Oscillation and global attractivity in hematopoiesis model with periodic coefficients

In this paper we shall consider the nonlinear delay differential equation p'(t) = beta(t)p(m) (t - komega)/1 + p(n) (t - komega) -gamma(t)p(t), where k is a positive integer, beta(t) and gamma(t) are positive periodic functions of period omega. In the nondelay case we shall show that (*) has a unique positive periodic solution (p) over bar (t), and we will study the global attractivity of p(t). In the delay case we shall establish some sufficient conditions for oscillation of all positive solutions of (*) about (p) over bar (t), and establish some sufficient conditions for the global attractivity of (p) over bar (t). Our results in this paper extend as well as improve the results in the autonomous case. (C) 2002 Elsevier Science Inc. All rights reserved.