1,720,976 research outputs found
High-Resolution Transmission Spectroscopy of Gas Giant Atmospheres
Get PDFThe discovery of exoplanets has revealed an intriguing class of planets unlike anything in the Solar System: ultra-hot Jupiters. These gas giants share similarities with Jupiter in size and in their hydrogen- and helium-dominated atmospheres, yet their proximity to their host stars results in vastly different atmospheric conditions. Intense stellar radiation heats them to temperatures exceeding 2000 K, allowing metals such as iron and titanium to exist in the gas phase rather than condensing out. Among these species, titanium oxide (TiO) is of particular interest, as it has long been hypothesised to drive thermal inversions—temperature increases with altitude—in highly irradiated atmospheres. This thesis investigates the atmospheric composition of the ultra-hot Jupiter WASP-189 b using high-resolution transmission spectroscopy, which probes a planet’s atmosphere by analysing starlight filtered through it during transit. A key result is the first unambiguous detection of TiO in the transmission spectrum of an ultra-hot Jupiter, confirmed through observations with multiple high-resolution spectrographs. Given the high signal-to-noise observations of the system, WASP-189 b serves as an ideal benchmark for atmospheric characterisation. This thesis also presents a wide chemical inventory of its optical transmission spectrum using both the cross-correlation technique and narrow-band spectroscopy, based on observations taken with HARPS, HARPS-N, ESPRESSO, and MAROON-X. Additionally, time-resolved absorption signals from these methods offer insights into the planet’s atmospheric variations over the course of the transit. Beyond ultra-hot Jupiters, this work explores the limitations of high-resolution transmission spectroscopy for warm Jupiters—gas giants on longer orbits where slower orbital velocities complicate atmospheric signal extraction. This analysis highlights the role of orbital configuration in the success of these techniques and identifies systems where observations remain feasible with current and future instruments. As exoplanet characterisation advances toward cooler planets in search of molecules such as carbon monoxide and water, overcoming these methodological challenges will be crucial for constraining elemental abundance ratios and linking atmospheric composition to planetary formation and migration histories
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
High-Resolution Transmission Spectroscopy of Gas Giant Atmospheres [Elektronisk resurs]
No full textThe discovery of exoplanets has revealed an intriguing class of planets unlike anything in the Solar System: ultra-hot Jupiters. These gas giants share similarities with Jupiter in size and in their hydrogen- and helium-dominated atmospheres, yet their proximity to their host stars results in vastly different atmospheric conditions. Intense stellar radiation heats them to temperatures exceeding 2000 K, allowing metals such as iron and titanium to exist in the gas phase rather than condensing out. Among these species, titanium oxide (TiO) is of particular interest, as it has long been hypothesised to drive thermal inversions—temperature increases with altitude—in highly irradiated atmospheres. This thesis investigates the atmospheric composition of the ultra-hot Jupiter WASP-189 b using high-resolution transmission spectroscopy, which probes a planet’s atmosphere by analysing starlight filtered through it during transit. A key result is the first unambiguous detection of TiO in the transmission spectrum of anultra-hot Jupiter, confirmed through observations with multiple high-resolution spectrographs. Given the high signal-to-noise observations of the system, WASP-189 b serves as an ideal benchmark for atmospheric characterisation. This thesis also presents a wide chemical inventory of its optical transmission spectrum using both the cross-correlation technique and narrow-band spectroscopy, based on observations taken with HARPS, HARPS-N, ESPRESSO, and MAROON-X. Additionally, time-resolved absorption signals from these methods offer insights into the planet’s atmospheric variations over the course of the transit. Beyond ultra-hot Jupiters, this work explores the limitations of high-resolution transmission spectroscopy for warm Jupiters—gas giants on longer orbits where slower orbital velocities complicate atmospheric signal extraction. This analysis highlights the role of orbital configuration in the success of these techniques and identifies systems where observations remain feasible with current and future instruments. As exoplanet characterisation advances toward cooler planets in search of molecules such as carbon monoxide and water, overcoming these methodological challenges will be crucial for constraining elemental abundance ratios and linking atmospheric composition to planetary formation and migration histories
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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