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Damon A.,Colegio de Mexico | Iturbide F.A.,Instituto Tecnologico Superior Of Irapuato Itesi | Olalde-Portugal V.,CINVESTAV
Plant Ecology and Evolution | Year: 2013

Context - Oncidium poikilostalix (Kraenzl.) M.W.Chase & N.H.Williams (Orchidaceae) was first reported in Mexico in 2008 and grows on coffee bushes in shaded plantations in Soconusco region in southeast Mexico. Goal - To study the reproductive characteristics and the endophytic fungi with which this orchid is associated to evaluate current conservation status, its possible influence on other epiphytic orchids sharing the same coffee agroecosystem and identify the morphological and adaptive response that have permitted successful colonization of this human landscape. Methods - We determined flower production and percent fruit set, percent loss of seeds due to mechanical or biological damage and total seed rain in two populations, during two years (2008-2009). We characterized morphologically the seed of O. poikilostalix and isolated the fungi associated with its roots. Results - Rapid growth and development of the populations were observed at various levels: recruitment and survival levels were high, with many more adult plants and flowers found in both populations in the second year. Combined percent pollination rose from 1.82% in 2008 to 3.37% in 2009, resulting in the production of 3,387,468 seeds in 2008, rising to 10,001,096 in 2009. We isolated and identified to genus level, thirteen taxa of fungi, including various strains of Rhizoctonia sp. Conclusions - O. poikilostalix interacts with a variety of mycorrhizal symbionts in new habitats. O. poikilostalix is a vigorous and weedy species which should be monitored to prevent it from displacing native, rare and slower growing species, such as Oncidium guatemalenoides M.W.Chase & N.H.Williams, growing in coffee plantations in southeast México. © 2013 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.

PubMed | Instituto Tecnologico Superior Of Irapuato Itesi and Hospital Regional Of Alta Especialidad Del Bajio Leon
Type: Journal Article | Journal: Safety and health at work | Year: 2015

Animal skin provides an ideal medium for the propagation of microorganisms and it is used like raw material in the tannery and footware industry. The aim of this study was to evaluate and identify the microbial load in oropharyngeal mucosa of tannery employees.The health risk was estimated based on the identification of microorganisms found in the oropharyngeal mucosa samples. The study was conducted in a tanners group and a control group. Samples were taken from oropharyngeal mucosa and inoculated on plates with selective medium. In the samples, bacteria were identified by 16S ribosomal DNA analysis and the yeasts through a presumptive method. In addition, the sensitivity of these microorganisms to antibiotics/antifungals was evaluated.The identified bacteria belonged to the families Enterobacteriaceae, Pseudomonadaceae, Neisseriaceae, Alcaligenaceae, Moraxellaceae, and Xanthomonadaceae, of which some species are considered as pathogenic or opportunistic microorganisms; these bacteria were not present in the control group. Forty-two percent of bacteria identified in the tanners group are correlated with respiratory diseases. Yeasts were also identified, including the following species: Candida glabrata, Candida tropicalis, Candida albicans, and Candida krusei. Regarding the sensitivity test of bacteria identified in the tanners group, 90% showed sensitivity to piperacillin/tazobactam, 87% showed sensitivity to ticarcillin/clavulanic acid, 74% showed sensitivity to ampicillin/sulbactam, and 58% showed sensitivity to amoxicillin/clavulanic acid.Several of the bacteria and yeast identified in the oropharyngeal mucosa of tanners have been correlated with infections in humans and have already been reported as airborne microorganisms in this working environment, representing a health risk for workers.

Zamora-Cardenas E.A.,Instituto Tecnologico Superior Of Irapuato Itesi | Fuerte-Esquivel C.R.,Universidad Michoacana de San Nicolás de Hidalgo
IEEE Power and Energy Society General Meeting | Year: 2012

This paper proposes a practical approach to incorporate Flexible AC Transmission Systems (FACTS) devices and synchronized phasor measurements into a Weighted Least Squares (WLS) state estimation algorithm. The FACTS devices included in the estimator are the Thyristor Controlled Series Compensator (TCSC) and the Unified Power Flow Controller (UPFC). Phasor measurements of currents and voltages are directly appended to traditional measurements to estimate the equilibrium point of the power system. The proposed approach simultaneously upgrades the estimated values of the state variables of FACTS devices and the state variables of the rest of the electric network, for a unified solution in a single-frame of reference. Results are presented to demonstrate the effectiveness of the proposed approach to assess the estimation of the system state and to set the parameters of FACTS controllers for given control specifications. © 2012 IEEE.

Vargas-Bernal R.,Instituto Tecnologico Superior Of Irapuato Itesi | De La Cruz Blas C.A.,Public University of Navarra | Gomez-Polo C.,Public University of Navarra
International Journal of Circuit Theory and Applications | Year: 2015

Nowadays, the design of magneto-impedance (MI) sensors requires the development of lumped circuit models that can be simulated through equivalent impedance circuits relied on Bessel functions. A new impedance model based on Senani's equivalent using the zeros of Bessel functions is developed in this paper. The model allows to describe the impedance as a transfer function that can be easily synthesized by means of current conveyor circuits and passive elements. The mathematical representation was verified under simulation of transfer functions involving different number of poles and zeros. Moreover, the model has been verified using SPICE simulations and measurement results from a fabricated prototype demonstrating its scope and validity. Finally, a study of finite tracking errors of CCIIs used in the implementation of magneto-impedance sensor has been realized. Copyright © 2014 John Wiley & Sons, Ltd.

Daniel-Perez G.,Instituto Tecnologico Superior Of Irapuato Itesi | Daniel-Perez G.,San Luis Potosí Institute of Scientific Research and Technology | Sanchez Llamazares J.L.,San Luis Potosí Institute of Scientific Research and Technology | Quintana-Nedelcos A.,San Luis Potosí Institute of Scientific Research and Technology | And 3 more authors.
Journal of Applied Physics | Year: 2014

Alloy ribbons of nominal composition MnNiGe1.05 were produced using the melt-spinning technique. As-quenched (aq) polycrystalline ribbons are single-phase showing the hexagonal Ni2In-type crystal structure. After thermal annealing at 1148 K, the formation of the orthorhombic TiNiSi-type crystal structure by martensitic transformation is favored. However, XRD patterns for different temperatures indicate that the phase transition from hexagonal to orthorhombic structure is incomplete. The starting and finishing temperatures for the direct and reverse martensitic transformation for aq (annealed) samples determined by DSC were MS = 264 (268) K M f = 235 (255) K, AS = 259 (266) K, and Af = 289 (276) K. Across this structural phase transition the annealed sample undergoes a drop in magnetization giving rise to a narrow temperature dependence of the magnetic entropy change with a peak value on heating (cooling) of 5.8 (4.8) Jkg-1K-1 for a field change of 5 T. © 2014 AIP Publishing LLC.

Segoviano-Garfias J.J.N.,Instituto Tecnologico Superior Of Irapuato Itesi | Mendoza-Diaz G.,University of Guanajuato | Moreno-Esparza R.,National Autonomous University of Mexico
Inorganica Chimica Acta | Year: 2014

The oxidative coupling of 2,6-di-methylphenol is an industrial reaction catalyzed by the copper(II)-di-tert-butylethylenediamine-dibromo complex. In order to get more insight about the behavior of the N,N′-dialkyl-diamine cupric complexes and the halide effect on the catalyic activity, a spectrophotometric study of the speciation in methanol of copper(II) coordinated with N,N′-di-tert-butylethylenediamine or 1,5-pentanediamine and their respective halides chloride and bromide, was carried out at 303 K. Formation constants and individual calculated electronic spectra of all species, were obtained. With the purpose to compare the catalytic activity of these complexes with other diamine complex systems in the oxidative coupling of 2,6-di-methylphenol, the oxidative coupling of 2,6-di-tert-butylphenol was used as a catalytic model system. Solutions with the most abundant complexes were tested and correlated to their catalytic activity. These data are compared with several studies of the copper(II) diamine complexes, with or without chloride or bromide ions. The catalytic activity in the oxidation of 2,6-di-tert- butylphenol was monitored in methanol solution, following the corresponding quinone formation, at 418 nm (ε = 3.95x104 L mol-1 cm-1 at 303 K). The obtained formation constants of the copper(II)-di-tert-butylethylenediamine system are: log β110 = 4.13 ± 0.12, log β120 = 6.56 ± 0.12. For the ternary copper(II)-di-tert-butylethylenediamine chloro or bromo systems are: log β111 = 6.10 ± 0.09 and log β111 = 6.69 ± 0.04, respectively. While of the copper(II)-1,5-pentanediamine system are log β110 = 3.32 ± 0.11, log β210 = 5.73 ± 0.10. Kinetic studies of the oxidative coupling of 2,6-di-tert-butylphenol catalyzed by the copper(II)-diamine systems indicate that the copper(II)-1,5-pentanediamine presents low activity, while the copper(II)-N,N′-di-tert-butylethylenediamine shows a very similar activity to the copper(II)-1,4-butanediamine system reported earlier. Further studies are needed in order to explain the reasons why the complexes generated with this two different diamines display such similar activity.© 2013 Elsevier B.V. All rights reserved.

Medina A.,Universidad Michoacana de San Nicolás de Hidalgo | Bejar L.,Universidad Michoacana de San Nicolás de Hidalgo | Borjas S.E.,Universidad Michoacana de San Nicolás de Hidalgo | Zarate J.,Universidad Michoacana de San Nicolás de Hidalgo | And 3 more authors.
Materials Letters | Year: 2012

Zinc oxide ZnO nanoparticles with hexagonal shape were produced using chemical precipitation synthesis with a molar ratio of 1:1. The morphology, chemical composition and microstructure were investigated with X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and field emission gun high resolution transmission electron microscopy (FEG-HRTEM). XRD demonstrated that all hexagonal particles formed are of wurtzite crystal structure with preferable [0001] growth direction. The hexagonal wurtzite crystalline structure was determined using the Fast Fourier Transform (FFT) technique. The experimental results indicate that chemical precipitation method provides a simple way for synthesis that can be applied to other materials. © 2012 Elsevier B.V. All rights reserved.

Medina A.,Universidad Michoacana de San Nicolás de Hidalgo | Bejar L.,Universidad Michoacana de San Nicolás de Hidalgo | Herrera-Perez G.,Instituto Tecnologico Superior Of Irapuato Itesi
Materials Research Society Symposium Proceedings | Year: 2013

Zinc oxide (ZnO) nanoparticles were produced using chemical precipitation synthesis with a molar ratio of 1:1, 1:2 and 1:3. The structure, chemical composition and morphology were investigated by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). XRD and EDS demonstrated that the all particles formed at different atomic proportion were of wurtzite crystal structure with the same chemical composition. SEM and TEM showed the formation of hexagonal particles with a molar ratio of 1:1 while the samples synthesized with a molar ratio 1:2 and 1:3 showed a circular shape. HRTEM and Fast Fourier Transform (FFT) demonstrated that the all particles were formed with a preferable [0001] growth direction. © 2012 Materials Research Society.

Medina A.,Universidad Michoacana de San Nicolás de Hidalgo | Bejar L.,Universidad Michoacana de San Nicolás de Hidalgo | Herrera-Perez G.,Instituto Tecnologico Superior Of Irapuato Itesi
Materials Research Society Symposium Proceedings | Year: 2013

Magnesium hydroxide (Mg(OH)2) nanoparticles were synthesized by chemical precipitation synthesis method. The influence of the nano-sized Mg(OH)2 on the structural modification was evaluated. The formation of Mg(OH)2 crystals were evaluated by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The particle size and morphology of Mg(OH)2 was confirmed by high resolution transmission electron microscopy (HRTEM). The crystalline structure of nanoparticles was characterized by fast Fourier transform (FFT) and X-Ray diffraction (XRD), like analytical tools. © 2012 Materials Research Society.

PubMed | Instituto Tecnologico Superior Of Irapuato Itesi
Type: Journal Article | Journal: Current pharmaceutical design | Year: 2016

The Ribonuclease III (RNase III) enzymatic class is involved in many important biological processes from bacteria to higher eukaryotes. Consequently, they have been useful as drug-target candidates for drug development. Despite their high molecular diversity, RNases III share common structural and catalytic features and some degree of enzymatic activity. However, the role of accessory domains as key determinants of substrate selectivity and over the biological function of each RNase III type is still under study.The in vitro enzymatic activity of three RNase III members from class I (Escherichia coli RNase III, Schizosaccharomyces pombe Pac1 and Saccharomyces cerevisiae Rntp1) and the human Drosha placed in class II was revisited against four different substrates. These two RNase III classes comprise members showing different domain organization. Enzymatic activity differences were found among members of the class I, which were even higher when the human Drosha (class II) was tested. The substrate promiscuity of the E. coli RNase III was corroborated in vivo through its expression in S. cerevisiae, as reported previously, but was extended here to Pichia pastoris. The putative molecular mechanisms contributing for the lethal effect of the heterologous RNase III on the yeast lives were deeply discussed.The new generated biochemical data integrated with previous available information affirmed that RNases III substrate specificity as well as their cellular biological role is highly influenced by its protein structure architecture. This fact also allowed drawing evolutionary links between RNase III members from their structural and substrate specificity differences.

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