Thesis--University of Rochester, 1965.

Indiana University-Purdue University Indianapolis (IUPUI) / Objective: The objective was to assess a multiple emission peak light-emitting-diode (LED) light-curing unit (LCU) by measuring the polymerization efficiency through the degree of conversion (DC) and Knoop microhardness (KHN) of a resin-based pit and fissure sealant at various light curing times and two distances compared to a single emission peak LED LCU. Method: Sixty disks of resin-based pit and fissure sealant (Delton, DENTSPLY, York, PA) samples (6x1mm) were fabricated (n=5/LCU/group). Prepared samples were polymerized using 10, 20 and 40 second curing time at 2 or 4 mm curing distances. The irradiance and radiant exposure received on the top/bottom surfaces of the samples were measured using the Managing Accurate Resin Curing-Resin Calibrator (MARC-RC) system. The samples were stored at 37°C for one hour. Then, the DC (n=3/surface) and KHN (n=5/surface) measurements were collected on the top and bottom surfaces using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and a microhardness tester (Instron) utilizing 25-gm at 10 seconds dwell time, respectively. Multiple-way ANOVA was performed followed by Tukey test (α=0.05). Result: The irradiance from the multiple emission peak LED LCU was significantly higher than the single emission peak LED LCU (1312.6 and 768.3 mW/cm2) respectively. Moreover, the multiple emission peak LED LCU displayed significantly higher DC (82.5%) and microhardness (26.2 KHN) compared to the single emission peak LED LCU (75.5% DC and 21.2 KHN) when curing samples at 2 and 4 mm curing distances assessed using 10, 20 and 40-second curing times. The 10 second cure at 4 mm showed significantly lower DC and KHN values compared to the other groups. Conclusion: The multiple emission peak LED LCU demonstrated significantly higher irradiance, DC and KHN compared to the single emission peak LED LCU on a resin-based pit and fissure sealant at 2 and 4 mm curing distances and 10, 20 and 40 second curing times. Therefore, the multiple emission peak LED LCU performed higher than the single emission peak LED LCU.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: The ability of sealants to prevent caries is directly related to the sealant being retained in teeth. The longer the material remains bonded to the occlusal surface, the more protection it provides to the tooth. Objective: The aim of this in-vitro study was to evaluate the influence of pit and fissure morphologies and sealant viscosity on sealant penetration and micro-leakage. 82 Study Hypothesis: The low viscosity dental sealant will express better penetration ability and less microleakage in permanent molars with any pit and fissure morphology than the high viscosity sealant. Material and methods: Permanent extracted molars (n = 150) were distributed into two groups based on two types of sealant (high and low viscosity) Permanent extracted molars (n = 150) were selected using the International Caries Detection Assessment system (ICDAS) criteria 0-1. Teeth were stored in 0.1-percent thymol and distilled water. Teeth were assigned to three subgroups according to the fissure’s morphology. Enamel was etched with 35-percent phosphoric acid for 30 seconds; two different light cured sealants were placed, Group A: Delton and Group B: Ultra X Plus. Specimens were thermocycled for 500 cycles between two water baths, having a 40°C temperature differential (4°C to 48°C). Teeth were coated with nail varnish and wax, except in the occlusal areas. All specimens were immersed in 1-percent methylene blue dye at 37°C for 24 hours. Specimens were sectioned longitudinally in a bucco-lingual direction, and the sections were photographed and analyzed by a previously trained examiner for fissure morphology, sealant penetration, and microleakage using a standardized grading system. Data were entered and statistically analyzed, at the 5-percent significance level. Results: Viscosity of sealant and morphology of fissures had significant effects on sealant penetration (p < 0.001). The interaction between viscosity of sealant and morphology of fissures was not significant (p = 0.4236). The sealant penetration for Delton was significantly higher than the UltraSeal XT Plus (p < 0.0001). The sealant penetration for fissure I-type was significantly lower than fissures U and V-types (p < 0.0001). Sealant penetration for Y-type was significantly lower than U and V-types (p < 83 0.0001). However, the viscosity of sealant and morphology of fissures did not have significant effect on microleakage (p = 0.5891 and p = 0.4857). The interaction between the viscosity of the sealant material and the morphology of pit and fissures was not significant (p = 0.6657). Conclusion: The results of the present study indicated the viscosity of the sealant and the morphology did not affect the microleakage. On the other hand, the viscosity of sealant affected the penetration ability of dental sealant. The low viscosity dental sealant (Delton) exhibited a better penetration than the high viscosity sealant (UltraSeal XT Plus). As the morphology of pit and fissure directly affected the penetration ability, the fissures types U and V exhibited a better penetration than fissure types Y and I.

Indiana University-Purdue University Indianapolis (IUPUI) / The concepts of using a pit and fissure sealant material to prevent dental caries have been well established in dental research. Effectiveness of a pit and fissure sealant material is limited to its ability to remain bonded to the occlusal surfaces. Adding a dentin-bonding agent between the etched enamel and the sealant material has been demonstrated as a way of optimizing bond strength in the face of moisture and salivary contamination. The purpose of this study was to examine if there was a difference in fissure penetration or microleakage between a conventional pit and fissure sealant or a flowable composite when used as a pit and fissure sealant, while using three different adhesive systems. Delton Direct Delivery System (Dentsply), an opaque, light cured pit and fissure sealant and the commercially available flowable composite, Revolution Formula 2 (Kerr) was selected for this study. Three clinically used adhesive systems selected for this study were: conventional phosphoric acid etching; Opti-bond Solo Plus(Kerr), a single bottle system; and Prompt L-Pop (3M ESPE), an all-in-one primer adhesive. One hundred fifty extracted caries-free third molars, selected for well-defined occlusal pits, were randomly divided into six treatment groups. Fissure penetration and microleakage was examined after immersion of the treated teeth in 5.0-percent methylene blue solution for 18 hours; the teeth were removed and thoroughly cleaned. Mesial and distal flat-ground sections were obtained and examined at X20; microleakage was recorded as either present or absent, and penetration was recorded as either complete or incomplete. The interaction between the material and the adhesive system was non-significant based on the logistic regression model for the penetration and the microleakage, so that only the main effects of material and adhesive system were included in the final model. Enamel conditioning with the total-etch and single-bottle adhesive system provided consistently microleakage resistance when compared with the use of the all-in-one bonding system. The all-in-one adhesive system demonstrated the most microleakage regardless of the material used for the pit and fissure sealant. The hypothesis of this thesis was that there would be no significant difference in fissure penetration or microleakage between the conventional pit and fissure sealant or the flowable composite, regardless of the adhesive system used. The results of this study support the hypothesis that there was no significant difference in fissure penetration between the materials. The result did demonstrate that there was significant difference in microleakage between the three different adhesive systems used.

Indiana University-Purdue University Indianapolis (IUPUI) / The concepts of using a pit and fissure sealant material to prevent dental caries have been well established in dental research. Effectiveness of a pit and fissure sealant material is limited to its ability to remain bonded to the occlusal surfaces . Adding a dentin-bonding agent between the etched enamel and the sealant material has been demonstrated as a way of optimizing bond strength in the face of moisture and salivary contamination. The purpose of this study was to examine if there was a difference in fissure penetration or microleakage between a conventional pit and fissure sealant or a flowable composite when used as a pit and fissure sealant, while using three different adhesive systems. Delton Direct Delivery System (Dentsply), an opaque, light cured pit and fissure sealant and the commercially available flowable composite, Revolution Formula 2 (Kerr) was selected for this study. Three clinically used adhesive systems selected for this study were: conventional phosphoric acid etching; Opti-bond Solo Plus(Kerr), a single bottle system; and Prompt L-Pop (3M ESPE), an all-in-one primer adhesive. One hundred fifty extracted caries-free third molars, selected for well-defined occlusal pits, were randomly divided into six treatment groups. Fissure penetration and microleakage was examined after immersion of the treated teeth in 5.0-percent methylene blue solution for 18 hours; the teeth were removed and thoroughly cleaned. Mesial and distal flat-ground sections were obtained and examined at X20; micro leakage was recorded as either present or absent, and penetration was recorded as either complete or incomplete. The interaction between the material and the adhesive system was non-significant based on the logistic regression model for the penetration and the microleakage, so that only the main effects of material and adhesive system were included in the final model. Enamel conditioning with the total-etch and single-bottle adhesive system provided consistently microleakage resistance when compared with the use of the all-in-one bonding system. The all-in-one adhesive system demonstrated the most microleakage regardless of the material used for the pit and fissure sealant. The hypothesis of this thesis was that there would be no significant difference in fissure penetration or microleakage between the conventional pit and fissure sealant or the flowable composite, regardless of the adhesive system used. The results of this study support the hypothesis that there was no significant difference in fissure penetration between the materials. The result did demonstrate that there was significant difference in microleakage between the three different adhesive systems used.

L'alliage N18 est utilisé pour la fabrication des disques de turbine des moteurs M88. Ce superalliage base Ni, élaboré par métallurgie des poudres (MDP), associe une bonne mise en œuvre à des propriétés mécaniques statiques très élevées au-dela de 650°c. La difficulté dans la maîtrise des alliages obtenus par MDP, réside dans le contrôle du taux d'inclusions entraînées pendant l'élaboration. La présence, même extrêmement faible, de ces défauts microstructuraux (<100µm) pourrait accidentellement entraîner l'amorçage de petites fissures de fatigue elliptiques, sous l'effet de concentrations de contraintes comme les entailles de fixation des aubes. Il est donc important de savoir si le comportement en propagation de ces petites fissures (0.1mm

Este trabalho trata de fissura, uma das principais patologias que podem ocorrer em edifícios residenciais em alvenaria estrutural, visando identificar os locais onde elas aparecem com mais frequência, para assim procurar formas de evitá-las. Inicialmente foram realizadas visitas a vários edifícios em alvenaria estrutural de forma a levantar as principais fissuras encontradas nesse tipo de estrutura. Identificou-se que as fissuras são mais frequentes nos contornos de aberturas, diante disse foi realizado um estudo teórico, com a utilização de um programa computacional, para se determinar algumas das principais causas prováveis dessas patologias através de modelos numéricos adequados. Finalmente, foram analisadas algumas das soluções para as patologias encontradas, tentando sugerir as melhores soluções para cada caso. / This paper deals with fissure, one of major diseases that can occur in a structural masonry residential buildings, in order to identify the locals they usually occur, to seek ways to avoid them. Initially were realized visits a several structural masonry buildings to analise the principals fissures in this type of structure. Was identified that the fissures are more frequently in the contours of openings, given this, was realized a theoretical study using a finite element computer program to identify some of the main possible causes of these pathologies through adequate numerical models. Finally, some possible solutions for the conditions found were analyzed, trying to suggest the best solutions for each case.

EDF souhaite conforter la justification de l'intégrité des cuves de réacteurs nucléaires à eau pressurisée, basées sur l'amorçage de fissure, par le concept d'arrêt de fissure. L'objectif de la thèse est de consolider les travaux de prévision de l'arrêt des fissures fragiles dans l'acier de cuve. Des essais d'arrêt de fissure isothermes réalisés entre -150°C et -50°C sur des éprouvettes CT et sur des anneaux en compression ont été analysés. Les analyses fractographiques montrent que la propagation et l'arrêt de fissure se produisent en clivage même si de la déchirure ductile précède la propagation instable de fissure. Un critère local d'arrêt de fissure fragile est appliqué lors de calculs par éléments finis en élastoviscoplasticité et en dynamique : la rupture se produit si la contrainte principale maximale est égale à une contrainte critique. Ce critère permet de bien prédire les vitesses de propagation ainsi que les longueurs de fissure à l'arrêt. La contrainte critique augmente avec la température en relation avec les signes de dissipation observés sur les surfaces de rupture. Une dépendance du critère à la géométrie est observée. Elle peut être liée aux hypothèses de calculs réalisés en bidimensionnel. L'étude de la dynamique de la structure montre que le phénomène d'arrêt de fissure est fortement lié à la dynamique globale de la structure : l'arrêt et la fermeture de la fissure interviennent simultanément.

La plupart de l'énergie en France est d'origine nucléaire. Le bâtiment de réaction comporte une enceinte interne et une externe. L'enceinte interne est en béton précontraint, pour limiter le débit de fuite dans l'espace interne-ence inte. La précontrainte diminue au cours du temps à cause du fluage du béton. Il risque de se propager des fissures par une pression accidentelle interne. On pose alors deux problèmes de recherche : propagation de macrofissures dans une structure viscoélastique ; comportement effectif d'un matériau viscoélastique microfissuré. On développe tout d'abord un modèle viscoélastique de Burger pour le béton avec deux approches de calcul numérique et analytique. On traite ensuite le problème de fissure unique en développant thermodynamiquement la notion du taux de restitution d'énergie. Dans la troisième partie, on établit un modèle viscoélastique pour modéliser le comportement effectif des matériaux microfissurés dans le cas sans propagation. Le problème de propagation de microfisures est étudié ultérieurement par une approche numérique basée sur le "motif morphologique représentative". Ces études sont finalement appliquées pour traiter les problèmes de propagation de fissure et endommagement d'une enceinte de confinement sous l'application d'une pression accidentelle interne

Les flyschs à grauwackes volcaniques (grès de Taveyanne et grès du val d'Illiez) du synclinal de Thônes ont été classés selon leur teneur en éléments volcaniques et la nature de ces derniers déterminées par une étude pétrographjque quantitati ve. Cette classification a permis d'établir une carte de répartition des différents types de flysch et de définir leurs situati ns tectoniques. L'étude pétrographique des conglomérats des grès du Val d'Illiez a montré qu'une grande partie des galets proviennent de la " nappe des Gets " (nappe à éléments ligures). Ces roches ont été métamorphisées avant la mise en place de cette nappe et avant la phase du métamorphisme d'enfouissement du domaine helvétique. Les flyschs du synclinal de Thônes se trouvent dans le faciès à zéolites (faciès à laumontite) équivalent de la zone de diagenèse profonde de certains auteurs caractérisées, dans les grauwackes à éléments volçaniques basiques, par la corrensite. L'intensité du métamorphisme diminue vers le SW du synclinal où la laumontite est encore accompagnée de la heulandite-clinoptilolite. Ces associations indiquent une température comprise entre 100° et 200° C. En admettant un gradient géothermique " normal " de 30° C/km et une température superficielle de 20° C, cela correspond à des profondeurs de 2,7 km et 6,0 km et des pressions de 0,7 kbar et 1,5 kbar. La laumontite est toujours associée à la corrensite. De ce fait, le faciès à laumontite pourrait être désigné plus exactement "faciès à laumontite*corrensite") (KOBLER, 1973b). Les éléments volcaniques du flysch nordhelvétique proviennent de deux séries de roches distinctes: les diabases et les andésites s. I .. Les diabases peuvent se rattacher au volcanisme océanique basaltique, d'âge jurassique supérieur à crétacé, du domaine piémontais-ligure. Les andésites s. l. doivent provenir d'un arc d'îles andésitiques, d'âge compris entre le Jurassique supérieur et la fin de l'Eocène, jalonnant une zone de subduction.