Pervasiveness of Parasites in Pollinators

Many pollinator populations are declining, with large economic and ecological implications. Parasites are known to be an important factor in the some of the population declines of honey bees and bumblebees, but little is known about the parasites afflicting most other pollinators, or the extent of interspecific transmission or vectoring of parasites. Here we carry out a preliminary screening of pollinators (honey bees, five species of bumblebee, three species of wasp, four species of hoverfly and three genera of other bees) in the UK for parasites. We used molecular methods to screen for six honey bee viruses, Ascosphaera fungi, Microsporidia, and Wolbachia intracellular bacteria. We aimed simply to detect the presence of the parasites, encompassing vectoring as well as actual infections. Many pollinators of all types were positive for Ascosphaera fungi, while Microsporidia were rarer, being most frequently found in bumblebees. We also detected that most pollinators were positive for Wolbachia, most probably indicating infection with this intracellular symbiont, and raising the possibility that it may be an important factor in influencing host sex ratios or fitness in a diversity of pollinators. Importantly, we found that about a third of bumblebees (Bombus pascuorum and Bombus terrestris) and a third of wasps (Vespula vulgaris), as well as all honey bees, were positive for deformed wing virus, but that this virus was not present in other pollinators. Deformed wing virus therefore does not appear to be a general parasite of pollinators, but does interact significantly with at least three species of bumblebee and wasp. Further work is needed to establish the identity of some of the parasites, their spatiotemporal variation, and whether they are infecting the various pollinator species or being vectored. However, these results provide a first insight into the diversity, and potential exchange, of parasites in pollinator communities

Les Polymères: l'Avenir du Photovoltaïque ?

12 juin 200

Refractive Index of Micro/Nano Structured Dielectric Materials

August 28-31 (2006

Reflexion on the Future of Photonics

Conférence invitée May 31- June 2, 200

Guided-wave Characterizations of Optical, Thermal and Electro-optical Properties of Thin Film Materials

Special Issue: "Challenges in Materials Properties Measurements", Editor B. Vinet (Inderscience

Optical Properties of Nanostructured Thin Films

June 18-22 (2006

ZnS vertical bar Ag vertical bar TiO2 multilayer electrodes with broadband transparency for thin film solar cells

International audienceA ZnS vertical bar Ag vertical bar TiO2 (ZAT) multilayer architecture is proposed as an alternative to symmetric TiO2 vertical bar Ag vertical bar TiO2 (TAT) electrodes. The TAT electrodes were proved to be among the best ITO-free transparent conductive electrodes. It is demonstrated that choosing ZnS instead of TiO2 as a substrate for Ag allows better optical and electrical performances. The complex refractive indices of both dielectric materials are determined by spectroscopic ellipsometry and implemented into a transfer matrix algorithm to optimize the optical transmittance of ZAT and TAT multilayers in the visible part of the spectrum. It is shown that both types of electrodes are equivalent in terms of optical behavior. Manufactured electrodes with symmetric 40 nm dielectric thicknesses are then fabricated on glass substrates by e-beam evaporation and the effect of the silver layer thickness on performances is studied. It is found that ZAT multilayer performances are systematically better, and on a broader transmittance range, when the Ag layer is very thin than TAT stacks. A state of the art 90.23% maximum transmittance is reached at lambda = 460 nm for a ZnS(36 nm)vertical bar Ag(12.7 nm)vertical bar TiO2(37 nm) multilayer, with a sheet resistance R-S of 5 Omega Sq(-1). Over 80% transmittance is achieved in the [380-855] nm wavelength range for a ZnS(36 nm)vertical bar Ag(7 nm)vertical bar TiO2(40 nm) multilayer, with a R-S of 11.3 Omega Sq(-1). Scanning electron microscopy (SEM) reveals continuous silver films grown on ZnS as opposed to those grown on TiO2, thus justifying the better performances of the ZAT

Demonstration of a Software for Automatic Optimization of the Electromagnetic Field in Organic Solar Cells

July 10-15 (2005

Software for automatic optimization of the electromagnetic field in organic solar cells

Poster présenté 14-16 novembre (2005)