arXiv subjects

K. Lawrence Galloway

Publications and source records attributed to K. Lawrence Galloway.

2 recordsLinked to original sources

arXiv2022

Phase-separation during sedimentation of dilute bacterial suspensions

Numerous natural systems depend on the sedimentation of passive particles in presence of swimming microorganisms. Here, we investigate the dynamics of the sedimentation of spherical colloids at various E. coli concentration within the dilute regime. Results show the appearance of two sedimentation fronts, a spherical particle front and the bacteria front. We find that the bacteria front behave diffusive at short times, whereas at long times decays linearly. The sedimentation speed of passive particles decays at a constant speed and decreases as bacteria concentration ($ϕ_b$) is increased. As $ϕ_b$ is increased further, the sedimentation speed becomes independent of $ϕ_b$. The timescales of the bacteria front is associated with the particle settling speeds. Remarkably, all experiments collapse onto a single master line by using the bacteria front timescale. A phenomenological model is proposed that captures the sedimentation of passive particles in active fluids.

cond-mat.soft↗

arXiv2020

Crystalline shielding mitigates structural rearrangement and localizes memory in jammed systems under oscillatory shear

The nature of yield in amorphous materials under stress has yet to be fully elucidated. In particular, understanding how microscopic rearrangement gives rise to macroscopic structural and rheological signatures in disordered systems is vital for the prediction and characterization of yield and for the study of how memory is stored in disordered materials. Here, we investigate the evolution of local structural homogeneity on an individual particle level in amorphous jammed two-dimensional systems under oscillatory shear, and relate this evolution to rearrangement, memory, and macroscale rheological measurements. We identify a new structural metric, crystalline shielding, that is predictive of rearrangement propensity and the structural volatility of individual particles under shear. We use this metric to identify localized regions of the system in which the material's memory of its preparation is preserved. Our results contribute to a growing understanding of how local structure relates to dynamic response and memory in disordered systems.

cond-mat.soft↗