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Carbon Copies


 Pitt's J. Karl Johnson
The latest jewel of science is a strand of carbon molecules called nanotubes.

In bulk, carbon nanotubes form a fluffy, gray powder that “looks like soot,” says J. Karl Johnson, an associate professor of chemical and petroleum engineering at Pitt. Someone who found a jarful would probably throw it away. That would be an unfortunate mistake, and expensive, to boot—up to $500 for each gram of “soot.”

All things considered, carbon is a pretty dull element, with one notable exception. The basic building block of life on Earth, it bonds with other elements in millions of combinations. In elemental form, it can be soft, like coal, or hard, like diamonds, “a phase of carbon that we all know and love,” jokes Johnson.

A form of carbon even more valuable than diamonds was discovered in the early 1980s, when scientists learned that under certain conditions, 60 carbon atoms would fuse into a shape like a soccer ball. Hollow and extraordinarily strong, these molecules were dubbed “buckyballs,” after the inventor of the geodesic dome, R. Buckminster Fuller. Researchers were no sooner thinking up uses for buckyballs than they discovered a close cousin—the nanotube—by accident in 1991.

Like buckyballs, nanotubes are a lattice of carbon atoms; but instead of spheres, they look like tiny wire screens rolled into a tiny tube. How tiny? A few nanometers—one billionth of a meter—in length. For comparison’s sake, the period at the end of this sentence is about 200,000 nanometers wide.

Yet carbon nanotubes are tremendously strong and versatile. Researchers think that if nanotubes are embedded in another material such as plastic, that plastic would be stronger than steel; depending on how they are rolled up, nanotubes could conduct electricity for tiny computer circuits.

While those ideas are intriguing, Johnson, the BP America faculty fellow at Pitt, is working toward a different end. He’s exploring the possibility of using nanotubes to store and filter gases.

Carbon provides a very attractive surface—literally—for gas molecules, Johnson says. Gases stick to carbon, lining up in an orderly fashion instead of bouncing around at random; in certain cases, putting carbon into a gas canister allows it to store more gas than if the canister was empty, he says. Nanotubes make gas storage even more efficient, because they can be “grown” to different sizes, depending on what type of gas scientists want to trap. “These things have a very ‘tunable’ diameter,” he says.

Theoretically, nanotubes could store hydrogen for use in pollution-free vehicles or they could remove harmful gases from smokestack emissions. A nanotube gas filter would be up to 10,000 times faster than existing methods, Johnson says.

There are still huge problems to overcome. It’s difficult to create nanotubes reliably, and their behavior is not fully understood; existing formulas often don’t predict what happens in experiments. That’s where Johnson comes in. He’s developing more accurate models to simulate how nanotubes work.

His peers have taken notice. Although a relatively young member of the Pitt faculty—Johnson earned his PhD from Cornell University in 1992—his work is widely quoted. Since 1997, Johnson has been awarded $300,000 in grants from Honda Motor Co., Sandia National Laboratories, and the National Science Foundation to continue his research.

The enormous potential of nanotubes makes the work exciting, Johnson says. “Nanotubes are still in their infancy,” he points out, predicting that someone, eventually, is going to create a commercially successful nanotube application.

—Jason Togyer

Circuit Breakers


Pitt professors work together to transform electric impulses into beams that travel at the speed of light.

As rivalries go, it doesn’t match Pitt vs. Penn State. Still, computer scientists and electrical engineers are known to view each other with suspicion. One group writes the software; the other designs the hardware. When computers crash, the finger pointing begins.

So it was unusual back in 1987 when Pitt’s newest electrical engineering professor, Steven Levitan, walked across campus to meet another new hire, Donald Chiarulli of the computer science department. Levitan had come here from the University of Massachusetts; Chiarulli from Louisiana State University.

Levitan took the walk after pitching an idea to his department, a new course on extremely compact chips called “very large scale integrated circuits” (VLSI), only to be told “this new guy” in computer science had beat him to it.

Chiarulli and Levitan struck up a friendship. “We talked about VLSI for two months,” Levitan recalls. “That spring, he said, ‘What about combining optics and computers?’ I said, ‘What a dumb idea.’”

Fortunately, Levitan reconsidered, because that “dumb idea” forms the basis of their collaboration. “There have been times when I’ve had more meals with Steve than I have with my wife,” Chiarulli says.

Their research has helped to push forward the technology by which tomorrow’s computers will collect and process data, at speeds unthinkable with today’s technology. Recently, they were awarded a $2 million grant from the Defense Department’s Advanced Research Projects Agency to develop computing tools that will help engineers design and test complete systems of electronic, optical, and mechanical devices that fit on single microchips.

Look at a computer chip. See the metal “legs” sticking out? Each carries electrical signals to and from the processors inside the chip. Unfortunately, as chips perform more functions, manufacturers are running out of room to make physical connections to those processors.

And the connections largely go from point A to point B. If data must be zapped to point C, then point C has to be connected physically to points A and B. Now multiply those connections by thousands of points. The longer the connection, the slower the electrical impulses flow, and the slower the circuit runs.

Using the technology of Levitan and Chiarulli, it may become possible to change those impulses into light and beam them through a tiny transparent space, where there will be no limit to the number of connections. Beams from point C instantly hit points A, B, and everywhere between X, Y, and Z. Unlike electrical circuits—which bog down with each new connection—light beams will travel at (surprise!) the speed of light, much faster than current through copper wires.

Chiarulli and Levitan are also designing interfaces that connect optical and electrical circuits with mechanical devices like wind or motion sensors.

For Pitt students, Levitan and Chiarulli helped create connections between their departments that led, five years ago, to an undergraduate major in computer engineering that’s jointly taught by computer science and electrical engineering faculty. Their teamwork provides an example of what they try to impart to their students.

—JT

Breakthroughs in the Making


Heartening News: Predicting the likelihood of a heart attack, especially in women, may be as simple as measuring the size and number of lipoproteins in the body. Pitt researcher Lewis H. Kuller, professor and chair of the Department of Epidemiology in the Graduate School of Public Health, says heart attack risk can be more than double for women who have a large number of small lipoprotein particles. These particles carry cholesterol from the liver to the tissues. Heart disease is the leading cause of death in women, and almost 60 percent of heart attack deaths occur outside the hospital.


Dennis Curran (right) and a research assistant
Short Cut: Breaking an old rule of organic chemistry is promising to speed discovery of new chemical compounds, Pitt Distinguished Service Professor and Bayer Professor of Chemistry Dennis P. Curran discovered. Finding new ways to make complex molecules, Curran and his research team mixed pure organic compounds—a no-no. But the team added highly fluorinated chemical tags to the mixtures, creating new compounds much faster. Making new drugs is one possible use of the process.


 Louise K. Comfort
Emergency Response: Paramedics, firemen, and police can respond faster to emergencies by using a Web-based software system developed by Louise K. Comfort, a Pitt professor in the Graduate School of Public and International Affairs. The Interactive Intelligent Spatial Information System (IISIS) provides real-time interactive information and communication among members of a response team, according to Comfort, who is the principal investigator on the IISIS staff.


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