An article of clothing comprising a phase change material which is a blend of at least two compounds and which has a melting point of from 5 deg C. The invention also relates to the cells derived from such lines which are particularly useful for the production of substances of interest. A signal demultiplexer is operatively positioned relative to the input optical connector so that optical signals passing into the selector assembly are demultiplexed by the demultiplexer into signal components, each signal component having a respective signal component beam path.