Iterative numerical methods for sampling from high dimensional Gaussian distributions

Many applications require efficient sampling from Gaussian distributions. The method of choice depends on the dimension of the problem as well as the structure of the covariance- (Σ) or precision matrix (Q). The most common black-box routine for computing a sample is based on Cholesky factorization. In high dimensions, computing the Cholesky factor of Σ or Q may be prohibitive due to accumulation of more non-zero entries in the factor than is possible to store in memory. We compare different methods for computing the samples iteratively adapting ideas from numerical linear algebra. These methods assume that matrix vector products, Qv, are fast to compute. We show that some of the methods are competitive and faster than Cholesky sampling and that a parallel version of one method on a Graphical Processing Unit (GPU) using CUDA can introduce a speed-up of up to 30x. Moreover, one method is used to sample from the posterior distribution of petroleum reservoir parameters in a North Sea field, given seismic reflection data on a large 3D grid.     

Human mobility and environmental degradation: Shaping rural Morocco

Environmental degradation constitutes a disruptive force in man-made and natural systems. The projected duplication of the frequency and duration of meteorological drought will contribute to a situation of water scarcity, which is expected to negatively impact the agricultural sector. This study focuses on Souss-Massa, Morocco, a leading agricultural region, and it seeks to map how human mobility fits within a wider adaptation response to environmental degradation. Over 30 semi-structured interviews were conducted with internal migrants and members of rural communities on the perceived impacts of environmental degradation and human mobility. Most of the interviewees perceive a reduction in the available water, and the agricultural sector is the most severely affected by those changes. Internal migration is the most frequent adaptation strategy mentioned, and the remittances it originates are supporting the communities of origin facing a deterioration of agricultural output.     

Decision-Making processes in the child protection system: A comparative study between students and professionals in Portugal

Abstract

This research aims to achieve a better understanding of factors that influence the assessments and decisions of professionals and students about the possibility to remove a child at risk from her birth family. The study also analyzes the influence of the attitudes of the child’s mother on that decision. It was used a questionnaire based on a case vignette of alleged child maltreatment. Compared with students, professionals were more pro-removal, more in favor of reunification and parents’ participation in the decisions, and had a higher assessment of emotional abuse, and emotional and physical neglect. Mother’s wish did not show to have any impact in the two samples regarding maltreatment, risk assessments, and intervention recommendations.     

Resident-to-resident elder mistreatment (R-REM): a study in residential structures for elderly people (ERI) in Portugal

This study explores patterns of resident-to-resident elder mistreatment (R-REM) in Portuguese Residential Structures for Elderly People (ERI: Estruturas Residenciais para Idosos). Results display a serious situation of R-REM, which occurs in different patterns.     

‘Just choose the easy option’: students talk about alcohol use and social influence

Previous research into young people’s drinking behaviour has studied how social practices influence their actions and how they negotiate drinking-related identities. Here, adopting the perspective of discursive psychology we examine how, for young people, social influences are bound up with issues of drinking and of identity. We conducted 19 focus groups with undergraduate students in Australia aged between 18 and 24 years. Thematic analysis of participants’ accounts for why they drink or do not drink was used to identify passages of talk that referred to social influence, paying particular attention to terms such as ‘pressure’ and ‘choice’. These passages were then analysed in fine-grained detail, using discourse analysis, to study how participants accounted for social influence. Participants treated their behaviour as accountable and produced three forms of account that: (1) minimised the choice available to them, (2) explained drinking as culture and (3) described resisting peer pressure. They also negotiated gendered social dynamics related to drinking. These forms of account allowed the participants to avoid individual responsibility for drinking or not drinking. These findings demonstrate that the effects of social influence on young people’s drinking behaviour cannot be assumed, as social influence itself becomes negotiable within local contexts of talk about drinking.     

Goodness-of-fit test of the mark distribution in a point process with non-stationary marks

Three procedures for testing the hypothesis that the marks of the point process belong to a given family of distributions, where the marks are independent conditionally on an unknown non-stationary parametric field θ(x), are described. The unknown parametric field was estimated by a kernel estimator and the estimate included in the procedures. The asymptotic distribution of the kernel estimator was derived because it is required in some of the procedures to take into account the estimation uncertainty. The procedures were compared by a simulation study and applied to two real datasets. First, the terminal dates of Maya sites and second, the heights of trees that have fallen during storms.     

“It’s Time to Ease Your Fears—and Your Sphincter”: Gender and Power in Contemporary Media Discourses of Heterosexual Anal Sex

Gender Issues - Heterosexual anal sex has become fashionable within popular culture, with unprecedented visibility in the media landscape. In this article I map the meanings ascribed to it across a...     

Acculturation and Psychological Functioning in Asian Indian Adolescents

The objective of this exploratory study was to understand how Asian Indian immigrant families adjust to U.S. culture by examining factors that influence acculturation preferences or styles and how these styles may be associated with their children's psychological functioning, as measured by self‐esteem and academic performance. 85 U.S.‐born Asian Indian adolescents (45 girls; 40 boys) and one of their immigrant parents completed questionnaires about family demography, self‐identification, acculturation, and religiosity. Adolescents also completed a self‐perception profile. Results showed parents and adolescents had similar styles of acculturation. However, adolescents were more likely to self‐identify as ‘Indian‐American’ than were their parents. For both adolescents and their parents, integrated and assimilated acculturation styles were related to family SES, years of U.S. residence, and religiosity scores. Adolescents who had an integrated acculturation style had higher GPAs and higher scores on the self‐perception profile than did adolescents who were separated or marginalized. The findings lend tentative support for an integrated style of acculturation in promoting positive outcomes for first generation Asian Indian adolescents.     

Medical tourism in the backcountry: alternative health and healing in the Arkansas Ozarks

Tourists travel to Arkansas' mountain regions to experience, appreciate, and consume multiple aspects of otherness, including sacred sites and pristine and authentic peoples and environments. A largely unexplored aspect of this consumption of authenticity is alternative medicine, provided to tourists and day travelers in search of physical and emotional restoration. Traditional forms of medicine are deeply rooted in women's social roles as community healers in the region and are perpetuated in part because of the lack of readily accessible forms of so-called modern medicine. Contemporary medical tourism in Arkansas has promoted access to folk health systems, preserving them by incorporating them into tourists' health care services, and also has attracted new and dynamic alternative medical practices while encouraging the transformation of existing forms of traditional medicine. Ultimately, the blend of alternative, folk, and conventional medicine in the Arkansas highlands is evidence of globalizing forces at work in a regional culture. It also serves to highlight a renewed appreciation for the historic continuity and the efficacy of traditional knowledge in the upper South.