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The Soul Of A New Knot


Developments to Watch

The Soul of a New Knot

WHEN RESEARCHERS AT THE CAVENDISH LABORATORY IN CAMBRIDGE, ENGLAND, DECIDE TO TIE ONE ON, THEY TAKE THE JOB SERIOUSLY. Thomas M.A. Fink and Yong Mao, seeking a fashion breakthrough, used computer models to find all the knots men might use to fasten their neckties. The researchers report in Nature that they came up with 85 of them. Taking into account aesthetic concerns such as symmetry and balance, the scientists were left with 10 knots--six of which have never been seen on Madison Avenue or Bond Street.

To study knot-tying, Fink and Mao defined the process as a series of half-turns initiated by bringing the wide end of the tie either over or under the narrow end. Subsequent moves had to obey two rules: With each half turn, the wide end of the tie must alternate between moving toward the shirt or away from it. And the wide end cannot move in the same direction--right, left, or center--two times in a row.

The last time a new knot appeared was in 1989 when the pratt knot made its debut on the front page of The New York Times. So far, the six Cavendish lab knots are nameless, but any one of them could become a runaway fashion hit.EDITED BY ELLEN LICKINGReturn to top

Zapping the Salt out of Seawater

ALTHOUGH 80% OF THE EARTH'S SURFACE IS WATER, MOST OF IT IS UNSUITABLE FOR DRINKING AND IRRIGATION. Many cities rely on technology to supply their inhabitants with water clean enough to drink. But, especially in the Middle East and North Africa, communities are struggling to meet the high price of purifying water. Now, engineers from the Lawrence Livermore National Laboratory may have a solution: They have developed a purification technology called capacitive deionization that uses 25% to 35% less energy than reverse osmosis, the leading competing technology. Because there are no moving parts to service or filters to change, the system is also cheaper to maintain than other purification systems.

The new technology is composed of stacks of foam bricks, each roughly 1 foot square and 8 inches tall, that themselves contain multiple cells. Each cell operates like a battery, with a pair of pancake-thin electrodes that are coated with a porous carbon material called aerogel. When a small electrical charge--just 1.2 volts--is generated across a pair of electrodes, impurities such as salts, heavy metals, and radioactivity are drawn out of the water and into the aerogel.

Once the aerogel is saturated, the electrodes are shorted, releasing the trapped pollutants into a stream of waste water. A stack of three bricks can remove salt from one liter of seawater in less than 30 minutes. The technology is now being commercialized by FarWest Group Inc., based in Tucson, Ariz. Its first project will be to clean up brackish water at a municipal plant in Carlsbad, Calif.EDITED BY ELLEN LICKINGReturn to top

Windshield Wipers for Mars

DURING ITS 1997 MISSION, MARS PATHFINDER WAS NO MATCH FOR THE STREAMS OF DUST THAT QUICKLY BLANKETED ITS SOLAR CELLS. Now, researchers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., have found a way to bust the dust: They have devised lightweight, flexible strips of plastic that bend, much like human fingers, when an electric voltage is applied. NASA plans to use these so-called electroactive polymers (EAPs) to make energy-efficient windshield wipers.

The JPL team, led by Yoseph Bar-Cohen, is designing two ribbon-shaped EAPs to go on a palm-size rover that will explore the Nereus asteroid, located near Mars, in 2002. Equipped with tiny brushes, the EAPs will clear the dust off the vehicle's camera window. They are lighter and consume less energy than than conventional, motor-driven wipers.

The team's next step, says Bar-Cohen, is to build a prototype where the plastic strips work together like the fibers of a muscle, stretching or shortening in order to pick up or drop small objects. The result will be a miniature robotic arm that is strong enough to handle soil and ice samples weighing tens of pounds. Someday, NASA scientists say, the technology could be used to create insect-like robots for space exploration, or even to replace damaged muscles in humans.EDITED BY ELLEN LICKINGReturn to top


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