Ecological Niche of the 2003 West Nile Virus Epidemic in the Northern Great Plains of the United States

Background: The incidence of West Nile virus (WNv) has remained high in the northern Great Plains compared to the rest of the United States. However, the reasons for the sustained high risk of WNv transmission in this region have not been determined. To assess the environmental drivers of WNv in the northern Great Plains, we analyzed the county-level spatial pattern of human cases during the 2003 epidemic across a seven-state region. Methodology/Principal Findings: County-level data on WNv cases were examined using spatial cluster analysis, and were used to fit statistical models with weather, climate, and land use variables as predictors. In 2003 there was a single large cluster of elevated WNv risk encompassing North Dakota, South Dakota, and Nebraska along with portions of eastern Montana and Wyoming. The relative risk of WNv remained high within the boundaries of this cluster from 2004–2007. WNv incidence during the 2003 epidemic was found to have a stronger relationship with long-term climate patterns than with annual weather in either 2002 or 2003. WNv incidence increased with mean May–July temperature and had a unimodal relationship with total May–July precipitation. WNv incidence also increased with the percentage of irrigated cropland and with the percentage of the human population living in rural areas. Conclusions/Significance: The spatial pattern of WNv cases during the 2003 epidemic in the northern Great Plains was associated with both climatic gradients and land use patterns. These results were interpreted as evidence that environmental conditions across much of the northern Great Plains create a favorable ecological niche for Culex tarsalis, a particularly efficient vector of WNv. Further research is needed to determine the proximal causes of sustained WNv transmission and to enhance strategies for disease prevention

Spatially resolved photoluminescence and Raman spectroscopy of bandgap gratings fabricated in GaAs/AlAs superlattice waveguide using quantum well intermixing

International audiencePhotoluminescence (PL) and Raman spectroscopy were devised to study bandgap gratings fabricated in a waveguide with a core consisting of GaAs/AlAs short superlattice (SSL) structure using quantum well intermixing (QWI). The spatially resolved PL is carried out on the superlattice layer from the sample surface, as well as from a cleaved facet to the side of the epitaxial layer. The PL from the sample surface showed a modulation in the PL wavelength with shoulders being observed. The root cause of this observation was resolved via PL scans of the cleaved side of the grating. The results were further supplemented via Raman spectroscopy measurements, where Raman spectra were collected at different depths of the SSL through probing the SSL layer cross-section. SSL-related phonon states were clearly observed for the lower part of the SSL layer where intermixing did not take place, while the Raman spectra for the intermixed regions showed regular bulk phonon modes, indicating the SSL layer intermixing

Investigation of BST thin films deposited by RF magnetron sputtering in pure Argon

International audienceBa0.5Sr0.5TiO3 (BST) thin films were deposited by rf magnetron sputtering using a Ba0.5Sr0.5TiO3 target in pure Argon on two electrodes (Pt and RuO2) at room temperature. The interface formation between BST and bottom electrode (Pt or RuO2) was investigated by XPS for thicknesses in the 1 to 50 nm range. The chemical composition of the BST layers can be modified by the electrode nature over the first five nanometers. A 1 h ex-situ annealing, under flowing oxygen at 600 degrees C, was necessary to obtain crystallized 150 nm thick BST films, as evidenced by XRD and TEM analysis