Figure 6.

A morphogen gradient forms through a combination of influx at the left-hand boundary and decay of morphogen particles throughout the domain. Panel (a) shows the initially empty domain. By t = 60, the system is assumed to have reached an approximately steady state. Panels (b,c) show the particle density profile according to algorithm 1 at times 15 and 60, respectively. Panels (d,e) show the same comparison for algorithm 2. Figure descriptions are as in figure 4. The simulation results are averaged over 100 repeats. (Online version in colour.)