Advanced Computational Modelling Centre, The University of Queensland, Brisbane Qld 4072, Australia. sjn@maths.uq.edu.au|Advanced Computational Modelling Centre, The University of Queensland, Brisbane Qld 4072, Australia. sjn@maths.uq.edu.au|Advanced Computational Modelling Centre, The University of Queensland, Brisbane Qld 4072, Australia. sjn@maths.uq.edu.au|Advanced Computational Modelling Centre, The University of Queensland, Brisbane Qld 4072, Australia. sjn@maths.uq.edu.au