2005-Oujda International Conference on Nonlinear Analysis,
Oujda, Morocco.
Electronic Journal of Differential Equations,
Conference 14 (2006), pp. 241-248. 

Title: Periodic solutions for small and large delays in a tumor-immune
       system model

Author: Radouane Yafia (Univ. Chouaib Doukkali, El Jadida, Morocco)
 
Abstract: 
 In this paper we study the Hopf bifurcation for
 the tumor-immune system model with one delay. This model  is
 governed by a system of two differential equations with one delay.
 We show that the system may have periodic solutions for small
 and large delays for some critical value of the delay parameter
 via Hopf bifurcation theorem bifurcating from the non trivial
 steady state.

Published September 20, 2006.
Math Subject Classifications: 34K18.
Key Words: Tumor-Immune system competition; delayed differential equations;
           stability; Hopf bifurcation; periodic solutions.