Figure 1.

Simple lattice ODN models. a. A 3 × 3 ODN where current or nutrient is supplied by the link from the origin (large open circle) to the lower left corner. Uptake sites are denoted by closed circles. b. An 8 × 8 ODN where current or nutrient is supplied by the link from the origin (large open circle) to the lower left corner. Uptake sites are denoted by closed circles. Note that there are four identical embedded 3 × 3 outward-directed networks (e.g. the network in the upper right corner) within the 8 × 8 network.