953 resultados para Bodley, Thomas, Sir, 1545-1613.


Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We use the Thomas-Fermi method to examine the thermodynamics of particles obeying Haldane exclusion statistics. Specifically, we study Calogero-Sutherland particles placed in a given external potential in one dimension. For the case of a simple harmonic potential (constant density of states), we obtain the exact one-particle spatial density and a {\it closed} form for the equation of state at finite temperature, which are both new results. We then solve the problem of particles in a $x^{2/3} ~$ potential (linear density of states) and show that Bose-Einstein condensation does not occur for any statistics other than bosons.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We analyze the performance of an SIR based admission control strategy in cellular CDMA systems with both voice and data traffic. Most studies In the current literature to estimate CDMA system capacity with both voice and data traf-Bc do not take signal-tlFlnterference ratio (SIR) based admission control into account In this paper, we present an analytical approach to evaluate the outage probability for voice trafllc, the average system throughput and the mean delay for data traffic for a volce/data CDMA system which employs an SIR based admission controL We show that for a dataaniy system, an improvement of about 25% In both the Erlang capacity as well as the mean delay performance is achieved with an SIR based admission control as compared to code availability based admission control. For a mixed voice/data srtem with 10 Erlangs of voice traffic, the Lmprovement in the mean delay performance for data Is about 40%.Ah, for a mean delay of 50 ms with 10 Erlangs voice traffic, the data Erlang capacity improves by about 9%.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Information spreading in a population can be modeled as an epidemic. Campaigners (e.g., election campaign managers, companies marketing products or movies) are interested in spreading a message by a given deadline, using limited resources. In this paper, we formulate the above situation as an optimal control problem and the solution (using Pontryagin's Maximum Principle) prescribes an optimal resource allocation over the time of the campaign. We consider two different scenarios-in the first, the campaigner can adjust a direct control (over time) which allows her to recruit individuals from the population (at some cost) to act as spreaders for the Susceptible-Infected-Susceptible (SIS) epidemic model. In the second case, we allow the campaigner to adjust the effective spreading rate by incentivizing the infected in the Susceptible-Infected-Recovered (SIR) model, in addition to the direct recruitment. We consider time varying information spreading rate in our formulation to model the changing interest level of individuals in the campaign, as the deadline is reached. In both the cases, we show the existence of a solution and its uniqueness for sufficiently small campaign deadlines. For the fixed spreading rate, we show the effectiveness of the optimal control strategy against the constant control strategy, a heuristic control strategy and no control. We show the sensitivity of the optimal control to the spreading rate profile when it is time varying. (C) 2014 Elsevier Inc. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Cytosolic nucleotidase II (cN-II) from Legionellapneumophila (Lp) catalyzes the hydrolysis of GMP and dGMP displaying sigmoidal curves, whereas catalysis of IMP hydrolysis displayed a biphasic curve in the initial rate versus substrate concentration plots. Allosteric modulators of mammalian cN-II did not activate LpcN-II although GTP, GDP and the substrate GMP were specific activators. Crystal structures of the tetrameric LpcN-II revealed an activator-binding site at the dimer interface. A double mutation in this allosteric-binding site abolished activation, confirming the structural observations. The substrate GMP acting as an activator, partitioning between the allosteric and active site, is the basis for the sigmoidicity of the initial velocity versus GMP concentration plot. The LpcN-II tetramer showed differences in subunit organization upon activator binding that are absent in the activator-bound human cN-II structure. This is the first observation of a structural change induced by activator binding in cN-II that may be the molecular mechanism for enzyme activation. DatabaseThe coordinates and structure factors reported in this paper have been submitted to the Protein Data Bank under the accession numbers and . The accession number of GMP complexed LpcN-II is . Structured digital abstract andby() andby() Structured digital abstract was added on 5 March 2014 after original online publication]

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Two new Ru(II)-complexes RuH(Tpms)(PPh3)(2)] 1 (Tpms - (C3H3N2)(3)CSO3, tris-(pyrazolyl) methane sulfonate) and Ru(OTf)(Tpms)(PPh3)(2)] 2 (OTf = CF3SO3) have been synthesized and characterized wherein Ru-H and Ru-OTf are the key reactive centers. Reaction of 1 with HOTf results in the Ru(eta(2)-H-2)(Tpms)(PPh3)(2)]OTf] complex 3, whereas reaction of 1 with Me3SiOTf affords the dihydrogen complex 3 and complex 1 through an unobserved sigma-silane intermediate. In addition, an attempt to characterize the sigma methane complex via reaction of complex 1 with CH3OTf yields complex 2 and free methane. On the other hand, reaction of Ru(OTf)(Tpms)(PPh3)(2)] 2 with H-2 and PhMe2SiH at low temperature resulted in sigma-H-2, 3 and a probable sigma-silane complexes, respectively. However, no sigma-methane complex was observed for the reaction of complex 2 with methane even at low temperature. (C) 2014 Elsevier B. V. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

By the semi-inverse method, a variational principle is obtained for the Thomas-Fermi equation, then the Ritz method is applied to solve an analytical solution, which is a much simpler and more efficient method.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Resumen: Este trabajo busca demostrar cómo la escena de “El Jardín de Isabel” (acto IV, escena ii) en la obra La tragedia española de Thomas Kyd es un ejemplo de una escena espejo. Inicialmente se observa cómo esta escena está laxamente conectada con el resto de la obra y la misma no sufriría un cambio significativo de ser la escena eliminada; la característica de “prescindible” de ésta, es propia de una escena espejo. La escena del Jardín de Isabel es luego estudiada en profundidad para dejar en evidencia cómo resume la obra y la simboliza. El personaje de Isabel es examinado en detalle, siguiendo una sensibilidad pictórica y, a través de una interpretación temática y simbólica, Isabel es presentada como Piedad, Testigo de Justicia Divina y Venganza. Finalmente el espacio es también analizado como locus amoenus al ser inicialmente un lugar de encuentro de los enamorados y locus eremus luego de la maldición de Isabel. Luego del estudio de estos aspectos de esta escena espejo, se pone en evidencia cómo la misma “refleja” los temas centrales de la obra: la verdad se revela con el tiempo, hay que ser paciente y esperar la justicia divina y, por último, la venganza sólo condena al vengador.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Tomás Tamayo de Vargas, historiador espanhol, nasceu em 1588 e morreu em 1641. Cronista do Reino, escreveu essa obra por ordem real, que foi publicada em 1628, utilizando documentação oficial e informações que as relações da época lhe proporcionavam. ‘Restauracion de la ciudad del Salvador, i Baia de Todos-Sanctos, en la Provincia del Brasil’ reflete a opinião oficial espanhola sobre a restauração da Bahia e mostra a repercussão que o acontecimento teve na metrópole espanhola que, na época, dominava o Brasil. Rodrigues considera essa uma edição ‘rara’ e Brunet afirma ser ‘muito rara’. Há uma edição brasileira, difícil de encontrar, publicada em Salvador pela Tipografia de Epifanio Pedroza (1847)

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The field of cavity-optomechanics explores the interaction of light with sound in an ever increasing array of devices. This interaction allows the mechanical system to be both sensed and controlled by the optical system, opening up a wide variety of experiments including the cooling of the mechanical resonator to its quantum mechanical ground state and the squeezing of the optical field upon interaction with the mechanical resonator, to name two.

In this work we explore two very different systems with different types of optomechanical coupling. The first system consists of two microdisk optical resonators stacked on top of each other and separated by a very small slot. The interaction of the disks causes their optical resonance frequencies to be extremely sensitive to the gap between the disks. By careful control of the gap between the disks, the optomechanical coupling can be made to be quadratic to first order which is uncommon in optomechanical systems. With this quadratic coupling the light field is now sensitive to the energy of the mechanical resonator and can directly control the potential energy trapping the mechanical motion. This ability to directly control the spring constant without modifying the energy of the mechanical system, unlike in linear optomechanical coupling, is explored.

Next, the bulk of this thesis deals with a high mechanical frequency optomechanical crystal which is used to coherently convert photons between different frequencies. This is accomplished via the engineered linear optomechanical coupling in these devices. Both classical and quantum systems utilize the interaction of light and matter across a wide range of energies. These systems are often not naturally compatible with one another and require a means of converting photons of dissimilar wavelengths to combine and exploit their different strengths. Here we theoretically propose and experimentally demonstrate coherent wavelength conversion of optical photons using photon-phonon translation in a cavity-optomechanical system. For an engineered silicon optomechanical crystal nanocavity supporting a 4 GHz localized phonon mode, optical signals in a 1.5 MHz bandwidth are coherently converted over a 11.2 THz frequency span between one cavity mode at wavelength 1460 nm and a second cavity mode at 1545 nm with a 93% internal (2% external) peak efficiency. The thermal and quantum limiting noise involved in the conversion process is also analyzed and, in terms of an equivalent photon number signal level, are found to correspond to an internal noise level of only 6 and 4 times 10x^-3 quanta, respectively.

We begin by developing the requisite theoretical background to describe the system. A significant amount of time is then spent describing the fabrication of these silicon nanobeams, with an emphasis on understanding the specifics and motivation. The experimental demonstration of wavelength conversion is then described and analyzed. It is determined that the method of getting photons into the cavity and collected from the cavity is a fundamental limiting factor in the overall efficiency. Finally, a new coupling scheme is designed, fabricated, and tested that provides a means of coupling greater than 90% of photons into and out of the cavity, addressing one of the largest obstacles with the initial wavelength conversion experiment.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Esta tese analisa a relação entre a ficcionalização da História Moderna e o desenvolvimento de uma ética da vida cotidiana no romance O arco-íris da gravidade, do norte-americano Thomas Pynchon. Para a sua análise e interpretação, será desenvolvido, no primeiro capítulo, um aporte teórico-metodológico que coteje a complexidade formal da narrativa (que dificulta a sua síntese temática) para se estabelecer, a partir daí, as condições de possibilidade de detecção de núcleos temáticos recorrentes que, numa rede de interconexões não-concêntrica ou dispersiva , perspectivizam no romance uma totalização fraturada do sistema-mundo moderno e contemporâneo. No segundo capítulo a ficcionalização do século XX é apresentada em suas configurações metafísica e intra-mundana, e no capítulo final são analisadas as condições que ela impõe para a formação, dentro do real ficcional, de rotinas e modos de vida eticamente positivos

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A presente pesquisa trata da análise da fundação da Neurologia. A maioria das obras que abordam o assunto a partir de uma perspectiva histórica, sobretudo, aquelas que privilegiam uma visão positivista, para a qual a investigação caminharia em direção a um ponto estático, tendem a alcançar o médico inglês seiscentista, Thomas Willis, como o inconteste precursor dessa já estabelecida especialidade médica. Nossa proposta é a de desconstruir essa ideia. A nosso ver, a historicidade do discurso científico estaria sempre em constante expansão e também em uma contínua transformação, pois diferentemente do ideal positivista, o instaurador do que Foucault designava como cientificidade não seria o descobridor de um objeto dado desde sempre, na medida em que seria enganoso supor uma história natural de um objeto cultural o objeto da história das ciências. Resta-nos, portanto, tentar compreender o sentido em que Willis funda o que ele mesmo denominava Doutrina dos Nervos. Entendemos que Willis instituiu um novo arquivo audiovisual, ou seja, uma nova articulação entre o visível e o enunciável, no que tange aos nervos. Propomos, enfim, que no horizonte da fundação a nova imbricação entre forma de representação e forma de vida emerge no mesmo processo em que Willis se consagra como um autor médico e cientista dos nervos.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Charles Henry Gilbert (1859-1928) was a pioneering ichthyologist who made major contributions to the study of fishes of the American West. As chairman of the Department ofZoology at Leland Stanford Junior University in Palo Alto, Calif., during 1891-1925, Gilbert was extremely devoted to his work and showed little patience with those ofa different mindset. While serving as Naturalist-in-Charge of the U.S. Fish Commission Steamer Albatross during her exploratory expedition to the Hawaiian Islands in 1902, Gilbert engaged in an acrimonious feud with the ship's captain, Chauncey Thomas, Jr. (1850-1919), U.S.N., over what Gilbert perceived to be an inadequate effort by the captain. This essay focuses on the conflict between two strong figures, each operatingf rom different world views, and each vying for authority. Despite the difficulties these two men faced, the voyage of the Albatross in 1902 must be considered a success, as reflected by the extensive biological samples collected, the many new species of animals discovered, and the resulting publication of important scientific papers.