Mathematical Biology Seminar Dr. Scott L. Diamond Director, Penn Center for Molecular Discovery Institute for Medicine and Engineering University of Pennsylvania "Stochastic Processes in Blood Biology: A test case in Systems Biology" Blood is a reactive biological fluid, essentially a multicellular organ, whose function is dictated by prevailing fluid mechanics as well as the states of platelets, neutrophils, and plasma proteins. Since blood is a moving biological fluid in vivo, it is important to study blood phenotype under flow conditions whereby the blood or blood cells come in contact with each other and with a surface. Importantly, the receptor-mediated bonding events between cells in blood occur under flow conditions that test the mechanical integrity of these linkages. We have used stochastic simulation to analyze various kinetic processes in blood associated with single-bond mechanics of receptor-mediated adhesion of platelets to surfaces, neutrophil adhesion to platelets in linear shear fields and on surfaces, as well as tissue-factor triggered activation of coagulation.