This study has evaluated the effect of different levels of cold rolling（from 0 to 50%）on the microstructural,magnetic,and mechanical properties and the corrosion behavior of 316L austenitic stainless steel in Na Cl...This study has evaluated the effect of different levels of cold rolling（from 0 to 50%）on the microstructural,magnetic,and mechanical properties and the corrosion behavior of 316L austenitic stainless steel in Na Cl（1 mol/L）＋H_2SO_4（0.5 mol/L）solution.Microstructural examinations using optical microscopy revealed the development of a morphological texture from coaxial to elongated grains during the cold-rolling process.Phase analysis carried out on the basis of X-ray diffraction confirmed the formation of the ferromagneticα′-martensite phase under the stresses applied during cold rolling.This finding is in agreement with magnetic measurements using a vibrating sample magnetometer.Mechanical properties determined by tensile and Vickers microhardness tests demonstrated an upward trend in the hardness-to-yield strength ratio with increasing cold-rolling percentage,representing a reduction in the material’s work-hardening ability.Uniform and localized corrosion parameters were estimated via potentiodynamic polarization corrosion tests and electrochemical impedance spectroscopy.In contrast to the uniform corrosion,wherein the corrosion current density increased with increasing cold-working degree because of the high density of microstructural defects,the passive potential range and breakdown potential increased by cold working,showing greater resistance to pit nucleation.Although pits were formed,the cold-rolled material repassivation tendency decreased because of the broader hysteresis anodic loop,as confirmed experimentally by observation of the microscopic features after electrochemical cyclic polarization evaluations.展开更多
The microstructure and mechanical properties of low carbon bainite high strength steel plate were studied via different cooling paths at the pilot scale. There was a significant increase in mechanical properties, and ...The microstructure and mechanical properties of low carbon bainite high strength steel plate were studied via different cooling paths at the pilot scale. There was a significant increase in mechanical properties, and notably, the yield strength, tensile strength, and toughness at-40 ℃ for the tested steel processed by ultra-fast cooling were 126 MPa, 98 MPa and 69 J, respectively, in relation to steel processed by accelerated cooling. The ultra-fast cooling rate not only refined the microstructure, precipitates, and martensiteaustenite（M/A） islands, but also contributed to the refinement of microstructure in thick plates. The large size M/A constituents formed at lower cooling rate experienced stress concentration and were potential sites for crack initiation, which led to deterioration of low-temperature impact toughness. In contrast, the acicular ferrite and lath bainite with high fraction of high-angle grain boundaries were formed in steel processed by ultra-fast cooling, which retarded cleavage crack propagation.展开更多
The present work is investigated the in-situ monitoring of local corrosion process of scratched epoxy coated carbon steel in saturated Ca(OH)<sub>2</sub> with and without 3% NaCl using SECM and correlated ...The present work is investigated the in-situ monitoring of local corrosion process of scratched epoxy coated carbon steel in saturated Ca(OH)<sub>2</sub> with and without 3% NaCl using SECM and correlated with EIS. The results obtained from EIS analysis showed that the corrosion resistance of scratched epoxy coated carbon steel decreases in Cl<sup>-</sup> containing solution as the increase in wet/ dry corrosion cycles. This was indicated by decrease in film resistance (R<sub>f</sub>) and charge transfer resistance (R<sub>ct</sub>), while the coated steel maintain the resistance values in saturated Ca(OH)<sub>2</sub>, most of which recovered after drying. The corrosion process was monitored using SECM by setting the tip potential at -0.70 V vs Ag/AgCl, where the consumption of dissolved oxygen occurred at the surface of test sample. The consumption of dissolved oxygen current (I’<sub>oxy-c</sub>) values was increased during the immersion in a solution with 3% NaCl. However, in wet/dry corrosion cycles, I’<sub>oxy-c</sub> was decreased due to the coverage of hydroxides/oxides at scratch area which suppressed the consumption of dissolved O<sub>2</sub>. It was found that the continuous decrease in corrosion was mainly attributed to continuous formation of corrosion products at anodic spots.展开更多
Introduction: The purpose of this retrospective study is to identify medical conditions impacting neurodevelopmental outcomes of extremely low birth weight and very low birth weight preterm infants at three years of a...Introduction: The purpose of this retrospective study is to identify medical conditions impacting neurodevelopmental outcomes of extremely low birth weight and very low birth weight preterm infants at three years of age. Methods: Infants born in Banner Diamond Children’s University Medical Center, receiving services in the Newborn Intensive Care Unit, and attending Neonatal Developmental Follow-Up Clinic were identified. Participants received developmental assessment and follow-up from August 2012 through December 2018. Relevant clinical conditions during initial hospital stay and up to three years of age were obtained by reviewing medical and developmental records. Bayley Scales of Infant Toddler Development (Bayley III) was used to evaluate skill development at 6, 9, 12, 18, 24, 30, 36 months. Results: Data analysis did not reveal significant p-values;it did demonstrate that some predictor variables impact neurodevelopmental outcomes in cognitive, language and motor skill development. Conclusion: This retrospective study reports significant association between birth weight and low cognitive scores. Correlations were also found between gestational age and Total Language, and the longer an infant stayed in the NICU, the poorer the Total Language Scaled Scores at 8 to 12 months, 15 to 18 months, and 24 to 36 months. Birth weight was found to be the greatest predictor of poor motor scores.展开更多
Barrett's esophagus (BE) is a metaplastic lesion of the distal esophagus arising as a consequence of chronic gastroesophageal reflux disease. Multiple studies show that BE is associated with increased risk of esop...Barrett's esophagus (BE) is a metaplastic lesion of the distal esophagus arising as a consequence of chronic gastroesophageal reflux disease. Multiple studies show that BE is associated with increased risk of esophageal adenocarcinoma (EAC). Epidemiological studies and animal models demonstrate that chronic inflammation triggered by repeated exposure to refluxate predisposes to the development of BE and EAC. The chronic inflammation is associated with cytokine alterations. Interleukin 6 (IL-6) is a cytokine that stimulates cell proliferation and apoptosis resistance is frequently increased in different cancers. Importantly, IL-6 and transcriptional factor signal transducer and activator of transcription 3 (STAT3) that is activated by IL-6 are also increased in BE and EAC. This review critically appraises the role of IL-6/STAT3 pathway in progression of BE to EAC from the published evidence currently available.展开更多
Background: Ventricular fibrillation and ventricular tachycardia are less common causes of cardiac arrest in children than in adults. These tachyarrhythmias can also begin during cardiopulmonary resuscitation(CPR), pr...Background: Ventricular fibrillation and ventricular tachycardia are less common causes of cardiac arrest in children than in adults. These tachyarrhythmias can also begin during cardiopulmonary resuscitation(CPR), presumably as reperfusion arrhythmias. We determined whether the outcome is better for initial than for subsequent ventricular fibrillation or tachycardia. Methods: All cardiac arrests in persons under 18 years of age were identified from a large, multicenter, in-hospital cardiac-arrest registry. The results from children with initial ventricular fibrillation or tachycardia, children in whom ventricular fibrillation or tachycardia developed during CPR, and children with no ventricular fibrillation or tachycardia were compared by chi-square and multivariable logistic-regression analysis. Results: Of 1005 index patients with in-hospital cardiac arrest, 272(27 percent) had documented ventricular fibrillation or tachycardia during the arrest. In 104 patients(10 percent), ventricular fibrillation or tachycardia was the initial pulseless rhythm; in 149 patients(15 percent), it developed during the arrest. The time of initiation of ventricular fibrillation or tachycardia was not documented in 19 patients. Thirty-five percent of patients with initial ventricular fibrillation or tachycardia survived to hospital discharge, as compared with 11 percent of patients with subsequent ventricular fibrillation or tachycardia(odds ratio, 2.6; 95 percent con-fidence interval, 1.2 to 5.8). Twenty-seven percent of patients with no ventricular fibrillation or tachycardia survived to hospital discharge, as compared with 11 percent of patients with subsequent ventricular fibrillation or tachycardia(odds ratio, 3.8; 95 percent confidence interval, 1.8 to 7.6). Conclusions: In pediatric patients with in-hospital cardiac arrests, survival outcomes were highest among patients in whom ventricular fibrillation or tachycardia was present initially than among those in whom it developed subsequently. The outcomes for patients with subsequent ventricular fibrillation or tachycardia were substantially worse than those for patients with asystole or pulseless electrical activity.展开更多
Nanoindentation measurement was performed to evaluate the local hardness distribution for quenched and tempered martensitic steel with ferrite-cementite constituent. The ratio of standard deviation to the average nano...Nanoindentation measurement was performed to evaluate the local hardness distribution for quenched and tempered martensitic steel with ferrite-cementite constituent. The ratio of standard deviation to the average nanohardness was 15.4% when nanoin-dentation tests were carried out at the peak load of 1000 μN, while that of the Vickers hardness was only 1.5% at 9.8 N. Electron backscatter diffraction analysis and SEM ob-servation all showed that the large scattering of nanohardness did not depend on the crystallographic orientation of each grain but from the inhomogeneous microstructure in the sub-micron scale such as cementite distribution. Compared with the results on tung-sten single crystals with different surface orientations as well as another martensite proc-essed by modified-ausforming with the same chemical composition but more homogene-ous cementite distribution, the nanohardness showed smaller scattering, supporting the conclusion.展开更多
基金Shahid Chamran University of Ahvaz for supporting this research
文摘This study has evaluated the effect of different levels of cold rolling（from 0 to 50%）on the microstructural,magnetic,and mechanical properties and the corrosion behavior of 316L austenitic stainless steel in Na Cl（1 mol/L）＋H_2SO_4（0.5 mol/L）solution.Microstructural examinations using optical microscopy revealed the development of a morphological texture from coaxial to elongated grains during the cold-rolling process.Phase analysis carried out on the basis of X-ray diffraction confirmed the formation of the ferromagneticα′-martensite phase under the stresses applied during cold rolling.This finding is in agreement with magnetic measurements using a vibrating sample magnetometer.Mechanical properties determined by tensile and Vickers microhardness tests demonstrated an upward trend in the hardness-to-yield strength ratio with increasing cold-rolling percentage,representing a reduction in the material’s work-hardening ability.Uniform and localized corrosion parameters were estimated via potentiodynamic polarization corrosion tests and electrochemical impedance spectroscopy.In contrast to the uniform corrosion,wherein the corrosion current density increased with increasing cold-working degree because of the high density of microstructural defects,the passive potential range and breakdown potential increased by cold working,showing greater resistance to pit nucleation.Although pits were formed,the cold-rolled material repassivation tendency decreased because of the broader hysteresis anodic loop,as confirmed experimentally by observation of the microscopic features after electrochemical cyclic polarization evaluations.
基金Funded by National Natural Science Foundation of China(No.51234002)National Key Research and Development Program of China(No.2016YFB0300602)
文摘The microstructure and mechanical properties of low carbon bainite high strength steel plate were studied via different cooling paths at the pilot scale. There was a significant increase in mechanical properties, and notably, the yield strength, tensile strength, and toughness at-40 ℃ for the tested steel processed by ultra-fast cooling were 126 MPa, 98 MPa and 69 J, respectively, in relation to steel processed by accelerated cooling. The ultra-fast cooling rate not only refined the microstructure, precipitates, and martensiteaustenite（M/A） islands, but also contributed to the refinement of microstructure in thick plates. The large size M/A constituents formed at lower cooling rate experienced stress concentration and were potential sites for crack initiation, which led to deterioration of low-temperature impact toughness. In contrast, the acicular ferrite and lath bainite with high fraction of high-angle grain boundaries were formed in steel processed by ultra-fast cooling, which retarded cleavage crack propagation.
文摘The present work is investigated the in-situ monitoring of local corrosion process of scratched epoxy coated carbon steel in saturated Ca(OH)<sub>2</sub> with and without 3% NaCl using SECM and correlated with EIS. The results obtained from EIS analysis showed that the corrosion resistance of scratched epoxy coated carbon steel decreases in Cl<sup>-</sup> containing solution as the increase in wet/ dry corrosion cycles. This was indicated by decrease in film resistance (R<sub>f</sub>) and charge transfer resistance (R<sub>ct</sub>), while the coated steel maintain the resistance values in saturated Ca(OH)<sub>2</sub>, most of which recovered after drying. The corrosion process was monitored using SECM by setting the tip potential at -0.70 V vs Ag/AgCl, where the consumption of dissolved oxygen occurred at the surface of test sample. The consumption of dissolved oxygen current (I’<sub>oxy-c</sub>) values was increased during the immersion in a solution with 3% NaCl. However, in wet/dry corrosion cycles, I’<sub>oxy-c</sub> was decreased due to the coverage of hydroxides/oxides at scratch area which suppressed the consumption of dissolved O<sub>2</sub>. It was found that the continuous decrease in corrosion was mainly attributed to continuous formation of corrosion products at anodic spots.
文摘Introduction: The purpose of this retrospective study is to identify medical conditions impacting neurodevelopmental outcomes of extremely low birth weight and very low birth weight preterm infants at three years of age. Methods: Infants born in Banner Diamond Children’s University Medical Center, receiving services in the Newborn Intensive Care Unit, and attending Neonatal Developmental Follow-Up Clinic were identified. Participants received developmental assessment and follow-up from August 2012 through December 2018. Relevant clinical conditions during initial hospital stay and up to three years of age were obtained by reviewing medical and developmental records. Bayley Scales of Infant Toddler Development (Bayley III) was used to evaluate skill development at 6, 9, 12, 18, 24, 30, 36 months. Results: Data analysis did not reveal significant p-values;it did demonstrate that some predictor variables impact neurodevelopmental outcomes in cognitive, language and motor skill development. Conclusion: This retrospective study reports significant association between birth weight and low cognitive scores. Correlations were also found between gestational age and Total Language, and the longer an infant stayed in the NICU, the poorer the Total Language Scaled Scores at 8 to 12 months, 15 to 18 months, and 24 to 36 months. Birth weight was found to be the greatest predictor of poor motor scores.
基金Supported by GI SPORE Grant p50 CA95060 from the National Cancer Institute, to Dvorak K
文摘Barrett's esophagus (BE) is a metaplastic lesion of the distal esophagus arising as a consequence of chronic gastroesophageal reflux disease. Multiple studies show that BE is associated with increased risk of esophageal adenocarcinoma (EAC). Epidemiological studies and animal models demonstrate that chronic inflammation triggered by repeated exposure to refluxate predisposes to the development of BE and EAC. The chronic inflammation is associated with cytokine alterations. Interleukin 6 (IL-6) is a cytokine that stimulates cell proliferation and apoptosis resistance is frequently increased in different cancers. Importantly, IL-6 and transcriptional factor signal transducer and activator of transcription 3 (STAT3) that is activated by IL-6 are also increased in BE and EAC. This review critically appraises the role of IL-6/STAT3 pathway in progression of BE to EAC from the published evidence currently available.
文摘Background: Ventricular fibrillation and ventricular tachycardia are less common causes of cardiac arrest in children than in adults. These tachyarrhythmias can also begin during cardiopulmonary resuscitation(CPR), presumably as reperfusion arrhythmias. We determined whether the outcome is better for initial than for subsequent ventricular fibrillation or tachycardia. Methods: All cardiac arrests in persons under 18 years of age were identified from a large, multicenter, in-hospital cardiac-arrest registry. The results from children with initial ventricular fibrillation or tachycardia, children in whom ventricular fibrillation or tachycardia developed during CPR, and children with no ventricular fibrillation or tachycardia were compared by chi-square and multivariable logistic-regression analysis. Results: Of 1005 index patients with in-hospital cardiac arrest, 272(27 percent) had documented ventricular fibrillation or tachycardia during the arrest. In 104 patients(10 percent), ventricular fibrillation or tachycardia was the initial pulseless rhythm; in 149 patients(15 percent), it developed during the arrest. The time of initiation of ventricular fibrillation or tachycardia was not documented in 19 patients. Thirty-five percent of patients with initial ventricular fibrillation or tachycardia survived to hospital discharge, as compared with 11 percent of patients with subsequent ventricular fibrillation or tachycardia(odds ratio, 2.6; 95 percent con-fidence interval, 1.2 to 5.8). Twenty-seven percent of patients with no ventricular fibrillation or tachycardia survived to hospital discharge, as compared with 11 percent of patients with subsequent ventricular fibrillation or tachycardia(odds ratio, 3.8; 95 percent confidence interval, 1.8 to 7.6). Conclusions: In pediatric patients with in-hospital cardiac arrests, survival outcomes were highest among patients in whom ventricular fibrillation or tachycardia was present initially than among those in whom it developed subsequently. The outcomes for patients with subsequent ventricular fibrillation or tachycardia were substantially worse than those for patients with asystole or pulseless electrical activity.
文摘Nanoindentation measurement was performed to evaluate the local hardness distribution for quenched and tempered martensitic steel with ferrite-cementite constituent. The ratio of standard deviation to the average nanohardness was 15.4% when nanoin-dentation tests were carried out at the peak load of 1000 μN, while that of the Vickers hardness was only 1.5% at 9.8 N. Electron backscatter diffraction analysis and SEM ob-servation all showed that the large scattering of nanohardness did not depend on the crystallographic orientation of each grain but from the inhomogeneous microstructure in the sub-micron scale such as cementite distribution. Compared with the results on tung-sten single crystals with different surface orientations as well as another martensite proc-essed by modified-ausforming with the same chemical composition but more homogene-ous cementite distribution, the nanohardness showed smaller scattering, supporting the conclusion.
