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Deciphering the gamma-ray sky
Get PDFThis thesis presents a novel spatial likelihood analysis for Imaging Atmospheric Cherenkov Telescopes (IACTs) and its use to analyse observations of the gamma-Cygni supernova remnant (SNR) with the MAGIC telescopes, a system of two IACTs. SNRs are the prime candidate source for the origin of the galactic component of cosmic rays (CRs).
These objects are sufficiently extended to be resolved with gamma-ray telescopes. This allows the determination of different acceleration regions of a source, but poses issues for the current analysis approach for IACT data. IACTs detect the Cherenkov light generated in air showers, which are cascades of energetic particle that result from the interaction of gamma-rays with the molecules in the atmosphere. Currently, the emission from a source is determined using the aperture photometry approach, in which the number of gamma-ray events from the source region is compared against a source-free background control region. In the case of superimposed emission regions, an event count cannot be attributed to one emission region. Furthermore, extended objects or objects of complex morphology make the definition of the source region a difficult task.
These issues can be overcome by a spatial likelihood analysis of the skymaps of IACTs. In this approach, a user-defined source template is convolved with the instrument response functions (IRFs) and the "realistic" model fitted to the event count maps via a Poissonian likelihood fit. The data analyses of space-based gamma-ray telescopes, such as the Fermi Large Area Telescope (LAT), are based on this technique. For IACTs the determination of the IRFs, however, is a challenging task: because the atmosphere is part of the detector, the IRFs cannot be measured in the laboratory but need to be computed from Monte-Carlo events for each observation individually. This thesis presents SkyPrism, a software package performing such an analysis on MAGIC data including the accurate determination of the IRFs.
Using SkyPrism it was possible to analyse observations of the ~7000 year old gamma-Cygni SNR taken with MAGIC between 2015 and 2017. CRs are accelerated and confined in the shock region by magnetic turbulences ahead and behind the shock, making the level of turbulence an important ingredient of the acceleration process. Only a small high energetic fraction of CRs may escape the fast shocks of young SNRs (10000 years) almost all CRs have already escaped. I studied the escape of CRs from the shock into the interstellar medium using 85 hours of MAGIC data and 9 years Fermi-LAT data covering the energy range from 5 GeV to 5TeV. Using the theoretical model of the diffusive shock acceleration, I determined that the maximum energy of the CRs confined in the shock region decreases faster with the lifetime of the SNR than expected and that the level of turbulence is not constant over the lifetime of the SNR.Diese Dissertation befasst sich mit der Entwicklung einer Likelihood basierten Analyse für Daten von abbildenden Luft Cherenkov Teleskopen (IACTs) und deren Anwendung auf Beobachtungen des gamma-Cygni Supernova Überrestes mit den MAGIC Teleskopen, einem System von zwei IACTs. Nach heutigem Wissensstand wird der galaktische Anteil der kosmischen Strahlung (CR), relativistischer Teilchen, welche hochenergetische Gammastrahlung erzeugen, hauptsächlich in den Schockwellen der Überreste von Supernovae (SNR) beschleunigt.
Diese Objekte sind ausgedehnt genug, sodass sie sich auch mit Gammastrahlen Teleskopen auflösen lassen. Dies ermöglicht einerseits eine genauere Untersuchung der verschiedenen Beschleunigungsregionen innerhalb des Objekts, stellt andererseits jedoch eine Herausforderung für die aktuellen Analysemethoden von IACTs dar. IACTs detektieren das Cherenkov Licht von Luftschauern, Teilchenkaskaden, die aus der Wechselwirkung von Gammastrahlung mit Luftmolekülen resultieren. Aktuell wird die Intensität einer Quelle aus den Daten von IACTs mittels der Apertur-Photometrie ermittelt. Dazu wird die Anzahl der detektierten Gammastrahlen-Ereignisse aus einem Gebiet um die Quelle mit der Anzahl an Ereignissen aus einem gleichgroßen Kontrollbereich ohne Quelle ermittelt. Überlagern sich jedoch Emissionsregionen, so lässt sich nicht bestimmen, zu welcher Region ein Ereignis zählt. Sehr ausgedehnte Quellen oder Objekte mit komplexer Morphologie stellen zudem ein Problem hinsichtlich der Wahl der Quellregion dar.
Durch eine räumliche Likelihood Analyse auf der Basis von Himmelskarten von IACTs lassen sich die Schwierigkeiten vermeiden. Dabei wird eine benutzerdefinierte Morphologie mit der Instrumentenantwort (IRF) gefaltet und dieses "realistische" Quellmodel mittels eines Poisson-Likelihood Fits an die Messdaten angepasst. Bei satellitengestützten Gamma-Teleskopen wie dem Fermi Large Area Telescope (LAT), wird diese Methode bereits angewandt. Die Schwierigkeit für IACTs ist die Bestimmung der IRF. Da die Atmosphäre ein Bestandteil des IACTs ist, kann die IRF nicht vorab im Labor ermittelt werden, sondern muss mit Hilfe von Monte-Carlo Simulationen für jede Beobachtung individuell bestimmt werden. Diese Arbeit präsentiert das Software Paket SkyPrism, das eine solche Analyse inklusive der Bestimmung der IRFs, für die MAGIC Teleskope durchführt.
Mit Hilfe von SkyPrism konnten MAGIC Beobachtungsdaten von dem ca. 7000 Jahren alten gamma-Cygni SNR analysiert werden. Während des Beschleunigungsvorgangs in SNR Schockwellen streut die CR an magnetischen Turbulenzen vor und hinter dem Schock, wodurch der Grad der Turbulenzen ein wichtiger Bestandteil des Beschleunigungsvorgangs wird. Aus den schnellen Schockwellen von jüngeren SNR (10000 Jahre) bereits nahezu die gesamte CR der Schockwelle entkommen ist und keine Beschleunigung mehr stattfindet. Die Beobachtungen mit den MAGIC Teleskopen (85 Stunden Beobachtungszeit) und dem Fermi-LAT (9 Jahre Daten) über einen Energiebereich von 5 GeV bis 5 TeV ermöglichten zum ersten Mal eine Untersuchung, wie die CR der Schockwelle eines SNR ins interstellare Medium entkommt. Mittels eines theoretischen Models für die Schockbeschleunigung konnte ermittelt werden, dass die maximale Energie, zu der die CR beschleunigt und im Schockbereich gehalten werden kann, schneller mit der Lebensdauer des SNR abnimmt als erwartet und der Grad an Turbulenzen über die Lebensdauer des SNR nicht konstant sein kann
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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