Effects of N and Zr on the as-cast microstructure and properties after annealing of high-speed steel （HSS） were investigated by using electronic probe micro-analysis, Rockwell hardness test, X-ray diffractometry and...Effects of N and Zr on the as-cast microstructure and properties after annealing of high-speed steel （HSS） were investigated by using electronic probe micro-analysis, Rockwell hardness test, X-ray diffractometry and differential scanning calorimetry with combination of microstructure analysis. The results indicate that the addition of N and Zr will refine the eutectic structures and enhance the stability of carbides which are mainly MC, M2C and M7C3. The coarse dendritic structures decrease significantly and most of the carbides are distributed in the microstructure uniformly. Moreover, a kind of Zr-Si compound which only exists in VC is discovered, and this new phase is speculated to be related with the spheroidization of VC. The annealing process is set up to 6 different time periods which are 1, 3, 6, 10, 15 and 20 h, respectively. In different annealing processes at 750 ℃ which is lower than austenitizing temperature, the addition of N and Zr makes the decrease of hardness more obvious and restrains the precipitation of secondary carbides with the extension of time. Moreover, when the annealing time reaches 20 h, some clusters appear in the matrix of the two samples, and the density of clusters in HSS1 is lower, but the matrix of HSS1 contains more C and alloying elements which indicate more carbides precipitate.展开更多
Background:Positive surgical margins are independent risk factor for biochemical recurrence,local recurrence,and distant metastasis after radical prostatectomy.However,limited predictive tools are available.This study...Background:Positive surgical margins are independent risk factor for biochemical recurrence,local recurrence,and distant metastasis after radical prostatectomy.However,limited predictive tools are available.This study aimed to develop and validate a preoperative nomogram for predicting positive surgical margins after laparoscopic radical prostatectomy(LRP).Methods:From January 2010 to March 2016,a total of 418 patients who underwent LRP without receiving neoadjuvant therapy at Peking University Third Hospital were retrospectively involved in this study.Clinical and pathological results of each patient were collected for further analysis.Univariable and multivariable logistic regression(backward stepwise method)were used for the nomogram development.The concordance index(CI),calibration curve analysis and decision curve analysis were used to evaluate the performance of our model.Results:Of 418 patients involved in this study,142 patients(34.0%)had a positive surgical margin on final pathology.Based on the backward selection,four variables were included in the final multivariable regression model,including the percentage of positive cores in preoperative biopsy,clinical stage,free prostate specific antigen(fPSA)/total PSA(tPSA),and age.A nomogram was developed using these four variables.The concordance index(C-index)of the nomogram was 0.722 in the development cohort and 0.700 in the bootstrap validations.The bias-corrected calibration plot showed a limited departure from the ideal line with a mean absolute error of 2.0%.In decision curve analyses,the nomogram showed net benefits in the range from 0.2 to 0.7.Conclusion:A nomogram to predict positive surgical margins after LRP was developed and validated,which could help urologists plan surgical procedures.展开更多
文摘Effects of N and Zr on the as-cast microstructure and properties after annealing of high-speed steel （HSS） were investigated by using electronic probe micro-analysis, Rockwell hardness test, X-ray diffractometry and differential scanning calorimetry with combination of microstructure analysis. The results indicate that the addition of N and Zr will refine the eutectic structures and enhance the stability of carbides which are mainly MC, M2C and M7C3. The coarse dendritic structures decrease significantly and most of the carbides are distributed in the microstructure uniformly. Moreover, a kind of Zr-Si compound which only exists in VC is discovered, and this new phase is speculated to be related with the spheroidization of VC. The annealing process is set up to 6 different time periods which are 1, 3, 6, 10, 15 and 20 h, respectively. In different annealing processes at 750 ℃ which is lower than austenitizing temperature, the addition of N and Zr makes the decrease of hardness more obvious and restrains the precipitation of secondary carbides with the extension of time. Moreover, when the annealing time reaches 20 h, some clusters appear in the matrix of the two samples, and the density of clusters in HSS1 is lower, but the matrix of HSS1 contains more C and alloying elements which indicate more carbides precipitate.
文摘Background:Positive surgical margins are independent risk factor for biochemical recurrence,local recurrence,and distant metastasis after radical prostatectomy.However,limited predictive tools are available.This study aimed to develop and validate a preoperative nomogram for predicting positive surgical margins after laparoscopic radical prostatectomy(LRP).Methods:From January 2010 to March 2016,a total of 418 patients who underwent LRP without receiving neoadjuvant therapy at Peking University Third Hospital were retrospectively involved in this study.Clinical and pathological results of each patient were collected for further analysis.Univariable and multivariable logistic regression(backward stepwise method)were used for the nomogram development.The concordance index(CI),calibration curve analysis and decision curve analysis were used to evaluate the performance of our model.Results:Of 418 patients involved in this study,142 patients(34.0%)had a positive surgical margin on final pathology.Based on the backward selection,four variables were included in the final multivariable regression model,including the percentage of positive cores in preoperative biopsy,clinical stage,free prostate specific antigen(fPSA)/total PSA(tPSA),and age.A nomogram was developed using these four variables.The concordance index(C-index)of the nomogram was 0.722 in the development cohort and 0.700 in the bootstrap validations.The bias-corrected calibration plot showed a limited departure from the ideal line with a mean absolute error of 2.0%.In decision curve analyses,the nomogram showed net benefits in the range from 0.2 to 0.7.Conclusion:A nomogram to predict positive surgical margins after LRP was developed and validated,which could help urologists plan surgical procedures.
