Este estudo teve como objetivo avaliar o selamento apical de canais radiculares obturados por diferentes técnicas. Cento e seis incisivos inferiores humanos tiveram seus canais instrumentados através da técnica escalonada regressiva. Após a instrumentação, cem dentes foram impermeabilizados nas superfícies externas da coroa e da raiz, exceto nas proximidades do forame apical, com uma camada de araldite e duas camadas de esmalte para unhas. Em seguida, foram divididos em cinco grupos de vinte elementos cada, de acordo com a técnica de obturação utilizada: 1. condensação lateral ativa realizada com lima tipo Kerr; 2. Onda Contínua de Condensação realizada com o System B; 3. guta-percha termoplastificada injetável realizada com o sistema Ultrafil; 4. guta-percha termoplastificada mecanicamente realizada com o sistema JS Quick-Fill; 5. gutapercha termoplastificada associada a um cone principal realizada com o sistema Microseal. Os seis dentes restantes foram utilizados como controles positivo e negativo. Após a obturação, as aberturas coronárias foram seladas e os dentes imersos em solução aquosa de azul de metileno a 2%, durante setenta e duas horas, a 37ºC. A seguir, os dentes foram seccionados longitudinalmente e a infiltração apical avaliada em um estereomicroscópio. O sistema Microseal apresentou a melhor capacidade de selamento apical, seguido pelo System B, JS Quick-Fill, Ultrafil e pela técnica da condensação lateral. A análise estatística dos resultados demonstrou que: 1. o sistema Microseal apresentou selamento apical semelhante ao do System B e melhor que dos demais grupos; 2. o System B apresentou selamento apical melhor que o da técnica da Condensação Lateral e semelhante ao dos demais grupos; 3. os grupos da Condensação Lateral, Ultrafil e JS Quick-Fill, apresentaram capacidade de selamento semelhante. / The purpose of this study was to compare the apical sealing of root canals obturated with different techniques. One hundred-six human mandibular incisors were submitted to instrumentation by means of the step-back technique. After instrumentation, one hundred teeth received an impermeable coating on the external surfaces of the crown and root (except for the area nearby the apical foramen) with one layer of araldite and two layers of nail polish. Afterwards, they were divided in five groups containing twenty elements each, according to the obturation technique employed: 1. lateral condensation with Kerr file; 2. continuous wave of condensation technique with System B; 3. thermoplasticized injectable gutta-percha technique with the Ultrafil system; 4. mechanically thermoplasticized gutta-percha with the JS Quick-Fill system and 5. thermoplasticized gutta-percha associated to a master cone with the Microseal system. The six remaining teeth were employed as negative and positive controls. After obturation, the access cavities were sealed and the teeth were immersed in aqueous 2% methylene blue dye for 72 hours at 37ºC. After that, the teeth were longitudinally sectioned and the apical leakage was evaluated in a stereomicroscope. The Microseal system presented the best apical sealing ability, followed by System B, JS Quick-Fill, Ultrafil and the lateral condensation technique. The statistical analysis of the results demonstrated that: 1. the Microseal system presented an apical sealing similar to System B and better than the other groups; 2. System B presented better apical sealing than the lateral condensation technique, being similar to the other groups; and 3. the lateral condensation, Ultrafil and JS Quick-Fill groups demonstrated similar sealing ability.

Thesis (M.D.S.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 67-83) Also available in print.

Thesis (M.D.S.)--University of Hong Kong, 1993. / Includes bibliographical references (p. 105-125). Also available in print.

Dans le contexte actuel où le spectre électromagnétique est saturé, une transmission efficace par les systèmes sans fils exige une connaissance approfondie du comportement du canal de propagation. La modélisation stochastique du canal permet d'évaluer les performances d'un système de communication dans un environnement donné. Ces dernières années, nous assistons à l'apparition de techniques mettant à profit les diversités du canal (diversité temporelle, diversité spatiale et diversité de polarisation). Pour évaluer leurs performances, les sondeurs de canal et les modèles proposés se sont complexifiés. Cette thèse est une contribution au sondage multiparamétrique d'un canal radiofréquence à l'intérieur des bâtiments. Elle aborde l'amélioration du sondeur de canal développé préalablement à TELECOM ParisTech. La caractéristique originale de ce sondeur est l'utilisation de récepteurs cinq-port. Le cinq-port est un circuit interférométrique qui permet de calculer le rapport complexe entre deux signaux hyperfréquences. Son faible coût permet d'exploiter seize chaînes parallèles en réception. Le signal utilisé pour le sondage est un signal chirp couvrant la bande de fréquences entre 2.2 et 2.7 GHz. Des estimations haute-résolution de direction de départ, direction d'arrivée, polarisation, fréquence Doppler et retard sont effectuées pour valider le sondeur. Cette thèse est aussi une contribution à la modélisation statistique des canaux UWB. Un modèle spatio-temporel est élaboré à partir de mesures SIMO (Single Input Multiple Output) couvrant la bande de fréquences entre 2 GHz et 8 GHz. Les valeurs des paramètres du modèle sont comparées pour différents environnements, de type bureau et de type résidentiel, en condition de visibilité et de non visibilité.

The Naples Bay Estuarine System, situated in southwest Florida, has undergone extensive modifications caused directly and indirectly by anthropogenic influences. These alterations include the substitution of mangrove-forested shorelines with concrete bulkheads, canalization of the watershed and along the bay shoreline, and navigational channel dredging. The system consists of northern Naples Bay, southern Naples Bay, and Dollar Bay, whose shorelines range from highly developed to undeveloped, respectively. This project explored the natural geological response of the system to these alterations using data from side scan sonar, sediment grab samples, and vibracores. In highly urbanized northern Naples Bay, benthic substrates consist primarily of muddy sands, with few oyster reefs. Southern Naples Bay and Dollar Bay, however, consist of coarser sediment, and are characterized by extensive mangrove shorelines and numerous oyster reefs. The impact of anthropogenic alterations has significantly shifted sediment distributions in northern Naples Bay from a coarser to a finer grained substrate. This shift has occurred to a lesser degree in southern Naples Bay, and Dollar Bay has not made this transition, due to the relative lack of anthropogenic modifications made to this part of the system.

Thesis (M.D.S.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 67-83).

Thesis (Ph. D.)--University of Michigan, 1964. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Inaug.-diss.--Würzburg. / Published also without thesis note. "Literatur-verzeichnis": p. [7]-8.

Thesis (M.A.)--University of California, San Diego, 2009. / Title from first page of PDF file (viewed January 19, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 82-86).

Thesis (M.A.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 46-49).