Urban centers present all over the world striking similarities which translate into universal laws describing their growth and morphology. In this paper, we study a simple 2-dimensional cellular automata model containing what we identfiy as essential ingredients in the dimographic change. the...

Populations may be regulated by both local density-dependent factors and spatial variation in habitat quality. I explore the influence of spatial autocorrelation in habitat quality on the survival of model populations. Dispersal is modeled as Markov transitions between patches. A finite rate of...

Rainforests are legendary because of their extreme species richness. In the richest rain forests every second tree on a hectare is a different species. As a consequence, most species are rare. Using field data from studies in different parts of the world, we show that species-rich plots often...

In a recent study, Ohira and Sawatari presented a simple model of computer network traffic dynamics. These authors showed that a phase transition point is present separating the low-traffic phase with no congestion from the congestion phase as the packet creation rate increases. We further...