On Bayesian Analysis of Mixtures with an Unknown Number of Components (with discussion)

New methodology for fully Bayesian mixture analysis is developed, making use of reversible jump Markov chain Monte Carlo methods that are capable of jumping between the parameter subspaces corresponding to different numbers of components in the mixture. A sample from the full joint distribution of all unknown variables is thereby generated, and this can be used as a basis for a thorough presentation of many aspects of the posterior distribution. The methodology is applied here to the analysis of univariate normal mixtures, using a hierarchical prior model that offers an approach to dealing with weak prior information while avoiding the mathematical pitfalls of using improper priors in the mixture context.     

Modeling and Forecasting Realized Volatility

We provide a framework for integration of high–frequency intraday data into the measurement, modeling, and forecasting of daily and lower frequency return volatilities and return distributions. Building on the theory of continuous–time arbitrage–free price processes and the theory of quadratic variation, we develop formal links between realized volatility and the conditional covariance matrix. Next, using continuously recorded observations for the Deutschemark/Dollar and Yen/Dollar spot exchange rates, we find that forecasts from a simple long–memory Gaussian vector autoregression for the logarithmic daily realized volatilities perform admirably. Moreover, the vector autoregressive volatility forecast, coupled with a parametric lognormal–normal mixture distribution produces well–calibrated density forecasts of future returns, and correspondingly accurate quantile predictions. Our results hold promise for practical modeling and forecasting of the large covariance matrices relevant in asset pricing, asset allocation, and financial risk management applications.     

Assassination of political leaders: The role of social conflict

Given human aggression and warfare are often described as the most pressing behavioral problems of our time, we focus on a related phenomenon, with large-scale social, political, and economic consequences: assassination of political leaders. We explore the role of social conflict as a predictor of political assassination and use historiometric methods and an extensive archival dataset to identify and code for contextual factors associated with social conflict and political homicide. Our results indicate an increase in social conflict increases the likelihood of assassination; moreover, environmental constraints and traditional culture predict leader assassination through social conflict. We discuss implications of these findings and suggest future research on contextual factors, assassination of political leaders, and their collective-level impact.     

Analysis of Affordance,Time, and Adaptation in the Assessment of Industrial Control System Cybersecurity Risk

Industrial control systems increasingly use standard communication protocols and are increasingly connected to public networks—creating substantial cybersecurity risks, especially when used in critical infrastructures such as electricity and water distribution systems. Methods of assessing risk in such systems have recognized for some time the way in which the strategies of potential adversaries and risk managers interact in defining the risk to which such systems are exposed. But it is also important to consider the adaptations of the systems’ operators and other legitimate users to risk controls, adaptations that often appear to undermine these controls, or shift the risk from one part of a system to another. Unlike the case with adversarial risk analysis, the adaptations of system users are typically orthogonal to the objective of minimizing or maximizing risk in the system. We argue that this need to analyze potential adaptations to risk controls is true for risk problems more generally, and we develop a framework for incorporating such adaptations into an assessment process. The method is based on the principle of affordances, and we show how this can be incorporated in an iterative procedure based on raising the minimum period of risk materialization above some threshold. We apply the method in a case study of a small European utility provider and discuss the observations arising from this.     

Nondictatorial social welfare functions with different discrimination structures

In societies where agents distinguish imperfectly among the alternatives, a necessary and sufficient condition for the existence of an Arrovian Social Welfare Function is the presence of an agent who only distinguishes two groups of alternatives or of two agents with complementary discrimination patterns. This result is based on the observation that differences in discrimination structures may lead to the absence of free triples, thus providing a way to escape Arrow's impossibility result.     

Communitas and reflexive social theory

The article develops a critique of the notion that anomie invariably results from socio-cultural dislocation (sudden, rapid and wide-spread social change). In exploring and developing the concept of communality (communitas), the author argues that persons can and not infrequently do respond to serious disruption in social life by meaningfully reaffirming social bonds. Informed by this recognition, social theory is able to better clarify its potential contribution to the minimization of the socially and psychologically destructive consequences of structural and cultural dissolution.     

EMPHASES OF THE MAJOR FAMILY THERAPY MODELS: A FAMILY FIRO ANALYSIS

This paper analyzes 13 models of family therapy according to their special emphases on the Family FIRO model's dimensions of inclusion, control and intimacy. We first examined chapters on each model in Gurman and Kniskern's Handbook of Family Therapy; we then sent our preliminary ratings to the authors of the chapters for comment. The final conceptual analysis of the models indicated that 4 family therapy models emphasize inclusion as a primary focus, 4 emphasize control, and 5 emphasize intimacy. We also rated the secondary and tertiary emphases of the models. This analysis provides a possible guide for therapists who wish to be eclectic or integrative in their work, specifically, by suggesting a way to match therapy techniques from different family therapy models to the presenting family issues that each model emphasizes most strongly.     

Tideline and turn: Possible reasons for the continuing low HIV prevalence among Glasgow's injecting drug users

This is an early report of data from an on-going, repeated, cross-sectional study of a community sample of Glasgow injecting drug users. Although HIV was first detected among Glasgow's drug injectors in 1985, data from the first two years of our annual samples (1990 and 1991) indicate that HIV prevalence continues to be low in this population, in the order of 1 or 2 per cent. Possible reasons for this apparent continuing low prevalence are examined. It is suggested that substantial risk reduction – reductions in injection equipment-sharing, reductions in numbers of sharing partners and restrictions in social circles of sharing partners – may have been sufficient reasons, in conjunction with limited contributions to near-stabilisation from the disproportionate attrition of the numerator population through death and cessation of injecting.