Gingival Recession, Oral Hygiene and Associated Factors Among Tanzanian Women.

Females are generally more motivated with regard to oral hygiene practices and thus brush their teeth more frequently than males. To determine the prevalence of gingival recession, oral hygiene status, oral hygiene practices and associated factors in women attending a maternity ward in Tanzania. Cross-sectional descriptive study. Maternity ward of Muhimbili National Hospital, Tanzania. Four hundred and forty six women were interviewed on oral hygiene practices and maternal factors, and a full-mouth examination was done to determine the presence of plaque, calculus, gingival bleeding and gingival recession at six sites per tooth. The prevalence of gingival recession (GR) > or =1 mm was 33.6%, calculus 99.3%, plaque 100%, and gingival bleeding 100%. Oral hygiene practices included toothbrushing (98.9%), brushing frequency > or =2 times/day (61.2%), horizontal brushing method (98%), and using a plastic toothbrush (97.8%). Factors that were significantly associated with gingival recession were age (OR = 2.0, 95% CI = 1.3-3.2), presence of calculus (OR(a) = 3.8, 95% CI=2.5-7.1), and gingival bleeding on probing (OR = 4.2, 95% CI = 2.5-7.1). Tooth cleaning practices and maternal factors, especially the number of pregnancies or deliveries were not significantly associated with gingival recession. In this study population, oral hygiene was poor and gingival recession was associated with age, calculus and gingival inflammation rather than with tooth cleaning practices

Development of an integrated BEM approach for hot fluid structure interaction

In the present work, the boundary element method (BEM) is chosen as the basic analysis tool, principally because the definition of temperature, flux, displacement and traction are very precise on a boundary-based discretization scheme. One fundamental difficulty is, of course, that a BEM formulation requires a considerable amount of analytical work, which is not needed in the other numerical methods. Progress made toward the development of a boundary element formulation for the study of hot fluid-structure interaction in Earth-to-Orbit engine hot section components is reported. The primary thrust of the program to date has been directed quite naturally toward the examination of fluid flow, since boundary element methods for fluids are at a much less developed state

Development of an integrated BEM approach for hot fluid structure interaction

The development of a boundary element formulation for the study of hot fluid-structure interaction in earth-to-orbit engine hot section components is described. The initial primary thrust of the program to date was directed quite naturally toward the examination of fluid flow, since boundary element methods for fluids are at a much less developed state. This required the development of integral formulations for both the solid and fluid, and some preliminary infrastructural enhancements to a boundary element code to permit coupling of the fluid-structure problem. Boundary element formulations are implemented in two dimensions for both the solid and the fluid. The solid is modeled as an uncoupled thermoelastic medium under plane strain conditions, while several formulations are investigated for the fluid. For example, both vorticity and primitive variable approaches are implemented for viscous, incompressible flow, and a compressible version is developed. All of the above boundary element implementations are incorporated in a general purpose two-dimensional code. Thus, problems involving intricate geometry, multiple generic modeling regions, and arbitrary boundary conditions are all supported

Measuring Dental Caries in the Mixed Dentition by ICDAS

Caries has traditionally been assessed with WHO criteria including only obvious caries lesions. ICDAS has been developed to detect also the enamel caries lesions. This study aims to study caries and the associations of the number of caries lesions between the permanent and primary molars with ICDAS in the mixed dentition of the first and second grade primary school children. The clinical examinations of 485 children were conducted by four examiners with high reproducibility (inter- and intraexaminer kappas >0.9). The mean number of caries lesions—especially dentine caries—seemed to be higher in the second primary molars than in the first permanent molars. There were significant correlations between the number of lesions on occlusal and lingual surfaces between the primary and permanent molars. Enamel caries lesions, restorations, and caries experience did not increase according to age. Therefore, caries might be increasing in this population. As a conclusion, ICDAS recording seems to give appropriate information from the occurrence of caries lesions and its correlations between the primary and permanent teeth and surfaces

The role of polaronic states in the enhancement of CO oxidation by single-atom Pt/CeO2

Single Atom Catalysts (SACs) have shown that the miniaturization of the active site implies new phenomena like dynamic charge transfer between isolated metal atoms and the oxide. To obtain direct proof of this character is challenging, as many experimental techniques provide averaged properties or have limitations with poorly conductive materials, leaving kinetic measurements from catalytic testing as the only reliable reference. Here we present an integrated Density Functional Theory-Microkinetic model including ground and metastable states to address the reactivity of Pt1/CeO2 for CO oxidation. Our results agree with experimentally available kinetic data in the literature and show that CO oxidation activity of Pt1/CeO2 is tunable via the electronic properties of the support. Particularly, samples with higher n-doping via oxygen depletion should be better in CO oxidation, as they help maintain the active state Pt0 of the catalyst. This provides an alternative strategy for tuning the performance of low-temperature oxidations in single-atom catalysts via charge transfer control

The effect of surface relaxation on the N-2 dissociation rate on stepped Ru: A Transition State Theory Study

van Harrevelt R, Honkala K, Norskov JK, Manthe U. The effect of surface relaxation on the N2 dissociation rate on stepped Ru: A Transition State Theory Study. Journal of Chemical Physics. 2006;124(2):026102: 026102

The reaction rate for dissociative adsorption of N-2 on stepped Ru(0001): Six-dimensional quantum calculations

van Harrevelt R, Honkala K, Norskov JK, Manthe U. The reaction rate for dissociative adsorption of N2 on stepped Ru(0001): Six-dimensional quantum calculations. Journal of Chemical Physics. 2005;122(23): 234702.Quantum-mechanical calculations of the reaction rate for dissociative adsorption of N-2 on stepped Ru(0001) are presented. Converged six-dimensional quantum calculations for this heavy-atom reaction have been performed using the multiconfiguration time-dependent Hartree method. A potential-energy surface for the transition-state region is constructed from density-functional theory calculations using Shepard interpolation. The quantum results are in very good agreement with the results of the harmonic transition-state theory. In contrast to the findings of previous model calculations on similar systems, the tunneling effect is found to be small. (C) 2005 American Institute of Physics

Including lateral interactions into microkinetic models of catalytic reactions

In many catalytic reactions lateral interactions between adsorbates are believed to have a strong influence on the reaction rates. We apply a microkinetic model to explore the effect of lateral interactions and how to efficiently take them into account in a simple catalytic reaction. Three different approximations are investigated: site, mean-field, and quasichemical approximations. The obtained results are compared to accurate Monte Carlo numbers. In the end, we apply the approximations to a real catalytic reaction, namely, ammonia synthesis. (c) 2007 American Institute of Physics

Quantum well states in two-dimensional gold clusters on MgO thin films

The electronic structure of ultra-small Au clusters on thin MgO/Ag(001) films has been analyzed by scanning tunneling spectroscopy and density functional theory. The clusters exhibit two-dimensional (2D) quantum well states, whose shapes resemble the eigen-states of a 2D electron gas confined in a parabolic potential. From the symmetries of the HOMO and LUMO of a particular cluster, its electron filling and charge state is determined. In accordance to a DFT Bader-charge analysis, aggregates containing up to twenty atoms accumulate one to four extra electrons due to a charge transfer from the MgO/Ag interface. The HOMO - LUMO gap is found to close for clusters containing between 70 and 100 atoms.Comment: 12 pages, 4 figure