Search Results (1,685)

Microscopes have long been an important tool for paleontology, but most researchers use biological microscopes that are designed for transmitted light illumination. Micropaleontology has traditionally involved investigations of individual organisms (e.g., foraminifera, radiolarian and diatoms), or fossil pollen. Optical microscopy can also be a useful method for the study of macrofossils. Polarized light illumination, long a mainstay of geological research, has largely been missing from paleontology investigations. However, adapting a standard microscope for polarized light is not a difficult task. The preparation of mineralized fossils as petrographic thin sections greatly expands the possibilities for microscopic examination of macrofossils. Scanning electron microscopy (SEM) has long been used for the study of fossils, most commonly for observing individual microfossils or anatomical features of larger organisms. X-ray fluorescence analysis (SEM/EDS), a standard method for geology research, has had minimal use by paleontologists, but it is a method that merits wider acceptance. This paper emphasizes inexpensive methods for researchers who want to expand their microscopy horizons without needing deep funding or access to specialized facilities. Full article

Accurate measurement of key optical system parameters (such as focal length, distortion, and modulation transfer function (MTF)) depends critically on obtaining sharp images. Conventional autofocus methods are susceptible to noise in complex imaging environments, prone to convergence to local optima, and often exhibit low efficiency. To address these limitations, this paper proposes a high-precision autofocus method based on dynamic MTF feedback. The method employs frequency-domain MTF as a real-time image sharpness metric, enhancing robustness in noisy conditions. For the search mechanism, particle swarm optimization (PSO) is combined with the golden-section search to establish a hybrid optimization framework of “global coarse localization–local fine search,” balancing convergence speed and focusing accuracy. Experimental results show that the proposed method achieves stable and efficient autofocus, providing reliable imaging assurance for high-precision measurement of optical system parameters and demonstrating strong engineering applicability. Full article

Background/Objectives: Nailfold videocapillaroscopy (NVC) is a non-invasive method for visualizing systemic micro-circulation, primarily used in rheumatology. Many ocular diseases (e.g., glaucoma, diabetic retinopathy (DR), and central serous chorioretinopathy (CSC)) involve microvascular disturbances. Since microangiopathies are often systemic, NVC findings may reflect ocular pathology. This narrative review aimed to summarize current evidence linking NVC alterations with retinal, choroidal, and optic nerve diseases. Methods: A literature search of PubMed, Scopus, and Web of Science (2000–2025) was conducted using the keywords “nailfold videocapillaroscopy,” “ocular diseases,” “retinopathy,” and “glaucoma”. Results: Most available studies were cross-sectional and exploratory. In glaucoma, NVC abnormalities suggesting systemic hypoperfusion (reduced capillary density, avascular areas, tortuosity, and microhemorrhages) were frequently reported. CSC was associated with capillary dilation patterns (megacapillaries and aneurysmal dilations), supporting a congestive rather than ischemic microvascular profile. In DR, NVC abnormalities (reduced density and neoangiogenesis) correlated with DR severity. Associations were also found for AMD and idiopathic macular telangiectasia type 2 (MacTel2, also known as IMT). However, only a limited number of prospective studies assessed diagnostic performance, and data on sensitivity, specificity, or ROC-based validation remain scarce. Conclusions: Current evidence suggests that NVC reflects systemic microvascular alterations associated with several ocular diseases. While NVC shows potential as an adjunctive tool for risk assessment and phenotyping, its diagnostic validity has not yet been established. Limitations include the predominantly observational nature of the studies, heterogeneity of methodologies, and the lack of standardized diagnostic thresholds. Prospective trials integrating NVC with ocular imaging modalities, such as OCT angiography, are needed to determine its clinical utility. Full article

Modifications in leaf architecture disrupt optical properties and internal light-scattering dynamics. Accurate modeling of leaf-scale light scattering is therefore essential not only for understanding how disease affects the availability of light for chlorophyll absorption, but also for evaluating its potential as an early optical marker for plant disease detection prior to visible symptom development. Conventional ray-tracing and radiative-transfer models rely on high-frequency approximations and thus fail to capture diffraction and coherent multiple-scattering effects when internal leaf structures are comparable to optical wavelengths. To overcome these limitations, we present a GPU-accelerated finite-difference time-domain (FDTD) framework for full-wave simulation of light propagation within plant leaves, using anatomically realistic dicot and monocot leaf cross-section geometries. Microscopic images acquired from publicly available sources were segmented into distinct tissue regions and assigned wavelength-dependent complex refractive indices to construct realistic electromagnetic models. The proposed FDTD framework successfully reproduced characteristic reflectance and transmittance spectra of healthy leaves across the visible and near-infrared (NIR) ranges. Quantitative agreement between the FDTD-computed spectral reflectance and transmittance and those predicted by the reference PROSPECT leaf optical model was evaluated using Lin’s concordance correlation coefficient. Higher concordance was observed for dicot leaves ($C_b=0.90$) than for monocot leaves ($C_b=0.79$), indicating a stronger agreement for anatomically complex dicot structures. Furthermore, simulations mimicking an early-stage fungal infection in a dicot leaf—modeled by the geometric introduction of melanized hyphae penetrating the cuticle and upper epidermis—revealed a pronounced reduction in visible green reflectance and a strong suppression of the NIR reflectance plateau. These trends are consistent with experimental observations reported in previous studies. Overall, this proof-of-concept study represents the first full-wave FDTD-based optical modeling of internal light scattering in plant leaves. The proposed framework enables direct electromagnetic analysis of pre- and post-penetration light-scattering dynamics during early fungal infection and establishes a foundation for exploiting leaf-scale light scattering as a next-generation, pre-symptomatic diagnostic indicator for plant fungal diseases. Full article

The remote monitoring and quantification of industrial gas emissions, such as sulfur dioxide (SO₂), are critical for environmental protection. This research demonstrates an integrated methodology for estimating SO₂ emission rates (kg/s) from an industrial chimney using passive Fourier transform infrared (FTIR) spectroscopy combined with atmospheric dispersion modeling. Infrared spectra were acquired at a stand-off distance of 570 m within the 7–14 $\mathsf{\mu }$m spectral range at a resolution of 4 cm⁻¹. Path-integrated SO₂ concentrations were determined through cross-sectional scanning of the gas plume. To translate these optical measurements into an emission rate, the atmospheric dispersion of the plume was modeled using the Pasquill–Briggs approach, incorporating source parameters and meteorological data. Over two experimental series, the calculated average SO₂ emission rates were 15 kg/s and 22 kg/s. While passive FTIR spectroscopy has long been applied to remote gas detection, this work demonstrates a consolidated framework for retrieving industrial emission rates from stand-off, line-integrated measurements under real industrial conditions. The proposed approach fills a niche between local in-stack measurements and large-scale remote sensing systems, which contributes to the development of flexible ways to monitor industrial emissions. Full article

Background/Objectives: Clinical differentiation between Parkinson’s disease (PD) and atypical parkinsonism (AP) remains complex. Current diagnostic procedures helpful in their distinction lack specificity, making non-invasive tools like optical coherence tomography (OCT) crucial in evaluating possible retinal changes as potential biomarkers. Our study examined the thickness of the ganglion cell inner plexiform layer complex (GCIPL), peripapillary retinal nerve fiber layer (RNFL) and macular segments in individuals with PD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and healthy controls (HC). The objective of our study was to determine if OCT analyses can effectively discriminate PD patients from HC and whether retinal thickness can distinguish typical PD patients from those with AP. Methods: Research was an observational, cross-sectional study. Multiple retinal layers measured with OCT of PD and AP patients were compared with age- and sex-matched HC. An intergroup assessment was conducted. Results: Patients with PD and PSP exhibit a thinner GCIPL compared to HC, with no difference observed in the MSA group. GCIPL thickness between investigational groups does not differentiate between PD and AP. The RNFL and central macula thickness were statistically significantly reduced in all patient groups compared to HC. The RNFL was thinner in PSP compared to PD. Nearly all inner and outer macular segments were thinner in the investigational groups compared to HC. The preservation of outer nasal segments distinguished HC from both typical and AP. Patients with PSP and PD differed in the thickness of all macular segments, being thinner in PSP patients. Conclusions: Thickness of multiple retinal layers and macular regions might serve as a distinguishing feature between PD, AP and HC. Full article

Accurately assessing collapse risks of high-elevation, concealed rock mass blocks within the steep cliffs of Bijiashan, Three Gorges Reservoir Area, is challenging. This study employed a multidimensional approach—integrating airborne Light Detection and Ranging (LiDAR), the transient electromagnetic method (TEM), close-range photogrammetry, horizontal drilling, and borehole optical imaging—to characterize the rock mass structure of the WD1 cliff belt and delineate 52 individual blocks. Stability analysis incorporated stereographic projection for macro-scale assessment and employed mechanical models specific to three primary failure modes (toppling, sliding, falling). Finite element strength reduction quantified the stress–strain response of a representative block under natural and rainstorm conditions. Particle Flow Code (PFC) simulated dynamic instability of the exceptionally large block W1-37. Results indicate the WD1 rock mass is highly fractured, with base sections prone to weakness. Toppling failure dominates (90.4%). Under rainstorm conditions, the average Factor of Safety (FOS) decreased by 14.7%, and 73.1% of the blocks that were stable under natural conditions were destabilized—specifically transitioning to marginally stable or substable states—often triggering chain-reaction instability characterized by “crack propagation—base buckling”. W1-37 exhibited staged failure under rainstorm: “strain localization at fissure tips—penetration of basal cracks—overturning of the upper rock mass”. Its frontal rock reached a peak sliding velocity of 15.17 m/s, indicative of base-breaking toppling. The integrated “multi-technology survey—multi-method evaluation—multi-scale simulation” framework provides a quantitative basis for risk assessment of rock mass disasters in the Three Gorges Reservoir Area and offers a technical paradigm for similar high-steep canyon regions. Full article

Background: Maximal safe resection remains a central determinant of outcomes in glioma surgery, yet intraoperative discrimination between tumor and normal brain tissue is limited by the speed and subjectivity of frozen-section analysis. Label-free techniques such as Raman spectroscopy, mass spectrometry (MS), and optical coherence tomography (OCT) offer real-time biochemical and structural characterization that may enhance surgical precision. Their comparative diagnostic accuracy across clinically relevant endpoints has not been comprehensively evaluated. Methods: Following PRISMA 2020 guidelines, a systematic review and quantitative meta-analysis were conducted using PubMed, Embase, Scopus, and Web of Science through December 2024. Original human studies evaluating Raman, MS, or OCT for intraoperative glioma margin assessment were included. Pooled sensitivity, specificity, and diagnostic odds ratios (DORs) were calculated using a random-effects model. Subgroup analyses addressed tumor versus normal brain tissue, infiltrated versus non-infiltrated margins, and IDH-mutant versus wild-type gliomas. Results: Twenty-four studies comprising 1768 patients met the inclusion criteria. Across all modalities, pooled sensitivity and specificity were 0.89 (95% CI 0.86–0.92) and 0.88 (95% CI 0.84–0.91), with a pooled DOR of 65.7 (95% CI 42.3–101.8; logDOR 4.18), indicating high overall discriminative performance. Tumor versus normal differentiation achieved DOR 72.4 (logDOR 4.28; I² = 26%), infiltrated margin detection DOR 41.8 (logDOR 3.73; I² = 41%), and IDH classification DOR 52.3 (logDOR 3.96; I² = 29%). No publication bias was observed. Raman and MS outperformed OCT. Conclusions: Raman spectroscopy, mass spectrometry, and OCT demonstrate strong diagnostic accuracy for real-time intraoperative glioma evaluation, enabling reliable tissue differentiation and molecular profiling that may enhance resection extent and support precision, molecularly informed neurosurgery. Full article

Neodymium-doped bioactive wollastonite–tricalcium phosphate (W-TCP:Nd) coatings were fabricated by combining dip-coating and laser floating zone (LFZ) techniques to investigate the dependence of optical emission on polarization. Structural and spectroscopic analyses were performed on both longitudinal and transversal sections of the coating to assess the effects of directional solidification on luminescence and vibrational behavior. Micro-Raman spectroscopy revealed that the coating exhibited sharp, well-defined peaks compared to the W-TCP:Nd glass, confirming its glass-ceramic nature. New Raman modes appeared in the longitudinal section, accompanied by red and blue shifts in some bands relative to the transversal section, suggesting the presence of anisotropic stress and orientation-dependent crystal growth. Optical emission measurements showed that while the ⁴F_3/2→⁴I_11/2 transition near 1060 nm was nearly polarization independent, the ⁴F_3/2→⁴I_9/2 transition around 870–900 nm exhibited strong polarization dependence with notable Stark splitting. The relative intensity and spectral position of the Stark components varied systematically with the rotation of the emission polarization. These findings demonstrate that directional solidification induces polarization-dependent optical behavior, indicating potential applications for polarization-sensitive optical tracking and sensing in bioactive implant coatings. Full article

The transition toward Industry 4.0 requires advanced sensing platforms capable of delivering real-time, high-fidelity data under extreme industrial conditions. Thin-film sensors, leveraging both photonic and functional approaches, are emerging as key enablers of this transformation. By exploiting optical phenomena such as Fabry–Pérot interference, guided-mode resonance, plasmonics, and photonic crystal effects, thin-film photonic devices provide highly sensitive, electromagnetic interference-immune, and remotely interrogated solutions for monitoring temperature, strain, and chemical environments. Complementarily, functional thin films including oxide-based chemiresistors, nanoparticle coatings, and flexible electronic skins extend sensing capabilities to diverse industrial contexts, from hazardous gas detection to structural health monitoring. This review surveys the fundamental optical principles, material platforms, and deposition strategies that underpin thin-film sensors, emphasizing advances in nanostructured oxides, 2D materials, hybrid perovskites, and additive manufacturing methods. Application-focused sections highlight their deployment in temperature and stress monitoring, chemical leakage detection, and industrial safety. Integration into Internet of Things (IoT) networks, cyber-physical systems, and photonic integrated circuits is examined, alongside challenges related to durability, reproducibility, and packaging. Future directions point to AI-driven signal processing, flexible and printable architectures, and autonomous self-calibration. Together, these developments position thin-film sensors as foundational technologies for intelligent, resilient, and adaptive manufacturing in Industry 4.0. Full article

Objectives: This study aimed to investigate the association between optical coherence tomography angiography (OCTA) parameters and cardiovascular (CV) risk scores in individuals with type 1 diabetes (T1D). Methods: A cross-sectional analysis of a large-scale prospective OCTA trial cohort (ClinicalTrials.gov NCT03422965) was performed. Demographic, systemic, and ocular data—including OCTA imaging—were collected. T1D participants were stratified into three CV risk categories: moderate (MR), high (HR), and very high risk (VHR). Individualized predictions for fatal and non-fatal CV events at 5 and 10 years were calculated using the STENO T1 Risk Engine calculator. Results: A total of 501 individuals (1 eye/patient; 397 T1D, 104 controls) were included. Subjects with MR (n = 37), HR (n = 152) and VHR (n = 208) exhibited significantly reduced vessel density (VD) (20.9 ± 1.3 vs. 20.2 ± 1.6 vs. 19.3 ± 1.8 mm⁻¹, p < 0.05), perfusion density (PD) (0.37 ± 0.02 vs. 0.36 ± 0.02 vs. 0.35 ± 0.02%, p < 0.05) and foveal avascular zone circularity (0.69 ± 0.06 vs. 0.65 ± 0.07 vs. 0.63 ± 0.09, p < 0.05). Statistically significant negative correlations were observed between CV risk and OCTA parameters including VD, PD, and retinal nerve fiber layer thickness, while central macular thickness (CMT) showed a positive correlation (p < 0.05). Notably, CMT was significantly associated with 5-year CV risk. Conclusions: OCTA-derived metrics, particularly reduced retinal VD and PD, are associated with elevated CV risk scores in T1D patients. These findings suggest that OCTA may serve as a valuable non-invasive tool for identifying individuals with increased CV risk scores. Full article

This study presents the first metallurgical analysis of twenty-five votive statuettes of Hercules from the National Archaeological Museum of Campobasso, Molise, Italy. These artifacts, which have previously been unexamined from a metallurgical perspective, were analyzed to understand their composition, manufacturing techniques, and current state of preservation. All the samples were first analyzed in situ using X-ray fluorescence (XRF) and then were sampled to conduct microstructural analyses on polished cross-sections by optical and scanning electron microscopy. The statuettes revealed a ternary Cu-Sn-Pb alloy, consistent with historical alloying practices and manufacturing techniques typical of the period. The study highlights a homogeneous biphasic microstructure with dispersed lead nodules within the bronze matrix. The corrosion products on the surface have peculiar colors and textures due to both the finishing process and the alteration accord over centuries of abandonment, aiding the understanding of the material’s behavior over time. The compositional results confirm the usage of materials and techniques in line with other coeval artifacts. Full article

The magnonic activity refers to a chiral effect in the field of magnetization dynamics that exhibits a high degree of analogy to optical activity. It manifests as the azimuthal continuous rotation of standing-wave nodes in the cross-section of spin waves during propagation in ferromagnetic nanowire waveguides. The study employs micromagnetic simulation methods to theoretically investigate the influence of the interfacial Dzyaloshinskii–Moriya interaction (iDMI) on the magnonic activity in longitudinally magnetized ferromagnetic nanotubes. The results demonstrate that iDMI-induced chirality effectively controls the magnonic activity’s rotatory power, which relies on the values of the iDMI constant D (from $-0.5 \mathrm{m}\mathrm{J}/{\mathrm{m}}^2$ to $1 \mathrm{m}\mathrm{J}/{\mathrm{m}}^2$). Additionally, nanotube thickness variations (from 3 nm to 15 nm) alter effective curvature, further influencing the rotatory power of the magnonic activity. Numerical simulations and semi-analytical calculations show excellent agreement, providing a theoretical foundation for chiral spin-wave manipulation in 3D curved nanostructures. Full article

Objective: Evaluate the efficacy and safety following intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy in patients with diabetic macular oedema (DME). Methods: To evaluate retinal microvascular remodelling and photoreceptor metrics using adaptive optics (AO) alongside systemic vascular status assessed by brachial/aortic hemodynamic and carotid ultrasound. We conducted a single-centre longitudinal study including twenty-one patients with DME. The following four diagnostic visits were performed: baseline (V1, no anti-VEGF treatment), 2–3 months (V2), 6–8 months (V3), and 12–14 months (V4). Adaptive optics (rtx1) measured foveal cone number (N) and regularity (Reg) within a standardised 80 × 80 µm window, and superior temporal retinal arteriole morphology after the first bifurcation (vessel diameter [VD], lumen diameter [LD], wall thickness [WT], wall-to-lumen ratio [WLR], and wall cross-sectional area [WCSA]). SphygmoCor provided peripheral (brachial) and central (aortic) pressures, augmentation pressure (AP), augmentation index (AIx), and carotid–femoral pulse wave velocity (PWV and PWVHR heart rate adjusted). Carotid ultrasound assessed intima–media thickness (IMT), carotid lumen diameter (CLD), and IMT/CLD ratio (IMTLR) 2 mm proximal to the bifurcation in diastole. Visual acuity (Visus), intraocular pressure (IOP), and central retinal thickness (CRT) were obtained at each visit. Results: In the treated eye (TE), WLR showed a significant overall change (Friedman p = 0.007), with a modest V4 vs. V1 increase (Wilcoxon p = 0.045); LD also varied across visits (Friedman p = 0.034). Cone metrics improved as follows: Reg increased over time (Friedman p = 0.019), with a significant rise at V4 vs. V1 (p = 0.018), and cone number increased at V3 vs. V1 (p = 0.012). Functional/structural outcomes improved as follows: visual acuity increased at V3 (p = 0.009) and V4 (p = 0.028), while CRT decreased at V3 (p = 0.002) and V4 (p = 0.030); IOP remained stable compared to V1. Systemic hemodynamics was largely unchanged; small fluctuations in DBP and cDBP across V1–V4 were observed (Friedman p = 0.034 and p = 0.022, respectively), whereas AIx, AP, PWV, and PWVHR showed no significant trends. Carotid IMT, CLD, and IMTLR did not change significantly across visits, supporting systemic vascular safety. Conclusions: Intravitreal anti-VEGF therapy in DME was associated with improvements in photoreceptor organisation and macular structure/function, with AO-derived arteriolar remodelling detectable over time, and no adverse changes in large-artery structure. These findings support ocular efficacy and systemic vascular safety; confirmation in larger cohorts is warranted. Full article

Background and Objectives: Keratoconus (KC) is a progressive ectatic corneal disease that can cause irregular astigmatism and visual impairment. To describe the demographic and clinical profile of KC patients attending major eye care centers in Riyadh City, Saudi Arabia, and to explore associations with laterality, disease severity, and management patterns. Materials and Methods: This multi-center hospital-based cross-sectional study enrolled consecutive patients with a confirmed diagnosis of KC (new or follow-up) presenting between April 2022 and April 2023. All participants underwent standardized ophthalmic assessment and Scheimpflug tomography (Pentacam). Disease severity was categorized as early, moderate, or advanced using Pentacam-derived keratoconus staging, and ocular parameters (refraction, keratometry, pachymetry, and higher-order aberrations) were compared across severity categories. Results: A total of 157 patients (264 eyes) were included (mean age 31.8 years; 56.7% female), with bilateral KC in 68.2%. Eye rubbing (67.8%) and allergic symptoms (61.7%) were common. Keratometric indices and higher-order aberrations differed significantly by severity grade (p < 0.001). Management patterns differed by sex and laterality, with corneal cross-linking and glasses reported more frequently in males, and soft contact lens use concentrated among bilateral cases. Conclusions: In this hospital-based Riyadh sample, KC was often associated with eye rubbing and allergic symptoms and showed clear stage-dependent worsening of tomographic indices and optical quality. These findings support early detection and targeted counseling on modifiable behaviors, while population-based studies with non-diseased comparators are needed to quantify incidence and prevalence in Riyadh. Full article