Johns Hopkins Magazine -- June 1998
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JUNE 1998

S C I E N C E    &    T E C H N O L O G Y

Making dummies more human-like... "cartography of the universe"... what we hear when we sleep ... yukking it up with engineers... an interstellar "water factory"... measuring brain work

Designing savvier crash test dummies (clockwise from left): APL's Matt Bevan, Bryan Jacobs, Jack Roberts, and Carl Nelson.
Photo by Johns Hopkins Applied Physics Laboratory
Making smarter dummies

A crash test dummy housed in a lab at Hopkins's Applied Physics Laboratory (APL) is getting a makeover. APL engineers are accoutering the poker-faced mannequin with new state-of-the-art optical and magnetic sensors.

"During a crash test, the dummy impacts the dashboard or the steering wheel very fast, in about 15 milliseconds," says APL mechanical engineer Jack Roberts. "We need sensors to pick up displacement of the chest over a very short time. That will tell us how much the chest is going in, which indicates whether ribs are fracturing or breaking, which could lacerate the liver or the lungs."

In conventional crash test dummies, five mechanical sensors in the chest cavity measure chest compression to within 1 to 3 millimeters. To improve on that, the APL team is developing a vest that will contain 10 to 12 magnetic sensors and fit over the dummy's chest. These sensors will measure chest compression to within 0.2 millimeters, and will be five times faster than conventional sensors.

The team also plans to implant magnetic sensors in a brain-like gel in the dummy's head. The sensors will measure shearing forces, which occur when the head rotates at high speed, causing nerves to tear, says Roberts. Damage caused by shearing forces generally does not appear on X- rays or CT scans, but such damage can be severe and even lead to death.

In addition, with funding from General Motors, the team is studying how to build a dummy that will help test another intelligent system, the smart air bag.

Currently in development, smart air bags may, for instance, deploy quickly during a crash if a seat is occupied by a large adult, more slowly and only partially if the seat is occupied by a child, or perhaps not deploy at all if the seat contains a bag of groceries. The system will "know" who or what is in a seat through information gathered by infrared, ultrasound, or laser-based sensors incorporated in the seats, ceiling, or other parts of the car, says Dennis Kershner, director of APL's transportation program development office.

So the APL team is evaluating systems designed to make crash test dummies more human-like. One contender is a heating element that warms the dummy to 98.6 degrees Fahrenheit.

Attempting to mimic the human form can get complicated. For one thing, "crash test dummies are flat on the bottom, not human-like," says Kershner. So if smart air bags ever include sensors in the car seat cushions, these scientists might need to reshape the dummy derrière. --Melissa Hendricks

Overlooking the New Mexico desert: The Sloan telescope
Astronomers begin mapping the universe

In May, astronomers from Hopkins and several other universities and research centers were scheduled to begin the humbling task of mapping the heavens. As planned, the Sloan Digital Sky Survey would turn its 2.5-meter telescope and array of cameras skyward to begin gathering every last glimmer of light in half the Northern Hemisphere.

Over the next five to seven years, astronomers will use these instruments to plot the position of 100 million galaxies and measure the distance from Earth to one million of these. They will produce a map that will help test theories about the grand design of the cosmos, and "how these huge structures formed," says Hopkins astronomer Tim Heckman, Sloan's chief executive officer. "It's cartography of the universe."

Situated on the side of a mountain, 8,500 feet above the New Mexican desert, Sloan contains 54 silicon electronic light sensors called charge-coupled devices (CCDs), attached to a 2.5-meter telescope. The complex of CCDs can take 54 images of the sky at once, in wavelengths ranging from ultraviolet to the near infrared. These images are used to plot galaxy position. In addition, two spectrographs, which were designed and built at Hopkins, are used to measure the precise distance to select galaxies. The spectrographs can analyze 640 galaxies per hour, or several thousand per night, says Heckman.

The amount of data collected by the Sloan Telescope will be enormous--equivalent to the entire contents of the Library of Congress. Hopkins professor of physics and astronomy Alex Szalay is directing efforts to develop intelligent software that will enable astronomers to use the immense data efficiently.

The Sloan Digital Sky Survey Web page is --MH

Illustration by Bonnie Matthews
To sleep, perchance to hear

Waaaaah! A baby cries in the night. One parent is catapulted out of bed, while the other parent continues to sleep peacefully. Not even a jackhammer will rouse some people. What do we hear when we sleep, and are there differences among people?

Hopkins undergraduate Serena Gondek '99 recently took a first step toward answering these questions. Gondek, a biomedical engineering major, pinpointed the region of the brain that apparently processes sound during sleep.

During waking hours, sounds stimulate the auditory cortex, which is located just under the ear, and analyzes basic features of sound, such as pitch, volume, and amplitude. But during sleep, sound also elicits responses from the brain's frontal lobe, Gondek found. She presented her results in April at a meeting of the American Academy of Neurology.

When a person is awake, Gondek explains, "the frontal lobe is involved in screening, deciding whether to physically act." In the sleeping person, she postulates, the frontal lobe may continue to serve as overseer by evaluating a sound and determining its importance. This discrimination may mean that a baby's cry becomes a wake-up call, while pouring rain is a mere background melody.

In the sleeping person, both the auditory cortext (left) and frontal lobe are activated.
Photo courtesy Serena Gondek
Gondek, who collaborated with Hopkins neurologist Gregory Krauss, piggybacked her experiment onto routine preoperative testing of epilepsy patients at Johns Hopkins Hospital. The patients were awaiting surgery to remove neural regions causing intractable seizures. About a week before the operations, neurosurgeons had implanted a grid of electrodes over large sections of each patient's cortex (the surface of the brain). The electrodes are used to determine which neural regions underly the patient's seizures and which are responsible for vital functions such as speech and movement.

On the night before surgery, each patient wore a set of earplugs connected to a sound source that played a variety of low-volume tones throughout the night. At the same time, the electrodes recorded brain activity. In four of the five volunteers Gondek tested, sounds elicited response in the frontal cortex.

Prior to this study, scientists had used electrodes placed on the scalp to explore how the brain processes sleep. But this technique is less precise than placing electrodes directly on the brain, notes Gondek.

Of course, a low-volume "beep" is a far cry from a honking horn or a baby's shrill cry. So during her senior year, Gondek will repeat the experiment using recordings of environmental noise. She also plans to look for gender differences, to see whether certain sounds tickle the brains of some slumberers more than others. --MH

Illustration by Peggy Fussell
Who says engineers don't have a sense of humor?

That's the "all call" for a planned Hopkins Web site devoted to engineering humor. The Whiting School of Engineering is looking for a few good (and tasteful) jokes to share on its Web page, http:/ Two of our favorites so far....

There are three engineers in a car: an electrical engineer, a chemical engineer, and a Microsoft engineer. Suddenly the car just stops by the side of the road, and the three engineers look at each other wondering what could be wrong.

The electrical engineer suggests stripping down the electronics of the car and trying to trace where a fault might have occurred.

The chemical engineer, not knowing much about cars, suggests that maybe the fuel is becoming emulsified and getting blocked somewhere.

Then, the Microsoft engineer, not knowing much about anything, comes up with a suggestion: "Why don't we close all the windows, get out, get back in, then open the windows again, and maybe it'll work?!"

You may be an engineer...

  • If you can quote scenes from any Monty Python movie

  • If you stare at an orange juice container because it says CONCENTRATE

  • If the only jokes you receive are through e-mail

  • If your wrist watch has more computing power than a 486DX50

  • If you look forward to Christmas only to put together the kids' toys

  • If your ideal evening consists of fast-forwarding through the latest sci-fi movie looking for technical inaccuracies

  • If the Circuit City salespeople can't answer any of your questions

  • An infrared satellite detected the unmistakable fingerprint of water in the Orion interstellar gas cloud, shown here in a Hubble Telescope photo.
    Photo by European Space Agency/NASA
    An interstellar "water factory"

    A Hopkins astronomer and his colleagues have discovered "a factory for making water" in a gas cloud in interstellar space. The region produces enough water vapor in one day to fill all of Earth's oceans 60 times, says Hopkins professor of physics and astronomy David Neufeld. Stated another way, "Every half hour, the region generates an ocean's worth of water."

    Neufeld and astrophysicists from Cornell University spotted the water vapor within the Orion molecular cloud, which is along the spiral arm of the Milky Way, 1,500 light-years from Earth. Using the European Space Agency's Infrared Space Observatory ISO satellite, the astronomers observed a concentration of water vapor 20 times larger than what has been seen in other interstellar gas clouds.

    The source of the water appears to be a young star that is in the process of forming within Orion, says Neufeld. "The star throws out material such as hydrogen gas at supersonic speeds," he says. "The material strikes the surrounding molecular gas, which creates a shock wave," causing the gas to be heated and compressed. In the process, oxygen and hydrogen atoms in the gas are converted into water.

    "Conceivably, such a reaction could be a major source of water in the universe," says Neufeld.

    Last year, Neufeld and another team of colleagues reported that, using ISO, they had discovered trace amounts of hydrogen fluoride gas in an interstellar gas cloud in the constellation Sagittarius (Hopkins Magazine, November 1997). --MH

    A new theory precisely links brain functions, such as cerebral blood flow (CBV) to changes seen in MRI.
    Photo courtesy Peter Van Zijl
    Measuring brain work

    When a promising imaging technique called fMRI was introduced eight years ago, clinicians and neuroscientists gleefully embraced the new technology for its exquisitely detailed images of the brain at work.

    Functional MRI, as its name implies, enables researchers to observe anatomy plus functional changes in the brain--changes that occur, for instance, when a person taps his finger or looks at a bright light. In contrast, traditional MRI basically depicts the anatomy of the brain (or another organ being visualized).

    However, scientists have not been able to explain precisely how fMRI works.

    "The problem was that no one could say what was happening quantitatively," says Hopkins professor of radiology Peter van Zijl.

    So van Zijl and his colleagues recently developed equations that provide that explanation. Having this quantitative grasp of fMRI could greatly expand the research possibilities of this new tool.

    "By doing these extra tests in this precise way, we go from anatomy to physiology," says Scott Eleff, an associate professor of anesthesiology who collaborated with van Zijl. "We'll be able to say not just that this particular area of the brain is being used, but how much, or how much less, it is being used. Scientists may also be able to measure differences between thinking and thinking harder.

    Moreover, the theory may even expand fMRI's use as a clinical tool, helping physicians identify changes in the brain that foreshadow stroke, for example. And techniques could also be applied for studying disease in other regions of the body, such as the heart, says Eleff.

    Other collaborators include Hopkins anesthesiologists John Ulatowski and Richard Traystman, and researchers from the University of Kuopio, in Finland.

    With traditional MRI, a person lies very still in a tubular magnet while a strong magnetic field is applied, which causes protons in the body to line up in the direction of the field. The magnetic field then changes, based on where protons are located-- a change that is translated into an MR image.

    The result: a snapshot of the brain, or heart, or leg. Doctors use MRI for numerous diagnoses, from looking for tumors to analyzing heart attack damage.

    Over the past several years, researchers discovered that MRI can also reveal tiny fluctuations in physiology. For example, looking at a bright light increases activity in the visual cortex. Scientists then developed MRI methods that highlight these very tiny functional changes. One of these techniques is called BOLD, or blood-oxygen-level dependent fMRI.

    Scientists recently concluded that the effects seen in BOLD fMRI reflect changes in the concentration of hemoglobin in the blood supply to the brain. But not until van Zijl's study had anyone demonstrated the mathematical equations that describe this relationship. --MH