Estimation in Dirichlet random effects models

We develop a new Gibbs sampler for a linear mixed model with a Dirichlet process random effect term, which is easily extended to a generalized linear mixed model with a probit link function. Our Gibbs sampler exploits the properties of the multinomial and Dirichlet distributions, and is shown to be an improvement, in terms of operator norm and efficiency, over other commonly used MCMC algorithms. We also investigate methods for the estimation of the precision parameter of the Dirichlet process, finding that maximum likelihood may not be desirable, but a posterior mode is a reasonable approach. Examples are given to show how these models perform on real data. Our results complement both the theoretical basis of the Dirichlet process nonparametric prior and the computational work that has been done to date.Comment: Published in at http://dx.doi.org/10.1214/09-AOS731 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Site characterisation and data analysis for µ±SR experiments

The muon-spin rotation (µSR) technique predominantly uses the positive muon to study a wide range of condensed matter systems exhibiting interesting physical properties such as magnetism and superconductivity. The µ−SR technique is far less common, mainly due to the fact that the absolute asymmetry is low, and for a comparable signal-to-noise ratio of the asymmetry it needs around 36 times more decay events to be counted than for a µ+SR experiment. Despite this, µ−SR has its uses and has seen a recent resurgence in the study of hydrogen storage and battery materials. There is a lack of suitable fitting programs for the analysis of µ−SR data. Also, the negative muon will strongly perturb its local environment when implanted into a sample, and these distortions must be accounted for. As part of this thesis, new techniques have been developed for the analysis of µ−SR data and implemented in the Windows Muon Data Analysis software package WiMDA. The software extension, dubbed Negative-WiMDA, has been tested on new experimental data obtained on graphite, MnO, and MgH2. It has facilitated the efficient subtraction of unwanted background signals and allowed the asymmetry spectra from each element of interest to be analysed in isolation. To account for the negative muon-induced perturbations, a new technique named DFT+µ− has been developed which adapts the DFT+µ+ code to include the case of a negative muon. The DFT+µ− technique developed in this thesis has been used to predict an asymmetrical ion configuration and a Jahn-Teller distortion in MnO. In both MgH2 and LiCoO2 the static field width, ∆, resulting from the randomly oriented nuclear spins has been calculated from the new atomic positions obtained through DFT+µ−. In addition, a layered oxyselenide, Sr2CoO2Ag2Se2, is studied with µ+SR. The Néel temperature is found to be 160.4(1) K, which is 30 K lower than that previously deduced from magnetic susceptibility measurements. A constraint for the magnetic structure is given using DFT+µ+ and dipole field simulations

The Five Accomplishments: A Framework for Obtaining Customer Feedback in a Health Service Community Learning Disability Team

The usefulness of using the philosophy of normalisation and, in particular, O`Brien`s (1992) Five Accomplishments as a basis for evaluating client satisfaction with a community based health service learning disabilities team was examined. A survey of a group of people with mild learning disabilities took place using the Five Accomplishments as a framework for a semi-structured interview. Areas of client satisfaction and dissatisfaction are discussed in the context of the use of a value-based means of obtaining feedback from clients. Limitations of interviewing techniques and specifically those used in this study are reviewed

Breaking the Cycle: Self-Esteem and African American Youth

Self-esteem has been cited as a primary factor in how well or how poorly an individual functions in society. African American youth may be among those particularly susceptible to feelings of low selfesteem. This study attempted to measure if participation in a African American Self-Esteem (AASE) course would have a positive effect on the self-esteem of participants. The AASE course is a ten week education,/support group that focuses on African American history and culture. Twenty-eight junior and senior high African American students from the Minneapolis metro area participated. Their self-esteem levels were measured, they then participated in the AASE course and their self-esteem levels were measured again. Data from the study do not support the hypothesis that participants\u27 self-esteem is positively effected. The study did not find a correlation between African American History and culture and self-esteem, but the data did suggest that future work in this area should concentrate on self-efficacy issues in African American youth

Personalized feedback based on a drink-pouring exercise may improve knowledge of, and adherence to, government guidelines for alcohol consumption

Background Although most people are aware of government guidelines for alcohol consumption, few have accurate knowledge of these and fewer still use these guidelines to monitor their drinking. Most people also lack accurate knowledge of the alcohol content of the drinks they consume. The aim of the study reported here was to examine whether or not personalized feedback on alcohol consumption based on performance in a drink-pouring task and self-reported alcohol intake would improve university students’ knowledge of alcohol consumption guidelines and reduce their alcohol intake. Methods A quasi-randomized control trial with a 2-month follow-up was conducted with 200 students aged 18 to 37 in the south of England. Participants were allocated to a “pour + feedback” group that completed a drink-pouring task and received personalized feedback, a “pour only” group that completed the drink-pouring task but did not receive feedback, and a control group. Results At follow-up, participants in the “pour + feedback” group had significantly better knowledge of government guidelines, and significantly lower weekly alcohol intake when compared to the “control” and “pour only” groups. Conclusions Further refinement of the drink-pouring intervention and feedback is reported in this paper, and assessment of their impact in various populations may lead to better understanding of which elements of personalized feedback have the greatest influence on young people's alcohol use

Anatomical Constraints on Attention: Hemifield Independence Is a Signature of Multifocal Spatial Selection

Previous studies have shown independent attentional selection of targets in the left and right visual hemifields during attentional tracking (Alvarez & Cavanagh, 2005) but not during a visual search (Luck, Hillyard, Mangun, & Gazzaniga, 1989). Here we tested whether multifocal spatial attention is the critical process that operates independently in the two hemifields. It is explicitly required in tracking (attend to a subset of object locations, suppress the others) but not in the standard visual search task (where all items are potential targets). We used a modified visual search task in which observers searched for a target within a subset of display items, where the subset was selected based on location (Experiments 1 and 3A) or based on a salient feature difference (Experiments 2 and 3B). The results show hemifield independence in this subset visual search task with location-based selection but not with feature-based selection; this effect cannot be explained by general difficulty (Experiment 4). Combined, these findings suggest that hemifield independence is a signature of multifocal spatial attention and highlight the need for cognitive and neural theories of attention to account for anatomical constraints on selection mechanisms.Psycholog

Setting priorities for development of emerging interventions against childhood diarrhoea

An expert panel exercise was conducted to assess feasibility and potential effectiveness of 10 emerging health interventions against childhood diarrhoea. Twelve international experts were invited to take part in a CHNRI priority setting process. This group used 12 different criteria relevant to successful development and implementation of the emerging interventions, nine of which were retained in the final analysis. They showed most collective optimism towards developing household or community-level water treatment, followed by sustainable, affordable latrine options; those two emerging interventions were followed by antibiotic therapy of Cryptosporidium diarrhoea, and oral or transcutaneous enteric vaccine development