Exploring small energy scales with x-ray absorption and dichroism

Soft x-ray linear and circular dichroism (XLD, XMCD) experiments at the Ce M$_{4,5}$ edges are being used to determine the energy scales characterizing the Ce $4f$ degrees of freedom in the ultrathin ordered surface intermetallic CeAg$_x$/Ag(111). We find that all relevant interactions, i. e. Kondo scattering, crystal field splitting and magnetic exchange coupling occur on small scales. Our study demonstrates the usefulness of combining x-ray absorption experiments probing linear and circular dichroism owing to their strong sensitivity for anisotropies in both charge distribution and paramagnetic response, respectively.Comment: 5 pages, 4 figure

Optimizing Replica Exchange Moves For Molecular Dynamics

In this short note we sketch the statistical physics framework of the replica exchange technique when applied to molecular dynamics simulations. In particular, we draw attention to generalized move sets that allow a variety of optimizations as well as new applications of the method.Comment: 4 pages, 3 figures; revised version (1 figure added), PRE in pres

Partition Function Zeros and Finite Size Scaling of Helix-Coil Transitions in a Polypeptide

We report on multicanonical simulations of the helix-coil transition of a polypeptide. The nature of this transition was studied by calculating partition function zeros and the finite-size scaling of various quantities. Estimates for critical exponents are presented.Comment: RevTex, 4 eps-files; to appear in Phys. Rev. Le

Modified 'Stable Schools' as a Consulting Tool for Organic Dairy Herds

The aim of this study was to examine the opinions of farmers on a consulting project, which was established for organic dairy farms in Northern Germany involving different animal health experts who participated in the meetings. Furthermore, the properties of measures that are of decisive importance for implementation on the farms were identified to improve consultancy services for dairy farming. Once a year, the farmers met on a host-farm in one of three groups consisting of five to nine farms, a facilitator and an expert. At each meeting, a host-farm was visited and the analysed data of all participating farms of the previous year were presented to the group members. Each farmer had the possibility to report on success stories and issues concerning his herd. During discussions, the farmers first proposed mutual farm-specific measures for improving herd health and animal welfare. Afterwards, the expert named possible interventions and commented on the given measures of the farmers. All measures were noted by the facilitator. At the end of each meeting, each farmer could choose which of the given measures he wanted to implement. Open group-interviews as well as anonymous questionnaires for the farmers were used at the meetings in winter 2016/2017 to evaluate their perception of this consulting project and to determine which properties of measures were important for implementation on the farms. Based on the results of this study, the participating farmers were very positive towards this kind of consulting project. They favoured the participation of an expert during the meetings and the analysis of farm specific data. Farmers mostly chose measures for implementation proposed by farmers and approved by the expert, followed by those proposed by the expert only. Measures were chosen when they were practical in the implementation, effective, efficient and took a low additional workload for implementation

Pseudogap of metallic layered nickelate R2-xSrxNiO4 (R=Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy

We have investigated charge dynamics and electronic structures for single crystals of metallic layered nickelates, R2-xSrxNiO4 (R=Nd, Eu), isostructural to La2-xSrxCuO4. Angle-resolved photoemission spectroscopy on the barely-metallic Eu0.9Sr1.1NiO4 (R=Eu, x=1.1) has revealed a large hole surface of x2-y2 character with a high-energy pseudogap of the same symmetry and comparable magnitude with those of underdoped (x<0.1) cuprates, although the antiferromagnetic interactions are one order of magnitude smaller. This finding strongly indicates that the momentum-dependent pseudogap feature in the layered nickelate arises from the real-space charge correlation.Comment: 4 pages, 4 figures. Accepted in Physical Review Letter

Multi-Overlap Simulations for Transitions between Reference Configurations

We introduce a new procedure to construct weight factors, which flatten the probability density of the overlap with respect to some pre-defined reference configuration. This allows one to overcome free energy barriers in the overlap variable. Subsequently, we generalize the approach to deal with the overlaps with respect to two reference configurations so that transitions between them are induced. We illustrate our approach by simulations of the brainpeptide Met-enkephalin with the ECEPP/2 energy function using the global-energy-minimum and the second lowest-energy states as reference configurations. The free energy is obtained as functions of the dihedral and the root-mean-square distances from these two configurations. The latter allows one to identify the transition state and to estimate its associated free energy barrier.Comment: 12 pages, (RevTeX), 14 figures, Phys. Rev. E, submitte