Female northern cardinals learn songs in one-third the time it takes male birds to learn the same number of songs, according to research at the University of California, Davis, by Ayako Yamaguchi, a former graduate student.
"It's the largest learning difference between sexes ever found," said Yamaguchi. Small sex-based differences in learning have been found in other animals, but these are usually so small that they are overwhelmed by individual variation.
Northern cardinals are unusual among temperate-zone birds because both males and females sing. In earlier work, Yamaguchi has shown that the birds can tell the difference between male and female songs. Birds learned songs by copying birds of either sex, but added sex-specific characteristics to them.
Young birds memorize songs during a time window called the sensitive period, and later practice their songs compared to the memory. Yamaguchi found that while the sensitive period started at around the same age for both sexes, it lasted more than three times as long in males as in females.
The ability to learn songs or language is very rare, having evolved only three times -- in birds, whales and humans -- said emeritus professor Peter Marler, who heads the Animal Communication Laboratory at UC Davis. Yamaguchi's research has opened up the whole area of gender-specific song learning, he said.
The study is to be published in the May 17 issue of the journal Nature. Yamaguchi is currently working as a postdoctoral researcher at Yale University.
Media contacts: Ayako Yamaguchi, Yale University School of Medicine, (203) 785-5235, ay64@columbia.edu; Andy Fell, News Service, (530) 752-4533, ahfell@ucdavis.edu.
Shaking Trucks Hit Bump in the Road
As heavy trucks roll down the road they create dips and bumps in the pavement. When other trucks run over the bumps, they vibrate in the same way, making those hills and valleys deeper, according to research by engineer Don Margolis of the University of California, Davis.
That makes for an uncomfortable, possibly unhealthy ride for truckers, as well as damaged roads, he said.
Margolis used data on trucks and bumpy road surfaces to build a computer simulation. Although it's known that heavy trucks damage roads, no one had previously shown that the shape and pattern of bumps was so important, or that trucks reinforce the rutting damage caused by other trucks, he said. It's not yet clear whether total weight, or the way the weight is loaded on individual axles, is more important in causing damage.
Moving trucks have two types of vibration caused by road surfaces. "Rigid body" movements are bounces, rolls and heaves of the whole vehicle, with a frequency of one or two a second. "Beaming" movements are caused by bending of the truck frame, and have a higher frequency. According to the computer model, roads where trucks travel at lower average speeds develop bumps causing rigid body movement, while higher-speed stretches develop beaming problems.
The computer model shows that it is possible to distribute weight to isolate the driver's cab from beaming, or rigid body movement, but not from both, Margolis said. In fact, truckers already try to smooth their ride by adjusting the coupling between tractor and trailer, he said. This trial-and-error approach can give them better isolation from the road surface, but can break U.S. regulations that require 14,000 pounds of load to be on the front axle.
The study is published in the January issue of the journal Vehicle System Dynamics.
Media contacts: Don Margolis, Mechanical and Aeronautical Engineering, (530) 752-1448, dlmargolis@ucdavis.edu; Andy Fell, News Service, (530) 752-4533, ahfell@ucdavis.edu.
Grant to Launch Graduate Program in Space Engineering
A new University of California, Davis, program to launch graduate students on careers in space engineering will be supported by a grant of $125,355 from the California Competitive Space Grants Program.
In recent years, the U.S. space industry has had increasing trouble recruiting qualified aerospace engineers, according to UC Davis engineering professor Nesrin Sarigul-Klijn, who leads the program. For example, NASA has more engineers over the age of 60 than under 30, she said.
The SpaceED program will build up the space aspect of the existing UC Davis graduate program in mechanical and aeronautical engineering, said Sarigul-Klijn. Initially, the state grant will partially support four graduate students, help with recruitment of additional students, and fund curriculum development, she said. It will also help attract further funding from government and private sources.
SpaceED participants will include industrial partners such as SpaceDev, a San Diego-based company that plans to develop commercially viable deep-space missions.
While the traditional aircraft industry has declined in California, there are several companies building rocket motors and satellite systems, and three government-supported space agencies in the state. California schools need to respond to this change by adding space components to engineering programs, Sarigul-Klijn said.
Currently, UC Davis researchers are studying topics such as flight mechanics, extreme heat during flight, space vehicle design, and the biological effects of space flight. Sarigul-Klijn's laboratory is developing a reusable space launch vehicle concept called SwiftLaunch. SwiftLaunch would be launched from a large cargo airplane and carry up to three people or a small payload into orbit. The proposal is currently being reviewed by NASA and the U.S. Air Force.
More information:
California Space Authority:
SpaceDev:
Media contacts: Nesrin Sarigul-Klijn, Mechanical and Aeronautical Engineering, (530) 752-0682, nsarigulklijn@ucdavis.edu; Andy Fell, News Service, (530) 752-4533, ahfell@ucdavis.edu.
Journal Issue Honors Late Professor
A special issue of the Journal of Theoretical Biology will honor University of California, Davis, mathematician Joel Keizer, who died in 1999.
Keizer was director of the Institute of Theoretical Dynamics at UC Davis from its inception in 1986 until his death. The institute brings together scientists from various disciplines who use mathematics and computers to solve problems in biology, medicine and engineering.
Trained as a chemist, Keizer became interested in mathematical problems in biology. He was particularly interested in changes in electrical potential in cells, and how the flow of calcium in and out of cells controls cell activity. At the time of his death, he was working on a textbook of mathematical biology, which is being completed by his colleagues.
"Joel was a master at bringing together people from different areas of the physical and biological sciences," said Angela Cheer, current director of the institute.
"Joel's example of a balanced life, pursuing both scientific and non-scientific interests with gusto, helped many students to deal with the pressures of starting out in science," said UC Davis mathematical biologist Alan Hastings, co-editor of the special issue.
Contributors to the memorial issue include colleagues from UC Davis as well as scientists from the National Institutes of Health, New York University, Oregon Health Sciences University, Virginia Tech and the Free University of Brussels, Belgium.
The special issue will be published May 21 by Academic Press.
Media contacts: Alan Hastings, Environmental Science and Policy, (530) 752-8116, amhastings@ucdavis.edu; Angela Cheer, Institute of Theoretical Dynamics, (530) 752-1912, aycheer@ucdavis.edu; Andy Fell, News Service, (530) 752-4533, ahfell@ucdavis.edu.