Search Results (963)

Tree mechanical stability is essential for forest management and urban safety. Although static pulling tests are currently the standard for non-destructive advanced risk assessments, these tests have significant methodological limitations. Large trees require high applied forces to produce measurable signals, which poses safety risks and causes equipment wear. Conversely, structurally compromised ancient, veteran, or dead trees (snags) may yield poor signal-to-noise ratios at low loads, leading to unstable model fits and unreliable safety factor extrapolations. Additionally, standard inclinometers often experience interference from motion-induced accelerations. This study introduces a high-resolution, low-noise measurement approach that resolves small basal inclinations and stem bending responses. This method uses laser-based tracking to monitor stem bending, torsion, and inclination under mechanical load. Experimental data were collected by combining traditional pulling tests with this novel system, as well as by conducting a pilot study that monitored tree movement during low-strength wind gusts. The proposed method enables more precise characterization of the initial load-response curve. Improving the signal-to-noise ratio at lower force levels allows for more robust safety extrapolations. When combined with a 3D LiDAR scan, the method can reveal deviations from the theoretical bending line in order to locate internal defects and variations in wood properties. These findings bridge a critical gap in tree risk assessment by improving the applicability of static testing to massive trees, as well as ecologically valuable yet structurally vulnerable snags and ancient and veteran trees. Full article

Low-noise and high-stability constant-current drivers are critical components in precision electronic and optoelectronic systems, as current fluctuations directly limit the achievable system performance. This work presents a low-noise constant-current driver based on a current-sensing architecture combined with a parameters adjustable closed-loop control scheme, enabling effective suppression of current noise over a wide frequency range. The electrical performance of the proposed driver is first characterized at the circuit level. At an output current of 300 mA, a current noise spectral density of 15.22 $nA/\sqrt{Hz}@1kHz$ is achieved, corresponding to an integrated RMS current noise of 942.88 nA over the 1 Hz–1 MHz bandwidth and a relative current fluctuation of 4.6 ppm. To further evaluate system-level performance, the driver is tested using a laser-based load, where current-induced noise is converted into measurable phase and frequency fluctuations through optical beat-note operation.The experimental results demonstrate that this design effectively suppresses current-induced noise and improves system stability. Owing to its low noise performance, this design provides a practical solution for precision electronic and optoelectronic applications requiring low-noise current power supply. 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

Ultrafast fiber lasers operating near 2 μm have emerged as a critical platform for advancing mid-infrared photonics due to their narrow pulse durations, high peak powers, and broad tunability. These sources exploit the rich energy-level structures of Tm³⁺ and Ho³⁺ doped fibers and reside within an atmospheric transmission window, enabling applications spanning nonlinear microscopy, precision micromachining, optical frequency metrology, biophotonics, and free-space optical communication. Recent progress in low-loss fiber fabrication, dispersion-engineered cavity design, and mode-locking technologies has significantly expanded the performance boundaries of 2 μm ultrafast fiber lasers. This review systematically examines the underlying pulse-formation mechanisms and categorizes state-of-the-art mode-locking approaches. Representative laser architectures are compared with respect to pulse duration, energy scalability, repetition-rate enhancement, spectral characteristics, and environmental stability. Key application pathways in high-resolution spectroscopy, biomedical diagnostics, and mid-IR supercontinuum generation are highlighted. Finally, the remaining challenges and prospective research directions are discussed to inform the development of next-generation ultrafast photonic sources in the 2 μm band. Full article

Hair loss, particularly androgenetic alopecia (AGA) and alopecia areata (AA), is a prevalent condition with widespread psychosocial impact. Recently, low-level laser therapy (LLLT) has emerged as a promising non-invasive therapeutic alternative due to its bioregulatory effects and favorable safety profile compared to conventional pharmacological treatments. In this study, we employed fluorescence lifetime imaging microscopy (FLIM) to investigate the effects of red-light irradiation on hair follicle dynamics and the cutaneous microenvironment in a C57BL/6 mouse model. A hair regeneration model was established to evaluate the efficacy of 650 nm red-light irradiation (bandwidth ± 20 nm). Then, the skin tissue was stained with hematoxylin and eosin (H&E) and followed by FLIM analysis to provide a multidimensional assessment of tissue morphology and metabolic status. Results showed that red-light irradiation significantly increased hair follicle numbers and enhanced adenosine triphosphate (ATP) levels in the skin tissue. FLIM analysis further revealed prolonged fluorescence lifetime values across different epidermal and dermal layers in the irradiated group, indicating significant alterations in the skin metabolic microenvironment. Furthermore, phasor plot analysis enabled precise differentiation between hair follicles and their surrounding skin structures, highlighting FLIM’s high sensitivity and accuracy in evaluating hair growth. In conclusion, this study has provided novel imaging-based insights into the mechanisms of LLLT-induced hair regeneration, highlighting the potential of FLIM as a powerful tool for characterizing the cutaneous microenvironment and quantitatively evaluating phototherapeutic efficacy in future translational applications. Full article

Modern dentistry increasingly relies on light-curing units (LCUs) and lasers in essential clinical procedures such as composite resin polymerization, caries treatment, and periodontal therapy. This review aims to outline the evolution of light-emitting technologies and to assess their potential biological risks, with particular emphasis on effects on the visual system, oral tissues, and microbiome. The development of curing devices is presented chronologically, from the first-generation ultraviolet (UV-A) lamps introduced in the 1970s to current light-emitting diode (LED-LCU) systems and dental lasers (e.g., Er:YAG, Nd:YAG). The progressive increase in light intensity—now exceeding 3000 mW/cm²—has shortened curing times but simultaneously raised safety concerns. Major hazards include the so-called blue-light hazard, where exposure to high-energy visible (HEV) blue light may accelerate macular degeneration, and temperature elevations in the pulp chamber, which may damage the dentin–pulp complex. Laser radiation also exerts significant microbiological effects: Er:YAG and diode lasers demonstrate bactericidal activity against biofilms and oral pathogens (e.g., P. gingivalis), although therapeutic outcomes depend on wavelength, dose, and exposure time. Suboptimal parameters may lead to microbiome disturbances, whereas low-level laser therapy (LLLT; 600–1200 nm) supports tissue regeneration and helps restore microbial balance. The individualization of irradiation parameters, combined with thorough theoretical knowledge, operator expertise, and technical understanding of LCUs and lasers, is essential for maximizing clinical benefits while minimizing health risks and preserving oral microbiome homeostasis. Full article

Pressure injuries remain highly prevalent in hospital and home settings, particularly among elderly patients, intensive care unit patients, and individuals with impaired mobility, generating significant healthcare and economic impacts. Although low-level laser therapy has been explored as an adjunctive therapy to accelerate healing, few validated protocols exist to guide its systematic application in clinical nursing practice. This methodological study aimed to develop and validate a nursing care protocol for low-level laser therapy in stage 1 pressure injuries, conducted in three stages: integrative literature review, protocol development, and content validation using the Delphi technique with specialist nurses selected via the Lattes Platform. Judges evaluated the protocol using a five-point Likert scale, and validity was assessed by the Content Validity Index (CVI) and Cronbach’s alpha, both with minimum acceptable values of 0.80. The integrative review identified four studies supporting low-level laser therapy efficacy, informing the protocol’s technical parameters. Thirty-one specialists participated in the first Delphi round and 25 in the second, achieving a Global CVI of 0.915 and Cronbach’s alpha of 0.91, with all items reaching consensus. The validated protocol demonstrated satisfactory content validity and internal consistency, supporting its clinical applicability and potential to standardize nursing practice and reinforce patient safety. Although the protocol demonstrated satisfactory methodological validity, further clinical studies are needed to assess feasibility, implementation, and effectiveness in routine nursing care. Full article

Unravelling the cellular and molecular mechanisms underlying lung injury and repair requires precise spatial context. Profiling cell-to-cell transcriptional variability and spatial orientation has become increasingly sophisticated, but validating results at the protein level still remains challenging, particularly for low-expressed proteins or small-scale samples. Here, we present a workflow established by our group for spatial protein analysis in the lung by combining two commercially available platforms: (1) laser-assisted microdissection (LMD) with (2) a capillary electrophoretic-based immunoassay (CEI). Using this workflow, we demonstrate a simple, accessible, and sensitive method for spatially capturing regions of interest to investigate small-scale samples or low-expressed proteins. This workflow provides an additional option for orthogonal validation for researchers using omics-based approaches. Furthermore, we validated transcriptome analysis results at the protein level by applying this workflow to a pre-clinical model of cigarette smoke (CS)-induced lung injury. In line with the previous findings, the results showed a significant downregulation of the endothelial cell marker in LMD-enriched alveolar regions, suggesting spatial capillary rarefaction, and activation of the mitogen-activated protein kinase (MAPK) signalling pathway in pulmonary vasculature of CS-exposed mice. Our approach overcomes traditional challenges and provides new opportunities for understanding complex disease pathomechanisms and identifying potential therapeutic targets. Full article

The use of long-distance transoceanic cables equipped with high-loss loopbacks enables distributed sensing with a resolution determined by amplifier spacing, typically in the order of 50–100 km. Microwave-frequency fiber interferometry is a promising trans-mission technique for investigating long links supported by periodic optical amplification. In this paper, we propose a variant of this technique that ensures compatibility with links containing high-loss loopbacks, thereby transforming the integrated sensing approach into a distributed one. We highlight the critical modifications required to overcome challenges associated with the detection of multiple return signals, and we conduct a proof-of-principle experiment using a two-loop configuration. We demonstrate the concept by detecting and localizing low-frequency (<10 Hz) events—whether human-generated or induced by fiber stretchers—with span-level resolution. This validates the potential of the modified microwave-frequency interferometry approach for transoceanic cable monitoring in scenarios where high-loss loopbacks are present. We also present a theoretical analysis that evaluates the limits of the technique across different frequency ranges, in comparison with optical interferometry methods based on high-spectral-purity fiber lasers. The analysis shows that for long amplifier spacings (~100 km), micro-wave-frequency fiber interferometry exhibits a signal-to-noise ratio advantage at sub-Hz frequencies (<0.1 Hz) compared to state-of-the-art optical interferometers. Full article

This paper documents the preliminary observations and applications of a Ka-band cloud radar newly installed at the Hong Kong International Airport. A special scanning strategy of the cloud radar was developed and is described in detail. The radar provides reasonable cloud base height data as compared with a co-located laser ceilometer, by identifying the lowest vertical layer with reflectivity > −30 dBZ and at least 150 m thick, filtering measurements influenced by rainfall, and removing noise with differential reflectivity thresholds. As demonstrated in a heavy rain case study, the radar provides good estimates of the cloud top height as well, consistent with the cloud liquid water content profiles from a microwave radiometer. The various applications of the cloud radar are then explored, including (1) observations of supercooled liquid water in clouds associated with a late-season tropical cyclone in the South China Sea, (2) monitoring of low visibility in light rain or mist at the airport region using reflectivity as well as Doppler velocity data, and (3) monitoring severe weather such as windshear and turbulence to be encountered by departing aircraft due to low-level jets and initiation of heavy rain, using the Doppler velocity and spectrum data. These observations demonstrated the robustness in the cloud radar in the observation of high clouds and the applicability of the radar’s Doppler velocity in plan position indicator scans under light rain situations. Potential research with the radar, such as visibility maps, turbulence intensity maps, and automatic cloud observations, is also discussed. Full article

Integrating existing tree-level information into harvester operator decision-making can significantly enhance precision forest management, particularly with respect to biodiversity preservation and climate-smart adaptation. During harvester operations, a primary challenge lies in positioning the machine with sufficient accuracy in real time to relate a priori individual-tree-level reference information to the operator. We propose a lightweight procedure using tree-to-tree matching to continuously register a real-time tree map collected from a harvester (or another mobile laser scanning system) to a precomputed reference map derived from an airborne laser scanner (ALS). We assess the robustness of the method using simulated tree maps and validate its real-world performance in experiments using a LiDAR-equipped harvester performing a thinning operation in a boreal forest. In simulations, registration was found to be robust up to a moderate tree density of approximately 1700 ha⁻¹, even when using a reference map with a lower positional accuracy and higher error rates than in our harvester experiments. Using real-world data from the thinning operation, the registration method was demonstrated to successfully mitigate meter-scale positioning drifts remaining in the LiDAR-inertial trajectory. After the continuous registration procedure, the positioning error was reduced to the level of 0.5 m, constrained by the accuracy of the prior map derived from sparse ALS data with ∼5 transmissions/m². Importantly, the registration procedure was shown to update in real time (at most 20 ms update time for stands with densities of at most 2000 ha⁻¹, after an initial computational phase. Notable features of the registration procedure are its low memory consumption, fast runtime and capacity to accurately position the harvester despite LiDAR-inertial positioning drift. While these results demonstrate the potential for real-time operation, full implementation requires the development of real-time tree detection and estimation of tree attributes. Full article

Laser acupuncture (LA) integrates principles of traditional acupuncture with photobiomodulation (PBM) and has gained increasing attention as a non-invasive modality for pain management. PBM-based integrative LA in medicine refers to the application of low-level laser irradiation to acupuncture points, combining contemporary biomedical mechanisms with holistic, system-oriented therapeutic principles. This narrative review aimed to critically assess the scientific evidence on the efficacy of LA for pain management within the framework of the Principles of Clinical Integration of Photobiomodulation (PCIPBM) in LA, summarizing frequently used laser parameters and clinical indications. LA involves special protocols in standardized acupoints, using defined parameters of wavelength, irradiation, and energy density, consistent with PBM dosing principles. Therapeutic effects are mediated through point-specific neuromodulation and photobiological mechanisms, including modulation of peripheral and central nociceptive processing, reduction in pro-inflammatory mediators, improvement of microcirculation, and mitochondrial activation via cytochrome c oxidase-dependent adenosine triphosphate (ATP) synthesis. Clinical studies report statistically and clinically significant analgesic effects, particularly in chronic musculoskeletal pain, osteoarthritis, low back and neck pain, temporomandibular disorders, neuropathic pain, and selected postoperative pain conditions, when appropriate laser parameters are applied. Reported adverse effects are minimal, and tolerability is high. LA represents a safe, non-invasive therapeutic option and patient-friendly approach with clinically relevant efficacy in pain management. When applied according to PCIPBM, including evidence-based PBM parameters, it may serve as an effective adjunct or alternative to conventional pharmacologic and interventional approaches. Further standardization and high-quality randomized controlled trials are still required. Full article

Chemotherapy- and/or radiotherapy-induced oral mucositis (CRIOM) is a common complication in patients with head and neck cancer, driven largely by excessive proinflammatory cytokine signalling and treatment-associated bacterial dysbiosis. This narrative review synthesizes current mechanistic evidence and summarizes emerging therapeutic strategies targeting these pathways. Research indicates that elevated levels of IL-1β, IL-6, TNF, iNOS, and nitric oxide amplify tissue injury and ulceration, while disruption of oral and gut microbial communities, characterized by loss of beneficial commensals and enrichment of pathogenic taxa, further exacerbates mucosal inflammation. Anti-inflammatory agents, including pentoxifylline, atorvastatin, trans-caryophyllene, azilsartan, recombinant human IL-11, and low-level laser therapy have been shown in preclinical models to reduce cytokine levels and promote mucosal healing. Similarly, microbiome-targeted approaches, such as oral microbiota transplantation and multi-strain probiotic formulations, have demonstrated potential in restoring microbial balance and attenuating CRIOM severity, with current evidence including both preclinical and clinical studies. Overall, current findings highlight cytokine toxicity and dysbiosis as synergistic drivers of CRIOM and support anti-inflammatory and microbiome-modulating strategies as promising adjunctive approaches; however, further well-designed clinical studies are required to validate their efficacy and guide clinical translation. Full article

Background: Atrophy of the alveolar ridge in the posterior maxilla often requires sinus floor elevation prior to implant placement. Photobiomodulation using low-level laser therapy (LLLT) has been suggested as a supportive approach for bone healing, although data based on histological evaluation are still limited. Methods: This study presents histological and radiological secondary outcomes of a randomized clinical trial on bone regeneration after lateral window sinus augmentation. Twenty patients were allocated according to grafting material (allogeneic or xenogeneic) and the use of adjunctive LLLT. After 6 months, bone core biopsies were obtained at the time of implant placement and processed for histological analysis. Radiological bone gain was assessed using CBCT. Results: Bone gain was achieved in all groups, allowing implant placement in every case. Mean bone gain reached 7.53 ± 3.32 mm in LLLT-treated sites and 7.02 ± 2.00 mm in controls, with no statistically significant differences. Histological analysis confirmed trabecular bone formation across all groups. Mild inflammatory cell infiltrates were observed more frequently in LLLT-treated sites (p = 0.029), although this finding was not associated with impaired tissue organization or compromised healing. Conclusions: Both allogeneic and xenogeneic grafts showed good biocompatibility and supported effective bone regeneration after sinus augmentation. The addition of photobiomodulation did not demonstrate statistically significant clinical or radiological benefits within this exploratory cohort, but it may be associated with subtle differences in tissue remodeling. Full article

According to the International Diabetes Federation, 589 million adults worldwide live with diabetes in 2025 (approximately 1 in 9 adults). The development of convenient noninvasive blood glucose monitoring systems has been a central focus in diabetes management. Optical spectroscopy has advanced significantly among all noninvasive glucose detection techniques. A photoacoustic system has been developed using a single-wavelength near-infrared laser, operating at 1625 nm, where glucose exhibits an overtone absorption band with relatively low water interference. The noninvasive system has been evaluated using artificial skin phantoms, with different glucose concentrations, covering both normoglycemic and hyperglycemic blood glucose levels. The detection sensitivity of the developed system has been enhanced to ±15 mg/dL across the entire clinically relevant glucose range. K-nearest neighbours and wide neural network machine learning models were developed for noninvasive glucose classification. The models achieved prediction accuracies of 80.0% and 81.5%, respectively, with 100% of the predicted data located within zones A and B of Clarke’s error grid analysis. These findings satisfy the regulatory requirements for glucose monitors established by Health Canada and the U.S. Food and Drug Administration. Full article