Thymic Medullary Epithelial Cell Differentiation, Thymocyte Emigration, and the Control of Autoimmunity Require Lympho–Epithelial Cross Talk via LTβR

Thymocytes depend on the interaction with thymic epithelial cells for the generation of a diverse, nonautoreactive T cell repertoire. In turn, thymic epithelial cells acquire their three-dimensional cellular organization via instructive signals from developing thymocytes. The nature of these signals has been elusive so far. We show that thymocytes and medullary epithelial cells (MECs) communicate via the lymphotoxin β receptor (LTβR) signaling axis. Normal differentiation of thymic MECs requires LTβR ligand on thymocytes and LTβR together with nuclear factor–κB-inducing kinase (Nik) in thymic epithelial cells. Impaired lympho–epithelial cross talk in the absence of the LTβR causes aberrant differentiation and reduced numbers of thymic MECs, leads to the retention of mature T lymphocytes, and is associated with autoimmune phenomena, suggesting an unexpected role for LTβR signaling in central tolerance induction

Electrochemical dealloying as a tool to tune the porosity, composition and catalytic activity of nanomaterials

Electrochemical dealloying as a post-Treatment can greatly improve the catalytic activity of nanoparticles. To date, selecting suitable conditions to reach desired porosity, composition and catalytic activity is based on trial-And-error-Attempts, due to insufficient understanding of the electrochemically induced morphological and compositional changes of the nanoparticles. These changes are elucidated here by combining electrochemistry with identical location electron microscopy analyses and linking them to the electrocatalytic properties of the obtained nanocatalysts. Using AgAu alloy nanoparticles and the hydrogen evolution reaction as a model system, the influence of cyclic voltammetry parameters on the catalytic activity upon electrochemical dealloying is investigated. Increasing the number of cycles initially results in a decreased Ag content and a sharp improvement in activity. Additional dealloying increases the nanoparticle porosity, while marginally altering their composition, due to surface motion of atoms. Since this is accompanied by particle aggregation, a decrease in catalytic activity results upon extensive cycling. This transition between porosity formation and particle aggregation marks the optimum for nanocatalyst post-production. The gained insights may aid speeding up the development of new materials by electrochemical dealloying as an easy-To-control post-processing route to tune the properties of existing nanoparticles, instead of having to alter usually delicate synthesis routes as a whole. © The Royal Society of Chemistry

Local Fuel Starvation Degradation of an Automotive PEMFC Full Size Stack

Special Issue: 23rd EFCF “Low‐Temperature Fuel Cells, Electrolyzers, H2‐Processing Forum” (EFCF2019

Fluorescent Silver Nanoclusters Embedded in Hydrogel Matrix and Its Potential Use in Environmental Monitoring

The optical absorption and fluorescence of silver nanoclusters (AgNCs) are widely exploited in many different application fields such as sensors, bio-imaging, drug delivery, etc. In the sensor field, optical devices are highly versatile thanks to their ease of fabrication and low costs and, therefore, are optimal candidates to replace expensive apparatuses commonly used. In this study, we synthesized AgNCs in aqueous phase by photochemical synthesis using poly methacrylic acid (PMAA) as a stabilizer. Colloidal water solutions of these NCs showed a very good sensitivity to Pb(II) ions, and in order to fabricate a solid-state sensor, we introduced them in a hydrogel material formed by poly(ethylene glycol) diacrylate with a molecular weight of 700 g/mol (PEGDA700). The systems were characterized using absorption and fluorescence spectroscopy and transmission electron microscopy (TEM). Finally, the sensitivity to Pb(II) ions has been tested with the aim to use these systems as solid-state optical sensors for water quality