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Postsynaptic Current Mediated by Metabotropic Glutamate Receptors in Cerebellar Purkinje Cells
No full text Tempia, Filippo, Maria Concetta Miniaci, Davide Anchisi, and Piergiorgio Strata. Postsynaptic current mediated by metabotropic glutamate receptors in cerebellar Purkinje cells. J. Neurophysiol. 80: 520–528, 1998. In rat cerebellar slices, repetitive parallel fiber stimulation evokes an inward, postsynaptic current in Purkinje cells with a fast component mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors and a slower component mediated by metabotropic glutamate receptors (mGluR). The mGluR-mediated excitatory postsynaptic current (mGluR-EPSC) is evoked selectively by parallel fiber stimulation; climbing fiber stimulation is ineffective. The mGluR-EPSC is elicited most effectively with increasing frequencies of parallel fiber stimulation, from a threshold of 10 Hz to a maximum response at ∼100 Hz. The amplitude of the mGluR-EPSC is a linear function of the number of stimulus pulses without any apparent saturation, even with >10 pulses. Thus mGluRs at the parallel fiber-Purkinje cell synapse can function as linear detectors of the number of spikes in a burst of activity in parallel fibers. The mGluR-EPSC is present from postnatal day 15 and persists into adulthood. It is inhibited by the generic mGluR antagonist (RS)-a-methyl-4-carboxyphenylglycine and by the group I mGluR antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid at a concentration selective for mGluR1. Although the intracellular transduction pathway involves a G protein, the putative mediators of mGluR1 (phospholipase C and protein kinase C) are not directly involved, indicating that the mGluR-EPSC studied here is mediated by a different and still unidentified second-messenger pathway. Heparin, a nonselective antagonist of inositol-trisphosphate (IP3) receptors, has no significant effect on the mGluR-EPSC, suggesting that also IP3 might be not required for the response. Buffering intracellular Ca2+ with a high concentration of bis-( o-aminophenoxy)- N,N,N′,N′-tetraacetic acid partially inhibits the mGluR-EPSC, indicating that Ca2+ is not directly responsible for the response but that resting Ca2+ levels exert a tonic potentiating effect on the mGluR-EPSC. </jats:p
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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