887 resultados para Col·lapse gravitacional


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

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Bees have a crucial role in pollination; therefore, it is important to determine the causes of their recent decline. Fipronil and imidacloprid are insecticides used worldwide to eliminate or control insect pests. Because they are broad-spectrum insecticides, they can also affect honeybees. Many researchers have studied the lethal and sublethal effects of these and other insecticides on honeybees, and some of these studies have demonstrated a correlation between the insecticides and colony collapse disorder in bees. The authors investigated the effects of fipronil and imidacloprid on the bioenergetic functioning of mitochondria isolated from the heads and thoraces of Africanized honeybees. Fipronil caused dose-dependent inhibition of adenosine 5'-diphosphate-stimulated (state 3) respiration in mitochondria energized by either pyruvate or succinate, albeit with different potentials, in thoracic mitochondria; inhibition was strongest when respiring with complex I substrate. Fipronil affected adenosine 5'-triphosphate (ATP) production in a dose-dependent manner in both tissues and substrates, though with different sensitivities. Imidacloprid also affected state-3 respiration in both the thorax and head, being more potent in head pyruvate-energized mitochondria; it also inhibited ATP production. Fipronil and imidacloprid had no effect on mitochondrial state-4 respiration. The authors concluded that fipronil and imidacloprid are inhibitors of mitochondrial bioenergetics, resulting in depleted ATP. This action can explain the toxicity of these compounds to honeybees. (c) 2014 SETAC

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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In our experiments, we studied the classical dynamic of a particle in vertical motion subject to a constant gravitational field and the partial shock with an elastic wall with oscillatory motion located below the particle. The motion of the particle was confined to the vertical direction by a glass guide tube, which was initially evacuated, allowing viscous drag forces to be disregarded. The time between impacts, as well as the time between the reference phase of the movement of the base and the moment of impact and the period of oscillation of the base will be acquired by a hardware and software to obtain the phases space to be compared later with the description of the system through mapping discrete variables via the 'particle velocity immediately after shock 'and' phase of the movement of the base at the instant of shock 'obtained by computer simulation. This requires developing an electronic analog system followed by Digital implemented in reconfigurable logic, more specifically a sequential machine able to discriminate the impact with the metal base from the impacts of the glass guide tube, based on the frequency spectrum of the response of the microphone to these different impacts

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Neste trabalho será analisado o comércio bilateral Brasil-China com embasamento teórico das vantagens comparativas (modelos ricardianos), do modelo de dotação de fatores “Heckscher-Ohlin” e do Modelo de Comércio Gravitacional. Tais conceitos serão corroborados por testes empíricos, utilizando-se a equação gravitacional simples e dois Indicadores de Comércio (IVCR e IOR), do ano de 1995 até 2005, demonstrando-se que o Brasil apresenta vantagens comparativas no comércio de soja com a China

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Measurement units are used almost automatically nowadays, but few people know the origin of the units of length (meter), mass (kilogram) and time (second). And do not care to know what were anciently units of which our ancestors used, the difficulties that existed to make a set of measures. The aim of this work is to make a historical approach, through various units of measure. They are old, unusual to others that have been forgotten since the standardization of meters, and is also discussed about the metric system Englih (Once and foot), AV system (eg pound grain) that are still used in some countries like United States and England, the Troy system consisting of units of measure for precious stones and metals (eg gold and diamond) are also cited some physical concepts as reference: inertial, non-inertial; mass: gravity, relativistic, inertial

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Diante do desenfreado uso da terra, gerando impactos muitas vezes irreversíveis, o planejamento ambiental insere-se como uma ferramenta atualmente necessária. Visto que é sob o relevo que se consolidam as atividades antrópicas, a cartografia do relevo surge como um importante instrumento, indicando setores cujas características naturais impõem limites ao uso da terra. Assim, o objetivo desta pesquisa é analisar as características geomorfológicas da alta bacia do Rio Itanhaém, com ênfase à questão morfográfica e morfométrica do relevo, avaliando também as modificações impostas a este em decorrência do uso da terra, contribuindo, portanto, com a gestão ambiental desta área. Para tanto, foram elaborados documentos cartográficos capazes de evidenciar as características do relevo que impõem limites ao uso antrópico, a saber: as cartas morfométricas (carta de declividade, carta de dissecação vertical, carta de dissecação horizontal e carta de energia do relevo), que são documentos que evidenciam a suscetibilidade potencial do relevo sob a influência da ação das águas e gravitacional; a carta geomorfológica (cenário de 1962), que possibilita a espacialização das formas do relevo, contribuindo para a análise da morfodinâmica; e as cartas de uso da terra (cenário de 1962 e 2000), que, em conjunto com os documentos já especificados, possibilitam a análise da influência da atuação antrópica sob o sistema relevo. De maneira geral, pôde-se detectar problemas na morfodinâmica da área de estudo, evidenciados pela presença de feições denudacionais localizadas, tais como sulcos erosivos, voçorocas, ravina e cicatrizes de escorregamentos, os quais vinculam-se ao potencial natural que o relevo da área de estudo possui ao desencadeamento de processos morfogenéticos; à dinamização de processos naturais pela atuação antrópica... (Resumo completo, clicar acesso eletrônico abaixo)

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The question of the solid waste is without a doubt one of the biggest problems faced for the world-wide population in the present time, resulting in the call “collapse of the garbage”. In this direction that appears the composting, in the scope of the treatment of organic waste origin, that in Brazil, approximately correspond 50% of the generated volume. However, the rare plants of selection and composting (UTC) existing at least do not obtain auto-to support themselves, increasing to each day the number of deactivations, almost always related the financial questions. In this direction, the present research brings the analysis of the economic viability of the implantation of a UTC for the city of Rio Claro-SP, relating it with the thick organic composition sales, for the cultures of vegetables cultivated in a ray of 30 km of the study area. For in such a way, they had been carried through, calculations concerning the regional demand for organic composition, and the verification of the implantation costs and operation of the plant. The reached results had been the flow of box for the first year of functioning of the UTC, as well as the break-even point between the gotten expenditures and prescriptions. From this relation investment profitability, it was verified that the UTC is presented impracticable under the economic point of view.

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In the present work it is proposed to do a revision on some studies on the dynamics of the Prometheus-Pandora system. In special, those studies that deal with anomalous behaviours observed on its components, identi ed as angular lags in these satellite`s orbits. Initially, it is presented a general description, contextualising the main characteristics of this system. The main publications related to this subject are analised and commented, in chronological order, showing the advances made in the knowledge of such dynamics. An analysis of the initial conditions, used by Goldreich e Rappaport (2003a ,b) e Cruz (2004), obtained through observations made by the Voyager 1 and 2 spacecrafts and by the Hubble space telescope, it is made in order to try to reproduce their results. However, no clear conclusion of the values used were found. The tests addopted in the analysis are from Cruz (2004), which reproduced the results and o ered a new explanation on the origin of the observed angular lags. The addopetd methodology involves the numerical integration of the equations of motion of the system, including the zonal harmonics J2, J4 and J6 of Saturn's gravitational potential. A fundamental consideration in this study is the use of geometric elements instead of osculating elements. It was found the set of initial data that best reproduces the results from Goldreich e Rappaport (2003a, b) and Cruz (2004)

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The aim of this work is to analyze the stability of the rotational motion’s artificial satellite using the Routh Hurwitz Algorithm (CRH) and the quaternions to describe the satellite’s attitude. This algorithm allows the investigation of the stability of the motion using the coefficients of the characteristic equation associated with the equation of the rotational motion in the linear form. The equations of the rotational motion are given by the four cinematic equations for the quaternion and the three equations of Euler for the spin velocity’s components. In the Euler equations are included the components of the gravity gradient torque (TGG) and the solar radiation torque (TRS). The TGG is generated by the difference of the Earth gravity force direction and intensity actuating on each satellite mass element and it depends on the mass distribution and the form of the satellite. The TRS is created by changing of the linear momentum, which happens due to the interactions of solar photons with the satellite surface. The equilibrium points are gotten by the equation of rotational motion and the CRH is applied in the linear form of these equations. Simulations are developed for small and medium satellites, but the gotten equilibrium points are not stable by CRH. However, when some of the eigenvalues of the characteristic equation are analyzed, it is found some equilibrium points which can be pointed out as stables for an interval of the time, due to small magnitude of the real part of these eigenvalue

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Pancreatitis is a predominantly disease of the exocrine pancreas, which occurs commonly in dogs. Acute pandreatitis is reversible, with the removal of the primary cause, whereas chronic pancreatitits is irreversible, with histopathological changes, such as atrophy and fibosis that occurs from persistent inflammation. In dogs, clinicl signs ranging among abdominal pain and anorexia until potential insufficiency of various organs and Disseminated Intravascular Coagulation. In general, dogs with acute illness presents vomiting, anorexia, abdominal pain and several degrees of dehydration, collapse and shock. The caim of this monograph is evaluate ultrassound changes in dogs with panceatitis. Ultrassound is a valuable technique to evaluate exocrine pancreas, with association with another diagnostic modalities will be able to increase the preciosion of the diagnosis