1,720,984 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Para-nonylphenol modulates ABCA1 levels in chorionic villous explants from first trimester human placenta
No full textEffects of estrogen-like compounds in human placenta
No full textAim: Estrogen-like compounds are a class of Endocrine Disrupter Chemicals (EDCs) which may interfere with the action of the steroid hormones. These compounds can cross the placenta and also act on this organ as shown in pregnant rats. We analyzed here the effect of selected estrogen-like compounds, Bisphenol A, para-nonylphenol and Resveratrol, on in vitro models of human placenta.
Methods: Studies were carried out on chorionic villous explants. Cultures were exposed to chemicals at concentrations reported to be present in the environment and/or in human tissues (1μM-1nM). Vehicle-treated cultures were used as negative controls. At 48-72 hours of exposure, cultures were analyzed for hormone and cytokine secretion, cell apoptosis and cell invasiveness.
Results: We demonstrated that chemicals were able to interfere with the functional processes in human placenta: trophoblast differentiation and apoptosis by increasing hormone (β-hCG) secretion and caspase-3 expression; trophoblast invasiveness by reducing secretion of metalloproteinase (MMP)-9 and increasing that of MMP-2; cytokine secretion by reducing the release of the macrophage migration inhibitory factor (MIF). Data were referred to control, vehicle-treated, cultures.
Conclusions: These results showing functional interference of estrogen-like compounds on human placenta raise concern about maternal exposure to these chemicals and possible effects on fetal growth and development
Effect of the endocrine disruptor Bisphenol A in in vitro models of human placenta
No full textEndocrine disrupter chemicals (EDCs) are environmental pollutants of agricultural or industrial origin which may influence human reproductive health. Bisphenol A (BPA) is widely used as a monomer in polycarbonate plastics and epoxy resins of dental sealants and in other types of plastics. This compound has estrogenic activity and human placenta is a target organ because it expresses Estrogen receptors α and β. In this study we investigated the effect of BPA on in vitro models of human placenta. We firstly, used the trophoblast cell lines BeWo to evaluate the median lethal concentration (LC50) assayed by alamar Blue test and the effective lethal concentration (EC50) by hormone β-hCG assay. Secondly, the model of primary cultures of villous explants from human placenta was used to evaluate the effect of non-toxic chemical concentrations on β-hCG secretion. Data on BeWo cells showed BPA toxicity at concentrations higher than 5x10-5M (LC50=1.32x10-4M and EC50=2.61x10-5M, for cell viability and hormone secretion, respectively). Although non-toxic BPA concentrations at 10-9M significantly induced the β-hCG secretion by primary chorionic villous explants. The findings suggest that low but environmentally relevant levels of BPA produce functional effects on human placenta when no evidence of toxicity is present
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