Non-linear state space modelling of fisheries biomass dynamics by using Metropolis-Hastings within-Gibbs sampling

State space modelling and Bayesian analysis are both active areas of applied research in fisheries stock assessment. Combining these two methodologies facilitates the fitting of state space models that may be non-linear and have non-normal errors, and hence it is particularly useful for modelling fisheries dynamics. Here, this approach is demonstrated by fitting a non-linear surplus production model to data on South Atlantic albacore tuna ( Thunnus alalunga ). The state space approach allows for random variability in both the data (the measurement of relative biomass) and in annual biomass dynamics of the tuna stock. Sampling from the joint posterior distribution of the unobservables was achieved by using Metropolis-Hastings within-Gibbs sampling.     

Smooth functional tempering for nonlinear differential equation models

Differential equations are used in modeling diverse system behaviors in a wide variety of sciences. Methods for estimating the differential equation parameters traditionally depend on the inclusion of initial system states and numerically solving the equations. This paper presents Smooth Functional Tempering, a new population Markov Chain Monte Carlo approach for posterior estimation of parameters. The proposed method borrows insights from parallel tempering and model based smoothing to define a sequence of approximations to the posterior. The tempered approximations depend on relaxations of the solution to the differential equation model, reducing the need for estimating the initial system states and obtaining a numerical differential equation solution. Rather than tempering via approximations to the posterior that are more heavily rooted in the prior, this new method tempers towards data features. Using our proposed approach, we observed faster convergence and robustness to both initial values and prior distributions that do not reflect the features of the data. Two variations of the method are proposed and their performance is examined through simulation studies and a real application to the chemical reaction dynamics of producing nylon.     

Occupational safety and profit maximization: Friends or foes?

The rise of the Industrial Revolution is often depicted as a cause of hazardous working conditions and is skillfully epitomized in William Blake's tale of a child chimney sweeper. Conventional wisdom puts firm profit in conflict with occupational safety. We reexamine this argument noting that injuries are very costly to firms because they lead to higher wage premiums, worker compensation, and costly work stoppages. We hypothesize that it is precisely for these reasons that firms in the industries with dangerous working conditions have the strongest incentives to innovate and substitute more capital for labor. Using a longitudinal panel of U.S. industries, we test and confirm our hypothesis that higher injury rates lead to higher capital stock per worker, over time. Moreover, our estimates suggest that firms provide more capital and equipment per worker than what would have been there based solely on the compensating wage differential.     

The Influence of Volunteer Recruitment Practices and Expectations on the Development of Volunteers’ Psychological Contracts

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - Volunteer recruitment and retention continue to be important issues for not-for-profit organisations. A theoretical...     

The Globalization of Penal Space in Nineteenth-Century Malta

In the second half of the nineteenth century an unprecedented number of prisons were built across the Western-influenced world. However, many more developed from repurposed and modified buildings. By applying space syntax analysis to examples from the then British colony of Malta, this article investigates the commonalities of penal space across a series of purpose-built and refashioned prisons, taking into consideration key architectural phases resulting from remodelling. Rejecting the notion that Maltese developments are merely symptomatic of British colonialism, the spread of Western prisons is cast in terms of wider trends and the global spread of a particular type of penal space.     

Role ambiguity and volunteer board member performance in nonprofit sport organizations

We explore the relationship between multidimensional role ambiguity and individual board member performance within nonprofit voluntary sport organizations. Role ambiguity accounted for 29 percent of the variance in perceived board member performance, and ambiguity about one's responsibilities was the strongest predictor. These findings extend our understanding of the drivers of individual board member performance within voluntary sport organizations and the multidimensional nature of role ambiguity. The study supports previous arguments that knowing what to do is fundamental to one's performance, and more critical than knowing how to do it, and what difference it makes.