969 resultados para Leach, Michael


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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Morphological aspects of spermatozoa in marine animals have been used in recent decades as phylogenetic criteria (spermiotaxonomy). This paper presents ultrastructural descriptions of the spermatozoa from Uca maracoani, U. thayeri, and U. vocator. A small portion of the vas deferens of each species was examined under the transmission and scanning electron microscopy. The ultrastructural analysis showed that each spermatophore consists of a varying number of spermatozoa embedded in a dense fibrillar matrix surrounded by a membrane. The spermatozoa of U. maracoani, U. thayeri, and U. vocator are typical of brachyurans. The Voluminous acrosome is characterized by three different layers. The postero-lateral surface of the acrosome is cupped by the reduced cytoplasm, and the anterior surface is covered by the operculum. The perforatorium consists of coiled, helicoidal membranous tubules and is continuous with the cytoplasm. The nucleus is composed by uncondensed chromatin and presents several lateral arms distributed over the entire equatorial plane of the cell. The presence of the apical button is a well defined character among all species of the genus Uca, but in U. thayeri it was not observed. The accessory opercular ring can be found in the three studied species, but in distinct development degree-Two centrioles were detected in U. thayeri and U. vocator, but only one was found in U. maracoani. The presence of centrioles in the mature spermatozoa is the first account for the genus Uca upto-date. Considering the ultrastructure of the spermatozoa of U. maracoani, U. thayeri, and U. vocator, we suggest that these three species partially follow the morphological patterns previously described in other Thoracotremata brachyurans. The absence of the apical button in U. thayeri spermatozoa may represent an evolutionary novelty in the genus Uca. (C) 2007 Elsevier Ltd. All rights reserved.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Estudando o trabalho experimental sobre eletromagnetismo realizado por Michael Faraday no início do século XIX, encontramos vários elementos que poderiam ser utilizados no Ensino de Ciências. Um conhecimento histórico sobre o trabalho experimental desenvolvido por Faraday e que o levou à descoberta da indução eletromagnética pode transmitir aos estudantes uma concepção mais adequada do processo de desenvolvimento da Ciência. No entanto, isso só pode ser feito utilizando-se um estudo detalhado e bem fundamentado do processo histórico ocorrido, deixando de lado as simplificações e os mitos que costumam ser apresentados.

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The phytochemical profile of ethanolic extract of Solanum lycocarpum fruits was analyzed and preliminary toxicity tests were performed against brine shrimp larvae. The extract was subjected to preliminary phytochemical analysis to identify the main classes of secondary metabolites and tested against the larvae of A. salina to obtain the median lethal concentrations (LC50%). The phytochemical tests showed the presence of phenols, tannins, saponins, alkaloids and free steroids. The extract was fractionated with various solvents for toxicity testing against the larvae and the hydroalcoholic fraction showed considerable cytotoxicity (CL50% = 285.546 g/mL).

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Ciências Sociais - FCLAR

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Pós-graduação em Estudos Literários - FCLAR

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Em sua vasta trajetória intelectual – que atravessa os múltiplos campos teóricos das ciências humanas – Michael Löwy destacou-se pela capacidade de estabelecer um diálogo profícuo entre tradições diversas do pensamento social. Partindo desta constatação, o objetivo deste artigo é a apresentação e sistematização de alguns aspectos decisivos da trajetória teórica e intelectual de Michael Löwy, com ênfase especial: 1) na importância da sua formação intelectual, ainda no Brasil (no final da década de 1950), para a constituição de uma leitura não-dogmática do marxismo; e 2) sua incorporação da dialética no diagnóstico weberiano da modernidade. O artigo argumenta que essa interpretação “aberta” do marxismo permitiu-lhe reinterpretar autores do passado — como Marx e Weber — a partir das condições de possibilidade do cenário histórico e intelectual contemporâneo. Esta disposição para enfrentar os desafios do presente sem abandonar as perspectivas do passado comprova a importância da obra de Löwy para as ciências sociais e, mais especificamente, para o marxismo contemporâneo.

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Patterns of spatio-temporal distribution of Brachyura are determined by the interaction among life history traits, inter and intraspecific relationships, as well as by the variation of abiotic factors. This study aimed to characterize patterns of spatio-temporal distribution of Persephona lichtensteinii, Persephona mediterranea and Persephona punctata in two regions of the northern coast of Sao Paulo State, southeastern region of Brazil. Collections were done monthly from July 2001 to June 2003 in Caraguatatuba and Ubatuba, using a shrimp fishery boat equipped with double-rig nets. The patterns of species distribution were tested by means of redundancy analysis (RDA) and generalized linear mixed models (GLMM) in relation to the recorded environmental factors (BT: bottom temperature, BS: bottom salinity, OM: organic matter and granulometry (Phi)). The most influent environmental factor over the species distribution was the Phi, and the ascendant order of influence was P. lichtensteinii, P. punctata and P. mediterranea. The greater abundance of P. mediterranea showed a conservative pattern of distribution for the genus in the sampled region. The greater occurrence of P. punctata and P. lichtensteinii, in distinct transects than those occupied by P. mediterranea, seems to be a strategy to avoid competition among congeneric species, which is related to the substratum specificity.

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The NbCl5 being a strong electrophile, is a potential candidate to act as a Lewis acid, and therefore it mediates various organic reactions. For this reason, it has received continuous attention by Brazilian researchers, especially in recent decades, since Brazil holds the largest reserves of niobium, besides being the largest producer of this element. The Michael addition reaction is one of the most widely used for forming carbon-carbon bonds and takes place by the addition of nucleophiles to activated olefins. Although this type of reaction is usually catalyzed by base, there are reports in the literature on the use of various Lewis acids in this type of reaction. The synthesis of enamines based acetilenodicarboxilates and amines, aromatic or alkyl, by Michael addition reaction is quite interesting, since these are valuable synthetic intermediates for the synthesis of heterocyclic and they are used in multicomponent reactions. The derivatives of anilino-fumarate also have a great potential for medical application. In this study we investigated the use of niobium pentachloride as Lewis acid to catalyze the Michael additions between the derivatives of aniline and acetilenodicarboxilates the synthesis of enamines