954 resultados para marina mercante


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Essa dissertação tem como objetivo a leitura comparativa dos contos de fadas da escritora inglesa Angela Carter, contidos no livro O quarto do Barba Azul, e os da ítalo-brasileira Marina Colasanti, presentes em livros como Uma ideia toda azul, Entre a rosa e a espada, Doze reis e a moça no labirinto do vento. Foram analisadas os modos pelo quais as duas autoras, através da reescrita dos contos de fadas, resistem a morte do narrador tradicional descrita por Walter Benjamin e criticam a sociedade patriarcal, revelando, naturalmente, uma postura feminista. Identificou-se, ainda, como estratégias poéticas comuns à escrita de ambas as autoras, aspectos intertextuais como a paródia, o palimpsesto e o pastiche

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Zostera marina is a member of a widely distributed genus of seagrasses, all commonly called eelgrass. The reported distribution of eelgrass along the east coast of the United States is from Maine to North Carolina. Eelgrass inhabits a variety of coastal habitats, due in part to its ability to tolerate a wide range of environmental parameters. Eelgrass meadows provide habitat, nurseries, and feeding grounds for a number of commercially and ecologically important species, including the bay scallop, Argopecten irradians. In the early 1930’s, a marine event, termed the “wasting disease,” was responsible for catastrophic declines in eelgrass beds of the coastal waters of North America and Europe, with the virtual elimination of Z. marina meadows in the Atlantic basin. Following eelgrass declines, disastrous losses were documented for bay scallop populations, evidence of the importance of eelgrass in supporting healthy scallop stocks. Today, increased turbidity arising from point and non-point source nutrient loading and sediment runoff are the primary threats to eelgrass along the Atlantic coast and, along with recruitment limitation, are likely reasons for the lack of recovery by eelgrass to pre-1930’s levels. Eelgrass is at a historical low for most of the western Atlantic with uncertain prospects for systematic improvement. However, of all the North American seagrasses, eelgrass has a growth rate and strategy that makes it especially conducive to restoration and several states maintain ongoing mapping, monitoring, and restoration programs to enhance and improve this critical resource. The lack of eelgrass recovery in some areas, coupled with increasing anthropogenic impacts to seagrasses over the last century and heavy fishing pressure on scallops which naturally have erratic annual quantities, all point to a fishery with profound challenges for survival.

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Mats (biomasses) of macroalgae, i.e. Ulva spp., Enteromorpha spp., Graciolaria spp., and Cladophora spp., have increased markedly over the past 50 years, and they cover much larger areas than they once did in many estuaries of the world. The increases are due to large inputs of pollutants, mainly nitrates. During the warm months, the mats lie loosely on shallow sand and mud flats mostly along shorelines. Ulva lactuca overwinters as buds attached to shells and stones, and in the spring it grows as thalli (leaf fronds). Mats eventually form that are several thalli thick. Few macroinvertebrates grow on the upper surfaces of their thalli due to toxins they produce, and few can survive beneath them. The fish, crabs, and wading birds that once used the flats to feed on the macroinvertebrates are denied these feeding grounds. The mats also grow over and kill mollusks and eelgrass, Zostera marina. An experiment was undertaken which showed that two removals of U. lactuca in a summer from a shallow flat in an estuarine cove maintained the bottom almost free of it.

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A través de esta serie intentaremos conocer diferentes facetas personales de los integrantes de nuestra “comunidad”. El cuestionario, además de su principal objetivo, con sus respuestas quizás nos ayude a encontrar entre nosotros puntos en común que vayan más allá de nuestros temas de trabajo y sea un aporte a futuros estudios históricos. Esperamos que esta iniciativa pueda ser otro nexo entre los ictiólogos de la región, ya que consideramos que el resultado general trascendería nuestras fronteras.

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Six enzyme systems, namely acid phosphatase, leucine aminopeptidase, phosphoglucose isomerase, tetrazolium oxidase, esterases and malate dehydrogenase were studied electrophoretically in Arenicola marina from various localities in United Kingdom. Out of 13 presumed loci, ten were found monomorphic. The three loci which appeared to be polymorphic are LAP-1, EST-2 and TO-1. Due to small sample size allele frequencies and genetic identity were not calculated. However, results indicate genetic difference among the population of A. marina.

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Hace treinta años se creaba el Instituto Interuniversitario de Biología Marina de Mar del Plata (IIBM), Argentina, posteriormente desaparecido por influjo de las vicisitudes políticas acontecidas desde entonces. Uno de sus fundadores analiza los principios institucionales y científicos que guiaron el accionar de aquella entidad, a la vez que reflexiona acerca de la situación actual de las ciencias del mar.

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La biología marina es una rama de las ciencias del mar de reciente desarrollo en la Argentina (oceáno Atlántico sudoccidental) que está en franco crecimiento. Se muestra un panorama del desarrollo de las diversas disciplinas, como los estudios sobre la biodiversidad marina y de la biología marina y pesquera, así como amenazas a los ambientes marinos y medidas de conservación tomadas. Se incluyen las perspectivas para futuros estudios de biología marina, los beneficios de las iniciativas de divulgación científica, entre otros temas, así como otras lecturas afines sugeridas.

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为检查特殊的涡鞭毛虫--尖尾藻(Oxyrrhis marina)是否已进化产生了核骨架结构,若有的话,又与典型真核细胞核骨架在形态结构上有何异同,用了两种方法。方法一是将分离出的尖尾藻细胞核,仿照P. R. Gook的方法用含高盐及去垢剂的分解液处理之后再经DNase除去DNA,用透射电镜观察。方法二是采用S. Penman实验室的分级抽提、DGD包埋-去包埋剂电镜技术,但根据尖尾藻的生理特性作了修改。此外还用了以热三氯醋酸除去核酸的方法。方法一的实验结果表明,尖尾藻细胞核内有一个起框架作用的纤维蛋白结构,此结构类似于用同一方法在典型真核细胞上所显示的“nuclear cage”结构。方法二的结果显示,尖尾藻细胞核内存在一个纤维网架结构,核仁与染色体都被网络于其间。其纤维粗细为2.8nm到24nm,它们与细胞(质)骨架中的中间纤维(IF)有着广泛的联系。此网架结构是由非DNA性质的纤维蛋白组成的,其中还含有对维持其三维结构所必需的RNA成分。它们的这些特点都十分相似于典型真核细胞核骨架的特点。另外尖尾藻的核纤层及核骨架纤维上所结合的核糖核蛋白颗粒(RNP)方面又与典型真核生物的有差别。本工作首次证明了特殊涡鞭毛虫毛类--尖尾藻已有了核骨结构。

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本工作采用单纯戊二醛、单纯四氧化锇、戊二醛加四氧化锇双固定及Ryter和Kellenberger的细菌类核体“标准固定方法”等四种固定方法,在尖尾藻与典型涡鞭毛虫双甲藻(Prorocentrum micans)、典型原核生物肠道细菌、眼虫(Euglean sp.)、典型真核细胞小鼠胸腺细胞之间比较了电镜下所观察到的染色体和类核体的固定特性。实验结果表明尖尾藻染色体的固定特性异于典型涡鞭毛虫染色体的固定特性。而与眼虫染色体的相同,与典型真核细胞异染色质的相似。这些结果支持关于重新确定尖尾藻分类地位的设想;实验结果还指出尖尾藻染色体和眼虫染色体在碱性蛋白被抽提尽后,它们的固定特性均与细菌类核体的相似,这提示除了染色体碱性蛋白或组蛋白的含量是染色体固定特性的一个决定因素外,染色体碱性蛋白与DNA纤维的结合方式也可能影响染色体的固定特性。