Action classification using a discriminative non-parametric hidden Markov model

We classify human actions occurring in videos, using the skeletal joint positions extracted from a depth image sequence as features. Each action class is represented by a non-parametric Hidden Markov Model (NP-HMM) and the model parameters are learnt in a discriminative way. Specifically, we use a Bayesian framework based on Hierarchical Dirichlet Process (HDP) to automatically infer the cardinality of hidden states and formulate a discriminative function based on distance between Gaussian distributions to improve classification performance. We use elliptical slice sampling to efficiently sample parameters from the complex posterior distribution induced by our discriminative likelihood function. We illustrate our classification results for action class models trained using this technique

Armillaria mellea can infect the perennial weed, Rumex obtusifolius , in the UK

Armillaria mellea is a common pathogen of trees, woody shrubs and some herbaceous plants, causing root, root-collar and butt rot (Fox, 2000). On examination of a wilted broad-leaved dock (Rumex obtusifolius), growing on the edge of woodland, near Reading, UK, in 1994, the main root and root-collar region was found to be colonised with mycelial fans, typical of Armillaria mellea. Rhizomorphs were found in the soil adjacent to the plant. The mycelium was isolated onto Malt Extract Agar and its identity was confirmed to be Armillaria mellea. To fulfil Koch's postulates, ten potted dock plants were each inoculated with an isolate of Armillaria mellea by placing colonised sections of hazel (Corylus avellana) branch (≈6cm long by 2.5cm in diameter; West, 2000) adjacent to the tap root of the plants. Additionally an isolate of Armillaria ostoyae, which is a serious pathogen of coniferous trees, was tested against ten similar plants. After 7 months, the foliage of most plants (7 out of ten, for both isolates) was observed to be wilted or senesced. Examination of the roots and collar region of these plants showed extensive rotting and fans of white mycelium confirming infection by Armillaria. All other plants also had infected roots, but as the infection had not yet reached the root collar, the foliage had not been affected. A. mellea and A. ostoyae were also found to infect artificially inoculated docks in field conditions. Broad-leaved dock is a common perennial weed of short-term leys and permanent pastureland. Salmon (1923) had noticed that "Armillaria mellea" (at that time "sensu lato" - which in Britain was a complex of several species) spread from an apple tree to brambles (Rubus sp.) and docks (Rumex sp.) but the species of dock was unknown and it was not reported whether the docks were killed. Our study confirms that there is potential for docks to assist the vegetative spread of both Armillaria mellea and Armillaria ostoyae across pasture or other treeless habitats and into woodlands in a similar way to that proposed for Epilobium angustifolium by Klein-Gebbinck et al. (1993)

Evaluating the impact of the Pyramid intervention on the emotional health and school performance of students in early secondary education

Background: Poor mental health in childhood and adolescence is associated with a range of negative outcomes. The unique role of schools to support pupils with psychological difficulties has been increasingly recognized (Layard and Clark, 2014; Fazel et al, 2014). However, gaps in school-based research have provoked a demand for real-world evaluations to provide models of good practice (DH, 2013; Fazel et al, 2014). Pyramid is a targeted, school-based intervention which promotes the socio-emotional well-being (SEWB) of vulnerable pupils. Evidence from primary school evaluations has demonstrated improvements in vulnerable children’s SEWB (Ohl et al 2008, 2012; McKenna et al, 2014). Aim(s): To examine the impact of Pyramid on adolescent pupils (aged 11-13), including secondary effects on school performance. To explore intervention facilitators which bring about change. Methods: The impact of the Pyramid intervention on 45 pupils from six secondary schools was examined through a mixed-methods design. Quantitative measures included cross-informant Strengths and Difficulties Questionnaires (SDQ: Goodman, 1997, 1998). Qualitative data was collected from focus groups. Results: Teacher–rated SDQ results demonstrated improvements in the intervention group’s socio-emotional competencies compared to a comparison group. A thematic analysis of the qualitative data supported the findings and also identified potential causal mechanisms facilitating change. Moreover, secondary outcomes on school performance were elicited. Conclusion: These findings will contribute to ongoing research on a larger cohort and provide preliminary support for Pyramid as a developmentally appropriate model for vulnerable young people in early secondary education. The supplementary impact of Pyramid on school performance warrants further investigation