Jung und Alt im Hörsaal:Erfahrungen jüngerer Studierender mit dem „Studium im Alter“ an der Universität Münster

Das „Studium im Alter“ ist ein Weiterbildungsangebot der Universität Münster für Personen im mittleren und höheren Lebensalter, die als Gasthörer gemeinsam mit jüngeren, regulären Studierenden Vorlesungen und Seminare an der Hochschule besuchen. In der Presse erschienen von Zeit zu Zeit Berichte über Konflikte, die das Gaststudium der Älteren in den Hörsälen verursacht. Das nahm eine Gruppe von Teilnehmern am „Studium im Alter“ zum Anlass, in einem zweisemestrigen Forschungsprojekt zu untersuchen, inwiefern solche Berichte die Regel oder Einzelfälle beschreiben. Das Ergebnis der schriftlichen Befragung regulärer Studierender zu Ihren Erfahrungen mit Studierenden im Alter liegt mit dieser Studie vor. Abgesehen von wenigen Ausnahmen belegt sie ein grundsätzlich harmonisches Miteinander von jüngeren und älteren Studierenden in den Hörsälen der Universität Münster

Effects of boundary conditions on magnetization switching in kinetic Ising models of nanoscale ferromagnets

Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and simulations of two-dimensional kinetic Ising systems with periodic boundary conditions. In this article we consider the effects of boundary conditions on the switching phenomena. A rich range of behaviors is predicted by droplet theory: the specific mechanism by which switching occurs depends on the structure of the boundary, the particle size, the temperature, and the strength of the applied field. The theory predicts the existence of a peak in the switching field as a function of system size in both systems with periodic boundary conditions and in systems with boundaries. The size of the peak is strongly dependent on the boundary effects. It is generally reduced by open boundary conditions, and in some cases it disappears if the boundaries are too favorable towards nucleation. However, we also demonstrate conditions under which the peak remains discernible. This peak arises as a purely dynamic effect and is not related to the possible existence of multiple domains. We illustrate the predictions of droplet theory by Monte Carlo simulations of two-dimensional Ising systems with various system shapes and boundary conditions.Comment: RevTex, 48 pages, 13 figure

Strukturuntersuchungen von adsorbatinduzierten Rekonstruktionen der Ni(110)- und Cu3_{3}Au(110)-Oberfläche mit niederenergetischer Ionenstreuung und Rastertunnelmikroskopie

The chemisorption of nitrogen and of oxygen induces reconstructions on the Ni(110) and Cu$_{3}$Au(110) surfaces. Tue resulting structures have been investigated by Low Energy Ion Scattering (LEIS), Direct Recoil Spectroscopy (DRS) and Scanning Tunnelling Microscopy (STM). The Ni(110) surface reconstructs after implantation of nitrogen and annealing at 700 K. With Low Energy Electron Diffraction (LEED) a (2x3) pattern is observed. The investigations show that the reconstruction is a modified missing row structure. Every third row of nickel atoms running along the [1$\overline{1}$0] direction is missing. In the so formed "double rows" in the first layer and in the ditches the nitrogen is placed 0.2 $\mathring{A}$ above the nickel atoms in every other four-fold-hollow-site. The nitrogen atoms bring about that the separation of the two nickel rows is 0.2 $\mathring{A}$ smaller than between corresponding rows in the [001]-direction on the unreconstructed surface. The clean Cu$_{3}$Au(110) surface exhibits two different reconstructions at room temperature. (i) a (2x1) phase, which is obtained after rapidly cooling the sample from 800 K to 300K, and (ii) a (4x1) phase after slowly (two hours) cooling from 800K to room temperature; the latter is apparently an equilibrium phase. After oxygen exposure and annealing of the quenched phase additional copper-oxygen-rows running along the [001]-direction are formed above the copper rows of the (2x1) reconstructed clean surface. These rows are shifted by 1.875 $\mathring{A}$ in the [001]-direction with respect to the firstlayer of the clean surface. The height difference between the cooper and the oxygen atoms in the added rows is 0.3 $\mathring{A}$. The initial stage of the reconstruction of the (4x1) phase of the clean Cu$_{3}$Au(110) surface has been investigated. After exposure of 11 L of oxygen the STM images show about 15 $\mathring{A}$ long worm like structures running along the [001]-direction. These "worms" are identified as the areas of the cooper double rows of the (4x1) phase, in which the oxygen is already adsorbed in the four-fold-hollow site. Increasing the oxygen exposure leads to an increase of the concentration of these "worms". Finally nitrogen induces on both, the clean (2x1) and the clean (4x1) Cu$_{3}$Au(110) surface a c(2x4) reconstruction. This reconstruction is well described by a first layer of pure copper in which copper double rows oriented in the [1$\overline{1}$0]-direction appears. In the [001]- direction the copper-copper distance in the double rows is 2.55 $\mathring{A}$ and between the double rows 4.95 $\mathring{A}$. The nitrogen is adsorbed at every other four-fold-hollow site in the double rows. In contrast to the N-Ni(110)-(2x3) reconstruction the double rows are not separated by a missing row. Instead, the position of the nitrogen in neighbouring double rows is shifted by one substrate lattice site in the [1$\overline{1}$0]-direction