{ diff(x1, t) = (-1)*k9*k1*x1*log(x1/x2)*k8/k9,
  diff(x2, t) = ((-1)*k9*k2*x2*k8 + 1*k9*k4*x1*k8 + (-1)*k9*k5*x2*x1^(2/3)*k8 + (-1)*k9*k6*x2*x3*k8)/k9,
  diff(x3, t) = ((-1)*k9*k3*x3*k8 + 1*k9*k7)/k9 }