Do Flow Rates Respond Asymmetrically to Water Level? Evidence from the Edwards Aquifer

This research examines the time series relationship between the Comal Springs flow rate and the water level in the Edwards Aquifer (Well J-17). The empirical methodology utilizes threshold autoregression (TAR) and momentum-TAR models that allow for asymmetry in responses and adjustments to a disequilibrium in the long-run cointegrating relationship. Based on the results, an asymmetric error-correction model (AECM) is proposed to characterize the short-run and long-run dynamic relationship between spring flow and water level. The results have implications for the management of water resources, water demand, and ecosystems.     

Maternal Into‐The‐Face Behavior,Shared Attention,and Infant Distress During Face‐to‐Face Play at 12 Months: Bi‐directional Contingencies

We describe a new maternal intrusion behavior, moving a toy or hand “into‐the‐face” of the infant, and we investigate its bi‐directional associations with infant‐initiated shared attention, infant distress, and infant gaze, during mother–infant face‐to‐face play at 12 months. The play was videotaped split‐screen, with infants seated in a high chair. Videotapes were coded on a 1‐sec time base for mother and infant gaze (at partner, toy, both, or gaze away); infant distress; and maternal intrusion behavior, “into‐the‐face.” We defined “infant‐initiated shared attention” as mother and infant looking in the same second at a toy that the infant‐initiated interest in. We documented that maternal into‐the‐face behavior decreased the likelihood of infant‐initiated shared attention, increased the likelihood of infant distress, and decreased the likelihood of infant gazing away. Reciprocally, infant distress and gazing away increased the likelihood of mother into‐the‐face. In moments when the dyad was engaged in infant‐initiated shared attention, mother into‐the‐face was less likely. This work documents bi‐directional contingencies in the regulation of maternal intrusion and infant behavior during face‐to‐face play at 12 months. We suggest that mother into‐the‐face behavior disturbs an aspect of the infant's experience of recognition.     

Performance Assessments of Nuclear Waste Repositories: A Dialogue on Their Value and Limitations

Performance Assessment (PA) is the use of mathematical models to simulate the long-term behavior of engineered and geologic barriers in a nuclear waste repository; methods of uncertainty analysis are used to assess effects of parametric and conceptual uncertainties associated with the model system upon the uncertainty in outcomes of the simulation. PA is required by the U.S. Environmental Protection Agency as part of its certification process for geologic repositories for nuclear waste. This paper is a dialogue to explore the value and limitations of PA. Two skeptics acknowledge the utility of PA in organizing the scientific investigations that are necessary for confident siting and licensing of a repository; however, they maintain that the PA process, at least as it is currently implemented, is an essentially unscientific process with shortcomings that may provide results of limited use in evaluating actual effects on public health and safety. Conceptual uncertainties in a PA analysis can be so great that results can be confidently applied only over short time ranges, the antithesis of the purpose behind long-term, geologic disposal. Two proponents of PA agree that performance assessment is unscientific, but only in the sense that PA is an engineering analysis that uses existing scientific knowledge to support public policy decisions, rather than an investigation intended to increase fundamental knowledge of nature; PA has different goals and constraints than a typical scientific study. The proponents describe an ideal, six-step process for conducting generalized PA, here called probabilistic systems analysis (PSA); they note that virtually all scientific content of a PA is introduced during the model-building steps of a PSA; they contend that a PA based on simple but scientifically acceptable mathematical models can provide useful and objective input to regulatory decision makers. The value of the results of any PA must lie between these two views and will depend on the level of knowledge of the site, the degree to which models capture actual physical and chemical processes, the time over which extrapolations are made, and the proper evaluation of health risks attending implementation of the repository. The challenge is in evaluating whether the quality of the PA matches the needs of decision makers charged with protecting the health and safety of the public.     

The Functional Analysis of Problematic Verbal behavior

The Analysis of Verbal Behavior - This study describes procedures and outcomes in a functional analysis of problem behavior of 2 public school students. For a 13-year-old honors student, bizarre...     

Railroad Construction and Antebellum Slave Prices*

Slave prices rose rapidly to historic highs in the late‐antebellum South. The boom in railroad construction in the South helps explain this large increase in slave prices. The economic connection between railroads and slave prices reconciles the views of traditional economic historians who thought slavery was economically irrational and the views of the new economic historians who have concluded that slavery was highly profitable. It was the massive public subsidies to railroads that explain it was public policy that provided the stimulant to slave prices, not the “peculiar” culture of the antebellum South or the planter efficient management of slave labor.     

Social capital and community building through an electronic network

This paper describes a social policy experiment that explores current and potential links between trends in Australian public policy. The central example is provided by the implementation of a wired community set up in a low‐income public housing estate by an entrepreneurial not‐for‐profit internet service provider, InfoXchange. ‘Reach for the Clouds’, the wired community being established at Atherton Gardens in Fitzroy, Melbourne, is attractive to policy‐makers and funding bodies, combining community‐building, public‐private partnerships, self‐help and place‐based management. However, although the project is promoted as an exercise in community‐building through technology, many of the key assumptions are untested. It seems self‐evident that low‐income people who are socially and economically excluded would benefit from greater ‘connectedness’ with one another. However, it is not clear that such exchanges, online or off‐line, will build ‘community’. The paper attempts to establish some distinctions between online communities of interest and place based communities, untangling the relationship between social connectedness and models of social capital.