The European Physical Journal Plus最新文献

In this paper, we investigate the influence of primary hair (l) on the shadows of hairy Schwarzschild and Reissner-Nordström black holes obtained through gravitational decoupling. In the context of hairy Schwarzschild black holes, l either has no effect or consistently enlarges the photon sphere radius. Notably, even when it violates the strong energy condition, it can decrease the radius. For Reissner-Nordström black holes, an additional matter field consistently expands the photon sphere radius, potentially reaching 3M, akin to the pure Schwarzschild case. Remarkably, we demonstrate that black holes can exist even when overcharged ((Q^2> M^2)), casting shadows. Specific intensity calculations reveal l consistently reduces it in both scenarios. Furthermore, we investigate the impact of pressureless plasma, finding l exerts a stronger influence on visible size than plasma. These results can help in our understanding of theoretical models of black hole shadows and can be tested by comparison with the images obtained by EHT collaboration.

Pollution is rising globally due to human activities like industrial discharge, agricultural runoff, and urbanization. Addressing this urgent issue is essential for protecting environmental and public health. The use of composite materials to address environmental problems has evolved significantly, notably in the development of strategies for eliminating pollutants/pathogens from wastewater. This work presents the co-precipitation modification of iron oxide with graphene (Fe₃O₄–graphene). The differential approach was utilized to calculate the optical band gaps for Fe₃O₄ and graphene in nanocomposites (NCs), which were found to be 1.62 and 3.42 eV, respectively. Malachite green degradation under visible-light irradiation was used to measure the photocatalytic activity. The Fe₃O₄–graphene NCs showed better photodegradation efficiency at 97%, outperforming malachite green (MG) degradation without any catalyst (70%). The increased photocatalytic activity is due to lower bandgap energy and a high-rate constant of 0.06367 min⁻¹, confirming first-order reaction kinetics. When tested against fungi, Gram-positive and Gram-negative bacteria, Candida albicans, Methicillin-resistant Staphylococcus aureus isolates 1 and 2, Escherichia coli, and Pseudomonas aeruginosa, the sample was more effective against Gram-positive bacteria than Gram-negative bacteria and fungi. These findings contribute to the ongoing research in environmental remediation by presenting a multifunctional material that combines high photocatalytic and antibacterial efficiency, offering a promising solution for the treatment of contaminated water sources.

Graphical abstract

A computational analysis was performed in a curve-shaped enclosure stuffed with a hybrid ({text{Fe}}_{3}{text{O}}_{4}-text{MWNTs}/{text{H}}_{2}text{O})) nanofluid influenced by a magnetic field. The free convective flow within the chamber is driven by the temperature variation between a cool external curve-shaped enclosure, a heated interior elliptical cylinder, and the upper horizontal wall. The Galerkin finite element method (GFEM) is applied to solve the governing equations, using COMSOL multiphysics as the simulation platform. A quantitative parametric study is conducted for different values of the Hartmann number, nanoparticle volume concentration, Rayleigh number, and varying radii of the interior elliptical cylinder. The findings are presented in terms of the streamlines, temperature contours, and both ({text{Nu}}_{text{Local}}) and ({text{Nu}}_{text{avg}}), taking into account variations in significant physical parameters. The outcomes show that the rate of thermal transport significantly escalates with higher concentrations of the hybrid nanofluid and (text{Ra}); on the other hand, a contrary trend is observed with an increased Hartmann number. Furthermore, the ({text{Nu}}_{text{avg}}) rises with higher values of (text{Ra}) and (phi ) but declines as the (text{Ha}) increase. The velocity profile grows by 93.5% as (text{Ra}) increases, but it diminishes by 25.8% with changes in the radius of the inner obstacle.

This paper describes a photonic crystal fiber (PCF) sensor designed to detect toxic gases in the THz frequency range. The proposed sensor demonstrates exceptional performance characterized by low confinement loss, minimal effective material loss, and high relative sensitivity across various gas types, including benzene (C₆H₆), methyl bromide (CH₃Br), sulfur trioxide (SO₃), tin (IV) chloride (SnCl₄), and vinyl chloride (C₂H₃Cl). Several crucial parameters of the proposed PCF were investigated throughout a broad THz spectrum ranging from 0.4 to 2.0 THz. To quantify the performance of the proposed fiber sensor, the finite element method (FEM) framework is used. The confinement loss is observed to be as low as 10^–19 dB/cm ensuring efficient light propagation and minimal leakage for accurate gas detection. A comprehensive analysis of the sensor’s performance reveals that it achieves a high relative sensitivity for methyl bromide which is 99.068%, low effective material loss of 0.013163 cm⁻¹, larger effective area of 3.0683 μm², core power fraction of 92.294%, low confinement loss of 1.67 × 10^–19 dB/cm, and high nonlinearity of 2.459 × 10^–09. The other toxic gases, such as benzene, tin (IV) chloride, sulfur trioxide, and vinyl chloride also showed very gratifying results with relative sensitivity of 98.464, 97.987, 98.729, and 98.516%, low effective material loss of 0.005516, 0.0048967, 0.014494, and 0.01522 cm⁻¹, and core power fraction of 96.677, 97.033, 91.53, and 91.112%. The sensing principles discussed provide a simple and effective way for detecting gases, making them appropriate for a variety of gas sensing applications.

In this paper, we analyze the dynamics, at the quantum level, of the self-dual field minimally coupled to bosons with Lorentz symmetry breaking. We quantize the model by applying the Dirac bracket canonical quantization procedure. In addition, we test the relativistic invariance of the model by computing the boson–boson elastic scattering amplitude. Therefore, we show that the Lorentz symmetry breaking has been restored at the quantum level. We finalize our analysis by computing the dual equivalence between the self-dual model with Lorentz symmetry breaking coupled with bosonic matter and the Maxwell–Chern–Simons with Lorentz invariance violation coupled with bosonic field.

This study describes a novel application of the Tribulus terrestris extract as a highly efficient corrosion inhibitor for steel in 1 M H₂SO₄ solution. The Tribulus terrestris extract contains considerable phytochemicals, notably Tribuloside, Kaempferol, and Kaempferol-3-glucoside that are basically for its anticorrosive behavior. Various studies including weight reduction analysis, electrochemical measurements (PDP and EIS), surface investigations, DFT calculations and simulation, etc. were performed to explore the Tribulus terrestris extract as a corrosion inhibitor. The highest inhibition efficiency of 96.25% was observed at 700 mg/L concentration of the Tribulus terrestris extract. The polarization curves obtained in the presence of the Tribulus terrestris extract indicate the extract behaved as a mixed type of inhibitor. In addition, the formation of a protective layer on the surface of steel was confirmed using the scanning electron microscope (SEM). The DFT analysis revealed a few electron-rich regions in the inhibitor's phytochemicals, which supported the high nucleophilicity. According to Frontier molecular orbital analysis, all three inhibitors contain electrons in their HOMO regions, which allow them to interact with vacant d-orbitals of iron on metal surfaces. Consequently, covalent bonds are formed between the metal surface and the corrosion inhibitor, which results in the inhibitor adsorption on the metal surface.

Graphical Abstract

The article investigated solutions of the Ginzburg–Landau equation in the phase approximation. Families of periodic steady-state traveling solutions branching off from the trivial zero solution were constructed analytically and numerically. The critical values of the parameters at which restructuring of such families takes place have been found. Limitations, beyond which the phase approximation equations widely used in the literature become unacceptable, were indicated. For this model, the structural relationship of periodic solutions with soliton ones was demonstrated. The numerical and analytical results were compared.

This paper explores the generalized ghost dark energy model in the framework of (f(textit{Q}, textit{L}_{m})) gravity, where (textit{Q}) represents the non-metricity scalar, and (textit{L}_{m}) denotes the matter-Lagrangian density. We take the homogeneous and isotropic universe with an ideal matter distribution and examine a scenario with interacting dark energy and dark matter. We then reconstruct (f(textit{Q}, textit{L}_{m})) model to examine the effects of this extended gravitational framework on the cosmic evolution. The behavior of numerous cosmic parameters is explored corresponding to distinct parametric values. The stability is evaluated by the squared sound speed method. The statefinder (r, s) and standard diagnostic pairs ((omega _D-omega '_{D})) are used to study the various cosmic eras. Our results align with recent observational evidence, indicating that the (f(textit{Q}, textit{L}_{m})) model effectively characterizes dark energy and cosmic evolution.

Studies are performed to investigate the flexibility of Armchair Graphene Nano Ribbon (AGNR) based nanoscale channels for electronic and spintronic devices. The role of the spatially varied Electric fields on the bandstructures, Local Density of States (LDOS), Landau Levels, and the Transmission functions of AGNR channels are studied under the Quantum Hall Effect (QHE) regime. Here, the electric potential across the transverse direction is modulated sinusoidally. Also, the electric field is spatially varied exponentially and hyperbolically across the transverse direction. The nature of the Quantum Landau levels(QLLs) show variations in the sub-bands that collapse for constant, exponential, and hyperbolic electric fields and show an oscillatory nature for the sinusoidal field. This is also reflected in the LDOS plots, which change due to the intermixing of the sub-bands and spatial variation of the transverse electric fields. This intermixing of the QLLs sub-bands suppresses the QHE regime’s cyclotron motion. Hence, applying electric and magnetic fields provides a picture of the tunability of AGNR channels.

Graphical abstract

Topological indices are numerical descriptors derived from the structure of molecular graphs, capturing key aspects of their topology and connectivity. They play a vital role in cheminformatics by correlating molecular structure with physical, chemical, and biological properties, enabling efficient property predictions and molecular design. In this article, we explored the applicability of several neighborhood degree-based structural descriptors, including the fifth M-Zagreb indices, fifth hyper-M-Zagreb indices, and NDe indices, in predicting key thermodynamic properties of benzenoid hydrocarbons. These indices serve as mathematical tools to capture structural and topological features of molecular graphs, providing valuable insights into molecular behavior. Our analysis demonstrates that these indices exhibit strong correlations with critical thermodynamic properties such as boiling point, entropy, enthalpy of formation, Kovats retention index, and octanol-water partition coefficient of benzenoid hydrocarbons. Among the studied descriptors, the fourth NDe index showed particularly impressive performance, with correlation coefficients exceeding 0.97 for all considered properties. These findings highlight the potential of neighborhood degree-based indices as reliable predictors of molecular properties, offering a cost-effective and computationally efficient alternative to experimental methods. Furthermore, the results underscore the utility of graph-theoretic descriptors in the broader context of cheminformatics and property prediction for organic compounds, paving the way for future research into their applications across diverse molecular systems.