[1] Northwestern Univ, Chicago, IL 60611 USA
[2] Univ Penn, Philadelphia, PA 19104 USA
[3] Univ Missouri, Columbia, MO USA
[4] Univ N Carolina, Chapel Hill, NC 27515 USA
[5] Univ Washington, Seattle, WA 98195 USA
[6] Trinity Hlth New England, Hartford, CT USA
[7] Oregon Hlth & Sci Univ, Portland, OR 97201 USA
[8] Duke Univ, Durham, NC USA