Figure 4.

Membrane capacitance near resonance. The membrane capacitance C _m(=C ₀ + C _nl) normalized to the linear capacitance C ₀ is plotted against the normalized frequency $\overline{\omega }(=\omega /{\omega }_r)$. Here the ratio ζ(=γnq ²/C ₀) of nonlinear capacitance at α = 1 (load-free) and $\overline{P}\mathrm{=1/2}$ to the linear capacitance C ₀ is assumed to be unity, i.e. βnq ²/4 = C ₀ (Notice $\gamma =\beta \overline{P}\mathrm{(1}-\overline{P})$ is maximized at $\overline{P}\mathrm{=1/2}$). Filled red circles indicate frequencies and the corresponding values of the membrane capacitance that maximize the power output. Other parameter values assumed are, α ² = 1.2 and ω _η/ω _r = 6, which is smaller than more realistic ratios (See Discussion). Traces respectively correspond to the values of $\overline{P}\mathrm{(1}-\overline{P})$: 0.25 (red), 0.13 (blue), and 0.06 (black), showing the dependence on the holding potential. The dotted line indicates the level of C ₀.