RESUMEN: Objetivo: Determinar las propiedades psicométricas de la Escala de Estilos de Vida Saludables para Estudiantes Universitarios (EEVSEU) en hombres y mujeres estudiantes universitarios mexicanos. Material y método: Fueron evaluadas las evidencias de validez respecto a la estructura e invarianza de medición de la EEVSEU mediante análisis factorial confirmatorio. Inicialmente se evaluaron dos modelos: el modelo original (8 dimensiones), y el modelo obtenido en mujeres mexicanas (4 dimensiones). Se determinó la magnitud de las cargas factoriales de cada ítem (≥0,50) y la fiabilidad de las puntaciones y del constructo de los modelos a través de los coeficientes alfa y omega. Finalmente se analizó la asociación entre los estilos de vida saludable con el bienestar psicológico y con la autorregulación de los hábitos alimentarios. Resultados: Luego de los análisis iniciales, se consideró un nuevo modelo con 7 dimensiones de la EEVSEU (ejercicio, comportamiento regular, comportamiento nutricional, responsabilidad en salud, apoyo social, manejo del estrés y apreciación por la vida) (M3), el cual evidencio parámetros factoriales adecuados (índices de ajuste y cargas factoriales), además ser invariante entre hombres y mujeres y asociarse de forma significativa con la autorregulación de los hábitos alimentarios y el bienestar psicológico. Conclusiones: La EEVSEU presenta adecuadas propiedades psicométricas para su aplicación en hombres y mujeres estudiantes universitarios mexicanos con fines de investigación.

ABSTRACT: Objective: To determine the psychometric properties of the Scale of Healthy Lifestyles for University Students (EEVSEU) for male and female university students in Mexico. Materials and methods: Validity evidence regarding the structure and measurement invariance of the EEVSEU was evaluated by confirmatory factor analysis. Initially, two models were evaluated: the original model (8 dimensions) and the model obtained in Mexican women (4 dimensions). The magnitude of the factorial loads of each item (≥0.50) and the reliability of the scores and the construct of the models were determined through the alpha and omega coefficients. Finally, the association between healthy lifestyles and psychological well-being and self-regulation of eating habits was analysed. Results: After the initial analyses, a new model was constructed with 7 dimensions of the EEVSEU (exercise, regular behaviour, nutritional behaviour, health responsibility, social support, stress management and appreciation for life) (M3). It evidenced adequate factorial parameters (adjustment indices and factorial loads), was invariant between men and women and significantly associated with the self-regulation of eating habits and psychological well-being. Conclusions: The EEVSEU has adequate psychometric properties for its application in studies involving male and female university students in Mexico.

ABSTRACT In areas with agricultural activity, the excessive use of pesticides can contaminate water resources. That is why a multi-residue method based on solid-phase extraction (SPE) and gas chromatography analysis coupled to mass spectrometry (GS-MS) was used to determine eleven pesticides and five degradation products in surface water of Central Chile. The parameters that can affect the efficiency of the SPE process were optimized considering the information available in bibliography. As in other studies, the best results were obtained when 500 mL of water was pre-concentrated using Oasis HLB polymer cartridges and acetone and acetonitrile were used as solvents for the elution. To ensure good quantification, matrix-matched standards were used, providing good linearity in the studied concentration range (0.10-1.5 μg L-1), with recovery percentages > 60%, precisions < 19% and quantification limits < 0.1 μg L-1. The surface water samples were collected at the end of summer and winter seasons, considering rivers, creeks and irrigation canals of Cachapoal River basin. A percentage > 87% of the pesticides analyzed in this research were detected in more than one sampled site in both seasons. The most ubiquitous compounds were desethylterbuthylazine (DET), pyrimethanil, cyprodinil and diazinon, and the compounds detected in highest concentration were simazine and degradation products derived from triazines. Las Cabras and Tahuilla irrigation canals presented the highest concentrations of pesticides. Significant differences were found in the total concentration of pesticides for sites sampled at the end of the summer and winter season.

ABSTRACT The effect of the sub-zero treatment temperature on the transformation of retained austenite to martensite in two high chromium white cast irons (ASTM A532 Class II Type B) was studied. The sub-zero treatment applied to each alloy in the as cast condition was performed at -40, -65 and -180 ° C for 10 minutes; after the holding time was completed the samples were cooled to room temperature. The microstructure of the as cast condition was analyzed by optical microscopy (LOM) and scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis was also performed with the aim to identify the microconstituents initially present in each alloy. The metallographic characterization of the specimens subjected to sub-zero treatment was performed by optical microscopy. Furthermore, Brinell hardness was measured in the as cast and sub-zero treated samples. The alloys studied have important differences in chemical composition, mainly in the molybdenum and copper content, which mainly determine its microstructure. The results showed an increase in the hardness of both alloys with decreasing treatment temperature; which is due to the fact that the amount of retained austenite transformed to martensite increases as the martensite finish temperature (Mf) is reached. It was also observed that a higher molybdenum content produces a metastable austenitic matrix in the as cast samples. Furthermore, the effect of Mo and other alloying elements substantially stabilizes the austenite, obtaining low amounts of martensite after the sub-zero treatment, even at -180 ° C.

RESUMEN En el siguiente trabajo de investigación se analizó el efecto de la temperatura de tratamiento sub-cero sobre la transformación de austenita retenida a martensita en dos fundiciones blancas de alto cromo ASTM A532 Clase II Tipo B. El tratamiento sub-cero aplicado a cada aleación, en estado de colada, fue realizado a temperaturas de -40, -65 y -180 °C con un tiempo de mantenimiento de 10 minutos; transcurridos los 10 minutos cada probeta fue expuesta a temperatura ambiente. Se realizó análisis metalográfico mediante microscopia óptica, microscopía electrónica de barrido (SEM) y análisis espectroscopia de energía dispersiva (EDS) a ambas aleaciones en estado de colada, con el objetivo de caracterizar los micro-constituyentes presentes en cada aleación. La caracterización metalográfica de las probetas sometidas a tratamiento sub-cero fue realizada mediante microscopia óptica. Además, se midió la dureza Brinell de ambas aleaciones, en estado de colada y sometidas a tratamiento sub-cero. Las aleaciones en estudio presentan diferencias importantes en su composición química, principalmente en el contenido de molibdeno y cobre, elementos determinantes en la microestructura de éstas. Los resultados obtenidos muestran un aumento en la dureza de ambas aleaciones conforme disminuye la temperaturas de tratamiento; esto, producto de un aumento en la cantidad de austenita retenida transformada a martensita a medida que se alcanza la temperatura de fin de la transformación martensítica, Mf. Se observó que un mayor contenido de molibdeno permite la obtención de una matriz austenítica metaestable de colada. Además, el efecto de este elemento en conjunto con los demás elementos de aleación fue estabilizar la austenita, obteniendo bajas cantidades de martensita al final del tratamiento sub-cero, incluso a -180 °C.

The contamination of human milk by xenobiotics is a common problem worldwide which is affected by the geographical, climate-related, cultural and socioeconomic variations in each individual location. Public health policies have dealt with this situation by means of ongoing monitoring and restrictive legislation in order to reduce the damaging effects on the populations and the environment, objectivatable data however being recorded particularly in the developing countries. Overall and individual aspects of waste and contaminating oganochlorines, organophosphorates, antibiotics, polychlorate biphenyls, dioxins and furans, their content values, toxic effects studies and the maximum limits permitted under international legislation are highlighted.

La contaminación de la leche humana por xenobióticos es un problema generalizado a nivel mundial, que se ve afectado por las variaciones geográficas, climáticas, culturales y socioeconómicas de cada lugar. Las políticas de salud pública han enfrentado la situación mediante una vigilancia sostenida y legislaciones restrictivas con el objeto de reducir los efectos perjudiciales sobre las poblaciones y el ambiente, sin embargo se registran datos objetivables, sobre todo en los países en desarrollo. En esta revisión se destacan aspectos generales y particulares de los residuos y contaminantes organoclorados, organofosforados, antibióticos, metales pesados, bifenilos policlorados, dioxinas y furanos, valores de sus contenidos, efectos tóxicos estudiados y los límites máximos permitidos por las legislaciones internacionales.

The contamination of human milk by xenobiotics is a common problem worldwide which is affected by the geographical, climate-related, cultural and socioeconomic variations in each individual location. Public health policies have dealt with this situation by means of ongoing monitoring and restrictive legislation in order to reduce the damaging effects on the populations and the environment, objectivatable data however being recorded particularly in the developing countries. Overall and individual aspects of waste and contaminating oganochlorines, organophosphorates, antibiotics, polychlorate biphenyls, dioxins and furans, their content values, toxic effects studies and the maximum limits permitted under international legislation are highlighted.

La contaminación de la leche humana por xenobióticos es un problema generalizado a nivel mundial, que se ve afectado por las variaciones geográficas, climáticas, culturales y socioeconómicas de cada lugar. Las políticas de salud pública han enfrentado la situación mediante una vigilancia sostenida y legislaciones restrictivas con el objeto de reducir los efectos perjudiciales sobre las poblaciones y el ambiente, sin embargo se registran datos objetivables, sobre todo en los países en desarrollo. En esta revisión se destacan aspectos generales y particulares de los residuos y contaminantes organoclorados, organofosforados, antibióticos, metales pesados, bifenilos policlorados, dioxinas y furanos, valores de sus contenidos, efectos tóxicos estudiados y los límites máximos permitidos por las legislaciones internacionales.