1,721,039 research outputs found
Search for dark galaxies through the ages
Full text linkThe work I have performed for this thesis covers a number of different areas of astronomy. My work on the LSBs is an in-depth exploration of the gas morphology and kinematics of these unusual objects. The focus is on the star forming abilities of the galaxy sample, but the HI observations also reveal a rich variety of gas morphology and motion, which are not necessarily apparent at other wavelengths. As well as being LSB, they are neutral gas-rich objects. As such they are more suited to being detected by HI surveys than by optical surveys. The Arecibo Galaxy Environment Survey (AGES) is a survey that expects to detect a large number of this type of galaxy and a large proportion of the thesis has been dedicated to my involvement with the survey. This has included designing and implementing the observing strategy, testing the data reduction pipeline, producing the final data, testing their quality and examining the efficiency of the survey detection methods. I have demonstrated some uses the AGES data can be put to from discovering hitherto undetected galaxies, through measuring the cosmic distribution of neutral hydrogen, to evaluating the cosmic significance of dark galaxies. The last point forms the central theme throughout the thesis. Of the 69 detections made by AGES in the first two datacubes, 55 do not have previous Hi measurements and 26 are previously uncatalogued. An Hi mass function (HIMF) was produced from the first galaxies detected by AGES. The best fit line to the data was a Schechter function with the parameters: a = -1.28 0.17, = 0.0076 0.0027 and M* = 7.7 1.8 x 109 M0. Using the HIMF the calculated value for the space density of neutral hydrogen was found to be pni = 7.5q3 x 107MQ Mpc-3, which is consistent with previous measurements. The overall contribution of HI to the Universal energy density was calculated from this value and found to be Qhi = 4.1 J x 10-4, confirming previous measurements of this value. Assuming the two candidates are indeed optically dark, based on this value the contribution of dark galaxies was calculated to be 4% to their respective mass bins, and less than 0.5% overall. The number density was found to be ndark 6.6 x 10-4 Mpc-3. Hence it would appear that dark galaxies are not numerous enough nor of substantial mass to be able to account for the 'missing mass' or to be able to fully represent the high number of dark matter haloes produced by CDM simulations.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Search for dark galaxies through the ages
Full text linkThe work I have performed for this thesis covers a number of different areas of astronomy. My work on the LSBs is an in-depth exploration of the gas morphology and kinematics of these unusual objects. The focus is on the star forming abilities of the galaxy sample, but the HI observations also reveal a rich variety of gas morphology and motion, which are not necessarily apparent at other wavelengths. As well as being LSB, they are neutral gas-rich objects. As such they are more suited to being detected by HI surveys than by optical surveys. The Arecibo Galaxy Environment Survey (AGES) is a survey that expects to detect a large number of this type of galaxy and a large proportion of the thesis has been dedicated to my involvement with the survey. This has included designing and implementing the observing strategy, testing the data reduction pipeline, producing the final data, testing their quality and examining the efficiency of the survey detection methods. I have demonstrated some uses the AGES data can be put to from discovering hitherto undetected galaxies, through measuring the cosmic distribution of neutral hydrogen, to evaluating the cosmic significance of dark galaxies. The last point forms the central theme throughout the thesis. Of the 69 detections made by AGES in the first two datacubes, 55 do not have previous Hi measurements and 26 are previously uncatalogued. An Hi mass function (HIMF) was produced from the first galaxies detected by AGES. The best fit line to the data was a Schechter function with the parameters: a = -1.28 0.17, = 0.0076 0.0027 and M* = 7.7 1.8 x 109 M0. Using the HIMF the calculated value for the space density of neutral hydrogen was found to be pni = 7.5q3 x 107MQ Mpc-3, which is consistent with previous measurements. The overall contribution of HI to the Universal energy density was calculated from this value and found to be Qhi = 4.1 J x 10-4, confirming previous measurements of this value. Assuming the two candidates are indeed optically dark, based on this value the contribution of dark galaxies was calculated to be 4% to their respective mass bins, and less than 0.5% overall. The number density was found to be ndark 6.6 x 10-4 Mpc-3. Hence it would appear that dark galaxies are not numerous enough nor of substantial mass to be able to account for the 'missing mass' or to be able to fully represent the high number of dark matter haloes produced by CDM simulations
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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