1,721,129 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
Ionization in atmospheres of brown dwarfs and giant gas planets
No full textRecent observations of ultra-cool objects suggest that the gas in their uppermost atmospheres is heated, ionised and magnetised to levels that radio and X-ray emission is possible. The aim
of this work is to identify which low mass objects are most susceptible to plasma and magnetic
processes by the effect of thermal ionisation and Lyman continuum photoionisation from the
irradiation of external sources in different environments. I focus my work on very low mass,
ultra-cool objects (late M-dwarfs, brown dwarfs and giant gas planets: T[sub]eff = 1000 . . . 3000 K)
to analyse the electrostatic and magnetic character of these atmosphere. This work has been
carried out in two distinct parts:
a) A reference study to identify which ultra-cool objects are most susceptible to plasma and
magnetic processes considering the thermal ionisation as the only mechanism to ionise
the atmospheric gas. This presents a theoretical framework using a set of fundamental
parameters to analyse the ionisation and magnetic coupling state of objects with
ultra-cool atmospheres. The DRIFT-PHOENIX model atmosphere simulations are used to
determine the local gas properties T[sub]gas [K], p[sub]gas [bar], pₑ [bar] of the atmospheres
structures from the global parameters T[sub]eff [K], log(g) [cm s⁻²] and [M/H]. Electrostatics
interactions dominance over electron-neutral interactions increases as T[sub]eff increases:
throughout the M-dwarf atmospheres, almost for the whole brown dwarf atmospheres
and only giant gas planets with T[sub]eff =1200 K, log(g)=3.0, [M/H]=+0.3 fulfil that criterion
at the most deeper atmosphere. A magnetised gas is found for M-dwarfs, brown
dwarfs and giant gas planet atmospheres even for those with a small degree of ionisation
except to the most deeper atmospheric regions. Hence, the upper atmosphere of
all of studied objects can be magnetically coupled. A large fraction of the atmospheric
volume of M-dwarfs and of early spectral subtypes of brown dwarfs is found to occur
plasma processes and magnetised gas, and are therefore the best candidates to emit in
Hα and radio wavelengths.
b) An analysis of how the Lyman continuum external irradiation effect the plasma and magnetic
state of an ultra-cool atmospheres in additional thermal ionisation. The Monte
Carlo radiative transfer code simulations provide the atmospheric ionisation structure
due to photoionisation. Three different cases are studied to see the effect of the Lyman
continuum irradiation given by an external source: free-floating ultra-cool objects
irradiated by Lyman continuum photons from the interstellar medium (dominated by
Galactic O and B stars), brown dwarfs in star forming regions irradiated by a nearby
(few parsecs) O star and binary systems where a brown dwarf atmosphere is photoionised
by a companion white dwarf. The effect of Lyman continuum irradiation from
external sources greatly increases the level of ionisation in the uppermost atmospheric
regions. Brown dwarfs in star forming regions and brown dwarfs in binary systems with
a companion white dwarf have upper atmospheres that are close to being fully ionised.
Adopting temperatures typical for a chromosphere or a corona, the resulting free-free
X-ray luminosities are found to be comparable with those observed from brown dwarfs
in star forming regions. The results of this study show that it is not unreasonable to
expect powerful energy emissions from brown dwarf atmospheres.
The conclusions of this study are that the thermal ionisation allows the establishment of a magnetised plasma in brown dwarf atmospheres as in particular the rarefied upper parts of the atmospheres despite having low degrees of thermal gas ionisation and that the Lyman continuum photoionisation allows to argue for a chromosphere/corona on brown dwarfs and for X-ray emissions from ultra-cool objects. However, other mechanisms, like Alfvén wave heating, are needed to occur which then lead to rise the local gas temperature in the chromosphere/corona on brown dwarfs
Modelling and detection of lightning signatures throughout the electromagnetic spectrum
No full textLightning is an important electrical phenomenon, known to exist in several Solar System planets. Amongst others, it carries information on convection and cloud formation, and may be important for pre-biotic chemistry. Exoplanets and brown dwarfs have been shown to host environments appropriate for the initiation of lightning discharges. In this PhD project, I aim to determine if lightning on exoplanets and brown dwarfs can be more energetic than it is known from Solar System planets, what are the most promising signatures to look for, and if these "exo-lightning" signatures can be detected from Earth.
This thesis focuses on three major topics. First I discuss a lightning climatology study of Earth, Jupiter, Saturn, and Venus. I apply the obtained lightning statistics to extrasolar planets in order to give a first estimate on lightning occurrence on exoplanets and brown dwarfs. Next, I introduce a short study of potential lightning activity on the exoplanet HAT-P-11b, based on previous radio observations. Related to this, I discuss a first estimate of observability of lightning from close brown dwarfs, with the optical Danish Telescope. The final part of my project focuses on a lightning radio model, which is applied to study the energy and radio power released from lightning discharges in hot giant gas planetary and brown dwarf atmospheres. The released energy determines the observability of signatures, and the effect lightning has on the local atmosphere of the object.
This work combines knowledge obtained from planetary and earth sciences and uses that to learn more about extrasolar systems. My main results show that lightning on exoplanets may be more energetic than in the Solar System, supporting the possibility of future observations and detection of lightning activity on an extrasolar body. My work provides the base for future radio, optical, and infrared search for "exo-lightning"
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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