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This dissertation explores the relationship between English phonotactics – sequential dependencies between adjacent segments – and the metrical parse, which relies on the division of words into syllables. Most current theories of syllabification operate under the assumption that the phonotactic restrictions which co-determine syllable boundaries are constrained by word edges. For example, a syllable can never begin with a consonant sequence that is not also attested as a word onset. This view of phonotactics as categorical is outdated: for several decades now, psycholinguistic research employing monosyllables has shown that phonotactic knowledge is gradient, and that this gradience is projected from the lexicon and possibly also based on differences in sonority among consonants located at word margins. This dissertation is an attempt to reconcile syllabification theory with this modern view of phonotactics. In what follows, I propose and defend a gradient metrical parsing model which assigns English syllable boundaries as a probabilistic function of the well-formedness relations that obtain between potential syllable onsets and offsets. I argue that this well-formedness is subserved by the same sources already established in the phonotactic literature: probabilistic generalizations over the word edges as well as sonority. In support of my proposal, I provide experimental evidence from five sources: (1) a pseudoword hyphenation experiment, (2) a reanalysis of a well-known, large-scale hyphenation study using real English words, (3) a forced-choice preference task employing nonwords presented as minimal stress pairs, (4) an online stress assignment experiment, and (5) a study of the speech errors committed by the participants of (4). The results of all studies converge in support of the gradient parsing model and correlate significantly with each other. Subsequent computer simulations suggest that the gradient model is preferred to the categorical alternative throughout all stages of lexical acquisition. This dissertation contains co-authored material accepted for publication.

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Foi realizada a implantação de um laboratório para testes de detectores com radiação de nêutrons. Uma sala foi reformada e adaptada para ser o Laboratório de TestescomNêutrons(LTN) no subsolo do prédio do Laboratório de Calibração de Instrumentos do IPEN. Foi criada uma sala de controle do sistema de exposição e posicionamento da fonte e para o operador responsável pelos procedimentos de testes dos instrumentos. Foi desenvolvida uma blindagem adequada para a fonte de 241Am(Be), previamente calibrada no Laboratório Nacional de Metrologia das Radiações Ionizantes (LNMRI), num sistema padrão primário. Um arranjo de irradiação automatizado foi implantado, possibilitando a variação da distância fonte-detector por meio de um comando à distância por um painel eletrônico localizado na sala de controle. Os resultados obtidos do levantamento radiométrico permitiram avaliar as condições existentes no LTN e a sua classificação. Foi realizado um estudo de estabilidade a curto e a médio prazo da resposta de vários detectores de nêutrons, que apresentaram resultados dentro do limite recomendado pela norma internacional. A influência da radiação espalhada foi determinada por duas técnicas: Método de Monte Carlo e método experimental, com a utilização de um cone de sombra e um detector de radiação de nêutrons portátil calibrado no LNMRI. Alguns monitores portáteis foram testados no arranjo estabelecido. Dos resultados obtidos por meio da simulação foi possível concluir que a estrutura do LTN está em concordância com os resultados obtidos em outros laboratórios que oferecem o mesmoserviço. / A laboratory for testing of detectors with neutron radiation was established. A room was renovated and adapted for the Testing Laboratory with Neutrons (LTN). A control room was created for the exposure and positioning of the source system and for localization of the operator responsible for the testing procedures of the instruments. An adequate shielding was developed for the 241Am(Be) source, previously calibrated at the National Metrology Laboratory of Ionizing Radiation (LNMRI), using a primary standard system. The set-up of the automated irradiation was established for the variation of the source-detector distance through a remote control by an electronic panel located in the control room. A radiometric survey was undertaken to evaluate the conditions at LTN and its classification. A study of the short and medium-term stability of the response of various detectors was realized, and the results were within the international recommended limits. The influence of the scattered radiation was determined by two techniques: Monte Carlo method and experimentally using a shadow cone and a portable radiation detector calibrated at LNMRI. Some portable monitors were tested at the established set-up. From the results obtained through the simulation, It was shown that the LTN structure is in agreement with the results obtained in other laboratories that offer the same service.