Figure 7.
Plots of deviation in concentration ΔX from the stationary state value versus time for the species of the mechanism in Fig. 6. In a, a perturbation of the concentration of species X1 causes a pulse to propagate through the linear chain X2, X3, ⋯, X8; the deviation of species X3 falls below the stationary state value, which indicates a possible feedback effect from one of the species farther in the chain. In b, a perturbation of species X7 causes the initial slopes of the deviations in X3, X4, and X8 to be nonzero and the deviations in X3 and X4 to be mirror images about the time axis (for short times); these observations indicate that X7 activates the reaction from X3 to X4 (because the peak of X4 occurs before that of X3, implying that X3 precedes X4 in the reaction sequence) and is the precursor to X8. The maximum deviations are approximately 10% of the stationary state values or larger, except X4 in b, which is 2% (the stationary state values of X1 − X8 are 0.05, 0.0125, 0.0166, 0.1, 0.0166, 0.025, 0.01, and 0.1, respectively).