# Activator-inhibitor system
#

G(u,v,J,K) = 2*u*K/(v-u+v*J+u*K+sqrt((v-u+v*J+u*K)^2-4*(v-u)*u*K))

dR/dt = k0*G(k3*R,k4,J3,J4) + k1*S - k2*R - k2'*X*R
dX/dt = k5*R - k6*X

par k0=4,k1=1,k2=1,k2'=1,k3=1,k4=1,J3=.3,J4=.3,k5=.1,k6=.075,S=.2

done