1,721,429 research outputs found
How phospholamban could affect the apparent affinity of Ca2+-ATPase for Ca2+ in kinetic experiments
No full textBinding of phospholamban (PLN) to the Ca2+-ATPase of muscle sarcoplasmic reticulum results in a decrease in apparent affinity for Ca2+ without affecting the true binding constant for Ca2+ determined in equilibrium binding experiments. It is shown that this can be explained by a scheme in which the ATPase shows two modes of binding for PLN, one of high and one of low affinity; the proposed scheme is not dependent on the kinetic model assumed for the Ca2+-ATPase.<br/
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
Interfacial binding sites for cholesterol on G protein-coupled receptors
No full textA docking procedure is described that allows the transmembrane surface of a G protein-coupled receptor (GPCR) to be swept rapidly for potential binding sites for cholesterol at the bilayer interfaces on the two sides of the membrane. The procedure matches 89% of the cholesterols resolved in published GPCR crystal structures, when cholesterols likely to be crystal packing artifacts are excluded. Docking poses are shown to form distinct clusters on the protein surface, the clusters corresponding to “greasy hollows” between protein ridges. Docking poses depend on the angle of tilt of the GPCR in the surrounding lipid bilayer. It is suggested that thermal motion could alter the optimal binding pose for a cholesterol molecule, with the range of binding poses within a cluster providing a guide to the range of thermal motions likely for a cholesterol within a binding site.</p
A database of predicted binding sites for cholesterol on membrane proteins, deep in the membrane
No full textThe outer membranes of animal cells contain high concentrations of cholesterol, of which a small proportion is located deep within the hydrophobic core of the membrane. An automated docking procedure is described that allows the characterization of binding sites for these deep cholesterol molecules on the membrane-spanning surfaces of membrane proteins and in protein cavities or pores, driven by hydrogen bond formation. A database of this class of predicted binding site is described, covering 397 high-resolution structures. The database includes sites on the transmembrane surfaces of many G-protein coupled receptors; within the fenestrations of two-pore K+ channels and ATP-gated P2X3 channels; in the central cavities of a number of transporters, including Glut1, Glut5, and P-glycoprotein; and in deep clefts in mitochondrial complexes III and IV.</p
Investigation of ballast flight under aerodynamic flow using computational fluid dynamics
No full textThis study focuses on the aerodynamics underneath a passing High-Speed Train that can cause ballast flight. Numerical studies have been carried out on simplified particles at different orientations and elevations (levels), to observe changes in aerodynamic forces. A cube and a hemisphere(0.06 m in diameter) were simulated at inlet flow speed up to 120 m/s. Studies using moving wall techniques were also carried out, to observe changes in aerodynamic forces on isolated ballast grains and different track sections. Results demonstrated that URANS has produced meaningful results but not as detailed as DDES at a higher computational cost. Certain ballast characteristics are identified that can trigger ballast movements such as the particle shape, its orientation and the mass of the ballast grain. It was determined that shapes with flatter surfaces (i.e. cube) facing the flow are more likely to move than smoothly shaped ballast (i.e. hemisphere) and ballast of smaller mass is also prone to ballast movement. Further studies included some simple wind tunnel experiments, in which the critical velocities for ballast were measured. CFD studies of different sleeper blocks were also conducted using periodic and moving wall boundary conditions,to determine the risk of ballast movement at various locations across the track at certain ballast depths. Aerodynamic forces and flow behaviour are presented for each case study isolating it from mechanical vibrations caused by the passing High-Speed Trains. These numerical studies show that be lowering the ballast bed depth and having a rough ballast bed surface can provide benefits by reducing the aerodynamic load on the ballast bed. These computational studies suggest that improper use of aerodynamic sleepers can increase the likelihood of ballast movement due to reduced flow separation, which is why new sleeper shapes should be considered to not only prevent ballast from settling on top of sleeper blocks but also increase the flow separation
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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