Youngwimon LenburyBujira OuncharoenNardtida TumrasvinMahidol University2018-09-072018-09-072000-01-01IMA Journal of Mathemathics Applied in Medicine and Biology. Vol.17, No.3 (2000), 243-261026507462-s2.0-0033768211https://repository.li.mahidol.ac.th/handle/20.500.14594/25813In this paper, geometric and singular perturbation arguments are utilized to develop a separation condition for the identification of limit cycles in higher-dimensional (n ≥ 4) dynamical systems characterized by highly diversified time responses, in which there exists an (n - 3)-dimensional subsystem which quickly reaches a quasi-steady state. The condition, which has been used up to now to analyze relaxation oscillation in slow-fast systems, is extended to accommodate dynamical systems in which more state variables are involved in a special manner which still allows for the use of singular perturbation techniques. Application is then made to a model of human immunodeficiency virus infection in T helper (T(H)) cell clones with limiting resting T(H) cell supply.Mahidol UniversityAgricultural and Biological SciencesMathematicsArticleSCOPUS