Vol. 65 No. 4 Jul-Aug (2019): Revista Mexicana de Física

Blazars are a subclass of AGN and flaring in multi-TeV gamma-ray seems to be the major activity in high energy blazars a subgroup 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 photohadronic model and taking EBL correction into account, flaring can be explained very well. Here in this review, photohadronic model is discussed and applied to explain the multi-TeV flaring from nearby high energy blazars:
Markarian 421, Markarian 501 and 1ES1959+650.

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.

Copaiba oils (COP), Andiroba (AND) and Brazil nuts (CDB) have been studied in several areas of science, mainly interests in the pharmacological and food industry. A rapid analysis by techniques such as Raman and Fourier Transform Infrared spectroscopy (FTIR) gives us a set of information concerning the molecular nature. Results of FTIR and Raman for COP, AND and CDB, present 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 regions 800-2000 cm$^{-1}$ and 2500-3000 cm$^{-1}$, which fit the general characteristics of the AFs, strongly associated with oleic, linoleic, and palmitic acids. COP presents mode with 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 that obtained by FTIR and Raman.

The bound state approximate solution of the Schrodinger equation is obtained for the q-deformed Hulthen plus generalized inverse quadratic Yukawa potential (HPGIQYP) in -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.

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 (XPS); while structural properties were investigated using X-ray diffraction (XRD). High-resolution XPS spectra present a gradual shift to higher binding energies on the Al_2ppeak when nitrogen pressure is incremented, indicating the formation of the AlN compound. At 30 mTorr nitrogen pressure, theAl_2p 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.

EPDM 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 that 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.

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 crystallize with a stannite structure in the tetragonal space group I2m (Nº 121), Z = 2, unit cell parameters a = 5.3384(1) Å, c = 10.5732(3) Å, V = 301.32(3) ų, acknowledged as a normal valence adamantane-structure.

The crystal structure of the ordered vacancy compound (OVC) Cu₃In₅Te₉ was analyzed using powder X-ray diffraction data. Several structural models were derived from the structure of the Cu-poor Cu-In-Se compound b-Cu_0.39In_1.2Se₂ by permuting the cations in the available site positions. The refinement of the best model by the Rietveld method in the tetragonal space group P2c (Nº 112), with unit cell parameters a = 6.1852(2) Å, c = 12.3633(9) Å, V = 472.98(4) ų, led to R_p = 7.1 %, R_wp = 8.5 %, R_exp = 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 (½,½,0), In2 in 2d (0,½,¼); Cu2-In3 in 2b (½,0,¼); in 2a (0,0,¼); Te in 8n (x,y,z).

Mesoscopic theory is applied to show the nanoparticles migration through a porous 3D cavity. Various amounts of Lorentz forces, buoyancy and Darcy number on working fluid behavior are considered and depicted. Al₂O₃-H₂O is selected including Brownian motion effect. Outputs are illustrated in views of streamlines, isokinetic and isotherms contours. Outputs display that the enhancing magnetic forces lead to rise in conduction mode. Nu_ave augments with the decrease in Lorentz forces while it improves for stronger Lorentz forces.

This article executes MHD heat transport augmentation in aqueous based  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.

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 of gravitational potential  $g_{tt}$ and the electric field. The choice of electric field implies that this model supports values of compactness
$u=GM/c^2R\leq 0.5337972212$, values higher than the case without electric charge ($u\leq 0.3581350065$), being this feature of relevance to get to represent compact stars. In addition, density and pressure are positive functions, bounded and decreasing monotones, the electric field is a monotonously increasing function as well as satisfying the condition of causality so the model is physically acceptable. In a complementary way, the internal behavior of the hydrostatic functions and their values are obtained taking as a data the corresponding to a star of $1 M_\odot$,for different values of the charge parameter, obtaining an interval for the central density $\rho_c\approx (7.9545,2.7279) 10^{19}$ $ Kg/m^3$ characteristic of compact stars.

A model for low mass compact objects with compactness ratio $u\leq 0.06092997016$ is presented here. Density, pressure and sound speed are regular and monotonic decreasing functions. The change between the central density $\rho_c$ and the density on the surface $\rho_b$ is lower than $3.94\%$ and the maximum change occurs for the biggest compactness, i.e. $\rho_c=1.039350237\rho_b$. 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 $R=2.6{\rm Km}$ and mass $M=0.2 M_\odot$. According to our model it comes out that the density on the surface is $\rho_b=5.388074 \times 10^{17} Kg/m^3$ and its central density $\rho_c=1.007150 \rho_b$ is slightly bigger than the surface density and larger than the nuclear density.

We study quantum properties of a two-dimensional anharmonic oscillator in the space-space and momentum-momentum in noncommutative variables. This work show ex- plicitly the effects of both deformations in the energy levels. The perturbation term in the Hamiltonian manifest the main difference of the noncommutative parameters. Particular nu- merical values of noncommutative parameters are examined and graphically illustrated for different nx and ny non-negative integers.

The elastic scattering angular distributions of weakly bound nucleus
$^{8}$Li on $^{7}$Li, $^{9}$Be, $^{12}$C, $^{13}$C, $^{14}$N,
$^{27}$Al, $^{51}$V, $^{58}$Ni, and $^{208}$Pb are analyzed at
various incident energies. For this purpose, the real potential is
generated for nine different density distributions of the $^{8}$Li
nucleus by using the double folding model 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.

We study the pairwise quantum correlations for teleported state via a symmetric multi-qubit
system. In the other words, the proposed model is considered as a quantum channel. Using the
quantum discord, super quantum discord and concurrence to quantify quantum correlations for
teleported state, some analytical and numerical results are presented. Moreover, we compare the
dynamical evolutions of quantum correlations and fidelity versus measurement strength and the
number of qubit channel for teleported state via symmetric multi-qubit model. Our main goal
now is to study how we can increase the quantum correlations and the fidelity of the teleported
state in the presence of decoherence. The results show that, 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, quantum correlations can provide an effective role in
quantum teleportation

Rev. Mex. Fis. 65 (4) 2019

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