995 resultados para Litopenaeus vannamei. Densidade. Comportamento. Crescimento. Ciclo de muda


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As várias teorias acerca da estrutura de capital despertam interesse motivando diversos estudos sobre o assunto sem, no entanto, ter um consenso. Outro tema aparentemente pouco explorado refere-se ao ciclo de vida das empresas e como ele pode influenciar a estrutura de capital. Este estudo teve como objetivo verificar quais determinantes possuem maior relevância no endividamento das empresas e se estes determinantes alteram-se dependendo do ciclo de vida da empresa apoiada pelas teorias Trade Off, Pecking Order e Teoria da Agência. Para alcançar o objetivo deste trabalho foi utilizado análise em painel de efeito fixo sendo a amostra composta por empresas brasileiras de capital aberto, com dados secundários disponíveis na Economática® no período de 2005 a 2013, utilizando-se os setores da BM&FBOVESPA. Como resultado principal destaca-se o mesmo comportamento entre a amostra geral, alto e baixo crescimento pelo endividamento contábil para o determinante Lucratividade apresentando uma relação negativa, e para os determinantes Oportunidade de Crescimento e Tamanho, estes com uma relação positiva. Para os grupos de alto e baixo crescimento alguns determinantes apresentaram resultados diferentes, como a singularidade que resultou significância nestes dois grupos, sendo positiva no baixo crescimento e negativa no alto crescimento, para o valor colateral dos ativos e benefício fiscal não dívida apresentaram significância apenas no grupo de baixo crescimento. Para o endividamento a valor de mercado foi observado significância para o Benefício fiscal não dívida e Singularidade. Este resultado reforça o argumento de que o ciclo de vida influência a estrutura de capital

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Among the species of freshwater shrimp being cultivated, Macrobrachium rosenbergii stands out. Knowledge about the behavior of this species and the influence of certain factors on its development can help optimize management practices and minimize the likely impacts shrimp farming has on the environment and the animals themselves. The objective of this study was to characterize the species' behavior during early stages of development under different stocking densities over a 24-hour cycle. Ten day old postlarvae were transferred from the Jundiaí School of Agriculture (EAJ - Escola Agrícola de Jundiaí) in Macaíba (RN), Brazil to the Shrimp Behavior Laboratory (LSPR - Laboratório de Estudos do Comportamento do Camarão) at the Federal University of Rio Grande do Norte (UFRN), where they were weighed and measured. Eight aquaria with constant temperature, aeration and filtration, and subjected to a12 h light/12 h dark cycle were used for each experiment. Each aquarium also contained two shelters made of bricks and the water quality was monitored weekly. Behavioral observations were made at two densities: 25 individuals/m-² and 40 individuals/m-². The methods for recording behaviors were: behavioral sampling – enter and leave the shelter, exploring on the substrate, exploring in the water column, move away, attack, pursuit and cannibalism; scan sampling - inactivity, feeding, exploration, digging, swimming, cleaning and staying in the shelter. Observations were made during a 15 minute period/per aquarium at a frequency of 4 times daily, for 4 days/week, and over 4 weeks. Food was provided 2 times/day for each aquarium population, immediately before the 1st and 3rd observation periods. Our results demonstrate that at high density, there is an increased frequency of agonistic behavior; during the light phase, there is a greater frequency of behaviors that result in less exposure (inactivity, cleaning and staying in the shelter); during the dark phase, there is an increased frequency of behaviors that result in greater exposure (feeding, exploration, swimming and digging); at times of feed offer, there is an increased frequency of leaving the shelter, moving away, pursuit, feeding, exploration and swimming. At low density, the animals showed a lower frequency of agonistic behaviors, greater weight gain and higher growth rates, which indicates that this is a more favorable growing environment for cultivation and when applied, can generate better living conditions, favor survival rates and increase management success

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From an economic standpoint, the powder metallurgy (P/M) is a technique widely used for the production of small parts. It is possible, through the P/M and prior comminution of solid waste such as ferrous chips, produce highly dense sintered parts and of interest to the automotive, electronics and aerospace industries. However, without prior comminution the chip, the production of bodies with a density equal to theoretical density by conventional sintering techniques require the use of additives or significantly higher temperatures than 1250ºC. An alternative route to the production of sintered bodies with high density compaction from ferrous chips (≤ 850 microns) and solid phase sintering is a compression technique under high pressure (HP). In this work, different compaction pressures to produce a sintered chip of SAE 1050 carbon steel were used. Specifically, the objective was to investigate them, the effect of high pressure compression in the behavior of densification of the sintered samples. Therefore, samples of the chips from the SAE 1050 carbon steel were uniaxially cold compacted at 500 and 2000 MPa, respectively. The green compacts obtained were sintered under carbon atmosphere at 1100 and 1200°C for 90 minutes. The heating rate used was 20°C/min. The starting materials and the sintered bodies were characterized by optical microscopy, SEM, XRD, density measurements (geometric: mass/volume, and pycnometry) and microhardness measurements Vickers and Rockwell hardness. The results showed that the compact produced under 2000 MPa presented relative density values between 93% and 100% of theoretical density and microhardness between 150 HV and 180 HV, respectively. In contrast, compressed under 500 MPa showed a very heterogeneous microstructure, density value below 80% of theoretical density and structural conditions of inadequate specimens for carrying out the hardness and microhardness measurements. The results indicate that use of the high pressure of ferrous chips compression is a promising route to improve the sinterability conditions of this type of material, because in addition to promoting greater compression of the starting material, the external tension acts together with surface tension, functioning as the motive power for sintering process. Additionally, extremely high pressures allow plastic deformation of the material, providing an intimate and extended contact of the particles and eliminating cracks and pores. This tends to reduce the time and / or temperature required for good sintering, avoiding excessive grain growth without the use of additives. Moreover, higher pressures lead to fracture the grains in fragile or ductile materials highly hardened, which provides a starting powder for sintering, thinner, without the risk of contamination present when previous methods are used comminution of the powder.

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Tese submetida à Universidade de Coimbra, Faculdade de Ciências e Tecnologia e aprovada em provas públicas para a obtenção do Grau de Doutor em Engenharia Mecânica (especialidade de Ciência dos Materiais)

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Sea urchins are common benthic organisms on coastal ecosystems of tropical and temperate shallow waters. The impact of sea urchins populations in shore communities is density-dependent, and therefore, knowledge of the life history of these animals is important to understand these interactions. Between 2000 and 2005 a population boom of Tripneustes ventricosus was observed in the Fernando de Noronha Archipelago. In 2004 a research program was started to monitor the population dynamics of T. ventricosus in the archipelago, when it noted a lack of basic information on the biology and reproduction of this species, despite its broad geographic distribution and economic importance in parts of its occurrence. In this context, this work focuses on the reproductive biology of T. ventricosus with emphasis on the description of the gametogenic stages. Between December 2006 and July 2007, ten urchins were collected by snorkeling in two sites of the archipelago, totaling 120 individuals. Gametogenic stages were described for both sexes through microscopic analysis, and were defined as: Recovery, Growing, Premature, Mature and Spawning. Results showed increasing in Gonad index throughout of months of sampling and suggest that the reproductive cycle of the species in the archipelago is annual

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Pretendemos com o nosso estudo demonstrar quais os efeitos de três determinantes no Investimento em Fundo de Maneio Necessário que é considerado por vários autores como vital tanto para o crescimento como para a sustentabilidade das empresas ao longo do seu Ciclo de Vida. Iremos também demonstrar que para além do comportamento e relação desses determinantes com o Investimento em Fundo de Maneio Necessário (FMN), registam-se influências provocadas pelos efeitos moderadores da Probabilidade de Insolvência e do próprio Ciclo de Vida das empresas. Através da análise dos nossos resultados mostraremos como a Rentabilidade Operacional, o Crédito Comercial Obtido e o Financiamento Bancário de Médio e Longo Prazo são os principais determinantes do Investimento em FMN e como estas relações se modificam ao longo do Ciclo de Vida das Empresas. O nosso estudo também vai permitir-nos estudar o efeito moderador da Probabilidade de Insolvência no tipo de financimento do investimento em FMN. O indicador da Probabilidade de Insolvência demonstra ter um feito moderador sobre o tipo de financiamento do FMN. Os fornecedores exibem uma percepção mais rápida e atempada do aparecimento das dificuldades financeiras dos seus clientes do que os financiadores bancários. Esta capacidade permite-lhes monitorizar o estado financeiro dos seus clientes sem restringir a concessão de crédito na sua totalidade. Os modelos estimados para amostras de duas fases do ciclo de vida das empresa fornecem-nos evidências empíricas de que a idade das empresas afecta a forma e a intensidade dos factores explicativos do Investimento em FMN. Nas empresas em fase de maturidade o Crédito Bancário de Médio e Longo Prazo apresenta-se como um substituto ao crédito comercial de fornecedores no financiamento do Ciclo de Exploração. Também demonstramos que os determinantes do Investimento em FMN são afectados pela fase do Ciclo de Vida, medido pela antiguidade da empresa.

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Realizou-se um trabalho experimental com o objectivo de obter informação sobre a evolução do crescimento de Staphylococcus aureus. Foram utilizadas duas estirpes de Staphylococcus aureus, uma isolada a partir de rissóis de frango e uma estirpe de referência, a ATCC n. 9213, estas estirpes foram sujeitas a 3 valores de pH diferentes (que representam os valores de pH que é possível, ou seja pH 4, 5,5 e 7, a 3 valores de concentração de NaCl, nomeadamente, 0,5%, 7% e 15%. A temperatura de desenvolvimento será de 7°C, 37°C e 50aC. Utilizaram-se dois métodos para avaliar o crescimento de Staphylococcus aureus, ao longo do tempo, nomeadamente o Método Turbidímétrico e o Método de contagem de unidades formadoras de colónias (método das diluições sucessivas). ABSTRACT: Carried out experimental work in order to obtain information on the evolution of the growth of Staphylococcus aureus. We used two strains of Staphylococcus aureus, a strain isolated from a chicken patties and one reference strain, ATCC Nº 29213, these strains were subjected to 3 different pH values (which represent the values of pH it is possible, or is pH 4, 5.5 and 7, the 3 values of NaCI concentration, namely, 0.5%, 7% and 15%. The growth temperature is 7 °C, 37°C and 50ºC. We used two methods to evaluate the growth of Staphylococcus aureus, over time, including the turbidimetric method and the method of counting colony forming units (method of successive dilutions).

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Apesar das gramíneas anuais de inverno apresentarem bom potencial para ganho, as leguminosas são alternativas interessantes para compor pastos mistos, pois ampliam o ciclo de utilização.

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Dissertação de mest. em Aquacultura, Unidade de Ciências e Tecnologias dos Recursos Aquáticos, Univ. do Algarve, 1997

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Sea urchins are common benthic organisms on coastal ecosystems of tropical and temperate shallow waters. The impact of sea urchins populations in shore communities is density-dependent, and therefore, knowledge of the life history of these animals is important to understand these interactions. Between 2000 and 2005 a population boom of Tripneustes ventricosus was observed in the Fernando de Noronha Archipelago. In 2004 a research program was started to monitor the population dynamics of T. ventricosus in the archipelago, when it noted a lack of basic information on the biology and reproduction of this species, despite its broad geographic distribution and economic importance in parts of its occurrence. In this context, this work focuses on the reproductive biology of T. ventricosus with emphasis on the description of the gametogenic stages. Between December 2006 and July 2007, ten urchins were collected by snorkeling in two sites of the archipelago, totaling 120 individuals. Gametogenic stages were described for both sexes through microscopic analysis, and were defined as: Recovery, Growing, Premature, Mature and Spawning. Results showed increasing in Gonad index throughout of months of sampling and suggest that the reproductive cycle of the species in the archipelago is annual