Irapuato, Mexico
Irapuato, Mexico

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De La Fuente-Salcido N.M.,Autonomous University of Coahuila | Barboza-Corona J.E.,Campus Irapuato Salamanca | Espino Monzon A.N.,Autonomous University of Coahuila | Pacheco Cano R.D.,Campus Irapuato Salamanca | And 4 more authors.
The Scientific World Journal | Year: 2012

Previously we described a rapid fluorogenic method to measure the activity of five bacteriocins produced by Mexican strains of Bacillus thuringiensis against B. cereus 183. Here we standardize this method to efficiently determine the activity of bacteriocins against both Gram-positive and Gram-negative bacteria. It was determined that the crucial parameter required to obtain reproducible results was the number of cells used in the assay, that is, ∼ 4×108cell/mL and ∼7×108cell/mL, respectively, for target Gram-positive and Gram-negative bacteria. Comparative analyses of the fluorogenic and traditional well-diffusion assays showed correlation coefficients of 0.88 to 0.99 and 0.83 to 0.99, respectively, for Gram-positive and Gram-negative bacteria. The fluorogenic method demonstrated that the five bacteriocins of B. thuringiensis have bacteriolytic and bacteriostatic activities against all microorganisms tested, including clinically significant bacteria such as Listeria monocytogenes, Proteus vulgaris, and Shigella flexneri reported previously to be resistant to the antimicrobials as determined using the well-diffusion protocol. These results demonstrate that the fluorogenic assay is a more sensitive, reliable, and rapid method when compared with the well-diffusion method and can easily be adapted in screening protocols for bacteriocin production by other microorganisms. © 2012 Norma M. de la Fuente-Salcido et al.


Barrientos-Garcia A.,Campus Irapuato Salamanca | Sukhoivanov I.A.,Campus Irapuato Salamanca | Andrade-Lucio J.A.,Campus Irapuato Salamanca | Guryev I.,University of Salamanca | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Here we propose a simple design for a solid-core photonic crystal fiber made of silica by keeping the golden ratio (1.618) between pitch and air hole diameter λ/d in a subset of six rings of air-holes with hexagonal arrangement. In the case when we have a pitch equal to one micron (λ =1 μm), we need air-holes diameters d=0.618 μm in order to obtain the golden ratio parameter (λ/d=1.618), and achieve two zero dispersion wavelength (ZDW) points at 725 nm and 1055 nm; this gives us the possibility to use this fiber in supercontinuum generation using a laser emission close to that points. We analyzed a series of fibers using this relation and show the possibilities of tunable ZDW in a wide range of wavelengths from 725 nm to 2000 nm with low losses and small effective area. In agreement with the ZDW point needed, the geometry of the structure can be modified to the point of having only three rings of air holes that surround the solid core with low losses and good confinement mode. The design proposed here is analyzed using the finite element method (FEM) with perfectly matched layers (PML), including the material dispersion directly into the model applying the Sellmeier's equation. © 2014 SPIE.


Mendoza-Miranda J.M.,National Polytechnic Institute of Mexico | Ramirez-Minguela J.J.,University of Guanajuato | Munoz-Carpio V.D.,Campus Irapuato Salamanca | Navarro-Esbri J.,Jaume I University
International Journal of Refrigeration | Year: 2015

This paper presents a model of shell and tube evaporator with micro-fin tubes using R1234yf and R134a. The model developed for this evaporator uses the ε-NTU method to predict the evaporating pressure, the refrigerant outlet enthalpy and the outlet temperature of the secondary fluid. The model accuracy is evaluated using different two-phase flow boiling correlations for micro-fin tubes and comparing predicted and experimental data. The experimental tests were carried out for a wide range of operating conditions using R134a and R1234yf as working fluids. The predicted parameter with maximum deviations, between the predicted and experimental data, is the evaporating pressure. The correlation of Akhavane Behabadi et al. was used to predict flow boiling heat transfer, with an error on cooling capacity prediction below 5%. Simulations, carried out with this validated model, show that the overall heat transfer coefficient of R1234yf has a maximum decrease of 10% compared with R134a. © 2014 Elsevier Ltd and IIR. All rights reserved.


Sierra-Hernandez J.M.,Campus Irapuato Salamanca | Rojas-Laguna R.,Campus Irapuato Salamanca | Vargas-Rodriguez E.,University of Guanajuato | Estudillo-Ayala J.M.,Campus Irapuato Salamanca | And 3 more authors.
Laser Physics | Year: 2013

In this paper a tunable multi-wavelength erbium doped fiber laser, based on a Mach-Zehnder interferometer, is presented. The interferometer is achieved by splicing a piece of photonic crystal fiber between two segments of a single-mode fiber. Here, by changing the curvature radius in the Mach-Zehnder interferometer, the single-, double- or triple-line emissions can be tuned from 1526 to 1550 nm. Finally it is shown, via experimental results, that the laser has high stability at room temperature. © 2013 Astro Ltd.

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