SCIENCE: LAB NOTES

Bi-weekly news from the world of science

THE MYSTERIOUS FATE OF ALEXANDER THE GREAT

An ancient conspiracy theory held that rivals poisoned Alexander the Great, who died unexpectedly in 323BC at the age of 32. But new analysis reveals that Alexander probably fell victim to typhoid fever. Infectious disease expert David Oldach of the University of Maryland and historian Eugene Borza of Pennsylvania State University were puzzled by the historical accounts which stated that Alexander's body did not begin to decay until days after his death. Oldach and Borza believe the conqueror probably succumbed to ascending paralysis, a complication of typhoid fever that can slow down a person's breathing and create the semblance of death.

CAPTURING ELECTRICITY WHATEVER THE WEATHER

Thermophotovoltaics is the process of drawing useful amounts of electricity directly from radiant heat. Its major advantage is that it can operate at night or when the sky is overcast, thereby eliminating the need for batteries to store electricity. It is also substantially more efficient than electric generators powered by natural gas or other fossil fuels.

At the heart of a thermophotovoltaic device is a converter cell, made from semiconductor materials not unlike those used in microchips. When photons of infrared energy (ie heat) strike the crystalline lattice in the converter cell, they dislodge electrons which can then be funnelled into circuitry. Work on thermophotovoltaics has been progressing for decades; the great stumbling block in development has been that the components of early systems could not channel enough heat to the conversion units. However, new materials have recently catapulted the technology forward.

Thermophotovoltaics is about to reach the commercial marketplace. J X Crystals, based in Issaquah, Washington, is building a propane-powered cylindrical generator 14cm wide by 43cm tall that will produce 30 watts of electricity. It is aimed at the sailboat market; the device could recharge batteries used for navigation and other electrical equipment. The unit would not only provide electricity, it would also function as a space heater. At $3,000, the device is more expensive than a conventional diesel generator, but has the advantage of running silently and reliably because it has no moving parts.

Other applications for thermophotovoltaic generators are under development, including small power units that would supply electricity to remote areas or roving military troops. The technology could also one day assist with hybrid electric vehicles, in which an electric battery complements the power from an internal combustion engine.

THE WORLD UNDER FIRE?

Every year, fires scorch some 175 million acres (71 million hectares) of forest and grassland worldwide. In 1997, drought brought on by El Nino exacerbated fires around the world - many of which were deliberately set to help clear land for agriculture.

According to a 1997 report by the World Wildlife Fund, Indonesia alone lost 2 million hectares to the flames. The devastation was particularly extreme because of the worst drought the country had seen in 50 years. Fires in the Amazon, Mexico, Florida and elsewhere promise to make 1998 another record year. Now the National Aeronautics and Space Administration has teamed up with the National Oceanic and Atmospheric Administration to provide weekly updates on fires the world over. Information can be found at http://modarch.gsfc.nasa.gov/fire_atlas/fires. html on the World Wide Web.

! Items are adapted from 'Scientific American' magazine. Copyright 1998, Scientific American, Inc. Visit the 'Scientific American' website at www.sciam.com. All rights reserved