Finite mixture models with concomitant information: assessing diagnostic criteria for diabetes

The World Health Organization (WHO) diagnostic criteria for diabetes mellitus were determined in part by evidence that in some populations the plasma glucose level 2 h after an oral glucose load is a mixture of two distinct distributions. We present a finite mixture model that allows the two component densities to be generalized linear models and the mixture probability to be a logistic regression model. The model allows us to estimate the prevalence of diabetes and sensitivity and specificity of the diagnostic criteria as a function of covariates and to estimate them in the absence of an external standard. Sensitivity is the probability that a test indicates disease conditionally on disease being present. Specificity is the probability that a test indicates no disease conditionally on no disease being present. We obtained maximum likelihood estimates via the EM algorithm and derived the standard errors from the information matrix and by the bootstrap. In the application to data from the diabetes in Egypt project a two-component mixture model fits well and the two components are interpreted as normal and diabetes. The means and variances are similar to results found in other populations. The minimum misclassification cutpoints decrease with age, are lower in urban areas and are higher in rural areas than the 200 mg dl^-1 cutpoint recommended by the WHO. These differences are modest and our results generally support the WHO criterion. Our methods allow the direct inclusion of concomitant data whereas past analyses were based on partitioning the data.     

Snake parasitism in an urban old-growth forest

Urban-associated changes can have immediate or long-term consequences on animal populations. Such changes may be assessed through parasite prevalence and abundance in wildlife hosts, as urbanization can influence parasitism and disease transmission in wildlife. Snakes are widespread and diverse vertebrates that often persist in urban environments; however, parasitism of snakes in urban environments has yet to be studied, leaving the roles of snakes in parasite transmission uncharacterized. Field ecology, microscopy, molecular techniques, and geographic information science (GIS) were integrated to characterize parasitism of snakes in an urban old-growth forest park. The species, sex, mass, length, location, and prevalence of ecto-, hemo-, and fecal parasites were determined for 34 snakes of 6 species. Ectoparasites (mite), hemoparasites (Hepatozoon spp.), and fecal parasites (Entamoeba spp., Trichomonas spp., Strongloides spp., and an unidentified helminth) were detected in snakes and 64.7?% of snakes were infected by at least one of these parasites. Parasite infections were generally not related to the sex, age, or body condition of snakes. The locations of infected snakes were used to produce risk maps indicating where parasite prevalence is predicted to be greatest. The analysis of these maps indicated that snakes with fecal parasites were closer than non-infected snakes to the edge of the forest. This study confirms that snakes may be important parasite hosts or reservoirs in parasite transmission pathways in urban environments and it provides an integrative multidisciplinary approach that may be used to monitor parasitism dynamics in other urban wildlife areas.     

Social Psychological Processes that Facilitate Sexual Assault within the Fraternity Party Subculture

Rape on the college campus has gained increasing amounts of attention in higher education, mainstream news, and public policy. The prevalence rates of rape are especially high among students who frequent campus parties, such as those hosted by fraternities. Researchers have described this increased risk by focusing on individual attitudes and behaviors of fraternity members or on the organizational norms and practices within the fraternity party subculture. To incorporate these studies into a single theoretical framework, this essay uses a social psychological approach to connect individual‐level attitudes, (sub)culture, and behavior. I describe and apply identity theory and affect control theory, two structural symbolic interactionist theories, to explain why certain men are drawn to high‐risk fraternities and how membership reinforces hostility toward and abuse of women. In doing so, I suggest several avenues for future research that would increase social psychological understanding of the heightened prevalence of sexual victimization within the fraternity party subculture.     

Risk,Resiliency, and Urban Governance: The Case of the 2010 Winter Olympic Games

This article uses preparations surrounding the 2010 Winter Olympic Games as an opportunity to examine the idea and practice of resiliency in the field of security, public safety, and urban governance. The enthusiasm for resiliency today is said to connect with broader shifts in the logics of security in response to the proliferation of disruptive events that are difficult to anticipate and potentially catastrophic in impact. How, though, is it possible to plan for an unknown and unknowable future? This article outlines three sets of practices for building urban resiliency that, while seemingly routine and mundane, and associated primarily with the domain of emergency management, exemplify a field of governmental activity that has flourished after 9/11 but received little scholarly attention to date.     

Leveraging the common and outsourcing the distinct: institutional difference and multinational company identity in emerging economies

ABSTRACT

This paper explores the challenges of outsidership faced by multinational companies (MNCs) accessing emerging economies. The paper departs from popular conceptualisations of culture drawing instead on social identity theory as part of an institutions-based view, to explain how employing a singularities approach can allow the identification of commonalities of Indianness and Australianness that can be leveraged to ameliorate negative socially embedded business norms that pose a challenge to MNC success in emerging economies. This study shows that despite recognised formal (regulatory) and informal (cultural) differences, managers of Australian MNCs operating in India were able to innovatively identify and exploit cultural commonalties/singularities to ease cultural adjustment and mitigate intergroup conflict, allowing them to achieve an innovative institutional fit. The paper discusses how, using this approach, sole-venture MNCs can access many of the benefits provided by collaborative entry modes while preserving MNC identity. We further propose that the singularities approach can provide a valuable starting point to develop culturally appropriate competence training initiatives.     

Class participation as a pedagogical tool in social work education

Class participation is an essential part of the social work pedagogy. However, active student engagement in classes is inconsistent and varies based on factors such as social backgrounds, educational background, and individual characteristics. Instructors often evaluate participation based on frequency of verbal contributions. Evaluation criteria are often unarticulated or difficult to measure, presenting numerous challenges for instructors and students alike. A model of reflective self-assessment of participation by students, paired with timely instructor feedback is put forth in this paper to mitigate these concerns. The steps in this model include initial self-assessment, goal setting, midterm review, and a final review. The process of continuous self-evaluation and problem-solving is discussed as strategies that aid the process of class participation. Three instructor touch points are suggested: at the goal-setting stage, the midterm review, and the final grade. Throughout the paper, connections to social work practice and social work pedagogy are highlighted. This model has yet to be implemented in a social work school’s curriculum. Challenges in the implementation and resolution of those challenges are also presented. This model suggests ways to enhance opportunities for student engagement and integration into graduate programs, in addition to fostering valuable skills for future practice in the field.     

Moving and union dissolution

This paper examines the effect of migration and residential mobility on union dissolution among married and cohabiting couples. Moving is a stressful life event, and a large, multidisciplinary literature has shown that family migration often benefits one partner (usually the man) more than the other Even so, no study to date has examined the possible impact of within-nation geographical mobility on union dissolution. We base our longitudinal analysis on retrospective event-history data from Austria. Our results show that couples who move frequently have a significantly higher risk of union dissolution, and we suggest a variety of mechanisms that may explain this.     

DO BETTER INFORMED INVESTORS ALWAYS DO BETTER? A BUYBACK PUZZLE

We explore the value of private investment information using data from a singular source: auctions of yearling racehorses. Horse breeders possess superior information about their own horses and have strong financial incentives to buy the best of these back at auction. However, those they repurchase subsequently perform significantly worse on average, earning 30% less at the racetrack than horses purchased by outsiders. Moreover, this underperformance is concentrated in male horses, despite these being purchased exclusively for racing purposes. These puzzling findings cannot be explained by differences in horse risk or breeder abilities, or by nonfinancial objectives, or by behavioral or selection biases. (JEL G02, G11, G14, L83, D44)