1,721,033 research outputs found
Chemical evolution of elliptical galaxies I: supernovae and AGN feedback
Full text linkWe study the formation and evolution of elliptical galaxies and how they
suppress star formation and maintain it quenched. A one-zone chemical model
which follows in detail the time evolution of gas mass and its chemical
abundances during the active and passive evolution, is adopted. The model
includes both gas infall and outflow as well as detailed stellar
nucleosynthesis. Elliptical galaxies with different infall masses, following a
down-sizing in star formation scenario, are considered. In the chemical
evolution simulation we include a novel calculation of the feedback processes.
We include heating by stellar wind, core-collapse SNe, Type Ia SNe (usually not
highlighted in galaxy formation simulations) and AGN feedback. The AGN feedback
is a novelty in this kind of models and is computed by considering a
Bondi-Eddington limited accretion onto the central supermassive black hole. We
successfully reproduce several observational features, such as the
[/Fe] ratios increasing with galaxy mass, mass-metallicity, and relations. Moreover, we show that stellar
feedback and in particular Type Ia SNe, has a main role in maintaining quenched
the star formation after the occurrence of the main galactic wind, especially
in low-mass ellipticals. For larger systems, the contribution from AGN to
thermal energy of gas appears to be necessary. However, the effect of the AGN
on the development of the main galactic wind is negligible, unless an
unreasonable high AGN efficiency or an extremely low stellar feedback are
assumed. We emphasize the important role played by Type Ia SNe in the energy
budget of early-type galaxies
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
Fusione nucleare: l’energia delle stelle
No full textIntervengono
Leonida Antonio Gizzi, Istituto Nazionale di Ottica del CNR, sede di Pisa, associato INFN
Francesca Matteucci, docente di Astrofisica, Università di Trieste, accademico dei Lincei
Modera
Stefano Sandrelli, divulgatore e astrofisico, INAF-Osservatorio Astronomico di Brera
E = mc2, diceva Einstein. Ovvero: la materia si può trasformare in energia e viceversa. Ma se per produrre energia bastasse solo un po’ di materia, non avremmo risolto ogni possibile crisi energetica? In che modo si realizza questa trasformazione in Natura? E a che punto è arrivata la ricerca per riprodurre questo fenomeno in laboratorio? Cercheremo di capirne di più, dialogando con Francesca Matteucci, docente di astrofisica presso l’Università di Trieste e Leonida Gizzi, Direttore del Laboratorio Laser Intensi dell’Istituto Nazionale di Ottica del CNR di Pisa. E scopriremo che le risposte a queste domande non solo ci illuminano sul nostro futuro prossimo, ma anche sul nostro passato remoto e sulla nostra origine cosmica
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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