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Automatic Graph-based Modeling of Brain Microvessels Captured with Two-Photon Microscopy
摘要： Graph models of cerebral vasculature derived from 2-photon microscopy have shown to be relevant to study brain microphysiology. Automatic graphing of these microvessels remain problematic due to the vascular network complexity and 2-photon sensitivity limitations with depth. In this work, we propose a fully automatic processing pipeline to address this issue. The modeling scheme consists of a fully-convolution neural network to segment microvessels, a 3D surface model generator and a geometry contraction algorithm to produce graphical models with a single connected component. Quantitative assessment using NetMets metrics, at a tolerance of 60 μm, false negative and false positive geometric error rates are 3.8% and 4.2%, respectively, whereas false negative and false positive topological error rates are 6.1% and 4.5%, respectively. Our qualitative evaluation confirms the efficiency of our scheme in generating useful and accurate graphical models.
关键词： segmentation,graph,Cerebral microvasculature,deep learning,convolution neural networks,two-photon microscopy
更新于2025-09-09 09:28:46
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STRUCTURING OF DIAMOND FILMS USING MICROSPHERE LITHOGRAPHY
摘要： In this study, the structuring of micro- and nanocrystalline diamond thin films is demonstrated. The diamond films are structured using the technique of microsphere lithography followed by reactive ion etching. Specifically, this paper presents a four-step fabrication process: diamond deposition (microwave plasma assisted chemical vapor deposition), mask preparation (by the standard Langmuir-Blodgett method), mask modification and diamond etching. A self-assembled monolayer of monodisperse polystyrene (PS) microspheres with close-packed ordering is used as the primary template. Then the PS microspheres and the diamond films are processed in capacitively coupled radiofrequency plasma using various plasma chemistries. This fabrication method illustrates the preparation of large arrays of periodic and homogeneous hillock-like structures. The surface morphology of the processed diamond films is characterized by scanning electron microscopy and with the use of an atomic force microscope. The potential applications of these diamond structures in various fields of nanotechnology are also briefly discussed.
关键词： polystyrene microspheres,nanostructuring,scanning electron microscopy,reactive ion etching,diamond thin films
更新于2025-09-09 09:28:46
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Scan-Less, Kilo-Pixel, Line-Field Confocal Phase Imaging with Spectrally Encoded Dual-Comb Microscopy
摘要： Confocal laser microscopy (CLM) is a powerful tool in life science research and industrial inspection, and its image acquisition rate is boosted by scan-less imaging techniques. However, optical-intensity-based image contrast in CLM makes it difficult to visualize transparent non-fluorescent objects or reflective objects with nanometer unevenness. In this paper, we introduce an optical frequency comb (OFC) to scan-less CLM to give optical-phase-based image contrast. One-dimensional (1-D) image pixels of a sample are separately encoded onto OFC modes via 1-D spectral encoding by using OFC as an optical carrier of amplitude and phase with a vast number of discrete frequency channels. Then, line-field confocal information of amplitude and phase are decoded from mode-resolved OFC amplitude and phase spectra obtained by dual-comb spectroscopy. The proposed confocal phase imaging will further expand the applications of CLM.
关键词： optical interferometry,optical microscopy,Biomedical imaging
更新于2025-09-09 09:28:46
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Surface potential and thin film quality of low work function metals on epitaxial graphene
摘要： Metal films deposited on graphene are known to influence its electronic properties, but little is known about graphene’s interactions with very low work function rare earth metals. Here we report on the work functions of a wide range of metals deposited on n-type epitaxial graphene (EG) as measured by Kelvin Probe Force Microscopy (KPFM). We compare the behaviors of rare earth metals (Pr, Eu, Er, Yb, and Y) with commonly used noble metals (Cr, Cu, Rh, Ni, Au, and Pt). The rare earth films oxidize rapidly, and exhibit unique behaviors when on graphene. We find that the measured work function of the low work function group is consistently higher than predicted, unlike the noble metals, which is likely due to rapid oxidation during measurement. Some of the low work function metals interact with graphene; for example, Eu exhibits bonding anomalies along the metal-graphene perimeter. We observe no correlation between metal work function and photovoltage, implying the metal-graphene interface properties are a more determinant factor. Yb emerges as the best choice for future applications requiring a low-work function electrical contact on graphene. Yb films have the strongest photovoltage response and maintains a relatively low surface roughness, ~5 nm, despite sensitivity to oxidation.
关键词： work function,Kelvin Probe Force Microscopy,photovoltage,rare earth metals,graphene
更新于2025-09-09 09:28:46
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Facile synthesis of Cu2O particles with different morphologies
摘要： Cu2O particles with cubic, octahedral, truncated octahedral and cubic truncated morphologies were synthesized using a simple chemical reduction method at room temperature. The nanocrystals were synthesized directly in aqueous solution by varying the molar concentration of CuCl2 precursor salt added to the sodium borohydride NaBH4 as a reducing agent. The solids obtained were characterized by ultraviolet-visible spectroscopy (UV-vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). UV-vis absorption spectra exhibit peaks with characteristic wavelengths of Cu2O. SEM and TEM reveal particles with a cubic morphology at 15 mM CuCl2, with an average particle size of 100 nm. Cu2O particles are also grown in an octahedral shape at 16 mM of CuCl2, having an average particle size of 150 nm. Finally, truncated octahedral and truncated cubic forms were produced for concentrations in the range of 17 to 20 mM with 100 nm of average size.
关键词： Electron microscopy,Chemical-reduction synthesis,Sodium borohydride,Different-shape morphologies,Cooper oxide
更新于2025-09-09 09:28:46
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Photo-Induced Depletion of Binding Sites in DNA-PAINT Microscopy
摘要： The limited photon budget of fluorescent dyes is the main limitation for localization precision in localization-based super-resolution microscopy. Points accumulation for imaging in nanoscale topography (PAINT)-based techniques use the reversible binding of fluorophores and can sample a single binding site multiple times, thus elegantly circumventing the photon budget limitation. With DNA-based PAINT (DNA-PAINT), resolutions down to a few nanometers have been reached on DNA-origami nanostructures. However, for long acquisition times, we find a photo-induced depletion of binding sites in DNA-PAINT microscopy that ultimately limits the quality of the rendered images. Here we systematically investigate the loss of binding sites in DNA-PAINT imaging and support the observations with measurements of DNA hybridization kinetics via surface-integrated fluorescence correlation spectroscopy (SI-FCS). We do not only show that the depletion of binding sites is clearly photo-induced, but also provide evidence that it is mainly caused by dye-induced generation of reactive oxygen species (ROS). We evaluate two possible strategies to reduce the depletion of binding sites: By addition of oxygen scavenging reagents, and by the positioning of the fluorescent dye at a larger distance from the binding site.
关键词： photo-induced DNA damage,surface-integrated fluorescence correlation spectroscopy (SI-FCS),reactive oxygen species,super-resolution microscopy,DNA-PAINT
更新于2025-09-09 09:28:46
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Structural, morphological and optical properties of Cu2ZnxFe1-xSnS4 thin films grown by thermal evaporation
摘要： In this study, Cu2ZnxFe1-xSnS4 (CZFTS) (0≤x≤1) thin films were grown under vacuum evaporation on unheated glass substrates followed by sulfurization at 400 °C. The effects of sulfurization on the structural, morphological and optical properties were investigated for CZFTS material by varying Fe content. Crystal structure and phase of CZFTS thin films were analyzed by X-ray diffraction technique and Raman spectroscopy. In addition, the elemental composition and the stoichiometry of films were studied using energy dispersive spectroscopy. Surface morphology of samples was examined by scanning electron microscopy. Optical properties such as absorption coefficient, and gap energies were determined by the measurement of transmittance and reflectance in the spectral range 300-1800 nm. X-ray analysis indicates that all sulfurized CZFTS films present a polycrystalline nature and exhibit a preferential orientation along (112) plane. Cu2FeSnS4 (x=0) and Cu2ZnSnS4 (x=1) crystallize in stannite structure with I-42m and kesterite structure with I-4 space group, respectively. Raman analysis and elemental composition confirm that only the Cu2ZnSnS4 (x=1) and CZ0.75F0.25TS (x=0.75) phases are present with good crystallinity. Transmittance and reflectance spectra revealed that the films are homogenous mostly for x=0.75 and 1. Structural and optical parameters like crystallite size, absorption coefficient and band gaps were estimated for all the x values.
关键词： Sulfurization,Scanning electron microscopy,X-ray diffraction,Copper zinc iron tin sulfide,Evaporation,Thin films
更新于2025-09-09 09:28:46
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Unlocking higher harmonics in atomic force microscopy with gentle interactions
摘要： In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.
关键词： composition,phase,heterogeneity,chemistry,higher harmonics,atomic force microscopy
更新于2025-09-09 09:28:46
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Gill Morphology in Two Bottom Feeder Mediterranean Sea Fishes: Grey Gurnard Fish (Eutrigla gurnardus, Linnaeus, 1758) and Striped Red Mullet Fish (Mullus barbatus surmuletus, Linnaeus, 1758) by Scanning Electron Microscopy
摘要： The purpose of the current investigation was to describe the gill morphology of two bottom feeders Mediterranean Sea fishes: Striped red mullet fish (M. surmuletus) and grey gurnard fish (E. gurnardus) that showed the same feeding habits. The gill system of the grey gurnard consisted of four pairs of gill arches while consisted of three pairs of gill arches in the striped red mullet. Our study focused on the scanning electron microscopical (SEM) features of the gills, where some differences in the gill arches and gill rakers surface in both species were observed. Our results marked that there was an interbranchial septum carrying a four transverse elevated crest in grey gurnard while in striped red mullet carrying a median longitudinal elevated crest. There are some similar structure on the gill arch of two fishes as; no angle between a ceratobranchial part and epibranchial part and also the gill arch has a region of many longitudinal microridges demarcated the region between gill rakers and gill filaments. By SEM, in striped red mullet, the smooth surface of gill arch and gill rakers was characterized by the presence of high number of taste buds. By SEM in grey gurnard, gill raker appeared as a round short projected body with high number of curved apex spines. Furthermore, in striped red mullet, gill raker appeared as short projected body with high number of rod-like spines. Gill filaments were long at middle and short at extremities of gill arch in both species.
关键词： Grey gurnard fish,Striped red mullet fish,Gill arch,Gill filament,Gill raker,Scanning electron microscopy
更新于2025-09-09 09:28:46
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Controlling the Phase Segregation in Mixed Halide Perovskite through Nanocrystal Size
摘要： Mixed halide perovskites are one of the promising candidates in developing solar cells and LEDs, among others applications due to their tunable optical properties. Nonetheless, photoinduced phase segregation, by forming segregated Br-rich and I-rich domains, limits the overall applicability. We tracked the phase segregation with increasing crystalline sizes of CsPbBr3-xIx and their photoluminescence under continuous-wave laser irradiation (405 nm, 10 mW cm-2), and observed the occurrence of the phase segregation from the threshold size of 46 ± 7 nm. This results have an outstanding agreement with the diffusion length (45.8 nm) calculated also experimentally from the emission lifetime, segregation rates. Furthermore, through Kelvin probe forced microscopy, we confirmed the correlation between the phase segregation and the reversible halide ion migration among grain center/boundaries. These results open a way to achieve segregation-free mixed halide perovskites and improve their performances in optoelectronic devices.
关键词： nanocrystal size,photoluminescence,phase segregation,Kelvin probe force microscopy,Mixed halide perovskites
更新于2025-09-09 09:28:46