1,721,022 research outputs found
Relation between winds and jets in radio-loud AGN
No full textWe have investigated the relation between the two modes of outflow (wind and jet) in radio-loud active galactic nuclei (AGN). For this study we have carried out a systematic and homogeneous analysis of XMM-Newton spectra of a sample of 16 suitable radio-loud Seyfert-1 AGN. The ionised winds in these AGN are parameterised through high-resolution X-ray spectroscopy and photoionisation modelling. We discover a significant inverse correlation between the column density NH of the ionised wind and the radio-loudness parameter R of the jet. We explored different possible explanations for this NH-R relation and find that ionisation, inclination, and luminosity effects are unlikely to be responsible for the observed relation. We argue that the NH-R relation is rather a manifestation of the magnetic driving mechanism of the wind from the accretion disc. Change in the magnetic field configuration from toroidal to poloidal, powering either the wind or the jet mode of the outflow, is the most feasible explanation for the observed decline in the wind NH as the radio jet becomes stronger. Our findings provide evidence for a wind-jet bimodality in radio-loud AGN and shine new light on the link between these two modes of outflow. This has far-reaching consequences for the accretion disc structure and the wind ejection mechanism
Probing the nature and origin of dust in the reddened quasar IC 4329A with global modelling from X-ray to infrared
No full textCosmic dust is a key tracer of structure formation and evolution in the universe. In active galactic nuclei (AGN) the origin and role of dust are uncertain. Here, we have studied dust in the X-ray bright and reddened type-1 quasar IC 4329A, which exhibits an ionised AGN wind. We incorporated high-resolution X-ray and mid-IR spectroscopy, combined with broad-band continuum modelling, to investigate the properties of dust in this AGN. We used new chandra HETGS observations taken in June 2017, as well as archival data from XMM-Newton, Swift, HST, Spitzer, IRAS, and Herschel for our IR-optical-UV-X-ray modelling. Two distinct components of dust in IC 4329A are found. One component is in the interstellar medium (ISM) of the host galaxy, and the other is a nuclear component in the AGN torus and its associated wind. The emitting dust in the torus is evident in mid-IR emission (9.7 and 18 μm features), while dust in the wind is present through both reddening and X-ray absorption (O, Si, and Fe edge features). The gas depletion factors into dust for O, Si, and Fe are measured. We derive an intrinsic reddening E(B – V) ≈ 1.0, which is most consistent with a grey (flat) extinction law. The AGN wind consists of three ionisation components. From analysis of long-term changes in the wind, we determine limits on the location of the wind components. The two lowest ionisation components are likely carriers of dust from the AGN torus. We find that the dust in the nuclear component of IC 4329A is different from dust in the Milky Way. The dust grains in the AGN torus and wind are likely larger than the standard Galactic dust, and are in a porous composite form (containing amorphous silicate with iron and oxygen). This can be a consequence of grain coagulation in the dense nuclear environment of the AGN
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
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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