{ diff(x1, t) = (1*k11*(k4 + k5*x1*x3) + (-1)*k11*k6*x1)/k11,
  diff(x2, t) = (-1)*k11*(k1*x2*log(k2*x2/k1) + k3*x1*x2)/k11,
  diff(x3, t) = (1*k11*k7*x2/(x2 + k10) + (-1)*k11*(k8*x1*x3 + k9*x2*x3))/k11 }