Seit dem 2. nachchristlichen Jahrhundert werden die Schriften von Aristoteles kommentiert. Diese Ausgabe enthält griechische Kommentare zu seinem Werk vom 3. bis 8. Jahrhundert n. Chr., u. a. von Alexander von Aphrodiensias, Themistios, Joh. Philoponus, Simplicius in griechischer Sprache.

When we solve problems there are usually a number of different strategies that we can use. It is a hallmark of intelligence that we, as humans, are able to flexibly choose between them. Siegler and...

Recently, there has been renewed interest in the search for low-mass magnetic monopoles. At the University of Oklahoma we are performing an experiment (Fermilab E882) using material from the old D0 and CDF detectors to set limits on the existence of Dirac monopoles of masses of the order of 500 GeV. To set such limits, estimates must be made of the production rate of such monopoles at the Tevatron collider, and of the binding strength of any such produced monopoles to (...) matter. Here we sketch the still primitive theory of such interactions, and indicate why we believe a credible limit may still be obtained. On the other hand, there have been proposals that the classic Euler–Heisenberg Lagrangian together with duality could be employed to set limits on magnetic monopoles having masses less than 1 TeV, based on virtual, rather than real processes. The D0 collaboration at Fermilab has used such a proposal to set mass limits based on the nonobservation of pairs of photons each with high transverse momentum. We critique the underlying theory, by showing that the cross section violates unitarity at the quoted limits and is unstable with respect to radiative corrections. We therefore believe that no significant limit can be obtained from the current experiments, based on virtual monopole processes. (shrink)