1,721,005 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
Is nebulin truly a component of the thin filament?
No full textThin filaments were prepared from rabbit and beef skeletal muscle with three different procedures, both at high and low ionic strength. Nebulin was always found to be associated with the myosin fraction and was always absent from the thin filament fraction
Protein cross talking through osmotic work: the free energy of formation of the MgADP-myosin complexes at the muscle protein osmotic pressure.
No full textA method is presented to determine the energy of formation of the myosin-ADP complexes at the muscle protein osmotic pressure. It is found that, at 18 kP, the putative protein osmotic pressure in skeletal muscle, the increase of MgADP from 0.05 to 2 mmolal, increases the free energy of myosin-ADP and of myosin-(ADP)2 by 0.756 and by 9.85 kJ/mol, respectively, and decreases the free energy of myosin by 8.34 kJ erg/mol. It is pointed out that the local changes of water chemical potential, induced by the binding of MgADP to myosin, can be sensed by other structures of the contractile machinery, which per se may even be insensitive to MgADP. Cross talking between macromolecules can thus be achieved by changes of the water chemical potential. Copyright (C) 1998 Elsevier Science B.V
The osmotic properties and free energy of formation of the actomyosin rigor complexes from rabbit muscle
No full textWe have studied the osmotic properties of the calcium-regulated actomyosin complexes from skeletal muscle at the protein osmotic pressure of 18 kPa and at different actin-to-myosin molar ratios. Essentially, protein solutions were equilibrated against a solution of poly(ethylene glycol) 40 000 of known macromolecular osmotic pressure. At the end of the equilibration the water and the protein masses of the protein solutions were determined gravimetrically and the protein molar concentration was calculated. In this reconstructed system we have found following, at the actin-to-molar ratio of 2.6 (the most likely stoichiometry of these two proteins in the dense region of the A band) the average distance between the myosin filaments is 34.2 nm, this equals the interfilament distance in the intact fibre of muscle in rigor, at the sarcomere length of 3.38 μm The formation of the F-actin-myosin and of the tropomyosin-F-actin-myosin rigor complexes involves the largest free energy changes, -5.38 kJ/mol myosin and 5.67 kJ/mol myosin, respectively. The formation of the troponin-tropomyosin-F-actin-myosin(Ca) rigor complex from myosin and troponin-tropomyosin-F-actin(Ca) occurs with the free energy change of -3.43 kJ/mol myosin. Of these -3.43 kJ, -1.81 kJ are provided by the endergonic conversion of troponin-tropomyosin-F-actin(EGTA) into troponin-tropomyosin-F-actin(Ca). The transition of myosin and of troponin-tropomyosin-F-actin(EGTA) into the -F-actin-myosin(Ca) rigor complex is accompanied by a 5.8% increase of volume. The increase of volume is due to a large influx of water, which is essentially protein-hydration water
The "in vitro motility assay" and phalloidin-F-actin
No full textWe have compared the osmotic properties of the hydrated, native actin filament and of hydrated phalloidin-F-actin. We have found that phalloidin-F-actin interacts much more strongly with water than native F-actin. It is therefore very likely that the interaction with myosin (that requires the expulsion of the protein solvation water) is more problematic for phalloidin-F-actin that for native F-actin. We conclude that phalloidin-F-actin is not a bona fide substitute for native F-actin in the "in vitro motility assay". © 1995 Academic Press. All rights reserved
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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