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WIEGNER

With CAP Packaging, Tomorrow's Bargain Could Be 100-Day-Old Bread

June 24, 1996|KATHLEEN WIEGNER

The day-old bread that stores sell at a cut rate may eventually go the way of the pickle barrel and penny candy.

According to researchers at the Technion-Israel Institute of Technology in Haifa, packaging bread in a gas mixture of 95% carbon dioxide and 5% oxygen will preserve the fresh taste of the bread for 100 days--without the use of chemical preservatives. Packaging cake in this gas mixture will preserve it for six months.

Keeping food edible for extended periods has traditionally been done either with chemical agents or airtight packaging. But controlled atmosphere packing, or CAP, is gaining attention.

Enriching the atmosphere in airtight packing with carbon dioxide prevents the growth of microbes, particularly molds, and retards staleness. Adding oxygen to the mix prevents the growth of harmful bacteria. Along with baked goods, CAP can be used to extend the shelf life of other low-acid foods, such as cooked meat, salads, spreads and dips.

Because little is known about how carbon dioxide preserves certain foods, there has been no way to efficiently and economically use it industrially. That's why researchers on at Technion are experimenting with bread, cake, grapefruit juice and chopped liver to see exactly what combination of food, packaging material and gases yields the best results.

Hi-Ho, Silver

One of the goals of companies trying to commercialize high-temperature superconductors has been to spin these materials into long, flexible wires. Wires made of superconducting materials could carry electricity with no resistance, vastly improving the performance of electrical motors, generators and transmission cables.

It has not been an easy task. That's because superconducting materials are not metals but ceramics, making them brittle and hard to handle. Now researchers at the Energy Department's Argonne National Laboratory and the University of Pittsburgh have developed a manufacturing process that may make it practical to manufacture these wires.

The new approach is based on an important refinement of the "powder-in-tube" method of making wire, in which high-temperature superconducting powder is sealed inside a silver tube and the tube is drawn and rolled into a wire. However, researchers found that the super current in these wires flowed almost exclusively through the layer closest to the silver casing.

Following a University of Pittsburgh design, Argonne researchers inserted a silver wire into a silver tube and filled the space in between with superconducting powder. After the wire was drawn and rolled, it was found to carry enough current for practical applications.

Argonne and the university are working with Intermagnetics General Corp. of Latham, N.Y., to make and test longer lengths of wire.

Cuppa Coolant

Gravity--it's not just a good idea, it's the law, as the old engineering joke goes. General Electric Co. thinks gravity is a good idea when it comes to nuclear reactors. The company is making use of gravity in a proposed design for a generation of simplified boiling-water nuclear reactors. The design relies on gravity rather than mechanical pumps to circulate coolant through the reactor during its normal operations. Without coolant, the reactor's core would overheat, causing a meltdown. The reactor's passive safety systems would also depend on gravity to automatically drain pools of water into the reactor in case of an accident.

The reactor, a scaled-down version of which is being tested at Purdue University's School of Nuclear Engineering, works something like a coffee percolator. In a percolator, steam and water rise because of buoyancy in the central pipe, they mix with the coffee, then flow back down outside the pipe. In the reactor, the nuclear core where heat is produced is submersed and surrounded by water. Above the core is a mixture of water and steam that is only one-tenth as dense as water.

The combination of gravity, density differences and the pressure of the dense water surrounding the core causes this mixture to circulate upward without pumps. At the top of the reactor, the steam and water mixture separates. The water flows back down while the steam goes out to power turbines.

Don't worry that the students will destroy Indiana as they test for accident possibilities: Their reactor uses electric heating elements, not fissionable materials.

Picture This, Quickly

Watching images from the World Wide Web develop on your computer screen can be akin to watching paint dry or grass grow. The wait often seems endless. Two astronomers have come up with a new software code that has the potential to deliver those images 10 to 100 times faster.

The software was developed by Jeffrey Percival of the University of Wisconsin and Richard White of the Space Telescope Science Institute in Baltimore.

Because astronomers now do remote observation, they need a fast way to send detailed pictures taken by modern telescopes using phone modems. That way an astronomer in Wisconsin remotely using the new observatory on Kitt Peak in Arizona can be sure the telescope is pointed at the right star cluster.

Using a standard modem, the software developed by White and Percival gives astronomers highly detailed images in less than a minute. To achieve this speed, the software uses a form of compression called wavelet transform, which compresses and rearranges images in such a way that only the most important information is sent first. This allows the computer to quickly build a quality picture. The image then improves over time as the vastly larger amount of less relevant information is transmitted.

The software could eventually be available for downloading from the Web.

Freelance writer Kathleen Wiegner can be reached at kkwrite@aol.com

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