1,721,003 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
Effect of silver nanoparticles on marine organisms belonging to different trophic levels
No full textSilver nanoparticles (Ag-NPs) are increasingly used in a wide range of consumer products and such an extensive use raises questions about their safety and environmental toxicity. We investigated the potential toxicity of Ag-NPs in the marine ecosystem by analyzing the effects on several organisms belonging to different trophic levels. Algae (Dunaliella tertiolecta, Skeletonema costatum), cnidaria (Aurelia aurita jellyfish), crustaceans (Amphibalanus amphitrite and Artemia salina) and echinoderms (Paracentrotus lividus) were exposed to Ag-NPs and different end-points were evaluated: algal growth, ephyra jellyfish immobilization and frequency of pulsations, crustaceans mortality and swimming behavior, and sea urchin sperm motility. Results showed that all the end-points were able to underline a dose-dependent effect. Jellyfish were the most sensitive species, followed by barnacles, sea urchins, green algae, diatoms and brine shrimps. In conclusion, Ag-NPs exposure can influence different trophic levels within the marine ecosystem
Morpho-functional approach to neurotransmission and osmoregulation in Amphibalanus amphitrite cyprid (Cirripedia, Crustacea)
No full textAcorn barnacles are cirripedian crustacea with a sessile adult stage, that live in a calcareous shell attached to a submersed substrate and filter food with its limbs. Barnacles show various naupliar stages and a cyprid, the final lecithotrophic stage competent for settlement. Due to their ability to adhere, barnacles are important constituents of biofouling. To obtain biological data useful to develop antifouling strategies, many studies are focused on cyprid anatomy and neuroendocrinology, especially in Amphibalanus amphitrite due to its worldwide distribution. With our work we wanted to map the distribution of neurotransmitters in the cyprid to provide data for research on barnacle development, new antifouling strategies and the use of cyprid as a model organism in ecotoxicology. We focused on the distribution of neuroactive substances related to different systems: serotonergic, cholinergic, FMRFamidergic-like, GABAergic, glutamatergic and nitrergic. Also the functional aspects were investigated through physiological assessment, pointing out on swimming and settling activities. The cholinergic (our data) and the octopaminergic (from the literature) systems are known as potential target in antifouling strategies; moreover we suggest that serotonergic and GABAergic systems could be pharmacologically targeted as well, because they are widely present in the cyprid sensory and nervous structures. We are now focusing also on osmoregulative processes, attempting to characterize the presence and distribution of aquaporins, as they could be of interest in both antifouling strategies and ecotoxicology. To date, our data are consistent with the literature about ion-exchanging sites in the cyprid
Adverse effects of the SSRI antidepressant sertraline on early life stages of marine invertebrates
No full textWidespread contamination of coastal environments by emerging compounds includes low concentrations of pharmaceuticals. These pollutants are not currently incorporated in monitoring programs despite their effects on non-target organisms are very little documented. Among the selective serotonin reuptake inhibitor (SSRI) antidepressants, sertraline (SRT) is one of the most prescribed globally. In this work, earlier life stages of Amphibalanus amphitrite, Brachionus plicatilis and Mytilus galloprovincialis were exposed to environmental concentrations of SRT in order to study both sub-lethal and lethal responses in 24/48 h-tests. Low concentrations of SRT altered significantly swimming behavior in A. amphitrite and B. plicatilis giving 48 h-EC50 (μg/L) of 113.88 and 282.23, respectively whereas higher values were observed for mortality and immobilization. EC50 embryotoxicity with M. galloprovincialis was 206.80 μg/L. This work add new data about SRT ecotoxicity on marine invertebrates and confirms the applicability of behavioral endpoints to evaluate the environmental impact of antidepressants in marine organisms
Cellulose pyrolysis kinetic model: Detailed description of volatile species
Full text linkLignocellulosic biomass is typically composed by a major fraction of cellulose. Its decomposition influences on large extent the biomass rate of pyrolysis and product distribution, affecting process behaviour in thermochemical conversion processes. Containing approximately 90 % of volatile matter, volatile products from cellulose pyrolysis are very important in the characteristics of flames and ignition properties. Recent developments in analytical methods allowed a detailed identification of these volatile products, giving valuable information to process development and better understanding of kinetics. Predictions of a previous kinetic model are compared with these new findings, revealing large space for improvements. In this work, we propose a multi-step kinetic model of cellulose pyrolysis, incorporating the most recent experimental findings into the detailed product description. The model consists of four main reactions for the decomposition of cellulose, with formation of gases, volatiles, char and metaplastic species. The release of metaplastic species is described by a set of six reactions. The formation and release of 13 oxygenated hydrocarbons is predicted by the model, including anhydrosugars, furans, aldehydes, alcohols, ketones and carboxylic acids. The model also describes the formation of levoglucosan in metaplastic state before its release, explaining high heating rate mass loss behaviour. The model is compared with a large variety of experiments from literature, and validated for mass loss rates and product distribution, achieving overall good agreement despite experimental uncertainties and the large simplifications characteristic of the model formulation. Besides effectively quantifying the yields of gaseous, condensable and solid products, the model accurately captures the distribution of volatiles in terms of functional groups and Cchain length
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
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