Existence of solutions for a biological model using topological degree   theory
  Topological degree theory is a useful tool for studying systems of differential equations. In this work, a biological model is considered. Specifically, we prove the existence of positive T-periodic solutions of a system of delay differential equations for a model with feedback arising on Circadian oscillations in the Drosophila period gene protein. 
Carlos H\'ector Daniel Alliera
math.DS