Stochastic modeling.

<p>(A) Results from fitting the fibroblast data to the stochastic model, as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033334#s4" target="_blank">Methods</a>. Fit values with the parameter <i>s</i><1 indicate that the oscillations are noise-induced (the deterministic system would be steady state), while fit values with <i>s</i>≥1 indicate that the oscillations are self-sustained. (B) Results of simulations of the stochastic model for different values of the parameter s, fixing the amplitude of <i>z</i> to be 500 molecules (by adjusting the value of Ω with respect to <i>s</i>). The mean value of the period CV over 500 simulations is shown for each value of <i>s</i>. The period CV is minimized for <i>s</i> in the range 1.1–1.2. (C) Example of a stochastic simulation with <i>s</i> = 1.03, where Ω is chosen so that the amplitude of <i>z</i> is 500 molecules. The period CV for this simulation is 0.073.