A physicist of the floating world. CAS Associate Professor of Physics Shuheng Pan and colleagues at the University of California-Berkeley hope to understand what makes high-temperature superconductivity work by investigating what makes it stop working.

Discovered in 1911, superconductivity is the complete lack of electrical resistance in solids cooled to near absolute zero, -459°F. It is the principle behind such applications as magnetic levitation, medical magnetic-imaging devices, and magnetic energy storage systems.

In 1986, new high-temperature materials were discovered that were superconductive at -300°F. At the time, scientists believed such materials could lead to cheap electrical power and magnetically levitated high-speed trains. Now, they hope to find substances that are superconductive at room temperature.

The research team used a scanning tunneling microscope customized to operate in low temperatures to study the effects of introducing "impure" atoms into superconducting materials. Impurities play a key role in superconductors, raising or lowering the temperature at which they become superconductive.

"When you put all these chemicals together in the right amounts, no one understands exactly why you get high-temperature superconductivity," says lead researcher J. C. Séamus David of UC Berkeley. The researchers hope that by studying how electrons move around copper oxide superconductors, they will find clues that will lead them to build better high-temperature superconductors.

The researchers moved the microscope's fine-tipped probe along the material's surface nanometer by nanometer, recording the strength of electron clouds at specific locations. They were able to see the alterations in electron clouds around impurities in the copper layer.

The team's next steps include introducing different impurities into the copper oxide to study how different magnetic scattering influences high-temperature conductivity.

The research is sponsored by the U.S. Department of Energy, and the study was reported in the Feburary 17 issue of the journal Nature.

Speakeasy. SAR Assistant Professor Margaret Denny, Instructor Barbara Oppenheimer, and Lecturer Mary Klimek have purchased new lab equipment that is greatly facilitating students' understanding of human speech patterns, thanks to a grant from the BU Instructional Technology Grant Program.

"An essential part of training speech-language pathologists is teaching them how to integrate all the signals -- physical, acoustic, neurological -- that go into speech production," says Denny, who specializes in communications disorders. "This new system, the Computerized Speech Lab, will help us develop lab exercises which give students hands-on experience measuring in real time the acoustics of individual speech sounds and analyzing voice characteristics."

Speech involves a highly complex, multidimensional, dynamic acoustical signal. Its precise characteristics are tightly coupled with both a speaker's movement and a listener's perception. Speech pathologists must understand the nature of sound, methods of acoustic analyses, the fundamentals of digital signal processing, and the special application of all these to both normal and abnormal speech.

"These are highly abstract mathematical concepts, more accessible to physicists and engineers than to students in communication disorders," says Denny. "The CSL hardware and software will help us create a better, integrative learning environment for our students."

One aspect of the CSL system will greatly assist speech-language pathology students in understanding neural control of speech, the physics of sound, and how the lungs, larynx, and oral and nasal cavities work together to produce the 46 different sounds in American English.

The CSL includes a real-time spectrogram ("voiceprint") to represent speech signals; a real-time pitch analyzer, which analyzes stress, timing, pitch, intonation, and amplitude patterns; and an International Phonetic Alphabet transcription tutorial. "The IPA is the lingua franca of linguistic and speech professionals," Denny explains.

For more information on communications disorder research, visit www.bu.edu/sargent/.

"Research Briefs" is written by Janice Zazinski in the Office of Public Relations. To read more about BU research, visit http://www.bu.edu/research.