Alumina-Based Composites Reinforced With Silver Particles

Al2O3/Ag composite ceramics were fabricated by the use of mechanical milling and pressureless sintering. Al2O3 + 10 wt.% Ag were mixed and milled during 12 h at 300 rpm in a horizontal mill, then with the powder mixture it was conformed cylindrical samples by uniaxial pressing using 300 MPa. The pressed samples were sintered during 1 h in an electrical furnace at 1300, 1400 and 1500°C respectively. Sinter was performed using an argon atmosphere inside the furnace in order to inhibit silver oxidation. XRD results established that silver retains its crystalline structure. On the other hand, density of samples is better with increments in temperature. However, the final relative density is small and about of 91%. Scanning electron microscopy observations show alumina’s microstructure with very fine and homogeneous distributions of silver particles. Increments in sintering temperature are reflected as enhancements of the density and consequently of the fracture toughness of the Al2O3/Ag composite ceramics

Alumina-Based Composites Reinforced with Ductile Particles

Al2O3/Metal composite ceramics were fabricated by the use of mechanical milling and pressureless sintering. Al2O3 + 10 vol.% of La, Mn, Si or Y were mixed and milled during 12 h at 300 rpm in a horizontal mill, then with the powder mixture it was conformed cylindrical samples by uniaxial pressing using 300 MPa. Pressed samples were sintered during 2 h in an electrical furnace at 1500°C. During sintered it was used an argon atmosphere inside the furnace in order to inhibit metal oxidation. XRD results indicate that alumina and metals retain its crystalline structure. Reached density by samples is small and less than 90%. Scanning electron microscopy observations show alumina’s microstructure with very fine and homogeneous distributions of metal particles. Both the Mn and Si are not suitable metals to improve the mechanical properties of alumina, in particular the fracture toughness. Considered rare earth metals such as yttrium and lanthanum, have yielded favorable results in improving the fracture toughness of the alumina. However, it should be made more dense materials with them to better explore this potential

Ampicilina como inhibidor orgánico de la corrosión para los aceros AISI 1018 y AISI 8620

En este trabajo se presenta la evaluación de la ampicilina como inhibidor orgánico de la corrosión en los aceros AISI 1018 y AISI 8620, se resalta la importancia de la reutilización de los antibióticos caducados como inhibidores útiles para la disminución de la corrosión como una alternativa. Se utilizó la técnica de espectroscopia de impedancia electroquímica (EIS) para observar los cambios en la resistencia de polarización (Rp) en los aceros, los resultados de la EIS muestran que conforme se añade una mayor cantidad de inhibidor, la resistencia de polarización Rp aumenta y dado que la Rp se relaciona de manera inversa con la velocidad de corrosión esto significa que disminuye el proceso de corrosión.In this work the evaluation of ampicillin as an organic corrosion inhibitor for AISI 1018 and AISI 8620 steels is presented, the importance of the reuse of expired antibiotics as useful inhibitors for the diminution of corrosion as an alternative option is remarked. Electrochemical impedance spectroscopy (EIS) technique was used to observe changes on the polarization resistance (Rp) on the steels, EIS results show that as the amount of the inhibitor is increased the polarization resistance Rp increases and since Rp is inversely related with the corrosion rate therefore the corrosion process is decreased

Metabolic syndrome prevalence in Guanajuato, Mexico’s teachers

Objetivos: Identificar la prevalencia del síndrome metabólico en profesores del nivel educativo básico del estado de Guanajuato, México. Diseño: Estudio observacional, transversal, retrospectivo. Institución: Universidad de Guanajuato, México. Participantes: Docentes de nivel educativo básico. Intervenciones: En 477 docentes, 208 hombres y 269 mujeres, se llevó a cabo una evaluación médica directa y exámenes de laboratorio de los componentes del síndrome metabólico (glucosa, triglicéridos y colesterol de densidad alta (HDL-C)), así como, medición de circunferencia de abdomen, presión arterial y nivel de actividad física. Principales medidas de resultados: Prevalencia del síndrome metabólico. Resultados: La prevalencia del síndrome metabólico fue 32,2% en los docentes hombres y 26,8% en las mujeres. Más de 40% de los profesores presentó tres factores de riesgo para el síndrome metabólico, siendo más prevalente la hipertrigliceridemia. Referente al nivel de actividad física, 24% correspondió a personas sedentarias, 65% hipoactivos y únicamente 11% practicaba ejercicio vigoroso regular. Conclusiones: El perfil de salud de los docentes de Guanajuato se encontró lejos del ideal esperado, observándose una elevada prevalencia del síndrome metabólico, por lo que se sugiere aplicar estrategias de prevención para modificar los estilos de vida del profesorado, en especial mejorar la dieta y promover mayor nivel de actividad física.Objectives: To identify the prevalence of metabolic syndrome in Guanajuato, Mexico’s teachers of basic education. Design: Observational, transversal, retrospective study. Setting: Universidad de Guanajuato, Mexico. Participants: Teachers of basic education. Interventions: In 477 teachers that included 208 men and 269 women, medical evaluation and laboratory tests were done including the metabolic syndrome components (glucose, triglycerides and high density cholesterol (HDL-C) analysis), abdominal circumference measurement, blood pressure, and level of physical activity. Main outcome measures: Metabolic syndrome prevalence. Results: The prevalence of metabolic syndrome was 32.2% in men and 26.8% in women teachers. Over 40% of teachers had three risk factors for metabolic syndrome, hypertriglyceridemia the most prevalent. Concerning the level of physical activity, 24% were sedentary people, 65% hypoactive, and only 11% practiced regular vigorous exercise. Conclusions: Guanajuato’s teacher’s health profile was far from ideal, showing high prevalence of metabolic syndrome. For prevention strategies we suggest lifestyle change, especially improving diet and promoting physical activity

Electro oxidación de metanol sobre catalizadores Au@Ptx/C y Pt/C mediante potenciales de inversión

En este trabajo se sintetizaron nanopartículas (NPs) del tipo núcleo envolvente soportadas en carbón Vulcan (Au@Ptx/C) con distintas relaciones de Pt en el envolvente (x=0.2, 0.5 y 1 relación atómica con respecto Au) para evaluar su actividad en la reacción de oxidación de metanol (MOR), teniendo como sistema de referencia NPs de Pt/C. Se encontró que el catalizador Au@Pt1/C favorece la MOR, lo anterior se asocia a la presencia del núcleo de oro en la estructura lo cual debilita el enlace Pt-COads evitando la desactivación del catalizador. Adicionalmente, se estudió la influencia del potencial de inversión de -0.2 a 1.4 V vs SCE, con el propósito de evaluar el cociente de la densidad de corriente de los picos asociados a la MOR durante el barrido de ida y el de regreso (jf/jb ), ya que en la literatura el cociente se asocia con la tolerancia del catalizador al CO, sin embargo se observó que el cociente jf/jb depende del límite de potencial anódico.In this work, core-shell type nanoparticles (NP) supported on carbon Vulcan (Au@ Ptx/C) were synthesized with different Au to Pt ratios (x=0.2, 0.5 and 1 atomic ratio with respect to Au) for the methanol oxidation reaction (MOR) evaluation, having as reference system Pt/C NPs. It was found that Au@Pt1/C catalyst favors the MOR, this was associated to the presence of gold-core in the structure, which weakens Pt-COads bond, preventing catalyst from deactivation. In addition, the influence of inversion potential from -0.2 to 1.4 V vs SCE was studied, with the purpose of assessing the ratio of current density of the forward and backward peaks associated to the MOR (jf/jb), in the literature it is associated to the catalyst´s CO-tolerance, however it was observed that the ratio jf/jb depends on the limit of the anodic potential

Phenol adsorption onto coffee waste - granular activated carbon: kinetics and equilibrium studies in aqueous solutions

abstract In this research, the production of granular activated carbon from coffee waste (CW) by chemical activation with zinc chloride was studied by using a 23 factorial design with the three responses (surface area, yield, and hardness) and studying three factors (the activation temperature, activation time, and impregnation ratio). The findings expose that after the experimental design, the highest response values were achieved at an activation temperature of 600°C, an activation time of 40 min, and an impregnation ratio of 1.5 g ZnCl2 g–1 CW. At these conditions, the experimental tests produced a surface area of 1,279 m2 g–1. Batch studies of phenol adsorption onto coffee waste-activated carbon (CW-GAC) were performed at different solution pH, stirring speeds, and initial phenol concentrations. The maximum phenol adsorption capacity onto CW-GAC was 160.52 mg g−1 at pH 7. The adsorption kinetics was affected by stirring speed, the required time to achieve equilibrium decreased from 150 to 120 min when stirring speed varied from 200 to 400 min–1. Film and intraparticle diffusion mechanisms controlled the adsorption of phenol onto CW-GAC. Finally, the porous material developed in this research is capable of sequestering phenol from aqueous solutions to a higher extent than similar lignocellulosic-based activated carbons. Keywords: Adsorption; Coffee; Factorial experimental design; Granular activated carbon; Lignocellulosic wast

Desarrollo multidisciplinario en investigación y docencia del centro universitario UAEM Valle de México

DESARROLLO MULTIDISCIPLINARIO EN INVESTIGACIÓN Y DOCENCIA DEL CENTRO UNIVERSITARIO UAEM VALLE DE MÉXICOLa Universidad Autónoma del Estado de México ha evolucionado a través de sus 188 años de historia, dedicada a la educación, la investigación, la cultura y el deporte, como sus grandes ejes rectores, formadora de hombres y mujeres con un alto sentido humanista y ético, contribuyendo a lograr nuevas y mejores formas de existencia y convivencia social. Durante el proceso de desconcentración de la UAEM, se crearon las Unidades Académicas y Centros Universitarios para brindar el servicio de educación a más jóvenes en todo el Estado de México, este Centro Universitario fue uno de los primeros y a sus veinte años de existencia se está consolidando como uno de los mejores. Es en los últimos años que se ha venido impulsando la investigación al contar con cuerpos académicos, en formación y en consolidación, con infraestructura de primera tanto en equipo como en laboratorios especializados, con profesores de tiempo completo que participan en congresos, seminarios y presentan publicaciones en revistas indexadas. Por ello para celebrar esos veinte años de existencia de esta honorable institución, se planeó la compilación de esta obra que es parte del quehacer multidisciplinario en investigación y docencia como parte del Plan de Desarrollo 2013-2017, de esta administración. Esta obra reúne investigaciones tanto de profesores como de alumnos desde las diferentes ramas del saber en las que se inscriben sus siete licenciaturas, Actuaría, Administración, Contaduría, Derecho, Economía, Relaciones Económicas Internacionales e Informática Administrativa, tanto presencial como a distancia, así como sus tres ingenierías, Industrial, en Computación y Sistemas y Comunicaciones, así como gracias a la vinculación y colaboración académico – científica que se tiene con otras instituciones de educación superior a nivel nacional, como el Instituto Tecnológico de Orizaba, la Universidad Autónoma de San Luis Potosí, la Universidad Nacional Autónoma de México, la Universidad Autónoma Metropolitana, Universidad Politécnica de Victoria, el Instituto Politécnico Nacional entre otras. En el capítulo 1 se abordan seis temáticas diferentes de vanguardia en el área de las Ingenierías, en los capítulos 2 y 3 se incluyen temas de interés y gran relevancia en materia de ciencias sociales, política y economía. Se hace extensivo un reconocimiento para todos los que participaron tanto en la revisión de los trabajos, como en la compilación del producto final de este Libro intitulado “Desarrollo Multidisciplinario en Investigación y Docencia del Centro Universitario UAEM Valle de México”

Evidence of spatial clustering of childhood acute lymphoblastic leukemia cases in Greater Mexico City: report from the Mexican Inter-Institutional Group for the identification of the causes of childhood leukemia

BackgroundA heterogeneous geographic distribution of childhood acute lymphoblastic leukemia (ALL) cases has been described, possibly, related to the presence of different environmental factors. The aim of the present study was to explore the geographical distribution of childhood ALL cases in Greater Mexico City (GMC).MethodsA population-based case-control study was conducted. Children <18 years old, newly diagnosed with ALL and residents of GMC were included. Controls were patients without leukemia recruited from second-level public hospitals, frequency-matched by sex, age, and health institution with the cases. The residence address where the patients lived during the last year before diagnosis (cases) or the interview (controls) was used for geolocation. Kulldorff’s spatial scan statistic was used to detect spatial clusters (SCs). Relative risks (RR), associated p-value and number of cases included for each cluster were obtained.ResultsA total of 1054 cases with ALL were analyzed. Of these, 408 (38.7%) were distributed across eight SCs detected. A relative risk of 1.61 (p<0.0001) was observed for the main cluster. Similar results were noted for the remaining seven ones. Additionally, a proximity between SCs, electrical installations and petrochemical facilities was observed.ConclusionsThe identification of SCs in certain regions of GMC suggest the possible role of environmental factors in the etiology of childhood ALL

Improving Toughness of Alumina-Based Composites to Be Used As Bone Substitute

In this study it is show the experimental results of alumina reinforced with titanium additions, forming a composite which by its components could be classified as a biomaterial. The experimental results indicate that Al2O3-X wt. % Ti, (X = 0.5, 1, 2 and 3) composite material is an alternative material for its use as human bone substitute, because its density, porosity and toughness are better than of the human bone. Composites were manufactured using powders techniques. The results indicate that these composites have densities between 3.6 - 3.9 g/cm3, values far higher than the density of the compact bone of 1.8 g/cm3. The microstructure observed by scanning electron microscopy, shows a homogeneous distribution of titanium particles in the alumina matrix. Fracture toughness of the proposed composite present’s values range between 3.3 to 8.76 MPam-0.5, whereas fracture toughness of compact bone has a value of 4.05-4.32 MPam-0.5

Fracture Toughness Enhancement of Mullite-Ceramics Reinforced with Metals

With the idea to determine ways of tailoring mullite-ceramics (3Al2O3∙2SiO2) in order that one or more toughening mechanisms are activated in service, investigations about the production of mullite-based composites with different reinforcement metals (Co, Ni, Ti) have been carried out. The synthesis of composites materials has been made by means of pressure less sintering of an intensive mechanical mixture of powders. With the use by separate of those metals in the chemical formulations, significant improvements in ceramic toughness have been obtained. From the fracture toughness measurements and microstructural observations, it can be commented that the toughening mechanism in mullite/metal reinforced composites is due to crack bridging and crack deflection, owed to the presence of ductile particles as metals in the ceramic matrix. On the other hand, the presence of metals in the composites helps to densities mullite