Why are anopheline mosquitoes not present in the Seychelles?

<p>Abstract</p> <p>Background</p> <p>Species of anopheline mosquitoes are largely distributed over emerged lands around the world and, within the tropics, few areas are without these insects, which are vectors of malaria parasites. Among the exceptions is the Seychelles archipelago in the western Indian Ocean. However, in the Aldabra island group, located in the extreme western portion of the archipelago, <it>Anopheles gambiae s.l. </it>was introduced, leading to massive proliferation and then elimination, with the most recent autochthonous malaria cases recorded in 1931.</p> <p>Methods</p> <p>In order to re-examine the absence of anopheline mosquitoes in the Seychelles, an entomological field survey was conducted in December 2008 at 17 sites on four granitic islands, including Mahé and Praslin, and ten sites on coralline atolls in the extreme west, including Aldabra.</p> <p>Results</p> <p>No evidence of larval or adult anophelines was found at the surveyed sites, which supports their absence in the Seychelles.</p> <p>Conclusions</p> <p>In the granitic islands of the Seychelles, the climate is favourable for anophelines. However, these islands are protected by their remoteness and prevailing seasonal winds. In addition, stagnant freshwater, required in anopheline larval development, is relatively uncommon on the granitic islands because of the steep slopes. In the southwestern atolls (Aldabra and Providence-Farquhar groups), the presence of a long dry season of up to nine months and the total absence of permanent natural freshwater prevents the breeding of anophelines and their successful colonization. The Seychelles does not have any native land mammals and like in other parts of the world (Antarctica, Iceland, New Caledonia, Central Pacific islands) their absence is associated with the lack of anophelines. This suggests an obligatory relationship for anophelines to feed on terrestrial mammals, without alternative for blood-feeding sources, such as bats, birds and reptiles.</p

Aspects collectifs dans le néon 19 et le fluor 17

Experimental results on 17F and 19Ne support the collective description in this region.Les résultats expérimentaux obtenus sur 17F et 19Ne peuvent s'expliquer à partir de calculs basés sur le modèle collectif

Évolution de la distribution angulaire des protons O16 (d, p) O17* au voisinage d'une résonance de capture du deutéron

L'étude des distributions angulaires des protons émis au cours de la réaction 16O(d, p)17O* (niveau à 875 keV) a été effectuée, par une méthode photographique, pour sept énergies différentes de deutérons comprises entre I,66 et 2,20 MeV (obtenues grâce à l'accélérateur électrostatique de Saclay). L'analyse des résultats montre que la distribution angulaire vers l'avant est, pour toutes ces énergies, en bon accord avec la théorie du « stripping » (l = o), même au maximum de la résonance de capture du deutéron située vers 2,I MeV. De plus, la section efficace différentielle à 7° passe par un maximum pour cette énergie de résonance