In x-ray dark-field imaging using dual phase grating interferometer,multi-contrast signals are extracted from a set of acquired phase-stepping data by using the least-squares fitting algorithm.The extracted mean inten...In x-ray dark-field imaging using dual phase grating interferometer,multi-contrast signals are extracted from a set of acquired phase-stepping data by using the least-squares fitting algorithm.The extracted mean intensity,amplitude and visibility signals may be intrinsically biased.However,it is still unclear how large these biases are and how the data acquisition parameters influence the biases in the extracted signals.This work set out to address these questions.Analytical expressions of the biases of the extracted signals were theoretically derived by using a second-order Taylor series expansion.Extensive numerical simulations were performed to validate the theoretical results.It is illustrated that while the estimated mean intensity signal is always unbiased,the estimated amplitude and visibility signals are both positively biased.While the biases of the estimated amplitude signals are proportional to the inverse of the total number of phase steps,the biases of the estimated visibility signals are inversely proportional to the product of the total number of phase steps and the mean number of photons counted per phase step.Meanwhile,it is demonstrated that the dependence of the biases on the mean visibility is quite different from that of Talbot-Lau interferometer due to the difference in the intensity model.We expect that these results can be useful for data acquisition optimizations and interpretation of x-ray dark-field images.展开更多
X-ray dark-field imaging using a grating interferometer has shown potential benefits for a variety of applications in recent years.X-ray dark-field image is commonly retrieved by using discrete Fourier transform from ...X-ray dark-field imaging using a grating interferometer has shown potential benefits for a variety of applications in recent years.X-ray dark-field image is commonly retrieved by using discrete Fourier transform from the acquired phasestepping data.The retrieval process assumes a constant phase step size and a constant flux for each stepped grating position.However,stepping errors and flux fluctuations inevitably occur due to external vibrations and/or thermal drift during data acquisition.Previous studies have shown that those influences introduce errors in the acquired phase-stepping data,which cause obvious moiréartifacts in the retrieved refraction image.This work investigates moiréartifacts in x-ray dark-field imaging as a result of flux fluctuations.For the retrieved mean intensity,amplitude,visibility and dark-field images,the dependence of moiréartifacts on flux fluctuation factors is theoretically derived respectively by using a first-order Taylor series expansion.Results of synchrotron radiation experiments verify the validity of the derived analytical formulas.The spatial frequency characteristics of moiréartifacts are analyzed and compared to those induced by phase-stepping errors.It illustrates that moiréartifacts can be estimated by a weighted mean of flux fluctuation factors,with the weighting factors dependent on the moiréphase and different greatly for each retrieved image.Furthermore,moiréartifacts can even be affected by object’s features not displayed in the particular contrast.These results can be used to interpret images correctly,identify sources of moiréartifacts,and develop dedicated algorithms to remove moiréartifacts in the retrieved multi-contrast images.展开更多
Objective： Hemodilution changes the physical properties of blood by reducing its hematocrit and blood viscosity. We tested whether prolonged hypervolemic hemodilution （HHD） impairs functional capillary density （FC...Objective： Hemodilution changes the physical properties of blood by reducing its hematocrit and blood viscosity. We tested whether prolonged hypervolemic hemodilution （HHD） impairs functional capillary density （FCD） of ileal mucosa in healthy mechanically-ventilated pigs and if there is any correlation between changes in FCD of ileal and sublingual mucosas during HHD. Methods： Sixteen domestic female pigs were anesthetized, mechanically-ventilated, and randomly assigned to the HHD （20 ml/（kg.h） Hartmann＇s solution for 3 h） or fluid restrictive （5 ml/（kg-h） Hartmann＇s solution for 3 h） group. Microcirculations of sublingual and ileal mucosas via ileostomy were visualized using sidestream dark-field （SDF） imaging at baseline conditions （t=0 h） and at selected time intervals of fluid therapy （t=-l, 2, and 3 h）. Results： A significant decrease of ileal FCD （285 （278-292） cm/cm^2） in the HHD group was observed after the third hour of HHD when compared to the baseline （360 （350-370） cm/cm2） （P〈0.01）. This trend was not observed in the restrictive group, where the ileal mucosa FCD was significantly higher after the third hour of fluid therapy as compared to the HHD group （P〈0.01）. No correlation between microhemodynamic parameters obtained from sublingual and ileal mucosas was found throughout the study. Conclusions： Prolonged HHD established by crystalloid solution significantly decreased ileal villus FCD when compared to restrictive fluid regimen. An inappropriate degree of HHD can be harmful during uncomplicated abdominal surgery.展开更多
The observation of single-particle surface-enhanced Raman scattering(SERS)has generated considerable interest both in the nanomaterials filed and in the single-particle spectroscopy community.It is a challenge to real...The observation of single-particle surface-enhanced Raman scattering(SERS)has generated considerable interest both in the nanomaterials filed and in the single-particle spectroscopy community.It is a challenge to realize rapid,facile,and high throughput SERS at single nanoparticle level.Here,without the complex experimental device and difficult experimental operations,a general single-particle SERS technique has been achieved by using dark-field-assisted surface-enhanced Raman spectroscopy(DFSERS).This advanced method provides in-situ characterization of the chemical reaction performance at single gold nanorod.展开更多
目的探究脓毒症及感染性休克时舌下微循环与肠系膜微循环的关系，以及舌下、肠系膜微循环与整体血流动力学的关系。方法采用12头五指山近交系小型猪，随机分为对照组（n=6）和脓毒症组（n=6）。采用自体粪便注入腹腔方法制备腹膜炎脓毒...目的探究脓毒症及感染性休克时舌下微循环与肠系膜微循环的关系，以及舌下、肠系膜微循环与整体血流动力学的关系。方法采用12头五指山近交系小型猪，随机分为对照组（n=6）和脓毒症组（n=6）。采用自体粪便注入腹腔方法制备腹膜炎脓毒症模型。对照组仅做肠扰动。两组皆连续监测动脉血压、中心静脉压及每小时尿量。实验组猪模型制备完成后，分别于0、4、8、12h采用旁流暗视野技术（sidestream dark field imaging techniques，SDF）采集舌下及肠系膜微循环图像，猪休克后[平均动脉压（MAP）≤65mmHg]分别采集0、2、4h舌下及肠系膜微循环图像，微循环采用总血管密度（TVD）、灌注血管密度（PVD）、灌注血管比例（PPV）、微血管流动指数（MFI）作为观察指标，微循环指标由AVA3．0软件进行半定量分析。同时留取动脉血监测动脉血氧分压（PaO2）、二氧化碳分压（PaCO2）及血乳酸（Lac），相同时间点监测心率（HR）、平均动脉压（MAP）、心指数（CI）。结果①脓毒症模型制备8h后实验组猪舌下微循环和肠系膜微循环PPV和MFI与基线比较明显下降（〉30％，P〈0．05），实验组猪在出现感染性休克时舌下和肠系膜微循环PPV和MFI下降更为明显（〉50％，P〈0．05）。PVD较晚出现明显差异，舌下微循环和肠系膜微循环分别在制模12h及休克后0h出现；舌下微循环和肠系膜微循环TVD在整个实验过程中变化差异无统计学意义。②实验组猪舌下微循环和肠系膜微循环变化有明显的相关性（MFI：r=0．60，P〈0．01；TVD：r=0．284，P〈0．01；PVD：r=0．492，P〈0．01；PPV：r=0．705，P〈0．01）。③实验组猪休克前，CI与舌下微循环及肠系膜微循环PPV、MFI均存在相关性。休克后CI与舌下微循环及肠系膜微循环各指标均无相关性。休克前后舌下微循环及肠系膜微循环与MAP均无相关性。在脓毒症模型制备后12h，MAP〉100mmHg，舌下微循环及肠系膜微循环PPV、MFI均在模型制备后8h出现明显下降。微循环改变发生在MAP下降之前。结论①脓毒症及感染性休克猪存在微循环改变，且在感染性休克时微循环障碍更严重；②舌下微循环与肠系膜微循环存在相关性，可以通过SDF技术监测舌下微循环间接反映脏器微循环的变化；③微循环的改变发生在MAP下降之前。展开更多
Surface particles growing in large aperture optical element （LAOE） have significant impact on LAOE＇s stable operation. It is a challenge for the online system to inspect the particles with long working distance, en...Surface particles growing in large aperture optical element （LAOE） have significant impact on LAOE＇s stable operation. It is a challenge for the online system to inspect the particles with long working distance, enough precision and high efficiency because of the system constraints. In this paper, an effective and portable inspection instrument is designed based on dark-field imaging principle. A Nikon lens and an industrial high definition （HD） camera are selected to construct the vision system to inspect particles of microns size spreading over hundreds of millimeters. Using two motors and other mechanical structure, the system can realize auto-focus and image rectification functions. The line light sources are installed on both sides of the LAOE in a sealed box while the vision system is portable and working outside the box. An adaptive binarization method is proposed to process the captured dark-field image. The distribution of particles on the LAOE＇s surface is investigated. Because of the high resolution of the captured image, the SSE2 instructions optimization method is used to reduce the time cost of the algorithm. Experiments show that the instrument can inspect LAOE effectively and accurately.展开更多
The effect of Cu on the evolution of the Al_(3)Zr phase in an Al-Cu-Zr cast alloy during solution treatment at 500℃has been thoroughly studied by combining atomic resolution high-angle annular dark-field scanning tra...The effect of Cu on the evolution of the Al_(3)Zr phase in an Al-Cu-Zr cast alloy during solution treatment at 500℃has been thoroughly studied by combining atomic resolution high-angle annular dark-field scanning transmission electron microscopy,energy-dispersive X-ray spectroscopy and first-principles cal-culations.The heat treatment initially produces a pure L1_(2)-Al_(3)Zr microstructure,allowing for about 13%Cu to be incorporated in the dispersoid.Cu incorporation increases the energy barrier for anti-phase boundary(APB)activation,thus stabilizing the L1_(2)structure.Additional heating leads to a Cu-induced“branched”path for the L1_(2)structural transformation,with the latter process accelerated once the first APB has been created.Cu atoms may either(i)be repelled by the APBs,promoting the transformation to a Cu-poor D0_(23) phase,or(ii)they may segregate at one Al-Zr layer adjacent to the APB,promoting a transformation to a new thermodynamically favored phase,Al4 CuZr,formed when these segregation layers are periodically arranged.Theoretical studies suggest that the branching of the L1_(2)transformation path is linked to the speed at which an APB is created,with Cu attraction triggered by a comparatively slow process.This unexpected transformation behavior of the L1_(2)-Al_(3)Zr phase opens a new path to un-derstanding,and potentially regulating the Al_(3)Zr dispersoid evolution for high temperature applications.展开更多
This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd(0.06 at.%).The precipitation hardening effect of T1 precipitate...This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd(0.06 at.%).The precipitation hardening effect of T1 precipitates in casting Al-Li-Cu alloys has long been ignored since it is difficult to achieve a high number density of fine precipitates without a large number of dislocations.A detailed transmission electron microscopy investigation shows that the Cd addition has changed the distribution of T1 precipitates from the conventional uneven distribution near dislocations or grain boundaries to a more homogeneous manner.Most of the Cd-rich nanoparticles were observed at the broad face and/or terminal of the T1 platelets.It is highly likely that these nanoparticles act as heterogeneous nucleation sites,which consequently leads to a higher number density of T1 precipitates.Moreover,Cd atoms were preferentially segregated withinδprecipitates,which can be attributed to the strong bonding between Li and Cd.The interactions between Cd and the T1(Al2CuLi)andδ′(Al3Li)precipitates in Al-Li-Cu alloy are first reported.The present study may propose a new mechanism to effectively improve precipitation kinetics and therefore the age-hardening effect of Al-Li-Cu alloys.展开更多
Nucleation behavior of amorphous Si–B–C–N ceramics derived from boron-modified polyvinylsilazane procusors was systematically investigated by transmission electron microscopy(TEM) combined with spatially-resolved e...Nucleation behavior of amorphous Si–B–C–N ceramics derived from boron-modified polyvinylsilazane procusors was systematically investigated by transmission electron microscopy(TEM) combined with spatially-resolved electron energy-loss spectroscopy(EELS) analysis. The ceramics were pyrolyzed at1000℃ followed by further annealing in N2, and SiC nano-crystallites start to emerge at 1200℃ and dominate at 1500℃. Observed by high-angle annular dark-field imaging, bright and dark clusters were revealed as universal nano-structured features in ceramic matrices before and after nucleation, and the growth of cluster size saturated before reaching 5 nm at 1400℃. EELS analysis demonstrated the gradual development of bonding structures successively into SiC, graphetic BNCxand Si3N4 phases, as well as a constant presence of unexpected oxygen in the matrices. Furthermore, EELS profiling revealed the bright SiC clusters and less bright Si3N4-like clusters at 1200–1400℃. Since the amorphous matrix has already phase separated into SiCN and carbon clusters, another phase separation of SiCN into SiC and Si3N4-like clusters might occur by annealing to accompany their nucleation and growth, albeit one crystallized and another remained in amorphous structure. Hinderance of the cluster growth and further crystallization was owing to the formation of BNCxlayers that developed between SiC and Si3N4-like clusters as well as from the excessive oxygen to form the stable SiO2.展开更多
Nanobubble is a rising research field,which attracts more and more attentions due to its potential applications in medical science,catalysis,electrochemistry and etc.To better implement these applications,it is urgent...Nanobubble is a rising research field,which attracts more and more attentions due to its potential applications in medical science,catalysis,electrochemistry and etc.To better implement these applications,it is urgent to understand one of the most important mechanisms of nanobubbles,the evolution.However,few attentions have been paid in this aspect because of the methodology difficulties.Here we successfully used dark-field microscopy to study the evolution process of single nanobubbles generated from formic acid dehydrogenation on single Pd-Ag nanoplates.We found some of the nanobubbles in this system can exhibit three distinct states representing different sizes,which can transform among each other.These transitions are not direct but through some intermediate states.Further kinetic analysis reveals complicated mechanisms behind the evolution of single nanobubbles.The results acquired from this study can be applicable to nanobubble systems in general and provide insights into the understanding of mechanisms affecting the stability of nanobubbles and their applications.展开更多
Integrating discrete plasmonic nanoparticles into assemblies can induce plasmonic coupling that produces collective plasmonic properties,which are not available for single nanoparticles.Theoretical analysis revealed t...Integrating discrete plasmonic nanoparticles into assemblies can induce plasmonic coupling that produces collective plasmonic properties,which are not available for single nanoparticles.Theoretical analysis revealed that plasmonic coupling derived from assemblies could produce stronger electromagnetic field enhancement effects.Thus,plasmonic assemblies enable better performance in plasmon-based applications,such as enhanced fluorescence and Raman effects.This makes them hold great potential for trace analyte detection and nanomedicine.Herein,we focus on the recent advances in various plasmonic nanoassembles such as dimers,tetramers,and core-satellite structures,and discuss their applications in biosensing and cell imaging.The fabrication strategies for self-assembled plasmonic nanostructures are described,including top-down strategies,self-assembly methods linked by DNA,ligand,polymer,amino acid,or proteins,and chemical overgrowth methods.Thereafter,their applications in biosensor and cell imaging based on dark-field imaging,surface-enhanced Raman scattering,plasmonic circular dichroism,and fluorescence imaging are discussed.Finally,the remaining challenges and prospects are elucidated.展开更多
Natural enzymes,such as horseradish peroxidase(HRP),are a class of important biocatalysts with the high specificity,but their catalytic efficiency is usually unsatisfactory.Thus,the higher catalytic efficiency induced...Natural enzymes,such as horseradish peroxidase(HRP),are a class of important biocatalysts with the high specificity,but their catalytic efficiency is usually unsatisfactory.Thus,the higher catalytic efficiency induced by the confinement effect is promising in optical sensing systems.In this work,a dark-field light scattering sensing platform was fabricated by the confinement effect of HRP from hybridization chain reaction(HCR)and then released to solution by the toehold-mediated strand displacement reaction(TSDR).Then,HRP catalyzed the 3,3,5,5-tetramethylbenzidine(TMB)to TMB^(2+)with the assistance of hydrogen peroxide,which etched the gold nanorods(Au NRs)with the weakened light scattering.The single-particle assay was established based on the decreased light scattering intensity of AuNRs under dark-field microscope.The proposed assay revealed excellent analytical performance within a linear range from 25 pmol/L to 600 pmol/L,and a low limit of detection of 3.12 pmol/L.Additionally,it also manifested satisfactory recovery of mi RNA-21 in human serum samples.The high sensitivity,excellent specificity,and universal applicability make this sensing platform promising for disease diagnosis.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1532113,11475170,11905041)Anhui Provincial Natural Science Foundation(Grant No.2208085MA18)Fundamental Research Funds for the Central Universities(Grant No.JZ2022HGTB0244)。
文摘In x-ray dark-field imaging using dual phase grating interferometer,multi-contrast signals are extracted from a set of acquired phase-stepping data by using the least-squares fitting algorithm.The extracted mean intensity,amplitude and visibility signals may be intrinsically biased.However,it is still unclear how large these biases are and how the data acquisition parameters influence the biases in the extracted signals.This work set out to address these questions.Analytical expressions of the biases of the extracted signals were theoretically derived by using a second-order Taylor series expansion.Extensive numerical simulations were performed to validate the theoretical results.It is illustrated that while the estimated mean intensity signal is always unbiased,the estimated amplitude and visibility signals are both positively biased.While the biases of the estimated amplitude signals are proportional to the inverse of the total number of phase steps,the biases of the estimated visibility signals are inversely proportional to the product of the total number of phase steps and the mean number of photons counted per phase step.Meanwhile,it is demonstrated that the dependence of the biases on the mean visibility is quite different from that of Talbot-Lau interferometer due to the difference in the intensity model.We expect that these results can be useful for data acquisition optimizations and interpretation of x-ray dark-field images.
基金the Natural Science Foundation of China(Grant Nos.U1532113,11475170,and 11905041)Fundamental Research Funds for the Central Universities(Grant No.PA2020GDKC0024)Anhui Provincial Natural Science Foundation(Grant No.2208085MA18).
文摘X-ray dark-field imaging using a grating interferometer has shown potential benefits for a variety of applications in recent years.X-ray dark-field image is commonly retrieved by using discrete Fourier transform from the acquired phasestepping data.The retrieval process assumes a constant phase step size and a constant flux for each stepped grating position.However,stepping errors and flux fluctuations inevitably occur due to external vibrations and/or thermal drift during data acquisition.Previous studies have shown that those influences introduce errors in the acquired phase-stepping data,which cause obvious moiréartifacts in the retrieved refraction image.This work investigates moiréartifacts in x-ray dark-field imaging as a result of flux fluctuations.For the retrieved mean intensity,amplitude,visibility and dark-field images,the dependence of moiréartifacts on flux fluctuation factors is theoretically derived respectively by using a first-order Taylor series expansion.Results of synchrotron radiation experiments verify the validity of the derived analytical formulas.The spatial frequency characteristics of moiréartifacts are analyzed and compared to those induced by phase-stepping errors.It illustrates that moiréartifacts can be estimated by a weighted mean of flux fluctuation factors,with the weighting factors dependent on the moiréphase and different greatly for each retrieved image.Furthermore,moiréartifacts can even be affected by object’s features not displayed in the particular contrast.These results can be used to interpret images correctly,identify sources of moiréartifacts,and develop dedicated algorithms to remove moiréartifacts in the retrieved multi-contrast images.
基金Project (No. MZO 00179906) supported by the Ministry of Health,Czech Republic
文摘Objective： Hemodilution changes the physical properties of blood by reducing its hematocrit and blood viscosity. We tested whether prolonged hypervolemic hemodilution （HHD） impairs functional capillary density （FCD） of ileal mucosa in healthy mechanically-ventilated pigs and if there is any correlation between changes in FCD of ileal and sublingual mucosas during HHD. Methods： Sixteen domestic female pigs were anesthetized, mechanically-ventilated, and randomly assigned to the HHD （20 ml/（kg.h） Hartmann＇s solution for 3 h） or fluid restrictive （5 ml/（kg-h） Hartmann＇s solution for 3 h） group. Microcirculations of sublingual and ileal mucosas via ileostomy were visualized using sidestream dark-field （SDF） imaging at baseline conditions （t=0 h） and at selected time intervals of fluid therapy （t=-l, 2, and 3 h）. Results： A significant decrease of ileal FCD （285 （278-292） cm/cm^2） in the HHD group was observed after the third hour of HHD when compared to the baseline （360 （350-370） cm/cm2） （P〈0.01）. This trend was not observed in the restrictive group, where the ileal mucosa FCD was significantly higher after the third hour of fluid therapy as compared to the HHD group （P〈0.01）. No correlation between microhemodynamic parameters obtained from sublingual and ileal mucosas was found throughout the study. Conclusions： Prolonged HHD established by crystalloid solution significantly decreased ileal villus FCD when compared to restrictive fluid regimen. An inappropriate degree of HHD can be harmful during uncomplicated abdominal surgery.
基金supported by the National Natural Science Foundation of China(Nos.21421004,21834001)sponsored by National Ten Thousand Talent Program for young top-notch talent。
文摘The observation of single-particle surface-enhanced Raman scattering(SERS)has generated considerable interest both in the nanomaterials filed and in the single-particle spectroscopy community.It is a challenge to realize rapid,facile,and high throughput SERS at single nanoparticle level.Here,without the complex experimental device and difficult experimental operations,a general single-particle SERS technique has been achieved by using dark-field-assisted surface-enhanced Raman spectroscopy(DFSERS).This advanced method provides in-situ characterization of the chemical reaction performance at single gold nanorod.
文摘目的探究脓毒症及感染性休克时舌下微循环与肠系膜微循环的关系，以及舌下、肠系膜微循环与整体血流动力学的关系。方法采用12头五指山近交系小型猪，随机分为对照组（n=6）和脓毒症组（n=6）。采用自体粪便注入腹腔方法制备腹膜炎脓毒症模型。对照组仅做肠扰动。两组皆连续监测动脉血压、中心静脉压及每小时尿量。实验组猪模型制备完成后，分别于0、4、8、12h采用旁流暗视野技术（sidestream dark field imaging techniques，SDF）采集舌下及肠系膜微循环图像，猪休克后[平均动脉压（MAP）≤65mmHg]分别采集0、2、4h舌下及肠系膜微循环图像，微循环采用总血管密度（TVD）、灌注血管密度（PVD）、灌注血管比例（PPV）、微血管流动指数（MFI）作为观察指标，微循环指标由AVA3．0软件进行半定量分析。同时留取动脉血监测动脉血氧分压（PaO2）、二氧化碳分压（PaCO2）及血乳酸（Lac），相同时间点监测心率（HR）、平均动脉压（MAP）、心指数（CI）。结果①脓毒症模型制备8h后实验组猪舌下微循环和肠系膜微循环PPV和MFI与基线比较明显下降（〉30％，P〈0．05），实验组猪在出现感染性休克时舌下和肠系膜微循环PPV和MFI下降更为明显（〉50％，P〈0．05）。PVD较晚出现明显差异，舌下微循环和肠系膜微循环分别在制模12h及休克后0h出现；舌下微循环和肠系膜微循环TVD在整个实验过程中变化差异无统计学意义。②实验组猪舌下微循环和肠系膜微循环变化有明显的相关性（MFI：r=0．60，P〈0．01；TVD：r=0．284，P〈0．01；PVD：r=0．492，P〈0．01；PPV：r=0．705，P〈0．01）。③实验组猪休克前，CI与舌下微循环及肠系膜微循环PPV、MFI均存在相关性。休克后CI与舌下微循环及肠系膜微循环各指标均无相关性。休克前后舌下微循环及肠系膜微循环与MAP均无相关性。在脓毒症模型制备后12h，MAP〉100mmHg，舌下微循环及肠系膜微循环PPV、MFI均在模型制备后8h出现明显下降。微循环改变发生在MAP下降之前。结论①脓毒症及感染性休克猪存在微循环改变，且在感染性休克时微循环障碍更严重；②舌下微循环与肠系膜微循环存在相关性，可以通过SDF技术监测舌下微循环间接反映脏器微循环的变化；③微循环的改变发生在MAP下降之前。
基金supported by National Natural Science Foundation of China(Nos.61473293,61227804 and 61303177)
文摘Surface particles growing in large aperture optical element （LAOE） have significant impact on LAOE＇s stable operation. It is a challenge for the online system to inspect the particles with long working distance, enough precision and high efficiency because of the system constraints. In this paper, an effective and portable inspection instrument is designed based on dark-field imaging principle. A Nikon lens and an industrial high definition （HD） camera are selected to construct the vision system to inspect particles of microns size spreading over hundreds of millimeters. Using two motors and other mechanical structure, the system can realize auto-focus and image rectification functions. The line light sources are installed on both sides of the LAOE in a sealed box while the vision system is portable and working outside the box. An adaptive binarization method is proposed to process the captured dark-field image. The distribution of particles on the LAOE＇s surface is investigated. Because of the high resolution of the captured image, the SSE2 instructions optimization method is used to reduce the time cost of the algorithm. Experiments show that the instrument can inspect LAOE effectively and accurately.
基金supported by the National Key Research and Development Program(No.2020YFA0405900)the National Natural Science Foundation of China(Grant No.52371111 and U2141215)the Natural Science Foundation of Jiangsu Province(No.BE2022159).
文摘The effect of Cu on the evolution of the Al_(3)Zr phase in an Al-Cu-Zr cast alloy during solution treatment at 500℃has been thoroughly studied by combining atomic resolution high-angle annular dark-field scanning transmission electron microscopy,energy-dispersive X-ray spectroscopy and first-principles cal-culations.The heat treatment initially produces a pure L1_(2)-Al_(3)Zr microstructure,allowing for about 13%Cu to be incorporated in the dispersoid.Cu incorporation increases the energy barrier for anti-phase boundary(APB)activation,thus stabilizing the L1_(2)structure.Additional heating leads to a Cu-induced“branched”path for the L1_(2)structural transformation,with the latter process accelerated once the first APB has been created.Cu atoms may either(i)be repelled by the APBs,promoting the transformation to a Cu-poor D0_(23) phase,or(ii)they may segregate at one Al-Zr layer adjacent to the APB,promoting a transformation to a new thermodynamically favored phase,Al4 CuZr,formed when these segregation layers are periodically arranged.Theoretical studies suggest that the branching of the L1_(2)transformation path is linked to the speed at which an APB is created,with Cu attraction triggered by a comparatively slow process.This unexpected transformation behavior of the L1_(2)-Al_(3)Zr phase opens a new path to un-derstanding,and potentially regulating the Al_(3)Zr dispersoid evolution for high temperature applications.
文摘This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd(0.06 at.%).The precipitation hardening effect of T1 precipitates in casting Al-Li-Cu alloys has long been ignored since it is difficult to achieve a high number density of fine precipitates without a large number of dislocations.A detailed transmission electron microscopy investigation shows that the Cd addition has changed the distribution of T1 precipitates from the conventional uneven distribution near dislocations or grain boundaries to a more homogeneous manner.Most of the Cd-rich nanoparticles were observed at the broad face and/or terminal of the T1 platelets.It is highly likely that these nanoparticles act as heterogeneous nucleation sites,which consequently leads to a higher number density of T1 precipitates.Moreover,Cd atoms were preferentially segregated withinδprecipitates,which can be attributed to the strong bonding between Li and Cd.The interactions between Cd and the T1(Al2CuLi)andδ′(Al3Li)precipitates in Al-Li-Cu alloy are first reported.The present study may propose a new mechanism to effectively improve precipitation kinetics and therefore the age-hardening effect of Al-Li-Cu alloys.
基金financially supported by National Natural Science Foundation of China (Grant Nos. 51172255 and 51532006)
文摘Nucleation behavior of amorphous Si–B–C–N ceramics derived from boron-modified polyvinylsilazane procusors was systematically investigated by transmission electron microscopy(TEM) combined with spatially-resolved electron energy-loss spectroscopy(EELS) analysis. The ceramics were pyrolyzed at1000℃ followed by further annealing in N2, and SiC nano-crystallites start to emerge at 1200℃ and dominate at 1500℃. Observed by high-angle annular dark-field imaging, bright and dark clusters were revealed as universal nano-structured features in ceramic matrices before and after nucleation, and the growth of cluster size saturated before reaching 5 nm at 1400℃. EELS analysis demonstrated the gradual development of bonding structures successively into SiC, graphetic BNCxand Si3N4 phases, as well as a constant presence of unexpected oxygen in the matrices. Furthermore, EELS profiling revealed the bright SiC clusters and less bright Si3N4-like clusters at 1200–1400℃. Since the amorphous matrix has already phase separated into SiCN and carbon clusters, another phase separation of SiCN into SiC and Si3N4-like clusters might occur by annealing to accompany their nucleation and growth, albeit one crystallized and another remained in amorphous structure. Hinderance of the cluster growth and further crystallization was owing to the formation of BNCxlayers that developed between SiC and Si3N4-like clusters as well as from the excessive oxygen to form the stable SiO2.
基金supported by Ministry of Science and Technology of China(Nos.2016YFA0200700,2016YFE0105700)the National Natural Science Foundation of China(Nos.21373264,21573275)+3 种基金the Natural Science Foundation of Jiangsu Province(No.BK20150362)Suzhou Institute of Nano-tech and Nanobionics(No.Y3AAA11004)Thousand Youth Talents Plan(No.Y3BQA11001)the Collaborative Innovation Center of Suzhou Nano Science and Technology。
文摘Nanobubble is a rising research field,which attracts more and more attentions due to its potential applications in medical science,catalysis,electrochemistry and etc.To better implement these applications,it is urgent to understand one of the most important mechanisms of nanobubbles,the evolution.However,few attentions have been paid in this aspect because of the methodology difficulties.Here we successfully used dark-field microscopy to study the evolution process of single nanobubbles generated from formic acid dehydrogenation on single Pd-Ag nanoplates.We found some of the nanobubbles in this system can exhibit three distinct states representing different sizes,which can transform among each other.These transitions are not direct but through some intermediate states.Further kinetic analysis reveals complicated mechanisms behind the evolution of single nanobubbles.The results acquired from this study can be applicable to nanobubble systems in general and provide insights into the understanding of mechanisms affecting the stability of nanobubbles and their applications.
基金supported by grants from the National Natural Science Foundation of China(Nos.22022412,22274076,21874155)the Primary Research&Development Plan of Jiangsu Province(No.BE2022793)。
文摘Integrating discrete plasmonic nanoparticles into assemblies can induce plasmonic coupling that produces collective plasmonic properties,which are not available for single nanoparticles.Theoretical analysis revealed that plasmonic coupling derived from assemblies could produce stronger electromagnetic field enhancement effects.Thus,plasmonic assemblies enable better performance in plasmon-based applications,such as enhanced fluorescence and Raman effects.This makes them hold great potential for trace analyte detection and nanomedicine.Herein,we focus on the recent advances in various plasmonic nanoassembles such as dimers,tetramers,and core-satellite structures,and discuss their applications in biosensing and cell imaging.The fabrication strategies for self-assembled plasmonic nanostructures are described,including top-down strategies,self-assembly methods linked by DNA,ligand,polymer,amino acid,or proteins,and chemical overgrowth methods.Thereafter,their applications in biosensor and cell imaging based on dark-field imaging,surface-enhanced Raman scattering,plasmonic circular dichroism,and fluorescence imaging are discussed.Finally,the remaining challenges and prospects are elucidated.
基金financial supported from the National Natural Science Foundation of China(No.22174115)the Graduate Education and Teaching Reform Research Project of Chongqing(No.yjg223038)the Fundamental Research Funds for the Central Universities(No.SWU-XDJH202321)。
文摘Natural enzymes,such as horseradish peroxidase(HRP),are a class of important biocatalysts with the high specificity,but their catalytic efficiency is usually unsatisfactory.Thus,the higher catalytic efficiency induced by the confinement effect is promising in optical sensing systems.In this work,a dark-field light scattering sensing platform was fabricated by the confinement effect of HRP from hybridization chain reaction(HCR)and then released to solution by the toehold-mediated strand displacement reaction(TSDR).Then,HRP catalyzed the 3,3,5,5-tetramethylbenzidine(TMB)to TMB^(2+)with the assistance of hydrogen peroxide,which etched the gold nanorods(Au NRs)with the weakened light scattering.The single-particle assay was established based on the decreased light scattering intensity of AuNRs under dark-field microscope.The proposed assay revealed excellent analytical performance within a linear range from 25 pmol/L to 600 pmol/L,and a low limit of detection of 3.12 pmol/L.Additionally,it also manifested satisfactory recovery of mi RNA-21 in human serum samples.The high sensitivity,excellent specificity,and universal applicability make this sensing platform promising for disease diagnosis.
