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21.
W. Chen S. -H. Wang R. Chu F. King T. R. Jack R. R. Fessler 《Metallurgical and Materials Transactions A》2003,34(11):2601-2608
A study was carried out to understand the effect of precyclic loading on stress-corrosion-crack initiation in an X-65 pipeline
steel exposed to a near-neutral-pH soil environment. The test specimens were precyclically loaded before corrosion exposure
to represent a service history of up to about 20 years, depending on the severity of pressure fluctuation. Microcracks had
initiated on the polished surface of the X-65 pipeline steel after long-time exposure at open-circuit potential (OCP) in a
near-neutral-pH synthetic soil solution. These microcracks were mostly initiated from pits at metallurgical discontinuities
such as grain boundaries, pearlitic colonies, and banded phases in the steel. Strong preferential dissolution was observed
along planes of the banded structures in the steel. The selective corrosion attack at these metallurgical discontinuities
is attributed to the galvanic nature of those areas to their neighbors. Cyclic loading prior to corrosion exposure had significant
effects on microcrack initiation and propagation during subsequent corrosion exposure. Cyclic loading prior to corrosion exposure
either reduced or increased the probability of crack initiation and the rate of crack propagation, depending upon the magnitude
of the stress cycles. The largest reduction was seen at a peak cyclic stress of about 0.8 of the yield strength. This cyclic-loading-dependent
cracking behavior might be related to the alteration of the substructures and the residual stress in the steel as a result
of precyclic loading. 相似文献
22.
Free and bound hydrosoluble protein extracts were prepared from four anatomical areas of a multiple sclerosis (MS) cerebrum and from corresponding anatomical areas of a normal (non-MS) control. Increased levels of IgG and anti-myelin basic protein antibodies (anti-MBP) were detected in all MS samples and they were undetectable in the controls. IgG and anti-MBP from free (unbound) hydrosoluble protein extracts are defined as free IgG and free anti-MBP while IgG and anti-MBP from tissue bound protein extracts are defined as bound IgG and bound anti-MBP. IgG was purified from free protein extracts by protein G Sepharose affinity chromatography and anti-MBP was further isolated from purified IgG by antigen specific (MBP) Sepharose affinity chromatography. Free and bound anti-MBP were reacted with 20 synthetic peptides of human MBP prepared by the Fmoc method. Free anti-MBP, whether in the context of whole protein extracts, or as purified IgG or as purified antibody was completely neutralized by peptides #12, #15, #56 and #56* containing overall residues 75-106, partially neutralized by peptides #27, #16 and #21 containing overall residues 61-83 and did not react with the remaining 13 peptides. Tissue bound anti-MBP was completely neutralized only by peptides #12, #15, #56 and #56* (overall residues 75-106) and showed no reactivity towards the remaining 16 peptides including peptides #27, #16 and #21. Synthetic peptide specificity of free anti-MBP purified from MS cerebrum was identical to previously reported specificity of free anti-MBP from MS cerebrospinal fluid (CSF), while tissue bound anti-MBP, as well as bound anti-MBP from CSF had a more restricted synthetic peptide specificity than free anti-MBP. This suggests that the most likely epitope of anti-MBP is located between residues 84 and 95 of human MBP just proximal to the tri-proline sequence (99-101). 相似文献
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Cortical implants for the blind 总被引:4,自引:0,他引:4
Arrays of stimulating electrodes can be placed in the brain itself, in the visual cortex, to bring vision to the profoundly blind. However, when designing such devices one needs to take into consideration the fact that the visual pathway maps images onto cortical structures in a complex and unpredictable way 相似文献
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This paper studies a system of partial differential equations modelling the behaviour of a reverse flow reactor. For the parameters appropriate for the oxidation of ammonia on a Pt/Al2O3 catalyst in a typical laboratory set-up, the reactor may be split into regions where approximate formulas that determine its behaviour are deduced. Numerical calculations are presented and can be used to compare with the analytical formulas. The physical insight gained from the asymptotic analysis suggests a new switching strategy which is the subject of numerical experiments. The switching strategy is found to be efficient at minimising the ammonia exiting the reactor after reversal. 相似文献
29.
King Abby C.; Taylor C. Barr; Haskell William L.; DeBusk Robert F. 《Canadian Metallurgical Quarterly》1989,8(3):305
Evaluated 120 healthy, sedentary, middle-aged adults randomly assigned to either a 6-mo home-based aerobic exercise training program or to an assessment-only control condition. Adherence across the 6-mo period by the exercise group was demonstrated by self-report and heart rate microprocessor methods to exceed 75%. A 14-item Likert rating scale was used to measure a variety of psychological variables. Significant between-groups differences favoring the exercise group were found on scale items closely associated with actual physical changes that occurred with exercise (satisfaction with shape/appearance, perceived fitness). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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