The Biomedical Physics Group of the Laboratory for Ultrasonics, headed by Professor Miller, is actively engaged in the application of ultrasonic techniques to physiological and medical problems. This research has led to two I-R 100 awards in the annual competition sponsored by Industrial Research/Development magazine. The Biomedical Physics Group is actively collaborating with the Division of Cardiology of the School of Medicine. The focus of this research is on characterization of the properties of myocardial tissue. One objective of this research is the noninvasive assessment of myocardial tissue injury based on the technique of ultrasonic tissue characterization. The hypotheses underlying this research are that pathological changes occurring in myocardium alter the physical (i.e. mechanical) properties of tissue and that these alterations can be measured quantitatively and used to provide an estimate of myocardial injury, using indices based on the frequency dependencies of ultrasonic attenuation and backscatter.

The magnetic resonance (MR) group of Professor Mark Conradi has teamed with members of the School of Medicine to develop techniques for magnetic resonance imaging of human lungs. The ultimate goal is to improve the diagnosis and treatment for severe emphysema. The work is truly interdisciplinary and requires knowledge of magnetic resonance, atomic and optical physics, and lung physiology.

The brain is the most complex system we know of. It is the result of an evolutionary process and consists of billions of interconnected neurons. Connectivity between neurons is neither random nor regular. Most neurons produce sequences of pulses, by which signals between the neurons are exchanged. The signal exchange is delayed. Neurons perform nonlinear transformations on the incoming pulse trains. Noise enters at every step.

The signal flow in the brain is not just feedforward. Rather, feedback dominates most pathways. Dr. Wessel's group studies signal processing with neural feedback loops using the vertebrate isthmotectal loop as a model system. The isthmic nuclei receive a topographically organized projection from the tectum, to which they project back. The isthmotectal loop is present in most vertebrates, has been anatomically characterized in bird, frog, and turtle, and is experimentally accessible in these species both in vivo and in vitro. Dr. Wessel's group and his collaborators use electrophysiological, anatomical, and computational methods to study the mechanisms and functional roles of the isthmotectal loops in visual processing. The combined in vivo, in vitro, computational, and comparative investigation of isthmotectal feedback promises to uncover general principles of active signal processing with neural feedback loops.

Prof. Wang's research interests focus on elucidating biological mechanisms at the molecular level using single molecule fluorescence imaging techniques. The imaging techniques involve labeling single molecules of interest with a light-activating fluorescence-tag. By capturing the pathways of the light-induced fluorescent molecule in solution or in a cell with a single-photon sensitive camera, the molecule's biological behaviors are revealed. Current biological systems of interest include gene expression and control mechanisms, where the kinetics and pathways of single gene regulator proteins and the their interactions with DNA are investigated in vitro and in vivo, and oligomerization kinetics of EGF receptors in live cells. To extract quantitative information from the frequently convoluted images of the molecules, novel analytical methods are constantly being explored and developed; to increase the versatility of the single molecule fluorescence techniques, alternative fluorescence labels are frequently being tested via close collaborations with biochemistry groups.