Bi 2 O 3 -Coated Zinc Oxide Nanoparticles Yield High-Quality Ceramics
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Want to feel something really weird? Swish your gloved hands around in a vat of magneto-rheological fluid and feel it morph from fluid to solid at the touch of a button. Make a pool of magnetic ferrofluid “dance” and manipulate blobs of ferrofluid with rare-earth magnets. Experience the interactive materials science exhibition:
Virginia Air & Space Center Hampton, VA May 29–September 6, 2004 www.vasc.org
Museum of Discovery and Science Ft. Lauderdale, FL June 11–September 6, 2004 www.mods.org To volunteer for activities with the exhibition, contact Kaveri Chaturvedi Community Resources Coordinator [email protected]
Strange Matter is presented by the Materials Research Society. This exhibition and its tour are made possible by the generous support of the National Science Foundation, Alcan Inc., Dow, Ford Motor Company Fund, Intel Innovation In Education, and the 3M Foundation.
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of the proper unset strand frees the right foot from the middle foothold, although it is still tethered to the left foot (state 2, Figure 1c). The addition of a set strand results in the right foot attaching to the right foothold (state 3, Figure 1d). The flexible linkers must be long enough to extend from the left to the right foothold, a gap of about 2 nm. Similar unset and set steps remove the left foot from the left foothold (state 4, Figure 1e) and attach it to the middle foothold (state 5, Figure 1f). The researchers verified each of the states by illuminating the structures with UV light, which resulted in covalent bonds between single-stranded DNA (due to the presence of the psoralen), and then performing polyacrylamide-gel electrophoresis. Sherman and Seeman said that their device has precise bidirectional control and that a longer gait can be achieved with longer footpaths, which might also accommodate multiple, independently addressable bipeds and multipeds. They said that rotational motion can be achieved with circular footpaths. The researchers envision applications such as the transportation of loads and the winding or threading of polymers. In addition, Sherman and Seeman believe that “algorithmically generated set strands could drive a device on a 2D footpath so that the positions of the feet could represent the state of a DNA-computational machine.” STEVEN TROHALAKI
Bi2O3-Coated Zinc Oxide Nanoparticles Yield High-Quality Ceramics Polycrystalline ceramic zinc oxide (ZnO) varistors, which include an intergranular bismuth-rich phase, are known to show excellent nonlinear current–voltage properties. These materials are typically made by sintering physically mixed precursors and thus often have poor microstructural uniformity and porosity. F. Yuan of the Chinese Academy of Sciences and the Korean Research Institute of Chemical Technology and H. Ryu, also of the Korean Research Institute, have found that sintering ZnO nanoparticles that have been uniformly coated with Bi2O3 results in ZnO ceramic varistors with perfect and homogenous ZnO grains, each of which is completely surrounded by a uniform Bi2O3 layer. As described
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