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31.
Deborah C. Blaine John D. Gurosik Seong Jin Park Randall M. German Donald F. Heaney 《Metallurgical and Materials Transactions A》2006,37(3):715-720
Sintering experiments with various molybdenum powders are rationalized using a master sintering curve concept that collapses
density, grain size, or other parameters onto a single curve. In this case, the integral work of sintering is developed and
customized for different green densities. Construction of the master sintering curve is described to show how the curve can
be normalized with respect to green density effects. Various grades of molybdenum for metal injection molding and die compaction
are included in the analysis, processed over a range of heating cycles. Die-compacted samples of varying green densities are
used to illustrate the efficacy of the new, normalized master sintering curve concept. Sintering cycle optimization is one
possible outcome from this analysis. 相似文献
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MN Janakiraman KD Watenpaugh PK Tomich KT Chong SR Turner RA Tommasi S Thaisrivongs JW Strohbach 《Canadian Metallurgical Quarterly》1998,8(10):1237-1242
Potent, non-peptidic, dihydropyrone sulfonamide HIV protease inhibitors have been previously described. Crystallographic analysis of dihydropyrone sulfonamide inhibitor/HIV protease complexes suggested incorporation of a second, C2 symmetry-related sulfonamide group. Selected bis-sulfonamide dihydropyrone analogues display high HIV protease inhibitory activity. 相似文献
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The lens epithelium of the human eye plays a crucial role in the pathogenesis of primary and secondary cataract. Sixty hematoxylin-eosinstained lens epithelia were examined using a light microscope. Cell parameters were compared to one another in the various age groups of patients, between patients with secondary cataract (radiation cataract, steroid cataract and traumatic cataract) and patients with senile cataract, and between male and female patients. The t-test was used for statistical comparison. The median cell density was 3116.5 cells/mm2. The median nucleus-plasma ratio was 1:2.74. Patients with secondary cataract had a larger medium cell and nucleus area as well as a higher nucleus-plasma ratio and a lower cell density than patients with senile cataract. A part from degenerative and proliferative cell changes we found various cell types. The age of patients and the cause of cataract correlate with morphometric changes of lens epithelium cells. However, there was no correlation between specific cytologic changes and causes of cataract. 相似文献
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Wurman J. Randall M. Frush C.L. Loew E. Holloway C.L. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(12):1861-1872
A bistatic dual-Doppler network consisting of an existing single transmitting pencil-beam weather radar and a remotely located, nontransmitting, passive bistatic receiver with a low-gain antenna was constructed and tested during 1993. High-quality dual Doppler vector winds were retrieved from this system. The windfields were compared with those collected with a traditional two-transmitter dual-Doppler system. Several interesting engineering challenges relating to frequency and timing synchronization were resolved in order to retrieve successfully Doppler velocities at a remote bistatic site. Frequency synchronization was achieved by using extremely stable local oscillators, linked by both Global Positioning Satellite (GPS) signals and transmitter sidelobe coupling. Both methods provided the necessary one part in 109 coherence necessary for calculating accurate Doppler velocities. Timing/gating synchronization with submicrosecond accuracy was achieved by using local oscillators at each site linked with GPS and sidelobe coupling. The successful testing of this system demonstrates that inexpensive and practical bistatic multiple-Doppler networks can be deployed. These systems can provide three-dimensional vector winds for a number of purposes in research, aviation, media, weather prediction, education, meteorological modeling and severe weather detection 相似文献
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Activation of auditory cortex during silent lipreading 总被引:1,自引:0,他引:1
GA Calvert ET Bullmore MJ Brammer R Campbell SC Williams PK McGuire PW Woodruff SD Iversen AS David 《Canadian Metallurgical Quarterly》1997,276(5312):593-596
Watching a speaker's lips during face-to-face conversation (lipreading) markedly improves speech perception, particularly in noisy conditions. With functional magnetic resonance imaging it was found that these linguistic visual cues are sufficient to activate auditory cortex in normal hearing individuals in the absence of auditory speech sounds. Two further experiments suggest that these auditory cortical areas are not engaged when an individual is viewing nonlinguistic facial movements but appear to be activated by silent meaningless speechlike movements (pseudospeech). This supports psycholinguistic evidence that seen speech influences the perception of heard speech at a prelexical stage. 相似文献
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ZR Gan Y Li TM Connolly MK Sardana PK Tsai SD Lewis JA Shafer 《Canadian Metallurgical Quarterly》1993,301(2):228-236
Site-directed mutagenesis was employed to assess the importance of the Arg-Gly-Asp triplet that comprises residues 197 to 199 in the B-chain of thrombin. Properties of the R197E and the D199E variants were compared with those of zeta-thrombin and the inactive S205A variant wherein the active site Ser is replaced by Ala. Relative to zeta-thrombin, the R197E thrombin variant under the assay conditions used exhibits 26% activity toward a small chromogenic substrate, 13% activity in the activation of protein C in the presence of thrombomodulin, < 3% activity in processing fibrinogen, and 1% activity in inducing platelet activation. Thus, the substrate specificity of thrombin was altered by the R197-->E replacement. The D199E variant was essentially inactive. It exhibited only 0.02% of the activity of thrombin toward the chromogenic substrate and its reactivity toward the active site-directed alkylating agent D-Phe-Pro-Arg-CH2Cl was 10,000-fold lower than that of thrombin. Like the inactive S205A thrombin variant, the D199E variant antagonized the interactions of thrombin with hirudin and thrombomodulin, but was a less effective antagonist. The dependence of the antagonism of the thrombin-thrombomodulin interaction on the concentration of D199E thrombin variant provided evidence suggesting the presence of two or more domains in thrombin that independently interact with their counterparts in thrombomodulin. Although the S205A thrombin variant antagonized the action of thrombin on platelets no such activity could be demonstrated for the D199E variant in the concentration range studied (< 800 nm). Comparison of the circular dichroism spectra of zeta-thrombin, the D199E, R197E, and S205A variants indicated that subtle differences in conformation exist between the D199E variant and the other thrombins. These differences in conformation might well account for the altered behavior of the D199E variant with respect to its interactions toward thrombomodulin, hirudin, and platelets. 相似文献
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