Browse Articles

Superluminal spacetime crystals induced by anomalous velocity modulation

Time-modulated media offer powerful opportunities for controlling light, yet extending such concepts to optical frequencies has remained challenging. Here, we propose a different route to photonic spacetime crystals based on modulation of the anomalous velocity in low-symmetry conductors, particularly Weyl semimetals. We show that when driven by a strong optical pump, the anomalous velocity of Bloch electrons induces an ultrafast spacetime modulation that propagates with a superluminal phase velocity relative to the dielectric background. This self-induced modulation enables unidirectional light transport below the optical gap and, near the epsilon-near-zero point, gives rise to collective parametric resonance and stimulated emission of volume plasmons. These findings identify Weyl semimetals as a promising platform for realizing optical spacetime crystals and open a pathway toward active and nonreciprocal photonic systems governed by quantum geometric effects.

Expression of concern: Protein solubility, digestibility and fractionation after germination of sorghum varieties

Origin of threshold voltage instability in vertical GaN trench MOSFETs characterized by charge pumping

We systematically investigate threshold voltage (Vth) instability in vertical GaN trench MOSFETs on sapphire using a charge pumping (CP) method combined with pulsed gate measurements. A negative Vth shift and reduced hysteresis are observed when switching the gate bias from DC to pulsed mode with a negative quiescent gate bias; this behavior is attributed directly to oxide trapping in the gate stack. Using the CP technique, we quantitatively extract the trap density, energy levels, and depth profiles of both border oxide traps and interface states in the Al2O3/p-GaN sidewall gate stack. An integrated border trap density of 7.28 × 1012 cm−2 is deduced, and amorphous Ga–O–Al bonds formed during atomic layer deposition are identified as the potential physical origin of the Vth shift and hysteresis (ΔVth). Our analysis demonstrates that the CP approach goes beyond offering valuable insights into interface properties; it provides a powerful, quantitative diagnostic tool to directly guide the optimization of gate dielectrics in next-generation reliable vertical GaN trench MOSFETs for power applications.

Explainable machine learning reveals diverse yield-determining factors among Thai rice farmer cohorts: Implications for targeted agricultural support

Rice yield prediction and optimization remain crucial challenges in Thailand’s agricultural sector. This study presents an explainable machine learning framework for predicting farm-level rice yields and identifying key factors affecting productivity. We collected comprehensive data from 1,722 smallholder farmers in central Thailand, encompassing 58 agronomic and economic variables. Four automated machine learning (AutoML) frameworks – AutoGluon, auto-sklearn, h2o, and mljar – were evaluated using 5-fold cross-validation, with AutoGluon achieving the best performance (root mean square error: 0.532 tonnes/hectare, mean absolute error: 0.372 tonnes/hectare, R²: 0.538). Using global SHapley Additive exPlanations (SHAP) analysis, we identified farmers’ social networks, rental costs during harvest, and total harvesting expenses as the most influential predictors of rice yields. Notably, stronger social network connectivity was associated with higher yields, suggesting that information sharing and collective knowledge within farming communities play a key role in improving productivity. Clustering analysis based on individual SHAP values revealed six distinct farmer cohorts, each characterized by unique patterns of feature importance. These cohort-specific insights demonstrate the potential of combining AutoML with explainability techniques to move beyond uniform agricultural recommendations towards precision support tailored to the specific needs of different farmer cohorts.

Enhancing nonreciprocal filtering through surface modification of ferrimagnetic insulators

To address the significant reduction in magnetostatic surface waves (MSSW) nonreciprocity as ferrimagnetic insulators are scaled to the nanometer level, this study demonstrates an effective interface engineering methodology through targeted surface oxidation of 100 nm yttrium iron garnet (YIG) thin films. By implementing a sequential chemical treatment using FeCl3 and piranha solutions, we introduce a 30-nm-deep oxygen gradient near the YIG surface and increase the surface Fe3+/Fe2+ ratio from 2.7 to 7.3. This surface modification effectively restored the asymmetric dynamic dipolar stray fields associated with MSSW precession, which are essential for nonreciprocity, while simultaneously reducing the Gilbert damping coefficient from 8.2 × 10−4 to 4.8 × 10−4. Experimental characterization of the resulting filter prototype at 6.9 GHz reveals that surface treatment enhances the nonreciprocal isolation from 1.1 to 16.2 dB, narrows the signal passband from 200 to 70 MHz, and achieves optimized microwave transmission with an insertion loss of 4.2 dB. Together with semi-analytical modeling, these results show that surface oxidation converts a chemical depth gradient into direction-dependent effective magnetic parameters, thereby enhancing MSSW nonreciprocity through direction-dependent frequency response and dynamic-loss asymmetry. This work establishes a physically grounded interface engineering route for high-isolation, low-loss nonreciprocal components in integrated radio frequency and microwave front-end systems.

Editorial Note: Regulation of Vapor Pressure Deficit by Greenhouse Micro-Fog Systems Improved Growth and Productivity of Tomato via Enhancing Photosynthesis during Summer Season

Oxygen vacancies-assisted carrier transport toward improved Au/HfO2−x/Si Schottky photodetectors

Au/Si Schottky junctions are important building blocks for fabricating inexpensive and efficient photodetectors (PDs), whereas Si surface defects induce severe interfacial non-radiative recombination that markedly degrades the performance of the resulting devices. Herein, oxygen vacancy (VO)-rich HfO2−x thin films are employed to passivate Si surface defects to fabricate improved Au/HfO2−x/n-Si Schottky PDs. It shows that HfO2 thin films effectively passivate n-Si surface defects, while the presence of VO defects compromises the passivation efficiency. This results in improved Au/HfO2/n-Si Schottky PDs, but the improvements are limited by inefficient interfacial hole transport caused by the insulating HfO2. In contrast, the interfacial hole transport is markedly enhanced in HfO2−x thin films owing to VO defect-assisted hole tunneling, thereby leading to highly improved Au/HfO2−x/n-Si Schottky PDs. These results demonstrate that efficient interfacial carrier transport is vital for realizing improved dielectric-passivated PDs and provide a promising pathway for fabricating high-performance Si-based heterojunction PDs.

Effects of local heat on metabolic health, frailty risk, and exercise adaptations in pre-diabetic older adults: Protocol for the Heat and Exercise in Aging as Therapy (HEAT) clinical trial

Introduction Glycemic dysregulation is a hallmark of type 2 diabetes (T2D) and contributes to skeletal muscle (SKM) loss and frailty risk, especially in older adults. Glycemic control and physical function are supported by SKM capillarization and mitochondrial function, and their impairment contributes to T2D development. While high-intensity interval training (HIIT) is a promising intervention, adherence and effectiveness remain concerns for prescribing HIIT among older adults at risk for T2D. Local heat therapy (LHT) may be a more practical initial strategy to improve SKM architectural factors and precondition SKM, enhancing physiological adaptations to exercise in this population. Methods and analysis Heat and Exercise in Aging as Therapy (HEAT) is a two-phase, randomized, sham-controlled clinical trial investigating the efficacy of LHT to improve glycemic control and decrease frailty risk via improved SKM architecture among older adults with prediabetes. LHT is tested as a standalone intervention and as a means to precondition SKM for subsequent HIIT, improving exercise adaptations. In Phase 1, LHT and sham (CON) groups apply heat pads for 90 minutes/day, 6 days/week, for 12 weeks. A separate HIIT group completes 4x4-minute cycling intervals at 90–95% VO₂peak, 3 days/week. In Phase 2, LHT and CON groups begin HIIT. Participants (≥50 years) have impaired fasting glucose (100–125 mg/dL) and/or HbA1c (5.7–6.4%). Biospecimen collection and clinical assessments occur at baseline (T1), after Phase 1 (T2), and Phase 2 (T3). To our knowledge, this is the first study to determine the use of local heat pad on pre-diabetic older population. If successful, LHT may be a practical, scalable, non-invasive intervention to improve glycemic control and reduce frailty risk in older adults with prediabetes, preventing progression to T2D.

Self-powered broadband UV–NIR photodetector based on NbOCl2/WSe2 van der Waals heterostructure

Achieving self-powered operation together with broadband photodetection in a single device remains a key challenge for next-generation optoelectronic systems, primarily due to limited spectral response and high power consumption of conventional photodetectors (PDs). Although two-dimensional van der Waals (vdW) heterostructures provide a highly viable framework for performance enhancement, efficient self-powered broadband detection is still hindered by insufficient built-in electric fields and incomplete carrier separation. Here, we report an NbOCl2/WSe2 vdW heterojunction PD that enables efficient self-powered broadband photodetection. By leveraging the intrinsic polarization of NbOCl2 and favorable type-II band alignment at the heterointerface, a robust internal electric field is induced, thereby accelerating the separation and transport of photogenerated carriers. Under 477 nm illumination, the PD delivers an open-circuit voltage of 100 mV and a short-circuit current of 0.264 nA, achieving a responsivity of 39.17 mA/W in the self-powered mode. The PD exhibits broadband spectral sensitivity spanning from 255 to 1010 nm, an on/off current ratio of approximately 102, and fast response times of 7.14/7.37 ms. Moreover, a signal identification system is demonstrated to demonstrate the broadband imaging capability, including wavelength-dependent image reconstruction and ASCII-coded optical signal transmission. These results highlight the strong potential of NbOCl2/WSe2 vdW heterostructures for self-powered broadband optoelectronic applications.

Expression of Concern: Analysis of antidiabetic, antiulcer and analgesic potential of traditional ethnomedicinal plant Emex spinosa (L.) Campd. from Azad Jammu and Kashmir

Electromechanical switching and momentum-selective transport in geometry-defined blue phosphorus homojunctions

Developing intrinsic homojunctions without chemical heterogeneity remains a key challenge for the development of future two-dimensional devices. Here, we report a geometry-defined metal–semiconductor–metal homojunction in bilayer blue phosphorus (BlueP) created by a localized bubble corrugation, without chemical doping or foreign-material interfaces. First-principles calculations show that enlarging the interlayer separation in the metallic A1B−1-stacked BlueP bilayer opens a bandgap, enabling a semiconducting barrier embedded between metallic segments. First-principles quantum-transport simulations reveal a crossover from ballistic to tunneling transport upon bubble formation. In the tunneling regime, transmission decreases exponentially with bubble width while remaining weakly sensitive to bubble height and bulging direction. The junction acts as an orientation-dependent k-space filter, producing transport anisotropy and momentum selectivity. Orbital-resolved scattering analysis shows that intralayer-bonding channels persist under deformation, whereas interlayer-hybridized channels are quenched, and that σ-type bonding yields higher conductance than π-type bonding. These insights motivate two electromechanical device concepts: a mechanically switchable memory element with ON/OFF ratios up to 30 and a nanoscale sliding rheostat with reproducible exponential resistance tuning for Ångström-scale displacement sensing.

Sensing nature in the city: The role of sight and sound in restorative tropical urban green spaces

Rapid urbanization has increased disconnection from nature, especially in cities. While research on restorative environments has largely focused on non-tropical regions, little is known about the restorative potential of tropical urban green spaces (UGSs). This study assessed the perceived restorativeness of tropical UGSs in Malaysia using 120 environmental stimuli from nature, urban, and mixed urban-nature settings. 87 participants were randomly assigned to one of the three modalities: audio-only, visual-only, or bimodal. Each participant rated a subset of 30 stimuli on perceived restorativeness. Results showed that nature and mixed urban-nature scenes were in general rated as more restorative than urban scenes. An interaction effect indicated that, in the visual-only modality, mixed urban-nature scenes were perceived as more restorative than nature scenes, while no significant differences were observed in the audio-only and bimodal modalities. Moreover, perceived restorativeness for nature scenes was comparable across bimodal, visual-only, and audio-only presentations. These findings suggest that small pockets of urban nature (e.g., tree-lined streets, rooftop gardens) can offer greater psychological restoration than wild, untamed forests. In addition, high-quality nature sounds (e.g., birdsong, flowing water) can provide restorative benefits comparable to visual exposure when access to green views is limited. Such insights can inform urban planning strategies to design more restorative and liveable cities.

Correction to “Structurally Simple Osmium(II) Polypyridyl Complexes as Photosensitizers for Photodynamic Therapy in the Near Infrared”

High sub-bandgap response and fast switching enabled by thermal quenching in carbon-doped semi-insulating GaN

Carbon-doped GaN is a promising material for sub-bandgap triggered optical switches. When incorporated in GaN, carbon introduces deep compensating centers that enable defect-mediated extrinsic photoconductivity. Here, we investigate the optical responsivity and switching kinetics of semi-insulating carbon-doped GaN actuated by sub-bandgap blue illumination. A high ON/OFF ratio exceeding 107 is achieved under low-irradiance 405-nm excitation. Temperature-dependent transient measurements reveal that the photocurrent decay is thermally quenched above a crossover temperature of ∼300 K. This behavior is attributed to hole-emission-assisted recombination. The extracted activation energies vary across samples; a commonly observed value of ∼0.83 eV is attributed to the CN defect. Notably, when heating above the crossover temperature, thermal quenching accelerates the photocurrent decay by up to a factor of five, enabling significantly faster switching.

Editorial Note: Subglacial Lake Vostok (Antarctica) Accretion Ice contains a diverse set of sequences from aquatic, marine and sediment-inhabiting Bacteria and Eukarya

Investigation of origin of polycrystalline defect in homoepitaxial (01¯1¯) <b> <i>β</i> </b> -Ga2O3 layers grown by halide vapor phase epitaxy using synchrotron x-ray topography and energy-dispersive x-ray spectroscopy

We demonstrate that (01¯1¯) [or (011)] β-Ga2O3 is a promising orientation for halide vapor phase epitaxy (HVPE) homoepitaxial growth for realization of thick epitaxial layers with low donor concentration. Mercury capacitance–voltage measurements indicate a net donor concentration in the range of 4 × 1014–2 × 1015 cm−3, which is suitable for high-power device applications. However, the presence of polycrystalline defects was confirmed over the entire as-grown HVPE surface, with a density of approximately 1.3 × 102 cm−2. X-ray topography measurements showed that the formation of these polycrystalline defects is not triggered by dislocations in the substrate. Optical microscopy observation confirmed the presence of cores within the polycrystalline defects near the epilayer/substrate interface. Additionally, cross-sectional energy-dispersive x-ray spectroscopy identified SiOx contaminations originating from the quartz of the chamber sidewall are the cause of the formation of these polycrystalline defects.

Revisiting the role of structural connectivity-based parcellation in thalamic nuclei segmentation: Benchmarking against recent state-of-the-art methods

Leveraging diffusion tractography, connectivity-based parcellation (CBP) is one of the oldest methods for thalamic nuclei segmentation. The goal of this work was to reassess CBP using higher spatial resolution diffusion MRI data and reconstruction algorithms, and to compare it with recent state-of-the-art methods for thalamic nuclei segmentation. Furthermore, these methods were systematically evaluated against three histological atlases and one functional MRI–based atlas to examine their relative anatomical similarities and differences. High resolution diffusion and T1-weighted MRI data from 67 healthy individuals in the Human Connectome Project Young Adult database were analyzed. CBP was performed using probabilistic tractography with cortical targets derived from combining labels of the Human Connectome Project Multi-Modal Parcellation 1.0 atlas into 8, 11, and 23 regions. Results were compared against three recent methods: orientation distribution function clustering (ODF), track density imaging (TDI), and structural MRI-based segmentation. Group level analyses were conducted in the Montreal Neurological Institute space, and Dice overlap coefficients were calculated using four atlases (three histological, one functional). CBP results using newer data and methods were still remarkably similar to the original CBP parcellation results. Across atlases, a consistent hierarchy was observed: HIPS-THOMAS performed best, followed by TDI, ODF, and CBP (Kendall’s W = 1.00, p = 0.007). Histological atlases showed strong mutual agreement (Pearson r  = 0.71–0.85), whereas the Zhang atlas demonstrated lower concordance (Pearson r  = 0.51–0.63). Despite methodological advances, CBP remains constrained in its ability to delineate thalamic nuclei with histological accuracy. By contrast, structural and diffusion microstructural approaches provided better nuclear localization. These findings highlight the need for hybrid workflows that integrate structural and diffusion-based information to enable more reliable thalamic segmentation for neuroscience research.

Characterization of trap dynamics via transient response in amorphous InGaZnO thin-film transistors

In this paper, the transient behavior of amorphous InGaZnO thin-film transistors is quantitatively investigated to clarify the charge trapping dynamics limiting high-speed operation. The transient drain current response is characterized by varying the gate pulse duration (tp) and the operating temperature (T). A power law-based model is employed to extract key parameters (αJT0,i, QT,i, and ni), revealing two temporal regimes separated at to ≈ 7 × 10−3 s. The fast regime (R1) is governed by tunneling-mediated electron capture into shallow traps, whereas the slow regime (R2) originates from thermally assisted transport into deeper traps under electrostatic coupling to accumulated trapped charge. A clear transition in R2 response occurs near T ≈ 333 K. Activation energy (Ea) analysis yields Ea ≈ 0 eV in R1 and Ea = 0.2–0.4 eV in R2 for low T, indicating a transition from tunneling to hopping conduction. These results provide a compact framework for separating fast/slow trapping and optimizing oxide thin-film transistor operation.

From global to local: Developing a context-specific BeSD-HPV tool through cultural and linguistic adaptation in Pakistan

Objectives A key challenge in preventing cervical cancer is the low uptake of the Human Papillomavirus (HPV) vaccine in low and middle-income countries (LMICs). Evidence indicates that, in addition to logistical and structural issues, this is often influenced by sociocultural factors. The objective of this study was to develop a culturally adapted Behavioral and Social Drivers (BeSD) of HPV vaccination framework that is linguistically appropriate, contextually grounded, and culturally sensitive, to evaluate the social, behavioral, and cultural factors influencing HPV vaccination in Pakistan. Methods This descriptive qualitative survey was conducted across several districts in Punjab, Pakistan, from February to August 2025. Study participants included adolescent girls, parents/guardians, healthcare providers, community workers, teachers, school administrators, and religious scholars. Results Data were analyzed using Braun and Clarke’s six-step thematic analysis with deductive and inductive coding. Deductive codes aligned with existing WHO BeSD domains, while inductive analysis revealed a new domain: Cultural Integration. Themes and subthemes were mapped to specific BeSD constructs, illustrated with participant quotes and rationales. The tool was subsequently translated into Urdu by a bilingual expert to ensure linguistic appropriateness. Table cell colors correspond to the WHO BeSD domains (Thinking and Feeling, Social Processes, Motivation, Practical Issues) and the emergent theme, Cultural Integration. Conclusion The culturally adapted BeSD-HPV tool provides a methodological framework for contextualizing global health models. It underscores the need for culturally informed, community-driven strategies to ensure the successful rollout of HPV vaccination in Pakistan and other LMICs.

Toward enhanced photocatalysis: High-mobility two-dimensional polar heterojunctions for water splitting

The efficiency of overall water splitting is often hampered by the bandgap constraint of photocatalysts, restricting solar energy harvesting. To address this issue, two-dimensional (2D) polar materials offer a distinct advantage: their intrinsic internal electric field induces energy level bending, effectively extending the light absorption spectrum. Using first-principles calculations, we systematically evaluate the photocatalytic performance of 25 MXYN4/MXYN4 (M = Mo, W; X, Y = Si, Ge) van der Waals heterojunctions (vdWHs) as a model system for polar heterostructures. These vdWHs exhibit superior electronic properties, such as suitable band alignments, high carrier mobility, and strong light-harvesting capability. Meanwhile, a pronounced intrinsic electric field is generated, driven by considerable interfacial charge transfer between the constituent MXYN4 monolayers. This synergistic effect enhances the spatial separation of charge carriers and suppresses their recombination, thereby facilitating efficient photocatalysis. Among the 25 polar heterojunctions, 20 are spontaneously active for the hydrogen evolution reaction (HER) and 13 for the oxygen evolution reaction (OER) under illumination. Remarkably, the polar vdWHs show markedly superior HER activity under acidic conditions and significantly boosted OER performance in alkaline environments. These findings underscore the potential of 2D polar vdWHs for high-performance photocatalysis.