Evaluation of Methods for Assessing the Oral Bioavailability of Inorganic Mercury in Soil

The risks associated with environmental exposures to inorganic mercury are typically assessed based on toxicity studies conducted with the soluble salt, mercuric chloride (HgCl₂). Evidence indicates, however, that inorganic mercury is present in soil as a variety of compounds and that oral absorption of inorganic mercury decreases with a decrease in the solubility of the mercury compound being studied. Thus, while HgCl₂ is approximately 15–20% bioavailable, the bioavailability of cinnabar (HgS) may be 30- to 60-fold less. The solubility and, hence, bioavailability of inorganic mercury in soil is expected to be substantially less than that of HgCl₂ due to the presence of less soluble compounds and their interactions with soil constituents. Quantification of this difference in bioavailability is important in assessing potential risks associated with exposure to mercury-containing soil. A review of available studies supports the expectation that mercury bioavailability in soils will be reduced. This paper reviews methods for assessing soil metal absorption with consideration of the characteristics of the oral absorption of elemental and inorganic mercury that should be evaluated in designing additional studies. Because of the very slow elimination of mercury in some species, it is recommended that a repeated-dose study be conducted. Such a study would yield an estimate of relative bioavailability based on a comparison of tissue mercury concentrations in animals ingesting soil with those of animals receiving HgCl₂. The dose, age, gender, and species of animal selected are not expected to affect relative bioavailability estimates; however, it is recommended that studies be conducted in two animal species. Rats should be used because they have been used in many studies of mercury absorption and toxicity. A species of large animals such as monkeys, swine, or dogs should also be used to provide confirmation in a species with greater similarities to humans in gastrointestinal physiology and anatomy. Other critical factors in designing these studies, such as selection and characterization of soil samples, are also addressed.     

An optimization interpretation of integration and back-fitting estimators for separable nonparametric models

We provide an optimization interpretation of both back-fitting and integration estimators for additive nonparametric regression. We find that the integration estimator is a projection with respect to a product measure. We also provide further understanding of the back-fitting method.     

Leading well is a matter of resources: Leader vigour and peer support augments the relationship between transformational leadership and burnout

ABSTRACT

Although studies suggest that transformational leaders play an important role in employee health and well-being, the relationship between transformational leadership and employee burnout remains unclear. One reason may be that moderators may play an important role. Building on conservation of resources theory, we examined if leaders’ perceptions of internal and external resources in terms of vigour and peer support augmented the relationship between transformational leadership and employee burnout in a sample of municipality workers and their leaders in Sweden (N?=?217). Multilevel analyses over two time points revealed that both vigour and peer support enhance this relationship, such that when leaders experience high levels of vigour or peer support, the negative relationship between transformational leadership behaviours and employee burnout was strengthened. Our findings suggest that both personal and contextual resources may help leaders to better engage in transformational leadership, which is important in order to protect employees from burning out.     

Transnational diaspora entrepreneurship in emerging markets: Bridging institutional divides

Transnational diasporan entrepreneurs are migrants and their descendants who establish entrepreneurial activities that span the national business environments of their countries of origin and countries of residence. We explore how business incubators contribute to the economic development of emerging markets by organizing their programs to bridge the institutional divides that transnational diaspora entrepreneurs face when establishing their multi-territorial ventures in these markets. Drawing on qualitative fieldwork conducted in the Netherlands during 2007, we present the case study of IntEnt, an incubator providing services exclusively to transnational diasporan entrepreneurs. We apply Bergek and Norrman's (2008) assessment framework to this case, examining IntEnt's goals, model (selection, business support, and mediation activities), and outcomes. Employing Eisenhardt's case-based theory development approach (1989), we then leverage case findings to generate theory about the institutional challenges faced by transnational diaspora entrepreneurs and the role that incubators can play in helping these entrepreneurs overcome these challenges.     

Workers’ Perception of Chemical Risks: A Focus Group Study

Workers’ perceptions with respect to health and safety at work are rarely taken into account when considering the development of prevention programs. The aim of this study was to explore workers’ perceptions of chemical risks at the workplace, in order to investigate the prerequisites for a workplace health program. A qualitative study was conducted involving seven focus groups of 5–10 participants (blue‐collar workers) each. All groups were homogeneous in terms of sex, work status, language, and company membership. Results showed that several factors have an important influence on workers’ perception of chemical risks. Workers assess risks by means of both sensory and empirical diagnosis and are concerned about the long‐term health consequences. They perceive the threat of chemical risks as high. Despite this, they are resigned to accepting the risks. Existing formal sources of information are rarely consulted because they are judged to be difficult to understand and not user friendly. Instead, workers tend to obtain information from informal sources. Communication problems with and lack of trust in prevention advisers and hierarchy are frequently mentioned. Workers feel that their specific knowledge of their working conditions and their proposals for practical, cost‐effective solutions to improve health and safety at the workplace are insufficiently taken into account. The use of focus groups yielded a useful insight into workers’ perceptions of chemical risks. Our findings suggest that training programs for prevention advisers should include topics such as understanding of workers’ perceptions, usefulness of a participatory approach, and communication and education skills.     

Integer‐valued Trawl Processes: A Class of Stationary Infinitely Divisible Processes

This paper introduces a new continuous‐time framework for modelling serially correlated count and integer‐valued data. The key component in our new model is the class of integer‐valued trawl processes, which are serially correlated, stationary, infinitely divisible processes. We analyse the probabilistic properties of such processes in detail and, in addition, study volatility modulation and multivariate extensions within the new modelling framework. Moreover, we describe how the parameters of a trawl process can be estimated and obtain promising estimation results in our simulation study. Finally, we apply our new modelling framework to high‐frequency financial data.     

No Degree,No Job: Adolescent Mothers’ Perceptions of the Impact that Adolescent Fathers’ Human Capital has on Paternal Financial and Social Capital

Becoming an adolescent father truncates young males’ opportunities to complete high school and secure employment, which can hinder their capacity to contribute financial and social capital to their children. Based on 69 adolescent mother reports, results suggest that whereas employment status is associated with adolescent fathers’ physical and financial presence, high school completion is strongly associated with the nature and quality of parenting and co-parenting behaviors. Implications for school counselors, teachers, social workers, and future research are discussed.     

Econometric Analysis of Realized Covariation: High Frequency Based Covariance,Regression, and Correlation in Financial Economics

This paper analyses multivariate high frequency financial data using realized covariation. We provide a new asymptotic distribution theory for standard methods such as regression, correlation analysis, and covariance. It will be based on a fixed interval of time (e.g., a day or week), allowing the number of high frequency returns during this period to go to infinity. Our analysis allows us to study how high frequency correlations, regressions, and covariances change through time. In particular we provide confidence intervals for each of these quantities.