1,720,974 research outputs found
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
Role of transglutaminase in pollen tube growth and in incompatibility-induced cell death
No full textRole of transglutaminase in pollen tube growth and in incompatibility-induced cell death
S. Del Duca, A. Di Sandro, A. Scarpellini and D. Serafini Fracassini
Dipartimento di Biologia e.s., Università di Bologna, via Irnerio 42, 40126 Bologna
Higher plant fertilization is a complex process controlled by a variety of interactions between the male and female gametophytes1. The growth of a pollen tube has been shown to require an apical tip based Ca2+-gradient, the function of which is not fully understood2. We demonstrate that a Ca2+-dependent extracellular pollen tube transglutaminase (TGase) is an essential modulator of pollen tube growth. The extracellular enzyme co-localises with annular structures surrounding the pollen tube. Inhibition of transglutaminase by specific inhibitors or an anti-TGase monoclonal antibody blocked pollen tube growth. The extracellular pollen transglutaminase was also able to crosslink amines and the histidine-tagged green fluorescent protein (His6-Xpr-GFP)3 into exogenous proteins, consistent with a possible role for the extracellular pollen transglutaminase in the stabilisation of proteins in the style, to which the pollen tube becomes anchored. As self incompatibility triggers programmed cell death in pollen4, the TGase activity has been analyzed during these phenomena.
References
1. Lord E. M. & Russel S. D. The mechanisms of pollination and fertilization in plants. Annu. Rev. Cell Dev. Biol. 18, 81-105 (2002).
2. Holdaway-Clarke T. L. & Hepler P. K. Control of pollen tube growth: role of ion gradients and fluxes. New Phytologist 159, 539–563 (2003).
3. Furutani Y., Kato A., Notoya M., Ghonei, M. A. & Hirose S. A Simple assay and histochemical localization of transglutaminase activity using a derivative of green fluorescent protein as a substrate. J. Histochem. Cytochem. 9, 247-258 (2001).
4. Thomas S.G. & Franklin-Tong V. Self-incompatibility triggers programmed cell death in Papaver pollen. Nature 429, 305-309 (2004)
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
A Zea mays 39-kDa thylakoid transglutaminase catalyses the modification by polyamines of light-harvesting complex II in a light-dependent way
No full textA transglutaminase (TGase; EC 2.3.2.13) activity, which shared many properties with the TGase activity of the Helianthus tuberosus chloroplast, was observed in the Zea mays L. chloroplast and in its fractions. This activity was found to be prevalent in thylakoids; bis-(glutamyl) spermidine and bis-(glutamyl) putrescine were the main polyamine conjugates formed. Light stimulated the endogenous thylakoid activity. Putrescine, spermidine and spermine were conjugated to the isolated light-harvesting complex of photosystem II (LHCII) with different degrees of efficiency, spermine being the polyamine most efficiently conjugated. A TGase with a light-sensitive activity was identified in the photosystem II-enriched fraction. Its partial purification on a sucrose gradient allowed the separation of a 39-kDa band, which was immunorecognised by two anti-TGase antibodies (Ab-3 and rat prostatic gland-TGase). Both a colorimetric and a radiometric assay for TGase activity, the former carried out in the presence of biotinylated cadaverine and the latter in the presence of polyamines labelled with radioactive isotopes and resulting in the isolation of glutamyl-polyamines, further confirmed that the thylakoid enzyme is indeed a calcium-dependent transglutaminase (Thyl-TGase). At variance with guinea pig liver and erythrocyte TGases, which are insensitive to light, the activity of the thylakoid transglutaminase is affected by light. Moreover, this enzyme, when tested with purified LHCII as substrate, catalysed the production of mono- and bis-glutamyl-polyamines in equal amounts, whereas the animal enzymes produced mainly mono-derivatives. Herein, it is discussed whether this light sensitivity is due to the enzyme or the substrate
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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