A necessary and sufficient condition for the existence of positive periodic solutions of a model of hematopoiesis
In this paper, we derive a sufficient condition as well as a necessary condition for existence of positive periodic solutions of the hematopoiesis model with periodic coefficients x' (t) = -delta(t)x(t) + p(t) . x(t -tau(t))/1 + [x(t -tau(t)](n), t >= 0, where delta, p epsilon C(R+, (0, infinity)) and tau E C(R+, R+) are T-periodic functions. When p(t) = gamma delta(t) with gamma > 0, a sufficient and necessary condition for the existence of a positive T-periodic solution is established. (c) 2007 Elsevier Ltd. All rights reserved.
existence positive periodic solution model of hematopoiesis coincidence degree positive equilibrium