1,721,715 research outputs found
Factors affecting the response of marine and estuarine bacterial communities to trace metal enrichment
No full textStudies of the effects of trace metal perturbation on microbial communities have, to date, concentrated on contaminated environments, single phylotypes or single metals. The effects of trace metals on bacterial communities in estuarine and marine environments have been largely overlooked. The aim of this research was to advance the scientific knowledge in this area by the implementation of incubation experiments. Experiments were designed to determine the effects of trace metal enrichment and aggregate formation on the structure and function of bacterial communities. Environmental samples included bacterioplankton from a pristine estuary (Erme, Devon), a moderately contaminated estuary (Tamar, Devon), a contaminated estuary (Fal, Cornwall), a coastal station (M1) and a truly marine station off the continental shelf (M2). Key factors influencing the response of bacterial communities to trace metal enrichment were identified. In marine communities the most influential factors were; environmental parameters, such as type and concentration of organic matter; initial community composition and ambient concentration of zinc. The addition of trace metals resulted in a decrease in diversity in the bacterial community from the Tamar Estuary, however, bacterial association with aggregates appeared to reduce this effect. Community dynamics of bacteria from a pristine estuary (Erme) demonstrated remarkable bacterial resilience under trace metal stress, particularly in samples dominated by bacteria from the Rhodobacteraceae. Some metals were shown to have a more profound effect on community dynamics than others, resulting in the division of trace metals into Type 1 and Type 2 categories as a function of bacterial response. RNA derived community fingerprints were more different between incubation conditions than DNA derived fingerprints, and were thus a more sensitive indication of response to trace metal enrichment. The wider implications of the effects of trace metals on bacterial communities in estuarine and marine environments are discussed, along with possible future research directions. Recommendations are made for future investigations of the effects of metal contamination in light of the results presented here
Using panel data to examine pregnancy attitudes over time
No full textThere is a lack of research examining changes in women’s fertility attitudes over relatively short periods of time. The aim of this study was to determine whether and how women’s attempts to get pregnant and their desire to avoid pregnancy changed over six months’ time as well as which characteristics and circumstances were associated with these changes. Using multinomial regression, we analyzed two panels of data from a sample of approximately 3,000 U.S. adult women gathered within six months apart. Only 4% of the women were trying to get pregnant at both time points, but six percent went from trying to not or vice versa. Two-thirds reported a strong desire to avoid pregnancy at both points, but 9% transitioned from strong to not strong and an additional 7% transitioned from not strong to strong. Women who transitioned to a more serious romantic relationship were at increased risk of transitioning to trying to become pregnant and, not surprisingly, to a weaker pregnancy avoidance. Some of the variables we tested, including changes in employment status and race/ethnicity, were associated with one outcome but not the other. The results highlight the importance of taking a holistic perspective of women’s lives when studying pregnancy intentions and in reproductive health care services such as contraceptive counseling. Context matters and it may change rapidly
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
