A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

Snow in the environment acts as a host to rich chemistry and provides a matrix for physical exchange of contaminants within the ecosystem. The goal of this review is to summarise the current state of knowledge of physical processes and chemical reactivity in surface snow with relevance to polar regions. It focuses on a description of impurities in distinct compartments present in surface snow, such as snow crystals, grain boundaries, crystal surfaces, and liquid parts. It emphasises the microscopic description of the ice surface and its link with the environment. Distinct differences between the disordered air–ice interface, often termed quasi-liquid layer, and a liquid phase are highlighted. The reactivity in these different compartments of surface snow is discussed using many experimental studies, simulations, and selected snow models from the molecular to the macro-scale. Although new experimental techniques have extended our knowledge of the surface properties of ice and their impact on some single reactions and processes, others occurring on, at or within snow grains remain unquantified. The presence of liquid or liquid-like compartments either due to the formation of brine or disorder at surfaces of snow crystals below the freezing point may strongly modify reaction rates. Therefore, future experiments should include a detailed characterisation of the surface properties of the ice matrices. A further point that remains largely unresolved is the distribution of impurities between the different domains of the condensed phase inside the snowpack, i.e. in the bulk solid, in liquid at the surface or trapped in confined pockets within or between grains, or at the surface. While surface-sensitive laboratory techniques may in the future help to resolve this point for equilibrium conditions, additional uncertainty for the environmental snowpack may be caused by the highly dynamic nature of the snowpack due to the fast metamorphism occurring under certain environmental conditions. Due to these gaps in knowledge the first snow chemistry models have attempted to reproduce certain processes like the long-term incorporation of volatile compounds in snow and firn or the release of reactive species from the snowpack. Although so far none of the models offers a coupled approach of physical and chemical processes or a detailed representation of the different compartments, they have successfully been used to reproduce some field experiments. A fully coupled snow chemistry and physics model remains to be developed.

Performance of HBsAg point-of-care tests for detection of diagnostic escape-variants in clinical samples

BACKGROUND Hepatitis B viruses (HBV) harboring mutations in the a-determinant of the Hepatitis B surface antigen (HBsAg) are associated with reduced reactivity of HBsAg assays. OBJECTIVES To evaluate the sensitivity and specificity of three HBsAg point-of-care tests for the detection of HBsAg of viruses harboring HBsAg mutations. STUDY DESIGN A selection of 50 clinical plasma samples containing HBV with HBsAg mutations was used to evaluate the performance of three HBsAg point-of-care tests (Vikia(®), bioMérieux, Marcy-L'Étoile, France. Alere Determine HBsAg™, Iverness Biomedical Innovations, Köln, Germany. Quick Profile™, LumiQuick Diagnostics, California, USA) and compared to the ARCHITECT HBsAg Qualitative(®) assay (Abbott Laboratories, Sligo, Ireland). RESULTS The sensitivity of the point-of-care tests ranged from 98% to 100%. The only false-negative result occurred using the Quick Profile™ assay with a virus harboring a D144A mutation. CONCLUSIONS The evaluated point-of-care tests revealed an excellent sensitivity in detecting HBV samples harboring HBsAg mutations.

Kongressorte der Frühen Neuzeit im europäischen Vergleich. Der Friede von Baden (1714)

Der europäische Kontinent wurde im 17. und 18. Jahrhundert von zahlreichen Kriegen überzogen. Zugleich wurden mit dem Kongresswesen neue Formen des Friedensschließens erprobt. Der vorliegende Band zeigt ausgehend von den Verhandlungen in Baden 1714 und weiteren Beispielen aktuelle Forschungsperspektiven zur räumlichen »Verortung« dieser frühneuzeitlichen Friedenskongresse auf. In den Gastorten bildeten diese von adliger Kultur geprägten Großveranstaltungen vorübergehende Fremdkörper, was aber nicht das Fehlen von Interaktionen mit den lokalen Gesellschaften bedeutete. Die Beherbergung zahlreicher Menschen unterschiedlichen Standes und Glaubens stellte für die gastgebenden Städte einerseits eine beträchtliche Herausforderung und Belastung dar. Andererseits bot sich damit für sie die Möglichkeit, sich in der europäischen Fürstengesellschaft zu positionieren. Die Frage nach den politischen und rechtlichen Voraussetzungen für die Wahl als Kongressort weist schließlich über den Kontext der einzelnen Städte hinaus und führt zu einer Geschichte frühneuzeitlicher Neutralisierungspraktiken.