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991.
Roy A. Vandermeer 《Metallurgical and Materials Transactions A》1976,7(6):871-878
The uranium +7.5 wt pct niobium +2.5 wt pct zirconium alloy when quenched from 1073 K was found to exist at room temperature
as a metastable phase which was a slight tetragonal distortion of the elevated temperature body-centered-cubic (bcc) phase.
Flat, asquenched specimens have been elastically deformed in four-point bending to maximum outer fiber stresses below the
stress required for plastic deformation to occur but into a range of stress where pseudoelastic behavior has been observed.
Aging of these elastically bent specimens in an oil bath at 423 K, while constrained by the bending jig, resulted in a permanent
deflection and shape change. Further isothermal aging, after removal from the bending apparatus, caused increasing deflection
and continued shape instability in spite of the absence of the applied load. X-ray examination of samples cut from a bent
and aged specimen revealed important preferred orientation and lattice parameter differences between the tension and compression
regions and the high and low stress parts of the specimen. These observations are described and compared to previous findings
on quenched samples of this alloy that had been either deformed separately or aged separately. A rationalization of the shape
instability is presented. Elastic twin nucleation and growth, preferred orientations, solute segregation and the interplay
of all these seem to be involved. 相似文献
992.
The proline residue in position 7 of oxytocin occupies one of the four corner positions in the two beta turns proposed for the preferred conformation of the pituitary hormone. It has been suggested that synthetic modifications of the residues in these corner positions will yield analogues in which one or more of the biological activities of the parent hormone is highly accentuated in terms of potency relative to other activities. In a continued effort to test this hypothesis the following analogues of oxytocin were prepared: [7-glycine]oxytocin, [1-beta-mercaptopropionic acid,7-glycine]oxytocin, [7-alanine]oxytocin, and [1-beta-mercaptopropionic acid,7-alanine]oxytocin. These peptides were found to possess the following specific activities, respectively: rat uterotonic, 65 +/- 2, 355 +/- 3, 22 +/- 1, 123 +/- 4; avian vasodepressor, 5.3 +/- 0.8, 17 +/- 0.4, 4.8 +/- 0.1, 9.8 +/- 0.5; rat antidiuretic, less than0.01, 0.062, 0.081 +/- 0.01, 0.17 +/- 0.01; rat pressor, 0.3, 0.5, 0.4, 0.5 unit/mg. Thus the analogues retain high uterotonic activity but exhibit strongly diminished renal and vascular activities relative to oxytocin. Especially noteworthy is [1-beta-mercaptopropionic acid,7-glycine]oxytocin with its high uterotonic activity but very low antidiuretic and pressor activities. The activity profile of this analogue combined with the fact that it is only slowly enzymatically degraded warrants further investigations of this peptide for clinical applications. 相似文献
993.
The trapping coefficient for hydrogen in Ti has been measured in the energy range from 300 eV to 8 keV and was compared with the trapping coefficient of Zr. In accordance with theory the trapping coefficient for Ti is higher than for Zr in the investigated energy range. The values for both materials fairly agree with computer calculations. Deviation has been found for Ti below 1 keV and for Zr below 1.5 keV. Room temperature irradiation produced swelling in the Ti target, most probably due to hydride formation. 相似文献
994.
Clarifies the authors' systematic distortion hypothesis (SDH) with reference to the J. Block et al (see record 1980-29222-001) critique. The "bipolar redundancy" effect is found to be an artifact of reduced variance in matrices of uncorrelated traits. It is contended that the SDH remains well supported and that the evidence for the existence of covarying, memory-based ratings remains dubious. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
The authors study the switching network structures with emphasis on the information theory aspects of the problem (definition of combinatorial power and complexity). Different routing rules and rearranging algorithms are surveyed. Finally, a numerical simulation points out the extensivity concept which is useful in the study of switching networks models of reduced size. 相似文献
996.
997.
998.
Kiecolt-Glaser Janice K.; Glaser Ronald; Williger Daniel; Stout Julie; Messick George; Sheppard Sharon; Ricker Denise; Romisher Stephen C.; Briner William; Bonnell George; Donnerberg Roy 《Canadian Metallurgical Quarterly》1985,4(1):25
Assessed the enhancement of immunocompetence by relaxation and social contact in 45 60–88 yr old geriatric residents of independent-living facilities. Ss were randomly assigned to 1 of 3 protocols: (1) relaxation training, (2) social contact, or (3) no contact. Ss in the relaxation and social-contact conditions were seen individually 3 times/wk for 1 mo. Blood samples and self-report data were obtained at baseline, at the end of the intervention, and at a 1-mo follow-up. At the end of the intervention, Ss in the relaxation group, who had been taught progressive relaxation and guided imagery as an active coping skill, showed a significant increase in natural killer cell activity and significant decreases in antibody titers to Herpes simplex virus and self-rated distress. The other 2 groups showed nonsignificant changes. There was a general increase in the T-lymphocyte response to phytohemagglutinin stimulation at the end of the intervention, with greater change at lower mitogen concentrations. Data suggest that cellular immunocompetence may be enhanced by psychosocial interventions. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
The series method of Chen and Chen is re-examined and applied to a variety of redistribution problems. It is seen that this analysis can play an important role in deriving closed-form solutions of the diffusion equation useful in semiconductor technology. In particular, series solutions are formulated for two alternative Si/SiO2 interface boundary conditions. Moreover, taken in conjunction with the Euler transformation it is shown to provide exact solutions to several redistribution problems for a wide class of initial dopant profiles and for realistic diffusion times. All solutions have been compared where ever possible with existing analytical techniques, and in all other cases reference has been made to results obtained from the numerical Crank-Nicolson technique. 相似文献
1000.
A naturally occurring 1.4 nm tobermorite and a synthetic jennite were characterized by 27Al and 29Si magic angle spinning nuclear magnetic resonance (MASNMR) spectroscopy and their cation exchange properties were measured. 27Al MASNMR spectroscopy revealed that both the 1.4 nm tobermorite and synthetic jennite contained trace quantities of Al in tetrahedral coordination. The 1.4 nm tobermorite also contained octahedrally coordinated Al probably due to the presence of an aluminum compound as a trace impurity. The 29Si MASNMR spectrum of 1.4 nm tobermorite exhibited a strong resonance at −85.2 ppm and a small shoulder at −80 ppm which are attributed to chain middle groups (Q2) and end groups (disilicates) respectively. 29Si MASNMR spectroscopy of the synthetic jennite showed a strong resonance at −85.7 ppm and a moderately strong resonance at −81.4 ppm which correspond to single chains and end groups respectively. Jennite showed a considerably larger quantity of end groups than the 1.4 nm tobermorite. The unsubstituted 1.4 nm tobermorite and synthetic jennite exhibited only small cation exchange capacities. 相似文献