1,721,132 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
Formal characterization and efficient verification of a biological robustness property
No full textRobustness is an observable property for which a chemical reaction network (CRN) can maintain its functionalities despite the influence of different perturbations. In general, to verify whether a network is robust, it is necessary to consider all the possible parameter configurations. This is a process that can entail a massive computational effort. In the work of Rizk et al., the authors propose a definition of robustness in linear temporal logic (LTL) through which, on the basis of multiple numerical timed traces obtained by considering different parameter configurations, they verify the robustness of a reaction network. In this paper, we focus on a notion of initial concentration robustness (alpha -robustness), that is related to the influence of the perturbation of the initial concentration of one species (i.e., the input) on the concentration of another species (i.e., the output) at the steady state. We characterize this notion of robustness in the framework proposed by Rizk et al., and we show that, for monotonic reaction networks, this allows us to drastically reduce the number of traces necessary to verify robustness of the CRN
Encoding Boolean networks into reaction systems for investigating causal dependencies in gene regulation
No full textGene regulatory networks represent the interactions among genes regulating the activation of specific cell functionalities. They have been successfully modelled using Boolean networks, where a set of Boolean variables model the activation state of each gene, and Boolean functions model positive and negative influences among genes. Moreover, when the effect of such influences is additive, threshold Boolean networks, in which Boolean functions are replaced by simpler threshold functions, turned out to be particularly effective. In this paper we propose a systematic translation of threshold Boolean networks into Ehrenfeucht and Rozenberg's reaction systems. Our translation produces a non redundant set of reactions, each using a minimal set of objects. This translation allows us to simulate the behaviour of a general threshold Boolean network by simply executing the (closed) reaction system we obtain, and to investigate causality relations among genes by applying tools available for reaction systems. We implemented our translation in an open-source tool and applied it in two case studies: the gene regulation network of segment polarity in Drosophila melanogaster and the one controlling the differentiation of Th cells in the immune system. In both case studies, we investigate causalities among genes in the reaction system obtained from the translation by applying a tool for the computation of formula based predictors. In the context of the second case study, we show that also Boolean networks with non-additive influences and modelling genes with multiple expression levels can be dealt with by our approach
Intossicazione saturnina non professionale da consumo di vino inquinato da piombo. Contributo casistico.
No full textAnalysis and Verification of Robustness Properties in Becker-Döring Model
No full textMany biochemical processes in living cells involve clusters of particles. Such processes include protein aggregation and the development of intracellular concentration gradients. To study these mechanisms, we can apply coagulation-fragmentation models describing populations of interacting components. In this context, the Becker-Döring equations - theorized in 1935 - provide the simplest kinetic model to describe condensations phenomena. Experimental works on this model reveal that it exhibits robustness, defined as the system’s capability to preserve its features despite noise and fluctuations. Here, we verify the robustness of the BD model, applying our notions of initial concentration robustness (α -robustness and β -robustness), which are related to the influence of the perturbation of the initial concentration of one species (i.e., the input) on the concentration of another species (i.e., the output) at the steady state. Then, we conclude that a new definition of robustness, namely the asymptotic robustness, is necessary to describe more accurately the model’s behavior
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
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