The fine-scale genetic structure of the malaria vectors Anopheles funestus and Anopheles gambiae (Diptera: Culicidae) in the north-eastern part of Tanzania

AbstractUnderstanding the impact of altitude and ecological heterogeneity at a fine scale on the populations of malaria vectors is essential to better understand and anticipate eventual epidemiological changes. It could help to evaluate the spread of alleles conferring resistance to insecticides and also determine any increased entomological risk of transmission in highlands due to global warming. We used microsatellite markers to measure the effect of altitude and distance on the population genetic structure ofAnopheles funestusandAnopheles gambiae s.s. in the Muheza area in the north-eastern part of Tanzania (seven loci for each species). Our analysis reveals strong gene flow between the different populations ofAn. funestusfrom lowland and highland areas, as well as between populations ofAn. gambiaesampled in the lowland area. These results highlight forAn. funestusthe absence of a significant spatial subpopulation structuring at small-scale, despite a steep ecological and altitudinal cline. Our findings are important in the understanding of the possible spread of alleles conferring insecticide resistance through mosquito populations. Such information is essential for vector control programmes to avoid the rapid spread and fixation of resistance in mosquito populations.</jats:p

Avoiding Loss of Catalytic Activity of Pd Nanoparticles Partially Embedded in Nanoditches in SiC Nanowires

Nanoditches from selective etching of periodically twinned SiC nanowires were employed to hinder the migration and coalescence of Pd nanoparticles supported on the nanowires, and thus to improve their catalytic stability for total combustion of methane. The results show that the etched Pd/SiC catalyst can keep the methane conversion of almost 100% while the unetched one has an obvious decline in the catalytic activity from 100 to 82% after ten repeated reaction cycles. The excellent catalytic stability originates from the limitation of the nanoditches to the migration and growth of Pd nanoparticles

A Solid Oxide Fuel Cell Operating in Gradual Internal Reforming Conditions under Pure Dry Methane

International audienceA planar solid oxide fuel cell (SOFC) was designed to be operated in gradual internal reforming conditions under pure dry methane. Stable operation was achieved for about 30 h. This result was obtained by deposition onto a Ni–yttria-stabilized zirconia cermet of a highly active and carbon-deposition-resistant catalyst layer consisting of Ir/CeO2. The performances of this layer were first evaluated in situ at open-circuit voltage, and then the principle of gradual internal reforming associated with electrocatalytic dissociation was demonstrated. The best cell performances with CH4/H2O=1/4 were 0.1  A  cm−2 at 0.55 V (about 55  mW cm−2) at 1173 K

Shell evolution and the N=34 “magic number”

Measurements of de–excitation gamma–rays in coincidence with target-like residues produced in deep inelastic transfer reactions of $^{238}$U on a $^{48}$Ca target at an energy near the Coulomb barrier are presented. A systematic analysis of the measured low lying states in the odd and even neutron-rich Ca isotopes shows the absence of a predicted shell closure at N = 34 in neutron-rich calcium isotopes

Catalytic steam reforming of methane over La0.8Sr0.2CrO3 based Ru catalysts

La0.8Sr0.2CrO3 based Ru catalysts were studied as potential new anodic materials for Solid Oxide Fuel Cells directly fed with methane and operating at intermediate temperature under water deficient conditions. Two kinds of materials very close in composition were obtained following two different preparation procedures. Catalyst samples were characterized by physicochemical methods (XRD, SEM, BET and Chemical Analysis) and studied in methane steam reforming under water deficient conditions. Carbon formation during catalytic testing was studied by temperature programmed oxidation (TPO). Both types of catalysts were found very active and resistant to carbon formation. The unusual oscillatory behavior of the catalytic activity observed for one type of catalyst was discussed. © 2007 Elsevier B.V. All rights reserved

Bimetallic Pd-Sn and Pd-Ga Catalysts for the Hydrogenation of 1,3-Butadiene

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