Volume 78, Issue 7

The local structures and electron paramagnetic resonance (EPR) parameters (the g factors g i and the hyperfine structure constants A i , with i = x , y , z ) of the V 4+ and Cu 2+ centers in WO 3 were theoretically investigated based on the perturbation formulas of the EPR parameters for 3d 1 and 3d 9 ions under rhombically compressed and elongated octahedra, respectively. In these formulas, the adopted crystal-field parameters (CFPs) are obtained from the superposition model which enables connection of the CFPs and hence the EPR parameters to the rhombic distortion. Based on the calculations, the impurity-ligand distances of the studied [VO 6 ] 8− (or [CuO 6 ] 10− ) cluster are found to suffer the axial compression (or elongation) δz of about 0.098 Å (or 0.132 Å) along the z -axis, and the additional planar bond length variation δr (≈0.052 or 0.047 Å) along x- and y- axis, respectively, due to the Jahn–Teller (JT) effect.

By using the Crank–Nicolson method, we investigate numerically the dynamical properties of bright–bright solitons in two species Bose–Einstein condensates (BECs) trapped in an optical lattice. We confirm that the soliton splitting behavior occurs at a critical depth of optical potential. The splitting behavior of solitons and the fusion behavior of condensates can be accurately controlled by adjusting the depth and lattice parameter of optical potential, the initial amplitude and position of solitons, and the interspecies interactions. When the lattice parameter is fixed but the interspecies interaction increased exponentially with the time, each soliton splits into two soltions with different amplitude, and partial fusion of two species BECs can be found. While the interspecies interaction remains unchanged but the lattice parameter increases exponentially with the time, interestingly, the bright solitons with zero initial velocity can pass through each other and accomplish a transmission collision. Furthermore, for the case of both the interspecies interaction and lattice parameter increased exponentially with the time, a head-on collision of the bright solitons in two species BECs occurred. After the collision, each soliton splits into two soltions with equal amplitude. Meanwhile, the complete fusion of two species BECs can be observed. The relevant results can provide help for the precise manipulation of BECs experiments.

The Heisenberg supermagnet model is a significant supersymmetric integrable model which is the superextension of the Heisenberg ferromagnet model. This paper is concerned with the construction of the multi-component (1+1) and (2+1)-dimensional Heisenberg supermagnet models with two distinct quadratic constraints of the superspin variables. In terms of the multi-component gauge transformation, we construct their multi-component gauge equivalent counterparts, i.e., the multi-component (1+1) and (2+1)-dimensional super nonlinear Schrödinger equations and fermionic nonlinear Schrödinger equations, respectively.

Despite having a reasonably successful account of accelerated cosmology, understanding of the early evolution of Universe has always been difficult for mankind. Our promising strategy is based on a novel class of symmetric teleparallel theories of gravity called f ( Q ), in which the gravitational interaction is caused by the non-metricity scalar Q , which may help to solve some problems. We consider the locally rotationally symmetric (LRS) Bianchi type-I spacetime cosmological models and derive the motion of equations to study the early evolution of the cosmos. By assuming the hybrid expansion law (HEL) for the average scale factor, we are able to determine the solutions to the field equations of Bianchi type-I spacetime. We discuss the energy density profile, the equation of state, and the skewness parameter and conclude that our models preserve anisotropic spatial geometry during the early stages of the Universe with the possibility of an anisotropic fluid present. However, as time goes on, even in the presence of an anisotropic fluid, the Universe may move towards isotropy due to inflation while the anisotropy of the fluid dims away at the same time. It is seen from the squared speed of sound that Universe shows phantom nature at the beginning then approaches to dark energy at present epoch. We analyze both geometrical and physical behaviours of the derived model.

The analytical observation of the simultaneous impacts of electrical resistivity, finite Larmor radius (FLR) correction, and electron inertia on the magnetohydrodynamic Rayleigh–Taylor unstable mode of incompressible rotating quantum plasma is carried out. The perturbation formulations of the problem are derived by applying the QMHD model to obtain the dispersion equation for the stratified quantum hydrodynamic fluid plasma. The dispersion equation is analyzed graphically and numerically for the various cases. It is obtained that the simultaneous impacts of rotation, resistivity, FLR correction, electron inertia, and quantum correction modify the Rayleigh–Taylor (RT) unstable mode of the stratified magnetized fluid plasma. The graphical studies show that the rotational effect destabilizes or stabilizes the Rayleigh–Taylor (RT) instability of the magnetized quantum plasma, with or without the impacts of electrical resistivity and electron inertia. This result may be useful for studying the magnetic reconnection process and its applications, viz., supernova explosions, neutron stars, white dwarfs, etc.

Some motion problems of Burgers fluids between parallel plates are analytically and numerically investigated when magnetic and porous effects are taken into account and a differential expression of the non-trivial shear stress is prescribed on the lower plate. Closed-form expressions are determined for the non-dimensional steady state velocity and shear stress fields and the corresponding Darcy’s resistances. They are the first exact solutions for hydromagnetic motions of Burgers fluids through porous media when a differential expression of shear stress is given on the boundary. The results that have been obtained are used to get the necessary time to reach the steady state and to bring to light the influence of magnetic field and porous medium on the flow resistance of the fluid. They can immediately be particularized to provide exact solutions for similar motions of Oldroyd-B, Maxwell, second grade and Newtonian fluids. It was found that the steady state is rather obtained in the presence of a magnetic field or porous medium. In addition, the flow resistance of the fluid declines in the presence of a magnetic field and, as expected, increases through porous media.

Plaque reduces the conductivity of the blood vessel and its shape is more important than its quantity. We show that, for given quantity, the conductivity is maximal if the plaque forms a uniform layer next to the vessel wall and leaves a circular hole in the middle. On the other hand, for any quantity of the plaque a shape can be found such that the conductivity of the vessel is arbitrary close to zero.

The neutron optical Lloyd interferometer can serve as a potent experiment for probing fundamental physics beyond the standard models of particles and cosmology. In this article, we provide a full Green’s function analysis of a Lloyd interferometer in the limit that the reflecting mirror extends to the screen. We consider two distinct situations: first, we will review the theoretical case of no external fields being present. Subsequently, we will analyze the case in which a gravitational field is acting on the neutrons. The latter case provides the theory necessary for using a Lloyd interferometer as a probe of gravitational fields.

The article presents research on the synthesis and characterization of a nanocomposite material consisting of graphene oxide (GO) decorated with calcium oxide (CaO), for the use in energy storage. The co-precipitation method was used to prepare the nanocomposite. The presence of CaO and GO in the sample was confirmed by X-ray diffraction (XRD), which revealed a crystallite size of 18 nm for CaO and 9 nm of CaO/GO. The scanning electron microscopy (SEM) images showed a well-dispersed nanocomposite structure, and energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of Ca, C, and O elements in the sample. Fourier-transform infrared (FTIR) spectroscopy was used to analyze the chemical composition and structural properties of the nanocomposite. UV-visible spectroscopy revealed a direct band gap of 3.78 eV for the nanocomposite, indicating its potential application for use in electrochemical energy storage and photoconductive devices. Zeta potential measurement indicated good physical stability of the nanocomposite. These results suggest that the CaO/GO nanocomposite has promising properties for various technological applications, particularly in the field of thermal energy storage.

Nanostructured thin films are one of the most valuable types of industrial semiconductors for a variety of optoelectronics and optical device applications, having recently been used as a transparent conductive oxide in solar cells. In this work, nanostructured thin films of pure ZnO, Ag doped ZnO, Mg doped ZnO and Ag–Mg co-doped ZnO were successfully synthesized on silicon and glass substrates, using rapid thermal evaporation. The impact of the doping elements on the surface morphology, structural, electrical, and optical properties of the deposited films were investigated. It was found that all films have polycrystalline hexagonal wurtzite structure using X-ray diffraction. Images obtained by scanning electron microscopy (SEM) revealed compact and smooth surfaces, with uniform coverage of all substrate regions. SEM images confirm the nanostructured nature of the surfaces with particle size varying as a function of doping. Raman spectroscopy showed A 1 (LO), E 2 (high) and LVM modes for all samples. The developed films’ optical transmission ranged from 74 % to 87 %, with an optical bandgap ranging from 3.09 for Mg:ZnO films to 3.8 eV for Ag:ZnO samples. Depending on the doping nature modification, these alterations were associated to structural and morphological changes in the films. All films were electrically conductive, while Ag:ZnO films exhibited the lowest resistivity value reaching 0.56 Ω cm.