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Some Considerations in Tribology Teaching Algunas recomendaciones en la ense anza de la Tribología
Francisco Martínez Pérez,Alejandra Elena García Toll
Revista Cubana de Ingeniería , 2011, DOI: 10.1234/rci.v2i2.45
Abstract: Tribology is defined as an interdisciplinary science and in order for one to understand fully its complexity it is important to first grasp the nature of its different aspects. Experience accumulated over the years in the different post graduate teaching field of this science permits the possibility to make comments on this topic. Moreover, the teaching of Tribology has some important aspects that need to be acknowledged and commented on. Thus, this article offers the supporting elements in fulfilling its objective. La tribología es una ciencia que por su complejidad e interdisciplinariedad requiere, para su estudio, de la comprensión de una serie de aspectos imprescindibles. La experiencia profesional desarrollada en diferentes programas de ense anza de posgrado, permite brindar recomendaciones referidas al tema. Por otra parte, la propia ense anza de la tribología tiene aspectos esenciales que se hacen necesario comentar. En este artículo se brindan los elementos fundamentales para cumplimentar este objetivo.
Origin Parameters of Fused Flux Grain Process Dispersion with Air Parámetros de origen del proceso de dispersión con aire de fundentes fundidos
Daniel Pérez Pérez,Carlos René Gómez Pérez,Francisco Arturo Ruiz Martínez,Eriel Pérez Zapico
Revista Cubana de Ingeniería , 2011, DOI: 10.1234/rci.v2i1.39
Abstract: Considerations about the fragmentation process with air of molten fluxes obtained by using raw Cuban materials for the welding process under submerged arch (S.A.W) are presented. The physical process of the flight trajectory and its validation during the granulation with air are not reported in the welding field. Therefore, the aim of this work is to establish a procedure that determines the rates and departure angles of pellets during impulsion and dispersion, in addition to contribute criteria on the frictional effect of the surrounding atmosphere on the shape of the trajectory curve of the pellets formed. These aspects may be corroborated with data obtained from the digital processing of filmed images of the fragmentation process and movement of the pellets formed. It is demonstrated that the efficiency of the procedure developed for the obtaining of the flight parameters and the non-influence of the air frictional force on the modification of the particle’s flight trajectory, allows the establishment of a methodology that makes it possible to begin studies about the fragmentation phenomena of molten fluxes by using air jets, which guarantee the necessary rank and granulometric types for an adequate performance of the welding process. Se plantean consideraciones sobre el proceso de fragmentación con aire de fundentes fundidos, obtenidos utilizando materias primas cubanas, para el proceso de soldadura bajo arco sumergido (SAW). El proceso físico de la trayectoria de vuelo y su validación durante la granulación con aire no se reportan en el campo de la soldadura. El objetivo de este trabajo es establecer un procedimiento para determinar las velocidades y ángulos de salida de los peles durante su impulsión y dispersión, además de aportar criterios del efecto friccional de la atmósfera circundante sobre la forma de la curva de trayectoria de los peles formados. Estos aspectos se pueden corroborar con los datos obtenidos mediante el procesamiento digital de las imágenes filmadas del proceso de fragmentación y desplazamiento de los peles formados. Se demuestran la eficacia del procedimiento desarrollado para la obtención de los parámetros de vuelo y la no influencia de la fuerza friccional del aire sobre la modificación de la trayectoria de vuelo de las partículas, permitiendo establecer una metodología, que posibilita iniciar estudios sobre los fenómenos de fragmentación de fundentes fundidos empleando chorros de aire, que garanticen los rangos y clases granulométricas necesarias para un adecuado desempe o del proceso de soldadura.
Síntesis de espirobrasinoesteroides análogos de la 6-desoxocastasterona
Iglesias Arteaga, Martín A.;Leliebre Lara, Vivian;Pérez Martínez, Carlos;Coll Manchado, Francisco;
Química Nova , 1997, DOI: 10.1590/S0100-40421997000400004
Abstract: the synthesis of two new spirostanic analogs of the natural occurring brassinosteroid 6-desoxocastasterone (1) is described. the scheme consists in the formation and elimination of tigogenin mesylate followed by catalytic dihydroxylation of the resulting d2-steroid (3) and acetylation of the 2a, 3a-diol introduced.treatment diacetate (5) with nano2/bf3.et2o and chromatography in alumina led to a 23-keto (6) which on reduction produced the 23s alcohol (8) as major product. saponification of the 2a, 3a-diacetoxy-23-keto compound (6) and the 2a,3a-diacetoxy-23-hydroxy compound (8) led to the spirobrasinosteroids (7) and (9).13c nmr and 1h rmn characteristics derived from substitution at c23 are briefly discussed.
Religious Self-definition, Mass Attendance, Importance of God, and Hopelessness among Spanish Undergraduates
García-Alandete,Joaquín; Martínez,Eva Rosa; Gallego-Pérez,José Francisco;
Escritos de Psicología (Internet) , 2011,
Abstract: the aim of this work was to examine the relationship between religious self-definition, attending mass, the importance of god, and hopelessness under the hy-pothesis that these religious variables and hopelessness are negatively related. the par-ticipants were 273 spanish undergraduates who were incidentally recruited. and who completed three religious items and the spanish version of a hopelessness scale. the chi-squared test and bonferroni test were used in the statistical analysis. the results indicate that there were no statistically significant differences between the religious self-definition and attending mass groups in relation to hopelessness, whereas there were differences between groups in the variable importance of god; this is not consis-tent with the findings of previous studies. we discuss the limitations of the study, offer suggestions for future research, and indicate the need to distinguish between the diverse aspects of religiosity to better explain their implications regarding hopelessness.
Producción de ésteres etílicos a partir de aceite de palma RBD
Martínez A.,óscar Mauricio; Sánchez C.,Francisco José; Suárez P.,Oscar Yesid;
Ingeniería e Investigación , 2007,
Abstract: this work develops a methodology for obtaining ethyl esters from rbd (refined, bleached and deodorised) palm oil by evaluating the oil?s transesterification and separation. two catalysts were first tested (koh and naoh) by studying the effect of water presence on the reaction. the separation process was then evaluated by using water and water-salt and water-acid mixtures, establishing the agent offering the best results and carrying out the purification stage. raw materials and products were characterised for comparing the latter with those obtained by traditional means and verifying the quality of the esters so produced; minimum differences were found between both. the proposed methodology thus allows esters to be used as raw material in petrochemical industry applications. a more profitable process can be obtained compared to those used today, given the amounts of separation agent so established (1% h3po4 solution, in water). the overall process achieved 74.4% yield, based on the oil being used.
Comparative effects of clomipramine and duloxetine on detrusor and striated sphincter function in male and female rabbits
Pérez Martínez,Francisco Carlos; Vela Navarrete,Remigio; Castilla Reparaz,Carlos;
Archivos Espa?oles de Urología (Ed. impresa) , 2006, DOI: 10.4321/S0004-06142006000800019
Abstract: objective: serotonin and norepinephrine systems are involved in the neural control of lower urinary tract function. the aim of this study was to compare the response on striated anal sphincter electromyographic (sas-emg) activity and cystometric parameters, when duloxetine and clomipramine were intravenously administrated. methods: the effects of intravenous 1 and 2 mg./kg. duloxetine or clomipramine on lower urinary tract function were studied in a total of 32 male and 32 female rabbits, under nonirritative conditions (intravesical infusion of saline) and in a model of bladder irritation (i.e., transvesical infusion of 0.5% acetic acid). a transurethral double-lumen catheter in male rabbits, and a subcutaneous cystostomy in female rabbits, were used for liquid infusion and recording of intravesical pressure during a cystometrogram. simultaneously, sas-emg was recorded through electromyography electrodes placed in the perianal striated muscle. results: cystometric parameters: under irritative conditions, 2mg./kg. clomipramine in male rabbits and 1 or 2 mg./kg. in female rabbits, depending on the dose, increased bladder capacity (bc), contraction duration (cd) and intercontraction interval (ici), and decreased baseline pressure (bp). in male and female rabbits, duloxetine dose-dependently increased bc, cd and ici. under nonirritative conditions, clomipramine at 2 mg./kg. and duloxetine dose-dependently solely increased bc in female rabbits. electromyographic activity: a marked effect on sas-emg activity of duloxetine under irritative conditions was revealed in male and female rabbits. under these conditions, clomipramine increased sas-emg activity only in female rabbits. under nonirritative conditions, 2 mg./kg. duloxetine increased sasemg activity only in female rabbits. conclusions: the stronger effects on the sas-emg activity were produced by duloxetine in female rabbits under irritated bladder conditions. clomipramine, under irritative conditions, had a relaxing
Bases para abordar la valoración del impacto social de un programa cubano de maestría en epidemiología
González Ochoa,Edilberto; Armas Pérez,Luisa; Cantelar Martínez,Beatriz; Cantelar de Francisco,Nereyda;
Revista Cubana de Higiene y Epidemiolog?-a , 2006,
Abstract: the master's degree program in epidemiology of “pedro kouri” institute began in 1984 as a result of the institutional and national development of this public health branch. its main objectives respond to a series of social, technical and scientific needs and tasks in the national, regional and international arena. as an educative program, it is subjected to internal and external evaluations. the evaluation of its effectivity and social impact is a very important aspect for its accreditation, so an adequate methodological approach of the object of the progam is required. the assessment of the short-term effect of the program on the graduates, the professors, the managers, the environment and the community expressed through the job appointment, the activities carried out, the scientific and research responsibilites, its scope, and the counselling given could measure its effectivity. to determine the social impact it would be necessary to delimit the community setting and to apply indicators of the general contribution, the scientific and technical contribution and the academic teaching influence on a longer term.
Bases para la valoración del impacto social de un programa de Maestría en Epidemiología
González Ochoa,Edilberto; Armas Pérez,Luisa; Cantelar Martínez,Beatriz; Cantelar de Francisco,Nereyda;
Revista Cubana de Higiene y Epidemiolog?-a , 2008,
Abstract: objeticve: to evaluate the effectiveness and social impact of the master's degree program in epidemiology. development: an appropriate methodological approach of the object of the program was necessary. the assessment of the effect of the program on a short term on the graduates, the professors, the administration, the setting and the community expressed in the posts of employment, the activity carried out, the scientific and investigative responsibilities, their environment and the counsel given, could be used to measure effectiveness. to measure the social impact it would be necessary to delimitate the setting of the community and to apply indicators of the general contribution, the scientific and technical contribution, and the academic teaching influence on a longer term. conclusions: the evaluation of the effectivity and of the social impact of the master's degree program in epidemiology is based on the policy and methodological aspects of the advanced education dictated by the ruling state bodies. it is necessary a peculiar multifaceted methodological approach for the evaluative object.
Epidemiología genética de la obesidad: estudios familiares
Santos M,José Luis; Martínez H,José Alfredo; Pérez B,Francisco; Albala B,Cecilia;
Revista médica de Chile , 2005, DOI: 10.4067/S0034-98872005000300012
Abstract: this review focuses on methodological aspects and main results of different family studies that have been conducted to assess the existence of a genetic contribution in human obesity. a genetic component in the etiology of obesity has been elucidated through specific study designs answering different research questions such as: a) do obesity aggregate in families? b) is there a genetic contribution to familial clustering? c) is it possible to localize chromosomal regions that contain susceptibility genes to obesity? d) is it possible to estimate the risk for developing obesity depending on the genotype profile in candidate genes? there are sufficient evidences indicating the existence of a moderate familial clustering of obesity defined as body mass index 330 with a stronger aggregation with more extreme values of body mass index. twin studies have demonstrated that the familial aggregation of obesity has a genetic component and is not only due to cultural or environmental factors clustered in families. linkage studies have identified markers and genes related to obesity in virtually all human chromosomes. however, some of these linkage studies have produced conflicting results. discordant results are even more pronounced in case-control studies that evaluate the association between alleles at candidate genes and obesity. topics related to study design will acquire increasing importance in order to avoid methodological problems related to trait definition, sample sizes, population stratification by ethnicity and other confounding factors (rev méd chile 2005; 133: 349-61)
Costos de las infecciones nosocomiales en pacientes atendidos en una unidad de cuidados intermedios
Clara Morales Pérez,Humberto Guanche Garcell,Francisco Gutiérrez García,Carlos Martínez Quesada
Revista Cubana de Enfermer?-a , 2004,
Abstract: Se estudiaron 129 pacientes egresados de la unidad de cuidados intermedios del hospital "Joaquín Albarrán" durante el primer trimestre de 2002. Se registró la edad, sexo, estadía hospitalaria, procederes de riesgo realizados, complicación con infecciones nosocomiales, la localización de las mismas y costo por estadía. Se utilizaron las pruebas estadísticas siguientes: t de homogeneidad y de Wilcoxon y en una segunda etapa, regresión lineal múltiple. Sin controlar la edad, la estadía global en la unidad y otras salas hospitalarias, resultó superior en los pacientes con infección nosocomial. Igual resultado se obtuvo para los costos por estadía y utilización de antimicrobianos (p = 0,00). Al ajustarse por edad, los resultados del estudio no cambiaron lo que sugirió que la infección nosocomial es un predictor independiente del incremento de los costos por estadía y utilización de antimicrobianos.
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