Figure 7.

Half the time period associated with dominant frequency of oscillation in the two-cell system T/2 = π/ω_max (a) and the corresponding phase lag between the cells (b). The system parameters are the same as in figure 3 but τ^(m)h = 20 in both cells and τ^(p)d and τ^(m)d are varied. The typical half-period varies around an average value of approximately 30 min. Although T/2 is dependent on the time delays τ^(p)d and τ^(m)d, it typically remains within approximately $10\text{\%}$ of this mean value. The phase lag switches between 0 and π along the lines ${\tau }^{(p)d}+{\tau }^{(m)d}={\tau }_i^{\mathrm{tot}}$ (where $i=1,2,3,$ …). The values ${\tau }_i^{\mathrm{tot}}$ at which the switch in phase occurs are separated by regular intervals such that ${\tau }_i^{\mathrm{tot}}-{\tau }_{i-1}^{\mathrm{tot}}\approx 30\hspace{0.17em}\text{min}$—roughly the typical half-period. (Online version in colour.)