1,720,955 research outputs found
Avaliação dos efeitos adversos da exposição ao agrotóxico metomil nos estágios iniciais de desenvolvimento do zebrafish (Danio rerio)
Get PDFOs agrotóxicos são definidos primariamente como substâncias químicas, físicas ou biológicas, que atuam no controle de organismos vivos considerados prejudiciais à agricultura, aos animais domésticos e ao próprio ser humano, e estão cada vez mais presentes no nosso cotidiano, sob diversas apresentações. Atualmente, o Brasil é um dos maiores produtores e exportadores de alimentos do mundo e (consequentemente) é o maior consumidor de agrotóxicos mundialmente. O manejo agrícola para a produção em massa de alimentos, inclui o uso dessas sustâncias, aumentando a preocupação com os riscos ambientais que esses produtos podem trazer para os recursos naturais e para biota, que podem vir a se contaminar com esses xenobióticos. Nesse sentido, o uso de organismos-modelo para avaliar os riscos in vivo é essencial e principal característica da ecotoxicologia. Neste trabalho foram investigados os efeitos letais e subletais da exposição aguda ao inseticida carbamato metomil em formulação comercial, utilizando embriões e larvas de zebrafish como organismomodelo. Inicialmente determinou-se a CL50 em 96h, e partir desta, as faixas de concentrações subletais de exposição.Na exposição subletal, foram analisados parâmetros de sobrevivência, eclosão; movimento espontâneo da cauda (STC); frequência cardíaca; morfologia; comportamento locomotor; atividade e expressão gênica da acetilcolinesterase (AChE). A exposição ao metomil afetou quase a totalidade dos parâmetros morfológicos, resultando em larvas com menor tamanho do corpo e dos olhos, falha na inflação da bexiga natatória e presença de deformidades. Parâmetros comportamentais também apresentaram significativas alterações: menor distância percorrida, velocidade, aceleração máxima, maior latência para entra na periferia, menor frequência de mudança entre zonas, maior ângulo de giro e meandro. Além disso, a atividade biológica da AChE diminuiu de maneira dependente da concentração, enquanto sua expressão gênica não foi alterada. O conjunto de dados corroboram o efeito (neuro)tóxico do metomil, com potencial para alterar parâmetros biológicos essenciais para a sobrevivência de organismos não-alvo, mesmo em concentrações subletais.Pesticides are primarily defined as chemical, physical, or biological substances that act in the control of living organisms considered harmful to agriculture, domestic animals and human. Currently, Brazil is one of the largest food producers and exporters in the world and (consequently), the largest consumer of pesticides worldwide. As a large producer, Brazil has substantial areas of land destined for this purpose. Agricultural management for mass food production include the use of such substances, raising environmental risks concerns on natural resources and biota that may become contaminated with these xenobiotics. In this sense, use of model organisms to assess risks in vivo is essential and a main characteristic of ecotoxicology field. In this work, lethal and sublethal effect of the carbamate insecticide methomyl commercial formulation exposure in zebrafish embryos and larvae. The 96h-LC50 was determine and then, sublethal concentration ranges specified. Sublethal exposures were analyzed in terms of survival; hatching; spontaneous tail coiling (STC); heart rate; morphology; locomotor behavior and acetylcholinesterase (AChE) activity and ache gene expression. Methomyl exposure affected almost all morphological parameters, resulting in larvae with smaller body and eyes size and swimming bladder inflation failure. Behavioral parameters also presented significant changes: shorter traveled distance, speed, maximum acceleration; greater latency to enter the periphery, less frequency of change between zones, higher absolute turn angles and meanders. In addition, AChE activity decreased in a concentration-dependent manner, while no changes in ache gene expression were observed. Together, results corroborate that the (neuro)toxic effect of methomyl, and its potential to alter essential biological parameters for the survival of non-target organisms, even in sublethal concentrations
O impacto do triflumuron sobre o organismo-modelo zebrafish (Danio rerio)
Get PDFIn the present study, we aim to evaluate the frequency of micronuclei and nuclear abnormalities in erythrocytes from zebrafish (Danio rerio), by the exposure of this species to different concentrations of triflumuron (Certero?), in acute (96 hours) and chronical (30 days) tests. In acute treatments the following concentrations of insecticide were used: 0,2 mL/L; 0,6 mL/L e 1,8 mL/L. In this tests there was complete fish mortality within 24 hours of exposure to the insecticide. In the chronicle treatment it was used the concentration of 0,2 mL/L. In this last test, there was no fish mortality before the end of the experiment, but through the statistical test it was verified that the triflumuron did not increase the frequencies of micronuclei and abnormalities in the blood cells of these animals.Neste trabalho buscou-se avaliar a frequ?ncia de micron?cleos e anormalidades nucleares em eritr?citos de zebrafish (Danio rerio), por meio da exposi??o desta esp?cie a diferentes concentra??es de triflumuron (Certero?), em testes agudos (96 horas) e cr?nico (30 dias). Nos testes agudos foram usadas as seguintes concentra??es do inseticida: 0,2 mL/L; 0,6 mL/L e 1,8 mL/L. Nesses testes, houve mortalidade total dos peixes em menos de 24 horas de exposi??o ao inseticida. No tratamento cr?nico foi utilizada a concentra??o de 0,2 mL/L. Neste ?ltimo n?o houve mortalidade de peixes antes do t?rmino do experimento, mas constatou-se por meio do teste estat?stico que o triflumuron n?o aumentou as frequ?ncias de micron?cleos e anormalidades nuclerares nas c?lulas sangu?neas destes animais
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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