Quality of approximating a mass-emitting object by a point source in a diffusion model

Abstract

For the sake of computational efficiency and for theoretical purposes, in mathematical modelling, the Dirac Delta distributions are often utilized as a replacement for cells or vesicles, since the size of cells or vesicles is much smaller than the size of the surrounding tissues. Here, we consider the scenario that the cell or the vesicle releases the diffusive compounds to the immediate environment, which is modelled by the diffusion equation. Typically, one separates the intracellular and extracellular environment and uses homogeneous Neumann boundary condition for the cell boundary (so-called spatial exclusion approach), while the point source approach neglects the intracellular environment. We show that extra conditions are needed such that the solutions to the two approaches are consistent. We prove a necessary and sufficient condition for the consistency. Suggested by the numerical results, we conclude that an initial condition in the form of Gaussian kernel in the point source approach compensates for a time-delay discrepancy between the solutions to the two approaches in the numerical solutions. Various approaches determining optimal amplitude and variance of the Gaussian kernel have been discussed.

References in corpus (1)

• Point Forces in Elasticity Equation and Their Alternatives in Multi Dimensions

Cited by in corpus (4)

• Approximation of a compound-exchanging cell by a Dirac point
• Positivity and long-term behaviour of a diffusion model with measure-valued nonlocal reaction term
• Approximating a spatially-heterogeneously mass-emitting object by multiple point sources in a diffusion model
• Using multiple Dirac delta points to describe inhomogeneous flux density over a cell boundary in a single-cell diffusion model