[ Eq(Derivative(x1, t), k1*x1),
  Eq(Derivative(x2, t), k2*x2**k8),
  Eq(Derivative(x3, t), k3*x3*(1 - x3/k9)),
  Eq(Derivative(x4, t), k4*x4/(x4 + k10)),
  Eq(Derivative(x5, t), k5*x5/(x5 + k11)**(1/3)),
  Eq(Derivative(x6, t), k6*x6*log(k12/(x6 + k14))),
  Eq(Derivative(x7, t), k7*x7**(2/3) - k13*x7) ]