La característica de una comunidad de conocimiento de ingeniería: El uso de la simultaneidad de la derivada

La matemática educativa ha evidenciado un conflicto entre la obra matemática y la matemática escolar, el cual ha generado tres fenómenos asociados al discurso matemático escolar (dME). Estos, reprimen la construcción social del conocimiento matemático; impidiendo la incorporación del conocimiento a la vida del humano y por tanto, la transformación de su realidad. Ante esto, es necesario generar un marco de referencia (MR) que incluya los usos de conocimiento matemático (U(CM)) del ciudadano, de manera que se adquieran elementos para el rediseño del dME (RdME). Para ello, se estudian los U(CM), simultaneidad y estabilidad, en el que hacer de una comunidad de conocimiento matemático de la ingeniería química (CCM(IQ)) en un escenario de trabajo. Específicamente en el diagnóstico del estado de los transformadores eléctricos de la comisión federal de electricidad, región peninsular. Tales U(CM), serán elementos para la construcción de un MR centrado en los usos que contribuya al RdME desde y con el ingeniero

On the deactivation of Zr-loading P-containing mesoporous carbon catalyst during methanol dehydration

Dimethyl ether (DME) has received much attention in the last few years due to its potential use as a diesel substitute and it can be obtained from dehydration of biomass-based methanol. γ-Alumina, ZSM-5 and HPAs were tested as catalysts. A carbon-supported zirconium phosphate catalyst was synthesized and tested for methanol dehydration reaction in a high temperature range. Carbon matrix was produced by olive stone waste activated with phosphoric acid (mass acid to olive stone ratio of 2:1) at 800ºC for 2 h. Then, after washing with distilled water and sieving between 100-300μm, the obtained carbon was impregnated with ZrO(NO3)2 and thermal treated at 250ºC for 2 h. Reaction was performed in a fixed-bed reactor at a space time of 75 gcat·s/mmolCH3OH, a partial pressure of 0.04 atm of methanol and temperatures between 450-600ºC. Deactivated samples were exposed to air at 350ºC for 100 min to study the catalyst regeneration. The catalyst showed a high selectivity to DME (≥95%) and an acceptable conversion at Tª lower than 400ºC without noticeable deactivation. At T>400 ºC, deactivation was detected, due to coke deposition, whose rate increases with operating temperature. However, a high selectivity to DME was observed (above 65%) even at very long times on stream (tos). N2 adsorption results pointed out that deposition of coke took place mainly on the surface of the narrow micropores of the catalyst, blocking much of this narrow porosity at long tos. According to XPS analysis, superficial concentration of phosphorus and zirconium were also diminished with coke deposition, although zirconium was decreased to a larger extend. A kinetic model was developed for the catalyst deactivation during methanol dehydration under different reaction conditions, based on coke deposition.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Análisis de precios de productos básicos en tiendas de autoservicio de Pachuca y el Comercio de Zacualtipán, Hidalgo, 2007-2008

Esta investigación se realizó en tiendas de autoservicio de Pachuca y el comercio local de Zacualtipán, Estado de Hidalgo. Se registraron precios de 24 productos: arroz, tortilla, jitomate, limón, chile jalapeño, leche, huevo, jamón, salchicha, carne de res, carne de pollo, papel sanitario, jabón de polvo, jabón de baño, pasta de dientes, frijol, cebolla, papa, aguacate, naranja, plátano, aceite, sal y azúcar. Las fechas de consulta de precios fueron: 26 de julio de 2007, 25 de enero y 29 de mayo de 2008. La importancia del estudio es el análisis comparativo y evolución de precios. Las tiendas de autoservicio ofrecen 9.7% más barato en el 62.5% de los productos. El comercio local ofrece el 12.7% más barato que las tiendas de autoservicio en frijol, cebolla, papa, aguacate, plátano, aceite, sal y azúcar. Durante el 26 de julio de 2007 al 29 de mayo de 2008, los precios aumentaron 19.8% y 19.6% en el comercio local y tiendas de autoservicio, respectivamente. Palabras clave: Precios, productos básicos, pequeñas y medianas empresas, tiendas de autoservicio, análisis comparativo, comercio

ANÃLISIS DE LA RENTABILIDAD ECONÓMICA DE LA PRODUCCIÓN DE JITOMATE BAJO INVERNADERO EN ACAXOCHITLÃN, HIDALGO

In this study there was evaluated the economic profitability of tomato production under greenhouse conditions four production projects, in an area of 9 040 m2., in the communities of San Martin, San Pedro and Los Reyes Acaxochitlán's municipality, Hidalgo State, during the 2008-2009 cycle. How indicator was used cost/benefit ratio (C/B). Acaxochitlán's municipality produces 1,582.3 tons of tomato in a surface of 65 200 m2. In the four projects reviewed obtained a production of 218 tons, the average selling cosprice was $ 8.25 per kilogram, and sold in the cities of Tulancingo, Acaxochitlán and Pachuca. Tomato production proved a profitable activity in the study region since the projects 1, 2, 3 and 4 showed a ratio C/B of 2.30, 2.65, 3.09 and 1.57, respectively.Economic profitability, cost/benefit ratio, tomato production, marketing., Agribusiness,

Synthesis and characterization of a new nanosorbent based on functionalized magnetic nanoparticles and its use in the determination of mercury by FI-CV-ETAAS

In this work, a new chelating sorbent which employs 1,5-bis(di-2-pyridil)methylene thiocarbohydrazide as the functional group and magnetic nanoparticles (MNPs) as its support (DPTH-MNP) was synthetized and characterized. The MNPs were prepared by coprecipitation of Fe+2 and Fe+3 with NH3 and then coated with silica in order to easily bind the support and the functionalizing molecule. The aim of the synthesis of this material is applying it as a solid-phase extracting agent and evaluating its potential for the extraction and pre-concentration of trace amounts of analytes present in biological and environmental samples with on-line methods. The MNPs’ magnetic core would allow overcoming the usual backpressure problems that happen in solid-phase extraction methods thanks to the possibility of immobilizing the MNPs by applying an external magnetic field. From the study of its adsorption capacity toward metal ions, mercury and antimony were the most retained. Thus, a flow injection solid phase extraction and cold vapor generation method for mercury determination based on the use of this new chelating nanosorbent was optimized. The greatest efforts were put into the reactor design to minimize compaction and loss of nanosorbent. The knotted reactor shown in Figure 1 was chosen as the best. Then, chemical and flow variables were optimized by Central composite designs (CCDs). The method developed has showed to be useful for the automatic pre-concentration and determination of mercury in environmental and biological samples. The determination was performed using electrothermal atomic absorption spectrometry (ETAAS). Under the optimum conditions, pH 5 and 120 s preconcentration time, the enrichment factor was 5.33; the detection limit (3σ) was 7.8 ng L-1; the determination limit (10σ) was 99 ng L-1; and the precisions (calculated for 10 replicate determinations at a 1 and 5 µg L-1 standards) were 1.7 and 1.9 % (RSD), respectively. Two linear calibration graphs were obtained, from the determination limits to 10 µg L-1 and from 10 to at least 50 µg L-1. From the comparison with other similar methods found in the bibliography, the detection limit and precisions calculated with our method were better. In order to evaluate the accurate and applicability of the method, the analysis of five certified samples LGC 6016 estuarine water, TMDA 54.4 fortified lake water, SRM 2976 mussel tissue, TORT-1 lobster hepatopancreas and DOLT-1 dogfish liver by standard addition and external calibration, were addressed. The results showed good agreement between the certified values, or added amounts of mercury, and the found concentrations. The method was successfully applied to the determination of mercury in sea-water samples collected in the Málaga Bay.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Star product approach for Loop Quantum Cosmology

Guided by recent developments towards the implementation of the deformation quantization program within the Loop Quantum Cosmology (LQC) formalism, in this paper we address the introduction of both the integral and differential representation of the star product for LQC. To this end, we consider the Weyl quantization map for cylindrical functions defined on the Bohr compactification of the reals. The integral representation contains all of the common properties that characterize a star product which, in the case under study here, stands for a deformation of the usual pointwise product of cylindrical functions. Our construction also admits a direct comparison with the integral representation of the Moyal product which may be reproduced from our formulation by judiciously substituting the appropriate characters that identify such representation. Further, we introduce a suitable star commutator that correctly reproduces both the quantum representation of the holonomy-flux algebra for LQC and, in the proper limit, the holonomy-flux classical Poisson algebra emerging in the cosmological setup. Finally, we propose a natural way to obtain the quantum dynamical evolution in LQC in terms of this star commutator for cylindrical functions as well as a differential representation of the star product using discrete finite differences. We expect that our findings may contribute to a better understanding of certain issues arising within the LQC program, in particular, those related to the semiclassical limit and the dynamical evolution of quantum states.Comment: 21 pages, no figure

Supplier selection prioritizing sustainable criteria for products: an AHP approach in Peruvian public procurement

Este trabajo se enfoca en las compras públicas sostenibles que buscan aminorar impactos ambientales negativos y mejorar los impactos sociales positivos, las cuales, para funcionar, requieren de cambios significativos dentro de la realidad del mercado de un país. En el caso peruano, la legislación establece la obligación de que los criterios sostenibles integren las compras del Estado homologadas a las necesidades para la adjudicación de bienes y servicios. De esta forma, la problemática que pretende resolver esta investigación reside en la inobservancia técnica para verificar el cumplimiento de la reglamentación vigente en el procedimiento de selección de proveedores que consideren los criterios de sostenibilidad, para ello, sugerimos la aplicación del proceso analítico jerárquico (AHP) como alternativa heurística de solución. Este modelo de selección permite mejorar el procedimiento administrativo al incrementar el grado de objetividad y reducir sesgos cognitivos. Con el fin de demostrar ello, aplicaremos la verificación en el proceso analítico jerárquico en un caso de estudio de selección de proveedores de lámparas LED de una institución pública.This paper focuses on sustainable public procurements that seek to minimize negative environmental impacts and improve positive social impacts, which require significant changes within the market reality of a country. In the case of Peru, legislation establishes the requirement that sustainable criteria be integrated into public procurement suited to the needs for the procurement of goods and services. In this way, the problem that this study seeks to resolve relies on technical non-observance to verify compliance with current regulations in force within the supplier selection process that consider sustainability criteria. Therefore, the application of the Hierarchy Analytic Process (AHP) is suggested as a heuristic solution alternative. This selection model makes it possible to improve the administrative process by increasing objectivity and reducing cognitive bias. To demonstrate this, the Analytic Hierarchy Process will be verified in a case study concerning the selection of LED lighting suppliers for a public institution

Sex wars: a female genital spine forces male damselflies to shorten copulation duration

In some species, males use weapons to harm females, increasing their short-term fitness. Here we show that females can use genital adaptations against males. Females of the damselfly Enallagma cyathigerum have a conspicuous vulvar spine on the eighth abdominal segment, which contacts with the male during copulation. We tested 3 hypotheses for its function: it (a) inflicts damage to the male during copulation; (b) facilitates endophytic oviposition; and (c) stimulates males during copulation to increase their investment. We found that males mated on average for 54 min with control females, but increased copulation to 99 min with females without spine. There was no evidence of physical harm of the spine on the male’s seminal vesicle, which shows 8- to 18-folds, exactly where the spine contacts during copulation. Females with and without spine exhibited the same egg-laying rates and showed similar fecundity and fertility. Longevity was also similar in males mated to control and spineless females. In contrast to many species where females resist male harassment by behavioral responses, the morphological adaptation observed in E. cyathigerum appears to act as a sexual weapon, allowing females to control copulation duration. We suggest that the spine has evolved because of sexual conflict over mating duration.Universidade de Vigo/CISUGMinisterio de Economía y Competitividad | Ref. CGL2014-53140-PAgencia Estatal de Investigación | Ref. PGC2018-096656-B-I0