1,721,034 research outputs found
Rez. zu: Uta George, Georg Lilienthal, Volker Roelcke, Peter Sandner, Christina Vanja (Hg.), Hadamar. Heilstätte – Tötungsanstalt – Therapiezentrum, Marburg 2006
No full textSchmuhl H-W. Rez. zu: Uta George, Georg Lilienthal, Volker Roelcke, Peter Sandner, Christina Vanja (Hg.), Hadamar. Heilstätte – Tötungsanstalt – Therapiezentrum, Marburg 2006. Westfälische Forschungen. 2010;60:732-735
Impacts of sperm competition on mating behaviour and life history traits in a simultaneous hermaphrodite
Get PDFEvolutionary theory suggests that post-copulatory sexual selection plays an important role in the evolution of reproductive traits of sexually reproducing animals. But despite its alleged universality empirical evidence is scarce for sexual selection operating in simultaneous hermaphrodites. I therefore investigated the potential for post-copulatory sexual selection in such an organism. Sexual selection can also act on phenotypic plasticity of traits. Flexible adjustments of an individual’s own sex allocation have been proposed to be a major advantage of hermaphrodites compared to separate-sexed organisms. The simultaneous hermaphrodite M. lignano flexibly adjusts its sex allocation to group size. I aimed to narrow down the cues on which this flatworm relies to make this adjustment, and I measured the costs of such phenotypically plastic responses to group size. I tested for mate limitation in a natural population of this outcrossing hermaphrodite as one possibile condition where simultaneous hermaphroditism is advantageous. In a double mating experiment I revealed genetic variation in paternity success and in five traits. One of them, mating rate, significantly predicted paternity success. This trait has recently been shown to be phenotypically plastic. I here demonstrate that it also exhibits genetic variation. Hence, it might be subjected to sexual selection. The findings of multiple paternity and genetic variation in paternity success clearly suggest that there is an opportunity for sexual selection in this simultaneous hermaphrodite. I discuss possible mechanisms of sexual selection (sperm competition, female bias in favour of one sperm donor) and random paternity skews that may underlie the paternity patterns observed in this species. Further results suggest that the well-documented phenotypically plastic response in sex allocation was based on indirect cues for sperm competition such as tactile cues of group size rather than direct cues such as assessment of the partner’s mating status. I also demonstrate that this response incurred significant production costs of phenotypic plasticity. However, since the magnitude of these costs was relatively low, I argue that flexible adjustments of sex allocation may still convey a net benefit to simultaneous hermaphrodites. Mate availability did not appear to seriously limit female fitness in a natural habitat of M. lignano. This is consistent with classical sexual selection theory, originally developed for separate-sexed species. Specifically, one aspect of Bateman’s principle states that female fecundity is not limited by the availability of mating partners but by resources available for egg production, which seems to apply to this simultaneous hermaphrodite. I conclude that sexual selection occurs in this simultaneous hermaphrodite. I rule out two presumptive cues for the phenotypically plastic response to group size and demonstrate production costs of this plasticity. Finally, I judge the significance of phenotypic plasticity and mate availability for the evolution of simultaneous hermaphroditism
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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