1,720,999 research outputs found
Fates of the endonuclear symbiotic bacteria Holospora obtusa and Holospora undulata injected into the macronucleus of Paramecium caudatum
No full textRecovery of the ciliate Paramecium multimicronucleatum following bacterial infection with Holospora obtusa
No full textAbstract: The macronucleus (Ma) of Paramecium multimicronucleatum can be experimentally infected with bacteria of the species Holospora obtusa, a macronuclear-specific parasite of P. caudatum. However, usually all bacteria disappear from the nucleus within 1-2 days after infection. The results of infecting several different stocks of P. multimicronucleatum with several different isolates of H. obtusa from P. caudatum were studied during some days after infection to investigate this disappearance. Using light, fluorescence and electron microscopy at different stages of bacterial disappearance, it was shown that what we call "cleaning" of the nucleus is a fast and active process. P. multimicronucleatum can be infected with the infectious forms of H. obtusa within 2 h, but the majority of the bacteria were lost from the Ma by 10-19h. They were released from the host nucleus into the cytoplasm and then to the surrounding medium. At first, the infected Ma shortened and became almost roun..
Bacterial endocytobionts of Ciliophora. Diversity and some interactions with the host
No full textAbstract: Some new cytoplasmic and mitochondrial (Spirostomum minus) as well as macronuclear bacteria (S. ambiguum) are recorded. The ciliate-bacteria system has high potential for investigations of endocytobiosis. New data are shown concerning antibacterial resistance of stocks of Paramecium caudatum. The results support a suggestion about food selection in this ciliate. Some possible ways of experimentally increasing the diversity of endonuclear bacteria in P. multimicronucleatum were demonstrated
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
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