Browsing by Author "Singh, Chamkor"

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    Anisotropic short-range attractions precisely model branched erythrocyte aggregates
    (Royal Society of Chemistry, 2023-10-17T00:00:00) Yadav, Megha; Vanshika, None; Singh, Chamkor
    Homogeneous suspensions of red blood cells (RBCs or erythrocytes) in blood plasma are unstable in the absence of driving forces and form elongated stacks, called rouleaux. These erythrocyte aggregates are often branched porous networks - a feature that existing red blood cell aggregation models and simulations fail to predict exactly. Here we establish that alignment-dependent attractive forces in a system of dimers can precisely generate branched structures similar to RBC aggregates observed under a microscope. Our simulations consistently predict that the growth rate of typical mean rouleau size remains sub-linear - a hallmark from past studies - which we also confirm by deriving a reaction kernel taking into account appropriate collision cross-section, approach velocities, and an area-dependent sticking probability. The system exhibits unique features such as the existence of percolated and/or single giant cluster states, multiple coexisting mass-size scalings, and transition to a branched phase upon fine-tuning of model parameters. Upon decreasing the depletion thickness we find that the percolation threshold increases but the morphology of the structures opens up towards an increased degree of branching. Remarkably the system self-organizes to produce a universal power-law size distribution scaling irrespective of the model parameters. � 2023 The Royal Society of Chemistry.
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    Guided run-and-tumble active particles: wall accumulation and preferential deposition
    (Royal Society of Chemistry, 2021-09-20T00:00:00) Singh, Chamkor
    Bacterial biofilms cost an enormous amount of resources in the health, medical, and industrial sectors. To understand early biofilm formation, beginning from planktonic states of active suspensions (such asEscherichia coli) to micro-colonization, it is vital to study the mechanics of cell accumulation near surfaces and subsequent deposition. Variability in bacterial motion strategies and the presence of taxis fields make the problem even more multifaceted. In this study, analytical expressions for the density and angular distributions, mean orientation, and deposition rates in such bacterial suspensions are derived, with and without the effects of external guiding or taxis fields. The derived results are closely verified by simulations of confined active particles using run-and-tumble statistics from multiple past experiments and utilizing a preferential sticking probability model for deposition. The behavioral changes in cell running strategies are modeled by varying the run-time distribution from an exponential to a heavy-tailed one. It is found that the deposition rates can be altered significantly by a guiding torque but are less affected by a change in the cell running behavior. However, both the mechanisms alter the pair correlation function of the deposited structures. The factor behind the changes in the architecture of deposited biomass under a torque generating guiding field turns out to be an asymmetrical rotational drift of planktonic cells, which can be an important physical mechanism behind the organization in confined active particle suspensions. � The Royal Society of Chemistry 2021.