Prediction of local cellular deformation in bone--influence of microstructure dimensions.

A multilevel finite element approach is applied to predict local cell deformations in bone tissue. The loads applied to a whole femur during the stance phase of the gait cycle were related to the strain at the level of a single lacuna and of canaliculi. Cell deformations were predicted from detailed linear FE analysis of the microstructure, consisting of an arrangement of cells embedded in bone matrix material. The local macroscopic stress assigned to each point was used to calculate the mesoscopic and consequently the microscopic nodal forces. The actual tissue principal strain along the femur deviated considerably from an average tissue value. The predicted bone matrix strains around osteocyte lacunae and canaliculi, were nonuniform and differed significantly from the macroscopically measured strains. Peak stresses and strains in the walls of the lacuna were up to six times those in the bulk extracellular matrix. Significant strain concentrations were observed at sites where the process meets the cell body. The dimensions of the lacunar axes influenced slightly the local strain.

Multilevel finite element modeling for the prediction of local cellular deformation in bone.

The underlying mechanisms by which bone cells respond to mechanical stimuli or how mechanical loads act on osteocytes housed in lacunae in bone are not well understood. In this study, a multilevel finite element (FE) approach is applied to predict local cell deformations in bone tissue. The local structure of the matrix dictates the local mechanical environment of an osteocyte. Cell deformations are predicted from detailed linear FE analysis of the microstructure, consisting of an arrangement of cells embedded in bone matrix material. This work has related the loads applied to a whole femur during the stance phase of the gait cycle to the strain of a single lacuna and of canaliculi. The predicted bone matrix strains around osteocyte lacunae and canaliculi were nonuniform and differed significantly from the macroscopically measured strains. Peak stresses and strains in the walls of the lacuna were up to six times those in the bulk extracellular matrix. Significant strain concentrations were observed at sites where the process meets the cell body.

Stakeholder involvement in nuclear crisis management in Greece.

The setting up of the Greek Stakeholders Group in the framework of the EC Food and Agriculture Restoration Management Involving Networked Groups (FARMING) project is described. The Group included members from more than 20 governmental and non-governmental organisations, having interest and/or responsibilities in the management of a crisis following a nuclear accident. The stakeholders, during their meetings in 2002, discussed the agricultural countermeasures and rural waste disposal options which have been compiled by the EC Sustainable Restoration and Long-Term Management of Contaminated Rural, Urban and Industrial Ecosystems (STRATEGY) project. All stakeholders agreed that the most preferable were those options that ensure public acceptance, minimise environmental impact and maintain farming practices and acceptable living and working conditions. Their views are synoptically presented along with the major conclusions from the stakeholders meetings regarding nuclear crisis management.