Search

We report here the first full-genome sequence of an avian paramyxovirus type 4 (APMV-4) strain isolated from a domestic mallard duck at a live bird market in South Korea. Phylogenetic analyses provide genetic information on a new genetic clade, APMV-4, isolated from a domestic duck and evidence of APMV-4 exchange between poultry and wild birds.

Herein we investigate the reaction intermediates formed during CO oxidation on copper-substituted ceria nanoparticles (Cu0.1Ce0.9O2-x) by means of in situ spectroscopic techniques and identify an activity descriptor that rationalizes a trend with other metal substitutes (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni). In situ X-ray absorption spectroscopy (XAS) performed under catalytic conditions demonstrates that O2-transfer occurs at dispersed copper centers, which are redox active during catalysis. In situ XAS reveals a dramatic reduction at the copper centers that is fully reversible under catalytic conditions, which rationalizes the high catalytic activity of Cu0.1Ce0.9O2-x. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) show that CO can be oxidized to CO32- in the absence of O2. We find that CO32- desorbs as CO2 only under oxygen-rich conditions when the oxygen vacancy is filled by the dissociative adsorption of O2. These data, along with kinetic analyses, lend support to a mechanism in which the breaking of copper-oxygen bonds is rate-determining under oxygen-rich conditions, while refilling the resulting oxygen vacancy is ratedetermining under oxygen-lean conditions. On the basis of these observations and density functional calculations, we introduce the computed oxygen vacancy formation energy (Evac) as an activity descriptor for substituted ceria materials and demonstrate that Evac successfully rationalizes the trend in the activities of M0.1Ce0.9O2-x catalysts that spans three orders of magnitude. The applicability of Evac as a useful design descriptor is demonstrated by the catalytic performance of the ternary oxide Cu0.1La0.1Ce0.8O2-x, which has an apparent activation energy rivaling those of state-of-the-art Au/TiO2 materials. Thus, we suggest that cost-effective catalysts for CO oxidation can be rationally designed by judicious choice of substituting metal through the co

Understanding how materials that catalyse the oxygen evolution reaction (OER) function is essential for the development of efficient energy-storage technologies. The traditional understanding of the OER mechanism on metal oxides involves four concerted proton-electron transfer steps on metal-ion centres at their surface and product oxygen molecules derived from water. Here, using in situ 18 O isotope labelling mass spectrometry, we provide direct experimental evidence that the O 2 generated during the OER on some highly active oxides can come from lattice oxygen. The oxides capable of lattice-oxygen oxidation also exhibit pH-dependent OER activity on the reversible hydrogen electrode scale, indicating non-concerted proton-electron transfers in the OER mechanism. Based on our experimental data and density functional theory calculations, we discuss mechanisms that are fundamentally different from the conventional scheme and show that increasing the covalency of metal-oxygen bonds is critical to trigger lattice-oxygen oxidation and enable non-concerted proton-electron transfers during OER.

Numerous studies have reported electronic activity descriptors of oxygen evolution reaction (OER) for oxide catalysts under a single reaction mechanism. However, recent works have revealed that a single mechanism is not at play across oxide chemistries. These works underscore a need to deeply investigate the electronic structure details of active oxide catalysts and how they align with the OER potential, which is critical to understanding the interfacial charge-transfer kinetics that dictate catalytic mechanisms. In this work, we use soft X-ray emission and absorption spectroscopy of perovskites to analyze the partial density of states on an absolute energy scale, from which energetic barriers for electron transfer and surface deprotonation were estimated and correlated with OER activity. Through this lens, we identify that decreasing the solid-state charge-transfer energy of perovskites can change the mechanisms of the OER from electron-transfer-limited to proton-electron-coupled, to proton-transfer-limited reactions. This concept is supported by the analysis of potential energy surfaces for sequential and concerted proton-electron transfer pathways using a Marcus model. Our work highlights the importance of understanding the physical origin of experimental OER activity trends with electronic descriptors and the need to promote surface deprotonation from oxides to discover new catalysts with enhanced activity.

A natural recombinant nephropathogenic K40/09 strain of infectious bronchitis virus (IBV) was heat-adapted for possible future use as live attenuated vaccine. The K40/09 strain was selected during successive serial passages in specific-pathogen free (SPF) embryonated eggs at sub-optimal higher temperature (56°C). Unlike the parental strain, the attenuated strain, designated K40/09 HP50, was found to be safe in 1-day-old SPF chicks, which showed neither mortality nor signs of morbidity, and rarely induced ciliostasis or histological changes in the trachea and kidney after intraocular and fine-spray administration. K40/09 HP50 provided almost complete protection against two distinct subgroups of a nephropathogenic strain (KM91-like and QX-like subgroup) and elicited the production of high titers of neutralizing antibody (neutralization index of 3.6). We conclude that the K40/09 HP50 vaccine virus is rapidly attenuated by heat adaptation and exhibits the desired level of attenuation, immunogenicity, and protective efficacy required for a live attenuated vaccine. These results indicate that the K40/09 vaccine could be helpful for the reduction of economic losses caused by recently emergent nephropathogenic IBV infection in many countries.