Appendix 6—figure 1. Wave dynamics with discrete sources.

(A) Cartoon showing the discrete lattice model of cell signaling relays for cells in 1D. Here, a concentration wave propagates rightward at speed v through a group of cells spaced by a constant distance d. The concentration at $\tilde{x}=t=0$ defines the threshold concentration in this discrete system and is a function of $v,D,$ and d: $C_{\text{th}}=C_{\text{th}}(v,D,d)$. (B) Wave speed v compared to the continuous theory value of ${\left(aD/d{h}^2{C}_{\text{th}}\right)}^{1/2}$ as a function of $vd/4D$ for cells in 1D with diffusion in 1D. We can see that the wave speed approaches the continuous theory value for $vd/4D\ll 1$. (C) Same as B but for cells in 1D and diffusion in 2D.