1,721,009 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
The formation of the faintest galaxies in cosmological simulations: from the impact of primordial magnetic fields to the metal enrichment of present day dwarfs by first stars
No full textIn the theory of the bottom-up assembly of cosmic structures, one of the main challenges is to connect the smallest, most inconspicuous galaxies we observe today to the building blocks of more massive galaxies such as our own, the Milky Way. Do these so-called dwarf galaxies resemble the first galaxies formed in the Universe? Their small size and the preponderance of dark matter in dwarf galaxies, as well as their inner mass distribution, reinforce this idea. These characteristics make them excellent probes for cosmological models on small scales and the nature of dark matter. Having the simplest assembly histories of all galaxies, dwarfs are also dominated by old stellar populations. They underwent little to no further evolution after the Epoch of Reionization and constitute pristine relics of the early-Universe.
In the first part of this thesis, using cosmological simulations, we show the impact of initial conditions generated in the early Universe, particularly primordial magnetic fields (PMFs), on the formation and evolution of dwarf galaxies. We show that the impact of primordial fields on galaxy formation is twofold: 1. The number of dark halos around the Milky Way able to host dwarf galaxies is boosted. 2. An earlier onset of star formation plus a higher rate of forming stars induces a large amount of ionizing photons at high redshifts. Through this work we show that PMFs have a significant role in initiating the structure formation in the Universe, and obtain strong constraints on the properties of PMFs.
Then we address the impact of PMFs on galaxy formation in opposition to the pressure support produced by magnetic fields in the interstellar medium of galaxies, to find the dominant agent.
We conclude that because of the shallow potential well in low mass dwarfs, magnetic pressure not only can immensely decrease the stellar mass, but also can delay the onset of star formation. This effect can entirely prevent the collapse of gas clouds in the lowest mass halos and result in an increased number of dark halos. Yet the impact of a primordially sourced magnetic field dominates over its later-time impacts.
In the third part of this thesis, we target the elusive characteristics of the faintest galaxies, ultra faint dwarfs (UFDs). We explore how the first generations of metal-free stars (Pop III) could increase the mean metallicity of these galaxies. In this work, we show that massive Pop III stars which explode as energetic pair-instability supernovae increase the metal content of UFDs. However, being very rare and sometimes absent in the faintest UFDs, they have a limited impact on the global faint end of the metallicity-luminosity relation.
Taken together these three parts have increased our knowledge of the early stages of galaxy formation. How the cosmology in the early-Universe, in particular the frequently neglected PMFs, impact the formation and evolution of the first galaxies. What is the impact of magnetic fields on the interstellar medium and the star formation history of dwarf galaxies? What is the impact of first stars on the metal-enrichment occurring during the process of galaxy formation? These questions have been explored in this PhD thesis.LASTR
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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