Physics colloquium addresses physics of sound A physics colloquium is set for 4 p.m. Friday, March 9 in 211 Witmer Hall. Timothy Bigelow, assistant professor of electrical engineering, will address "Applying the Physics of Sound to Revolutionize Medicine." Coffee and cookies will be served at 3:30 p.m. in 215 Witmer Hall. The physics of sound has been extensively studied for over a hundred years. One of the most fascinating areas of study has been the cavitation of micron-sized bubbles upon exposure to high-intensity sound fields. For high amplitude sound, the bubbles expand to be many times their original size before violently collapsing. The collapse of the bubble results in transient pressures inside the bubble from 1,000 to 70,000 atm and transient temperatures from 1,000 to 20,000 K. As a result, some have proposed using cavitation to produce nuclear fusion. When the bubble collapses near a boundary, the collapse is asymmetric resulting in the formation of the microjet that impinges on the boundary and has been used to pit and erode metals in industrial applications. In medicine, lower sound amplitudes and higher frequencies are used than are typically found in industrial applications resulting in less violent bubble collapse. However, the cavitation of microbubbles has been effectively used to produce contrast in ultrasound images allowing for the quantification of blood flow dynamics even for very slow flow such as the perfusion of blood through malignant tumor tissue. In addition to imaging, cavitation of microbubbles has also shown great potential for enhancing drug delivery to cells, performing gene therapy, and “liquefying” tissue killing the cells in the process. Before the full benefit of these technologies can be exploited, the ultrasound exposure parameters used to excite the bubbles needs to be optimized using the physics of the bubble/sound interaction while quantifying the biological impact of the bubble collapse on surrounding tissue. -- Connie Cicha, Administrative Secretary, Physics, connie_cicha@und.nodak.edu, 7-2911