1,721,007 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
Growth, peroxidase activity and cytological modifications in Pisum sativum seedlings exposed to Ni2+ toxicity.
No full textNi2+ accumulation and the toxic effects of Ni2+ On growth were investigated in pea seedlings. In roots, Ni2+ absorption increased as a function of metal supply, while in the shoots the accumulation of the metal was restricted, particularly with higher treatments. Ten mu mol/L Ni2+ was found to be the lowest effective concentration to cause a significant reduction in root growth. Ni2+ did not induce changes in shoot length, even though biomass production was affected in both roots and shoots. The toxic effects of Ni2+ on K+ uptake and on water content were markedly higher in roots than in shoots. In the Ni-treated roots, these effects, and the concomitant increase in phenol content and extracellular peroxidase activity with affinity towards syringaldazine, were associated with an early induced cellular differentiation. The significance of this senescent-like slate, together with other cellular defence mechanisms such as the stimulation of intracellular peroxidase activity, is discussed in relation to Ni-stress
Somatic embryogenesis in vitis vinifera: A proteomic approach
No full textIn this study, we have identified a number of proteins involved in different pathways during early embryo induction. Proteins were extracted from embryogenic and non-embryogenic calli of Vitis vinifera grown on a 2,4-D containing media. The protein extracts were separated by two dimensional gel electrophoresis and identified by mass spectrometry. Some of the differentially expressed proteins identified may be involved in detoxification or in the maintenance of redox state. This suggests that an oxidative burst occurs during the development of somatic embryos and might lead to programmed cell death (PCD) of certain cells. Glutathione-S-transferase (GST) and cytosolic ascorbate peroxidase during acquisition of embryogenic potential are likely to be involved in protecting cells against the harmful effects of reactive oxygen species (ROS); however, the redox status of cells and the glutathione content may have important roles in developmental processes, especially in triggering cell division. In fact, it has recently been proposed that GST may serve as carrier for plant hormones, including auxin. A proteasome subunit was also identified. It is known that protea-some activity is closely aligned with cell proliferation processes; moreover, knockout mutants of Physcomitrella patens show developmental defects partially reversed by auxin and cytokinin, suggesting that the responses to these hormones may require degradation of short-lived regulators by the proteasome. An intriguing possibility is that this regulator acts as a repressor, preventing development in the absence of appropriate hormonal signals. When a sufficient concentration of hormone is reached, these repressors are removed by degradation. NDPK was differentially expressed; its role remains to be elucidated in somatic embryogenesis but the literature suggests a possible function in the regulation of cell morphogenesis. These proteins are candidates for further investigation in term of functional relevance for somatic embryo-genesis
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
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