Volcanic architecture and chemostratigraphy within the Kalkarindji Continental Flood Basalt Province, Northern Territory : implications for eruption style from multiple fissure eruptions

This thesis was the first to define individual lava flow chemical variation and a detailed definition of the Kalkarindji Continental Flood Basalt Province, a lesser known province of the Phanerozoic eon. This thesis conducted an intensive field study that yielded numerous samples for petrography and chemical analyses as well as the generation of a detailed map of a portion of the Kalkarindji province.

Arresting occlusal enamel caries lesions with pit and fissure sealants

The aim of this study was to evaluate the feasibility of pit and fissure sealants and the effectiveness of the two sealant methods applied in every-day practice in public dental health care in Finland. Two sealant methods were evaluated according to their effectiveness in preventing dentin caries and sealant retention. Application time with these sealant methods was compared. The survival rate of sealed first and second molars was followed for nine and 13 year periods, respectively. Caries risk evaluation and observed increased caries risk were the basis for considering sealant application. A questionnaire, sent to all public dental health centers in Finland, monitored the attitudes of the dental profession towards sealant application and explored the current policies used as well as changes noted in the sealant application protocol. DMFT (Decayed, Missing or Filled Teeth) index values collected from the health centers were evaluated. The difference in caries rate between two methods investigated was highly significant. When compared to the glass ionomer sealant method (GIC), the effectiveness of the resin-based method (RB) in preventing dentin caries was 74% and the rate difference 3%. The relative risk for RB-sealed surfaces vs. GIC-sealed surfaces of having detectable dentin caries was 0.3 (95% CI 0.12, 0.57). The retention rate of sealants was higher with RB than GIC (P<0.001). Application of RB sealant material was less time-consuming than application of GIC sealant. Occlusal dentin caries lesions were found in 4% and proximal caries in less than 2% of sealed teeth. The majority of respondents reported application of sealants on a systematic basis along with caries-risk evaluation. Those health centers sealing over suspected or detected enamel caries had lower average DMFT index values (1.0) when compared to DMFT values (1.2) of health centers applying sealants by alternative criteria. It is concluded that the RB sealant method is more effective than the GIC sealant method in preventing dentin caries. Sealant maintenance may increase the costs of a sealant program. Occlusal caries management may be improved if the applied sealant policies are changed towards an interceptive approach i.e. applying the sealants over detected or suspected enamel caries lesions instead of sealing sound teeth in a preventive manner.

Experimental Investigation and Numerical Simulation on the Effect of Fissure Water Pressure in Vertical Sliding Surface

This paper studies the effect of fissure water pressure in different fractures on the critical angle of landslide by laboratory investigation and numerical simulation in order to understand the mechanisms of fissure water pressure on landslide stability. Laboratory observations show that the effect of fissure water pressure on the critical angle of landslide is little when the distance between water-holding fracture and slope toe is three times greater than the depth of fissure water. These experimental results are also simulated by a three-dimensional face-to-face contact discrete element method. This method has included the fissure water pressure and can accurately calculate the critical angle of jointed slope when fissure water pressure in vertical sliding surface exists. Numerical results are in good agreement with experimental observations. It is revealed that the location of water-holding structural surface is important to landslide stability. The ratio of the distance between water-holding fissure and slope toe to the depth of fissure water is a key parameter to justify the effect of fissure water pressure on the critical angle of landslide.

Application of Three-Dimensional Discrete Element Face-to-Face Contact Model with Fissure Water Pressure to Stability Analysis of Landslide in Panluo Iron Mine

Three-dimensional discrete element face-to-face contact model with fissure water pressure is established in this paper and the model is used to simulate three-stage process of landslide under fissure water pressure in the opencast mine, according to the actual state of landslide in Panluo iron mine where landslide happened in 1990 and was fathered in 1999. The calculation results show that fissure water pressure on the sliding surface is the main reason causing landslide and the local soft interlayer weakens the stability of slope. If the discrete element method adopts the same assumption as the limit equilibrium method, the results of two methods are in good agreement; while if the assumption is not adopted in the discrete element method, the critical phi numerically calculated is less than the one calculated by use of the limit equilibrium method for the same C. Thus, from an engineering point of view, the result from the discrete element model simulation is safer and has more widely application since the discrete element model takes into account the effect of rock mass structures.

Acid damage to vegetation following the Laki Fissure eruption in 1783 - an historical review

Grattan, John and Pyatt, Brian. 'Acid damage to vegetation following the laki fissure eruption in 1783 - an historical review' The Science of the Total Environment. 26 August 1993. 151 pgs 241-247

Illness and elevated Human Mortality in Europe Coincident with the Laki Fissure eruption

Grattan, J. Durand, M. Taylor, S., Illness and elevated Human Mortality in Europe Coincident with the Laki fissure eruption. In: 'Volcanic Degassing: Geological Society, Special Publication 213', Oppenheimer, C., Pyle, D.M. and Barclay, J. (eds). Geological Society, London, Special Publications, 410-414, 2003.

In situ evaluation of the remineralizing capacity of pit and fissure sealants containing amorphous calcium phosphate and/or fluoride

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The Influence of Pit and Fissure Sealants on Infrared Fluorescence Measurements

The aim of this in vitro study was to evaluate the influence of pit and fissure sealants on fluorescence readings using lasers. We selected 166 permanent molars and randomly divided them into 4 groups which were each treated with a different sealant (a commercially available clear sealant, 2 opaque sealants and an experimental nanofilled clear sealant). The teeth were independently measured twice by 2 experienced dentists using conventional laser fluorescence (LF) and a laser fluorescence pen device (LFpen), before and after sealing, and again after thermocycling to simulate the thermal stressing between the tooth and the dental materials. Friedman test showed no statistically significant changes using LF and LFpen for the commercial clear sealant group, although values tended to increase after sealing. However, the values increased significantly after thermocycling. There was a statistically significant decrease in fluorescence after application of opaque sealants. After application of the experimental nanofilled clear sealant, LF values increased only after thermocycling, whereas the LFpen values increased after sealing and after thermocycling as well. The intraclass correlation coefficient ranged from 0.87 to 0.96 for interexaminer and 0.82 to 0.94 for intraexaminer reproducibility. It was shown that pit and fissure sealants influence LF and LFpen readings, with the values increasing or decreasing according to the material used. In conclusion, both laser fluorescence devices could be useful as an adjunct to detect occlusal caries under unfilled clear sealants. Nevertheless, surfaces sealed with clear nanofilled material could be assessed using only the LF device. Copyright (C) 2008 S. Karger AG, Basel.