arXiv subjects

Ruben van Drongelen

Publications and source records attributed to Ruben van Drongelen.

3 recordsLinked to original sources

arXiv2018

Active particle dynamics beyond the jamming density

Many biological systems form colonies at high density. Passive granular systems will be jammed at such densities, yet for the survival of biological systems it is crucial that they are dynamic. We construct a phase diagram for a system of active particles interacting via Vicsek alignment, and vary the density, self-propulsion force, and orientational noise. We find that the system exhibits four different phases, characterized by transitions in the effective diffusion constant and in the orientational order parameter. Our simulations show that there exists an optimal noise such that particles require a minimal force to unjam, allowing for rearrangements.

cond-mat.soft↗

arXiv2018

Mechanics of epithelial tissue formation

A key process in the life of any multicellular organism is its development from a single egg into a full grown adult. The first step in this process often consists of forming a tissue layer out of randomly placed cells on the surface of the egg. We present a model for generating such a tissue, and find that the resulting cellular pattern corresponds to the Voronoi tessellation of the nuclei of the cells. Experimentally, we obtain the same result in both fruit flies and flour beetles, with a distribution of cell shapes that matches that of the model, without any adjustable parameters. Finally, we show that this pattern is broken when the cells do not all grow at the same rate.

physics.bio-ph↗

arXiv2016

Collective dynamics of soft active particles

We present a model of soft active particles that leads to a rich array of collective behavior found also in dense biological swarms of bacteria and other unicellular organisms. Our model uses only local interactions, such as Vicsek-type nearest neighbor alignment, short-range repulsion, and a local boundary term. Changing the relative strength of these interactions leads to migrating swarms, rotating swarms and jammed swarms, as well as swarms that exhibit run-and-tumble motion, alternating between migration and either rotating or jammed states. Interestingly, although a migrating swarm moves slower than an individual particle, the diffusion constant can be up to three orders of magnitude larger, suggesting that collective motion can be highly advantageous, for example, when searching for food.

cond-mat.soft↗