Metal–organic frameworks(MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1,2]It is challenging to visualize MOFs with transmissi...Metal–organic frameworks(MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1,2]It is challenging to visualize MOFs with transmission electron microscopy(TEM) due to their inherent instability under electron beam irradiation. Here, we employ cryo-electron microscopy(cryoEM) to capture images of MOF ZIF-8, revealing inverted-space structural information at a resolution of up to about 1.7A and enhancing its critical electron dose to around 20 e^(-)/A^(2). In addition, it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis, and the structure of ZIF-8 is more stable along the [100] direction under electron beam irradiation. Meanwhile, since the high-resolution electron microscope images are modulated by contrast transfer function(CTF) and it is difficult to determine the positions corresponding to the atomic columns directly from the images. We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8. As a result, the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.展开更多
Audio signal separation is an open and challenging issue in the classical“Cocktail Party Problem”.Especially in a reverberation environment,the separation of mixed signals is more difficult separated due to the infl...Audio signal separation is an open and challenging issue in the classical“Cocktail Party Problem”.Especially in a reverberation environment,the separation of mixed signals is more difficult separated due to the influence of reverberation and echo.To solve the problem,we propose a determined reverberant blind source separation algorithm.The main innovation of the algorithm focuses on the estimation of the mixing matrix.A new cost function is built to obtain the accurate demixing matrix,which shows the gap between the prediction and the actual data.Then,the update rule of the demixing matrix is derived using Newton gradient descent method.The identity matrix is employed as the initial demixing matrix for avoiding local optima problem.Through the real-time iterative update of the demixing matrix,frequency-domain sources are obtained.Then,time-domain sources can be obtained using an inverse short-time Fourier transform.Experi-mental results based on a series of source separation of speech and music mixing signals demonstrate that the proposed algorithm achieves better separation performance than the state-of-the-art methods.In particular,it has much better superiority in the highly reverberant environment.展开更多
健康的社会决定因素(social determinants of health,SDH)纳入医学教育,是以健康为中心,弥合公共卫生与临床医学教育裂痕、卫生系统协调发展的需要。各学校将其纳入医学教育的形式和教育侧重点各不相同,有的以短期课程形式,有的将其融...健康的社会决定因素(social determinants of health,SDH)纳入医学教育,是以健康为中心,弥合公共卫生与临床医学教育裂痕、卫生系统协调发展的需要。各学校将其纳入医学教育的形式和教育侧重点各不相同,有的以短期课程形式,有的将其融入临床实习,有的以专设项目形式贯穿教育教学环节,覆盖领域也各有侧重。以SDH教育为切入点推动了教学方法变革,参与式的课堂、实践中的体验式学习、批判性反思、协作学习等转化式学习方式,为SDH纳入医学教育实践提供了良好的方法支撑。未来需进一步关注消除课程壁垒、整合教育教学过程的教育模式变革。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074409 and 12374021)。
文摘Metal–organic frameworks(MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1,2]It is challenging to visualize MOFs with transmission electron microscopy(TEM) due to their inherent instability under electron beam irradiation. Here, we employ cryo-electron microscopy(cryoEM) to capture images of MOF ZIF-8, revealing inverted-space structural information at a resolution of up to about 1.7A and enhancing its critical electron dose to around 20 e^(-)/A^(2). In addition, it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis, and the structure of ZIF-8 is more stable along the [100] direction under electron beam irradiation. Meanwhile, since the high-resolution electron microscope images are modulated by contrast transfer function(CTF) and it is difficult to determine the positions corresponding to the atomic columns directly from the images. We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8. As a result, the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.
基金This research was partially supported by the National Natural Science Foundation of China under Grant 52105268Natural Science Foundation of Guangdong Province under Grant 2022A1515011409+2 种基金Key Platforms and Major Scientific Research Projects of Universities in Guangdong under Grants 2019KTSCX161 and 2019KTSCX165Key Projects of Natural Science Research Projects of Shaoguan University under Grants SZ2020KJ02 and SZ2021KJ04the Science and Technology Program of Shaoguan City of China under Grants 2019sn056,200811094530423,200811094530805,and 200811094530811.
文摘Audio signal separation is an open and challenging issue in the classical“Cocktail Party Problem”.Especially in a reverberation environment,the separation of mixed signals is more difficult separated due to the influence of reverberation and echo.To solve the problem,we propose a determined reverberant blind source separation algorithm.The main innovation of the algorithm focuses on the estimation of the mixing matrix.A new cost function is built to obtain the accurate demixing matrix,which shows the gap between the prediction and the actual data.Then,the update rule of the demixing matrix is derived using Newton gradient descent method.The identity matrix is employed as the initial demixing matrix for avoiding local optima problem.Through the real-time iterative update of the demixing matrix,frequency-domain sources are obtained.Then,time-domain sources can be obtained using an inverse short-time Fourier transform.Experi-mental results based on a series of source separation of speech and music mixing signals demonstrate that the proposed algorithm achieves better separation performance than the state-of-the-art methods.In particular,it has much better superiority in the highly reverberant environment.
文摘健康的社会决定因素(social determinants of health,SDH)纳入医学教育,是以健康为中心,弥合公共卫生与临床医学教育裂痕、卫生系统协调发展的需要。各学校将其纳入医学教育的形式和教育侧重点各不相同,有的以短期课程形式,有的将其融入临床实习,有的以专设项目形式贯穿教育教学环节,覆盖领域也各有侧重。以SDH教育为切入点推动了教学方法变革,参与式的课堂、实践中的体验式学习、批判性反思、协作学习等转化式学习方式,为SDH纳入医学教育实践提供了良好的方法支撑。未来需进一步关注消除课程壁垒、整合教育教学过程的教育模式变革。
