Leech, Vivienne;
(2025)
Modelling alignment of self propelled particles: from two interacting cells to collective behaviour.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Alignment and self-organisation of particles is a phenomenon observed in various contexts and at different scales in biology. In nature, we see alignment in schools of fish, flocks of birds, and groups of people. Zooming in at a cellular level, we observe alignment in bacterial swarms and the alignment of fibroblasts in tissue. Fibrotic tissue is associated with numerous pathologies, including cancer, liver disease, and cystic fibrosis, and is believed to contribute to up to 45% of worldwide deaths. One key difference between fibrotic tissue and healthy tissue is that the fibroblasts, the cells which make up the bulk of the tissue, align with each other over a relatively large length scale of up to 10 cell lengths, whereas there is little cell alignment in healthy tissue. In this thesis, we develop an agent-based modelling framework to model the alignment of fibrotic tissue; specifically, self-propelled, interacting ellipse-shaped particles. Although there are existing continuum models that consider the alignment of self-propelled particles, we choose to use an agent-based model so that we can fully understand the underlying mechanisms in our model and more easily relate model parameters directly to experimental data. We start by deriving a minimal model to understand if alignment of self- propelled particles with overlap avoidance is sufficient to replicate the observed experimental alignment. We obtain analytical results for two interacting cells and then examine if these results are reflected in simulations with many particles. Next, we computationally analyse the effect of model parameters on alignment and com- pare the model output with experimental data. We then introduce additional mechanisms into the model. The first mechanism is the ability for cells to change their aspect ratio in response to overlap avoidance. The second added feature is cell-cell junctions, which can act on their own or pro- vide a site for trans-cellular actin bundles to form. Again, we analytically examine the model for two interacting cells and then computationally examine the model for many interacting cells to relate it back to experimental data.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Modelling alignment of self propelled particles: from two interacting cells to collective behaviour |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Mathematics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10204019 |
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