TABLE 1. Criteria for the local performance of the system in Fig. 1.

Criterion number	Definition	Calculation
1	Maximize the gain in concentration X2 in response to changes in input flux ϕ0	Max L (X2, ϕ0)
2	Maximize ratio of X2 to X1	Max (X2/X1)
3	Maximize robustness of concentration X2 to variations in parameters pi	Min Σi|S(X2, pi)|
4	Maximize response time	Max τ1/2 (Max λ)