1,721,144 research outputs found
Multi-frequency long-term monitoring of the ultracool dwarf TVLM 513-46546
No full textAbstract. Recently, observations of three ultracool dwarfs have shown that the emission is in fact due to the electron cyclotron maser instability operating in the low plasma density, high magnetic field strength regions above the poles of a large-scale magnetic field, i.e. it is similar to that of the magnetized planets in the Solar system. The M8.5 dwarf TVLM 513-46546 is one of the most studied radio emitting dwarfs. It has been found to display periodic pulses of 100% circularly polarized radio emission, the periodicity of the bursts being consistent with the rotational period of the dwarf as confirmed by optical I band observations . Here we present a systematic review and analysis of all observations of TVLM 513-46546 conducted in the radio X and C bands, including our latest VLA and Arecibo observations. Key words: pulsars: general -radiation mechanisms: non-thermal -radio continuum: stars -stars: activity -stars: low-mass, brown dwarfs -stars: magnetic fields Дългосрочни наблюдения на ултра-хладната звезда-джудже TVLM 513-46546 в няколко честоти Антоанета Антонова, Джон Джерард Дойл, Грег Халинан, Аарон Голден, Стивън Бърк Неотдавна, радио наблюдения на три ултра-хладни джуджета показаха, че радиоиз-лъчването всъщност се дължи на механизма електронен циклотронен мазер, опериращ в районите с висок интензитет на магнитното поле и ниска плазмена плътност, намира-щи се над полюсите на глобално магнитно поле, т.е. подобно на излъчването от магне-тизираните планети от Слънчевата система. Звездата TVLM 513-46546, джужде от спектрален клас М8.5, е еднин от най-изследваните ултра-хладни обекти, активни в радиодиапазона. Неговото излъчване се характеризира с периодични, 100% кръгово поляризирани пулсации. Периодът на пуслациите е съвместим с периода на околоосно въртене на джуджето, което бе потвърдено чрез наблюдения в оптичният филтър I. Тук ние представяме систематичен обзор и анализ на всички радионаблюдения на TVLM 513-46546, включително нашите последни наблюдения с радиотелескопите VLA и Arecibo
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
Rotational modulation of the radio emission from the m9 dwarf tvlm 513−46546: broadband coherent emission at the substellar boundary?
No full textThe Very Large Array was used to observe the ultracool rapidly rotating M9 dwarf TVLM 513-46546 simultaneously at 4.88 and 8.44 GHz. The radio emission was determined to be persistent, variable, and periodic at both frequencies with a period of similar to 2 hr. This periodicity is in excellent agreement with the estimated period of rotation of the dwarf based on its v sin i of similar to 60 km s(-1). This rotational modulation places strong constraints on the source size of the radio-emitting region and hence the brightness temperature of the associated emission. We find the resulting high brightness temperature, together with the inherent directivity of the rotationally modulated component of the emission, difficult to reconcile with incoherent gyrosynchrotron radiation. We conclude that a more likely source is coherent, electron cyclotron maser emission from the low-density regions above the magnetic poles. This model requires the magnetic field of TVLM 513-46546 to take the form of a large-scale, stable dipole or multipole with surface field strengths up to at least 3 kG. We discuss a mechanism by which broadband, persistent electron cyclotron maser emission can be sustained in the low-density regions of the magnetospheres of ultracool dwarfs. A second nonvarying, unpolarized component of the emission may be due to depolarization of the coherent electron cyclotron maser emission or, alternatively, incoherent gyrosynchrotron or synchrotron radiation from a population of electrons trapped in the large-scale magnetic field
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