) infrared spectroscopy, CHN elemental analysis and thermogravimetric analyses (TGA). The obtained organoclays were then used to modify the surface ofa glassy carbon electrode (GCE), and the permselectivity and accumulation properties of the resulting films were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicated that MtH-NH2 modified GCE (GCE/MtH-NH2) exhibited some charge selectivity features and can be applied to the electrochemical oxidation of catechol (CT).By plotting the double logarithmic variation of anodic peak currents (Ipa) versus potential scan rate, the obtained slope valueof 0.49 revealed a diffusion-controlled electron-transfer mechanisms for the redox process. The electrochemical behavior of CT on the modified electrode was also studied using differential pulse voltammetry (DPV). The sensitivities of GCE/MtH-NH2 for CT were 1.71, 3.87 and 1.35-fold greater than signals obtained on the bare GCE, GCE/Mt-Na and GCE/Mt-NH2 respectively, due to the ability of the aminated materials to strongly accumulate CT. After optimization, GCE/MtH-NH2 was used for CT determination by differential pulse voltammetry that gave rise to a linear response in the concentration range from 5 μM to 80 μM (R2 = 0.999), and to a detection limit of 0.65 μM. The proposed method was applied to CT detection in water samples and in a tea sample.

This thesis dissertation whose topic is " La Guinée Équatoriale face au couple Cameroun-Gabon en Afrique Centrale (1960-2012) : Histoire d’un petit État en quête d’émancipation et de puissance ”, aims at tracing the history of relations between the Cameroon-Gabon pair and Equatorial Guinea in the process of regional integration in Central Africa, emphasizing the quest of power by Equatorial Guinea in the sub-region. It also aims at answering the main question: How do the attitude and acts of Equatorial Guinea in Central Africa explain the quest for emancipation and power vis-à-vis the Cameroon-Gabon pair? This thesis uses an interdisciplinary approach based on qualitative and content Analysis from various sources.From 1960 to 1979, relations between Equatorial Guinea and Cameroon-Gabon pair fluctuated between cooperation, aid and conflict. Following a coup overthrowing Macías Nguema, Obiang Nguema Mbasogo soothed relations with his two francophone neighbors, which led to the accession of his country to the UDEAC. Being very poor, Equatorial Guinea had no position of senior responsibility; any community institution had its headquarter in Equatorial Guinea and the country did not claimed it. In 1990, the discovery and exploitation of oil in Equatorial Guinea changed the face of this country in the sub-region and enabled him to claim and have the institutional reform of CEMAC. This institutional reform enabled Equatorial Guinea to gain senior leadership positions within the CEMAC to the dismay of the Cameroon-Gabon pair. The thesis concludes that despite all the maneuvers of Equatorial Guinea in the CEMAC zone about leadership; it does not have all the criteria enabling it to become the leading power in the sub-region., La présente thèse dont le thème est « La Guinée Équatoriale face au couple Cameroun-Gabon en Afrique Centrale (1960-2012) : Histoire d’un petit État en quête d’émancipation et de puissance », a pour objet de retracer l’histoire des relations entre le couple Cameroun-Gabon et la Guinée Équatoriale dans le processus d’intégration régionale en Afrique Centrale en insistant sur la quête de puissance de la Guinée Équatoriale dans la sous-région. Cette thèse a pour ambition de répondre à la question principale suivante : en quoi l’attitude et les actes de la Guinée Équatoriale en Afrique Centrale relèvent-ils d’une quête d’émancipation et de puissance vis-à-vis du couple Cameroun-Gabon ? Cette thèse utilise une approche interdisciplinaire basée sur une analyse qualitative et de contenu de diverses sources.De 1960 à 1979, les relations entre la Guinée Équatoriale et le couple Cameroun-Gabon ont oscillé entre coopération, aide et conflictualité. À la suite d’un coup d’État renversant Macías Nguéma, Obiang Nguéma Mbasogo apaisa les relations avec ses deux voisins francophones, ce qui conduisit à l’adhésion de son pays à l’UDEAC. Étant très pauvre, la Guinée Équatoriale ne disposait d’aucun poste de responsabilité de haut niveau, n’abritait aucune institution communautaire et n’en revendiquait pas. En 1990, la découverte et l’exploitation du pétrole en Guinée Équatoriale ont changé le visage de ce pays dans la sous-région et lui ont permis de revendiquer et d’avoir la réforme institutionnelle de la CEMAC. Cette réforme institutionnelle a permis à la Guinée Équatoriale de s’adjuger des postes de responsabilité de haut niveau dans la CEMAC au grand dam du couple Cameroun-Gabon. La thèse conclut que malgré toutes les manœuvres entreprises par la Guinée Équatoriale en zone CEMAC à propos du leadership, elle ne dispose pas de tous les critères lui permettant de devenir la première puissance de la sous-région.

Wireless sensor networks (WSN) face many implementation’s problems such as connectivity, security, energy saving, fault tolerance, interference, collision, routing problems, etc. In this paper, we consider a low-density WSN where the distribution of the sensors is poor, and the virtual architecture introduced by Wadaa and al which provides a powerful and fast partitioning of the network into a set of clusters. In order to effectively route the information collected by each sensor node to the base station (sink node, located at the center of the network), we propose a technique based on multiple communication frequencies in order to avoid interferences during the communications. Secondly, we propose an empty clusters detection algorithm, allowing to know the area actually covered by the sensors after the deployment, and therefore, giving the possibility to react accordingly. Finally, we also propose a strategy to allow mobile sensors (actuators) to move in order to: save the WSN’s connectivity, improve the routing of collected data, save the sensors’ energy, improve the coverage of the area of interest, etc. Les réseaux de capteurs sans fil (RCSF) font face à de nombreux problèmes dans leur mise en oeuvre, notamment aux problèmes de connectivité des noeuds, de sécurité, d'économie d'énergie, de tolérance aux pannes, d'interférence, de collision, de routage, etc. Dans ce document, nous considérons un RCSF peu dense, caractérisé par une mauvaise couverture de la zone d'inté-rêt, et l'architecture virtuel introduite par Wadaa et al qui permet de partitionner efficacement ce type de réseau en clusters. Dans l'optique de router optimalement les informations collectés par chaque capteur jusqu'à une station de base (noeud sink, supposé au centre du réseau), nous proposons une technique d'utilisation des fréquences multiples pour limiter les interférences lors des communications. Ensuite, nous proposons un algorithme de détection de clusters vides permettant d'avoir une vue globale de la répartition réelle des capteurs dans la zone d'intérêt, et ainsi donner la possibilité de réagir en conséquence. Nous proposons également une stratégie de déplacement des capteurs mobiles (actuators) afin de: sauvegarder la connectivité du RCSF, optimiser le routage, économiser l'énergie des capteurs, améliorer la couverture de la zone d'intérêt, etc.