Molecular markers of resistance to amodiaquine plus sulfadoxine-pyrimethamine in an area with seasonal malaria chemoprevention in south central Niger.

BACKGROUND: In Niger, malaria transmission is markedly seasonal with most of the disease burden occurring in children during the rainy season. Seasonal malaria chemoprevention (SMC) with amodiaquine plus sulfadoxine-pyrimethamine (AQ + SP) is recommended in the country to be administered monthly just before and during the rainy season. Moreover, clinical decisions on use of SP for intermittent preventive treatment in pregnancy (IPTp) now depend upon the validated molecular markers for SP resistance in Plasmodium falciparum observed in the local parasite population. However, little is known about molecular markers of resistance for either SP or AQ in the south of Niger. To address this question, clinical samples which met clinical and biological criteria, were collected in Gabi, Madarounfa district, Maradi region, Niger in 2011-2012 (before SMC implementation). Molecular markers of resistance to pyrimethamine (pfdhfr), sulfadoxine (pfdhps) and amodiaquine (pfmdr1) were assessed by DNA sequencing. RESULTS: Prior to SMC implementation, the samples showed a high proportion of clinical samples that carried the pfdhfr 51I/59R/108N haplotype associated with resistance to pyrimethamine and pfdhps 436A/F/H and 437G mutations associated with reduced susceptibility to sulfadoxine. In contrast mutations in codons 581G, and 613S in the pfdhps gene, and in pfmdr1, 86Y, 184Y, 1042D and 1246Y associated with resistance to amodiaquine, were less frequently observed. Importantly, pfdhfr I164L and pfdhps K540E mutations shown to be the most clinically relevant markers for high level clinical resistance to SP were not detected in Gabi. CONCLUSIONS: Although parasites with genotypes associated with the highest levels of resistance to AQ + SP are not yet common in this setting, their importance for deployment of SMC and IPTp dictates that monitoring of these markers of resistance should accompany these interventions. This study also highlights the parasite heterogeneity within a small spatial area and the need to use caution when extrapolating results from surveys of molecular markers of resistance in a single site to inform regional policy decisions

Usefulness of the Reversible Jump Markov Chain Monte Carlo Model in Regional Flood Frequency Analysis

Regional flood frequency analysis is a convenient way to reduce estimation uncertainty when few data are available at the gauging site. In this work, a model that allows a non-null probability to a regional fixed shape parameter is presented. This methodology is integrated within a Bayesian framework and uses reversible jump techniques. The performance on stochastic data of this new estimator is compared to two other models: a conventional Bayesian analysis and the index flood approach. Results show that the proposed estimator is absolutely suited to regional estimation when only a few data are available at the target site. Moreover, unlike the index flood estimator, target site index flood error estimation seems to have less impact on Bayesian estimators. Some suggestions about configurations of the pooling groups are also presented to increase the performance of each estimator

Caractérisation des systemes de production à base de maïs dans les principales zones de culture au Bénin

La présente recherche vise à caractériser les systèmes de production à base de maïs au Bénin pour un appui-conseil ciblé aux producteurs de maïs. La base de sondage est la base de données du sous-projet "Centre National de Spécialisation sur le Maïs", exécuté par l’Institut National des Recherches Agricoles du Bénin, sur financement du Projet de Productivité Agricole en Afrique de l’Ouest, dans les huit zones agroécologiques du Bénin. L’analyse a été appliquée à un extrait de 411 exploitants maïzicoles issus de trois zones agroécologiques de façon aléatoire. Les villages échantillonnés concernent ceux ayant produit du maïs au cours de la campagne agricole 2012-2013. Sur cet échantillon, il a été procédé, à l’aide des logiciels SPSS 16.0 et R, à une classification des systèmes de production. Les résultats de la typologie des exploitations à l’aide de l’Analyse en Composantes Principales et de la Classification Ascendante Hiérarchique montrent qu’il se dégage quatre systèmes de production que sont : grandes exploitations à production intensive, exploitations moyennes, petites exploitations de subsistance peu productives optant pour la sécurité alimentaire de l’exploitant, et très grandes exploitations à production extensive à gros investissements.Mots-clés: Caractérisation, typologie, analyses multivariées, maïs, BéninEnglish Title: Characterization of maize’s production systems in the main cropping zones of BeninEnglish AbstractThe purpose of this research is to characterize maize production systems in Benin for targeted support to maize producers. The sampling frame is the database of the sub-project "National Center of Specialization on Maize", implemented by the National Institute of Agricultural Research of Benin, one financed by the Project of Agricultural Productivity in West Africa, in the 8 agro-ecological zones of Benin. The analysis was applied to an extract of 411 maize growers from 3 agro-ecological zones randomly. The sampled villages are those produced maize during the 2012-2013 crop year. Using the SPSS 16.0 and R software, a classification of the production systems was performed. The results of the typology of the farms using the Principal Component Analysis and the Hierarchical Ascending Classification show that there are four production systems: large farms with intensive production system, medium farms system, small  subsistence farms system opting for the farmer’s food security of the farmer, and very large extensive farms with large investments.Keywords : Characterization, typology, multivariate analysis, maize, Beni

Optimization of SiN x Single and Double Layer ARC for Silicon Thin Film Solar Cells on Glass

Abstract: The aim of this study is the optimization of the antireflection effect of SiN x in silicon on glass based structure. A numerical calculation is performed and a SiNx double stack antireflection coating is found to have significant advantages over single-layer due to their broad-range coverage of the solar spectrum. Moreover, it was found that minimum reflection losses is obtained for SiN x /SiN x double-layer ARC with refractive indexes of 1.9 et 2.3 for the top and the bottom layer, respectively. The effect of the incident angle on reflectance is also studied. The numerical optimization procedure and its results are presented