1,720,972 research outputs found
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
Dynamic scaling in natural swarms
Get PDFCollective behaviour in biological systems presents theoretical challenges beyond the borders of classical statistical physics. The lack of concepts such as scaling and renormalization is particularly problematic, as it forces us to negotiate details whose relevance is often hard to assess. In an attempt to improve this situation, we present here experimental evidence of the emergence of dynamic scaling laws in natural swarms of midges. We find that spatio-temporal correlation functions in different swarms can be rescaled by using a single characteristic time, which grows with the correlation length with a dynamical critical exponent z ≈ 1, a value not found in any other standard statistical model. To check whether out-of-equilibrium effects may be responsible for this anomalous exponent, we run simulations of the simplest model of self-propelled particles and find z ≈ 2, suggesting that natural swarms belong to a novel dynamic universality class. This conclusion is strengthened by experimental evidence of the presence of non-dissipative modes in the relaxation, indicating that previously overlooked inertial effects are needed to describe swarm dynamics. The absence of a purely dissipative regime suggests that natural swarms undergo a near-critical censorship of hydrodynamics.Fil: Cavagna, Andrea. Consiglio Nazionale delle Ricerche; ItaliaFil: Conti, Daniele. Università degli studi di Roma "La Sapienza"; ItaliaFil: Creato, Chiara. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma "La Sapienza"; ItaliaFil: Del Castello, Lorenzo. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma "La Sapienza"; ItaliaFil: Giardina, Irene. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma "La Sapienza"; Italia. INFN; ItaliaFil: Grigera, Tomas Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Melillo, Stefania. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma "La Sapienza"; ItaliaFil: Parisi, Leonardo. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma "La Sapienza"; ItaliaFil: Viale, Massimiliano. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma "La Sapienza"; Itali
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
Pathways of glomerular toxicity of cyclosporine-A: An "in vitro" study.
No full textBackground/Aims. Knowledge of renal toxicity of cyclosporine-A (CyA) is clouded by multiple effects on different glomerular and tubular cells and on kidney and systemic hemodynamics. To focus on glomerular action of CyA we used glomeruli isolated in vitro, with the aim of dissecting the effects on recruitment of glomerular vasoconstricting systems, like endothelin-1 (ET) and angiotensins (AI and AII). Methods. We studied the pathways of CyA damage on pig glomeruli isolated in vitro with the technique of sieving through mesh filters of different sizes, and incubated in an appropriate culture medium. The supernatant was sampled at different time intervals to measure ET, AI and All concentrations upon addition of ET 10(-12) or CyA 4(.)10(-7) M, with or without either selective endothelin receptor A (ETA) or B (ETB), or unselective ETA-ETB receptor inhibitors. Results. CyA increased ET concentration (from 9.7 +/- 0.3 to 11.4 +/- 0.4 pg(.)ml(-1), p < 0.002), and the added ET released AI in the medium (from 26.6 +/- 4.7 to 39.1 +/- 4.6 pg(.)ml(-1), p < 0.05) when ETB receptors were blocked. In contrast, CyA stimulated angiotensins release independent of ET receptors blockade, hence, irrespective of ET concentration in the medium, from 26.6 +/- 4.7 to 38.0 +/- 2.1 pg(.)ml(-1) for AI, p < 0.05, and from 12.3 +/- 1.0 to 14.8 +/- 0.9 pg(.)ml(-1) for AII, p < 0.05. Conclusion. CyA releases ET and angiotensins independently by a direct action. Glomerular CyA toxicity might be mediated by recruitment of vasoconstricting peptides and modulated by relative ETA and ETB receptor occupancy
Short-range interactions versus long-range correlations in bird flocks
No full textBird flocks are a paradigmatic example of collective motion. One of the prominent traits of flocking is the presence of long range velocity correlations between individuals, which allow them to influence each other over the large scales, keeping a high level of group coordination. A crucial question is to understand what is the mutual interaction between birds generating such nontrivial correlations. Here we use the maximum entropy (ME) approach to infer from experimental data of natural flocks the effective interactions between individuals. Compared to previous studies, we make a significant step forward as we retrieve the full functional dependence of the interaction on distance, and find that it decays exponentially over a range of a few individuals. The fact that ME gives a short-range interaction even though its experimental input is the long-range correlation function, shows that the method is able to discriminate the relevant information encoded in such correlations and single out a minimal number of effective parameters. Finally, we show how the method can be used to capture the degree of anisotropy of mutual interactions
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