1,720,962 research outputs found
Point configurations, phylogenetic trees, and dissimilarity vectors
Get PDFIn 2004 Pachter and Speyer introduced the higher dissimilarity maps for
phylogenetic trees and asked two important questions about their relation to
the tropical Grassmannian. Multiple authors, using independent methods,
answered affirmatively the first of these questions, showing that dissimilarity
vectors lie on the tropical Grassmannian, but the second question, whether the
set of dissimilarity vectors forms a tropical subvariety, remained opened. We
resolve this question by showing that the tropical balancing condition fails.
However, by replacing the definition of the dissimilarity map with a weighted
variant, we show that weighted dissimilarity vectors form a tropical subvariety
of the tropical Grassmannian in exactly the way that Pachter--Speyer
envisioned. Moreover, we provide a geometric interpretation in terms of
configurations of points on rational normal curves and construct a finite
tropical basis that yields an explicit characterization of weighted
dissimilarity vectors.Comment: Final version. To appear in Proceedings of the National Academy of
Sciences of the United States of America (PNAS
Determinantal Varieties From Point Configurations on Hypersurfaces
No full textWe consider the scheme parametrizing ordered points in projective space that lie on a common hypersurface of degree . We show that this scheme has a determinantal structure and we prove that it is irreducible, Cohen--Macaulay, and normal. Moreover, we give an algebraic and geometric description of the singular locus of in terms of Castelnuovo--Mumford regularity and -normality. This yields a characterization of the singular locus of and
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
Consequences of the compatibility of skein algebra and cluster algebra on surfaces
Get PDFWe investigate two algebra of curves on a topological surface with punctures
- the cluster algebra of surfaces defined by Fomin, Shapiro, and Thurston, and
the generalized skein algebra constructed by Roger and Yang. By establishing
their compatibility, we resolve Roger-Yang's conjecture on the deformation
quantization of the decorated Teichmuller space. We also obtain several
structural results on the cluster algebra of surfaces. The cluster algebra of a
positive genus surface is not finitely generated, and it differs from its upper
cluster algebra.Comment: 32 pages, a main result (Theorem C) has been strengthened. Comments
are welcome
- …
