Rarity of Organisms in the Sand Pine Scrub Habitat of Florida

Naturalists conceive of "rare" organisms as those narrow in geographic range, restricted to few habitats, or small in population sizes. Because rare organisms may be rare in a variety of ways, a particular conservation strategy that purports to protect them may not do so effectively in all cases; therefore, categorization of rarity in advance could help ensure that the chosen strategy has a reasonable chance of success in a particular case. We placed plants, amphibians, and reptiles resident in the Sand Pine scrub habitat of Florida into categories of rarity. Determining if and in what way a particular organism is rare proved difficult, because the process requires exact specification of what is meant by "narrow,""restricted," and "small." Furthermore, the process requires choice of a scale for judging rarity and relies upon data that are likely to be of variable availability and reliability. We categorized rarity by several schemes, and they produced distributions of taxa among categories of rarity that largely were similar to one another but that diverged in telling ways. The distributions of taxa among categories of rarity produced by any scheme were different for scrub plants than for scrub amphibians and reptiles. Likewise, these distributions were different than those produced by previously published studies of rarity. We found that the results of our categorization schemes did not match particularly well with the official listing of scrub organisms as endangered or potentially endangered.     

The socialization of union loyalty

The present study investigated the effects of a specific union socialization program on union attitudes and loyalty. Seventy-one apprentices undergoing a union-management training program were surveyed. Using linear structural relations modelling, the research found that union attitudes and training satisfaction were the most important predictors of loyalty to the union. Furthermore, attitudes to unions were related to the union socialization process and the transformational leadership characteristics of the socializing agents.     

Bayesian estimation of age-specific bird nest survival rates with categorical covariates

The populations of many North American landbirds are showing signs of declining. Gathering information on breeding productivity allows critical assessment of population performance and helps identify good habitat-management practices. He (Biometrics (2003) 59 962–973) proposed a Bayesian model to estimate the age-specific nest survival rates. The model allows irregular visiting schedule under the assumption that the observed nests have homogeneous nest survival. Because nest survival studies are often conducted in different sites and time periods, it is not realistic to assume homogeneous nest survival. In this paper, we extend He’s model by incorporating these factors as categorical covariates. The simulation results show that the Bayesian hierarchical model can produce satisfactory estimates on nest survival and capture different factor effects. Finally the model is applied to a Missouri red-winged blackbird data set.     

Mass exchange in a shallow channel flow with a series of groynes: LES study and comparison with laboratory and field experiments

The exchange of dissolved matter between a straight open channel and a series of shallow embayments present at one of its sides is investigated using large eddy simulation (LES). The direct link between the mechanism of mass exchange and the dynamics of coherent structures is demonstrated. It is shown that for the geometrical configuration considered in the present study, the mass exchange process is very non-uniform over the depth in the vicinity of the channel–embayment interface. Most of the contaminant is ejected from the embayments close to the free surface. The amount of contaminant re-entrained into the embayments situated downstream of the one in which contaminant was introduced is quantified. The mass exchange coefficient predicted by LES does not vary significantly with the embayment rank and is in very good agreement with the one predicted by the model proposed by Weitbrecht et al. (J Hydraul Eng 134(2):173–183, 2008) based on the value of a dimensionless morphometric groyne-field parameter. Field experiments were purposely performed in a natural stream with embayments whose length over width ratios were close to the ratio in the LES study. The concentration fields predicted by LES are compared with video-records of colored dye used to visualize the mass exchange in the field experiment. It is shown that, for both LES and the field experiment, the dominant passage frequency of the eddies inside the interfacial mixing layer is well predicted by the analytical model of Sukhodolov and Sukhodolova (in: Cowen et al (eds) Hydraulic measurements & experimental methods. Proceedings of international conference, Lake Placid, USA, pp 172–177, 2007). The model is then used to scale the time in the LES animations and field video-records showing the temporal evolution of the concentration field. The results of the comparison indicate several similarities in the mixing process, despite the differences in the bathymetry and the large difference in the Reynolds number between LES and the field experiment. This proves the usefulness of performing detailed LES and laboratory studies in well-controlled environments to understand mass-exchange processes around river groyne fields.     

How big is big? How often is often? Characterizing Texas petroleum refining upset air emissions

This work examines the magnitude and frequency of Texas petroleum refineries upset air emissions over a 44-month period. Upset emissions occur during plant start-ups, shut-downs, maintenance, malfunctions and flaring incidents, and these emissions are typically exempt from regulation. These emissions contain a variety of chemicals, including benzene, nitrogen oxides, sulfur dioxide, and butadiene. Unlike other states, Texas has detailed reporting requirements, regulations in place, and an extensive upset emissions database. A key scientific and public policy question is whether upset emissions have significant impacts on local air quality and public health. However, it is not possible to address this question without first understanding the magnitude and properties of upsets. We merge related databases to examine over 3,900 upset emission events and find that upset emissions are significant in both size and occurrence when compared to routine operation emissions. It is determined that these events are not random, being more likely to occur during the summer, in the morning, and early in the workweek. A regional analysis of Port Arthur suggests that upset emissions from co-located refineries are equivalent to having an additional refinery within the region. Because of uncertainties within the reporting process and an obvious underestimation by some refineries, there is a need for better tracking of upset emissions.     

A review of the public health impacts of unconventional natural gas development

The public health impact of hydraulic fracturing remains a high profile and controversial issue. While there has been a recent surge of published papers, it remains an under-researched area despite being possibly the most substantive change in energy production since the advent of the fossil fuel economy. We review the evidence of effects in five public health domains with a particular focus on the UK: exposure, health, socio-economic, climate change and seismicity. While the latter would seem not to be of significance for the UK, we conclude that serious gaps in our understanding of the other potential impacts persist together with some concerning signals in the literature and legitimate uncertainties derived from first principles. There is a fundamental requirement for high-quality epidemiological research incorporating real exposure measures, improved understanding of methane leakage throughout the process, and a rigorous analysis of the UK social and economic impacts. In the absence of such intelligence, we consider it prudent to incentivise further research and delay any proposed developments in the UK. Recognising the political realities of the planning and permitting process, we make a series of recommendations to protect public health in the event of hydraulic fracturing being approved in the UK.     

Behavioral externalities in natural resource production possibility frontiers: integrating biology and economics to model human-wildlife interactions

Production possibility modeling has been applied to a variety of wildlife management issues. Although it has seen only limited employment in modeling human-wildlife output decisions, it can be expected that the theory's use in this area will increase as human interactions with and impacts on wildlife become more frequent. At present, most models applying production possibility theory to wildlife production can be characterized in that wildlife output quantities are determined by physically quantifiable functions representing rivalrous resources. When the theory is applied to human-wildlife interactions, it may not be sufficient to model the production tradeoffs using only physical constraints. As wildlife are known to respond to human presence, it could be expected that human activity may appear in wildlife production functions as an externality. Behavioral externalities are revealed by an output's response to the presence of another output and can result in a loss of concavity of the production possibilities frontier. Ignoring the potential of a behavioral externality can result in an unexpected and inefficient output allocation that may compromise a wildlife population's well-being. Behavioral externalities can be included in PPF models in a number of ways, including the use of data or cumulative effects modeling. While identifying that behavioral externalities exist and incorporating them into a model is important, correctly interpreting their implications will be critical to improve the efficiency of natural resource management. Behavioral externalities may cause a loss of concavity anywhere along a PPF that may compel managerial decisions that are inconsistent with multiple use doctrines. Convex PPFs may result when wildlife species are extremely sensitive to any level of human activity. It may be possible to improve the PPF's concavity by reducing the strength of the behavioral effect. Any change in the PPF that increases the convexity of the production set could offer natural resource managers additional opportunities to optimally provide multiple natural resource outputs. Techniques that minimize the effect could focus on either the human or wildlife outputs, or both. Methods could focus on reducing the externality itself through changing the production of the offending output or to reduce the impact of the externality through a change in the production of the affected output. Managers unfamiliar with PPF modeling can employ PPF thinking by recognizing that every decision involves tradeoffs and that sometimes these tradeoffs are unnecessary negative impacts that could be mitigated without compromising the resource.     

The "unintended pedestrian" on expressways

OBJECTIVE: To explore the epidemiology of pedestrian deaths in Dallas County, Texas, and to compare factors associated with pedestrian deaths on expressways versus those that occurred on other roadways. METHODS: We studied all pedestrian deaths among persons 15 years of age or older in Dallas County, Texas, from 1997 to 2004 by linking data from Medical Examiner's office, the Fatality Analysis Reporting System, and local police records. Univariate and multivariate analysis compared various factors associated with death on an expressway. RESULTS: Among 437 pedestrian deaths who were 15 years of age or older, 197 (45%) occurred on expressways; the proportion that occurred on expressways was highest among 15- to 29-year-olds (65%) and was lower with advancing age group (p < 0.01, chi square for trend). At least 36% of these expressway-related pedestrian deaths were known to have been "unintended pedestrians," who had exited a vehicle after being on the roadway, compared with 11% of pedestrian deaths on surface streets (OR 4.6, 95% CI, 2.7-8.1), and this was also highest among younger age groups. Pedestrian deaths on an expressway, compared with deaths on surface streets, remained strongly associated with having been an "unintended pedestrian" (OR 6.2, 95% CI, 3.1-14.0), after controlling for several other variables, including age, sex, race, nighttime of crash, and alcohol involvement. CONCLUSIONS: Expressways are the predominant site of fatal pedestrian crashes among young adults in this urban area. Since many of these deaths were "unintended pedestrians," procedures for management of occupants of disabled vehicles on expressways could have a large impact on pedestrian deaths in young adults.