Modelling human immunodeficiency virus ribonucleic acid levels with finite mixtures for censored longitudinal data

The measurement of human immunodeficiency virus ribonucleic acid levels over time leads to censored longitudinal data. Suitable models for dynamic modelling of these levels need to take this data characteristic into account. If groups of patients with different developments of the levels over time are suspected the model class of finite mixtures of mixed effects models with censored data is required. We describe the model specification and derive the estimation with a suitable expectation-maximization algorithm. We propose a convenient implementation using closed form formulae for the expected mean and variance of the truncated multivariate distribution. Only efficient evaluation of the cumulative multivariate normal distribution function is required. Model selection as well as methods for inference are discussed. The application is demonstrated on the clinical trial ACTG 315 data.     

The Slaughtered and the Survivors: Collaboration Between Social Economy Organizations as a Key to Success in Times of Financial Crisis

The objective of this study is to analyze the aspects that allowed a critical part of Social Economy Organizations (SEOs) to survive a recession period, especially participation in collaborative networks. The financial stress of an SEO will depend on the resources and capabilities available to the organization. To analyze the financial stress of Spanish SEOs, we defined a sample of 714 SEOs. Approximately half of these organizations suffered from financial stress in the analyzed period (2009–2012). The results obtained in this study reveal the existence of three factors that distinguish organizations under financial stress: (a) a high dependence on government funding; (b) changes in the relationship between staff and volunteers; and (c) a lack of access to markets. The combination of these three elements results in an unsustainable situation for the organization. The development of a collaborative profile increases the SEO’s probability of surviving the adverse manifestations of its environment.     

Immigrant Occupational Mobility: Longitudinal Evidence from Spain

This article examines the occupational mobility of immigrants between their countries of origin and Spain on the basis of one of the few surveys available internationally with longitudinal information on immigrant employment in home and host countries. The evidence shows that the occupational status of immigrants in the Spanish labour market is, in general, substantially worse than in their countries of origin. The severe loss of occupational status experienced by immigrants is explained by the combined effect of the intense initial downgrading they experience when entering the Spanish labour market and their very slow occupational progress during their stay in Spain. These findings are more in line with the segmented assimilation theory, which suggests a limited or blocked immigrant occupational mobility, than with the assimilation theory, which predicts a U shaped evolution in the occupational status of immigrants between their home and host countries. As a result, the Spanish case contrasts sharply with previous evidence for other advanced countries, which tends to support the assimilation perspective. Finally, the empirical evidence suggests that one of the elements impeding the occupational mobility of immigrants in Spain is the significant size of the secondary segment of the labour market, which restricts immigrants’ opportunities mainly to low-status occupations.     

An empirical comparison of two approaches for CDPCA in high-dimensional data

Statistical Methods & Applications - Modified principal component analysis techniques, specially those yielding sparse solutions, are attractive due to its usefulness for interpretation...     

What is Sexual Satisfaction? Thematic Analysis of Lay People's Definitions

Sexual satisfaction is an important indicator of sexual health and is strongly associated with relationship satisfaction. However, research exploring lay definitions of sexual satisfaction has been scarce. We present thematic analysis of written responses of 449 women and 311 men to the question “How would you define sexual satisfaction?” The participants were heterosexual individuals with a mean age of 36.05 years (SD = 8.34) involved in a committed exclusive relationship. In this exploratory study, two main themes were identified: personal sexual well-being and dyadic processes. The first theme focuses on the positive aspects of individual sexual experience, such as pleasure, positive feelings, arousal, sexual openness, and orgasm. The second theme emphasizes relational dimensions, such as mutuality, romance, expression of feelings, creativity, acting out desires, and frequency of sexual activity. Our results highlight that mutual pleasure is a crucial component of sexual satisfaction and that sexual satisfaction derives from positive sexual experiences and not from the absence of conflict or dysfunction. The findings support definitions and models of sexual satisfaction that focus on positive sexual outcomes and the use of measures that incorporate items linked to personal and dyadic sexual rewards for both men and women.     

Maternal union instability and childhood mortality risk in the Global South, 2010–14

Efforts to improve child survival in lower-income countries typically focus on fundamental factors such as economic resources and infrastructure provision, even though research from post-industrial countries confirms that family instability has important health consequences. We tested the association between maternal union instability and children’s mortality risk in Africa, Latin America and the Caribbean, and Asia using children’s actual experience of mortality (discrete-time probit hazard models) as well as their experience of untreated morbidity (probit regression). Children of divorced/separated mothers experience compromised survival chances, but children of mothers who have never been in a union generally do not. Among children of partnered women, those whose mothers have experienced prior union transitions have a higher mortality risk. Targeting children of mothers who have experienced union instability—regardless of current union status—may augment ongoing efforts to reduce childhood mortality, especially in Africa and Latin America where union transitions are common.     

Effects of the social dominance orientation on environmental attitudes of Chilean university students / Efectos de la orientación a la dominancia social sobre las actitudes ambientales de universitarios chilenos

By adopting a multidimensional approach to environmental attitudes (apathy, anthropocentrism, connectedness and emotional affinity with nature), this study explores the relationships between these dimensions, social dominance orientation (SDO) and political orientation. Two hundred and sixty-two Chilean university students filled out an ad hoc online questionnaire. Two confirmatory factorial analyses showed the four typologies of environmental attitudes and the two factors for SDO, which are labelled group dominance and opposition to equality. Through hierarchical regressions, group dominance showed higher explanatory power of environmental attitudes than political orientation. Furthermore, using the bootstrap procedure we showed that group dominance mediated between political orientation and attitudes of apathy, anthropocentrism and connectedness, while opposition to equality mediated between apathy and emotional affinity. We conclude that SDO is an important variable for measuring political ideology while also providing new nuances when analysing the relationships with environmental attitudes.     

Response‐adaptive designs for binary responses: How to offer patient benefit while being robust to time trends?

Response‐adaptive randomisation (RAR) can considerably improve the chances of a successful treatment outcome for patients in a clinical trial by skewing the allocation probability towards better performing treatments as data accumulates. There is considerable interest in using RAR designs in drug development for rare diseases, where traditional designs are not either feasible or ethically questionable. In this paper, we discuss and address a major criticism levelled at RAR: namely, type I error inflation due to an unknown time trend over the course of the trial. The most common cause of this phenomenon is changes in the characteristics of recruited patients—referred to as patient drift. This is a realistic concern for clinical trials in rare diseases due to their lengthly accrual rate. We compute the type I error inflation as a function of the time trend magnitude to determine in which contexts the problem is most exacerbated. We then assess the ability of different correction methods to preserve type I error in these contexts and their performance in terms of other operating characteristics, including patient benefit and power. We make recommendations as to which correction methods are most suitable in the rare disease context for several RAR rules, differentiating between the 2‐armed and the multi‐armed case. We further propose a RAR design for multi‐armed clinical trials, which is computationally efficient and robust to several time trends considered.     

Activity patterns and temporal niche partitioning of dogs and medium-sized wild mammals in urban parks of Xalapa,Mexico

Urban Ecosystems - Free-ranging domestic dogs are the world most common exotic carnivore species that could negatively interact with the native wildlife as predators, competitors, and disease...