1,721,185 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
Sequence-specific gene silencing by transitive signals in plants
Full text linkThis work contributes to a research field that aims at unraveling the process of RNA silencing, in particular of transitive silencing. In the first, application-oriented part of the thesis, we examined the potential of transitive silencing as a tool for functional genomics, and in the second, more fundamental part, we focused on factors that influence the efficiency of transitive silencing, such as the processivity of the key enzyme RDR6, the length of homology between primary and secondary target, and the presence of viroid sequences in the primary target.
Frequently used methods that exploit RNA silencing for gene discovery in plants are hairpin-induced or virus-induced gene silencing. Transitivity could be an alternative silencing technology, but in plants it has not been shown yet whether amplification products are able to induce silencing of endogenous targets. To address the first goal of this thesis, we developed a transitive XYZ system in Nicotiana tabacum (Chapter 3; Van Houdt et al., 2003) and in Arabidopsis thaliana (Chapter 4). In both plant species we analyzed the ability of a sense transgene IR locus (X) to induce transitivity along a transgenic primary target (Y), resulting in silencing of a transgenic secondary target (Z) without homology to the silencing inducer. In tobacco, we also investigated the methylation status of the silencing inducer X and of the target sequences (Chapter 3). In Arabidopsis, we examined whether the in trans-silenced Y transcripts can produce a transitive silencing signal that is able to induce silencing of an endogenous gene target (Chapter 4).
The second goal of this work was to clarify some characteristics of transitive silencing. VIGS has been shown to spread over a distance of at least 1000 nt from the 5’ end to the 3’ end of the target mRNA, while 3’ to 5’ spreading can extend at least through 332 nt, with a possible limit of 600 nt (Petersen and Albrechtsen, 2005; Vaistij et al., 2002). We examined the extent of 3’ to 5’ spreading induced by the IR locus X and looked at the influence of an increasing distance between primary and secondary target sequences in a primary target Y on the onset of transitive silencing of a transgenic target Z (Chapter 5). In the same study, we investigated the influence of the length of sequence homology between primary and secondary target on the frequency and efficiency of transitive silencing of an endogenous target. Finally, we examined whether inserting a viroid sequence into a primary target Y inhibited transitive silencing induced by IR locus X (Chapter 6), because results from the research group of M. Wassenegger recently demonstrated in tobacco that viroid-induced silencing did not induce spreading along a GFP-viroid fusion transgene (Vogt et al., 2004)
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
Analysis of Petunia flower development by forward and reverse genetic approaches : Miet, Meawest and the MADS-box gene family
No full textDispelling 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
Development of enabling technologies to modify gene expression in Arabidopsis thaliana
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