Ziyi Cui | Searcharxiv

arXiv2026

Trapping and Fracture of Particles in Three-Sphere Ball-Milling Collisions

We numerically investigate the collision and fracture processes of ball milling based on a minimal model of a three-sphere geometry using discrete element method (DEM) simulations combined with Christensen-type and Weibull-type normalized fracture criteria. The outcome of the brittle target particle (ejected versus trapped, fractured versus intact) depends on the impact geometry and velocity. We develop a reduced three-sphere collision description in which trapping is governed by impact geometry and friction, while fracture inside the trapping regime is evaluated from DEM output using stress-based and contact-force-based normalized criteria. The trapping regime follows a closed-form geometric condition, while the critical conditions for fracture vary with impact angle, obliquity angle, impact velocity, and particle size ratio. Head-on collisions with larger size ratios require lower critical impact velocities for fracture.

cond-mat.soft↗

arXiv2026

An Investigation of the Channel Capacity of Bacterial Chemotactic Sensors for Low Chemoattractant Concentrations

Bacterial chemotactic sensing converts noisy chemical signals into running and tumbling. We analyze the static sensing limits of mixed Tar/Tsr chemoreceptor clusters in individual \textit{Escherichia coli} cells using a heterogeneous Monod--Wyman--Changeux (MWC) model. Across a seven-dimensional parameter sweep, we compute three sensing-performance metrics -- channel capacity, dynamic range, and effective Hill coefficient -- in the limit that the cells are constantly in such low concentrations of chemoattractant that they need not adapt to new baseline chemoattractant concentration levels. What results are an upper bound on the trajectory mutual information rate given by the static capacity divided by a finite perceptual timescale, a quantitative understanding of the tight connection between channel capacity and dynamic range, and the finding that in this regime channel capacity is well described by a closed-form ceiling depending only on the receptor's baseline activity, which every wild-type and mutant strain in our sample achieves to within a few percent. In more realistic scenarios, adaptation plays a larger role and so do the exact temporal dynamics of chemoattractant concentrations seen by bacteria as they swim. This manuscript thus points to the importance of mapping out naturalistic chemoattractant concentration statistics in the wild as has been done for natural scene statistics.

q-bio.QM↗