1. Department of Statistics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
2. Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
3. Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
4. Department of Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
5. Department of Computer Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.