Figure 7. Scaling properties of instabilities in iOS-HEK cells.
A)Frequency of near-field alternans onset as a function of gap junction coupling strength. The onset frequency varies by < 2% over a 100-fold variation in gcxn. Pseudocolor shows the spatial extent of alternans, measured as the distance over which alternans beats decay to half of their value in the stimulus region. B-D) Nonlinear dispersion relations show which frequencies are stable in far-field and the corresponding wave numbers (inverse of peak-to-peak wavelength) selected by each frequency. In panels B-D, bottom branches of nonlinear dispersion relations are stable and the top branches are unstable. B) Left: nonlinear dispersion relation under conditions corresponding to experimental data. Right: spatial structure of voltage waves in the far-field with frequencies 2 and 3.5 Hz. Position on nonlinear dispersion relation indicated by correspondingly colored dots. C) Effect of varying the isradipine binding rate, α, on the nonlinear dispersion relation. Increasing α decreases the maximum frequency that propagates to the far field. D) Changes in the connexin strength, gcxn, affect the wavelength but have little effect on the maximum stably propagating frequency. Thus the maximum frequency prior to alternans onset is a parameter that is largely independent of gap junction strength, and by extension, tissue geometry. See also Fig. S2.