Search Results (1,336)

In this paper, we propose a lightweight authentication and identification protocol based on different phosphorescent Strontium aluminate color labels. The excitation sources are pulsed UV LEDs emitting at 365 nm and 385 nm, causing different RGB-dependent time responses of the label that are measured using a smartphone recording at 30 FPS. The rise and decay time responses as measured by the red (R), green (G) and blue (B) pixels were separately analyzed and were found to follow a power law with individual parameters depending on the excitation wavelength, pulse duration and duty cycle, which serve as security features and are suitable for authentication purposes in IoT applications. Our solution uses simple cryptographic functions such as HMAC and XOR. We performed a security analysis of our protocol to prove its resistance to known attack vectors. The proposed scheme has minimal computation and communication costs and can be deployed on resource-constrained Internet of Things devices. Full article

In this study, four types of anti-ultraviolet aging agents—layered double hydroxides (LDHs), organic montmorillonite (OMMT), titanium dioxide (TiO₂), and ultraviolet absorber (UV326)—were employed to modify asphalt. The modified asphalt samples underwent Rolling Thin Film Oven Test (RTFOT) and xenon-lamp aging treatments, and we examined the evolution of their physical properties, rheological performance, and chemical composition. A principal component analysis (PCA) model built on representativeness, discriminative power, and non-redundancy reduced the multidimensional data to two principal components, which together captured 87.540% of the total variance. The dynamic principal component trajectories, plotted from the reduced-dimension data for the unaged–short-term-aged–xenon-lamp-aged process, revealed that anti-aging agents sharing the same protection mechanism led to comparable rates of high- and low-temperature performance deterioration during xenon-lamp aging, whereas agents with different mechanisms resulted in distinctly different patterns of performance deterioration. In the critical xenon-lamp aging stage, the neat asphalt exhibited a trajectory vector change of ΔPC1 = 0.92 and ΔPC2 = 1.25, corresponding to an angle of 54°, reflecting a low-temperature degradation. By contrast, the physical shielding agents LDHs and OMMT produced much steeper trajectories with angles of approximately −80°, where ΔPC2 values rose to as high as 3.67 and 2.19 respectively despite modest reductions in overall aging. The reflective agent TiO₂ showed a more moderate angle of 84°, with ΔPC1 and ΔPC2 values of 0.16 and 1.45, indicating a slight retardation of high-temperature performance loss. Notably, the UV absorber UV326 maintained the same trajectory angle of 56° as the neat asphalt but with reduced magnitudes of ΔPC1 = 0.63 and ΔPC2 = 0.94, suggesting a balanced delay in aging without altering its relative progression. This study proposes a novel analytical framework for mechanism-based clustering analysis and the precise selection of anti-aging agents for asphalt. Full article

Ribavirin (RBV) and chloroquine phosphate (CQP) are two typical pharmaceutical contaminants with distinct hydrophilic (RBV) and hydrophobic (CQP) properties. This polarity contrast led to markedly different degradation behaviors. Interestingly, hydrophobic CQP consistently degraded faster and with lower E_EO than hydrophilic RBV across all combined systems, highlighting pollutant polarity as a key determinant. This study systematically compared their degradation by three UV-based advanced oxidation processes (UV/AOPs): UV/H₂O₂, UV/PMS, and UV/KMnO₄. Degradation kinetics, electrical energy per order (E_EO), radical pathways, and water matrix effects were investigated. Sole UV or sole oxidant achieved negligible removal (<7.2%). All UV/AOPs greatly enhanced degradation in a dose-dependent manner. At equal molar oxidant concentration (0.2 mM), the efficiency order was UV/PMS > UV/H₂O₂ ≫ UV/KMnO₄, with the gap widening at higher dosages. UV/H₂O₂ exhibited the best overall performance, with remarkably low E_EO values (0.59 kWh/m³ for RBV and 0.46 kWh/m³ for CQP at 0.2 mM), whereas UV/PMS showed faster kinetics but much higher energy consumption (e.g., 28.67 kWh/m³ for RBV and 28.60 kWh/m³ for CQP at 0.4 mM) and secondary pollution risks. UV/KMnO₄ had low energy but poor degradation. Radical quenching experiments revealed that in UV/H₂O₂, hydroxyl radicals (•OH) predominantly drove degradation regardless of pollutant polarity. In UV/PMS, •OH primarily drove RBV degradation, while CQP removal involved the combined action of •OH, sulfate radicals (SO₄•⁻), and other reactive species. For the optimal UV/H₂O₂ process, acidic pH (5.0) favored degradation; Cl⁻ slightly promoted CQP removal but inhibited RBV, whereas SO₄²⁻, CO₃²⁻, and HCO₃⁻ suppressed both pollutants. Collectively, UV/H₂O₂ is recommended as the most energy-efficient and robust UV/AOP for treating both hydrophilic and hydrophobic pharmaceuticals, with the additional insight that pollutant polarity governs both degradation kinetics and radical mechanisms. Full article

Advanced oxidation processes using titanium dioxide (TiO₂) have emerged as a promising approach for the photocatalytic degradation of contaminants in water and have drawn extensive research attention despite limited translation of this technology to large-scale applications. The limitations of this technology include immobilization of the photocatalyst, scalability, and compatibility with available light sources. Using 3D printing to immobilize TiO₂-based photocatalysts, we systematically evaluated the rates of photocatalytic degradation of methylene blue (MB) with different light-emitting diode (LED) ultraviolet (UV) light sources and modified TiO₂-based photocatalytic materials. The UV LED lights successfully decreased the MB concentrations with half-lives ranging from 0.9 to 2.4 h, with relative photocatalytic performance of UVA-365 > UVA-395 > UVC-280. The photocatalytic degradation rates under UV LEDs were slower (0.9–2.4 h) than those achieved using a low-pressure mercury UV-C lamp (0.5 h) and were also lower than those observed under solar simulated lights (0.6 h). The TiO₂ modified by an alkyl silane entity and embedded in a polylactic acid polymeric system with 3D printing exhibited the fastest methylene blue (MB) removal among the three TiO₂-based structures evaluated, with a half-life of 0.6 h compared to the 1.6–17.7 h for the other materials. This research demonstrated that 3D printing enables the integration of functionalized photocatalysts, and, when paired with low-cost, low-energy UV LED lights, can achieve environmentally relevant rates of performance. Ultimately, these findings represent an incremental step toward improving the performance of 3D-printed photocatalytic materials. Full article

Electrospinning (ES) can produce nonwoven fibrous mats with high surface area and interconnected porosity, making them attractive for biomedical and functional material applications. However, conventional ES often relies on volatile organic solvents, raising safety, environmental, and translational concerns. Fully aqueous (“green”) ES offers an appealing alternative, although many water-soluble polymers remain difficult to spin and may show limited stability under hydrated conditions. In this study, two fully aqueous binary systems, poly(vinylpyrrolidone)–sodium alginate (PVP–SA) and poly(vinylpyrrolidone)–riboflavin (PVP–RF), were investigated to decouple the roles of sodium alginate (SA) and riboflavin (RF) on solution behaviour, fibre formation, morphology, dry-state mechanical properties, and surface chemistry. Aqueous PVP solutions (20% w/v; molecular weight 1.3 MDa) were blended with SA (1–5 wt% relative to PVP) or RF (1–10 wt% relative to PVP). Electrical conductivity and rheological properties were evaluated prior to ES under controlled conditions, with simultaneous ultraviolet (UV) exposure at 344 nm during fibre collection. RF did not significantly alter conductivity (~0.74–0.75 µS·cm⁻¹), whereas SA increased conductivity up to 2.75 ± 0.03 µS·cm⁻¹ at 5 wt%. All formulations exhibited shear-thinning behaviour, while 10 wt% RF increased the zero-shear viscosity relative to neat PVP. Morphological analysis showed that low SA contents produced uniform fibres, whereas higher SA levels (4–5 wt%) led to bead defects and reduced fibre diameter (down to 85 ± 25 nm). Dry-state mechanical performance decreased with increasing SA content, while 10 wt% RF improved tensile strength and toughness, reaching an ultimate tensile strength of 5.21 ± 0.15 MPa and toughness of 40.51 ± 1.53 MJ·m⁻³. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated subtle UV-driven redistribution of surface chemical states, consistent with mild photo-oxidative microstructural modification rather than extensive covalent network formation. Because the UV irradiance was not directly measured and wet-state stability was not assessed, the UV-related findings are interpreted as preliminary chemical evidence rather than confirmation of stabilized fibre mats. Overall, this work establishes a solvent-free aqueous ES platform in which ionic and photoactive additives can be used to tailor fibre morphology, dry-state mechanical behaviour, and surface characteristics without toxic reagents. Full article

Fungal iterative non-reducing polyketide synthases (NR-PKS) contain a unique product template (PT) domain for aromatic cyclization. Among them, some NR-PKSs, such as the sorbicillin NR-PKS (SorB), have an apparently inactive PT. It is unknown what role such PT plays in NR-PKS programming. In this study, the PT domain of SorB was first dissected and engineered. Removal of the PT domain from SorB did not change the product profile, but the yield decreased. Meanwhile, a significantly lower transcriptional level of the ketoacyl synthase (KS) domain was observed in the knockout mutant (UvSorB∆PT). Phylogenetic tree analysis and multiple sequence alignments revealed this PT belongs to group I (C2–C7, monocyclic ring), and mutations were found at catalytic dyad sites when compared with functional fungal PTs. However, mutating these residues back to the conserved ones did not give rise to products corresponding to a functional PT, but rendered the NR-PKS unproductive. Likewise, removal of the C-methyltransferase (CMT) domain from SorB destroyed the polyketide production. Furthermore, in an attempt to alter the methylation pattern, mutations of the key substrate-binding sites of the CMT domain were made. Site-directed mutations of the C-MT led to cessation of the polyketide production. This reveals CMT is vulnerable to engineering in a collaborating NR-PKS (SorB). These results provide additional insights for catalytic reprogramming in fungal NR-PKS. Full article

Filamentous cyanobacteria in the genus Nostoc show color diversity in their natural habitats, ranging from bright green to yellow–green to brown. In contrast, laboratory cultures are typically uniform in color, which is attributed to differences in light spectrum and intensity. Nostoc contains several bioactive pigments, including phycocyanin, phycoerythrin, allophycocyanin, carotenoids, and scytonemin, which are involved in light harvesting, photoprotection, and UV screening. Variations in light spectrum and intensity regulate the abundance and organization of these pigments, altering colony coloration and affecting photosynthetic performance, stress tolerance, and growth. These changes impact biomass and pigment productivity. In this review, we synthesize recent findings on how light regulates pigment biosynthesis in Nostoc and examine how wavelength, irradiance, and photoperiod influence pigment composition, biomass accumulation, and pigment productivity, considering both underlying photoregulatory mechanisms and cultivation design. This perspective connects photophysiological insights with practical strategies, including staged lighting and LED-based systems, to improve pigment yield while maintaining biomass production. These insights support the future application of Nostoc pigments in food, cosmetic, and pharmaceutical sectors. Full article

Fluorescence emission-excitation matrices for cow milk samples with different fat contents in the range of 0.05–10% and a constant protein content of 3%, as well as for butter and extracted milk components such as casein and lactose, have been measured using a spectrofluorometer. The influence of the increased fat content on the shape of the fluorescence spectra of milk has been studied. In addition, fluorescence spectra measured for serial dilutions of high-fat milk with water and skim milk, along with aqueous dilutions of skim milk, have shown that the fluorescence diagnostics of fat and protein content in milk can be implemented using excitation at only two wavelengths: 280 and 320 nm. The optimal spectral ranges proposed for detecting the content of milk components via fluorescence measurements can be useful when designing UV LED-based fluorescence analyzers of milk composition. Full article

The oral cavity harbors a complex microbial community where pathogens implicated in dental caries and periodontitis can heavily colonize toothbrushes, transforming them into persistent sources of contamination that threaten both oral and systemic health. Consequently, this study evaluated the bactericidal efficacy of 275 nm ultraviolet light-emitting diode (UV-LED) irradiation against common oral bacteria in vitro and its practical utility for extraoral toothbrush sanitization. Suspensions of Streptococcus mutans, Streptococcus sanguinis, Porphyromonas gingivalis, and Fusobacterium nucleatum were irradiated for 3 min, 6 min, and 9 min. Bacterial growth and bactericidal effects were measured using growth curve and colony-forming unit assays, respectively. LIVE/DEAD staining and crystal violet staining were used to evaluate the bacterial viability and multispecies biofilm formation after irradiation. Additionally, the sanitization effects of a 275 nm UVC-based portable device on used toothbrushes were investigated. Direct UVC irradiation at 275 nm exhibited strong bactericidal effects against common oral bacteria in vitro. UVC irradiation also showed great sanitization effects on used toothbrushes. In summary, the vulnerability of common oral bacteria to 275 nm UVC, combined with its sanitizing efficacy on used toothbrushes, establishes a solid basis for extraoral sanitization, offering a reliable strategy to mitigate the risk of oral pathogen transmission from contaminated toothbrushes. Full article

Low-cost and portable analytical devices are increasingly relevant for decentralized measurements, in situ monitoring, and educational applications. This study presents the design, construction, and validation of a low-cost, portable colorimeter for the indirect determination of ethanol in aqueous solutions via dichromate oxidation. Built with accessible components, including an Arduino microcontroller, an RGB LED, and a light-dependent resistor (LDR) photodetector, the device provides a simple open-hardware platform for visible-range colorimetric measurements without the need for optical filters. Ethanol concentration is determined through oxidation in an acidic medium, generating an optical response proportional to the analyte concentration. Data processing is performed using open-source Python scripts combined with Gaussian fitting for signal extraction and calibration. The main novelty of the system lies in integrating simplified optical components, open-hardware architecture, and computational signal processing to obtain reliable analytical responses in a portable, accessible format. The device’s performance was compared with a commercial UV–Vis spectrophotometer, showing linear behavior over 0.5–1.5% (v/v) ethanol (R² = 0.99) and relative errors below 11% for beverage samples. These results demonstrate that the proposed system is a reliable and cost-effective alternative for rapid ethanol analysis in relatively simple alcoholic matrices. Full article

The present study evaluates the optical and colorimetric properties of Polylactic acid (PLA)-based films blended with Poly(3-hydroxybutyrate) (PHB) and Poly(butylene succinate) (PBS) and impregnated with mango leaf extract (MLE) using supercritical solvent impregnation (SSI) under different operating conditions (pressure: 10–30 MPa; temperature: 35–55 °C). Additionally, the relationship between impregnation load (IL) and color properties, as well as the release kinetics of the impregnated compounds, was investigated. The incorporation of PHB and PBS into the PLA matrix prior to impregnation led to a slight increase in the b* parameter (from 1.64 to 2.61), indicating a tendency toward yellowish tones. After SSI, all films exhibited noticeable color changes, with a shift toward yellowish-green hues and a decrease in lightness, regardless of processing conditions. Statistical analysis confirmed that polymer composition and its interaction with pressure and temperature significantly affected color properties (p-value < 0.001). The addition of PHB and PBS, as well as MLE impregnation, enhanced UV-barrier properties, while also modifying film transparency and opacity. In particular, PLA-PBS films showed higher opacity (more than 20 times) and lower transparency compared to neat PLA. These films also exhibited the highest IL values (2.41–4.75 mg MLE/100 mg polymer). Multivariate regression analysis demonstrated a strong correlation between CIELAB parameters (L*, a*, and b*) and IL (R² > 85%, p-value < 0.001). Release studies in a food simulant showed partial release profiles, well described by Peleg’s model (R² > 0.90). Furthermore, Korsmeyer–Peppas model fitting yielded diffusion exponents (n < 0.5), indicating quasi-Fickian diffusion mechanisms governing the release process. Full article

Germicidal UV (GUV) technology, which utilizes light in the UV-C portion of the electromagnetic spectrum, has become a viable alternative to traditional chemical disinfectants to sanitize surfaces in the built environment. However, the degradation of polymers that have been exposed to UV-C light is a concern due to the potential change in structural integrity and visual appearance. The resistance to UV-C degradation is often tabulated in relative qualitative terms, making it rather difficult for designers to understand the implications of the choice of a material of construction. This study was initiated to develop a systematic, standardized method of exposing polymeric materials to UV-C light to ensure that the subsequent property measurements can be compared quantitatively. The exposure method is based on an apparatus that can be readily duplicated using commercially available materials and equipment. To demonstrate the proposed exposure framework, samples of six formulated polymer resins were exposed to three UV-C light sources with different peak wavelengths (KrCl excimer lamp [222 nm], low-pressure mercury lamp [254 nm], and LED lamp [280 nm]). Exposures were conducted at five independent laboratories, and subsequent property testing was performed at multiple facilities using established materials-characterization methods. This coordinated approach enables comparative evaluation of material responses across UV-C source types, wavelengths, and dose levels, providing a practical foundation for developing standardized exposure methodologies and informing future formulation development efforts. Post-exposure testing included quantifying changes in optical, mechanical, and physical properties, including color, gloss, reflectivity, spectral transmittance (haze), flammability, tensile strength, and elastic modulus. These measurements were conducted using established laboratory methods commonly employed throughout the polymer and materials industries. Together, these results provide a comparative dataset illustrating how polymer properties respond to coordinated UV-C exposure conditions, supporting the development of standardized approaches for evaluating material durability in germicidal UV applications. Full article

In this study, a UV surface modification method was applied to polyamide (PA) fibers, and its effect on certain fresh and hardened properties of fiber-reinforced cementitious systems was investigated. Within the scope of the study, the individual and interactive effects of fiber volume fraction and UV surface modification time were optimized using the Response Surface Methodology (RSM) based on Central Composite Design (CCD). The optimal performance parameters with CCD were identified at 0.50% fiber content and 18 min of UV exposure. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were utilized to analyze the fibers and examine the impacts of surface modification. Three different sample groups were prepared to test the effect of UV treatment after optimization: a control cement mortar without fibers, a polyamide fiber-reinforced mortar without UV treatment, and a polyamide fiber-reinforced mortar with UV surface modification. The tensile, flexural, and compressive strength values of the specimens were determined. The results indicated that UV surface modification led to changes in fiber roughness and an increase in oxygen-containing functional groups on the fiber surface. The data revealed that the mechanical performance of fiber-reinforced composites subjected to surface modification improved (with a 27.4% increase in flexural strength and an 11.3% increase in compressive strength compared to the control samples). The findings indicate that UV surface modification improves the fiber–matrix bond in cement-based systems reinforced with polyamide fibers. UV surface modification emerges as an effective and environmentally friendly method for enhancing the performance properties of fiber-reinforced cement-based systems. Full article

UV-curable polymer composites are attractive for fabricating complex components by digital light processing (DLP), but improving thermal transport while preserving printability remains challenging at high filler loadings. In this work, solvent-free UV-curable formulations filled with hexagonal boron nitride (h-BN) and h-BN/graphite hybrids were developed for DLP 3D printing using commercially available equipment. The effects of filler composition on viscosity, printability, microstructure, through-thickness thermal conductivity, electrical conductivity, and tensile behavior were investigated. Viscosity increased markedly with filler loading, yet reliable DLP printing was achieved up to 40 wt% h-BN through composition-dependent adjustment of build parameters. Thermal analysis supported negligible macroscopic sedimentation during printing, while optical and FE-SEM observations revealed generally uniform platelet dispersion, visible 50 μm layer stratification, and limited phase segregation in the hybrid systems. The through-thickness thermal conductivity increased from ~0.25 W/mK for the neat resin to ~1.95 W/mK at 40 wt% h-BN. At a fixed 20 wt% h-BN, graphite addition led to a smaller increase in thermal conductivity, up to ~1.16 W/mK, while increasing electrical conductivity and reducing mechanical performance. A phenomenological percolation-type model captured the thermal-conductivity trend of the h-BN series. Overall, h-BN-rich formulations provided the most effective route to enhance thermal conductivity while preserving electrical insulation. Full article

Marine coastal ecosystems provide a variety of habitats for biodiversity. However, they are affected by bycatch, the unintentional capture of non-target species during fishing operations such as gillnets, trammel nets, and longlines. To mitigate bycatch, modifications such as LED and UV lights in gillnets and trammel nets and C-type (circle) hooks in longlines have been studied worldwide. Yet, studies remain limited in Türkiye. This study aimed to evaluate the effectiveness of these gear modifications in small-scale fisheries along the Aegean coast of Türkiye. Paired trials were conducted to compare standard (control) and modified (LED, UV, or C-type hook) fishing gears. Trials resulted in four sea turtles caught in LED and UV nets with no significance. Other vulnerable species caught in UV trammel nets showed significance. Overall, modified gears showed a significant reduction in commercial species catch, while increasing non-target species captures. These preliminary findings contradict much of the literature, which generally reports these modifications as effective bycatch reduction tools. The results emphasize the necessity of developing regionally adapted gear modifications and conducting more extensive experiments to validate their performance. The implementation of locally optimized bycatch mitigation tools may help achieve a balance between marine conservation and the socioeconomic sustainability of small-scale fisheries. Full article