A Note on the Implementation of Hierarchical Dirichlet Processes

The implementation of collapsed Gibbs samplers for non-parametric Bayesian models is non-trivial, requiring considerable book-keeping. Goldwater et al. (2006a) presented an approximation which significantly reduces the storage and computation overhead, but we show here that their formulation was incorrect and, even after correction, is grossly inaccurate. We present an alternative formulation which is exact and can be computed easily. However this approach does not work for hierarchical models, for which case we present an efficient data structure which has a better space complexity than the naive approach.4 page(s

Marine exploration

Less than 50 years ago knowledge of the geology of the UK continental shelf (UKCS) was extremely limited. The BGS marine geoscience programme began about 40 years ago in response to the development of the UK oil and gas industry. The BGS was funded by the then Department of Energy to carry out a national mapping programme based on geophysical data, seabed samples and boreholes. By the 1990s, geological maps at a scale of 1:250 000 were published for the shelf regions showing seabed sediments, Quaternary geology and bedrock. The deeper water areas to the north and west continue to be explored with support from the oil industry. A series of regional reports, the offshore equivalent of the BGS regional guides, were published and reports for the Atlantic Margin will be published in 2010. MAREMAP is a new multidisciplinary environmental mapping programme designed to underpin the new marine industries and environmental issues

Translating data between MySQL and Stata

As web-based and other electronic data collection methods become more widely used in research, the opportunities to use statistical software in conjunction with conventional database systems are increasing. Among such systems, MySQL is particularly well suited for research purposes. For example, MySQL's ENUM and SET column types are ideal for storing data collected via the multiple choice questions typically used in social surveys. At the same time, Stata is uniquely suited for working in conjunction with a database; for example, its implementation of characteristics makes it possible to preserve (in a usable form) important information about how the database and front-end application are constructed (e.g., column types and other attributes). In this presentation, we shall describe a Python script we have developed for translating data from MySQL to Stata, and will indicate briefly how we are using it in the development of tools for the collection and management of research data.

Should we teach primary pupils about chemical change?

Thirty six pupils from three 6th grade classes (ages 11/12, n=75) in Greece were interviewed pre and post intervention in a piece of research on explanations of chemical phenomena. Software concerning chemical phenomena was incorporated in a teaching scheme, where the particle theory was used. After 13 hours intervention, pupils' explanations were categorized in five discrete categories. Only a few pupils could give satisfactory explanations, involving the integration of particle ideas at the level of atoms. The idea of chemical change seemed to be very difficult for the majority of pupils. Implications for the teaching of chemical phenomena at young ages are discussed

Primary teachers' particle ideas and explanations of physical phenomena: the effect of an in-service training course

This paper presents a study concerning Greek primary school teachers' (n=162) ideas about the particulate nature of matter and their explanations of physical phenomena. The study took place during an in-service training course where the effectiveness of a specially designed intervention was tested. A key feature was an approach based on the concept of a substance and its states rather than 'solids, liquids and gases'. Pre-intervention, the teachers held misconceptions similar to those of pupils. Also, there seemed to be some relationship between the teachers' particle model ideas and their explanations of phenomena. Post-intervention, the teachers' descriptions and explanations were found to be significantly improved, with almost zero correlation between pre and post intervention scores. Implications for science education are discussed