Immune cells use active tugging forces to distinguish affinity and accelerate evolution

Cells are known to exert forces to sense their physical surroundings for guidance of motion and fate decisions. Here, we propose that cells might do mechanical work to drive their own evolution, taking inspiration from the adaptive immune system. Growing evidence indicates that immune B cells - capable of rapid Darwinian evolution - use cytoskeletal forces to actively extract antigen from other cells' surface. To elucidate the evolutionary significance of force usage, we develop a theory of tug-of-war antigen extraction that maps receptor binding characteristics to clonal reproductive fitness, revealing physical determinants of selection strength. This framework unifies mechanosensing and affinity-discrimination capabilities of evolving cells: pulling against stiff antigen tethers enhances discrimination stringency at the expense of absolute extraction. As a consequence, active force usage can accelerate adaptation but may also cause extinction of cell populations, resulting in an optimal range of pulling strength that matches molecular rupture forces observed in cells. Our work suggests that nonequilibrium, physical extraction of environmental signals can make biological systems more evolvable at a moderate energy cost.Comment: 14 pages, 6 figure

An efficient two-phase flow calculation method based on grid mergence and dimension transformation

Two-phase flow numerical methods are applied in internal ballistics widely, which has made higher fidelity analysis with minimal cost become an urgent demand. Current methods are based on independent dimension, and there is no definite conversion criterion and data transmission method, which have limited the application of efficient hybrid models applied to calculation. In this paper, we propose a hybrid method by linking a two dimensional (2D) model to a one dimensional (1D) model for two-phase flow. First, 1D and 2D two-phase flow models are established according to the flow field states in different phases. Next, the criterion of conversion between the two models is established, which is a quantitative index to judge the degree of radial effect and axial effect. Finally, dimension transformation in the radial direction and grid mergence in the axial direction are conducted to complete the whole computing model. The simulation results show that the hybrid method is more efficient in the interior ballistic process and maintains the level of trust in classical codes. Compared with the 2D method, the hybrid method significantly improves the computational efficiency by 86.5%. By analyzing the state in the chamber, the accuracy of the conversion criterion is confirmed. This criterion can be used as the transformation criterion of the hybrid model to form the standard multi-dimensional calculation transformation criterion of interior ballistics and may be promising for the rapid simulation of two-phase flow in interior ballistics

Internally/Externally Bubble-Propelled Photocatalytic Tubular Nanomotors for Efficient Water Cleaning

We describe a highly effective bubble-propelled nanomotor for the photocatalytic decomposition of organic pollutants in water. Two different tubular TiO₂ nanomotor systems are presented: one with Pt nanoparticles decorated on the inner surface and the other with Pt nanoparticles decorated on the outer surface. This is the first time that we have observed the autonomous movement of a tubular nanomotor without the aid of any surfactant, as well as a tubular nanomotor externally decorated with Pt propelled by oxygen bubbles. The synergy between the Pt nanoparticles and the superhydrophilic wetting behavior of the TiO₂ nanotubes endows the two nanomotor systems with high speed at very low H₂O₂ fuel concentrations without the addition of any surfactant. The efficient photodecomposition of rhodamine B demonstrates the intermixing and photocatalytic ability of the two nanomotor systems, which opens new avenues for the development of multifunctional bubble-propelled micro/nanomotors with myriad practical applications