Search Results (5,731)

Multisensory integration is fundamental for coherent perception and interaction with the environment. While cortical mechanisms of multisensory convergence are well studied, emerging evidence implicates specialized retinal ganglion cells—particularly melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs)—in crossmodal processing. This review explores how hierarchical brain networks (e.g., superior colliculus, parietal cortex) and ipRGCs jointly shape perception and behavior, focusing on their convergence in multisensory plasticity. We highlight ipRGCs as gatekeepers of environmental light cues. Their anatomical projections to multisensory areas like the superior colliculus are well established, although direct evidence for their role in human audiovisual integration remains limited. Through melanopsin signaling and subcortical projections, they may modulate downstream multisensory processing, potentially enhancing the salience of crossmodal inputs. A key theme is the spatiotemporal synergy between melanopsin and melatonin: melanopsin encodes light, while melatonin fine-tunes ipRGC activity and synaptic plasticity, potentially creating time-sensitive rehabilitation windows. However, direct evidence linking ipRGCs to audiovisual rehabilitation remains limited, with their role primarily inferred from anatomical and functional studies. Future implementations should prioritize quantitative optical metrics (e.g., melanopic irradiance, spectral composition) to standardize light-based interventions and enhance reproducibility. Nonetheless, we propose a translational framework combining multisensory stimuli (e.g., audiovisual cues) with circadian-timed melatonin to enhance recovery in visual disorders like hemianopia and spatial neglect. By bridging retinal biology with systems neuroscience, this review redefines the retina’s role in multisensory processing and offers novel, mechanistically grounded strategies for neurorehabilitation. Full article

Gases emitted from active volcanic systems constitute a primary natural source of global atmospheric pollution. Atmospheric sulfur dioxide (SO₂) concentrations were monitored using a near-continuous network based on Scan-DOAS (Differential Optical Absorption Spectroscopy) technology. Complementary intermittent measurements were performed using a UV Thermo^® analyzer deployed at fixed locations and along predefined transects on the island. SO₂ flux data derived from the Scan-DOAS measurements, coupled with atmospheric dispersion maps generated using the AERMOD modeling software, enabled the estimation of SO₂ distribution across the volcanic crater region and inhabited areas of the island, including Vulcano Village and Vulcano Piano. The results of the estimation of SO₂ concentration in the atmosphere, integrated with the dispersion modeling, exhibited consistency with direct SO₂ concentration measurements obtained by the Thermo^® analyzer, demonstrating coherence between the two methodologies, although some overestimations of ambient SO₂ were noted. This study provided valuable insights into areas with anomalous SO₂ concentrations exceeding the threshold limits established by the World Health Organization (WHO) and the European Union (EU). These limits are generally exceeded in the crater zone and surrounding areas. The findings also highlighted the influence of prevailing winds and the temporal variations in volcanic degassing activity observed over the preceding 17 years, characterized by four periods of unrest degassing with SO₂ emission rates from the summit solfataric area reaching up to 250 tonnes per day (td⁻¹). Full article

Optical properties and chemical composition of atmospheric fine particles (PM_2.5) are critical to their environmental and health effects. In this study, we analyzed the organic aerosols (OA) in PM_2.5 samples in Nanjing, China, collected during the summer and winter of 2019 and 2023. Results show a decline in both concentrations and light-absorbing abilities of methanol—soluble organic carbon (MSOC) and water-soluble OC (WSOC) in OA from 2019 to 2023. Due to increased combustion activities, MSOC and WSOC concentrations, and their corresponding mass absorption efficiencies were all higher in winter than in summer. Furthermore, fluorescence indices suggest that OA in Nanjing was influenced by a mix of microbial/biogenic sources. Fluorescent properties of both WSOC and MSOC were dominated by humic-like components but the remaining contribution from protein-like components was more significant in MSOC. The molecular composition of OA did not show a remarkable difference between 2019 and 2023. Overall, CHON compounds were the most abundant species, followed by CHO and CHN compounds, and aliphatic compounds dominated all molecular types except for CHN (in positive mode) and CHON, CHOS (in negative mode). Regarding the OA sources, the numbers of molecules from fossil fuel combustion and biomass burning (BB) were a bit more in 2023 than in 2019, and signal intensities of BB-related molecules were also higher in winter than in summer; the presence of organosulfates indicate the contribution of aqueous-phase oxidation to OA, especially during high relative humidity conditions. At last, correlations between OA molecules and light absorption efficiencies indicate that the key light-absorbing species in winter and summer were likely quite different despite similar chemical compositions, and in summer, CH and CHN compounds were important to light absorption, whereas CHNS compounds became more important in winter. Full article

Bimetals—materials composed of two metal components with dissimilar standard reduction–oxidation (redox) potentials—offer unique electronic, optical, and catalytic properties, surpassing monometallic systems. These materials exhibit not only the combined attributes of their constituent metals but also new and novel properties arising from their synergy. Although many reviews have explored the synthesis, properties, and applications of bimetallic systems, none have focused exclusively on iron (Fe)- and aluminum (Al)-based bimetals. This systematic review addresses this gap by providing a comprehensive overview of conventional and emerging techniques for Fe-based and Al-based bimetal synthesis. Specifically, this work systematically reviewed recent studies from 2014 to 2023 using the Scopus, Web of Science (WoS), and Google Scholar databases, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and was registered under INPLASY with the registration number INPLASY202540026. Articles were excluded if they were inaccessible, non-English, review articles, conference papers, book chapters, or not directly related to the synthesis of Fe- or Al-based bimetals. Additionally, a bibliometric analysis was performed to evaluate the research trends on the synthesis of Fe-based and Al-based bimetals. Based on the 122 articles analyzed, Fe-based and Al-based bimetal synthesis methods were classified into three types: (i) physical, (ii) chemical, and (iii) biological techniques. Physical methods include mechanical alloying, radiolysis, sonochemical methods, the electrical explosion of metal wires, and magnetic field-assisted laser ablation in liquid (MF-LAL). In comparison, chemical protocols covered reduction, dealloying, supported particle methods, thermogravimetric methods, seed-mediated growth, galvanic replacement, and electrochemical synthesis. Meanwhile, biological techniques utilized plant extracts, chitosan, alginate, and cellulose-based materials as reducing agents and stabilizers during bimetal synthesis. Research works on the synthesis of Fe-based and Al-based bimetals initially declined but increased in 2018, followed by a stable trend, with 50% of the total studies conducted in the last five years. China led in the number of publications (62.3%), followed by Russia, Australia, and India, while Saudi Arabia had the highest number of citations per document (95). RSC Advances was the most active journal, publishing eight papers from 2014 to 2023, while Applied Catalysis B: Environmental had the highest number of citations per document at 203. Among the three synthesis methods, chemical techniques dominated, particularly supported particles, galvanic replacement, and chemical reduction, while biological and physical methods have started gaining interest. Iron–copper (Fe/Cu), iron–aluminum (Fe/Al), and iron–nickel (Fe/Ni) were the most commonly synthesized bimetals in the last 10 years. Finally, this work was funded by DOST-PCIEERD and DOST-ERDT. Full article

OT 355 (4FGL J1734.3 + 3858) is a relatively rarely studied but highly variable, moderate-redshift (z = 0.975) flat-spectrum radio quasar (blazar). With this work, we aim to study its optical variability on different timescales, which can help us to better understand the physical processes in relativistic jets operating in blazar-type active galactic nuclei. OT 355 was observed in four colors (BVRI) during 41 nights between 2017 and 2023 using three 1 and 2 m class telescopes. The object was also monitored on intra-night timescales, for about 100 h in total. In addition, secondary standard stars in the field of OT 355 were calibrated in order to facilitate future photometric studies. We detected significant intra-night and night-to-night variations of up to 0.5 mag. Variability characteristics, color changes, and a possible “rms-flux” relation were studied and discussed. Using simple arguments, we show that a negative “rms-flux” relation should be expected if many independent processes/regions drive the short-term variability via Doppler factor changes, which is not observed in this and other cases. This finding raises arguments for the idea that more complex multiplicative processes are responsible for blazar variability. Studying blazar variability, especially on the shortest possible timescales, can help to estimate the strength and geometry of their magnetic fields, the linear sizes of the emitting regions, and other aspects, which may be of importance for constraining and modeling blazars’ emitting mechanisms. Full article

A stereoselective and scalable strategy for the synthesis of phosphorus-containing bicyclic and tricyclic compounds from 1-phenylphosphin-2-en-4-one 1-oxide is presented. This activated dienophile, available in both racemic and enantiopure forms, undergoes smooth [4+2] cycloadditions with acyclic and cyclic dienes, affording products with excellent yields and controlled stereochemistry. Notably, the cis/trans-fusion of the cycloadducts (phosphadecalones and phosphahexahydrochrysene) can be selectively controlled by fine-tuning the conditions of microwave-assisted cycloaddition reaction. The influence of temperature, time, and steric effects on cis/trans and endo/exo selectivity was examined in detail. The molecular structure, including the absolute configuration, of eight products has been determined by X-ray crystallography. These analyses further established the endo-selective nature of the cycloaddition, favoring the P=O face of the dienophile. Post-cycloaddition transformations of selected P-stereogenic phosphadecalone, such as isomerization, reduction and deoxygenation, demonstrate the synthetic versatility of the resulting products. Full article

Photochromic materials have attracted widespread attention due to their potential applications in optical information storage, optoelectronic devices, and fluorescence probes. As a typical photochromic system, diarylethene derivatives are considered one of the most promising photochromic materials due to their outstanding photostability and significant bistable properties. Based on an aggregation-induced emission (AIE) mechanism, this study employed a molecular structural engineering strategy to design and synthesize a series of diarylethene derivatives containing ethyl benzoate substituents. A systematic investigation of the structure–activity relationship between their photochromic behavior and AIE characteristics revealed a dual-state light response mechanism in the solid and solution states. This study demonstrates that the target compounds exhibited significant photochromic responses under UV–visible light irradiation, with enhanced emission in the solid state compared to the solution state, confirming the remarkable enhancement effect of AIE on aggregation. Structural characterization techniques such as nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectrometry (H RMS) were employed to elucidate the correlation between molecular conformation and photophysical properties. Furthermore, these materials demonstrated potential for multi-level anti-counterfeiting, high-density optical storage, and bioimaging applications, providing experimental foundations for the development of novel multifunctional photochromic materials. Full article

In this study, TiO₂-Fe₂O₃/polyvinylpyrrolidone (PVP) hybrids were prepared using the sol–gel method. The iron content in the synthesized samples was 10 and 20 wt%. The influence of PVP on the phase transformation, morphology and optical properties of the as-prepared hybrids was characterized by various physicochemical methods—XRD analysis, UV–Vis spectroscopy, IR spectroscopy and SEM. The obtained sol–gel powders were tested for photocatalytic activity against tetracycline hydrochloride in distilled water under ultraviolet and simulated solar light illumination. The obtained results were compared to commercial TiO₂ P25 (Evonik). The investigated samples exhibited good photocatalytic efficiency for the degradation of tetracycline hydrochloride; however, better activity was demonstrated by the 90TiO₂-10Fe₂O₃/PVP sample. The latter one displayed weak antibacterial action against E. coli ATCC 25922 in the presence of UVA light. Full article

Nowadays, underwater activities are becoming more and more important. As the number of underwater sensing devices grows rapidly, the amount of bandwidth needed also increases very quickly. Apart from underwater communication, direct communication across the water–air interface is also highly desirable. Air-to-water wireless transmission is crucial for sending control information or instructions from unmanned aerial vehicles (UAVs) or ground stations above the sea surface to autonomous underwater vehicles (AUVs). On the other hand, water-to-air wireless transmission is also required to transmit real-time information from AUVs or underwater sensor nodes to UAVs above the water surface. Previously, we successfully demonstrated a water-to-air optical camera-based OWC system, which is also known as optical camera communication (OCC). However, the reverse transmission (i.e., air-to-water) using OCC has not been analyzed. It is worth noting that in the water-to-air OCC system, since the camera is located in the air, the image of the light source is magnified due to diffraction. Hence, the pixel-per-symbol (PPS) decoding of the OCC pattern is easier. In the proposed air-to-water OCC system reported here, since the camera is located in the water, the image of the light source in the air will be diminished in size due to diffraction. Hence, the PPS decoding of the OCC pattern becomes more difficult. In this work, we propose and experimentally demonstrate a wide field-of-view (FOV) air-to-water OCC system using CUDA Deep-Neural-Network Long-Short-Term-Memory (CuDNNLSTM). Due to water turbulence and air turbulence affecting the AUV and UAV, a precise line-of-sight (LOS) between the AUV and the UAV is difficult to achieve. OCC can provide wide FOV without the need for precise optical alignment. Results revealed that the proposed air-to-water OCC system can support a transmission rate of 7.2 kbit/s through a still water surface, and 6.6 kbit/s through a wavy water surface; this satisfies the hard-decision forward error correction (HD-FEC) bit-error-rate (BER). Full article

Recently, technologies monitoring users’ physiological signals in consumer electronics such as smartphones or kiosks with cameras and displays are gaining attention for their potential role in diverse services. While many of these technologies focus on photoplethysmography for the measurement of blood flow changes, respiratory measurement is also essential for assessing an individual’s health status. Previous studies have proposed thermal camera-based and body movement-based respiratory measurement methods. In this paper, we adopt an approach to extract respiratory signals from RGB face videos using photoplethysmography. Prior research shows that photoplethysmography can measure respiratory signals, due to its correlation with cardiac activity, by setting arterial vessel regions as areas of interest for respiratory measurement. However, this correlation does not directly reflect real-time respiratory components in photoplethysmography. Our new approach measures the respiratory rate by capturing changes in skin brightness from motion artifacts. We utilize these brightness factors, including facial movement, for respiratory signal measurement. We applied the wavelet transform and smoothing filters to remove other unrelated motion artifacts. In order to validate our method, we built a dataset of respiratory rate measurements from 20 individuals using an RGB camera in a facial movement-aware environment. Our approach demonstrated a similar performance level to the reference signal obtained with a contact-based respiratory belt, with a correlation above 0.9 and an MAE within 1 bpm. Moreover, our approach offers advantages for real-time measurements, excluding complex computational processes for measuring optical flow caused by the movement of the chest due to respiration. Full article

Recently, engineering companies have started to digitise documents in image form to analyse their meaning and extract important content. However, many engineering and contract documents contain different types of components such as texts, tables, and forms, which often hinder accurate interpretation by simple optical character recognition. Therefore, document object detection (DOD) has been studied as a preprocessing step for optical character recognition. Given the ease of acquiring image data, reducing annotation time and effort through transfer learning and active learning has emerged as a key research challenge. In this study, a cost-efficient active transfer learning (ATL) framework for DOD is presented to minimise the effort and cost of time-consuming image annotation for transfer learning. Specifically, three new sample evaluation measures are proposed to enhance the sampling performance of ATL. The proposed framework performed well in ATL experiments of DOD for invitation-to-bid documents. In the experiments, the DOD model was trained on only half of the labelled images, but, in terms of the F1-score, it achieved a similar performance as a DOD model trained on all labelled images. In particular, one of the proposed sampling measures, ambiguity, showed the best sampling performance compared to existing measures, such as entropy and uncertainty. The efficient sample evaluation measures proposed in this study are expected to reduce the time and effort required for ATL. Full article

Coupling organic light-harvesting materials with lead halide perovskite quantum dots (LHP QDs) is an attractive approach that could provide great potential in optoelectronic applications owing to the diversity of organic materials available and the intriguing optical and electronic properties of LHP QDs. Here, we demonstrate energy collection by CsPbI₃ QDs from a near-infrared (NIR) light-harvesting upconversion system. The upconversion system consists of Pd-tetrakis-5,10,15,20-(p-methoxycarbonylphenyl)-tetraanthraporphyrin (PdTAP) as the sensitizer to harvest NIR photons and rubrene as the annihilator to generate upconverted photons via triplet fusion. Steady-state and time-resolved photoluminescence spectra reveal that CsPbI₃ QDs are energized via radiative energy transfer from the singlet excited rubrene with photophysics fidelity of respective components. In addition, a volumetric display demo incorporating CsPbI₃ QDs as light emitters employing triplet fusion upconversion was developed, showing bright luminescent images from CsPbI₃ QDs. These results present the feasibility of integrating organic light-harvesting systems and perovskite QDs, enabling diverse light harvesting and activation of perovskite materials for optoelectronic applications. Full article

This study investigates the impact of hydrolysis on the crystallization behavior of poly(butylene succinate-co-adipate) (PBSA), a biodegradable polyester. Hydrolysis was conducted in a controlled environment using phosphate-buffered saline at 70 °C to isolate the impact of hydrolytic degradation on the polymer’s properties. The consequent changes in molecular weight characteristics were tracked using gel permeation chromatography (GPC), revealing a decrease in both weight average molecular weight (M_w) and an increase in polydispersity index (PDI) as hydrolysis progressed. The thermal behavior of PBSA during hydrolysis was thoroughly investigated using differential scanning calorimetry (DSC), which demonstrated significant changes in melting temperature (T_m), glass transition temperature (T_g), and crystallinity (X). These changes in T_m and T_g suggest a change in copolymer composition, likely due to the greater susceptibility of the adipic acid unit to hydrolysis compared to the succinic acid unit. Furthermore, polarized optical microscopy (POM) was employed to observe the morphological evolution of PBSA, showing a transition from spherulitic structures in the early stages of hydrolysis to dendritic structures with prolonged hydrolysis time. The decrease in nucleation activity led to a reduction in the number of spherulites, which in turn allowed the remaining spherulites to grow larger. Full article

Coherent anti-Stokes Raman scattering (CARS) is a powerful nonlinear spectroscopic technique widely used in biological imaging, chemical analysis, and combustion and flame diagnostics. The adoption of pulse shapers in CARS has emerged as a useful approach, offering precise control of optical waveforms. By tailoring the phase, amplitude, and polarization of laser pulses, the pulse shaping approach enables selective excitation, spectral resolution improvement, and non-resonant background suppression in CARS. This paper presents a comprehensive review of applying pulse shaping techniques in CARS spectroscopy for biophotonics. There are two different pulse shaping strategies: passive pulse shaping and active pulse shaping. Two passive pulse shaping techniques, hybrid CARS and spectral focusing CARS, are reviewed. Active pulse shaping using a programmable pulse shaper such as spatial light modulator (SLM) is discussed for CARS spectroscopy. Combining active pulse shaping and passive shaping, optimizing CARS with acousto-optic programmable dispersive filters (AOPDFs) is discussed and illustrated with experimental examples conducted in the authors’ laboratory. These results underscore pulse shapers in advancing CARS technology, enabling improved sensitivity, specificity, and broader applications across diverse scientific fields. Full article

Underwater polarization imaging has emerged as a fundamental technique for detecting and imaging underwater targets. However, the effectiveness of this technique is hampered by the low light intensity and optical system deformation induced by water pressure in deep-water environments, particularly for the detection of polarized signals. To address this issue, a wide-field-of-view oil-immersion lens tailored for deep-sea operations is designed, offering robust imaging performance and an extensive observation range. A Mueller matrix is deployed to scrutinize the polarization properties of the entire optical system across diverse fields of view, and the measurement errors in the polarization degree under incident polarization states are discussed. Simulation results demonstrate that the measurement error for linearly polarized light is greater than that for circularly polarized light. Therefore, the system adopts circularly polarized light as the active illumination source, characterized by minimal polarization effects and high detection accuracy. Finally, a deep-sea camera lens is produced and manufactured. The resulting lens is shown to pass a test in a hydrodynamic simulator machine, demonstrating that it can operate properly and capture images. Full article