IntroductionBisphenol A is highly debated and studied in relation to a variety of health outcomes. This large variation in the literature makes BPA a topic that is prone to selective use of literature, in order to underpin one’s own findings and opinion. Over time, selective use of literature, by means of citations, can lead to a skewed knowledge development and a biased scientific consensus. In this study, we assess which factors drive citation and whether this results in the overrepresentation of (...) harmful health effects of BPA.MethodsA citation network analysis was performed to test various determinants of citation. A systematic search identified all relevant publications on the human health effect of BPA. Data were extracted on potential determinants of selective citation, such as study outcome, study design, sample size, journal impact factor, authority of the author, self-citation, and funding source. We applied random effect logistic regression to assess whether these determinants influence the likelihood of citation.ResultsOne hundred sixty-nine publications on BPA were identified, with 12,432 potential citation pathways of which 808 citations occurred. The network consisted of 63 cross-sectional studies, 34 cohort studies, 29 case-control studies, 35 narrative reviews, and 8 systematic reviews. Positive studies have a 1.5 times greater chance of being cited compared to negative studies. Additionally, the authority of the author and self-citation are consistently found to be positively associated with the likelihood of being cited. Overall, the network seems to be highly influenced by two highly cited publications, whereas 60 out of 169 publications received no citations.ConclusionIn the literature on BPA, citation is mostly driven by positive study outcome and author-related factors, such as high authority within the network. Interpreting the impact of these factors and the big influence of a few highly cited publications, it can be questioned to which extent the knowledge development in human literature on BPA is actually evidence-based. (shrink)

Citing of previous publications is an important factor in knowledge development. Because of the great amount of publications available, only a selection of studies gets cited, for varying reasons. If the selection of citations is associated with study outcome this is called citation bias. We will study determinants of citation in a broader sense, including e.g. study design, journal impact factor or the funding source of the publication. As a case study we assess which factors drive citation in the human (...) literature on phthalates, specifically the metabolite mono phthalate. A systematic literature search identified all relevant publications on human health effect of MEHP. Data on potential determinants of citation were extracted in duplo. Specialized software was used to create a citation network, including all potential citation pathways. Random effect logistic regression was used to assess whether these determinants influence the likelihood of citation. 112 Publications on MEHP were identified, with 5684 potential citation pathways of which 551 were actual citations. Reporting of a harmful point estimate, journal impact factor, authority of the author, a male corresponding author, research performed in North America and self-citation were positively associated with the likelihood of being cited. In the literature on MEHP, citation is mostly driven by a number of factors that are not related to study outcome. Although the identified determinants do not necessarily give strong indications of bias, it shows selective use of published literature for a variety of reasons. (shrink)

BackgroundKnowledge development depends on an unbiased representation of the available evidence. Selective citation may distort this representation. Recently, some controversy emerged regarding the possible impact of swimming on childhood asthma, raising the question about the role of selective citation in this field. Our objective was to assess the occurrence and determinants of selective citation in scientific publications on the relationship between swimming in chlorinated pools and childhood asthma.MethodsWe identified scientific journal articles on this relationship via a systematic literature search. The (...) following factors were taken into account: study outcome (authors’ conclusion, data-based conclusion), other content-related article characteristics (article type, sample size, research quality, specificity), content-unrelated article characteristics (language, publication title, funding source, number of authors, number of affiliations, number of references, journal impact factor), author characteristics (gender, country, affiliation), and citation characteristics (time to citation, authority, self-citation). To assess the impact of these factors on citation, we performed a series of univariate and adjusted random-effects logistic regressions, with potential citation path as unit of analysis.ResultsThirty-six articles were identified in this network, consisting of 570 potential citation paths of which 191 (34%) were realized. There was strong evidence that articles with at least one author in common, cited each other more often than articles that had no common authors (odds ratio (OR) 5.2, 95% confidence interval (CI) 3.1–8.8). Similarly, the chance of being cited was higher for articles that were empirical rather than narrative (OR 4.2, CI 2.6–6.7), that reported a large sample size (OR 5.8, CI 2.9–11.6), and that were written by authors with a high authority within the network (OR 4.1, CI 2.1–8.0). Further, there was some evidence for citation bias: articles that confirmed the relation between swimming and asthma were cited more often (OR 1.8, CI 1.1–2.9), but this finding was not robust.ConclusionsThere is clear evidence of selective citation in this research field, but the evidence for citation bias is not very strong. (shrink)

This long-awaited book replaces Hughes and Cresswell's two classic studies of modal logic: _An Introduction to Modal Logic_ and _A Companion to Modal Logic_. _A New Introduction to Modal Logic_ is an entirely new work, completely re-written by the authors. They have incorporated all the new developments that have taken place since 1968 in both modal propositional logic and modal predicate logic, without sacrificing tha clarity of exposition and approachability that were essential features of their earlier works. The book takes (...) readers from the most basic systems of modal propositional logic right up to systems of modal predicate with identity. It covers both technical developments such as completeness and incompleteness, and finite and infinite models, and their philosophical applications, especially in the area of modal predicate logic. (shrink)

A quantum theory of the photon is developed in a natural manner. Newton-Wigner and Wightman demonstrated that the photon could not be strictly localized according to natural criteria. These investigations involved the identification of an elementary system with a uirrep of the Poincare group. We identify a particle with the localized measurement of the states satisfying the uirrep. In the case of zero mass and unit spin, the photon is identified with those components of the state that can be localized. (...) A c-number four-vector potential and Lorentz condition are derived from the relativistic wave equation. The Wightman localization is demonstrated for the three independent space components of the vector potential, and the photon is identified with these components. A position operator and probability density follow immediately from the localization. A consequence of the subjective definition of a photon is that the transformations of the vector potential are unitary, and hence the unitary scalar product can be obtained for the four-vector potential. A Hilbert space is defined for the three space components of the vector potential. A position operator and probability density are derived from the scalar product, which compare directly with those obtained from the localization and the non-relativistic theory. As the longitudinal and scalar polarizations do not contribute to the measured transition probability, they are considered virtual. Lastly, a conserved four-vector current is derived from the scalar product. The possibility of observing a strict localization of the photon in the laboratory is suggested. (shrink)

This study investigated the use of mobile telephones by males and females in a public bar frequented by professional people. We found that, unlike women, men who possess mobile telephones more often publicly display them, and that these displays were related to the number of men in a social group, but not the number of women. This result was not due simply to a greater number of males who have telephones: we found an increase with male social group size in (...) the proportion of available telephones that were on display. Similarly, there was a positive relationship between the number of visible telephones and the ratio of males to females. Our results further show that the increased display of telephones in groups with more males is not due to the ostensive function of these devices (i.e., the making and receiving of calls), although single males tended to use their phones more. We interpret these results within the framework of male-male competition, with males in larger group sizes functioning in an increasingly competitive environment. This competitive environment is suggested to be akin to a lek mating system in which males aggregate and actively display their qualities to females who assess males on a number of dimensions. We suggest that mobile telephones might be used by males as an indicator of their status and wealth (sensu “cultural ornaments”). (shrink)

Residency training in the Netherlands is to be restructured over the coming years. To this end a general competence profile for medical specialists has been introduced. This profile is nearly the same as the Canadian CanMEDS 2000 model, which describes seven general areas of medical specialist competence, one of which is professionalism. In order to establish a training programme for residents and their instructors based on this competence, it is necessary to develop a vision that does justice to everyday medical (...) practice. The two most prevailing views of professionalism—as personal, or as a behavioural characteristic—fall short of this. Only when professionalism is understood as reflective professionalism does it encompass the fundamental contextuality of medical treatment. This means that the focus of training and assessment must be shifted to accountability for treatment. (shrink)

Institutional ethics committees (IECs) are part of a growing phenomenon in the American health care system. Although a major force driving hospitals to establish IECs is the desire to resolve difficult clinical dilemmas in a quick and systematic way, in this paper we argue that such a goal is naive and, to some extent, misguided. We assess the growing trend of these committees, analyse the theoretical assumptions underlying their establishment, and evaluate their strengths and shortcomings. We show how the 'medical (...) consultation' model is often inappropriately applied to IECs and suggest that IECs must operate under a different framework. Finally, we argue that IECs should be valued for the process they facilitate, and not for the product that they are, often unreasonably, expected to deliver. (shrink)