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The Cutting Edge: Computing / Technology / Innovation : Copying Chlorophyll Conversion

Nature easily beats any human efforts to capture energy from the sun: Nothing matches photosynthesis, the process by which plants use chlorophyll to convert light into food.

A study by a University of Southern California chemist shows that a purple bacteria found in pond scum uses light energy with almost 95% efficiency--more than four times that of the best manufactured solar cells. By better understanding the bacteria’s energy-conversion process, the chemist, Chi Ho Mak, believes it may be possible to one day re-create it as an artificial solar energy cell.

Mak and Reinhold Egger of the University of Freiburg, Germany, have used a supercomputer to create a model of chlorophyll’s energy conversion process. In the purple bacteria the two studied, photosynthesis began when a special pair of chlorophyll molecules absorbed a unit of green light radiation (a photon). In a reaction lasting only three-trillionths of a second, the chlorophyll transferred a high-energy electron to a nearby molecule of a substance called pheophytin, storing the solar energy in what amounts to a biochemical battery.

A complex series of chemical reactions then converted the energy of the electron into products the bacterium needed to live, grow and reproduce. The research has a long way to go, but it is a first step toward re-creating a photosynthetic reaction center in a manufactured device.

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Running on Air: Student researchers at UC Riverside have come up with a novel twist on that much-sought-after vehicle, the non-polluting, gasoline-free automobile. They’ve developed a modified golf cart that runs on the electricity generated by hydrogen and oxygen in the air around us.

The cart uses a fuel cell originally developed for space applications. When hydrogen stored in a tank comes into contact with oxygen and phosphoric acid, it gives off electrons that are collected in the fuel cell, which then becomes a source of electricity. The only byproduct is water vapor.

The fuel cell promises to be about 2 1/2 times more efficient than the internal combustion engine. The hydrogen itself is produced at UC Riverside’s Solar Hydrogen Research Facility, by a solar-powered electrolyzer that splits ordinary water molecules into individual hydrogen and oxygen atoms. James Heffel, the project manager, believes the hydrogen can be produced for the equivalent of $2 to $3 a gallon.

Such fuel-cell vehicles could meet the zero-emissions standards recently adopted by the California Air Resources Board. In theory, they would have greater range than electric cars that have to be recharged from an outlet.

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The Sound of Location: When bats fly, they send out a sonar signal to guide them along. But how does one bat distinguish its own signal from those of hundreds of other bats around it? The answer to this question has relevance, it seems, not only for mouse-like flying mammals and sonar-guided torpedoes but for electric companies trying to locate downed power lines.

Inspired by the bat’s enviable signal-processing capabilities, Edward Titlebaum, a professor of electrical engineering at the University of Rochester in New York, developed a series of codes for the Navy several years ago. The codes guaranteed that signals from sonar-guided torpedoes remained distinct and did not become crossed.

Now Titlebaum is working with engineers from Rochester Gas & Electric Corp. to apply these codes to help track down faulty power lines. Now utilities must wait for customers to telephone complaining of a downed line. Titlebaum’s idea is to outfit each power line with a transmitter that every so often sends a distinctive signal back to the utility. A missing signal would indicate that a line was down.

Using a family of codes known as hyperbolic congruence frequency hop codes--in which a signal hops across several frequencies per second--Titlebaum was able to create these distinguishable signals. The reason these codes are distinctive is that only one or two frequencies are congruent. A correlation receiver looks for the exact sequence of frequencies it is supposed to receive.

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