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Search Results: 1 - 10 of 512986 matches for " A. Martínez-Luévanos "
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Comparative Study between D2EHPA and Cyanex 272 as Extractants of Mn(II) from a Leached Liquor Produced by Reductive Leaching of a Pyrolusite Ore with SO2  [PDF]
R. Pérez-Garibay, J. Martínez-Jiménez, A. Uribe-Salas, A. Martínez-Luévanos
Engineering (ENG) , 2012, DOI: 10.4236/eng.2012.49067
Abstract: This paper compares the efficiency of D2EHPA and Cyanex 272 to extract the divalent manganese cation from an actual leaching solution obtained by reductive leaching of a low-grade pyrolusite ore, using SO2 gas. The studied variables were the extractant concentration in the organic phase, the pH of the leached liquor and the volume ratio between organic phase and leached liquor. It was observed that D2EHPA is a better extractant than Cyanex272. Therefore, with the best experimental conditions found, both extractants reach a manganese recovery around 95% with five extraction stages conducted under the following conditions: 25?C, O/A = 2, 10% volume of extractant concentration in the organic phase, pH of the leached liquor before the mixing between 8 and 8.5, and one minute of mixing time for each extraction stage.
Mecanosíntesis y caracterización de ferrita de manganeso
Vera-Serna, Pedro;Bolarín-Miró, Ana M.;Sánchez-De Jesús, Félix;Martínez-Luévanos, Antonia;
Superficies y vacío , 2011,
Abstract: mechanosynthesis process was applied to obtain manganese ferrite with formula mnfe2o4, powder oxides of mno (99% purity) and fe2o3 (99% purity) was used as raw materials. the high energy milling was performed under air atmosphere using stainless steel vials and hardness steel balls. x-ray diffraction, scanning electronic microscopy, termogravimetric analysis, miliohmmeter (four-point resistivity measurement), light scattering and magnetometer were used to characterize the synthesis powders. the results shown that the mnfe2o4 was obtained at 12 hours of milling time, the material present saturation magnetic of 48 emu/g and electric conductivity of 0.033 s m-1.
A comparative study of two models for the seismic analysis of buildings
Luévanos,A;
Ingeniería e Investigación , 2012,
Abstract: this paper presents a model for the seismic analysis of buildings, taking two lumped masses at each level in a structure's free nodes and comparing them to the traditional model which considers lumped masses per level, i.e., a mass for each floor of the entire building. this is usually done in the seismic analysis of buildings; not all values are conservative in the latter, as can be seen in the table of results. both models took shear deformations into account. therefore, the usual practice of considering a lumped mass per each level would not be a recommended solution; using two lumped masses per level is thus proposed and is also more related to real conditions.
Glosario de términos farmacológicos Glossary of pharmacological terms
Aurora Benítez Gener,Luís Guerra García,Dionisio Pérez Martínez,Yunior Martínez Contreras
Revista de Ciencias M??dicas de Pinar del R?-o , 2007,
Abstract: Este glosario se confeccionó con el objetivo de brindarles a los estudiantes de Ciencias Médicas y a los profesionales de la salud en general, información acerca de los medicamentos de mayor uso, mostrando su nombre en espa ol e inglés, la correcta pronunciación, sus indicaciones y tratamiento. Este compila 142 medicamentos, ordenados alfabéticamente con una traducción al espa ol de sus correspondientes categorías y aplicaciones. Algunos de los medicamentos compilados en este folleto fueron impartidos en las clases de inglés con fines médicos en 4to a o de la carrera de Medicina durante este curso, y ha sido de gran interés y utilidad para los futuros profesionales. Se concluye que el folleto es de gran utilidad porque no solo puede servir de referencia a los estudiantes de Ciencias Médicas, sino también a todo el personal de la salud o a cualquier persona interesada en el tema, incluyendo a profesores de inglés de la institución. Aimed at providing medical students and health professionals information about the most used medications showing their names in Spanish and English as well as the correct pronunciation, indications and treatment, a glossary of pharmacological terms was made. This compiles 142 medications in alphabetical order having a translation into Spanish of their corresponding categories and applications. Some of the medications compiled in this pamphlet were taught in the English lessons with medical purposes in the 4th academic year of the medical major during this course, being of great interest and usefulness for the future health professionals. Concluding that this glossary can be a tool of reference for medical students and for all health personnel or any other people interested in the topic, including professors of English in the institution.
Mecanismos de formación de cementita intergranular de aceros sinterizados Fe-Cu-C
A. Bolarín,F. Sánchez,A. Luévanos,J. Core?o
Revista de la Sociedad Química de México , 2001,
Abstract: La aleación Fe-Cu-C es de gran uso en la fabricación de piezas mediante metalurgia de polvos, debido a que confiere a las piezas buenas propiedades mecánicas (dureza, resistencia, etc.) a bajo costo. El principal inconveniente es la formación de cementita intergranular (Fe3C), la cual produce una disminución en la ductilidad y tenacidad, transformando al material en sumamente frágil. En este trabajo, se presenta el efecto que ejercen algunas de las variables de proceso pulvimetalúrgico: porcentaje de cobre, estado de difusión del cobre en la matriz férrea, temperatura de sinterización y velocidad de enfriamiento, sobre la proporción de cementita intergranular, de la aleación Fe-Cu-C. Los resultados muestran que la formación de cementita está íntimamente relacionada con la secuencia en que difunden el cobre y el carbono en el hierro, realizando cada una de las variables mencionadas anteriormente un efecto particular. Sobre la base de los resultados experimentales obtenidos, se propone un modelo teórico que explica los mecanismos de difusión de cobre y carbono en la matriz metálica durante la sinterización en este tipo de aleaciones.
Análisis del Comportamiento Presión-Temperatura en la Transición Isotrópico-Nemático del p-Azoxianisol al variar el alcance del Potencial
García-Sánchez,Eduardo; Martínez,Francisco J; Mendoza-Huizar,Luís H;
Información tecnológica , 2009, DOI: 10.4067/S0718-07642009000400006
Abstract: this work shows a study on the effect of the potential range in the second order perturbation theory developed by garcía-sánchez et al. for potential range values of 3.5, 4, 10, 15, 17 and 20 with a/b=3.5, it was observed a better theoretical prediction for the potential range of 20, which is in agreement with the theoretical formulation of the perturbation theory that includes the long range approximation of ponce and renon. in this approximation the potential range is considered to have an infinite value. from the present study, it is possible to conclude that if during the theoretical prediction, higher values of the square well potential range are considered in the theoretical model, it is possible to get a better prediction of the experimental behavior pressure-temperature in the isotropic-nematic phase transition for liquid crystal p-azoxianisol.
Trauma químico del segmento anterior Chemical trauma of the anterior segment
Justo Luís Noriega Martínez,Roberto Alejandro Guerra García
Revista Cubana de Oftalmolog?-a , 2012,
Abstract: Se realizó una revisión de la situación actual y manejo de la urgencia de este tipo particular de trauma ocular. Se detectó el trauma químico por álcalis (58,5 %) como el agente etiológico más importante, además de ser el más peligroso entre las sustancias que pueden provocarlo. El lavado profuso con agua o soluciones balanceadas, continúa como el tratamiento de elección en el manejo inicial, y depende de este, la integridad de las estructuras oculares y la agudeza visual final que alcanzará el paciente. Se propone un flujograma con la conducta a seguir en estos casos de forma general. A review of the current situation and management of the ocular chemical injury in the emergency room was made. Alkalis was the most frequent and dangerous etiological agent (58,5 %) of chemical injuries in the eye. Ocular washing with abundant water or balanced solutions remains the treatment of choice as initial management, which determines the ocular structure integrity and the final visual acuity. A general flowchart containing the behavior to be adopted in these cases was submitted.
Análisis del Comportamiento Presión-Temperatura en la Transición Isotrópico-Nemático del p-Azoxianisol al variar el alcance del Potencial Analysis of Pressure-Temperature Behavior in the Isotropic-Nematic Transition of PAA to vary of SW Range
Eduardo García-Sánchez,Francisco J Martínez,Luís H Mendoza-Huizar
Información Tecnológica , 2009,
Abstract: En este trabajo se muestra un estudio del efecto del alcance del potencial en la teoría de perturbaciones de segundo orden desarrollada por García-Sánchez et al. para valores del alcance del potencial de 3.5, 4, 10, 15, 17 y 20 con a/b=3.5. Se observó una mejor predicción teórica para un valor del alcance de potencial de 20, lo que está de acuerdo con el planteamiento teórico en el desarrollo de la teoría de perturbación que incorpora la aproximación de largo alcance de Ponce y Renon. En esta aproximación el alcance de potencial se considera toma un valor de infinito. De este estudio es posible concluir que si durante la predicción teórica son considerados valores bastante grandes del alcance del potencial de pozo cuadrado en el modelo teórico, es posible tener mejores predicciones del comportamiento experimental presión-temperatura en la transición de fase isotrópico-nemático del cristal líquido P-azoxianisol. This work shows a study on the effect of the potential range in the Second Order Perturbation Theory developed by García-Sánchez et al. for potential range values of 3.5, 4, 10, 15, 17 and 20 with a/b=3.5, It was observed a better theoretical prediction for the potential range of 20, which is in agreement with the theoretical formulation of the perturbation theory that includes the long range approximation of Ponce and Renon. In this approximation the potential range is considered to have an infinite value. From the present study, it is possible to conclude that if during the theoretical prediction, higher values of the square well potential range are considered in the theoretical model, it is possible to get a better prediction of the experimental behavior pressure-temperature in the isotropic-nematic phase transition for liquid crystal P-azoxianisol.
Caracterización biopsicosocial del síndrome de down en San Juan y Martínez, 2008
Herrera Miranda,Guillermo Luís; Fernández Martín,María Eugenia; Martínez Orraca,Berkis; Morales Piloto,Yasmín;
Revista de Ciencias M??dicas de Pinar del R?-o , 2008,
Abstract: a longitudinal descriptive study was conducted after analysing the psychosocial study performed in cuba in year 2003 on disability and mental ratardation in order to determine the prenatal causes which contribute to increase the rates in pinar del rio province, particularly in our territory and aimed at characterizing the down's syndrome in san juan y martínez in year 2008.data base showed a prevalence of mental retardation (29 cases).the family was interviewed for being aware of how they manage these patients and how they include them in the society.the characterization of the family was done taking into account the selected variables.it was demonstrated that 79.3% present some cardiac malformations, 72,4% live in rural areas and 44.8% need special orientation.these patients are guided by members of the family properly. data were processed using the percentage statistical method and the chi-square test.
Aspectos clínico-epidemiológicos de la cardiopatía isquémica en San Juan y Martínez, 2009 Clinical and epidemiological aspects of ischemic heart disease in San Juan y Martinez, 2009
Guillermo Luís Herrera Miranda,Berkis Martínez Orraca,Yaima Camejo Brito,María E Fernández Martín
Revista de Ciencias M??dicas de Pinar del R?-o , 2010,
Abstract: La cardiopatía isquémica es un problema de salud que cobra un gran número de vidas y es la causa de invalidez en la población mundial. Con el objetivo de identificar los aspectos clínicos epidemiológicos que caracterizan a la cardiopatía isquémica en 150 pacientes de 15 a os y más, pertenecientes a tres consultorios médicos del Consejo Popular "Galope, San Juan y Martínez", en el periodo comprendido enero _ julio del a o 2009, y por ser este el de mayor incidencia y prevalencia en el municipio se realizó una investigación descriptiva y transversal, que incluyó el interrogatorio, examen físico y electrocardiograma a la totalidad de la muestra, procesándose los datos a través del valor porcentual y Ji cuadrado en los casos necesarios. Se encontró un mayor número de hombres que mujeres en la muestra estudiada. En ambos grupos predominaron las edades superiores a 56 a os. La cardiopatía isquémica sin angina fue la forma clínica que prevaleció, mientras que las alteraciones del segmento S-T predominaron entre los hallazgos electrocardiográficos. El hábito de fumar, el sedentarismo y la hipertensión arterial fueron los factores de riesgo más frecuentes en la serie. Los mismos se incrementaron a medida que aumento la edad, y todos predominaron de manera significativa en el grupo con cardiopatía isquémica. Se encontró una relación directamente proporcional entre los factores de riesgo asociados entre sí y la cardiopatía isquémica. Ischemic Heart Disease is a health problem that takes a great number of lives off and it is a cause of disability all over the world. The objective of this research was to identify clinical and epidemiological aspects that characterize ischemic heart disease in 150 patients (15 years or older), belonging to three doctor's offices in the Popular Council of "Galope", San Juan y Martinez, Pinar del Rio during January-July 2009. This place presents the greatest incidence and prevalence in the municipality. A descriptive and cross-sectional research was conducted including questioning, physical examination and electrocardiogram to the total of the sample chosen. Data were processed using percentage value and chi square when necessary. In the sample male sex prevailed over the female, and ages older than 56 in both groups. Ischemic heart disease without angina was the prevailing clinical manifestation; meanwhile alterations of the ST-segment were the most common electrocardiographic findings. Smoking, sedentary life and hypertension were the most frequent risk factors in the series, increasing with age and all of them prevailed in the group
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