1. University of Texas at Austin, Austin, TX, USA
2. University of Texas at Austin, Austin, Texas, USA
3. Arizona State University, Tempe, AZ, USA
4. University of Pennsylvania, Philadelphia, Pennsylvania, USA
5. University of California San Diego, La Jolla, California, USA
6. The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
7. California Institute of Technology, Pasadena, California, USA