1,721,074 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
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
Free-radical propagation rate coefficient of nonionized methacrylic acid in aqueous solution from low monomer concentrations to bulk polymerization
No full textThe propagation rate coefficient, k(p), for free-radical polymerization of nonionized methacrylic acid (MAA) in aqueous solution has been studied via pulsed laser polymerization (PLP) in conjunction with aqueous-phase size-exclusion chromatography (SEC). The PLP-SEC experiments were carried out between 20 and 80 degrees C within the entire concentration range from dilute solution containing 1 wt % MAA up to bulk MAA polymerization. The k(p) values which are determined under the assumption that the relevant monomer concentration at the radical site is identical to the known overall MAA concentration decrease by about 1 order of magnitude between 1 and 100 wt % MAA. This significant lowering is almost entirely due to a reduction in the Arrhenius preexponential factor, A(k(p)), whereas the activation energy, E-A(k(p)), stays essentially constant. The decrease in A(k(p)) is assigned to intermolecular interactions between the transition state (TS) structure for MAA propagation and an MAA environment being significantly stronger than the ones between this TS structure and an H2O environment. In an MAA-rich environment, the barrier to rotational motion of the relevant degrees of motion of the TS thus experiences enhanced friction, which is associated with a lowering of the preexponential factor and thus of k(p)
Determination of addition and fragmentation rate coefficients in RAFT polymerization via time-resolved ESR spectroscopy after laser pulse initiation
No full textA method for simultaneous determination of both the addition and fragmentation rate coefficients of the RAFT equilibrium reactions is presented, which is based on laser single pulse initiation in conjunction with microsecond time-resolved ESR spectroscopy. The build-up and subsequent decay in concentration of the intermediate radical are measured and k(ad) and k(beta) values are deduced from fitting the concentration versus time profiles to simple kinetic models
Free-radical polymerization kinetics of 2-acrylamido-2-methylpropanesulfonic acid in aqueous solution
No full textThe SP-PLP-NIR technique, which combines Pulsed laser polymerization (PLP) initiated by a single pulse (SP) with time-resolved monitoring of the resulting monomer conversion via near-infrared (NIR) spectroscopy, was used to investigate the kinetics in aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid (AMPS). For initial AMPS concentrations of 2.79 mol(.)L(-1) (50 wt% AMPS) and 1.04 mol(.)L(-1) (20 wt% AMPS), the ratio of (chain length averaged) termination and propagation rate coefficients, /k(p), was measured up to almost complete monomer conversion at temperatures between 10 and 40 degrees C and ambient pressure. Up to 80% monomer conversion, /k(p) is only slightly lowered, whereas there is a clear decrease upon further increasing conversion. Variation of temperature and of pH does not significantly affect /k(p). For estimating individual rate coefficients, and k(p), in addition chemically initiated polymerizations have been carried out, in which AMPS conversion was monitored via in-line FT-NIR spectroscopy. The resulting and k(p) values, for 40 degrees C and an initial AMPS concentration of 2.79 mol(.)L(-1), are 2 x 10(7) L(.)mol(-1.)s(-1) and 1 x 10(5) L(.)mol(-1.)s(-1), respectively. Both rate coefficients are significantly higher at the lower AMPS content of 1.04 mol(.)L(-1). at this lower AMPS content may be understood in terms of termination Occurring under reaction diffusion control. The lowering in rate coefficients measured at the higher AMPS content is indicative of a reduced poly(AMPS) chain mobility
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