Ultrafast photoemission electron microscopy:A multidimensional probe of nonequilibrium physics

Exploring the realms of physics that extend beyond thermal equilibrium has emerged as a crucial branch of condensed matter physics research.It aims to unravel the intricate processes involving the excitations,interactions,and annihilations of quasi-and many-body particles,and ultimately to achieve the manipulation and engineering of exotic non-equilibrium quantum phases on the ultrasmall and ultrafast spatiotemporal scales.Given the inherent complexities arising from many-body dynamics,it therefore seeks a technique that has efficient and diverse detection degrees of freedom to study the underlying physics.By combining high-power femtosecond lasers with real-or momentum-space photoemission electron microscopy(PEEM),imaging excited state phenomena from multiple perspectives,including time,real space,energy,momentum,and spin,can be conveniently achieved,making it a unique technique in studying physics out of equilibrium.In this context,we overview the working principle and technical advances of the PEEM apparatus and the related laser systems,and survey key excited-state phenomena probed through this surface-sensitive methodology,including the ultrafast dynamics of electrons,excitons,plasmons,spins,etc.,in materials ranging from bulk and nano-structured metals and semiconductors to low-dimensional quantum materials.Through this review,one can further envision that time-resolved PEEM will open new avenues for investigating a variety of classical and quantum phenomena in a multidimensional parameter space,offering unprecedented and comprehensive insights into important questions in the field of condensed matter physics.

Investigation of reflection anisotropy induced by micropipe defects on the surface of a 4H-SiC single crystal using scanning anisotropy microscopy

Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy(SAM)system.The reflection anisotropy(RA)image with a'butterfly pattern'is obtained around the micropipes by SAM.The RA image of the edge dislocations is theoretically simulated based on dislocation theory and the photoelastic principle.By comparing with the Raman spectrum,it is verified that the micropipes consist of edge dislocations.The different patterns of the RA images are due to the different orientations of the Burgers vectors.Besides,the strain distribution of the micropipes is also deduced.One can identify the dislocation type,the direction of the Burgers vector and the optical anisotropy from the RA image by using SAM.Therefore,SAM is an ideal tool to measure the optical anisotropy induced by the strain field around a defect.

A review of understanding electrocatalytic reactions in energy conversion and energy storage systems via scanning electrochemical microscopy

To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.

Characterization of local chemical ordering and deformation behavior in high entropy alloys by transmission electron microscopy

Short-range ordering(SRO)is one of the most important structural features of high entropy alloys(HEAs).However,the chemical and structural analyses of SROs are very difficult due to their small size,complexed compositions,and varied locations.Transmission electron microscopy(TEM)as well as its aberration correction techniques are powerful for characterizing SROs in these compositionally complex alloys.In this short communication,we summarized recent progresses regarding characterization of SROs using TEM in the field of HEAs.By using advanced TEM techniques,not only the existence of SROs was confirmed,but also the effect of SROs on the deformation mechanism was clarified.Moreover,the perspective related to application of TEM techniques in HEAs are also discussed.

Capturing the non-equilibrium state in light–matter–free-electron interactions through ultrafast transmission electron microscopy

Ultrafast transmission electron microscope(UTEM) with the multimodality of time-resolved diffraction, imaging,and spectroscopy provides a unique platform to reveal the fundamental features associated with the interaction between free electrons and matter. In this review, we summarize the principles, instrumentation, and recent developments of the UTEM and its applications in capturing dynamic processes and non-equilibrium transient states. The combination of the transmission electron microscope with a femtosecond laser via the pump–probe method guarantees the high spatiotemporal resolution, allowing the investigation of the transient process in real, reciprocal and energy spaces. Ultrafast structural dynamics can be studied by diffraction and imaging methods, revealing the coherent acoustic phonon generation and photoinduced phase transition process. In the energy dimension, time-resolved electron energy-loss spectroscopy enables the examination of the intrinsic electronic dynamics of materials, while the photon-induced near-field electron microscopy extends the application of the UTEM to the imaging of optical near fields with high real-space resolution. It is noted that light–free-electron interactions have the ability to shape electron wave packets in both longitudinal and transverse directions, showing the potential application in the generation of attosecond electron pulses and vortex electron beams.

Correlation of work function and stacking fault energy through Kelvin probe force microscopy and nanohardness in diluteα-magnesium

Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca,Mg-Sr and Mg-Ba systems.This investigation incorporated the difference in the‘Work Function'(ΔWF)measured via Kelvin Probe Force Microscopy(KPFM),as a property directly affected by interatomic bond types,i.e.the electronic structure,nanoindentation measurements,and Stacking Fault Energy values reported in the literature.It was shown that the nano-hardness of the solid-solutionα-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba.Thus,it was shown,by also considering the nano-hardness levels,that SFE of a solid-solution is closely correlated with its‘Work Function'level.Nano-hardness measurements on the eutectics andΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys.Correlation withΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree,relatively simple atomic models and a number of assumptions.As asserted by this investigation,if the results of measurement techniques can be qualitatively correlated with those of the computational methods,it can be possible to evaluate the electronic structures in alloys,starting from binary systems,going to ternary and then multi-elemental systems.Our investigation has shown that such a qualitative correlation is possible.After all,the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level,that is,free electron density distributions.Our study indicated that the principles of‘electronic metallurgy'in developing multi-elemental alloy systems can be followed via practical experimental methods,i.e.ΔWF measurements using KPFM and nanoindentation.

Al-SCM-25分子筛的合成及其催化性能研究

将Al引入硅锗分子筛骨架是提升其骨架稳定性、增强酸性的有效手段。本工作首次采用直接合成法将Al引入SCM-25分子筛骨架,制备了不同铝含量的Al-SCM-25分子筛。考察了水量、铝含量、晶种添加对合成的影响,发现与SCM-25分子筛的合成相比,Al-SCM-25分子筛需要在更高的水量和晶种存在的条件下才可以完全结晶。采用N_(2)物理吸附、^(27)Al魔角旋转固体核磁(^(27)Al MAS NMR)、氨气程序升温脱附(NH_(3)-TPD) 等手段表征了Al-SCM-25分子筛的孔结构性质、铝配位状态及酸性。结果表明,Al-SCM-25具有与SCM-25相近的比表面积和微孔体积;大部分铝以四配位形式进入骨架中,从而产生了比SCM-25分子筛数量更多、 强度更高的酸性位。在环己酮Baeyer-Villiger氧化制备 ε-己内酯反应中,Al-SCM-25分子筛相较SCM-25分子筛表现出更高的环己酮转化率和目标产物的收率,并且具有较好的循环稳定性。

基于SCM320单片机的智能速断开关系统设计

传统跌落式熔断器由于工作机制原理限制存在一定的固有缺陷,在一定程度上影响了配网故障隔离,为克服此类缺陷,进一步减小故障区间,提高线路重合闸成功率,减少客户受累停运情况的发生,结合当前配网发展一二次融合的要求,提出一种新型的、参数可调的配网开关系统。该系统基于SCM320单片机,采用冗余设计,由多模块构成,以实现快速智能断电功能。在硬件、软件设计基础上进行点火驱动信号、绝缘及开断实验,结果表明该系统在智慧配网开关设备中具有可行性,且有助于提高供电可靠性,对于智慧电网的建设和发展具有一定的参考和应用价值。

基于SCM视角的高校数字化工会组织协同建设研究

数字化转型是新形势下高校工会建设的工作重点之一,对高校工会组织运行模式、建设方向提出了新的要求。如何优化高校工会组织架构、组织服务链条以迎合数字化技术的智能扶持,是急需解决的问题。结合当前高校数字化智能工会建设现状,引入供应链管理(supply chain management, SCM)指导思路,从2条主线、5个方面提出优化数字化智慧工会组织建设的路径,以期为高校工会数字化转型提供参考。

From static to dynamic:live observation of the support system after ischemic stroke by two photon-excited fluorescence laser-scanning microscopy

Ischemic stroke is one of the most common causes of mortality and disability worldwide.However,treatment efficacy and the progress of research remain unsatisfactory.As the critical support system and essential components in neurovascular units,glial cells and blood vessels(including the bloodbrain barrier)together maintain an optimal microenvironment for neuronal function.They provide nutrients,regulate neuronal excitability,and prevent harmful substances from entering brain tissue.The highly dynamic networks of this support system play an essential role in ischemic stroke through processes including brain homeostasis,supporting neuronal function,and reacting to injuries.However,most studies have focused on postmortem animals,which inevitably lack critical information about the dynamic changes that occur after ischemic stroke.Therefore,a high-precision technique for research in living animals is urgently needed.Two-photon fluorescence laser-scanning microscopy is a powerful imaging technique that can facilitate live imaging at high spatiotemporal resolutions.Twophoton fluorescence laser-scanning microscopy can provide images of the whole-cortex vascular 3D structure,information on multicellular component interactions,and provide images of structure and function in the cranial window.This technique shifts the existing research paradigm from static to dynamic,from flat to stereoscopic,and from single-cell function to multicellular intercommunication,thus providing direct and reliable evidence to identify the pathophysiological mechanisms following ischemic stroke in an intact brain.In this review,we discuss exciting findings from research on the support system after ischemic stroke using two-photon fluorescence laser-scanning microscopy,highlighting the importance of dynamic observations of cellular behavior and interactions in the networks of the brain’s support systems.We show the excellent application prospects and advantages of two-photon fluorescence laser-scanning microscopy and predict future research developments and directions in the study of ischemic stroke.

家具智能制造ERP/SCM/CRM管理系统集成方法研究

在定制家具企业中依靠软件进行智能化管理成为主要的管理手段,如何将各大管理系统相互融合、建立系统集成管理平台对定制家具企业的发展起到至关重要的作用。定制家具企业要实现数字化智能制造,需要的是各类信息系统的集成,其中ERP与SCM、CRM的集成显得尤为重要。分析了定制家具企业智能制造的发展现状,得出智能制造存在不完善的地方;通过对家具企业智能化管理主要软件解读,得出智能化管理平台软件集成存在问题和必要性;在此基础上,提出构建定制家具ERP与SCM、CRM集成方法,包括:建立系统功能统一标准、ERP与SCM、CRM业务流程集成、ERP与SCM、CRM集成管控;为我国智能制造的定制家具产业的发展提供新的路径。

SCM-36分子筛纳米片用于乙烯和2,5-二甲基呋喃转化制可再生对二甲苯

分子筛是一类重要的结晶多孔材料,广泛应用于化学工业.开发新型分子筛特别是硅铝酸盐分子筛,一直是该领域的研究热点.分子筛的晶化过程一般需要结构导向剂的参与,包括碱(土)金属离子为代表的无机阳离子,有机胺或季铵盐为代表的有机物以及分子筛晶种.采用两种及以上结构导向剂的分子筛合成策略,具有调节分子筛骨架原子、晶体形貌和化学组成的作用,是开发新分子筛的有效手段.对二甲苯(PX)是合成对苯二甲酸乙二醇酯(PET)的重要原料.PX主要来源于石油资源,开发基于生物质原料生产PX的技术有利于缓解日益严峻的环境和能源危机.本文采用两种有机结构导向剂,以四甲基氢氧化铵(TMAOH)为有机结构导向剂,同时向体系中加入十六烷基溴化吡啶(C_(16)Py Br)或正辛基三甲基氯化铵(OTMAC),合成了一种新型铝硅酸盐分子筛,命名为SCM-36(Sinopec Composite Material No.36).SCM-36分子筛具有独特的X射线粉末衍射谱图(XRD)和纳米片状形貌.原位XRD结果表明,SCM-36分子筛在焙烧过程中由于晶胞收缩而导致衍射峰的偏移.扫描电子显微镜(SEM)、原子力显微镜以及共聚焦荧光成像显微镜表征结果表明,分子筛为纳米片形貌,厚度为6.9-14.9 nm.N_(2)和Ar物理吸附-脱附结果表明,SCM-36分子筛的BET表面积为355 m^(2)/g,其具有0.59 nm和0.67 nm左右孔尺寸的微孔孔道.两种有机结构导向剂都进入了分子筛孔道,在焙烧时于不同的温度区间发生分解.原位CO傅里叶变换红外光谱结果表明,SCM-36的Brönsted酸强度(△υ(CO…OH)=313 cm^(-1))与ZSM-5相当.采用原位紫外可见光吸收光谱监测4-甲氧基苯乙烯和4-氟苯乙烯的低聚探针反应过程,证实了SCM-36分子筛同时具有强酸和弱酸,且以弱酸为主的酸性质.在催化DMF和乙烯制备PX的反应中,SCM-36分子筛不仅表现出与传统分子筛(ZSM-5,Beta)相当的高转化率,而且表现出更高的PX选择性(93%).其较好的催化性能归因于该分子筛良好的扩散性能和适宜的酸性质.且SCM-36分子筛的稳定性较好,可重复使用.综上,利用双有机结构导向剂合成分子筛是开发新分子筛的有效策略,采用该策略合成的SCM-36纳米片分子筛具有潜在的应用价值.

碳交易绿色发展效应的地区异质性如何?——基于PSM-DID和SCM模型的实证研究

本文以2006-2021年我国30个省份为研究样本,基于SBM-GML指数测度绿色全要素生产率衡量绿色发展水平。首先,使用倾向得分匹配-双重差分探讨碳排放权交易试点总体的绿色发展效应;其次,采用SCM研究碳排放交易绿色发展效应的试点异质性并进行排序检验。研究结果表明:(1)试点省份的碳交易绿色发展效应显著;(2)碳交易对试点省份绿色发展的影响效应存在地区异质性,即碳交易在北京和重庆的绿色发展效应最佳,其次为天津和上海,效应相对欠佳的为广东和湖北试点;(3)能源强度下降、国际贸易和环境污染治理投资是碳交易机制推动绿色发展的路径。

Nonlinear optical microscopy for skin in vivo:Basics,development and applications

Multi-photon microscopy(MPM)and coherent anti-Stokes Raman scattering(CARS)are two advanced nonlinear optical imaging techniques,which provide complementary information and have great potential in combination for noninvasive in vrito biomedical applications.This paper provides a detailed discussion of the basics,development and applications of these technologies for in vrivo skin research,covering the following topics:The principle and advantage of MPM and CARS,instrumentation development for in vino applications,MPM and CARS of normal skin,application of MPM and CARS in skin cancer and disease diagnosis;application of MPM in skin disease intervention,ie.,imaging guided two-photon photothermolysis.

Comparative Performance of Microscopy and Nested PCR for the Detection of Cryptosporidium Species in Patients Living with HIV/AIDS in Abidjan (Côte d’Ivoire)

Cryptosporidium spp. infection is one of the causes of diarrhea in people living with HIV/AIDS. The objective of this study is to compare the sensitivity of microscopy and molecular biology to determine the prevalence of Cryptosporidium spp. in Patients Living With HIV (PLWH). This is a descriptive cross-sectional study conducted in three care centers for people living with HIV/AIDS in Abidjan. It took place from November 2018 to March 2020. Sociodemographic data were obtained via a questionnaire. Stool and blood samples were collected and analyzed for microscopy and Nested PCR detection of Cryptosporidium spp. Blood samples were analyzed for CD4+ count. A total of 363 stool samples were collected from the three sites. Individuals aged 40 - 50 years (36.52%) were most likely to participate in the study. HIV Type 1 accounted for 86.22% of the study population. The samples collected consisted of 47.65% diarrheal stool. Microscopic examination of the stool yielded a prevalence of 3.86% for Cryptosporidium spp. while the prevalence was 3.96% with molecular identification. No statistically significant difference was observed between these two prevalences (χ2 = 0.26;p = 0.609). CD4+ count was the factor associated with Cryptosporidium spp. infection for both microscopy (OR = 0.887, p = 0.001) and PCR (OR = 0.896, p = 0.001). This study demonstrated that Nested PCR improves the detection of Cryptosporidium spp. in patient diagnosis.

Light field microscopy in biological imaging

Light field microscopy(LFM),featured for high threedimensional imaging speed and low pho-totoxicity,has emeged as a technique of choice for instantaneous volumetric inaging.In contrast with other scanning-based three dimensional(3D)imaging approaches,LFM enables to encode 3D spatial information in a snapshot manner,permitting high-speed 3D imaging that is only limited by the frame rate of the camera.In this review,we first introduce the fundamental theory of LFM and current corresponding advanced approaches.Then,we summarize various applica-tions of LFM in biological imaging.

Correlating the Interfacial Polar-Phase Structure to the Local Chemistry in Ferroelectric Polymer Nanocomposites by Combined Scanning Probe Microscopy

Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region.However,the structure-property correlation of the interface remains unestablished,and thus,the design of ferroelectric polymer nanocompos-ite has largely relied on the trial-and-error method.Here,a strategy that combines multi-mode scanning probe microscopy-based electrical charac-terization and nano-infrared spectroscopy is developed to unveil the local structure-property correlation of the interface in ferroelectric polymer nano-composites.The results show that the type of surface modifiers decorated on the nanoparticles can significantly influence the local polar-phase content and the piezoelectric effect of the polymer matrix surrounding the nano-particles.The strongly coupled polar-phase content and piezoelectric effect measured directly in the interfacial region as well as the computed bonding energy suggest that the property enhancement originates from the formation of hydrogen bond between the surface modifiers and the ferroelectric polymer.It is also directly detected that the local domain size of the ferroelectric polymer can impact the energy level and distribution of charge traps in the interfacial region and eventually influence the local dielectric strength.

电力生产计划自动传达SCM控制系统的技术探讨

本研究介绍了智能化技术、SCM控制系统的基本概况,并总结了电力生产计划自动传达SCM控制系统的技术要点。

Comparison of point detection and area detection for point-scanning structured illumination microscopy

Structured illumination microscopy(SIM)is suitable for biological samples because of its relatively low-peak illumination intensity requirement and high imaging speed.The system resolution is affected by two typical detection modes:Point detection and area detection.However,a systematic analysis of the imaging performance of the different detection modes of the system has rarely been conducted.In this study,we compared laser point scanning point detection(PS-PD)and point scanning area detection(PS-AD)imaging in nonconfocal microscopy through theoretical analysis and simulated imaging.The results revealed that the imaging resolutions of PSPD and PS-AD depend on excitation and emission point spread functions(PSFs),respectively.Especially,we combined the second harmonic generation(SHG)of point detection(P-SHG)and area detection(A-SHG)with SIM to realize a nonlinear SIM-imaging technique that improves the imaging resolution.Moreover,we analytically and experimentally compared the nonlinear SIM performance of P-SHG with that of A-SHG.

Classification of Human Protein in Multiple Cells Microscopy Images Using CNN

The subcellular localization of human proteins is vital for understanding the structure of human cells.Proteins play a significant role within human cells,as many different groups of proteins are located in a specific location to perform a particular function.Understanding these functions will help in discoveringmany diseases and developing their treatments.The importance of imaging analysis techniques,specifically in proteomics research,is becoming more prevalent.Despite recent advances in deep learning techniques for analyzing microscopy images,classification models have faced critical challenges in achieving high performance.Most protein subcellular images have a significant class imbalance.We use oversampling and under sampling techniques in this research to overcome this issue.We have used a Convolutional Neural Network(CNN)model called GapNet-PL for the multi-label classification task on the Human Protein Atlas Classification(HPA)Dataset.Authors have found that the ParametricRectified LinearUnit(PreLU)activation function is better than the Scaled Exponential LinearUnit(SeLU)activation function in the GapNet-PL model in most classification metrics.The results showed that the GapNet-PL model with the PReLU activation function achieved an area under the ROC curve(AUC)equal to 0.896,an F1 score of 0.541,and a recall of 0.473.