The invention builds a structure of software objects that captures the historically contingent development of an asynchronous program. The method including: providing a heat source with an output of radiation in a predetermined spectrum; generating a first portion of the power from the absorption of the radiation; and generating a second portion of the power from a temperature difference between a first element heated by the heat source and a second element at least partially thermally insulated from the first element. The light source optical system is characterized in that the first light and the second light have mutually differing spectral distributions. Further provided is a method for screening a treatment or a therapeutic agent for efficacy in treating neurogenic pain as well as a method for screening an analgesic agent for analgesic effect in neurogenic pain.