Publications by authors named "D L Opdyke"

Groundwater professionals require tools to evaluate a variety of technical issues related to per- and polyfluoroalkyl substances (PFAS). These include the potential impact of PFAS precursors on groundwater plumes of perfluoroalkyl acids (PFAAs). Numerical modeling results show that, by adjusting the mass loading rate, source zones with or without a precursor can produce similar PFAA plumes.

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Risk assessment for per- and polyfluoroalkyl substances (PFAS) is complicated by the fact that PFAS include several thousand compounds. Although new analytical methods have increased the number that can be identified in environmental samples, a significant fraction of them remain uncharacterized. Perfluorooctane sulfonate (PFOS) is the PFAS compound of primary interest when evaluating risks to humans and wildlife owing to the consumption of aquatic organisms.

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The efficacy of virtual reality (VR) exposure therapy was examined for the fear of flying. Virtual reality exposure involved six sessions of graded exposure to flying in a virtual airplane. The specific contribution of anxiety management techniques (AMT) and the VR exposure was examined in a single case design.

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Objective: The authors' goal was to examine the efficacy of computer-generated (virtual reality) graded exposure in the treatment of acrophobia (fear of heights).

Method: Twenty college students with acrophobia were randomly assigned to virtual reality graded exposure treatment (N = 12) or to a waiting-list comparison group (N = 8). Seventeen students completed the study.

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