Phase portraits of the system at x = L/2 for T
= 30 (dashed contour) and T
= 60 (solid contour). Nullcline of u is given by thick N-shaped line. Dashed and solid lines with intercepts at v
= 0.23 and v
= 0.16 are nullclines of v for T0 = 30 and T0 = 60, respectively.