Blackbox Lernprozess und informelle Lernszenarien

Im Kontrast zu weit verbreiteten Auffassungen ist es aus der Sicht von Lernpsychologie und Hirnforschung nicht möglich, individuelle Lernprozesse exakt zu steuern. Im Gegenteil: Der individuelle Lernprozess stellt sich als Blackbox dar, deren Output immer wieder nur erstaunt zur Kenntnis genommen werden kann. Alle Versuche, dieses Problem zu lösen, erweisen sich regelmäßig als Ressourcenverschwendung. Als deutlich effizienter könnte es sich hingegen offenbaren, informelle Lernformen als Methode der Wahl massiv einzusetzen und somit den - ohnehin unrealistischen - Kontrollanspruch als Lehrende endgültig aufzugeben. (DIPF/Orig.

Tau, the chieftain's son

4 pdf filesOriginal book digitized with financial support from Media24by G.H. Franz ; illustrations by B.K. Franz.http://explore.up.ac.za/record=b1728737pm201

On the role of the time scale Delta t in Bose-Einstein correlations

The time scale $\Delta t$ parameter, which appears in the Bose-Einstein Correlations (BEC) treated in term of the Heisenberg uncertainty relations, is reexamined. Arguments are given for the role of $\Delta t$ as a measure of the particles' emission time rather than representing the strength property of the correlated particles. Thus in the analyzes of the $Z^0$ hadronic the $\Delta t$ given value of ~$10^{-24}$ seconds is the particles' emission time prescribed by the $Z^0$ lifetime. In heavy ion collisions $\Delta t$ measures the emission time duration of the particles produced from a nucleus of atomic number $A$ which is here shown to be equal to \Delta t =(m_{\pi}a^2)/(\hbar c^2})*A^{2/3} where a is about 1 fm, that is, proportional to the nucleus surface area. This dependence agrees rather well with the experimental $\Delta t$ values deduced from the BEC analyzes of heavy ion collisions.Comment: 8 pages, 5 figure

First Measurement of the 96^{96}Ru(p,γ\gamma)97^{97}Rh Cross Section for the p-Process with a Storage Ring

This work presents a direct measurement of the $^{96}$Ru($p, \gamma$)$^{97}$Rh cross section via a novel technique using a storage ring, which opens opportunities for reaction measurements on unstable nuclei. A proof-of-principle experiment was performed at the storage ring ESR at GSI in Darmstadt, where circulating $^{96}$Ru ions interacted repeatedly with a hydrogen target. The $^{96}$Ru($p, \gamma$)$^{97}$Rh cross section between 9 and 11 MeV has been determined using two independent normalization methods. As key ingredients in Hauser-Feshbach calculations, the $\gamma$-ray strength function as well as the level density model can be pinned down with the measured ($p, \gamma$) cross section. Furthermore, the proton optical potential can be optimized after the uncertainties from the $\gamma$-ray strength function and the level density have been removed. As a result, a constrained $^{96}$Ru($p, \gamma$)$^{97}$Rh reaction rate over a wide temperature range is recommended for $p$-process network calculations.Comment: 10 pages, 7 figs, Accepted for publication at PR

Measurements of proton-induced reactions on ruthenium-96 in the ESR at GSI

8th International Conference on Nuclear Physics at Storage Rings Stori11, October 9-14, 2011 Laboratori Nazionale di Frascati, Italy. Storage rings offer the possibility of measuring proton- and alpha-induced reactions in inverse kinematics. The combination of this approachwith a radioactive beamfacility allows, in principle, the determination of the respective cross sections for radioactive isotopes. Such data are highly desired for a better understanding of astrophysical nucleosynthesis processes like the p-process. A pioneering experiment has been performed at the Experimental Storage Ring (ESR) at GSI using a stable 96Ru beam at 9-11 AMeV and a hydrogen target. Monte-Carlo simulations of the experiment were made using the Geant4 code. In these simulations, the experimental setup is described in detail and all reaction channels can be investigated. Based on the Geant4 simulations, a prediction of the shape of different spectral components can be performed. A comparison of simulated predictions with the experimental results shows a good agreement and allows the extraction of the cross section

SU(4) Chiral Quark Model with Configuration Mixing

Chiral quark model with configuration mixing and broken SU(3)\times U(1) symmetry has been extended to include the contribution from c\bar c fluctuations by considering broken SU(4) instead of SU(3). The implications of such a model have been studied for quark flavor and spin distribution functions corresponding to E866 and the NMC data. The predicted parameters regarding the charm spin distribution functions, for example, \Delta c, \frac{\Delta c}{{\Delta \Sigma}}, \frac{\Delta c}{c} as well as the charm quark distribution functions, for example, \bar c, \frac{2\bar c}{(\bar u+\bar d)}, \frac{2 \bar c}{(u+d)} and \frac{(c+ \bar c)}{\sum (q+\bar q)} are in agreement with other similar calculations. Specifically, we find \Delta c=-0.009, \frac{\Delta c}{{\Delta \Sigma}}=-0.02, \bar c=0.03 and \frac{(c+ \bar c)}{\sum (q+\bar q)}=0.02 for the \chiQM parameters a=0.1, \alpha=0.4, \beta=0.7, \zeta_{E866}=-1-2 \beta, \zeta_{NMC}=-2-2 \beta and \gamma=0.3, the latter appears due to the extension of SU(3) to SU(4).Comment: 10 RevTeX pages. Accepted for publication in Phys. Rev.