Wehmeier, Kai http://members.cox.net/wehmeier/
UC Irvine - semantics and proof theory of intuitionistic arithmetic, logical analysis of modal discourse, the logic of Gottlob Frege.
Plotkin, Gordon http://www.inf.ed.ac.uk/people/staff/Gordon_Plotkin.html
Institute for Communicating and Collaborative Systems, UK - denotational and operational semantics of programming languages, type theory; domain-theoretic and categorical analyses of computation, proof theory, the semantics of natural language, process calculi, computational biology.