Pinpointing sources of unhealthy air pollutants, investigating nanoscale thermal transport, and understanding cardiovascular flows are the goals of three Virginia Tech College of Engineering researchers who recently received Faculty Early Career Development Program (CAREER) awards, the National Science Foundation’s most prestigious grants for creative junior faculty considered likely to become academic leaders of the future.

Assistant professors Linsey Marr of the Via Department of Civil and Environmental Engineering and Scott Huxtable and Pavlos Vlachos of the Department of Mechanical Engineering won five-year CAREER grants, each worth about $400,000.

“Air pollution is a serious health problem that causes heart attacks, asthma, and premature deaths,” Marr said. “It also degrades visibility and drives global climate change. My CAREER project takes a novel approach to measuring air pollutant emissions.”

Marr and her graduate students will mount instruments that measure pollutant concentrations and wind velocity on the top of a van with an extendable mast — “like a TV news van,” she said. The research team will travel to Roanoke, Va., the Shenandoah Valley of Virginia, and Baltimore, Md., parking the van in various locations.

The pollutant trackers will measure carbon dioxide, which is a greenhouse gas; nitrogen oxides and organic compounds, which are key ingredients in smog formation; and airborne particles — the chief culprits for health effects.

“Current estimates of air pollutant emissions are highly uncertain,” said Marr, who developed a fuel-based motor vehicle emission inventory for central California while a doctoral student at the University of California at Berkeley. “We anticipate that our measurements will add considerable new insight to the quantification of different types of emissions. Scientists can use this information to improve their understanding of air pollution, and policy makers can devise more effective plans to improve air quality.”

Every CAREER project includes an educational component, and Marr will take the research van to K-12 schools near the field sites and offer tours for students. She also plans to test the effectiveness of new remote-control keypad technology in her Introduction to Environmental Engineering class.

Marr came to Virginia Tech in 2003 after a year of post-doctoral studies at the Massachusetts Institute of Technology. She completed her Ph.D. in environmental engineering at Berkeley, where she was a NSF Graduate Research Fellow and a U.S. Environmental Protection Agency STAR Graduate Research Fellow. She earned her bachelor’s degree in engineering science at Harvard University in 1996.

Understanding the mechanisms responsible for thermal transport, or heat flow, between dissimilar materials at the molecular level is the focus of Huxtable’s CAREER project.

Huxtable will use laser techniques — timed by the picosecond, or one-trillionth of a second — to determine at the nanoscale how heat is transferred across the boundary between two materials. A primary goal of his project will be discovering what types of chemical modifications can be made to the surfaces of materials to control the flow of heat.

Understanding heat flow at this level could help engender the design of nanostructured composite materials capable of controlling thermal conductivity. “This research could impact a wide variety of technologies,” said Huxtable, who began studying nanoscale thermal transport as a graduate student at Berkeley.

One example would be improved design of thermoelectric coolers, which offer distinct advantages over conventional refrigerators and other cooling devices: they have no moving parts to break down and do not use harmful chemicals, such as ozone-depleting CFCs. However, thermoelectric devices are still highly inefficient. Better control of thermal conductivity could lead to the development of high-efficiency coolers.

Managing the tremendous amount of heat generated by power electronics is another anticipated result of thermal transport research. “A severe side-effect of the continual miniaturization of power electronics devices, including computers and cell phones, is a dramatic increase in the heat generated,” Huxtable said. “This is becoming the limiting factor in device performance.” Controlling thermal transport at the nanoscale could help minimize the problem.

Composite materials design could also get a boost. The tiles on the exterior of the Space Shuttle, for example, must be made from insulating materials capable of extremely low thermal conductivity. “The engineering community is always trying to create materials with properties at the thermal extremes,” Huxtable said. “Nanostructured materials are a new approach to achieving both high and low conductivity composites.”

The educational component of Huxtable’s CAREER project is twofold. In a partnership with the Young Scholars Program in Utica, N.Y., which provides tutoring for underprivileged students from area high schools, he plans to bring two students to his lab at Virginia Tech each year “for a summer of research and learning. These students will be mentored in hopes that they will be motivated to attend college and to pursue degrees in science or engineering.” He also is developing a new course on nanoengineering to teach at Virginia Tech.

Huxtable received his bachelor’s degree from Bucknell University and his master’s and Ph.D. from UC-Berkeley. He conducted post-doctoral research in materials science, focusing on thermal transport, at the University of Illinois at Urbana-Champaign before joining the Virginia Tech faculty in 2003.

Vlachos hopes his CAREER research will help advance the understanding of cardiovascular flows in order to improve the diagnosis and treatment of heart disease.

“Cardiovascular disease has historically been the leading cause of death in the U.S. and accounts for about one-third of all deaths worldwide,” Vlachos said. “However, cardiovascular flows are not well understood. To improve disease diagnostic tools and treatments for heart disease, we need to understand the physics of blood flow through the body.”

As the heart pumps blood through the arteries and veins of the cardiovascular system, it transfers nutrients and oxygen to all of the body’s tissues and organs, Vlachos explained. “The arteries and vessels in this large network are short, curved, flexible pipes with many branches that deform as pressure increases during each heartbeat.”

The curvature, branching, flexibility and pressure pulse characteristics of these “pipes” result in a complex environment where flow disturbances can lead to the formation of plaque and arterial stenosis, or narrowing.

Vlachos will construct experimental models of the cardiovascular system through which fluids can be pumped. Using advanced optical imaging tools that will perform tens of thousands of measurements simultaneously across the arterial models, he hopes to discover how flow disturbances influence a variety of cardiovascular disease conditions.

“Another focus of this project is determining how stent implants affect arterial flow dynamics,” Vlachos said. “Identifying the flow-related causes of implant failure could lead to design improvements for stents.”

Vlachos also plans to develop educational models based on engineering “icons” — tangible, everyday examples of engineering practice — for use in demonstrating fundamental engineering principles to students from middle school through college.

Vlachos joined the Virginia Tech mechanical engineering faculty in 2003 after spending three years as a visiting assistant professor and research assistant professor of engineering science and mechanics at the university. He also is on the faculty of the Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences.

Vlachos received his bachelor’s degree in mechanical engineering from the National University of Athens, Greece and completed his master’s and doctorate in engineering mechanics at Virginia Tech.

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