Phylogeography and evolutionary history of reassortant H9N2 viruses with potential human health implications

Avian influenza viruses of the H9N2 subtype have seriously affected the poultry industry of the Far and Middle East since the mid-1990s and are considered one of the most likely candidates to cause a new influenza pandemic in humans. To understand the genesis and epidemiology of these viruses, we investigated the spatial and evolutionary dynamics of complete genome sequences of H9N2 viruses circulating in nine Middle Eastern and Central Asian countries from 1998 to 2010. We identified four distinct and cocirculating groups (A, B, C, and D), each of which has undergone widespread inter- and intrasubtype reassortments, leading to the generation of viruses with unknown biological properties. Our analysis also suggested that eastern Asia served as the major source for H9N2 gene segments in the Middle East and Central Asia and that in this geographic region within-country evolution played a more important role in shaping viral genetic diversity than migration between countries. The genetic variability identified among the H9N2 viruses was associated with specific amino acid substitutions that are believed to result in increased transmissibility in mammals, as well as resistance to antiviral drugs. Our study highlights the need to constantly monitor the evolution of H9N2 viruses in poultry to better understand the potential risk to human health posed by these viruses.     

Hydrogen Flux through Size Selected Pd Nanoparticles into Underlying Mg Nanofilms

The application of Mg for hydrogen storage is hindered due to the slow absorption of hydrogen in Mg films. Herein, the hydrogenation process is explored theoretically using density functional theory calculations, and energy barriers are compared for hydrogen diffusion through Pd nanoparticle/Mg film interfaces and their variations, i.e., Pd(H)/Mg(O). Decomposing the mechanism into basic steps, it is shown that Pd undergoes a strain‐induced crystallographic phase transformation near the interface, and indicated that hydrogen saturation of Pd nanoparticles enhances their efficiency as nanoportals. Using energetic arguments, it is explained why hydrogen diffusion is practically prohibited through native Mg oxide and seriously suppressed through existing hydride domains. Hydrogen flux is experimentally investigated through the nanoportals in Pd‐nanoparticle decorated Mg films by pressure‐composition isotherm measurements. An r ≈ t^1/3 relationship is theoretically calculated for the radial growth of hemispherical hydride domains, and this relationship is confirmed by atomic force microscopy. The diffusion constant of hydrogen in Mg films is estimated as D_H^film ≈ 8 × 10^?18 m² s^?1, based on transmission electron microscopy characterization. The unique nanoportal configuration allows direct measurement of hydride domain sizes, thus forming a model system for the experimental investigation of hydrogenation in any material.