Degradation of tooth structure and restorative materials: A review

The use of artificial materials to replace natural dental tissue is a common practice in dentistry. Due to health aspects one must be concerned about the risks that the corrosion and wear of these materials may induce. Vertical loss and the release of wear particles are especially of interest. The insight into corrosion-wear processes in that field is however still in its infancy. This paper gives an overview of the degradation processes that one may encounter on artificial materials commonly used in dentistry and more especially in restorative dentistry. Corrosion-wear as such is not yet well documented from in vivo data. Wear of restorative materials must mimic the wear behaviour of natural enamel and dentin under function. In vitro test results are presented elsewhere in this special issue of WEAR.     

Effect of an alkaline salt (papad khar) and its substitute (2:1 sodium carbonate:sodium bicarbonate) on acrylamide formation in papads

The formation of acrylamide in papads processed by flame roasting, frying and microwave roasting as a function of the alkaline salt, papad khar and its substitute, 2:1 sodium carbonate:sodium bicarbonate (w/w) at various concentrations was examined. Addition of papad khar and 2:1 sodium carbonate:sodium bicarbonate makes the product alkaline, which is known to be conducive for the formation of acrylamide. While a correlation was found between acrylamide content and pH with respect to fried and flame roasted papads, microwave roasting did not show any acrylamide formation at all the levels of alkaline salts tested in this study. Flame roasting generated higher levels of acrylamide as compared to frying. Use of microwave roasting is therefore recommended as a consumer-friendly, healthy and safe technology for processing papads.     

Effect of damaged starch on acrylamide formation in whole wheat flour based Indian traditional staples, chapattis and pooris

Variation in acrylamide content of two Indian traditional products, chapatti and poori was observed with respect to the damaged starch content in whole wheat flour of different wheat varieties from which these products were prepared. Wheat cultivar ‘lokwan’ was milled by altering mill aperture, feed rate and moisture content to obtain whole wheat flour with damaged starch contents ranging from 6.23% to 28.12%. Acrylamide content of the chapatti and pooris prepared from such flours ranged from 12.5 to 65.5 μg/kg in chapatti, and 25.5 to 130.5 μg/kg in pooris. Impact of several additives showed 10 μmol/g flour citric acid, and 100 μmol/g flour calcium chloride to reduce acrylamide in pooris by approximately 54% and 72%, respectively, without altering the sensory analysis of the products.     

Development of Pt-Carbon catalysts using MCM-41 template for HI decomposition reaction in S–I thermochemical cycle

Different Pt-Carbon catalysts have been synthesized by hard templating route and have been employed for production of hydrogen from liquid phase HI decomposition at 160 °C temperature. The physical properties and catalytic activities of these catalysts are compared with that of the platinum on activated carbon catalysts. These catalysts have been characterised by X-Ray diffraction, Raman, SEM and BET surface area. Eluant analysis has been carried out using ICP-OES for evaluation of the extent of noble metal leaching under the catalytic activity test conditions. From the present study we have concluded that MCM-41 based Pt/carbon has higher catalytic activity and stability than other Pt/carbon catalysts.     

Cylindrical object contact detection for use in discrete element method simulations. Part I – Contact detection algorithms

This article is the first of two parts in which algorithms are presented concerning the contact detection between two cylinders, and a cylinder and a flat surface. This first part presents the equations for contact detection, contact location, contact overlap, and normal contact direction. The second part focuses on validation of the algorithm. These articles are the first to present validated algorithms and relations for all potential cylinder-plane and cylinder-cylinder contact scenarios (ten in all).     

Cylindrical object contact detection for use in discrete element method simulations,Part II—Experimental validation

This article is the second of two focusing on cylindrical object contact detection. The first part presents algorithms for determining if contact occurs between a cylindrical object and a plane, and between two cylindrical objects, in addition to expressions for contact overlap, contact normal vector, and contact location. This article presents the tests and results used to quantitatively validate the algorithms implemented in three-dimensional discrete element method (DEM) simulations. In particular, four tests are performed. The first consists of a comparison against analytical expressions for post-collision translational and rotational velocities for a single cylinder impacting a flat wall. The second involves comparisons against experimental residence time measurements of a cylindrical particle moving within a baffled, rotating horizontal cylinder. The third test consists of comparisons against experimental bulk density measurements of cylindrical particles dropped into a cylindrical container. The last test compares experimental and computational values of the dynamic angle of repose in a rotating drum. In addition to true cylindrical objects, comparisons are also made in the first three tests against two cylindrical object approximations using glued spheres. The true cylinder model performs well in each of the tests while the glued sphere approximations perform poorly, especially when fewer spheres are used to represent the cylinder shape. These studies demonstrate that the cylinder contact algorithms presented in the first article perform correctly, and more accurately model real cylinder behavior than glued sphere approximations.     

Fuzzy Computational Models of Trust and Distrust for Enhanced Recommendations

Trust models have received considerable attention in the recent past and have been employed in many of today's most successful recommender systems (RSs) for alleviating sparsity by enhancing their interuser connectivity obtained from historical preference data and to address the cold start problem. However, the incorporation of distrust in addition to trust for improved recommendations has not been analyzed fully because of the absence of publically available data sets containing gradual information about trust and distrust concepts. Our work in this paper is an attempt toward introducing recommendation strategies exploiting both the trust and the distrust in the RSs to further enhance their quality of recommendations through fuzzy computational models for trust and distrust. Since trust and distrust concepts are gradual phenomenon, therefore these can be represented more naturally by fuzzy logic using linguistic expressions. The contributions of this paper are three fold: First, we propose fuzzy computational models for both the trust and distrust concepts through similarity as well as knowledge factors based on linguistic expressions. Second, we suggest appropriate propagation and aggregation operators to deal with the data sparsity. Finally, we present a comparative analysis of proposed recommendation strategies utilizing both the trust and distrust concepts.     

Delineation of phase fields at the Te-rich end of the Ru–Te binary system

The tellurium rich side of the ruthenium–tellurium binary system was studied by differential thermal analysis. To avoid reported problems of Te loss by evaporation and reactive interference of Te to the thermocouples of the thermal analyzer, the present study made use of specially designed sealed quartz capsules as DTA containers. The thermal analyses were carried out over the compositional range of 0.66  x_Te  1.00 with the help of SETARAM TG/DTA and other indigenously built thermal analyzers available in this laboratory. The thermal data generated for fifteen different compositions were interpreted for the nature of phase transitions occurring at their characteristic temperatures. The Ru–Te binary system was found to have a eutectic transformation at 444 °C at a composition of x_Te = 0.918 and a monotectic transformation at 447 °C at a composition of x_Te = 0.700. Up to 6 at.% Ru is soluble in Te at about 440 °C.     

Modification of the photocatalytic properties of self doped TiO2 nanoparticles for hydrogen generation using sunlight type radiation

Synthetic approaches/methodologies can change the properties of nanoparticles significantly. In this study, the photocatalytic property of self (Ti³⁺) doped TiO₂ nanoparticles was modified by synthesizing through different routes. Solvothermal (T-Sol), sonochemical (T-Son) and polyol (T-Pol) methods were employed to prepare TiO₂ nanoparticles and the photocatalytic activities of these samples were compared with that of the sample prepared by precipitation using ammonia solution (T-Ppt). All samples had particle size below 30 nm except T-Son, where small nanoparticles existed as large spherical agglomerates with size around 500 nm. Surface area and porosity measurements of these different TiO₂ samples showed a significant dependency on the synthesis method. UV–Visible absorption spectra showed the onset of absorption at ∼440 nm for all samples due to the presence of defect levels originating from anion vacancies. Photocatalytic activity for hydrogen generation decreased in the order T-Sol > T-Son > T-Pol > T-Ppt and the observed activity is correlated with their physical properties such as surface area and crystallinity. The hydrogen yield was highly enhanced by the addition of Pd metal as co-catalyst on the surface of TiO₂ photocatalysts. Present experiments clearly demonstrate the importance of synthesis route to improve the photocatalytic activity of TiO₂.