Overview

Cooling small computers or miniature systems requires novel cooling systems. Many could employ Brownian motion with coupled convection as in heomocoels. Can we learn from bees and insects how they cool themselves, so we then may incorporate insect techniques into our devices?

We now examine how things move around through hemo-lymph and the hemocoel. Topology, geometry, and microphy-sics influence how particles distribute themselves. Diffusion, a metabolically cheap transport mechanism, is the process where random molecular motions move matter from one part of a system to another. However, diffusion's effectiveness decreases rapidly with distance. An advantage of small hemocoels, then, over larger ones might be that they increase diffusion's effectiveness. Pumping of the heart and movements of legs and wings supply convection and perhaps even superdiffusion.

Were we with a light microscope to watch visible particles small enough to share the molecular motions of the hemolymph, we would see them move randomly. In a dilute solution, each particle collides with molecules of solvent but behaves independently of the other solute particles that it seldom encounters. As a result of so many collisions on all sides, particles have no preferred directions, moving sometimes towards a region of their higher and sometimes towards a region of their lower concentrations.

Our conventional, familiar assumption is that concentration differences determine rates of diffusion and that steep gradients create faster displacements. However, this simplistic assumption only approximates a much more complicated situation (Ref: Diffusion).

Our particles proceed by random walk or Brownian motion, so that in a quiet hemocoel we may calculate the mean-squared distances each travels in an interval of time, but we cannot foresee in what direction any particle will travel. Brownian motion, due to bombardment of particles by the thermally excited particles of their solvent, was one of the first natural geometries recognized as being a self-similar fractal. If we view a finite segment of a two-dimensional random walk and then re-scale its time and length, we see that the two patterns resemble each other and are self-similar.

Now imagine particles in the hemolymph of a bee following cardiac arrest so the hemolymph is still and two separated locations in the hemocoel. Particles might be nutrients entering the hemolymph through the wall of the midgut that are diffusing towards a cell in a flight muscle in the thorax that will absorb and then consume them. In addition, let us assume a gradient of concentration for our nutrient molecules, such that the particles exist in higher concentration near the wall of the midgut, so they diffuse away from the midgut towards sinks in the thorax muscles. These particles on the average progress from a region of their higher concentration to regions where they are less concentrated.

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