The London Underground Diagram (LUD) is a cognitive artifact and a well-known example of representational efficiency, having been copied by urban transportation systems worldwide. Here we describe the design of the LUD as an example of cognitive niche construction happening through iconic meaning of a problem space. We argue that the LUD's meaning is grounded on the offer of opportunities for a...

Particle candidates for astrophysical dark matter are reviewed, with particular emphasis on the lightest supersymmetric particle and the axion. The former is now constrained by accelerator experiments to have a mass above about 40 GeV, and ongoing searches at accelerators, in space, and in underground experiments have a good chance to detect it. A reevaluation of the constraint on the axion fro...