Traveling-Wave Chemotaxis
  A simple model is studied for the chemotactic movement of biological cells in the presence of a periodic chemical wave. It incorporates the feature of adaptation that may play an important role in allowing for ``rectified" chemotaxis: motion opposite the direction of wave propagation. The conditions under which such rectification occurs are elucidated in terms of the form and speed of the chemical wave, the velocity of chemotaxis, and the time scale for adaptation. An experimental test of the adaptation dynamics is proposed. 
Raymond E. Goldstein