1. School of Natural and Environmental SciencesNewcastle University Newcastle upon Tyne UK
2. Now at Chemostrat Ltd Welshpool UK
3. Now at Max Planck Institute for Dynamics of Complex Technical Systems Magdeburg Germany
4. School of EngineeringNewcastle University Newcastle upon Tyne UK
5. Department of PhysicsDurham University, Science Laboratories Durham UK
6. Department of Earth SciencesDurham University, Science Laboratories Durham UK