In this study, a composite catalytic layer (CL) featuring multiple bubble nucleation sites was constructed by two-step electrodeposition and phosphorus doping to regulate bubble behavior on the electrode surface during oxygen evolution reaction (OER). Firstly, the porous nickel framework layer constructed in the first electrodeposition provided ample anchoring sites for nickel-iron layered double hydroxide precursors in the second electrodeposition, thereby increasing the loading and accessibility of active species. Secondly, the resulting CL exhibited an abundant microporous structure. On one hand, this structure was expected to enhance capillary-driven electrolyte infiltration into the CL pores, which could improve electrolyte contact with active sites, increase site exposure, and enable efficient electrolyte renewal. On the other hand, the high tortuosity of the CL may create a spatial confinement effect on dissolved oxygen (DO), slowing DO diffusion into the bulk solution during OER. This could favor local DO accumulation near the electrode surface, providing a possible condition for bubble formation. Additionally, the porous structure with ample exposed edges and defects forms discontinuous "gas-liquid-solid" three-phase interfaces, which are likely to provide favorable interfacial regions for bubble formation, weaken bubble retention, and facilitate gas release. Finally, Ni2P and Fe2P heterojunctions formed by phosphorus doping enhanced CL conductivity and facilitated electron transport during OER. Ultimately, the optimized NiFeP@NF-skeleton exhibited overpotentials of 306 and 418 mV at 100 and 300 mA cm(-2), respectively, and showed acceptable operational durability under the tested conditions, outperforming the commercial IrO2-loaded electrode.
Here, for the first time, we have designed a dual-band metamaterial absorber based on the principle of terahertz absorption, using temperature-controlled vanadium dioxide (VO2) and externally pumped gallium arsenide (GaAs) to achieve logic function of a half-adder in the terahertz domain. On one hand, as the power of the external pump light increases, the conductivity of GaAs changes accordingly. On the other hand, due to the insulator-to-metal phase transition (IMT) characteristic of VO2, the conductivity of VO2 can be altered by temperature changes. By adjusting these two materials, we ultimately achieve tunability in the absorption spectrum. Using the states of VO2 and GaAs as the two inputs of the half-adder and encoding them, our designed half-adder can obtain the output results at 1.0214 THz and 1.9616 THz. We simulated and optimized the characteristics of the half-adder using the finite integration time domain (FITD) method and analyzed and compared the device's performance. The half-adder exhibits a maximum modulation depth (MD) of 98.10
Abstract The total solar eclipse on 8 April 2024 provided a unique opportunity to investigate the three‐dimensional (3‐D) ionospheric response under enhanced solar activity over North America. In this study, we processed high‐density GNSS observations from ∼1,700 stations to derive vertical total electron content and applied a multi‐term sinusoidal detrending algorithm to extract differential TEC disturbances. A compressed sensing (CS)‐based tomography framework, incorporating a singular value decomposition‐derived dictionary, was employed to reconstruct 3‐D electron density (Ne) distributions with high spatial and temporal resolution. The results reveal pronounced altitude‐dependent electron density depletion, with maximum reductions in the F2 region (200–300 km) exceeding 2 × 1011 el/m3. The depletion exhibited clear longitudinal and latitudinal propagation, with recovery times increasing eastward, highlighting strong horizontal‐vertical coupling. Post‐eclipse enhancements and a secondary depletion on 9 April were characterized with finer spatial detail than previous studies, and traveling ionospheric disturbances were quantified, revealing anisotropic zonal (1304 km, 0.81 km/s) and meridional (571 km, 0.42 km/s) propagation. Comparative analysis with the 2017 eclipse demonstrates that near‐solar‐maximum conditions led to deeper depletions and prolonged recovery. These findings advance understanding of multi‐scale eclipse‐induced ionospheric dynamics, provide robust 3‐D characterization of electron density evolution, and underscore the critical role of dense GNSS networks combined with CS tomography for resolving rapidly evolving ionospheric disturbances.
The rapid development of recombinase polymerase amplification (RPA) has driven a growing demand for UvsX, the key DNA recombinase for this technique. During bioreactor cultivation for UvsX production in Escherichia coli, biomass and substrate are critical factors affecting its efficient expression. However, the real-time monitoring techniques for these parameters remain immature, leading to delayed process control, hindering stable high-level production and precise process optimization. Using an online Raman spectrometer, this study developed synchronous quantitative prediction models for critical process parameters by partial least squares (PLS). Robust multivariate regression models showed strong correlations between predicted and measured values for biomass (R2 = 0.994), glucose (R2 = 0.979), UvsX (R2 = 0.989), and total product (R2 = 0.983). Based on these predictive models, the study implemented online monitoring and feedback control of critical fermentation parameters, successfully raising UvsX and total product titer to 8.23 g/L and 9.17 g/L, representing increases of 33.17
Multi-wing hyperchaotic systems with large Lyapunov exponents and controllable topological structures are more useful in practical applications. This paper proposes a novel four-dimensional hyperchaotic system that generates multi-wing attractors through a hierarchical harmonic modulation mechanism. A nonlinear hierarchical harmonic modulation controller is designed to generate multi-wing attractors with adjustable wing counts by varying the number and distribution of equilibrium points. The proposed system exhibits robust hyperchaotic characteristics with two positive Lyapunov exponents, and the largest Lyapunov exponent is substantially elevated due to the enhanced nonlinearity and additional dimension introduced by the modulation mechanism. Furthermore, the integer-order system is extended to the fractional-order domain using the Caputo derivative. The 0-1 test confirms that the system exhibits strong chaotic behavior down to a fractional order of 0.88. Complexity analysis reveals that the Spectral Entropy of the proposed system significantly outperforms the original system. Finally, a DSP hardware implementation successfully captures the multi-wing hyperchaotic attractors, validating the scientific soundness and practical feasibility of the proposed model.
