1,721,433 research outputs found
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
Criticality in models for fracture in disordered media
No full textIt has been recently noticed that heterogeneous media undergoing a fracturing process display a set of properties characteristic of systems at the critical state. In the present work we focus on the way in which the critical regime is reached. It is possible to define a branching ratio, for the breaking processes in the material, that represents the probability to trigger future breakdowns given an initial failure. This probability takes the value 1 when the system is critical thereby representing a measure of the distance of the system from the critical state. We show that, although the models considered in literature become really critical only in correspondence of the global failure, different dynamical rules may drive the system close to the critical state at different rates, such that the duration of the `quasi-critical' stage largely varies from model to model
Chronic treatment with MK-801 affects the behavioral response to both D1 and D2 dopamine agonist in the one-trial inhibitory avoidance
No full textCritical behaviour in the fracture of disordered media
No full textIn this paper we investigate the influence of different boundary conditions on the final breakdown of a lattice model for the fracture of heterogeneous media. Experimental evidence shows that disordered media subject to stress display some features that are characteristic of critical systems, therefore suggesting an interpretation of the global breakdown of the system as a kind of critical transition. Many of the observed features are well reproduced at least at a qualitative level by lattice models; however, mechanisms at the base of the onset of criticality are not well understood. Besides disorder, there are many parameters that seem to influence the critical properties of the system. The system size and the boundary conditions are among these. We find that the statistical properties of the final breakdown are strongly influenced by the boundary condition. In particular constant-stress relaxation leads to a final breakdown always involving the breaking of a finite number of bonds, which is also large if compared with the number of bonds broken during the formation of each localized crack preceding the final breakdown. When the lattice undergoes constant-strain relaxation instead, the breakdown may involve a vanishingly small number of bond-breaking events. © 1999 Taylor & Francis Group, LLC
Filter bubble effect in the multistate voter model
No full textSocial media influence online activity by recommending to users content strongly correlated with what they have preferred in the past. In this way, they constrain users within filter bubbles strongly limiting their exposure to new or alternative content. We investigate this type of dynamics by considering a multistate voter model where, with a given probability λ, a user interacts with "personalized information,"suggesting the opinion most frequently held in the past. By means of theoretical arguments and numerical simulations, we show the existence of a nontrivial transition between a region (for small λ) where a consensus is reached and a region (above a threshold λ c) where the system gets polarized and clusters of users with different opinions persist indefinitely. The threshold always vanishes for large system size N, showing that a consensus becomes impossible for a large number of users. This finding opens new questions about the side effects of the widespread use of personalized recommendation algorithms
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