Aerotactic Waves in Dictyostelium discoideum : When Self-Generated Gradients interact with Expansion by Cell Division.
Using a self-generated hypoxic assay, it is shown that Dictyostelium discoideum displays a remarkable collective aerotactic behavior: when a cell colony is covered, cells quickly consume the available oxygen and form a dense ring moving outwards at constant speed and density.
We propose a simple, yet original PDE model, that enables an analytical qualitative and quantitative study of the phenomenon and reveals that the collective migration gives rise to traveling wave solutions, whose propagation can be explained through the interplay between cell division and the modulation of aerotaxis. The modeling and its conclusions supplement and are confirmed by an experimental investigation of the cell population behavior. This approach also gives rise to an explicit and novel formula of the collective migration speed of cells that encapsulates a surprising combination of expansion by cell division, such as described by the Fisher/KPP equation, and aerotaxis. The conclusions of this model appear to extend to more complex models.
Lecture 1, Physical Nature of Information – How to receive, send and forget information
How the engineering question of thermal engine efficiency spawned two hundred years of ever-accelerating progress in fundamental science, communications and computations. Thermodynamic and statistical entropy. The puzzle of the second law of thermodynamics. How irreversible entropy growth appears from reversible flows in phase space via dynamical chaos. Entropy decrease and non-equilibrium fractal measures.
Lecture 2: Physical Nature of Information – How to receive, send and forget information
Asymptotic equipartition as a universal mathematical tool of statistical physics and information theory. Information as a choice. Entropy as the rate of information transfer. Two greatest code inventions: alphabet and positional numeral system. Entropy of the language and the genetic code.
