Recent advancement of proton exchange membrane fuel cells has led to commercial sales of fuel-cell cars but market barrier exists because this technology heavily relies on platinum catalyst.Given the permission of ado...Recent advancement of proton exchange membrane fuel cells has led to commercial sales of fuel-cell cars but market barrier exists because this technology heavily relies on platinum catalyst.Given the permission of adopting platinum-group-metal-free catalysts,anion-exchange membrane fuel cell has received notable attention.However,the sluggish kinetics of anodic hydrogen oxidation reaction(HOR)largely limit the cell efficiency.Although many high-performance HOR catalysts have been reported,there are analytical uncertainties in the literature concerning the assessment of the catalyst activity.Here we determine the origin of false HOR currents in the recorded polarization curves and propose a rigorous approach to eliminate them.We unveil experimentally the uncertainties of obtaining exchange current densities(j0)using Tafel plot from Bulter–Volmer equation and recommend employing the micro-polarization region method.For bulky catalysts that cannot establish a well-defined diffusion layer,we suggest applying external stirring bar to offer certain level of enforced convection and using j0 to compare the activity.展开更多
In order to explore and foster innovation in international exchange and cooperation,this study focuses on the background of the construction of the Hainan Free Trade Port.It delves into the current development status,...In order to explore and foster innovation in international exchange and cooperation,this study focuses on the background of the construction of the Hainan Free Trade Port.It delves into the current development status,characteristic demands,and potential challenges of its international exchange and cooperation mechanisms.Through a comprehensive analysis of relevant cases,survey questionnaires,and literature,this study aims to provide feasible innovative models and recommendations to promote the sustained development of the Hainan Free Trade Port in the field of international exchange and cooperation,injecting new vitality into China’s economic globalization.This exploration contributes to a deeper understanding of the development of free trade ports and provides insights and references for other countries and regions.展开更多
Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high i...Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high ionic conductivity. Solvent(e.g., isopropanol(IPA)) has been commonly applied for preparing LLZO powders and ceramics. However, the deterioration of the proton-exchange between LLZO and IPA/absorbed moisture during the mixing and tailoring route has aroused less attention. In this study, a solvent-free dry milling route was developed for preparing the LLZO powders and ceramics. For orthogonal four categories of samples prepared using solvent-free and IPA-assisted routes in the mixing and tailoring processes, the critical evaluation was conducted on the crystallinity, surficial morphology, and contamination of ascalcinated and as-tailored particles, the cross-sectional microstructure of green and sintered pellets,the morphology and electro-chemical properties of grain boundaries in ceramics, as well as the interfacial resistance and performance of Li anode based symmetric batteries. The wet route introduced Li-rich contaminations(e.g., Li OH·H)_(2)O and Li)_(2)CO)_(3)) onto the surfaces of LLZO particles and Li-Ta-O segregations at the adjacent and triangular grain boundaries. The LLZO solid electrolytes prepared through dry mixing in combination with the dry tailoring route without the use of any solvent were found to the optimal performance. The fundamental material properties in the whole LLZO preparation process were found, which are of guiding significance to the development of LLZO powder and ceramic production craft.展开更多
Bit Torrent文件共享系统中的搭便车(free-riding)节点会使系统性能大幅下降,目前,Bit Torrent主要采用choking策略来抑制搭便车行为,但与choking合作而存在的随机选择节点的unchoking策略仍然给搭便车行为提供了机会.提出了一种基于概...Bit Torrent文件共享系统中的搭便车(free-riding)节点会使系统性能大幅下降,目前,Bit Torrent主要采用choking策略来抑制搭便车行为,但与choking合作而存在的随机选择节点的unchoking策略仍然给搭便车行为提供了机会.提出了一种基于概率连接交换(probabilistic link exchange,简称PLX)的unchoking策略,在实现unchoking功能的同时,有效地抑制了搭便车行为.由于搭便车节点不提供上传,所以choking以后没有指向搭便车节点的连接,此时,PLX的连接交换机制就能抑制搭便车节点进入文件共享系统.另外,通过对连接交换概率的数学控制,PLX可以区分节点对共享系统的贡献,并根据贡献大小调整其在共享网络中的位置,进一步保证了公平性.最后,对PLX的影响进行了深入的理论分析和模拟实验验证,结果表明:PLX unchoking策略较现有的抵抗搭便车的方法更简单、直接,在效果上有明显提升.展开更多
Biomedical imaging,especially molecular imaging,has been a driving force in scientific discovery,technological innovation,and precision medicine in the past two decades.While substantial advances and discoveries in ch...Biomedical imaging,especially molecular imaging,has been a driving force in scientific discovery,technological innovation,and precision medicine in the past two decades.While substantial advances and discoveries in chemical biology have been made to develop molecular imaging probes and tracers,translating these exogenous agents to clinical application in precision medicine is a major challenge.Among the clinically accepted imaging modalities,magnetic resonance imaging(MRI)and magnetic resonance spectroscopy(MRS)exemplify the most effective and robust biomedical imaging tools.Both MRI and MRS enable a broad range of chemical,biological diagnosis and characterization of many diseases and image-guided interventions.Using chemical,biological,and nuclear magnetic resonance properties of specific endogenous metabolites and native MRI contrast-enhancing biomolecules,label-free molecular and cellular imaging with MRI can be achieved in biomedical research and clinical management of patients with various diseases.This review article outlines the chemical and biological bases of several label-free chemically and molecularly selective MRI and MRS methods that have been applied in imaging biomarker discovery,preclinical investigation,and image-guided clinical management.Examples are provided to demonstrate strategies for using endogenous probes to report the molecular,metabolic,physiological,and functional events and processes in living systems,including patients.Future perspectives on label-free molecular MRI and its challenges as well as potential solutions,including the use of rational design and engineered approaches to develop chemical and biological imaging probes to facilitate or combine with label-free molecular MRI,are discussed.展开更多
基金supported by the National Basic Research Program of China(No.2018YFA0702001)the National Natural Science Foundation of China(Nos.22225901,21975237,and 22175162)+3 种基金the Anhui Provincial Research and Development Program(No.202004a05020073)the Fundamental Research Funds for the Central Universities(No.WK2340000101)the USTC Research Funds of the Double First-Class Initiative(No.YD2340002007)the Open Funds of the State Key Laboratory of Rare Earth Resource Utilization(No.RERU2022007).
文摘Recent advancement of proton exchange membrane fuel cells has led to commercial sales of fuel-cell cars but market barrier exists because this technology heavily relies on platinum catalyst.Given the permission of adopting platinum-group-metal-free catalysts,anion-exchange membrane fuel cell has received notable attention.However,the sluggish kinetics of anodic hydrogen oxidation reaction(HOR)largely limit the cell efficiency.Although many high-performance HOR catalysts have been reported,there are analytical uncertainties in the literature concerning the assessment of the catalyst activity.Here we determine the origin of false HOR currents in the recorded polarization curves and propose a rigorous approach to eliminate them.We unveil experimentally the uncertainties of obtaining exchange current densities(j0)using Tafel plot from Bulter–Volmer equation and recommend employing the micro-polarization region method.For bulky catalysts that cannot establish a well-defined diffusion layer,we suggest applying external stirring bar to offer certain level of enforced convection and using j0 to compare the activity.
文摘In order to explore and foster innovation in international exchange and cooperation,this study focuses on the background of the construction of the Hainan Free Trade Port.It delves into the current development status,characteristic demands,and potential challenges of its international exchange and cooperation mechanisms.Through a comprehensive analysis of relevant cases,survey questionnaires,and literature,this study aims to provide feasible innovative models and recommendations to promote the sustained development of the Hainan Free Trade Port in the field of international exchange and cooperation,injecting new vitality into China’s economic globalization.This exploration contributes to a deeper understanding of the development of free trade ports and provides insights and references for other countries and regions.
基金the financial support from the National Key R&D Project (2018YFE0181300)the National Natural Science Foundation of China (Grant No. 52102284)+2 种基金the China Postdoctoral Science Foundation (2020M682871)the Guangdong Natural Science Funds (2019A1515010675)the Science and Technology Project of Shenzhen (JCYJ20190808142209376 and JCYJ20210324094206019)。
文摘Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high ionic conductivity. Solvent(e.g., isopropanol(IPA)) has been commonly applied for preparing LLZO powders and ceramics. However, the deterioration of the proton-exchange between LLZO and IPA/absorbed moisture during the mixing and tailoring route has aroused less attention. In this study, a solvent-free dry milling route was developed for preparing the LLZO powders and ceramics. For orthogonal four categories of samples prepared using solvent-free and IPA-assisted routes in the mixing and tailoring processes, the critical evaluation was conducted on the crystallinity, surficial morphology, and contamination of ascalcinated and as-tailored particles, the cross-sectional microstructure of green and sintered pellets,the morphology and electro-chemical properties of grain boundaries in ceramics, as well as the interfacial resistance and performance of Li anode based symmetric batteries. The wet route introduced Li-rich contaminations(e.g., Li OH·H)_(2)O and Li)_(2)CO)_(3)) onto the surfaces of LLZO particles and Li-Ta-O segregations at the adjacent and triangular grain boundaries. The LLZO solid electrolytes prepared through dry mixing in combination with the dry tailoring route without the use of any solvent were found to the optimal performance. The fundamental material properties in the whole LLZO preparation process were found, which are of guiding significance to the development of LLZO powder and ceramic production craft.
基金supported in parts by the grants from NIH(R01CA203388−04,R01AG067736−02)to HM,(R01CA261974,R33HL161756)to GL.CCF is supported,in part,by NIH grant DP2NS127704−01.
文摘Biomedical imaging,especially molecular imaging,has been a driving force in scientific discovery,technological innovation,and precision medicine in the past two decades.While substantial advances and discoveries in chemical biology have been made to develop molecular imaging probes and tracers,translating these exogenous agents to clinical application in precision medicine is a major challenge.Among the clinically accepted imaging modalities,magnetic resonance imaging(MRI)and magnetic resonance spectroscopy(MRS)exemplify the most effective and robust biomedical imaging tools.Both MRI and MRS enable a broad range of chemical,biological diagnosis and characterization of many diseases and image-guided interventions.Using chemical,biological,and nuclear magnetic resonance properties of specific endogenous metabolites and native MRI contrast-enhancing biomolecules,label-free molecular and cellular imaging with MRI can be achieved in biomedical research and clinical management of patients with various diseases.This review article outlines the chemical and biological bases of several label-free chemically and molecularly selective MRI and MRS methods that have been applied in imaging biomarker discovery,preclinical investigation,and image-guided clinical management.Examples are provided to demonstrate strategies for using endogenous probes to report the molecular,metabolic,physiological,and functional events and processes in living systems,including patients.Future perspectives on label-free molecular MRI and its challenges as well as potential solutions,including the use of rational design and engineered approaches to develop chemical and biological imaging probes to facilitate or combine with label-free molecular MRI,are discussed.
