Graphene has demonstrated its potential in several practical applications owing to its remarkable electronic and physical properties. In this study, we successfully fabricated a suspended graphene device with a width ...Graphene has demonstrated its potential in several practical applications owing to its remarkable electronic and physical properties. In this study, we successfully fabricated a suspended graphene device with a width down to 20 nm. The morphological evolution of graphene under various electric field effects was systematically examined using an in-situ transmission electron microscope （TEM）. The hourglass-shaped graphene sample instantly broke apart at 7.5 mA, indicating an impressive breakdown current density. The current-carrying capacity was calculated to be -1.6 × 10^9 A.cm-2, which is several orders higher than that of copper. The current-carrying capacity depended on the resistivity of graphene. In addition, atomic volume changes occurred in the multilayer graphene samples due to surface diffusion and Ostwald ripening （OR）, indicating that the breakdown mechanism is well approximated by the electric field. This study not only provides a theory to explain the breakdown behavior but also presents the effects on materials contacted with a graphene layer used as the transmission path.展开更多
Background：Contrast-enhanced ultrasound is a dynamic and continuous modality providing real-time view of vascularization and flow distribution patterns of different organs and tumors.In order to evaluate the diagnost...Background：Contrast-enhanced ultrasound is a dynamic and continuous modality providing real-time view of vascularization and flow distribution patterns of different organs and tumors.In order to evaluate the diagnostic significance of intraoperative contrast-enhanced ultrasound in assessing the resection degree of brain glioma by transmission electron microscopic （TEM） examination,it is important to have specific knowledge about contrast-enhanced ultrasound.Methods：Ultrasound contrast was applied in operations of 120 cases of brain glioma,to evaluate the degree of tumor resection.Biopsy tissues were obtained the suspicious residual tumors surrounding the tumor cavity.The sensitivity and specificity of the residual tumors were determined by the intraoperative ultrasound contrast according to TEM examination results.Results：There were 44 cases of low-grade gliomas and 76 cases of high-grade gliomas.Three hundred and sixty biopsy tissues were obtained.The sensitivity of intraoperative ultrasound contrast in diagnosing the residual tumor was 62.2%,while the specificity degree of it was 92.8%.The consistency coefficient of the ultrasound contrast diagnosis and TEM examination results was 0.584 （Kappa =0.584）,which was between 0.4 and 0.6,therefore it was of medium consistency.Conclusions：Intraoperative ultrasound contrast was of a high sensitivity and specificity in evaluating the excision degree of tumor.The consistency of the residual tumor rate detected,respectively,by ultrasound contrast and TEM examination was of medium consistency.The application of intraoperative ultrasound contrast can improve the resection rate of brain glioma.展开更多
Identification of atomic disorders and their subsequent control has proven to be a key issue in predicting, understanding, and enhancing the properties of newly emerging topological insulator materials. Here, we demon...Identification of atomic disorders and their subsequent control has proven to be a key issue in predicting, understanding, and enhancing the properties of newly emerging topological insulator materials. Here, we demonstrate direct evidence of the cation antisites in single-crystal SnBi2Te4 nanoplates grown by chemical vapor deposition, through a combination of sub-angstr6m-resolution imaging, quantitative image simulations, and density functional theory calculations. The results of these combined techniques revealed a recognizable amount of cation antisites between Bi and Sn, and energetic calculations revealed that such cation antisites have a low formation energy. The impact of the cation antisites was also investigated by electronic structure calculations together with transport measurement. The topological surface properties of the nanoplates were further probed by angle-dependent magnetotransport, and from the results, we observed a two-dimensional weak antilocalization effect associated with surface carriers. Our approach provides a pathway to identify the antisite defects in ternary chalcogenides and the application potential of SnBi2Te4 nanostructures in next-generation electronic and spintronic devices.展开更多
文摘Graphene has demonstrated its potential in several practical applications owing to its remarkable electronic and physical properties. In this study, we successfully fabricated a suspended graphene device with a width down to 20 nm. The morphological evolution of graphene under various electric field effects was systematically examined using an in-situ transmission electron microscope （TEM）. The hourglass-shaped graphene sample instantly broke apart at 7.5 mA, indicating an impressive breakdown current density. The current-carrying capacity was calculated to be -1.6 × 10^9 A.cm-2, which is several orders higher than that of copper. The current-carrying capacity depended on the resistivity of graphene. In addition, atomic volume changes occurred in the multilayer graphene samples due to surface diffusion and Ostwald ripening （OR）, indicating that the breakdown mechanism is well approximated by the electric field. This study not only provides a theory to explain the breakdown behavior but also presents the effects on materials contacted with a graphene layer used as the transmission path.
文摘Background：Contrast-enhanced ultrasound is a dynamic and continuous modality providing real-time view of vascularization and flow distribution patterns of different organs and tumors.In order to evaluate the diagnostic significance of intraoperative contrast-enhanced ultrasound in assessing the resection degree of brain glioma by transmission electron microscopic （TEM） examination,it is important to have specific knowledge about contrast-enhanced ultrasound.Methods：Ultrasound contrast was applied in operations of 120 cases of brain glioma,to evaluate the degree of tumor resection.Biopsy tissues were obtained the suspicious residual tumors surrounding the tumor cavity.The sensitivity and specificity of the residual tumors were determined by the intraoperative ultrasound contrast according to TEM examination results.Results：There were 44 cases of low-grade gliomas and 76 cases of high-grade gliomas.Three hundred and sixty biopsy tissues were obtained.The sensitivity of intraoperative ultrasound contrast in diagnosing the residual tumor was 62.2%,while the specificity degree of it was 92.8%.The consistency coefficient of the ultrasound contrast diagnosis and TEM examination results was 0.584 （Kappa =0.584）,which was between 0.4 and 0.6,therefore it was of medium consistency.Conclusions：Intraoperative ultrasound contrast was of a high sensitivity and specificity in evaluating the excision degree of tumor.The consistency of the residual tumor rate detected,respectively,by ultrasound contrast and TEM examination was of medium consistency.The application of intraoperative ultrasound contrast can improve the resection rate of brain glioma.
文摘Identification of atomic disorders and their subsequent control has proven to be a key issue in predicting, understanding, and enhancing the properties of newly emerging topological insulator materials. Here, we demonstrate direct evidence of the cation antisites in single-crystal SnBi2Te4 nanoplates grown by chemical vapor deposition, through a combination of sub-angstr6m-resolution imaging, quantitative image simulations, and density functional theory calculations. The results of these combined techniques revealed a recognizable amount of cation antisites between Bi and Sn, and energetic calculations revealed that such cation antisites have a low formation energy. The impact of the cation antisites was also investigated by electronic structure calculations together with transport measurement. The topological surface properties of the nanoplates were further probed by angle-dependent magnetotransport, and from the results, we observed a two-dimensional weak antilocalization effect associated with surface carriers. Our approach provides a pathway to identify the antisite defects in ternary chalcogenides and the application potential of SnBi2Te4 nanostructures in next-generation electronic and spintronic devices.
