[ Diff(x[3], t) = (1*k[15]*1/(1 + (k[8]/x[3])^k[10])*k[4]*x[3]*(log[10](k[9]) - log[10](x[3]))/log[10](k[9]) + (-1)*k[15]*k[5]*x[1]*x[3]/(k[11] + x[1] + x[3]))/k[15],
  Diff(x[1], t) = piecewise(t <= k[12], k[1]*x[1]*x[3]/(k[3] + x[1] + x[3]), (-(k[6] + k[2]))*x[1]),
  Diff(x[2], t) = piecewise(t <= k[12], 0, k[6]*x[1] - k[7]*x[2]) ]