Scientific Highlights
In-situ Studies of the Reactivity of Model Catalysts: Surface Chemistry from flat surfaces to nanoparticles
On 7th February Dr. Christian Papp from University Erlangen (Germany) is visiting the SIM beamline and will give a Photon Science Seminar talk with the title: "In-situ Studies of the Reactivity of Model Catalysts: Surface Chemistry from flat surfaces to nanoparticles"
A Miniaturized Biaxial Deformation Rig for in situ Mechanical Testing
Researchers at PSI have developed a new unique miniaturized biaxial deformation rig, which allows to apply in-plane biaxial stress states with arbitrary stress ratios and to perform strain path changes on thin-sheet metals. The device is optimized for in situ usage inside a scanning electron microscope and at synchrotron beam lines.
Full Elasticity Tensor from Thermal Diffuse Scattering
We present a method for the precise determination of the full elasticity tensor from a single crystal diffraction experiment using monochromatic X-rays. For the two benchmark systems calcite and magnesium oxide, we show that the measurement of thermal diffuse scattering in the proximity of Bragg reflections provides accurate values of the complete set of elastic constants.
Annual Retreat of the Microscopy & Magnetism Group
The Magnetism and Microscopy group has met for its annual retreat meeting in Lungern 11- 15.1.2017 (in the central mountain region of Switzerland) for extensive discussions on its science program. As for other years, after some general introductory lecture into the techniques used, current and future projects have been presented by the PhD students, postdocs, and scientists as well as from guests who collaborate with the group. Discussion went into the time where dinner has been prepared together, followed by some leisure activities on Saturday.
Suppression of magnetic excitations near the surface of the topological Kondo insulator SmB6
We present a detailed investigation of the temperature and depth dependence of the magnetic properties of the three-dimensional topological Kondo insulator SmB6, in particular, near its surface. We find that local magnetic field fluctuations detected in the bulk are suppressed rapidly with decreasing depths, disappearing almost completely at the surface.
Structure and Interaction in the pH-Dependent Phase Behavior of Nanoparticle−Protein Systems
The pH-dependent structure and interaction of anionic silica nanoparticles (diameter 18 nm) with two globular model proteins, lysozyme and bovine serum albumin (BSA), have been studied. Cationic lysozyme adsorbs strongly on the nanoparticles, and the adsorption follows exponential growth as a function of lysozyme concentration, where the saturation value increases as pH approaches the isoelectric point (IEP) of lysozyme.
A three-dimensional movie of structural changes in bacteriorhodopsin
Snapshots of bacteriorhodopsinBacteriorhodopsin is a membrane protein that harvests the energy content from light to transport protons out of the cell against a transmembrane potential. Nango et al. used timeresolved serial femtosecond crystallography at an x-ray free electron laser to provide 13 structural snapshots of the conformational changes that occur in the nanoseconds to milliseconds after photoactivation. These changes begin at the active site, propagate toward the extracellular side of the protein, and mediate internal protonation exchanges that achieve proton transport.
Can a metal nanotip array device be a low-emittance and coherent cathode?
A nanofabricated low emittance field emitter array cathode was demonstrated for the first time, and successfully applied to observe the low-energy electron diffraction from suspended monolayer graphene. The work has an impact on the future development of compact X-ray free electron lasers, THz/RF vacuum electronic sources, and ultrafast electron imaging and diffraction experiments.
The Dynamics of Nuclear Reactors
Nuclear reactor dynamics deals with the transient behaviour of nuclear reactors which mostly refers to time changes of the imbalance between heat production and removal. Since the prediction of the dynamic behaviour is crucial for the safety of a reactor, computational models and methodologies have been developed in the framework of the STARS project, at the Laboratory for Reactor Physics and Thermal-Hydraulics (LRT), with the main goal to simulate the complex behaviours of reactors under various conditions with a high level of fidelity.
Tuning magnetic spirals beyond room temperature with chemical disorder
Frustrated magnets with spiral magnetic orders are of high current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low magnetic order temperatures (typically <100K) greatly restrict their fields of application. Researchers of PSI have demonstrated that the stability domain of the spiral phase in the perovskite YBaCuFeO5 can be enlarged by more than 150K through a controlled manipulation of the Fe/Cu chemical disorder.