Scielo RSS <![CDATA[Revista mexicana de física]]> vol. 65 num. 6 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Complex dielectric behavior of doped polyaniline conducting polymer at microwave frequencies using time domain reflectometry]]> Abstract Nano size Tin Oxide is prepared in the laboratory from tin tetrachloride SnCl4 and ammonia solution. The polyaniline (PAni) conducting polymer is synthesized by chemical oxidation method using ammonium persulphate as oxidizing agent. The PAni-SnO2 composite was prepared by insitu method. Scanning electron microscopy (SEM) results confirm the particle size of SnO2 in the range of 30-48 nm. Dielectric behavior of nanocomposite of PAni-SnO2 was studied in the frequency range 0.01- 20 GHz at -5, 0, 5, 10, 15, 20 and 25°C. The dielectric constant (real part 𝜀') and dielectric loss (imaginary part 𝜀") have been evaluated. The relaxation time (τ, τ0, and τ1) are calculated. The relaxation time was found to be of the order of ps. The dielectric properties of the solids in the form of powders may be useful in understanding the structural behavior of particles in an alternating field. These studies may also be used to formulate models for predicting the dielectric properties. The microwave absorbing property is decided from the dielectric loss of the material. It is observed that the PAni-SnO2 composite can be a good electromagnetic shielding material. <![CDATA[Gallium-assisted growth of InSb nanowire]]> Abstract Indium antimony (InSb) nanowires have been synthesized by chemical vapor deposition, and we found that adding gallium as the other evaporation resource can increase the density of nanowires and no doping pollution. For the growth of InSb nanowire, Au film was annealed to form Au nanoparticles as catalysts and explain its catalytic principle. We thought that gallium which coated on the surface of Au nanoparticles assisted nucleation and growth of InSb nanowire in the early stage. The diameter of the InSb nanowires was 60-100 nm and 1-5 μm in length. The grown nanowires have good crystallinity. We found that the surface of InSb was oxidized, and the main oxide was indium oxide. We discovered the tip morphologies of nanowires are different and discussed the causes of this phenomenon in detail. <![CDATA[Structural and electrical properties of dodecylbenzene sulphonicacid doped polypyrrole/zirconium oxide composites]]> Abstract Polypyrrole (PPy) dispersed in organic solvents was synthesized utilizing of dodecylbenzene sulphonic acid (DBSA) as a useful dopant. Composites of doped PPy with DBSA and also mixed with zirconium oxide (ZrO2) nanoparticles were achieved by the chemical polymerization method. Raman spectroscopy has been adopted to confirm the interaction between PPy-DBSA and ZrO2. The SEM also confirms the dual-phase structure of platelet and eggshell in PPy-DBSA-ZrO2. Temperature -dependant DC conductivity exhibited three- dimensional variable ranges hopping (3D-VRH) model. The density of states, hopping length and to activation energy were calculated and it was observed to be effected by increasing the weight ratio of ZrO2 into PPy-DBSA. <![CDATA[The Feynman-Dyson propagators for neutral particles (locality or non-locality?)]]> Abstract An analog of the S = 1/2 Feynman-Dyson propagator is presented in the framework of the S = 1 Weinberg's theory. The basis for this construction is the concept of the Weinberg field as a system of four field functions differing by parity and by dual transformations. Next, we analyze the recent controversy in the definitions of the Feynman-Dyson propagator for the field operator containing the S = 1/2 self/anti-self charge conjugate states in the papers by D. Ahluwalia et al. [11] and by W. Rodrigues Jr. et al [18,19]. The solution to this mathematical controversy is obvious. It is related to the necessary doubling of the Fock Space (as in the Barut and Ziino works), thus extending the corresponding Clifford Algebra. However, the logical interrelations of different mathematical foundations with physical interpretations are not so obvious. We present some insights with respect to. <![CDATA[On fractional liénard-type systems]]> Abstract In this work, we present numerical results of classical Lienard-type systems in a very general context, since we consider several types of derivatives (integer order and fractional order, global and local). Additionally, we made theoretical-methodological observations.<hr/>Resumen En este trabajo, presentamos resultados numericos de sistemas tipo Lienard en un contexto muy general, puesto que consideramos varios tipos de derivadas (de orden entero y fraccionario, globales y locales). Adicionalmente, hacemos observaciones teóricas y metodológicas. <![CDATA[Soliton propagation of electromagnetic field vectors of polarized light ray traveling along with coiled optical fiber on the unit 2-sphere 𝕊<sup>2</sup>]]> Abstract In this paper, we relate the evolution equation of the electric field and magnetic field vectors of the polarized light ray traveling along with a coiled optical fiber on the unit 2-sphere 𝕊2 into the nonlinear Schrodinger's equation, by proposing new kinds of binormal motions and new kinds of Hasimoto functions, in addition to commonly known formula of the binormal motion and Hasimoto function. All these operations have been conducted by using the orthonormal frame of spherical equations, that is defined along with the coiled optical fiber lying on the unit 2-sphere 𝕊 2. We also propose perturbed solutions of the nonlinear Schrodinger's evolution equation that governs the propagation of solitons through the electric field (E) and magnetic field (M) vectors. Finally, we provide some numerical simulations to supplement the analytical outcomes. <![CDATA[The relation of Zakharov-Shabat scattering problem to Schrödinger equation with complex potential and approximations for soliton parameters]]> Abstract The relation of Zakharov-Shabat scattering problem to Schrödinger equation with complex potential is used to analytically approximate parameters of high power solitons produced in positive Kerr media with chirped parabolic pulses. The soliton parameters are estimated for different types of chirp and intensity distortions. The comparison with numerics is discussed. <![CDATA[Projective method for spinorial techniques: unifying calculational framework for Dirac amplitudes]]> Abstract There have been numerous methodologies to perform the calculation of spin-dependent amplitudes for Dirac particles. All of them have their own advantages and properties, but there is no general framework to address the analytic calculation of such amplitudes. In this work, we use the closure property of massive spinors to present a new and general approach to compute transition amplitudes for general spin states. We argue that this perspective can be used to reformulate all other techniques and to relate all of them. Particularly, it is shown that the massless spinor and the helicity spinor techniques can be formulated through this language. Finally, we give an example of this calculation as a procedure by computing the spin-dependent amplitude for the Compton process and comment some of the strengths of our method. <![CDATA[Low-cost embedded system for optical imaging of intrinsic signals]]> Abstract This paper describes the proof-of-concept evaluation of a low-cost imaging system for obtaining functional connectivity maps of in vivo murine models. This non-contact system is based on the Raspberry Pi 3 and its V2 camera and offers a method for obtaining resting-state images of brain activity without the use of extrinsic contrast agents. The system was fully characterized in terms of dark signal, linearity, sensor noise resolution, and spatial frequency response. One mouse was observed in vivo, and functional connectivity maps were obtained by combining resting-state analysis and optical intrinsic signals imaging. Intra-mouse variations in functional connectivity remain consistent across multiple imaging sessions. In principle, inexpensive optical imaging of intrinsic signals allows the study of the mechanisms underlying human brain disorders in well-controlled murine models. <![CDATA[Analytical treatment in optical metamaterials with anti-cubic law of nonlinearity by improved exp(-Ω(η))-expansion method and extended sinh-Gordon equation expansion method]]> Abstract Here, the improved exp(-Ω(η))-expansion method and extended sinh-Gordon equation expansion method are being applied on (1+2)-dimensional non-linear Schrödinger equation (NLSE), optical metamaterials, with anti-cubic nonlinearity. Materials like photovoltaic-photorefractive, polymer and organic consists of spatial solitons and optical nonlinearities, which can be identified by seeking help from NLSE with anti-cubic nonlinearity. Abundant exact traveling wave solutions consisting of free parameters are established in terms of bright, dark, singular, kink-singular, and combined dark-bright soliton solutions. Various arbitrary constants obtained in the solutions help us to discuss the graphical behavior of solutions and also grants flexibility to formulate solutions that can be linked with a large variety of physical phenomena. Moreover, graphical representation of solutions are shown vigorously in order to visualize the behavior of the solutions acquired for the equation. <![CDATA[Thermal performance comparison of recycled and clay roof tiles due heat radiation by digital holographic interferometry]]> Abstract It is through the recycling process that disposed waste materials could regain a new purpose on their use, take for instance the tetrapakTM packaging. This material consists of thermally joint layers of paper, aluminum, and polyethylene. Once recycled, the two latter materials form a new composite named poly-aluminum, which is employed to manufacture roof tiles that serve as environmental protection against solar radiation and rain. This work reports an optical nondestructive comparison study of the surface deformation in poly-aluminum and clay roof tiles exposed to heat radiation. The optical system, based on a sensitive out-of-plane interferometer configuration, records several image holograms from a controlled heat source that raises the temperature on the tile's surface. The retrieved optical phase renders the tiles surface's deformation at three different temperature values: 26, 36 and 46 degrees on a Celsius scale. The results show a greater deformation profile from the poly-aluminum tile compared with the classic clay tile. However, its thermal insulation properties are better than those of the clay roof tile. <![CDATA[Influencing factor analysis of the short circuit ratio on grid-connected photovoltaic systems]]> Abstract Over the past few years, solar energy conversion technology is sharply developing. An important first step is to make this conversion system more effective and more reliable. The main objective of this paper is to study the influence of the power of the electricity network on the connection of the solar energy source. The photovoltaic source has been examined under the effect of the variation of the parameters of the networks such as the power of short-circuit and the frequency. The results obtained by the simulation have shown that the photovoltaic source has amazing performance if the power system is of high or medium power and with constant parameters. <![CDATA[Preparation, optical characterization and stability of gold nanoparticles by facile methods]]> Abstract Gold nanoparticles were obtained by reduction of chloroauric acid HAuCl4 by two methods: conventional heating and microwave synthesis. In the microwave method, different cycles and sonication time were analyzed to establish the synthesis with smaller nanoparticle size and higher absorbance. The influence of synthesis method, cycles quantity and sonication time in the gold nanoparticles size and plasmon resonance were studied. Gold nanoparticles were analyzed by UV-Vis spectrophotometry, dynamic light scattering and surface electron microscopy. The results indicate that the nanoparticles obtained by microwave have bigger size than those obtained by conventional heating, however, present higher absorption. The microwave nanoparticles were analyzed one year after its synthesis and it was found that the plasmon resonance signal remains almost unchanged. Finally, two equations were derived from the analyzes for estimate molar extinction coefficient, molar concentration, and nanoparticle average diameter.