Search Results (665)

Background and Clinical Significance: Localized amyloidoma rarely affects the tongue base, a site far less commonly involved than the larynx. When it does occur at this location, the clinical and radiological presentation can closely mimic oropharyngeal malignancy, making it a genuine diagnostic pitfall for head and neck surgeons. Establishing the diagnosis demands histological proof, and ruling out systemic amyloidosis is an essential prerequisite. Case Presentation: An 80-year-old nonsmoking woman was evaluated for progressive dysphagia and globus sensation that had worsened over several years. Endoscopy revealed a firm, lobulated mass at the tongue base, centered on the glossotonsillar sulcus. Incisional biopsy under local anesthesia showed amyloid deposits. MRI demonstrated an avidly enhancing, well-circumscribed lesion without invasion of the deep neck spaces. A comprehensive systemic evaluation—including serum and urine protein electrophoresis with immunofixation, serum free light chains (κ/λ ratio 1.05), echocardiography, and bone marrow biopsy—yielded no evidence of systemic AL amyloidosis or plasma-cell dyscrasia. The mass was excised through transoral robotic surgery (TORS). Histopathology confirmed Congo red-positive, apple-green birefringent amyloid with lambda light-chain restriction; staining for AA amyloid and transthyretin was negative. The patient was diagnosed with primary localized lingual amyloidoma of the AL lambda type and remained symptom-free, with no endoscopic evidence of recurrence, at 12-month follow-up. Discussion: Amyloidoma deserves a place in the differential diagnosis of tongue base masses, particularly when the clinical picture does not fit squamous cell carcinoma. Congo red staining under polarized light, immunohistochemical light-chain typing, and a rigorous systemic workup are the cornerstones of diagnosis. Robotic-assisted transoral excision provides excellent access to the tongue base with low morbidity. Conclusions: This case underscores the need to consider amyloidoma when evaluating tongue base lesions, the central role of Congo red staining and light-chain typing, and the utility of TORS as an effective treatment option for selected symptomatic cases. Full article

In this study, we employed one of the green synthesis methods utilizing water extracts prepared from solid industrial wastes of Rosa damascena Mill. (RD) and Oriental variety tobacco (Nicotiana tabacum)-mixed stems and leaves (O) as a natural reducing agent for PdCl₂ to obtain environmentally friendly Pd nanoparticles (PdNPs). Transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDX) in TEM were applied to determine the morphology, microstructure, phase, and elemental composition of PdNPs synthesized. The concentration of PdNPs in the suspensions was quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES), which is essential for their intended application. Furthermore, the synthesized PdNPs were incorporated as dopant into a polymer matrix (PAZO) developed for optical applications. As will be demonstrated, doping PAZO with specific concentrations (0.1, 0.2, 0.25, 0.3, 0.4, 0.5, and 1 wt. %) of green PdNPs enhances the maximal value of the photoinduced birefringence by more than 50%. This improvement enables more efficient inscription of polarization-selective holographic optical elements in the resulting photoanisotropic nanocomposite materials with nearly 25% higher diffraction efficiency. Using a digital polarization holographic setup, the spatial modulation of polarization was recorded on thin nanocomposite films of the azopolymer PAZO, doped with certain concentrations of the green PdNPs. Full article

The pervasive contamination of aquatic environments by microplastic particles necessitates the development of rapid, cost-effective and field-deployable detection methodologies to complement established but laboratory-bound spectroscopic techniques such as Fourier-transform infrared and Raman microscopy. The demand for field-suitable methods with a broad accessibility comes from researchers themselves. In this review we systematically examine recent advances in optical methods for microplastics identification with a particular emphasis on birefringence as a key diagnostic feature of partially crystalline synthetic polymers. In particular, we analyze three complementary technological directions: liquid crystal-based sensors that exploit orientational order disruptions at interfaces for label-free microplastics detection; polarization holographic imaging combined with machine learning for high-throughput particle classification; and on-chip polarization light microscopy enabling compact and portable analyzing systems. Liquid crystal platforms demonstrate exceptional sensitivity to submicron particles and enable real-time visualization of microplastics aggregation at aqueous interfaces, though they currently lack polymer-specific chemical identification. Conversely, smart polarization holography integrated with Stokes polarimetry and deep learning algorithms achieves over 90% accuracy in distinguishing microplastics from natural particles while processing up to 10,000 particles per minute. Emerging on-chip polarized light microscopy offers a pathway toward miniaturized, low-cost devices suitable for field applications. By synthesizing insights from foundational studies, this review identifies convergent interdisciplinary trends—particularly the integration of artificial intelligence with multimodal optical imaging—and outlines persistent challenges including standardization, interference from natural organic matter, and the transition from laboratory prototypes to robust field-deployable instruments. The systematization of birefringence-based approaches aims to guide future research towards integrated monitoring systems capable of addressing water quality concerns. Full article

Accurate intraocular pressure (IOP) assessment is essential for glaucoma diagnosis and follow-up. Conventional contact tonometry (e.g., Goldmann and rebound devices) remains widely used, but its accuracy is affected by operator dependence, alignment errors, and patient discomfort. We present a non-contact IOP estimation framework based on corneal stress birefringence and full-field fringe inversion. Ex vivo porcine corneas were imaged under controlled pressure loading from 15 to 20 mmHg, and a coupled stress-optic/shell mechanics model was used to generate pressure-indexed synthetic fringe fields for inverse fitting. In the 15–18 mmHg range, more than 75% of the estimates were within plus or minus 1 mmHg of the reference pressure; performance declined at 19–20 mmHg, consistent with a stronger nonlinear biomechanical response and reduced fringe separability. Defect experiments further showed that local stiffness loss caused both near-defect distortion and far-field stress redistribution, supporting the need for full-field rather than point-wise analysis. These results indicate that stress-birefringence imaging is a promising route toward non-contact, region-sensitive IOP assessment. Full article

Fully dense monoclinic zirconia ceramics were successfully fabricated by pressureless sintering and/or HIP. Although monoclinic zirconia exhibits unique physicochemical properties, fabrication of fully dense polycrystalline bodies has remained challenging due to catastrophic volume expansion during the tetragonal-to-monoclinic transformation. By introducing a synergistic ternary (Ga₂O₃-ZnO-TiO₂) sintering aid, a relative density exceeding 99.6% with an average grain size of 0.5–2 µm was achieved by sintering under an oxygen atmosphere at 1070 °C for 3–100 h, well below the phase-transition temperature. X-ray diffractometry confirmed a single-phase monoclinic structure. Subsequent hot isostatic pressing at 1080 °C and 180 MPa for 2 h eliminated residual porosity, yielding a 4-point bending strength of 328 MPa, a fracture toughness of 2.7 MPa·m^0.5, and a Vickers hardness HV₁ of 805. This monoclinic zirconia ceramic exhibited ~30% total transmittance, while in-line transmittance remained below 0.1% due to intrinsic birefringence of the monoclinic lattice. These results established a low-temperature route for densifying phase-sensitive ceramics while achieving long-term stability. Full article

This study presents unique polymeric materials applicable to plastic substrates for use in flexible-display devices that overcome the trade-off between low linear coefficients of thermal expansion (CTE) and low thickness-direction birefringence (Δn_th) while combining a very high T_g, sufficiently high thermal stability, excellent optical transparency, good solubility, and minimum-required ductility. Polyimide (PI) films obtained from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) with 2,2′-bis(trifluoromethyl)benzidine (TFMB) under different conditions resulted in widely varying CTE values and provided a clear CTE–Δn_th correlation, which can be regarded as a virtual lower boundary in the CTE–Δn_th relationship for various PI systems. The pristine CBDA/TFMB and CpODA/TFMB (CpODA = norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride) systems were modified using numerous specifically designed monomers, i.e., a vertical-alignment-type liquid-crystalline diamine and cardo-type and spiro-type monomers. However, it was very challenging to overcome the trade-off between low CTE and low Δn_th, that is, to significantly exceed this lower boundary by modifying the pristine systems, while ensuring other target properties. One of the keys to achieving the present goal was compatibility with chemical imidization or one-pot polymerization processes (i.e., high solubility of the PIs), because these processes were more advantageous in reducing CTE and enhancing film transparency than the conventional two-step process. The modifications using phenyl-substituted xanthene-pendant 2,7-diaminofluorene and fluorene-pendant 2,3,6,7-xanthenetetracarboxylic dianhydride exhibited a prominent effect on overcoming the trade-off without the help of any fillers, while combining other excellent target properties. Polarized FT-IR difference spectra measured at varying incidence angles suggested that these side groups, which are connected perpendicularly to the PI main chains, align in the Z-direction, rationalizing the observed prominent effect. Thus, unique high-temperature transparent materials applicable to plastic substrates were successfully obtained in this study. Full article

To address the polarization fading noise in coherent detection phase-sensitive optical time-domain reflectometry (Φ-OTDR) for distributed low-frequency vibration sensing, a Φ-OTDR sensing scheme integrating polarization diversity reception and the variational mode decomposition (VMD) algorithm is proposed. The mechanism of polarization fading induced by fiber birefringence and external perturbations is systematically analyzed. A signal–noise mathematical model for polarization diversity reception is established, and the adaptive decomposition capability of the VMD algorithm for non-stationary phase signals is elaborated. This scheme can accurately separate the additional noise introduced by polarization diversity reception from the target low-frequency vibration signals. Experimental results demonstrate that, compared with the single-path detection scheme, the proposed method eliminates the amplitude attenuation of beat frequency signals caused by polarization mismatch at the optical path level. Meanwhile, it effectively suppresses both the additional noise introduced by polarization diversity and the low-frequency phase drift resulting from unstable laser frequency. It achieves precise phase restoration of vibration signals excited at 50 Hz under three typical sensing distances of 5 km, 10 km, and 30 km. Additionally, it successfully restores low-frequency vibration signals as low as 0.6 Hz at the sensing distance of 30 km. Full article

Background: Standardized and ethically compliant animal models remain essential for improving translational research in Alzheimer’s disease. Although Aβ_1–42-induced rodent models are widely used, methodological variability continues to limit reproducibility. Methods: We explored the feasibility of a stereotactic intrahippocampal Aβ_1–42 rat model established by bilaterally injecting pre-aggregated peptide into the hippocampus of adult Sprague Dawley rats. Model feasibility and targeting accuracy were assessed intraoperatively. Cognitive performance was evaluated using the Y-maze for spatial recognition memory and the novel object recognition (NOR) test. Histological examination was performed using hematoxylin–eosin (H&E) and Congo red staining to assess cytoarchitecture and to provide supportive evidence of amyloid-like deposits. Results: The surgical procedure was well-tolerated, and the injected animals showed reduced performance in behavioural testing, including reduced spatial recognition memory in the Y-maze and decreased discrimination indices in the NOR test. The animals also showed histological changes, including Congo red-positive birefringent structures consistent with amyloid-like congophilic material. Conclusions: This study presents a feasible experimental framework for intrahippocampal Aβ_1–42 administration, showing behavioural and histological changes under the present experimental conditions. However, further validation, including sham-operated controls and molecular characterization, will be required before these findings can be interpreted as specific to Aβ-driven pathology. Full article

Traditional polymer-dispersed liquid crystal (PDLC) faces limitations in smart dimming applications due to high driving voltage and poor high-temperature stability. In this study, a high-birefringence liquid crystal (QYPDLC-901) was used to prepare PDLC films with liquid crystal contents ranging from 72 wt% to 80 wt%, achieved through synergistic regulation of a low-functional acrylic polymer system and a low-intensity curing process. The effects of liquid crystal content, cell gap, and temperature on electro-optical properties were systematically investigated. Optimal performance was obtained at a liquid crystal content of 77 wt%, with a low threshold voltage of 2.9 V, saturation voltage of 7 V, fast response (rise time 4.2 ms, decay time 47 ms), and a favorable balance between high on-state and low off-state transmittance. Microstructural analysis revealed that the superior performance results from uniform droplet dispersion and low interfacial energy. Furthermore, the PDLC exhibited excellent switching stability from 23 °C to 90 °C, maintaining a maximum transmittance of 93% at 90 °C, with increases of only 0.4 V in threshold voltage and 0.1 V in saturation voltage. This study provides an experimental basis for designing smart dimming devices suitable for low-voltage driving and extreme environments. Full article

Vertical-External-Cavity Surface-Emitting Lasers (VECSELs) have gained significant attention over the past two decades due to their versatility in a wide range of photonic applications. This review focuses on VECSEL configurations for dual-wavelength emission, highlighting their use in high-resolution spectroscopy, terahertz (THz) generation, and advanced optical communication. We explore recent developments in VECSEL designs, including systems utilizing birefringent crystals for polarization-based frequency separation and configurations with dual-VECSEL chips or dual-gain regions within a single cavity. These two-wavelength VECSELs enable diverse operation modes, including narrow-linewidth, pulsed, multimode, and frequency-converted emission, with high-brightness output, excellent beam quality, and tunable wavelengths. Additionally, the review discusses advancements in dual-frequency VECSELs, with applications in LIDAR systems for environmental monitoring, highly stable optical clocks, and fiber sensors. We examine improvements in cavity design, semiconductor structures, and power stabilization, which have enhanced frequency stability and spectral purity, making VECSELs suitable for precision metrology and sensing applications. Full article

Birefringence, arising from the low-symmetry structure in orthorhombic LaFeO₃, limits the observation and utilization of magneto-optical effects. In this study, the pure-phase perovskite-typed La_1−xCe_xFe_1−xTi_xO₃/SiO₂ thin films were successfully fabricated via radio-frequency magnetron sputtering, where the co-doping of Ce³⁺ and Ti⁴⁺ ions effectively induced a structure transition from orthorhombic to a highly symmetric cubic phase, eliminating birefringence effect and thus reducing optical transmission loss. At the same time, the doped Ce³⁺ ions also effectively enhanced the magnetic and magneto-optical effects of the system due to their strong spin coupling effect and superexchange interaction with Fe³⁺ ions. The results show that the cubic-phase La_0.5Ce_0.5Fe_0.5Ti_0.5O₃/SiO₂ thin film exhibits excellent magnetic and magneto-optical performance. Their saturation magnetization reaches 180 emu/cm³ with an in-plane easy magnetic axis. And their magnetic circular dichroic ellipticity |ψ_F| reaches 3054 degrees/cm. Full article

Second harmonic (SH) radiation can only be generated in non-centrosymmetric bulk crystals under electric dipole approximation. Nonlinear thin films made from bulk crystals are technologically challenging because of complex and high-temperature fabrication processes. In this work, heterostructures made of two distinct amorphous materials, namely SiO₂ and TiO₂, were prepared through plasma-enhanced atomic layer deposition (PEALD) with deposition temperature of 100 °C. By using the uniaxial dispersion model, we characterized the form birefringence of the deposited films, which can play a crucial role for the phase-matching condition in nonlinear waveguides or other nonlinear optical applications. By applying a fringe-based technique, we determined the largest diagonal component of the effective bulk second-order susceptibility, ${\chi }_{zzz}^{\left(2\right)}$ = 1.30 ± 0.13 pm/V, at a wavelength of 1032 nm. Noteworthy, we observed strong SHG signals from two-component nanolaminates, which are several orders of magnitude larger than those from single layers. The SHG signals from our samples only require the broken inversion symmetry at the interface. Here, optical properties of nanocomposites can be precisely engineered using the promising PEALD technology. Full article

The effect of structure on the properties of cotton fibers is yet to be fully understood even after many years of research. This is due to the presence of convolutions that occur at various intervals in cotton fibers. An attempt was made in this investigation to remove these convolutions using liquid ammonia treatment. The optical and X-ray orientation angles of two varieties of G. hirsutum cotton fibers were investigated at various stages of maturity, and results were compared. An American upland variety was also studied. Four-hour treatment of cotton fibers in liquid ammonia at a temperature of −50 °C ensures a complete change of the lattice structure from cellulose I polymorph to cellulose III polymorph. The cellulose I lattice structure is restored by boiling it in distilled water for 24 h. X-ray diffractograms confirm these conversions. Mature fibers after treatments are devoid of convolutions and are rounded in appearance with no central lumen. The scanning electron micrographs revealed these morphological structures. A close correlation exists between the optical and X-ray orientation measurements and are both strongly dependent on fiber maturity. In all the varieties studied, a maturity ratio of at least 0.8 is required for a cotton fiber to be of commercial value, in terms of strength and durability The progressive build-up of both the primary and secondary walls as the fiber matures shows a gradual decrease in helix angles and, hence, an increase in the orientation of the fibrils, conforming to the constant pitch model. The effect of convolutions on both the optical and X-ray orientation angle is found to be higher than 10%. Full article

We report a highly sensitive label-free optical biosensor based on nematic liquid crystals, for the detection of proteins. The principles of biosensing are based on the change in the liquid crystal alignment induced by biomolecules adsorbed on the cell inner surface, which can be easily detected with a polarizing optical microscope. Although this approach is well-known, we propose here an experimental strategy that allows us to reach a detection limit of the order of 10⁻¹³ g/mL, orders of magnitude higher than the one reported in the literature for similar biosensors. Furthermore, our method leads to assessing a well-defined, specific dependence of protein concentration on cell birefringence, for rapid quantitative biosensing. The proposed biosensor can additionally be used for the detection of antibodies. Full article

Polarisation encoding is widely used in fibre-based Quantum Key Distribution (QKD), but random birefringence in optical fibres causes the transmitted states to drift, requiring active compensation at the receiver. Electronic Polarisation Controllers (EPCs) are commonly used for this purpose, yet the relationship between their control voltages and the resulting polarisation transformation is highly nonlinear and difficult to model. While optimisation algorithms are frequently employed to align and stabilise polarisation states, their comparative performance has not been systematically studied in realistic QKD settings. In this work, we benchmark four optimisation algorithms for electronic polarisation control, using both a numerical model and a 50 km fibre-based experimental setup. We evaluate each algorithm in terms of convergence time, failure rate, and stability, under both initial alignment and continuous drift compensation scenarios. Coordinate Descent achieved the fastest average alignment time (2.1 ms in simulation; 34.6 s experimentally), while Simulated Annealing delivered perfect reliability. We further propose a hybrid control strategy that combines fast initial alignment with high-reliability realignment. This approach was validated over a continuous 2 h QKD simulation with real fibre drift, demonstrating robust polarisation control without manual intervention. Our results provide guidance for algorithm selection in practical QKD deployments and suggest a pathway to resilient, autonomous polarisation tracking in long-distance quantum networks. Full article