Empirical study of correlated survival times for recurrent events with proportional hazards margins and the effect of correlation and censoring.

Background: In longitudinal studies where subjects experience recurrent incidents over a period of time, such as respiratory infections, fever or diarrhea, statistical methods are required to take into account the within-subject correlation. Methods: For repeated events data with censored failure, the independent increment (AG), marginal (WLW) and conditional (PWP) models are three multiple failure models that generalize Cox"s proportional hazard model. In this paper, we revise the efficiency, accuracy and robustness of all three models under simulated scenarios with varying degrees of within-subject correlation, censoring levels, maximum number of possible recurrences and sample size. We also study the methods performance on a real dataset from a cohort study with bronchial obstruction. Results: We find substantial differences between methods and there is not an optimal method. AG and PWP seem to be preferable to WLW for low correlation levels but the situation reverts for high correlations. Conclusions: All methods are stable in front of censoring, worsen with increasing recurrence levels and share a bias problem which, among other consequences, makes asymptotic normal confidence intervals not fully reliable, although they are well developed theoretically.

Power supply noise and logic error probability

Voltage fluctuations caused by parasitic impedances in the power supply rails of modern ICs are a major concern in nowadays ICs. The voltage fluctuations are spread out to the diverse nodes of the internal sections causing two effects: a degradation of performances mainly impacting gate delays anda noisy contamination of the quiescent levels of the logic that drives the node. Both effects are presented together, in thispaper, showing than both are a cause of errors in modern and future digital circuits. The paper groups both error mechanismsand shows how the global error rate is related with the voltage deviation and the period of the clock of the digital system.

Salivary cotinine concentrations in daily smokers in Barcelona, Spain: a cross-sectional study

Background: Characterizing and comparing the determinant of cotinine concentrations in different populations should facilitate a better understanding of smoking patterns and addiction. This study describes and characterizes determinants of salivary cotinine concentration in a sample of Spanish adult daily smoker men and women. Methods: A cross-sectional study was carried out between March 2004 and December 2005 in a representative sample of 1245 people from the general population of Barcelona, Spain. A standard questionnaire was used to gather information on active tobacco smoking and passive exposure, and a saliva specimen was obtained to determine salivary cotinine concentration. Two hundred and eleven adult smokers (>16 years old) with complete data were included in the analysis. Determinants of cotinine concentrations were assessed using linear regression models. Results: Salivary cotinine concentration was associated with the reported number of cigarettes smoked in the previous 24 hours (R2 = 0.339; p < 0.05). The inclusion of a quadratic component for number of cigarettes smoked in the regression analyses resulted in an improvement of the fit (R2 = 0.386; p < 0.05). Cotinine concentration differed significantly by sex, with men having higher levels. Conclusion: This study shows that salivary cotinine concentration is significantly associated with the number of cigarettes smoked and sex, but not with other smoking-related variables.

¿Cómo optimizar una matriz de datos? Utilidades básicas del SPSS

Una vez se dispone de los datos introducidos en el paquete estadístico del SPSS (Statistical Package of Social Science), en una matriz de datos, es el momento de plantearse optimizar esa matriz para poder extraer el máximo rendimiento a los datos, según el tipo de análisis que se pretende realizar. Para ello, el propio SPSS tiene una serie de utilidades que pueden ser de gran utilidad. Estas utilidades básicas pueden diferenciarse según su funcionalidad entre: utilidades para la edición de datos, utilidades para la modificación de variables, y las opciones de ayuda que nos brinda. A continuación se presentan algunas de estas utilidades.

Análisis Discriminante mediante SPSS

El análisis discriminante es un método estadístico a través del cual se busca conocer qué variables, medidas en objetos o individuos, explican mejor la atribución de la diferencia de los grupos a los cuales pertenecen dichos objetos o individuos. Es una técnica que nos permite comprobar hasta qué punto las variables independientes consideradas en la investigación clasifican correctamente a los sujetos u objetos. Se muestran y explican los principales elementos que se relacionan con el procedimiento para llevar a cabo el análisis discriminante y su aplicación utilizando el paquete estadístico SPSS, versión 18, para el desarrollo del modelo estadístico, las condiciones para la aplicación del análisis, la estimación e interpretación de las funciones discriminantes, los métodos de clasificación y la validación de los resultados.

Kernel-PCA data integration with enhanced interpretability

Background Nowadays, combining the different sources of information to improve the biological knowledge available is a challenge in bioinformatics. One of the most powerful methods for integrating heterogeneous data types are kernel-based methods. Kernel-based data integration approaches consist of two basic steps: firstly the right kernel is chosen for each data set; secondly the kernels from the different data sources are combined to give a complete representation of the available data for a given statistical task. Results We analyze the integration of data from several sources of information using kernel PCA, from the point of view of reducing dimensionality. Moreover, we improve the interpretability of kernel PCA by adding to the plot the representation of the input variables that belong to any dataset. In particular, for each input variable or linear combination of input variables, we can represent the direction of maximum growth locally, which allows us to identify those samples with higher/lower values of the variables analyzed. Conclusions The integration of different datasets and the simultaneous representation of samples and variables together give us a better understanding of biological knowledge.

Com fer una anàlisi quantitativa de dades de tipus descriptiu amb el paquet estadístic de l"SPSS?

En l"actualitat és difícil parlar de processos estadístics d"anàlisi quantitativa de dades sense fer referència a la informàtica aplicada a la recerca. Aquests recursos informàtics es basen sovint en paquets de programes informàtics que tenen l"objectiu d"ajudar al/a la investigador/a en la fase d"anàlisi de dades. En aquests moments un dels paquets més perfeccionats i complets és l"SPSS (Statistical Package for the Social Sciences). L"SPSS és un paquet de programes per tal de dur a terme l"anàlisi estadística de les dades. Constitueix una aplicació estadística força potent, de la qual s"han anat desenvolupant diverses versions des dels seus inicis, als anys setanta. En aquest manual les sortides d"ordinador que es presenten pertanyen a la versió 11.0.1. No obstant això, tot i que la forma ha anat variant des dels inicis, pel que fa al funcionament segueix essent molt similar entre les diferents versions. Abans d"iniciar-nos en la utilització de les aplicacions de l"SPSS és important familiaritzarse amb algunes de les finestres que més farem servir. En entrar a l"SPSS el primer que ens trobem és l"editor de dades. Aquesta finestra visualitza, bàsicament, les dades que anirem introduint. L"editor de dades inclou dues opcions: la Vista de les dades i la de les variables. Aquestes opcions es poden seleccionar a partir de les dues pestanyes que es presenten en la part inferior. La vista de dades conté el menú general i la matriu de dades. Aquesta matriu s"estructura amb els casos a les files i les variables a les columnes.

Empirical study of correlated survival times for recurrent events with proportional hazards margins and the effect of correlation and censoring.

Background: In longitudinal studies where subjects experience recurrent incidents over a period of time, such as respiratory infections, fever or diarrhea, statistical methods are required to take into account the within-subject correlation. Methods: For repeated events data with censored failure, the independent increment (AG), marginal (WLW) and conditional (PWP) models are three multiple failure models that generalize Cox"s proportional hazard model. In this paper, we revise the efficiency, accuracy and robustness of all three models under simulated scenarios with varying degrees of within-subject correlation, censoring levels, maximum number of possible recurrences and sample size. We also study the methods performance on a real dataset from a cohort study with bronchial obstruction. Results: We find substantial differences between methods and there is not an optimal method. AG and PWP seem to be preferable to WLW for low correlation levels but the situation reverts for high correlations. Conclusions: All methods are stable in front of censoring, worsen with increasing recurrence levels and share a bias problem which, among other consequences, makes asymptotic normal confidence intervals not fully reliable, although they are well developed theoretically.

Com optimitzar una matriu de dades? Utilitats bàsiques de l"SPSS

Una vegada es disposa de les dades introduïdes al paquet estadístic de l"SPSS (Statistical Package of Social Science) en una matriu de dades, és el moment de plantejar-se optimitzar aquesta matriu per poder extreure el màxim rendiment a les dades, segons el tipus d"anàlisi que es pretengui dur a terme. Per a això, el mateix SPSS té una sèrie d"utilitats que poden ser de gran utilitat. Aquestes utilitats bàsiques poden diferenciar-se segons la seva funcionalitat entre: les utilitats per a l"edició de dades, les utilitats per a la modificació de variables i les opcions d"ajuda que ens brinda. A continuació es presenten algunes d"aquestes utilitats.

Claves para la elaboración de un artículo científico

La meta final de la profesión de enfermería es mejorar la actitud práctica de sus miembros de modo que los servicios prestados a la comunidad tengan la máxima calidad, por lo que para garantizar su status profesional debe apostar por el desarrollo constante de un conjunto de conocimientos científicos que son fundamentales para su práctica, y esto sólo puede conseguirse mediante la investigación. La publicación de un artículo científico...

A measure of stability as a criterion for the verification and analysis of simulation models

The aim of this study is to define a new statistic, PVL, based on the relative distance between the likelihood associated with the simulation replications and the likelihood of the conceptual model. Our results coming from several simulation experiments of a clinical trial show that the PVL statistic range can be a good measure of stability to establish when a computational model verifies the underlying conceptual model. PVL improves also the analysis of simulation replications because only one statistic is associated with all the simulation replications. As well it presents several verification scenarios, obtained by altering the simulation model, that show the usefulness of PVL. Further simulation experiments suggest that a 0 to 20 % range may define adequate limits for the verification problem, if considered from the viewpoint of an equivalence test.

Informática en Pediatría: aplicaciones prácticas

INFORMACION E INFORMATICA La evolución del ser humano se ha comparado a una espiral ascendente cuyo radio es cada vez menor, queriendo simbolizar con ella el incremento en la velocidad con la que se adquieren nuevas conocimientos y aplicaciones de los mismos que son en definitiva, una consecuencia de toda la experiencia acumulada previamente...

Revisión actualizada sobre orientación de la producción científica enfermera

Este año se cumplen los veinticinco años de la enfermería española en la Universidad. Todos nos felicitamos. Y como es habitual en todas las celebraciones se pondrán en evidencia los logros conseguidos y la importancia de los servicios enfermeros para mantener la salud de la población.

Análisis Discriminante mediante SPSS.

El análisis discriminante es un método estadístico a través del cual se busca conocer qué variables, medidas en objetos o individuos, explican mejor la atribución de la diferencia de los grupos a los cuales pertenecen dichos objetos o individuos. Es una técnica que nos permite comprobar hasta qué punto las variables independientes consideradas en la investigación clasifican correctamente a los sujetos u objetos. Se muestran y explican los principales elementos que se relacionan con el procedimiento para llevar a cabo el análisis discriminante y su aplicación utilizando el paquete estadístico SPSS, versión 18, para el desarrollo del modelo estadístico, las condiciones para la aplicación del análisis, la estimación e interpretación de las funciones discriminantes, los métodos de clasificación y la validación de los resultados.

The Transformation of Practical Teaching Focusing on Dialogic Learning

This study investigates the transformation of practical teaching in a Catalan school, connected to the design, implementation and development of project-based learning, and focusing on dialogic learning to investigate its limits and possibilities. Qualitative and design-based research (DBR) methods are applied. These methods are based on empirical educational research with the theory-driven of learning environments. DBR is proposed and applied using practical guidance for the teachers of the school. It can be associated with the current proposals for Embedding Social Sciences and Humanities in the Horizon 2020 Societal Challenges. This position statement defends the social sciences and the humanities as the most fundamental and important ideas to face all societal challenges. The results of this study show that before the training process, teachers apply dialogic learning in specific moments (for example, when they speak about the weekend); however, during the process and after the process, they work systematically with dialogic learning through the PEPT: they start and finish every activity with a individual and group reflection about their own processes, favouring motivation, reasoning and the implication of all the participants. These results prove that progressive transformations of teaching practice benefit cooperative work in class