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121.
Cho A 《Science (New York, N.Y.)》2004,303(5660):942-943
122.
Cho A 《Science (New York, N.Y.)》2002,295(5562):1992-1993
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Previous measurements of the hydroxyl (OH-) ion content of the calcium phosphate crystals of bone mineral have indicated a substantial depletion or near-absence of OH-, despite its presumed status as a constituent of the hydroxyapatite lattice. Analytical methods for determining bone crystal OH- content have depended on procedures or assumptions that may have biased the results, such as chemical pretreatment to eliminate interference from the organic matrix. We demonstrate a two-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy technique that detects the proton spectrum of bone crystals while suppressing the interfering matrix signals, eliminating the need for specimen pretreatment other than cryogenic grinding. Results on fresh-frozen and ground whole bone of several mammalian species show that the bone crystal OH- is readily detectable; a rough estimate yields an OH- content of human cortical bone of about 20% of the amount expected in stoichiometric hydroxyapatite. This finding sheds light on the biochemical processes underlying normal and abnormal bone mineral metabolism. 相似文献
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Cho A 《Science (New York, N.Y.)》2003,301(5637):1169-1171
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Kyung?Min?Yoo Seok?Won?Lee Jae?Ryoun?YounEmail author Do?Heum?Yoon Young?Eun?Cho Jae-Pil?Yu Hyung?Sang?Park 《Fibers and Polymers》2003,4(2):89-96
A vertebral cage is a hollow medical device which is used in spine surgery. By implanting the cage into the spine column,
it is possible to restore disc and relieve pressure on the nerve roots. Most cages have been made of titanium alloys but they
detract the biocompatibility. Currently PEEK (polyether ether ketone) is applied to various implants because it has good properties
like heat resistance, chemical resistance, strength, and especially biocompatibility. A new shape of vertebral cage is designed
and injection molding of PEEK is considered for production. Before injection molding of the cage, it is needed to evaluate
process conditions and properties of the final product. Variables affecting the shrinkage of the cage are considered, e.g.,
injection time, packing pressure, mold temperature, and melt temperature. By using the numerical simulation program, MOLDFLOW,
several cases are studied. Data files obtained by MOLDFLOW analysis are used for stress analysis with ABAQUS, and shrinkage
and residual stress fields are predicted. With these results, optimum process conditions are determined. 相似文献
129.
In order to investigate the relationship between subjective sensation for fabric sound and touch and the objective measurements,
eight different apparel fabrics were selected as specimens. Sound parameters of fabrics including level pressure of total
sound (LPT), level range (ΔL), and frequency differences (Δf) and mechanical properties by Kawabata Evaluation System (KES) were obtained. For subjective evaluation, seven aspects of
the sound (softness, loudness, pleasantness, sharpness, clearness, roughness, and highness) and eight of the touch (hardness,
smoothness, fineness, coolness, pliability, crispness, heaviness, and thickness) were rated using semantic differential scale.
Polyester ultrasuede was evaluated to sound softer and more pleasant while polyester taffeta to sound louder and rougher than
any other fabrics. Wool fabrics such as worsted and woolen showed similar sensation for sound but differed in some touch sensation
in that woolen was coarsest, heaviest, and thickest in touch. In the prediction model for sound sensation, LPT affected postively
subjective roughness and highness as well as loudness, whileΔL was found as a parameter related positively with softness and pleasantness. Touch sensation was explained by some of mechanical
properties such as surface, compressional, shear, and bending properties implying that a touch sensation could be expressed
by a variety of properties. 相似文献
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