Pramana最新文献

Nanotechnology offers innovative and sustainable solutions for environmental remediation. However, enhancing photocatalytic efficiency remains a significant challenge. In this study, we developed a cost-effective method for synthesising carbon quantum dot (CQD)-incorporated cerium oxide (CeO₂) nanocomposites for efficient methyl orange (MO) degradation under direct sunlight. CeO₂ nanosols and CQDs were synthesised via sol–gel and hydrothermal processes, respectively, and combined using a hydrothermal route with sonication-assisted mixing. The nanocomposites were calcinated at 600 °C and characterised using XRD, FTIR, Raman, PL spectroscopy, SEM and EDX to analyse their structural, morphological and surface properties. The specific surface area of the CQDs(/)CeO₂ composites was determined to be 72.3 m²(/)g from the sol–gel method and 96.7 m²(/)g from the hydrothermal method, as measured by Brunauer–Emmett–Teller (BET) analysis. The optimised CQDs(/)CeO₂ (1:100 ratio) exhibited enhanced MO degradation, with the MO degradation rate constant for the hydrothermal composite. The energy band gap of the sol–gel composite was found to be 2.78 eV, while the hydrothermal composite showed a band gap of 2.73 eV, facilitating improved light absorption. The degradation efficiency was further influenced by MO concentration, pH and catalyst loading. Additionally, CQDs(/)CeO₂ demonstrated excellent catalytic stability over multiple cycles. These findings highlight the potential of CQDs(/)CeO₂ nanocomposites for cost-effective water purification and disinfection applications.

Graphical abstract

The purpose of this paper is to study the trajectory controllability (which is said to be the strongest notion rather than other controllabilities) and null controllability of a control system commanded by fractional-order composite relaxation semi-linear differential equation. The linear control system under consideration addresses a classical problem in fluid dynamics, specifically focussing on the dynamics of a particle experiencing unsteady movement within a viscous fluid while subjected to gravitational forces. Initially, we derive the mild solution of the considered control system employing the results on (a, k)-regularised families of bounded linear operator (matrices). Under some appropriate assumptions regarding non-linear terms and by utilising the Gronwall’s inequality, we establish the trajectory controllability and null controllability with constrained controls via fixed point technique. Finally, a few examples are shown to illustrate and explore the applications of the obtained findings.

Precision observables are well known for constraining most of the beyond standard model (BSM) scenarios tightly, among which the electroweak precision observables (EWPO) play a significant role. Recent measurement of the W boson mass ((M_W)) at CDF-II has put a renewed focus on the EWPO and its ensuing constraints. In this study, we look at the scenarios where these BSM effects are encoded primarily in ten dimension-6 standard model effective field theory (SMEFT) operators (in the Warsaw basis) which contribute to the EWPO at tree-level. After presenting the fitting procedure and testing it on the S, T and V parameters, we go on to fit various BSM scenarios consisting of different well-motivated subsets of the 10 operators of our interest. To constrain these scenarios further, we augment the EWPO with (Delta _{textrm{CKM}}) measurement using 1-loop matching of the low-energy effective field theory to SMEFT operators at the Z-pole. We show that the inclusion of the (Delta _{textrm{CKM}}) constraint indeed results in stronger bounds on our Wilson coefficients. One of our operator subsets caters to the models of vector-like leptons, where we find out that such a minimal extension is in tension with the forward–backward asymmetry in the b-sector ((A_b^{textrm{FB}})) and (M_W). Finally, we also include the LEP-II observables pertaining to the WW production, thereby lifting the two associated blind directions, helping us present the results for the full fit.

This paper investigates the geodesic motion and circular motion of particles around a linear Maxwell (f(R)) black hole in a modified gravity black hole field, using a specific metric. It focusses on framing the effective potential function for photon-like as well as massive particles, revealing differences in the behaviour of coordinate and proper time relative to radial distance in the space–time geometry. The analysis focusses on effective potential curves obtained from specific equations, examining the dynamics of massless and massive particles in different scenarios. Moreover, it examines the stability of particle orbits using the Lyapunov exponent and explains how the circular orbit of a particle moving under the influence of gravitational field of the black hole is conditionally stabilised. This paper examines how the cosmological constant and gravitational modification parameter influence the circular and geodesic motion of the particle. Finally, this paper provides a graphical analysis of the radius of the innermost stable circular orbit and outermost stable circular orbit of the particles moving in the field of modified gravity.

Current biosocial theories, such as the influence of neurotransmitters on the behaviour, ecological perspectives that consider cultural, political, and institutional factors and interpersonal views like attachment, have shaped our understanding of romantic and interpersonal relationships as typical social experiences. However, these theories fail to offer a comprehensive framework for the relationship dynamics and a fully integrated theoretical approach is still missing. Here, we have developed a mathematical model to investigate the dynamics of romantic and interpersonal relationships between male, female, child and society via a system of fractional differential equations (SFDEs) to provide insight into the love/hate behaviour. The model comprises four classes describing the love/hate of males, females, children and society. The modified operational matrix of integration (OMI) of the Legendre wavelets is presented and used to solve the SFDEs. The model is solved using RK4, NDSolve and the Legendre wavelet collocation method (LWCM) for numerical analysis and comparison of the solutions. Numerical and graphical study of fractional order is done for different values of (gamma ). The pictorial analysis of various values of parameters to show the variation of classes is done. The Mathematica software has been used for numerical computations. This study reveals how the internal relationship and status affect the status of the society.

This paper constructs a spreading model driven by positive and negative feedback interactions to study the impact of inter-individual feedback interaction on message spreading in online social networks. By analysing the network topology and the social attributes of the propagators, we introduce feedback interaction rules. In addition, the individual’s spreading motivation comes from the direct feedback interactions of multilevel neighbours and the group-level pressure of the social environment. Therefore, we established a feedback efficiency function. Experimental results show that the model is effective in promoting the positive spread of messages. Meanwhile, it is found that the increased social distance between individuals weakens the feedback strength, the group feedback rate enhances the expected spreading ability of the upline nodes and the group feedback has a more significant incentive effect than the neighbour feedback. Finally, the reasonableness of the model is verified by comparing with real cases.

This paper constructs the travelling wave solutions of the stochastic resonant nonlinear Schrödinger equation that contains the stochastic term with multiplicative white noise based on the complete discriminant system for the polynomial method. By systematically investigating the polynomial law, we derive more abundant forms of travelling wave solutions. Notably, our new insight reveals that the non-averaged state of the solutions enables the characteristics of solitons and periodic modes to be maintained. In contrast, stochastic averaging will lead to changes in the periodic and soliton characteristics. In addition, we present the model diagrams for several specific parameters, which endows physical interpretations to the spatiotemporal structure in the white noise environment.

In this manuscript, a modified (R_I)-type recurrence relation is considered whose recurrence coefficients are perturbed by the addition or multiplication of a constant. Using the perturbed system of recurrence coefficients, perturbed extended relativistic Toda equations are derived. These equations are then represented in a matrix form. This matrix representation helps recover a Lax pair that has already been studied in the literature. Inferences about the stability of the resulting perturbed system of the Toda equations are drawn based on numerical experiments.

We explore the (beta )-decay features of the doubly magic nucleus (^{100})Sn and proton-rich Sn isotopes within the mass range 100(le ) A (le ) 110. Our calculations yield a Gamow–Teller (GT) strength of 4.157 for the transition from the ground state to the lowest excited state of (^{100})Sn, which closely aligns with the recently measured value of 4.381 at RIKEN. The GT strength distributions computed for (^{102-104, 106, 108})Sn exhibit good agreement with experimental observations. Additionally, we compare our GT data with previous theoretical calculations. The predicted half-lives are reproduced within a factor of 2 relative to the experimental values for (^{100-110})Sn. For the first time, we present microscopic calculations of electron capture, (beta ^{+}) decay, and proton emission rates for proton-rich Sn isotopes under stellar conditions. As the core density of a star reaches (10^{11}) g/cm(^3), electron capture rates calculated by up to seven orders of magnitude. In contrast, (beta ^{+}) decay rates remain largely unchanged with variations in core density but exhibit changes of up to three orders of magnitude with increasing core temperatures. A decreasing trend in stellar rates is observed with increasing neutron number N, specifically for even-even and odd-A Sn isotopes. The reported stellar rates provide valuable insights for the rp-process and simulation of post-silicon evolution of massive stars.

This study examines spherically symmetric static empty space solutions within the framework of the (f(R, Sigma , T))-gravity, where (f(R, Sigma , T)) is a general function of the scalar curvature R, the torsion scalar (Sigma ) and the trace of the energy–momentum tensor T. We reduce the modified Einstein equations to a single equation and demonstrate how to construct exact solutions across various (f(R, Sigma , T))-gravity models. Notably, we establish that for a broad class of models, including the (f(R, Sigma , T)=R+Sigma +2 eta T) model, the Schwarzschild metric serves as an exact solution to the field equations, alongside other classes of solutions. We discuss the significance of these findings in the context of solar system constraints on (f(R, Sigma , T)) theories of gravity. Additionally, the effects of space–time torsion and particle spin on the solar system are also explored.