1,720,973 research outputs found
Analyzing Unusual Stars in Kepler
Get PDFThe Kepler field contains two distinct groups of cool evolved stars: the red giant branch (RGB) of shell hydrogen burning stars and the red clump (RC) of core helium burning stars Typically, RC stars are hotter than RGB stars and are restricted to a narrower range of intermediate luminosities. In this project, the focus is to look at unusually hot and unusually cool RGB stars, focusing on those with luminosities below the RC. I used spectroscopic data from APOGEE and Kepler asteroseismology to define the bottom edge of the red clump. Hot stars below this threshold were defined as unusually hot RGB stars. I also discovered an unusually cool RGB population. I followed this up with a systematic study of these unusual stars-- first seismically, and then further spectroscopically. We then further analyze the stellar oscillations of the hot star region by looking at their power spectra, theoretical correspondence, SIMBAD information, and seismic information to explain their behavior. The results from the hot star region correspond to a truly unusual population of stars, containing binaries, rapid rotators, and other rare types of stars.No embargoAcademic Major: Astronomy and Astrophysic
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
Analyse sismique des géantes rouges : une vision détaillée à grande échelle de la structure du coeur et de l'enveloppe
Get PDFRed giant stars correspond to one of the last evolutionary states in the life of solar-like stars. They undergo severe changes in their internal structure when they evolve. These changes remain poorly constrained due to the difficulty to model the internal structure of red giants, especially during the last stages. A recent way to observationally constrain the internal structure of the stars derives from the analysis of their pulsations. This method is called asteroseismology. During three years, I have used ultra-precise photometric data obtained by the Kepler satellite (NASA) which has observed 15000 red giants during more than four years (from 2009 to 2013). The study of these continuous and extremely precise light-curves allow the precise characterization of their stellar structure. The first study I have conducted corresponds to the characterization of the properties of the region of second helium ionization. The location of this region has been measured and different properties between the different evolutionary states of the stars were put into light. Secondly, I have created an automated method to measure a seismic parameter directly linked to the size of the stars radiative core. I applied this method on the 15000 red giants stars present in the Kepler public data. This study bring new informations on the way the stars climb the red giant branch and evolve towards later evolutionary states depending on their mass and metallicity. The results allowed me to reveal in several stars the signature of structure discontinuities in their radiative core.Les étoiles géantes rouges sont des objets correspondant à la fin de vie des étoiles de faible masse telles que le Soleil. Ces étoiles passent par différents stades évolutifs, caractérisés par une forte variation de leur structure interne, avant de mourir. La structure de ces objets reste peu connue à cause de la difficulté pour les modèles de la simuler. La seule façon de contraindre observationnellement l'intérieur des étoiles reste la méthode de la sismologie stellaire : l'étude des tremblements d'étoiles. Durant cette thèse, j'ai utilisé les données du satellite Kepler (NASA) qui a mesuré, très précisément, les variations de la photométrie de plus de 15 000 étoiles géantes rouges pendant 4 ans, de 2009 à 2013. L'étude de ces données extrêmement précises, permet d'en déduire les propriétés de la structure de l'étoile. La première étude menée durant cette thèse concerne la caractérisation des propriétés de la région de seconde ionisation de l'hélium. J'ai mesuré sa position et mis en évidence une différence de comportement entre les différents états évolutifs de l'étoile. La seconde partie de la thèse consiste en la création d'une méthode automatique de détermination de la taille du cœur radiatif de l'étoile. Cette méthode, appliquée sur les 15 000 étoiles géantes rouges observées par Kepler, permet de savoir à quel stade d'évolution en sont ces objets ainsi qu'apporter des contraintes observables pour les modèles stellaires. Enfin, j'ai pu mettre à jour dans plusieurs étoiles la signature de discontinuités de structure se situant dans le cœur de ces objets
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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