1,721,098 research outputs found
Limitations on shapelet-based weak-lensing measurements
No full textAims: We seek to understand the impact on shape estimators obtained from circular and elliptical shapelet models under two realistic conditions: (a) only a limited number of shapelet modes are available for the model, and (b) the intrinsic galactic shapes are not restricted to shapelet models.
Methods: We create a set of simplistic simulations, in which the galactic shapes follow a Sérsic profile. By varying the Sérsic index and applied shear, we quantify the amount of bias on shear estimates that arises from insufficient modeling. Additional complications from PSF convolution, pixelation, and pixel noise are also discussed.
Results: Highly elliptical galaxy shapes cannot be accurately modeled within the circular shapelet basis system and are biased towards less elongated shapes. This problem can be cured by allowing elliptical basis functions. Another problem occurs for galaxies whose radial profile differs strongly from the Gaussian weighting function employed in both the circular and the elliptical shapelet bases. For galaxies with large Sérsic indices, shear estimates from circular shapelets are biased low even for small apparent ellipticities because of the preference for round models, and shear estimates from elliptical shapelets depend critically on accurate ellipticity priors. Independent of the particular form of the estimator, the bias depends on the true intrinsic galaxy morphology, but also on the size and shape of the PSF.
Conclusions: As long as the issues discussed here are not solved, we question that the shapelet method can provide weak-lensing measurements for all observable galaxies (independent of their Sérsic index) with an accuracy demanded by upcoming missions and surveys. An accurate and reliable calibration, specific for the dataset under investigation, would be required but is difficult to infer consistently from the data
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
A comparison of structure formation in minimally and non-minimally coupled quintessence models
Full text linkWe study structure formation in non-minimally coupled dark energy models, where there is a coupling in the Lagrangian between a quintessence scalar field and gravity via the Ricci scalar. We consider models with a range of different non-minimal coupling strengths and compare these to minimally coupled quintessence models with time-dependent dark energy densities. The equations of state of the latter are tuned to either reproduce the equation of state of the non-minimally coupled models or their background history. Thereby they provide a reference to study the unique imprints of coupling on structure formation. We show that the coupling between gravity and the scalar field, which effectively results in a time-varying gravitational constant G, is not negligible and its effect can be distinguished from a minimally coupled model. We extend previous work on this subject by showing that major differences appear in the determination of the mass function at high masses, where we observe differences of the order of 40 per cent at z = 0. Our new results concern effects on the non-linear matter power spectrum and on the lensing signal (differences of ≈10 per cent for both quantities), where we find that non-minimally coupled models could be distinguished from minimally coupled ones
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
- …
