UNIVERSITY PARK, Pa. -- John Clarke, a professor of physics at the University of California at Berkeley, will present the Russell Marker Lectures in the Physical Sciences on Feb. 19 to 21. The free public lectures are sponsored by the Penn State Eberly College of Science.

The series includes a lecture intended for a general audience, titled "Superconductivity: From Trains to Brains," at 8 p.m. Feb. 20, in 119 Osmond Laboratory with light refreshments following the talk. In the lecture, Clarke will present recent advances in the physics and the application of superconductivity -- a phenomenon where electricity can flow in metals and oxides with zero resistance when they are cooled below a critical temperature. Large scale applications include magnetic resonance imaging, particle accelerators and levitated trains. Small-scale applications include the SQUID -- Superconducting QUantum Interference Device -- an ultrasensitive sensor that operates near the limit set by Heisenberg's Uncertaintiy Principle. Clarke has played the dominant role in advancing the theory, the fabrication and the applications of SQUID. Clarke also will present two additional, more-specialized lectures, titled "Magnetic Flux 1/f Noise: A 30-Year Saga," at 3:30 p.m. Feb. 19, in 339 Davey Laboratory; and "The Ubiquitous SQUID: Then and Now," at 4 p.m. Feb. 21, in 117 Osmond Laboratory.

Clarke has used the SQUID in a wide variety of applications, including ultrasensitive voltmeters, magnetometers and amplifiers. He has deployed SQUIDs in desert locations to locate geothermal reservoirs, he has developed SQUID multiplexers for detectors of far-infrared radiation on a telescope in Antarctica and he has used SQUIDs in novel schemes for immunoassays. Currently, Clarke's group is using SQUIDs to obtain magnetic resonance images in magnetic fields four orders of magnitude lower than those used in conventional MRI machines and to study various phenomena related to quantum physics.

Clarke has mentored approximately 100 graduate students and postdoctoral scholars. He has received a number of awards and honors for his research. He is a Fellow of the Royal Society, from which he received the Hughes Medal, and a Foreign Associate of the National Academy of Sciences, from which he received the Comstock Prize in Physics. He also received the University of California at Berkeley's Distinguished Teaching Award.

Clarke received bachelor's, master's and doctoral degrees from Cambridge University in 1964, 1968 and 1968, respectively. He became a postdoctoral scholar at the University of California at Berkeley in 1968, and he joined the faculty there in 1969.

The Marker Lectures were established in 1984 through a gift from Russell Earl Marker, professor emeritus of chemistry at Penn State, whose pioneering synthetic methods revolutionized the steroid-hormone industry and opened the door to the current era of hormone therapies, including the birth-control pill. The Marker endowment allows the Penn State Eberly College of Science to present annual Marker Lectures in astronomy and astrophysics, the chemical sciences, evolutionary biology, genetic engineering, the mathematical sciences and physics. For more information about the lectures, contact Amanda Powers at arp24@psu.edu.