The stability of the hydromagnetic Couette flow is investigated when a constant current is applied along the axis of the cylinders. It is shown that if the resulting toroidal magnetic field depends only on this current, no linear instability to axisymmetric disturbances is possible. c © 2005 Elsevier Ltd. All rights reserved.

When action potentials from a stimulated biological preparation are recorded i t is essential to isolate the stimulus resistively and capacitively from the ground in order to minimize stimulation artifacts. Such isolation can be achieved by using a transformer of special low-capacitance construction in the output of a stimulus generator (Donaldson 1958). The most widely used arrangement for the...