1,720,991 research outputs found
Orbital constraints for young low-mass visual M-dwarf binaries
No full textWe have procured astrometric epochs for 15 low-mass visual M-dwarf binaries for which we are able to place orbital constraints. From the Keplerian motions of the binaries we are able to extract dynamical masses, which will be compared to current state-of-the-art theoretical evolutionary models. The dynamical masses will eventually be used for constructing empirical models, and to improve isochronal dating of young moving groups and associations. Here we present the current status and the preliminary results from the survey
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Characterising Emblematic Binaries at the Lowest Stellar and Substellar Masses
No full textStars are involved in most research fields of astronomy, ranging from studies of faraway galaxies, exploding supernovae, to more nearby exoplanets and even our own Sun. As such, it is paramount that our physical interpretation of stars is accurate. By observing stars at different epochs, we can fashion evolutionary models to predict important events that occur at different phases during their life-cycle. Thus, exemplary stars where properties including mass, age and luminosity can be observed become increasingly valuable as benchmarks for calibrating said models with. Sometimes, all of these essential properties can be measured for a single system. For instance, for a binary star which circles a common centre of mass we can from its orbital motion calculate the dynamical mass of the system. If the stellar system also has a well-determined age we may use it as a benchmark for our models, and hence refer to it as an emblematic binary system. In this thesis we are searching for exactly these emblematic binaries, both among lowmass stars and substellar brown dwarfs. We also show how to measure the different characteristics that make the systems into exemplary touchstones. We provide an overview over the different types of stellar binaries, how mass and age estimates are performed, as well as discuss the implications multiplicity has for the formation and evolution of stars and brown dwarfs. In Paper I we present the results from an orbital fit we constrained for a low-mass binary with a known age, making into a valuable and relatively rare benchmark. We also show in Paper II how long baseline astrometry can be exploited in order to place better constraints for orbital fits and dynamical masses for low-mass companions to stars by measuring the perturbation in proper motion over time. The dynamical masses are sequentially tested against evolutionary models, which at these low masses display several discrepancies compared to the observables, and are thus questioned. We explore more uncharted mass-regimes in Paper III, where we employ laser guide star assisted adaptive optics to search for multiplicity among faint substellar objects in young moving groups, detecting 3 new young brown dwarf binary systems. These new binaries will prove to be highly valuable systems for future research of brown dwarfs, and will be able to be studied further with for instance the Extremely Large Telescope or James Webb Space Telescope, which also makes them into prominent benchmarks for substellar evolutionary models. Furthermore, age estimation typically dominates the error budget for low-mass stars and brown dwarfs, requiring several different approaches for a robust assessment. In Paper IV we test and compare different techniques for age determination of 7 low-mass binary stars. These binaries have had their orbital motion monitored for a longer time, and will soon be constrained well enough that dynamical masses may be procured. As such, these low-mass binaries will extend the so far scarce number of exemplary systems where both mass, luminosity and age can be determined, to later be used to calibrate theoretical evolutionary models.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted. </p
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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