Figure 1.

An example of the full computer-generated contact network (Upper Inset) and a magnified section (main graph). Individuals are placed at random within the environment at an average density of one per unit area. The probability kernel determining the connection of two nodes (shown at the same scale as the full network in the Lower Inset) is the sum of a localized Gaussian (whose height and breadth may be specified) and a fixed probability representing global connections. Hence, the probability of connection between nodes a distance d apart is P(d) = U + μe^−d2/2σ2, where U, μ, and σ may be varied. The majority of the neighbors of a node are close by, with a smaller number of long-distance edges. To indicate the heterogeneities present in the network structure, two connected nodes are highlighted on the main figure. One node has only two relatively local neighbors, whereas the other possesses seven local and one longer range (out of shot) connection. Throughout the paper U = 0.0025, μ = 0.21, and σ = 2.5.