1,721,269 research outputs found
Relic—Shock Connection in Abell 115
Full text linkGiant radio relics are arc-shaped diffuse sources with Mpc-scale found in the peripheries of some dynamically disturbed galaxy clusters. According to the leading scenario of relic formation, shock waves occurring in merger events amplify the local magnetic field and (re)accelerate particles. However, Mach numbers associated with merger shocks are typically low, and hence inefficient at accelerating particles from the thermal pool. We analyzed a deep Chandra observation (334 ks) to study the relic region in the cluster Abell 115. Temperature and surface brightness profiles taken across the relic both show a clear discontinuity, which is consistent with a shock. This result supports the relic–shock connection and represents a test case to study the origin of radio relics. In this particular case, we suggest that a re-acceleration scenario is more suitable. The relic morphology and position are consistent with a shock produced in an off-axis merger between clusters with different masses
AGN and starburst radio activity in the A3558 cluster complex
No full textWe present Very Large Array (VLA) 1.4 GHz (21 cm)
observations of the region between the centres of A3558 and A3562, in the major
cluster merger complex of the Shapley Concentration.
Our final catalogue includes a total of 174 radio sources above the
flux density limit of 0.25 mJy b-1. By cross-correlation with optical
and spectroscopic catalogues we found 33 optical counterparts
belonging to the Shapley Concentration.
We investigated the effects of cluster merger on the radio emission
properties of the galaxy population by means of the radio source
counts and the radio luminosity functions (RLF). We found that the radio
source counts are consistent with the field source counts.
The RLF of elliptical and S0 galaxies in the region surveyed,
is consistent with the “universal” RLF for early-type galaxies.
This result suggests that the deficit in radio galaxies found in our
previous work over the whole A3558 chain is entirely due to the
cluster A3558.
A population of faint radio
galaxies (log (W Hz-1) \la 22) is also found.
Half of these objects are also blue, suggesting that
starburst is the main mechanism driving the radio emission.
Finally, we detected 14 spiral radio galaxies, whose ratio between
radio and optical emission is similar to those found in galaxies located
in rich and dynamically evolved clusters.
Our results are briefly discussed in the light of the age and stage
of the merger in the A3558 cluster complex
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
Proprietà degli ammassi di galassie
Full text linkIn questa tesi di laurea triennale vengono esposte le conoscenze fondamentali che descrivono gli ammassi di galassie. I galaxy clusters sono strutture gravitazionalmente legate composte di galassie, gas denominato ICM (Intra Cluster Medium) e materia oscura. Queste 3 diverse componenti sono responsabili rispettivamente del 5%, 15% e 80% circa della massa totale dell’ammasso; per la maggior parte degli ammassi la massa totale è 10^{14-15} masse solari.
Nella prima parte della tesi si illustrano brevemente queste 3 componenti e le si inquadrano nelle diverse classificazioni morfologiche degli ammassi.
Nella seconda parte ho passato in rassegna alcune delle funzioni più importanti per descrivere un ammasso di galassie.
Nella terza ed ultima parte sono esposti i principali meccanismi grazie ai quali conosciamo gli ammassi di galassie
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