Control of superluminal transit through a heterogeneous medium

We consider pulse propagation through a two component composite medium (metal inclusions in a dielectric host) with or without cavity mirrors. We show that a very thin slab of such a medium, under conditions of localized plasmon resonance, can lead to significant superluminality with detectable levels of transmitted pulse. A cavity containing the heterogeneous medium is shown to lead to subluminal-to-superluminal transmission depending on the volume fraction of the metal inclusions. The predictions of phase time calculations are verified by explicit calculations of the transmitted pulse shapes. We also demonstrate the independence of the phase time on system width and the volume fraction under specific conditions.Comment: 21 Pages,5 Figures (Published in Journal of Modern Optics

Assessment of agro-ecological influence on the seed quality of groundnut (Arachis hypogaea) in The Gambia

A survey was conducted to assess the quality of groundnut seed produced and stored under ambient environment across various agro-ecologies of The Gambia, with a view to understanding regions with comparative advantage for its production and storage. Seed production activities of 60 seed growers in 26 communities were collected using structured questionnaires, interviews and observations. The Global Positioning System (GPS) coordinates of the communities were geo-referenced to identify the geographical positioning of the production sites. Samples of the groundnut pods were taken from the seed stores, threshed and subjected to seed quality analysis. Descriptive analysis was used to categorize the seed sources, hectarage cultivated, while seed quality data were subjected to analysis of variance of Nested Design. Means of significant factors were separated using Duncan Multiple Range Test (DMRT) at 5% significant level. The study showed that groundnut seed production is better concentrated in regions with optimum and sustainable rainfall that will reduce abiotic stress during seed development like the Lower River Region, West Coast Region and Central River Region. Fleur-11 variety was identified as one of the most promising varieties for groundnut cultivation in The Gambia and Tropical Africa

Resting behaviour of Anopheles gambiae s.l. and its implication on malaria transmission in Uyui District, western Tanzania

An entomological survey to determine resting behaviour and species composition of malaria vectors was carried out in Uyui District in western Tanzania in May 2009. Mosquitoes were collected using indoor resting catch, window exit trap and outdoor “bed-net” techniques. They mosquitoes were identified using morphological key and polymerase chain reaction (PCR). A total of 672 Anopheles gambiae sensu lato were collected. Of these, 661 (98.4%) were collected outdoor whereas few (1.6%) were collected indoor. The exit trap catch: mechanical aspirator catch ratio was 1:1.75. The overall indoor resting density of An. gambiae s.l. as determined by mechanical aspirator and exit trap was 0.7 and 0.5 mosquitoes per room, respectively. The overall density of the host-seeking as determined by bed net trap outdoor was 44.1 mosquitoes per person. A sample of 44 specimens taken randomly from morphologically identified An.gambiae s.l. population was further analyzed to species level using PCR techniques. Of these 44 specimens 26 (59%) and 18 (41%) were Anopheles arabiensis and Anopheles gambiae sensu stricto respectively. This study contributes to the understanding of the distribution of malaria vectors with respect to species composition and their resting behaviour that could contribute to vector control operations in western Tanzania. A longitudinal study considering dry and wet seasons is recommended to provide more information on the seasonal distribution, abundance and biting behaviour of malaria vectors in the study area

Etude préliminaire portant sur le dépistage de la protéinurie à l’aide de bandelette urinaire chez les patients vivants avec le VIH au CHNU de Fann à Dakar.

Les glomérulopathies et autres affections rénales sont fréquentes au cours de l’histoire naturelle du VIH même si leur incidence a diminué avec la trithérapie. Elles sont pratiquement toujours responsables d’une protéinurie et/ou d’une hématurie. Nous avons fait une étude préliminaire portant sur la prévalence de la protéinurie dépistée à l’aide de bandelettes urinaires chez les PVVIH suivies à la clinique des maladies infectieuses du CHNU de Fann à Dakar. Il s’agissait d’une étude prospective allant du 1er Août au 30 Octobre 2008. Ont été inclus de façon exhaustive les patients séropositifs pour le VIH à la fois vus en ambulatoire et en hospitalisation présentant une protéinurie sans infection urinaire intercurrente. Nous avons recueilli leurs données sociodémographiques, les éléments de l’histoire naturelle, les facteurs en rapport avec la protéinurie et la néphropathie. La saisie et l’analyse des données ont été faites avec le logiciel Epi Info version 6.04. Nous avons utilisé le test de Chi2 pour comparer les variables qualitatives et p<0,05 a été retenu comme significative. Au total 100 patients ont été inclus, la moyenne d’âge était de 43± 9,8 ans chez les hommes et de 39± 10 ans pour les femmes. Les femmes étaient prédominantes (sex ratio H/F = 0,5). Tous les patients étaient infectés par le VIH1, ils avaient été dépistés à un stade tardif d’immunodépression, la moitié était sous ARV avec le plus souvent le protocole AZT +3TC+ EFV. La prévalence de la protéinurie était de 47,9%. Les facteurs significativement associés à la présence d’une protéinurie étaient : le sexe ; le taux de CD4<350/mm3 ; la charge virale > 100000copies/mm3 ; l’IMC <18,5 ; le taux d’hémoglobine<8,5 g/dl, la chimioprophylaxie au cotrimoxazole et les stades cliniques OMS 3 et 4. La fréquence de la néphropathie au cours du VIH au service des maladies infectieuses de Fann à Dakar suggère d’inclure son dépistage à la bandelette dans le bilan initial et de suivi de tout patient infecté par le VIH. Dans tous les cas il faudrait corriger tout facteur favorisant la survenue de cette néphropathie. La ponction biopsie rénale pourrait permettre des études plus approfondies

Measurements of Submicron Particle Adsorption and Particle Film Elasticity at Oil-Water Interfaces

The influence of particle adsorption on liquid/liquid interfacial tension is not well understood, and much previous research has suggested conflicting behaviors. In this paper we investigate the surface activity and adsorption kinetics of charge stabilized and pH-responsive polymer stabilized colloids at oil/water interfaces using two tensiometry techniques: (i) pendant drop and (ii) microtensiometer. We found, using both techniques, that charge stabilized particles had little or no influence on the (dynamic) interfacial tension, although dense silica particles affected the "apparent" measured tension in the pendent drop, due to gravity driven elongation of the droplet profile. Nevertheless, this apparent change additionally allowed the study of adsorption kinetics, which was related qualitatively between particle systems by estimated diffusion coefficients. Significant and real interfacial tension responses were measured using ∼53 nm core-shell latex particles with a pH-responsive polymer stabilizer of poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (pMMA-b-pDMAEMA) diblock copolymer. At pH 2, where the polymer is strongly charged, behavior was similar to that of the bare charge-stabilized particles, showing little change in the interfacial tension. At pH 10, where the polymer is discharged and poorly soluble in water, a significant decrease in the measured interfacial tension commensurate with strong adsorption at the oil-water interface was seen, which was similar in magnitude to the surface activity of the free polymer. These results were both confirmed through droplet profile and microtensiometry experiments. Dilational elasticity measurements were also performed by oscillation of the droplet; again, changes in interfacial tension with droplet oscillation were only seen with the responsive particles at pH 10. Frequency sweeps were performed to ascertain the dilational elasticity modulus, with measured values being significantly higher than previously reported for nanoparticle and surfactant systems, and similar in magnitude to protein stabilized droplets.</p

Effect of filter media thickness on the performance of sand drying beds used for faecal sludge management

The effect of sand filter media thickness on the performance of faecal sludge (FS) drying beds was determined in terms of: dewatering time, contaminant load removal efficiency, solids generation rate, nutrient content and helminth eggs viability in the dried sludge. A mixture of VIP-latrine sludge and septage in the ratio 1:2 was dewatered using three pilot-scale sludge drying beds with sand media thicknesses of 150 mm, 250 mm and 350 mm. Five dewatering cycles were conducted and monitored for each drying bed. Although 150 mm filter had the shortest average dewatering time of 3.65 days followed by 250 mm and 350 mm filters with 3.83 and 4.02 days, respectively, there was no significant difference ( p > 0.05) attributable to filter media thickness configurations. However, there was a significant difference for the percolate contaminant loads in the removal and recovery efficiency of suspended solids, total solids, total volatile solids, nitrogen species, total phosphorus, COD, DCOD and BOD, with the highest removal efficiency for each parameter achieved by 350 mm filter. There were also significant differences in the nutrient content (NPK) and helminth eggs viability of the solids generated by the tested filters. Filtering media configurations similar to 350 mm have the greatest potential for optimising nutrient recovery from FS

The human resource implications of improving financial risk protection for mothers and newborns in Zimbabwe

Peer reviewedPublisher PD

Rapid onset of mafic magmatism facilitated by volcanic edifice collapse

Volcanic edifice collapses generate some of Earth's largest landslides. How such unloading affects the magma storage systems is important for both hazard assessment and for determining long-term controls on volcano growth and decay. Here we present a detailed stratigraphic and petrological analyses of volcanic landslide and eruption deposits offshore Montserrat, in a subduction zone setting, sampled during Integrated Ocean Drilling Program Expedition 340. A large (6–10 km3) collapse of the Soufrière Hills Volcano at ~130 ka was followed by explosive basaltic volcanism and the formation of a new basaltic volcanic center, the South Soufrière Hills, estimated to have initiated <100 years after collapse. This basaltic volcanism was a sharp departure from the andesitic volcanism that characterized Soufrière Hills' activity before the collapse. Mineral-melt thermobarometry demonstrates that the basaltic magma's transit through the crust was rapid and from midcrustal depths. We suggest that this rapid ascent was promoted by unloading following collapse