978 resultados para Cristais fotônicos. Polaritons. Fonons e quasi-periódicos


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A Administração Financeira surge no início do século XIX juntamente com o movimento de consolidação das grandes empresas e a formação dos mercados nacionais americano enquanto que no Brasil os primeiros estudos ocorrem a partir da segunda metade do século XX. Desde entãoo país conseguiu consolidar alguns centros de excelência em pesquisa, formar grupo significativo de pesquisadores seniores e expandir as áreas de pesquisa no campo, contudo, ainda são poucos os trabalhos que buscam retratar as características da produtividade científica em Finanças. Buscando contribuir para a melhor compreensão do comportamento produtivo dessa área a presente pesquisa estuda sua produção científica, materializada na forma de artigos digitais, publicados em 24 conceituados periódicos nacionais classificados nos estratos Qualis/CAPES A2, B1 e B2 da Área de Administração, Ciências Contábeis e Turismo. Para tanto são aplicadas a Lei de Bradford, Lei do Elitismo de Price e Lei de Lotka. Pela Lei de Bradford são identificadas três zonas de produtividade sendo o núcleo formado por três revistas, estando uma delas classificada no estrato Qualis/CAPES B2, o que evidencia a limitação de um recorte tendo como único critério a classificação Qualis/CAPES. Para a Lei do Elitismo de Price, seja pela contagem direta ou completa, não identificamos comportamento de uma elite semelhante ao apontado pela teoria e que conta com grande número de autores com apenas uma publicação.Aplicando-se o modelo do Poder Inverso Generalizado, calculado por Mínimos Quadrados Ordinários (MQO), verificamos que produtividade dos pesquisadores, quando feita pela contagem direta, se adequa àquela definida pela Lei de Lotka ao nível de α = 0,01 de significância, contudo, pela contagem completa não podemos confirmar a hipótese de homogeneidade das distribuições, além do fato de que nas duas contagens a produtividade analisada pelo parâmetro n é maior que 2 e, portanto, a produtividade do pesquisadores de finanças é menor que a defendida pela teoria.

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We study solutions of the two-dimensional quasi-geostrophic thermal active scalar equation involving simple hyperbolic saddles. There is a naturally associated notion of simple hyperbolic saddle breakdown. It is proved that such breakdown cannot occur in finite time. At large time, these solutions may grow at most at a quadruple-exponential rate. Analogous results hold for the incompressible three-dimensional Euler equation.

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Objective: To assess the net 5 year effects of intervention of a community based demonstration project, the Heartbeat Wales programme, on modifiable behavioural risks for prevention of cardiovascular disease.

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There is a variety of optical evidence for some unification of different types of active galactic nuclei and quasi-stellar objects (QSOs). The case is very strong for the unification of at least some Seyfert galaxies, where polarization data show that the type assigned to the Seyfert galaxy must depend on viewing direction. It has been proposed that Fanaroff-Riley type 2 (FR2) radio galaxies are quasars seen in a direction from which the quasar is obscured, and there is some limited direct evidence for this picture. The broad absorption line QSOs may be normal QSOs seen from a special direction. Some of the sources observed to have high luminosities in the far infrared could be obscured QSOs and active nuclei. Mergers and interactions are likely to play an important role in nuclear activity, and active galaxies and QSOs could change their apparent types through these encounters followed by subsequent evolution.

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Parallel recordings of spike trains of several single cortical neurons in behaving monkeys were analyzed as a hidden Markov process. The parallel spike trains were considered as a multivariate Poisson process whose vector firing rates change with time. As a consequence of this approach, the complete recording can be segmented into a sequence of a few statistically discriminated hidden states, whose dynamics are modeled as a first-order Markov chain. The biological validity and benefits of this approach were examined in several independent ways: (i) the statistical consistency of the segmentation and its correspondence to the behavior of the animals; (ii) direct measurement of the collective flips of activity, obtained by the model; and (iii) the relation between the segmentation and the pair-wise short-term cross-correlations between the recorded spike trains. Comparison with surrogate data was also carried out for each of the above examinations to assure their significance. Our results indicated the existence of well-separated states of activity, within which the firing rates were approximately stationary. With our present data we could reliably discriminate six to eight such states. The transitions between states were fast and were associated with concomitant changes of firing rates of several neurons. Different behavioral modes and stimuli were consistently reflected by different states of neural activity. Moreover, the pair-wise correlations between neurons varied considerably between the different states, supporting the hypothesis that these distinct states were brought about by the cooperative action of many neurons.

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El interés de los medios por acercarse al mundo educativo fue significativo en los años 80 del siglo pasado cuando varios diarios comenzaron a realizar actividades destacadas que conectaban el periodismo y las aulas. Además, en 1985, la Asociación de Editores de Diarios Españoles (AEDE) y el Ministerio de Educación lanzaron una iniciativa denominada “Programa Prensa-Escuela” que concluyó en 1990. En la actualidad, algunos de esos proyectos pioneros, como “La Voz de la Escuela” o “Ideal en Clase”, siguen adelante, junto a otros que, posteriormente, han ido engrosando el abanico de posibilidades periodístico-escolares para el alumnado, el profesorado y, en menor medida, los padres. En la presente Tesis doctoral se ha llevado a cabo una revisión de la bibliografía en torno al término “programa prensa-escuela”, que no obedece a la misma idea gestada en el Programa de 1985. Por este motivo, se ha propuesto una conceptualización inédita de los proyectos agrupados bajo esa etiqueta, atendiéndose a la trayectoria de cada uno de los que se ajustan a la nueva definición. Con el ánimo de concretar qué programas existen en el 2015, se ha recabado información de las 48 cabeceras con mayor tirada en España, para después estructurar esos datos y presentar las actividades que los periódicos desarrollan entre el alumnado de Educación Secundaria. Posteriormente, se sientan las bases de un futuro análisis de contenido mediante la descripción de los suplementos escolares de La Voz de Galicia y El País, de notable relevancia y que dan cuenta de la coexistencia de diferentes perspectivas de la función de la prensa en la educación. Brevemente, se ha considerado también la relación de estas iniciativas con otras de diferentes países, haciendo hincapié en sus similitudes y sus objetivos pedagógicos. De esta manera, se ha logrado dar testimonio de las líneas metodológicas por las que se rigen las múltiples actividades, lo que, finalmente, ha conducido a abordar el papel del profesorado y algunas valoraciones de éstos sobre los proyectos. Por último, se han aportado unas indicaciones de mejora, donde han quedado reflejados los diversos aspectos previamente analizados.

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Research performed in this thesis studies the growth and evolution of advertising investment in digital media compared to traditional printed media, in particular daily newspapers. By means of advertising inserts in printed newspaper and online newspapers, the study’s objective was to confirm that digital media consolidate as an advertising platform. Throughout this study we used different quantitative and qualitative tools to demonstrate the starting hypothesis of this thesis. We used a combined methodology that included: a) joint analysis of printed newspaper “El Mundo” and online newspaper “elmundo.es” advertising content; b) analysis of advertising investment state-of-the-art; c) deep interviews to different media professionals, including advertisers, publicists, media planning, and researchers. A comparative study between the printed newspaper “El Mundo” and the online newspaper “elmundo.es” supported the analysis of contents in a realistic situation. Therefore a deep study of advertising inserts in both the printed and online version of “El Mundo” was performed. The main goal of this work was to show how advertising invesment is moving from traditional printed media to digital media The results of this study reveal that investment in digital media increases, meanwhile investment reduces in traditional media. At the same time, new reading habits along with technological innovation attracts readers to digital platforms. As a consequence, traditional printed newspapers have the immediate need to somehow engage online-newspaper readers into printed platforms. Hence, many advertisers already invest large sums of money in digital media, with marketing strategies and plans focused to online advertising campaigns in Internet. It is also true that in recent years printed and online media stopped “fighting”, which lead to the possibility of joint marketing and communication strategies between the aforementioned digital and online media. This research has different implications, one of them is that printed media seems to be a bussiness model which needs to be reinvented to adapt itself to the media’s current situation in order to be profitable and not to disappear. On the other hand, digital media must have a well-defined strategy with concrete and viable goals in online investment. Finally, it is important that new readers are taken into account by newspapers, this is: new readers mostly use digital platforms, thus interaction between readers and newspapers is much different than what it used to be when only printed newspapers existed. Media must go and be where the new reader is.

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En este proyecto se ha desarrollado una aplicación Web cuya finalidad es ofrecer al usuario datos provenientes del análisis de texto de las noticias que se encuentran en periódicos online. La aplicación permite al usuario realizar búsquedas personalizadas sobre temáticas específicas y configurar algunos tipos de análisis sobre la información recuperada. Entre los análisis que son llevados a cabo destaca el análisis del sentimiento. Para ello se ofrece la posibilidad de que el usuario utilice sus propios diccionarios de pares palabra-valor, utilizados para realizar este tipo de análisis. Para la codificación de la herramienta, se ha utilizado el lenguaje de programación Python y la framework web Django. El almacenamiento de la información de la aplicación se ha realizado sobre una base de datos NoSQL de tipo MongoDB.

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(Sa)-Binam-D-prolinamide (20 mol%), instead of (Sa)-binam-L-prolinamide, in combination with chloroacetic acid (100 mol%) is an efficient organocatalyst for the direct aldol reaction between α-keto esters as electrophiles and alkyl and α-functionalised ketones, under quasi solvent-free conditions, providing access to highly functionalised chiral quaternary γ-keto α-hydroxyesters with up to 92% ee.

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We have observed a large spin splitting between "spin" +1 and -1 heavy-hole excitons, having unbalanced populations, in undoped GaAs/AlAs quantum wells in the absence of any external magnetic field. Time-resolved photoluminescence spectroscopy, under excitation with circularly polarized light, reveals that, for high excitonic density and short times after the pulsed excitation, the emission from majority excitons lies above that of minority ones. The amount of the splitting, which can be as large as 50% of the binding energy, increases with excitonic density and presents a time evolution closely connected with the degree of polarization of the luminescence. Our results are interpreted on the light of a recently developed model, which shows that, while intraexcitonic exchange interaction is responsible for the spin relaxation processes, exciton-exciton interaction produces a breaking of the spin degeneracy in two-dimensional semiconductors.

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We study the optically induced coupling between spins mediated by polaritons in a planar microcavity. In the strong-coupling regime, the vacuum Rabi splitting introduces anisotropies in the spin coupling. Moreover, due to their photonlike mass, polaritons provide an extremely long spin coupling range. This suggests the realization of two-qubit all-optical quantum operations within tens of picoseconds with spins localized as far as hundreds of nanometers apart.

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We consider quasi-Newton methods for generalized equations in Banach spaces under metric regularity and give a sufficient condition for q-linear convergence. Then we show that the well-known Broyden update satisfies this sufficient condition in Hilbert spaces. We also establish various modes of q-superlinear convergence of the Broyden update under strong metric subregularity, metric regularity and strong metric regularity. In particular, we show that the Broyden update applied to a generalized equation in Hilbert spaces satisfies the Dennis–Moré condition for q-superlinear convergence. Simple numerical examples illustrate the results.

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The purpose of this paper is to analyze the quasi-elastic deformational behavior that has been induced by groundwater withdrawal of the Tertiary detrital aquifer of Madrid (Spain). The spatial and temporal evolution of ground surface displacement was estimated by processing two datasets of radar satellite images (SAR) using Persistent Scatterer Interferometry (PSI). The first SAR dataset was acquired between April 1992 and November 2000 by ERS-1 and ERS-2 satellites, and the second one by the ENVISAT satellite between August 2002 and September 2010. The spatial distribution of PSI measurements reveals that the magnitude of the displacement increases gradually towards the center of the well field area, where approximately 80 mm of maximum cumulated displacement is registered. The correlation analysis made between displacement and piezometric time series provides a correlation coefficient greater than 85% for all the wells. The elastic and inelastic components of measured displacements were separated, observing that the elastic component is, on average, more than 4 times the inelastic component for the studied period. Moreover, the hysteresis loops on the stress–strain plots indicate that the response is in the elastic range. These results demonstrate the quasi-elastic behavior of the aquifer. During the aquifer recovery phase ground surface uplift almost recovers from the subsidence experienced during the preceding extraction phase. Taking into account this unique aquifer system, a one dimensional elastic model was calibrated in the period 1997–2000. Subsequently, the model was used to predict the ground surface movements during the period 1992–2010. Modeled displacements were validated with PSI displacement measurements, exhibiting an error of 13% on average, related with the inelastic component of deformation occurring as a long-term trend in low permeability fine-grained units. This result further demonstrates the quasi-elastic deformational behavior of this unique aquifer system.