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February 2003

News about Science, Technology and Engineering at Iowa State University

Thin polymer film aids nerve regeneration
Using microscale channels cut in ultra-thin biodegradable polymers, Surya Mallapragada, a chemical engineering professor at Iowa State and an associate in materials chemistry at the U.S. Department of Energy's Ames Laboratory, is working to regrow nerve cells. The technique has been proven to work for peripheral nerve regeneration in laboratory rats.

When a nerve is severed, the part of the neuron "downstream" of the injury typically dies off. Neurons in humans are several feet long. Grafting, which works well for other tissue such as skin, isn't the best option because of loss of nerve function where the donor tissue is removed and the difficulty in getting the nerve cells to line up and reconnect.

"Nerve cells aren't able to easily bridge gaps of more than one centimeter," Mallapragada says. "Peripheral nervous system axons -- the part of the nerve cell that carries the impulses -- normally have a connective tissue sheath of myelin guide their growth, and without that guidance, they aren't able to grow productively."

By working on a cellular scale, she has developed a way to help guide neurons so they grow in the right direction. Starting with biodegradable polymer films only a few hundred microns thick (100 microns equals 0.004 in. -- significantly less than the thickness of a human hair), Mallapragada and her colleagues have developed methods for making minute patterns on these incredibly thin materials.

After promising in vitro tests, Mallapragada collaborated on trials on rats, where small segments of the rats' sciatic nerves were removed and the severed nerves "spliced" using the polymer film. Though initially unable to use their legs, the rats started to regain use of their legs after three weeks and were able to function normally after six weeks. For more information, contact Mallapragada at (515) 294-7407, or Kerry Gibson, Ames Lab Public Affairs, (515) 294-1405.

Predicting bridge frost
They hit the deck, bridge deck that is, early many mornings in the name of research. Tina Greenfield, a graduate student in geological and atmospheric sciences and two other meteorology students -- Brian Tentinger and Jose Alamo -- are usually outside on bridge decks checking for frost before 5 a.m on most chilly Iowa mornings.

Virtually every morning one of the three will observe whether or not frost has developed on three Story County bridges. Each day that frost can develop, Greenfield, Tentinger or Alamo will drive over the bridge and then use an infrared thermometer to record the bridge pavement's temperature. Frost develops when bridge temperature is less than freezing and the dew point temperature is greater than the bridge temperature.

"This is a very sensitive reading," Greenfield says. "If you are off by just a degree or two, it can mean nothing will happen or you could get a large amount of frost."

This is the second year of Greenfield's research (she plans three years of observable data), which is funded by a two-year grant from the Iowa Department of Transportation. DOT is interested in the project because of hazardous driving conditions on frosty bridges.

"From these observations, hopefully we can develop computer models that will tell us when frost will occur and how much will accumulate," said Gene Takle, professor of geological and atmospheric sciences. "If we are able to develop a model that can predict 18 hours in advance whether frost will occur, then the DOT can have trucks ready to go."

For more information, contact Greenfield, (515) 231-4794; Gene Takle, (515) 294-9871; or Dave Gieseke, LAS Public Relations, (515) 294-7742.

Thompson elected to NAE
R. Bruce Thompson, an Iowa State University distinguished professor of engineering in two disciplines -- aerospace engineering and materials science and engineering -- has been elected to the National Academy of Engineering (NAE). Election to NAE is considered one of the highest professional distinctions accorded an engineer.

Thompson -- also the director of Iowa State's Center for Nondestructive Evaluation and a senior scientist with the U.S. Department of Energy's Ames Laboratory -- was chosen based largely on his work in the field of nondestructive evaluation (NDE), which is the practice of testing a material's ability to perform its intended function and prevent failure without destroying the sample. NDE is commonly used in aviation and space industries to test the flight worthiness of vehicles. It also is used in the energy industry to determine the integrity of critical structures like those in nuclear power plants and pipelines. NDE recently has branched out into new areas, such as the testing of bridges, highways and other infrastructure; testing of machinery, like that used in agriculture; and the monitoring of manufacturing processes.

Thompson's research covers a wide range of NDE issues and methods, including ultrasonics, electromagnetics, material property measurements and flaw characterization. Among his accomplishments is the development of a set of novel sensors that can perform ultrasonic inspection without contacting a part.

He is one of only three NAE members who have made nondestructive evaluation their career work. One of the others is retired Iowa State distinguished professor Donald Thompson. For more information, contact Thompson at (515) 294-8152, or Skip Derra, ISU News Service, (515) 294-4917.


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