WebStress: A web interface to explore a multidatabase bibliographic corpus on occupational stress

A bibliographic study on a multidisciplinary subject, such as occupational stress, requires a multidatabase query facility. Given this, we searched eight databases belonging to different fields (medicine, psychology, etc.) and from different countries. Thus, more than 26000 references on occupational stress were gathered. A bibliographic corpus of this sort is unusable because of the heterogeneous format of the records and the number of duplicate entries. Considering the limitations of commercial programs, we have developed a system, called WebStress, for reformatting the data and removing duplicates. The huge number of references and the research needs of updating and searching have necessitated the addition of several other functions to WebStress. Therefore WebStress comprises a web interface that makes it possible to search the corpus with advanced features (using clustering, a specialized thesaurus on stress and Boolean queries). In addition to the usual bibliographic queries on a specific database such as Medline, WebStress provides bibliometric analysis of the corpus, which might contribute to a detailed analysis on occupational stress in order to highlight the networks of researchers and to find the main topics studied in this area. WebStress is not yet available to researchers in general. It is being further developed, and also permission needs to be obtained from the eight commercial bibliographic databases that it consults.     

Immigration-related political culture and support for radical right parties

Radical right parties are not equally successful across or within all countries. Most studies have up to now relied on socio-economic, socio-structural and political factors to explain these differences. We examine whether the immigration-related political culture – consisting of integration policies and shared conservative values – in which voters are embedded influences radical right voting. We argue that more exclusive immigration-culture is related to more support for radical right parties. Furthermore, the relationship between immigration attitudes and radical right support is expected to be moderated by immigration-culture. With multilevel regression models using data from the 2011 Swiss Electoral Studies (SELECTS) we compare the effect of immigration-culture in 26 Swiss cantons. We find that cantonal immigration-culture (assessed with integration regimes and shared conservative beliefs) increases radical right support and the effect of individuals' immigration attitude on radical right support is stronger when immigration-culture is exclusive.     

Comprehensive definitions of breakdown points for independent and dependent observations

Summary. We provide a new definition of breakdown in finite samples, with an extension to asymptotic breakdown. Previous definitions centre on defining a critical region for either the parameter or the objective function. If for a particular outlier configuration the critical region is entered, breakdown is said to occur. In contrast with the traditional approach, we leave the definition of the critical region implicit. Our proposal encompasses previous definitions of breakdown in linear and non-linear regression settings. In some cases, it leads to a different and more intuitive notion of breakdown than other procedures that are available. An important advantage of our new definition is that it also applies to models for dependent observations where current definitions of breakdown typically fail. We illustrate our suggestion by using examples from linear and non-linear regression, and time series.     

Expressive Vocabulary in Language Learners From Two Ecological Settings in Three Language Communities

This study compared multiple characteristics of girls' and boys' vocabulary in 6 different linguistic communities—1 urban and 1 rural setting in each of 3 countries. Two hundred fifty‐two mothers in Argentina, Italy, and the United States completed vocabulary checklists for their 20‐month‐old children. Individual variability was substantial within each linguistic community. Minimal cross‐linguistic differences were found in children's vocabulary size; however, differences among languages in the composition of children's vocabularies appeared possibly related to cultural valuing of different categories of words. Ecological setting differences within cultures appeared in children's vocabulary size, even when the composition of children's vocabularies was examined: Children living in urban areas were reported by their mothers to say significantly more words than children living in rural areas, particularly for Argentine and U.S. children. Girls had consistently larger vocabularies than boys. These findings are discussed in terms of contextual and child factors that together influence first language learning.     

Modelling forces of infection by using monotone local polynomials

Summary. On the basis of serological data from prevalence studies of rubella, mumps and hepatitis A, the paper describes a flexible local maximum likelihood method for the estimation of the rate at which susceptible individuals acquire infection at different ages. In contrast with parametric models that have been used before in the literature, the local polynomial likelihood method allows this age-dependent force of infection to be modelled without making any assumptions about the parametric structure. Moreover, this method allows for simultaneous nonparametric estimation of age-specific incidence and prevalence. Unconstrained models may lead to negative estimates for the force of infection at certain ages. To overcome this problem and to guarantee maximal flexibility, the local smoother can be constrained to be monotone. It turns out that different parametric and nonparametric estimates of the force of infection can exhibit considerably different qualitative features like location and the number of maxima, emphasizing the importance of a well-chosen flexible statistical model.     

Variation in Dual Citizenship Policies in the Countries of the EU

While the concept of citizenship has received considerable scholarly attention in recent years, few studies focus on the increasingly prevalent reality of dual citizenship, or full membership – with its respective rights, privileges, and obligations – in two different countries. The main objective of this article is to conceptualize, measure, and classify variation in dual citizenship in the countries of the European Union. I start by recounting the historical opposition to dual citizenship and by describing its emergence in recent decades. I then develop a “Citizenshi Policy Index” that accounts for some of the intricacies associated with citizenship policies in general and dual citizenship policies in particular. I go on to apply these measures to the fifteen “older” EU countries in both the 1980s and the contemporary period – thus allowing for an analsis of the changes that have taken place over the past two decades members. Overall, the findings point to surprisingly resilient national differences that stand out in contrast to the EU's institutional “harmonization” in so many other areas.     

Efficient volatility estimation in a two-factor model

We statistically analyze a multivariate Heath-Jarrow-Morton diffusion model with stochastic volatility. The volatility process of the first factor is left totally unspecified while the volatility of the second factor is the product of an unknown process and an exponential function of time to maturity. This exponential term includes some real parameter measuring the rate of increase of the second factor as time goes to maturity. From historical data, we efficiently estimate the time to maturity parameter in the sense of constructing an estimator that achieves an optimal information bound in a semiparametric setting. We also nonparametrically identify the paths of the volatility processes and achieve minimax bounds. We address the problem of degeneracy that occurs when the dimension of the process is greater than two, and give in particular optimal limit theorems under suitable regularity assumptions on the drift process. We consistently analyze the numerical behavior of our estimators on simulated and real datasets of prices of forward contracts on electricity markets.     

A novel approach to estimation of the time to biomarker threshold: applications to HIV

In longitudinal studies of biomarkers, an outcome of interest is the time at which a biomarker reaches a particular threshold. The CD4 count is a widely used marker of human immunodeficiency virus progression. Because of the inherent variability of this marker, a single CD4 count below a relevant threshold should be interpreted with caution. Several studies have applied persistence criteria, designating the outcome as the time to the occurrence of two consecutive measurements less than the threshold. In this paper, we propose a method to estimate the time to attainment of two consecutive CD4 counts less than a meaningful threshold, which takes into account the patient‐specific trajectory and measurement error. An expression for the expected time to threshold is presented, which is a function of the fixed effects, random effects and residual variance. We present an application to human immunodeficiency virus‐positive individuals from a seroprevalent cohort in Durban, South Africa. Two thresholds are examined, and 95% bootstrap confidence intervals are presented for the estimated time to threshold. Sensitivity analysis revealed that results are robust to truncation of the series and variation in the number of visits considered for most patients. Caution should be exercised when interpreting the estimated times for patients who exhibit very slow rates of decline and patients who have less than three measurements. We also discuss the relevance of the methodology to the study of other diseases and present such applications. We demonstrate that the method proposed is computationally efficient and offers more flexibility than existing frameworks. Copyright © 2016 John Wiley & Sons, Ltd.