Djellab, NadjateBoureghda, A.2022-05-242022-05-242019-04-23Djellab, Nadjate; Boureghda, A.. Approximate method for oxygen diffusion and absorption in sick cell. 3rd International Conference in Operator Theory, PDE and Applications. April 23-24- 2019. Faculty of Exact Science. Mathematics Department. University of ElOued. [visited in ../../….]. available from [copy the link here]http://dspace.univ-eloued.dz/handle/123456789/11079Working paper.3rd International Conference in Operator Theory, PDE and Applications. April 23-24- 2019. Faculty of Exact Science. Mathematics Department. University of ElOuedwe consider the oxygen di usion problem where the injection of oxygen into a sick cell and di usion of the injected oxygen inside the cell. The problem mathematically formulated through two di erent steps. At the rst stage, the stable case having no oxygen transition in the isolated cell is searched while at the second stage the moving boundary of oxygen absorbed by the tissues in the cell is searched. In this study, trace of moving boundary of the oxygen di usion problem is determined using constrained integral method, the pro le of moving boundary is determined by third order polynomial.enOxygen di usion; Constrained integral method; Moving boundary prob- lem; Stefan problem.Working Paper