Johns Hopkins Magazine -- February 1999
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Dirt that purifies... thermometer on a mission... shrinking solids... a Web-based snare... drowsy drivers get a wake-up call... a solution found close to home

Riverbank soil may provide a natural filter for groundwater, making riverbank wells a promising source for drinking water.
Filtering water the natural way

The cleanest water may yet flow through the dirt.

At least that's the premise behind "riverbank filtration," a natural filtering process being reviewed by a team of Hopkins researchers testing riverside, underground wells.

Their hypothesis: Soil provides a natural filter that can help eliminate harmful viruses, protozoa, and bacteria, as well as natural organic matter that, through processing, could contaminate drinking water supplies.

Currently, many treatment plants draw water directly from rivers, rather than riverside wells. Such "raw water" contains tiny bits of organic matter that can be nearly invisible or make water the color of iced tea. By itself, that material poses no health risks. But when treatment plants add a disinfectant to kill pathogens in the water, the disinfectant can react with the organic matter, creating harmful by-products. (Chlorine mixed with dissolved plant material, for example, can produce chloroform, a suspected carcinogen.)

Concerned, the Environmental Protection Agency recently lowered the allowable level of such by-products in drinking water, forcing some plants to review their treatment processes.

The Hopkins team, led by Edward J. Bouwer, professor of geography and environmental engineering, will draw river water and groundwater from riverside wells, then treat each using standard methods used by treatment plants.

"The question is whether the riverbank can remove natural organic matter in a way that reduces disinfection by-products," says William P. Ball, a team member and associate professor in the department. "If this works out, one thing [for treatment plants] to consider is: Don't take the river water, take the groundwater."

The three-year Hopkins study, funded by a $300,000 EPA grant, will focus on water drawn from the Wabash, Ohio, and Missouri rivers, near the towns of Terra Haute and Jeffersonville, Indiana, and Parkville, Missouri.

"This could work very well for smaller communities and smaller systems that can't afford more elaborate treatment systems and personnel," Bouwer says.

The wells are owned by American Waterworks Service Co., which is providing about $250,000 in equipment, testing, and analysis, researchers say. That firm, like plants in Germany and elsewhere, already draws from riverside wells.

"Drinking water is something found in everybody's daily life," says Ball. "The simplicity of this is appealing."
--Joanne P. Cavanaugh

Photo by David Sussman
A not-so-hard pill to swallow

When John Glenn made his historic return journey aboard the space shuttle this past fall, a tiny thermometer went along for the ride--inside the astronaut/senator's gullet.

During the space mission, Glenn ingested a three-quarter-inch long, silicone-coated capsule. Inside the capsule were a quartz crystal temperature sensor, a tiny battery, and a radio transmitter. Researchers at Hopkins's Applied Physics Laboratory developed these tools to monitor astronauts' core body temperature. The quartz crystal vibrates at a rate that varies with temperature, producing a magnetic flux that transmits a signal.

Body temperature normally rises and falls throughout the day in a predictable cycle. NASA scientists are using the ingestible temperature sensor to study how space travel disrupts this daily rhythm.

The temperature pill was licensed to Human Technologies Inc., in St. Petersburg, Florida, in 1988. The device has also been used to monitor the internal body temperature of firefighters as they work in burning buildings and of divers entering deep, cold waters.
--Melissa Hendricks

Graphic by Collin Broholm
Honey, I shrank the ZrW2O 8

Elementary school pupils learn that solids expand when they are heated and contract when cooled. (Think of a wooden door that is more difficult to open in the summer.) But a few solids violate that supposedly inviolable rule. When heated, they shrink!

Hopkins physicist Collin Broholm reports that he has discovered the molecular contortions that enable one of these unusual solids to perform its amazing heat-induced shrinking act. His findings appear in the November 12 Nature.

The material is called zirconium tungstate (ZrW 2O8)-- "the ideal engineering material," Broholm notes. By blending materials that shrink when heated with more traditional substances that expand when heated, scientists could create a composite that neither shrinks nor expands as the temperature changes.

In his recent study, Broholm collaborated with physicists from Bell Labs, the R & D arm of Lucent Technologies, in Murray Hill, New Jersey. The scientists are testing a zirconium tungstate composite, hoping to use it to build devices for fiber optics that maintain their dimensions under a wide range of temperatures. Even the slightest amount of expansion or contraction can impair a signal.

But to use zirconium tungstate and similar materials, researchers would first like to understand how they work. So Broholm used a technique called neutron scattering to examine the structure of zirconium tungstate while gradually increasing its temperature. For technical reasons, he first cooled the solid to an extremely cold temperature (0 degrees Kelvin), and then heated it. When the compound reached about 50 degrees Kelvin (-370 degrees Fahrenheit), it began to shrink. It continued to shrink at a regular rate until reaching room temperature. What occurred at the atomic level?

For simplicity, suggests Broholm, imagine the situation in two dimensions. A solid is made up of a long line of balls (atoms) connected by springs (bonds). Heating increases the movement of atoms (which are always vibrating to a certain degree). Two types of movement are possible, explains Broholm:

1) An accordian type of motion in which neighboring atoms move toward and away from each other along the line. Atoms bump into each other and spread apart to make room for their neighbors. When most materials are heated, explains Broholm, this first type of movement dominates. The atoms spread out and the solid expands.

2) Atoms move up or down, perpendicular to the line. In zirconium tungstate, the bonds between atoms are especially stiff. Little if any movement occurs along the line of atoms. However, heating does cause atoms to move perpendicular to the line. And because the bonds between atoms are so stiff, when one atom moves perpendicular to the line, the neighbors on either side of it are drawn together. The result is that the line of atoms becomes shorter--and the material shrinks.

The more complicated three-dimensional version of this principle is shown in the illustration at left.

Snaring cheaters on the Web

Warren Brantner (MS'97) wants to tear down the Evil House of Cheat.

Brantner, an information technology buff and self-styled inventor, has developed a Web-based program to help take the edge off a booming new cheating resource: on-line term paper mills.

"Purchased term papers have just mushroomed in the last year," says Brantner, who earned a master's in information and telecommunication systems at the School of Continuing Studies. "I loathe these places, and what they are doing to academia."

Check out, for example, (the Evil House of Cheat). For $11.95 a year, students can access 9,500 essays. The company's Web page touts: "Our essays can help in many ways [for] ideas, for research, or for when that deadline is a few moments away and you still haven't started that assignment. We cater for all!" About 13,000 students apparently visit the site daily.

Several other online services charge a variety of fees ranging from $15 to $65 a paper. "Need a term paper on the Fall of the Roman Empire?" one service poses. "Instantly, you've got what you need."

With Brantner's service, (, instructors register and pay a monthly fee of $4.95. Students in their courses then electronically submit all their papers to a related site. The system checks students' work passages against a database of 600 papers Brantner bought from one of the services.

As time goes on, the IntegriGuard database will grow--fed mostly by the papers students submit through his service, Brantner says. (The online paper mills' databases are closed to such scans). Though a plagiarized paper could slip through if it's not yet on his database, Brantner says the act of filing would be enough to keep students from cheating.

"The database gets more powerful over time," Brantner says. "It's a psychological deterrent. As universities start implementing the [anti-cheating] service, students will be less likely to purchase the papers and companies providing the term papers will close."

Online papers apparently aren't yet popular at Hopkins. Marc Donohue, professor of chemical engineering, chairs an ad hoc committee on academic integrity. "I haven't heard professors talk about getting one in class, although I don't know how they would know," he says.

Just in case, history professor Ron Walters has a term paper Web site "bookmarked" for quick access. He has received at least one paper he suspects may have come from the Internet mills.

Brantner launched the site last fall, sending mailers to 800 schools. He and a partner pulled together about $6,000 to create this technological antidote to a computer-borne disease. "I'm an entrepreneur at heart, an inventor, a tinkerer," he says. "If it helps humanity at the same time..."

Rover: equipped for the inattentive
Photo courtesy APL
Droopy drivers get a GRIPP

Driving on the Interstate late one night, a drowsy truck driver begins to veer off the highway. But just as he is about to careen over a cliff, a buzzer shrieks and a dashboard light flashes scarlet. The now wide-awake driver steers back onto the road and soon stops at a rest station to sleep.

This scenario could be realized in the not-too-distant future, say engineers at the Johns Hopkins Applied Physics Laboratory. Just as vehicles now routinely contain seatbelts and airbags, they may one day feature smart technology that alerts sleepy, drunk, or otherwise inattentive drivers who meander off the roadway.

The amazing thing about the technology, say the engineers, is that it will use satellites 11,000 miles away to determine if a vehicle has strayed the diameter of a quarter.

The APL researchers have built a prototype known as GRIPPS (for GPS Roadside Integrated Precision Positioning System), which they've installed and tested in a custom Ford van named Rover. Though GRIPPS currently responds a few feet too late, the researchers say that reducing response time is only a matter of improving the software.

Many new car models feature Global Positioning System (GPS) receivers, which are navigation systems that communicate with a network of satellites, allowing drivers to gauge their latitude and longitude to within a few hundred feet. But that is not precise enough. "We want inches," says team leader Tommy Thompson.

With GRIPPS, one GPS receiver sits on Rover's roof and another is on a base station (in this case, it is mounted to the roof of an APL building). GRIPPS calculates the distance between the GPS satellites and Rover, and between the satellites and the base station. Determining Rover's distance from the base station then simply involves solving a vector equation.

GRIPPS then compares Rover's location to the coordinates of an electronic map of the road. If the two locations are out of sync, Rover has strayed from its lane.

Dense foliage, tunnels, even tall buildings can block the GPS signal. So the engineers built several back-up sensors. One counts wheel turns, for example, which can be used to determine how many feet Rover has moved since the last GPS contact.

Thompson and another GRIPPS colleague, Ed Westerfield, helped to build the GPS's forerunner, Transit, which was the first satellite navigation system. Other team members are Larry Levy, Tom Murdock, Brian Truckenbrodt, Tom Hattox, and Dave Hohman.

Currently, GRIPPS's equipment--which includes two computers with large monitors--fills most of Rover's interior. On the roof sits a large GPS receiver with an antenna that resembles a miniature UFO.

All this technology will eventually be reduced to a computer chip, says Thompson.

Just right for the job: the telescope installed at Apache Point
Photo courtesy Alan Uomoto
A solution found close to home

Last year, as astronomers from Johns Hopkins and six other research institutions were assembling the instruments for an ambitious project called the Sloan Digital Sky Survey, they acknowledged they had a problem. A minor but essential piece of their equipment would not work. The instrument was a 24-inch telescope that was to be used to calibrate a larger wide-angle telescope. With these instruments and some others, which were being assembled at Apache Point Observatory in New Mexico, astronomers planned to create a map of more than 100 million stars and galaxies--the largest map of the universe.

But after months of troubleshooting and tinkering, says Hopkins astronomer Alan Uomoto, he and other Sloan astronomers concluded that the small telescope was fundamentally flawed.

A replacement telescope could be built but it would take 14 months, too long for the eager scientists. So after exploring some alternatives, Uomoto found a solution close to home--so close, in fact, it was perched on the roof of the Hopkins Bloomberg Center for Physics and Astronomy. Under a copper and aluminum dome, a modest telescope, which was used by students and astronomy buffs on visitor nights, was just the right size for the job. So a few months ago, Uomoto and some colleagues packed up the 3,000-pound telescope and trucked it to Apache Point. It looks like the telescope will work just fine, he reports.

Hopkins astronomy buffs won't be without a telescope for long. In several months, a new one will take its place under the dome on the roof of Bloomberg, gratis, thanks to the Sloan project's directors, the Astrophysical Research Consortium (ARC).