Continuous correlated beta processes

In this paper we consider a (possibly continuous) space of Bernoulli experiments. We assume that the Bernoulli distributions are correlated. All evidence data comes in the form of successful or failed experiments at different points. Current state-ofthe-art methods for expressing a distribution over a continuum of Bernoulli distributions use logistic Gaussian processes or Gaussian copula processes. However, both of these require computationally expensive matrix operations (cubic in the general case). We introduce a more intuitive approach, directly correlating beta distributions by sharing evidence between them according to a kernel function, an approach which has linear time complexity. The approach can easily be extended to multiple outcomes, giving a continuous correlated Dirichlet process, and can be used for both classification and learning the actual probabilities of the Bernoulli distributions. We show results for a number of data sets, as well as a case-study where a mixture of continuous beta processes is used as part of an automated stroke rehabilitation system.

Is it time for integration of surgical skills simulation into the United Kingdom undergraduate medical curriculum? A perspective from King’s College London School of Medicine

PURPOSE: Changes in undergraduate medical curricula, combined with reforms in postgraduate education, have training implications for surgical skills acquisition in a climate of reduced clinical exposure. Confidence and prior experience influences the educational impact of learning. Currently there is no basic surgical skills (BSS) programme integrated into undergraduate curricula in the United Kingdom. We explored the role of a dedicated BSS programme for undergraduates in improving confidence and influencing careers in King's College London School of Medicine, and the programme was evaluated. METHODS: A programme was designed in-line with the established Royal College of Surgeons course. Undergraduates were taught four key skills over four weeks: knot-tying, basic-suturing, tying-at-depth and chest-drain insertion, using low-fidelity bench-top models. A Likert-style questionnaire was designed to determine educational value and influence on career choice. Qualitative data was collected. RESULTS: Only 29% and 42% of students had undertaken previous practice in knot-tying and basic suturing, respectively. 96% agreed that skills exposure prior to starting surgical rotations was essential and felt a dedicated course would augment undergraduate training. There was a significant increase in confidence in the practice and knowledge of all skills taught (p<0.01), with a greater motivation to be actively involved in the surgical firm and theatres. CONCLUSION: A simple, structured BSS programme can increase the confidence and motivation of students. Early surgical skills targeting is valuable for students entering surgical, related allied, and even traditionally non-surgical specialties such as general practice. Such experience can increase the confidence of future junior doctors and trainees. We advocate the introduction of a BSS programme into United Kingdom undergraduate curricula

Mass movement susceptibility mapping using satellite optical imagery compared with InSAR monitoring: Zigui County, Three Gorges region, China

Mass movements on steep slopes are a major hazard to communities and infrastructure in the Three Gorges region, China. Developing susceptibility maps of mass movements is therefore very important in both current and future land use planning. This study employed satellite optical imagery and an ASTER GDEM (15 m) to derive various parameters (namely geology; slope gradient; proximity to drainage networks and proximity to lineaments) in order to create a GIS-based map of mass movement susceptibility. This map was then evaluated using highly accurate deformation signals processed using the Persistent Scatterer (PS) InSAR technique. Areas of high susceptibility correspond well to points of high subsidence, which provides a strong support of our susceptibility map

The NIOO-approach as evaluation method of the benthic ecological quality within the Water Framework Directive

The EU Water Framework Directive (WFD) requires development of biological indicators and ecological classification for assessment of the ecological quality status of rivers, lakes, coastal and transitional waters. The NIOO - approach is developed to evaluate the ecological status of benthic invertebrates in coastal and transitional waters. This approach aims to be representative for the important structural and functional characteristics of coastal and estuarine ecosystems. The method uses a set of indicators that take into account the different scales of variability in coastal and transitional waters and evaluate the water body (ecosystem) as a whole and not by evaluating sampling station by sampling station. This approach evaluates the ecological status on three different levels (Escaravage et al., 2004; Ysebaert and Herman, 2004). On the level of the whole ecosystem (e.g. a water body) one can evaluate if the benthic macrofauna fulfils the functional role one might expect given the current ecological circumstances. At this level also integration with other quality measures is most appropriate, and information on the water body can be summarised. On the subsequent level the distribution of habitats (habitat completeness, complexity and presence of certain ecoelements [e.g. mussel banks]) can be evaluated. Finally the biological quality of each distinguished habitat based on benthic macrofauna will be evaluated (within-habitat level), based on four indicators (biomass, density, species richness and species composition changes). These four indicators aim at providing a signal that is capable of showing significant changes/deviations from a certain defined reference state. The indicator results strongly depend on the sampling effort (sediment surface) that is deployed in a habitat and water body. Therefore, the reference values for the indicators were calculated per habitat from permutations executed over increased sampling surfaces. This allows estimating, for any given sampling surface, the reference value that can be expected. The expected reference values for each indicator, based on this randomisation, were determined for each ecological status boundary of the WFD. The ecological status for each indicator is finally determined by classifying the observed assessment value in the right ecological status class, based on their defined reference values. The NIOO - approach uses easily interpretable indicators that are evaluated separately. This allows a transparent assessment method and for any deviation of the overall ecological quality ratio from the reference condition the underlying responsible indicator can be easily traced back and evaluated individually. This tool is currently used by the Netherlands and Belgium to evaluate the ecological status of the benthos, following the requirements of the WFD