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Non-linear finite element analysis has been used to investigate the contact problem between a buttock and a cushion of varying properties. The buttock tissue has been modelled on the macroscale by assuming it to be a hyperelastic (rubber-like) material with properties that correspond to the overall buttock response. Both rigid and $exible cushions have been considered. The contact between the cushion and the buttock has been modelled assuming both friction and friction-jiree conditions. The effect of these parameters on the buttock-cushion deformation and the tissue compressive and shear stress distributions have been presented. This study forms part of work towards the development of body segment simulatorsfor use in investigations of seating and other support surfaces.

We investigate the Franz-Keldysh effect and exciton ionization in semiconductor quantum wires. Absorption spectra are calculated near the band gap by solution of the low-density semiconductor Bloch equations in real space. The Sommerfeld factor and field-induced tunnel ionization of the exciton significantly affect the continuum portion of the absorption spectrum and remove the well known divergence problem associated with the 1D density of states at all field strengths. For reasonable electric field strengths substantial and tunable absorption oscillations appear above the band gap. Moreover, for very large fields, transparency can be achieved in the continuum for certain spectral positions.

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