Silicon carbide X-ray beam position monitors for synchrotron applications.

In this work, the performance of thin silicon carbide membranes as material for radiation hard X-ray beam position monitors (XBPMs) is investigated. Thermal and electrical behavior of XBPMs made from thin silicon carbide membranes and single-crystal diamond is compared using finite-element simulations. Fabricated silicon carbide devices are also compared with a 12 µm commercial polycrystalline diamond XBPM at the Swiss Light Source at the Paul Scherrer Institute. Results show that silicon carbide devices can reach equivalent transparencies while showing improved linearity, dynamics and signal-to-noise ratio compared with commercial polycrystalline diamond XBPMs. Given the obtained results and availability of electronic-grade epitaxies on up to 6 inch wafers, it is expected that silicon carbide can substitute for diamond in most beam monitoring applications, whereas diamond, owing to its lower absorption, could remain the material of choice in cases of extreme X-ray power densities, such as pink and white beams.

Designing cryo-enzymatic reactions in subzero liquid water by lipidic mesophase nanoconfinement.

Cryo-enzymology provides the possibility to develop unconventional biological reactions and detect intermediates in ultrafast enzymatic catalysis processes, but also illuminates the understanding of life principles in extremely cold environments. The scarcity of biological or biomimetic host systems that provide liquid water at subzero temperatures inhibits the prosperity of cryo-enzymology. Here we introduce cryo-enzymatic reactions in subzero water nanoconfined within lipid mesophases formed by conventional lipids. We show that the enzymatic reactions that ensue outperform the homologue catalytic processes run at standard temperatures. We use phytantriol-based lipidic mesophases (LMPs), within which water remains in the liquid state down to -120 °C, and combine crystallization and dynamic studies of the confined water to provide a fundamental understanding of the physical status of water at subzero temperatures, which sets the stage for cryo-enzymatic reactions in these environments. In the model horseradish peroxidase oxidization, the cation free-radical product is stabilized in LMPs at -20 °C, in contrast to the fast-consuming reactions at temperatures above 0 °C. Furthermore, the LMP system also supports the cascade reaction and lipase reaction at subzero temperatures, at which enzymatic reactions with both hydrophilic and hydrophobic substrates are successfully carried out. Our designed LMP system opens access to the nature of confined water in the biomimetic environment and provides a platform for low-temperature biomacromolecule reconstitution and the cryogenic control of enzymatic reactions in bionanotechnology.