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Metastable crystalline phase in two-dimensional metallic oxide nanoplates
摘要： Structural phase transition in crystals induced by high-pressure or high-temperature conditions may result in the development of unusual physical and chemical properties; these properties are often difficult to stabilize under ambient conditions. Here we adopted a simple method in which ultrathin cerium oxide nanoplates (< 1.4 nm) were synthesized to increase the surface atomic content, allowing transformation from a face-centered cubic (fcc) phase to a body-centered tetragonal (bct) phase. Three types of cerium oxide nanoparticles of different thicknesses, i.e., 1.2-nm ultrathin nanoplates, 2.2-nm nanoplates, and 5.4-nm nanocubes, were examined using transmission electron microscopy and X-ray diffraction. The metastable bct phase was observed only in ultrathin nanoplates. Thermodynamic energy analysis confirmed that the surface energy of the ultrathin nanoplates is the cause of the remarkable stabilization of the metastable bct phase. The mechanism of surface energy regulation can be expanded to other metallic oxides, thus providing a new means for manipulating and stabilizing novel materials under ambient conditions that otherwise would not be recovered.
关键词： metastable phase,thickness,surface unsaturated coordination ratio,Ultrathin nanoplates,metallic oxide nanoparticles
更新于2025-09-04 15:30:14
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<i>In Vivo</i> Confocal Microscopy Analysis of Corneal Microstructural Changes in Neurosurgically-Induced Neurotrophic Keratitis
摘要： Purpose: To investigate the changes of the corneal microstructure of neurosurgically-induced neurotrophic keratitis patients compared to normal human corneas using in vivo confocal microscope (IVCM). Methods: Ten eyes in the normal control group and 11 eyes in the neurosurgically-induced neurotrophic keratitis patient group were included in the present study. After corneal sensitivity tests were performed, thickness of each layer and number of endothelial cells and stromal keratocytes in the cornea were assessed using IVCM. Morphological characteristics of the corneal nerves were measured by ImageJ software. Results: After analysis of corneal thickness layer by layer, the Bowman’s layer was significantly reduced in the neurosurgically-induced neurotrophic keratitis patient group compared with the normal control group (p = 0.016) and the portion of Bowman’s layer was significantly reduced in the neurosurgically-induced neurotrophic keratitis patient group compared with the control group (p = 0.024). The nerve fiber length per square-millimeter became significantly shorter compared to the normal control group (p = 0.042). The nerve fiber length per square millimeter showed significant correlations with the number of fibers, number of beading, branching patterns, and nerve tortuosity (p = 0.002, 0.002, 0.013 and 0.034, respectively). The number of endothelial cells and stromal keratocytes, the number of nerve fibers and beading, and the pattern of branching and nerve tortuosity showed no significant differences between the normal and neurosurgically-induced neurotrophic keratitis patient groups. Conclusions: Our results showed that decreased thickness of Bowman’s layer may be related to the decreased corneal nerve distribution, secondary to the dysfunction of trigeminal nerve branch innervating the cornea. The microstructural changes of Bowman’s layer can help diagnose the disease and evaluate the current status in neurosurgically-induced neurotrophic keratitis patients.
关键词： Neurosurgically-induced neurotrophic keratitis,Corneal thickness,Corneal nerve,Confocal microscopy,Neurosurgery
更新于2025-09-04 15:30:14
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Evaluation of retinal nerve fiber layer thickness in Alzheimer disease usingspectral-domain optical coherence tomography
摘要： To evaluate the retinal nerve fiber layer (RNFL) thickness in patients with Alzheimer disease (AD) and to compare the results with those of healthy controls. Forty patients (mean age: 75.02 ± 6.34 years; 23 women) with untreated AD and 40 age-, sex-, and education-matched healthy patients were examined in this case-control prospective study. All patients underwent detailed ophthalmic and neurological examination. The Mini Mental State Examination (MMSE) was performed and RNFL thickness was measured using spectral-domain optical coherence tomography. The association between RNFL and MMSE score was also assessed. The average RNFL thickness was 84 ± 7.0 μm in AD patients and 107 ± 6.3 μm in healthy subjects (P < 0.001). The mean MMSE score was 21.9 ± 2.13 in AD patients. There was no significant correlation between the RNFL thickness and MMSE score. Patients with AD had reduced RNFL thickness in all quadrants compared with the control group. This finding suggests that RNFL thickness analysis may be useful in the early diagnosis of AD.
关键词： optical coherence tomography,retinal nerve fiber layer thickness,Alzheimer disease
更新于2025-09-04 15:30:14
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Handbook of Advanced Non-Destructive Evaluation || Terahertz Techniques in NDE
摘要： So far, terahertz measurement technology has rarely been used in industry. This book chapter presents therefore the underlying technologies, the resulting possibilities and exemplary applications. The introduction describes the basic properties of terahertz systems and the advantages of terahertz technology over established techniques such as infrared, X-rays and ultrasound. The two industrially relevant terahertz techniques, time domain spectrometer and FMCW system, are described in detail. In addition, the metrological basics for their main applications are introduced. Imaging is required in many applications. Different approaches are presented. Before the chapter concludes with an outlook on future applications, current application examples are discussed. This concerns applications in the fields of coating thickness measurement, safety, materials research, testing of lightweight materials and inline testing. An extensive reference list provides a deeper insight into the topics addressed.
关键词： lightweight materials,materials research,coating thickness measurement,terahertz,NDE,FMCW,imaging,inline testing,time-domain spectroscopy
更新于2025-09-04 15:30:14
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Resonant Plasmon-Enhanced Upconversion in Monolayers of Core-Shell Nanocrystals: Role of Shell Thickness
摘要： The upconversion luminescence (UCL) of colloidal lanthanide-doped upconversion nanocrystals (UCNCs) can be improved either by precise encapsulation of the surface by optically inert shells around the core, by an alteration of the nearby environment via metal nanoparticles, or by a combination of both. Considering their potential importance in crystalline silicon photovoltaics,the present study investigates both effects for two-dimensional arrangements of UCNCs. Using excitation light of 1500 nm wavelength, we study the variation in the upconversion luminescence from an Er3+-doped NaYF4 core as a function of the thickness of a NaLuF4 shell in colloidal solutions as well as in spin-cast-assisted self-assembled monolayers of UCNCs. The observed UCL yields and decay times of Er3+ ions of the UCNCs increase with increasing shell thickness in both cases, and nearly no variation in decay times is observed in the transition of the UCNCs from solution to film configurations. The luminescence efficiency of the UCNC monolayers is further enhanced by electron-beam-lithographic-designed Au-nanodiscs deposited either on top or buried within of the monolayer. It is observed that the improvement by the nanocrystal shells is greater than that of the Au-nanodiscs.
关键词： shell thickness,core-shell nanocystals,monolayer,upconversion,Plasmon enhancement
更新于2025-09-04 15:30:14
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Optical Sectioning Microscopy For Multilayer Structure With Micro-Scale Air Gaps Measurement
摘要： In this letter, we propose a new method based on the optical sectioning microscopy to characterize the multilayer structure with micro-scale air gaps. With this technique, sinusoidal fringe patterns having a predefined shifted phase produced by digital micro-mirror devices are illuminated onto the sample. The contrast response curve (CRC) of the reflected patterns along the scanning direction is determined by the phase-shifting algorithm while the object is scanned through the focus of the microscope. The maximum contrast value of the CRC occurs at the position where the sample is on the focal plane. The peak positions of the CRC are extracted through the Gaussian fitting and then implemented to achieve the surface topography and gap thickness distribution. To suppress the noise influence caused by the environment fluctuations or other factors, the frequency domain analysis (FDA) has been introduced in this work. The simulations and experiments are conducted to verify the feasibility of this technique, demonstrating the potential to be applied in such fields as semiconductor and biochip, where the air gap may play crucial roles.
关键词： thickness measurement,microscopy,surface topography
更新于2025-09-04 15:30:14
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Impact of image averaging on wide-field choroidal thickness measurements using enhanced-depth imaging optical coherence tomography
摘要： Background: The aim of this study was to examine the influence of B-scan averaging on choroidal thickness using wide-field enhanced-depth imaging optical coherence tomography. Methods: Six high-resolution trans-foveal horizontal enhanced-depth imaging line scans (spanning a 60° field) were acquired consecutively from the right eye of 10 healthy adults (mean age 30 ± 5 years), with each line scan an average of 10, 20, 30, 40, 50 or 100 B-scans, using the automated real-time image averaging and follow-up features of a Spectralis device. The impact of B-scan averaging on regional measures of wide-field choroidal thickness (across macular and peripheral regions) and their accuracy was investigated, assuming that averaging 100 B-scans would provide the most accurate estimate of choroidal thickness. Results: Regional estimates of wide-field choroidal thickness did not vary across the different B-scan averaging conditions (all p > 0.05). The mean choroidal thickness averaged across the full wide-field area exhibited the closest agreement to measures obtained with 100 averaged B-scans, when frame averaging exceeded 30 B-scans (95 per cent limits of agreement +10 to ?7, +7 to ?7 and +6 to ?3 μm for 30, 40 and 50 averaged B-scans, respectively), compared to 10 and 20 averaged B-scans (95 per cent limits of agreement +13 to ?8 and +13 to ?6 μm, respectively; p < 0.01 and p < 0.02 compared to the accuracy of 50 averaged B-scans). Conclusion: Averaging 30 B-scans for an individual enhanced-depth imaging optical coherence tomography line scan provided accurate measures of choroidal thickness across a wide-field (60°) area in young healthy eyes. This information can assist in designing the volumetric scan protocols required for detailed examination of the macular and peripheral choroid.
关键词： wide-field imaging,choroidal thickness,optical coherence tomography,enhanced-depth imaging,B-scan averaging
更新于2025-09-04 15:30:14
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Choroidal Thickness at the Outside of Fovea in Diabetic Retinopathy Using Spectral-Domain Optical Coherence Tomography
摘要： Purpose: To evaluate choroidal thickness at the outside of the fovea in patients with diabetic retinopathy using spectral-domain optical coherence tomography. Methods: We examined 87 eyes of 87 patients with diabetic retinopathy and 40 eyes of 40 normal patients. Patients with diabetic retinopathy were divided into 3 groups according to the grade of diabetic retinopathy and macular edema. The choroidal thickness was obtained at the fovea and outside of the fovea using enhanced depth imaging of Spectralis optical coherence tomography. One foveal and 8 peripheral images were selected and choroidal thickness was measured from the outer border of the retinal pigment epithelium to the inner scleral border. Results: Subfoveal choroidal thickness was thinner with increasing severity of diabetic retinopathy. However, there was no significant difference between groups without the nasal side of the fovea. A statistically significant difference was observed over the fovea at the superotemporal area. Conclusions: The choroidal thickness outside of the fovea was thinner with the severity of diabetic retinopathy and was more pronounced in the superotemporal area.
关键词： Optical coherence tomography,Diabetic retinopathy,Choroidal thickness,Enhanced depth imaging
更新于2025-09-04 15:30:14
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New Insights for Detecting and Deriving Thermal Properties of Lava Flow Using Infrared Satellite during 2014–2015 Effusive Eruption at Holuhraun, Iceland
摘要： A new lava ?eld was formed at Holuhraun in the Icelandic Highlands, north of Vatnaj?kull glacier, in 2014–2015. It was the largest effusive eruption in Iceland for 230 years, with an estimated lava bulk volume of ~1.44 km3 covering an area of ~84 km2. Satellite-based remote sensing is commonly used as preliminary assessment of large scale eruptions since it is relatively ef?cient for collecting and processing the data. Landsat-8 infrared datasets were used in this study, and we used dual-band technique to determine the subpixel temperature (Th) of the lava. We developed a new spectral index called the thermal eruption index (TEI) based on the shortwave infrared (SWIR) and thermal infrared (TIR) bands allowing us to differentiate thermal domain within the lava ?ow ?eld. Lava surface roughness effects are accounted by using the Hurst coef?cient (H) for deriving the radiant ?ux (Φ rad) and the crust thickness (?h). Here, we compare the results derived from satellite images with ?eld measurements. The result from 2 December 2014 shows that a temperature estimate (1096 ?C; occupying area of 3.05 m2) from a lava breakout has a close correspondence with a thermal camera measurement (1047 ?C; occupying area of 4.52 m2). We also found that the crust thickness estimate in the lava channel during 6 September 2014 (~3.4–7.7 m) compares closely with the lava height measurement from the ?eld (~2.6–6.6 m); meanwhile, the total radiant ?ux peak is underestimated (~8 GW) compared to other studies (~25 GW), although the trend shows good agreement with both ?eld observation and other studies. This study provides new insights for monitoring future effusive eruption using infrared satellite images.
关键词： TEI,radiant ?ux,SWIR,crust thickness,TIR,dual-band,Landsat-8,effusive eruption,Hurst coef?cient
更新于2025-09-04 15:30:14
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In <sub/>0.49</sub> Ga <sub/>0.51</sub> P/GaAs heterojunction bipolar transistors (HBTs) on 200 mm Si substrates: Effects of base thickness, base and sub-collector doping concentrations
摘要： We report performance of InGaP/GaAs heterojunction bipolar transistors (HBTs) fabricated on epitaxial films directly grown onto 200 mm silicon (Si) substrates using a thin 100% germanium (Ge) buffer layer. Both buffer layer and device layers were grown epitaxially using metalorganic chemical vapor deposition (MOCVD). With the assistance of numerical simulation, we were able to achieve high performance GaAs HBTs with DC current gain of ～100 through optimizing the base doping concentration (C-doped, ～ 1.9×1019/cm3), base layer thickness (～55 nm), and the sub-collector doping concentration (Te-doped, > 5×1018/cm3). The breakdown voltage at base (BV ceo) of higher than 9.43 V was realized with variation of < 3% across the 200 mm wafer. These results could enable applications such as power amplifiers for mobile phone handsets and monolithic integration of HBTs with standard Si-CMOS transistors on a common Si platform.
关键词： InGaP/GaAs heterojunction bipolar transistors,base doping concentrations,base thickness,Si substrates,HBTs,sub-collector doping concentrations
更新于2025-09-04 15:30:14