1,720,968 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
Measurement of the (30)Si Mole Fraction in the New Avogadro Silicon Material by Neutron Activation and High-Resolution γ-Spectrometry
Full text linkThe use of new silicon single crystals highly enriched in (28)Si recently produced for the upcoming redetermination of the Avogadro constant requires knowledge of their molar masses. The isotopic composition data are collected independently in different laboratories but all using the virtual element technique with multicollector inductively coupled plasma mass spectrometers. In this framework, the comparison of the results with an independent measurement of the amount of at least one of the depleted isotopes is useful to limit hidden systematic errors. To this aim, the (30)Si mole fraction of a sample of the new material was measured using a relative measurement protocol based on instrumental neutron activation analysis. The protocol is similar to that previously applied with the AVO28 silicon material used for the last determination of the Avogadro constant value with the exception that unknown and standard samples are not coirradiated. The x((30)Si) = 5.701 × 10(-7) mol mol(-1) estimate is close to the expected one and is given with a standard uncertainty of 8.8 × 10(-9) mol mol(-1). This value, if adopted, gives a contribution to the relative standard uncertainty of the Avogadro constant of 6.3 × 10(-10)
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
Si-30 Mole Fraction of a Silicon Material Highly Enriched in Si-28 Determined by Instrumental Neutron Activation Analysis
Full text linkThe latest determination of the Avogadro
constant, carried out by counting the atoms in a pure silicon
crystal highly enriched in 28Si, reached the target 2 × 10−8
relative uncertainty required for the redefinition of the kilogram
based on the Planck constant. The knowledge of the isotopic
composition of the enriched silicon material is central; it is
measured by isotope dilution mass spectrometry. In this work,
an independent estimate of the 30Si mole fraction was obtained
by applying a relative measurement protocol based on
Instrumental Neutron Activation Analysis. The amount of 30Si
isotope was determined by counting the 1266.1 keV γ-photons
emitted during the radioactive decay of the radioisotope 31Si
produced via the neutron capture reaction 30Si(n,γ)31Si. The
x(30Si) = 1.043(19) × 10−6 mol mol−1 is consistent with the value currently adopted by the International Avogadro
Coordination.The latest determination of the Avogadro constant, carried out by counting the atoms in a pure silicon crystal highly enriched in Si-28, reached the target 2 x 10(-8) relative uncertainty required for the redefinition of the kilogram based on the Planck constant. The knowledge of the isotopic composition of the enriched silicon material is central; it is measured by isotope dilution mass spectrometry. In this work, an independent estimate of the Si-30 mole fraction was obtained by applying a relative measurement protocol based on Instrumental Neutron Activation Analysis. The amount of Si-30 isotope was determined by counting the 1266.1 keV gamma-photons emitted during the radioactive decay of the radioisotope Si-31 produced via the neutron capture reaction Si-30(n,gamma)Si-31. The (x)(Si-30) = 1.043(19) x 10(-6) mol mol(-1) is consistent with the value currently adopted by the International Avogadro Coordination
Photoelektronenspektroskopie an Rhenium- und Rheniumoxidcluster-Anionen im Molekularstrahl
No full textDispelling 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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