  We prove that spiral sinks (stable foci of vector fields) can be transformed
into strange attractors exhibiting sustained, observable chaos if subjected to
periodic pulsatile forcing. We show that this phenomenon occurs in the context
of periodically-kicked degenerate supercritical Hopf bifurcations. The results
and their proofs make use of a new multi-parameter version of the theory of
rank one maps developed by Wang and Young.
