Tunability of Critical Casimir Interactions by Boundary Conditions

We experimentally demonstrate that critical Casimir forces in colloidal systems can be continuously tuned by the choice of boundary conditions. The interaction potential of a colloidal particle in a mixture of water and 2,6-lutidine has been measured above a substrate with a gradient in its preferential adsorption properties for the mixture's components. We find that the interaction potentials at constant temperature but different positions relative to the gradient continuously change from attraction to repulsion. This demonstrates that critical Casimir forces respond not only to minute temperature changes but also to small changes in the surface properties.Comment: 4 figures; http://www.iop.org/EJ/article/0295-5075/88/2/26001/epl_88_2_26001.htm

Holographic Conformal Window - A Bottom Up Approach

We propose a five-dimensional framework for modeling the background geometry associated to ordinary Yang-Mills (YM) as well as to nonsupersymmetric gauge theories possessing an infrared fixed point with fermions in various representations of the underlying gauge group. The model is based on the improved holographic approach, on the string theory side, and on the conjectured all-orders beta function for the gauge theory one. We first analyze the YM gauge theory. We then investigate the effects of adding flavors and show that, in the holographic description of the conformal window, the geometry becomes AdS when approaching the ultraviolet and the infrared regimes. As the number of flavors increases within the conformal window we observe that the geometry becomes more and more of AdS type over the entire energy range.Comment: 20 Pages, 3 Figures. v2: references adde

Komplexe proximale Humerusfraktur beim alten Menschen: Winkelstabile Plattenosteosynthese vs. Hemiarthroplastik

Zusammenfassung: Hintergrund: Ziel der vorliegenden Untersuchung ist ein direkter Vergleich der Schulterhemiarthroplastik (SHA) mit der winkelstabilen Plattenosteosynthese (WSPOS) beim alten Patienten mit komplexer proximaler Humerusfraktur. Patienten und Methoden: Zwischen 2003 und 2005 wurden alle Patienten (n=52, Alter ≥70Jahre) mit 3- und 4-Segment-Frakturen des proximalen Humerus, welche mit einer WSPOS (PHILOS®) versorgt wurden, prospektiv erfasst und nach einem Jahr mittels Constant-Score (CS), Oxford Shoulder Score (OSS) und radiologisch nachkontrolliert. Verglichen wurde die WSPOS mit einem historischen Kollektiv mit identischen Einschlusskriterien, welches zwischen 1995 und 1997 an der gleichen Institution mittels SHA versorgt wurde (n=59). Ergebnisse: Beide Patientenkollektive zeigten keine Unterschiede bezüglich Alter, Geschlechterverteilung und Frakturtypen. Der CS war signifikant besser für die WSPOS (median 71 vs. 41). Bezüglich Schmerzen zeigte sich im OSS kein Unterschied zwischen den Gruppen. In der WSPOS-Gruppe mussten signifikant mehr Revisionseingriffe durchgeführt werden (25% vs. 2%). Schlussfolgerung: Die WSPOS liefert beim alten Patienten, bei komplexen proximalen Humerusfrakturen deutlich bessere funktionelle Resultate, ist jedoch mit mehr Rezidiveingriffen behaftet. Die Selbständigkeit der Patienten kann bei beiden Operationsmethoden bei guter Schmerzfreiheit meist erhalten werde

Microwave cavity perturbation studies on H-form and Cu ion-exchanged SCR catalyst materials: correlation of ammonia storage and dielectric properties

Ammonia-based selective catalytic reduction (SCR) has become the major control strategy for NOx emissions from light and heavy duty diesel engines. Before reducing NOx on the SCR active material, ammonia storage on the active sites of the catalyst is crucial. The in operando measurement of the dielectric properties of the catalyst material using microwave cavity perturbation is a promising indicator of ammonia loading. In this work, the influence of copper ion-exchange of the zeolite-based SCR material ZSM-5 on the NH3 storage and the dielectric properties is highlighted. The catalyst powder samples were monitored by microwave cavity perturbation as a function of the stored ammonia content at a frequency of approximately 1.2 GHz in a temperature range between 200 and 350 °C. Due to ion exchange, the NH3 storage behavior changes, what could be monitored in the sensitivity of the dielectric permittivity to NH3. The dependence of the complex dielectric permittivity on ammonia loading is decreased by ion exchange, hinting that mostly ammonia storage on Brønsted sites affects the dielectric permittivity. This finding adds new knowledge to the electrical conduction and polarization mechanisms occurring in these zeolite materials