We address the problem of enhancing the sensitivity of biosensors to the
influence of toxicants, with an entropy method of analysis, denoted as
CASSANDRA, recently invented for the specific purpose of studying
non-stationary time series. We study the specific case where the toxicant is
tetrodotoxin. This is a very poisonous substance that yields an abrupt drop of
the rate of spike production at t approximatively 170 minutes when the
concentration of toxicant is 4 nanomoles. The CASSANDRA algorithm reveals the
influence of toxicants thirty minutes prior to the drop in rate at a
concentration of toxicant equal to 2 nanomoles. We argue that the success of
this method of analysis rests on the adoption of a new perspective of
complexity, interpreted as a condition intermediate between the dynamic and the
thermodynamic state.Comment: 6 pages and 3 figures. Accepted for publication in the special issue
of Chaos Solitons and Fractal dedicated to the conference "Non-stationary
Time Series: A Theoretical, Computational and Practical Challenge", Center
for Nonlinear Science at University of North Texas, from October 13 to
October 19, 2002, Denton, TX (USA