Evaluación de dos diferentes técnicas de instrumentación Light Speed y Profile en conductos moderadamente curvos (Un estudio comparativo)

Tesis ( Maestría en Ciencias Odontológicas con Especialidad en Endodoncia) U.A.N.L.

Few-cycle relativistic solitons in plasmas

A set of exact one-dimensional solutions to coupled nonlinear equations describing the propagation of a relativistic ultrashort circularly polarized laser pulse in a cold collisionless and bounded plasma where electrons have an initial velocity in the laser propagating direction is presented. The solutions investigated here are in the form of quickly moving envelop solitons at a propagation velocity comparable to the light speed. The features of solitons in both underdense and overdense plasmas with electrons having different given initial velocities in the laser propagating direction are described. It is found that the amplitude of solitons is larger and soliton width shorter in plasmas where electrons have a larger initial velocity. In overdense plasmas, soliton duration is shorter, the amplitude higher than that in underdense plasmas where electrons have the same initial velocity.

Se(r) um leitor em um ambiente virtual e aprendizagem: a utilização do insólito como estratégia de leitura e escrita no ensino superior

Este trabalho relata as estratégias e atividades realizadas em disciplinas semipresenciais desenvolvidas durante os períodos letivos de 2008 a 2012 com alunos dos cursos de Administração e de Ciências Contábeis, no ambiente virtual de aprendizagem Moodle. As disciplinas foram desenvolvidas segundo os princípios das abordagens colaborativas de aprendizagem com o objetivo de examinar as possibilidades de uso dos insólitos como estratégia de leitura e escrita. Buscou-se ainda apontar a aplicabilidade das estratégias didáticas descritas como forma de aprimorar as competências de leitura e escrita em alunos ingressantes no ensino superior e fornecer subsídios para a continuação da pesquisa. O trabalho mantém uma relação interdiscursiva com a obra Se um Viajante numa Noite de Inverno, de ítalo Calvino (1982), o que lhe possibilita não somente a titulação dos capítulos, mas também a construção sutil de uma presença que os perpassa. Do autor, retira também seis propostas ( leveza, rapidez, exatidão, visibilidade, multiplicidade e consistência) capazes de aprimorar a qualidade da comunicação em ambientes informáticos. Busca, ainda, na produção teórica de Michael Serres, um conceito singular de comunicação, algo capaz de transcender a substancialidade e de compreender e estimular a construção da presencialidade por meio de trocas e relações em ambientes virtuais de aprendizagem. Em vista disso, a pesquisa apoia-se na construção -reflexão- reconstrução de oficinas on-line que utilizam o insólito - concebido como algo surpreendente e propiciador de desestabilização - na construção de estratégias propiciadoras de aprimoramento da leitura e da produção textual de estudantes universitários. Recorre também às pesquisas desenvolvidas por Mikhail Bakhtin, Ângela Kleiman, Carla Coscarelli e Vilson Leffa, contribuições decisivas tanto na elaboração das oficinas on-line, quanto na reflexão que se tece ao longo da pesquisa. Por fim, busca apoio nos estudos sobre Estilos de Aprendizagem e na aplicação do Teste de Cloze para o aprimoramento das reflexões construídas

An analog model for quantum lightcone fluctuations in nonlinear optics

We propose an analog model for quantum gravity effects using nonlinear dielectrics. Fluctuations of the spacetime lightcone are expected in quantum gravity, leading to variations in the flight times of pulses. This effect can also arise in a nonlinear material. We propose a model in which fluctuations of a background electric field, such as that produced by a squeezed photon state, can cause fluctuations in the effective lightcone for probe pulses. This leads to a variation in flight times analogous to that in quantum gravity. We make some numerical estimates which suggest that the effect might be large enough to be observable. © 2012 Elsevier Inc.

Avaliação radiográfica e microscópica (MEV-Microscopia eletrônica de varredura), do preparo apical promovido por três diferentes técnicas para preparo biomecânico dos canais radiculares, empregando sistemas rotatórios

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Velocidades superluminais na relatividade geral: métrica de Alcubierre

The constancy of the speed of light appears to be an unbreakable barrier for future interstellar journeys, tending to infinite energy would be needed to achieve such speed. However in the general relativity one can circumvent this limit and get arbitrarily higher global speeds, without violating the constancy of the speed of light. The so-called “warp-drive metrics is a theoretical means to achieve global superluminal speeds. The Alcubierre metric is one case in which the science fiction inspired reality, from which was drawn the term “warp-drive. In the present work, a study of the theories of special and general relativity and of some works on solutions that allow superluminal speeds will be done

Effects of current speed and turbidity on stationary light-trap catches of larval and juvenile fishes

Light traps are one of a number of different gears used to sample pelagic larval and juvenile fishes. In contrast to conventional towed nets, light traps primarily collect larger size classes, including settlement-size larvae (Choat et al., 1993; Hickford and Schiel, 1999 ; Hernandez and Shaw, 2003), and, therefore, have become important tools for discerning recruitment dynamics (Sponaugle and Cowen, 1996; Wilson, 2001). The relative ease with which multiple synoptic light trap samples can be taken means that larval distribution patterns can be mapped with greater spatial resolution (Doherty, 1987). Light traps are also useful for sampling shallow or structurally complex habitats where towed nets are ineffective or prohibited (Gregory and Powles, 1985; Brogan, 1994; Hernandez and Shaw, 2003).

Gasoline fuelled partially premixed compression ignition in a light duty multi cylinder engine: A study of low load and low speed operation

The objective of this study was to examine the operating characteristics of a light duty multi cylinder compression ignition engine with regular gasoline fuel at low engine speed and load. The effects of fuel stratification by means of multiple injections as well as the sensitivity of auto-ignition and burn rate to intake pressure and temperature are presented. The measurements used in this study included gaseous emissions, filter smoke opacity and in-cylinder indicated information. It was found that stable, low emission operation was possible with raised intake manifold pressure and temperature, and that fuel stratification can lead to an increase in stability and a reduced reliance on increased temperature and pressure. It was also found that the auto-ignition delay sensitivity of gasoline to intake temperature and pressure was low within the operating window considered in this study. Nevertheless, the requirement for an increase of pressure, temperature and stratification in order to achieve auto-ignition time scales small enough for combustion in the engine was clear, using pump gasoline. Copyright © 2009 SAE International.

Investigation on integrated high speed DFB light source and narrow bandwidth RCE photodetector for WDM fiber communication network application

Electroabsorption (EA) modulator integrated with partially gain coupling distributed feedback (DFB) lasers have been fabricated and shown high single mode yield and wavelength stability. The small signal bandwidth is about 7.5 GHz. Strained Si1-chiGechi/Si multiple quantum well (MQW) resonant-cavity enhanced (RCE) photodetectors with SiO2/Si distributed Bragg reflector (DBR) as the mirrors have been fabricated and shown a clear narrow bandwidth response. The external quantum efficiency at 1.3 mum is measured to be about 3.5% under reverse bias of 16 V. A novel GaInNAs/GaAs MQW RCE p-i-n photodetector with high reflectance GaAs/ALAs DBR mirrors has also been demonstrated and shown the selectively detecting function with the FWHM of peak response of 12 nm.

Influence of curd cutting programme and stirring speed on the prediction of syneresis indices in cheese-making using NIR light backscatter

An NIR reflectance sensor, with a large field of view and a fibre-optic connection to a spectrometer for measuring light backscatter at 980 nm, was used to monitor the syneresis process online during cheese-making with the goal of predicting syneresis indices (curd moisture content, yield of whey and fat losses to whey) over a range of curd cutting programmes and stirring speeds. A series of trials were carried out in an 11 L cheese vat using recombined whole milk. A factorial experimental design consisting of three curd stirring speeds and three cutting programmes, was undertaken. Milk was coagulated under constant conditions and the casein gel was cut when the elastic modulus reached 35 Pa. Among the syneresis indices investigated, the most accurate and most parsimonious multivariate model developed was for predicting yield of whey involving three terms, namely light backscatter, milk fat content and cutting intensity (R2 = 0.83, SEy = 6.13 g/100 g), while the best simple model also predicted this syneresis index using the light backscatter alone (R2 = 0.80, SEy = 6.53 g/100 g). In this model the main predictor was the light backscatter response from the NIR light back scatter sensor. The sensor also predicted curd moisture with a similar accuracy.

Cosmological constant and the speed of light

By exploring the relationship between the propagation of electromagnetic waves in a gravitational field and the light propagation in a refractive medium, it is shown that, in the presence of a positive cosmological constant, the velocity of light will be smaller than its special relativity value. Then, restricting again to the domain of validity of geometrical optics, the same result is obtained in the context of wave optics. It is argued that this phenomenon and the anisotropy in the velocity of light in a gravitational field are produced by the same mechanism.

Towards a new test of time dilation: Laser spectroscopy on lithium ions stored at a velocity of 33.8 % of the speed of light

The subject of the presented thesis is the accurate measurement of time dilation, aiming at a quantitative test of special relativity. By means of laser spectroscopy, the relativistic Doppler shifts of a clock transition in the metastable triplet spectrum of ^7Li^+ are simultaneously measured with and against the direction of motion of the ions. By employing saturation or optical double resonance spectroscopy, the Doppler broadening as caused by the ions' velocity distribution is eliminated. From these shifts both time dilation as well as the ion velocity can be extracted with high accuracy allowing for a test of the predictions of special relativity. A diode laser and a frequency-doubled titanium sapphire laser were set up for antiparallel and parallel excitation of the ions, respectively. To achieve a robust control of the laser frequencies required for the beam times, a redundant system of frequency standards consisting of a rubidium spectrometer, an iodine spectrometer, and a frequency comb was developed. At the experimental section of the ESR, an automated laser beam guiding system for exact control of polarisation, beam profile, and overlap with the ion beam, as well as a fluorescence detection system were built up. During the first experiments, the production, acceleration and lifetime of the metastable ions at the GSI heavy ion facility were investigated for the first time. The characterisation of the ion beam allowed for the first time to measure its velocity directly via the Doppler effect, which resulted in a new improved calibration of the electron cooler. In the following step the first sub-Doppler spectroscopy signals from an ion beam at 33.8 %c could be recorded. The unprecedented accuracy in such experiments allowed to derive a new upper bound for possible higher-order deviations from special relativity. Moreover future measurements with the experimental setup developed in this thesis have the potential to improve the sensitivity to low-order deviations by at least one order of magnitude compared to previous experiments; and will thus lead to a further contribution to the test of the standard model.

High-speed video-oculography applied to assess pupil light reflex

Póster presentado en el VII European/ I World Meeting in Visual and Physiological Optics