Parameter estimation in high dimensional Gaussian distributions

In order to compute the log-likelihood for high dimensional Gaussian models, it is necessary to compute the determinant of the large, sparse, symmetric positive definite precision matrix. Traditional methods for evaluating the log-likelihood, which are typically based on Cholesky factorisations, are not feasible for very large models due to the massive memory requirements. We present a novel approach for evaluating such likelihoods that only requires the computation of matrix-vector products. In this approach we utilise matrix functions, Krylov subspaces, and probing vectors to construct an iterative numerical method for computing the log-likelihood.     

Eliciting Donor Preferences

Most charity organizations depend on contributions from the general public, but little research is conducted on donor preferences. Do donors have geographical, recipient, or thematic preferences? We designed a conjoint analysis experiment in which people rated development aid projects by donating money in dictator games. We find that our sample show strong age, gender, regional, and thematic preferences. Furthermore, we find significant differences between segments. The differences in donations are consistent with differences in donors’ attitudes toward development aid and their beliefs about differences in poverty and vulnerability of the recipients. The method here used for development projects can easily be adapted to elicit preferences for other kinds of projects that rely on gifts from private donors.     

Will it never end? The narratives of incest victims on the termination of sexual abuse

The aim of this study is to investigate how child sexual abuse is terminated. This study attempts to gain insight into how people exposed to incest narrate the termination of the incest relationship. Seven women and one man were recruited from the Incest Support Centre and from snowballing for a 1-2-hour-long in-depth interview using a narrative approach. The subjects' narratives varied according to how they perceived their own role in the termination process, their relationship with the offender, and how well they remembered the stage of termination. A common feature of the narratives was that the feeling of being a victim lasted after the abuse stopped. In this respect, the lack of support from family, friends, and healthcare personnel and the psychological power exercised by the offender were important issues in the narratives. It is suggested that the termination process is affected by the victims' ability to regulate influence and mentalization. Furthermore, a transfer of cultural meanings from the social environment to the individual must have taken place. Future research should focus on the significance of the termination process in terms of psychological functioning and the construction of self and identity.     

Development and Validation of HIV-Related Dyadic Measures for Men Who Have Sex with Men

The aim of this study is to investigate how child sexual abuse is terminated. This study attempts to gain insight into how people exposed to incest narrate the termination of the incest relationship. Seven women and one man were recruited from the Incest Support Centre and from snowballing for a 1–2-hour-long in-depth interview using a narrative approach. The subjects' narratives varied according to how they perceived their own role in the termination process, their relationship with the offender, and how well they remembered the stage of termination. A common feature of the narratives was that the feeling of being a victim lasted after the abuse stopped. In this respect, the lack of support from family, friends, and healthcare personnel and the psychological power exercised by the offender were important issues in the narratives. It is suggested that the termination process is affected by the victims' ability to regulate influence and mentalization. Furthermore, a transfer of cultural meanings from the social environment to the individual must have taken place. Future research should focus on the significance of the termination process in terms of psychological functioning and the construction of self and identity.     

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.     

Supply chain strategies for speciality foods: a Norwegian case study

Despite strong market interest in speciality foods, producers find market access and distribution challenging. This exploratory research includes a literature review and five case studies of supply chains relating to shellfish, cheese, meat, potato and miscellaneous speciality foods in the mid-Norway region. The study identifies key supply chain configuration parameters from the extant literature, and these are used to analyse the cases. The study makes three main contributions to the literature: an analytical framework for analysing the supply chain characteristics of speciality foods; important supply chain factors for accessing the conventional food supply chain; and five propositions for improving market access. We argue that the speciality foods supply chain should be configured according to these propositions to ensure responsiveness to customer needs and to strengthen market access.     

The role of corruption in reintegration: experiences of Iraqi Kurds upon return from Europe

This article examines how corruption affects reintegration. The literature on return and reintegration shows that return migrants often struggle to adjust and adapt to life in their place of origin because that environment can be very different from what they grew accustomed to abroad. One stark difference is the prevalence and meaning of corruption. In many sending countries that migrants come from and then return to, corruption is endemic. By contrast, in many receiving countries that migrants go to and return from, it is incidental. Yet, we know little about how the discrepancy affects reintegration. This study examines how corruption affects the psychosocial and economic reintegration of Iraqi Kurds returning to Iraqi Kurdistan from Norway and the United Kingdom. Interviews with returnees reveal that they consider corruption a major challenge for their own reintegration. Psychosocially, it alienates them from the ideology of the Kurdish nation-building project, challenges their identities, undermines a sense of belonging and creates insecurity. Economically, it shapes economic behaviour and outcomes by obstructing entrepreneurship, producing relative deprivation and conditioning their employability.