Analyse des effects de la pluviometrie sur le PIB Agricole au Senegal

RESUMELe secteur agricole au Sénégal est dominé par les cultures pluviales dont l’arachide et le mil qui occupent la majeure partie des terres cultivables en hivernage. Sa contribution au PIB reste faible par rapport aux secteurs tertiaire et secondaire. Une des principales raisons de cette situation est sa forte dépendance aux conditions climatiques et notamment à la pluviométrie. Dans cette recherche nous nous proposons d’étudier l’analyse des effets de la pluviométrie sur le PIB du sous- secteur agricole au Sénégal. L’étude couvre une période de 35 ans allant de 1980 à 2015 et concerne tout le territoire national. Les résultats des tests économétriques par la technique des Moindres Carrés Ordinaires (MCO) montrent que la variation pluviométrique influence les résultats économiques du secteur agricole. L’étude montre qu’à chaque fois que la pluviométrie baisse, les productions et les valeurs économiques du mil et de l’arachide suivent la même tendance. Ainsi une bonne pluviométrie a un effet positif sur la production agricole qui à son tour influence positivement le PIB agricole. ABSTRACTANALYSIS OF THE EFFECTS OF RAINFALL ON AGRICULTURAL GDP IN SENEGALThe agricultural sector in Senegal is dominated by rainfed crops, with groundnuts and millet occupying most of the land. Its contribution to GDP remains low compared to the tertiary and secondary sectors. One of the main reasons for this situation is its strong dependence on climatic conditions and in particular on rainfall. In this research we propose to study the analysis of the effects of rainfall on the GDP of the agricultural sub-sector in Senegal. The study covers a 35-year period from 1980 to 2015 and concerns the entire national territory. The results of econometric tests using the Ordinary Least Squares (OLS) technique show that rainfall variation influences the economic performance of the agricultural sector. The study shows that each time the rainfall drops, the production and economic values of millet and peanuts follow the same trend. Thus, good rainfall has a positive effect on agricultural production which in turn positively influences agricultural GDP

Direct observation of the influence of the As-Fe-As angle on the Tc of superconducting SmFeAsO1−x_{1-x}Fx_{x}

The electrical resistivity, crystalline structure and electronic properties calculated from the experimentally measured atomic positions of the compound SmFeAsO$_{0.81}$F$_{0.19}$ have been studied up to pressures ~20GPa. The correlation between the pressure dependence of the superconducting transition temperature (Tc) and crystallographic parameters on the same sample shows clearly that a regular FeAs$_{4}$ tetrahedron maximizes Tc, through optimization of carrier transfer to the FeAs planes as indicated by the evolution of the electronic band structures.Comment: 15pages, 4 figure

Mesophilic and thermophilic methane fermentation of Euphorbia tirucallis

La méthanisation d'#Euphorbia tirucalli$ a été réalisée en conditions mésophile et modérément thermophile. Trois différents pré-traitements de cette plante ont été testés : simple fragmentation, broyat, séchage puis broyage. Les digesteurs ont été alimentés avec 5 % de matière sèche en batch. Lors d'une expérimentation de 35 jours, le meilleur rendement (0,78 1/1/j) a été obtenu avec les fragments de plante en condition thermophile modérée. (Résumé d'auteur

Pressure Dependence of Fragile-to-Strong Transition and a Possible Second Critical Point in Supercooled Confined Water

By confining water in nano-pores of silica glass, we can bypass the crystallization and study the pressure effect on the dynamical behavior in deeply supercooled state using neutron scattering. We observe a clear evidence of a cusp-like fragile-to-strong (F-S) dynamic transition. Here we show that the transition temperature decreases steadily with an increasing pressure, until it intersects the homogenous nucleation temperature line of bulk water at a pressure of 1600 bar. Above this pressure, it is no longer possible to discern the characteristic feature of the F-S transition. Identification of this end point with the possible second critical point is discussed.Comment: 4 pages, 3 figure

Determining Pair Interactions from Structural Correlations

We examine metastable configurations of a two-dimensional system of interacting particles on a quenched random potential landscape and ask how the configurational pair correlation function is related to the particle interactions and the statistical properties of the potential landscape. Understanding this relation facilitates quantitative studies of magnetic flux line interactions in type II superconductors, using structural information available from Lorentz microscope images or Bitter decorations. Previous work by some of us supported the conjecture that the relationship between pair correlations and interactions in pinned flux line ensembles is analogous to the corresponding relationship in the theory of simple liquids. The present paper aims at a more thorough understanding of this relation. We report the results of numerical simulations and present a theory for the low density behavior of the pair correlation function which agrees well with our simulations and captures features observed in experiments. In particular, we find that the resulting description goes beyond the conjectured classical liquid type relation and we remark on the differences.Comment: 7 pages, 6 figures. See also http://rainbow.uchicago.edu/~grier

Inherent-opening-controlled pattern formation in carbon nanotube arrays

We have introduced inherent openings into densely packed carbon nanotube arrays to study self-organized pattern formation when the arrays undergo a wetting–dewetting treatment from nanotube tips. These inherent openings, made of circular or elongated hollows in nanotube mats, serve as dewetting centres, from where liquid recedes from. As the dewetting centres initiate dry zones and the dry zones expand, surrounding nanotubes are pulled away from the dewetting centres by liquid surface tension. Among short nanotubes, the self-organized patterns are consistent with the shape of the inherent openings, i.e. slender openings lead to elongated trench-like structures, and circular holes result in relatively round nest-like arrangements. Nanotubes in a relatively high mat are more connected, like in an elastic body, than those in a short mat. Small cracks often initialize themselves in a relatively high mat, along two or more adjacent round openings; each of the cracks evolves into a trench as liquid dries up. Self-organized pattern control with inherent openings needs to initiate the dewetting process above the nanotube tips. If there is no liquid on top, inherent openings barely enlarge themselves after the wetting–dewetting treatment

Hepatitis B testing and treatment in HIV patients in The Gambia - compliance with international guidelines and clinical outcomes

Background Compliance with WHO guidelines on HBV screening and treatment in HIV-coinfected patients is often challenging in resource limited countries and has been poorly assessed in sub-Saharan Africa. Methods Between 2015 and 2016, we assessed physician’s compliance with WHO guidelines on HIV-HBV coinfection in the largest HIV clinic in The Gambia, and the hepatic outcomes in HIV-HBV coinfected patients as compared to randomly selected HIV-monoinfected controls. Results 870 HIV-infected patients regularly seen in this clinic agreed to participate in our study. Only 187 (21.5%, 95% CI 18.8–24.3) had previously been screened for HBsAg, 23 (12.3%, 95% CI 8.0–17.9) were positive of whom none had liver assessment and only 6 (26.1%) had received Tenofovir. Our HBV testing intervention was accepted by all participants and found 94/870 (10.8%, 95% CI 8.8–13.1) positive, 78 of whom underwent full liver assessment along with 40 HBsAg-negative controls. At the time of liver assessment, 61/78 (78.2%) HIV-HBV coinfected patients received ART with 7 (11.5%) on Tenofovir and 54 (88.5%) on Lamivudine alone. HIV-HBV coinfected patients had higher APRI score compared to controls (0.58 vs 0.42, p = 0.002). HBV DNA was detectable in 52/53 (98.1%) coinfected patients with 14/53 (26.4%) having HBV DNA >20,000 IU/L. 10/12 (83.3%) had at least one detectable 3TC-associated HBV resistance, which tended to be associated with increase in liver fibrosis after adjusting for age and sex (p = 0.05). Conclusions Compliance with HBV testing and treatment guidelines is poor in this Gambian HIV programme putting coinfected patients at risk of liver complications. However, the excellent uptake of HBV screening and linkage to care in our study suggests feasible improvements

Controlling structural distortion in the geometrically frustrated layered cobaltate YBaCo4O7+{\delta} by Fe substitution and its role on magnetic correlations

Effects of Fe-substitution on the crystal structure and magnetic correlations of the geometrically frustrated antiferromagnets YBaCo4-xFexO7+{\delta} (x = 0, 0.2, 0.4, 0.5, 0.6, and 0.8) have been studied by neutron diffraction, M\"ossbauer spectroscopy, and ac susceptibility. The compounds YBaCo4-xFexO7+{\delta} have a special layered-type crystal structure with an alternating Kagom\'e (6c site) and triangular (2a site) layers along the c axis. Fe3+ ions are found to be substituted at both the crystallographic 2a and 6c sites of Co ions. M\"ossbauer results show a high spin state of Fe3+ ions in a tetrahedral coordination. A reduction in the distortion of the Kagom\'e lattice has been observed with the Fe-substitution. The correlation length of the short-range antiferromagnetic ordering decreases with the Fe-substitution. The sharpness of the magnetic transition also decreases with the Fe-substitution.Comment: 26 pages, 8 figures, 3 table