A C Lawson | PubMed Health

PubMed2004

Unusual phonon softening in delta-phase plutonium.

The phonon density of states and adiabatic sound velocities were measured on fcc-stabilized 242Pu0.95Al0.05. The phonon frequencies and sound velocities decrease considerably (soften) with increasing temperature despite negligible thermal expansion. The frequency softening of the transverse branch along the [111] direction is anomalously large ( approximately 30%) and is very sensitive to alloy composition. The large magnitude of the phonon softening is not observed in any other fcc metals and may arise from an unusual temperature dependence of the electronic structure in this narrow 5f-band metal.

Journal Article↗

PubMed1998

Collagen--calcium phosphate composites.

There is a widespread clinical need for bone augmentation and replacement. The major solid phases of bone are collagen and calcium phosphate and a bone analogue based on these two constituents should have some useful properties. In this review this theme is developed and the properties of natural and naturally based composites are compared. Composites have been produced by the precipitation of calcium phosphates on to collagen and a summary of the methods and results from mechanical testing and scanning electron microscopy are presented. Composites with mechanical properties intermediate between cancellous and cortical bone have been produced. The review concludes by explaining some of the mechanical properties of the composites, using knowledge of the hierarchical architecture of bone and results from microscopical examination of the fractured composites.

Biomechanical Phenomena↗