Brazilian Journal of Physics最新文献

Titanium dioxide nanoparticles (TiO₂NPs) exhibit optical, electrical, and magnetic properties and are potential candidates for biomedical uses. The cytotoxicity comparison among undoped as well as iron-doped TiO₂NPs is supported by the current study. The antibacterial test was also conducted for five different bacteria. Pure and iron-doped TiO₂NPs were synthesized using titanium isopropoxide and iron nitrate nonahydrate as precursors using the co-precipitation method. The synthesized TiO₂NPs were characterized by XRD (X-ray diffraction), UV-Vis (UV-visible diffuse reflectance spectroscopy), EDAX (energy dispersive X-ray spectroscopy) analysis, and FTIR (Fourier transform infrared spectroscopy) analysis. XRD examination revealed a shift in peak when TiO₂ is doped with iron. EDAX analysis verified that (Fe³⁺) iron particles were present in the TiO₂ crystal structure. Band gap energy was calculated from UV-Vis, and it was confirmed that with an increase in doping concentration, band gap energy seems to decrease. FTIR analysis established the presence of different functional groups within TiO₂NPs. The in-vitro cytotoxic effect was determined using the MTT assay method. The study showed that the iron-doped TiO₂NPs are comparatively less cytotoxic than pure TiO₂NPs.

The role of continuum coupling to the breakup of the deuteron is clearly shown through microscopic continuum discretized coupled channel (CDCC) calculations carried out with and without this coupling. The analysis was further extended to construct an effective potential (U_eff) from the sum of cluster folding (CF) and dynamical polarization (DPP) potentials that allow the continuum coupling to be more easily visualized. The considered d + ⁹⁰Zr and ¹¹⁶Sn ADs are reasonably reproduced within the U_eff without any additional adjustments over the wide energy range of this study from ~ 23 to 196 MeV. Both methods clearly show the growth in the influence of coupling to the breakup channel as a function of an increase in deuteron energy. The findings of this study provide evidence supporting the use of the U_eff to describe elastic angular distribution (AD) data across a wide range of energies.

A facile approach was developed for a novel polymer-ceramic nanocomposite, specifically gadolinium-substituted bismuth ferrites (Bi_1−xGd_xFeO₃) for flexible radio-frequency (RF) antenna applications. The polymer-ceramic nanocomposite was developed by synthesizing gadolinium-substituted bismuth ferrite (Bi_1−xGd_xFeO₃) nanoparticles through a methoxy-aided sol–gel process followed by dispersion in PVA polymer. The structural and morphological characteristics of the nanoparticles were extensively examined using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The study revealed a rhombohedral distorted perovskite structure and increased crystallite size with higher gadolinium concentrations. Dielectric properties of the nanocomposite material was investigated at low and high frequencies to assess the material’s suitability for high-frequency conformal antennas. The PVA/Bi_0.9Gd_0.1FeO₃ nanocomposite films exhibited a relative wave impedance of 0.6 with a miniaturization factor of 1.89 making it eligible for microwave device applications. The microstrip patch antenna modeled and simulated with the PVA/Bi_0.9Gd_0.1FeO₃ composite exhibited a return loss of − 21.9 dB in the X band of the frequency spectrum. The functionality of the antennas was tested for the bending conditions of radius 10 mm and 30 mm, exhibiting a return loss of − 41.2 dB and − 23.5 dB in the X band with an ultrawide bandwidth of 5 GHz. The results of PVA/Bi_0.9Gd_0.1FeO₃ nanocomposite substrate antennas exhibit enhanced performance for application in wireless wearable devices.

Transparent ceramics nowadays finds applications in infrared windows, lamps covers, optoelectronic devices, smart phone screens and especially as host materials for solid-state lasers. One such ceramic material, Y₂O₃ was considered in the present investigation and the effect of neodymium (Nd) and erbium (Er) at different concentrations (0.5, 1.0, 1.5 and 2.0 at%) was studied. Transparent ceramic pellets were synthesized by co-precipitation method, sintered at high vacuum and finally polished. Structural characterizations confirmed the presence of cubic phase and scanning electron micrographs established the compactness of the samples with no secondary phase. The ceramics were found to have good transparency around 75%. Refractive index measurements showed least absorption at higher wavelengths which ensures good transmission properties. The upconversion and downconversion mechanisms are discussed in detail with varying Er concentration for different excitation wavelengths. The observations clearly indicate green and red emissions which ensure the effective utilization of these transparent ceramics as dual mode emitters.

Bubble nuclei are an exotic class of nuclear systems showing a central region of reduced nucleon density. The occurrence of such depletion (a bubble)is an interesting nuclear phenomenon, whose underlying microscopic origin provides a rapidly developing field of research in nuclear structure. In the present work, the properties of (medium) bubble nuclei are analyzed using shell model calculations. We addressed the question of deriving a criterion that allows identifying experimentally bubble nuclei using the form factor. As an extension of the seminal work of Wong in the 70 s, different mean fields have been proposed and their properties discussed. In addition, the effect of a bubble structure on the charge density distribution, the form factor and the single-particle levels, is discussed through their dependence on the inner-to-outer radius ratio p. In this way, level crossing and inversion have been obtained. Such results lead to the magic numbers 18 and 32, low angular momentum state occupancy reduction, and hence to candidates for bubble structure in exotic nuclei.

Perovskite based compounds have demonstrated unique performance in range of applications. Particularly, KMnF₃ has gained much importance in recent years. However, loading various contents of H ion to be situated at F site would improve the desired physical properties of the pristine KMnF₃. This account carries out density functional theory (DFT) calculations via using CASTEP code. GGA approximation and PW91 functional were adopted to investigate the structural, optoelectronic, and mechanical properties of KMnH_xF_3-x at (x = 0.25 and 0.50). The optimized lattice constants of the pure configuration were in good agreements with the published literature. Moreover, KMnF₃ exhibits a semiconducting nature with a direct electronic band gap of 2.177 eV. The modelled configurations demonstrate negative values of formation energies indicating the possibility of experimental synthesis. The analysed band structure reveals reducing tendency after H insertion. Furthermore, Optical results show an enhancement in the absorption spectra after the insertion of Hydrogen toward visible region of the electromagnetic radiation. Finally, elastic properties have been recorded and suggested that these compounds are mechanically stable. The current findings would significantly contribute in the field of solar cell applications and optoelectronic devices.

The effects of electron-acoustic (EA) waves’ head-on collisions and rogue wave (RW) production are studied in a collisionless, unmagnetized plasma composed of stationary ions, deformed Kaniadakis-distributed hot electrons, and cold fluid electrons. The nonlinear Schrödinger equation is generated using the standard reductive perturbation (SRP) approach, and the Korteweg-de Vries (KdV) equations (KdVEs) and modified KdVEs (mKdVEs) are determined via the general case using the extended Poincaré-Lighthill-Kuo (ePLK) perturbation method (ePLKM). In particular, the influence of the density ratio and the deformed Kaniadakis parameter on the RW structure, the creation of EA soliton structures, and phase shifts resulting from head-on collisions are examined. The construction of EA solitons, the generation of RW, and the variations of phase shifts are found to be significantly influenced by the parameters in question. In this work, the collisions of KdV solitons show positive and negative phase shifts. Though both the positive and negative phase shifts result from the interaction of mKdV solitons and the influence of the relevant parameters, only the positive phase shifts are studied here.

This study explores the origins of cosmic rays and their secondary messengers, focusing on the potential role of four BL Lacs—W Comae, 1ES 1959+650, PKS 2005-489, and PKS 2155-304—as potential sources of astrophysical neutrinos and gamma rays. We analyzed a single-zone model to understand the interactions between high-energy protons and ambient photons within blazar jets, leading to neutrino production observables and gamma-ray emission. This modeling contextualizes the emissions within multiwavelength observations and evaluates the capabilities of the next-generation Cherenkov Telescope Array Observatory (CTAO) in detecting these emissions. Our estimations suggest that these sources could be effective emitters of CRs, highlighting the need for future multimessenger observations to further investigate and constrain this class of sources.