1,720,988 research outputs found
The properties of post-novae
No full textThe impact of nova eruptions on the long-term evolution of Cataclysmic Variables (CVs) is one of the least understood and intensively discussed topics in the field. A decisive ingredient to improve this would be to establish a large sample of post-novae with known properties. Novae are objects that are well studied in the maximum stage, but after the eruption a significant amount of time on large telescopes is needed to study them, due to them mostly turning into very faint objects.
In order to obtain a significant sample of post-novae, Tappert et al. started a project to enlarge the sample since 2009, called “Life after eruption”. This thesis is the direct continuation of their project, which is based on observations both photometric and spectroscopically using a variety of telescopes located in Chile. The steps to recover post-novae consist of (i) identifying post-nova candidates in the field through color-color diagrams (ii) confirming them through their spectral characteristics and (iii) if possible, obtaining the orbital period through time-series data either photometrically or spectroscopically, with the ultimate goal to obtain a significant and reliable sample in order to update some general aspects of the post-nova population, such as the orbital period distribution and their spectral characteristics.
In this work, we present the spectroscopic confirmation for eleven post-novae. Collecting spec- troscopic parameters from the literature including these new data, we present an updated spectral study of the post-novae. With all data from the “Life after eruption” project the observational lack of objects that erupted more than 60 years ago is significant filled. The main result points to there being no correlation between the mass transfer rate and the time since eruption, in good agree- ment with previous studies. The interpretation that strong equivalent widths would be indicators of low-mass transfer rate is not entirely correct (e.g. Patterson 1984), because they appear to be indicators of inclination rather than of the mass transfer rate. A more conclusive result for the behavior of the mass transfer can only be obtained with a larger sample of novae erupted especially more than 100 years ago.
We also present an updated orbital period distribution of novae using the new orbital periods found here, identifying the false-claims ones in the literature and stated reasons why they are not reliable. We compare the observational data with a theoretical period distribution calculated using both an empirical and the classical recipe for angular momentum loss. We find that neither model reproduces the observed peak in the 3 – 4 h range, suggesting that the prescription for magnetic braking usually used in CV evolution above the period gap is not totally understood.CONICYT-PFCHA Doctorado Nacional 2017-2117109
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
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