Johns Hopkins Magazine -- November 1999
Johns Hopkins 
     Magazine Home




Coral's salvation-- in a culture?
Exploring a world of extremes
Two-wheeled efficiency
Building better sniffers
Relativity in action
Postdocs make progress

Cultured coral (bottom) may hold the key to saving the world's coral reefs.
Photo courtesy
Gary Ostrander
Coral's salvation-- in a culture?

Coral reefs around the world are dying. Pollution, global warming, and bacterial and fungal diseases are probably to blame. But parsing one culprit from the next in the great mixing bowl of the ocean is extremely difficult. So Hopkins biologist Gary Ostrander developed a method for isolating coral cells and keeping them alive in a culture dish.

The primary cultures provide a vehicle for pinpointing which organisms and pollutants decimate coral and for tracking the progression of the diseases they cause.

Other scientists have tried to maintain viable coral cells, but have kept them alive only about six hours. Ostrander, associate dean for research at the Krieger School of Arts and Sciences, and biologist Elizabeth Kopecky at the National Aquarium in Baltimore, succeeded in keeping cells from several different species of branching coral alive for 300 hours.

At that length of time, says Ostrander, "we can do some neat things"--such as observing the course of a disease from start to finish. Ostrander next plans to initiate such studies.

"A lot of the trick to keeping coral alive is to focus on keeping the algae alive," Ostrander explains. Coral lives in symbiosis with algae. The coral provides a protective structure for the algae, which in turn supplies sugar as fuel for the coral. The key, the scientists found, was providing the coral cells with the amount of sunlight and nutrients that are optimal for algae.

In Vitro Cellular and Developmental Biology will soon publish a report on the researchers' technique.

The coral cells are primary cultures, notes Ostrander, meaning that they are not growing since they do not divide. That is a next, much harder, step to achieve, he says.

The lyrical nooks and crannies of a coral reef provide safe haven for myriad algae, plants, and fish and other marine animals. So when a reef dies, its many inhabitants lose a home. Marine scientists have noted an alarming decline in coral all over the world, says Ostrander. Most notably, 90 percent of the coral in the Galapagos Islands is gone, as are significant portions of the Barrier Reef.
--Melissa Hendricks

The MESSENGER spacecraft (above) will fly by Mercury twice in 2008.
Photo courtesy
Max Peterson, APL
Exploring a world of extremes

More than a quarter century after the first flyby investigation of Mercury, a new space mission to the enigmatic planet closest to the sun will be designed and managed by Hopkins's Applied Physics Laboratory.

Named MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), the spacecraft--filled with miniaturized data-collecting instruments and a telecommunications system--will fly by Mercury twice in 2008, gathering data for a more detailed orbital investigation the following year.

What researchers hope to discover are answers to long-standing questions about the small planet's metal-rich core, its tenuous atmosphere, its Earth-like magnetosphere, and geological history.

Mercury is a world of extremes: it's the smallest major planet, is extremely dense, and records the largest daily variation of surface temperatures: from 90 degrees K to 700 degrees K. But what are the origins of Mercury's high density? What is the nature of its mysterious polar caps? If there is water, will that reveal the building blocks of life?

The hope is that by understanding the secrets of Mercury, scientists will learn more about the evolution of other planets like Earth, says Max Peterson, MESSENGER project manager at APL.

Much of what is known today about Mercury was culled from photographs taken in the mid-1970s by Mariner 10, the first spacecraft to fly by the planet. Yet only 45 percent of the planet has been seen. The surface appears to be cratered and ancient--like the moon's--but the nature of that surface has been up for debate.

Mercury's high density implies that 65 percent of the planet is metal-rich core--twice that of Earth's. Theories about the origin of that density include the idea that extreme heat from a young sun vaporized part of the outer rock layer of a "proto-Mercury," leaving the planet a metal-rich cinder.

As part of its fact-finding mission, MESSENGER will measure the planet surface's composition using X-ray and gamma-ray spectrometers to determine which elements make up the crust. If the surface rock shows little evidence of easily evaporated sodium or potassium, the vaporizing theory could be true. These discoveries in turn could help explain the formation, and geological behavior, of Earth.

MESSENGER's mission, like the Mariner 10's jaunt by Mercury, is challenging partly because of the planet's fast rotation, distance from Earth, and proximity to the sun. Under the $286 million APL proposal accepted by NASA this summer, several innovations make the mission more economical and efficient.

MESSENGER's unique propulsion system, for example, is integrated into the craft's structure, making it lighter and more compact. MESSENGER also will use the gravitational pulls of Earth and Venus to pick up speed via newly plotted "trajectories" around those planets. These and other developments mean each kilogram of fuel delivers more velocity to match Mercury's fast-moving orbit around the sun (88 Earth days equal a Mercury year). A state-of-the-art lightweight thermal shade will shield the craft from the sun.

MESSENGER is scheduled for launch starting March 23, 2004. For more information, visit the APL website at
--Joanne Cavanaugh Simpson

Illustration by
Chad Martin

Two-wheeled efficiency

As any 11-year-old child or most communists could tell you, bicycles are an efficient way to get around.

Hopkins researchers agree. A recent study shows that many bicycle train drives--especially those with good chain tension--have an energy efficiency score of up to 98.6. That means less than 2 percent of the power used to turn a bike train is lost (mostly as friction-related heat).

"Everybody can relate to bicycles because everybody grows up with them," says James B. Spicer, Hopkins associate professor of materials science and engineering, who led the study. "We wanted to look at it and get at what makes this thing tick."

Though the bicycle has been around for 100 years, there's been scant published work about the efficiency of the bike's roller chain and sprocket system. So engineers at Hopkins aimed an infrared camera at a computer-controlled bicycle drive train to measure friction-generated heat, since heat represents wasted energy. Investigators also looked at whether various gear ratios, rotation rates, and lubricants aided the drive chain, among other tests.

One finding of the study: bigger sprockets apparently work better, a possible tinker that could lead to faster bikes, or even more efficient chain-driven devices such as cafeteria conveyor belts or factory production lines. The yearlong study, which cost about $100,000, was sponsored by Shimano Inc., which makes bike components.

The study shows that simplicity is the bike train's saving grace. "We are talking about a front sprocket, a rear sprocket, and a chain in between," Spicer says. But the broader efficiency of bike power includes one big X factor: the rider.

"If you analyze the entire bicycle system, [the ingestion of] food that's converted to useful muscle power, which is transferred to the pedals and then to the road, the efficiency probably isn't very high," Spicer adds. "Human beings aren't that efficient."

Engineering's Priebe is striving to mimic electronically the canine's intricate sniff analysis.
Photo by
Jay Van Rensselaer
Building better sniffers

In one of his classic columns, humorist Dave Barry described his dog's inevitable response to all the sensory stimuli encountered daily outside the front door. The canine mental process Barry envisioned went something like this: "Could it be? Oh my gosh. It's the YARD!!!"

The acute olfactory sensors in the dog's nose, specifically, were jazzed by the intriguing array of smells outside. The happy animal could quickly pick out the odor he wanted to check out first.

Now researchers are trying to mimic the intricate sniff analysis that goes on in the dog's nose--and brain.

The first electronic odor-detection device--quickly dubbed the artificial dog nose--came on the technological landscape about 20 years ago. Since then, artificial noses have been used in various industries, including perfume development, beer processing, environmental monitoring, and health care.

Increasingly, scientists are working to improve the acuity of such electronic noses for wider use in situations that are less controlled and more hazardous (i.e., bomb detection land mines, or toxic chemicals). In addition to keeping canines and their trainers out of harm's way, the devices can offer more dependable readings.

Bomb detection, for instance, is now aided by dogs--with some drawbacks. "Dogs have to be trained and the answers they give require some interpretation," explains Carey Priebe, associate professor of mathematical sciences. "That's why we have automation. It doesn't get tired. It doesn't need breaks."

As of yet, the devices, also known as E-noses, still can't match the varied odor detection and complicated processing done by humans or their olfactory superiors--dogs, which can detect concentrations of odorants down to parts per trillion. The problem of replicating that accuracy leads to some very complicated high-math statistical analysis and a $500,000, two-year research grant won by Priebe.

Priebe, aided by Hopkins math science students, is now analyzing data collected from a fiberoptic-based artificial dog nose created by researchers at Tufts University. That device was developed to detect various chemicals, including trichloroethylene or TCE, a carcinogenic industrial solvent sometimes found in groundwater.

In basic terms, the Tufts artificial nose works like this: The tips of 19 fibers in a fiberoptic cable are treated with dyes that become more intense in color when exposed to certain chemicals. Number 1 fiber may illuminate, for example, if TCE is detected in the sample. The process, of course, is not that simple. The fibers, just like the olfactory sensory neurons inside the mammalian nose, are cross-reactive, meaning they respond differently depending on other compounds in the sample. Maybe No. 1 doesn't illuminate when kerosene is also present, but 7 and 8 do.

The less controlled the situation, the more sophisticated the means of detection required. Priebe gives the example of a mine-ridden former battlefield. "Who knows what's in the air?" he asks. And factors like moisture, if not taken into account, can dramatically affect efforts to detect, say, TNT.

The fibers in the E-nose device Priebe is evaluating also react differently depending on the concentration of odorants. That means there's a seemingly endless array of patterns that could indicate the presence of a chemical, among other complications.

"One would need millions and millions of observations. We don't have [that], so we have to get clever," Priebe says.

Analyzing the Tufts' TCE database--which contains a high number of fiber illumination patterns for various chemical mixtures and concentrations--requires computer-aided computation. The goal: to find clusters of patterns in various circumstances that show TCE is present.

The project, sponsored by the Defense Advanced Research Projects Agency (DARPA) through the Air Force Office of Scientific Research, is being developed mostly for use in the detection of abandoned land mines. There are also possibilities for use in protecting troops or civilians from chemical weapons or environmental hazards.

The artificial nose could act like the canary in the coal mine, Priebe agrees, but it doesn't have to die to detect the poisonous air.

Above and below: AGN, one emitting a jet from a nucleus.
Top photo by
Duccio Macchetto
Bottom photo by
Alen Bridle

R elativity in action

When astronomers look at very old light emitted eons ago by very young and now distant galaxies, they sometimes find something remarkable: energetic central objects so powerful that the energy they emit may be 1,000 times brighter than the energy emitted by all the galaxy's stars combined. These objects are called active galactic nuclei. Julian Krolik has written the book on them.

Krolik, Hopkins professor of theoretical astrophysics, recently published Active Galactic Nuclei: From Central Black Hole to the Galactic Environment (Princeton University Press, 1999), one of the defining textbooks on the subject. In it, he surveys all that is known about AGN, as astronomers call them. He notes that 20 or 30 years ago, astronomers of different stripes were studying what they thought was a variety of phenomena--Seyfert galaxies, quasars, radio galaxies, what Krolik terms "a whole zoo of things"--without realizing that all these sources of energy were the same thing: active galactic nuclei. Krolik's book documents the fundamental unity beyond the sometimes arbitrary and misleading distinctions made over the last few decades. "The different names are a distraction," he says. "The phenomena all probably have the same underlying object, and that underlying object is almost certainly a monumental black hole." Not all black holes are AGN, but all AGN appear to be black holes.

Evidence of AGN was unwittingly collected at least as far back as 1870. But study of them kicked into gear in the 1950s when radio astronomers first began to detect the powerful energy sources. In 1963, researchers discovered, by analyzing the spectrogram of one of these startlingly bright objects, that to their amazement it was quite far away. For something to be both so bright and so distant, it had to be a powerful energy source indeed, more powerful than anything yet encountered, or explained.

Not all AGN are distant; there are some near, and thus more contemporary, examples. The more astronomers study these objects, near and far, the more peculiarities they have found. For example, their energy output can fluctuate dramatically, doubling in a matter of hours; one increased its power a hundred-fold over a period of months. Whereas the radiation from stars is almost entirely visible light, AGN emit the whole spectrum--gamma rays, X-rays, infrared, ultraviolet, visible light. All have been found in the center of galaxies, nowhere else. A minority of them have been discovered to shoot out streams of gas at 99 percent the speed of light.

In the last few years, Krolik says, scientists have been able to begin measuring the mass of AGN. "The first couple of examples have come in at a few tens of millions of solar masses," he says. (The mass of the sun equals one solar mass.) "But we have good reason to believe that the true range is likely to be much broader, both up and down." X-ray astronomy has measured the orbits of material revolving near the centers of AGN at one-third to one-half the speed of light. These and other readings convince astronomers that at the hearts of AGN are black holes; nothing else generates gravitational force strong enough to create such high orbital speed. But much remains to be answered. The lifespans of AGN have not been determined. Does every galaxy, at some point in its existence, have one? Do they just occur in young galaxies? How do they form? Perhaps several ordinary black holes, derived from collapsed stars, somehow merge.

One of the most exciting aspects of studying AGN, says Krolik, is observing places in the universe where general relativity is in action, so to speak. Einstein's theory predicted curvature of space-time by material bodies, the shift of light from receding bodies toward the red end of the spectrum, and deflection of light by gravity. In our corner of the galaxy, Krolik explains, Newtonian physics holds up well in predicting the behavior of matter; deviations predicted by relativity still occur, but they're tiny. But near AGN, he says, the differences between what the two theories predict grow to be very large. Says Krolik, "We can see a region where Newton would be really wrong." In those places, relativity becomes more than just mathematics. It becomes the visible governor of the universe.
--Dale Keiger

Postdocs make progress

Hopkins's postdoctoral fellows, the research "trainees" caught in a sort of lingering limbo between student and professional status, are getting a lot more attention lately.

Since being featured in Johns Hopkins Magazine last February (see "The Postdoc's Plight"), the situation for fellows on campus has improved, especially at the School of Medicine, where several changes recommended by the Johns Hopkins Postdoctoral Assocation (JHPDA)- -in pay, status, and benefits--are being adopted.

Postdoctoral fellows are postgraduate researchers who do two- and three-year stints in labs, ostensibly to learn techniques needed to direct their own research. But, partly because the faculty job market in the sciences has been tight, many of those low-paying fellowships have stretched on for several years.

The postdoc's plight nationwide has sparked several industry and media reports, including a 23-page cover story in the September 3 Science. "People who didn't realize the situation are more aware of it," says Sharyl Nass, former co-vice president of the JHPDA.

New policies adopted at Hopkins this year by the Advisory Board of the Medical Faculty, made up of department heads, put Hopkins ahead of many other universities. Those policies include:

A plan to offer dental insurance to postdocs.

Strict time limits on postdoctoral appointments: three years for an initial appointment, with a maximum of six years total to avoid the "research temp" status of fellows. Any exceptions would require upper-level approval.

An oversight committee in each department that will meet with postdocs to monitor their progress, expanding opportunities for counseling and evaluation.

Salary standards set by the National Institutes of Health, which the School of Medicine follows in setting fellows' minimum salaries, will increase 25 percent (Hopkins will phase in the increases over three years).

Postdocs' status, benefits, and pay elsewhere at JHU also are under review. At Homewood, where a few hundred postdocs work mostly in physics, math, and engineering, a committee appointed by Arts & Sciences Dean Herbert Kessler is discussing a possible postdoc center that could offer counseling, office space, and other amenities, says Gary Ostrander, associate dean for research at Arts & Sciences.

Meanwhile, the lobbying continues. The JHPDA this summer submitted a detailed policy proposal to Hopkins administrators that includes other demands: standard contracts that specify pay and responsibilities; access to career counseling, as well as an ombudsperson to mediate disputes. The advisory board supports these ideas, and a career counseling office is now being planned.

"I think we have helped to empower and incorporate them into our medical faculty," says Levi Watkins Jr., the medical school's associate dean for postdoctoral programs, who has supported postdocs' progress since the early 1990s. "We are going to continue with the changes."