Department of Mathematical Sciences

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https://scholar.sun.ac.za/handle/10019.1/223

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Browsing Department of Mathematical Sciences by browse.metadata.advisor "Banasiak, Jacek"

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    Analysis of the effects of growth-fragmentation-coagulation in phytoplankton dynamics
    (Stellenbosch : Stellenbosch University, 2011-12) Omari, Mohamed; Banasiak, Jacek; Rewitzky, Ingrid; Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences. Mathematics Division.
    ENGLISH ABSTRACT: An integro-differential equation describing the dynamical behaviour of phytoplankton cells is considered in which the effects of cell division and aggregation are incorporated by coupling the coagulation-fragmentation equation with growth, and the McKendrick-von Foerster renewal model of an age-structured population. Under appropriate conditions on the model parameters, the associated initial-boundary value problem is shown to be well posed in a physically relevant Banach space using the theory of strongly continuous semigroups of operators, the theory of perturbation of positive semigroups and the semilinear abstract Cauchy problems theory. In particular, we provide sufficient conditions for honesty of the model. Finally, the results on the effects of the growth-fragmentation-coagulation on the overall evolution of the phytoplankton population are summarised.
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    Mathematical modelling of the stages of solid tumours growth and the nonlocal interactions in cancer invasion
    (Stellenbosch : Stellenbosch University, 2011-12) Onana Eloundou, Jeanne Marie; Banasiak, Jacek; Rewitzky, Ingrid; Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences.
    ENGLISH ABSTRACT: For solid tumours to grow and metastise, they need to pass through two distinct stages: the avascular growth phase in which the tumour remains in a limited diffusion size and the vascular growth phase where the invasion may take place. In order to accomplish the transition from the former to the latter growth phase, a solid tumour may secrete a substance known as tumour angiogenesis factor (TAF) into the surrounding tissues to stimulate its own blood vessels. Once the tumour has its own blood supply, it can invade other parts of the body destroying healthy tissues organs by secreting the matrix degrading enzymes (MDE). During the invasion, the adhesion both cell-cell and cell-matrix play an extremely important role. In this work, we review some mathematical models dealing with various stages of development of solid tumours and the resulting reaction diffusion equations are solved using the Crank-Nicolson finite differences scheme. We also present a system of reaction-diffusion-taxis partial differential equations, with nonlocal (integral) terms describing the interactions between cancer cells and the host tissue. We then investigate the local and global existence of the solution of the previous model using the semigroup method and Sobolev embeddings.