Modulating the effective ionic radii of trivalent dopants in ceria using a combination of dopants to improve catalytic efficiency for the oxygen evolution reaction.

Aliovalent doping in ceria and defect engineering are important aspects in tuning the properties of ceria for advanced technological applications, especially in the emerging field of electrocatalytic water-splitting for harvesting renewable energy. However, the ambiguity regarding the choice of dopants/co-dopants and ways to deal with the size difference between dopants and lattice hosts remains a long-standing problem. In this study, ceria was aliovalently codoped with Sc3+ and La3+ while keeping the total concentration of dopants constant; the ionic radius of the former is smaller and that of the latter is larger than Ce4+. Variations in the relative amounts of these dopants helped to modulate the effective ionic radii and match that of the host. A systematic study on the role of these aliovalent dopants in defect evolution in ceria and in modulating the Ce3+ fraction using powder XRD, Rietveld refinement, positron annihilation lifetime spectroscopy, X-ray photoelectron spectroscopy, Eu3+ photoluminescence, and Raman spectroscopy is presented here. The evolved defects and their dependence on subtle factors other than charge compensation are further correlated with their electrocatalytic activity towards oxygen evolution reaction (OER) in alkaline medium. The catalyst with an optimum defect density, maximum Ce3+ fraction at the surface and the least effective ionic radius difference between the dopants and the host demonstrated the best performance towards the OER. This study demonstrates how effective ionic radius modulation in defect-engineered ceria through a judicious choice of codopants can enhance the catalytic property of ceria and provides immensely helpful information for designing ceria-based heterogeneous catalysts with desired functionalities.

Origin of Strong Hydrogen Bonding and Preferred Orientation of Water at Uncharged Polyethylene Glycol Polymer/Water Interface.

Polyethylene glycol (PEG), a water-soluble non-ionic polymer, finds diverse applications from Li-ion batteries to drug delivery. The effectiveness of PEG in these contexts hinges on water's behavior at PEG/water interfaces. Employing heterodyne-detected vibrational sum frequency generation and Raman spectroscopy along with a novel analytical approach, termed difference spectroscopy with simultaneous curve-fitting analysis, we observed that water exhibits both "hydrogen-up" and "hydrogen-down" orientations at PEG(≥400u)/water interfaces. As the molar mass of PEG increases, the contribution of the strongly hydrogen-bonded and H-up-oriented water rises. We propose that the PEG-affected interfacial water originates from the asymmetrical hydration of the surface-adsorbed PEG, as evidenced by the resemblance between the water spectra in the hydration shell of PEG and those at the PEG/water interface. These findings elucidate the molecular mechanism underlying PEG's catalytic role in water splitting at membrane interfaces.

Vibrational Coupling and Hydrogen-Bond Structure of Water in the Extended Hydration Shell of Metal Ions.

Intra- and intermolecular vibrational coupling (VC) and hydrogen bonding (H-bonding) of water are sparsely understood in the hydration shell (HS) of a metal ion, though the corresponding knowledge for an anion is quite extensive. This is primarily due to the overwhelming effect of anions on water, which masks the subtle perturbing influence of most of the cations. Using Raman difference spectroscopy with simultaneous curve fitting (Raman-DS-SCF) in combination with isotopic dilution and polarized Raman spectroscopy, we have elucidated the VC and H-bonding of water in the HS of bi- and trivalent metal ions─Mg2+, Ca2+, La3+, Gd3+, Dy3+. Polarized Raman measurement of the HS water with VC "turned on" and "turned off" (using isotopically diluted water, HOD) reveals that water retains the intra- and intermolecular vibrational coupling in the HS of high-charge-density metal ions, which is in stark contrast to that of an anion. Hydration shell spectroscopy in HOD unambiguously shows that the average H-bonding of water becomes stronger in the HS than that of bulk water. The first HS water strongly donates two H-bonds to the second HS water (ν̅max ≈ 3200 cm-1) but weakly accepts a H-bond from the second HS water (ν̅max ≈ 3590 cm-1), which makes the HS water heterogeneous in terms of its H-bond structure. The weakly interacting OH (ν̅max 3585 cm-1 in HOD) red-shifts by ∼ 15 cm-1 while the VC is "turned on" (ν̅max ≈ 3600 cm-1 in H2O), revealing the intramolecular coupling of water in the HS of metal ions.

Panton-Valentine leucocidin-producing Staphylococcus aureus: a clinical review.

Panton-Valentine leucocidin (PVL) is a virulence factor produced by certain strains of Staphylococcus aureus (SA). Through its cytolytic action on the cell membranes of human polymorphonuclear neutrophils, PVL causes a range of pathologies collectively known as PVL-SA disease. The hallmark clinical signs of PVL-SA are recurrent boils and necrotizing skin and soft tissue infections (SSTIs) in otherwise healthy patients; however, it can lead to more severe and invasive presentations, including necrotizing haemorrhagic pneumonia, necrotizing fasciitis and purpura fulminans. Young adults with minimal previous exposure to healthcare settings tend to be at highest risk for acquiring PVL-SA disease, with close physical contact playing a central role in disease transmission. The prevalence of PVL-SA varies globally; however, this is often underestimated owing to a lack of routine PVL testing. In the UK, PVL-positive SA isolates have been rising over the past decade alongside an increasing prevalence of multidrug resistance in larger cities. This review article aims to raise awareness of the PVL toxin, to aid clinicians with diagnostic pointers and to provide guidance with treatment, with an emphasis on the need for further population-based studies.

Evaluating the utility of an international webinar as a platform to educate students and doctors on the UK core surgical training portfolio.

BACKGROUND: Core Surgical Training (CST) is a competitive two-year postgraduate training program in the UK that is scored based on three equally weighted stations: management, clinical and portfolio. Preparing a surgical portfolio can start in medical school, however, there is limited guidance on what forms a competitive portfolio with the majority of advice coming from university resources and national societies which are variable throughout the country. Our aim was to assess the utility of a webinar to educate students and doctors on the CST portfolio to address this disparity. METHODS: Pre- and post-event questionnaires that included demographic data, 10-point Likert scales to self-report confidence on the understanding of the CST portfolio and its domains, and questions on utilising webinars were distributed to attendees. Pre- and post-event responses were paired, and scores were assessed for normality via the Shapiro-Wilk test; the Mann-Whitney U test was used to assess statistical significance. Cohen's d effect sizes were calculated to report standardised differences between pre-and post-event scores. RESULTS: A total of 177 participants from over 24 countries responded to both questionnaires. A statistically significant improvement in awareness of how to score maximum points was demonstrated across all nine CST domains (p < 0.0001). Regardless of whether they were UK-based or international, approximately half of the participants stated a preference for a webinar over an in-person format. Interestingly, most attendees did not feel that their university had provided them with adequate information on preparing for a surgical career with over half of the attendees stating that they had to attend events by external organisations to obtain such information. CONCLUSIONS: This study has demonstrated that a webinar can be effectively utilised to educate students and doctors on the various domains of the CST portfolio and how to maximise points in each section. Such events could address the variability of university resources and national societies across the country and provide equal opportunities for students. Further studies that directly compare webinars with in-person events and investigate long-term outcomes, such as success in CST applications, are required.