Exploring Biopolymers by the Fibre Bundle Model
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- Institutt for fysikk 
Bundles of polymeric chains in biological systems represent the analogue of macroscopic fibrous materials such as textile, wood or paper, scaled down to nanometric dimensions, and performing the same mechanical functions of their macroscopic counter-parts. The scale reduction, however, does not leave the physical picture unchanged, but it amplifies surface effects, fluctuations, and affects phase transformations taking place into the system. The thesis is devoted to the exploration of these size and time scale effects, using molecular dynamics approach based on an idealised force field model. The focus of the investigation is on creep and fatigue, that represent irreversible aging processes due to the thermal breaking of bonds. On the long time scale, and under tensile load, both processes cause the breaking of fibre bundles. My work, based on a preliminary study carried out in my host group, aimed at developing, implementing and validating a simulation approach intermediate between fibre bundle models and the atomistic simulation models prevalent in biophysics and materials science. The main portion of the thesis reports results from representative simulations, showing that the new model opens the possibility of investigating a wider range of phenomena than otherwise possible. In this respect, the thesis achieved all the aims set in the original plan. The thesis work has many possible developments and applications in biophysics and in nanotechnology, that are briefly outlined at the end of the thesis.