Effectiveness of Dentin Bonding Agents

The interface between a composite resin restoration and dentin is still a problem with regard to secondary caries and esthetics. With conventional restorative techniques the absence of bonding between the restorative material and the dentin produces marginal gaps. These gaps are populated with microorganisms or trap pigments. Therefore, adhesive techniques are required for functional and esthetic restorations. In extracted teeth stored in 0.1% thymol solution, 8 cylindrical cavities (diameter: 3 mm; depth: 2 mm) and 8 class V cavities (1/2 of the margin in dentin) were prepared in each group and filled with composite resin. Before actual placement the following dentin adhesives were used: Scotchbond 2 (3M), Gluma (Bayer), Scotchbond LC (3M), Dentin Adhesit (Ivoclar), Dentin Adhesive (Kulzer) and Durafill-Bond (Kulzer) as a control. Before and after thermocycling (TC) (2000 cycles, 5° C to 55° C) replicas were taken and a quantitative margin analysis in the SEM was performed at 200 x magnification. To analyze the data, a rating scale (four criteria) was used to characterize the marginal configuration. Statistical analysis of the results showed that the materials Gluma, Scotchbond LC and Scotchbond 2 yielded significantly (p \u3c 0.05) better margins than the other materials in both cylindrical and class V cavities. Before TC values \u3e 90% were found with Gluma, Scotchbond LC and Scotchbond 2 in Class V cavities. However, after TC, these values decreased significantly to 66% for Gluma, 42% for Scotchbond LC and 81% for Scotchbond 2. Scotchbond 2 showed approximately 80% excellent margins in both cavity forms after TC. A subsequent clinical study should be done to confirm these favourable results in vivo

Comment on "On the Origin of the Highest Energy Cosmic Rays"

We show that the photodisintegration of heavy cosmic ray nuclei with energies above 10^20 eV is dominated by interactions with photons from the cosmic microwave background radiation, rather than from infrared ones. This implies that the observed air shower events with energies 2-3 10^20 eV cannot originate from Fe nuclei coming from distances beyond 10 MpcComment: 1 page, 2 figure

Peatlands and the carbon cycle: from local processes to global implications - a synthesis

Peatlands cover only 3% of the Earth's land surface but boreal and subarctic peatlands store about 15-30% of the world's soil carbon ( C) as peat. Despite their potential for large positive feedbacks to the climate system through sequestration and emission of greenhouse gases, peatlands are not explicitly included in global climate models and therefore in predictions of future climate change. In April 2007 a symposium was held in Wageningen, the Netherlands, to advance our understanding of peatland C cycling. This paper synthesizes the main findings of the symposium, focusing on (i) small-scale processes, (ii) C fluxes at the landscape scale, and (iii) peatlands in the context of climate change. The main drivers controlling most are related to some aspects of hydrology. Despite high spatial and annual variability in Net Ecosystem Exchange ( NEE), the differences in cumulative annual NEE are more a function of broad scale geographic location and physical setting than internal factors, suggesting the existence of strong feedbacks. In contrast, trace gas emissions seem mainly controlled by local factors. Key uncertainties remain concerning the existence of perturbation thresholds, the relative strengths of the CO2 and CH4 feedback, the links among peatland surface climate, hydrology, ecosystem structure and function, and trace gas biogeochemistry as well as the similarity of process rates across peatland types and climatic zones. Progress on these research areas can only be realized by stronger co-operation between disciplines that address different spatial and temporal scales

Quantitative Margin Analysis in the Scanning Electron Microscope.

Interface between restorative materials and tooth hard substances must be morphologically as perfect as possible to avoid plaque accumulation and subsequent secondary caries or pulpal diseases. Therefore the marginal behavior of restorations is an important parameter to predict their longevity. Morphologically, the quality of margins is characterized by different well defined criteria. Using a replica technique it is possible to assess the complete marginal circumference of restorations in the SEM. Margins of restorations show a large variety of their morphology. This publication describes a method to quantify the quality of dental restorations. The restoration margins are traced on the SEM screen with a digitizer and an interface to measure the margin\u27s length. Simultaneously the margin quality is assessed and assigned to the corresponding lengths. The % distribution of the quality criteria for each restoration is then calculated. Using a comparative light microscope, the replicas are aligned and mounted identically in the SEM for longitudinal studies. The results presented are limited to tests for the accuracy of the method. Using 5 criteria to characterize the margin quality, it was found that the difference between two measurements by the same operator, 4 weeks apart was 3% ± 2.6%. The largest difference for one group was 9%. In another accuracy test where 4 criteria for margin characterization were used, the difference between two measurements was 1.9% ± 0.9%. The largest difference between two groups found was 3.4%. This method can be used for longitudinal studies in vivo, but also for in vitro screening tests with new materials

EPIQR-TOBUS: a new generation of refurbishment decision aid methods

In a large majority of European countries, the amount of maintenance and refurbishment works represents nearly 50% of the total amount spent in the building sector. New requirements are being added to the necessity of maintaining or re-establishing the building stock's usage value. They are linked to the determination to reduce energy consumption, pollutant emissions, work site wastes, to improve the Indoor Environment Quality (IEQ) and all the modern conveniences inside buildings. Two European projects, EPIQR (réf. nr.: JOR3-CT96-0044) and TOBUS (réf. nr.: JOR3-CT98-Û235), developed in the IIIrd and IVth framework programs put the foundations of a new generation of refurbishment decision aid tools. A structured diagnosis scheme covering the state of deterioration of the building elements, energy performance, indoor environment quality, functional obsolescence offer a new concept which helps architects and engineers to approach the building refurbishment with a global view of the whole process, to take informed decisions, to construct coherent refurbishment scenarii and calculate a reasonable investment budget in the very first stage of the refurbishment project. EPIQR project addresses residential buildings and it has been finished in 1998, TOBUS addresses office buildings and it is still in course. The support of these methods is a multimedia computer program. Several modules help the users to treat the data collected during a diagnosis survey, to set up refurbishment scenarii and calculate their cost or energy performance, and finally to visualise the results in a comprehensive way and to prepare quality reports. This paper presents the structure and the main features of the method and softwar

The role of posterior fossa decompression in acute cerebellitis

Background: We present two cases of children who were diagnosed with cerebellitis with acute cerebellar swelling. This rare pathology is potentially fatal, and no clear treatment guidelines are described in the literature. Discussion: Considering our experience, we discuss the different therapeutic strategies and propose aggressive surgical measures consisting of external ventricular drainage and posterior fossa decompression in case of failure of early response to medical treatment to limit secondary cerebellar and brainstem lesion

McGill wetland model: evaluation of a peatland carbon simulator developed for global assessments

We developed the McGill Wetland Model (MWM) based on the general structure of the Peatland Carbon Simulator (PCARS) and the Canadian Terrestrial Ecosystem Model. Three major changes were made to PCARS: (1) the light use efficiency model of photosynthesis was replaced with a biogeochemical description of photosynthesis; (2) the description of autotrophic respiration was changed to be consistent with the formulation of photosynthesis; and (3) the cohort, multilayer soil respiration model was changed to a simple one box peat decomposition model divided into an oxic and anoxic zones by an effective water table, and a one-year residence time litter pool. MWM was then evaluated by comparing its output to the estimates of net ecosystem production (NEP), gross primary production (GPP) and ecosystem respiration (ER) from 8 years of continuous measurements at the Mer Bleue peatland, a raised ombrotrophic bog located in southern Ontario, Canada (index of agreement [dimensionless]: NEP = 0.80, GPP = 0.97, ER = 0.97; systematic RMSE [g C m<sup>−2</sup> d<sup>−1</sup>]: NEP = 0.12, GPP = 0.07, ER = 0.14; unsystematic RMSE: NEP = 0.15, GPP = 0.27, ER = 0.23). Simulated moss NPP approximates what would be expected for a bog peatland, but shrub NPP appears to be underestimated. Sensitivity analysis revealed that the model output did not change greatly due to variations in water table because of offsetting responses in production and respiration, but that even a modest temperature increase could lead to converting the bog from a sink to a source of CO<sub>2</sub>. General weaknesses and further developments of MWM are discussed

Quantum Rotor Engines

This chapter presents autonomous quantum engines that generate work in the form of directed motion for a rotor. We first formulate a prototypical clock-driven model in a time-dependent framework and demonstrate how it can be translated into an autonomous engine with the introduction of a planar rotor degree of freedom. The rotor plays both the roles of internal engine clock and of work repository. Using the example of a single-qubit piston engine, the thermodynamic performance is then reviewed. We evaluate the extractable work in terms of ergotropy, the kinetic energy associated to net directed rotation, as well as the intrinsic work based on the exerted torque under autonomous operation; and we compare them with the actual energy output to an external dissipative load. The chapter closes with a quantum-classical comparison of the engine's dynamics. For the single-qubit piston example, we propose two alternative representations of the qubit in an entirely classical framework: (i) a coin flip model and (ii) a classical magnet moment, showing subtle differences between the quantum and classical descriptions.Comment: Chapter of the upcoming book "Thermodynamics in the Quantum Regime - Recent Progress and Outlook

Wear of human teeth: a tribological perspective

The four main types of wear in teeth are attrition (enamel-on-enamel contact), abrasion (wear due to abrasive particles in food or toothpaste), abfraction (cracking in enamel and subsequent material loss), and erosion (chemical decomposition of the tooth). They occur as a result of a number of mechanisms including thegosis (sliding of teeth into their lateral position), bruxism (tooth grinding), mastication (chewing), toothbrushing, tooth flexure, and chemical effects. In this paper the current understanding of wear of enamel and dentine in teeth is reviewed in terms of these mechanisms and the major influencing factors are examined. In vitro tooth wear simulation and in vivo wear measurement and ranking are also discussed