Figure 5.

Phase portraits of the cubic-autocatalytic reaction represented by equations (3.1) and (3.2) performing a NAND operation. Frames (a–e) each indicate a different phase of the computation where the system is placed in one of three parameter regimes (RA, RB or RC). The duration of each phase is indicated in table 4 and at the top of each frame. Trajectories from initial conditions corresponding to each of the possible inputs are colour coded such that the blue trajectory corresponds to an input of (true,true), the black trajectory corresponds to an input of (false,false) and the grey trajectory corresponds to an input of (true,false) or (false,true). Frame (f) shows the entire sequence. In frame (a), the separatrix between the two basins of attraction in this regime is indicated by a dashed line. Note that frames (c), (d) and (f) have a different vertical scale. (Online version in colour.)