By Barbara A. Hale
Public Information
Engineers have developed a new computer-controlled, flexible manufacturing process that promises to make carbon fiber concrete reinforcement grids more competitive with the heavier, corrosion prone, labor-intensive steel rods currently used.
The team, which includes Renata S. Engel and Charles E. Bakis, both associate professors of engineering science and mechanics, and Thomas E. Boothby, associate professor of architectural engineering, also has developed a computer-based analytical method that simulates the grid's behavior. The simulation can be used as a tool, they said, to tailor the grid's strength and stiffness for use in specific new concrete bridge or building construction or as strengthening material that can be applied to the outside of older, damaged structures. The group is currently developing grids for use in box culverts, prefabricated concrete structures used as water channels under roadways.
Although the new Penn State grids look somewhat like stiff fishnet or the orange plastic netting often used to section off construction sites, the product is far stronger and stiffer. Bakis said that carbon fiber itself has a strength of 500,000 pounds per square inch.
An automated, com-puter-controlled machine at Penn State's Composites Manufacturing Technology Center (CMTC) weaves the new grids from a continuous one-eighth inch wide carbon fiber bundle impregnated with liquid polymer resins which is laid down in a flexible mold. The grid is then pressed and heated to harden it.
The weaving pattern is the key to the grid's stiffness and strength.
Bakis, who is CMTC director, said that the team worked on controlling and modifying stiffness first because it affects the "bounce" that a reinforced concrete structure will have in response to a load. Motorists traveling over a concrete bridge, for example, usually prefer less bounce and more stiffness.
Using the team's new simulation method coupled with its flexible manufacturing process, they can tailor the weave, by combining the staircase and cross patterns, to meet special needs for any particular application, he said.
While carbon fiber grids are probably more expensive when compared to equivalent steel reinforcing rods, Engel said they have several other advantages. For example, steel reinforcing rods must be tied, by hand, into a grid pattern at the site. The carbon fiber grids need no assembly. The lightweight carbon fiber grids also can be handled easily without heavy equipment. In addition, the grids offer the economy and reliability of mass-produced, prefabricated materials.
Best of all, said Engel, the grids will not corrode as do steel rods and, for that reason, they promise to lengthen the life of the bridges and other structures they reinforce.
By Barbara Hale
Public Information
Eating your usual amount but selecting low energy density meals, which have fewer calories per ounce and contain lots of fruits, vegetables or grains, offers a way to cut back on calories and still leave the table feeling full and satisfied, suggests a study directed by Barbara Rolls, who holds the Guthrie Chair in Nutrition.
"You need to eat a satisfying amount of food to control hunger. Fat can make food taste good but it doesn't necessarily make you feel satiated," said Rolls, who worked with Elizabeth A. Bell, doctoral candidate in nutrition; Victoria H. Castellanos, former postdoctoral student; Mosuk Chow, assistant professor of biostatistics; Christine L. Pelkman, doctoral candidate in biobehavioral health; and Michelle L. Thorwart, research technologist.
"When we first started this study, we thought that fat played an important role in satiety. We found that, when you keep the calories and volume of food that a person eats fairly constant, you don't see any special effects for fat in terms of reducing hunger," said Rolls.
The experiment resembled real-life situations in which a person who is concerned about his or her food intake may select some foods that are reduced in fat or calories but also may consume high-fat or high-calorie foods.
Rolls said that following your usual eating habits but modifying some favorite recipes to reduce the energy density would be a sensible way of applying these research findings in a home kitchen. For example, reduce energy density by adding more water to turn a casserole into soup, or add leaner meat, celery, extra tomatoes and mushrooms to chili to increase bulk but not calorie content.
"People on diets often substitute pretzels for high-fat, high-calorie snacks. But pretzels have a low water content and don't fill you up, so you eat more of them. A snack with higher water and fiber content, for example, an apple, would be a better choice," Rolls said.
A study conducted by researchers from Penn State and the Tokyo Institute of Technology shows that the whale and the hippo are each other's closest living relatives. The genetic analysis was conducted by Alejandro P. Rooney in the Institute of Molecular Evolutionary Genetics at Penn State, along with Masato Nikaido and Norihiro Okada of the Tokyo Institute of Technology.
"We knew from previous work that whales were closely related to even-toed hoofed mammals, but the studies had been inconclusive or unreliable regarding exactly where they fit in the family tree of this group of mammals." Rooney said.
This new study, like previous ones, found that animals such as the hippo, camel, pig, giraffe, sheep and cow do share many segments of DNA with whales, porpoises and dolphins, indicating that at some point they all had a common ancestor. However, DNA segments found only in whales and hippos indicate that they have a common ancestor that is not part of the evolutionary history of the other animals.
"Ours is the first study to provide reliable confirmation that hippos are the sister-group to whales," said Rooney. Whales and hippos share several adaptations to life in an aquatic environment, including oil-producing skin glands, the lack of hair and the use of underwater vocalizations for communication.