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IAP Notebook

MIT sleuths on trail of missing benzene

Call it "The Case of the Missing Benzene."

The scene of the "crime" is the Halls Brook Storage Area, a lake in the Aberjona watershed near Boston. At a January 12 IAP talk, Ford Professor of Engineering Philip Gschwend explained how during World War I, the production of explosives near the lake also polluted the area -- and eventually the lake -- with benzene, a component of the explosives and a known carcinogen.

But when Professor Gschwend and colleagues in the Department of Civil and Environmental Engineering (CEE) began studying the benzene in the lake, they made a surprising discovery: although benzene flows into the lake every day via groundwater, the total amount present was less than expected. Only small quantities of the chemical flow out of the lake or go into the atmosphere, Professor Gschwend said, so where is the missing benzene?

The researchers may have solved the mystery. It appears that bacteria present in the lake could be gobbling up the chemical. These bacteria, which primarily dine on methane, "can also use their enzymes to degrade a lot of other things -- like benzene," Professor Gschwend said. Another possible explanation: a chemical reaction between the benzene and hydroxyl radicals (from hydrogen peroxide) in the water.

"We think the [bacteria] are a better explanation than the hydroxyl reaction, but we haven't proven it," Professor Gschwend said.

The talk was part of a series called "Environmental Perspectives: Research at MIT" sponsored by CEE and the student group Share a Vital Earth (SAVE).

-Elizabeth Thomson

Return trip for hacks

The police car placed on top of the Great Dome in 1994 by ingenious hackers was re-assembled and displayed under the Little Dome in Lobby 7 on January 15, considerably brightening a dreary, snowy day.

The effort was the centerpiece of an IAP project to publicize the special Hack Flashback exhibit at the MIT Museum, which continues through this weekend. The car, carefully broken down the previous evening and transported in sections to Lobby 7 in the morning, took about an hour to reassemble. It was tedious work.

"I don't think you'll see us doing it again," said Museum Director Jane Pickering. "The pieces are really quite fragile and we want to preserve them. It is the epitome of all hacks."

The car, complete with flashing lights, uniformed mannequin and a half-eaten box of donuts, was the center of attention in Lobby 7 from 10am-4pm. It was then taken apart and returned to the Museum's IHTFP Gallery, where it was reassembled once again for the special exhibit.

Hack Flashback and The MIT Hall of Hacks are on view at the Museum's main exhibition center at 265 Massachusetts Ave. Hours are 10am-5pm on weekdays and noon-5pm on Saturday and Sunday. Admission is free to members of the MIT community.

-Robert J. Sales

Catching those Zs

"We're not very good at determining whether we're awake or asleep," said John Winkelman, a sleep researcher at Brigham and Women's Hospital who taught "Zzzzzz: All About Sleep."

Seventy-five years ago, sleep was defined as the absence of wakefulness, he said. Now researchers define it as the absence of alpha waves. Oddly enough, people whose EEGs clearly indicate a state of sleep will claim 50 percent of the time that they were actually awake.

Dr. Winkelman went over the main stages of sleep: REM (rapid eye movement) and non-REM (four stages of increasing depth requiring greater external stimulation to awaken), and he talked about common sleep disorders.

The main culprits of sleep disturbance are "the legal drugs -- caffeine and alcohol," he said. "Coffee is used irresponsibly. After dinner at a restaurant they shouldn't ask if you want coffee. If they said, 'Can I get you 5mg of Ritalin and a cup of warm water?' would you say 'Yes'?" He also recommended not drinking either alcohol or caffeine within six hours of bedtime.

Because sleep requirements and habits are a function of age, so is the need to nap, which decreases during childhood and then begins a slow climb. The average 20-year-old takes one nap in an eight-week period, a 35-year-old takes four, and a 50-year-old takes six. The differences, he speculates, are based on a breakdown of the internal clock.

-Denise Brehm

Mach, MIGs and Gs: Flying an F-15

Chasing an F-15 fighter plane down a runway in a panel truck may not be most people's idea of a good time, but for a couple of dozen aero/astro majors, it was downright exhilarating.

Air Force Col. Peter Young of aero/astro arranged three IAP trips to Otis Air National Guard Base near Falmouth, where students were given the enviable opportunity of viewing these incredible flying machines close-up. They learned what it's like to prepare for and fly a mission, watched the $20 million aircraft take off and land, and even got to sit in the cockpit of an F-15 in the hangar.

Capt. Gary Cundiff, a former Air Force pilot who now flies for the Air National Guard, spent half a day hosting the students and describing the capabilities of the F-15A Eagle and how it differs from its counterparts in other countries, as well as from the older F-14s and newer F-16s.

He said that training is key to winning battles, even when up against a plane with a superior characteristic, like the Russian MIG's 180-degree viewing angle. On average, a US Air Force pilot flies about 200 hours each year. The average Russian flies only 50. (It costs about $10,000 an hour to fly the Eagles, he said.)

"If you've watched any movies with fighter planes -- like Top Gun -- you're probably real confused about how we actually fight," said Capt. Cundiff as he outlined a few of the tactics used by pilots when they enter a "merge" with an enemy aircraft. The Navy pilots in that movie flew two-seater F-14s. By contrast, F-15s are designed specifically for air-to-air encounters and carry a single pilot, who has to manage everything alone.

The fighters carry three types of missiles and a six-barrel gun that fires high-incendiary explosives at 100 rounds per second. They fly up to Mach 2.5 (two and a half times the speed of sound) and accelerate up to 9 Gs.

By contrast, a passenger in a commercial aircraft at takeoff feels about 1.2 Gs; a sports car rounding a curve hits about an eighth of a G. In an F-15 at 8 Gs, a 20-pound helmet weighs 120 pounds. During an acceleration, "I can't lift my arm at all. I can move my fingers on the stick, but that's about it," said Capt. Cundiff.

Most pilots are between 23 and 35. "It's a young man's game. When you get older, you just can't take the Gs," he said.

-Denise Brehm

A version of this article appeared in MIT Tech Talk on January 27, 1999.

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