Population-average mediation analysis for zero-inflated count outcomes

Mediation analysis is an increasingly popular statistical method for explaining causal pathways to inform intervention. While methods have increased, there is still a dearth of robust mediation methods for count outcomes with excess zeroes. Current mediation methods addressing this issue are computationally intensive, biased, or challenging to interpret. To overcome these limitations, we propose a new mediation methodology for zero-inflated count outcomes using the marginalized zero-inflated Poisson (MZIP) model and the counterfactual approach to mediation. This novel work gives population-average mediation effects whose variance can be estimated rapidly via delta method. This methodology is extended to cases with exposure-mediator interactions. We apply this novel methodology to explore if diabetes diagnosis can explain BMI differences in healthcare utilization and test model performance via simulations comparing the proposed MZIP method to existing zero-inflated and Poisson methods. We find that our proposed method minimizes bias and computation time compared to alternative approaches while allowing for straight-forward interpretations.Comment: 34 pages, 2 figures, 4 tables, 49 pages of Supplemental material, 2 supplemental figure

Bacterial communities in penile skin, male urethra, and vaginas of heterosexual couples with and without bacterial vaginosis

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Microbiome 4 (2016): 16, doi:10.1186/s40168-016-0161-6.The epidemiology of bacterial vaginosis (BV) suggests it is sexually transmissible, yet no transmissible agent has been identified. It is probable that BV-associated bacterial communities are transferred from male to female partners during intercourse; however, the microbiota of sexual partners has not been well-studied. Pyrosequencing analysis of PCR-amplified 16S rDNA was used to examine BV-associated bacteria in monogamous couples with and without BV using vaginal, male urethral, and penile skin specimens. The penile skin and urethral microbiota of male partners of women with BV was significantly more similar to the vaginal microbiota of their female partner compared to the vaginal microbiota of non-partner women with BV. This was not the case for male partners of women with normal vaginal microbiota. Specific BV-associated species were concordant in women with BV and their male partners. In monogamous heterosexual couples in which the woman has BV, the significantly higher similarity between the vaginal microbiota and the penile skin and urethral microbiota of the male partner, supports the hypothesis that sexual exchange of BV-associated bacterial taxa is common.This work was supported by National Institute of Health Grant R01 AI079071-01A1

A Plasmodium falciparum S33 proline aminopeptidase is associated with changes in erythrocyte deformability

Infection with the apicomplexan parasite Plasmodium falciparum is a major cause of morbidity and mortality worldwide. One of the Striking features of this parasite is its ability to remodel and decrease the deformability of host red blood cells, a process that contributes to disease. To further understand the virulence of Pf we investigated the biochemistry and function of a putative Pf S33 proline aminopeptidase (PJPAP). Unlike other P. falciparum aminopeptidases, PJPAP contains a predicted protein export element that is non-syntenic with other human infecting Plasmodium species. Characterization of PJPAP demonstrated that it is exported into the host red blood cell and that it is a prolyl aminopeptidase with a preference for N-terminal proline substrates. In addition genetic deletion of this exopeptidase was shown to lead to an increase in the deformability of parasite-infected red cells and in reduced adherence to the endothelial cell receptor CD36 under flow conditions. Our studies suggest that PJPAP plays a role in the rigidification and adhesion of infected red blood cells to endothelial surface receptors, a role that may make this protein a novel target for anti-disease interventions strategies. (C) 2016 Elsevier Inc. All rights reserved

Psychometric properties of the mock interview rating scale for autistic transition-age youth

BackgroundEmployment is a major contributor to quality of life. However, autistic people are often unemployed and underemployed. One potential barrier to employment is the job interview. However, the availability of psychometrically-evaluated assessments of job interviewing skills is limited for autism services providers and researchers.ObjectiveWe analyzed the psychometric properties of the Mock Interview Rating Scale that was adapted for research with autistic transition-age youth (A-MIRS; a comprehensive assessment of video-recorded job interview role-play scenarios using anchor-based ratings for 14 scripted job scenarios).MethodsEighty-five transition-age youth with autism completed one of two randomized controlled trials to test the effectiveness of two interventions focused on job interview skills. All participants completed a single job interview role-play at pre-test that was scored by raters using the A-MIRS. We analyzed the structure of the A-MIRS using classical test theory, which involved conducting both exploratory and confirmatory factor analyzes, Rasch model analysis and calibration techniques. We then assessed internal consistency, inter-rater reliability, and test–retest reliability. Pearson correlations were used to assess the A-MIRS’ construct, convergent, divergent, criterion, and predictive validities by comparing it to demographic, clinical, cognitive, work history measures, and employment outcomes.ResultsResults revealed an 11-item unidimensional construct with strong internal consistency, inter-rater reliability, and test–retest reliability. Construct [pragmatic social skills (r = 0.61, p < 0.001), self-reported interview skills (r = 0.34, p = 0.001)], divergent [e.g., age (r = −0.13, p = 0.26), race (r = 0.02, p = 0.87)], and predictive validities [competitive employment (r = 0.31, p = 0.03)] received initial support via study correlations, while convergent [e.g., intrinsic motivation (r = 0.32, p = 0.007), job interview anxiety (r = −0.19, p = 0.08)] and criterion [e.g., prior employment (r = 0.22, p = 0.046), current employment (r = 0.21, p = 0.054)] validities were limited.ConclusionThe psychometric properties of the 11-item A-MIRS ranged from strong-to-acceptable, indicating it may have utility as a reliable and valid method for assessing the job interview skills of autistic transition-age youth

"Influences on European Union Nuclear Waste Transport Policy"

This paper identifies the evolution of pro- and anti-nuclear advocacy coalitions to their incorporation of the shipments issue in the late 1980's. The pro-nuclear waste transport advocacy coalition has come to include developed nuclear powers, such as Germany, France, the United Kingdom, the United States, the former Soviet Union, pro-nuclear scientific experts and business entities. In contrast, the anti-nuclear nuclear waste transport advocacy coalition originated with a narrow band of support in Denmark and the Community's growing Green parties to include most European nations, the EU Commission, the EU Council, the media, and a number of technical and scientific experts. The paper concludes that, prior to 1992, the European Commission played the major role in setting the agenda for nuclear and radioactive waste policy. However, the Council, with support from pro-nuclear business entities and developed countries managed to exclude nuclear issues from the agenda of EU environmental policy including the Basel Convention, various directives an even within OECD discussions. Following several public nuclear and radioactive waste incidents and the 1992 Rio Conference, the anti nuclear waste transport advocacy coalition gained considerable strength and finally received legislative attention from the European Council

"Advocacy Coalitions and the 'Greening' of the Single European Act"

Before the promulgation of the 1987 Single European Act (SEA), the European Communities (EC) had undertaken three multi-year Environmental Action Programmes and generated more than 100 measures to coordinate and harmonize environmental protection. However, the 1957 Treaty of Rome, the legal basis for the organization, did not authorize joint action in the area of environmental protection. Pre-1987 environmental legislation was justified on the grounds that divergent environmental regulations in the Member States distorted trade competition and constituted a non-tariff barrier to free trade, and that the Treaty specified as objectives the promotion of "an accelerated raising of the standard of living" and the improvement of the living and working conditions of EC citizens. The SEA represented a seachange in the legal mandate of the organization in that it amended the Treaty of Rome to require that environmental protection be incorporated into every aspect of Community policy. Utilizing an advocacy coalition model, this paper aspires to describe and explain the policy stages, actors, and political interactions associated with the incorporation of environmental objectives into the EC's mission via the Single European Act. The activities of advocacy coalitions are examined during the agenda setting, policy option delineation, and decision making stages to ascertain the relative importance of policy ideas, national/power interests, institutional factors, and political interactions to explaining the "greening" of the SEA. The study concludes that although coalitional activities were not evident in processes that placed environmental provisions on the SEA agenda, they were important during the policy delineation and decision making stages. Environmental provisions were added to the agenda as a consequence of a process of policy evolution. All major participants agreed that the constitutionalization of the de facto functions was desirable. The Commission as a policy initiator and broker played the most significant role in placing environmental concerns on the SEA agenda. Once these concerns were on the agenda, the member states aligned themselves in coalitions on the basis of their positions on the specificity and stringency of the proposed legislation. "Green/clean” states feared that the legislation would require downward harmonization of their high national standards, while less environmentally-concerned states feared the economic costs of meeting strengthened EC regulations. In the end, the substantive content of the legislation was shaped by Commission-brokered compromise. The most contentious issues were "side-stepped" so that the overall initiative might move forward. All parties to the final decision making were eager that this "fringe" area bring positive incentives rather than confrontation to the SEA negotiations

"Multi-level and cross-level governance and the implementation and revision of European Union water legislation"

National domestic factors, members' interests and power, negotiating dynamics, transnational interest groups and regional actors and structures may be important shapers of EU policy. No single interest factor adequately explains its complicated politics and procedures--the more important objective is to identify a model sufficiently nuanced to explain how these factors interact to yield regional policy. This qualitative study delineates the panoply of actors, the interactions, and strategies associated with British-EU disputes over the implementation and revision of water quality directives between 1985 and the mid-1990s, to explore the possibility that the evolving concept of "governance" may very well provide an umbrella broad enough to account for EU decision making. The data suggest that governance is a heuristically useful and empirically valid way to conceptualize EU water politics. Political interactions to affect the water legislation were based on an intersubjective consensus that clean water is a worthy policy objective. A multiplicity of factors influenced the policy process: many actors, interactions and strategies; power assets and coalitions; consensual knowledge, informational and propaganda factors; institutional procedures; etc. Activities to influence policy moved outwardly toward regional actors such as EU bodies and transnational alliances, and inwardly toward subnational interest groups rather than remaining strictly confined to those with legal and constitutional authority to negotiate and legislate

A Proposed Framework for Global Leadership Education: Learning Objectives and Curricula

Many traditional leadership education paradigms are challenged by the transformational nature of globalization and are limited in application in diverse and complex contexts. In order to address these issues, a new framework must be adopted within higher education leadership programs to educate the next generation of global leaders. This paper introduces a potential framework of learning objectives, reviews strengths and weaknesses of the proposed model, provides sample curricular and co-curricular programs, and discusses recommendations for additional research