Search Results (117)

A comprehensive beyond density functional theory study of the structural, energetic, and electronic properties of the technologically most relevant SiC polytypes 3C, 2H, 4H, and 6H-SiC, together with the single Shockley-type stacking fault (1SSF or 31SSF) in 4H-SiC, was conducted. Lattice constants computed at the PBEsol and HSE06 level match experimental values within 0.1% accuracy. Total energies evaluated at the random-phase approximation level yield a physically consistent hierarchy of polytypes with 3C-SiC as the most stable phase, which is in agreement with low-temperature experimental results. Quasiparticle band gaps computed with both the single-shot G0W0@PBE and the partially self-consistent GW0@PBE formulations quantitatively match well with the experimental values. The band structure of 31SSF reveals fault-induced sub-gap band splitting at the M point of 0.21 eV at the GGA level, which increases to 0.28 eV upon G0W0 correction. To our knowledge, this provides the first GW-level treatment of the 31SSF electronic structure in 4H-SiC. These results collectively provide a many-body perturbation theory (MBPT) level reference dataset for SiC polytypes and the commonly found stacking fault in 4H-SiC. Full article

Nova eruptions exhibit diverse photometric and spectroscopic properties traditionally classified using empirical light-curve morphology and spectral taxonomy. However, these observational classifications do not uniquely constrain the underlying eruption physics. This review examines the coupling between light-curve evolution, spectral development, ejecta dynamics, and multi-wavelength emission in classical and recurrent novae, with particular emphasis on the role of shocks and multi-phase outflows. Recent observations across optical, radio, X-ray, and gamma-ray wavelengths demonstrate that nova ejecta are intrinsically structured, anisotropic, and dynamically interacting systems, challenging the traditional interpretation of novae as spherically symmetric thermonuclear explosions. We synthesise observational and theoretical studies that link decline timescales, spectral transitions, expansion velocities, and high-energy emission to fundamental physical parameters, including white dwarf mass, accretion rate, ejecta geometry, and shock energetics. Using a compiled multi-parameter dataset of classical, recurrent, and symbiotic novae, we demonstrate that many commonly used observational diagnostics are intrinsically degenerate, with similar observable properties arising from different physical conditions. We argue that nova diversity is better understood within a continuous multi-dimensional parameter space rather than through purely empirical classifications. The implications of this framework for mass retention efficiency and the evolution of recurrent novae toward Type Ia supernova progenitors are discussed. Finally, we outline a predictive observational framework integrating photometric, spectroscopic, and high-energy diagnostics for future nova studies. Full article

The electrocatalytic reduction of CO₂ (CO₂RR) into value-added chemicals represents a promising strategy for achieving carbon-neutral energy conversion. However, it is fundamentally limited by sluggish reaction kinetics, insufficient product selectivity, and the competitive hydrogen evolution reaction (HER). Herein, density functional theory (DFT) calculations were employed to systematically investigate transition-metal single-atom catalysts anchored on boron and nitrogen co-doped graphene (TM@BNG), with the aim of elucidating the role of heteroatom-induced coordination engineering in modulating catalytic performance. The results demonstrate that B, N co-doping effectively tailors the electronic structure of the metal active sites, thereby optimizing the adsorption energetics of key intermediates and dictating the reaction pathways. Among the 27 candidates examined, Pd@BNG, Ag@BNG, Sc@BNG, Cu@BNG, Co@BNG, Cd@BNG, and Y@BNG exhibit superior catalytic activity and selectivity toward CO or HCOOH production, featuring low limiting potentials down to −0.06 V while simultaneously suppressing HER. Mechanistic analysis reveals that product selectivity is governed by the relative stabilization of *COOH and *HCOO intermediates during the initial proton-coupled electron transfer step. Furthermore, a physically interpretable descriptor (φ), derived from intrinsic electronic properties using machine-learning approaches, establishes a volcano-type correlation with the limiting potential and provides an effective activity-screening criterion within the investigated TM@BNG dataset. Collectively, these findings clarify the electronic-structure modulation of TM@BNG single-atom catalysts and provide a system-specific framework for screening related B/N-coordinated CO₂RR electrocatalysts. Full article

The Oxygen Evolution Reaction (OER) is the bottleneck in the water splitting reaction since it involves four intermediate steps, constituting the adsorption–desorption of oxygen-based radical groups, and not all of them are energetically favorable. Rapidly growing research interest is focusing on carbon-based materials as novel, highly active and durable non-precious electrocatalysts for the OER, representing a valuable alternative to precious and rare materials with electrochemical properties tuned by defect creation. In this work, we propose a facile and green methodology based on the modification of graphene oxide by laser irradiation to obtain an alternative OER catalyst. GO flakes were chemically and physically modified using pulsed laser irradiation at $532\mathrm{nm}$ with fluences of $1.5\mathrm{J}/{\mathrm{cm}}^2$ and $2.5\mathrm{J}/{\mathrm{cm}}^2$. Different analyses were carried out to correlate the electrochemical performance with the structural, optical, and morphological properties; after that, we correlated the improvements in the OER with respect to the pristine GO with the increase in OH functional groups obtained by laser treatment. The best-performing sample exhibited an overpotential of $380\mathrm{mV}$, comparable to that of catalysts reported in the literature but with the advantage of not being a precious or rare material. Full article

High-synchrotron-peaked (HSP) BL Lac objects are extreme particle accelerators whose synchrotron emission peaks at high frequencies, typically in the UV-to-X-ray band (${\nu }_{\mathrm{peak}}>{10}^{15}$ Hz; ${\nu }_{\mathrm{peak}}\ge {10}^{17}$ for EHSPs), implying electron Lorentz factors of order ${10}^5$–${10}^6$. Their relative proximity ($z\lesssim 0.5$), clean radiation environments, and favorable Hillas parameters make them prime candidates for ultra-high-energy cosmic ray (UHECR) acceleration beyond ${10}^{19}$ eV and for neutrino production above 100 TeV. The 2017 association of IceCube-170922A with the flaring blazar TXS 0506+056 provided compelling evidence for blazars as neutrino sources, while an archival neutrino flare from 2014–2015 with no clear electromagnetic counterpart (13 events) revealed additional complexity in the emission mechanism. This review examines HSP physical properties, identifies them through WISE-based infrared selection (the 2WHSP and 3HSP catalogs, ∼2000 sources), and contrasts leptonic synchrotron self-Compton models with hadronic alternatives. We assess the observational evidence linking HSPs to high-energy neutrinos and UHECRs, finding that extreme baryonic loading ($L_p/L_e\sim {10}^3$–${10}^5$) strains energetic budgets, Auger composition measurements favor heavy nuclei over proton-dominated scenarios, and the near-isotropy of UHECR arrival directions is difficult to reconcile with rare beamed sources. Potential resolutions involving magnetic reconnection, structured jets, and duty cycle effects are discussed. Next-generation facilities, including IceCube-Gen2, KM3NeT, CTAO, IXPE, and AugerPrime/TA × 4, will probe key observables to either establish HSP BL Lacs as sources of the highest-energy cosmic particles or redirect the search toward alternative accelerator classes. Full article

In this study, the feasibility of electrospraying as an alternative processing technique for the preparation of composite solid rocket propellants (SRPs) was investigated. The main objective was to improve microstructural homogeneity and interfacial contact between the oxidizer, energetic additive, and metallic fuel without altering the chemical composition of the formulation. Additionally, porous electrosprayed SRP formulations were prepared to examine the influence of controlled porosity on thermal decomposition behavior. The prepared materials were characterized using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM/EDS) to assess microstructural features and component distribution. Thermal decomposition behavior and kinetic parameters were evaluated using simultaneous DSC/TG analysis conducted at multiple heating rates. Safety-related properties were assessed through friction sensitivity testing, while post-decomposition solid residues were analyzed using SEM/EDS and X-ray diffraction. The results show that electrospraying improves structural homogeneity, reduces solid residue formation after thermal decomposition, and decreases apparent activation energy, while maintaining unchanged friction sensitivity. These findings demonstrate the potential of electrospraying as a physical processing route for tailoring the microstructure and thermal behavior of composite solid rocket propellants. Full article

This study experimentally demonstrates that a bentonite–vermiculite composite (1:2 mass ratio) is the most effective formulation for the treatment of crude oil–contaminated wastewater. The sorbents were characterized using XRD, SEM/EDS, ζ-potential, DLS, and TGA/DSC to evaluate their structural, surface, and adsorption-related properties. Kinetic analysis showed that the adsorption process followed the pseudo-second-order (PSO) model (R² = 0.96–0.99), suggesting that surface interactions and intraparticle diffusion within the layered composite governed the overall adsorption rate. Thermodynamic analysis revealed negative Gibbs free energy values (ΔG < 0) and a moderately positive enthalpy change (ΔH ≈ 26 kJ·mol⁻¹), confirming that adsorption is spontaneous and endothermic, with contributions from physical interactions, ion exchange, and hydrophobic effects. After adsorption, the ζ-potential shifted toward less negative values, indicating partial surface charge neutralization by hydrocarbon species. TGA/DSC data further confirmed strong oil retention and preserved structural stability of the sorbents, while the DSC-derived enthalpy increased from 2.0 kJ·g⁻¹ to 141.6 kJ·g⁻¹ after hydrocarbon uptake, indicating pronounced energetic effects associated with sorbate incorporation. Techno-economic evaluation under industrially relevant conditions (Q = 120,000 L·h⁻¹; C₀ = 392 mg·L⁻¹) showed effective oil removal to residual concentrations below regulatory discharge limits at a low treatment cost. Full article

Research shows that neurodegenerative processes do not develop from a single “broken” biochemistry process; rather, they develop when a complex multi-physics environment gradually loses its ability to stabilize the neuron via a collective action between the protein, ion, field and fluid dynamics of the neuron. The use of new technologies such as quantum-informed molecular simulation (QIMS), dielectric nanoscale mapping, fluid dynamics of the cell, and imaging of perivascular flow are allowing researchers to understand how the collective interactions among proteins, membranes and their electrical properties, along with fluid dynamics within the cell, form a highly interconnected dynamic system. These systems require fine control over the energetic, mechanical and electrical interactions that maintain their coherence. When there is even a small change in the protein conformations, the electric properties of the membrane, or the viscosity of the cell’s interior, it can cause changes in the high dimensional space in which the system operates to lose some of its stabilizing curvature and become prone to instability well before structural pathologies become apparent. AI has allowed researchers to create digital twin models using combined physical data from multiple scales and to predict the trajectory of the neural system toward instability by identifying signs of early deformation. Preliminary studies suggest that deviations in the ergodicity of metabolic–mechanical systems, contraction of dissipative bandwidth, and fragmentation of attractor basins could be indicators of vulnerability. This study will attempt to combine all of the current research into a cohesive view of the role of progressive loss of multi-physics coherence in neurodegenerative disease. Through integration of protein energetics, electrodynamic drift, and hydrodynamic irregularities, as well as predictive modeling utilizing AI, the authors will provide mechanistic insights and discuss potential approaches to early detection, targeted stabilization, and precision-guided interventions based on neurophysics. Full article

Nano-aluminum (nAl), characterized by its high combustion enthalpy and enhanced reactivity, serves as a critical component in advanced energetic materials like solid propellants and micro-ignition devices. However, the atomic-scale mechanisms governing its core–shell structure evolution, oxidation dynamics, and interfacial interactions remain elusive to experimental probes due to spatiotemporal limitations. Molecular dynamics (MD) simulations, particularly the synergistic use of a ReaxFF reactive force field (for large-scale systems) and ab initio MD (for electronic-level accuracy), have emerged as a powerful tool to overcome this barrier. This review systematically delineates the oxidation mechanisms and core–shell structure regulation of nAl, with a focus on the multi-scale simulation paradigm integrating DFT, AIMD, and ReaxFF MD that directly supports nAl research. It critically examines the pivotal role of MD simulations in guiding the surface modification of nAl, elucidating combustion mechanisms at the atomic level, and designing interfaces in energetic composite systems. By synthesizing recent advances (2022–2025), this study establishes a clear structure–property relationship between microscopic features and macroscopic performance of nAl. Furthermore, it identifies prevailing challenges, including simulations under multi-physics loading, multi-scale bridging, and quantitative experiment-simulation validation that specifically affect nAl-based energetic systems. Finally, future research directions are prospected, encompassing the development of machine learning-empowered force fields tailored for nAl systems, multi-scale and multi-field coupling simulation frameworks targeting nAl applications, and closed-loop experiment-simulation systems for nAl-based energetic materials. This review aims to provide fundamental insights and a technical framework for the rational design and engineering application of nAl-based energetic materials in fields such as aerospace propulsion. Full article

Supernovae (SNe) are among the most energetic and transient events in the universe, offering crucial insights into stellar evolution, nucleosynthesis, and cosmic expansion. Optical observations have historically played a central role in the discovery, classification, and physical interpretation of SNe. In this review, we summarize recent progress in the optical study of SNe, with a focus on advancements in time-domain surveys and photometric and spectroscopic follow-up strategies. High-cadence optical monitoring is pivotal in capturing the diverse behaviors of SNe, from early-time emission to late-phase decline. Leveraging data from ARIES telescopes and national/international collaborations, we systematically investigate various SN types, including Type Iax, IIP/L, IIb, IIn/Ibn and Ib/c events. Our analysis includes light curve evolution and spectral diagnostics, providing insights into early emission signatures (e.g., shock breakout), progenitor systems, explosion mechanisms, and circumstellar medium (CSM) interactions. Through detailed case studies, we demonstrate the importance of both early-time and nebular-phase observations in constraining progenitor and CSM properties. This comprehensive approach underscores the importance of coordinated global efforts in time-domain astronomy to deepen our understanding of SN diversity. We conclude by discussing the challenges and opportunities for future optical studies in the era of wide-field observatories such as the Vera C. Rubin Observatory (hereafter Rubin), with an emphasis on detection strategies, automation, and rapid-response capabilities. Full article

New compostable materials have been developed to replace single-use soft materials such as polyurethane foams (PUR). To this end, eco-friendly systems have been formulated on the basis of agar gels prepared in mixed solvent (glycerol/water) to meet specifications, i.e., stiffness of several hundred kPa, reasonable extensibility, and good stability when exposed to open air. While the addition of glycerol slows down gelation kinetics, mechanical properties are improved up to a glycerol content of 80 wt%, with enhanced extensibility of the gels while maintaining high Young’s moduli. Swelling analyses of mixed gels, in water or pure glycerol, demonstrate the preservation of an energetic network, with no change in volume, in pure water and the transition towards an entropic network in glycerol related to the partial dissociation of helix bundles. Dimensional and mechanical analysis of gels aged in an open atmosphere at room temperature shows that the hygroscopic character of glycerol enables sufficient water retention to maintain the physical network, with antagonistic effects linked to relative increases in glycerol, which tends to weaken the network, and agar, which on the contrary strengthens it. Complementary analyses carried out on aged agar gels formulated with an initial glycerol/water mass composition of 60/40, the most suitable for the targeted development, enabled the comparison of the properties of agar gels favorably with those of PURs and verified their stability during long-term storage, as well as their non-toxicity and compostability. Full article

Nanothermites are widely applied as specific power sources for microscale initiators and pyrotechnics. Increasing the charge density enhances energy storage within a confined combustion chamber, but it also alters the reaction kinetics. To systemically explore this phenomenon, the combustion and pressurization characteristics of electrosprayed nanothermite-based hybrid energetic materials (THEMs) with different metallic oxides (Fe₂O₃, CuO, and Bi₂O₃) and various energetic additives (nitrocellulose (NC), octogen (HMX), ammonium perchlorate (AP), and hexanitrohexaazaisowurtzitane (CL-20)) across various loading densities were tested. The results showed that increasing the loading density decreased the porosity of the loaded nanothermites and then rapidly decreased the convective heat transfer efficiency during the combustion propagation process. When the loading density exceeded a critical value, a dramatic decrease in the peak pressure, several orders-of-magnitude decrease in the pressurization rate, and an order-of-magnitude increase in the combustion duration occurred. Due to the dual effects of the porous microstructure on heat and mass transfer, the critical density of both the electrosprayed Al/CuO/NC/CL-20 composites and their physically mixed counterparts is between 37.9 and 43.9% theoretical maximum density (TMD). Because of the different synergistic catalytic effects, the fast reactivity at the high-loading-density maintaining capacity of the applied additives was AP > HMX ≈ CL-20 > NC. Owing to their intrinsic properties of low ignition temperature and high gas yield, the Bi₂O₃-THEMs could maintain high-speed reactivity even at 59.7% TMD. These results provide valuable insights into the rational design and tailoring of the reactivity of nanothermites for specific applications. Full article

The China Seismo Electromagnetic Satellite (CSES) mission provides in situ measurements of the electromagnetic field, plasma, and charged particles in the topside ionosphere. Each CSES spacecraft carries several different scientific payloads delivering a wealth of information about the ionospheric plasma dynamics and properties, as well as measurement about energetic particles precipitating in the ionosphere. In this work, we introduce CSESpy, a Python package designed to provide an interface to CSES data products, with the aim of easing the pathway for scientists to carry out analyses of CSES data. Beyond simply being an interface to the data, CSESpy aims to provide higher-level analysis and visualization tools, as well as methods for combining concurrent measurements from different instruments, so as to allow multipayload studies in a unified framework. Moreover, CSESpy is designed to be highly flexible as such, it can be extended to interface with datasets from other sources and can be embedded in wider software ecosystems. We highlight some applications, also demonstrating that CSESpy is a powerful visualization tool for investigating complex events involving variations across multiple physical observables. Full article

The oscillatory properties of pendular motion, along with the associated energetic conditions, are used to induce analytical functions capable of simultaneously describing the angular position and velocity. To describe the angular position of a generic pendulum, for very large amplitudes of oscillation, we used the numerical solutions obtained from the numerical resolution of the differential equation of motion. The solver software needed was built using the LabView 2019 platform, but any other ODE solver containing peak and valley detectors can be used. The fitting software and plots were performed with the ORIGIN 7.0 program, but also other equivalent programs can be used. For a non-damped pendulum, an analytical model is proposed, built from simple trigonometric functions, but containing the important physical information of the dependence between the period and amplitude of oscillation. The application of the proposed model, using the numerical solutions of the non-approximated differential equation of motion, shows very good agreement, less than 0.01%, for large amplitudes, up to 3π/4. Full article

Considering previous studies on the high-pressure phases and compressibility of Ba–Au alloys with stoichiometries Au₂Ba, AuBa, and Au₂Ba₃, the concentration of the alkaline-earth metal Ba increased, and a particle-swarm optimization algorithm was employed to conduct comprehensive structure searches for the Ba₄Au compound at 0, 10, 20, and 50 GPa. First-principles calculations were subsequently carried out to investigate its structural evolution and electronic properties under compression. Enthalpy-difference calculations indicate that the I4/mmm phase of Ba₄Au transforms to the Cmmm phase at approximately 0.4 GPa. As pressure increases above 5.7 GPa, the I4/m structure becomes energetically more favorable than Cmmm-Ba₄Au, indicating that the Cmmm phase transforms to the I4/m phase at 5.7 GPa. Both phase transitions are first-order and accompanied by discernible volume collapses. Additionally, a comparative analysis of the electronic properties of Ba₄Au was performed before and after the phase transitions. In this study, theoretical guidance is provided for the exploration of the high-pressure structural evolution of Ba₄Au, and critical insights are offered regarding the changes that occur in its physical and chemical properties under compression. Full article