Department of Mathematics and Computer Science, Emory University, Atlanta, GA, USA.|Department of Mathematics, Shanghai Normal University, Shanghai, China.|Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA.|Department of Human Genetics, Rollins School of Public Health, Emory University, Atlanta, GA, USA.|Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA.|Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA.