{ diff(x1, t) = (1*k6*x5 + (-1)*k7*x1 + (-1)*(k8*x1 - k9*x3))/k19,
  diff(x2, t) = (1*k10*x5 + (-1)*k11*x2 + (-1)*(k12*x2 - k13*x4))/k19,
  diff(x3, t) = 1*(k8*x1 - k9*x3)/k18,
  diff(x4, t) = 1*(k12*x2 - k13*x4)/k18,
  diff(x5, t) = (1*(k1 + k14*(1 + tanh(2*(t - 24*floor(t/24) - k15)))*(1 - tanh(2*(t - 24*floor(t/24) - k16)))/4)*k2^k3/(k2^k3 + (x3 + x4)^k3) + (-1)*k4*x5/(k5 + x5))/k18 }