Search Results (1,494)

Terahertz (THz) fingerprint spectroscopy enables label-free identification of molecular vibrational signatures, but trace biomolecular absorption is too weak to be reliably resolved in free-space measurements. To address this limitation, we propose a four-degree-of-freedom geometrically encoded THz metasurface for broadband multichannel fingerprint sensing. The substrate-free self-supporting aluminum structure incorporates four independently tunable geometric parameters: gap angle θ, outer ring radius R, scaling factor S, and ring width W. By regulating these parameters, multiple resonance-tuning pathways are established, enabling designable multiband spectral coverage over 0.6–1.4 THz and flexible matching with the fingerprint bands of L-hydroxyproline (L-HYP). Numerical simulations show that the metasurface achieves a refractive-index sensitivity of 512.66 GHz/RIU with a linear fitting coefficient of R² = 0.99708 and a mean Q factor of 4.72. For biomolecular fingerprint sensing, the encoded resonances overlap with the L-HYP absorption bands near 0.73 and 1.17 THz, producing AIT-like spectral modulation and envelope-derived attenuation enhancement. Compared with an unstructured analyte reference, the valid 0.73 THz readout gives enhancement factors of 5.76 and 7.09 for the R and S channels, respectively, while the four encoded channels provide enhancement factors of 3.53–4.45 at 1.17 THz. This design provides a compact strategy for broadband multichannel THz fingerprint enhancement, offering a promising route for monitoring collagen-metabolism-related biomarkers and advancing label-free biochemical sensing, fibrosis-related molecular screening, and integrated broadband THz detection. Full article

Diabetes is a major worldwide health concern, which emphasizes the critical need for precise and continuous glucose monitoring devices. This paper introduces a novel, non-invasive method for continuous blood glucose monitoring using on-chip multi-arm sensors designed as earbuds by using UMC 0.18 μm technology. The proposed sensor uses the dielectric characteristics of the earbud to detect variations in glucose levels while operating at various resonant frequencies, including 32, 42, 64, and 94 GHz. The sensitivity of the proposed method was evaluated using a reflection coefficient criterion of $\mid S_{11}\mid \le -6\mathrm{dB}$, confirming its ability to achieve accurate detection when implemented within an earbud device. A 3D electromagnetic high-frequency structure simulator (HFSS) is used to validate the simulation. Only |S₁₁| data are used to determine the glucose concentrations in the blinded prediction group. The results demonstrate a strong correlation between sensor responses and glucose levels. The sensor achieved a sensitivity of 12.4 $\mathrm{M}\mathrm{H}\mathrm{z}/\mathrm{m}\mathrm{g}/\mathrm{d}\mathrm{L}$, 6 $\mathrm{d}\mathrm{B}/\mathrm{m}\mathrm{g}/\mathrm{d}\mathrm{L}$. Moreover, the earbud’s homogeneous tissue architecture and naturally low eccrine sweat gland density lessen susceptibility to confounding physiological variables commonly observed in microwave-based glucose detection. As a major advancement in biomedical sensing technology, this wearable system provides a precise and useful method for non-invasive glucose monitoring. Full article

The controlled formation of coherent interfaces in lattice-mismatched II–VI semiconductor heterostructures remains challenging. In this work, ZnSe/ZnS laminar nanomaterials were synthesized by an ultrasound-assisted reverse micelle method to determine how ultrasonic power (150 and 200 W) and water-to-surfactant molar ratio (16:1, 32:1, and 48:1) jointly regulate morphology, crystal structure, lattice accommodation, optical response, and photoelectrochemical behavior. Higher ultrasonic power favored more clearly defined laminar morphologies, whereas increasing the water-to-surfactant ratio produced more heterogeneous growth domains. XRD and Raman spectroscopy confirmed the presence of zinc-blende ZnSe and ZnS phases and provided indirect evidence consistent with partial pseudomorphic lattice accommodation, with calculated mismatch values of 1.59–3.07%, compared with the theoretical value of 4.43%. The apparent optical band gap decreased from 3.39 to 3.06 eV at 200 W and from 3.34 to 3.04 eV at 150 W as the water content increased. Photochronoamperometry showed predominantly cathodic responses, whereas P1R1 exhibited an anodic response. These results establish ultrasonic power and micellar composition as coupled synthesis parameters for tuning lamellar growth, interfacial strain, and optoelectronic response in ZnSe/ZnS heterostructures. Full article

In femtosecond-laser processing of titania in water, light can induce reduction and oxidation simultaneously. We follow this redox energy partitioning, in this perspective, from colloidal titania synthesis to hot-electron devices. Femtosecond ablation/fragmentation of an aqueous anatase suspension (515 nm, 230 fs, $5\mathsf{\mu }$J, fluence $F\approx 25.5$ J cm⁻²/pulse at clamped intensity ∼${10}^{13}$ W cm⁻²) yields surface-reduced, Ti³⁺-rich bluish TiO_2−x, while the same optical breakdown generates reactive oxygen species (ROS), among them H₂O₂ and HO^• radicals, which compete by re-oxidising Ti³⁺. When the reduced titania is decorated with plasmonic nanoparticles (e.g., Au), an n-type plasmonic photo-electrode is realised: $sp$ hot electrons are injected over the Schottky barrier, while the deep d-band supplies oxidising holes. The oxygen evolution reaction (OER) proceeds in stages at potentials well above the formal $1.23$ V via the two-electron peroxide route (∼$1.77$ V) or, for sufficiently energetic holes, via the one-electron HO^• route (∼$2.7$ V). In a biased cell, H₂ evolves on Pt through the adsorbed (H₂⁺)_ad intermediate. The same Au/semiconductor physics on silicon enables sub-band-gap hot-electron photo-detection. Energy-level diagrams (flat-band and in-contact) and the $sp$- vs. d-band origin of the injected carriers are discussed. Full article

We present a simulation study of bidirectionally pumped distributed Raman amplification (DRA) noise performance for two recirculating-loop span configurations—50 km and 75 km—evaluated over a 50-channel C-band grid (191,200–196,100 GHz, 100 GHz spacing) representative of dense WDM transmission. For each span length, the forward pump power was first optimized on a central channel (193,600 GHz) to minimize signal power variation (SPV), yielding optimum values of 1.2 W for the 50 km span and 2 W for the 75 km span; the backward pump power was then set to achieve 0 dB net gain on the same central channel. These optimized pump conditions were applied uniformly across all 50 channels to characterize on–off gain variation for each single-span configuration. Using an input OSNR of 30 dB, recirculating-loop simulations were then performed for both spans across 1 to 60 (50 km) and 1 to 40 (75 km) round trips, covering a common reach of up to 7500 km. The OSNR degrades more slowly with distance for the 50 km than for the 75 km span up to 7500 km. Under the conditions studied, shorter DRA spans give better noise performance, even though more recirculations are required for the same reach.  Full article

Wave energy in short-fetch, semi-enclosed seas depends on how closely the response of a converter matches locally generated, short-period waves. This study makes that match explicit for the Black Sea, the Sea of Marmara, the Aegean, and the Eastern Mediterranean, the four seas around Türkiye, as four distinct regions within a single study area. Twenty years (May 2006 to March 2026) of three-hourly significant wave height and energy period from the Copernicus Marine global wave reanalysis (0.2°) were combined with GEBCO 2026 bathymetry to map the wave power flux, to screen cells inside a first-order 25–100 m deployment-depth band, and to rank three candidate sites in each region. Specific power matrices were applied to three full-scale reference converters (Pelamis P-750, AquaBuOY and Wave Dragon) and to two shallow-water archetypes, the Oyster surge flap and the Wavestar multi-float machine, standing for contemporary shallow-water design classes, at full scale and under Froude similitude. The best deployable sites of the Black Sea and the Aegean carry mean fluxes of 3.1–3.6 kW m⁻¹, and the Marmara sites define the low-resource end member at 0.2–0.8 kW m⁻¹; mean energy periods at the twelve sites range from 2.7 to 5.4 s. At their original scale the three reference converters reach capacity factors of up to 3.4%, because their specific power matrix response bands fall largely outside the regional sea-state distribution. Scaling changes that. Froude scaling to 0.20–0.25 of the original linear dimensions moves the response into the dominant 4–5 s band and raises the capacity factor to 30–47% at the seven sites where the mean flux exceeds 2.5 kW m⁻¹, at scaled rated powers of about 2–25 kW; the two archetypes reach 7–19% at full scale and 49–59% once scaled at the same sites. Both the preferred scale and the achievable capacity factor are near-uniform along the Black Sea rim, the Aegean archipelago, and the Levantine shore, so the analysis yields a single regional design specification, as follows: a small, short-period converter deployed in modular arrays. Full article

We demonstrate a high-power broadband continuous mode-hop-free (MHF) tunable singly resonant optical parametric oscillator (SRO). To obtain broadband continuous MHF operation, a synchronous etalon-angle locking technique and a feedback-optimized temperature controller were developed based on theoretical investigation. At a pump power of 21 W that was eight times the pump threshold, the measured signal was tuned from 1551.9087 nm to 1568.6549 nm, and the corresponding idler was tuned from 3384.3030 nm to 3307.3073 nm simultaneously. A continuous MHF tuning bandwidth of 2.064 THz was achieved at a tuning speed of 4.7 GHz/s. Continuous MHF operation in the whole tuning band was verified by high-resolution absorption spectroscopy of acetylene and methane, and by the continuous sinusoidal transmission through a Fabry–Perot etalon. The measured powers of the signal at 1560 nm and idler at 3346 nm were 4.12 W and 2.26 W with peak-to-peak fluctuations of ±0.42% and ±0.18%, respectively. These results represent, to the best of our knowledge, the widest continuous MHF tuning bandwidth achieved by a temperature-tuned SRO at high pump power, providing a high-power dual-band coherent source for precision spectroscopy. Full article

Just-in-time adaptive interventions require timely and low-burden state estimation, while olfaction offers a programmable output channel with limited attentional demand. We describe a prototype architecture that links electroencephalography (EEG)-based emotion estimation to a six-channel odorant device and evaluate only the EEG sensing and decoding module. Forty EEG sessions from 39 adults were recorded with a 14-channel Emotiv EPOC X headset (128 Hz) during six standardized emotion-induction conditions. No odor was administered. Band-power, frontal alpha asymmetry (FAA) and global field power (GFP) were analyzed with rank-based repeated-measures tests and explicit multiple-comparison correction. Emotion decoding used subject-aware cross-validation. Frontal beta power, the beta/alpha ratio and GFP differed across conditions after false-discovery-rate correction, although effect sizes were small (Kendall’s W = 0.089–0.155). On-line affective metrics showed larger effects (W = 0.130–0.365). Six-class accuracy was 45.1% ± 13.2% within participants (n = 29; chance 16.7%; p < 10⁻⁸) and 23.1% across participants after per-subject normalization (macro-F1 = 0.23; permutation p = 0.005). FAA did not differ. Consumer-headset EEG contained person-specific information about laboratory-induced states, but performance was not sufficient to establish a clinically usable regulator. The results validate neither a complete closed loop nor olfactory efficacy; end-to-end latency, artifact and temporal robustness, chemical characterization and controlled odor-regulation effects require prospective evaluation. Full article

To address the need for low-power, real-time underwater acoustic signal processing and autonomous target detection on deep-sea unmanned mobile platforms, such as profiling acoustic buoys and underwater gliders, this study developed an embedded Linux-based signal processing system for buoy platforms. Conventional digital signal processing hardware platforms are often constrained by large size, high power consumption, and limited data communication capability. The proposed system adopts a compact, low-power architecture and a multithreaded processing framework based on the AM6254 heterogeneous multicore processor. It acquires four-channel vector-hydrophone signals together with attitude data from an inertial navigation module and performs band-pass filtering, fast Fourier transform (FFT), direction-of-arrival (DOA) estimation, and constant false alarm rate (CFAR) detection for autonomous target detection. The measured typical power consumption was approximately 2.3 W. Anechoic-tank and sea-trial results showed the lowest tested spectral level at which autonomous detection was achieved was 54 dB at 1 kHz, corresponding to an average in-band level of 46 dB. Under sea state 3, the system maintained continuous bearing tracking after target acquisition for a surface target traveling at 7 kn, up to a range of approximately 7 km, and provided unambiguous bearing estimation. These results demonstrate the target-detection capability and practical applicability of the system under representative operating conditions and indicate its potential for marine environmental monitoring and unmanned-platform observation and detection. Full article

Background/Objectives: Consciousness fluctuations involve brain network reorganization, yet the underlying neural synchronization mechanisms remain unclear. This study examined the static and dynamic characteristics of alpha-band functional connectivity during propofol sedation from two dimensions: phase synchrony and amplitude coupling. Methods: Electroencephalography data from 20 healthy volunteers across baseline, mild sedation, moderate sedation, and recovery were analyzed. Source-level signals for 68 cortical regions of interest were reconstructed using sLORETA. Dynamic functional connectivity matrices for both weighted Phase Lag Index (wPLI) and amplitude envelope correlation (AEC) were computed using 5 s sliding windows. Dynamic connectivity states were identified through clustering analysis, and state occurrence rates were compared between drowsy and responsive participants across sedation levels. Results: Static analysis revealed a dissociation between the two metrics: during moderate sedation, wPLI showed significant suppression in posterior parieto-occipital regions, whereas AEC exhibited widespread whole-brain coupling enhancement. Dynamic clustering identified three wPLI states and five AEC states. Critically, although the two metrics exhibited spatially distinct dynamic reconfiguration patterns, with deepening sedation, the occurrence rate of the ventral connectivity pattern in wPLI and that of the medial prefrontal pattern in AEC both increased significantly, and these two patterns showed synergistic co-occurrence. This effect was more pronounced in the drowsy subgroup, with greater increases in both patterns. Conclusions: Propofol-induced alterations in consciousness are not characterized by linear attenuation along a single neural synchrony dimension, but rather by differential reorganization of phase- and amplitude-based functional connectivity across spatial configurations and temporal dynamics. Full article

The increasing demand for broadband and self-powered optoelectronic devices has stimulated the development of two-dimensional (2D) material-based photodetectors. Here, we construct a self-powered photodetector based on a MoSe₂/SnS₂ van der Waals (vdW) heterostructure. The unique combination of MoSe₂ and SnS₂ provides complementary light absorption and a type-II band alignment, which generates an interfacial built-in electric field to facilitate photogenerated carrier separation and transport, enabling efficient self-powered operation without external bias. The device exhibits a broad spectral photoresponse from ultraviolet (UV) to infrared (IR) wavelengths (350–1050 nm). Under zero bias, the photodetector achieves a responsivity of 0.6 mA/W and a rapid response time of 5.8/6.1 ms (rise/fall) under 405 nm illumination, demonstrating effective self-driven photoresponse. With an applied reverse bias of −2 V, the device further reaches a responsivity of 161 mA/W and a detectivity of 8.6 × 10¹⁰ Jones under 405 nm illumination. In addition, the device exhibits a low dark current of 5 pA and a high on/off ratio of 1180. These results demonstrate the potential of the MoSe₂/SnS₂ vdW heterostructure for broadband and self-powered optoelectronic applications. Full article

Photosynthetically active radiation (PAR) is a fundamental driver of terrestrial photosynthesis and a key input for light use efficiency-based estimates of gross primary productivity (GPP). However, existing PAR products are typically designed for regional to global applications and often remain spatially mismatched with the finer-resolution land surface variables now commonly derived from optical satellite observations. In this study, we present a semi-empirical framework for deriving daily clear-sky and all-sky PAR from Sentinel-2 Level-2A imagery. The approach combines solar geometry, daily extraterrestrial radiation, and simplified atmospheric transmittance parameterizations using Sentinel-2 aerosol, water vapor, and scene classification information to estimate clear-sky PAR, and further extends this formulation to all-sky conditions through a cloud-transmission factor derived from cloud probability to generate a spatially explicit PAR product aligned with Sentinel-2 observations. The resulting estimates are evaluated against flux tower observations from 172 AmeriFlux sites across North and South America for the period 2017–2024 and compared with MODIS MCD18, VIIRS VNP18, and CERES SYN1deg PAR products. The clear-sky Sentinel-2 formulation showed a moderate positive bias of 6.38 W m⁻², while the all-sky cloud adjustment reduced the mean bias to −1.44 W m⁻² with an RMSE of 23.53 W m⁻² and correlation of r = 0.87. The largest improvements occurred in spring and summer seasons, when atmospheric attenuation has the strongest influence on the clear-sky estimates. MODIS and CERES all-sky PAR products achieved lower overall errors with RMSE of 17.60 W m⁻² and 15.56 W m⁻², respectively, but at substantially coarser spatial resolution. The proposed framework therefore provides a practical high-resolution approximation of daily PAR that is spatially consistent with Sentinel-2 observations. Rather than replacing dedicated radiative transfer-based products, the method is intended to support analyses in which PAR needs to be evaluated together with Sentinel-2 bands, vegetation indices, and other Sentinel-2-derived variables within a common observational framework. Full article

This study focuses on the deposition of nickel thin-films onto glass fiber fabric via DC magnetron sputtering and explores their potential for broadband microwave absorption applications. A total of twelve laminate samples were prepared by integrating the coated fabrics with epoxy resin, with sputtering powers ranging from 0.5 to 2 kW and deposition times ranging from 10 to 90 min. The microstructure, surface resistance, electromagnetic parameters, and microwave absorption performance were systematically characterized using SEM, XRD, four-point probe measurements, and vector network analysis, supplemented by the Lorentz model fitting and simulation validation. The results indicate that the nickel coatings exhibit a non-uniform arc-like morphology, with preferential growth along the (111) crystallographic plane, while the (200) and (220) planes form under specific conditions. The surface resistance reaches up to 10⁸ Ω·m, suggesting the absence of a continuous conductive network. Electromagnetic parameter analysis reveals that the laminates display dielectric-loss-dominated microwave absorption, and the Lorentz fitting identifies double resonance peaks under prolonged or high-power sputtering. The addition of a dielectric matching layer further enhances the absorption performance. All samples achieve wideband absorption within the Ku-band. Notably, the samples prepared at 1 kW for 30 min and at 1 kW for 90 min both exhibit a reflectivity of ≤−10 dB across the entire 8–18 GHz frequency range. The experimental results are in good agreement with simulations. The bulk density of the laminates is approximately 1.8 g/cm³. These findings confirm that magnetron-sputtered nickel-coated continuous glass fiber fabrics hold considerable promise for wideband microwave absorption applications. Full article

Background/Objectives: Electroencephalography (EEG) connectivity and microstate analysis have shown great potential for Alzheimer’s disease (AD) diagnosis; however, their clinical application remains limited by the low spatial resolution of EEG and the lack of standardized microstate analysis. To address these challenges, this study proposes a multi-domain feature fusion framework, namely Source-localized Microstate and Multi-frequency Synchronization (SMMS), which integrates EEG source localization (ESL)-based weighted phase lag index (wPLI) functional connectivity with EEG microstate features. Methods: Specifically, ESL was employed to improve the spatial resolution of EEG signals for constructing functional connectivity matrices, while multi-frequency-band wPLI features were extracted to characterize functional synchronization among cortical regions. Meanwhile, EEG microstate features were utilized to capture the temporal dynamics of brain functional states. The proposed framework was evaluated on a public OpenNeuro dataset comprising 36 AD patients, 23 frontotemporal dementia (FTD) patients, and 29 healthy controls (HCs), as well as an additional clinical dataset collected from 48 AD patients at Sir Run Run Shaw Hospital, Hangzhou, China. Results: Experimental results showed that the proposed SMMS framework achieved high classification performance on both datasets. Conclusions: These findings demonstrate its effectiveness for EEG-based Alzheimer’s disease diagnosis. Full article

Active Reconfigurable Intelligent Surface (RIS) architectures require unit-cell-level gain while keeping the per-element power consumption and fabrication cost low. This work presents a compact low-power reflection amplifier operating in C-band for 5G and 6G applications, implemented with a single SiGe HBT on a standard FR4 substrate. The design was carried out using nonlinear circuit simulations and layout-level electromagnetic co-simulation. The fabricated prototype, biased at $1.8\mathrm{V}$, provides a measured reflection gain of approximately $13\mathrm{dB}$ around the target frequency with a sub-mW DC power consumption. The measurement campaign aimed to verify the negative resistance condition, the gain value, and the absence of self-sustained oscillations. These results demonstrate the feasibility of a compact low-power C-band reflection amplifier on low-cost FR4 for scalable active RIS implementations. Full article