1,721,275 research outputs found
The low frequency array and the transient and variable radio sky
No full textThis thesis addresses the topic of exploring and characterising the transient and variable radio sky, using both existing radio telescopes, and the next generation of radio facilities such as the Low Frequency Array (LOFAR). Studies of well known variable radio sources are presented in conjunction with blind searches of parameter space for unknown sources. Firstly, a three year campaign to monitor the low luminosity Active Galactic Nucleus NGC 7213 in the radio and X-ray bands is presented. Cross-correlation functions are used to calculate a global time lag between inflow (X-ray) and outflow (radio) events. Through this work the previously established scaling relationship between core radio and X-ray luminosities and black hole mass, known as the ‘fundamental plane of black hole activity’ is also explored with respect to NGC 7213. Secondly, the technical and algorithmic procedures to search for transient and variable radio sources within radio images is presented. These algorithms are intended for deployment on the LOFAR telescope, however, they are heavily tested in a blind survey using data obtained from the VLA archive. Through this work an upper limit on the rate of transient events on the sky at GHz frequencies is placed and compared with those found from other dedicated transient surveys. Finally, the design, operation and data reduction procedure for the Low Frequency Array, which will revolutionise our understanding of low frequency time domain astrophysics is explored. LOFAR commissioning observations are reduced and searched for transient and variable radio sources. The current quality of the calibration limits accurate variability studies, however, two unique LOFAR transient candidates that are not present in known radio source catalogues are explored (including multi-wavelength followup observations). In the conclusion to this thesis the parameter space that future radio telescopes may probe - including the potential rates of such events - is presented. At the nano-Jansky level up to 107 transients deg?2 yr?1 are predicted, which will form an unprecedented torrent of data, followup and unique physics to classif
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
6633 Tracing their steps: predictive mapping of Upper Palaeolithic and Mesolithic archaeology
No full textThe project attempted to produce a model capable of predicting the occurrence of early prehistoric land surfaces and remains, using the Middle Kennet Valley, Berkshire as a case study. Work targeted deep Late Upper Palaeolithic and Mesolithic floodplain and wetland edge archaeology and associated sedimentary sequences. The key aims were to contribute, in conjunction with a number of other Historic England projects, towards the further advancement and implementation of the National Heritage Protection Plan for wetland regions throughout England generally; to raise awareness of the finite and significant Late Upper Palaeolithic and Mesolithic archaeology of the Middle Kennet Valley specifically; and to provide guidance to West Berkshire Council in identifying appropriate mitigation measures in response to development proposals. In fulfilment of these aims, the project produced a comprehensive database of all known Upper Palaeolithic and Mesolithic archaeology, lithology and palaeoenvironmental data in the Study Area, and a general predictive sedimentary model arising from that database. The model was tested and refined by targeted field investigations and dating at Thatcham and Victoria Park, Newbury, alongside case studies at Ufton Bridge and geoarchaeological investigations at Wawcott. A development control leaflet was produced, providing guidance on methodologies and approaches, based on the results of the model
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
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