Soledad Diez Gutierrez, Mexico

Technological Institute of San Luis Potosi
Soledad Diez Gutierrez, Mexico

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Garcia-Maldonado J.Q.,Northwestern Center for Biological Research | Bebout B.M.,Ames Research Center | Celis L.B.,Technological Institute of San Luis Potosi | Lopez-Cortes A.,Northwestern Center for Biological Research
International Microbiology | Year: 2012

Methanogens have been reported in complex microbial communities from hypersaline environments, but little is known about their phylogenetic diversity. In this work, methane concentrations in environmental gas samples were determined while methane production rates were measured in microcosm experiments with competitive and non-competitive substrates. In addition, the phylogenetic diversity of methanogens in microbial mats from two geographical locations was analyzed: the well studied Guerrero Negro hypersaline ecosystem, and a site not previously investigated, namely Laguna San Ignacio, Baja California Sur, Mexico. Methanogenesis in these microbial mats was suspected based on the detection of methane (in the range of 0.00086 to 3.204 %) in environmental gas samples. Microcosm experiments confirmed methane production by the mats and demonstrated that it was promoted only by non-competitive substrates (trimethylamine and methanol), suggesting that methylotrophy is the main characteristic process by which these hypersaline microbial mats produce methane. Phylogenetic analysis of amino acid sequences of the methyl coenzyme-M reductase (mcrA) gene from natural and manipulated samples revealed various methylotrophic methanogens belonging exclusively to the family Methanosarcinaceae. Moderately halophilic microorganisms of the genus Methanohalophilus were predominant (>60 % of mcrA sequences retrieved). Slightly halophilic and marine microorganisms of the genera Methanococcoides and Methanolobus, respectively, were also identified, but in lower abundances.

Perez-Aguilar N.V.,Technological Institute of San Luis Potosi | Diaz-Flores P.E.,Technological Institute of San Luis Potosi | Diaz-Flores P.E.,Autonomous University of San Luis Potosi | Rangel-Mendez J.R.,Technological Institute of San Luis Potosi
Journal of Colloid and Interface Science | Year: 2011

Oxidized nitrogen-doped multiwall carbon nanotubes (ox-N-MWCNTs), oxidized multiwall carbon nanotubes (ox-MWCNTs), and oxidized single-wall carbon nanotubes (ox-SWCNTs) were evaluated via batch adsorption kinetic experiments to determine the effect of nanotube morphology on the adsorption rate of cadmium. The nanotubes were characterized by HRTEM, XRD and Raman spectroscopy. Cadmium adsorption isotherms were determined at pH 6. Analyses of the kinetic data with an external mass transport model and an intraparticle diffusion model considered two cases: (1) single nanotubes suspended in aqueous solution and (2) agglomerates of nanotubes suspended in aqueous solution. The intraparticle diffusion model produced the best fit to the experimental data. However, only the diffusivity coefficients for single nanotubes suspended in solution were similar to literature values: about 4×10-9, 1×10-9 and 2.4×10-11cm2/s for ox-N-MWCNTs, ox-MWCNTs and ox-SWCNTs, respectively. The morphology of the various carbon nanotubes might determine cadmium diffusivity. The high amount of sidewall pores observed in the single-walled carbon nanotubes could limit cadmium diffusion and account for the slow diffusion rate of 180min. Conversely, the short length, small surface area and bamboo-type morphology observed with nitrogen-doped multiwall carbon nanotubes may account for the relatively fast adsorption rate of 15min as this morphology prevents cadmium diffusion through the internal tubular space of these nanotubes. © 2011 Elsevier Inc.

Medellin-Castillo H.I.,Autonomous University of San Luis Potosi | De J. Garcia-Zugasti P.,Technological Institute of San Luis Potosi | De Lange D.F.,Autonomous University of San Luis Potosi | Colorado-Alonso F.J.,Autonomous University of San Luis Potosi
International Journal of Advanced Manufacturing Technology | Year: 2013

This paper presents a theoretical, numerical and experimental analysis of the allowable (maximum) deep drawing height (DDH) of rectangular cups made of steel. In particular, a new expression to calculate the allowable DDH of rectangular deep drawing, based on the equivalent diameter concept and the volume conservation principle, is proposed and compared with those theoretical expressions currently available in the literature. Finite element method simulations together with experimental data taken from a set of 20 industrial steel parts are used to evaluate the accuracy of each theoretical expression. The results have shown that the new expression has superior precision than those existing in the literature. © 2012 Springer-Verlag London Limited.

Chapa-Vargas L.,Technological Institute of San Luis Potosi | Robinson S.K.,University of Florida
Ecography | Year: 2013

We studied the effects of habitat composition and distance from edges on nesting success and brood parasitism of forest birds in the Kaskaskia River Bottoms, one of the largest remaining tracts of floodplain forest in the agricultural Midwestern United States. Our goal was to help the private landowners, who have maintained this region in forest cover, enhance the value of these forests for nesting birds. We measured nest predation rates and levels of brood parasitism of four species, the indigo bunting Passerina cyanea, Acadian flycatcher Empidonax virescens, northern cardinal Cardinalis cardinalis and prothonotary warbler Protonotaria citrea in relation to distances from natural and anthropogenic edges and proportion of natural and anthropogenic habitats within fixed radii around nests. We predicted that nesting success would increase with increasing distance from anthropogenic habitats and with increasing land cover in natural habitats. Our results showed no strong effect of any of these variables on avian nesting success, although parasitism levels increased slightly with increasing proportion of agricultural land around nests for two of the species. Nevertheless, nesting success for at least three of these species was much higher than in more fragmented forest tracts elsewhere in the agricultural Midwest where most forest tracts appear to be population sinks for most species. These results suggest that forest tracts in the Kaskaskia may be saturated with nest predators and brood parasites, but are not super-saturated in a way that would cause these tracts to become 'black hole' population sinks. Our data further suggest that, as long as landowners maintain their private landholdings in forest cover, the details of how they manage their land may have little effect on songbird nesting success. These results also suggest that reforestation efforts in areas with many openings may still benefit forest birds. © 2012 The Authors.

Kante K.,City College of New York | Nieto-Delgado C.,Technological Institute of San Luis Potosi | Rangel-Mendez J.R.,Technological Institute of San Luis Potosi | Bandosz T.J.,City College of New York
Journal of Hazardous Materials | Year: 2012

Activated carbons were prepared from spent ground coffee. Zinc chloride was used as an activation agent. The obtained materials were used as a media for separation of hydrogen sulfide from air at ambient conditions. The materials were characterized using adsorption of nitrogen, elemental analysis, SEM, FTIR, and thermal analysis. Surface features of the carbons depend on the amount of an activation agent used. Even though the residual inorganic matter takes part in the H 2S retention via salt formation, the porous surface of carbons governs the separation process. The chemical activation method chosen resulted in formation of large volume of pores with sizes between 10 and 30Å, optimal for water and hydrogen sulfide adsorption. Even though the activation process can be optimized/changed, the presence of nitrogen in the precursor (caffeine) is a significant asset of that specific organic waste. Nitrogen functional groups play a catalytic role in hydrogen sulfide oxidation. © 2011 Elsevier B.V..

Perez-Aguilar N.V.,Technological Institute of San Luis Potosi | Munoz-Sandoval E.,Technological Institute of San Luis Potosi | Diaz-Flores P.E.,Technological Institute of San Luis Potosi | Rangel-Mendez J.R.,Technological Institute of San Luis Potosi
Journal of Nanoparticle Research | Year: 2010

Nitrogen-doped multiwall carbon nanotubes (CNx) were chemically oxidized and tested to adsorb cadmium and lead from aqueous solution. Physicochemical characterization of carbon nanotubes included morphological analysis, textural properties, and chemical composition. In addition, the cadmium adsorption capacity of oxidized-CNx was compared with commercially available activated carbon and single wall carbon nanotubes. Carboxylic and nitro groups on the surface of oxidized CNx shifted the point of zero charge from 6.6 to 3.1, enhancing their adsorption capacity for cadmium and lead to 0.083 and 0.139 mmol/g, respectively, at pH 5 and 25 °C. Moreover, oxidized-CNx had higher selectivity for lead when both metal ions were in solution. Kinetic experiments for adsorption of cadmium showed that the equilibrium was reached at about 4 min. Finally, the small size, geometry, and surface chemical composition of oxidized-CNx are the key factors for their higher adsorption capacity than activated carbon. © Springer Science+Business Media B.V. 2009.

Nieto-Delgado C.,Technological Institute of San Luis Potosi | Terrones M.,Technological Institute of San Luis Potosi | Rangel-Mendez J.R.,Technological Institute of San Luis Potosi
Biomass and Bioenergy | Year: 2011

This work has the aim to employ the agave bagasse, a waste from Tequila and Mescal industries, to obtain a product of high commercial value such as activated carbon. The activated carbon production methodology was based on a chemical activation, by using ZnCl2 and H3PO4 as activating agent and agave bagasse as a natural source of carbon. The activation temperature (150-450 °C), activation time (0-60 min) and weight ratio of activating agent to precursor (0.2-4) were studied. The produced carbon materials were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and nitrogen physisorption at -196 °C. In addition, the activating agent recovery was evaluated. We were able to obtain highly microporous activated carbons with micropore volumes between 0.24 and 1.20 cm3/g and a surface area within 300 and 2139 m2/g. These results demonstrated the feasibility to treat the industrial wastes of the Tequila and Mescal industries, being this wastes an excellent precursor to produce highly microporous activated carbons that can be processed at low activation temperatures in short times, with the possibility of recycling the activating agent. © 2010 Elsevier Ltd.

Huerta-Ocampo J.A.,Technological Institute of San Luis Potosi | de la Rosa A.P.B.,Technological Institute of San Luis Potosi
Current Nutrition and Food Science | Year: 2011

Amaranth is a highly nutritious and non-allergenic crop with remarkable nutraceutical properties. Seed protein extracts following enzymatic digestion have been shown to inhibit Angiotensin Converting Enzyme (ACE). A possible mechanism of action of ACE inhibitor (ACEi) peptides involving the induction of Nitric Oxide (NO) production through endogenous Nitric Oxide Synthase (eNOS) activation has been proposed. The presence of lunasin, a peptide with proven antitumoral properties, has been confirmed in amaranth seeds and the gene encoding the amaranth lunasin peptide appears homologous to the bifunctional inhibitor/lipid transfer protein/seed storage 2S of the albumin family. Amaranth consumption has been shown to improve the plasma lipid profiles in animals. Methanolic extracts of amaranth have demonstrated anti-hyperlipidemic, anti-diabetic and anti-helmintic properties, while aqueous extracts have demonstrated anti-diarrheic, anti-fungal and anti-malarial properties. Specific polyphenols such as rutin, isoquercetin and nicotiflorin and some phenolic acids and amides with antioxidant effects have also been found in amaranth seeds. The aim of this mini-review is to provide an overview of the nutraceutical properties of amaranth. © 2011 Bentham Science Publishers Ltd.

Rodriguez Licea M.A.,Technological Institute of San Luis Potosi | Cervantes I.,Technological Institute of San Luis Potosi
Mathematical Problems in Engineering | Year: 2014

The aim of this paper is to propose a differential braking rollover mitigation strategy for wheeled vehicles. The strategy makes use of a polytopic (piecewise linear) description of the vehicle and includes translational and rotational dynamics, as well as suspension effects. The braking controller is robust and the system states are predicted to estimate the rollover risk up to a given time horizon. In contrast to existing works, the switched predictive nature of the control allows it to be applied only when risk of rollover is foreseen, interfering a minimum with driver's actions. The stability of the strategy is analyzed and its robustness is illustrated via numerical simulations using CarSim for a variety of vehicles. © 2014 Martín Antonio Rodríguez Licea and Ilse Cervantes.

Diaz-Diaz I.A.,Technological Institute of San Luis Potosi
IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society | Year: 2015

Power quality has always been an important issue to electric power utilities, and it is gaining important awareness among consumers, who are beginning to understand the importance of having power quality. In this paper, a b-learning methodology for a power quality course is applied. A virtual environment which allows the execution of complementary experimental exercises for teaching how the power quality affects the network has been developed. The developed b-learning system is able to provide real data about the performance of the power quality parameters such as peak and RMS voltage or current, phase angle as well as active, reactive and apparent power. Furthermore, the system allows remote access and signals acquisition (for voltage and current), enabling students to perform experiments at their own place, without being physically in the actual laboratory. The web-based virtual environment empowers students by granting them access to the laboratory during their free time. A practical example is presented in order to show the results and capabilities of the system. © 2015 IEEE.

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