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Local magnetization of GeTe/Sb <sub/>2</sub> Te <sub/>3</sub> superlattice films using a scanning probe microscope
摘要： Local magnetization of chalcogenide superlattices (SL) of [(GeTe)2 (Sb2Te3)]n (n=4 and 8) was performed using a magnetic force microscopy (MFM) at room temperature. We show that stripe patterns appeared in MFM phase images after magnetizing of the SL by holding the MFM probe at a short distance to the SL surface at room temperature. The probe-induced stripe pattern remained after storage for several days, and which differs from electric poling. We attributed the SL magnetization to the imbalance in the amount of spin-up and spin-down carriers in helical interface bands under the stray magnetic field.
关键词： local magnetization,magnetic force microscopy,spin polarization,GeTe/Sb2Te3 superlattice,scanning probe microscope
更新于2025-09-09 09:28:46
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Comprehensive Characterization of Cerebrovascular Dysfunction in Blast Traumatic Brain Injury Using Photoacoustic Microscopy
摘要： Blast traumatic brain injury (bTBI) is a leading contributor to combat-related injuries and death. Although substantial emphasis has been placed on blast-induced neuronal and axonal injuries, co-existing dysfunctions in the cerebral vasculature, particularly the microvasculature, remain poorly understood. Here, we studied blast-induced cerebrovascular dysfunctions in a rat model of bTBI (blast overpressure: 187.8±18.3 kPa). Using photoacoustic microscopy, we quantified changes in cerebral hemodynamics and metabolism—including blood perfusion, oxygenation, flow, oxygen extraction fraction, and the metabolic rate of oxygen—4 hours post-injury. Moreover, we assessed the effect of blast exposure on cerebrovascular reactivity to vasodilatory stimulation. With vessel segmentation, we extracted these changes at the single-vessel level, revealing their dependence on vessel type (i.e., artery vs. vein) and diameter. We found that bTBI at this pressure level did not induce pronounced baseline changes in cerebrovascular diameter, blood perfusion, oxygenation, flow, oxygen extraction and metabolism, except for a slight sO2 increase in small veins (<45 μm) and blood flow increase in large veins (≥45 μm). In contrast, this blast exposure almost abolished cerebrovascular reactivity, including arterial dilation, flow upregulation, and venous sO2 increase. This study is the most comprehensive assessment of cerebrovascular structure and physiology in response to blast exposure to date. The observed impairment in cerebrovascular reactivity can potentially cause cognitive decline due to the mismatch between cognitive metabolic demands and vessel’s ability to dynamically respond to meet the demands. Also, the impaired cerebrovascular reactivity can lead to increased vulnerability of the brain to metabolic insults, including hypoxia and ischemia.
关键词： blast traumatic brain injury,cerebrovascular reactivity,photoacoustic microscopy,oxygen metabolism,hemodynamics
更新于2025-09-09 09:28:46
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Surface area, optical and electrical studies on PbS nanosheets (PbSNSs) for visible light photo-detector application
摘要： Herein, we report the morphological, surface area and detailed electrical properties of PbS nanosheets (PbSNSs). Scanning electron microscope elemental mapping confirms the formation of PbS and homogeneous distribution of Pb and S in final product. Morphology was confirmed as NSs by Transmission electron microscopy. Specific surface area was found to be ~ 7 m2/g through Brunauer–Emmett–Teller analysis. Diffused reflectance spectrum was measured and optical energy gap was estimated ~ 1.284 eV. Such value of energy gap makes it suitable for solar cell and other optoelectronic applications. An increase in photosensitivity with increasing the light intensity was observed due to increase in generation rate of photo-carriers. The recombination value is calculated ~ 0.59, it indicates that the defect states continuously distributed in energy gap. Differential lifetime increases with time and also life time of current carrier is enhanced with light intensity.
关键词： Electron microscopy,Electronic materials,Semiconductor,Electrical properties
更新于2025-09-09 09:28:46
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Fluorescence protein complementation in microscopy: applications beyond detecting bi-molecular interactions
摘要： Conventional fragments of fluorescent proteins used in bimolecular fluorescence complementation technique (BiFC), form light-emitting species only when they are kept in close proximity by interacting proteins of interest. By contrast, certain fluorescent protein fragments complement spontaneously, namely those corresponding to the 1st to 10th beta-strands (GFP1-10) and the 11th beta-strand of superfolder GFP (GFP11). They were designed as folding reporters for high throughput expression and structure biology. Besides, for light microscopy, self-associating fluorescent protein fragments constitute a valuable and sometimes unique tool. The GFP11 tag is very advantageous when a full-length fluorescent protein cannot be fused to a protein of interest, namely for live imaging of certain pathogens. Self-associating GFP fragments enable live labelling of specific synapses, visualization of proteins topology and their exposure to particular subcellular compartments. Present review aims to attract attention of scientific community to these tools and to inspire their further development and applications.
关键词： fluorescent protein,superfolder GFP,imaging,microscopy,self-associating fluorescent protein fragments
更新于2025-09-09 09:28:46
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Nonlinear Optical Properties of Oxide Thin Films
摘要： This work contains description of the oxide thin films fabricated by Physical Vapor Deposition technique in high vacuum on transparent (quartz) and semiconductor (n-type silicon) substrates kept at room temperature during the deposition process. Titanium, tin and indium oxides were chosen as the material for investigation. Selected films were annealed after fabrication in ambient atmosphere for 12 hours at the temperature equal to 100 °C, 150 °C, 250 °C and 450 °C. Structural properties were examined by optical images and AFM measurements. The films exhibit high structural dependence on the temperature of the annealing process. Quality of the films can be improved by using an appropriate temperature during the annealing process. Nonlinear optical effects were studied using Third Harmonic Generation with Nd:YAG laser at 1064 nm wavelength as a fundamental beam. The values of third-order NLO susceptibilities were calculated and analyzed. We find that the nonlinear optical properties were strictly connected with the morphology. Moreover the temperature of annealing process can change the structural and optical properties of the tested oxide thin films.
关键词： third harmonic generation,atomic force microscopy,oxide thin films,physical vapor deposition
更新于2025-09-09 09:28:46
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Scaling rules in optomechanical semiconductor micropillars
摘要： Semiconductor pillar microcavities have recently emerged as a promising optomechanical platform in the unprecedented 20-GHz frequency range. Currently established models for the mechanical behavior of micropillars, however, rely on complete numerical simulations or semianalytical approaches, which makes their application to experiments notoriously difficult. Here we overcome this challenge with an effective model by reducing the full, hybridized mechanical mode picture of a micropillar to an approach that captures the observed global trends. We show experimentally the validity of this approach by studying the lateral size dependence of the frequency, amplitude, and lifetime of the mechanical modes of square-section pillar microcavities, using room-temperature pump-probe microscopy. General scaling rules for these quantities are found and explained through simple phenomenological models of the physical phenomena involved. We show that the energy shift (Δωm) of the modes due to confinement is dependent on the inverse of their frequency ω0 and lateral size L (Δωm ∝ 1/ω0L2) and that the mode lifetime τ is linear with pillar size and inversely proportional to their frequency (τ ∝ L/ω0). The mode amplitude is in turn inversely proportional to the lateral size of the considered resonators. This is related to the dependence of the optomechanical coupling rate (g0 ∝ 1/L) with the spatial extent of the confined electromagnetic and mechanical fields. Using a numerical model based on the finite-element method, we determine the magnitude and size dependence of g0 and, by combining the results with the experimental data, we discuss the attainable single-photon cooperativity in these systems. The effective models proposed and the scaling rules found constitute an important tool in micropillar optomechanics and in the future development of more complex micropillar based devices.
关键词： scaling rules,semiconductor micropillars,optomechanics,mechanical modes,pump-probe microscopy
更新于2025-09-09 09:28:46
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Visualizing topological edge states of single and double bilayer Bi supported on multibilayer Bi(111) films
摘要： Freestanding single bilayer Bi(111) is a two-dimensional topological insulator with edge states propagating along its perimeter. Given the interlayer coupling experimentally, the topological nature of Bi(111) thin films and the impact of the supporting substrate on the topmost Bi bilayer are still under debate. Here, combined with scanning tunneling microscopy and first-principles calculations, we systematically study the electronic properties of Bi(111) thin films grown on a NbSe2 substrate. Two types of nonmagnetic edge structures, i.e., a conventional zigzag edge and a 2 × 1 reconstructed edge, coexist alternately at the boundaries of single bilayer islands, the topological edge states of which exhibit remarkably different energy and spatial distributions. Prominent edge states are persistently visualized at the edges of both single and double bilayer Bi islands, regardless of the underlying thickness of Bi(111) thin films. We provide an explanation for the topological origin of the observed edge states that is verified with first-principles calculations. Our paper clarifies the long-standing controversy regarding the topology of Bi(111) thin films and reveals the tunability of topological edge states via edge modifications.
关键词： topological insulator,scanning tunneling microscopy,edge states,first-principles calculations,Bi(111) thin films
更新于2025-09-09 09:28:46
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Fully Convolutional DenseNets for Segmentation of Microvessels in Two-photon Microscopy*
摘要： Segmentation of microvessels measured using two-photon microscopy has been studied in the literature with limited success due to uneven intensities associated with optical imaging and shadowing effects. In this work, we address this problem using a customized version of a recently developed fully convolutional neural network, namely, FC-DensNets. To train and validate the network, manual annotations of 8 angiograms from two-photon microscopy was used. Segmentation results are then compared with that of a state-of-the-art scheme that was developed for the same purpose and also based on deep learning. Experimental results show improved performance of used FC-DenseNet in providing accurate and yet end-to-end segmentation of microvessels in two-photon microscopy.
关键词： deep learning,two-photon microscopy,FC-DenseNets,microvessels,Segmentation
更新于2025-09-09 09:28:46
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In vivo multiphoton microscopy imaging of melasma
摘要： Melasma is a skin disorder characterized by hyperpigmented patches due to increased melanin production and deposition. In this pilot study we evaluate the potential of multiphoton microscopy (MPM) to characterize non-invasively the melanin content, location, and distribution in melasma and assess the elastosis severity. We employed a clinical MPM tomograph to image in-vivo morphological features in melasma lesions and adjacent normal skin in 12 patients. We imaged dermal melanophages in most dermal melasma lesions and occasionally in epidermal melasma. The melanin volume fraction values measured in epidermal melasma (14±4%) were significantly higher (p<0.05) than the values measured in peri-lesional skin (11±3%). The basal keratinocytes of melasma and perilesions showed different melanin distribution. Elastosis was predominantly more severe in lesions than in perilesions and was associated with changes in melanin distribution of the basal keratinocytes. These results demonstrate that MPM may be a non-invasive imaging tool for characterizing melasma. Identifying the depth of excess pigment is critical for successful treatment of melasma. Multiphoton microscopy demonstrates the ability to visualize non-invasively the melanophages, a sign of a prior inflammatory response, key in the differential diagnosis of melasma. Patients with melasma may be diagnosed more accurately using a rapid, label-free, non-invasive microscopy technique.
关键词： in vivo imaging,melasma,microscopy
更新于2025-09-09 09:28:46
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Synthesis, Characterization and Photocatalytic Efficiency of ZnO/MWCNT Nanocomposites Prepared Under Different Solvent Conditions
摘要： Here we report the application of zinc oxide (ZnO) coated multi-walled carbon nanotube (MWCNT) composites in the photocatalytic decomposition of acetaldehyde (AA). Zinc oxide nanoparticles were successfully coated on the multi-walled carbon nanotube via impregnation process using zinc acetate (Zn(CH3COO)2 × 2H2O) as precursor and sodium dodecyl sulfate (SDS) treated multi-walled carbon nanotube as raw material under different solvent conditions. The applied solvents during preparation were ethanol (EtOH) and water (H2O). As-prepared materials were characterized by thermal analysis (TG), X-ray diffraction (XRD), specific surface area measurement (BET) and transmission electron microscopy (TEM) techniques. Photocatalytic efficiencies of as-prepared composites were investigated in a stationary reactor equipped with UV lamp. Decomposition of acetaldehyde was followed by using gas chromatography (GC). Observations revealed that using impregnation method and different solvents the preparation of ZnO/MWCNT nanocomposites can be controlled easily. The highest degradation rate was achieved with the nanocomposite was synthetized using ethanol as solvent. The photocatalytic experiments revealed that the composite has higher photocatalytic activity than that of both the zinc oxide nanoparticles and the mechanical mixture of multi-walled carbon nanotube and zinc oxide.
关键词： Transmission Electron Microscopy,Zinc Oxide,Photocatalysis,Gas Chromatography,Nanocomposite
更新于2025-09-09 09:28:46