目的探讨全数字化乳腺X线摄影(full-field digital mammography,FFDM)对乳腺导管原位癌的诊断价值。方法回顾性分析52例经穿刺或手术病理证实的乳腺导管原位癌的X线摄影表现。结果以恶性钙化为主要征象32例,钙化表现为微细、多形性,呈...目的探讨全数字化乳腺X线摄影(full-field digital mammography,FFDM)对乳腺导管原位癌的诊断价值。方法回顾性分析52例经穿刺或手术病理证实的乳腺导管原位癌的X线摄影表现。结果以恶性钙化为主要征象32例,钙化表现为微细、多形性,呈簇状、群集或段性分布,其中单纯钙化24例,钙化合并局灶性致密8例;表现为肿块8例,其中3例肿块边缘见毛刺;单纯局灶性致密3例;结构扭曲2例;导管造影显示导管内占位性病变3例;X线无异常发现4例。结论 FFDM可以清晰显示微小钙化、小结节、局灶致密及结构扭曲等征象,尤其对微小钙化敏感,对乳腺导管原位癌的诊断具有重要价值。展开更多
目的探讨乳腺癌全数字化乳腺摄影(full-field digital mammography,FFDM)与乳腺MRI的影像学表现,评价其对乳腺癌的诊断价值。方法收集68例经穿刺或手术病理证实的乳腺癌病例,对比分析其X线摄影及MRI表现。全数字化乳腺摄影采用常规方法...目的探讨乳腺癌全数字化乳腺摄影(full-field digital mammography,FFDM)与乳腺MRI的影像学表现,评价其对乳腺癌的诊断价值。方法收集68例经穿刺或手术病理证实的乳腺癌病例,对比分析其X线摄影及MRI表现。全数字化乳腺摄影采用常规方法摄片,MRI采用自旋回波T1WI,T2WI序列及动态增强扫描等。结果 68例乳腺恶性肿瘤中,浸润性导管癌57例,浸润性小叶癌3例,叶状囊肉瘤1例,血管肉瘤1例,导管内癌2例,炎性乳癌2例,印戒细胞癌1例,Paget’s病1例。乳腺X线摄影诊断正确61例,诊断准确率89.7%。MRI诊断正确66例,诊断准确率97.1%。结论乳腺X线摄影是乳腺恶性病变的首选检查方法,MRI能更多的显示乳腺病灶的内部特征,二者联合应用对乳腺癌的临床诊断具有重要意义。展开更多
Diamond has an ultrawide bandgap with excellent physical properties,such as high critical electric field,excellent thermal conductivity,high carrier mobility,etc.Diamond with a hydrogen-terminated(H-terminated)surface...Diamond has an ultrawide bandgap with excellent physical properties,such as high critical electric field,excellent thermal conductivity,high carrier mobility,etc.Diamond with a hydrogen-terminated(H-terminated)surface has a negative electron affinity(NEA)and can easily produce surface electrons from valence or trapped electrons via optical absorption,thermal heating energy or carrier transport in a PN junction.The NEA of the H-terminated surface enables surface electrons to emit with high efficiency into the vacuum without encountering additional barriers and promotes further development and application of diamond-based emitting devices.This article reviews the electron emission properties of H-terminated diamond surfaces exhibiting NEA characteristics.The electron emission is induced by different physical mechanisms.Recent advancements in electron-emitting devices based on diamond are also summarized.Finally,the current challenges and future development opportunities are discussed to further develop the relevant applications of diamond-based electronemitting devices.展开更多
This work proposed to change the structure of the sample susceptor of the microwave plasma chemical vapor deposition(MPCVD)reaction chamber,that is,to introduce a small hole in the center of the susceptor to study its...This work proposed to change the structure of the sample susceptor of the microwave plasma chemical vapor deposition(MPCVD)reaction chamber,that is,to introduce a small hole in the center of the susceptor to study its suppression effect on the incorporation of residual nitrogen in the MPCVD diamond film.By using COMSOL multiphysics software simulation,the plasma characteristics and the concentration of chemical reactants in the cylindrical cavity of MPCVD system were studied,including electric field intensity,electron number density,electron temperature,the concentrations of atomic hydrogen,methyl,and nitrogenous substances,etc.After introducing a small hole in the center of the molybdenum support susceptor,we found that no significant changes were found in the center area of the plasma,but the electron state in the plasma changed greatly on the surface above the susceptor.The electron number density was reduced by about 40%,while the electron temperature was reduced by about 0.02 eV,and the concentration of atomic nitrogen was decreased by about an order of magnitude.Moreover,we found that if a specific lower microwave input power is used,and a susceptor structure without the small hole is introduced,the change results similar to those in the surface area of the susceptor will be obtained,but the spatial distribution of electromagnetic field and reactant concentration will be changed.展开更多
Unintentional nitrogen incorporation has been observed in a set of microwave plasma chemical vapor deposition(MPCVD)-grown samples.No abnormality has been detected on the apparatus especially the base pressure and fee...Unintentional nitrogen incorporation has been observed in a set of microwave plasma chemical vapor deposition(MPCVD)-grown samples.No abnormality has been detected on the apparatus especially the base pressure and feeding gas purity.By a comprehensive investigation including the analysis of the plasma composition,we found that a minor leakage of the system could be significantly magnified by the thermal effect,resulting in a considerable residual nitrogen in the diamond material.Moreover,the doping mechanism of leaked air is different to pure nitrogen doping.The dosage of several ppm of pure nitrogen can lead to efficient nitrogen incorporation in diamond,while at least thousands ppm of leaked air is required for detecting obvious residual nitrogen.The difference of the dosage has been ascribed to the suppression effect of oxygen that consumes nitrogen.As the unintentional impurity is basically detrimental to the controllable fabrication of diamond for electronic application,we have provided an effective way to suppress the residual nitrogen in a slightly leaked system by modifying the susceptor geometry.This study indicates that even if a normal base pressure can be reached,the nitrogen residing in the chamber can be“activated”by the thermal effect and thus be incorporated in diamond material grown by a MPCVD reactor.展开更多
文摘目的探讨全数字化乳腺X线摄影(full-field digital mammography,FFDM)对乳腺导管原位癌的诊断价值。方法回顾性分析52例经穿刺或手术病理证实的乳腺导管原位癌的X线摄影表现。结果以恶性钙化为主要征象32例,钙化表现为微细、多形性,呈簇状、群集或段性分布,其中单纯钙化24例,钙化合并局灶性致密8例;表现为肿块8例,其中3例肿块边缘见毛刺;单纯局灶性致密3例;结构扭曲2例;导管造影显示导管内占位性病变3例;X线无异常发现4例。结论 FFDM可以清晰显示微小钙化、小结节、局灶致密及结构扭曲等征象,尤其对微小钙化敏感,对乳腺导管原位癌的诊断具有重要价值。
文摘目的探讨乳腺癌全数字化乳腺摄影(full-field digital mammography,FFDM)与乳腺MRI的影像学表现,评价其对乳腺癌的诊断价值。方法收集68例经穿刺或手术病理证实的乳腺癌病例,对比分析其X线摄影及MRI表现。全数字化乳腺摄影采用常规方法摄片,MRI采用自旋回波T1WI,T2WI序列及动态增强扫描等。结果 68例乳腺恶性肿瘤中,浸润性导管癌57例,浸润性小叶癌3例,叶状囊肉瘤1例,血管肉瘤1例,导管内癌2例,炎性乳癌2例,印戒细胞癌1例,Paget’s病1例。乳腺X线摄影诊断正确61例,诊断准确率89.7%。MRI诊断正确66例,诊断准确率97.1%。结论乳腺X线摄影是乳腺恶性病变的首选检查方法,MRI能更多的显示乳腺病灶的内部特征,二者联合应用对乳腺癌的临床诊断具有重要意义。
基金the National Natural Sci-ence Foundation of China(Grant No.62274084)the Fun-damental Research Funds for the Central Universities(Grant No.0210-14380193).
文摘Diamond has an ultrawide bandgap with excellent physical properties,such as high critical electric field,excellent thermal conductivity,high carrier mobility,etc.Diamond with a hydrogen-terminated(H-terminated)surface has a negative electron affinity(NEA)and can easily produce surface electrons from valence or trapped electrons via optical absorption,thermal heating energy or carrier transport in a PN junction.The NEA of the H-terminated surface enables surface electrons to emit with high efficiency into the vacuum without encountering additional barriers and promotes further development and application of diamond-based emitting devices.This article reviews the electron emission properties of H-terminated diamond surfaces exhibiting NEA characteristics.The electron emission is induced by different physical mechanisms.Recent advancements in electron-emitting devices based on diamond are also summarized.Finally,the current challenges and future development opportunities are discussed to further develop the relevant applications of diamond-based electronemitting devices.
基金financial support from the National Natural Science Foundation of China(Grant Nos.61974059,61674077,and 61774081)the Fundamental Research Funds for the Central Universities,China。
文摘This work proposed to change the structure of the sample susceptor of the microwave plasma chemical vapor deposition(MPCVD)reaction chamber,that is,to introduce a small hole in the center of the susceptor to study its suppression effect on the incorporation of residual nitrogen in the MPCVD diamond film.By using COMSOL multiphysics software simulation,the plasma characteristics and the concentration of chemical reactants in the cylindrical cavity of MPCVD system were studied,including electric field intensity,electron number density,electron temperature,the concentrations of atomic hydrogen,methyl,and nitrogenous substances,etc.After introducing a small hole in the center of the molybdenum support susceptor,we found that no significant changes were found in the center area of the plasma,but the electron state in the plasma changed greatly on the surface above the susceptor.The electron number density was reduced by about 40%,while the electron temperature was reduced by about 0.02 eV,and the concentration of atomic nitrogen was decreased by about an order of magnitude.Moreover,we found that if a specific lower microwave input power is used,and a susceptor structure without the small hole is introduced,the change results similar to those in the surface area of the susceptor will be obtained,but the spatial distribution of electromagnetic field and reactant concentration will be changed.
基金Project supported by the National Key R&D Program of China(Grant Nos.2018YFB0406502,2017YFF0210800,and 2017YFB0403003)the National Natural Science Foundation of China(Grant Nos.61974059,61674077,and 61774081)+1 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20160065)the Fundamental Research Funds for the Central Universities
文摘Unintentional nitrogen incorporation has been observed in a set of microwave plasma chemical vapor deposition(MPCVD)-grown samples.No abnormality has been detected on the apparatus especially the base pressure and feeding gas purity.By a comprehensive investigation including the analysis of the plasma composition,we found that a minor leakage of the system could be significantly magnified by the thermal effect,resulting in a considerable residual nitrogen in the diamond material.Moreover,the doping mechanism of leaked air is different to pure nitrogen doping.The dosage of several ppm of pure nitrogen can lead to efficient nitrogen incorporation in diamond,while at least thousands ppm of leaked air is required for detecting obvious residual nitrogen.The difference of the dosage has been ascribed to the suppression effect of oxygen that consumes nitrogen.As the unintentional impurity is basically detrimental to the controllable fabrication of diamond for electronic application,we have provided an effective way to suppress the residual nitrogen in a slightly leaked system by modifying the susceptor geometry.This study indicates that even if a normal base pressure can be reached,the nitrogen residing in the chamber can be“activated”by the thermal effect and thus be incorporated in diamond material grown by a MPCVD reactor.
