We study axial gravitational perturbations of the neutral regular black hole generated by a non-local, T-duality-inspired zero-point length and the associated gravitational self-energy. In this geometry, the usual point source is replaced by a regular core, and the zero-point length controls the departure from the Schwarzschild limit. We compute the fundamental quasinormal modes and several overtones with high-order WKB-Pad & eacute; methods, and we check the dominant mode with a direct time-domain evolution. When the zero-point length is turned on, the real parts of the ADM-scaled frequencies increase for the gravitational modes with l = 2, 3, 4, so the ringdown oscillates faster than in the Schwarzschild limit. The damping rates change more mildly: they first grow slightly and then decrease near the largest deformation values considered here. This behavior is consistent with the effective potential, whose barrier becomes higher as the deformation parameter increases. We also compute the corresponding excitation factors and find that their magnitudes vary much less strongly than the quasinormal frequencies.
Hydrogen peroxide (H2O2) is an eco-friendly oxidant widely used in clean synthesis, water treatment, and energy conversion. Graphitic carbon nitride (g-C3N4) has been explored as a photocatalyst for sustainable H2O2 production, but achieving high selectivity in pure water remains challenging. Here, a controllable vacancy-engineering strategy is developed to introduce nitrogen (NV) and carbon vacancies (CV) into g-C3N4 via alkali-assisted thermal treatment. The optimized CV-g-C3N4 and NV-g-C3N4 achieve remarkable H2O2 selectivity in the pure water increasing from 49.7% to 81.2% and 87.5%, with a surface-area-normalized H2O2 production rate of 65.3 μmol/(L·m2·h). Vacancies reshape the electronic structure by introducing defect states and shifting the N-2p p-band center upward. NV generates shallow defect states that promote electron delocalization, favor end-on O2 adsorption and lower the Gibbs free energies for *OOH formation, thereby promoting selective two-electron oxygen reduction reaction (2e– ORR). In contrast, CV forms deeper defect states that strengthen H2O adsorption and reduce the Gibbs free energies for *OH formation, enabling a coupled 2e– ORR and two-electron water oxidation reaction (2e– WOR) pathway. This study elucidates the distinct redox roles of Nv and CV in photocatalysis and provides a vacancy-engineering blueprint for designing efficient, metal-free photocatalysts toward sustainable H2O2 generation.
The chemical composition of Mg-based welding wires plays a decisive role in determining the microstructure and mechanical properties of wire arc additive-manufactured (WAAM) components. Herein, an innovative CO2 -induced wire fabrication strategy was proposed to achieve the in-situ synthesis of T2-Al2 MgC2 phase within the AZ91D Mg-based alloy. The fine T2-Al2 MgC2 phase was synthesized through the insitu reaction between CO2 and AZ91D Mg-based alloy, after which Mg-based welding wires were prepared through hot extrusion and used for WAAM of thin-walled structures. Microstructural evolution, mechanical properties, and the refinement mechanism of the T2-Al2 MgC2 phase during the WAAM process were investigated. The as-built WAAM components were characterized by a predominantly equiaxed microstructure and an average grain size of approximately 14.7 & micro;m. Grain refinement was attributed to the orientation relationship (0 0 01) T2 -Al2 Mg C2 //(0 0 01)alpha- Mg , which enabled T2-Al2 MgC2 to act as effective heterogeneous nuclei for alpha-Mg. MgO nanoparticles were synchronously formed to impede grain-boundary migration and suppress the coarsening of the B-Mg17 Al12 . The horizontal direction of the components exhibited an ultimate tensile strength of 320.6 MPa and an elongation of 9.2 %, while the vertical direction showed corresponding values of 269.2 MPa and 6.8 %, respectively. Furthermore, the components exhibited pronounced quasi-cleavage fracture characteristics. This work provides a new pathway for developing high-performance Mg-based welding wires suitable for the WAAM process. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
Nickel manganese spinel ferrites (Ni0.3Mn0.7CexFe2−xO4, x = 0.0, 0.01, 0.02, and 0.03) with substitution of cerium (Ce) were synthesized by a hydrothermal technique and investigated to determine how the substitution of Ce affected the physical properties of the material samples. The samples were characterized by various techniques including X-ray diffraction (XRD) to observe the structure of the prepared material, scanning electron microscopy (SEM) to study the morphology, and Fourier transform infrared (FTIR) spectroscopy to determine the bands within the samples. Additionally, vibrating-sample magnetometry (VSM) was applied to investigate the magnetic characteristics including remanent magnetization (Mr), saturation magnetization (Ms), and coercivity (Hc). The material was found to have a face-centered cubic (FCC), single-phase structure, confirmed by XRD. An increase in cerium concentration resulted in an increase in the lattice constant from 8.36 Å to 8.61 Å. SEM images showed agglomeration of the nanoparticles, which varied in size. The FTIR spectrum showed that light was absorbed at wavelengths of 500–4000 cm−1. It was found that the band shifted toward a higher frequency when cerium content was added to the pure nickel manganese ferrites. As the scan rate increased, the specific capacitance decreased, and the loop area increased. The suitability of the synthesized material for use as an anode in storage devices was investigated via cyclic voltammetry (CV). The prepared samples were found to have specific capacitance of 578–892 F g−1, estimated through galvanostatic charge–discharge (GCD) and CV measurements.
We construct an analytic geodesic-optics description of quasinormal ringing, black-hole shadows, strong lensing, and grey-body factors for the static spherical metric introduced in Bakopoulos et al. (2024). Working in a weak-hair regime, we derive closed first-order formulas for the photon-sphere radius, orbital frequency, and Lyapunov exponent. These invariants are then employed within the Schutz-Will WKB approach to obtain eikonal quasinormal frequencies, mapped to shadow and strong-deflection observables through exact identities for static spherical geometries, and used to build a closed analytic form for the transmission probability. At leading eikonal order, these relations are controlled by null geodesics and are therefore spin-universal for test scalar/electromagnetic/gravitational sectors, up to subleading corrections. Besides the standard ringdown-shadow correspondence, we present three additional results: (i) an explicit quality-factor correction, (ii) limiting core-size expansions that show when damping ratios are nearly insensitive to the scalarized core, and (iii) a comparative study of grey-body factors for moderate multipoles and several core-size ratios. The resulting construction provides a concise one-parameter connection from the metric function to ringdown, lensing, and scattering observables.
