The Superconducting Proximity Effect as a Tool to Investigate Metal Films and Interfaces

052The superconducting proximity effect is measured in sandwiches of thin Pb films and the alkali metals Cs, Rb, K and Na. The $T_{c}$-dependence provides information about the interface barriers between Pb and the alkalis. Such a barrier is particularly large in Pb/Cs sandwiches. It is not due to impurities or oxydation. In the presence of a sufficiently strong barrier a special form of the Cooper limit can be applied to calculate the transition temperature of the sandwich

Coherent Transport of Angular Momentum - The Ranque-Hilsch Tube as a Paradigm

The mechanism for efficient and coherent angular momentum transport remains one of the unsolved puzzles in astrophysics despite the enormous efforts that have been made. We suggest that important new insight could be gained in this problem through an experimental and theoretical study of a laboratory device (Ranque-Hilsch tube) that displays a similar enhanced angular momentum transfer which cannot be explained by a simple turbulent model. There is already good experimental evidence to suggest that the cause of this enhancement is the formation of aligned vortices that swirl around the symmetry axes very much like virtual paddle blades.Comment: Proceedings of the 14th Florida Workshop in Nonlinear Astronomy and PHysics, "Astrophysical Turbulence and Convection", Eds. J.R. Buchler and H. Kandrup, to appear in the Annals of the New York Academy of Science

Die Juden in Böhmen und Mähren im Mittelalter und die ersten Privilegien : (bis zum Ende des 13. Jahrhunderts)

Bei der Kärglichkeit des Quellenmaterials zur früh- und hochmittelalterlichen Geschichte der Juden in den böhmischen Ländern erscheint es sinnvoll, den Blick immer wieder vergleichend über die Grenzen unseres eigentlichen Untersuchungsraums auf ganz Mitteleuropa hinauszulenken. Wir wissen von der Existenz einer jüdischen Gemeinde im römischen Köln schon für die Spätantike, aber nach einer langen Überlieferungslücke ist uns für das Mittelalter die Anwesenheit von Juden im östlichen Frankenreich erst seit der Zeit Karls des Großen bezeugt