
Positive feedback systems 181
0 50 100 150
0
50
100
150
200
Time
G
3
0 50 100 150
0
100
200
300
Time
G
i
0 50 100 150
0
1
2
3
4
Time
G
4
0 50 100 150
0
20
40
60
80
100
Time
G
3a,80
FIGURE 5.14: Free evolutions, for different initial conditions, of the concen-
trations of four species of the galactose regula tory network model (5.16) with
parameter value s given in Table 5.3. The curves funnel into either one of two
steady-states, c onfirming the bistable nature of the system.
ditions: the plots confirm the bistable behaviour of the proposed galactose
model. In particular, when at time zero G
3
, G
i
, G
4
and G
3a,80
are low, the
system reaches the low equilibrium value, while the high equilibrium ...