Vera E.E.,Polytechnic University of Pachuca |
Vite M.,Tribology Group |
Lewis R.,University of Sheffield |
Gallardo E.A.,Tribology Group |
Laguna-Camacho J.R.,University of Veracruz
Wear | Year: 2011
In this study, the performance of the coatings TiN, CrN and WC/C applied on steel substrates that were subjected to sliding wear was analyzed. These materials normally exhibit an efficient performance in applications such as coatings of cutting tools, stamping processes, forming and plastic injection tooling where the contact and sliding conditions are severe. Due to this fact, this research was conducted to characterize the materials in relation to the wear process. The sliding wear test was performed using a reciprocating wear test machine. All tests were conducted in dry conditions with a room temperature between 20. °C and 23. °C and 45% to 50% relative humidity. A sliding velocity of 0.08 m/s and 2 mm amplitude were used. The applied loads were 11.76. N (Po = 1.74. GPa) and 7.84. N (1.52. GPa), respectively. Optical microscopy and scanning electron microscopy (SEM) were used to observe and analyze the wear mechanisms. Additionally, the variation of the friction coefficient versus the number of cycles was obtained. This was used to determine with a higher precision the time (presented as number of cycles) where the coating presented the initial signs of wear damage. In addition, energy dispersive X-ray analysis (EDS) was performed to obtain the chemical composition of the materials and hardness tests on the wear tracks were also carried out. It was possible to know the wear life of these coatings and possible causes of life variations. The load was an important factor in the variation of the wear life results, although other factors such as surface roughness and coating thickness were also significant. © 2011 Elsevier B.V.
Garcia-Barrientos A.,Polytechnic University of Pachuca |
Palankovski V.,Vienna University of Technology
Applied Physics Letters | Year: 2011
Numerical simulations of amplification and propagation of space charge waves in InP films is investigated theoretically. A microwave frequency conversion using the negative differential conductivity phenomenon is carried out when the harmonics of the input signal are generated. An increment in the amplification is observed in n -InP films at essentially higher frequencies f<70 GHz, when compared with n -GaAs films f<44 GHz. This work provides a way to achieve a frequency conversion and amplification of micrometer and millimeter waves. © 2011 American Institute of Physics.
Rivera-Orduna F.N.,CINVESTAV |
Suarez-Sanchez R.A.,CINVESTAV |
Flores-Bustamante Z.R.,CINVESTAV |
Gracida-Rodriguez J.N.,Polytechnic University of Pachuca |
Flores-Cotera L.B.,Polytechnic University of Pachuca
Fungal Diversity | Year: 2011
The aim of this work was the isolation and taxonomic characterization of endophytic fungi from Taxus globosa at the Sierra Alta Hidalguense, Mexico. A total of 116 fungi were isolated from the bark, branches, leaves and roots of healthy yew trees. Based on morphological characteristics 57 were selected for taxonomic characterization through phylogenetic analysis of their 28S rDNA sequences. The fungal isolates belonged to Ascomycota (77.2%) and Basidiomycota (22.8%). Twelve different fungal groups were identified: Coniochaetales, Eurotiales, Hypocreales, Phyllachorales, Pleosporales, Pezizales, Sordariomycetidae, Sordariales, Trichosphaeriales, Xylariales, Agaricales and Polyporales. The taxa Alternaria sp. Aspergillus sp., Cochliobolus sp., Coprinellus domesticus, Hypoxylon sp., Polyporus arcularius, Xylaria juruensis and Xylariaceae were the most frequently isolated. The genera Annulohypoxylon, Cercophora, Conoplea, Daldinia, Lecythophora, Letendraea, Massarina, Phialophorophoma, Sporormia, Xylomelasma, Coprinellus, Polyporus and Trametes for the first time were isolated from yews; this suggests that T. globosa harbours novel and highly diverse fungi. The Shannon-Weaver and Simpson diversity index values for the overall fungal community were H?=3.139 and 1-D=0.941 respectively.© Kevin D. Hyde 2010.
Juarez-Santillan L.F.,Autonomous University of the State of Hidalgo |
Lucho-Constantino C.A.,Polytechnic University of Pachuca |
Vazquez-Rodriguez G.A.,Autonomous University of the State of Hidalgo |
Ceron-Ubilla N.M.,Autonomous University of the State of Hidalgo |
Beltran-Hernandez R.I.,Autonomous University of the State of Hidalgo
Bioresource Technology | Year: 2010
Soil, sediments, water and plant samples from the mining zone of Molango were collected and analyzed and Mn-tolerant and Mn-accumulator plants were identified. Soil and sediments presented moderately alkaline and reducing conditions, a normal electrical conductivity, a sandy texture and medium-to-high cation exchange capacities. These properties favored the presence of Mn2+, which is the form most easily assimilated by plants, and the total Mn concentration (11,637-106,104 mg kg-1 dried weight, DW) was at phytotoxic level. Water was also an important Mn source. Equisetum hyemale and Telypteris kunthii survived in the presence of such Mn concentrations using an exclusion strategy, while Cnidoscolus multilobus, Platanus mexicana, Solanum diversifolium, Asclepius curassavica L. and Pluchea sympitifolia employed an accumulation strategy. These plants could be useful to re-vegetate and stabilize Mn tailings in order to decrease the erosion effects. © 2010 Elsevier Ltd. All rights reserved.
Muro Urista C.,Toluca Institute of Technology |
Alvarez Fernandez R.,University of Oviedo |
Riera Rodriguez F.,University of Oviedo |
Arana Cuenca A.,Polytechnic University of Pachuca |
Tellez Jurado A.,Polytechnic University of Pachuca
Food Science and Technology International | Year: 2011
In recent years, research on the production of active peptides obtained from milk and their potential functionality has grown, to a great extent. Bioactive peptides have been defined as specific protein fragments that have a positive impact on body functions or conditions, and they may ultimately have an influence on health. Individual proteins of casein or milk-derived products such as cheese and yogurt have been used as a protein source to study the isolation and activity of peptides with several applications. Currently, the milk whey waste obtained in the production of cheese also represents a protein source from which active peptides could be isolated with potential industrial applications. The active properties of milk peptides and the results found with regard to their physiological effects have led to the classification of peptides as belonging to the group of ingredients of protein nature, appropriate for use in functional foods or pharmaceutical formulations. In this study, the main peptides obtained from milk protein and the past research studies about its production and biological activities will be explained. Second, an analysis will be made on the methods to determinate the biological activities, the separation of bioactive peptides and its structure identification. All of these form the base required to obtain synthetic peptides. Finally, we explain the experimental animal and human trials done in the past years. Nevertheless, more research is required on the design and implementation of equipment for the industrial production and separation of peptides. In addition, different authors suggest that more emphasis should therefore be given to preclinical studies, proving that results are consistent and that effects are demonstrated repeatedly by several research human groups. © The Author(s) 2011.
Vite-Torres M.,National Polytechnic Institute of Mexico |
Laguna-Camacho J.R.,University of Veracruz |
Baldenebro-Castillo R.E.,National Polytechnic Institute of Mexico |
Gallardo-Hernandez E.A.,National Polytechnic Institute of Mexico |
And 2 more authors.
Wear | Year: 2013
In this study, the performance of AISI 420 stainless steel that was subjected to solid particle erosion tests was analyzed. This material can be used to the manufacture of brake discs, turbine blades, injection molds, piston submerged in fresh water pumps, wagons, containers and equipment to the sugar industry transporters. The erosion tests were performed by using a rig developed according to some parameters of the ASTM G76-95 standard. The samples had a rectangular shape with dimensions of 50×25mm2 and 3mm in thickness. Two abrasive were used, angular silicon carbide (SiC) and steel round grit, both, with a particle size of 400-420μm (Mesh 60). This allowed comparing the erosion severity of each abrasive particle. The tests were performed using four different incident angles 30°, 45°, 60° and 90° with an approximate particle speed of 24±2m/s and a flow rate of 21±2.5g/min for the silicon carbide and of 48.5±3.5g/min for the steel round grit. The exposure testing time was 10min, although the specimens were removed every 2min to measure the amount of mass loss. Subsequently, the surface damage was analyzed with a scanning electron microscope (SEM) to identify the wear mechanisms. Additionally, atomic force microscopy (AFM) was carried out in order to obtain roughness, deepness and topography of the surface damage at 60°. The results indicated that a higher amount of mass loss was obtained as the specimens were attacked by angular silicon carbide particles. In respect to the erosion rate, it was decreasing as the impact angle was increased; the higher erosion rate was reached at 30°. © 2013 Elsevier B.V.
Juarez-Perez E.J.,CSIC - Institute of Materials Science |
Vinas C.,CSIC - Institute of Materials Science |
Teixidor F.,CSIC - Institute of Materials Science |
Santillan R.,CINVESTAV |
And 4 more authors.
Macromolecules | Year: 2010
Fluorescent Fréchet-type poly(aryl ether) dendrimers that incorporate the 1, 3, 5-triphenylbenzene as core molecule and 3, 6, 9, or 12 terminal allyl ether groups have been prepared in very good yield by following the Frechet convergent approach. Regiospecific hydrosylilation reactions on the allyl ether functions with the cobaltabisdicarbollide derivative Cs[1, 1'-μ-SiMeH-3, 3'-Co(l, 2-C2B9H10) 2] lead to different generations of Féchet-type polyanionic metallodendrimers decorated with 3, 6, and 9 cobaltabisdicarbollide units. Starting dendrimers exhibit photoluminescence properties at room temperature under ultraviolet irradiation; nevertheless, after functionalization with cobaltabisdicarbollide derivatives, the fluorescence properties are quenched. Products are fully characterized by FTIR, NMR, and UV-vis spectroscopies. For metallodendrimers, the UV-vis absorptions have been a good tool for estimating the experimental number of cobaltabisdicarbollide units peripherally attached to the dendrimeric structure and consequently to corroborate the unified character of the dendrimers. Because of the anionic character of these compounds and the boron-rich content, we actually focus our research on biocompatibility studies and potential applications. © 2009 American Chemical Society.
Ordaz P.,Polytechnic University of Pachuca |
Poznyak A.,National Polytechnic Institute of Mexico
IMA Journal of Mathematical Control and Information | Year: 2013
This paper presents the development of an adaptive state estimator and an output controller based on the attractive ellipsoid method (AEM) for a class of uncertain non-linear systems (quasi-Lipschitz with external perturbations). The proposed method guarantees that, under a specific persistent excitation condition, the controlled system trajectories converge to an ellipsoid having a smaller trace of the corresponding inverse ellipsoidal matrix comparing to classical AEM without adaptation. An underactuated vertical double pendulum is considered as an experimental illustrative example of the suggested approach. © The authors 2014. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.
Campos-Silva I.,National Polytechnic Institute of Mexico |
Bravo-Barcenas D.,National Polytechnic Institute of Mexico |
Meneses-Amador A.,National Polytechnic Institute of Mexico |
Ortiz-Dominguez M.,Polytechnic University of Pachuca |
And 3 more authors.
Surface and Coatings Technology | Year: 2013
In this study, new data about the growth kinetics and indentation properties of cobalt boride layers formed on the surface of the ASTM F-75 biomedical alloy were estimated. The boron diffusion at the surface of the biomedical alloy was conducted using a powder-pack boriding process at temperatures of 1223-1273K with different exposure times for each temperature. Two mathematical approaches were proposed to determine the boron diffusion coefficients of the CoB and Co2B layers in the range of boriding temperatures, in which the experimental results of the kinetics of the cobalt boride layers were compared with those estimated using diffusion models.Finally, the mechanical characterization of the cobalt boride layers was evaluated by indentation techniques with applied loads of 0.98. N and 50. mN, respectively. According to the nanoindentation tests, a maximum hardness value (30. GPa) and a maximum Young's modulus (380. GPa) were obtained near the surface region (5. μm) of the borided cobalt alloy. © 2013 Elsevier B.V.
Medina-Moreno S.A.,Polytechnic University of Pachuca |
Perez-Cadena R.,Polytechnic University of Pachuca |
Jimenez-Gonzalez A.,Polytechnic University of Francisco I. timber |
Tellez-Jurado A.,Polytechnic University of Pachuca |
Lucho-Constantino C.A.,Polytechnic University of Pachuca
Bioresource Technology | Year: 2012
A biodecolorization model that considers the simultaneous mechanism of biosorption and biodegradation of a synthetic dye by immobilized white-rot fungus Trametes subectypus B32 in a fixed bed bioreactor was developed. The model parameters (biokinetic, biosorption and macroscopic transport) were determined by independent experiments. The biodecolorization model was used to determine the effect of variables such as immobilized biomass content, volumetric flow of wastewater, dye feeding concentration and initial dye concentration. By means of the model was possible to predict in the steady state, the limits of immobilized T. subectypus to biodecolorize polluted influent, being the model predictions similar in extent to previous reports. A dimensionless module of biosorption-bioreaction (φ=qmaxvz/rmaxL) was proposed to be used like criterion whenever one of the two mechanisms controls the biodecolorization. The model could be used for the designing and scaling up of fixed bed bioreactors with immobilized white-rot fungi for the biodecolorization process. © 2012 Elsevier Ltd.