November 19, 2010

All wrapped up

It’s not easy being a nanontube. Yes, the small-scale carbon structures are enticing because of their unworldly, strength, quantum mechanical and lectrical properties. But the tubes have issues. First, they’re almost always in bundles, making them difficult to manipulate. And they really only like to live in water;in any other medium, their alluring characteristics disappear.

Now, Duke chemist Michael Therien and postdoctoral fellow Pravas Deria have devised a way to sort out the nanotubes' issues. The key is an uncommon polymer, poly[2,6-{1,5-bis(3-propoxysulfonicacidsodiumsalt)}naphthylene]ethynylene, that Derias designed. The polymer, or chain of molecules, untangles the bundles, then helically wraps itself around each individual nanotube, like hair wrapped around a curling iron, or like the helix of a single strand of DNA.

DNA, the blueprint of life, was, in fact, the inspiration for creating a polymer. Deria said that a single strand of DNA is highly charged, and charge was a characteristic Therien’s team thought was essential to guarantee the nanotube bundles would stay separated even in media other than water.

After several trials, the polymer worked as planned. Deria was surprised to find that the space between each helical loop on a nanotube was the same, roughly 10 nanometers. (That’s just a bit longer than a man’s whiskers will grow in the time it takes him to lift a razor to his face.) The nanotubes stayed wrapped with polymer and kept their electric properties, even when they were tested in carbon-based liquids.

That’s significant because nanotubes are important tools for creating new and better materials, Therien said. The next step will be to focus on some of the nanotubes' other issues so scientists can harness the structures' optical properties.

November 12, 2010

The Gravity of Numbers

Gravity isn’t just for the physicists. The force, or at least the notion of it, actually influences how we interpret scientific data, so much so that when shown a donut chart, some people thought it might actually roll away, says Robert Kosara, a researcher at UNC Charlotte.

Kosara and his graduate student found that people interpret charts that had an unequal distribution of "weight,” or darker and lighter colors, as unstable. The donut can roll away because gravity can turn the color imbalance into movement. The question why or how we do this has no scientific answers, yet. Researchers in information visualization, InfoVis, should focus on building the theory of visualization as much as they focus on creating new systems and developing new techniques to represent data, Kosara argued while presenting the Nov. 12 Visualization Friday Forum lecture.

Data visualization is a standard practice in the scientific method. Changing numbers into pictures lets scientists use their human prowess with reading visual data to spot patterns, trends and outliers, Kosara says. But visualizing data is also becoming a popular trend in the media. It produces pretty pictures for publications and provides another way to tell a story.

Because scientists do not yet know how and why some visualizations work and some don’t, it’s hard to know which visualizations to use. Kosara illustrated this point with a bar graph and a line graph charting sex versus height. When shown the bar graph, subjects interpret that, on average, males are taller than females. When shown a line graph representing the same data, subjects argue that as one becomes more male, he or she, becomes taller.

“That’s bad,” Kosara says. The subjects are attaching meaning to the representation rather than the actual data. The example is an exaggeration, but sheds light on the challenge of deciding what graph or picture best represents more complex data sets. If he can determine scientifically why men do better looking at tree graphs compared to females or how people rationalize gravity in an abstract donut chart, Kosara says, it might better transform scientific numbers into real-world stories.

November 2, 2010

Lasers in focus

Definitions don’t seem to come easy to scientists. Consider Pluto’s planethood, or the question of what constitutes life. More recently, the definition debate has even stymied how to describe a laser.

Sure, the acronym LASER stands for Light Amplification Stimulated Emission of Radiation. But fifty years of studying amplified light sources has moved the device far beyond simple laser pointers, so much so that a large consortium of scientists could only agree that a laser is, “hard to define, but I know one when I see one,” said Warren Warren, chair of Duke’s chemistry department and a speaker at the 2010 Fitzpatrick Institute for Photonics, or FIP, symposium.

The event, held Oct. 27-28, featured talks, poster sessions and themed lab visits on Frontiers in Photonics: Science and Technology. It also celebrated the 50-year anniversary of the laser’s discovery and the 10-year anniversary of Duke’s photonics institute.

Warren, part of the Technical Advisory Committee for LaserFest, a yearlong celebration of the 50th anniversary of the laser, said dozens of scientists weighed in as the committee tried to develop a satisfactory definition of the laser for the LaserFest Website, laserfest.org. "Up to about three months ago, on no place on the site did it say what a laser was."

LaserFest.org, after considerable scientific discussion, now defines the laser as a “device that strengthens light waves.” Some lasers have a well-directed, very bright beam with a very specific color; some have extremely short pulses. “The key feature is that the amplification makes light that is very well defined and reproducible, unlike ordinary light sources such as the sun or a lamp,” the site states.

Warren added that a definition for Congress might also include "economic engine." Ten billion dollars in laser research has enabled four trillion in technology, he said.

He, along with thoracic surgeon Thomas D’Amico and biomedical engineers Joseph Izatt and Cynthia Toth, then went on to describe the laser technologies they are developing at Duke to diagnose and treat skin, lung and esophagus cancer as well as macular degeneration and other eye diseases.

The second day of the symposium also highlighted biological and medical uses of lasers. Biomedical engineer Adam Wax, neurosurgeon Gerald Grant and radiologist James Provenzale described technologies they are testing to detect cancer cells during surgery.

The 1999 Nobel Laureate in Chemistry, Ahmed Zewail, director of the Center for Physical Biology at Caltech University, provided the symposium's keynote lecture. Progress and peace would come with greater global collaboration and cooperation, beginning in science, he said. And quite possibly, with those debatable definitions.