February 3, 2011

LCS-like dynamics may describe evolvable frontiers, New arXiv paper

Earlier this week, I submitted a manuscript to the arXiv, cross-listed between the nlin.AO, physics.bio-ph, and q-bio.PE categories. It is entitled "Lagrangian Coherent Structures (LCS) may describe evolvable frontiers in natural populations", and here is the abstract:

The evolution of organismal populations is not typically thought of in terms of classical mechanics. However, many of the conceptual models used to approximate evolutionary trajectories have implicit parallels to dynamical physical systems. Therefore, it stands to reason that dynamical physical models can be adapted to model less explored aspects of evolutionary (biological) systems. In this paper, I will present the parallels between currently-used evolutionary models and a type of model called Lagrangian Coherent Structures (LCS). Based on this comparison, I will then introduce a new model for characterizing evolvability in living (biological) systems based on the LCS approach (an LCS-like model that shares attributes with agent-based approaches). It is my contention that the limits of evolvability in a population can be treated in a way analogous to fronts, waves, and other aggregate formations observed in fluid dynamics. To accomplish this, the various measures and architectures that constitute this approach will be introduced. Relevant evolutionary scenarios will also be reinterpreted using this framework. Specifically, I will provide examples of how this model can be applied to modeling so-called evolvable boundaries and related scenarios involving evolutionary neutrality, such as migrations, demographic bottlenecks, and island biogeography. While still in the conceptual stages, the LCS-like model introduced here could eventually be applied to a wide range of problems, including open problems in theoretical biology and controller design.

Below is a summary cartoon describing the evolutionary process discussed in the paper:

If you are so motivated, take a look at the full paper. As usual, comments would be appreciated.

Paper(s) of the Week (Colloids and Parallelism)

This week, I found two papers in Science that are worth taking a look at:

One is a materials science paper called "Supracollidal Reaction Kinetics of Janus Spheres". Science, 331, 199 (2011). link

In the first paper, particles called "Janus spheres" are used to build clusters and other structures. The term "Janus sphere" refers to their two-faced nature -- hydrophobic (water-repelling) on one hemisphere, and hydrophilic (water-loving) on the other. In this sense, they behave like dipoles. The authors did molecular dynamics simulations to show that these particles can self-assemble into higher-order structures such as fibrillar triple helices. A good article for anyone interested in molecular self-assembly.

The other is a biomimetics paper called "A Biological Solution to a Fundamentally Distributed Computing Problem". Science, 331, 183 (2011). link

The second paper is an attempt to design an algorithm that mimics cell autonomy in insect development for the purpose of designing "smart" autonomous distributed systems (such as networks or robot teams). The model system is molecular signaling during the development of sensory organ precursors in insects. Sensory organ precursor (SOP) cells are selected in development from many other like cells in a single proneural cluster to become bristles. This occurs through an "election" process whereby every cell in the cluster is connected to an SOP with no two SOPs being adjacent. This is similar to the maximal independent set problem in computing, where a network of processors are sorted into a topology similar to that of insect development using an election criterion. The authors come up with a 15-step algorithm which may be useful for students of optimization and many other topical areas.