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Retinal vascular density evaluated by optical coherence tomography angiography in macular telangiectasia type 2
摘要： Purpose To evaluate the retinal and choroidal vascular changes through optical coherence tomography angiography (OCTA) in patients with macular telangiectasia type 2 (MacTel 2). Methods Our study included 20 patients (40 eyes) with MacTel 2, and age-matched and sex-matched 18 subjects (36 eyes) in the control group. Fundus color photographs, fundus autofluorescence, fundus fluorescein angiography, spectral-domain optical coherence tomography and OCTA were performed. Foveal vascular density and parafoveal vascular density (PFVD), and foveal retinal thickness and parafoveal retinal thickness, choroidal thickness (CT) and retinal ganglion cell–inner plexiform layer (GCIPL) were compared between MacTel 2 patients and normal age-matched controls. Results The retinal whole vascular density and PFVD of the deep plexus were significantly lower in patients with MacTel 2 than that of the control group (56.93% vs. 58.54%, p = 0.003; and 60.38% vs. 61.66%, p = 0.045). The foveal avascular zone (FAZ) of the deep plexus was significantly enlarged in patients with MacTel 2 than that of the control group (0.44 vs. 0.36, p = 0.009). There was a positive and statistically significant correlation between the FAZ of the superficial and deep plexus and CT in patients with MacTel 2. There was a positive and statistically significant correlation between retinal whole, parafoveal temporal quadrant vascular density of the superficial and deep plexus and GCIPL thickness in patients with MacTel 2. Conclusions Our study demonstrated that important retinal vascular density and FAZ changes in MacTel 2 occur in the deep capillary plexus of the retina.
关键词： Macular telangiectasia type 2,Vascular density,Choroidal thickness,Retinal ganglion cell–inner plexiform layer,Optical coherence tomography angiography
更新于2025-09-23 15:23:52
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Non-ionized, High-resolution Measurement of Internal and Marginal Discrepancies of Dental Prosthesis Using Optical Coherence Tomography
摘要： An internal and marginal fit between prosthesis and abutment are important factors of the durability of dental prosthesis. In this study we have proposed the use of swept-source optical coherence tomography (SS-OCT) as a novel application for non-ionized and high-resolution measurements of internal and marginal discrepancies at anatomically critical four points, such as occlusal, angle, axial, and margin during prosthesis attachment. A tooth model was fabricated by 3D printing technique and the dental prosthesis was designed using dental CAD software. The cross-sectional images along with intensity peak profile analysis of the sample were acquired using OCT system for measurements of fit. The demonstrated qualitative and quantitative evaluations can be well-utilized for assessment of the internal and marginal fit of dental prosthesis.
关键词： Intensity analysis,Dental prosthesis,Internal and marginal fit,Swept-source optical coherence tomography
更新于2025-09-23 15:23:52
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High-Definition Optical Coherence Tomography in the Diagnosis of Basal Cell Carcinoma Evaluated by an Experienced Versus Inexperienced Investigator
摘要： Background: Histopathology is the gold standard in the diagnosis of basal cell carcinoma (BCC) but biopsies are invasive and often not the preferred diagnostic method for patients. In this context, non-invasive diagnostic imaging tools such as high definition optical coherence tomography (HD-OCT) have shown promising results in diagnosing BCC in real time, atraumatically and repeatedly. Objective: To evaluate the sensitivity and specificity of HD-OCT in the diagnosis of BCC by an experienced versus an inexperienced investigator and describe typical features in common differential diagnosis of BCC. Patients and methods: Forty three patients with clinical suspicion for BCC were included. The HD-OCT images were evaluated in a blinded manner by an experienced and inexperienced investigator. The results were compared to the histopathological diagnosis. Results: Histopathology revealed 22 BCC, 10 fibrous papules of the face, 5 actinic keratoses, 3 intradermal nevi, 2 squamous cell carcinomas and 1 sebaceous hyperplasia. The sensitivity and specificity in diagnosing BCCs correctly by HD-OCT in the experienced investigator was 86.4% and 90.5%, respectively. In the inexperienced investigator the sensitivity and the specificity was 77.3% and 81.0%, respectively. There was a good inter-observer agreement found between experienced and inexperienced investigators. Conclusion: HD-OCT can be used as auxiliary diagnostic tool in the evaluation and treatment of BCC even by inexperienced investigators.
关键词： Differential,Basal cell carcinoma,Optical coherence tomography,Diagnosis
更新于2025-09-23 15:23:52
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A Hyperspectral Imaging Instrumentation Architecture Based on Accessible Optical Disc Technology and Frequency-Domain Analyses
摘要： Hyperspectral imaging (HSI) is an emergent instrumentation technology with great potential in many applications, due to its ability to measure important spectral features. However, the widespread adoption of HSI requires the development of accessible (i.e., inexpensive and uncomplicated) HSI instrumentation architectures. In this paper, we present, design, develop, and evaluate an accessible HSI instrumentation architecture, with snapshot operation, based on the integration of readily available components and frequency multiplexing with Fourier analyses. In the experimental work, an incident image beam is divided into spatial image channels, each with an assigned dynamic binary code via a dynamic coded aperture. This dynamic coded aperture is constructed from repurposed diffractive optical disc technologies and is patterned with strategic opaque and transparent regions. When it is rotated by a motor, dynamic binary codes are used, along with Fourier analyses, to identify the diffraction of each spatial image channel. The spatially overlapped spectra from the diffraction are directed onto a charge-coupled device sensor, and each spatial image channel is distinguished through Fourier analyses. The resulting Fourier amplitude spectra are transformed into corresponding functions of wavelength, and this transformation is based on the experimental instrumentation geometry. The performance of the HSI instrumentation architecture is evaluated using a comparison with data from a commercial spectrometer. The presented HSI instrumentation architecture can be adapted for 2-D operation. Ultimately, the presented HSI instrumentation architecture can benefit regions of the world that have limited financial resources and a need for accessible HSI technologies.
关键词： Electromagnetic devices,optical diffraction,hyperspectral sensors,multispectral imaging
更新于2025-09-23 15:23:52
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Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus
摘要： Two-dimensional (2D) horizontal fields of cloud optical thickness derived from airborne measurements of solar spectral radiance during the Vertical Distribution of Ice in Arctic Clouds (VERDI) campaign (carried out in Inuvik, Canada in April/May 2012) are compared with semi-idealized Large Eddy Simulations (LES) of Arctic stratus performed with the COnsortium for Small-Scale MOdeling (COSMO) atmospheric model. The input for the LES is obtained from collocated airborne dropsonde observations. Four consecutive days of a persistent Arctic stratus observed above the sea-ice free Beaufort Sea are selected for the comparison. Macrophysical cloud properties such as cloud top altitude and vertical extent are well captured by COSMO. Cloud horizontal inhomogeneity quantified by the standard deviation and one-dimensional (1D) inhomogeneity parameters show that COSMO produces only half of the measured horizontal cloud inhomogeneities, while the directional structure of the cloud inhomogeneity is well represented by the model. Differences between the individual cases are mainly associated with the wind shear near cloud top and the vertical structure of the atmospheric boundary layer. A sensitivity study changing the wind velocity in COSMO by a vertically constant scaling factor shows that the directional cloud inhomogeneity structures strongly depend on the mean wind speed. A threshold wind velocity is identified, which determines when the cloud inhomogeneity stops increasing with increasing wind velocity.
关键词： airborne measurements,COSMO model,horizontal inhomogeneity,wind speed sensitivity,Large Eddy Simulation,Arctic stratus,cloud optical thickness
更新于2025-09-23 15:23:52
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Structural and Diffuse Reflectance Study of Cr-Doped ZnO Nanorod-Pigments Prepared via Facile Thermal Decomposition Technique
摘要： Ceramic coloured nanopigments are promising for commercial cool paint applications. This study was carried out to examine the near infrared (NIR) reflectivity of Cr-doped ZnO nanopigments prepared by simple thermal decomposition of zinc acetate dihydrate and chromium(III) acetate hydroxide as precursors of Zn and Cr, respectively. XRD, FTIR and SEM have been used to characterize the microstructure and morphological properties of the synthesized nanopigments. The obtained results referred to ZnO wurtzite hexagonal structure in absence of other ZnO phases or any phases based on chromium. The obtained particles of the investigated samples are uniform rod-like shape with average diameter about 50 nm. The diffuse reflectance measurements exhibited the decrease in NIR reflectance with increasing Cr content. The sample with lower content of Cr, 0.5 wt% of Cr precursor to Zn precursor, exhibited a maximum value of NIR solar reflectance (R*) of 53.1% with respect to the other doped samples. The optical energy gap (Eg) of the investigated nanopigments were calculated using diffuse reflectance spectrum in view of Kubelka–Munk assumptions and the obtained average value of Eg is 3.219 eV with small standard deviation ± 0.015 eV.
关键词： Thermal decomposition technique,ZnO,Structure and optical properties,Pigments
更新于2025-09-23 15:23:52
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The influence of the thermal wake due to pulsating optical discharge on the aerodynamic-drag force
摘要： The influence of a thermal wake due to gas injection and due to a pulsating optical discharge (POD) on the aerodynamic-drag force of a body in a supersonic air flow with Mach number M = 1.45 are experimentally examined. With the help of a single-component aerodynamic balance, the influence of the injected subsonic jet and the thermal wake produced by POD on the aerodynamic drag of a hemisphere-on-cylinder model was studied. It is shown that the observed aerodynamic-force reduction phenomenon can be made more pronounced by increasing the laser power and pulse repetition frequency, or by decreasing the distance between the model and the pulsating optical discharge. The maximum aerodynamic-force reduction (up to 15%) due to the thermal-wake action was observed at a maximum laser-radiation power of W = 2.3 kW and at a pulse rate of f = 90 kHz. The joint effect due to the argon jet and due to the POD caused an aerodynamic-drag force reduction reaching 30%.
关键词： thermal wake,gas injection,CO2-laser,supersonic flow,pulsating optical discharge,aerodynamic-drag force
更新于2025-09-23 15:23:52
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Underwater optical wireless sensor networks using resource allocation
摘要： Optical wireless communications is an energy efficient and cost-effective solution for high speed and high secure wireless connections. In this paper, we propose an underwater optical wireless sensor network using multiple input multiple output technique and power allocation algorithm for supporting multiple users with the impacts of underwater channel uncertainty interferences. In proposed power allocation algorithm, all the LED nodes in are coordinated and controlled by a central controller; each LED node supports all the users within its field of view. To separate users, optical code division multiple access is used; cyclic optical orthogonal code working as CDMA code is employed. At the receiver, a minimal mean squared error (MMSE) filter is uniquely designed for each user. The MMSE filters and the assigned power can be jointly optimized to improve the overall throughput and signal to noise ratio. Since the system performance may be impacted by the underwater channel uncertainty, the proposed power allocation can use the predicted channel uncertainty variance to reduce the interference of the channel uncertainty and improve the signal to noise ratio. Compared to the equal power allocation algorithm, the proposed algorithm can support longer transmission distance, higher bit rate and lower bit error rate.
关键词： Multiple access interference,Underwater communications,Wireless sensor networks,Channel uncertainty,MIMO system,CDMA,Optical wireless communications,Resource allocation
更新于2025-09-23 15:23:52
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Temperature dependence simulation and characterization for InP/InGaAs avalanche photodiodes
摘要： Based on the newly proposed temperature dependent dead space model, the breakdown voltage and bandwidth of InP/InGaAs avalanche photodiode (APD) have been investigated in the temperature range from -50°C to 100°C. It was demonstrated that our proposed model is consistent with the experimental results. Our work may provide a guidance to the design of APDs with controllably low temperature coefficient.
关键词： separate absorption, grading, charge, and multiplication avalanche photodiode (SAGCM APD),optical communication,temperature coefficient,dead space effect
更新于2025-09-23 15:23:52
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Sol–Gel Spin-Coating Followed by Solvothermal Synthesis of Nanorods-Based ZnO Thin Films: Microstructural, Optical, and Gas Sensing Properties
摘要： Zinc oxide thin films with nanorod morphology were investigated for microstructural and optical properties as well as their performance as a liquid petroleum gas sensing material. A two-step synthesis procedure consisting of sol–gel spin-coating and solvothermal methods was employed where several factors such as rational utilization of metal precursors, solvent, stabilizing, and structure directing agents, a repetitive drying-coating process, as well as post-thermal annealing were found influential to obtain qualified nanorods and a final homogeneous thin film. Compositional and optical investigations were pursued to characterize features, namely morphology, poly crystallinity, porous structure, nanocrystallite size, lattice oriented growth, textural atomic ratio, lattice purity and transparency, phonon and exciton transitions, as well as the formed structural defects via field-emission scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray, UV–Vis spectroscopy, Raman, and photoluminescence techniques. The as-prepared thin film was then used as an active LPG sensing material via a home-made gas sensor where the control sensing parameters were chamber testing temperature and gas concentration. Results showed a quantitative response of 92.7% as sensor sensitivity at an operation temperature of 250°C and a LPG concentration of 800 ppm in addition to fast response and recovery times of 44.1 s and 218.7 s, respectively.
关键词： Zinc oxide nanorods,thin film,optical characteristics,gas sensing,microstructural properties,liquid petroleum gas
更新于2025-09-23 15:23:52