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Gravity science in the Saturnian system: the masses of Phoebe, Iapetus, Dione and Enceladus
No full textMass and interior of Enceladus from Cassini data analysis
No full textGravity results are available from radio Doppler data acquired by the Deep Space Network during the encounter of the Cassini spacecraft with Enceladus in February 2005. We report the mass of Enceladus to be (1.0798±0.0016)× 10^20 kg, which implies a density of 1608.9±4kg*m^−3. For a core made of hydrated silicates with a density of 2500kg*m^−3 the core radius is about 190 km and the quadrupole moment C22 = 1.4×10^−3. If Enceladus is in hydrostatic equilibrium, the larger than previously anticipated density implies that the recently proposed secondary spin–orbit resonance cannot be present. Therefore, the source of endogenic activity of Enceladus remains unexplained
A non-hydrostatic rhea
Get PDFRadiometric data obtained during Cassini's close flyby of Rhea, on 26 November 2005, has been subject to several published analyses aiming to determine the satellite's mass and quadrupole gravity moments. Combining aspects of two of these analyses we present our best, unbiased estimates of the gravity field parameters and point out how the constraint of hydrostatic equilibrium adopted by previous analysts affects the results. We present solutions based on a broad range of geophysical assumptions, such as the presence of degree 3 and 4 gravity field constrained at different levels. The result is a balanced approach which describes our current knowledge of Rhea's gravity field. In the case of a gravity field limited to second degree harmonics the most reliable estimates are GM = 153.9398 +/- 0.0008 km(3) s(-2), 10(6) J(2) = 931.0 +/- 12.0, 10(6) C(22) = 237.2 +/- 4.5, and 10(6) S(22) = 3.8 +/- 3.8
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
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