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Hydrogen insertion effects on the electronic structure of equiatomic MgNi traced by ab initio calculations
No full textInternational audienceFor equiatomic MgNi which can be hydrogenated up to the composition MgNiH1.6 at an absorption/desorption temperature of 200 °C, the effects of hydrogen absorption are approached with the model structures MgNiH, MgNiH2 and MgNiH3. From full geometry optimization and calculated cohesive energies obtained within DFT, the MgNiH2 composition close to the experimental limit is identified as most stable. Charge density analysis shows an increasingly covalent character of hydrogen: MgNiH (H−0.67) → MgNiH2 (H−0.63) → MgNiH3 (H−0.55). While Mg-Ni bonding prevails in MgNi and hydrogenated model phases, extra itinerant low-energy Ni states appear when hydrogen is introduced signaling Ni-H bonding which prevails over Mg-H as evidenced from total energy calculations and chemical bonding analyses
ENVIRONNEMENT ET GESTION DURABLE DES ÉCOSYSTÈMES NATURELS AU MOYEN-ORIENT
No full textInternational audienceLe développement des sociétés passe aujourd'hui par une maîtrise des questions environnementales qui sont aussi un enjeu des relations internationales de ce début du 21ème siècle. Les savoirs et connaissances dans ce domaine sont de créations très récentes ; ils mobilisent davantage diverses disciplines. L'Agence favorisera l'émergence et le développement d'une expertise de la communauté scientifique francophone sur l'environnement. Elle le fera notamment par le renforcement des capacités des enseignants-chercheurs et des décideurs (fonctionnaires des ministères concernés) des pays francophones en développement. Cela concerne la consolidation des compétences institutionnelles en matière de négociation internationale et la formation d'experts locaux pour la mise en place de stratégies nationales d'adaptation aux changements climatiques
La sensibilité potentielle du sol à l’érosion hydrique dans la Bekaa Ouest, une approche effectuée à l’aide d’un S.I.G.
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Pairs Trading comme Arbitrage Statistique à la Bourse de Beyrouth: La Co-intégration entre les Cours des Actions Solidere A et B*.
No full textInternational audienceLe’Pairs Trading’ est une forme particulière d’arbitrage statistique destiné à l’exploitation des déviations temporaires de prix d’équilibre de long terme entre deux produits financiers. Cette étude utilise l’approche de co-intégration selon R. Engle & C. Granger (1987) sur les cours de clôture journalière des actions Solidere A et B à la Bourse de Beyrouth à partir de Septembre 2003 à Novembre 2010. Le résultat montre que les cours des actions Solidere A et B peuvent être réunis dans une régression linéaire authentique de sorte que la dynamique de son résidu résultant suit un processus de retour à la moyenne modélisée comme un modèle de correction d’erreur (MCE). Sur la base de cette constatation, nous développons une stratégie de’Pairs Trading’ qui produit un certain bénéfice hors risque. Nous vérifions la validité de ce résultat par l’application de la méthode du bootstrap sur le spread. Ces résultats significatifs et positifs s’accordent avec des conclusions antérieures sur la performance de tel type d’arbitrage statistique dans les marchés développés. Notamment, cette étude peut servir d’exemple pour la construction de tels portefeuilles aux marchés boursiers du Moyen-Orient et de l’Afrique du Nord
CRM Failure to Apply Optimal Management Information Systems: Case of Lebanese Financial Sector
No full textInternational audienceFinancial markets in Lebanon are constrained by government influence, Islamic financial principles, and some barriers to foreign participation. Productivity in the Lebanese financial sector ranks below its occidental counterpart in spite the fact that regulatory, supervisory, and accounting standards are generally consistent with international norms. This paper aims to give the reasons and recommendations of the failure of applying the optimal management information system in the Lebanese Financial Sector. Our results show that the reasons include among others the systems by it selves, their functionalities, but also, companies’ strategy and human capital issues
The importance of the knowledge of flow stream in water sump pump
No full textNational audienceNumerous different experimental and numerical methods have been developed and are already improved in order to get rather good flow descriptions inside pump components. These calculations are generally realized assuming uniform and steady flow conditions, in particular for the inlet conditions. However, few studies are devoted to non-uniform upstream conditions, especially in case of water pump sump before entering the pump inlet tube. Free air-core vortex occurring at the water-intake pipe is an important problem encountered in hydraulic engineering because they reduce pump performances and may have large effects on the operating conditions. The paper deals with flow pattern inside sump pump. Experiments were conducted in order to select best positions of the suction pipe of water-intake specific configurations. The numerical studies try to reproduce the flow pattern of these experiments and confirm the influence of geometrical parameters on the flow structure in such a sump. These numerical studies points out the need of unsteady calculation in order to get a better understanding of flow behaviour including two-phases flow models
Children's reward responses to picture- and odor-cued food stimuli: a developmental analysis between 6 and 11 years.
No full textInternational audienceThe reward system is largely involved in the control of food intake. Whether components of this system (i.e., wanting and liking) change during development remains understudied, as well as how proximate factors (sensory cues, motivational state) modulate reward reactivity across development. We examined the developmental pattern of wanting and liking for sensorily-cued food stimuli in 6-11year old children as a function of the child's motivational state (hunger/satiety), gender, and the nature of foods. School children were exposed before or after their lunch on alternative days to visual and odor stimuli representing different categories of familiar foods. Their task was to rate wanting and liking of pictures and odorants of pizza, meat, vegetables, fruits, and chocolate. The following results were found: (1) While liking appeared to be stable from age 6 to 11, more particularly for visually-cued foods, wanting decreased, as well as did subjective hunger perception; (2) there were smaller or absent state-effects in 7-to-9-year-olds; (3) reward ratings were higher in boys than in girls; (4) reward ratings of vegetables were the lowest at all ages. These results suggest that wanting, but not liking, is developmentally variable over childhood, and that this variation depends on age, gender, motivational state (hunger/satiety), the nature of the food and the modality of the sensory cue representing it. Such developmental changes are discussed in relation to biological (adiposity rebound) and cognitive (dietary restraint) factors influencing the motivation to eat during middle (6-7years) and late (9-11years) childhood
A proximal approach for signal recovery based on information measures
No full textInternational audienceRecently, methods based on Non-Local Total Variation (NLTV) minimization have become popular in image processing. They play a prominent role in a variety of applications such as denoising, compressive sensing, and inverse problems in general. In this work, we extend the NLTV framework by using some information divergences to build new sparsity measures for signal recovery. This leads to a general convex formulation of optimization problems involving information divergences. We address these problems by means of fast parallel proximal algorithms. In denoising and deconvolution examples, our approach is compared with '2- NLTV based approaches. The proposed approach applies to a variety of other inverse problems
Traffic-related air pollution. A pilot exposure assessment in Beirut, Lebanon
No full textInternational audienceTraffic-related volatile organic compounds (VOCs) pollution has frequently been demonstrated to be a serious problem in the developing countries. Benzene and 1,3-butadiene (BD) have been classified as a human carcinogen based on evidence for an increased genotoxic and epigenotoxic effects in both occupational exposure assessment and in vivo/in vitro studies. We have undertaken a biomonitoring of 25 traffic policemen and 23 office policemen in Beirut, through personal air monitoring, assessed by diffusive samplers, as well as through the use of biomarkers of exposure to benzene and BD. Personal benzene, toluene, ethylbenzene, and xylene (BTEX) exposure were quantified by GC-MS/MS, urinary trans, trans-muconic acid (t,t-MA) by HPLC/UV, S-phenyl mercapturic acid (S-PMA), monohydroxy-butenyl mercapturic acid (MHBMA) and dihydroxybutyl mercapturic acid (DHBMA) by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC/ESI(-)-MS/MS) in MRM (Multiple Reaction Monitoring) mode. We found that individual exposure to benzene in the traffic policemen was higher than that measured in traffic policemen in Prague, in Bologna, in Ioannina and in Bangkok. t,t-MA levels could distinguish between office and traffic policemen. However, median MHBMA levels in traffic policemen were slightly elevated, though not significantly higher than in office policemen. Alternatively, DHBMA concentrations could significantly distinguish between office and traffic policemen and showed a better correlation with personal total BTEX exposure. DHMBA, measured in the post-shift urine samples, correlated with both pre-shift MHMBA and pre-shift DHMBA. Moreover, there was not a marked effect of smoking habits on DHBMA. Taken together, these findings suggested that DHBMA is more suitable than MHBMA as biomarker of exposure to BD in humans. Traffic policemen, who are exposed to benzene and BD at the roadside in central Beirut, are potentially at a higher risk for development of diseases such as cancer than office policemen