No Longer Quashing Oscillations

Professor Chris V. Hollot

University of Massachusetts - Amherst

Department of Electrical and Computer Engineering

Perhaps like many in the field of feedback control, I have spent my professional life combating potential oscillation – always struggling to maintain phase margins, avoiding the slippery slope of Bode's gain-phase relationship, and developing anxiety attacks when near the Nyquist critical point. Now, I embrace oscillations.

For the past few years I have been drawn to the fascinating field of chronobiology, or biological time keeping, where it has been discovered that most organisms (even single cells) possess multiple endogenous oscillators, referred to as circadian oscillators or pacemakers, some of which may be masters and others slaves. Hierarchical arrangements predominate and we focus not only on entrainment of the pacemaker by the environment but also on that of the slaves by the master pacemaker. I was immediately smitten by this topic where "limit-cycles", "interlocking negative and positive feedback loops", and "entrainment" trip off the tongues of its practitioners from physiology, neuroscience, molecular biology and genetics.

In this talk, I will introduce the topic of chronobiology and summarize some of this field's main findings from its conception, nearly 50 years ago, to today. In the latter part of this talk I will focus on my particular research on circadian oscillators, and attempt to illustrate how someone with a feedback control background may possibly make contribution to the modeling side of chronobiology

that is already inhabited with theoretical biologists.

Friday, December 8, 2006

3:30 – 4:30 p.m.

Rm. 1500 EECS