1. Department of Social Medicine, CB 7240, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
2. HW Odum Institute for Research in Social Science, CB 3355, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
3. Department of Anthropology, CB 3115, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
4. Center for Bioethics, Department of Social Medicine, CB 7240, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.