- 标题
- 摘要
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- 实验方案
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Transport properties of Cu-AlF3-W and Cu-AlF3-Cu heterojunctions using STS measurements and a DFT-NEGF approach
摘要： To understand and to analyze the transport properties of different metal-insulator systems, we developed an experimental study of the electronic transport properties of AlF3 thin films deposited over a Cu(1 0 0) substrate, and a theoretical study to model systems composed by an AlF3 molecule between two metallic Cu(1 0 0)-W(1 0 0) and Cu(1 0 0)-Cu(1 0 0) electrodes with different geometries. The left common electrode is always a Cu(1 0 0) layer, meanwhile the right changing electrode, W(1 0 0) or Cu(1 0 0), in some cases is represented as a layer and in others as having a tip ending. Tunnelling current against voltage (I-V) characteristic curves have been obtained by Scanning Tunneling Spectroscopy (STS) measurements and computed using density functional theory (DFT) with the non equilibrium Green function method (NEGF) within a bias voltage range from ?2.5 to 5.0 V. The theoretical curves show low current values, in the order of 10?12 to 10?9, in good agreement with the I-V experimental curves in the same range. This reveals that breakdown response currents begin at higher voltages than 5.0 V. The transmission spectrum, total (DOS) and partial (PDOS) density of states are also presented being the transmission variations addressed in terms of the DOS.
关键词： Scanning Tunneling Spectroscopy (STS),Non Equilibrium Green Functions (NEGF),Scanning Tunneling Microscopy (STM),Electronic transport,AlF3 thin films
更新于2025-09-04 15:30:14
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Automated Neuron Reconstruction from 3D Fluorescence Microscopy Images Using Sequential Monte Carlo Estimation
摘要： Microscopic images of neuronal cells provide essential structural information about the key constituents of the brain and form the basis of many neuroscientific studies. Computational analyses of the morphological properties of the captured neurons require first converting the structural information into digital tree-like reconstructions. Many dedicated computational methods and corresponding software tools have been and are continuously being developed with the aim to automate this step while achieving human-comparable reconstruction accuracy. This pursuit is hampered by the immense diversity and intricacy of neuronal morphologies as well as the often low quality and ambiguity of the images. Here we present a novel method we developed in an effort to improve the robustness of digital reconstruction against these complicating factors. The method is based on probabilistic filtering by sequential Monte Carlo estimation and uses prediction and update models designed specifically for tracing neuronal branches in microscopic image stacks. Moreover, it uses multiple probabilistic traces to arrive at a more robust, ensemble reconstruction. The proposed method was evaluated on fluorescence microscopy image stacks of single neurons and dense neuronal networks with expert manual annotations serving as the gold standard, as well as on synthetic images with known ground truth. The results indicate that our method performs well under varying experimental conditions and compares favorably to state-of-the-art alternative methods.
关键词： Sequential Monte Carlo estimation,Bayesian filtering,Neuron reconstruction,Fluorescence microscopy,Particle filtering
更新于2025-09-04 15:30:14
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Selection and Quantification of Objects in Microscopic Images: from Multi-Criteria to Multi-Threshold Analysis
摘要： Due to the increased number of applications of both microscopic imaging and image analysis including biomedical studies, the design of specialized algorithms and tools to facilitate quantitative assessment of objects in the image content is of urgent need. Recently, a number of approaches ranging from object counting by machine learning methods to statistical image analysis have been suggested and successfully implemented to resolve the cell quantification problem. Here, we revisit the above problem considering samples where objects presented in the same images have to be explicitly distinguished and quantified without involving any dedicated experimental setting like differential fluorescent staining. We consider several possible classification criteria and show explicitly how their combination in a single algorithm can be used to improve results in complex images where single criteria-based rules inevitably fail. Finally, we suggest a possible approach for the analysis of non-homogeneous images based on combining object selection results for different threshold values thus enhancing the algorithm from multi-criteria to multi-threshold analysis. To demonstrate the performance of the suggested solutions, we show several prominent examples of complex structures ranging from images containing both live and apoptotic cells as well as containing mixtures of globular and fibrous forms of heat-shock protein IbpA.
关键词： Microscopy,Image analysis,Apoptotic,Cell sub-populations,Fibers
更新于2025-09-04 15:30:14
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In-doped As2Se3 thin films studied by Raman and X-ray photoelectron spectroscopies
摘要： Amorphous In-doped As2Se3 films with nominal indium contents x up to 7 at. % were prepared by thermal evaporation. Atomic force microscopy studies confirm the uniform film structure with a surface roughness near 5 nm, noticeably higher than for similarly prepared undoped As2Se3 film. X-ray photoelectron spectroscopy (XPS) studies enabled the chemical composition of the films to be examined. As follows from the XPS data, the In content in the film strongly decreases with the film depth. For films with x ≥ 2 at.%, Raman features attributed to transverse and longitudinal optical phonons of InAs are revealed in the Raman spectra as an evidence for the formation of InAs nanocrystallites in the As2Se3:In film under laser illumination.
关键词： X-ray photoelectron spectroscopy,amorphous,film,Raman scattering,atomic force microscopy,semiconductor nanocrystals
更新于2025-09-04 15:30:14
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Formation mechanism of twin structures in p-type (Bi0.25Sb0.75)2Te3 thermoelectric compound
摘要： The formation mechanism of twin structures in p-type (Bi0.25Sb0.75)2Te3 compound was examined using high-resolution transmission electron microscopy (HR-TEM) and computer simulations. The results shown that the formation of twins is analogous to the twinning mechanism via synchronized activation of Shockley partial dislocations commonly observed terminating {111} growth and annealing twins in face centered cubic (FCC) metals. The f1010g boundary, as an incoherent twin boundary (ITB), is mobile due to its lower shear stress compared to that of the coherent {0001} twin boundary; thickness of the twin region can be reduced or increased according to the direction of the movement.
关键词： Twin structure,Interfacial step,Transmission electron microscopy (TEM),(Bi, Sb)2Te3 thermoelectric compound
更新于2025-09-04 15:30:14
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A Two-Photon Ratiometric Probe for Hydrogen Polysulfide (H2Sn): Increase in Mitochondrial H2Sn Production in a Parkinson’s Disease Model
摘要： Hydrogen polysulfide (H2Sn, n>1), which is primarily generated during the crosstalk between H2S and reactive species (ROS and RNS), is receiving increasing attention in biochemical research. H2Sn is mostly generated in the mitochondria, and abnormal mitochondrial function and oxidative stress are directly related to many disorders including Parkinson's disease (PD). We now report a two-photon fluorescent probe (SPS-M1) for in situ detection of H2Sn and its application to a PD model to account the H2Sn levels. The probe exhibited selective and fast response to H2Sn along with a marked blue-to-green color change. SPS-M1 is sensitive enough to quantitative detection of endogenous H2Sn content in mitochondria using two-photon microscopy (TPM). Ratiometric TPM imaging of live neurons and brain slices using SPS-M1 revealed that H2Sn production is increased to a greater extent in the A53T α-synuclein (α-syn) overexpressing model than in the wild-type control. These findings suggest that the interactions of H2S and the increased ROS caused by α-syn overexpression may generate more H2Sn. By employing our recently published TP probe for mitochondrial H2S, we also found the relationship between the H2Sn and H2S; increased H2Sn and decreased H2S levels, indicating that H2S and H2Sn may play a significant role in the pathogenesis of PD. This result may be useful to biomedical studies, including PD.
关键词： two-photon microscopy,fluorescent probe,Parkinson’s disease,Hydrogen polysulfide,mitochondria
更新于2025-09-04 15:30:14
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Electrochromic effect of indium tin oxide in lithium iron phosphate battery cathodes for state of charge determination
摘要： In this paper, we discuss the origin of an optical effect in lithium iron phosphate (LFP) battery cathodes, which depends on the electrical charge transferred into the battery. Utilizing indium tin oxide (ITO) as an electrode additive, we were able to observe a change in reflectivity of the cathode during charging and discharging with lithiation and delithiation being clearly visible in the form of lithiation fronts. Further investigations using in situ video microscopy and in situ Raman spectroscopy on test cells with an optical window indicates that ITO additionally acts as an electrochromic marker within the LFP cathode. This enhances the optical effect due to local potentials around the lithiation fronts, which enables the voltage-dependent reflectivity of the ITO to be visible in the LFP cathode. Structural analysis with scanning electron microscopy (SEM) and X-ray crystallography (XRD) are presented as well. The observed effect allows for novel battery research methods and for a possible commercial application as a sensor for state of charge (SOC) estimation similar to the optical fiber approach reported by Ghannoum et al. for a graphite anode.
关键词： lithium ion batteries,battery state determination,lithium iron phosphate,raman spectroscopy,indium tin oxide,electrochromic marker,video microscopy,state of charge
更新于2025-09-04 15:30:14
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Label-Free Identification of Lymphocyte Subtypes Using Three-Dimensional Quantitative Phase Imaging and Machine Learning
摘要： We describe here a protocol for the label-free identification of lymphocyte subtypes using quantitative phase imaging and machine learning. Identification of lymphocyte subtypes is important for the study of immunology as well as diagnosis and treatment of various diseases. Currently, standard methods for classifying lymphocyte types rely on labeling specific membrane proteins via antigen-antibody reactions. However, these labeling techniques carry the potential risks of altering cellular functions. The protocol described here overcomes these challenges by exploiting intrinsic optical contrasts measured by 3D quantitative phase imaging and a machine learning algorithm. Measurement of 3D refractive index (RI) tomograms of lymphocytes provides quantitative information about 3D morphology and phenotypes of individual cells. The biophysical parameters extracted from the measured 3D RI tomograms are then quantitatively analyzed with a machine learning algorithm, enabling label-free identification of lymphocyte types at a single-cell level. We measure the 3D RI tomograms of B, CD4+ T, and CD8+ T lymphocytes and identified their cell types with over 80% accuracy. In this protocol, we describe the detailed steps for lymphocyte isolation, 3D quantitative phase imaging, and machine learning for identifying lymphocyte types.
关键词： lymphocyte identification,machine learning,holotomography,immune cell,immunology,Immunology and Infection,Quantitative phase imaging,optical diffraction tomography,holographic microscopy,label-free imaging
更新于2025-09-04 15:30:14
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Cancellation of Bessel beam side lobes for high-contrast light sheet microscopy
摘要： An ideal illumination for light sheet fluorescence microscopy entails both a localized and a propagation invariant optical field. Bessel beams and Airy beams satisfy these conditions, but their non-diffracting feature comes at the cost of the presence of high-energy side lobes that notably degrade the imaging contrast and induce photobleaching. Here, we demonstrate the use of a light droplet illumination whose side lobes are suppressed by interfering Bessel beams of specific k-vectors. Our droplet illumination readily achieves more than 50% extinction of the light distributed across the Bessel side lobes, providing a more efficient energy localization without loss in transverse resolution. In a standard light sheet fluorescence microscope, we demonstrate a two-fold contrast enhancement imaging micron-scale fluorescent beads. Results pave the way to new opportunities for rapid and deep in vivo observations of large-scale biological systems.
关键词： light sheet microscopy,Bessel beams,fluorescence imaging,droplet illumination,Airy beams
更新于2025-09-04 15:30:14
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Quantitative determination of a model organic/insulator/metal interface structure
摘要： By combining X-ray photoelectron spectroscopy, X-ray standing waves and scanning tunneling microscopy, we investigate the geometric and electronic structure of a prototypical organic/insulator/metal interface, namely cobalt porphine on monolayer hexagonal boron nitride (h-BN) on Cu(111). Specifically, we determine the adsorption height of the organic molecule and show that the original planar molecular conformation is preserved in contrast to the adsorption on Cu(111). In addition, we highlight the electronic decoupling provided by the h-BN spacer layer and find that the h-BN–metal separation is not significantly modified by the molecular adsorption. Finally, we find indication of a temperature dependence of the adsorption height, which might be a signature of strongly-anisotropic thermal vibrations of the weakly bonded molecules.
关键词： hexagonal boron nitride,X-ray standing waves,X-ray photoelectron spectroscopy,cobalt porphine,Cu(111),scanning tunneling microscopy,organic/insulator/metal interface
更新于2025-09-04 15:30:14