Colloides / Electric Field / Electrical Properties / Microemulsions / Percolation Water-in-oil microcmulsions, stabilized by the nonionic surfactant Igepal CO-520, show a temperature dependent structure change which can be monitored by electric conductivity. We show that the transition which involves the percolation of the aqueous phase can also be induced by high electric fields. A system is investigated which contains only a few volume percent of the aqueous phase (0.1 M KCI) in a mixture of n-and c-hexanc but still exhibits a highly cooperative transition from the conducting state at lower temperature to the almost nonconducting state at highcr temperature. Electric fields, applied up to ca. 10 k V cm-', shift the transition curves to the high temperature side, i.e. restore a structure with continuous water channels. The percolation point exhibits a quadratic field strength dependence. The dynamics of the transition in the micro-to millisecond range shows characteristic differences below and above the percolation point. The transient behavior and the electric field strength dependence of the conductivity change are discussed with respect to a theory [9] developed for ionic microemulsions. -A special field pulse method is described which allows measurement of current relaxation and electric birefringence.

The method of constructing equivalent regular two-body potentials by a unitary transformation of the two-body Hamiltonian has been generalized to spin-parity dependent nuclear potentials containing tensor-and spin-orbit terms. Starting from the Gammel-Christian-Thaler potential, which includes tensor forces, we obtained a class of equivalent regular, but nonloeal potentials depending on a parameter ~, --the range of nonlocality. --These potentials have been used in a Hartree-Fock calculation for the closed-shell nuclei He 4, C 12, 016, Si 2s, S 32, Ca 4~ The calculated binding energies show a slow ~,-variation with a minimum in the region of 0.7 f. The nuclear radii decrease with increasing 2 and are in general too small. The sequence of single particle levels of the nuclei with closed/-shells is in agreement with that obtained with the usual nuclear shell model potential including spin-orbit coupling.

In order to calculate the spin-orbit splitting and the magnetic moments of nuclei a Hartree-method was carried out with the assumption of parity-mixed one-particle wave functions. Together with a phenomenological determined scalar potential there was used a pseudoscalar potential derived as the contribution of the one-pion exchange potential selfconsistently determined. By using this method of parity-mixing, one obtains a spin-orbit splitting and also magnetic moments, which lie automatically between the Schmidt-lines in good agreement with the experimental values. Only the pion-nucleon coupling constant was used as a parameter in this selfconsistent method. It is shown that we obtain a smaller coupling constant when using the exact solution of this problem than by using perturbation theory. This effective coupling constant is of the same order of magnitude as the one obtained from the scattering data.

A unitary transformed two-body hard-core potential contains nonlocal terms, which will produce a deviation of the magnetic moments from the Schmidtlines. These deviations were calculated for several nuclei up to Ca 41 using an oscillator basis, and they are positive for odd-neutron and negative for odd-proton nuclei. Thus it is not possible to describe the experimental deviation from the Schmidtlines; but for the magnetic moments of C 13, 015 and N 15, the only nuclei where the experimental values are outside of the Schmidtlines, these nonlocal terms yield the right magnitude in the right direction of the deviation.