Ana I. Muñoz

A free boundary problem in glaciology: The motion of grounding lines

In this paper we consider stationary ice sheet modelled as a Stokes flow in a bounded two-dimensional domain. In particular, we study the behavior of the grounding line, where different boundary conditions meet: no-slip conditions for the grounded part and force balance conditions for the floating part whose shape is a priori undetermined. This yields a free boundary problem with mixed boundary conditions and a contact line, called “grounding line” in the glaciological context, that might move along the solid substrate. We show that solutions with moving grounding lines and zero contact angle do exist and determine the shape and asymptotic properties of the free boundary.

On a mathematical model of bone marrow metastatic niche

We propose a mathematical model to describe tumor cells movement towards a metastasis location into the bone marrow considering the influence of chemotaxis inhibition due to the action of a drug. The model considers the evolution of the signaling molecules CXCL-12 secreted by osteoblasts (bone cells responsible of the mineralization of the bone) and PTHrP (secreted by tumor cells) which activates osteoblast growth. The model consists of a coupled system of second order PDEs describing the evolution of CXCL-12 and PTHrP, an ODE of logistic type to model the Osteoblasts density and an extra equation for each cancer cell. We also simulate the system to illustrate the qualitative behavior of the solutions. The numerical method of resolution is also presented in detail.

Numerical resolution of a reinforced random walk model arising in haptotaxis

In this paper we study the numerical resolution of a reinforced random walk model arising in haptotaxis and the stabilization of solutions. The model consists of a system of two differential equations, one parabolic equation with a second order non-linear term (haptotaxis term) coupled to an ODE in a bounded two dimensional domain. We assume radial symmetry of the solutions. The scheme of resolution is based on the application of the characteristics method together with a finite element one. We present some numerical simulations which illustrate some features of the numerical stabilization of solutions.

Uniqueness and collapse of solution for a mathematical model with nonlocal terms arising in glaciology

In this paper we study a nonlinear system of differential equations which arises from a stationary two-dimensional Ice-Sheet Model describing the ice-streaming phenomenon. The system consists of a multivalued nonlinear PDE of parabolic type coupled with a first-order PDE and an ODE involving a nonlocal term. We study the uniqueness of weak solution under suitable assumptions (physically reasonable). We also establish that the ice thickness collapses at a finite distance (by employing a comparison principle).

Mathematical Analysis and Numerical Simulation in Magnetic Recording

AbstractThe head-tape interaction in magnetic recording is described in the literature by a coupled system of partial differential equations. In this paper we study the limit case of the system which reduces the problem to a second order nonlocal equation on a one-dimensional domain. We describe the numerical method of resolution of the problem, which is reformulated as an obstacle one to prevent head-tape contact. A finite element method and a duality algorithm handling Yosida approximation tools for maximal monotone operators are used in order to solve numerically the obstacle problem. Numerical simulations are introduced to describe some qualitative properties of the solution. Finally some conclusions are drawn.

Mathematical analysis and numerical simulation of a model of morphogenesis

We consider a simple mathematical model of distribution of morphogens (signaling molecules responsible for the differentiation of cells and the creation of tissue patterns). The mathematical model is a particular case of the model proposed by Lander, Nie and Wan in 2006 and similar to the model presented in Lander, Nie, Vargas and Wan 2005. The model consists of a system of three equations: a PDE of parabolic type with dynamical boundary conditions modelling the distribution of free morphogens and two ODEs describing the evolution of bound and free receptors. Three biological processes are taken into account: diffusion, degradation and reversible binding. We study the stationary solutions and the evolution problem. Numerical simulations show the behavior of the solution depending on the values of the parameters.