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Using the activitation method (n,2n) excitation-functions were measured for54Fe,70Ge,74Se,85Rb,8688Sr,89Y,92Mo, and204Hg in the neutron-energy region 13–18 MeV. The results are checked for consistency by means of a systematic of (n, 2n) cross-sections as a function of the nuclear neutron excess (N-Z)/A. Furthermore the data are compared with results from the statistical nuclear reactions theory which were calculated using optical model absorption cross-sections and the Fermi-gas-model formula for the nuclear level density. In the case of204Hg the influence of preequilibrium nucleon emission was taken into account.

Summary In a comparative study, the differences between the values measured for 26 blood and serum components in both winter and summer were determined in 78 healthy subjects. Comparable conditions during the preparation of test persons, sampling, processing of specimens, and measurement were strictly observed. The term “season” is defined more precisely by meteorological data.

The FitzHugh-Nagumo equations for action potential propagation along nerve axons and the corresponding ordinary differential equations for travelling waves are solved numerically. Above a critical value, a constant bias current can drive a wave-front solution. At the critical value, a global bifurcation occurs. As a result, the wave front switches into a pulse.