AIM:To evaluate the relationship of overweight and obesity with retinal and choroidal thickness in adults without ocular symptoms by swept-source optical coherence tomography(SS-OCT).METHODS:According to the body mass...AIM:To evaluate the relationship of overweight and obesity with retinal and choroidal thickness in adults without ocular symptoms by swept-source optical coherence tomography(SS-OCT).METHODS:According to the body mass index(BMI)results,the adults enrolled in the cross-sectional study were divided into the normal group(18.50≤BMI<25.00 kg/m^(2)),the overweight group(25.00≤BMI<30.00 kg/m^(2)),and the obesity group(BMI≥30.00 kg/m^(2)).The one-way ANOVA and the Chi-square test were used for comparisons.Pearson’s correlation analysis was used to evaluate the relationships between the measured variables.RESULTS:This research covered the left eyes of 3 groups of 434 age-and sex-matched subjects each:normal,overweight,and obesity.The mean BMI was 22.20±1.67,26.82±1.38,and 32.21±2.35 kg/m^(2) in normal,overweight and obesity groups,respectively.The choroid was significantly thinner in both the overweight and obesity groups compared to the normal group(P<0.05 for all),while the retinal thickness of the three groups did not differ significantly.Pearson’s correlation analysis showed that BMI was significantly negatively correlated with choroidal thickness,but no significant correlation was observed between BMI and retinal thickness.CONCLUSION:Choroidal thickness is decreased in people with overweight or obesity.Research on changes in choroidal thickness contributes to the understanding of the mechanisms of certain ocular disorders in overweight and obese adults.展开更多
BACKGROUND Ferroptosis has recently been associated with multiple degenerative diseases.Ferroptosis induction in cancer cells is a feasible method for treating neoplastic diseases.However,the association of iron proli...BACKGROUND Ferroptosis has recently been associated with multiple degenerative diseases.Ferroptosis induction in cancer cells is a feasible method for treating neoplastic diseases.However,the association of iron proliferation-related genes with prognosis in HER2+breast cancer(BC)patients is unclear.AIM To identify and evaluate fresh ferroptosis-related biomarkers for HER2+BC.METHODS First,we obtained the mRNA expression profiles and clinical information of HER2+BC patients from the TCGA and METABRIC public databases.A four gene prediction model comprising PROM2,SLC7A11,FANCD2,and FH was subsequently developed in the TCGA cohort and confirmed in the METABRIC cohort.Patients were stratified into high-risk and low-risk groups based on their median risk score,an independent predictor of overall survival(OS).Based on these findings,immune infiltration,mutations,and medication sensitivity were analyzed in various risk groupings.Additionally,we assessed patient prognosis by combining the tumor mutation burden(TMB)with risk score.Finally,we evaluated the expression of critical genes by analyzing single-cell RNA sequencing(scRNA-seq)data from malignant vs normal epithelial cells.RESULTS We found that the higher the risk score was,the worse the prognosis was(P<0.05).We also found that the immune cell infiltration,mutation,and drug sensitivity were different between the different risk groups.The highrisk subgroup was associated with lower immune scores and high TMB.Moreover,we found that the combination of the TMB and risk score could stratify patients into three groups with distinct prognoses.HRisk-HTMB patients had the worst prognosis,whereas LRisk-LTMB patients had the best prognosis(P<0.0001).Analysis of the scRNAseq data showed that PROM2,SLC7A11,and FANCD2 were significantly differentially expressed,whereas FH was not,suggesting that these genes are expressed mainly in cancer epithelial cells(P<0.01).CONCLUSION Our model helps guide the prognosis of HER2+breast cancer patients,and its combination with the TMB can aid in more accurate assessment of patient prognosis and provide new ideas for further diagnosis and treatment.展开更多
Objective: To establish a prediction model of activities of daily living (ADL) as an auxiliary evaluation scheme of hospitalized Parkinson’s disease patients. Methods: The hospitalization data of Parkinson’s disease...Objective: To establish a prediction model of activities of daily living (ADL) as an auxiliary evaluation scheme of hospitalized Parkinson’s disease patients. Methods: The hospitalization data of Parkinson’s disease in patients in the Department of Neurology, Affiliated Brain Hospital of Guangzhou Medical University were collected. Firstly the NSE values and each BI item were analyzed by Pearson correlation analysis. Secondly, The NSE, Age, Body weight and Education level related to the total score of Barthel index were obtained by correlation analysis. At last, a multiple linear regression model was established with NSE, Age, Body weight and Education level as independent variables and BI as dependent variables. Results: A total of 95 patients with PD were enrolled in this study, including 53 males (55.8%) and 42 females (44.2%). The effects of the four independent variables incorporated in the model on the total score of Barthel index were statistically significant, as well as the regression model (F = 9.531, P Conclusion: The prediction model established in this research can effectively predict the activities of daily living of Parkinson’s patients and can be used as an auxiliary evaluation scheme of the hospitalized PD patients.展开更多
This study proposed an effective plastic deformation technique,rotating backward extrusion(RBE),for producing high performance AZ80 magnesium alloy cup-shaped pieces.The RBE process was carried on the Gleeble-3500 tes...This study proposed an effective plastic deformation technique,rotating backward extrusion(RBE),for producing high performance AZ80 magnesium alloy cup-shaped pieces.The RBE process was carried on the Gleeble-3500 test machine at 653 K,and the conventional backward extrusion(CBE)was also conducted for comparison.A detailed microstructure analysis was performed using the optical microscopy(OM)and electron back-scatter diffraction(EBSD).The results shown that the equivalent strain and deformation uniformity of the cup pieces could be substantially increased by the RBE process compared with the CBE process.Furthermore,the RBE process could significantly improve the grain refining capacity and the proportion of dynamic recrystallization(DRX),of which the maximum reduction of grain size was 88.60%,and the maximum increase of DRX proportion was 55.30%in the cup bottom.The main deformation mechanism of the RBE process was the discontinuous DRX(DDRX),while the continuous DRX(CDRX)was also occurred in the cup transition.Compared with the CBE sample,the texture of the cup bottom was weakened for the RBE sample.The microhardness value of the RBE sample was higher than that of the CBE sample,which can be attributed to the grain refinement strengthening.展开更多
AIM:To evaluate the potential effectiveness of hydroxynaphthoquinone mixture(HM)in rats with 2,4,6-trinitrobenzene sulfonic acid(TNBS)-induced colitis.METHODS:Colitis was induced by intracolonic administration of TNBS...AIM:To evaluate the potential effectiveness of hydroxynaphthoquinone mixture(HM)in rats with 2,4,6-trinitrobenzene sulfonic acid(TNBS)-induced colitis.METHODS:Colitis was induced by intracolonic administration of TNBS(80 mg/kg,dissolved in 50%ethanol).Rats were treated daily for 7 d with HM(2.5,5,10 mg/kg)and mesalazine 100 mg/kg 24 h after TNBS instillation.Disease progression was monitored daily by observation of clinical signs and body weight change.At the end of the experiment,macroscopic and histopathologic lesions of rats were scored,and myeloperoxidase(MPO)activity was determined.We also determined inflammatory cytokine tumor necrosis factor(TNF)-αlevel by ELISA,Western blotting and immunochemistry to explore the potential mechanisms of HM.RESULTS:After intracolonic instillation of TNBS,animals developed colitis associated with soft stool,diarrhea and marked colonic destruction.Administration of HM significantly attenuated clinical and histopathologic severity of TNBS-induced colitis in a dose-dependent manner.It abrogated body weight loss,diarrhea and inflammation,decreased macroscopic damage score,and improved histological signs,with a significant reduction of inflammatory infiltration,ulcer size and the severity of goblet cell depletion(all P<0.05 vs TNBS alone group).HM could reduce MPO activity.In addition,it also decreased serum TNF-αlevel and down-regulated TNF-αexpression in colonic tissue.This reduction was statistically significant when the dose of HM was 10 mg/kg(P<0.05 vs TNBS alone group),and the effect was comparable to that of mesalazine and showed no apparent adverse effect.The underlying mechanism may be associated with TNF-αinhibition.CONCLUSION:These findings suggest that HM possesses favourable therapeutic action in TNBS-induced colitis,which provides direct pharmacological evidence for its clinical application.展开更多
Dear Editor, We reported the first case of acute exogenous postoperative endophthalmitis caused by a normal human microbiota in the nasopharynx, Streptococcus anginosus. The patient had a successful cataract surgery, ...Dear Editor, We reported the first case of acute exogenous postoperative endophthalmitis caused by a normal human microbiota in the nasopharynx, Streptococcus anginosus. The patient had a successful cataract surgery, but he felt uncomfortable in the surgery eye 4 d post-surgery. Besides.展开更多
According to the meteorological requirements of maize and potato,using the data of meteorological observations and soil moisture of Pengzhou City,the agricultural climatic resources of spring maize and spring potato p...According to the meteorological requirements of maize and potato,using the data of meteorological observations and soil moisture of Pengzhou City,the agricultural climatic resources of spring maize and spring potato planting and the advantages of agricultural climatic resources of their intercropping were analyzed. The suitable sowing dates for spring maize and spring potato are late March to early April,early February to early March,respectively. During the growth period,the heat resources are abundant,the soil moisture is sufficient,the precipitation and overall distribution are suitable,and the sunshine is still sufficient,which can meet the needs of each growth period. The overall configuration of agricultural meteorological resources is coordinated,which is suitable for the planting of the two. Spring maize-spring potato intercropping can make the most of land,time and space,improve light and heat utilization,reduce pests and diseases,and increase output per unit area,thereby maximizing economic benefits.展开更多
It is a developed photosynthetic co-culture system to alleviate the hypoxia and hypoxia/reoxygenation(H/R)-injured human umbilical vein endothelial cells(HUVECs).The algae,Chlorella vulgaris,were encapsulated to slow ...It is a developed photosynthetic co-culture system to alleviate the hypoxia and hypoxia/reoxygenation(H/R)-injured human umbilical vein endothelial cells(HUVECs).The algae,Chlorella vulgaris,were encapsulated to slow their growth while not affecting the photosynthetic oxygen-producing capacity by Layer-by-layer(LbL)using gelatin and sodium alginate as the positive and negative charges materials,respectively.Then,the photosynthetic co-culture system of HUVECs and self-oxygenating alginate hydrogel(Algae-gel)was constructed in which the optimal ratios between algae and HUVECs were 5:1 and 20:1 for a 2D or 3D co-cultured manner,respectively.It indicated that the 3D cocultured manner of HUVECs needed more O_(2) by the production of algae than it did in a 2D co-cultured manner.The co-cultured Algae-gel could alleviate hypoxia and the oxidative stress injury of hypoxia and hypoxia/reoxygenation(H/R)-treated HUVECs in the proliferation,intracellular ROS and cellular migratory ability.In addition,the Algaegel could downregulate the expression of hypoxia-inducible factors 1α(HIF-1α)and vascular endothelial growth factor(VEGF)of hypoxia and H/R-injured HUVECs due to the improvement of hypoxia and H/R injury.This photosynthetic co-culture system could offer a promising approach for repairing hypoxia and H/R-injured cells or tissue by providing safe and stable O_(2).展开更多
In order to understand the effect of Mo element on the high-temperature fatigue behavior of 15CrNbTi ferritic stainless steel, the stress-controlled fatigue tests have been performed for both 15CrNbTi and 15Cr0.5MoNbT...In order to understand the effect of Mo element on the high-temperature fatigue behavior of 15CrNbTi ferritic stainless steel, the stress-controlled fatigue tests have been performed for both 15CrNbTi and 15Cr0.5MoNbTi ferritic stainless steels at 800 ℃ in laboratory air. The fatigue test results indicate that the fatigue resistance of 15Cr0.5MoNbTi steel is manifestly higher than that of 15CrNbTi steel at the maximum stress below 57 MPa; the 15Cr0.5MoNbTi steel possesses a fatigue limit of 35 MPa, which is higher than that of 15CrNbTi steel. The TEM observations reveal that the Mo element can suppress the formation of coarsened Fe3Nb3C precipitates and result in the fatigue resistance enhancement. The dislocation networks formed during the cyclic load favor to improve the fatigue resistance of 15Cr0.5MoNbTi steel at 800 ℃.展开更多
In order to investigate the high-temperature fatigue and fatigue-creep behavior of 15CrNbTi ferritic stainless steel at 800°C,fatigue tests without holding time in laboratory air and with 10 s holding time induce...In order to investigate the high-temperature fatigue and fatigue-creep behavior of 15CrNbTi ferritic stainless steel at 800°C,fatigue tests without holding time in laboratory air and with 10 s holding time induced at maximum cyclic stress under argon atmosphere were conducted on an electrohydraulic servo fatigue testing machine.In addition,the morphologies of fatigue fracture surfaces were observed,and the precipitates and dislocation substructures were characterized.The experimental results show that the fatigue limit of 15CrNbTi ferritic stainless steel is 30 MPa at 800°C.The fatigue life of the experimental steel obviously decreases if holding time of 10 s is introduced at maximum cyclic stress.Under two test conditions,the fatigue cracks transgranularly initiate at the free surface of fatigue specimens and then propagate in a transgranular mode.It is dem on strated that three kinds of precipitates inclu ding(Nb,Ti)C phase,Fe2Nb phase and Fe3Nb3C phase can be observed in 15CrNbTi ferritic stainless steel,and the Fe2Nb and Fe3Nb3C phases are mainly precipitated during the fatigue tests.In the fatigue deformation area,both dislocation tangles and dislocation arrays are observed.Furthermore,the sub-grains which form during the cycling deformation with holding time of 10 s are also found.Moreover,the formation of sub-grains leads to the deterioration of the fatigue life of 15CrNbTi steel.展开更多
基金Supported by the Science and Technology Commission of Shanghai Municipality(No.20Y11910800).
文摘AIM:To evaluate the relationship of overweight and obesity with retinal and choroidal thickness in adults without ocular symptoms by swept-source optical coherence tomography(SS-OCT).METHODS:According to the body mass index(BMI)results,the adults enrolled in the cross-sectional study were divided into the normal group(18.50≤BMI<25.00 kg/m^(2)),the overweight group(25.00≤BMI<30.00 kg/m^(2)),and the obesity group(BMI≥30.00 kg/m^(2)).The one-way ANOVA and the Chi-square test were used for comparisons.Pearson’s correlation analysis was used to evaluate the relationships between the measured variables.RESULTS:This research covered the left eyes of 3 groups of 434 age-and sex-matched subjects each:normal,overweight,and obesity.The mean BMI was 22.20±1.67,26.82±1.38,and 32.21±2.35 kg/m^(2) in normal,overweight and obesity groups,respectively.The choroid was significantly thinner in both the overweight and obesity groups compared to the normal group(P<0.05 for all),while the retinal thickness of the three groups did not differ significantly.Pearson’s correlation analysis showed that BMI was significantly negatively correlated with choroidal thickness,but no significant correlation was observed between BMI and retinal thickness.CONCLUSION:Choroidal thickness is decreased in people with overweight or obesity.Research on changes in choroidal thickness contributes to the understanding of the mechanisms of certain ocular disorders in overweight and obese adults.
基金The Science and Technology Commission of Shanxi province,No.201901D111428.
文摘BACKGROUND Ferroptosis has recently been associated with multiple degenerative diseases.Ferroptosis induction in cancer cells is a feasible method for treating neoplastic diseases.However,the association of iron proliferation-related genes with prognosis in HER2+breast cancer(BC)patients is unclear.AIM To identify and evaluate fresh ferroptosis-related biomarkers for HER2+BC.METHODS First,we obtained the mRNA expression profiles and clinical information of HER2+BC patients from the TCGA and METABRIC public databases.A four gene prediction model comprising PROM2,SLC7A11,FANCD2,and FH was subsequently developed in the TCGA cohort and confirmed in the METABRIC cohort.Patients were stratified into high-risk and low-risk groups based on their median risk score,an independent predictor of overall survival(OS).Based on these findings,immune infiltration,mutations,and medication sensitivity were analyzed in various risk groupings.Additionally,we assessed patient prognosis by combining the tumor mutation burden(TMB)with risk score.Finally,we evaluated the expression of critical genes by analyzing single-cell RNA sequencing(scRNA-seq)data from malignant vs normal epithelial cells.RESULTS We found that the higher the risk score was,the worse the prognosis was(P<0.05).We also found that the immune cell infiltration,mutation,and drug sensitivity were different between the different risk groups.The highrisk subgroup was associated with lower immune scores and high TMB.Moreover,we found that the combination of the TMB and risk score could stratify patients into three groups with distinct prognoses.HRisk-HTMB patients had the worst prognosis,whereas LRisk-LTMB patients had the best prognosis(P<0.0001).Analysis of the scRNAseq data showed that PROM2,SLC7A11,and FANCD2 were significantly differentially expressed,whereas FH was not,suggesting that these genes are expressed mainly in cancer epithelial cells(P<0.01).CONCLUSION Our model helps guide the prognosis of HER2+breast cancer patients,and its combination with the TMB can aid in more accurate assessment of patient prognosis and provide new ideas for further diagnosis and treatment.
文摘Objective: To establish a prediction model of activities of daily living (ADL) as an auxiliary evaluation scheme of hospitalized Parkinson’s disease patients. Methods: The hospitalization data of Parkinson’s disease in patients in the Department of Neurology, Affiliated Brain Hospital of Guangzhou Medical University were collected. Firstly the NSE values and each BI item were analyzed by Pearson correlation analysis. Secondly, The NSE, Age, Body weight and Education level related to the total score of Barthel index were obtained by correlation analysis. At last, a multiple linear regression model was established with NSE, Age, Body weight and Education level as independent variables and BI as dependent variables. Results: A total of 95 patients with PD were enrolled in this study, including 53 males (55.8%) and 42 females (44.2%). The effects of the four independent variables incorporated in the model on the total score of Barthel index were statistically significant, as well as the regression model (F = 9.531, P Conclusion: The prediction model established in this research can effectively predict the activities of daily living of Parkinson’s patients and can be used as an auxiliary evaluation scheme of the hospitalized PD patients.
基金financially supported by the National Natural Science Foundation of China(No.51775520)the National Key Research and Development Program(No.2016YFB0301103-3)+1 种基金the Key R&D program of Shanxi Province(International Cooperation)(No.201903D421036)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.2018002)。
文摘This study proposed an effective plastic deformation technique,rotating backward extrusion(RBE),for producing high performance AZ80 magnesium alloy cup-shaped pieces.The RBE process was carried on the Gleeble-3500 test machine at 653 K,and the conventional backward extrusion(CBE)was also conducted for comparison.A detailed microstructure analysis was performed using the optical microscopy(OM)and electron back-scatter diffraction(EBSD).The results shown that the equivalent strain and deformation uniformity of the cup pieces could be substantially increased by the RBE process compared with the CBE process.Furthermore,the RBE process could significantly improve the grain refining capacity and the proportion of dynamic recrystallization(DRX),of which the maximum reduction of grain size was 88.60%,and the maximum increase of DRX proportion was 55.30%in the cup bottom.The main deformation mechanism of the RBE process was the discontinuous DRX(DDRX),while the continuous DRX(CDRX)was also occurred in the cup transition.Compared with the CBE sample,the texture of the cup bottom was weakened for the RBE sample.The microhardness value of the RBE sample was higher than that of the CBE sample,which can be attributed to the grain refinement strengthening.
基金Supported by National Program for Important New Drugs R and D,No.2011ZX9102-006-04Programs for Science and Technology Development and Plan of Yantai,No.2013ZH086
文摘AIM:To evaluate the potential effectiveness of hydroxynaphthoquinone mixture(HM)in rats with 2,4,6-trinitrobenzene sulfonic acid(TNBS)-induced colitis.METHODS:Colitis was induced by intracolonic administration of TNBS(80 mg/kg,dissolved in 50%ethanol).Rats were treated daily for 7 d with HM(2.5,5,10 mg/kg)and mesalazine 100 mg/kg 24 h after TNBS instillation.Disease progression was monitored daily by observation of clinical signs and body weight change.At the end of the experiment,macroscopic and histopathologic lesions of rats were scored,and myeloperoxidase(MPO)activity was determined.We also determined inflammatory cytokine tumor necrosis factor(TNF)-αlevel by ELISA,Western blotting and immunochemistry to explore the potential mechanisms of HM.RESULTS:After intracolonic instillation of TNBS,animals developed colitis associated with soft stool,diarrhea and marked colonic destruction.Administration of HM significantly attenuated clinical and histopathologic severity of TNBS-induced colitis in a dose-dependent manner.It abrogated body weight loss,diarrhea and inflammation,decreased macroscopic damage score,and improved histological signs,with a significant reduction of inflammatory infiltration,ulcer size and the severity of goblet cell depletion(all P<0.05 vs TNBS alone group).HM could reduce MPO activity.In addition,it also decreased serum TNF-αlevel and down-regulated TNF-αexpression in colonic tissue.This reduction was statistically significant when the dose of HM was 10 mg/kg(P<0.05 vs TNBS alone group),and the effect was comparable to that of mesalazine and showed no apparent adverse effect.The underlying mechanism may be associated with TNF-αinhibition.CONCLUSION:These findings suggest that HM possesses favourable therapeutic action in TNBS-induced colitis,which provides direct pharmacological evidence for its clinical application.
基金National Natural Science Foundation of China (No.81900879)。
文摘Dear Editor, We reported the first case of acute exogenous postoperative endophthalmitis caused by a normal human microbiota in the nasopharynx, Streptococcus anginosus. The patient had a successful cataract surgery, but he felt uncomfortable in the surgery eye 4 d post-surgery. Besides.
基金Three Rural Issues Service Project of Chengdu Meteorological Bureau(2014007)
文摘According to the meteorological requirements of maize and potato,using the data of meteorological observations and soil moisture of Pengzhou City,the agricultural climatic resources of spring maize and spring potato planting and the advantages of agricultural climatic resources of their intercropping were analyzed. The suitable sowing dates for spring maize and spring potato are late March to early April,early February to early March,respectively. During the growth period,the heat resources are abundant,the soil moisture is sufficient,the precipitation and overall distribution are suitable,and the sunshine is still sufficient,which can meet the needs of each growth period. The overall configuration of agricultural meteorological resources is coordinated,which is suitable for the planting of the two. Spring maize-spring potato intercropping can make the most of land,time and space,improve light and heat utilization,reduce pests and diseases,and increase output per unit area,thereby maximizing economic benefits.
基金National Natural Science Foundation of China,Grant/Award Number:52035012Medical Research Project of Chengdu Municipal Health Commission,Grant/Award Number:Q114323Q01001Medical Research Project of Sichuan Health Commission,Grant/Award Number:23LCYJ044。
文摘It is a developed photosynthetic co-culture system to alleviate the hypoxia and hypoxia/reoxygenation(H/R)-injured human umbilical vein endothelial cells(HUVECs).The algae,Chlorella vulgaris,were encapsulated to slow their growth while not affecting the photosynthetic oxygen-producing capacity by Layer-by-layer(LbL)using gelatin and sodium alginate as the positive and negative charges materials,respectively.Then,the photosynthetic co-culture system of HUVECs and self-oxygenating alginate hydrogel(Algae-gel)was constructed in which the optimal ratios between algae and HUVECs were 5:1 and 20:1 for a 2D or 3D co-cultured manner,respectively.It indicated that the 3D cocultured manner of HUVECs needed more O_(2) by the production of algae than it did in a 2D co-cultured manner.The co-cultured Algae-gel could alleviate hypoxia and the oxidative stress injury of hypoxia and hypoxia/reoxygenation(H/R)-treated HUVECs in the proliferation,intracellular ROS and cellular migratory ability.In addition,the Algaegel could downregulate the expression of hypoxia-inducible factors 1α(HIF-1α)and vascular endothelial growth factor(VEGF)of hypoxia and H/R-injured HUVECs due to the improvement of hypoxia and H/R injury.This photosynthetic co-culture system could offer a promising approach for repairing hypoxia and H/R-injured cells or tissue by providing safe and stable O_(2).
基金supported by the National Natural Science Foundation of China (No. 51134010)
文摘In order to understand the effect of Mo element on the high-temperature fatigue behavior of 15CrNbTi ferritic stainless steel, the stress-controlled fatigue tests have been performed for both 15CrNbTi and 15Cr0.5MoNbTi ferritic stainless steels at 800 ℃ in laboratory air. The fatigue test results indicate that the fatigue resistance of 15Cr0.5MoNbTi steel is manifestly higher than that of 15CrNbTi steel at the maximum stress below 57 MPa; the 15Cr0.5MoNbTi steel possesses a fatigue limit of 35 MPa, which is higher than that of 15CrNbTi steel. The TEM observations reveal that the Mo element can suppress the formation of coarsened Fe3Nb3C precipitates and result in the fatigue resistance enhancement. The dislocation networks formed during the cyclic load favor to improve the fatigue resistance of 15Cr0.5MoNbTi steel at 800 ℃.
基金National Natural Science Foundation of China(Nos.51134010 and U1660205).
文摘In order to investigate the high-temperature fatigue and fatigue-creep behavior of 15CrNbTi ferritic stainless steel at 800°C,fatigue tests without holding time in laboratory air and with 10 s holding time induced at maximum cyclic stress under argon atmosphere were conducted on an electrohydraulic servo fatigue testing machine.In addition,the morphologies of fatigue fracture surfaces were observed,and the precipitates and dislocation substructures were characterized.The experimental results show that the fatigue limit of 15CrNbTi ferritic stainless steel is 30 MPa at 800°C.The fatigue life of the experimental steel obviously decreases if holding time of 10 s is introduced at maximum cyclic stress.Under two test conditions,the fatigue cracks transgranularly initiate at the free surface of fatigue specimens and then propagate in a transgranular mode.It is dem on strated that three kinds of precipitates inclu ding(Nb,Ti)C phase,Fe2Nb phase and Fe3Nb3C phase can be observed in 15CrNbTi ferritic stainless steel,and the Fe2Nb and Fe3Nb3C phases are mainly precipitated during the fatigue tests.In the fatigue deformation area,both dislocation tangles and dislocation arrays are observed.Furthermore,the sub-grains which form during the cycling deformation with holding time of 10 s are also found.Moreover,the formation of sub-grains leads to the deterioration of the fatigue life of 15CrNbTi steel.
