Physical configurations of a cell doublet with line tension, a theoretical study

As a first approximation, early embryos may be modeled as foams whose shape depends on the surface tensions of each cell. However it has been remarked that exist line tensions at polarized exterior cellular interfaces (apical). In order to understand the changes it may imply on the usual foam model, a simple case study is considered: a double cell with line tension. Phase diagrams, bifurcations, possible new configurations are studied

Compartmental analysis of dynamic nuclear medicine data: models and identifiability

Compartmental models based on tracer mass balance are extensively used in clinical and pre-clinical nuclear medicine in order to obtain quantitative information on tracer metabolism in the biological tissue. This paper is the first of a series of two that deal with the problem of tracer coefficient estimation via compartmental modelling in an inverse problem framework. Specifically, here we discuss the identifiability problem for a general n-dimension compartmental system and provide uniqueness results in the case of two-compartment and three-compartment compartmental models. The second paper will utilize this framework in order to show how non-linear regularization schemes can be applied to obtain numerical estimates of the tracer coefficients in the case of nuclear medicine data corresponding to brain, liver and kidney physiology

Electrical impedance tomography with point electrodes

We consider the two-dimensional inverse electrical impedance problem in the case of piecewise constant conductivities with the currents injected at adjacent point electrodes and the resulting voltages measured between the remaining electrodes. Our approach is based on nonlinear integral equations for the unknown shape of an inclusion with conductivity different from the background conductivity. It extends a method that has been suggested by Kress and Rundell [7] for the case of a perfectly conducting inclusion. We describe the method in detail and illustrate its feasibility by numerical examples.German Ministry of Education and Researc

Electrical impedance tomography using a point electrode inverse scheme for complete electrode data

For the two dimensional inverse electrical impedance problem in the case of piecewise constant conductivities with the currents injected at adjacent point electrodes and the resulting voltages measured between the remaining electrodes, in [3] the authors proposed a nonlinear integral equation approach that extends a method that has been suggested by Kress and Rundell [10] for the case of perfectly conducting inclusions. As the main motivation for using a point electrode method we emphasized on numerical difficulties arising in a corresponding approach by Eckel and Kress [4, 5] for the complete electrode model. Therefore, the purpose of the current paper is to illustrate that the inverse scheme based on point electrodes can be successfully employed when synthetic data from the complete electrode model are used.German Ministry of Education and Researc

Identification de fissures par ondes acoustiques

Cette thèse porte sur le problème de reconstruction de fissures par ondes acoustiques. Le premier objectif consiste à développer une méthode d'inversion rapide utilisant un unique couple de données de Cauchy sur la frontière d'un domaine entourant la fissure sous l'hypothèse que la fissure cherchée est plane. L'utilisation de la fonctionnelle Écart à la Réciprocité nous fournit alors une méthode de reconstruction quasi explicite. Le second objectif consiste à trouver une méthode d'inversion pour le problème de Helmholtz en milieu inhomogène. L'utilisation de la fonctionnelle Écart à la Réciprocité combinée à une méthode de type "Sampling Method" permet alors la reconstruction de fissures de formes quelconques à partir de données en champ proche.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF