1,721,312 research outputs found
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
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No full textThe Timewise Subtraction Pipeline produces mid-infrared difference photometry based on measurements by the WISE satelit
Search for High-Energy Neutrinos from TDE-like Flares with IceCube
Get PDFThe collected data of IceCube, a cubic kilometre neutrino detector array in
the Antarctic ice, reveal a diffuse flux of astrophysical neutrinos. The
extragalactic sources of the majority of these neutrinos however have yet to be
discovered. Tidal Disruption Events (TDEs), disruption outbursts from black
holes that accrete at an enhanced rate, are candidates for being the sources of
extragalactic, high-energy neutrinos. Stein et al. (2021) and Reusch et al.
(2022) have reported the coincidence of two likely TDEs from supermassive black
holes and public IceCube neutrino events (alerts). Further work by van Velzen
et al. (2021) identified a third event in coincidence with a high-energy
neutrino alert and a correlation between a broader set of similar
TDE-like flares and IceCube alerts. We conducted a stacking analysis with a
29-flare subset of the TDE-like flares tested by van Velzen et al. This work
was done with neutrinos with energies above GeV. The
resulting p-value of 0.45 is consistent with background. In this contribution,
I will discuss the results of the stacking analysis, as well as the impact of
using different reconstruction algorithms on the three correlated realtime
alerts.Comment: Presented at the 38th International Cosmic Ray Conference (ICRC2023).
See arXiv:2307.13047 for all IceCube contribution
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
Searching for High-Energy Neutrinos from Transient Sources with IceCube
No full textDas Ziel dieser Arbeit ist es, astrophysikalische Transienten als Neutrinoquellen zu untersuchen. Vorhergehender Arbeit zufolge sind sogenannte Akkretionsflares, mit >100 TeV Neutrinos korreliert, deren Messung IceCube in Echtzeit publiziert. Diese Ausbrüche zeichnen sich durch helle Infrarotemissionen aus, die als Staubechos bezeichnet werden. Zum ersten Mal wird diese Population mit dem gesamten IceCube Datensatz an Muonneutrinos analysiert. Das Ergebnis ist mit der Nullhypothese konsistent, und der Beitrag zum diffusen Neutrinofluss bei einem Spektralindex von 2.5 liegt unter 7.1%. Neutrinoproduktion durch die Wechselwirkung von Hadronen mit Röntgenphotonen ist ausgeschlossen und die Wechselwirkung mit optischen/UV Photonen ist benachteiligt. Hadronenwechselwirkung mit den Infrarotphotonen kann noch nicht ausgeschlossen werden, aber Modellparameter werden auf wenig optimistische Werte eingeschränkt. Es wurde auch eine verbesserte Methode zur Kalibrierung der Lokalisierungsunsicherheit für die hochenergetischen IceCube Neutrinos entwickelt, die auf durchgehende Myonenereignisse anwendbar ist, und zum ersten Mal auf für solche mit ungewöhnlichen Energiedepositionsmustern. Die Ergebnisse für die Neutrinos, die im Zusammenhang mit Akkretionsflares gemeldet wurden, zeigen, dass die entsprechenden Unsicherheitskonturen einer robusten Kalibrierung bedürfen. Um eine empfindlichere Suche nach Akkretionsflares mit hellen Staubechos zu ermöglichen, wird ein Katalog von staubechoähnlichen Helligkeitsausbrüchen zusammengestellt, der die Stichprobengröße im Vergleich zur vorherigen Analyse um den Faktor zehn erhöht. Es ist der erste, der eine genügende Anzahl an Beobachtungen bei höheren Rotverschiebungen liefert, um die Entwicklung der TDE Rate zu untersuchen. Zumindest für Massen von Schwarzen Löchern, die die Zerstörung eines sonnenähnlichen Sterns ermöglichen, stimmt das Ergebnis mit der Erwartung überein, die sich aus der Entwicklung der Anzahldichte von SMBHs ergibt.The goal of this thesis is to probe astrophysical transients as neutrino sources. Bright flares from enhanced accretion onto supermassive black holes (SMBHs) were reported to be correlated with IceCube's high-energy (>100 TeV) neutrino alerts. They are characterized by bright, transient infrared emission, called dust echos. For the first time, this work probes the general population of accretion flares using the full IceCube muon neutrino sample with a stacking analysis. The non-detection constrains their contribution to the diffuse neutrino flux to below around 7.1\% for a spectral index of 2.5. Neutrino production through interaction with X-ray photons from the accretion disk is excluded, and interaction with optical/UV photons is disfavoured. Although high-energy neutrino production through proton interaction with the infrared photons can still not be excluded, model parameters are constrained to below optimistic values. An improved method for calibration of the localization uncertainty for IceCube's high-energy neutrino alerts is also developed, applicable to through-going muon events, and for the first time also for events with unusual energy deposition patterns. Results for the neutrinos reported in coincidence with accretion flares indicate that the corresponding uncertainty contours need robust calibration. To enable a more sensitive search for neutrinos from accretion flares with bright dust echos, a catalog of dust-echo-like flares is compiled. This is the widest and deepest such catalog to date, increasing the sample size compared to the previous analysis by a factor of ten. Assuming the sample is dominated by TDEs, it is the first one to provide enough statistics at higher redshifts to probe the evolution of their rate. At least for black hole masses that enable the disruption of a solar mass star, the evolution is consistent with expectations from number density evolutions of SMBHs
timewise_sup
No full textThe Timewise Subtraction Pipeline produces mid-infrared difference photometry based on measurements by the WISE satelit
timewise_sup
No full textThe Timewise Subtraction Pipeline produces mid-infrared difference photometry based on measurements by the WISE satelit
timewise_sup
No full textThe Timewise Subtraction Pipeline produces mid-infrared difference photometry based on measurements by the WISE satelit
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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