1,185 research outputs found
Epiconvergence of a Sequence of Level Sums of Convex Functions
We consider the problem of minimizing the max of two convex functions
from both approximation and sensitivity point of view.This lead up to study
the epiconvergence of a sequence of level sums of convex functions and the related
dual problems
Utilisation de plaques d'aluminium afin d'évaluer le résultat d'une interruption volontaire des traitements larvicides, en saison sÚche, dans une zone du Programme de Lutte contre l'Onchocercose dans le bassin de la Volta
Effect of compost and soil properties on the availability of compost phosphate for white clover ( Trifolium repens L.)
Wide variation in results exists in the literature on the effectiveness of composts to sustain the phosphorus (P) nutrition of crops. The aim of this work was to assess the importance of some soil and composts properties on the utilization of compost-P by white clover (Trifolium repens L.). This study was carried out with samples collected from four composts made from solid kitchen and garden wastes, and with two soil samples taken from the A horizon of a P-rich sandy acidic Dystrochrept and of a P-limited clayey calcareous Eutrochrept. Changes in the amount of inorganic P (Pi) isotopically exchangeable within 1 min (E1min) were measured during 32 weeks in incubated soil-composts or soil-KH2PO4mixtures where P sources had been added at the rate of 50 mg P kgâ1 soil. Uptake of compost-P or KH2PO4-P by white clover was measured on the same amended soils during 16 weeks. In both soils, the application of composts resulted after 32 weeks of incubation in E1min values ranging between those observed in the control without P and those observed in the KH2PO4treatment, i.e., in values ranging between 4.2 and 5.9 mg P kgâ1 in the sandy acidic soil and between from 1.6 to 4.3 mg P kgâ1 in the clayey calcareous soil. The total coefficient of utilization of compost-P (CU-P) by white clover reached values in both soils for the four composts ranging between 6.5% and 11.6% of the added P while in the presence of KH2PO4 the CU-P reached values ranging between 14.5% in the clayey calcareous soil and 18.5% in the sandy acidic soil. Results obtained in the sandy acidic soil suggest, that white clover initially used a fraction of the rapidly exchangeable compost P, while at a latter stage plant roots enhanced the mineralisation of compost organic P and took up a fraction of the mineralized P. These relations were not observed in the clayey calcareous soil probably because of its high sorbing capacity for P. In the sandy acidic soil, composts application increased the uptake of soil P by the plant from 31.4 mg P kgâ1 soil in the control without P to values ranging between 37.9 to 42.7 mg P kgâ1 soil in the presence of composts. This indirect effect was related to a general improvement of plant growth conditions in this soil induced by compost addition (from 9.9 g DM kgâ1 soil in the control without P to values ranging between 14.0 to 16.1 g DM kgâ1 soil in the presence of composts) and/or to the release of Al- or Fe bound soil P to the solution due to soil pH increase following compost application. Finally the total coefficient of utilization of P (CU-P) derived from KH2PO4 and composts was related to the total amount of N exported by white clover in the P-limited clayey calcareous soil but not in the P-rich sandy acidic soil. This suggests that in a soil where N2 biological fixation is limited by low P availability, the CU-P of a compost by white clover is not only related to the forms of P present in the compost but also to its effect on N nutrition. However, it is not clear whether this improved N nutrition was due to compost mineralisation, or to an indirect compost effect on the N2 biological fixatio
Infection par le VIH chez les patientes atteintes de cancer du sein en GuinĂ©e (Afrique de lâOuest)
L'objectif Ă©tait de dĂ©terminer la prĂ©valence de l'infection Ă VIH chez les patientes atteintes de cancer du sein et de comparer les caractĂ©ristiques anatomocliques et thĂ©rapeutiques de ces cancers du sein par rapports aux patientes non infectĂ©es par le VIH. Il s'agissait d'une Ă©tude rĂ©trospective et analytique comparant les dossiers de patientes atteintes de cancers du sein histologiquement confirmĂ©s, infectĂ©es ou non par le VIH Ă l'unitĂ© de chirurgie oncologique de Donka, CHU de Conakry, de 2007 Ă 2012. Nous avons colligĂ© 278 patientes prĂ©sentant un cancer du sein dont 14 (5,0%) infectĂ©es par le VIH et 264 (95,0%) non infectĂ©es par le VIH. Les diffĂ©rences observĂ©es entre ces deux groupes de patientes Ă©taient respectivement: Ăąge mĂ©dian (36,8 vs 49,0 ans), la mĂ©nopause (21,4% vs 53,4%), le nombre des patientes traitĂ©es (50,0% contre 77,1%) et la survenue de dĂ©cĂšs (78,6% vs 50,8%). Aucune diffĂ©rence n'a Ă©tĂ© notĂ©e dans la prĂ©sentation clinique, histologique et le retard de consultation. Dans notre Ă©tude, la prĂ©valence de l'infection Ă VIH chez les patients atteints de cancer du sein est Ă©levĂ©e. L'Ăąge jeune des patients, la faible accessibilitĂ© au traitement et la mortalitĂ© Ă©levĂ©e doivent ĂȘtre confirmĂ©s par une Ă©tude sur un Ă©chantillon plus large
Characterization of Anaerovibrio burkinabensis sp. nov., a lactate-fermenting bacterium isolated from rice field soils
Assessing Long-Term Trends In Vegetation Productivity Change Over the Bani River Basin in Mali (West Africa)
Using time series of Normalized Difference Vegetation Index (NDVI) and rainfall
data, we investigated historical vegetation productivity trends from 1982 to 2011
over the Bani River Basin in Mali. Statistical agreements between long-term trends
in vegetation productivty, corresponding rainfall and rate of land cover change from
Landsat time-series imagery was used to discern climate versus human-induced
vegetation cover change. Spearman correlation was used to investigate the
relationship between metrics of vegetation, rainfall trends and land cover change
categories. The results show there is a positive correlation between increases in
rainfall and some land cover classes, while some classes such as settlements were
negatively correlated with vegetation productivity trends. Croplands and Natural
Vegetation were positively correlated (r=0.89) with rainfall while settlements have a
negative correlation with NDVI time series trend (r=-057). Despite the fact that
rainfall is the major determinant of vegetation cover dynamics in the study area, it
appears that other human-induced factors such as urbanization have negatively
influenced the change in vegetation cover in the study area. The results show that a
combined analysis of NDVI, rainfall and spatially explicit land cover change
provides a comprehensive insight into the drivers of vegetation cover change in
semi-arid Africa
Assessing the inter-relationship between vegetation productivity, rainfall, population and land cover over the Bani River Basin in Mali (West Africa)
This research investigated the inter-relationship between vegetation productivity, measured using
the Normalized Difference Vegetation Index (NDVI), change in rainfall and population density in the context of
perceived greening and degradation trends over the Bani River Basin (BRB). A 30-year (1982-2011), 8-km
gridded rainfall data sets was produced by inverse distance weighted (IDW) interpolation of monthly data from
40 meteorological stations contained within the basin. Population data were retrieved from the National
Population Statistic data base for 1987, 1997, and 2009. Rainfall and NDVI time-series trends were computed
for the 30-year period and analysed. The relationship between rainfall and NDVI at pixel level, and NDVI and
population densities was analysed using a Pearson correlation. Land Use and Land Cover (LULC) conversion
rates were computed for the same period using multi-temporal 30-meter Landsat imagery; ground surveys for
selected areas within the basin were used for further cross-verification. The computed NDVI trends revealed
that, vegetation 'greening' trends are mostly associated with areas where natural vegetation is still well
represented. Concurrent with increases in rainfall over the period analysed, this finding supports the hypothesis
that re-greening observed in that area is the result of multi-decadal fluctuations in climate, rather than improved
land management
Optimisation de la production de biométhane à partir des déchets organiques municipaux
La gestion des dĂ©chets municipaux est devenue une prĂ©occupation majeure dans les pays en dĂ©veloppement, due au manque de politique et de stratĂ©gie adaptĂ©es. LâĂ©tude rĂ©alisĂ©e a portĂ© sur la valorisation biotechnologique de la fraction biodĂ©gradable des dĂ©chets au Burkina Faso. Une analyse physico-chimique des dĂ©chets Ă©chantillonnĂ©s dans trois (3) centres de prĂ©collecte de dĂ©chets municipaux de Ouagadougou a Ă©tĂ©Â rĂ©alisĂ©e. Lâinfluence du type dâinoculum (eaux usĂ©es, bouse bovine, flux de broyat de termites et une mixture de ces 3 inocula) et de la charge en substrat (dĂ©chets organiques) a Ă©tĂ© Ă©valuĂ©e au cours dâessais de fermentation mĂ©thanique. Les rĂ©sultats obtenus ont montrĂ© que les dĂ©chets organiques municipaux constituent un substrat de prĂ©dilection pour la mĂ©thanisation avec un ratio C/N de 31,65. Les essais de fermentation ont permis de noter que la bouse bovine comme inoculum avec une charge en dĂ©chets municipaux de 2% donnait la meilleure production de biomĂ©thane (297,65 l CH4 / Kg MSV). Il ressort de cette Ă©tude que les dĂ©chets municipaux peuvent ĂȘtre traitĂ©s par la voie de la biomĂ©thanisation car prĂ©sentant un potentiel de bioconversion intĂ©ressant.© 2015 International Formulae Group. All rights reserved.Mots clĂ©s: DĂ©chets organiques, digestion anaĂ©robie, biomĂ©thane, environnement, Burkina FasoEnglish Title: Optimization of biomethane production from municipal solid organic wastesEnglish AbstractMunicipal solid organic wastes management became a major preoccupation. The achieved study focuses the biotechnological valorization of the biodegradable fraction of solid organic wastes in Burkina Faso.  Physicochemical characterization analysis of solid wastes sampled in 03 Ouagadougouâs centers of municipal wastes deposits was achieved. The influence of inoculum source (wastewater, bovine dung, termitesâ homogenate and mixture) and substrate concentration (municipal solid waste) were evaluated during biomethane production tests. Results showed that organic fraction of solid wastes represent a source of predilection for methanization with 31.65 C/N cow. Fermentation tests showed that bovine dung used as inoculum in 2% of municipal solid waste gave the highest rate of biomethane production (297.65 l CH4 / Kg vs). The results demonstrate that municipal wastes can be valorized by biomethanization way because presenting interesting bioconversion potential.© 2015 International Formulae Group. All rights reserved.Keywords: Organic wastes, anaerobic digestion, biomethane, environment, Burkina Fas
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