FIGURE 12.

Expectation value of for given projected onto the latter, and measured in units of the latter's length, i.e., as function of Here and are consecutive velocities computed from positions measured with 15-min time lapses; see Appendix A. In the OU model, the quantity plotted here is constant, independent of speed. (A) Data points are experimental values from HaCaT cell trajectories. Their consistency with a constant value suggests a linear velocity dependence of the noise-averaged acceleration in a HaCaT model. Thick curve surrounded by two thin curves is the theoretical result for same quantity, ± 1 SD, computed from HaCaT model in Eq. 6 fitted to data shown in Fig. 4, B, E, and F, and here. It's small, but nonvanishing dependence on speed, is due to a combination of time-lapse sampling and speed dependence of the model's noise term. (B) Data points are experimental values from NHDF cell trajectories. Their distinct speed dependence suggests a nonlinear velocity dependence of the acceleration in an NHDF model. Thick curve surrounded by two thin curves is the theoretical result for same quantity, ± 1 SD, computed from the NHDF model fitted to data shown in Fig. 5, B, E, and F, and here.