1,721,500 research outputs found
Giant planets: insights on their formation and internal structure
Full text linkThis thesis addresses two complementary aspects of exoplanetary science: the study of planetary interiors through Love numbers and observable tidal interactions, and the investigation of Giant Exoplanets around M dwarf Stars (GEMS). The work is based on three first-author publications that pursue different but synergetic approaches to the study of giant planets.
The internal structure of exoplanets is often challenging to constrain due to a degeneracy between their mass, radius, and interior structure. This degeneracy can be addressed using the second-order fluid Love number k2p, which provides crucial insights into the mass distribution within celestial bodies. I demonstrate how tidal effects, such as apsidal motion and orbital decay, can be detected by combining long baselines of transit timing variations and radial velocities. These observations enable precise derivation of k2p, offering information about planetary interiors and composition. I present the detection of apsidal motion in the WASP-19 system and the first determination of its planetary Love number, k2p = 0.20 (+0.02 / -0.03). I analyse the complexities of a second case study, WASP-43, marking the first simultaneous detection of both apsidal motion — with a rate of 0.1726 (+0.0082 / -0.0090) degrees per day — and orbital decay — with a rate of 1.86 ± 0.50 milliseconds per year — in an exoplanetary system. The thesis also explores how these tidal effects can be used to probe planetary composition and formation mechanisms, highlighting the potential of future missions like PLATO and JWST to refine these measurements.
Moreover, I explore the emerging population of GEMS, giant planets around low-mass stars. These planets challenge traditional models of planet formation, with core accretion and gravitational instability processes being less efficient in the smaller, cooler discs of M dwarfs. I present the discovery of TOI-6383Ab, a newly detected GEMS with a mass of 1.040 ± 0.094 times the mass of Jupiter and a radius of 1.008 (+0.036 / -0.033) times the radius of Jupiter. It orbits a 0.46 solar mass star in a stellar binary system with an orbital period of approximately 1.791 days. I discuss the implications for the formation and evolution of TOI-6383Ab in a low-mass stellar system, which supports a hybrid formation scenario, suggesting that giant planet formation around M dwarfs involves a complex interaction of disc characteristics and dynamics. My findings highlight the need for continued surveys to deepen our understanding of the diversity of planetary systems
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
Suche nach extrasolaren Planeten durch Beobachtungen von Transitzeitvariationen
No full textHomogene Beobachtung und Auswertung von Transitlichtkurven von sehr hoher Qualität kann zur Identifizierung von Transitzeitvariationen führen. Bei den boden-gebundenen Beobachtungen wurden nur Transitzeiten berücksichtigt, die in einer der an “Transit Timing Variations @ YETI” (TTV@YETI) beteiligten Sternwarten gewonnen wurden. Zusätzlich wurden Daten des NASA-Weltraumteleskops Kepler ausgewertet. Für den Transitplaneten TrES-2 wurden fünf Jahre Beobachtungen der Universitäts-Sternwarte Jena und von TTV@YETI zusammen mit sechs Beobachtungsquartalen von Kepler ausgewertet. Der lange Beobachtungszeitraum ermöglicht die sehr präzise Neubestimmung der Transitephemeriden. Für insgesamt 210 Transits von TrES-2 wurde die Zeit des Transitmittelpunkte bestimmt. Die Transitzeiten zeigen weder Variationen auf langen noch auf kurzen Zeitskalen. Die nahezu kontinuierlichen Beobachtungen von Kepler zeigen keine statistisch signifikante Zu- oder Abnahme der Systemparameter. Die Zusammenfassung von 84 Kepler-Lichtkurven erzielt ein Signal-Rausch-Verhältnis von 761. Die Modellierung mit einer analytischen Lichtkurve und linearer Randverdunklung zeigt eine Abweichung von der beobachteten Lichtkurve, während das quadratische Randverdunklungsgesetz die Beobachtungen gut wiedergibt. Die CCD-Kamera STK am 90/60 cm Teleskop der Universitäts-Sternwarte Jena ist durch ihr großes Gesichtsfeld ein exzellentes Gerät für die Beobachtung der Transits von WASP-14b. Zur Bestimmung der Systemparameter vom WASP-14 wurden fünf Transits zusammengefasst. Die Genauigkeit der Literaturwerte wurde erreicht. Anhand der Systemparameter wurden die physikalischen Eigenschaften des Systems berechnet. WASP-14b zeigt in Beobachtungen der Jahre 2009 und 2011 nach der Neubestimmung der Ephemeriden Hinweise auf sinusförmige Transitzeitvariationen. Dieses Signal konnte mit den neusten Beobachtungen Anfang 2012 nicht bestätigt werden
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