ABSTRACT
CONTENTS 7.1 Signals, Detection, and Measurement ........................................................................... 169 7.2 Specificity ........................................................................................................................... 170 7.3 Signal-to-Noise Ratio........................................................................................................ 171 7.4 Detection Criteria.............................................................................................................. 173 7.5 Equilibrium Noise ............................................................................................................ 173 7.6 Nonequilibrium Noise ..................................................................................................... 180 7.7 Chemical Noise ................................................................................................................. 190 7.8 Interpretation of Experiments......................................................................................... 195 Acknowledgment....................................................................................................................... 196 References ................................................................................................................................... 196
Measurement is a quantitative observation and well known to be of great importance to science. However, measurements involving biological systems are complicated by the complexity of cells and tissues, particularly if fields are expected to interact weakly and field-induced changes are found to be small. Some key parameters, for example, temperature coefficient of a measured quantity, may be inadequately characterized, and related quantities may be determined incompletely (e.g., measurement or modeling of the time-dependent temperature throughout the volume of the biological system being studied). Detection is a special case of measurement, that is, the measurement is so coarse that an observer can only distinguish between ‘‘signal’’ and ‘‘no signal.’’ Generally speaking, the smaller the change in an observed quantity (e.g., cell biomass)
due to a stimulus (e.g., an applied electromagnetic field), the more difficult the experimental interpretation. There may be multiple candidate causes if small changes in biomass are found, for example, any of many growth-altering biochemical changes, unnoticed and uncharacterized temperature variations, or even changes in ambient light or mechanical vibration. In physical science a model can often be made of the experiment. This allows estimates of the influence of various quantities and parameters on the expected experimental outcome (change in observed quantity in response to a stimulus) and is valuable in the interpretation of experiments. Similar approaches to bioelectromagnetics should also be valuable.
