New prostate treatment plan
In one method of treating prostate cancer, called brachytherapy, doctors implant 50 to 100 radioactive iodine-125 or palladium-103 "seeds," each just a few millimeters long, in the gland to eradicate diseased tissue. To plan the seeds' placement for maximum effectiveness and minimal damage to healthy tissue, they map an ultrasound view of the prostate on a 3-D grid, and use optimization software to calculate several sets of possible seed locations and determine which configuration will work best.
Inspired by a reactor physics technique called adjoint or "backward" transport, Associate Professor Douglass Henderson, Medical Physics Associate Professor Bruce Thomadsen and graduate student Sua Yoo have developed a method that could reduce the time of this treatment-planning step from as long as 40 minutes to a couple of seconds. Using the adjoint information, they assign a numerical rank to each possible seed location, based on its potential to deliver radiation where it's needed. A greedy algorithm optimization software then computes the best seed arrangement. This method also could make it easier for doctors to plan treatments using combinations of seeds with varied characteristics.
Fusion experiment takes a "break"
When members of the Fusion Technology Institute began a project with Sandia National Laboratories to study whether high-energy X-rays could induce fusion in material samples, they knew that given X-ray doses, the materials' support structures would rapidly fragment and generate shrapnel inside their containment vessel. What they didn't know was what size the shrapnel would be, how it would behave inside the vessel, and whether it would penetrate the vessel.
The problem presented Professor Walt Drugan with an opportunity to participate in one of the department's many cross-disciplinary research studies. Drugan used his knowledge of fracture mechanics to develop fundamental theoretical models that predict how and when material ruptures dynamically, given such variables as the material, how the energy is delivered, and how much and at what rate energy is delivered.
Now Drugan is continuing his fundamental research on dynamic fragmentation with a grant from Lawrence Livermore National Laboratory. His predictions apply to a variety of situations, from designing space structures resistant to high-energy, fast-moving space debris, to planning safe, targeted mining blasts.
Readying reactors for the future
Someday advanced nuclear reactors now on the drawing board will generate power with simpler technology, less waste and at two-thirds of today's cost. At UW-Madison, ground-breaking experiments with novel, corrosion-resistant materials will yield a more efficient design for one future reactor concept.
A supercritical water reactor (SCWR) will produce electricity efficiently via steam made at an extremely high temperature and pressure, but those extreme conditions corrode reactor materials more quickly. Using plasma-source ion implantation, Wisconsin Distinguished Professor Michael Corradini, Assistant Professor Paul Wilson, Associate Scientist Mark Anderson and Senior Scientist Kumar Sridharan hope to make the surfaces of high-temperature alloys zircaloy, stainless steel and nickel more corrosion-resistant under SCWR operating conditions. They will test their theories under prototypic reactor conditions in a scale-model SCWR "flow loop."
A three-year, $1.4 million Nuclear Energy Research Initiative grant from the U.S. Department of Energy funds their research. Eventually the four, who are collaborating with researchers from Argonne National Laboratory and Global Nuclear Fuel, also will use the loop to conduct associated natural-convection heat-transfer experiments and will design and build a second test facility to study SCWR safety behavior under transient conditions.
Working out ligament stretch
Ligaments stretch easily at first, but as they continue to stretch, they become stiffer. And as many weekend athletes have learned the hard way, there are limits to how much and what kind of stretching ligaments can tolerate.
Wisconsin Distinguished Professor Roderic Lakes and Ray Vanderby Jr. (School of Medicine) are discovering what those limits are. In novel research, they coupled studies of creep (continued stretching during a steady force) with studies of relaxation (a decrease in resistance under a steady stretch deformation) at different load and strain levels to examine how these areas are interrelated. They have learned that the rate of creep depends on the level of load, while the rate of relaxation depends on the level of stretch. The two have derived new equations that interrelate the behavior. In addition, they found that damage to a ligament's cells starts to occur at lower load levels than those that cause damage to collagen fibers.
Funded by a three-year grant from the National Science Foundation, the two also will develop principles they can expand to stretch in non-biological materials such as metals in lawnmower engines or outboard motors.