The mechanical properties of very small systems are often strikingly different from the properties of everyday objects. As one considers ever-smaller objects, thermal fluctuations, and then quantum fluctuations start to be important. In this thesis I explain some unusual nanoscale mechanical effects, and predict some new effects. The bulk of the thesis is devoted to calculating the forces between bodies that are closely spaced, but not touching. These van der Waals forces have been studied in detail for bodies in thermal equilibrium. Most of the world is not in thermal equilibrium, and van der Waals forces in this regime are very different from their equilibrium cousins. In contrast to equilibrium forces, nonequilibrium forces are much stronger and may show chemical specificity. There is a <i>friction</i> associated with the van der Waals force between bodies in relative motion. When the bodies are at different temperatures, this friction may be negative. Intermolecular forces with one molecule excited are far stronger than ground-state forces and may be attractive or repulsive. Any optical effect in matter modifies the forces between the constituent molecules. The second part of this thesis is on solitonic kinks in fibrillar materials (e.g. polymers, actin bundles, microtubules, carbon nanotubes). All of these materials support stable kinks, and these kinks play an important role in determining the mechanical properties; often more important than the detailed chemical makeup of the materials.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:597814 |
| Date | January 2004 |
| Creators | Cohen, A. E. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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