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Influencia de la estructura de los datos en la selección de los métodos de análisis estadísticos
Utra,Isabel María Barroso; Ca?izares Pérez,Mayilée; Lera Marqués,Lydia;
Revista Espa?ola de Salud Pública , 2002, DOI: 10.1590/S1135-57272002000200003
Abstract: in medical research, data is grouped either as per the design of the study or the selection of the sample. this structure must be taken into account in order to make correct estimates of the of the parameters and standard errors involved.. this study is of the methodological type and is aimed at illustrating methods for estimating population-related methods and regression models with grouped data. for this purpose, nine variables from the first national risk factor and preventive measure survey conducted in cuba in 1995 are employed. the prevalence of high blood pressure is overestimated by 15% when the conventional estimators are used as compared with the weight-based and adjusted analysis. in the regression models for the body mass index based on the conventional procedures, sex, degree of schooling, degree of sedentariness, smoking habit, diastolic and systolic blood pressure were found to be significant. however, when the method taking into account the structure of conglomerates was employed, the degree of schooling and sedentariness ceased to be significant. when the random intercept model was adjusted, the 91.3% total variability was found to be explained by individual variables, the 8.7% variability being attributed to larger units. when estimating population-related parameters based on conglomerate-structure data involving inconsistent selection probabilities, the use of sample-related weights and analysis methods that take in the correlation among subjects (potential) for one same conglomerate. when adjusting regression models, it is not only important to efficiently estimate the coefficients, but rather the focus (aggregated or disaggregated) must be taken into account for modeling the problem under study.
CONSUMO DE VERDURAS Y FRUTAS EN CENTROS DE SALUD Y SUPERMERCADOS, DE LA REGIóN METROPOLITANA DE CHILE: PROGRAMA 5 AL DíA VEGETABLES AND FRUITS CONSUMPTION IN HEALTH CENTRES AND SUPERMARKETS IN THE CHILEAN METROPOLITAN REGION: 5 A DAY PROGRAM
Isabel Zacarías H,Lorena Rodríguez O,Lydia Lera M,Renée Hill D
Revista Chilena de Nutricíon , 2009,
Abstract: Objetivo: Evaluar la frecuencia de consumo de verduras y frutas y el conocimiento del mensaje "5 al día", en usuarios de Supermercados y de Centros de Salud Pública, para ser utilizados como línea base para planificar una intervención bimodal, controlada, para la promoción del consumo de frutas y verduras. Sujetos y métodos: a 1897 adultos entre 17 y 60 a os, del área urbana de la Región Metropolitana, se les aplicó una encuesta de frecuencia de consumo, etapa de cambio de conducta y conocimiento del mensaje. Resultados: 58.8% se aló consumir entre 1-2 porciones/día y 33.5% entre 3-4. 91,2% indicó que ha mantenido este consumo por más de seis meses, 7,7% cumple con la recomendación "5 al día" sólo 9,4% conocía el mensaje. No hubo diferencias significativas entre los grupos de intervención salvo en el nivel educacional y en el número de porciones de consumo diario. Conclusiones: El consumo de verduras y frutas estuvo bajo la recomendación en todos los grupos estudiados y existe un desconocimiento del mensaje promocional "5 al día". Objective: To evaluate the consumption frequency of vegetables and fruits and the knowledge of the i5 a dayi message in users of supermarkets and Public Health Centers to be utilized as a baseline to plan a bimodal controlled intervention for the promotion of fruits and vegetables consumption. Individuals and methods: A frequency consumption survey, the behavioral change stage and the message understanding was applied to 1.897 adults aged between 17 and 60 years in the urban area of the Metropolitan Region. Results: 58.8% stated that they ate between 1 -2 portions! day, 33.5% between 3-4,91.2% indicated that they had maintained this consumption for over six months and 7.7% complied with the recommendation of 15 a dayi; only 9.4% knew the message. There were no significant differences among the intervention groups except in the educational level and the number of daily consumption portions. Conclusions: The consumption of vegetables and fruits was under the recommendation in all the studied groups and there is a lack of knowledge regarding the i5 a dayi promotional message.
ESTADO NUTRICIONAL Y CONSUMO DE ALIMENTOS SELECCIONADOS EN ESCOLARES DE LA REGIóN METROPOLITANA: LINEA BASE PARA UN PROYECTO DE PROMOCIóN DEL CONSUMO DE PESCADO NUTRITIONAL STATUS AND CONSUMPTION OF SELECTED FOODS IN SCHOOL SCHILDREN FROM SANTIAGO: BASELINE INFORMATION FOR AN INTERVENTION TO INCREASE THE INTAKE OF FISH
Sonia Olivares C,Isabel Zacarías H,Lydia Lera M,Bárbara Leyton D
Revista Chilena de Nutricíon , 2005,
Abstract: En 1.431 escolares de 4o básico (748 hombres y 683 mujeres) asistentes a escuelas de nivel socioeconómico (NSE) medio y bajo en Santiago, se evaluó el estado nutricional y el consumo de alimentos seleccionados como línea base de una intervención para promover el consumo de pescado. La prevalencia de obesidad alcanzó al 17 y 11,6% en los ni os y ni as de NSE bajo y al 13,2 y 12,6% en el NSE medio, respectivamente (NS). El consumo de lácteos fue insuficiente, mayor en el NSE medio que en el bajo (356 vs 316 ml/promedio/día) (p<0.001). El consumo de frutas y verduras fue bajo en ambos grupos y el de pan mayor en el NSE bajo que en el medio (220 vs 203 g/promedio/día) (p<0.001). El consumo de pescado sólo alcanzó a los 9 g/promedio/día, sin diferencias por NSE. Los resultados del estudio muestran la necesidad de realizar intervenciones para aumentar el consumo de pescado en la población escolar Nutritional status and food intake of 1.431 school children of 4th grade (748 boys and 683 girls) were evaluated as a baseline of a project for promoting fish consumption The school children attended 20 schools of low and medium socioeconomic level (SEL) from Santiago. The resulting prevalence of obesity was 17 and 11.6% in boys and girls of low SEL, respectively, and 13.2 and 12.6%, in medium SEL (NS). The intake of dairy products was insufficient, higher in medium than in low SEL (356 vs 316 g/average/day) (p<0.001). Fruit and vegetable intake was low in both groups and bread intake higher in low than in medium SEL (220 vs 203 g/average/day) (p<0.001). The quantity of fish consumed was only 9 g/average/day, with no differences by SEL. The results of this study show the importance of developing interventions to improve fish intake among school children
PREVENCIóN DE LA OBESIDAD EN ESCUELAS BáSICAS DE PE ALOLéN: COMPONENTE ALIMENTACIóN Y NUTRICIóN OBESITY PREVENTION IN PRIMARY SCHOOLS IN PE ALOLEN: FOOD AND NUTRITION COMPONENT
Fernando Vio del R,Isabel Zacarías H,Lydia Lera,María Cecilia Benavides
Revista Chilena de Nutricíon , 2011,
Abstract: Se plantea una intervención en educación alimentaria y nutricional en nueve escuelas de la comuna de Pe alolén, con una escuela control. El objetivo es evaluar los cambios en el estado nutricional, conocimiento y consumo de alimentos de los ni os de prebá-sica y básica durante el primer a o de la intervención, comparados con el colegio control. Es un estudio cuasi-experimental, de seguimiento longitudinal en 1556 ni os de prekinder, kínder, primero y segundo básico (1225 ni os de las escuelas intervenidas y 331 de la escuela control) seguidos durante un a o escolar. Se realizaron actividades educativas con profesores y alumnos y la evaluación consistió en una medición de su estado nutricional en marzo-abril y octubre-noviembre del a o 2010; una medición de las colaciones en los ni os de prekinder y kínder, con una encuesta alimentaria a los de primero y segundo básico. Los resultados mostraron que no hubo cambio en el estado nutricional en el total de los ni os intervenidos, aumentando levemente el sobrepeso y obesidad en el colegio control. Sin embargo, al hacer el análisis por colegio, en siete de los nueve colegios intervenidos disminuyó la obesidad. En cuanto a consumo, un alto porcentaje de ni os de prebásica llevaban jugos y bebidas en las colaciones y en los ni os de básica se produjo un incremento significativo del consumo de frutas y lácteos durante el a o. En conocimiento, los ni os de primero y segundo básico tuvieron una buena comprensión en frutas y lácteos, no así para el pescado y legumbres. A pesar del corto período de intervención, este estudio permite se alar que cuando las intervenciones en alimentación y nutrición se realizan en forma estructurada y son evaluadas, pueden tener un impacto positivo en el cambio de hábitos alimentarios y en la disminución de la obesidad en preescolares y escolares de escuelas municipales. A food and nutrition education intervention was implemented in nine public schools in Pe alolen, Chile, with one control school. The objective was to determine the trend in obesity prevalence and in food knowledge and food consumption in preschool and school-age children followed longitudinally in the first year of intervention, compared with the control school. The sample included 1556pre-school, first and second grade (1225 children in experimental schools and 331 in the control school) followed during one school year. Nutrition education activities were performed with teachers and students, and the evaluation of nutritional status was carried out in two points, March-April and October-November 2010. There was also on
Efecto de los parámetros de deformación y de la temperatura de precalentamiento sobre la temperatura de no recristalización en aceros microaleados con Nb y Nb-Ti
Abad Lera, Raquel,Fernández Calvo, Ana Isabel,López Soria, Beatriz
Revista de Metalurgia , 2001,
Abstract: The main objective of the present work has been to determinate the no-recrystallisation temperature (Tnr) of two Nb-bearing steels and two Nb-Ti microalloyed steels. The Tnr has been obtained performing multipass torsion tests under continuous cooling conditions. The influence of deformation parameters: interpass time, tep, pass strain, ε, and strain rate, and reheating temperature, T, on the non-recrystallisation temperature has been investigated. In the range of short interpass time (tep < 20 s), recrystallisation is retarded by solute drag so the Tnr decreases as interpass time increases. For intermediate interpass time, precipitation takes place leading to an increase in the Tnr. However, in the range of long interpass time (tep > 60 s), precipitated particles coarse loosing its effectiveness as recrystallisation retarding agents, which leads again to a decrease in the no-recrystallisation temperature. The Tnr decreases with increasing pass strain following this type of relationship: Tnr = β ε-α. Moreover, an increase in the strain rate leads to a decrease in the non-recrystallisation temperature. By increasing the reheating temperature, the amount of dissolved elements that can precipitate at lower temperatures rises, which results in an increase of the Tnr. 18 Leaching of vanadium from sulphuric acid manufacture spent catalysts Lixiviación de vanadio de catalizadores agotados procedentes de la fabricación del ácido sulfúrico El principal objetivo del presente trabajo fue la determinación de la temperatura de no recristalización (Tnr) de dos aceros microaleados con niobio y otros dos con niobio y titanio. La obtención de (Tnr) se llevó a cabo mediante ensayos de torsión en caliente de múltiples pasadas, realizados en condiciones de enfriamiento continuo. Se ha analizado la influencia que, sobre (Tnr), ejercen los diferentes parámetros de deformación: tiempo entre pasadas (tep), deformación por pasada (ε), y velocidad de deformación ( ), así como la temperatura de precalentamiento del material (T). En el rango de tiempos cortos entre pasadas Tnr, los elementos en solución son los únicos responsables del retraso en la recristalización, produciéndose una disminución de (Tnr) conforme aumenta el tiempo entre pasadas. Para tiempos intermedios tiene lugar la precipitación, lo que da lugar a un aumento de (Tnr). Sin embargo, en el rango de tiempos de espera prolongados (tep > 60 s), las partículas precipitadas aumentan de tama o perdiendo su efectividad como agentes retardadores de la recristalización y produciendo, de nuevo, una disminución de la temper
Influencia de la estructura de los datos en la selección de los métodos de análisis estadísticos
Utra Isabel María Barroso,Ca?izares Pérez Mayilée,Lera Marqués Lydia
Revista Espa?ola de Salud Pública , 2002,
Abstract: En las investigaciones médicas se encuentran datos agrupados ya sea por el dise o del estudio o la selección de la muestra. Esta estructura debe ser considerada para obtener estimaciones apropiadas de los parámetros y sus errores estándares. El presente trabajo es de naturaleza metodológica y se destina a ilustrar métodos para estimar parámetros poblacionales y modelos de regresión con datos agrupados. Para ello se utilizan nueve variables de la I Encuesta Nacional de Factores de Riesgo y Actividades Preventivas, realizada en Cuba en 1995. La prevalencia de hipertensión arterial se sobreestima en un 15% cuando se utilizan los estimadores convencionales comparado con el análisis con pesos y el ajustado. En los modelos de regresión para el índice de masa corporal se encontró que con los procedimientos convencionales: sexo, nivel de educacional, condición de sedentarismo, tabaquismo, tensión diastólica y sistólica resultaron significativas. Sin embargo, con el método que considera la estructura de conglomerados dejaron de ser significativas el nivel educacional y la condición de sedentarismo. Al ajustar el modelo de intercepto aleatorios se encontró que el 91,3% de la variabilidad total se explica por variables individuales y el 8,7% se atribuye a unidades superiores. Al estimar parámetros poblacionales en datos con estructura de conglomerados y con desigualdad en las probabilidades de selección hay que considerar el uso de pesos muestrales y métodos de análisis que contemplen la correlación entre sujetos (potencial) de un mismo conglomerado. Al ajustar modelos de regresión no sólo importa obtener eficiencia en la estimación de los coeficientes sino que se debe considerar el enfoque (agregado o desagregado) para modelar el problema objeto de estudio.
PREVENCIóN DE LA OBESIDAD EN ESCUELAS BáSICAS DE PE?ALOLéN: COMPONENTE ALIMENTACIóN Y NUTRICIóN
Vio del R,Fernando; Zacarías H,Isabel; Lera,Lydia; Benavides,María Cecilia; Gutiérrez,Ana María;
Revista chilena de nutrición , 2011, DOI: 10.4067/S0717-75182011000300002
Abstract: a food and nutrition education intervention was implemented in nine public schools in pe?alolen, chile, with one control school. the objective was to determine the trend in obesity prevalence and in food knowledge and food consumption in preschool and school-age children followed longitudinally in the first year of intervention, compared with the control school. the sample included 1556pre-school, first and second grade (1225 children in experimental schools and 331 in the control school) followed during one school year. nutrition education activities were performed with teachers and students, and the evaluation of nutritional status was carried out in two points, march-april and october-november 2010. there was also one measurement of snack consumption in pre-school children and a food and nutrition survey in school age children at the beginning and at the end of the year. results showed that there was no change in overweight and obesity in the intervened school-age children, and a small increase in the control school. however, analyzing nutritional status by school, in seven of the nine experimental schools there was a decrease in obesity. a high percentage ofpreschool children carried soft drinks and juices to school. in school age children there was a significant increase in fruit and dairy consumption during the year. school age children had a good knowledge offruits and dairy food, but not offish and legumes. despite the short period of food and nutrition intervention, this study shows that interventions implemented in a structured way with an evaluation can have a positive impact on changing eating habits and improving the nutritional status of municipal preschool and school children.
A Parallel Algorithm for Global Optimization Problems in a Distribuited Computing Environment  [PDF]
Marco Gaviano, Daniela Lera, Elisabetta Mereu
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.330194
Abstract: The problem of finding a global minimum of a real function on a set S \"\"Rn occurs in many real world problems. Since its computational complexity is exponential, its solution can be a very expensive computational task. In this paper, we introduce a parallel algorithm that exploits the latest computers in the market equipped with more than one processor, and used in clusters of computers. The algorithm belongs to the improvement of local minima algorithm family, and carries on local minimum searches iteratively but trying not to find an already found local optimizer. Numerical experiments have been carried out on two computers equipped with four and six processors; fourteen configurations of the computing resources have been investigated. To evaluate the algorithm performances the speedup and the efficiency are reported for each configuration.
Implementing Good Governance Principles for the Public Sector in Information Technology Governance Frameworks  [PDF]
Carlos Juiz, Carlos Guerrero, Isaac Lera
Open Journal of Accounting (OJAcct) , 2014, DOI: 10.4236/ojacct.2014.31003
Abstract: In this paper, we are showing how Information Technology (IT) governance frameworks contribute to the implementation of the key principles of the good corporate governance, particularly, in the public sector. We demonstrate that there are numerous links, explicitly and implicitly expressed through a set of IT governance instruments, matching the proposals of good governance principles with the behavioral goals of an IT governance framework implementation. We also provide a real experience of using a set of possible instruments, in our public university, through an IT governance framework based on the ISO/IEC 38500 standard. We also present the maturity of the good governance principles implementation with this set of instruments, after governing IT in our university during the period 2007-2013. We show that using an IT governance framework in a public entity mutually reinforces the key principles of good governance, especially the transparency and accountability goals for the IT assets.
A Safer Technique for Nasal Intubation: A Literature Review  [PDF]
Stephanie Lera, Melissa Machan, George Derefaka
Open Journal of Anesthesiology (OJAnes) , 2017, DOI: 10.4236/ojanes.2017.78028
Abstract: Nasotracheal intubation (NTI) is the most widely used method to establish an airway during anesthesia for oral surgery. It has the advantage of providing exceptional accessibility and optimal working conditions in the oral cavity for surgeons. Anesthesia providers are highly trained in managing and securing the airway. Because the oral intubation route is the most widely used technique for securing the airway, nasal intubation can be cumbersome for anesthetists who do not routinely perform this skill. Moreover, anesthesia providers who do not routinely perform NTI may feel apprehension out of concern for nasopharyngeal bleeding and trauma. The number of dental and oromaxillofacial procedures requiring nasal intubation has been steadily growing annually. Although NTI is generally safe, it still presents a risk for complications. The purpose of this literature review was to examine current literature and evidence-based practices of NTI to determine whether the use of a catheter-guided technique will improve patient care outcomes by way of decreased trauma to the airway compared to current clinical practices. The goal of this review is to recommend the use of a catheter-guided technique for NTI as the preferred method for securing the airway during oral surgery as it is less traumatizing to the airway than conventional methods.
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