Uniformity of Rocks at Lower Levels of Deep Boreholes May Facilitate Burial of Radioactive Waste
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ceria crystals are anchored to the BHA and are separated from one another, even at very high temperatures they cannot fuse together. The ceria-coated BHA has a light-off of just about 400°C and can withstand temperatures higher than 1100°C. The catalyst is stable in the presence of water vapor and other potential poisons. “This combination of low-temperature catalytic activity, high-temperature thermal stability, and poisoning resistance renders our catalysts interesting for potential practical applications in ultralean catalytic combustion of methane,” the authors conclude. Ying said that the procedure for creating the material paves the way for materials that could improve other high-temperature processes such as the production of some chemicals.
Positrons Help Locate Nano-Surface Defects in Gold In a paper published in the November 29 issue of Physical Review Letters, a team from Oak Ridge National Laboratory, Lucent Technologies, Fisk University, and Japan’s Electrotechnical Laboratory document an experiment using positrons to find clusters of four atomic vacancies at the surface of gold nanoparticles embedded in a magnesia matrix. These clusters of vacancies explain changes in the optical properties when the materials are subjected to different fabrication processes. Positrons were generated by smashing gamma rays against a tungsten target. The gamma rays divide into negatively charged electrons and their antimatter, positrons. The decay of unstable sodium22 provided an alternative source of positrons. The positrons are injected into the gold nanoparticles, and through advanced spectroscopy, the researchers are able to determine the size, location, and concentration of the vacancy clusters. According to the researchers, possible future applications for this work include higher-speed computer chips than available now, manipulation of the properties of optical devices, less brittle ceramic material than currently available, and improved fiber-composite materials than currently available.
Spray-on Skin of Polymer Fibers May Allow Wounds to Heal Without Scarring Researchers at Electrosols, a biotechnology company based in Haslemere, Surrey, United Kingdom, have developed a spray that could help wounds heal without scarring. The spray produces a fine web of biodegradable polymer fibers that collagen-making cells called fibroblasts can MRS BULLETIN/MARCH 2000
grow on. As more and more fibroblasts grow on the polymer webbing, they produce a regular collagen structure, much like that in normal skin. Electrosols researcher Ron Coffee believes that controlling the formation of collagen in this way will lead to normal skin growth instead of scarring. As reported in the January 8 issue of New Scientist, to make the spray, Coffee mixes ethanol and a biodegradable polymer—such as polylactic acid—in a small semiconducting container, and then gives it an electric charge by putting an electric field across the container. Because the wound is at a far lower electrical potential than the polymer, the solution is attracted to
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