Biomedical subjects

S F Edwards

Publications and source records attributed to S F Edwards.

4 recordsLinked to original sources

PubMed2006

Geometric partition functions of cellular systems: explicit calculation of the entropy in two and three dimensions.

A method is proposed for the characterisation of the entropy of cellular structures, based on the compactivity concept for granular packings. Hamiltonian-like volume functions are constructed both in two and in three dimensions, enabling the identification of a phase space and making it possible to take account of geometrical correlations systematically. Case studies are presented for which explicit calculations of the mean vertex density and porosity fluctuations are given as functions of compactivity. The formalism applies equally well to two- and three-dimensional granular assemblies.

Aerosols↗

PubMed2004

Persisting roughness when deposition stops.

Useful theories for growth of surfaces under random deposition of material have been developed by several authors. The simplest theory is that introduced by Edwards and Wilkinson (EW), which is linear and soluble. Its nonlinear generalization by Kardar, Parisi, and Zhang (KPZ) resulted in many subsequent studies. Yet both EW and KPZ theories contain an unphysical feature. When deposition of material is stopped, both theories predict that as time tends to infinity, the surface becomes flat. In fact, of course, the final surface is not flat, but simply has no gradients larger than the gradient related to the angle of repose. We modify the EW and KPZ theories to accommodate this feature and study the consequences for the simpler system which is a modification of the EW equation. In spite of the fact that the equation describing the evolution of the surface is not linear, we find that the steady state in the presence of noise is not very different in the long-wavelength limit from that of the linear EW equation. The situation is quite different from that of EW when deposition stops. Initially there is still some rearrangement of the surface, but that stops as everywhere on the surface the gradient is less than that related to the angle of repose. The most interesting feature observed after deposition stops is the emergence of history-dependent steady-state distributions.

Journal Article↗

PubMed1989

Estimates of future demographic changes in the coastal zone.

"This paper reports estimates of the relative and absolute sizes of the coastal population in the United States in the years 1990, 2000, and 2010. The estimates vary greatly among states in both the rate and direction of change, with increases expected for most marine coastal states and declines for most states bordering the Great Lakes. Together, only about 52.9 percent, 53.3 percent, and 53.6 percent of the United States's population is predicted to live in counties entirely or substantially within 50 miles of coastlines in the years 1990, 2000, and 2010, respectively. The need for long-range planning is not diminished, however, since the absolute size of the coastal population is estimated to increase to nearly 143 million people by the turn of the century."

Americas↗

PubMed1986

The theory of macromolecular networks.

Network theory has evolved from the simplest rubber materials and is just entering the biological area. The existing theories are studied and the modifications required for biological applications are reviewed. The issues involved are: the balance between entropy and internal energy, the rigidity and flexibility of molecules, the stability of the networks, the origin of the intermolecular forces and the entanglement problems of swelling and precipitation.

Macromolecular Substances↗