Magister Scientiae Dentium - MSc(Dent) / Resin composite is one of the most commonly used materials in restorative dentistry. However, it has undergone continuous developments like changes in the fillers and initiators. One such improvement is the new bulk-fill composites which are materials intended for bulk placement up to 4mm. However, an optimum polymerization to the full depth of the restoration i.e. complete depth of cure is of utmost importance in order to obtain proper mechanical and physical properties of resin composites. Aim: The aim of this study was to measure the surface hardness of the top and bottom surfaces of the composites and to determine the depth of cure of bulk-fill composites using two different types of light curing units. Material and methods: A total of 160 specimens were used in this study: four bulk-fill composite were used of which two were conventional viscosity bulk-fill composites namely, Tetric N Ceram (Ivoclar Vivadent) and SureFil bulk-fill composite (Densply Caulk) and two were low viscosity flowable bulk-fill composites namely, SDR flowable (Densply Caulk) and Filtek bulk-fill flowable restorative (3M ESPE). Two different curing light were used namely, LED (Elipar Freelight, 3M ESPE) at 1500mW/cm2 and a Quartz Tungsten Halogen (QTH) curing unit (Megalux CS, Megadenta, Germany) at 600 mW/cm2. To evaluate micro-hardness, Vickers hardness at top and bottom of each sample was measured immediately after light curing and after 24 hours post curing using a Zwick micro-hardness machine load 300g/15 seconds. The mean hardness values obtained from the top and the bottom surface of each material were used to compare the micro-hardness of the various materials. The mean values obtained from the bottom surface were compared to the respective values of the top surface of each material (bottom/top ratio) and used to calculate the depth of cure. Results: The micro-hardness test showed a significant difference between the four materials (ANOVA, p<0.05) immediately after curing and after 24 hours post curing. The material with the greatest micro-hardness was SureFil followed by Tetric N Ceram, Filtek bulk-fill flowable and SDR flowable respectively. The material with the greatest depth of cure was Filtek bulk-fill flowable followed by SDR flowable, Tetric N Ceram and SureFil. When the curing lights were compared the Light Emitting Diode Curing Unit (LED) obtained significantly better depth of cure compared to Quartz Tungsten Halogen Light Curing Units. The LED curing light showed greater micro-hardness values than the QTH curing light except for Tetric N Ceram where the QTH curing showed more hardness values than the LED curing light. For all materials, the surface hardness and depth of cure values increased when tested 24hrs after light curing. Conclusion: There was a difference in the micro-hardness values between the four materials where the conventional viscosity materials showed greater surface hardness values than the low viscosity materials but the depth of cure compared to the bulk-fill flowable LED curing lights showed higher hardness values than QTH curing light except for Tetric N Ceram. Depth of cure ratios were found to be lower than 0.80 for all composite types, however the flowable bulk-fill materials showed higher depth of cure than the conventional viscosity bulk-fills. In general LED curing light produced better hardness and depth of cure values than QTH curing light. The low micro-hardness values for the bulk-fill flowable composites and the inadequate polymerization raises a concern regarding placing these materials in bulk. In such cases, the flowable bulk-fills should be protected with a conventional composite "covering or capping" especially in posterior teeth and in deeper cavities. Furthermore, bulk-fill composites should be used in layering incremental technique to ensure sufficient depth of cure.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In the mining industry, the mining cycle is a very important part in the operating stage of every mining unit. Through the exploitation method used, the mining cycle provides mineral ore, which subsequently undergoes various metallurgical processes and its commercialization and thereby generates profits to the mining company. Currently, within this cycle, the hauling and transportation stages are those that have a lower efficiency with respect to the drilling and blasting stages. Therefore, the sector is always seeking effective ways to optimize these processes, reduce downtime and increase productivity. Six Sigma is a technique that allows for the continuous process improvement. In this study, the factors that generate inefficiency in the hauling cycle are determined, and alternatives are implemented to solve the main problem and improve the operations cycle.

Indiana University-Purdue University Indianapolis (IUPUI) / Objectives: To investigate the effect of bulk-fill resin based composite materials on cuspal deflection in large slot mesio-occlusal-distal cavities (MOD) in premolar teeth. Methodology: Thirty-two sound maxillary premolar teeth with large slot MOD cavities were distributed to four groups (n=8). Three groups were restored with bulk-fill resin composite materials (Tetric EvoCeram, x-tra fil, and Sonic Fill, respectively) in a single increment. The conventional composite group, Filtek Z100, was used to restore the cavities in 2mm increments. Cusp deflection was recorded post irradiation using a Nikon measurescope UM-2 (Nikon, Tokyo, Japan), by measuring the changes in the bucco-palatal width of the premolar teeth at 5 minutes, 24 hours, and 48 hours after completion of the restoration. The cuspal deflection was obtained by recording the difference between the baseline measurements and the other measurements for each tooth. Results: Cuspal deflection was significantly higher in Conventional Composite than in Tetric EvoCeram Bulk Fill (p=0.0031), x-tra Fil Bulk (p=0.0029), and SonicFill Bulk (p=0.0002). There was no significant difference in cuspal deflection for Tetric EvoCeram Bulk, X-tra Fil Bulk, and SonicFill Bulk Composites. Conclusions: All the investigated bulk-fill resin composites exhibited cuspal deflection lower than conventional resin composite. One of the aims of research and studies on the resin composite materials is improving their clinical longevity, and simplifying their use. For that purpose bulk-fill materials are considered promising materials and further clinical studies should be conducted.

Lightweight cellular concrete (LCC) is an aerated or foamed concrete where 25-80% of the concrete matrix consists of air voids. The high volume of air voids reduces the strength but significantly decreases the weight of the material, which has made it an attractive alternative to soil for retaining structure backfills. Though the use of LCC has increased, little research has been performed on the large-scale behavior of retaining structures containing LCC as backfill. This research test attempts to fill knowledge gaps found with regard to the use of LCC in a mechanically stabilized earth (MSE) wall with a trapezoidal or sliver fill by examining the nature of LCC strength criteria from large-scale failure, failure mechanisms, and failure criteria. A large-scale test box (10 ft. wide x 12 ft. long x 10 ft. high), surrounded by a steel resisting frame, was constructed and filled with a silty sand backfill soil in a 1:1 stair-stepped slope and an LCC sliver fill. The west-facing wall was a two-paneled MSE wall with 16 ribbed steel strip reinforcements running through the LCC backfill. The LCC was poured over three days in equal height lifts to ensure stability. A total of 64 sample cylinder molds and four split mold shear boxes were filled with LCC during placement to help identify LCC material properties, which included density, unconfined compressive strength (UCS), and shear strength. A surcharge test was performed on the large-scale test box six days after initial placement of the LCC due to the unanticipated high strength gain and density found within the placed LCC. Instrumentation collected data on displacement, shear plane, lateral wall pressure, and reinforcement strain throughout testing. Initially, four hydraulic jacks were used during surcharge testing to induce a uniform surcharge load to fail the sliver-fill MSE wall. The strength limit of the steel resisting frame was reached before failure, at which point the number of hydraulic jacks was switched to three for a more critical loading condition. The test was again terminated before complete failure when the steel resisting frame strength limit was met. Though failure was not completed, the sliver-fill MSE wall failure had initiated before testing was terminated at a surcharge load of 70 psi. Results identify the initiation of shear failure within the LCC at about 65 psi, with maximum lateral and axial displacements of about 0.5 in. and 1.2 in., respectively. The shear failure occurs at about 52% of the average UCS of 123 psi. An arcuate shear plane, contrary to the traditional bilinear MSE wall failure surface with inextensible reinforcements, was identified within the LCC backfill, which initiated from the toe of the MSE wall and ended about 8 ft. back from the top of the MSE wall, using lateral displacements from Sondex tube profilometers in the backfill.

Ontario’s rock barrens landscape consists of exposed bedrock ridges which host a mosaic of thin lichen- and moss- covered soil patches, forested valleys, beaver ponds, and depressional wetlands. Peat-filled ephemeral wetlands within bedrock depressions act as gatekeepers to hydrological connectivity between their small headwater catchments and the rest of the landscape downstream through strong fill-and-spill dynamics. We developed a water balance model, RHO, with inputs of precipitation and potential evapotranspiration (PET) to better understand the factors impacting water table (WT) and storage dynamics and in turn the hydrological connectivity of ephemeral wetlands. Field surveys were conducted at six wetlands to obtain and determine the variability in measurable site characteristics, in particular the wetland depression morphometry, to parameterize RHO. Three sites were used in a calibration and validation procedure where modelled WTs were compared to measured WT data from the snow-free seasons for each site to determine the best parameter values. We show that RHO is capable of predicting WT dynamics with inputs of precipitation and PET, when parameterized for specific sites. Wildfire disturbance is known to increase the run-off from hillslopes and remove surface organic soils through combustion. To predict the impacts of wildfire disturbance on ephemeral wetland hydrological connectivity, a generic model wetland depression was parameterized in RHO and used to predict the changes in hydrological connectivity under various wildfire scenarios and test the sensitivity of modelled connectedness to impacted parameters. Modelled results show that connectivity increases under all scenarios tested, and that changes to connectivity are primarily due to increases in run-in. Water balance models, like RHO, can be used to better understand the hydrological connectivity of wetlands in a rock barrens landscape. These models are useful in predicting impacts on the hydrological connectivity, and hydrological ecosystem services, from disturbances such as wildfire and can inform future field research experimental designs. / Thesis / Master of Science (MSc) / Rock barrens landscapes provide several important ecosystem services, which are influenced by hydrological flow paths and water storage on the landscape. Central to these hydrological dynamics is the storage and discharge of water in small wetlands which form in bedrock depressions. Here we develop a simple hydrological model to simulate the water storage and discharge of rock barrens wetlands. We then use this model to explore how wildfire disturbance is likely to change the supply of water to the rest of the landscape by simulating several different scenarios and testing which changes in the model have the largest impact on the water supply. We show that wetlands discharge more water after wildfire disturbance, mainly because of increases in run-off from areas upstream of the impacted wetlands. This modelling approach helps us better understand how wildfire is likely to impact the ecosystem services of a rock barrens landscapes.

No description available.

Questions as to the tempo and mode of changes in faunal composition at the Triassic/Jurassic boundary remain unanswered. Inquiries are hampered by a general paucity of sections containing correlatable Late Triassic/Early Jurassic strata. Vertebrate fossil material from Cromhall Quarry, recovered as part of an extended project centered on Late Triassic fissure infillings in southwestern Britain, was organized into a biostratigraphic scheme in 1993. This scheme could prove important in correlating Late Triassic continental strata. The Cromhall data consists of taxonomic counts from individual Stratigraphic levels within a series of fissures. Level counts were sorted into a series of sequential sedimentary and faunal associations that rest on the assumption that significant differences in faunal composition occur between individual fissures, but do not exist between individual sedimentary strata within any one fissure. Before the biostratigraphic framework could be utilized, the actual degree of similarity between the fissure faunas had to be quantified and tested. The original database, and counts from newly processed material, were subjected to Principle Components and Cluster Analyses. The analyses suggest that the majority of stratigraphic levels within any one fissure contain faunas with very similar composition. Levels from fissures that are temporally sequential contain faunas that are somewhat similar in composition. Overlap, in faunas found in strata at the top and bottom of sequential fissures, can be detected. In addition, there is a trend toward increased presence of certain taxa in the younger levels. These results indicate that the biostratigraphic framework may be used to enhance Triassic-Jurassic boundary research. / Master of Science

Up to 75 percent of new construction between 2000 and 2030 may â be redirected inward or into more compact, mixed-use suburban developments (Nelson, 2004). If this assertion is even nearly true, and if the goals of the Clean Water Act are to be met in the next generation of American cities, then we must find feasible and effective ways of improving urban watershed health using retrofit and infill development as a primary means. The aim of this study is to evaluate the patterns and approaches of suburban infill developments in order to determine which methods and extents are deemed capable of improving the health, sustainability and natural services of urban streams and watersheds. Water is considered to be foundational to urban and suburban sustainability and is treated as a primary indicator of overall health and sustainability within the context of this study. This thesis presents three pilot studies that examine urban watershed health using a single case as a vehicle. The studies, in the order they are presented, are: 1) Form- analyzing the relationship between landuse patterns and imperviousness, 2) Planning- relating questions of development scale planning and design to natural and cultural systems at the watershed scale and 3) Valuation- illustrating three possibilities for determining the economic value of improving urban watershed health. / Master of Landscape Architecture

Yes / Mechanochemical synthesis has the potential to change the way in which chemistry is conducted, particularly with regard to removing or dramatically reducing the need for solvents. Recently, it has been demonstrated that mechanochemistry can be carried out continuously and on large scale through the use of twin-screw extrusion (TSE). TSE has successfully been applied to the synthesis of cocrystals, metal organic frameworks (MOFs), deep eutectic solvents (DESs), metal complexes, and organic condensation reactions. However, while TSE provides a route for mechanochemical synthesis to be developed into a continuous, high-volume manufacturing process, little is currently understood about how to best optimize the various process parameters involved. Herein, we investigate the use of a batch mixer that has been previously used in polymer processing, to optimize mechanochemical reactions performed by extrusion. In particular, reactions between 8-hydroxyquinoline (Hq) and metal acetate salts of zinc or aluminum to give quinolinate complexes Znq2·AcOH and Alq3·AcOH, which are of interest for organic light-emitting diode (OLED) applications, have been investigated. The manner in which the progress of the reaction correlates with the machine torque, temperature, and specific mechanical energy (SME) imparted by the batch mixer has been elucidated. Significantly, this knowledge enabled optimization of the mechanochemical reactions by TSE through the key parameters of screw speed, feed rate, temperature, and particle size. / EPSRC (EP/L019655/1).

Os materiais restauradores estão evoluindo rapidamente e novas técnicas de inserção do compósito na cavidade restauradora estão sendo propostos. Dependendo da técnica, poderá ocorrer maior ou menor formação de bolhas na restauração final. A incorporação de bolhas entre as camadas do material restaurador pode gerar uma maior degradação da restauração em virtude da menor obtenção de propriedades físico-mecânicas do material. Assim, a necessidade de estudos sobre a prevalência de bolhas em restaurações confeccionadas com diferentes técnicas de inserção se faz necessária para a melhor compreensão do uso e do manuseio dos materiais. O objetivo desse trabalho foi analisar a ocorrência de bolhas e o volume de espaços presentes no interior de restaurações com resina composta, inserida na cavidade dental através das técnicas restauradoras: incremental e bulk fill. Quarenta e oito dentes molares humanos (n=24, duas restaurações por dente) foram selecionados e, nestes, foram confeccionados dois preparos por dente, um em cada região proximal, com profundidade de 4mm, largura de 4mm e distância axio-proximal de 2mm. Posteriormente, foram restaurados de acordo com os grupos: FiltekTM One Bulk Fill Restorative (FOB; 3M Oral Care); FiltekTM Z350 XT (FXT; 3M Oral care); FiltekTM Bulk Fill Flowable Restorative (FBF+FXT; 3M Oral care) e FiltekTM Z350 XT Flow (FF+FXT; 3M Oral care) . As resinas fluidas foram cobertas com a resina FiltekTM Z350 XT (3M Oral Care). Após 24 horas, os dentes restaurados foram submetidos à ciclagem térmica (5.000 ciclos) e posteriormente foi realizada a Tomografia de Coerência Ótica (OCT). Através da análise das imagens obtidas pelo OCT foram medidos os valores de quantidade de bolhas e porcentagem de espaços presentes nas restaurações. Os dados da presença de bolhas foram analisados estatisticamente com o teste Qui-Quadrado, os dados de número de bolhas e porcentagem de espaços obtidos foram analisados com o teste de Kruskall Wallis e a comparação entre os grupos foi feita pelo método de Dunn , com nível de significância de 5%. FF+FXT, apresentou bolhas em todas as restaurações e foi significativamente maior quando comparado a FXT (p=0,015). FF+FXT apresentou quantidade significativamente maior de bolhas (p<0,05) quando comparada com os outros três grupos. FBF+FXT apresentou a maior porcentagem de porosidade, devido ao maior tamanho de bolhas, porém esta porcentagem foi significantemente maior apenas quando comparada com FXT (p<0,05). Todos os grupos apresentaram bolhas. As técnicas restauradoras que apresentaram o pior desempenho, considerando o número de bolhas e a porcentagem de porosidade, foram aquelas realizadas com resina composta fluída. Não houve diferença estatisticamente significante quanto ao número de bolhas e à porcentagem de espaços entre as restaurações confeccionadas somente com resinas de alta viscosidade para as diferentes técnicas utilizadas neste estudo. / Dental restorative materials are quickly evolving, and new techniques are being proposed to change the way of filling dental cavities. Depending on the technique, a different number of voids could be generated inside the restauration. The appearance of these voids between layers of resin composite can significate a greater degradation of the material determined by low mechanical and physical properties. Therefore, to investigate voids prevalence at different restorative techniques is needed, in order to get a better understanding of the resin composites and their best handling. The objective of this project was to analyze the voids frequency inside and between the layers of the resin composite, filling class II cavities using incremental technique and bulk fill technique. Forty eight human teeth (n=24, two restorations per tooth) were selected and two cavities per tooth were made, one per each proximal area, 4mm of depth, 4mm height and 2mm of axio-proximal distance. After, they were divided in four groups and restored using FiltekTM One Bulk Fill Restorative (FOB; 3M Oral Care); FiltekTM Z350 XT (FXT; 3M Oral care); FiltekTM Bulk Fill Flowable Restorative (FBF+FXT; 3M Oral care) e FiltekTM Z350 XT Flow (FF+F; 3M Oral care), handled according to manufacturer instructions. Flowable resin composite was covered with FiltekTM Z350 (3M Oral Care). 24 hours later, thermocycling was conducted (5,000 cycles) and later Optical Coherence Tomography was performed. By analyzing the OCT images, number of voids and percentage of void volume were calculated. Presence of voids were analyzed by Chi-squared test, number of voids and percentage of void volume were analyzed by Kruskall Wallis test, and comparisons were performed by Dunn Method, at significance level of 5%.. FF+FXT had voids in all the restorations of the group, and it was significantly greater when compared with FXT (p=0.015). FF+FXT had statistically significant more number of voids (p<0.05) when compared with the others 3 groups. FBF+FXT had the highest percentage of voids volume, because the size of its voids, but this percentage was significantly different only when compared with FXT (p<0,05). All groups had voids. Restorative techniques that presented worst performance, considering number of voids and percentage of voids volume, were the ones made with flowable resin composite. Non statistical differences referred to a number of voids, neither percentage of voids volume among restorations made using only high viscosity resin.