Particularités et stratification du paludisme à Madagascar

Les facteurs de diversité du paludisme à Madagascar sont de trois ordres: les parasites ; en sus de #P. falciparum, #P. vivax est très important ; la transmission qui détermine la stabilité du paludisme et provoque le développement de défenses spécifiques ; l'homme : la présence d'éléments d'origine asiatique explique la présence de #P. vivax ; les activités humaines sont fortement responsables de la prolifération des vecteurs. Les vecteurs, #An. gambiae, #An. arabiensis, #An. funestus appartiennent à la faune de l'Afrique continentale et sont probablement d'introduction récente car ils n'ont pas subi de processus d'endémisation. Les gîtes créés par l'homme, en particulier les rizières, jouent un rôle prépondérant dans le développement d'#An. gambiae et d'#An. funestus sur les plateaux et dans le sud. On distingue cinq faciès épidémiologiques très voisins de leurs homologues du continent africain : faciès équatorial sur la côte orientale ; faciès tropical sur la côte occidentale au nord de Morondava ; faciès des plateaux analogue au faciès austral du sud du continent ; faciès du sud qui se rapproche du faciès sahélien ; enfin, les zones sans paludisme. Dans les deux premiers, le paludisme est stable, dans les deux suivants, il est instable et c'est sur les plateaux que se manifestent les grandes épidémies, en particulier celle de 1985-88. Cette variété des faciès épidémiologiques impose une diversification des méthodes de lutte prise en compte dans le plan d'opération actuel. Les pulvérisations intradomiciliaires limitées aux plateaux ont donné des résultats spectaculaires. (Résumé d'auteur

The puzzle of the soft X-ray excess in AGN: absorption or reflection?

The 2-10 keV continuum of AGN is generally well represented by a single power law. However, at smaller energies the continuum displays an excess with respect to the extrapolation of this power law, called the ''soft X-ray excess''. Until now this soft X-ray excess was attributed, either to reflection of the hard X-ray source by the accretion disk, or to the presence of an additional comptonizing medium, giving a steep spectrum. An alternative solution proposed by Gierlinski and Done (2004) is that a single power law well represents both the soft and the hard X-ray emission and the impression of the soft X-ray excess is due to absorption of a primary power law by a relativistic wind. We examine the advantages and drawbacks of reflection versus absorption models, and we conclude that the observed spectra can be well modeled, either by absorption (for a strong excess), or by reflection (for a weak excess). However the physical conditions required by the absorption models do not seem very realistic: we would prefer an ''hybrid model''.Comment: 4 pages, 3 figures, abstracts SF2A-2005, published by EDP-Sciences Conference Serie

The Warm Absorber constrained by the coronal lines in Seyfert 1 galaxies

We present results of the photoionization code IRIS, which calculates the spectrum emitted by the Warm Absorber (WA) in Seyfert 1 galaxies for a large grid of parameters (density, column density, ionization parameter...). We show that in Seyfert 1s, coronal lines ([Fe X], [Fe XI], [Fe XIV]...), unlike the absorption edges, such as those of O VII and O VIII observed in soft X-rays which are produced by the WA, strongly constrain the physical parameters of the WA, especially the hydrogen density. Indeed, in order to avoid producing coronal line equivalent widths larger than observed, a high density ($n_{H} models (photoionized medium in or out of thermal equilibrium). This result is obtained for the mean observed Seyfert 1 features, as well as for the case study of MCG-6-30-15. It implies that the distance of the WA from the incident radiation source is of the order of that of the Broad Line Region (BLR)

Bioinspired coating for bird-safe glazing optimised for avian and human vision

Bird-window collisions often lead to the death of the bird and damage to the window. However, many animals, including birds, can perceive UV light. Many species have hence developed visual communication in this wavelength range, for instance, thanks to photonic structures. Such structures allowed us to design a new UV-reflecting multilayered coating for bird-safe glazing, through a bioinspiration approach. This coating was optimised for bird and human visual perception.</p

Introduction et acclimatation d'une simulie anthropophile dans l'île San Cristobal, archipel des Galapagos. (Diptera, Simulidae)

Abedraabo Sandra, Le Pont François, Shelley A. J., Mouchet Jean. Introduction et acclimatation d'une simulie anthropophile dans l'île San Cristobal, archipel des Galapagos, (Diptera, Simulidae). In: Bulletin de la Société entomologique de France, volume 98 (2), juin 1993. p. 108

Bioinspired coating for bird-safe glazing optimised for avian and human vision

Bird-window collisions often lead to the death of the bird and damage to the window. However, many animals, including birds, can perceive UV light. Many species have hence developed visual communication in this wavelength range, for instance, thanks to photonic structures. Such structures allowed us to design a new UV-reflecting multilayered coating for bird-safe glazing, through a bioinspiration approach. This coating was optimised for bird and human visual perception.</p