1,720,976 research outputs found
Avaliação da toxicidade de biocidas utilizados em tintas anti-incrustantes
Full text linkAs tintas á base de compostos orgânicos de estanho (COEs), como TBT (Tributilestanho) e TPT (Trifenilestanho), são altamente efetivas contra a bioincrustração. No entanto, devido aos efeitos danosos ao ambiente, em janeiro de 2008 estes compostos foram banidos das tintas anti-incrustantes. Deste modo, diferentes compostos orgânicos, como os herbicidas Irgarol 1051 e Diuron, estão sendo utilizados como biocidas principais das tintas ou como aditivos para potencializar os efeitos de outras substâncias presentes nas formulações. Apesar disso, não há registro de estudos utilizando espécies nativas da costa brasileira na avaliação da toxicidade de compostos anti-incrustantes. Portanto, o presente trabalho teve como objetivo investigar isoladamente a toxicidade dos principais biocidas utilizados como anti-incrustantes, tanto dos recentemente banidos TBT e TPT, quanto dos substitutos Irgarol 1051 e Diuron. Através de ensaios com diferentes espécies animais foram analisadas: (1) Toxicidade aguda em matriz aquosa (água do mar filtrada), utilizando os organismos costeiros Kalliapseudes shubartii, Acartia tonsa e Mysidopsis juniae; (2) Toxicidade crônica, através de ensaios de toxicidade com embriões do ouriço-do-mar Lytechinus variegatus e identificação de efeitos sobre os estágios embrio-larvais; e (3) Toxicidade aguda em sedimentos (fase sólida), utilizando o anfípodo escavador Tiburonella viscana. Os resultados dos ensaios em matrizes aquosas mostraram o mesmo padrão de toxicidade para todas as espécies estudadas sendo TBT > TPT > Irgarol 1051 > Diuron. Além disso, os organismos genuinamente de coluna d'água se mostraram altamente sensíveis ao TBT e TPT, com respectivos valores médios das CL50 - 48 h de 1,5 e 2,8 ug L-1 para A. tonsa , e CL50 - 96 h de 2,8 e 4,2 ugL-1 para M. juniae, que equivalem aos níveis já reportados para amostras ambientais de água. Já para o tanaidáceo bentônico K. shubartii as CL50 - 96 h foram de 23,5 ug L-1 para TBT e de 34,0 ugL-1 para TPT. Diferente dos observados nos ensaios com matrizes aquosas, em sedimentos o TPT foi mais tóxico para T. viscana que o TBT, com CL50 - 10 d de 1,2 e 1,7 ug g-1, respectivamente. Níveis de TBT nesta faixa de concentração já foram registrados em sedimentos da costa brasileira, o que sugere comprometimento ecológico dessas áreas.Já ensaios (agudos e crônicos) com Irgarol e Diuron indicaram que os níveis ambientais reportados, tanto em coluna d'água quanto em sedimentos, são inferiores aos que causaram toxicidade às espécies estudadas. Considerando a legislação ambiental brasileira, os ensaios crônicos mostraram que a concentração máxima de TBT apresentada pela resolução CONAMA 357/2005 é suficiente para inviabilizar o desenvolvimento embrionário de L. variegatus.Deste modo, destaca-se a importância de avaliar a toxicidade dos contaminantes sobre espécies nativas, como subsídios para a inclusão de limites seguros nas legislações ambientais. Em linhas gerais, as espécies utilizadas mostraram-se adequadas para avaliar a toxicidade dos compostos anti-incrustantes na costa brasileira.Organotins-based (OTs) antifouling paints, such as TBT (tributyltin) and TPT (triphenyltin),
are highly effective against most fouling organisms. However, use of OTs in antifouling paints
was worldwide banned in January 2008, in response to toxicity and harmful effects to aquatic
environment. Since the ban of OTs in antifouling paints, new organic compounds (i.e. Irgarol
1051 and Diuron) have been introduced in antifouling paint formulations, either as principal
or booster biocides. In Brazil, there are no studies evaluating the toxicity of both new and old
antifouling compounds to native species. Therefore, the aim of this work was to investigate
single toxicity of four of the most widely used antifouling biocides (TBT, TPT, Irgarol 1051
and Diuron). The toxic effects of these compounds were performed by using different
bioassays to assess the: (1) Acute toxicity (in filtered seawater) using the coastal marine
organisms Kalliapseudes schubartii, Acartia tonsa and Mysidopsis juniae; (2) Chronic toxicity
using Lytechinus variegatus embryo-larval bioassay and analysis of their early
developmental stages; and (3) Sediment toxicity using the burrowing amphipod Tiburonella
viscana. For the studied species, the toxicity pattern was: TBT> TPT> Irgarol 1051> Diuron.
The planktonic organisms were highly sensitive to OTs. The 48h-LC50 for A. tonsa was
estimated as 1.5 μg L-1 for TBT and 2.8 μg L-1 for TPT, while for M. juniae the 96h-LC50
values were 2.8 for TBT and 4.2 μg L-1 for TPT, which is in the same reported environmental
levels. However, the 96h-LC50 for K. schubartii was 23.5 μg L-1 for TBT and 34.0 μg L-1 for
TPT. In whole sediment toxicity tests, TPT was more toxic than TBT for T. viscana, showing
a 10 day-LC50 of 1.2 and 1.7 μg g-1, respectively. Since TBT concentrations at this level have
been reported for the Brazilian coastal sediments, the amphipod population of those sites
might be at risk. On contrary, toxicity tests (acute and chronic) with Irgarol and Diuron
indicated that levels reported for the environmental, both for water column and sediment, are
lower than those that caused toxicity. Nevertheless, the results of chronic toxicity bioassays
showed that TBT levels established by the Brazilian legislation (CONAMA 357/2005) are
sufficient to affect the embryonic development of L. variegatus. These results highlight the
importance of assessing the toxicity of contaminants on native species as a way to include
safe concentration to the environmental legislation. In general, the species used were
suitable to evaluate the toxicity of antifouling in environmental samples
Ecological Risk Assessment due to metal contamination in the South of the Estuarine Complex of Cananeia-Iguape
No full textO histórico de contaminação por metais no Vale do Rio Ribeira de Iguape é bem conhecido, com evidências de transporte destes contaminantes ao Complexo Estuarino Lagunar de Cananéia-Iguape (CELCI), adsorvidos ao material em suspensão. Assim, os metais podem alcançar o setor sul do CELCI, podendo acumular nos sedimentos e nos organismos filtradores. Neste estudo foi realizada uma avaliação de risco ecológico no CELCI associado à presença de metais oriundos das antigas áreas de mineração do Alto Ribeira, utilizando diferentes linhas de evidência. Os resultados foram avaliados de forma integrada, incluindo análises geoquímicas e biológicas (ensaios de toxicidade aguda, medidas de bioacumulação e biomarcadores bioquímicos em brânquias de bivalves). Os sedimentos apresentaram níveis moderados a altos de metais e toxicidade aguda, a qual foi associada, especialmente, com as concentrações de Cu, Pb e Zn. Da mesma forma estes metais foram encontrados em concentrações altas nos tecidos de bivalves. Os biomarcadores bioquímicos (MT, GSH, GST, GPx, GR, AChE, LPO e danos em DNA) indicaram a ocorrência de efeitos significativos nos bivalves. Portanto, os resultados mostram que os metais estão sendo carreados para a porção sul do estuário, causando bioacumulação e efeitos nos organismos aquáticos e, portanto, gerando riscos ecológicos para o CELCI.The historic of contamination by metals in the Valley of Ribeira de Iguape River is well known, and there are evidences that these chemicals are carried to the Estuarine Complex of Cananeia-Iguape (ECCI), adsorbed on the suspended particles. Metals can thus reach the south of the ECCI, where they may accumulate in the sediments and filter feeding organisms. This study aimed to evaluate the ecological risks associated to the metals originated from the former mining areas of the upstream Ribeira de Iguape River, by using different lines of evidence, which included geochemical and biological analysis (acute toxicity tests, bioaccumulation and biochemical biomarkers in bivalves\' gills). The sediments presented moderate to high levels of metals and acute toxicity, which was correlated with the concentrations of metals (Cu, Pb and Zn). These elements were found in high concentrations in the bivalves soft tissues. The biochemical biomarkers (MT, GSH, GST, GPx, GR, AChE, LPO, and DNA damage) indicated the occurrence of significant effects in the bivalves. Therefore, the results showed that metals are carried into the South portion of the estuary, accumulating in the biota and causing negative effects to the aquatic organisms, producing thus ecological risks to the ECCI
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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