Narrow Results

In this paper, we examine certain aspects of magnetized spacetime solutions within the Einstein–Maxwell–dilaton theory. Specifically, we discuss the Melvin-like universe and compare it to the equivalent solution in the Einstein–Maxwell case. Additionally, we analyze the equatorial circular motions and corresponding electromagnetic fields within this spacetime. Some distinguished properties compared to the magnetized black hole in Einstein–Maxwell case are found.

We study the propagation of electromagnetic (EM) waves in extremely dense exotic systems with very unique properties. These EM waves develop a longitudinal component due to interactions with the medium. Renormalization scheme of QED is used to understand the propagation of EM waves in both longitudinal and transverse directions. The propagation of EM waves in a quantum statistically treatable medium affects the properties of the medium itself. The electric permittivity and the magnetic permeability of the medium are modified and influence the related behavior of the medium. All the electromagnetic properties of a medium become a function of temperature and chemical potential of the medium. We study in detail the modifications of electric permittivity and magnetic permeability and other related properties of a medium in the superdense stellar objects.

The doping effects of low melting-point nonmagnetic Sb³⁺ ions on the microstructure and electromagnetic properties of Mn–Zn ferrites were studied. All the samples were prepared by traditional ceramic technique. According to the investigation on the microstructure, it was found that all the samples consisted of ferrite phases with typical spinel cubic structure, and with increasing doping content of Sb³⁺ ions, the lattice constant of the ferrites decreased but the grain size increased; the elemental analysis taken on the ferrite grain and grain boundary indicated that a portion of Sb³⁺ ions entered into the ferrite lattice. Through the measurement of magnetic properties, it was revealed that, the saturation magnetization and initial permeability of the samples rose with small doping content of Sb³⁺ ions but decreased with additional Sb³⁺ doping; the Curie temperature decreased monotonously with Sb³⁺ doping; and the coercivity rose with increasing doping content of Sb³⁺ ions. The analysis of dielectric properties indicated that the dielectric constant of the doped Mn–Zn ferrites increased with increasing doping content of Sb³⁺ ions.

Some positive and negative parity energy bands of odd-A isotopes of Europium ${}^{\text{153–159}}\text{Eu}$ have been studied within the Projected Shell Model (PSM) framework. Calculated excitation energy spectra, transition energies, E2 and M1 transition probabilities, quadrupole and magnetic moments are compared with experimental data wherever available. Reasonably good agreement is obtained with the observed data.

BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄/Polypyrrole composite film [including three doping acids, dodecyl benzene sulfonic acid (DBSA), camphor sulfonic acid (CSA) and p-toluenesulfonic acid (TSA)] was prepared by sol–gel method and in situ chemical oxidative polymerization. The structure, morphologies, conductivities, magnetic properties and microwave absorption properties of the composite film were characterized by using XRD, FESEM, FTIR, Four-probe tester, VSM and Vector network analyzer. The results show that the conductivity of acid-doped Polypyrrole composite film is higher than that of pure Polypyrrole composite film. The saturation magnetization (M_s) and remanent magnetization (M_r) of the composite film are lower than those of BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄ film. However, the electromagnetic properties are in the contrary. The microwave absorption properties of the composite film are much better than those of BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄, which mainly depends on the increasing of the dielectric loss. A minimum reflection loss of the DBSA-doped composite film is −17.6 dB at 9.3 GHz with the thickness at 3.0 mm.

Low-density Fe-doped ordered mesoporous carbon (CMK-3)-silica (SBA-15) nanocomposites with different Fe contents have been prepared by a catalytic carbonization procedure followed by high-temperature calcination in N₂. From field emission-scanning electron microscope (FE-SEM) and high resolution-transmission electron microscope (HR-TEM) images, it can be concluded that CMK-3 particles are dispersed homogeneously into a silica matrix and form a novel, special and interesting composite nanostructure. The metal species ($\sim$18nm) are dispersed on the surface of frameworks during the catalytic carbonization procedure and endow a magnetic property to the carbon–silica nanocomposites. The optimal reflection loss (RL) calculated from the measured permittivity and permeability is $-$19dB at 17.2GHz for an absorber thickness of 2.00mm. Moreover, the electromagnetic (EM) wave absorption less than $-$10dB is found to exceed 5.76GHz as the layer thickness is 2.37 mm. The permittivity dispersion behaviors have been explained based on the Cole–Cole model and the conductivity contribution model. A new simple empirical model was also supposed to find the fitted curves of the multi-resonance imaginary permeability spectra of the composites. The EM wave can hardly be reflected on the absorber surface because of a better match between dielectric loss and magnetic loss, which originates from the combination of dielectric carbon–silica and magnetic Fe species.

Core–shell Cu@Ni chains were successfully synthesized through a mild hydrothermal reaction. The morphology, structure and microwave electromagnetic properties of the composite were then characterized by X-ray diffraction, energy-dispersive spectroscopy, scanning electron microscopy and vector network analysis. The formation mechanisms of the core–shell structure and one-dimensional chains were ascribed to the varying redox potentials of Cu and Ni ions and the magnetic dipole–dipole attraction. Furthermore, a minimal reflection loss (RL) of $-$20.7dB was observed at 9.6GHz with a thickness of 2.0mm and the effective absorption ($\le$10dB, 90% microwave attenuation) bandwidth can be adjusted between 5.2GHz and 16.6GHz for the thin absorber thickness of 2.0–4.0mm. The novel core–shell chain-like Cu@Ni alloy can be used as a promising absorbing material because it shows numerous features such as thin thickness, strong absorption, low cost and lightweight.

Multifunctional composite nanostructure prepared via electrospinning has attracted wide attention. In this study, Fe₂O₃-carbon composite nanofiber with particle–nanorod structure was successfully prepared via electrospinning and followed calcination. Then, the electromagnetic properties of this material have been fully characterized, and the influence of different preparation conditions on these properties has been studied. In addition, compared to pure $\gamma$-Fe₂O₃ nanoparticles and hollow Fe₂O₃ nanofibers, the composite nanofibers with a thickness of 2.64mm exhibited an additional absorption peak at a frequency of 13.92GHz and an enhancement in absorption at a frequency of 15.45GHz, which may be attributed to the increase in electrical loss introduced by amorphous carbon and the enhanced magnetic loss resulting from the multi-stage reflection introduced by the particle–nanorod structure. This study shows that the composite of Fe₂O₃ and carbon, and the introduction of the particle–nanorod structure can improve the microwave absorption efficiency of materials, and more nanocomposites can be designed like this to further improve their electromagnetic properties and absorption efficiency in the future.

We determine the magnetic dipole moment of the rho meson using preliminary data from the BaBar Collaboration for the e⁺e^- → π⁺π^-2π⁰ process, in the center of mass energy range from 0.9 to 2.2 GeV. We describe the γ* → 4π vertex using a vector meson dominance model, including all intermediate resonance contributions. We find that μ_ρ = 2.1 ± 0.5 [e/2m_ρ].

Ferromagnetic nanocrystalline alloy flake composites can be useful in microwave absorbers, since flakes exhibit excellent electromagnetic properties. This paper reviews and updates our experiments and understanding of nanostructure flakes. Structural and morphological influence of flakes on microwave properties are discussed, with respect to the exchange coupling and surface effect of nanocrystals, particle shape dependence of dielectric constant and percolation threshold. It's found that percolation threshold for FeSiB nanocrystalline flake composite is around 35%.

The observation of two approximately degenerate ΔI = 1 rotational bands with the same parity has been often taken as a sign of chiral bands. A critical analysis of observed electromagnetic properties of the doublet bands in the nucleus , which is so far experimentally best studied, is carried out. It is concluded that chiral pair bands have not yet been identified in nuclei.