Search Results (1,815)

We systematically investigated the parent anthracene (abbreviated as en-1, C₁₄H₁₀) and three N,N′-disubstituted derivatives: the 1,5-diethylanthracene (en-2, C₁₈H₁₈), the 1,5-divinylanthracene (en-3, C₁₈H₁₄), and the 1,5-diphenylanthracene (en-4, C₂₆H₁₈), using a rigorous density functional theory (DFT)/time-dependent density functional theory (TD-DFT) approach. Following full geometric optimization and frequency validation (no imaginary frequencies), frontier molecular orbital analysis revealed an inverse correlation between conjugation extent and the HOMO-LUMO energy gap. Electrostatic potential (ESP) analysis further indicated a progressive increase in surface potential variance upon substitution, reflecting charge redistribution. TD-DFT calculations yielded vertical excitation wavelengths of 438 nm, 441 nm, 464 nm, and 496 nm for en-1, en-2, en-3, and en-4, respectively. Complementary color theory predicts visual colors of yellow, yellow, red, and orange for these compounds based on their absorption characteristics. This work establishes a closed-loop “computation-spectra-color” model for anthracene-based dyes, providing a transferable design paradigm for novel functional pigments with high molar extinction coefficients. Full article

Optical transmission gratings with quasi-sinusoidal surface-relief profiles were inscribed in IOG and Pyrex glasses and in Bi₁₂GeO₂₀, Er: LiNbO_3, and Er: Fe: LiNbO₃ crystals by microbeams of carbon, nitrogen, and oxygen ions at ion energies of 5, 6, and 10.5 MeV. Grating constants were 4, 8, and 16 μm. Amplitudes of the surface-relief gratings were in the 10–2000 nm range. The diffraction efficiency of the gratings was measured at a wavelength of 640 nm. Maximum diffraction efficiencies were close to the theoretical maximum of 33% for thin gratings. Grating profiles were measured by optical microscopic profilometry. Measurement of the diffraction efficiencies at higher orders and Fourier analysis of the grating profiles revealed the dependence of the residual nonlinearity of the grating profiles on the implanted ion fluence. The ion microbeam-written gratings can be used as light coupling elements in integrated optics for sensors and telecommunication. Full article

The present study investigates the luminescent behaviour of sol–gel derived Y₂SiO₅ powders doped with Eu³⁺ ions, subjected to spark plasma sintering. The sintering process induces the partial reduction of Eu³⁺ to Eu²⁺, and the phenomenon is strongly dependent on the holding time within the SPS chamber. The luminescent properties are tunable via the initial Eu concentration, holding time and excitation wavelength, resulting in a wide range of emission colours from red (Eu³⁺) at 220 nm excitation to blue (Eu²⁺) at 365 nm, and mixed colours at 257 nm. Moreover, the Eu³⁺/Eu²⁺ redox process is reversible. Overall, the results demonstrate that SPS conditions can be exploited to modulate the valence state of luminescent centres, which is reversible by oxidation under ambient conditions, enabling controlled modulation of the optical properties. Full article

Diabetes has become a global health challenge, driving the demand for innovative, non-invasive diagnostic technologies to improve glucose monitoring. Urinary glucose concentration, a reliable indicator of metabolic changes, provides a practical alternative for frequent monitoring without the discomfort of invasive methods. In this simulation-based study, we propose a novel asymmetric photonic structure that integrates Tamm plasmon polariton (TPP) modes and a cavity mode for high-precision refractive index sensing, with a conceptual focus on the potential detection of urinary glucose. The structure supports three distinct resonance modes, each with unique field localization. Both the TPP modes, confined at the metallic–dielectric interfaces, serve as stable references whose wavelengths are unaffected by refractive-index variations in human urine, whereas the cavity mode exhibits a redshift with increasing refractive index, enabling high responsiveness to analyte changes. The evaluation of sensing performance employs a sensitivity formulation that leverages either TPP mode as a reference and the cavity mode as a probe, thereby achieving dependable measurement and spectral stability. The optimized design achieves a sensitivity of 693 nm·RIU⁻¹ and a maximum figure of merit of 935 RIU⁻¹, indicating high detection resolution and spectral sharpness. The device allows both reflectance and transmittance measurements to ensure enhanced versatility. Moreover, the coupling between TPP and cavity modes demonstrates hybrid resonance, empowering applications such as polarization-sensitive or angle-dependent filtering. The figure of merit is analyzed further, considering resonance wavelength shifts and spectral sharpness, thus manifesting the structure’s robustness. Although this study does not provide experimental data such as calibration curves, recovery rates, or specificity validation, the proposed structure offers a promising conceptual framework for refractive index-based biosensing in human urine. The findings position the structure as a versatile platform for advanced photonic systems, offering precision, tunability, and multifunctionality beyond the demonstrated optical sensing capabilities. Full article

This study investigates the magneto-optical properties of a ferrofluid using an accessible Ferrocell device. Our findings demonstrate that the ferrofluid’s behavior is critically dependent on its concentration. At high concentrations, the medium is optically dense, with inter-particle scattering and absorption dominating, which prevents the formation of clear light patterns. However, with intermediate dilution, the system enters a “pattern formation zone” where the magnetic field effectively aligns the nanoparticles, creating complex, visible light patterns like horocycles. The appearance of these patterns provides evidence of field-induced ordering and structural coloration. The colors observed are not due to pigments, but result from the interaction of light with the periodic structures formed by the aligned nanoparticles. Our analysis, supported by the Mueller matrix framework, confirms that the ferrofluid acts as a retarder. The birefringence induced by the magnetic field varies across the film, leading to a chromatic dispersion that selectively suppresses certain wavelengths. This process explains how a specific color, such as blue, can be blocked at one location while others pass through, creating structural colors observed in the patterns. Full article

This study investigates the effect of temperature on the performance of the single-walled carbon nanotube (SWCNT) film/Si photodetector. Specifically, the photocurrent across a SWCNT/Si heterojunction when illuminated with light of 632.8 nm wavelength of different powers was studied in detail in a wide temperature range, from 20 to 300 K. The objective was to determine the parameters of the heterojunction, which is inherently inhomogeneous, and to identify the main ones that determine the optoelectronic figures of merit of a photodetector based on it. The barrier height and its temperature dependence were determined within the framework of the theory of thermionic emission, taking into account the non-uniform distribution of the barrier height over the heterojunction area. The parameters of the heterojunction and SWCNT/Si interface and their temperature dependences were calculated based on the known temperature dependences of the concentration of charge carriers and ionized impurities in Si using the Poisson equation based on Fermi–Dirac statistics. The obtained results indicate the importance of interplay between the effects of reducing the barrier height and the processes of decreasing the separation efficiency of nonequilibrium charge carriers and increasing the rate of their recombination. Full article

Jack-up offshore platforms, supported by truss legs, are integral to the development of marine energy resources, including oil, gas, and offshore wind. Due to the structural complexity of truss legs, accurately quantifying wave loads is crucial for ensuring the safety and efficiency of energy extraction operations. In this work, a numerical wave tank approach combined with theoretical analysis is employed comprehensively to investigate wave loads on truss legs, with a particular emphasis on the effects of component forces and inflow angle. The results demonstrate that wave loads are not solely dependent on member dimensions. The influencing factors affecting component forces include water depth and phase differences between structural units, which amplify the contribution of the component forces of members near the free surface and without phase difference to the total force. Furthermore, the total force varies periodically with the inflow angle in cycles of 60°. Notably, the influence of inflow angle on the total force becomes negligible when the wavelength substantially exceeds the pile spacing. This framework fundamentally provides a theoretical basis for the structural optimization of Jack-up offshore platform support systems, thereby enhancing the safety and reliability of energy infrastructure. Full article

Light is a powerful environmental factor with proven effects on human cognitive activity. This study investigated the effects of two types of light—LED with an enhanced long-wavelength spectrum and classic fluorescent—on concentration and attention of undergraduate students. Concentration was assessed through EEG, while attention was evaluated using d2 and TP psychometric tests. The experiment was carried out in a classroom equipped with both lighting systems, with each participant completing two testing sessions under different light conditions, separated by at least seven days to allow for washout. Results showed that during the first administration, LED lighting supported better performance across both EEG and psychometric measures compared to fluorescent light, suggesting enhanced concentration and attention. By the second administration, these differences were less evident, likely due to learning and task familiarization effects. Nonparametric ANOVA-type analyses further indicated that the effect of lighting on performance depended not only on the light type but also on the order of exposure, with students who switched from fluorescent to LED showing improvement, whereas the reverse sequence was associated with a decline. Overall, the findings suggest that LED lighting enriched in warm tones may positively influence attention and concentration, though results should be viewed as exploratory due to the small sample size. Full article

Synthetic Aperture Radar (SAR) is one of the few instruments capable of providing high-resolution global two-dimensional (2D) measurements of ocean waves. Since 2014 and then 2016, the Sentinel-1A/B satellites, whenever operating in a specific wave mode (WV), have been providing ocean swell spectrum data as Level-2 (L2) OCeaN products (OCN), derived through a quasi-linear inversion process. This WV acquires small SAR images of 20 × 20 km footprints alternating between two sub-beams, WV1 and WV2, with incidence angles of approximately 23° and 36°, respectively, to capture ocean surface dynamics. The SAR imaging process is influenced by various modulations, including hydrodynamic, tilt, and velocity bunching. While hydrodynamic and tilt modulations can be approximated as linear processes, velocity bunching introduces significant distortion due to the satellite’s relative motion with respect to the ocean surface and leads to constructive but also destructive effects on the wave imaging process. Due to the associated azimuth cut-off, the quasi-linear inversion primarily detects ocean swells with, on average, wavelengths longer than 200 m in the SAR azimuth direction, limiting the resolution of smaller-scale wave features in azimuth but reaching 10 m resolution along range. The 2D spectral partitioning technique used in the Sentinel-1 WV OCN product separates different swell systems, known as partitions, based on their frequency, directional, and spectral characteristics. The accuracy of these partitions can be affected by several factors, including non-linear effects, large-scale surface features, and the relative direction of the swell peak to the satellite’s flight path. To address these challenges, this study proposes a novel quality control framework using a machine learning (ML) approach to develop a quality flag (QF) parameter associated with each swell partition provided in the OCN products. By pairing collocated data from Sentinel-1 (S1) and WaveWatch III (WW3) partitions, the QF parameter assigns each SAR-derived swell partition one of five quality levels: “very good,” “good,” “medium,” “low,” or “poor”. This ML-based method enhances the accuracy of wave partitions, especially in cases where non-linear effects or large-scale oceanic features distort the data. The proposed algorithm provides a robust tool for filtering out problematic partitions, improving the overall quality of ocean wave measurements obtained from SAR. Moreover, the variability in the accuracy of swell partitions, depending on the swell direction relative to the satellite’s flight heading, is effectively addressed, enabling more reliable data for oceanographic studies. This work contributes to a better understanding of ocean swell dynamics derived from SAR observations and supports the numerical swell modeling community by aiding in the refinement of models and their integration into operational systems, thereby advancing both theoretical and practical aspects of ocean wave forecasting. Full article

Multifunctional phosphors that integrate optical temperature measurement and counterfeit detection capabilities have garnered considerable interest owing to their diverse application potential. In this study, novel CaLaLiTeO₆:Mn⁴⁺/Er³⁺ phosphors were prepared via the high-temperature solid-phase method. The phase structure and morphology characterization confirmed the successful synthesis of CaLaLiTeO₆ material with effective doping of Mn⁴⁺ and Er³⁺ into the host lattice. Upon excitation at 379 nm, the CaLaLiTeO₆:Mn⁴⁺/Er³⁺ material exhibits far-red emission at 716 nm (Mn⁴⁺:²E_g → ⁴A_2g) and green emission at 525/548 nm (Er³⁺:²H_11/2/⁴S_3/2 → ⁴I_15/2). The emission peak intensities of Er³⁺ and Mn⁴⁺ ions in the CaLaLiTeO₆:0.015Mn⁴⁺/0.01Er³⁺ sample displayed distinct variations with temperature under different excitation wavelengths (325 nm, 379 nm, and 980 nm). Subsequently, a dual-mode optical temperature sensing system was developed based on the fluorescence intensity ratio and the dual excitation single-band ratiometric method, which achieved a maxed relative sensitivity of 1.12% K⁻¹ at 343 K. Moreover, the excitation-dependent luminescence color changes of CaLaLiTeO₆:Mn⁴⁺/Er³⁺ make it particularly suitable for anti-counterfeiting applications. The present study underscores the dual-functional capabilities in sophisticated non-contact optical temperature measurement and anti-counterfeiting applications. Full article

Electrons localized by water molecules are known as hydrated electrons. The composition of the aqueous environment determines their state and behavior. In this experimental and theoretical work, hydrated electrons were formed in aqueous solutions upon high-energy electron impact, and the dependence of their characteristics on the presence of nanobubbles generated during vibrational treatment was investigated. To explain the results, quantum chemical simulations were carried out, and diverse possible kinetic schemes were considered. Absorbance of deionized water and NaCl aqueous solution was measured at a wavelength of 600 nm, which falls in the range typical of hydrated electrons. The principal differences in the spectral responses of the samples were discovered depending on whether they were preliminarily subjected to repeated vigorous shaking or not. Vigorous shaking caused a noticeable increase in both the integral and maximum absorbance, and the absorbance decay was significantly slower. The effects observed in the vibrationally treated aqueous samples were found to be explained only in the framework of a kinetic scheme that assumes the repeated solvation of electrons, which are transferred from a localized to a delocalized (free) state upon the energy absorption. This repeated solvation is possible only when the secondary electrons are localized on the inner surfaces of the boundary hydration shells of nanobubbles, which are formed in the process of shaking. Thus, nanobubbles substantially change the apparent gross lifetime and properties of hydrated electrons, and these changes, in turn, can indicate the presence of nanobubbles in water and aqueous solutions. Full article

Heat spots caused by standing waves in an inspected object can pose practical challenges in nondestructive inspection using ultrasonic excitation thermography. This study investigates the dominant wave mode excited during inspection and explores methods to suppress heat generation caused by standing waves. Comparison of experimental results and theoretical calculations showed that the waves propagating in plate objects were dominated by the A₀ mode Lamb waves. As a result, the distribution of the heat spots caused by standing waves varied depending on the frequency of the excitation wave and plate thickness. Based on these findings, we propose a suppression method that eliminates unwanted heat spots by superimposing two Lamb waves with a phase difference that is a natural multiple of half the wavelength. Full article

This study investigates the effect of paint-related properties on the accuracy of delamination detection in lined oil paintings using pulsed phase thermography (PPT). Mock-ups of lined oil paintings were examined by PPT under both normal and angled illumination to induce apparently localized heating. Spectral characteristics in the excitation and detection wavelength ranges were analyzed and related to phase contrast variations in the resulting images. While paint-dependent energy absorption under localized heating may blur phase contrast and lead to misidentification of delamination, emissivity properties appear to contribute to stabilizing phase signals. These findings underscore the importance of accounting for paint properties in conservation diagnostics. Full article

Bi-phasic (with a local minimum) response of fluorescence to scattering when probed by a single fiber (SF) was first observed in 2003. Subsequent experiments and Monte Carlo studies have shown the bi-phasic turning of SF fluorescence to occur at a dimensionless reduced scattering of ~1 and vary with absorption. The bi-phase of SF fluorescence received semi-empirical explanations; however, better understandings of the bi-phase and its dependence on absorption are necessary. This work demonstrates a quasi-analytical projection of a bi-phasic pattern comparable to that of SF fluorescence via photon-transport analyses of fluorescence in a center-illuminated-area-detection (CIAD) geometry. This model-approach is principled upon scaling of the diffuse fluorescence between CIAD and a SF of the same size of collection, which expands the scaling of diffuse reflectance between CIAD and a SF discovered for steady-state and time-domain cases. Analytical fluorescence for CIAD is then developed via radial-integration of radially resolved fluorescence. The radiance of excitation is decomposed to surface, collimated, and diffusive portions to account for the surface, near the point-of-entry, and diffuse portion of fluorescence associated with a centered illumination. Radiative or diffuse transport methods are then used to quasi-analytically deduce fluorescence excited by the three portions of radiance. The resulting model of fluorescence for CIAD, while limiting to iso-transport properties at the excitation and emission wavelengths, is compared against the semi-empirical model for SF, revealing bi-phasic turning [0.5~2.6] at various geometric sizes [0.2, 0.4, 0.6, 0.8, 1.0 mm] and a change of three orders of magnitude in the absorption of the background medium. This model projects a strong reduction in fluorescence versus strong absorption at high scattering, which differs from the semi-empirical SF model’s projection of a saturating pattern unresponsive to further increases in the absorption. This framework of modeling fluorescence may be useful to project frequency-domain and lifetime pattens of fluorescence in an SF and CIAD. Full article

Neutrophils are the first line of defense of the human immune system against pathogens. Photobiomodulation, mediated by mitochondrial photoacceptors such as cytochrome c oxidase, has emerged as a method to modulate neutrophil function through targeted light exposure. Despite the extensive characterization of neutrophil extracellular traps (NETs) formation (NETosis), the wavelength-specific modulation of neutrophil photoactivation and the involvement of redox pathways remain poorly defined. In this study, the effects of monochromatic (365 nm, 415 nm, 437 nm, and 625 nm) and dichromatic LED-light irradiation on NETs formation were systematically examined. The highest netotic responses were elicited by UV-A (365 nm) and violet-blue light (415 nm), whereas 437 nm showed the lowest induction and 625 nm stimulated a moderate netotic response. The pharmacological inhibition of NETosis induced by 365 nm and 415 nm irradiation with specific NADPH oxidase inhibitor, apocynin, and mitochondrial reactive oxygen species (mtROS) scavenger, MitoTEMPO, attenuated NETs formation by engaging both enzymatic and mitochondrial oxidative sources. Notably, mtROS played a dominant role under 415 nm stimulation in contrast to 365 nm-induced NETosis as demonstrated by higher sensitivity to MitoTEMPO. Importantly, combined simultaneous irradiation with 415 nm and 625 nm LEDs resulted in a significant suppression of NETs formation by more than 50%, highlighting a potent inhibitory synergy observed for the first time and suggesting a new approach of wavelength pairing to modulate neutrophil activation. These results were further supported by measurements of ROS production using a luminol-amplified chemiluminescence assay. Collectively, these findings delineate a wavelength- and ROS-dependent framework for light-induced neutrophil activation, with mitochondrial pathways exerting central control particularly under short-wavelength irradiation. Full article