MONTE CARLO SIMULATION OF POLONIUM ION COLLECTION IN ELECTROSTATIC FIELD FOR THE PURPOSE OF RADON DETECTOR DEVELOPMENT.

Radon detectors based on an electrostatic collection of polonium and detection of its alpha decay are a popular choice for the measurement of radon activity. Due to the nature of $^{222}$Rn decays, 88% of radon progeny have a positive charge, thus enabling their collection on an electrode. A simulation software focused on the drift and diffusion of ions in an electric field has been developed, providing a tool to study and characterise such detectors.

Surface fissures in articular cartilage: effect of pathological changes in synovial fluid.

Objective: A unified mathematical model of two different modes of inception of fissures at the surface of articular cartilage in healthy and pathological joints.

Design: The superficial tangential zone of articular cartilage is modeled as a three-phase medium consisting of collagen fibers, matrix, and of infiltrated thin constituent of synovial fluid.

Background: The author's general mesomechanical concept is applied to the analysis of deterioration of articular cartilage.

Surface fissures in articular cartilage: new concepts, hypotheses and modeling.

Objective: Clarification and mesomechanical modeling of the inception of fissures at the surface of articular cartilage.

Design: Articular cartilage is described as a macroscopically heterogeneous medium consisting of zones - layers - with different orientation of collagen fibers.

Background: Degradation of mechanical properties of cartilage is a serious, still not fully clarified problem that deserves attention.

On the mechanical function of tendon.

A mesoscopic approach is followed for mathematical modelling of the specific deformation properties of tendon. The approach starts from our general concept of modelling mechanical behaviour of heterogeneous media and assumes that the structure of tendon is optimized in such a way that it enables its adjacent muscle to work with a constant performance in the course of increasing loading (acting like a gearbox in a car). The model based on this assumption gives results that are in a very good accordance with observed properties of tendons.

Determination of material constants and hydraulic strengthening of trabecular bone through an orthotropic structural model.

A statistical mathematical model is used to describe the viscoelastic behavior of trabecular bone from the description of its microstructure. Trabecular bone is regarded as an orthotropic composite material consisting of two phases: The trabeculae, modelled as a non-linear elastic material, and the marrow, modelled as a Maxwell element. The macroscopic constitutive equation contains, as parameters, the constants of the material phases' constitutive equations, the respective volume fractions and parameters descriptive of the geometry of trabecular bone.