Figure 4

The phase portrait for the cell populations with \(M ( 0 ) =0.7\), \(H ( 0 ) = 0.01\), and \(R ( 0 ) =0.993\) in the case (a) \(\tau < \tau _{0}\), where the steady-state is asymptotically stable and (b) \(\tau = \tau _{0}\), where a limit cycle is born around the steady-state with \(r_{1} =0.4\)