Modeling of Ni Diffusion Induced Austenite Formation in Ferritic Stainless Steel Interconnects

Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell and electrolysis cell stacks. During stack production and operation, nickel from the Ni/yttria stabilized zirconia fuel electrode or from the Ni contact component layer diffuses into the interconnect plate, causing transformation of the ferritic phase into an austenitic phase in the interface region. This is accompanied with changes in volume, and in mechanical and corrosion properties of the interconnect plates. In this work, kinetic modeling of the inter-diffusion between Ni and FeCr based ferritic stainless steel was conducted, using the CALPHAD (CALculation of PHAse Diagrams) approach with the DICTRA (DIffusion Controlled TRAnsformation) software. The kinetics of inter-diffusion and austenite formation was explored in detail. The simulation was further validated by comparing with experiments. The results show that after 2000 h at 800°C Ni diffuses more than 100 μm deep into Crofer 22 APU. Along with the Ni diffusion, part of the ferritic steel with 50–60 μm in thickness has transformed into the austenitic phase. Growth of the austenite phase in commercial interconnect materials was predicted to take place under practical stack operation conditions

Multiplex PCR for detection of plasmid-mediated colistin resistance determinants, mcr-1, mcr-2, mcr-3, mcr-4 and mcr-5 for surveillance purposes

Background and aim: Plasmid-mediated colistin resistance mechanisms have been identified worldwide in the past years. A multiplex polymerase chain reaction (PCR) protocol for detection of all currently known transferable colistin resistance genes (mcr-1 to mcr-5, and variants) in Enterobacteriaceae was developed for surveillance or research purposes. Methods: We designed four new primer pairs to amplify mcr-1, mcr-2, mcr-3 and mcr-4 gene products and used the originally described primers for mcr-5 to obtain a stepwise separation of ca 200 bp between ampli-cons. The primer pairs and amplification conditions allow for single or multiple detection of all currently described mcr genes and their variants present in Enterobacteriaceae. The protocol was validated testing 49 European Escherichia coli and Salmonella isolates of animal origin. Results: Multiplex PCR results in bovine and porcine isolates from Spain, Germany, France and Italy showed full concordance with whole genome sequence data. The method was able to detect mcr-1, mcr-3 and mcr-4 as singletons or in different combinations as they were present in the test isolates. One new mcr-4 variant, mcr-4.3, was also identified. Conclusions: This method allows rapid identification of mcr-positive bacteria and overcomes the challenges of phenotypic detection of colistin resistance. The multiplex PCR should be particularly interesting in settings or laboratories with limited resources for performing genetic analysis as it provides information on the mechanism of colistin resistance without requiring genome sequencing. © 2018, European Centre for Disease Prevention and Control (ECDC). All rights reserved

Effects of boundary conditions on magnetization switching in kinetic Ising models of nanoscale ferromagnets

Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and simulations of two-dimensional kinetic Ising systems with periodic boundary conditions. In this article we consider the effects of boundary conditions on the switching phenomena. A rich range of behaviors is predicted by droplet theory: the specific mechanism by which switching occurs depends on the structure of the boundary, the particle size, the temperature, and the strength of the applied field. The theory predicts the existence of a peak in the switching field as a function of system size in both systems with periodic boundary conditions and in systems with boundaries. The size of the peak is strongly dependent on the boundary effects. It is generally reduced by open boundary conditions, and in some cases it disappears if the boundaries are too favorable towards nucleation. However, we also demonstrate conditions under which the peak remains discernible. This peak arises as a purely dynamic effect and is not related to the possible existence of multiple domains. We illustrate the predictions of droplet theory by Monte Carlo simulations of two-dimensional Ising systems with various system shapes and boundary conditions.Comment: RevTex, 48 pages, 13 figure

Concepts of Animal Health and Welfare in Organic Livestock Systems

In 2005, The International Federation of Organic Agricultural Movements (IFOAM) developed four new ethical principles of organic agriculture to guide its future development: the principles of health, ecology, care, and fairness. The key distinctive concept of animal welfare in organic agriculture combines naturalness and human care, and can be linked meaningfully with these principles. In practice, a number of challenges are connected with making organic livestock systems work. These challenges are particularly dominant in immature agro-ecological systems, for example those that are characterized by industrialization and monoculture. Some of the current challenges are partly created by shortages of land and manure, which encourage zero-grazing and other confined systems. Other challenges are created in part by the conditions for farming and the way in which global food distribution systems are organized, e.g., how live animals are transported, how feed is traded and transported all over the globe, and the development of infrastructure and large herds. We find that the overall organic principles should be included when formulating guidelines for practical organic animal farming. This article explores how the special organic conceptions of animal welfare are related to the overall principles of organic agriculture. The aim is to identify potential routes for future development of organic livestock systems in different contexts and with reference to the specific understanding of animal welfare in organic agriculture. We include two contrasting cases represented by organic livestock systems in northwestern Europe and farming systems in tropical low-income countries; we use these cases to explore the widely different challenges of organic livestock systems in different parts of the world