Inference in hybrid Bayesian networks using dynamic discretization

We consider approximate inference in hybrid Bayesian Networks (BNs) and present a new iterative algorithm that efficiently combines dynamic discretization with robust propagation algorithms on junction trees. Our approach offers a significant extension to Bayesian Network theory and practice by offering a flexible way of modeling continuous nodes in BNs conditioned on complex configurations of evidence and intermixed with discrete nodes as both parents and children of continuous nodes. Our algorithm is implemented in a commercial Bayesian Network software package, AgenaRisk, which allows model construction and testing to be carried out easily. The results from the empirical trials clearly show how our software can deal effectively with different type of hybrid models containing elements of expert judgment as well as statistical inference. In particular, we show how the rapid convergence of the algorithm towards zones of high probability density, make robust inference analysis possible even in situations where, due to the lack of information in both prior and data, robust sampling becomes unfeasible.     

Interrogating Mixed-Race: A Crisis of Ambiguity?

In many respects, issues surrounding ‘mixed-race’ identities rupture and dislocate much current thinking within post-race and new ethnicities paradigms. This article seeks to critically engage with what is arguably a marginalized and diverse ‘community’. An evaluation of theories emanating from the UK and USA seeks to challenge hybrid degenerative theories, and more recent attempts at explaining how such identities are negotiated in complex social arenas. What emerges is that some theories are underpinned by static and linear behavioural patterns, which appear oversimplified. Key questions are raised in order to further explore whether ‘mixed-race’ identities are genuinely marginalized and remain ambiguous in a range of physical, social, emotional and ideological contexts. Reflecting upon such issues seeks to prompt questions as to whether there can be a more sophisticated and sensitive understanding of the unique experiences (both positive and negative) of ‘mixed-race’ individuals. By doing so, it is hoped that such a topic becomes more central to considerations of how prejudice and discrimination operate across and within a wide variety of settings.     

Identity,difference and community in Southern Irish Protestantism: The Protestants of West Cork

This article looks at how the Protestants of West Cork came to terms with Irish independence, and how they have responded to the major social and political changes of the past decades. West Cork Protestants are geographically peripheral to the Southern Protestant population as a whole, and have a weaker socio-economic profile. They live in an area that saw some of the fiercest fighting and worst atrocities in the war of independence and civil war. Their experience throws considerable light on issues of whether Protestants were a privileged or oppressed minority, and whether and how they integrated into the new state. Extensive in-depth interviews are used to show how West Cork Protestants reconstructed their identity, defined their differences from Catholics and maintained community in the years since independence.     

The EPA Health Risk Assessment of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

This paper describes the U.S. Environmental Protection Agency's assessment of potential health risks associated with the possible widespread use of a manganese (Mn)-based fuel additive, methylcyclopentadienyl manganese tricarbonyl (MMT). This assessment was significant in several respects and may be instructive in identifying certain methodological issues of general relevance to risk assessment. A major feature of the inhalation health risk assessment was the derivation of Mn inhalation reference concentration (RfC) estimates using various statistical approaches, including benchmark dose and Bayesian analyses. The exposure assessment component used data from the Particle Total Exposure Assessment Methodology (PTEAM) study and other sources to estimate personal exposure levels of particulate Mn attributable to the permitted use of MMT in leaded gasoline in Riverside, CA, at the time of the PTEAM study; on this basis it was then possible to predict a distribution of possible future exposure levels associated with the use of MMT in all unleaded gasoline. Qualitative as well as quantitative aspects of the risk characterization are summarized, along with inherent uncertainties due to data limitations.     

Principles for Conduct of Pest Risk Analyses: Report of an Expert Workshop

The North American Free Trade Agreement (NAFTA) and the General Agreement on Tariffs and Trade (GATT) have focused attention on risk assessment of potential insect, weed, and animal pests and diseases of livestock. These risks have traditionally been addressed through quarantine protocols ranging from limits on the geographical areas from which a product may originate, postharvest disinfestation procedures like fumigation, and inspections at points of export and import, to outright bans. To ensure that plant and animal protection measures are not used as nontariff trade barriers, GATT and NAFTA require pest risk analysis (PRA) to support quarantine decisions. The increased emphasis on PRA has spurred multiple efforts at the national and international level to design frameworks for the conduct of these analyses. As approaches to pest risk analysis proliferate, and the importance of the analyses grows, concerns have arisen about the scientific and technical conduct of pest risk analysis. In January of 1997, the Harvard Center for Risk Analysis (HCRA) held an invitation-only workshop in Washington, D.C. to bring experts in risk analysis and pest characterization together to develop general principles for pest risk analysis. Workshop participants examined current frameworks for PRA, discussed strengths and weaknesses of the approaches, and formulated principles, based on years of experience with risk analysis in other setting and knowledge of the issues specific to analysis of pests. The principles developed highlight the both the similarities of pest risk analysis to other forms of risk analysis, and its unique attributes.     

Rewarding growth or profit?: Top management team compensation and governance in Japanese MNEs

Japanese multinational enterprises (MNEs) have been popularly characterized as pursuing competitive strategies emphasizing long-term performance, especially growth in sales and market share, rather than shorter term profit performance. Though prior research has emphasized the importance of linking compensation to organizational goals and performance, the relationship between performance and compensation of Japanese executives has received limited empirical attention. This paper provides a preliminary examination of how Japanese top management teams in the 106 largest industrial MNEs were compensated, particularly for performance on sales growth and profitability criteria, over the 1976–1993 time period. The relationships revealed between organizational performance and the bonus compensation of top management teams suggest that the emphasis of Japanese industrial MNEs regarding sales growth versus profitability may not be as simple as suggested by prior studies and popular characterizations.     

A Trivariate Distribution for the Height,Weight, and Fat of Adult Men*

Using exploratory data analysis, probability plots, scatterplots, and computer animations to rotate and visualize the data, we fit a trivariate Normal distribution to data for the height, the natural logarithm of body weight, and the body fat for 646 men between the ages of 50 and 80 years as reported by the medical staff of the U.S. Veterans Administration's “Normative Aging Study” in Boston, MA. Although these data do not include any children, women, or young men, the measurements represent the best data that we could find through a 4-year search. We believe that these data are well measured and reliable for men in the specified age range and that these data reveal an interesting statistical pattern for use in probabilistic PBPK models.     

Modelling Variability in the Branching Structure of Strawberry Inflorescences

The branching structure of inflorescences of the cultivated strawberry ( Fragaria × ananassa Duch.) is very variable. This paper demonstrates that some aspects of this variability are well described by a simple stochastic model of branching that has two adjustable parameters. The model is shown to provide a good fit to data from a set of almost 700 inflorescences of the cultivar Elsanta, collected over two successive years. For one parameter the maximum likelihood estimator is a moment estimator which is fully efficient even if the detailed branching structure of the inflorescences is not recorded. This parameter provides a convenient summary of branching vigour. The maximum likelihood estimator of the second parameter must be determined iteratively and can be quite inefficient unless the full branching structure is recorded. The model demonstrates that branching structure is affected by the order in which inflorescences emerge on the plant.