Search Results (39)

We develop a fully gauge-invariant analysis of gravitational-wave polarizations in metric $f\left(R\right)$ gravity with a particular focus on the modified Starobinsky model $f\left(R\right)=R+\alpha R^2-2\mathsf{\Lambda }$, whose constant-curvature solution $R_d=4\mathsf{\Lambda }$ provides a natural de Sitter background for both early- and late-time cosmology. Linearizing the field equations around this background, we derive the Klein–Gordon equation for the curvature perturbation $\delta R$ and show that the scalar propagating mode acquires a mass $m_{\psi }^2=1/\left(6\alpha \right)$, highlighting how the same scalar degree of freedom governs inflationary dynamics at high curvature and the propagation of gravitational waves in the current accelerating Universe. Using the scalar–vector–tensor decomposition and a decomposition of the perturbed Ricci tensor, we obtain a set of fully gauge-invariant propagation equations that isolate the contributions of the scalar, vector, and tensor modes in the presence of matter. We find that the tensor sector retains the two transverse–traceless polarizations of General Relativity, while the scalar sector contains an additional massive scalar propagating degree of freedom, which manifests through breathing and longitudinal tidal responses depending on the wave regime and detector frame. Through the geodesic deviation equation—computed both in a local Minkowski patch and in fully covariant de Sitter form—we independently recover the same polarization content and identify its tidal signatures. The resulting framework connects the extra scalar polarization to cosmological observables: the massive scalar propagating mode sets the range of the fifth force, influences the time evolution of gravitational potentials, and affects the propagation and dispersion of gravitational waves on cosmological scales. This provides a unified, gauge-invariant link between gravitational-wave phenomenology and the cosmological implications of metric $f\left(R\right)$ gravity. Full article

The construction of heterostructures has been recognized as an effective strategy for enhancing material activity and stability. Herein, a ternary heterojunction FeSe₂-BiSe₂-CoSe₂ was synthesized via a hydrothermal selenidation reaction. The significant electronegativity difference between Bi and Fe/Co triggers charge transfer within the FeSe₂-BiSe₂-CoSe₂ lattice. Furthermore, the abundant pore structure of FeSe₂-BiSe₂-CoSe₂ provides efficient pathways for electron diffusion, significantly enhancing the HER catalytic kinetics. Results demonstrate that FeSe₂-BiSe₂-CoSe₂ exhibits outstanding HER activity in both acidic and alkaline media. In 0.5 M H₂SO₄, it exhibits an overpotential of only 44 mV with a Tafel slope of 108 mV dec⁻¹. In 1 M KOH, the corresponding overpotential is 188 mV, with a Tafel slope of 45 mV dec⁻¹ at 10 mA cm⁻². This study constructs electron-rich active sites through electronic structure regulation, providing valuable insights for designing low-cost, high-performance transition metal selenide HER catalysts. Full article

Magnesium–sulfur (Mg-S) batteries represent a novel category of multivalent energy storage systems, characterised by enhanced theoretical energy density, material availability, and ecological compatibility. Notwithstanding these benefits, the practical implementation of this approach continues to be hindered by ongoing issues, such as polysulfide shuttle effects, slow Mg²⁺ transport, and significant interfacial instability. This study emphasises recent progress in utilising transition metal chalcogenides (TMCs) as cathode materials and modifiers to overcome these challenges. We assess the structural, electrical, and catalytic characteristics of TMCs such as MoS₂, CoSe₂, WS₂, and TiS₂, highlighting their contributions to improving redox kinetics, retaining polysulfides, and enabling reversible Mg²⁺ intercalation. The review synthesises results from experimental and theoretical studies to offer a thorough comprehension of structure–function interactions. Particular emphasis is placed on morphological engineering, modulation of electronic conductivity, and techniques for surface functionalisation. Furthermore, we examine insights from density functional theory (DFT) simulations that corroborate the observed enhancements in electrochemical performance and offer predictive direction for material optimisation. This paper delineates nascent opportunities in Artificial Intelligence (AI)-enhanced materials discovery and hybrid system design, proposing future trajectories to realise the potential of TMC-based Mg-S battery systems fully. Full article

Transition-metal dichalcogenides have emerged as promising non-noble-metal electrocatalysts for efficient hydrogen production through the hydrogen evolution reaction (HER). In this work, we fabricated the graphitic carbon nitride-decorated cobalt diselenide (gC₃N₄-CoSe₂) nanocomposites via the facile hydrothermal method. The prepared gC₃N₄-CoSe₂ nanocomposites displayed an interconnected and aggregated morphology of gC₃N₄-decorated CoSe₂ nanoparticles with offering large surface area of 82 m²/g. The gC₃N₄-CoSe₂ nanocomposites exhibited excellent HER activity with a low overpotential (141 mV) and tiny Tafel slope (62 mV/dec) with excellent durability for 100 h at 10 mA/cm² in an alkaline electrolyte. These outstanding HER performances of gC₃N₄-CoSe₂ can be ascribed to the synergistic interaction between the electrochemically active porous CoSe₂ nanoparticles and the highly conductive gC₃N₄ nanosheets. These results indicate that the gC₃N₄-CoSe₂ nanocomposites hold promising and efficient HER electrocatalysts for sustainable green hydrogen production. Full article

The canonical quantization of gravity in general relativity is greatly simplified by the artificial decomposition of space time into a 3 + 1 formalism. Such a simplification appears to come at the cost of general covariance. This quantization procedure requires tangential and perpendicular infinitesimal diffeomorphisms generated by the symmetry group under the Legendre transformation of the given action. This gauge generator, along with the fact that Weyl curvature scalars may act as “intrinsic coordinates” (or a dynamical reference frame) that depend only on the spatial metric ($g_{ab}$) and the conjugate momenta ($p^{cd}$), allows for an alternative approach to canonical quantization of gravity. In this paper, we present the tensorial solution of the set of Weyl scalars in terms of canonical phase-space variables. Full article

This paper focuses on the efficient fine-tuning of large language models within the federated learning framework. To address the performance bottlenecks caused by multi-source heterogeneity and structural inconsistency, a structure-aware federated fine-tuning method is proposed. The method incorporates a graph representation module (GRM) to model internal structural relationships within text and employs a segmentation mechanism (SM) to reconstruct and align semantic structures across inputs, thereby enhancing structural robustness and generalization under non-IID (non-Independent and Identically Distributed) settings. During training, the method ensures data locality and integrates structural pruning with gradient encryption (SPGE) strategies to balance privacy preservation and communication efficiency. Compared with representative federated fine-tuning baselines such as FedNLP and FedPrompt, the proposed method achieves consistent accuracy and F1-score improvements across multiple tasks. To evaluate the effectiveness of the proposed method, extensive comparative experiments are conducted across tasks of text classification, named entity recognition, and question answering, using multiple datasets with diverse structures and heterogeneity levels. Experimental results show that the proposed approach significantly outperforms existing federated fine-tuning strategies on most tasks, achieving higher performance while preserving privacy, and demonstrating strong practical applicability and generalization potential. Full article

In modern industrial control systems (ICSs), communication protocols such as Modbus TCP remain widely used due to their simplicity, interoperability, and real-time performance. However, these communication protocols (e.g., Modbus TCP) were originally designed without security considerations, lacking essential features such as encryption, integrity protection, and authentication. This exposes ICS deployments to severe security threats, including eavesdropping, command injection, and replay attacks, especially when operating over unsecured networks. To address these critical vulnerabilities while preserving the lightweight nature of the protocol, we propose a Modbus TCP security enhancement scheme that integrates ASCON, an NIST-standardized authenticated encryption algorithm, with the CBOR Object Signing and Encryption (COSE) framework. Our design embeds COSE_Encrypt0 structures into Modbus application data, enabling end-to-end confidentiality, integrity, and replay protection without altering the protocol’s semantics or timing behavior. We implement the proposed scheme in C and evaluate it in a simulated embedded environment representative of typical ICS devices. Experimental results show that the solution incurs minimal computational and memory overhead, while providing robust cryptographic guarantees. This work demonstrates a practical pathway for retrofitting legacy ICS protocols with modern lightweight cryptography, enhancing system resilience without compromising compatibility or performance. Full article

The exploration of high-performance, low-cost, and dual-function electrodes is crucial for anion exchange membrane water electrolysis (AEMWE) to meet the relentless demand for green H₂ production. In this study, a heteroatom-doped carbon-cage-supported CoSe₂@MoSe₂@NC catalyst with a formicarium structure has been fabricated using a scalable one-step selenization strategy. The component-refined bifunctional catalyst exhibited minimal overpotential values of 116 mV and 283 mV at 10 mA cm⁻² in 1 M KOH for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. Specifically, rationally designed heterostructures and flexible carbonaceous sponges facilitate interfacial reaction equalization, modulate local electronic distributions, and establish efficient electron transport pathways, thereby enhancing catalytic activity and durability. Furthermore, the assembled AEMWE based on the CoSe₂@MoSe₂@NC bifunctional catalysts can achieve a current density of 106 mA cm⁻² at 1.9 V and maintain a favorable durability after running for 100 h (a retention of 95%). This work highlights a new insight into the development of advanced bifunctional catalysts with enhanced activity and durability for AEMWE. Full article

This research introduces an original approach to time series forecasting through the use of multi-scale convolutional neural networks with Transformer modules. The objective is to focus on the limitations of short-term load forecasting in terms of complex spatio-temporal dependencies. The model begins with the convolutional layers, which perform feature extraction from the time series data to look for features with different temporal resolutions. The last step involves making use of the self-attention component of the Transformer block, which tries to find the long-range dependencies within the series. Also, a spatial attention layer is included to handle the interactions among the different samples. Equipped with these features, the model is able to make predictions. Experimental results show that this model performs better compared to the time series forecasting models in the literature. It is worth mentioning that the MSE score or mean square error of the model was 0.62, while the measure of fit R² was 0.91 in predicting the individual household electric power consumption dataset. The baseline models for this dataset such as the LSTM model had an MSE of 2.324 and R² value of 0.79, showing that the proposed model was significantly improved by a margin. Full article

Although lithium–sulfur batteries possess the advantage of high theoretical specific capacity, the inevitable shuttle effect of lithium polysulfides is still a difficult problem restricting its application. The design of highly active catalysts to promote the redox reaction during charge–discharge and thus reduce the existence time of lithium polysulfides in the electrolyte is the mainstream solution at present. In particular, bimetallic compounds can provide more active sites and exhibit better catalytic properties than single-component metal compounds by regulating the electronic structure of the catalysts. In this work, bimetallic compounds-nitrogen-doped carbon nanotubes (NiCo)Se₂-NCNT and (CuCo)Se₂-NCNT are designed by introducing Ni and Cu into CoSe₂, respectively. The (CuCo)Se₂-NCNT delivers an optimized adsorption–catalytic conversion for lithium polysulfide, benefitting from adjusted electron structure with downshifted d-band center and increased electron fill number of Co in (CuCo)Se₂ compared with that of (NiCo)Se₂. This endows (CuCo)Se₂ moderate adsorption strength for lithium polysulfides and better catalytic properties for their conversion. As a result, the lithium–sulfur batteries with (CuCo)Se₂-NCNT achieve a high specific capacity of 1051.06 mAh g⁻¹ at 1C and an enhanced rate property with a specific capacity of 838.27 mAh g⁻¹ at 4C. The work provides meaningful insights into the design of bimetallic compounds as catalysts for lithium–sulfur batteries. Full article

Binary transition metal selenides (BTMSs) are more promising than single transition metal selenides (TMS) as anode materials of sodium-ion batteries (SIBs). However, it is still very challenging to prepare high-performance BTMSs in the pure phase, instead of a mixture of two TMSs. In this study, a binary metal center-based MOF derived selenization strategy was developed to prepare iron–cobalt selenide (Fe₂CoSe₄@NC) and iron–nickel selenide (Fe₂NiSe₄@NC) nanocomposites in the single phase and when wrapped with carbon layers. As the anode material of SIBs, Fe₂CoSe₄@NC exhibits higher long-term cycling performance than Fe₂NiSe₄@NC, maintaining a capacity of 352 mAh g⁻¹ after 2100 cycles at 1.0 A g⁻¹, which is ascribed to the higher percentage of the nanopores, larger lattice spacing, and faster Na+ diffusion rate in the electrode materials of the former rather than the latter. Full article

Molybdenum diselenide (MoSe₂) is a promising anode for alkali-ion storage due to its intrinsic advantages. However, MoSe₂ still encounters the issues of structural instability and poor rate performance caused by drastic volume change and sluggish reaction kinetics. Reasonable design of electrode structure is crucial for achieving superior electrochemical performance. Herein, a novel hierarchical structure coupled with 1D/1D subunits is elaborately designed and constructed, in which the MoSe₂/CoSe₂ heterostructure is the “trunk” and the N-doped carbon nanotubes are the “branches” (MoSe₂/CoSe₂/NCNTs). Benefiting from the properties endowed by unique configurations, MoSe₂/CoSe₂/NCNTs electrodes manifest faster reaction kinetics and better structure durability. Evaluated as an anode for LIBs and SIBs, MoSe₂/CoSe₂/NCNTs deliver high reversible capacity, superior rate capability (452 at 10 A g⁻¹ in LIBs and 296 at 10 A g⁻¹ in SIBs), and prominent cycle life (553 after 2000 cycles at 5 A g⁻¹ in LIBs and 310 after 2000 cycles at 5 A g⁻¹ in SIBs). Such design conception can also provide guidance for the development of other high-performance electrodes. Full article

The aim of this study was to investigate the concentrations of essential trace and toxic elements in the milk of Lacaune sheep during lactation in intensive rearing systems. This research was conducted with 30 Lacaune sheep that were monitored in the early (60 days of lactation), medium (120 days of lactation), and late (180 days of lactation) stages of lactation. The sheep were fed a pelleted feed mixture (1 kg/day), a cereal mixture (600 g/day), and alfalfa hay (ad libitum). The essential (Fe, Zn, Cu, Co, Mn, Mo, Se, Cr, and Ni) and toxic element (heavy metals: Cd, Pb, As, and Hg) concentrations in the feed and milk were determined using an inductively coupled plasma mass spectrometer. Significant variations in the main essential trace and toxic elements, except for the Mo, Se, Ni, As, and Hg concentrations, were found in the milk of Lacaune sheep during lactation. As lactation progressed, in the late stage of lactation, significantly higher concentrations of Co, Mn, Mo, Cr, and Pb were found, while Zn and Cu in the milk of Lacaune sheep decreased significantly (4.15 and 0.21 mg/kg) compared to their concentrations in the early stage of lactation (5.66 and 0.43 mg/kg). Significantly lower concentrations of Fe and higher concentrations of Cd were found in the medium stage (0.23 mg/kg and 1.08 µg/kg) of lactation compared to both the early and late stages of lactation. An analysis of the correlation coefficients between the essential trace and toxic elements in Lacaune sheep milk during lactation determined a significantly positive correlation between Fe:Cr, Fe:Mn, Fe:Co, Fe:Se, Zn:Ni, Zn:Se, Cr:Mn, Cr:Co, Cr:Se, Cr:Mo, Mn:Co, Mn:Pb, Co:Ni, Co:Se, Ni:Se, Se:Mo, Se:Pb, and Cd:Pb. A significantly negative correlation was also found between Cu:Mn, Zn:Mo, Cg:Hg, and Hg:Pb. Based on the obtained results, it is recommended that the influence of the stage of lactation, as well as the breed of sheep, should be included when designing experiments. In general, sheep milk is rich in essential trace elements, but it also contains a very low content of toxic elements, which provides justification for increasing the breeding of Lacaune sheep and indicates the convenience of consuming their milk without risking the consumer’s health. Full article

Water electrolysis is a compelling method for the production of environmentally friendly hydrogen, minimizing carbon emissions. The electrolysis of water heavily relies on an effective and steady oxygen evolution reaction (OER) taking place at the anode. Herein, we introduce a highly promising catalyst for OER called CoSe₂@NiFeOOH arrays, which are supported on nickel foam. This catalyst, referred to as CoSe₂@NiFeOOH/NF, is fabricated through a two-step process involving the selenidation of a Co-based porous metal organic framework and subsequent electrochemical deposition on nickel foam. The CoSe₂@NiFeOOH/NF catalyst demonstrates outstanding activity for the OER in an alkaline electrolyte. It exhibits a low overpotential (η) of 254 mV at 100 mA cm⁻², a small Tafel slope of 73 mV dec⁻¹, and excellent high stability. The good performance of CoSe₂@NiFeOOH/NF can be attributed to the combination of the high conductivity of the inner layer and the synergistic effect between CoSe₂ and NiFeOOH. This study offers an effective method for the fabrication of highly efficient catalysts for an OER. Full article

Lithium–sulfur (Li-S) batteries are regarded as highly promising energy storage devices due to their high theoretical specific capacity and high energy density. Nevertheless, the commercial application of Li-S batteries is still restricted by poor electrochemical performance. Herein, beaded nanofibers (BNFs) consisting of carbon and CoSe₂ nanoparticles (CoSe₂/C BNFs) were prepared by electrospinning combined with carbonization and selenization. Benefitting from the synergistic effect of physical adsorption and chemical catalysis, the CoSe₂/C BNFs can effectively inhibit the shuttle effect of lithium polysulfides and improve the rate performance and cycle stability of Li-S batteries. The three-dimensional conductive network provides a fast electron and ion transport pathway as well as sufficient space for alleviating the volume change. CoSe₂ can not only effectively adsorb the lithium polysulfides but also accelerate their conversion reaction. The CoSe₂/C BNFs-S cathode has a high reversible discharge specific capacity of 919.2 mAh g⁻¹ at 0.1 C and presents excellent cycle stability with a low-capacity decay rate of 0.05% per cycle for 600 cycles at 1 C. The combination of the beaded carbon nanofibers and polar metal selenides sheds light on designing high-performance sulfur-based cathodes. Full article