Lateral inhibition model. Comparison between the lateral inhibition models of Collier et al.  that employed hexagonal cells and the models used in this work with naturally shaped cells. In both models, P
(σ) (Delta) is driven to the opposite of P
(σ) (Notch) within each cell, while cell-cell communication across contacting membranes regulates P
(σ). The length of the common border between σ and ρ is lρ, σ, which is the count of all 8-connected lattice sites between and ρ, and σ, and n(σ) returns the set of cells that are direct neighbors of σ.