# gst: apropos of avoidance, packing of stiff rods on ellipsoids; the effects of self-avoidance

AA << study the effects of geometry and self-avoidance on the ordering of slender filaments inside nonisotropic containers, considering cortical microtubules in plant cells, and packing of genetic material inside viral capsids as concrete examples. >>

<< Within a mean-field approximation, (AA) show analytically how the shape of the container, together with self-avoidance, affects the ordering of the stiff rods. (They)  find that the strength of the self-avoiding interaction plays a significant role in the preferred packing orientation, leading to a first-order transition for oblate cells, where the preferred orientation changes from azimuthal, along the equator, to a polar one, when self-avoidance is strong enough. >>

<< While for prolate spheroids the ground state is always a polar-like order, strong self-avoidance results with a deep metastable state along the equator. >>

<< the critical behavior of this system is in fact related to the butterfly catastrophe model. >>

Doron Grossman, Eytan Katzav. Effects of self-avoidance on the packing of stiff rods on ellipsoids. Phys. Rev. E 109, 054111. May 9, 2024. 

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.054111

Also: spheroids, self-assembly, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, ellipsoids, spheroids,  oblate- prolate spheroids, avoidance, self-avoidance

# gst: transitional dynamics among gyrotactic (prolate spheroid) swimmers in turbulence

<< In this study, (AA) consider small, elongated, gyrotactic, swimming particles in homogenous isotropic turbulence (..). Many motile phytoplankton species are gyrotactic, i.e., their swimming direction results from the competition between shear-induced viscous torque and the stabilizing torque due to bottom-heaviness. (..)  Moreover, both single phytoplankton cells and multicellular phytoplankton chains can have elongated shapes, which makes the study of gyrotactic active particles with prolate shapes necessary. >>

AA addressed the following problems:

<< (i) How the clustering is affected by the swimming number Φ and the stability number Ψ? In particular, how to characterize the extent of clustering based on the three-dimensional Voronoi analysis?

(ii) How the clustering is related to the flow structures? This question has two perspectives.  From the space perspective, what are the regions that particles accumulate in? From the time perspective, how long do particles exist in an aggregated state? >>

Zehua Liu, Linfeng Jiang, Chao Sun. Accumulation and alignment of elongated gyrotactic swimmers in turbulence. arXiv:2202.04351v1 [physics.flu-dyn]. Feb 9, 2022.

https://arxiv.org/abs/2202.04351

Also

The effect of noise on the dynamics of microswimmers in externally-driven fluid flows.  

https://flashontrack.blogspot.com/2021/10/gst-effect-of-noise-on-dynamics-of.html

keywords 'turbulence' in FonT   

https://flashontrack.blogspot.com/search?q=turbulence

keywords 'turbolento' in Notes (quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=turbolento

keywords: transition, swimmers,  gyrotactic swimmers, spheroids,  prolate spheroids, stability, turbulence