1,720,959 research outputs found
Effetti embriotossici del pesticida carbaryl mediante il Frog Embryo Teratogenesis Assay-Xenopus (FETAX)
No full textToxicity of tire debris leachates
No full textData on the indicators of environmental impact of tire debris, originated from the tire abrasion on roads, are extremely scarce, while it is well known that tires may produce deleterious effects. Tire debris contains significant quantities of zinc (Zn) which may be released by tire rubber. We have used tire particles (TD) produced in laboratory from new rubber. Two sets of experiments were set up to obtain eluates. One set used 50 and 100 g/L TD to produce eluates at pH 3-7. The Zn quantity was measured with a Inductively Coupled Plasma-Atomic Emission Spectrometry. The eluates at 1%,10%,50%,100% concentrations in culture media were tested on Raphidocelis subeapitata, Daphnia magna and Xenopus laevis embryos (FETAX test). The other set of experiments was performed putting 250 mg/L TD in a column with glass beads to control particle dispersion during the elution process. We demonstrate that factors such as pH, size and particles aggregation deeply influence the elution process, that the amount of Zn leached from particles is related to their aggregation rather than their quantity. These results, even though do not reflect the real environmental toxicity of the leachates, can be successfully used for comparative purposes allowing an initial assessment of the potential effect of tire derived particles
Axial-skeletal defects caused by Carbaryl in Xenopus laevis embryos
No full textEmbryotoxic effects of Carbaryl (CB), a widely used carbamate insecticide, was evaluated by modified Frog Embryo Teratogenesis Assay-Xenopus (FETAX), coupled with a histopathological screening of the survived larvae. X. laevis embryos were exposed to 1, 2, 4, 8, 16 and 24 mg/L CB from stage 8 to stage 47. From an estimated LC50 of 20.28 mg/L and TC50 of 8.43 mg/L a TI of 2.41 was derived, indicating that CB is to be considered teratogenic for X. laevis embryos. The most characteristic terata, classified as abnormal tail flexure, involved a significant percentage of larvae from 1 mg/L CB onward, reaching 100% at 24 mg/L CB. Histopathological screening revealed tail musculature and notochord as the main targets for CB. Skeletal muscle lesions consisted of myotomes reduced in size, showing myocytes with disorganized contractile systems and irregular myosepta, coupled with disarranged myocyte apexes. Notochords from CB exposed larvae appeared wavy or bent, with irregular connective sheaths and histologically characterized by protrusions of fibrous matrix and inclusions of ectopic cell masses. This axial–skeletal damage was hypothesized to be related both to the inhibition of acetylcholinesterase, with consequent muscular tetanic spasms, and to disorders in the organization of the connective tissue matrix surrounding the notochord
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
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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