arXiv subjects

Louis González

Publications and source records attributed to Louis González.

3 recordsLinked to original sources

arXiv2026

Seabird trajectories map onto a reduced optimal-control bound for dynamic soaring

Dynamic soaring allows seabirds to harvest mechanical energy from vertical wind shear, yet there is no common benchmark for comparing flight performance across species based on their trajectories. We derive a reduced lower bound on transport effort from a simplified Hamilton-Jacobi-Bellman optimal-control model in which slow flight incurs an induced-drag penalty, fast flight incurs a dissipative penalty, and wind shear supplies an effective energetic subsidy. \add{We rescale each of the four species to its own baseline speed and accelerometer-based effort, then map them onto a common reduced speed--effort plane and estimate each one's lower frontier. We calibrate the optimal-control bound to one species, the wandering albatross, and test the other three against it. Two further dynamic soarers, the Buller's albatross and short-tailed shearwater, lie progressively above the bound. The common crane, a thermal soarer of comparable body mass, lies about 33 times as far from it as the albatross. Proximity to the boundary, therefore, measures the extent to which a bird's transport is powered by wind shear. More generally, our work offers a framework for testing optimal-control limits in bird flight using field data.

physics.bio-ph↗

arXiv2025

Exosome-mediated chemotaxis optimizes leader-follower cell migration

Cells frequently employ extracellular vesicles, or exosomes, to signal across long distances and coordinate collective actions. Exosomes diffuse slowly, can be actively degraded, and contain stochastic amounts of molecular cargo. These features raise the question of the efficacy of exosomes as a directional signal, but this question has not be systematically investigated. We develop a theoretical and computational approach to quantify the limits of exosome-mediated chemotaxis at the individual cell level. In our model, a leader cell secretes exosomes, which diffuse in the extracellular space, and a follower cell guides its migration by integrating discrete exosome detections over a finite memory window. We combine analytical calculations and stochastic simulations and show that the chemotactic velocity exhibits a non-monotonic dependence on the exosome cargo size. Small exosomes produce frequent but weak signals, whereas large exosomes produce strong but infrequent encounters. In the presence of nonlinear signal transduction, this tradeoff leads to an optimal cargo size that maximizes information throughput, as quantified by the average speed of the follower cell. Using a reduced one-dimensional model, we derive closed-form expressions coupling the optimal cargo size to follower speed as a function of secretion rate, memory time, and detection sensitivity. These results identify molecular packaging and memory integration as key determinants of exosome-mediated information transmission and highlight general design principles for optimization of migration under guidance by discrete and diffusible signaling particles.

physics.bio-ph↗

arXiv2023

Collective effects in flow-driven cell migration

Autologous chemotaxis is the process in which cells secrete and detect molecules to determine the direction of fluid flow. Experiments and theory suggest that autologous chemotaxis fails at high cell densities because molecules from other cells interfere with a given cell's signal. Based on observations of collective cell migration in diverse biological contexts, we propose a mechanism for cells to avoid this failure by forming a collective sensory unit. Formulating a simple physical model of collective autologous chemotaxis, we find that a cluster of cells can outperform single cells in terms of the detected anisotropy of the signal. We validate our results with a Monte-Carlo-based motility simulation, demonstrating that clusters chemotax faster than individual cells. Our simulation couples spatial and temporal gradient sensing with cell-cell repulsion, suggesting that our proposed mechanism requires only known, ubiquitous cell capabilities.

physics.bio-ph↗