Susceptibility of carrion crows to experimental infection with lineage 1 and 2 West Nile viruses

West Nile virus (WNV) outbreaks in North America have been characterized by substantial die-offs of American crows (Corvus brachyrhynchos). In contrast, a low incidence of bird deaths has been observed during WNV epidemic activity in Europe. To examine the susceptibility of the western European counterpart of American crows, we inoculated carrion crows (Corvus corone) with WNV strains isolated in Greece (Gr-10), Italy (FIN and Ita09), and Hungary (578/10) and with the highly virulent North American genotype strain (NY99). We also inoculated American crows with a selection of these strains to examine the strains’ virulence in a highly susceptible bird species. Infection with all strains, except WNV FIN, resulted in high rates of death and high-level viremia in both bird species and virus dissemination to several organs. These results suggest that carrion crows are highly susceptible to WNV and may potentially be useful as part of dead bird surveillance for early warning of WNV activity in Europe

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

New PEMFC active layer architectures for optimized Pt utilization rate,

Keynote LectureInternational audienceBefore proton exchange membrane fuel cell (PEMFC) technology can gain a significant share of the electrical power market, important issues have to be addressed. In a PEMFC, energy conversion is achieved with costly Pt-based catalysts, and the low oxygen reduction reaction (ORR) kinetics implies high Pt loadings at the cathode. Electrode reactions can occur only at confined spatial sites, the triple-phase boundaries, where the reactant, the ionic conducting polymer, and the electronic conducting substrate are present on the same platinum particle. Efforts to increase the amount of such active sites are therefore of paramount importance in enhancing the cell performance by increasing the platinum utilization efficiency in 3D Pt/C porous electrodes. In current systems, triple-phase boundaries are achieved by adding Nafion ionomer to the catalytic ink used for the preparation of the active layer. Most of the investigations concerning the effect of the amount of ionomer in fuel cell electrodes concluded that the optimal Nafion content depends on the fuel cell working point; high Nafion content increases the electrode active area and the cell performance at low current densities, whereas it induces mass transport limitations at high current densities because the pores fill up. To balance both of these antagonist effects, a compromise of ca. 30 wt % Nafion is often used in electrodes. Moreover, the Pt utilization efficiency in current commercially offered prototype fuel cell electrodes remains very low (20-30%), and reaching higher utilization efficiency is still a crucial and therefore very active research topic. The combination of the limiting ORR kinetics at the cathode with the low Pt utilization efficiency becomes detrimental to the cell performance and cost. To overcome these limitations, the current electrode active-layer architecture paradigm has to be abandoned. The transposition of the triple-phase boundaries on the molecular scale by grafting ionic conducting molecules directly either onto platinum nanoparticles or carbon support leads to nanocomposite materials with great potency as cathode catalysts. This nanomaterial design is expected to allow creating a proton-conducting pathway between platinum active sites and the conducting membrane. The possibility of modifying the catalytic powder without altering its catalytic activity and selectivity is very attractive for potentially lowering the electrode material processing and PEMFC system costs by increasing the metal utilization efficiency, by avoiding the addition of an ionomer to the active layer, and by making possible the use of membrane alternatives to Nafion as a solid electrolyte

Susceptibility of European jackdaws (Corvus monedula) to experimental infection with lineage 1 and 2 West Nile viruses

Mass bird mortality has been observed in North America after the introduction of West Nile virus (WNV), most notably massive die-offs of American crows (Corvus brachyrhynchos). In contrast, WNV epidemic activity in Europe has been characterized by very low incidences of bird mortality. As the general susceptibility of European corvids to strains of WNV remains in question, European jackdaws (Corvus monedula) were inoculated with WNV strains circulating currently in Greece (Greece-10), Italy (FIN and Ita09) and Hungary (578/10), as well as a North American (NY99) genotype with a demonstrated corvid virulence phenotype. Infection with all strains except WNV-FIN resulted in mortality. Viraemia was observed for birds inoculated with all strains and virus was detected in a series of organs upon necropsy. These results suggested that jackdaws could potentially function as a sentinel for following WNV transmission in Europe; however, elicited viraemia levels might be too low to allow for efficient transmission of virus to mosquitoes