[ Diff(x[1], t) = (1*(1 - x[4])*(k[1]*(x[2]*1/2)^4/(x[2]*1/2 + k[7])^4 + k[10])*x[3] + (-1)*k[2]*(x[1]*1/100)^2/((x[1]*1/100)^2 + k[8]^2))/k[12],
  Diff(x[2], t) = (1*k[3]*(1 - k[9]/(x[1]*1/100 + k[9])*1/(1 + k[11])) + (-1)*k[4]*x[2]*1/2)/k[12],
  Diff(x[3], t) = ((-1)*(1 - x[4])*(k[1]*(x[2]*1/2)^4/(x[2]*1/2 + k[7])^4 + k[10])*x[3] + 1*k[2]*(x[1]*1/100)^2/((x[1]*1/100)^2 + k[8]^2))/k[13],
  Diff(x[4], t) = (1*k[5]*(x[1]*1/100)^4*(1 - x[4]) + (-1)*k[6])/k[12] ]