Detection of biotic responses to urbanization using fish assemblages from small streams of western Georgia,USA

We examined relationships between stream fish assemblages and land use alteration associated with urbanization in 15 lower Piedmont watersheds along an urbanization gradient north of Columbus, western Georgia. Based on land cover data from 2002 Landsat 7 TM imagery aerial photos, streams drained watersheds that were largely urban, developing (suburban), agricultural (pasture), managed pine forest, and unmanaged mixed-forest. We quantified fish seasonally from 3 run-pool segments in each stream, and used a variety of metrics as response variables in analyses of relationships between fish assemblage structure and land use and natural basin variation. In general, Georgia-Index of Biotic Integrity (GA-IBI) values, Bray-Curtis faunal similarity of streams to mean conditions within reference streams, proportions of fish as lithophilic spawners, and fish lacking eroded fins, lesions, tumors decreased with increasing urbanization. Multiple regression indicated that assemblages were explained by a combination of land use and natural basin variables (basin size, average discharge, nearest distance to a larger downstream tributary [colonization source]), with land use variables being important predictors of summer assemblages and natural basin variables being more important in winter and spring assemblages. Non-metric multidimensional scaling (NMDS) ordinations revealed strong separation between assemblages in urban watersheds and forested watersheds, whereas assemblages in agricultural and developing watersheds were intermediate between those in urban and forested watersheds. Our data suggest that fish are reliable indicators of anthropogenic disturbance at the landscape scale, at least seasonally, and may be used to forecast the magnitude of landscape-level changes in stream structure and function associated with the conversion of forests to urban/suburban land in the Southeast.     

Movement and structure as determinants of spatial representations

It was hypothesized that the cognitive representation of distances between locations in an environment is a function not only of the environment's structure, but also of a person's pattern of travel within the environment. In the present study subjects were exposed to an experimental environment in which some locations were separated either by an opaque or a transparent barrier and other locations were not separated by any barrier. As subjects learned where the locations were, they were required to follow a specific route that allowed travel between some locations in each category but not others. Afterward subjects were asked to reproduce from memory the separation between pairs of locations. The results supported the hypothesis. Recalled distance between locations was significantly affected by both movement patterns of subjects and structural aspects of the environment (type of barrier and actual separation between locations). These results are interpreted in terms of the types of information made available through particular movement patterns and the corresponding salience of that information.     

Are dual and single exposures differently associated with clinical levels of trauma symptoms? Examining physical abuse and witnessing intimate partner violence among young children

A significant portion of children living in the United States have experienced trauma. Informed by the developmental traumatology model, we explored the effects of physical abuse and witnessing intimate partner violence (IPV) on childhood trauma symptoms. This study utilizes a convenience sample of 580 high‐risk children between 3 and 12 years who received services from one‐child advocacy centre during a 12‐month period. We performed a series of binary logistic regression analyses to examine if physical abuse, exposure to IPV, and dual exposure (i.e., both physical abuse and IPV) are distinctly associated with six trauma symptoms, including anxiety, depression, posttraumatic stress (PTS), dissociation, anger, and sexual concerns. The results indicated that dual exposure was predictive of all trauma symptoms, except for dissociation. Additionally, physical abuse was associated with PTS, anger, and sexual concerns, whereas exposure to IPV was associated with depression, PTS, and sexual concerns. Research and implications for practitioners working with young children are discussed.     

Stochastic superiority

This paper introduces a definition of stochastic superiority. One random variable is stochastically superior to another whenever it stochastically dominates the other after the risk in each random variable has been optimally reduced. Stochastic superiority is implied by stochastic dominance, but the reverse is not true. Stochastic superiority allows more pairs of random alternatives to be ranked, and efficient sets to be smaller. A very strong sufficient condition for stochastic superiority is demonstrated to also be necessary when preferences are risk averse. This condition provides a relatively easy way to conduct stochastic superiority tests. As an alternative to “almost stochastic dominance,” stochastic superiority also provides a natural solution to the “left tail problem” that arises often when comparing random alternatives.

     

Research evidence utilization in policy development by child welfare administrators

An exploratory qualitative study was conducted to explore how child welfare administrators use research evidence in decision-making. Content analysis revealed that a cultural shift toward evidence-based practice (EBP) is occurring in Canadian child welfare organizations and multiple types of evidence inform policy decisions. Barriers to using evidence include individual, organizational, and environmental factors. Facilitating factors include the development of internal champions and organizational cultures that value EBP. Integrating research into practice and policy decisions requires a multifaceted approach of creating organizational cultures that support research utilization and supporting senior bureaucrats to use research evidence in policy development.     

Gender dysphoric/gender variant (GD/GV) children and adolescents: summarizing what we know and what we have yet to learn

The optimal approach to treating minors with gender dysphoria/gender variance (GD/GV) is much more controversial than treating these phenomena in adults. This is because children have limited capacity to participate in decision making regarding their own treatment, and even adolescents have no legal ability to provide informed consent. Minors must, therefore, depend on parents or other caregivers to make treatment decisions on their behalf, including those that will influence the course of their lives in the long term. Presently, the highest level of evidence available for selecting among the various approaches to treatment is best characterized as "expert opinion." Yet, opinions vary widely among experts and are influenced by theoretical orientation and assumptions and beliefs regarding the origins of gender identity, as well as its perceived malleability at particular stages of development. This article outlines some of the more salient points raised by the clinicians who treat GD/GV and their discussants. This article summarizes what the editors believe is known and what has yet to be learned about minors with GD/GV, their families, their treatment, and their surrounding cultures.     

Asymptotics for Statistical Treatment Rules

This paper develops asymptotic optimality theory for statistical treatment rules in smooth parametric and semiparametric models. Manski (2000, 2002, 2004) and Dehejia (2005) have argued that the problem of choosing treatments to maximize social welfare is distinct from the point estimation and hypothesis testing problems usually considered in the treatment effects literature, and advocate formal analysis of decision procedures that map empirical data into treatment choices. We develop large‐sample approximations to statistical treatment assignment problems using the limits of experiments framework. We then consider some different loss functions and derive treatment assignment rules that are asymptotically optimal under average and minmax risk criteria.     

Excluded losses and the demand for insurance

The demand for insurance is examined when the insured asset can incur losses that are excluded from insurance coverage. These losses are negatively correlated with covered losses and hence cannot be treated as background risk. Excluded losses have strikingly different effects on the demand for insurance than does background risk and lead to a modification of many standard insurance demand results. A number of new theorems concerning the effects of excluded losses are also presented. Risk-averse and prudent decision makers reduce their demand for insurance when excluded losses increase in size or riskiness. Excluded losses are a possible explanation for why many decision makers fail to take up insurance when it is offered.