. >> my name's charles peskin, i am a professor of mathematics at the courant institute of mathematicalciences, new york university. what i do is math and computing applied to biology and medicine. and my kind of main project is the heart, a computer simulation of the heart. the question is how can we understand the basic laws that govern the heart well enough that we can make a model heart in a computer that works the way the real heart does? so the equations which i use to describe the heart are differential equations, so calculus is absolutely fundamental to what i do. the heart has its own pacemaker, it's called the sinoatrial node. it's a clump of cells which send out waves that synchronize the heart. and what's amazing about these cells is if you grow them in tissue culture separately, they beat on their own, but they're not synchronized. and then when they grow and come in contact, they synchronize with each other. so the question is basically how does synchronization work, and what's involved in synchronization? it's an amazing fact that i don't know exactly how to explain, but