{ diff(x1, t) = ((-1)*k19*k1*x1*x2 + 1*k19*k2*x4 + (-1)*k19*k3*x1*x3 + 1*k19*k4*x5 + (-1)*k19*k6*x6*x1 + 1*k19*k7*x9 + 1*k19*k10*x5 + (-1)*k19*k11*x1)/k19,
  diff(x2, t) = ((-1)*k19*k1*x1*x2 + 1*k19*k2*x4 + (-3)*k19*k5*x2^3 + 2*k19*k6*x6*x1 + 1*k19*k8*x3*x4 + (-1)*k19*k9*x5*x2)/k19,
  diff(x3, t) = ((-1)*k19*k3*x1*x3 + 1*k19*k4*x5 + (-1)*k19*k8*x3*x4 + 1*k19*k9*x5*x2 + 1*k19*(1 - 2/5/exp(piecewise(37, t <= 10, 42) - 37))*3/100*(7/5)^(piecewise(37, t <= 10, 42) - 37)*k18)/k19,
  diff(x4, t) = (1*k19*k1*x1*x2 + (-1)*k19*k2*x4 + 1*k19*k6*x6*x1 + (-1)*k19*k8*x3*x4 + 1*k19*k9*x5*x2)/k19,
  diff(x5, t) = (1*k19*k3*x1*x3 + (-1)*k19*k4*x5 + (-1)*k19*k10*x5 + 1*k19*k8*x3*x4 + (-1)*k19*k9*x5*x2)/k19,
  diff(x6, t) = (1*k19*k5*x2^3 + (-1)*k19*k6*x6*x1 + (-1)*k19*k13*x6*x7 + 1*k19*k14*x8)/k19,
  diff(x7, t) = ((-1)*k19*k13*x6*x7 + 1*k19*k14*x8)/k19,
  diff(x8, t) = (1*k19*k13*x6*x7 + (-1)*k19*k14*x8)/k19,
  diff(x9, t) = ((-1)*k19*k7*x9 + 1*k19*k12*x8)/k19 }