No abstract

The electrophoretic mobilities of three bacterial strains were investigated by capillary electrophoresis (CE) and were compared with results obtained by microelectrophoresis (ME). The CE measurements yielded bimodal electropherograms for two of the strains, thus illustrating for the first time that surface charge variations within a monoclonal population can be probed by CE. Intrapopulation variations were not detected by ME. The mobilities of three chemically distinct types of latex microspheres were also measured. Differences between the mean mobilities obtained by CE and ME were not statistically significant (P ≤ 0.50); the standard deviations of the CE measurements were typically 2 to 10 times smaller than those obtained by comparable ME measurements. The reproducibility of CE permitted batch-to-batch mobility variations to be probed for the bacteria (one of the strains exhibited such variations), and aggregation was evident in one of the latex suspensions. These effects were not measurable with ME.

The dynamic response of electrorheological (ER) suspensions has received little attention relative to the effort devoted to the study of the steady shear response. We report on simulation and experimental investigations of the dynamic oscillatory response of ER suspensions, in particular focusing on the relationship between suspension structure and the rheological response. We consider the response of monodisperse and polydisperse suspensions under linear deformation, as well as the response in the nonlinear regime. Dimensional analysis of the equations of motion predict that the linear rheological response obeys a time-field strength superposition principle, which is confirmed by experiment. The response is found to exhibit a sharp dispersion that is only broadened slightly by polydispersity. Nonlinear deformation is found to significantly broaden the observed dispersion.