1,721,236 research outputs found
“Flessibilità” degli orari di lavoro e salute: per una ergonomia degli orari di lavoro
No full textThe search for ways and methods able to increase the " flexibility" of working hours deal with several forms of intervention that depend on political choices and work management, according to specific interests and needs of the companies, the individual worker and the whole society. The main problem on the carpet is to evaluate whether that interferes with worker's health and well-being. According to the data of the last European Survey on Working Conditions (EURF 2000), it appears the workers engaged in working hours different from the traditional daywork are nowadays the vast majority of the population; moreover, organisational forms which allow more flexibility, that is more autonomy, in working time arrangement are associate to better health and well-being
Ageing, working hours and work ability
No full textThe current paper reports the main results of several studies carried out on
Italian workers using the work ability index as a complementary tool for workers’ periodical health surveillance. The work ability index shows a general decreasing trend over the years, but it changes differently according to working conditions and personal health status. In jobs with higher mental involvement and autonomy, but lower physical constraint it remains quite
constant and high over the years, while it significantly decreases with a steeper trend the higher the physical work load and the lower the job control are. Sex and working hours appear to act concurrently in influencing work ability, particularly in association with more physically demanding jobs. It is therefore necessary to adopt flexible interventions, able to give ageing shift workers a proper support for maintaining a satisfactory work ability, by means of actions addressed both to work organisation and psycho-physical conditions
PENALIZED REGRESSION: BOOTSTRAP CONFIDENCE INTERVALS AND VARIABLE SELECTION FOR HIGH-DIMENSIONAL DATA SETS
Full text linkHigh dimensional and ultrahigh dimensional variable selection is a formidable challenge in biomedical statistics.
To face this problem, a number of promising approaches have recently been proposed. A very attractive method is penalized regression. This class of procedures shows many advantages but is still not very popular, mainly due to its computational cost. In this work, we focus our attention on these techniques and on their applications to genome-wide association studies (GWAS).
An overview of some of the most interesting penalization methods is given in the first chapter: Lasso, Least Angle Regression, Elastic Net, Adaptive Lasso, Scad, Combined Penalization and Relaxed Lasso. For each technique, we consider from a theoretical point of view the main ideas behind the method and we examine its pros and cons compared to other methods.
An important open problem in the field of L1-penalized regression is the construction of confidence intervals for the model coefficients. A popular approach to calculating confidence intervals is to use bootstrap simulation algorithms. In the second chapter, we investigate four bootstrap methods for regression models (parametric bootstrap, vector resampling, residual bootstrap, and two variants of one-step bootstrap - vector and residual resampling) and we consider their application to generalized linear model (GLMs).
We review their functioning, we describe their implementation algorithms and we evaluate their performance by simulation studies.
In the third chapter, we start considering the residual bootstrap method for the lasso estimator of the regression parameters in a multiple linear regression model, recently proposed by [Chatterjee and Lahiri (2010)]. In the following section we extend this idea to penalized GLMs, using the notion of standardized Pearson’s residuals. The results of the simulation studies show that this method has some serious drawbacks. As a result, in the sections that follows, we explore a completely different approach based on the fact that the coefficients of lasso for linear models can be approximated by ridge regression. After generalizing this result to L1-penalized GLMs, we develop a one-step (residual) resampling method for this class of models in the spirit of the one-step bootstrap for GLMs proposed by [Moulton and Zeger (1991)].
Then, applying the results of [Vinod (1995)], we build confidence intervals (CIs) for the coefficients of the class of L1-penalized GLMs. The simulation studies suggest that by this method we are able to build CIs with good empirical coverage probabilities. In the final section, we consider the double bootstrap of Beran (1987) in order to further reduce the coverage errors of single bootstrap and to build confidence intervals with a higher order of accuracy.
Chapter four contains an overview of one of the most challenging and fascinating problems of modern biomedical statistics: ultrahigh dimensional variable selection in GWAS and gene environment-wide interaction (GEWI) studies, with particular attention on the evaluation of gene-gene and gene environment interactions. This is a fundamental task in the investigation of complex patterns for complex disease. Sure Independence Screening (SIS), Iterative SIS (ISIS) and their variants are novel and effective methods for variable selection in ultrahigh dimensional settings. They are based on a prescreening step for dimension reduction followed by a selection/estimation step performed using L1-penalized regression. We test this method on a simulated dataset obtaining interesting results
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Flexible work hours, ageing and well-being
No full textThe increasing diversification of working time patterns reflects broader societal reasons, involving social development, economic efficiency and individual preferences. The modern society is changing quite rapidly not only in terms of economic and productive strategies, but mainly in terms of social organisation and individual behaviours and careers, and this is certainly due also to the progressive ageing of the general and working populations. Over the last decades an increasing interest in "temporal flexibility" can be observed: that leads, on one hand, to a demand for an increase in the number of hours during which the production is possible (Company-oriented flexibility) and, on the other hand, to a desire for a reduction of individual working hours and/or an increase in the autonomy of their regulation (Individual-oriented flexibility). Also the society is interested in flexible working hours, as many advantages can derive from a more flexible arrangement of social activities and services. According to the results of a recent SALTSA project, longer and irregular working hours are in general associated with lower levels of health and well-being. Moreover, low (individual) flexibility and high variability of work hours (that is company based flexibility) were consistently associated with poor health and well-being, while low variability combined with high autonomy were associated with positive effects
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
