Tuesday, August 24, 2004


Immunology is the branch of biomedicine that is concerned with the structure and function of the immune system. Subtopics include innate and acquired immunity, histocompatibility, the various cells of the immune system and the interaction of antigens with specific antibodies.

There has been exponential growth in the development, refinement and implementation of various laboratory techniques in immunology research. Early methods used tehcniques such as viral plaque assays, but more recent and advanced techniques include ELISA and ELISPOT assays. This is a meaty subject matter though, better suited for a more thorough discussion at a later date.

Thursday, August 12, 2004

Arachnid pedipalps

Upon viewing some of the larger spiders (e.g. tarantulas, wolf spiders), many people are surprised to find that they appear to have ten legs, rather than eight. That's because apart from their legs, they also have two arm-like limbs calld pedipalps. These are used for seizing their prey, and in the case of males, they also use them for mating purposes. They dip the pedipalp tips in their own sperm webs, this infusing them with live sperm cells.

Friday, August 06, 2004

Chaos theory

Chaos theory deals with the behaviour of certain nonlinear dynamical systems that, under the proper conditions, exhibit chaotic behavior -- that is, behavior which is characterised by long-term sensitivity to initial conditions. This means that the final outcome will vary tremendously, based on minor variations in the initial conditions. This has been observed in mathematics, economics, fluid dynamics, plate tectonics and a wide variety of other systems.

This is NOT the same as noise or modeling uncertainty. In a non-chaotic system ( e.g. a linear system), the variability in the outcome (if any) will depend on the degree of noise present. As a result, establishing bounds on the amount of noise in the initial conditions will likewise establish bounds on the final outcome variability. In a chaotic system, however, even the tiniest variation will be amplified to essentially unpredictable results. (See: Butterfly effect.)

One consequence of chaotic behavior is that even the most precise measuring instruments cannot be used to predict the final outcome with any degree of precision. Even with a perfect model of the system, finite measurement precision and computational round-off errors will combine to produce uncertain results.