Scielo RSS <![CDATA[Revista mexicana de física]]> vol. 65 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Multi-TeV flaring in nearby high energy blazars: A photohadronic scenario]]> Abstract Blazars are a subclass of Active Galactic Nuclei and flaring in multi-TeV gamma-ray seems to be the major activity in high energy blazars a subgrup of blazars. Flaring is also unpredictable and switches between quiescent and active states involving different time scales and fluxes. While in some high energy blazars a strong temporal correlation between X-ray and multi-TeV gamma-ray has been observed, outbursts in some other have no low energy counterparts and explanation of such extreme activity needs to be addressed through different mechanisms, as it is not understood well. The extragalactic background light (EBL) plays an important role in the observation of these high energy gamma-rays as it attenuates through pair production of electron-positron and also changes the spectral shape of the high energy photons. In the context of the photohadronic model and taking EBL correction into account, flaring can be explained very well. In a series of papers, we have developed this model to explain multi-TeV flaring events form many blazars. In this review, the photohadronic model is discussed and applied to explain the multi-TeV flaring from nearby high energy blazars: Markarian 421, Markarian 501 and 1ES1959+650. <![CDATA[Polymer weight determination from numerical and experimental data of the reduced viscosity of polymer in brine]]> Abstract The molecular weight of poly[acrylamide-co-vinylpyrrolidone-co-(vinyl benzyl) trimethyl ammonium] chloride is determined from numerical and experimental data of the reduced viscosity of polymer in brine (with 0.1M NaCl) at normal temperature and pressure. The methodology is based on the numerical results of the mean radius of gyration of polymer and reduced viscosity which is derived from the molecular dynamics simulation of the mixture by using the NPT ensemble. The formula of the reduced viscosity as a function of the polymer radius of gyration and the polymer concentration in brine is proposed. <![CDATA[Approach by Raman and infrared spectroscopy in three vegetable oils from the Brazilian Amazon]]> Abstract Copaiba oils (COP), Andiroba (AND) and Brazil nuts (CDB) have been studied in several areas of science, mainly due to the interest from the pharmacological and food industries. A rapid analysis by techniques such as Raman and Fourier Transform Infrared spectroscopy (FTIR) gives us information concerning thier molecular nature. Results of FTIR and Raman for COP, AND and CDB, show modes of vibrations linked to fatty acids (AFs) in the sample composition, whose structures are rich in C=O, C=C and C-H. The results suggest modes in the 800-2000 cm-1 and 2500-3000 cm-1 regions, which fit the general characteristics of the AFs, strongly associated with oleic, linoleic, and palmitic acids. COP presents a mode with an intense peak at 2800-3000 cm-1, just related to the copalic acid, that presents contributions of rings of carbon. Finally, the results were discussed with DFT calculations complementing those obtained by FTIR and Raman. <![CDATA[Any <em>l</em>-state solutions of the Schrödinger equation for <em>q</em>-deformed Hulthen plus generalized inverse quadratic Yukawa potential in arbitrary dimensions]]> Abstract The bound state approximate solution of the Schrodinger equation is obtained for the q-deformed Hulthen plus generalized inverse quadratic Yukawa potential (HPGIQYP) in D-dimensions using the Nikiforov-Uvarov (NU) method and the corresponding eigenfunctions are expressed in Jacobi polynomials. Seven special cases of the potential are discussed and the numerical energy eigenvalues are calculated for two values of the deformation parameter in different dimensions. <![CDATA[Deposit of AlN thin films by nitrogen reactive pulsed laser ablation using an Al target]]> Abstract We report the synthesis of AlN hexagonal thin films by pulsed laser ablation, using Al target in nitrogen ambient over natively-oxidized Si (111) at 600°C. Composition and chemical state were determined by X-ray photoelectron spectroscopy, while structural properties were investigated using X-ray diffraction. High-resolution XPS spectra present a gradual shift to higher binding energies on the Al2p peak when nitrogen pressure is incremented, indicating the formation of the AlN compound. At 30 mTorr nitrogen pressure, the Al2p peak corresponds to AlN, located at 73.1 eV, and the XRD pattern shows a hexagonal phase of AlN. The successful formation of the AlN compound is corroborated by UV-Vis reflectivity measurements. <![CDATA[Effect of foaming agent on the mechanical properties of sulfur and peroxide cured ethylene propylene diene monomer rubbers]]> Abstract Ethylene Propylene Diene Monomer rubbers loaded with different concentration of azodicarbonamide as a foaming agent using two different cross-linking systems were subjected to the mechanical, compression and swelling tests at room temperature (300°K). Samples vulcanized by peroxide reveal more advantage over those vulcanized by sulfur especially for the amount of specific gravity and the compression test. The tensile test shows a noticeable increase in the true stress and strain at break for the sulfur cross-linking system than the peroxide one. For the swelling test, the empirical equation used by Kumnuantip and Sombatsompop shows the best fitting for the degree of swelling - time data. <![CDATA[Synthesis and crystal structure of the quaternary semiconductor Cu<sub>2</sub>NiGeS<sub>4</sub>, a new stannite-type compound]]> Abstract The crystal structure of the quaternary compound Cu2NiGeS4, belonging to the system I2-II-IV-VI4, was characterized by Rietveld refinement using X-ray powder diffraction data. This material crystallizes with a stannite structure in the tetragonal space group I42m (N°121), Z = 2, unit cell parameters a = 5.3384 (1) Å, c = 10.5732 (3) Å, V = 301.32 (3) Å3, acknowledged as a normal valence adamantane-structure. <![CDATA[On the crystal structure of the ordered vacancy compound Cu3In5◻Te9]]> Abstract The crystal structure of the ordered vacancy compound (OVC) Cu3In5◻Te9 was analyzed using powder X-ray diffraction data. Several structural models were derived from the structure of the Cu-poor Cu-In-Se compound β-Cu0.39In1.2Se2 by permuting the cations in the available site positions. The refinement of the best model by the Rietveld method in the tetragonal space group P42c (N° 112), with unit cell parameters a = 6.1852(2) Å, c = 12.3633(9) Å, V = 472.98(4) Å3, led to Rp = 7.1 %, Rwp = 8.5 %, Rexp = 6.4 %, S = 1.3 for 162 independent reflections. This model has the following Wyckoff site atomic distribution: Cu1 in 2e (0,0,0); In1 in 2f (1/2,1/2,0), In2 in 2d (0,1/2,1/4); Cu2-In3 in 2b (1/2,0,1/4); ◻ in 2a (0,0,1/4); Te in 8n (x, y, z). <![CDATA[Lattice Boltzmann method modeling of magnetic water-based nanofluid through a permeable three-dimensional enclosure]]> Abstract In this work, the mesoscopic theory is invoked to depict nanoparticle transportation through a porous cavity. Different amounts of Lorentz forces, Rayleigh number and permeability on the working fluid treatment have been examined. Al2O3-H2O is selected including the Brownian motion effect. Isokinetic, streamlines, and isotherms contours are various shapes of outputs. Results illustrate that the increase in magnetic forces lead toan increase in the conduction mode. Dispersing nanoparticles aids to incrase the Hartmann number. <![CDATA[Heat transfer augmentation in water-based TiO<sub>2</sub> nanoparticles through a converging/diverging channel by considering Darcy-Forchheimer porosity]]> Abstract This article executes MHD heat transport augmentation in aqueous based TiO2 nanoparticles fluid flow over convergent/divergent channel. Joule heating, magnetic field and Darcy-Forchheimer effects are explained for concentration and temperature distributions. Darcy-Forchheimer theory is utilized to explore the impact of porous medium. The system of partial differential expressions is transformed into ordinary ones and evaluated numerically by implementing RKF-45 scheme. Expressions for velocity and temperature profile are derived and plotted under the assumption of flow parameter. Influence of various parameters on heat transfer rates and surface drag force are discussed with the help of table and plots. <![CDATA[A charged perfect fluid model with high compactness]]> Abstract A relativistic, static and spherically symmetrical stellar model is presented, constituted by a perfect charged fluid. This represents a generalization to the case of a perfect neutral fluid, whose construction is made through the solution to the Einstein-Maxwell equations proposing a form for the gravitational potential gtt and the electric field. The choice of electric field implies that this model supports values of compactness u = GM / c2R ≤ 0.5337972212, wich are higher than the case without electric charge (u = 0.3581350065), being this feature of relevance to represent compact stars. In addition, density and pressure are positive functions, bounded and decreasing monotones while the electric field is a monotonously increasing function as well as satisfying the condition of causality, so the model is physically acceptable. Additionally, the internal behavior of the hydrostatic functions and their values are obtained taking as data the corresponding to a star of 1 Mʘ for different values of the charge parameter, obtaining an interval for the central density ρc ≈ (7.9545, 2.7279)1019 Kg/m3 characteristic of compact stars. <![CDATA[A model for low mass compact objects]]> Abstract A model for low mass compact objects with compactness ratio u ≤ 0.06093 is presented here. Density, pressure and sound speed are regular and monotonic decreasing functions. The change between the central density ρc and the density on the surface ρb is lower than 3.94% and the maximum change occurs for the biggest compactness, i.e. ρc = 1.0394ρb. This allows us to apply this model for the case of compact stars in which the density variation is very small. In particular, we can use this model for PSR B0943 + 10, a quark star candidate, with radius R = 2.6 km and mass M = 0.02 Mʘ. According to our model it turns out that the density on the surface is ρb = 5.3881x1017 kg/m3 and the central density, ρc = 1.0072ρb, is slightly large than the surface density and larger than the nuclear density. <![CDATA[On the noncommutative energy level in a two-dimensional anharmonic oscillator]]> Abstract We study quantum properties of a two-dimensional anharmonic oscillator in the space-space and momentum-momentum in noncommutative variables. This work shows explicitly the effects of both deformations in the energy levels. The perturbation term in the Hamiltonian manifest the main difference of the noncommutative parameters. Particular numerical values of noncommutative parameters are examined and graphically illustrated for different nx and ny non-negative integers. <![CDATA[Microscopic analysis of elastic scattering cross sections for different densities of <sup>8</sup>Li nucleus on light, medium and heavy mass targets]]> Abstract The elastic scattering angular distributions of the weakly bound nucleus 8Li on 7Li, 9Be, 12C, 13C, 14N, 27Al, 51V, 58Ni, and 208Pb are analyzed at various incident energies. For this purpose, the real potential is generated for nine different density distributions of the 8Li nucleus by using the double folding within the optical model. The theoretical results are in good agreement with the experimental data. In our study, also, new and practical sets of imaginary potentials for the investigated densities are derived. <![CDATA[The pairwise quantum correlations for teleported state via a symmetric multi-qubit system]]> Abstract The dynamics of pairwise quantum correlations for teleported state via a symmetric multi-qubit system is investigated. Using the quantum discord, super quantum discord and concurrence to quantify quantum correlations for teleported state, some analytical and numerical results are presented. We compare the dynamical evolutions of quantum correlations and fidelity versus the measurement strength and the number of qubit channel for teleported state via symmetric multi-qubit model. The results show that the measurement strength and the number of qubit can control the quantum information obtained through the quantum channel. Therefore, measurement strength can be a good option for measuring exchanged information in the teleportation process. In addition to, this quantum correlations can provide an effective role in quantum teleportation.