1,721,086 research outputs found
A dust-parallax distance of 19 megaparsecs to the supermassive black hole in NGC 4151
No full textThe active galaxy NGC 4151 has a crucial role as one of only two active galactic nuclei for which black hole mass measurements based on emission line reverberation mapping can be calibrated against other dynamical techniques1, 2, 3. Unfortunately, effective calibration requires accurate knowledge of the distance to NGC 4151, which is not at present available4. Recently reported distances range from 4 to 29 megaparsecs5, 6, 7. Strong peculiar motions make a redshift-based distance very uncertain, and the geometry of the galaxy and its nucleus prohibit accurate measurements using other techniques. Here we report a dust-parallax distance to NGC 4151 of megaparsecs. The measurement is based on an adaptation of a geometric method that uses the emission line regions of active galaxies8. Because these regions are too small to be imaged with present technology, we use instead the ratio of the physical and angular sizes of the more extended hot-dust emission9 as determined from time delays10 and infrared interferometry11, 12, 13, 14. This distance leads to an approximately 1.4-fold increase in the dynamical black hole mass, implying a corresponding correction to emission line reverberation masses of black holes if they are calibrated against the two objects with additional dynamical masses
Identification of Sr in the spectrum of the kilonova AT2017gfo
No full textThe rapid (r) neutron capture process that creates half of all the elements heavier than iron was first postulated six decades ago. But the event or events in which the r-process creates the heavy elements is still not spectroscopically confirmed. Neutron star mergers are prime candidates for the main site of the r-process. The kilonova, AT2017gfo, emerging from the gravitational-wave–discovered neutron star merger, GW170817, was the first kilonova where detailed spectra were recorded. AT2017gfo was argued to have properties broadly consonant with this hypothesis, however, no robust spectroscopic identification of neutron-capture elements has thus far been made. We identify the neutron-capture element strontium in the spectra of AT2017gfo. This identification of a neutron-capture element associated with the collision of two extreme-density stars firmly establishes the origin of r-process elements
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Enhancing student research projects with new technologies
Get PDFA critical component in supervising thesis students is helping them maintain focus on the final outcome and continue working consistently for the full project duration. However, it can be difficult for a supervisor to gather concrete data on the progress of a student throughout the project period. Poor outcomes can occur in the middle part of the project as initial excitement flags, complexity grows and the supervisor is typically busy with other tasks. I report here on a test of a coupled set-up of an integrated rich text, code, and data application, a web-based version control system, and cloud-based team collaboration tool, designed to improve consistency of overview of the progress of thesis students. The tools may also increase the rapidity and quality of communication and help maintain consistent supervision and focus for the student over the full project period. I used Jupyter Notebooks, Github, and Slack respectively as a supervision tool with a Master’s student over a full year. Quantitative data from these tools are used to analyse how well the monitoring set up worked. The technical set up works well. There is an initial investment cost for the student to learn the various tools and from the supervisor in ensuring the student gets used to using them consistently and correctly. However, the overall benefits appear to be significant in terms of the supervisor’s overview of the student’s progress, leading to potentially greater consistency of supervision. Secondary effects were also positive, with significant development of transferable skills such as software coding ability and team-working. Modifications were made to improve the use of the set up for the following year and the initial data on a student in the next year are provided
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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