Fig. 1.

Example experimental system under consideration. a Here we consider cells growing in culture on top of a solid reservoir of nutrients, such as agar. b The surface (cellular) region denoted ${\mathrm{\Omega }}_S$ has height $H_{\epsilon }$ and contains both reaction and diffusion terms, whereas the bulk (nutrient) region ${\mathrm{\Omega }}_B$ is of height H and is assumed to have no reactions, but permits diffusion. Both have lateral extent L, with no-flux conditions on all boundaries except for the interface between the two regions, where a coupling condition is applied (Color figure online)