Power spectra in extended tachyon cosmologies

In the present work the power spectrum of a particular class of tachyon fields is compared with the one corresponding to a cosmological constant model. This is done for different barotropic indexes $\gamma_0$ and the background space time is assumed to be of the spatially flat Friedmann-Robertson-Walker type. The differential equation describing the perturbations is solved numerically and the power spectrum at the scale factor value $a=1$ is plotted for each case. The result is that the power spectrum of the standard tachyon field differs in many magnitude orders from the $\Lambda$CDM. However, the one with $\gamma_0=1.91$, which corresponds to a complementary tachyon field, coincides fairly well with the concordance model. Therefore, we conclude that the perturbed solutions constitute an effective method to distinguish between the different $\gamma_0$ values for the tachionization $\Lambda$CDM model and the fiducial model. The Statefinder parameters $\{r, s\}$, measuring the deviations of the analysed model from the concordance model, are also explicitly calculated. Our result suggest that, depending on the value of $\gamma_0$, these models can explain the observed expansion history or the perturbation power spectrum of the universe, but they may have problems in describing both features simultaneously.Comment: 7 pages, 7 figures, accepted for publication in General Relativity and Gravitatio

Emergent Universe as an interaction in the dark sector

A cosmological scenario where dark matter interacts with a variable vacuum energy for a spatially flat Friedmann-Robertson-Walker space-time is proposed and analysed to show that with a linear equation of state and a particular interaction in the dark sector it is possible to get a model of an Emergent Universe. In addition, the viability of two particular models is studied by taking into account recent observations. The updated observational Hubble data and the JLA supernovae data are used in order to constraint the cosmological parameters of the models and estimate the amount of dark energy in the radiation era. It is shown that the two models fulfil the severe bounds of $\Omega_{x}(z\simeq 1100)<0.009$ at the $2\sigma$ level of Planck.Comment: 15 pages, 8 figure

Exploring cloudy gas accretion as a source of interstellar turbulence in the outskirts of disks

High--resolution 2D--MHD numerical simulations have been carried out to investigate the effects of continuing infall of clumpy gas in extended HI galactic disks. Given a certain accretion rate, the response of the disk depends on its surface gas density and temperature. For Galactic conditions at a galactocentric distance of ~20 kpc, and for mass accretion rates consistent with current empirical and theoretical determinations in the Milky Way, the rain of compact high velocity clouds onto the disk can maintain transonic turbulent motions in the warm phase (~2500 K) of HI. Hence, the HI line width is expected to be ~6.5 km/s for a gas layer at 2500 K, if infall were the only mechanism of driving turbulence. Some statistical properties of the resulting forcing flow are shown in this Letter. The radial dependence of the gas velocity dispersion is also discussed.Comment: 13 pages, 3 figures, accepted for publication in ApJ Letter

Bending behavior analysis of geogrid reinforced adobe walls

La tierra cruda constituye el material de construcción más importante en muchas regiones del planeta. Dado el riesgo sísmico existente en la mayor parte de estas regiones, es necesario el desarrollo de técnicas de refuerzo eficaces y adecuadas desde un punto de vista tecnológico y socioeconómico. Este artículo analiza desde un punto experimental y analítico el comportamiento a flexión de muros de adobe reforzados con geomallas. Las leyes momento-curvatura de los muros ensayados son aproximadas mediante una serie de modelos analíticos que permiten analizar el comportamiento del material compuesto adobe-geomalla. Los resultados obtenidos muestran como la geomalla mejora el comportamiento de la mampostería de adobe en términos de resistencia y ductilidad, mejorando así su comportamiento en caso de movimiento sísmico.Rammed earth is a widely used building material in many regions of the world. Due to the high seismic risk in those areas, earthen constructions require suitable and efficient reinforcement techniques from a technological and socioeconomic point of view. This paper analyzes the bending behavior of geogrid reinforced adobe walls from an experimental and analytical point of view. The experimental bending moment-curvature relationships are analytically approached. The results show how geogrid reinforcement improves the performance of adobe masonry in terms of strength and ductility. Thus, a better seismic performance is achieve

Bending behavior analysis of geogrid reinforced adobe walls

La tierra cruda constituye el material de construcción más importante en muchas regiones del planeta. Dado el riesgo sísmico existente en la mayor parte de estas regiones, es necesario el desarrollo de técnicas de refuerzo eficaces y adecuadas desde un punto de vista tecnológico y socioeconómico. Este artículo analiza desde un punto experimental y analítico el comportamiento a flexión de muros de adobe reforzados con geomallas. Las leyes momento-curvatura de los muros ensayados son aproximadas mediante una serie de modelos analíticos que permiten analizar el comportamiento del material compuesto adobe-geomalla. Los resultados obtenidos muestran como la geomalla mejora el comportamiento de la mampostería de adobe en términos de resistencia y ductilidad, mejorando así su comportamiento en caso de movimiento sísmico.Rammed earth is a widely used building material in many regions of the world. Due to the high seismic risk in those areas, earthen constructions require suitable and efficient reinforcement techniques from a technological and socioeconomic point of view. This paper analyzes the bending behavior of geogrid reinforced adobe walls from an experimental and analytical point of view. The experimental bending moment-curvature relationships are analytically approached. The results show how geogrid reinforcement improves the performance of adobe masonry in terms of strength and ductility. Thus, a better seismic performance is achieve

Molecular thermodynamics of adsorption using discrete-potential systems

A molecular thermodynamics approach has been developed in order to describe the adsorption of fluids onto solid surfaces based on the use of discrete-potential fluid models. Using perturbation theories for fluids such as the Statistical Associating Fluid Theory (SAFT) and the Discrete Potential Theory (DPT), in combination with molecular simulation, we have formulated a two-dimensional approach to describe systems of interest for the oil industry, such as adsorption isotherms of carbon dioxide and asphaltenes

Organizational Capabilities of Retail Companies to Develop Green Marketing Strategies

The human being has damaged the planet by the indiscriminate consumption of products that are not friendly to the environment, hence now the trend of consumers to choose sustainable products. This is the reason why companies are changing the way they make their products, as well as the style of communication to inform that their products are favorable to the environment. The scope of this work is to assess retail enterprises ability for developing green marketing strategies. The study is quantitative-exploratory based on a non-probabilistic sample. A questionnaire was applied to 30 business owners and/or managers. Data was analyzed by using the principal components method. It was observed that the retail companies in Rioverde city, San Luis Potosí (S.L.P.) are able to develop green marketing strategies. The correlation matrix shows acceptable correlations and the values of the Sample Adequacy Measure (MSA) values are greater than 0.500: These values allow corroborating that the data structure is adequate to be examined by factor analysis. The analysis detects two latent factors that together explain 69.18% of the common variance. The results indicate that green marketing strategies require that owners or managers reformulate their business and processes from different perspectives: internally and with their customers. With respect the first point, staff must be trained on the importance of ecological products for the environment, health and the benefits for the company. With reference to, the second point, the owner or manager must identify the specific market for these products, because customers are varied and with different needs.

Flagellar Motility of Trypanosoma cruzi Epimastigotes

The hemoflagellate Trypanosoma cruzi is the causative agent of American trypanosomiasis. Despite the importance of motility in the parasite life cycle, little is known about T. cruzi motility, and there is no quantitative description of its flagellar beating. Using video microscopy and quantitative vectorial analysis of epimastigote trajectories, we find a forward parasite motility defined by tip-to-base symmetrical flagellar beats. This motion is occasionally interrupted by base-to-tip highly asymmetric beats, which represent the ciliary beat of trypanosomatid flagella. The switch between flagellar and ciliary beating facilitates the parasite's reorientation, which produces a large variability of movement and trajectories that results in different distance ranges traveled by the cells. An analysis of the distance, speed, and rotational angle indicates that epimastigote movement is not completely random, and the phenomenon is highly dependent on the parasite behavior and is characterized by directed and tumbling parasite motion as well as their combination, resulting in the alternation of rectilinear and intricate motility paths