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Disposal of contaminated dredged material may pose risks to ecological and human populations. These risks are highly uncertain. Measures to confine the dredged material and reduce these risks are likely to increase disposal costs. Risk and cost assessments for dredged material management alternatives often are associated with very large uncertainties. These uncertainties must be explicitly incorporated into risk-cost analysis to ensure that appropriate management alternatives are selected. However, considering these uncertainties may cause difficulties in decision making by making management alternatives effectively indistinguishable. A risk-cost analysis methodology that evaluates uncertainty directly in the decision framework is developed. A multi-criteria decision-making method that incorporates uncertainties using fuzzy set theory, is proposed to trade-off risks and costs (including uncertainties) so that disposal alternatives can be compared and selected.

doi: 10.1017/S0009640708001212 Religious and Laity in Western Europe, 1000-1400. Edited by Emilia Jamroziak and Janet Burton. Europa Sacra 2. Turnhout: Brepols, 2006. xiv + 401 pp. € 75.00 cloth. The [...]

Step-growth thiol-Michael photopolymerizable resins, constituting an alternative chemistry to the current methacrylate-based chain-growth polymerizations, were developed and evaluated for use as dental restorative materials. The beneficial features inherent to anion-mediated thiol-Michael polymerizations were explored, such as rapid photocuring, low stress generation, ester content tunability, and improved mechanical performance in a moist environment. An ester-free tetrafunctional thiol and a ultraviolet-sensitive photobase generator were implemented to facilitate thiol-Michael photopolymerization. Thiol-Michael resins of varied ester content were fabricated under suitable light activation. Polymerization kinetics and shrinkage stress were determined with Fourier-transform infrared spectroscopy coupled with tensometery measurements. Thermomechanical properties of new materials were evaluated by dynamic mechanical analysis and in 3-point bending stress-strain experiments. Photopolymerization kinetics, polymerization shrinkage stress, glass transition temperature, flexural modulus, flexural toughness, and water sorption/solubility were compared between different thiol-Michael systems and the BisGMA/TEGDMA control. Furthermore, the mechanical performance of 2 thiol-Michael composites and a control composite were compared before and after extensive conditioning in water. All photobase-catalyzed thiol-Michael polymerization matrices achieved >90% conversion with a dramatic reduction in shrinkage stress as compared with the unfilled dimethacrylate control. One prototype of ester-free thiol-Michael formulations had significantly better water uptake properties than the BisGMA/TEGDMA control system. Although exhibiting relatively lower Young's modulus and glass transition temperatures, highly uniform thiol-Michael materials achieved much higher toughness than the BisGMA/TEGDMA control. Moreover, low-ester thiol-Michael composite systems show stable mechanical performance even after extensive water treatment. Although further resin/curing methodology optimization is required, the photopolymerized thiol-Michael prototype resins can now be recognized as promising candidates for implementation in composite dental restorative materials. [ABSTRACT FROM AUTHOR]

Composite dental restorations represent a unique class of biomaterials with severe restrictions on biocompatibility, curing behavior, esthetics, and ultimate material properties. These materials are presently limited by shrinkage and polymerization-induced shrinkage stress, limited toughness, the presence of unreacted monomer that remains following the polymerization, and several other factors. Fortunately, these materials have been the focus of a great deal of research in recent years with the goal of improving restoration performance by changing the initiation system, monomers, and fillers and their coupling agents, and by developing novel polymerization strategies. Here, we review the general characteristics of the polymerization reaction and recent approaches that have been taken to improve composite restorative performance. [ABSTRACT FROM AUTHOR]

Measured atrazine concentrations in Nebraska surface water have been shown to exceed water-quality standards, posing risks to humans and to the ecosystem. To assess this risk, atrazine runoff was simulated at the field-scale in Nebraska based on the pesticide component of the AGNPS model. This project's objective was to determine the frequency that the atrazine concentration at the field outlet exceeded three different atrazine water-quality criteria. The simulation was conducted for different farm management practices, soil moisture conditions, and five Nebraska topographic regions. If the criteria were exceeded, a risk to the drinking water consumer or freshwater aquatic life was hypothesized to exist. Three pesticide fate and transport processes were simulated with the model. Degradation was simulated using first-order kinetics. Adsorption/desorption was modeled assuming a linear soil-water partitioning coefficient. Advection (runoff) was based primarily on the USDA-NRCS curve number method. Daily rainfall from the National Weather Service was used to compute the soil moisture conditions for the 1985-2000 growing seasons. After each runoff event, the pesticide runoff concentration was compared with each of the three atrazine water-quality criteria. The results show that environmental receptors (i.e., freshwater aquatic species) are exposed to unacceptable atrazine runoff concentrations in 20- 50% of the runoff events. [ABSTRACT FROM AUTHOR]

Since considerable shrinkage stress develops during the curing of dental composites, various soft-start photocuring protocols, aiming to lower stress but not compromise conversion, have been proposed. We hypothesized that utilizing soft-start photocuring will result in not only reduced stress, but also decreased conversion. We evaluated the impact of 3 protocols (soft-start, pulse, and standard) on the stress development and polymerization extent of an experimental composite. A novel set-up capable of simultaneous shrinkage stress, conversion, and temperature measurements on the same specimen was utilized. Analysis of the data shows that stress rises dramatically as a function of conversion in the vitrified state, and the utilization of soft-start or pulse curing results in specimens with reduced final conversion and shrinkage stress, compared with specimens cured according to the standard full-intensity protocol. Finally, this study demonstrates that the predominant reason for the reduced shrinkage stress attained with soft-start or pulse curing is a modest decrease in final conversion. [ABSTRACT FROM AUTHOR]