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Sample records for model dental multilayer

  1. Bio-inspired design of dental multilayers: experiments and model.

    PubMed

    Niu, Xinrui; Rahbar, Nima; Farias, Stephen; Soboyejo, Wole

    2009-12-01

    This paper combines experiments, simulations and analytical modeling that are inspired by the stress reductions associated with the functionally graded structures of the dentin-enamel-junctions (DEJs) in natural teeth. Unlike conventional crown structures in which ceramic crowns are bonded to the bottom layer with an adhesive layer, real teeth do not have a distinct "adhesive layer" between the enamel and the dentin layers. Instead, there is a graded transition from enamel to dentin within a approximately 10 to 100 microm thick regime that is called the Dentin Enamel Junction (DEJ). In this paper, a micro-scale, bio-inspired functionally graded structure is used to bond the top ceramic layer (zirconia) to a dentin-like ceramic-filled polymer substrate. The bio-inspired functionally graded material (FGM) is shown to exhibit higher critical loads over a wide range of loading rates. The measured critical loads are predicted using a rate dependent slow crack growth (RDEASCG) model. The implications of the results are then discussed for the design of bio-inspired dental multilayers.

  2. Substrate Creep on The Fatigue Life of A Model Dental Multilayer Structure

    SciTech Connect

    Zhou, J; Huang, M; Niu, X; soboyejo, W

    2006-10-09

    In this paper, we investigated the effects of substrate creep on the fatigue behavior of a model dental multilayer structure, in which a top glass layer was bonded to a polycarbonate substrate through a dental adhesive. The top glass layers were ground using 120 grit or 600 grit sand papers before bonding to create different sub-surface crack sizes and morphologies. The multilayer structures were tested under cyclic Hertzian contact loading to study crack growth and obtain fatigue life curves. The experiment results showed that the fatigue lives of the multilayer structures were impaired by increasing crack sizes in the sub-surfaces. They were also significantly reduced by the substrate creep when tested at relatively low load levels i.e. P{sub m} < 60 N (Pm is the maximum magnitude of cyclic load). But at relatively high load levels i.e. P{sub m} > 65 N, slow crack growth (SCG) was the major failure mechanisms. A modeling study was then carried out to explore the possible failure mechanisms over a range of load levels. It is found that fatigue life at relatively low load levels can be better estimated by considering the substrate creep effect (SCE).

  3. Bio-inspired dental multilayers: effects of layer architecture on the contact-induced deformation.

    PubMed

    Du, J; Niu, X; Rahbar, N; Soboyejo, W

    2013-02-01

    The ceramic crown structures under occlusal contact are idealized as flat multilayered structures that are deformed under Hertzian contact loading. Those multilayers consist of a crown-like ceramic top layer, an adhesive layer and the dentin-like substrate. Bio-inspired design of the adhesive layer proposed functionally graded multilayers (FGM) that mimic the dentin-enamel junction in natural teeth. This paper examines the effects of FGM layer architecture on the contact-induced deformation of bio-inspired dental multilayers. Finite element modeling was used to explore the effects of thickness and architecture on the contact-induced stresses that are induced in bio-inspired dental multilayers. A layered nanocomposite structure was then fabricated by the sequential rolling of micro-scale nanocomposite materials with local moduli that increase from the side near the soft dentin-like polymer composite foundation to the side near the top ceramic layer. The loading rate dependence of the critical failure loads is shown to be well predicted by a slow crack growth model, which integrates the actual mechanical properties that are obtained from nanoindentation experiments.

  4. Creep-assisted slow crack growth in bio-inspired dental multilayers.

    PubMed

    Du, Jing; Niu, Xinrui; Soboyejo, Wole

    2015-06-01

    Ceramic crown structures under occlusal contact are often idealized as flat multilayered structures that are deformed under Hertzian contact loading. Previous models treated each layer as linear elastic materials and resulted in differences between the measured and predicted critical loads. This paper examines the combined effects of creep (in the adhesive and substrate layers) and creep-assisted slow crack growth (in the ceramic layer) on the contact-induced deformation of bio-inspired, functionally graded multilayer (FGM) structures and the conventional tri-layers. The time-dependent moduli of each of the layers were determined from constant load creep tests. The resulting modulus-time characteristics were modeled using Prony series. These were then incorporated into a finite element model for the computation of stress distributions in the sub-surface regions of the top ceramic layer, in which sub-surface radial cracks, are observed as the clinical failure mode. The time-dependent stresses are incorporated into a slow crack growth (SCG) model that is used to predict the critical loads of the dental multilayers under Hertzian contact loading. The predicted loading rate dependence of the critical loads is shown to be consistent with experimental results. The implications of the results are then discussed for the design of robust dental multilayers.

  5. Multilayer weighted social network model

    NASA Astrophysics Data System (ADS)

    Murase, Yohsuke; Török, János; Jo, Hang-Hyun; Kaski, Kimmo; Kertész, János

    2014-11-01

    Recent empirical studies using large-scale data sets have validated the Granovetter hypothesis on the structure of the society in that there are strongly wired communities connected by weak ties. However, as interaction between individuals takes place in diverse contexts, these communities turn out to be overlapping. This implies that the society has a multilayered structure, where the layers represent the different contexts. To model this structure we begin with a single-layer weighted social network (WSN) model showing the Granovetterian structure. We find that when merging such WSN models, a sufficient amount of interlayer correlation is needed to maintain the relationship between topology and link weights, while these correlations destroy the enhancement in the community overlap due to multiple layers. To resolve this, we devise a geographic multilayer WSN model, where the indirect interlayer correlations due to the geographic constraints of individuals enhance the overlaps between the communities and, at the same time, the Granovetterian structure is preserved.

  6. Dental cell sheet biomimetic tooth bud model.

    PubMed

    Monteiro, Nelson; Smith, Elizabeth E; Angstadt, Shantel; Zhang, Weibo; Khademhosseini, Ali; Yelick, Pamela C

    2016-11-01

    Tissue engineering and regenerative medicine technologies offer promising therapies for both medicine and dentistry. Our long-term goal is to create functional biomimetic tooth buds for eventual tooth replacement in humans. Here, our objective was to create a biomimetic 3D tooth bud model consisting of dental epithelial (DE) - dental mesenchymal (DM) cell sheets (CSs) combined with biomimetic enamel organ and pulp organ layers created using GelMA hydrogels. Pig DE or DM cells seeded on temperature-responsive plates at various cell densities (0.02, 0.114 and 0.228 cells 10(6)/cm(2)) and cultured for 7, 14 and 21 days were used to generate DE and DM cell sheets, respectively. Dental CSs were combined with GelMA encapsulated DE and DM cell layers to form bioengineered 3D tooth buds. Biomimetic 3D tooth bud constructs were cultured in vitro, or implanted in vivo for 3 weeks. Analyses were performed using micro-CT, H&E staining, polarized light (Pol) microscopy, immunofluorescent (IF) and immunohistochemical (IHC) analyses. H&E, IHC and IF analyses showed that in vitro cultured multilayered DE-DM CSs expressed appropriate tooth marker expression patterns including SHH, BMP2, RUNX2, tenascin and syndecan, which normally direct DE-DM interactions, DM cell condensation, and dental cell differentiation. In vivo implanted 3D tooth bud constructs exhibited mineralized tissue formation of specified size and shape, and SHH, BMP2 and RUNX2and dental cell differentiation marker expression. We propose our biomimetic 3D tooth buds as models to study optimized DE-DM cell interactions leading to functional biomimetic replacement tooth formation.

  7. Dental cell sheet biomimetic tooth bud model.

    PubMed

    Monteiro, Nelson; Smith, Elizabeth E; Angstadt, Shantel; Zhang, Weibo; Khademhosseini, Ali; Yelick, Pamela C

    2016-11-01

    Tissue engineering and regenerative medicine technologies offer promising therapies for both medicine and dentistry. Our long-term goal is to create functional biomimetic tooth buds for eventual tooth replacement in humans. Here, our objective was to create a biomimetic 3D tooth bud model consisting of dental epithelial (DE) - dental mesenchymal (DM) cell sheets (CSs) combined with biomimetic enamel organ and pulp organ layers created using GelMA hydrogels. Pig DE or DM cells seeded on temperature-responsive plates at various cell densities (0.02, 0.114 and 0.228 cells 10(6)/cm(2)) and cultured for 7, 14 and 21 days were used to generate DE and DM cell sheets, respectively. Dental CSs were combined with GelMA encapsulated DE and DM cell layers to form bioengineered 3D tooth buds. Biomimetic 3D tooth bud constructs were cultured in vitro, or implanted in vivo for 3 weeks. Analyses were performed using micro-CT, H&E staining, polarized light (Pol) microscopy, immunofluorescent (IF) and immunohistochemical (IHC) analyses. H&E, IHC and IF analyses showed that in vitro cultured multilayered DE-DM CSs expressed appropriate tooth marker expression patterns including SHH, BMP2, RUNX2, tenascin and syndecan, which normally direct DE-DM interactions, DM cell condensation, and dental cell differentiation. In vivo implanted 3D tooth bud constructs exhibited mineralized tissue formation of specified size and shape, and SHH, BMP2 and RUNX2and dental cell differentiation marker expression. We propose our biomimetic 3D tooth buds as models to study optimized DE-DM cell interactions leading to functional biomimetic replacement tooth formation. PMID:27565550

  8. A MULTILAYER BIOCHEMICAL DRY DEPOSITION MODEL 1. MODEL FORMULATION

    EPA Science Inventory

    A multilayer biochemical dry deposition model has been developed based on the NOAA Multilayer Model (MLM) to study gaseous exchanges between the soil, plants, and the atmosphere. Most of the parameterizations and submodels have been updated or replaced. The numerical integration ...

  9. Zirconia-parylene multilayer thin films for enhanced fracture resistance of dental ceramics.

    PubMed

    Teixeira, E C; Piascik, J R; Stoner, B R; Thompson, J Y

    2009-10-01

    Recent research has shown that the application of specific thin films can enhance the material properties of a laminate construct. In this study, the effect of different mono/multilayered films on the strength of a ceramic specimen is demonstrated. It is well established that cracks can initiate and/or propagate from the internal surfaces of all-ceramic dental restorations. Modifying that surface by thin-film deposition might help increase clinical longevity and applicability. Specimens were divided into the following groups according to different surface treatments received: uncoated (control group), 10 microm yttria-stabilized zirconia (YSZ) thin film, 10 microm parylene thin film, 9.75 microm YSZ + 0.25 microm parylene film, and a multilayered film (five layers of 1.25 microm YSZ + 0.75 microm parylene). Depositions were performed using a radio-frequency magnetron sputter system (working pressure 15 mT, 150 degrees C, 30:1 Ar/O2 gas ratio) to produce the YSZ layers, and a vapour deposition process was used to produce the parylene layers. Flexural strength measurements were carried out by three-point bending (span = 10 mm) in a servo-electric material testing system in deioinized (DI) water (37 degrees C). The results showed that the strength of the specimen significantly increased with the deposition of all types of coating, showing the greatest increase with the multilayered film (approximately 32 per cent). It is hypothesized that a multilayer thin film (brittle/ductile) can promote crack deflection, causing strength enhancement of the brittle construct.

  10. Multilayered models for electromagnetic reflection amplitudes

    NASA Technical Reports Server (NTRS)

    Linlor, W. I.

    1976-01-01

    The remote sensing of snowpack characteristics with surface installations or with an airborne system could have important applications in water resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayer snow models is analyzed. Normally incident plane waves are assumed at frequencies ranging from 10 to the 6th power to 10 to the 10th power Hz, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice sheets. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients, versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the reflection coefficient variations as a function of frequency.

  11. A MULTILAYER BIOCHEMICAL DRY DEPOSITION MODEL 2. MODEL EVALUATION

    EPA Science Inventory

    The multilayer biochemical dry deposition model (MLBC) described in the accompanying paper was tested against half-hourly eddy correlation data from six field sites under a wide range of climate conditions with various plant types. Modeled CO2, O3, SO2<...

  12. Epidemic Model with Isolation in Multilayer Networks

    NASA Astrophysics Data System (ADS)

    Zuzek, L. G. Alvarez; Stanley, H. E.; Braunstein, L. A.

    2015-07-01

    The Susceptible-Infected-Recovered (SIR) model has successfully mimicked the propagation of such airborne diseases as influenza A (H1N1). Although the SIR model has recently been studied in a multilayer networks configuration, in almost all the research the isolation of infected individuals is disregarded. Hence we focus our study in an epidemic model in a two-layer network, and we use an isolation parameter w to measure the effect of quarantining infected individuals from both layers during an isolation period tw. We call this process the Susceptible-Infected-Isolated-Recovered (SIIR) model. Using the framework of link percolation we find that isolation increases the critical epidemic threshold of the disease because the time in which infection can spread is reduced. In this scenario we find that this threshold increases with w and tw. When the isolation period is maximum there is a critical threshold for w above which the disease never becomes an epidemic. We simulate the process and find an excellent agreement with the theoretical results.

  13. A refined model for characterizing x-ray multilayers

    SciTech Connect

    Oren, A.L.; Henke, B.L.

    1987-12-01

    The ability to quickly and accurately characterize arbitrary multilayers is very valuable for not only can we use the characterizations to predict the reflectivity of a multilayer for any soft x-ray wavelength, we also can generalize the results to apply to other multilayers of the same type. In addition, we can use the characterizations as a means of evaluating various sputtering environments and refining sputtering techniques to obtain better multilayers. In this report we have obtained improved characterizations for sample molybdenum-silicon and vanadium-silicon multilayers. However, we only examined five crystals overall, so the conclusions that we could draw about the structure of general multilayers is limited. Research involving many multilayers manufactured under the same sputtering conditions is clearly in order. In order to best understand multilayer structures it may be necessary to further refine our model, e.g., adopting a Gaussian form for the interface regions. With such improvements we can expect even better agreement with experimental values and continued concurrence with other characterization techniques. 18 refs., 30 figs., 7 tabs.

  14. Multilayered model in optics and quantum mechanics

    NASA Astrophysics Data System (ADS)

    Kovalev, M. D.

    2009-08-01

    Three types of dispersion equations are analyzed that describe the eigenvalues of the effective refractive index of a multilayer plane optical waveguide and the energy eigenvalues of a quantum particle placed in a piecewise constant potential field. The first equation (D1) is derived by setting to zero the determinant of the system of linear equations produced by matching the solutions in the layers. The second equation (D2) is obtained using the well-known method of characteristic matrices. The third equation has been obtained in the general case by the author and is known as a multilayer equation. Simple relations between the three equations are established. It is shown that the set of roots of D2 exactly coincides with the set of eigenvalues of the multilayer problem, while the roots of D1 and the multilayer equation contain those equal to the refractive index in the optical case (or to the potential in the quantum case) in internal layers of the system, which may be superfluous. Examples are presented.

  15. Variable variance Preisach model for multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Franco, A. F.; Gonzalez-Fuentes, C.; Morales, R.; Ross, C. A.; Dumas, R.; Åkerman, J.; Garcia, C.

    2016-08-01

    We present a variable variance Preisach model that fully accounts for the different magnetization processes of a multilayer structure with perpendicular magnetic anisotropy by adjusting the evolution of the interaction variance as the magnetization changes. We successfully compare in a quantitative manner the results obtained with this model to experimental hysteresis loops of several [CoFeB/Pd ] n multilayers. The effect of the number of repetitions and the thicknesses of the CoFeB and Pd layers on the magnetization reversal of the multilayer structure is studied, and it is found that many of the observed phenomena can be attributed to an increase of the magnetostatic interactions and subsequent decrease of the size of the magnetic domains. Increasing the CoFeB thickness leads to the disappearance of the perpendicular anisotropy, and such a minimum thickness of the Pd layer is necessary to achieve an out-of-plane magnetization.

  16. Modeling of thermal stresses in elastic multilayer coating systems

    NASA Astrophysics Data System (ADS)

    Gao, Chunxue; Zhao, Zhiwei; Li, Xuehua

    2015-02-01

    The performance and reliability of multilayer coating systems are strongly influenced by thermal stresses. The present study develops an alternative analytical model to predict the thermal stresses in elastic multilayer coating systems. An exact closed-form solution is obtained which is independent of the number of coating layers. In addition, with the definition of the coordinate system, the closed-form solution is concisely formulated. Specific results are calculated for thermal stresses in HfO2/SiO2 multilayer optical coatings, and a finite element analysis is performed to confirm the analytical results. The two results agree fairly well with each other. Also, when the thicknesses of the coating layers are much less than the substrate thickness, the approximate solution is obtained based on the exact closed-form solution, and its accuracy is examined.

  17. Conventional modeling of the multilayer perceptron using polynomial basis functions.

    PubMed

    Chen, M S; Manry, M T

    1993-01-01

    A technique for modeling the multilayer perceptron (MLP) neural network, in which input and hidden units are represented by polynomial basis functions (PBFs), is presented. The MLP output is expressed as a linear combination of the PBFs and can therefore be expressed as a polynomial function of its inputs. Thus, the MLP is isomorphic to conventional polynomial discriminant classifiers or Volterra filters. The modeling technique was successfully applied to several trained MLP networks.

  18. Conventional modeling of the multilayer perceptron using polynomial basis functions

    NASA Technical Reports Server (NTRS)

    Chen, Mu-Song; Manry, Michael T.

    1993-01-01

    A technique for modeling the multilayer perceptron (MLP) neural network, in which input and hidden units are represented by polynomial basis functions (PBFs), is presented. The MLP output is expressed as a linear combination of the PBFs and can therefore be expressed as a polynomial function of its inputs. Thus, the MLP is isomorphic to conventional polynomial discriminant classifiers or Volterra filters. The modeling technique was successfully applied to several trained MLP networks.

  19. Numerical modeling of hydrofracturing in a multilayer coal seam

    SciTech Connect

    Nasedkina, A.A.; Trufanov, V.N.

    2006-01-15

    The mathematical model of the process for hydrodynamic fracturing in a multilayer coal seam is proposed. The model is based on the equation of continuity and Darcy's law. The filtration-temperature analogy allows solving the obtained non-linear, non-stationary problem in an axisymmetric statement for the pressure function as the heat-conductivity problem, by the finite-element method. The calculation results yield estimation of the radius of degassing borehole influence zone.

  20. A topological multilayer model of the human body.

    PubMed

    Barbeito, Antonio; Painho, Marco; Cabral, Pedro; O'Neill, João

    2015-11-04

    Geographical information systems deal with spatial databases in which topological models are described with alphanumeric information. Its graphical interfaces implement the multilayer concept and provide powerful interaction tools. In this study, we apply these concepts to the human body creating a representation that would allow an interactive, precise, and detailed anatomical study. A vector surface component of the human body is built using a three-dimensional (3-D) reconstruction methodology. This multilayer concept is implemented by associating raster components with the corresponding vector surfaces, which include neighbourhood topology enabling spatial analysis. A root mean square error of 0.18 mm validated the three-dimensional reconstruction technique of internal anatomical structures. The expansion of the identification and the development of a neighbourhood analysis function are the new tools provided in this model.

  1. Development of a dental model hardener.

    PubMed

    He, Li-Hong; van Vuuren, Ludwig Jansen

    2012-03-01

    The paper presents a novel method of strengthening dental gypsum materials by infiltrating with a low-viscosity autopolymerising monomer. Gypsum specimens were infiltrated with diluted butyl-cyanoacrylate monomer at different concentrations. Nanoindentation was employed to measure their hardness and elastic modulus. A standard single-edge-notched beam (SENB) method was used to measure fracture toughness. Biaxial strength was measured using a universal test machine with a piston-on-ring jig. Scanning Electron Microscopy (SEM) and affiliated energy dispersive X-ray spectroscopy (EDX) were used to observe the fracture topography and the depth of infiltration. Infiltration and autopolymerisation of the cyanoacrylate improved the biaxial strength and fracture toughness of the gypsum by around 39% and around 30%, respectively. The hardness and elastic modulus for the treated specimens were also higher, albeit slightly. The proposed method provides a convenient way to strengthen and repair dental gypsum models in situ. PMID:22439316

  2. Experimentally validated finite element model of electrocaloric multilayer ceramic structures

    SciTech Connect

    Smith, N. A. S. E-mail: maciej.rokosz@npl.co.uk Correia, T. M. E-mail: maciej.rokosz@npl.co.uk; Rokosz, M. K. E-mail: maciej.rokosz@npl.co.uk

    2014-07-28

    A novel finite element model to simulate the electrocaloric response of a multilayer ceramic capacitor (MLCC) under real environment and operational conditions has been developed. The two-dimensional transient conductive heat transfer model presented includes the electrocaloric effect as a source term, as well as accounting for radiative and convective effects. The model has been validated with experimental data obtained from the direct imaging of MLCC transient temperature variation under application of an electric field. The good agreement between simulated and experimental data, suggests that the novel experimental direct measurement methodology and the finite element model could be used to support the design of optimised electrocaloric units and operating conditions.

  3. Evaluation of the SEI using a multilayer spectroscopic ellipsometry model

    SciTech Connect

    Eric J. Dufek

    2014-08-01

    A multilayer spectroscopic ellipsometry (SE) model has been developed to characterize SEI formation. The model, which consists of two Cauchy layers, is constructed with an inner layer meant to model primarily inorganic compounds adjacent to an electrode and an outer layer which mirrors polymeric, organic constituents on the exterior of the SEI. Comparison of 1:1 EC:EMC and 1:4 EC:EMC with 1.0 M LiPF6 shows distinct differences in the two modeled layers. The data suggest that the thickness of both layers change over a wide potential range. These changes have been linked with other reports on the growth of the SEI.

  4. Evaluation of the SEI using a multilayer spectroscopic ellipsometry model

    DOE PAGES

    Dufek, Eric J.

    2014-08-28

    A multilayer spectroscopic ellipsometry (SE) model has been developed to characterize SEI formation. The model, which consists of two Cauchy layers, is constructed with an inner layer meant to model primarily inorganic compounds adjacent to an electrode and an outer layer which mirrors polymeric, organic constituents on the exterior of the SEI. Comparison of 1:1 EC:EMC and 1:4 EC:EMC with 1.0 M LiPF₆ shows distinct differences in the two modeled layers. The data suggest that the thickness of both layers change over a wide potential range. These changes have been linked with other reports on the growth of the SEI.

  5. Multilayer neural network with randomized learning: Model and applications

    SciTech Connect

    Terekhov, S.A.

    1995-03-01

    A randomized annealing-simulation scheme for learning by a multilayer neural network is examined. The fractal properties of the learning trajectories in the phase space of the network are studied. It is proposed that the learning temperature be controlled by the phenomenological characteristics of the trajectory. The errors of generalization of a multilayer perceptron and of the method of splines in time-series prediction are compared. It is shown that for nonsmooth functions that generate a stochastic time series, a neural network is preferable to a spline for the same number of parameters. The learning scheme is used to construct a cybernetic neural-network model of the phenomenon of magnetic implosion as well as for fault classification in the coolant system of a nuclear-power-plant reactor.

  6. Modeling of Indentation Damage in Single and Multilayer Coatings

    NASA Astrophysics Data System (ADS)

    Chen, J.; Bull, S. J.

    In many coating applications damage resistance is controlled by the mechanical properties of the coating, interface and substrate. As coatings become thinner and more complex, with multilayer and graded architectures now in widespread use, it is very important to obtain the mechanical properties (such as hardness, elastic modulus, fracture toughness, etc.) of individual coating layers for use in design calculations and have failure-related design criteria which are valid for such multilayer systems. Nanoindentation testing is often the only viable approach to assess the damage mechanisms and properties of very thin coatings (< 1 µm) since it can operate at the required scale and provides fingerprint of the indentation response of the coating/substrate system. Finite element analysis of indentation load displacement curves can be used to extract materials properties for design; as coating thicknesses decrease it is observed that the yield strength required to fit the curves increases and scale-dependent materials properties are essential for design. Similarly the assessment of fracture response of very thin coatings requires modeling of the indentation stress field and how it is modified by plasticity during the indentation cycle. An FE approach using a cohesive zone model has been used to assess the locus of failure and demonstrates the complexity of adhesive failure around indentations for multilayer coatings.

  7. Modelling of the Peltier effect in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Juarez-Acosta, Isaac; Olivares-Robles, Miguel A.; Bosu, Subrojati; Sakuraba, Yuya; Kubota, Takahide; Takahashi, Saburo; Takanashi, Koki; Bauer, Gerrit E. W.

    2016-02-01

    We model the charge, spin, and heat currents in ferromagnetic metal|normal metal|normal metal trilayer structures in the two current model, taking into account bulk and interface thermoelectric properties as well as Joule heating. The results include the temperature distribution as well as resistance-current curves that reproduce the observed shifted parabolic characteristics. Thin tunneling barriers can enhance the apparent Peltier cooling. The model agrees with the experimental results for wide multilayer pillars, but the giant effects observed for diameters ≲100 nm are still under discussion.

  8. Model multilayer structures for three-dimensional cell imaging

    NASA Astrophysics Data System (ADS)

    Kozole, Joseph; Szakal, Christopher; Kurczy, Michael; Winograd, Nicholas

    2006-07-01

    The prospects for SIMS three-dimensional analysis of biological materials were explored using model multilayer structures. The samples were analyzed in a ToF-SIMS spectrometer equipped with a 20 keV buckminsterfullerene (C 60+) ion source. Molecular depth information was acquired using a C 60+ ion beam to etch through the multilayer structures at specified time intervals. Subsequent to each individual erosion cycle, static SIMS spectra were recorded using a pulsed C 60+ ion probe. Molecular intensities in sequential mass spectra were monitored as a function of primary ion fluence. The resulting depth information was used to characterize C 60+ bombardment of biological materials. Specifically, molecular depth profile studies involving dehydrated dipalmitoyl-phosphatidylcholine (DPPC) organic films indicate that cell membrane lipid materials do not experience significant chemical damage when bombarded with C 60+ ion fluences greater than 10 15 ions/cm 2. Moreover, depth profile analyses of DPPC-sucrose frozen multilayer structures suggest that biomolecule information can be uncovered after the C 60+ sputter removal of a 20 nm overlayer with no appreciable loss of underlying molecular signal. The experimental results support the potential for three-dimensional molecular mapping of biological materials using cluster SIMS.

  9. A probabilistic model for the fault tolerance of multilayer perceptrons.

    PubMed

    Merchawi, N S; Kumara, S T; Das, C R

    1996-01-01

    This paper presents a theoretical approach to determine the probability of misclassification of the multilayer perceptron (MLP) neural model, subject to weight errors. The type of applications considered are classification/recognition tasks involving binary input-output mappings. The analytical models are validated via simulation of a small illustrative example. The theoretical results, in agreement with simulation results, show that, for the example considered, Gaussian weight errors of standard deviation up to 22% of the weight value can be tolerated. The theoretical method developed here adds predictability to the fault tolerance capability of neural nets and shows that this capability is heavily dependent on the problem data.

  10. Radon diffusion through multilayer earthen covers: models and simulations

    SciTech Connect

    Mayer, D.W.; Oster, C.A.; Nelson, R.W.; Gee, G.W.

    1981-09-01

    A capability to model and analyze the fundamental interactions that influence the diffusion of radon gas through uranium mill tailings and cover systems has been investigated. The purpose of this study is to develop the theoretical basis for modeling radon diffusion and to develop an understanding of the fundamental interactions that influence radon diffusion. This study develops the theoretical basis for modeling radon diffusion in one, two and three dimensions. The theory has been incorporated into three computer models that are used to analyze several tailings and cover configurations. This report contains a discussion of the theoretical basis for modeling radon diffusion, a discussion of the computer models used to analyze uranium mill tailings and multilayered cover systems, and presents the results that have been obtained.

  11. Numerical FEM modeling in dental implantology

    NASA Astrophysics Data System (ADS)

    Roateşi, Iulia; Roateşi, Simona

    2016-06-01

    This paper is devoted to a numerical approach of the stress and displacement calculation of a system made up of dental implant, ceramic crown and surrounding bone. This is the simulation of a clinical situation involving both biological - the bone tissue, and non-biological - the implant and the crown, materials. On the other hand this problem deals with quite fine technical structure details - the threads, tapers, etc with a great impact in masticatory force transmission. Modeling the contact between the implant and the bone tissue is important to a proper bone-implant interface model and implant design. The authors proposed a three-dimensional numerical model to assess the biomechanical behaviour of this complex structure in order to evaluate its stability by determining the risk zones. A comparison between this numerical analysis and clinical cases is performed and a good agreement is obtained.

  12. Finite element modeling of multilayered structures of fish scales.

    PubMed

    Chandler, Mei Qiang; Allison, Paul G; Rodriguez, Rogie I; Moser, Robert D; Kennedy, Alan J

    2014-12-01

    The interlinked fish scales of Atractosteus spatula (alligator gar) and Polypterus senegalus (gray and albino bichir) are effective multilayered armor systems for protecting fish from threats such as aggressive conspecific interactions or predation. Both types of fish scales have multi-layered structures with a harder and stiffer outer layer, and softer and more compliant inner layers. However, there are differences in relative layer thickness, property mismatch between layers, the property gradations and nanostructures in each layer. The fracture paths and patterns of both scales under microindentation loads were different. In this work, finite element models of fish scales of A. spatula and P. senegalus were built to investigate the mechanics of their multi-layered structures under penetration loads. The models simulate a rigid microindenter penetrating the fish scales quasi-statically to understand the observed experimental results. Study results indicate that the different fracture patterns and crack paths observed in the experiments were related to the different stress fields caused by the differences in layer thickness, and spatial distribution of the elastic and plastic properties in the layers, and the differences in interface properties. The parametric studies and experimental results suggest that smaller fish such as P. senegalus may have adopted a thinner outer layer for light-weighting and improved mobility, and meanwhile adopted higher strength and higher modulus at the outer layer, and stronger interface properties to prevent ring cracking and interface cracking, and larger fish such as A. spatula and Arapaima gigas have lower strength and lower modulus at the outer layers and weaker interface properties, but have adopted thicker outer layers to provide adequate protection against ring cracking and interface cracking, possibly because weight is less of a concern relative to the smaller fish such as P. senegalus. PMID:25300062

  13. Finite element modeling of multilayered structures of fish scales.

    PubMed

    Chandler, Mei Qiang; Allison, Paul G; Rodriguez, Rogie I; Moser, Robert D; Kennedy, Alan J

    2014-12-01

    The interlinked fish scales of Atractosteus spatula (alligator gar) and Polypterus senegalus (gray and albino bichir) are effective multilayered armor systems for protecting fish from threats such as aggressive conspecific interactions or predation. Both types of fish scales have multi-layered structures with a harder and stiffer outer layer, and softer and more compliant inner layers. However, there are differences in relative layer thickness, property mismatch between layers, the property gradations and nanostructures in each layer. The fracture paths and patterns of both scales under microindentation loads were different. In this work, finite element models of fish scales of A. spatula and P. senegalus were built to investigate the mechanics of their multi-layered structures under penetration loads. The models simulate a rigid microindenter penetrating the fish scales quasi-statically to understand the observed experimental results. Study results indicate that the different fracture patterns and crack paths observed in the experiments were related to the different stress fields caused by the differences in layer thickness, and spatial distribution of the elastic and plastic properties in the layers, and the differences in interface properties. The parametric studies and experimental results suggest that smaller fish such as P. senegalus may have adopted a thinner outer layer for light-weighting and improved mobility, and meanwhile adopted higher strength and higher modulus at the outer layer, and stronger interface properties to prevent ring cracking and interface cracking, and larger fish such as A. spatula and Arapaima gigas have lower strength and lower modulus at the outer layers and weaker interface properties, but have adopted thicker outer layers to provide adequate protection against ring cracking and interface cracking, possibly because weight is less of a concern relative to the smaller fish such as P. senegalus.

  14. Dental caries: an updated medical model of risk assessment.

    PubMed

    Kutsch, V Kim

    2014-04-01

    Dental caries is a transmissible, complex biofilm disease that creates prolonged periods of low pH in the mouth, resulting in a net mineral loss from the teeth. Historically, the disease model for dental caries consisted of mutans streptococci and Lactobacillus species, and the dental profession focused on restoring the lesions/damage from the disease by using a surgical model. The current recommendation is to implement a risk-assessment-based medical model called CAMBRA (caries management by risk assessment) to diagnose and treat dental caries. Unfortunately, many of the suggestions of CAMBRA have been overly complicated and confusing for clinicians. The risk of caries, however, is usually related to just a few common factors, and these factors result in common patterns of disease. This article examines the biofilm model of dental caries, identifies the common disease patterns, and discusses their targeted therapeutic strategies to make CAMBRA more easily adaptable for the privately practicing professional.

  15. Multilayer Stock Forecasting Model Using Fuzzy Time Series

    PubMed Central

    Javedani Sadaei, Hossein; Lee, Muhammad Hisyam

    2014-01-01

    After reviewing the vast body of literature on using FTS in stock market forecasting, certain deficiencies are distinguished in the hybridization of findings. In addition, the lack of constructive systematic framework, which can be helpful to indicate direction of growth in entire FTS forecasting systems, is outstanding. In this study, we propose a multilayer model for stock market forecasting including five logical significant layers. Every single layer has its detailed concern to assist forecast development by reconciling certain problems exclusively. To verify the model, a set of huge data containing Taiwan Stock Index (TAIEX), National Association of Securities Dealers Automated Quotations (NASDAQ), Dow Jones Industrial Average (DJI), and S&P 500 have been chosen as experimental datasets. The results indicate that the proposed methodology has the potential to be accepted as a framework for model development in stock market forecasts using FTS. PMID:24605058

  16. A Model Program for Dental Assisting Education in California.

    ERIC Educational Resources Information Center

    California State Dept. of Education, Sacramento. Bureau of Industrial Education.

    Intended to provide assistance for developing new programs and improving existing ones, the guide was constructed by dental assisting instructors and other professional participants in a 196 5 workshop conference. Elements of the model program were derived from a statistical analysis of California junior colleg e programs in dental assisting and…

  17. Light dosimetry for focused and defocused beam irradiation in multi-layered tissue models

    NASA Astrophysics Data System (ADS)

    Petrova, Kremena S.; Stoykova, Elena V.

    2006-09-01

    Treatment of acupuncture points, trigger points, joint inflammations in low level laser therapy as well as various applications of lasers for treatment of soft tissues in dental medicine, require irradiation by a narrow converging laser beam. The aim of this study is to compare light delivery produced by focused or defocused narrow beam irradiation in a multi-layered skin tissue model at increasing depth of the target. The task is solved by 3-D Monte-Carlo simulation for matched and mismatched refractive indices at the tissue/ambient medium interface. The modeled light beams have a circular cross-section at the tissue entrance with uniform or Gaussian intensity distribution. Three are the tissue models used in simulation : i) a bloodless skin layer; ii) a bloodless skin layer with embedded scattering object; iii) a skin layer with small blood vessels of varying size, which are modeled as infinite cylinders parallel to the tissue surface located at different depths. Optical properties (absorption coefficient, scattering coefficient, anisotropy factor, g, and index of refraction) of different tissue constituents are chosen from the literature.

  18. Interactive Tooth Separation from Dental Model Using Segmentation Field

    PubMed Central

    2016-01-01

    Tooth segmentation on dental model is an essential step of computer-aided-design systems for orthodontic virtual treatment planning. However, fast and accurate identifying cutting boundary to separate teeth from dental model still remains a challenge, due to various geometrical shapes of teeth, complex tooth arrangements, different dental model qualities, and varying degrees of crowding problems. Most segmentation approaches presented before are not able to achieve a balance between fine segmentation results and simple operating procedures with less time consumption. In this article, we present a novel, effective and efficient framework that achieves tooth segmentation based on a segmentation field, which is solved by a linear system defined by a discrete Laplace-Beltrami operator with Dirichlet boundary conditions. A set of contour lines are sampled from the smooth scalar field, and candidate cutting boundaries can be detected from concave regions with large variations of field data. The sensitivity to concave seams of the segmentation field facilitates effective tooth partition, as well as avoids obtaining appropriate curvature threshold value, which is unreliable in some case. Our tooth segmentation algorithm is robust to dental models with low quality, as well as is effective to dental models with different levels of crowding problems. The experiments, including segmentation tests of varying dental models with different complexity, experiments on dental meshes with different modeling resolutions and surface noises and comparison between our method and the morphologic skeleton segmentation method are conducted, thus demonstrating the effectiveness of our method. PMID:27532266

  19. Interactive Tooth Separation from Dental Model Using Segmentation Field.

    PubMed

    Li, Zhongyi; Wang, Hao

    2016-01-01

    Tooth segmentation on dental model is an essential step of computer-aided-design systems for orthodontic virtual treatment planning. However, fast and accurate identifying cutting boundary to separate teeth from dental model still remains a challenge, due to various geometrical shapes of teeth, complex tooth arrangements, different dental model qualities, and varying degrees of crowding problems. Most segmentation approaches presented before are not able to achieve a balance between fine segmentation results and simple operating procedures with less time consumption. In this article, we present a novel, effective and efficient framework that achieves tooth segmentation based on a segmentation field, which is solved by a linear system defined by a discrete Laplace-Beltrami operator with Dirichlet boundary conditions. A set of contour lines are sampled from the smooth scalar field, and candidate cutting boundaries can be detected from concave regions with large variations of field data. The sensitivity to concave seams of the segmentation field facilitates effective tooth partition, as well as avoids obtaining appropriate curvature threshold value, which is unreliable in some case. Our tooth segmentation algorithm is robust to dental models with low quality, as well as is effective to dental models with different levels of crowding problems. The experiments, including segmentation tests of varying dental models with different complexity, experiments on dental meshes with different modeling resolutions and surface noises and comparison between our method and the morphologic skeleton segmentation method are conducted, thus demonstrating the effectiveness of our method. PMID:27532266

  20. Multilayer adsorption model for the protein-ligand interaction

    NASA Astrophysics Data System (ADS)

    Varela, L. M.; Garcia, M.; Perez-Rodriguez, M.; Taboada, P.; Ruso, J. M.; Mosquera, V.

    2001-05-01

    In the present work we present a theoretical formalism based on the combination of the Brunauer-Emmet-Teller multilayer adsorption model with an electrolytic adsorbate, and the results are used to predict binding isotherms of several synthetic penicillin drugs onto human serum albumin. The occurrence of adsorption maxima in these binding processes is correctly predicted by this noncooperative binding model and it is demonstrated to be due to the ionic character of the adsorbate. The effect of the hydrophobic interactions between adsorbate monomers on the value of the maximum number of adsorbed particles is also a matter of study, and it is proven that this number increases with increasing hydrophobic character of the adsorbate.

  1. Preventive Dental Practices Motivational Model for Elementary Teachers in Training Institutions; Dental Health Instruction Project. Final Report.

    ERIC Educational Resources Information Center

    Dennison, Darwin

    An investigation was conducted to determine the effects of instruction upon the dental health behavior of university students. The experimental group of 68 subjects, all elementary education majors, were exposed to a three--stage dental health motivational model: Dental Health Skills Instruction (four hours of laboratory instruction), Cognitive…

  2. Soil moisture dynamics modeling considering multi-layer root zone.

    PubMed

    Kumar, R; Shankar, V; Jat, M K

    2013-01-01

    The moisture uptake by plant from soil is a key process for plant growth and movement of water in the soil-plant system. A non-linear root water uptake (RWU) model was developed for a multi-layer crop root zone. The model comprised two parts: (1) model formulation and (2) moisture flow prediction. The developed model was tested for its efficiency in predicting moisture depletion in a non-uniform root zone. A field experiment on wheat (Triticum aestivum) was conducted in the sub-temperate sub-humid agro-climate of Solan, Himachal Pradesh, India. Model-predicted soil moisture parameters, i.e., moisture status at various depths, moisture depletion and soil moisture profile in the root zone, are in good agreement with experiment results. The results of simulation emphasize the utility of the RWU model across different agro-climatic regions. The model can be used for sound irrigation management especially in water-scarce humid, temperate, arid and semi-arid regions and can also be integrated with a water transport equation to predict the solute uptake by plant biomass. PMID:23579833

  3. Analytical Modeling of Variable Density Multilayer Insulation for Cryogenic Storage

    NASA Technical Reports Server (NTRS)

    Hedayat, A.; Hastings, L. J.; Brown, T.; Cruit, Wendy (Technical Monitor)

    2001-01-01

    A unique foam/Multilayer Insulation (MLI) combination concept for orbital cryogenic storage was experimentally evaluated at NASA Marshall Space Flight Center (MSFC) using the Multipurpose Hydrogen Test Bed (MHTB). The MLI was designed for an on-orbit storage period of 45 days and included several unique features such as: a variable layer density and larger but fewer perforations for venting during ascent to orbit. Test results with liquid hydrogen indicated that the MLI weight or heat leak is reduced by about half in comparison with standard MLI. The focus of this paper is on analytical modeling of the Variable Density MLI (VD-MLI) on-orbit performance (i.e. vacuum/low pressure environment). The foam/VD-MLI combination model is considered to have five segments. The first segment represents the optional foam layer. The second, third, and fourth segments represent three MLI segments with different layer densities. The last segment is considered to be a shroud that surrounds the last MLI layer. Two approaches are considered. In the first approach, the variable density MLI is modeled layer by layer while in the second approach, a semi-empirical model is applied. Both models account for thermal radiation between shields, gas conduction, and solid conduction through the layer separator materials.

  4. Multilayer Control Hierarchy in an Integrated Hydrological Model

    NASA Astrophysics Data System (ADS)

    Park, J.; Obeysekera, J.; Vanzee, R.

    2005-05-01

    Considerable progress has been made in the functionality of integrated hydrological models which can provide evaluation of anthropogenic control and management policies of water resources. Nonetheless, there is still room for improvement in the coupling and expression of water control policies into hydrological models [1]. The Management Simulation Engine (MSE) component of the Regional Simulation Model (RSM) incorporates a multi-level hierarchical control architecture which emphasizes the decoupling of hydrological state information from the management information processing applied to the states. The MSE is intended to allow a flexible, extensible expression of a wide variety anthropogenic water resource control schemes integrated with the hydrological state evaluations of the RSM. Synergy between the multilayer control hierarchy and decoupled hydrologic state and management information facilitates a water resource management feature set not typical of integrated hydrological models. Some of these features include: interoperation and compatibility of diverse management algorithms such as PID, Fuzzy control, LP; and dynamic switching of control processors. This paper describes the MSE control hierarchy with a focus on the aforementioned features and their implementation. [1] Belaineh, G., Peralta, R. C., Hughes, T. C., Simulation/ Optimization Modeling for Water Resources Management, ASCE Journal Water Resources Planning Management, 125(3), p 154-61, 1999

  5. SENSITIVITY OF THE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION MULTILAYER MODEL TO INSTRUMENT ERROR AND PARAMETERIZATION UNCERTAINTY

    EPA Science Inventory

    The response of the National Oceanic and Atmospheric Administration multilayer inferential dry deposition velocity model (NOAA-MLM) to error in meteorological inputs and model parameterization is reported. Monte Carlo simulations were performed to assess the uncertainty in NOA...

  6. Modelling community, family, and individual determinants of childhood dental caries.

    PubMed

    Duijster, Denise; van Loveren, Cor; Dusseldorp, Elise; Verrips, Gijsbert H W

    2014-04-01

    This cross-sectional study empirically tested a theoretical model of pathways and inter-relationships among community, family, and individual determinants of childhood dental caries in a sample of 630, 6-year-old children from the Netherlands. Children's decayed, missing, and filled teeth (dmft) scores were extracted from dental records. A validated parental questionnaire was used to collect data on sociodemographic characteristics, psychosocial factors, and oral hygiene behaviours. Data on neighbourhood quality were obtained from the Dutch Central Bureau of Statistics. Structural equation modelling indicated that the model was valid after applying a few modifications. In the revised model, lower maternal education level was related to poorer family organization, lower levels of social support, lower dental self-efficacy, and an external dental health locus of control. These, in turn, were associated with poorer oral hygiene behaviours, which were linked to higher levels of childhood dental caries. In addition, lower maternal education level and poorer neighbourhood quality were directly associated with higher caries levels in children. This model advances our understanding of determinants of childhood dental caries and the pathways in which they operate. Conception of these pathways is essential for guiding the development of caries-preventive programmes for children. Clues for further development of the model are suggested.

  7. Treating dental caries as an infectious disease. Applying the medical model in practice to prevent dental caries.

    PubMed

    Limeback, H

    1996-01-01

    The above diagnostic and treatment principles may be self evident to most dental practitioners. To many, however, this treatment philosophy is a new one. Continuing dental education and quality assurance programs will play a significant role in helping dentists make the philosophical shift from a highly technical restorative approach to one that uses the medical model and treats dental caries as an infectious disease. While a total cure in humans suffering from dental disease may never be attainable, dental practitioners should soon be better able to direct more of their attention to the patients who already demonstrate a high incidence of dental decay and to those who are clearly at risk to develop future dental decay. PMID:9470624

  8. NASA/MSFC multilayer diffusion models and computer program for operational prediction of toxic fuel hazards

    NASA Technical Reports Server (NTRS)

    Dumbauld, R. K.; Bjorklund, J. R.; Bowers, J. F.

    1973-01-01

    The NASA/MSFC multilayer diffusion models are discribed which are used in applying meteorological information to the estimation of toxic fuel hazards resulting from the launch of rocket vehicle and from accidental cold spills and leaks of toxic fuels. Background information, definitions of terms, description of the multilayer concept are presented along with formulas for determining the buoyant rise of hot exhaust clouds or plumes from conflagrations, and descriptions of the multilayer diffusion models. A brief description of the computer program is given, and sample problems and their solutions are included. Derivations of the cloud rise formulas, users instructions, and computer program output lists are also included.

  9. Multi-layer VEB modeling: capturing interlayer etch process effects for multi-patterning process

    NASA Astrophysics Data System (ADS)

    Hu, Lin; Jung, Sunwook; Li, Jianliang; Kim, Young; Bar, Yuval; Lobb, Granger; Liang, Jim; Ogino, Atsushi; Sturtevant, John; Bailey, Todd

    2016-03-01

    Self-Aligned Via (SAV) process is commonly used in back end of line (BEOL) patterning. As the technology node advances, tightening CD and overlay specs require continuous improvement in model accuracy of the SAV process. Traditional single layer Variable Etch Bias (VEB) model is capable of describing the micro-loading and aperture effects associated with the reactive ion etch (RIE), but it does not include effects from under layers. For the SAV etch, a multi-layer VEB model is needed to account for the etch restriction from metal trenches. In this study, we characterize via post-etch dimensions through pitch and through metal trench widths, and show that VEB model prediction accuracy for SAV CDs after SAV formation can be significantly improved by applying a multi-layer scheme. Using a multi-layer VEB, it is demonstrated that the output via size changes with varying trench dimensions, which matches the silicon results. The model also reports via shape post-etch as a function of trench environment, where elliptical vias are correctly produced. The multi-layer VEB model can be applied both multi-layer correction and verification in full chip flow. This paper will also suggest that the multi-layer VEB model can be used in other FEOL layers with interlayer etch process effects, such as gate cut, to support the robustness of new model.

  10. Model Teacher - School Dental Hygiene Program.

    ERIC Educational Resources Information Center

    Smith, Lowell W.

    The purpose of this study, which was carried out during the 1972-73 school year at three parochial schools in the Houston area, was to determine the effectiveness of the Toothkeeper Program, a multimedia program of oral hygiene training carefully developed and packaged to establish effective long-term dental hygiene practice. The study population…

  11. Simple solutions of multilayered discs subjected to biaxial moment loading.

    SciTech Connect

    Hsueh, Chun-Hway; Kelly, J R

    2009-01-01

    The purpose of this study was to derive a simple closed-form solution for the stress distribution through the thickness of multilayered discs subjected to biaxial moment loading, such that it can be used readily to evaluate the biaxial strength of multilayered dental ceramics using biaxial flexure tests. Methods A simple analytical model was developed to derive the stress distribution through the thickness of multilayered discs subjected to biaxial moment loading. The accuracy of the solution was verified by comparing with previous rigorous analytical solutions and finite element results. The results obtained from Roark's formulas for bilayered discs were also included for comparison.

  12. NASA/MSFC multilayer diffusion models and computer programs, version 5

    NASA Technical Reports Server (NTRS)

    Dumbauld, R. K.; Bjorklund, J. R.

    1975-01-01

    The transport and diffusion models and algorithms developed for use by NASA in predicting concentrations and dosages downwind from normal and abnormal launches of rocket vehicles are described along with the associated computer programs for use in performing the calculations. Topics discussed include: the mathematical specifications and procedures used in the Preprocessor Program to calculate rocket exhaust cloud rise, cloud dimensions, and other input parameters to the transport and diffusion models; the revised mathematical specifications for the Multilayer Diffusion Models; users' instructions for implementing the Preprocessor and Multilayer Diffusion Models Programs; and worked example problems illustrating the use of the models and computer programs.

  13. Assessing risk factors for dental caries: a statistical modeling approach.

    PubMed

    Trottini, Mario; Bossù, Maurizio; Corridore, Denise; Ierardo, Gaetano; Luzzi, Valeria; Saccucci, Matteo; Polimeni, Antonella

    2015-01-01

    The problem of identifying potential determinants and predictors of dental caries is of key importance in caries research and it has received considerable attention in the scientific literature. From the methodological side, a broad range of statistical models is currently available to analyze dental caries indices (DMFT, dmfs, etc.). These models have been applied in several studies to investigate the impact of different risk factors on the cumulative severity of dental caries experience. However, in most of the cases (i) these studies focus on a very specific subset of risk factors; and (ii) in the statistical modeling only few candidate models are considered and model selection is at best only marginally addressed. As a result, our understanding of the robustness of the statistical inferences with respect to the choice of the model is very limited; the richness of the set of statistical models available for analysis in only marginally exploited; and inferences could be biased due the omission of potentially important confounding variables in the model's specification. In this paper we argue that these limitations can be overcome considering a general class of candidate models and carefully exploring the model space using standard model selection criteria and measures of global fit and predictive performance of the candidate models. Strengths and limitations of the proposed approach are illustrated with a real data set. In our illustration the model space contains more than 2.6 million models, which require inferences to be adjusted for 'optimism'.

  14. Refractive power of a multilayer rotationally symmetric model of the human cornea and tear film

    NASA Astrophysics Data System (ADS)

    Barbero, Sergio

    2006-07-01

    Optical models of the human cornea and tear film typically employ a single homogeneous cornea with an average refractive index. I propose to use a more realistic multilayer model based on morphological data from the literature. The mathematical methodology to derive the refractive power equation of this model is presented. Special attention is given to the axial gradient index of the refraction structure of the stroma layer because of its optical implications. The importance of considering this multilayer model is quantified in a specific example (orthokeratology) with the help of the derived power equation.

  15. Models for Delivering School-Based Dental Care.

    ERIC Educational Resources Information Center

    Albert, David A.; McManus, Joseph M.; Mitchell, Dennis A.

    2005-01-01

    School-based health centers (SBHCs) often are located in high-need schools and communities. Dental service is frequently an addition to existing comprehensive services, functioning in a variety of models, configurations, and locations. SBHCs are indicated when parents have limited financial resources or inadequate health insurance, limiting…

  16. Modeling of light intensification by conical pits within multilayer coatings

    SciTech Connect

    Qiu, S R; Wolfe, J E; Monterrosa, A; Feit, M D; Pistor, T V; Stolz, C J

    2009-11-02

    Removal of laser-induced damage sites provides a possible mitigation pathway to improve damage resistance of coated multilayer dielectric mirrors. In an effort to determine the optimal mitigation geometry which will not generate secondary damage precursors, the electric field distribution within the coating layers for a variety of mitigation shapes under different irradiation angles has been estimated using the finite difference time domain (FDTD) method. The coating consists of twenty-four alternating layers of hafnia and silica with a quarter-wave reflector design. A conical geometrical shape with different cone angles is investigated in the present study. Beam incident angles range from 0{sup o} to 60{sup o} at 5{sup o} increments. We find that light intensification (square of electric field, |E|{sup 2}) within the multilayers depends strongly on the beam incident direction and the cone angle. By comparing the field intensification for each cone angle under all angles of incidence, we find that a 30{sup o} conical pit generates the least field intensification within the multilayer film. Our results suggest that conical pits with shallow cone angles ({le} 30{sup o}) can be used as potential optimal mitigation structures.

  17. A 3-D elasticity theory based model for acoustic radiation from multilayered anisotropic plates.

    PubMed

    Shen, C; Xin, F X; Lu, T J

    2014-05-01

    A theoretical model built upon three-dimensional elasticity theory is developed to investigate the acoustic radiation from multilayered anisotropic plates subjected to a harmonic point force excitation. Fourier transform technique and stationary phase method are combined to predict the far-field radiated sound pressure of one-side water immersed plate. Compared to equivalent single-layer plate models, the present model based on elasticity theory can differentiate radiated sound pressure between dry-side and wet-side excited cases, as well as discrepancies induced by different layer sequences for multilayered anisotropic plates. These results highlight the superiority of the present theoretical model especially for handling multilayered anisotropic structures. PMID:24815294

  18. Modelling migration in multilayer systems by a finite difference method: the spherical symmetry case

    NASA Astrophysics Data System (ADS)

    Hojbotǎ, C. I.; Toşa, V.; Mercea, P. V.

    2013-08-01

    We present a numerical model based on finite differences to solve the problem of chemical impurity migration within a multilayer spherical system. Migration here means diffusion of chemical species in conditions of concentration partitioning at layer interfaces due to different solubilities of the migrant in different layers. We detail here the numerical model and discuss the results of its implementation. To validate the method we compare it with cases where an analytic solution exists. We also present an application of our model to a practical problem in which we compute the migration of caprolactam from the packaging multilayer foil into the food.

  19. Multilayer Model: A New Regional Ionospheric Model For Near Real-Time Applications

    NASA Astrophysics Data System (ADS)

    Magnet, N.; Weber, R.

    2012-12-01

    The ionosphere is part of the upper atmosphere which affects electromagnetic waves by its ionization. The resulting propagation delay is frequency dependent, so it can be determined with dual frequency measurements. In case of single frequency users ionospheric models are used to correct the measurements. At the Institute of Geodesy and Geophysics (Vienna University of Technology) a new ionospheric model, labeled Multilayer Model, is under development. It consists of nine horizontal equidistant electron layers within the height range of the F2 layer, where the maximum of the ionization can be found. The remaining ionospheric layers (e.g. the E-layers) are currently not considered. The electron content of each of the nine layers is obtained from a simple model with very few parameters, like the current maximum VTEC and weighting functions to account for the spherical distance between the coordinates of the electron maximum and the IPP-points of interest. All parameters are calculated with hourly time resolution from a combination of global (IGS-stations) and regional GNSS observation data. The Multilayer Model focuses on regional densification of global ionosphere models (e.g. IGS VTEC SH models) by means of a small and easy predictable set of parameters. The final ionospheric TEC grids provided by IGS (International GNSS Service) have a resolution of 2 hours x 5° Longitude x 2.5° Latitude. Daily files can be downloaded from the IGS web page (http://www.igs.org/). IRI (International Reference Ionosphere) is a joint project of the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI). An empirical standard model of the ionosphere is provided which is based on a worldwide network of ionosondes, incoherent scatter radars and other data sources. In this presentation the VTEC values calculated with the regional Multilayer Model are compared to the results of the IGS global TEC grids and IRI. This comparison covers days with low

  20. Empirical model development and validation with dynamic learning in the recurrent multilayer perception

    SciTech Connect

    Parlos, A.G.; Chong, K.T.; Atiya, A.F. . Dept. of Nuclear Engineering)

    1994-02-01

    A nonlinear multivariable empirical model is developed for a U-tube steam generator using the recurrent multilayer perceptron network as the underlying model structure. The recurrent multilayer perceptron is a dynamic neural network, very effective in the input-output modeling of complex process systems. A dynamic gradient descent learning algorithm is used to train the recurrent multilayer perceptron, resulting in an order of magnitude improvement in convergence speed over static learning algorithms. In developing the U-tube steam generator empirical model, the effects of actuator, process,and sensor noise on the training and testing sets are investigated. Learning and prediction both appear very effective, despite the presence of training and testing set noise, respectively. The recurrent multilayer perceptron appears to learn the deterministic part of a stochastic training set, and it predicts approximately a moving average response. Extensive model validation studies indicate that the empirical model can substantially generalize (extrapolate), though online learning becomes necessary for tracking transients significantly different than the ones included in the training set and slowly varying U-tube steam generator dynamics. In view of the satisfactory modeling accuracy and the associated short development time, neural networks based empirical models in some cases appear to provide a serious alternative to first principles models. Caution, however, must be exercised because extensive on-line validation of these models is still warranted.

  1. Hybrid Finite Element-Fast Spectral Domain Multilayer Boundary Integral Modeling of Doubly Periodic Structures

    SciTech Connect

    T.F. Eibert; J.L. Volakis; Y.E. Erdemli

    2002-03-03

    Hybrid finite element (FE)--boundary integral (BI) analysis of infinite periodic arrays is extended to include planar multilayered Green's functions. In this manner, a portion of the volumetric dielectric region can be modeled via the finite element method whereas uniform multilayered regions can be modeled using a multilayered Green's function. As such, thick uniform substrates can be modeled without loss of efficiency and accuracy. The multilayered Green's function is analytically computed in the spectral domain and the resulting BI matrix-vector products are evaluated via the fast spectral domain algorithm (FSDA). As a result, the computational cost of the matrix-vector products is kept at O(N). Furthermore, the number of Floquet modes in the expansion are kept very few by placing the BI surfaces within the computational unit cell. Examples of frequency selective surface (FSS) arrays are analyzed with this method to demonstrate the accuracy and capability of the approach. One example involves complicated multilayered substrates above and below an inhomogeneous filter element and the other is an optical ring-slot array on a substrate several hundred wavelengths in thickness. Comparisons with measurements are included.

  2. Application of the recurrent multilayer perceptron in modeling complex process dynamics

    SciTech Connect

    Parlos, A.G. . Dept. of Nuclear Engineering); Chong, K.T. . Dept. of Mechanical Engineering); Atiya, A.F. . Dept. of Computer Engineering)

    1994-03-01

    A nonlinear dynamic model is developed for a process system, namely a heat exchanger, using the recurrent multilayer perceptron network as the underlying model structure. The recurrent multilayer perceptron is a dynamic neural network, which appears effective in the input-output modeling of complex process systems. A dynamic gradient descent learning algorithm is used to train the recurrent multilayer perceptron, resulting in an order of magnitude improvement in convergence speed over a static learning algorithm used to train the same network. In developing the empirical process model the effects of actuator, process, and sensor noise on the training and testing sets are investigated. Learning and prediction both appear very effective, despite the presence of training and testing sets are investigated. Learning and prediction both appear very effective, despite the presence of training and testing set noise, respectively. The recurrent multilayer perceptron appears to learn the deterministic part of a stochastic training set, and it predicts approximately a moving average response of various testing sets. Extensive model validation studies with signals that are encountered in the operation of the process system modeled, that is steps and ramps, indicate that the empirical model can substantially generalize operational transients, including accurate prediction of process system instabilities not included in the training set. However, the accuracy of the model beyond these operational transients has not been investigated. Furthermore, on-line learning becomes necessary during some transients and for tracking slowly varying process dynamics.

  3. Multilayer Joint Gait-Pose Manifolds for Human Gait Motion Modeling.

    PubMed

    Ding, Meng; Fan, Guolian

    2015-11-01

    We present new multilayer joint gait-pose manifolds (multilayer JGPMs) for complex human gait motion modeling, where three latent variables are defined jointly in a low-dimensional manifold to represent a variety of body configurations. Specifically, the pose variable (along the pose manifold) denotes a specific stage in a walking cycle; the gait variable (along the gait manifold) represents different walking styles; and the linear scale variable characterizes the maximum stride in a walking cycle. We discuss two kinds of topological priors for coupling the pose and gait manifolds, i.e., cylindrical and toroidal, to examine their effectiveness and suitability for motion modeling. We resort to a topologically-constrained Gaussian process (GP) latent variable model to learn the multilayer JGPMs where two new techniques are introduced to facilitate model learning under limited training data. First is training data diversification that creates a set of simulated motion data with different strides. Second is the topology-aware local learning to speed up model learning by taking advantage of the local topological structure. The experimental results on the Carnegie Mellon University motion capture data demonstrate the advantages of our proposed multilayer models over several existing GP-based motion models in terms of the overall performance of human gait motion modeling.

  4. Modeling and characterization of multilayered d 15 mode piezoelectric energy harvesters in series and parallel connections

    NASA Astrophysics Data System (ADS)

    Zhu, Y. K.; Yu, Y. G.; Li, L.; Jiang, T.; Wang, X. Y.; Zheng, X. J.

    2016-07-01

    A Timoshenko beam model combined with piezoelectric constitutive equations and an electrical model was proposed to describe the energy harvesting performances of multilayered d 15 mode PZT-51 piezoelectric bimorphs in series and parallel connections. The effect of different clamped conditions was considered for non-piezoelectric and piezoelectric layers in the theoretical model. The frequency dependences of output peak voltage and power at different load resistances and excitation voltages were studied theoretically, and the results were verified by finite element modeling (FEM) simulation and experimental measurements. Results show that the theoretical model considering different clamped conditions for non-piezoelectric and piezoelectric layers could make a reliable prediction for the energy harvesting performances of multilayered d 15 mode piezoelectric bimorphs. The multilayered d 15 mode piezoelectric bimorph in a series connection exhibits a higher output peak voltage and power than that of a parallel connection at a load resistance of 1 MΩ. A criterion for choosing a series or parallel connection for a multilayered d 15 mode piezoelectric bimorph is dependent on the comparison of applied load resistance with the critical resistance of about 55 kΩ. The proposed model may provide some useful guidelines for the design and performance optimization of d 15 mode piezoelectric energy harvesters.

  5. [Polarization Modeling and Analysis of Light Scattering Properties of Multilayer Films on Slightly Rough Substrate].

    PubMed

    Gao, Hui; Gao, Jun; Wang, Ling-mei; Wang, Chi

    2016-03-01

    To satisfy the demand of multilayer films on polarization detection, polarized bidirectional reflectance distribution function of multilayer films on slightly rough substrate is established on the basis of first-order vector perturbation theory and polarization transfer matrix. Due to the function, light scattering polarization properties are studied under multi-factor impacts of two typical targets-monolayer anti-reflection film and multilayer high-reflection films. The result shows that for monolayer anti-reflection film, observing positions have a great influence on the degree of polarization, for the left of the peak increased and right decreased compared with the substrate target. Film target and bare substrate can be distinguished by the degree of polarization in different observation angles. For multilayer high-reflection films, the degree of polarization is significantly associated with the number and optical thickness of layers at different wavelengths of incident light and scattering angles. With the increase of the layer number, the degree of polarization near the mirror reflection area decreases. It reveals that the calculated results coincide with the experimental data, which validates the correctness and rationality of the model. This paper provides a theoretical method for polarization detection of multilayer films target and reflection stealth technology. PMID:27400497

  6. [Polarization Modeling and Analysis of Light Scattering Properties of Multilayer Films on Slightly Rough Substrate].

    PubMed

    Gao, Hui; Gao, Jun; Wang, Ling-mei; Wang, Chi

    2016-03-01

    To satisfy the demand of multilayer films on polarization detection, polarized bidirectional reflectance distribution function of multilayer films on slightly rough substrate is established on the basis of first-order vector perturbation theory and polarization transfer matrix. Due to the function, light scattering polarization properties are studied under multi-factor impacts of two typical targets-monolayer anti-reflection film and multilayer high-reflection films. The result shows that for monolayer anti-reflection film, observing positions have a great influence on the degree of polarization, for the left of the peak increased and right decreased compared with the substrate target. Film target and bare substrate can be distinguished by the degree of polarization in different observation angles. For multilayer high-reflection films, the degree of polarization is significantly associated with the number and optical thickness of layers at different wavelengths of incident light and scattering angles. With the increase of the layer number, the degree of polarization near the mirror reflection area decreases. It reveals that the calculated results coincide with the experimental data, which validates the correctness and rationality of the model. This paper provides a theoretical method for polarization detection of multilayer films target and reflection stealth technology.

  7. The research Of Multilayer Thermal Insulation With Mechanical Properties Based On Model Analysis Test

    NASA Astrophysics Data System (ADS)

    Lianhua, Yin

    The heat shield of aircraft is made of the major thrusts structure with multilayer thermal insulation part. For protecting against thermo-radiation from larger thrusting force engine,the heat shield is installed around this engine nearby.The multilayer thermal insulation part with multilayer radiation/reflection structure is made of reflection layer and interval layer.At vacuum condition,these materials is higher heat insulation capability than other material,is applied for lots of pats on aircraft extensively.But because of these material is made of metal and nonmetal,it is impossible to receive it's mechanical properties of materials from mechanical tests.These paper describes a new measure of mechanical properties of materials in the heat shield based on model analysis test.At the requirement for the first order lateral frequency,these measure provide for the FEM analysis foundation on the optimization structure of the heat shield.

  8. Mobile agent and multilayer integrated distributed intrusion detection model for clustering ad hoc networks

    NASA Astrophysics Data System (ADS)

    Feng, Jianxin; Wang, Guangxing

    2004-04-01

    Ad hoc networks do not depend on any predefined infrastructure or centralized administration to operate. Their security characters require more complex security preventions. As the second line of defense, Intrusion detection is the necessary means of getting the high survivability. In this paper the security characters of ad hoc networks and the related contents of intrusion detection are discussed. Mobile Agent and Multi-layer Integrated Distributed Intrusion Detection Model (MAMIDIDM) and a heuristic global detection algorithm are proposed tentatively by combining the mobile agent technology with the multi-layer conception. This heuristic global detection algorithm combines the mobile agent detection engine with the multi-layer detection engines and analyzes the results obtained by the corresponding detection engines. MAMIDIDM has the better flexibility and extensibility, can execute the intrusion detection in clustering ad hoc networks effectively.

  9. Modelling self-assembling of colloid particles in multilayered structures

    NASA Astrophysics Data System (ADS)

    Adamczyk, Zbigniew; Weroński, Paweł; Barbasz, Jakub; Kolasińska, Marta

    2007-04-01

    Simulations of particle multilayer build-up in the layer by layer (LbL) self-assembling processes have been performed according to the generalized random sequential adsorption (RSA) scheme. The first (precursor) layer having an arbitrary coverage of adsorption centers was generated using the standard RSA scheme pertinent to homogeneous surface. Formation of the consecutive layers (up to 20) was simulated by assuming short-range interaction potentials for two kinds of particles of equal size. Interaction of two particles of different kind resulted in irreversible and localized adsorption upon their contact, whereas particles of the same kind were assumed to interact via the hard potential (no adsorption possible). Using this algorithm theoretical simulations were performed aimed at determining the particle volume fraction as a function of the distance from the interface, as well as the multilayer film roughness and thickness as a function of the number of layers. The simulations revealed that particle concentration distribution in the film was more uniform for low precursor layer density than for higher density, where well-defined layers of closely packed particles appeared. On the other hand, the roughness of the film was the lowest at the highest precursor layer density. It was also predicted theoretically that for low precursor layer density the film thickness increased with the number of layers in a non-linear way. However, for high precursor layer density, the film thickness increased linearly with the number of layers and the average layer thickness was equal to 1.58 of the particle radius, which is close to the closely packed hexagonal layer thickness equal to 1.73. It was concluded by analysing the existing data for colloid particles and polyelectrolytes that the theoretical results can be effectively exploited for interpretation of the LbL processes involving colloid particles and molecular species like polymers or proteins.

  10. Snow modeling within a multi-layer soil-vegetation-atmosphere model

    NASA Astrophysics Data System (ADS)

    McGowan, L. E.; Paw U, K. T.; Pyles, D. R.

    2014-12-01

    Estimates of snow depth, extent, and melt in the Sierra Nevada Mountain Range are critical to estimating the amount of water that will be available for crops during the growing season within California's Central Valley. Numerical simulations utilizing a fourth order turbulent closure transport scheme in a multi-layer soil-vegetation-atmosphere model, Advanced Canopy-Atmosphere-Soil algorithm (ACASA), were used to explore snow model improvements in the physics-based parameterization for the Sierra Nevada Range. A set of alterations were made separately to the existing snowpack model within ACASA focusing on improvements to snow cover simulations on complex terrain slopes and over varying canopy cover. Three winter seasons were simulated; a climatological average, dry, and wet winter. The simulated output from the models are compared to observations to determine which model alterations made the largest improvements to snow simulations.

  11. Nonlinear finite element modeling of dental composite polymerization behavior

    NASA Astrophysics Data System (ADS)

    Laughlin, Gayle A.

    2003-07-01

    Polymerization shrinkage has been one of the primary shortcomings preventing the use of resin composites as a universal dental restorative material. This shrinkage of the bonded restoration causes residual stresses in the composite which in turn are transferred to the adhesive interface. The deleterious effects of this stress environment include compromise of the interface itself and the decrease in the mechanical properties of the cured composite. Novel materials which claim to produce less shrinkage have been presented as a new class of restorative materials that could reduce the effects of this problem. One difficulty in assessing the actual in vivo benefits of these new materials is the fact that there is currently no direct way to measure the stress environment at the composite/tooth clinical interface. Computer modeling using finite element analysis (FEA) could provide helpful information regarding the clinical stress performance of dental composites. The purpose of this study was to develop a model that accurately simulates the nonlinear polymerization behavior of light-cured dental composites using a commercial FEA program, which could be accessible for future research. Two phases were needed to accomplish this purpose. First, a data collection phase included volumetric shrinkage, shrinkage stress, tooth analog strain, and dynamic mechanical analysis experiments. Three composites, a standard methacrylate(Z250) and two experimental low stress epoxy-based composites (oxirane and silorane), were tested. The experimental results revealed an intriguing range of polymerization behavior exhibited by the three composites, indicating that the development of a low stress composite is possible. The information gathered from this phase supplied the necessary material input for the computer modeling, and provided empirical validation data for the model solutions. In the second modeling phase, an FEA approach based on a elastic/viscoplastic material model was used to

  12. Analytical Modeling for the Bending Resonant Frequency of Multilayered Microresonators with Variable Cross-Section

    PubMed Central

    Herrera-May, Agustín L.; Aguilera-Cortés, Luz A.; Plascencia-Mora, Hector; Rodríguez-Morales, Ángel L.; Lu, Jian

    2011-01-01

    Multilayered microresonators commonly use sensitive coating or piezoelectric layers for detection of mass and gas. Most of these microresonators have a variable cross-section that complicates the prediction of their fundamental resonant frequency (generally of the bending mode) through conventional analytical models. In this paper, we present an analytical model to estimate the first resonant frequency and deflection curve of single-clamped multilayered microresonators with variable cross-section. The analytical model is obtained using the Rayleigh and Macaulay methods, as well as the Euler-Bernoulli beam theory. Our model is applied to two multilayered microresonators with piezoelectric excitation reported in the literature. Both microresonators are composed by layers of seven different materials. The results of our analytical model agree very well with those obtained from finite element models (FEMs) and experimental data. Our analytical model can be used to determine the suitable dimensions of the microresonator’s layers in order to obtain a microresonator that operates at a resonant frequency necessary for a particular application. PMID:22164071

  13. Modeling Multilayer Antireflection Coating Systems Based on LiNbO3

    NASA Astrophysics Data System (ADS)

    Karaomerlioglu, Filiz

    Antireflection coatings have had the greatest impact on optics. The antireflection (AR) coating is the critically important technology in obtaining high performance of optoelectronic devices. In the present paper, characteristics of the ferroelectric based multilayered antireflection coating systems are investigated. Multilayer antireflection coatings consisting of insulator thin films have been modeled in the region between the 400 nm and 800 nm visible bands of electromagnetic spectrum to reduce reflectance from ferroelectric based substrate. In this type of antireflection coating we can regulate the optical properties of a system by external electric (or thermal field) and design a broadband low reflection coating system for optoelectronic devices. In order to design and simulate the normal incidence wideband visible multilayer AR coatings, we have developed a Fortran software program based upon Fresnell equations. Different types of layers which are two-different materials like ZnSe and ZrO2 for even-folded multilayer (two-, four-, six-, eight-, ten-, and twelve-layer) antireflection coatings are used. Ferroelectric material, LiNbO3 is used as the substrate. The optical thicknesses of each layer are equal to a quarter-wave thick at a certain wavelength.

  14. Modelling single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources.

    PubMed

    Loch, R A; Sobierajski, R; Louis, E; Bosgra, J; Bijkerk, F

    2012-12-17

    The single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources are theoretically investigated, using a model developed on the basis of experimental data obtained at the FLASH and LCLS free electron lasers. We compare the radiation hardness of commonly used multilayer optics and propose new material combinations selected for a high damage threshold. Our study demonstrates that the damage thresholds of multilayer optics can vary over a large range of incidence fluences and can be as high as several hundreds of mJ/cm(2). This strongly suggests that multilayer mirrors are serious candidates for damage resistant optics. Especially, multilayer optics based on Li(2)O spacers are very promising for use in current and future short-wavelength radiation sources.

  15. A General Reliability Model for Ni-BaTiO3-Based Multilayer Ceramic Capacitors

    NASA Technical Reports Server (NTRS)

    Liu, Donhang

    2014-01-01

    The evaluation of multilayer ceramic capacitors (MLCCs) with Ni electrode and BaTiO3 dielectric material for potential space project applications requires an in-depth understanding of their reliability. A general reliability model for Ni-BaTiO3 MLCC is developed and discussed. The model consists of three parts: a statistical distribution; an acceleration function that describes how a capacitor's reliability life responds to the external stresses, and an empirical function that defines contribution of the structural and constructional characteristics of a multilayer capacitor device, such as the number of dielectric layers N, dielectric thickness d, average grain size, and capacitor chip size A. Application examples are also discussed based on the proposed reliability model for Ni-BaTiO3 MLCCs.

  16. A General Reliability Model for Ni-BaTiO3-Based Multilayer Ceramic Capacitors

    NASA Technical Reports Server (NTRS)

    Liu, Donhang

    2014-01-01

    The evaluation for potential space project applications of multilayer ceramic capacitors (MLCCs) with Ni electrode and BaTiO3 dielectric material requires an in-depth understanding of the MLCCs reliability. A general reliability model for Ni-BaTiO3 MLCCs is developed and discussed in this paper. The model consists of three parts: a statistical distribution; an acceleration function that describes how a capacitors reliability life responds to external stresses; and an empirical function that defines the contribution of the structural and constructional characteristics of a multilayer capacitor device, such as the number of dielectric layers N, dielectric thickness d, average grain size r, and capacitor chip size A. Application examples are also discussed based on the proposed reliability model for Ni-BaTiO3 MLCCs.

  17. Continuum damage modeling and simulation of hierarchical dental enamel

    NASA Astrophysics Data System (ADS)

    Ma, Songyun; Scheider, Ingo; Bargmann, Swantje

    2016-05-01

    Dental enamel exhibits high fracture toughness and stiffness due to a complex hierarchical and graded microstructure, optimally organized from nano- to macro-scale. In this study, a 3D representative volume element (RVE) model is adopted to study the deformation and damage behavior of the fibrous microstructure. A continuum damage mechanics model coupled to hyperelasticity is developed for modeling the initiation and evolution of damage in the mineral fibers as well as protein matrix. Moreover, debonding of the interface between mineral fiber and protein is captured by employing a cohesive zone model. The dependence of the failure mechanism on the aspect ratio of the mineral fibers is investigated. In addition, the effect of the interface strength on the damage behavior is studied with respect to geometric features of enamel. Further, the effect of an initial flaw on the overall mechanical properties is analyzed to understand the superior damage tolerance of dental enamel. The simulation results are validated by comparison to experimental data from micro-cantilever beam testing at two hierarchical levels. The transition of the failure mechanism at different hierarchical levels is also well reproduced in the simulations.

  18. Digital modeling technology for full dental crown tooth preparation.

    PubMed

    Dai, Ning; Zhong, Yicheng; Liu, Hao; Yuan, Fusong; Sun, Yuchun

    2016-04-01

    A dental defect is one of the most common oral diseases, and it often requires a full crown restoration. In this clinical operation, the dentist must manually prepare the affected tooth for the full crown so that it has a convergence angle between 4° and 10°, no undercuts, and uniform and even shoulder widths and depths using a high speed diamond bur in the patient׳s mouth within one hour, which is a difficult task that requires visual-manual operation. The quality of the tooth preparation has an important effect on the success rate of the subsequent prosthodontic treatment. This study involved research into digital modeling technology for full dental crown tooth preparation. First, the margin line of the tooth preparation was designed using a semi-automatic interactive process. Second, the inserting direction was automatically computed. Then, the characteristic parameters and the constraints on the tooth preparation were defined for the model. Next, the shoulder and axial surface of the tooth preparation were formed using parametric modeling. Finally, the implicit surface of a radial basis function was used to construct the tooth preparation׳s occlusal surface. The experimental results verified that the method of digital modeling for full crown preparation proposed in this study can quickly and accurately implement personalized designs of various parameters, such as the shoulder width and the convergence angle; it provides a digital design tool for full crown preparation.

  19. Digital modeling technology for full dental crown tooth preparation.

    PubMed

    Dai, Ning; Zhong, Yicheng; Liu, Hao; Yuan, Fusong; Sun, Yuchun

    2016-04-01

    A dental defect is one of the most common oral diseases, and it often requires a full crown restoration. In this clinical operation, the dentist must manually prepare the affected tooth for the full crown so that it has a convergence angle between 4° and 10°, no undercuts, and uniform and even shoulder widths and depths using a high speed diamond bur in the patient׳s mouth within one hour, which is a difficult task that requires visual-manual operation. The quality of the tooth preparation has an important effect on the success rate of the subsequent prosthodontic treatment. This study involved research into digital modeling technology for full dental crown tooth preparation. First, the margin line of the tooth preparation was designed using a semi-automatic interactive process. Second, the inserting direction was automatically computed. Then, the characteristic parameters and the constraints on the tooth preparation were defined for the model. Next, the shoulder and axial surface of the tooth preparation were formed using parametric modeling. Finally, the implicit surface of a radial basis function was used to construct the tooth preparation׳s occlusal surface. The experimental results verified that the method of digital modeling for full crown preparation proposed in this study can quickly and accurately implement personalized designs of various parameters, such as the shoulder width and the convergence angle; it provides a digital design tool for full crown preparation. PMID:26945598

  20. A mathematical model for the progression of dental caries.

    PubMed

    Fabregas, L Rene I; Rubinstein, J

    2014-12-01

    A model for the progression of dental caries is derived. The analysis starts at the microscopic reaction and diffusion process. The local equations are averaged to derive a set of macroscopic equations. The global system includes features such as anisotropic diffusion and local changes in the geometry due to the melting of the enamel. The equations are then solved numerically. The simulations highlight the effect of anisotropy. In addition, we draw conclusions on the progression rate of caries, and discuss them in light of a number of experiments. PMID:23803287

  1. Modeling and sensitivity analysis of mass transfer in active multilayer polymeric film for food applications

    SciTech Connect

    Bedane, T.; Di Maio, L.; Scarfato, P.; Incarnato, L. Marra, F.

    2015-12-17

    The barrier performance of multilayer polymeric films for food applications has been significantly improved by incorporating oxygen scavenging materials. The scavenging activity depends on parameters such as diffusion coefficient, solubility, concentration of scavenger loaded and the number of available reactive sites. These parameters influence the barrier performance of the film in different ways. Virtualization of the process is useful to characterize, design and optimize the barrier performance based on physical configuration of the films. Also, the knowledge of values of parameters is important to predict the performances. Inverse modeling and sensitivity analysis are sole way to find reasonable values of poorly defined, unmeasured parameters and to analyze the most influencing parameters. Thus, the objective of this work was to develop a model to predict barrier properties of multilayer film incorporated with reactive layers and to analyze and characterize their performances. Polymeric film based on three layers of Polyethylene terephthalate (PET), with a core reactive layer, at different thickness configurations was considered in the model. A one dimensional diffusion equation with reaction was solved numerically to predict the concentration of oxygen diffused into the polymer taking into account the reactive ability of the core layer. The model was solved using commercial software for different film layer configurations and sensitivity analysis based on inverse modeling was carried out to understand the effect of physical parameters. The results have shown that the use of sensitivity analysis can provide physical understanding of the parameters which highly affect the gas permeation into the film. Solubility and the number of available reactive sites were the factors mainly influencing the barrier performance of three layered polymeric film. Multilayer films slightly modified the steady transport properties in comparison to net PET, giving a small reduction

  2. Modeling and sensitivity analysis of mass transfer in active multilayer polymeric film for food applications

    NASA Astrophysics Data System (ADS)

    Bedane, T.; Di Maio, L.; Scarfato, P.; Incarnato, L.; Marra, F.

    2015-12-01

    The barrier performance of multilayer polymeric films for food applications has been significantly improved by incorporating oxygen scavenging materials. The scavenging activity depends on parameters such as diffusion coefficient, solubility, concentration of scavenger loaded and the number of available reactive sites. These parameters influence the barrier performance of the film in different ways. Virtualization of the process is useful to characterize, design and optimize the barrier performance based on physical configuration of the films. Also, the knowledge of values of parameters is important to predict the performances. Inverse modeling and sensitivity analysis are sole way to find reasonable values of poorly defined, unmeasured parameters and to analyze the most influencing parameters. Thus, the objective of this work was to develop a model to predict barrier properties of multilayer film incorporated with reactive layers and to analyze and characterize their performances. Polymeric film based on three layers of Polyethylene terephthalate (PET), with a core reactive layer, at different thickness configurations was considered in the model. A one dimensional diffusion equation with reaction was solved numerically to predict the concentration of oxygen diffused into the polymer taking into account the reactive ability of the core layer. The model was solved using commercial software for different film layer configurations and sensitivity analysis based on inverse modeling was carried out to understand the effect of physical parameters. The results have shown that the use of sensitivity analysis can provide physical understanding of the parameters which highly affect the gas permeation into the film. Solubility and the number of available reactive sites were the factors mainly influencing the barrier performance of three layered polymeric film. Multilayer films slightly modified the steady transport properties in comparison to net PET, giving a small reduction

  3. Numerical simulation of multi-layer graphene structures based on quantum-chemical model

    NASA Astrophysics Data System (ADS)

    Kasper, Y.; Tuchin, A.; Bokova, A.; Bityutskaya, L.

    2016-08-01

    The electronic structure of the multi-layer graphene has been studied using the density functional theory (DFT). The dependence of the average interlayer distance on the number of layers (n = 2 ÷ 6) has been determined. The analysis of the charge redistribution and the electron density of the bi- and three-layer graphene under the external pressure up to 50 GPa has been performed. The model of the interlayer conductivity of compressed multigraphene was offered

  4. Modeling of the Thermal Protection of a Multilayer Material Under Fire Conditions

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, V. A.; Yakimov, A. S.

    2016-05-01

    On the basis of the theoretical and known experimental results, a refined mathematical model of the thermochemical destruction of a multilayer heat-shield coating has been developed. Account of the flow across the body has made it possible to forecast more exactly the state of the protected structure under fire conditions. A comparison between the results of numerical calculations and the known data has been made.

  5. Multi-layer composite mechanical modeling for the inhomogeneous biofilm mechanical behavior.

    PubMed

    Wang, Xiaoling; Han, Jingshi; Li, Kui; Wang, Guoqing; Hao, Mudong

    2016-08-01

    Experiments showed that bacterial biofilms are heterogeneous, for example, the density, the diffusion coefficient, and mechanical properties of the biofilm are different along the biofilm thickness. In this paper, we establish a multi-layer composite model to describe the biofilm mechanical inhomogeneity based on unified multiple-component cellular automaton (UMCCA) model. By using our model, we develop finite element simulation procedure for biofilm tension experiment. The failure limit and biofilm extension displacement obtained from our model agree well with experimental measurements. This method provides an alternative theory to study the mechanical inhomogeneity in biological materials. PMID:27122202

  6. Evaluation of digital dental models obtained from dental cone-beam computed tomography scan of alginate impressions

    PubMed Central

    Jiang, Tingting; Lee, Sang-Mi; Hou, Yanan; Chang, Xin

    2016-01-01

    Objective To investigate the dimensional accuracy of digital dental models obtained from the dental cone-beam computed tomography (CBCT) scan of alginate impressions according to the time elapse when the impressions are stored under ambient conditions. Methods Alginate impressions were obtained from 20 adults using 3 different alginate materials, 2 traditional alginate materials (Alginoplast and Cavex Impressional) and 1 extended-pour alginate material (Cavex ColorChange). The impressions were stored under ambient conditions, and scanned by CBCT immediately after the impressions were taken, and then at 1 hour intervals for 6 hours. After reconstructing three-dimensional digital dental models, the models were measured and the data were analyzed to determine dimensional changes according to the elapsed time. The changes within the measurement error were regarded as clinically acceptable in this study. Results All measurements showed a decreasing tendency with an increase in the elapsed time after the impressions. Although the extended-pour alginate exhibited a less decreasing tendency than the other 2 materials, there were no statistically significant differences between the materials. Changes above the measurement error occurred between the time points of 3 and 4 hours after the impressions. Conclusions The results of this study indicate that digital dental models can be obtained simply from a CBCT scan of alginate impressions without sending them to a remote laboratory. However, when the impressions are not stored under special conditions, they should be scanned immediately, or at least within 2 to 3 hours after the impressions are taken. PMID:27226958

  7. Material parameter computation for multi-layered vocal fold models.

    PubMed

    Schmidt, Bastian; Stingl, Michael; Leugering, Günter; Berry, David A; Döllinger, Michael

    2011-04-01

    Today, the prevention and treatment of voice disorders is an ever-increasing health concern. Since many occupations rely on verbal communication, vocal health is necessary just to maintain one's livelihood. Commonly applied models to study vocal fold vibrations and air flow distributions are self sustained physical models of the larynx composed of artificial silicone vocal folds. Choosing appropriate mechanical parameters for these vocal fold models while considering simplifications due to manufacturing restrictions is difficult but crucial for achieving realistic behavior. In the present work, a combination of experimental and numerical approaches to compute material parameters for synthetic vocal fold models is presented. The material parameters are derived from deformation behaviors of excised human larynges. The resulting deformations are used as reference displacements for a tracking functional to be optimized. Material optimization was applied to three-dimensional vocal fold models based on isotropic and transverse-isotropic material laws, considering both a layered model with homogeneous material properties on each layer and an inhomogeneous model. The best results exhibited a transversal-isotropic inhomogeneous (i.e., not producible) model. For the homogeneous model (three layers), the transversal-isotropic material parameters were also computed for each layer yielding deformations similar to the measured human vocal fold deformations.

  8. Finite element analysis and equivalent parallel-resistance model for conductive multilayer thin films

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Yi; Juang, Jia-Yang

    2016-07-01

    The standard collinear four-point probe method is an indispensable tool and has been extensively used for characterizing conductive thin films with homogeneous and isotropic electrical properties. In this paper, we conduct three-dimensional (3D) finite element simulations on conductive multilayer films to study the relationship between the reading of the four-point probe and the conductivity of the individual layers. We find that a multilayer film may be modeled as a simple equivalent circuit with multiple resistances, connected in parallel for a wide range of resistivity and thickness ratios, as long as its total thickness is smaller than approximately half of the probe spacing. As a result, we may determine the resistivity of each layer sequentially by applying the four-point probe, with the original correction factor π/ln(2), after deposition of each layer.

  9. New models of dental education and curricular change: their potential impact on dental education.

    PubMed

    Pyle, Marsha A

    2012-01-01

    The collective body of work over the last seventy-five years in the Journal of Dental Education has chronicled the ongoing critical issues and trends in dental education. The evolution of the curriculum has run in fits and starts across the twentieth century and into the twenty-first. Today, there has been a resurgence in the introspective work of the profession to examine what is taught, how it is taught, in what sequence it is taught, and the context relating dental education to other health professions and the global reach of the educational and professional environment. In the context of contemporary times, individual as well as organizational leadership has refocused the educational environment from teaching to learning. This article discusses the types of curricular changes documented in the Journal of Dental Education.

  10. New models of dental education and curricular change: their potential impact on dental education.

    PubMed

    Pyle, Marsha A

    2012-01-01

    The collective body of work over the last seventy-five years in the Journal of Dental Education has chronicled the ongoing critical issues and trends in dental education. The evolution of the curriculum has run in fits and starts across the twentieth century and into the twenty-first. Today, there has been a resurgence in the introspective work of the profession to examine what is taught, how it is taught, in what sequence it is taught, and the context relating dental education to other health professions and the global reach of the educational and professional environment. In the context of contemporary times, individual as well as organizational leadership has refocused the educational environment from teaching to learning. This article discusses the types of curricular changes documented in the Journal of Dental Education. PMID:22262553

  11. Modeling of Multi-Layered Protection Systems for Chloride Penetration in Concrete Bridge Decks

    NASA Astrophysics Data System (ADS)

    Harajli, Ali A.

    Modeling of Multi-Layered Protection Systems for Chloride Penetration in Concrete Bridge Decks. This paper covers the development of a new methodology for predicting the chloride concentration and corrosion initiation times for a multi-layer protection overlay system. The first topic will be presenting an innovative method to predict the chloride concentrations using different diffusion coefficients for each protective layer. The new method covers the cases where the applied surface chloride concentrations are either a constant or linear functions with time. The second topic will implement the results from field data about the chloride variations due to the presence of applied topical layers for comparison with the theoretical models. This section will also apply damage factors that are time-dependent to simulate external factors such as traffic loading or vibrations. The third topic will investigate the sensitivity of the single and multi-layer systems due to diffusivity parameter changes. The fourth topic will analyze the random variation of the diffusivity values to predict the mean and standard deviation of chloride concentrations. The diffusivity values are selected from published values by NIST and are based on certain water cement (w/c) ratios.

  12. Ferromagnetic resonance of an heterogeneous multilayer system with interlayer exchange coupling: an accessible model

    NASA Astrophysics Data System (ADS)

    Franco, A. F.; Landeros, P.

    2016-09-01

    We present a general model for the coupled magnetic resonances of an exchange interacting multilayer system, which can be implemented without complex analytical calculations or numerical simulations. The model allows one to study the spin wave modes of a multilayer structure with any number of layers, accounting for individual uniaxial and cubic anisotropies, and (static and dynamic) demagnetizing and external fields as well, assuming that only the interlayer exchange coupling mechanism is relevant between such magnetic layers. This scheme is applied to recent measurements of a NiFe/CoFe bilayer, and to studying the influence of the strength of ferromagnetic and antiferromagnetic exchange interactions and the applied field orientation on the spin wave modes and intensities of the ferromagnetic resonance response. We find that the acoustic oscillation mode tends to stabilize in frequency if the magnetizations of the layers are parallel to each other, while the optical mode stabilizes when the magnetizations are antiparallel. Furthermore, we find that each oscillation mode is governed by either the NiFe or the CoFe. The modes swap the governing layer as the perpendicular field increases, inducing a gap between their frequencies, which appears to be proportional to the exchange coupling. Finally, we find that the field linewidth of the bilayer due to Gilbert damping has a dependence on the frequency very similar to the linear dependence of the linewidth in single layers. The theoretical scheme presented here can be further used to explore magnetization dynamics in different multilayer architectures—such as exchange springs, structures with perpendicular magnetic anisotropy, and complex compositions of layer stacks—and can be useful as a basis to study multilayers with chiral and dipolar interactions.

  13. Frequency-dependent dielectric response model for polyimide-poly(vinilydenefluoride) multilayered dielectrics

    NASA Astrophysics Data System (ADS)

    Di Lillo, Luigi; Bergamini, Andrea; Albino Carnelli, Dario; Ermanni, Paolo

    2012-07-01

    A physical model for the frequency-dependent dielectric response of multilayered structures is reported. Two frequency regimes defined by the relative permittivities and volume resistivities of the layers have been analytically identified and experimentally investigated on a structure consisting of polyimide and poly(vinilydenefluoride) layers. The relative permittivity follows an effective medium model at high frequency while showing a dependence on the volume resistivity at low frequency. In this regime, relative permittivities exceeding those expected from effective medium model are recorded. These findings provide insights into inhomogeneous dielectrics behavior for the development of high energy density dielectric films.

  14. An in vitro model of human dental pulp repair.

    PubMed

    Magloire, H; Joffre, A; Bleicher, F

    1996-12-01

    Pulp tissue responds to dentin injury by laying down reactionary dentin secreted by existing odontoblasts or reparative dentin elaborated by odontoblast-like cells that differentiated from precursor cells in the absence of inner dental epithelium and basement membrane. Furthermore, growth factors or active dentin matrix components are fundamental signals involved in odontoblast differentiation. In vitro, dental pulp cells cultured under various conditions are able to express typical markers of differentiation, but no culture system can re-create pulp response to dentin drilling. This paper reports the behavior of thick slices from human teeth drilled immediately after extraction and cultured from 3 days to 1 month. Results show that the damaged pulp beneath the cavity is able to develop, in vitro, some typical aspects correlated to tissue healing, evidenced by cell proliferation (BrdU-positive cells), neovascularization (positive with antitype-IV collagen antibodies), and the presence of functional (3H proline-positive) cuboidal cells close to the injured area. After 30 days of culture, elongated spindle-shaped cells can be seen aligned along the edges of the relevant dentin walls, whereas sound functional odontoblasts are well-preserved beneath healthy areas. This tissue recovery leads us to believe that such a culture model will be a useful system for testing factors regulating pulp repair.

  15. Experimentally verified model of viscoelastic behavior of multilayer unimorph dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Kadooka, Kevin; Imamura, Hiroya; Taya, Minoru

    2016-10-01

    This work presents a linear viscoelastic model to describe the time-dependent actuation behavior of multilayer unimorph dielectric elastomer actuators (MUDEA), with experimental validation by actuators produced by a robotic dispenser system. MUDEA are a type of soft actuator which can produce large bending deformation without prestretch typically required by dielectric elastomer actuators. Current analytical and finite element models of MUDEA do not consider material viscoelasticity and cannot predict the change over time of performance metrics such as tip displacement and blocking force. The linear viscoelastic model presented in this work is based on a linear elastic model for the MUDEA extended to account for viscous effects by the elastic-viscoelastic correspondence principle. The model is easily implemented because it is based on explicit expressions which can be evaluated numerically by any computer algebra system. The model was used to predict the tip displacement and blocking force of MUDEAs consisting of two, four, six, eight, and ten layers of dielectric elastomer material. The model predictions agreed well with experimental data obtained from MUDEA produced by a robotic dispenser system, which was capable of producing multilayered structures of thin layers of dielectric elastomer and carbon nanotube based electrode material.

  16. Multi-layered coarse grid modelling in 2D urban flood simulations

    NASA Astrophysics Data System (ADS)

    Chen, Albert S.; Evans, Barry; Djordjević, Slobodan; Savić, Dragan A.

    2012-11-01

    SummaryRegular grids are commonly used in 2D flood modelling due to wide availability of terrain models and low pre-processing required for input preparation. Despite advances in both computing software and hardware, high resolution flood modelling remains computationally demanding when applied to a large study area when the available time and resources are limited. Traditional grid coarsening approach may reduce not only the computing demands, but also the accuracy of results due to the loss of detailed information. To keep key features that affect flow propagation within coarse grid, the approach proposed and tested in this paper adopts multiple layers in flood modelling to reflect individual flow paths separated by buildings within a coarse grid cell. The cell in each layer has its own parameters (elevation, roughness, building coverage ratio, and conveyance reduction factors) to describe itself and the conditions at boundaries with neighbourhood cells. Results of tests on the synthetic case study and the real world urban area show that the proposed multi-layered approach greatly improves the accuracy of coarse grid modelling with an insignificant additional computing cost. The proposed approach has been tested in conjunction with the UIM model by taking the high resolution results as the benchmark. The implementation of the proposed multi-layered methodology to any regular grid based 2D model would be straightforward.

  17. Numerical models for the prediction of failure for multilayer fusion Al-alloy sheets

    SciTech Connect

    Gorji, Maysam; Berisha, Bekim; Hora, Pavel; Timm, Jürgen

    2013-12-16

    Initiation and propagation of cracks in monolithic and multi-layer aluminum alloys, called “Fusion”, is investigated. 2D plane strain finite element simulations are performed to model deformation due to bending and to predict failure. For this purpose, fracture strains are measured based on microscopic pictures of Nakajima specimens. In addition to, micro-structure of materials is taken into account by introducing a random grain distribution over the sheet thickness as well as a random distribution of the measured yield curve. It is shown that the performed experiments and the introduced FE-Model are appropriate methods to highlight the advantages of the Fusion material, especially for bending processes.

  18. Arcjet Testing and Thermal Model Development for Multilayer Felt Reusable Surface Insulation

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Scott, Carl Douglas; Papa, Steven V.

    2012-01-01

    Felt Reusable Surface Insulation was used extensively on leeward external surfaces of the Shuttle Orbiter, where the material is reusable for temperatures up to 670 K. For application on leeward surfaces of the Orion Multi-Purpose Crew Vehicle, where predicted temperatures reach 1620 K, the material functions as a pyrolyzing conformal ablator. An arcjet test series was conducted to assess the performance of multilayer Felt Reusable Surface Insulation at high temperatures, and a thermal-response, pyrolysis, and ablation model was developed. Model predictions compare favorably with the arcjet test data

  19. Mass Conservation in Modeling Moisture Diffusion in Multi-Layer Carbon Composite Structures

    NASA Technical Reports Server (NTRS)

    Nurge, Mark A.; Youngquist, Robert C.; Starr, Stanley O.

    2009-01-01

    Moisture diffusion in multi-layer carbon composite structures is difficult to model using finite difference methods due to the discontinuity in concentrations between adjacent layers of differing materials. Applying a mass conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite epoxy composite sandwich coupon with a Rohacell foam core.

  20. Continuum damage model for ferroelectric materials and its application to multilayer actuators

    NASA Astrophysics Data System (ADS)

    Gellmann, Roman; Ricoeur, Andreas

    2016-05-01

    In this paper a micromechanical continuum damage model for ferroelectric materials is presented. As a constitutive law it is implemented into a finite element (FE) code. The model is based on micromechanical considerations of domain switching and its interaction with microcrack growth and coalescence. A FE analysis of a multilayer actuator is performed, showing the initiation of damage zones at the electrode tips during the poling process. Further, the influence of mechanical pre-stressing on damage evolution and actuating properties is investigated. The results provided in this work give useful information on the damage of advanced piezoelectric devices and their optimization.

  1. FPGA Implementation of Multilayer Perceptron for Modeling of Photovoltaic panel

    SciTech Connect

    Mekki, H.; Belhout, K.; Mellit, A.; Salhi, H.

    2008-06-12

    The Number of electronic applications using artificial neural network-based solutions has increased considerably in the last few years. However, their applications in photovoltaic systems are very limited. This paper introduces the preliminary result of the modeling and simulation of photovoltaic panel based on neural network and VHDL-language. In fact, an experimental database of meteorological data (irradiation, temperature) and output electrical generation signals of the PV-panel (current and voltage) has been used in this study. The inputs of the ANN-PV-panel are the daily total irradiation and mean average temperature while the outputs are the current and voltage generated from the panel. Firstly, a dataset of 4x364 have been used for training the network. Subsequently, the neural network (MLP) corresponding to PV-panel is simulated using VHDL language based on the saved weights and bias of the network. Simulation results of the trained MLP-PV panel based on Matlab and VHDL are presented. The proposed PV-panel model based ANN and VHDL permit to evaluate the performance PV-panel using only the environmental factors and involves less computational efforts, and it can be used for predicting the output electrical energy from the PV-panel.

  2. Modeling of the photodetector based on the multilayer graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Liu, Haiyue; Niu, Yanxiong; Yin, Yiheng; Liu, Shuai

    2016-07-01

    Graphene nanoribbon (GNR), which has unique properties and advantages, is a crucial component of nanoelectornic devices, especially in the development of photoelectric detectors. In this work, an infrared photodetector based on the structure of stacked multiple-GNRs, which is separated by a little thick barrier layers (made of tungsten disulfide or related materials) to prevent tunneling current, is proposed and modeled. Operation of photoelectric detector is related to the electron cascaded radiative transition in the adjacent GNRs strengthened by the electrons heated due to the incident light. With a developed model, the working principle is analyzed and the relationships for the photocurrent and dark current as functions of the intensity of the incident radiation are derived. The spectral dependence of the responsivity and detectivity for graphene nanoribbons photodetector (GNRs-PT) with different Fermi energy, band gaps and numbers of GNRs layers are analyzed as well. The results demonstrate that the spectral characteristics depend on the GNRs band gap, which shows a potential on GNRs-PT application in the multi-wavelength systems. In addition, GNRs-PT has a better spectrum property and higher responsivity compared to photodetectors based on InxGaxAs in room temperature.

  3. Robust estimation of cerebral hemodynamics in neonates using multilayered diffusion model for normal and oblique incidences

    NASA Astrophysics Data System (ADS)

    Steinberg, Idan; Harbater, Osnat; Gannot, Israel

    2014-07-01

    The diffusion approximation is useful for many optical diagnostics modalities, such as near-infrared spectroscopy. However, the simple normal incidence, semi-infinite layer model may prove lacking in estimation of deep-tissue optical properties such as required for monitoring cerebral hemodynamics, especially in neonates. To answer this need, we present an analytical multilayered, oblique incidence diffusion model. Initially, the model equations are derived in vector-matrix form to facilitate fast and simple computation. Then, the spatiotemporal reflectance predicted by the model for a complex neonate head is compared with time-resolved Monte Carlo (TRMC) simulations under a wide range of physiologically feasible parameters. The high accuracy of the multilayer model is demonstrated in that the deviation from TRMC simulations is only a few percent even under the toughest conditions. We then turn to solve the inverse problem and estimate the oxygen saturation of deep brain tissues based on the temporal and spatial behaviors of the reflectance. Results indicate that temporal features of the reflectance are more sensitive to deep-layer optical parameters. The accuracy of estimation is shown to be more accurate and robust than the commonly used single-layer diffusion model. Finally, the limitations of such approaches are discussed thoroughly.

  4. Density functional theory modeling of multilayer "epitaxial" graphene oxide.

    PubMed

    Zhou, Si; Bongiorno, Angelo

    2014-11-18

    CONSPECTUS: Graphene oxide (GO) is a complex material of both fundamental and applied interest. Elucidating the structure of GO is crucial to achieve control over its properties and technological applications. GO is a nonstoichiometric and hygroscopic material with a lamellar structure, and its physical chemical properties depend critically on synthesis procedures and postsynthesis treatments. Numerous efforts are in place to both understand and exploit this versatile layered carbon material. This Account reports on recent density functional theory (DFT) studies of "epitaxial" graphene oxide (hereafter EGO), a type of GO obtained by oxidation of graphene films grown epitaxially on silicon carbide. Here, we rely on selected X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and X-ray diffraction (XRD) measurements of EGO, and we discuss in great detail how we utilized DFT-based techniques to project out from the experimental data basic atomistic information about the chemistry and structure of these films. This Account provides an example as to how DFT modeling can be used to elucidate complex materials such as GO from a limited set of experimental information. EGO exhibits a uniform layered structure, consisting of a stack of graphene planes hosting predominantly epoxide and hydroxyl groups, and water molecules intercalated between the oxidized carbon layers. Here, we first focus on XPS measurements of EGO, and we use DFT to generate realistic model structures, calculate core-level chemical shifts, and through the comparison with experiment, gain insight on the chemical composition and metastability characteristics of EGO. DFT calculations are then used to devise a simplistic but accurate simulation scheme to study thermodynamic and kinetic stability and to predict the intralayer structure of EGO films aged at room temperature. Our simulations show that aged EGO encompasses layers with nanosized oxidized domains presenting a high concentration of

  5. Applying the Cognitive Vulnerability Model to the analysis of cognitive and family influences on children's dental fear.

    PubMed

    Crego, Antonio; Carrillo-Diaz, Maria; Armfield, Jason M; Romero, Martin

    2013-06-01

    Negative experiences, cognitions, and family variables are involved in the etiology of child dental fear, but previous research has frequently considered them separately. This study uses the Cognitive Vulnerability Model to explore the influence of negative dental experiences and family members on children's dental anxiety. The participants were 185 children who completed a questionnaire comprising measures of dental fear and cognitive vulnerability-related perceptions. Measures were obtained for 88 of the participants' fathers and for 97 of the participants' mothers. Cognitive vulnerability perceptions had the strongest association with children's dental fear (β = 0.40), explaining 14-21% of the variance in dental fear scores beyond that explained by other variables. Furthermore, vulnerability perceptions mediated the relationship between negative dental experiences and dental fear. Children's dental fear and cognitive vulnerability perceptions were significantly associated with those of their fathers (r = 0.23 and r = 0.40, respectively) and mothers (r = 0.28 and r = 0.35, respectively). Moreover, fathers' (β = 0.24) and mothers' (β = 0.31) levels of cognitive vulnerability significantly predicted the children's levels of dental fear. The Cognitive Vulnerability Model offers a framework to understand child dental fear. Furthermore, this cognitive approach may help explain why some children develop dental fear problems after suffering a negative dental experience and how dental anxiety is passed on from parents to children.

  6. Multilayer Markov Random Field models for change detection in optical remote sensing images

    NASA Astrophysics Data System (ADS)

    Benedek, Csaba; Shadaydeh, Maha; Kato, Zoltan; Szirányi, Tamás; Zerubia, Josiane

    2015-09-01

    In this paper, we give a comparative study on three Multilayer Markov Random Field (MRF) based solutions proposed for change detection in optical remote sensing images, called Multicue MRF, Conditional Mixed Markov model, and Fusion MRF. Our purposes are twofold. On one hand, we highlight the significance of the focused model family and we set them against various state-of-the-art approaches through a thematic analysis and quantitative tests. We discuss the advantages and drawbacks of class comparison vs. direct approaches, usage of training data, various targeted application fields and different ways of Ground Truth generation, meantime informing the Reader in which roles the Multilayer MRFs can be efficiently applied. On the other hand we also emphasize the differences between the three focused models at various levels, considering the model structures, feature extraction, layer interpretation, change concept definition, parameter tuning and performance. We provide qualitative and quantitative comparison results using principally a publicly available change detection database which contains aerial image pairs and Ground Truth change masks. We conclude that the discussed models are competitive against alternative state-of-the-art solutions, if one uses them as pre-processing filters in multitemporal optical image analysis. In addition, they cover together a large range of applications, considering the different usage options of the three approaches.

  7. Resolving the cycle skip introduced by the multi-layer static model using a hybrid approach

    NASA Astrophysics Data System (ADS)

    Tawadros, Emad Ekladios Toma

    Cycle skips (breaks) in seismic data are occasionally irresolvable using conventional static correction programs. Such artificial cycle skips can be misleading for interpreters and introduce false subsurface images. After applying datum static corrections using either the single-layer or multi-layer models, artificial cycle skips might develop in the data. Although conventional residual static correction techniques are occasionally able to solve this problem, they fail in solving many other cases. A new approach is introduced in this study to resolve this problem by forming a static model that is free of these artificial cycle skips, which can be used as a pilot volume for residual statics calculation. The pilot volume is formed by combining the high-frequency static component of the single-layer model which show better static solution at the static problem locations and the low-frequency static component of the two-layer model. This new approach is applied on a 3-D seismic data set from Haba Field of Eastern Saudi Arabia where a major cycle skip was introduced by the multilayer model. Results show a better image of the subsurface structure after application of the new approach.

  8. A mathematical simulation approach to testing innovative models of dental education.

    PubMed

    Tennant, Marc; Kruger, Estie

    2010-03-01

    A combination of the increasing costs associated with providing a complex clinical program and an ever-reducing education-based income finds dental schools throughout Australia continuing to face serious financial risk. Even more important is the growing workforce crisis in academic staffing faced in almost all dental schools as the impact of the widening gap between private practice incomes and academic remuneration takes effect. This study developed a model of core variables and their relationship that was then transformed into a mathematical simulation tool that can be applied to test various scenarios and variable changes. The simulation model was tested against a theoretical dental education arrangement and found that this arrangement was a commercially viable pathway for new providers to enter the dental education market. This type of mathematical simulation approach is an important technique for analysis of the complex financial and operational management of modern dental schools. PMID:20203326

  9. Nonlinear numerical modelling and experimental validation of multilayer piezoelectric vibration energy scavengers

    NASA Astrophysics Data System (ADS)

    Blažević, D.; Zelenika, S.

    2015-05-01

    Scavenging of low-level ambient vibrations i.e. the conversion of kinetic into electric energy, is proven as effective means of powering low consumption electronic devices such as wireless sensor nodes. Cantilever based scavengers are characterised by several advantages and thus thoroughly investigated; analytical models based on a distributed parameter approach, Euler-Bernoulli beam theory and eigenvalue analysis have thus been developed and experimentally verified. Finite element models (FEM) have also been proposed employing different modelling approaches and commercial software packages with coupled analysis capabilities. An approach of using a FEM analysis of a piezoelectric cantilever bimorph under harmonic excitation is used in this work. Modal, harmonic and linear and nonlinear transient analyses are performed. Different complex dynamic effects are observed and compared to the results obtained by using a distributed parameter model. The influence of two types of finite elements and three mesh densities is also investigated. A complex bimorph cantilever, based on commercially available Midé Technology® Volture energy scavengers, is then considered. These scavengers are characterised by an intricate multilayer structure not investigated so far in literature. An experimental set-up is developed to evaluate the behaviour of the considered class of devices. The results of the modal and the harmonic FEM analyses of the behaviour of the multilayer scavengers are verified experimentally for three different tip masses and 12 different electrical load values. A satisfying agreement between numerical and experimental results is achieved.

  10. Strategies for tuning phonon transport in multilayered structures using a mismatch-based particle model

    NASA Astrophysics Data System (ADS)

    Le, Nam Q.; Duda, John C.; English, Timothy S.; Hopkins, Patrick E.; Beechem, Thomas E.; Norris, Pamela M.

    2012-04-01

    The performance of many micro- and nanoscale devices depends on the ability to control interfacial thermal transport, which is predominantly mediated by phonons in semiconductor systems. The phonon transmissivity at an interface is therefore a quantity of interest. In this work, an empirical model, termed the thermal mismatch model, is developed to predict transmissivity at ideal interfaces between semiconductor materials, producing an excellent agreement with molecular dynamics simulations of wave packets. To investigate propagation through multilayered structures, this thermal mismatch model is then incorporated into a simulation scheme that represents wave packets as particles, showing a good agreement with a similar scheme that used molecular dynamics simulations as input [P. K. Schelling and S. R. Phillpot, J. Appl. Phys. 93, 5377 (2003)]. With these techniques validated for both single interfaces and superlattices, they are further used to identify ways to tune the transmissivity of multilayered structures. It is shown that by introducing intermediate layers of certain atomic masses, the total transmissivity can either be systematically enhanced or reduced compared to that of a single interface. Thus, this model can serve as a computationally inexpensive means of developing strategies to control phonon transmissivity in applications that may benefit from either enhancement (e.g., microelectronics) or reduction (e.g., thermoelectrics) in thermal transport.

  11. Simulation of rainfall interception using multilayer model in evergreen broadleaf forest, Cambodia

    NASA Astrophysics Data System (ADS)

    Nobuhiro, T.; Shimizu, A.; Tanaka, K.; Kabeya, N.; Tamai, K.; Chann, S.; Keth, N.

    2006-12-01

    The proportion of forest area is relatively high in Cambodia compared with neighboring countries. Therefore forest is one of the important factors on the water cycle in this country. The rainfall interception by a tree canopy and evaporation after the rainfall event are one of the important factors for considering such a water cycle. To clarify those processes, a rainfall interception measurement plot (25 x 25 m) was constructed in the evergreen broadleaf forest area in Kampong Thom province, central part of Cambodia. We measured rainfall, through fall and stem flow in the interception plot, and then we analyzed the relationship between those components. Moreover, the simulation of rainfall interception was carried out using multilayer model. Model parameters such as canopy structure and leaf characteristics were estimated using observed interception components and meteorological elements during large rainfall event. Annual rainfall interception was reproduced using multilayer model with obtained parameters and observed meteorological elements. The simulation results were in agreement with the observed value. The rainfall interception rate in the interception plot was considered to be about 15 % against annual rainfall.

  12. Experimental validation of coupled heat, air and moisture transfer modeling in multilayer building components

    NASA Astrophysics Data System (ADS)

    Ferroukhi, M. Y.; Abahri, K.; Belarbi, R.; Limam, K.; Nouviaire, A.

    2016-10-01

    The present paper lies to study the coupled heat, air and moisture transfer in multi-layer building materials. Concerning the modeling part, the interest is to predict the hygrothermal behavior, by developing a macroscopic model that incorporates simultaneously the diffusive, convective and conductive effects on the building elements. Heat transfer is considered in the strongly coupled situation where the mass and heat flux are temperature, vapor pressure and total pressure dependents. The model input parameters are evaluated experimentally through the development of various experimental prototypes in the laboratory. Thereafter, an experimental setup has been established in order to evaluate the hygrothermal process of several multilayer walls configurations. The experimental procedure consists to follow the temperature and relative humidity evolutions within the samples thickness, submitted to controlled and fixed boundary conditions. This procedure points out diverging conclusion between different testing materials combinations (e.g. red-brick and polystyrene). In fact, the hygrothermal behavior of the tested configurations is completely dependent on both materials selection and their thermophysical properties. Finally, comparison between numerical and experimental results showed good agreement with acceptable errors margins with an average of 3 %.

  13. Advancing the educational training of dental educators: review of a model program.

    PubMed

    Graham, Roseanna; Bitzer, Laureen A Zubiaurre; Anderson, O Roger; Klyvert, Marlene; Moss-Salentijn, Letty; Lamster, Ira B

    2012-03-01

    Very few dental educators have formal pedagogical training, and the availability of degree-granting programs for dental educators is very limited. A joint D.D.S.-M.A. program for predoctoral students and a Ph.D. program for faculty members have been established at Columbia University's College of Dental Medicine in conjunction with the Graduate School of Education, Teachers College. Six students have completed the joint degree program, five are currently enrolled, and an additional three have taken courses at Teachers College without pursuing a degree. One faculty member has completed the Ph.D. program, and one is enrolled. This article describes the details of both programs and discusses preliminary outcomes. The model described here may serve as an example for other dental schools that may choose to implement degree programs in education for dental educators. PMID:22383598

  14. Reduction of fear-related dental management problems with use of filmed modeling.

    PubMed

    Melamed, B G; Weinstein, D; Katin-Borland, M; Hawes, R

    1975-04-01

    In this study of the modification of anxiety-related disruptive behavior in dental treatment, matched groups of inner-city children attending a pedodontic clinic were shown a videotaped demonstration of a 4-year-old black child undergoing a dental restorative procedure or were given an unrelated drawing task before dental treatment. Children who viewed the videotape demonstration of a peer model coping with dental procedures showed significantly fewer fear-related disruptive behaviors during restoration of lesions. Observations of children's anxiety levels made by dentists and independent observers validated the effectiveness of viewing the videotaped demonstration. No significant correlation was found between the children's reports of their anxiety and their behavior during dental treatment. PMID:123932

  15. An Evaluation of in Vivo Desensitization and Video Modeling to Increase Compliance with Dental Procedures in Persons with Mental Retardation

    ERIC Educational Resources Information Center

    Conyers, Carole; Miltenberger, Raymond G.; Peterson, Blake; Gubin, Amber; Jurgens, Mandy; Selders, Andrew; Dickinson, Jessica; Barenz, Rebecca

    2004-01-01

    Fear of dental procedures deters many individuals with mental retardation from accepting dental treatment. This study was conducted to assess the effectiveness of two procedures, in vivo desensitization and video modeling, for increasing compliance with dental procedures in participants with severe or profound mental retardation. Desensitization…

  16. Optical response of cylindrical multilayers in the context of hydrodynamic convection-diffusion model

    NASA Astrophysics Data System (ADS)

    Dong, Tianyu; Shi, Yi; Lu, Lizhen; Chen, Feng; Ma, Xikui; Mittra, Raj

    2016-09-01

    In this work, we generalize the cascading scattering matrix algorithm for calculating the optical response of concentric multilayered structures comprised of either plasmonic metal or dielectric, within the framework of hydrodynamic convection-diffusion model of electrodynamics. Two additional boundary conditions, namely, the continuity of first order pressure of free electron density and the continuity of normal components of free charge velocity, respectively, are adopted in order to handle the behaviour at interfaces involving metals. Scattering matrices at interfaces can be readily obtained and cascaded to obtain the modal coefficients in each layer by expanding electromagnetic waves in harmonic modes with cylindrical vector wave functions. We have validated the proposed method by analyzing the optical responses of several configurations of nanostructures, including a bi-metallic nanocylinder and a hyperlens. We found that nonlocal effects can be important for small structures, when the characteristic size is comparable to the Fermi wavelength. The proposed method shows its capability and flexibility to solve hybrid metal-dielectric multilayer structures even when the number of layers is large. Although we have discussed our method in the context of the retarded radiation regime, it can be applied in quasi-static scenarios without any difficulties. Furthermore, it may be extended to solve similar problems in other areas of physics, such as acoustics.

  17. A Corrected Formulation of the Multilayer Model (MLM) for Inferring Gaseous Dry Deposition to Vegetated Surfaces

    NASA Technical Reports Server (NTRS)

    Saylor, Rick D.; Wolfe, Glenn M.; Meyers, Tilden P.; Hicks, Bruce B.

    2014-01-01

    The Multilayer Model (MLM) has been used for many years to infer dry deposition fluxes from measured trace species concentrations and standard meteorological measurements for national networks in the U.S., including the U.S. Environmental Protection Agency's Clean Air Status and Trends Network (CASTNet). MLM utilizes a resistance analogy to calculate deposition velocities appropriate for whole vegetative canopies, while employing a multilayer integration to account for vertically varying meteorology, canopy morphology and radiative transfer within the canopy. However, the MLM formulation, as it was originally presented and as it has been subsequently employed, contains a non-physical representation related to the leaf-level quasi-laminar boundary layer resistance that affects the calculation of the total canopy resistance. In this note, the non-physical representation of the canopy resistance as originally formulated in MLM is discussed and a revised, physically consistent, formulation is suggested as a replacement. The revised canopy resistance formulation reduces estimates of HNO3 deposition velocities by as much as 38% during mid-day as compared to values generated by the original formulation. Inferred deposition velocities for SO2 and O3 are not significantly altered by the change in formulation (less than 3%). Inferred deposition loadings of oxidized and total nitrogen from CASTNet data may be reduced by 10-20% and 5-10%, respectively, for the Eastern U. S. when employing the revised formulation of MLM as compared to the original formulation.

  18. Model based multilayers fix for litho hotspots beyond 20nm node

    NASA Astrophysics Data System (ADS)

    Rabie, Asmaa; Madkour, Kareem; George, Kirolos; ElManhawy, Wael; Brunet, Jean-Marie; Kwan, Joe

    2014-03-01

    Sub-20nm node designs are getting more sophisticated, and printability issues become more critical which need more advanced techniques to fix. It is mandatory for designers to run lithography checks before tapeout, and it is very challenging to fix all of the generated hotspots manually without introducing unintentional hotspots, or DPT violations. This paper presents a methodology for fixing hotspots on DPT layouts, using the same Model Based Hints (MBH) engine used for detecting hotspots. The fix is based on DRC and DPT constrained minimum movement of edges causing the hotspot, which guarantees that the fix does not violate any of the specified DRC or DPT constraints, nor does it need recoloring. The fix is extended along multilayers to fulfill the specified DRC and DPT constraints and guarantees circuit connectivity along the layers stack. This multilayers approach fixes hotspots that were impossible to fix previously. This methodology is demonstrated on industrial designs, where real hotspots were fixed and the fixing rate is reported.

  19. Approximating Gaussian mixture model or radial basis function network with multilayer perceptron.

    PubMed

    Patrikar, Ajay M

    2013-07-01

    Gaussian mixture models (GMMs) and multilayer perceptron (MLP) are both popular pattern classification techniques. This brief shows that a multilayer perceptron with quadratic inputs (MLPQ) can accurately approximate GMMs with diagonal covariance matrices. The mapping equations between the parameters of GMM and the weights of MLPQ are presented. A similar approach is applied to radial basis function networks (RBFNs) to show that RBFNs with Gaussian basis functions and Euclidean norm can be approximated accurately with MLPQ. The mapping equations between RBFN and MLPQ weights are presented. There are well-established training procedures for GMMs, such as the expectation maximization (EM) algorithm. The GMM parameters obtained by the EM algorithm can be used to generate a set of initial weights of MLPQ. Similarly, a trained RBFN can be used to generate a set of initial weights of MLPQ. MLPQ training can be continued further with gradient-descent based methods, which can lead to improvement in performance compared to the GMM or RBFN from which it is initialized. Thus, the MLPQ can always perform as well as or better than the GMM or RBFN.

  20. The Integration of Ecological processes into a Multi-layer Higher order closure Land Surface Model

    NASA Astrophysics Data System (ADS)

    Chang, K. Y.; Paw U, K. T.; Chen, S. H.

    2015-12-01

    The ecological impacts on biogeophysical and biogeochemical processes were investigated by a series of simulations conducted by a multi-layer higher order closure land surface model (UCD-ACASA) driven by a variety of meteorological and ecological conditions. The results show that the implementation of a more realistic ecological dataset, once carefully quality controlled, can significantly improve the biogeophysical and biogeochemical simulations, which suggests that the ecological impacts on surface layer simulations are as important as the reliability of the selected land surface model. Therefore, the ability to simulate realistic ecological conditions is imperative and beneficial to improve weather and climate simulations. We coupled the ecological processes in UCD-ACASA by adapting the fully prognostic plant carbon and nitrogen dynamics from the version 4.5 of the Community Land Model (CLM4.5). The simulated ecological conditions are sensitive to both radiative transfer processes and leaf distribution inside the canopy, and the multi-layer feature built in UCD-ACASA enables it to describe these properties more realistically as compared to the other big-leaf models. We conducted another set of simulations to examine the reliability of the simulated biogeophysical, biogeochemical and ecological results. The simulated Leaf Area Index (LAI) was compared with a high resolution remotely sensed LAI dataset, and the results show that the simulated LAI tends to overestimate mean LAI and underestimate annual LAI variation at the selected sites. However, the simulated LAI is reasonable enough to produce comparable simulation results against the simulations driven directly by remotely sensed LAI for the tested biogeophysical and biogeochemical fluxes. The results show that ecological impacts on biogeophysical and biogeochemical simulations are significant, and the implementation of biogeochemical processes into a land surface model has the potential to improve weather and

  1. A generalized voter model with time-decaying memory on a multilayer network

    NASA Astrophysics Data System (ADS)

    Zhong, Li-Xin; Xu, Wen-Juan; Chen, Rong-Da; Zhong, Chen-Yang; Qiu, Tian; Shi, Yong-Dong; Wang, Li-Liang

    2016-09-01

    By incorporating a multilayer network and time-decaying memory into the original voter model, we investigate the coupled effects of spatial and temporal accumulation of peer pressure on the consensus. Heterogeneity in peer pressure and the time-decaying mechanism are both shown to be detrimental to the consensus. We find the transition points below which a consensus can always be reached and above which two opposed opinions are more likely to coexist. Our mean-field analysis indicates that the phase transitions in the present model are governed by the cumulative influence of peer pressure and the updating threshold. We find a functional relation between the consensus threshold and the decay rate of the influence of peer is found. As to the pressure. The time required to reach a consensus is governed by the coupling of the memory length and the decay rate. An intermediate decay rate may greatly reduce the time required to reach a consensus.

  2. A multilayer model of time dependent deformation following an earthquake on a strike-slip fault

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.

    1981-01-01

    A multilayer model of the Earth to calculate finite element of time dependent deformation and stress following an earthquake on a strike slip fault is discussed. The model involves shear properties of an elastic upper lithosphere, a standard viscoelastic linear solid lower lithosphere, a Maxwell viscoelastic asthenosphere and an elastic mesosphere. Systematic variations of fault and layer depths and comparisons with simpler elastic lithosphere over viscoelastic asthenosphere calculations are analyzed. Both the creep of the lower lithosphere and astenosphere contribute to the postseismic deformation. The magnitude of the deformation is enhanced by a short distance between the bottom of the fault (slip zone) and the top of the creep region but is less sensitive to the thickness of the creeping layer. Postseismic restressing is increased as the lower lithosphere becomes more viscoelastic, but the tendency for the width of the restressed zone to growth with time is retarded.

  3. Formal Model for the Reduction of the Dynamic Energy Consumption in Multi-Layer Memory Subsystems

    NASA Astrophysics Data System (ADS)

    Zhu, Hongwei; Luican, Ilie I.; Balasa, Florin; Pradhan, Dhiraj K.

    In real-time data-dominated communication and multimedia processing applications, a multi-layer memory hierarchy is typically used to enhance the system performance and also to reduce the energy consumption. Savings of dynamic energy can be obtained by accessing frequently used data from smaller on-chip memories rather than from large background memories. This paper focuses on the reduction of the dynamic energy consumption in the memory subsystem of multidimensional signal processing systems, starting from the high-level algorithmic specification of the application. The paper presents a formal model which identifies those parts of arrays more intensely accessed, taking also into account the relative lifetimes of the signals. Tested on a two-layer memory hierarchy, this model led to savings of dynamic energy from 40% to over 70% relative to the energy used in the case of flat memory designs.

  4. Modelling the longevity of dental restorations by means of a CBR system.

    PubMed

    Aliaga, Ignacio J; Vera, Vicente; De Paz, Juan F; García, Alvaro E; Mohamad, Mohd Saberi

    2015-01-01

    The lifespan of dental restorations is limited. Longevity depends on the material used and the different characteristics of the dental piece. However, it is not always the case that the best and longest lasting material is used since patients may prefer different treatments according to how noticeable the material is. Over the last 100 years, the most commonly used material has been silver amalgam, which, while very durable, is somewhat aesthetically displeasing. Our study is based on the collection of data from the charts, notes, and radiographic information of restorative treatments performed by Dr. Vera in 1993, the analysis of the information by computer artificial intelligence to determine the most appropriate restoration, and the monitoring of the evolution of the dental restoration. The data will be treated confidentially according to the Organic Law 15/1999 on 13 December on the Protection of Personal Data. This paper also presents a clustering technique capable of identifying the most significant cases with which to instantiate the case-base. In order to classify the cases, a mixture of experts is used which incorporates a Bayesian network and a multilayer perceptron; the combination of both classifiers is performed with a neural network.

  5. Modelling the Longevity of Dental Restorations by means of a CBR System

    PubMed Central

    Aliaga, Ignacio J.; Vera, Vicente; García, Alvaro E.

    2015-01-01

    The lifespan of dental restorations is limited. Longevity depends on the material used and the different characteristics of the dental piece. However, it is not always the case that the best and longest lasting material is used since patients may prefer different treatments according to how noticeable the material is. Over the last 100 years, the most commonly used material has been silver amalgam, which, while very durable, is somewhat aesthetically displeasing. Our study is based on the collection of data from the charts, notes, and radiographic information of restorative treatments performed by Dr. Vera in 1993, the analysis of the information by computer artificial intelligence to determine the most appropriate restoration, and the monitoring of the evolution of the dental restoration. The data will be treated confidentially according to the Organic Law 15/1999 on 13 December on the Protection of Personal Data. This paper also presents a clustering technique capable of identifying the most significant cases with which to instantiate the case-base. In order to classify the cases, a mixture of experts is used which incorporates a Bayesian network and a multilayer perceptron; the combination of both classifiers is performed with a neural network. PMID:25866792

  6. Nanoindentation and finite element modelling of chitosan-alginate multilayer coated hydrogels.

    PubMed

    Sherstova, Tatyana; Stokke, Bjørn Torger; Skallerud, Bjørn; Maurstad, Gjertrud; Prot, Victorien Emile

    2016-09-21

    Composite soft materials are used as compounds for determining the effects of mechanical cues on cell behavior and cell encapsulation and for controlling drug release. The appropriate composite soft materials are conventionally prepared by selective deposition of polymers at the surface of an ionic hydrogel. In the present study we address the impact of a mechanically stratified two-layer structure of these materials on their overall mechanical characterization by applying a combination of nanoindentation, confocal microscopy and finite element modelling. We prepare covalent cross-linked hydrogels based on acrylamide (AAM) and including an anionic group, and impregnate them using a multilayer deposition strategy of alternating exposure to cationic chitosan and anionic alginate. The thickness of the chitosan-alginate layer on the hydrogels was determined to be 0.4 ± 0.05 μm for 4 bilayers, and 0.7 ± 0.1 μm for the 8 bilayer deposition procedure employing a fluorescently labelled chitosan and confocal microscopy. The force-indentation data for the AAM gels were highly reproducible, whereas 77% and 50% of the force-indentation data were reproducible following the 4 and 8 bilayer deposition. The main trends in the reproducible force-distance data were found to yield an apparent increased Young's modulus after the deposition. Finite element modelling showed that adaption of a homogeneous Young's modulus for the specimens with deposited layers yields approximately three times too low stiffness compared to the estimate of the mechanical properties of the outer part in the two-layered mechanical model. The thickness of the multilayer region determined by confocal microscopy was used in the model. This study shows that the mechanical layered property needs to be included in the interpretation of the nanoindentation data when there is a significant mechanical contrast.

  7. A model of psychosocial work environment, stress, and satisfaction among dental students in Sweden.

    PubMed

    Schéle, Ingrid A; Hedman, Leif R; Hammarström, Anne

    2012-09-01

    Dental students are often described as stressed. The stress has, among other things, been connected to stressors in their psychosocial environment and inconsistent feedback. The hypothesis of this study was that the psychosocial work environment in dental schools leads to stress and affects the satisfaction of dental students and that tolerance for ambiguity shields students from stress. A web-based survey was sent to the entire Swedish dental student population in clinical training (N=805); the response rate was 40 percent. Structural equation modeling used in the analyses contains four main constructs: psychosocial work environment, tolerance for ambiguity, perceived stress, and student satisfaction (χ(2)=267.437, d.f.=174, p<0.001, Normed χ(2)=1.537, RMSEA= 0.041, CFI=0.98). Psychosocial work environment influenced both perceived stress and satisfaction: it accounted for almost all of the explained variance in perceived stress for women, while about half of the variance for the men was explained by tolerance for ambiguity. This study concluded that about 40 percent of the total perceived stress of these female dental students was related to their psychosocial work environment. Tolerance for ambiguity shielded men but not women from stress. An improved psychosocial work environment in dental schools would decrease the stress of both male and female dental students.

  8. Phase constitution and interface structure of nano-sized Ag-Cu/AlN multilayers: Experiment and ab initio modeling

    SciTech Connect

    Pigozzi, Giancarlo; Janczak-Rusch, Jolanta; Passerone, Daniele; Antonio Pignedoli, Carlo; Patscheider, Joerg; Jeurgens, Lars P. H.; Antusek, Andrej; Parlinska-Wojtan, Magdalena; Bissig, Vinzenz

    2012-10-29

    Nano-sized Ag-Cu{sub 8nm}/AlN{sub 10nm} multilayers were deposited by reactive DC sputtering on {alpha}-Al{sub 2}O{sub 3}(0001) substrates. Investigation of the phase constitution and interface structure of the multilayers evidences a phase separation of the alloy sublayers into nanosized grains of Ag and Cu. The interfaces between the Ag grains and the quasi-single-crystalline AlN sublayers are semi-coherent, whereas the corresponding Cu/AlN interfaces are incoherent. The orientation relationship between Ag and AlN is constant throughout the entire multilayer stack. These observations are consistent with atomistic models of the interfaces as obtained by ab initio calculations.

  9. In Vitro Evaluation of New Approach to Digital Dental Model Articulation

    PubMed Central

    Chang, Yu-Bing; Xia, James J.; Gateno, Jaime; Xiong, Zixiang; Teichgraeber, John F.; Lasky, Robert E.; Zhou, Xiaobo

    2015-01-01

    Purpose The purpose of the present study was to evaluate the accuracy of our newly developed approach to digital dental model articulation. Materials and Methods Twelve sets of stone dental models from patients with craniomaxillofacial deformities were used for validation. All the models had stable occlusion and no evidence of early contact. The stone models were hand articulated to the maximal intercuspation (MI) position and scanned using a 3-dimensional surface laser scanner. These digital dental models at the MI position served as the control group. To establish an experimental group, each mandibular dental model was disarticulated from its original MI position to 80 initial positions. Using a regular office personal computer, they were digitally articulated to the MI position using our newly developed approach. These rearticulated mandibular models served as the experimental group. Finally, the translational, rotational, and surface deviations in the mandibular position were calculated between the experimental and control groups, and statistical analyses were performed. Results All the digital dental models were successfully articulated. Between the control and experimental groups, the largest translational difference in mandibular position was within 0.2 mm ± 0.6 mm. The largest rotational difference was within 0.1° ± 1.1°. The averaged surface deviation was 0.08 ± 0.07. The results of the Bland and Altman method of assessing measurement agreement showed tight limits for the translational, rotational, and surface deviations. In addition, the final positions of the mandibular articulated from the 80 initial positions were absolutely agreed on. Conclusion The results of our study have demonstrated that using our approach, the digital dental models can be accurately and effectively articulated to the MI position. In addition, the 3-dimensional surface geometry of the mandibular teeth played a more important role in digital dental articulation than the

  10. The influence of "new science" on dental education: current concepts, trends, and models for the future.

    PubMed

    Iacopino, Anthony M

    2007-04-01

    Advances in all aspects of science and discovery continue to occur at an exponential rate, leading to a wealth of new knowledge and technologies that have the potential to transform dental practice. This "new science" within the areas of cell/ molecular biology, genetics, tissue engineering, nanotechnology, and informatics has been available for several years; however, the assimilation of this information into the dental curriculum has been slow. For the profession and the patients it serves to benefit fully from modern science, new knowledge and technologies must be incorporated into the mainstream of dental education. The continued evolution of the dental curriculum presents a major challenge to faculty, administrators, and external constituencies because of the high cost, overcrowded schedule, unique demands of clinical training, changing nature of teaching/assessment methods, and large scope of new material impacting all areas of the educational program. Additionally, there is a lack of personnel with adequate training/experience in both foundational and clinical sciences to support the effective application and/or integration of new science information into curriculum planning, implementation, and assessment processes. Nonetheless, the speed of this evolution must be increased if dentistry is to maintain its standing as a respected health care profession. The influence of new science on dental education and the dental curriculum is already evident in some dental schools. For example, the Marquette University School of Dentistry has developed a comprehensive model of curriculum revision that integrates foundational and clinical sciences and also provides a dedicated research/scholarly track and faculty development programming to support such a curriculum. Educational reforms at other dental schools are based on addition of new curricular elements and include innovative approaches that introduce concepts regarding new advances in science, evidence

  11. In-to-Out Body Antenna-Independent Path Loss Model for Multilayered Tissues and Heterogeneous Medium

    PubMed Central

    Kurup, Divya; Vermeeren, Günter; Tanghe, Emmeric; Joseph, Wout; Martens, Luc

    2015-01-01

    In this paper, we investigate multilayered lossy and heterogeneous media for wireless body area networks (WBAN) to develop a simple, fast and efficient analytical in-to-out body path loss (PL) model at 2.45 GHz and, thus, avoid time-consuming simulations. The PL model is an antenna-independent model and is validated with simulations in layered medium, as well as in a 3D human model using electromagnetic solvers. PMID:25551483

  12. A Program for Calculating and Plotting Synthetic Common-Source Seismic-Reflection Traces for Multilayered Earth Models.

    ERIC Educational Resources Information Center

    Ramananantoandro, Ramanantsoa

    1988-01-01

    Presented is a description of a BASIC program to be used on an IBM microcomputer for calculating and plotting synthetic seismic-reflection traces for multilayered earth models. Discusses finding raypaths for given source-receiver offsets using the "shooting method" and calculating the corresponding travel times. (Author/CW)

  13. Pretreatment modeling. A technique for reducing children's fear in the dental operatory.

    PubMed

    Greenbaum, P E; Melamed, B G

    1988-10-01

    Research on modeling indicates that this technique offers dentists a means of reducing fear in child patients of all ages. As a preventive measure used with children who have had no prior exposure to dental treatment, it can be particularly efficacious. Based on the assumption that much of adult dental avoidance is based on dental fears acquired in childhood treatment, the reduction of children's dental fear would have a positive effect on the individual's tendency to seek out dental health care throughout his or her lifespan. For the dentist, there are also short- and long-term benefits. Dental management of the child is prerequisite to providing good dental care. Pedodontics as a specialty recognizes behavioral management of the child cannot be separated from the quality of the dentist's work. Fear has been identified as an important factor in disruptive behavior of school age children in the dental office. Practicing dentists consider the fearful, disruptive child to be among the most troublesome of problems in their clinical work. The child must cooperate or at least passively comply with the dentist's procedures in order to have the technical work completed. By reducing disruptive patient behavior (crying, screaming children whose peripheral and gross motor movements often make direct contact with the dentist or his equipment) the most unpalatable aspect of pediatric dentistry is minimized. Further, the actual time for treatment becomes shorter rather than longer. Although modeling is not restricted to videotape media, the emergence of current videotape technology provides the practitioner with the means for incorporating patient viewing of prerecorded modeling tapes as part of the usual waiting period. Such a procedure would mean that in the long run, the dentist will spend more time doing dentistry and less in behavioral management tasks.

  14. A multilayer evaluation approach for protein structure prediction and model quality assessment.

    PubMed

    Zhang, Jingfen; Wang, Qingguo; Vantasin, Kittinun; Zhang, Jiong; He, Zhiquan; Kosztin, Ioan; Shang, Yi; Xu, Dong

    2011-01-01

    Protein tertiary structures are essential for studying functions of proteins at molecular level. An indispensable approach for protein structure solution is computational prediction. Most protein structure prediction methods generate candidate models first and select the best candidates by model quality assessment (QA). In many cases, good models can be produced, but the QA tools fail to select the best ones from the candidate model pool. Because of incomplete understanding of protein folding, each QA method only reflects partial facets of a structure model and thus has limited discerning power with no one consistently outperforming others. In this article, we developed a set of new QA methods, including two QA methods for evaluating target/template alignments, a molecular dynamics (MD)-based QA method, and three consensus QA methods with selected references to reveal new facets of protein structures complementary to the existing methods. Moreover, the underlying relationship among different QA methods were analyzed and then integrated into a multilayer evaluation approach to guide the model generation and model selection in prediction. All methods are integrated and implemented into an innovative and improved prediction system hereafter referred to as MUFOLD. In CASP8 and CASP9, MUFOLD has demonstrated the proof of the principles in terms of both QA discerning power and structure prediction accuracy. PMID:21997706

  15. A multilayer evaluation approach for protein structure prediction and model quality assessment.

    PubMed

    Zhang, Jingfen; Wang, Qingguo; Vantasin, Kittinun; Zhang, Jiong; He, Zhiquan; Kosztin, Ioan; Shang, Yi; Xu, Dong

    2011-01-01

    Protein tertiary structures are essential for studying functions of proteins at molecular level. An indispensable approach for protein structure solution is computational prediction. Most protein structure prediction methods generate candidate models first and select the best candidates by model quality assessment (QA). In many cases, good models can be produced, but the QA tools fail to select the best ones from the candidate model pool. Because of incomplete understanding of protein folding, each QA method only reflects partial facets of a structure model and thus has limited discerning power with no one consistently outperforming others. In this article, we developed a set of new QA methods, including two QA methods for evaluating target/template alignments, a molecular dynamics (MD)-based QA method, and three consensus QA methods with selected references to reveal new facets of protein structures complementary to the existing methods. Moreover, the underlying relationship among different QA methods were analyzed and then integrated into a multilayer evaluation approach to guide the model generation and model selection in prediction. All methods are integrated and implemented into an innovative and improved prediction system hereafter referred to as MUFOLD. In CASP8 and CASP9, MUFOLD has demonstrated the proof of the principles in terms of both QA discerning power and structure prediction accuracy.

  16. Field theoretical model of multilayered Josephson junction and dynamics of Josephson vortices

    NASA Astrophysics Data System (ADS)

    Fujimori, Toshiaki; Iida, Hideaki; Nitta, Muneto

    2016-09-01

    Multilayered Josephson junctions are modeled in the context of a field theory, and dynamics of Josephson vortices trapped inside insulators are studied. Starting from a theory consisting of complex and real scalar fields coupled to a U(1) gauge field which admit parallel N -1 domain-wall solutions, Josephson couplings are introduced weakly between the complex scalar fields. The N -1 domain walls behave as insulators separating N superconductors, where one of the complex scalar fields has a gap. We construct the effective Lagrangian on the domain walls, which reduces to a coupled sine-Gordon model for well-separated walls and contains more interactions for walls at short distance. We then construct sine-Gordon solitons emerging in an effective theory in which we identify Josephson vortices carrying singly quantized magnetic fluxes. When two neighboring superconductors tend to have the same phase, the ground state does not change with the positions of domain walls (the width of superconductors). On the other hand, when two neighboring superconductors tend to have π -phase differences, the ground state has a phase transition depending on the positions of domain walls; when the two walls are close to each other (one superconductor is thin), frustration occurs because of the coupling between the two superconductors besides the thin superconductor. Focusing on the case of three superconductors separated by two insulators, we find for the former case that the interaction between two Josephson vortices on different insulators changes its nature, i.e., attractive or repulsive, depending on the positions of the domain walls. In the latter case, there emerges fractional Josephson vortices when two degenerate ground states appear due to spontaneous charge-symmetry breaking, and the number of the Josephson vortices varies with the position of the domain walls. Our predictions should be verified in multilayered Josephson junctions.

  17. A new physical model with multilayer architecture for facial expression animation using dynamic adaptive mesh.

    PubMed

    Zhang, Yu; Prakash, Edmond C; Sung, Eric

    2004-01-01

    This paper presents a new physically-based 3D facial model based on anatomical knowledge which provides high fidelity for facial expression animation while optimizing the computation. Our facial model has a multilayer biomechanical structure, incorporating a physically-based approximation to facial skin tissue, a set of anatomically-motivated facial muscle actuators, and underlying skull structure. In contrast to existing mass-spring-damper (MSD) facial models, our dynamic skin model uses the nonlinear springs to directly simulate the nonlinear visco-elastic behavior of soft tissue and a new kind of edge repulsion spring is developed to prevent collapse of the skin model. Different types of muscle models have been developed to simulate distribution of the muscle force applied on the skin due to muscle contraction. The presence of the skull advantageously constrain the skin movements, resulting in more accurate facial deformation and also guides the interactive placement of facial muscles. The governing dynamics are computed using a local semi-implicit ODE solver. In the dynamic simulation, an adaptive refinement automatically adapts the local resolution at which potential inaccuracies are detected depending on local deformation. The method, in effect, ensures the required speedup by concentrating computational time only where needed while ensuring realistic behavior within a predefined error threshold. This mechanism allows more pleasing animation results to be produced at a reduced computational cost.

  18. Simulation of arrested salt wedges with a multi-layer Shallow Water Lattice Boltzmann model

    NASA Astrophysics Data System (ADS)

    Prestininzi, P.; Montessori, A.; La Rocca, M.; Sciortino, G.

    2016-10-01

    The ability to accurately and efficiently model the intrusion of salt wedges into river beds is crucial to assay its interaction with human activities and the natural environment. We present a 2D multi-layer Shallow Water Lattice Boltzmann (SWLB) model able to predict the salt wedge intrusion in river estuaries. The formulation usually employed for the simulation of gravity currents is here equipped with proper boundary conditions to handle both the downstream seaside outlet and the upstream river inlet. Firstly, the model is validated against highly accurate semi-analytical solutions of the steady state 1D two-layer Shallow Water model. Secondly, the model is applied to a more complex, fully 3D geometry, to assess its capability to handle realistic cases. The simple formulation proposed for the shear interlayer stress is proven to be consistent with the general 3D viscous solution. In addition to the accuracy, the model inherits the efficiency of the Lattice Boltzmann approach to fluid dynamics problems.

  19. A multi-layer land surface energy budget model for implicit coupling with global atmospheric simulations

    NASA Astrophysics Data System (ADS)

    Ryder, J.; Polcher, J.; Peylin, P.; Ottlé, C.; Chen, Y.; van Gorsel, E.; Haverd, V.; McGrath, M. J.; Naudts, K.; Otto, J.; Valade, A.; Luyssaert, S.

    2016-01-01

    In Earth system modelling, a description of the energy budget of the vegetated surface layer is fundamental as it determines the meteorological conditions in the planetary boundary layer and as such contributes to the atmospheric conditions and its circulation. The energy budget in most Earth system models has been based on a big-leaf approach, with averaging schemes that represent in-canopy processes. Furthermore, to be stable, that is to say, over large time steps and without large iterations, a surface layer model should be capable of implicit coupling to the atmospheric model. Surface models with large time steps, however, have difficulties in reproducing consistently the energy balance in field observations. Here we outline a newly developed numerical model for energy budget simulation, as a component of the land surface model ORCHIDEE-CAN (Organising Carbon and Hydrology In Dynamic Ecosystems - CANopy). This new model implements techniques from single-site canopy models in a practical way. It includes representation of in-canopy transport, a multi-layer long-wave radiation budget, height-specific calculation of aerodynamic and stomatal conductance, and interaction with the bare-soil flux within the canopy space. Significantly, it avoids iterations over the height of the canopy and so maintains implicit coupling to the atmospheric model LMDz (Laboratoire de Météorologie Dynamique Zoomed model). As a first test, the model is evaluated against data from both an intensive measurement campaign and longer-term eddy-covariance measurements for the intensively studied Eucalyptus stand at Tumbarumba, Australia. The model performs well in replicating both diurnal and annual cycles of energy and water fluxes, as well as the vertical gradients of temperature and of sensible heat fluxes.

  20. Analytical Modeling and Test Correlation of Variable Density Multilayer Insulation for Cryogenic Storage

    NASA Technical Reports Server (NTRS)

    Hastings, L. J.; Hedayat, A.; Brown, T. M.

    2004-01-01

    A unique foam/multilayer insulation (MLI) combination concept for orbital cryogenic storage was experimentally evaluated using a large-scale hydrogen tank. The foam substrate insulates for ground-hold periods and enables a gaseous nitrogen purge as opposed to helium. The MLI, designed for an on-orbit storage period for 45 days, includes several unique features including a variable layer density and larger but fewer perforations for venting during ascent to orbit. Test results with liquid hydrogen indicated that the MLI weight or tank heat leak is reduced by about half in comparison with standard MLI. The focus of this effort is on analytical modeling of the variable density MLI (VD-MLI) on-orbit performance. The foam/VD-MLI model is considered to have five segments. The first segment represents the optional foam layer. The second, third, and fourth segments represent three different MLI layer densities. The last segment is an environmental boundary or shroud that surrounds the last MLI layer. Two approaches are considered: a variable density MLI modeled layer by layer and a semiempirical model or "modified Lockheed equation." Results from the two models were very comparable and were within 5-8 percent of the measured data at the 300 K boundary condition.

  1. A multiple degree of freedom modeling approach of piezoelectret foam in a multilayer stack configuration

    NASA Astrophysics Data System (ADS)

    Tefft, Edward C.; Anton, Steven R.

    2016-04-01

    As electronic devices become both ubiquitous and more energy efficient, powering them with energy harvested from, for example, piezoelectric materials has become a subject of much interest. The field does indeed show promise, as harvesting energy from smart materials has the potential to replace batteries completely in some low-power applications. This paper presents modeling of piezo-electret foam assembled in a multilayer stack configuration, with the required adhesives and conductors, as a multiple degree of freedom (MDOF) system. The benefits of using the foam over some piezo-ceramics include its high flexibility, its light weight, and its lead-free composition. This model predicts the mechanical and electromechanical response to base excitation for any number of layers of piezo-electret foam. Building upon previous work which modeled the piezo-electret stack as a single degree of freedom (SDOF) system, the MDOF model provides information concerning the response of internal stack layers. The MDOF model is validated against the experimentally determined mechanical and electrical responses of a 20-layer piezo-electret foam stack. Also, the internal stack dynamics at higher order vibration modes suggest that charge cancellation is a serious outcome of vibration at these modes that designers need to consider.

  2. Analytical Models for Variable Density Multilayer Insulation Used in Cryogenic Storage

    NASA Technical Reports Server (NTRS)

    Hedayat, A.; Hastings, L. J.; Brown, T.

    2001-01-01

    A unique multilayer insulation concept for orbital cryogenic storage was experimentally evaluated at NASA Marshall Space Flight Center (MSFC) using the Multipurpose Hydrogen Test Bed (MHTB). A combination of foam/Multi layer Insulation (MLI) was used. The MLI (45 layers of Double Aluminized Mylar (DAM) with Dacron net spacers) was designed for an on-orbit storage period of 45 days and included several unique features such as: a variable layer density and larger but fewer DAM perforations for venting during ascent to orbit. The focus of this paper is on analytical modeling of the variable density MLI performance during orbital coast periods. The foam/MLI combination model is considered to have five segments. The first segment represents the foam layer. The second, third, and fourth segments represent the three layers of MLI with different layer densities and number of shields. Finally, the last segment is considered to be a shroud that surrounds the last MLI layer. The hot boundary temperature is allowed to vary from 164 K to 305 K. To simulate MLI performance, two approaches are considered. In the first approach, the variable density MLI is modeled layer by layer while in the second approach, a semi-empirical model is applied. Both models account for thermal radiation between shields, gas conduction, and solid conduction through the separator materials. The heat flux values predicted by each approach are compared for different boundary temperatures and MLI systems with 30, 45, 60, and 75 layers.

  3. Hybrid diffusion and two-flux approximation for multilayered tissue light propagation modeling.

    PubMed

    Yudovsky, Dmitry; Durkin, Anthony J

    2011-07-20

    Accurate and rapid estimation of fluence, reflectance, and absorbance in multilayered biological media has been essential in many biophotonics applications that aim to diagnose, cure, or model in vivo tissue. The radiative transfer equation (RTE) rigorously models light transfer in absorbing and scattering media. However, analytical solutions to the RTE are limited even in simple homogeneous or plane media. Monte Carlo simulation has been used extensively to solve the RTE. However, Monte Carlo simulation is computationally intensive and may not be practical for applications that demand real-time results. Instead, the diffusion approximation has been shown to provide accurate estimates of light transport in strongly scattering tissue. The diffusion approximation is a greatly simplified model and produces analytical solutions for the reflectance and absorbance in tissue. However, the diffusion approximation breaks down if tissue is strongly absorbing, which is common in the visible part of the spectrum or in applications that involve darkly pigmented skin and/or high local volumes of blood such as port-wine stain therapy or reconstructive flap monitoring. In these cases, a model of light transfer that can accommodate both strongly and weakly absorbing regimes is required. Here we present a model of light transfer through layered biological media that represents skin with two strongly scattering and one strongly absorbing layer.

  4. Evaluation strategies for vertical profiles of physical properties simulated by multilayer snowpack models

    NASA Astrophysics Data System (ADS)

    Morin, Samuel; Hagenmuller, Pascal; Dumont, Marie; Lafaysse, Matthieu

    2016-04-01

    Multilayer snowpack models aim at representing processes responsible for the layering of a one-dimensional snowpack, and its time evolution. Their evaluation should ideally not only rely on observations of vertically integrated properties (depth, albedo, snow water equivalent, surface temperature) but also vertical profiles of properties such as density, liquid water content, specific surface area, penetration resistance etc. However, even at well-documented sites where meteorological conditions are monitored with the highest possible accuracy, the direct comparison of simulated and observed profiles has proven challenging. This is due, not only to intrinsic model errors and snow observation uncertainties, which are classically considered, but also to errors of the meteorological observations used to drive the snowpack models and snowpack heterogeneity. These sources of errors stratigraphic mismatches, i.e. a layer at the same depth in the simulated and observed snowpack may not necessarily correspond to the same stratigraphic horizon. In addition, such errors accumulate during the course of a snow season. Altogether, this makes it particularly difficult to disentangle errors due to the snowpack model itself (which is the primary goal of such comparisons) from other sources of errors. This presentation will review various approaches already developed (e.g. Lehning and Fierz, CRST 2001) and introduce yet-to-implement methods, with the aim to provide a framework allowing improved comparisons between observed and simulated snow profiles, which is a long-lasting need of the snow modelling community.

  5. Hybrid diffusion and two-flux approximation for multilayered tissue light propagation modeling

    NASA Astrophysics Data System (ADS)

    Yudovsky, Dmitry; Durkin, Anthony J.

    2011-07-01

    Accurate and rapid estimation of fluence, reflectance, and absorbance in multilayered biological media has been essential in many biophotonics applications that aim to diagnose, cure, or model in vivo tissue. The radiative transfer equation (RTE) rigorously models light transfer in absorbing and scattering media. However, analytical solutions to the RTE are limited even in simple homogeneous or plane media. Monte Carlo simulation has been used extensively to solve the RTE. However, Monte Carlo simulation is computationally intensive and may not be practical for applications that demand real-time results. Instead, the diffusion approximation has been shown to provide accurate estimates of light transport in strongly scattering tissue. The diffusion approximation is a greatly simplified model and produces analytical solutions for the reflectance and absorbance in tissue. However, the diffusion approximation breaks down if tissue is strongly absorbing, which is common in the visible part of the spectrum or in applications that involve darkly pigmented skin and/or high local volumes of blood such as port-wine stain therapy or reconstructive flap monitoring. In these cases, a model of light transfer that can accommodate both strongly and weakly absorbing regimes is required. Here we present a model of light transfer through layered biological media that represents skin with two strongly scattering and one strongly absorbing layer.

  6. Electromagnetic fields inside a lossy, multilayered spherical head phantom excited by MRI coils: models and methods.

    PubMed

    Liu, Feng; Crozier, Stuart

    2004-05-21

    The precise evaluation of electromagnetic field (EMF) distributions inside biological samples is becoming an increasingly important design requirement for high field MRI systems. In evaluating the induced fields caused by magnetic field gradients and RF transmitter coils, a multilayered dielectric spherical head model is proposed to provide a better understanding of electromagnetic interactions when compared to a traditional homogeneous head phantom. This paper presents Debye potential (DP) and Dyadic Green's function (DGF)-based solutions of the EMFs inside a head-sized, stratified sphere with similar radial conductivity and permittivity profiles as a human head. The DP approach is formulated for the symmetric case in which the source is a circular loop carrying a harmonic-formed current over a wide frequency range. The DGF method is developed for generic cases in which the source may be any kind of RF coil whose current distribution can be evaluated using the method of moments. The calculated EMFs can then be used to deduce MRI imaging parameters. The proposed methods, while not representing the full complexity of a head model, offer advantages in rapid prototyping as the computation times are much lower than a full finite difference time domain calculation using a complex head model. Test examples demonstrate the capability of the proposed models/methods. It is anticipated that this model will be of particular value for high field MRI applications, especially the rapid evaluation of RF resonator (surface and volume coils) and high performance gradient set designs.

  7. A multi-layer land surface energy budget model for implicit coupling with global atmospheric simulations

    NASA Astrophysics Data System (ADS)

    Ryder, J.; Polcher, J.; Peylin, P.; Ottlé, C.; Chen, Y.; van Gorsel, E.; Haverd, V.; McGrath, M. J.; Naudts, K.; Otto, J.; Valade, A.; Luyssaert, S.

    2014-12-01

    In Earth system modelling, a description of the energy budget of the vegetated surface layer is fundamental as it determines the meteorological conditions in the planetary boundary layer and as such contributes to the atmospheric conditions and its circulation. The energy budget in most Earth system models has long been based on a "big-leaf approach", with averaging schemes that represent in-canopy processes. Such models have difficulties in reproducing consistently the energy balance in field observations. We here outline a newly developed numerical model for energy budget simulation, as a component of the land surface model ORCHIDEE-CAN (Organising Carbon and Hydrology In Dynamic Ecosystems - CANopy). This new model implements techniques from single-site canopy models in a practical way. It includes representation of in-canopy transport, a multilayer longwave radiation budget, height-specific calculation of aerodynamic and stomatal conductance, and interaction with the bare soil flux within the canopy space. Significantly, it avoids iterations over the height of tha canopy and so maintains implicit coupling to the atmospheric model LMDz. As a first test, the model is evaluated against data from both an intensive measurement campaign and longer term eddy covariance measurements for the intensively studied Eucalyptus stand at Tumbarumba, Australia. The model performs well in replicating both diurnal and annual cycles of fluxes, as well as the gradients of sensible heat fluxes. However, the model overestimates sensible heat flux against an underestimate of the radiation budget. Improved performance is expected through the implementation of a more detailed calculation of stand albedo and a more up-to-date stomatal conductance calculation.

  8. The development of a composite bone model for training on placement of dental implants

    PubMed Central

    Alkhodary, Mohamed Ahmed; Abdelraheim, Abdelraheim Emad Eldin; Elsantawy, Abd Elaleem Hassan; Al Dahman, Yousef Hamad; Al-Mershed, Mohammed

    2015-01-01

    Objectives It takes a lot of training on patients for both undergraduate to develop clinical sense as regards to the placement of dental implants in the jaw bones, also, the models provided by the dental implant companies for training are usually made of strengthened synthetic foams, which are far from the composition, and tactile sense provided by natural bone during drilling for clinical placement of dental implants. Methodology This is an in-vitro experimental study which utilized bovine femur bone, where the shaft of the femur provided the surface compact layer, and the head provided the cancellous bone layer, to provide a training model similar to jaw bones macroscopic anatomy. Both the compact and cancellous bone samples were characterized using mechanical compressive testing. Results The elastic moduli of the cancellous and cortical femur bone were comparable to those of the human mandible, and the prepared training model provided a more lifelike condition during the drilling and placement of dental implants. Conclusion The composite bone model developed simulated the macroscopic anatomy of the jaw bones having a surface layer of compact bone, and a core of cancellous bone, and provided a better and a more natural hands-on experience for placement of dental implants as compared to plastic models made of polyurethane. PMID:26309434

  9. New Dental Accreditation Standard on Critical Thinking: A Call for Learning Models, Outcomes, Assessments.

    PubMed

    Johnsen, David C; Williams, John N; Baughman, Pauletta Gay; Roesch, Darren M; Feldman, Cecile A

    2015-10-01

    This opinion article applauds the recent introduction of a new dental accreditation standard addressing critical thinking and problem-solving, but expresses a need for additional means for dental schools to demonstrate they are meeting the new standard because articulated outcomes, learning models, and assessments of competence are still being developed. Validated, research-based learning models are needed to define reference points against which schools can design and assess the education they provide to their students. This article presents one possible learning model for this purpose and calls for national experts from within and outside dental education to develop models that will help schools define outcomes and assess performance in educating their students to become practitioners who are effective critical thinkers and problem-solvers.

  10. A Multilayer Naïve Bayes Model for Analyzing User's Retweeting Sentiment Tendency.

    PubMed

    Wang, Mengmeng; Zuo, Wanli; Wang, Ying

    2015-01-01

    Today microblogging has increasingly become a means of information diffusion via user's retweeting behavior. Since retweeting content, as context information of microblogging, is an understanding of microblogging, hence, user's retweeting sentiment tendency analysis has gradually become a hot research topic. Targeted at online microblogging, a dynamic social network, we investigate how to exploit dynamic retweeting sentiment features in retweeting sentiment tendency analysis. On the basis of time series of user's network structure information and published text information, we first model dynamic retweeting sentiment features. Then we build Naïve Bayes models from profile-, relationship-, and emotion-based dimensions, respectively. Finally, we build a multilayer Naïve Bayes model based on multidimensional Naïve Bayes models to analyze user's retweeting sentiment tendency towards a microblog. Experiments on real-world dataset demonstrate the effectiveness of the proposed framework. Further experiments are conducted to understand the importance of dynamic retweeting sentiment features and temporal information in retweeting sentiment tendency analysis. What is more, we provide a new train of thought for retweeting sentiment tendency analysis in dynamic social networks. PMID:26417367

  11. Wideband dynamic behavioral modeling of reflective semiconductor optical amplifiers using a tapped-delay multilayer perceptron.

    PubMed

    Liu, Zhansheng; Violas, Manuel Alberto; Carvalho, Nuno Borges

    2013-02-11

    In this paper, we propose a wideband dynamic behavioral model for a bulk reflective semiconductor optical amplifier (RSOA) used as a modulator in colorless radio over fiber (RoF) systems using a tapped-delay multilayer perceptron (TDMLP). 64 quadrature amplitude modulation (QAM) signals with 20 Msymbol/s were used to train, validate and test the model. Nonlinear distortion and dynamic effects induced by the RSOA modulator are demonstrated. The parameters of the model such as the number of nodes in the hidden layer and memory depth were optimized to ensure the generality and accuracy. The normalized mean square error (NMSE) is used as a figure of merit. The NMSE was up to -44.33 dB when the number of nodes in the hidden layer and memory depth were set to 20 and 3, respectively. The TDMLP model can accurately approximate to the dynamic characteristics of the RSOA modulator. The dynamic AM-AM and dynamic AM-PM distortions of the RSOA modulator are drawn. The results show that the single hidden layer TDMLP can provide accurate approximation for behaviors of the RSOA modulator.

  12. A Multilayer Naïve Bayes Model for Analyzing User's Retweeting Sentiment Tendency.

    PubMed

    Wang, Mengmeng; Zuo, Wanli; Wang, Ying

    2015-01-01

    Today microblogging has increasingly become a means of information diffusion via user's retweeting behavior. Since retweeting content, as context information of microblogging, is an understanding of microblogging, hence, user's retweeting sentiment tendency analysis has gradually become a hot research topic. Targeted at online microblogging, a dynamic social network, we investigate how to exploit dynamic retweeting sentiment features in retweeting sentiment tendency analysis. On the basis of time series of user's network structure information and published text information, we first model dynamic retweeting sentiment features. Then we build Naïve Bayes models from profile-, relationship-, and emotion-based dimensions, respectively. Finally, we build a multilayer Naïve Bayes model based on multidimensional Naïve Bayes models to analyze user's retweeting sentiment tendency towards a microblog. Experiments on real-world dataset demonstrate the effectiveness of the proposed framework. Further experiments are conducted to understand the importance of dynamic retweeting sentiment features and temporal information in retweeting sentiment tendency analysis. What is more, we provide a new train of thought for retweeting sentiment tendency analysis in dynamic social networks.

  13. Multilayer Perceptron Model for Nowcasting Visibility from Surface Observations: Results and Sensitivity to Dissimilar Station Altitudes

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Sutapa; Das, Debanjana; Sarkar, Ishita; Goswami, Sayantika

    2015-10-01

    The reduction in the visibility during fog significantly influences surface as well as air transport operations. The prediction of fog remains difficult despite improvements in numerical weather prediction models. The present study aims at identifying a suitable neural network model with proper architecture to provide precise nowcast of the horizontal visibility during fog over the airports of three significantly affected metropolises of India, namely: Kolkata (22°32'N; 88°20'E), Delhi (28°38'N; 77°12'E) and Bengaluru (12°95'N; 77°72'E). The investigation shows that the multilayer perceptron (MLP) model provides considerably less error in nowcasting the visibility during fog over the said metropolises than radial basis function network, generalized regression neural network or linear neural network. The MLP models of different architectures are trained with the data and records from 2000 to 2010. The model results are validated with observations from 2011 to 2014. Our results reveal that MLP models with different configurations (1) four input layers, three hidden layers with three hidden nodes in each layer and a single output; (2) four input layers with two hidden layers having one hidden node in the first hidden layer and two hidden nodes in the second hidden layer, and a single output layer; and (3) four input layers with two hidden layers having two hidden nodes in each hidden layer and a single output layer] provide minimum error in nowcasting the visibility during fog over the airports of Kolkata, Delhi and Bengaluru, respectively. The results show that the MLP model is well suited for nowcasting visibility during fog with 6 h lead time, however, the study reveals that the MLP model sensitive to dissimilar station altitudes in nowcasting visibility, as the minimum prediction error for the three metropolises having dissimilar mean sea level altitudes is observed through different configurations of the model.

  14. Multifunctional lipid multilayer stamping.

    PubMed

    Nafday, Omkar A; Lowry, Troy W; Lenhert, Steven

    2012-04-10

    Nanostructured lipid multilayers on surfaces are a promising biofunctional nanomaterial. For example, surface-supported lipid multilayer diffraction gratings with optical properties that depend on the microscale spacing of the grating lines and the nanometer thickness of the lipid multilayers have been fabricated previously by dip-pen nanolithography (DPN), with immediate applications as label-free biosensors. The innate biocompatibility of such gratings makes them promising as biological sensor elements, model cellular systems, and construction materials for nanotechnology. Here a method is described that combines the lateral patterning capabilities and scalability of microcontact printing with the topographical control of nanoimprint lithography and the multimaterial integration aspects of dip-pen nanolithography in order to create nanostructured lipid multilayer arrays. This approach is denoted multilayer stamping. The distinguishing characteristic of this method is that it allows control of the lipid multilayer thickness, which is a crucial nanoscale dimension that determines the optical properties of lipid multilayer nanostructures. The ability to integrate multiple lipid materials on the same surface is also demonstrated by multi-ink spotting onto a polydimethoxysilane stamp, as well as higher-throughput patterning (on the order of 2 cm(2) s(-1) for grating fabrication) and the ability to pattern lipid materials that could not previously be patterned with high resolution by lipid DPN, for example, the gel-phase phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or the steroid cholesterol. PMID:22307810

  15. A Model for Dental Practice in the 21st Century

    PubMed Central

    Eaves, Kayleigh

    2011-01-01

    The dental profession is responsible for the prevention, diagnosis, and treatment of diseases and disorders of the oral cavity and related structures. Although the majority of the US population receives excellent oral health care, a significant portion is unable to access regular care. Along with proposals to develop midlevel providers, the scope of practice for dentists needs to be reconceptualized and expanded. A broad number of primary health care activities may be conducted in the dental office, such as screening for hypertension, diabetes mellitus, and dermatopathology; smoking prevention and cessation activities; and obesity interventions. More than 70% of adults saw a dentist in the past year, which represents an unrealized opportunity to improve both oral health and general health. PMID:21852631

  16. Analytic Element Modeling of Steady Interface Flow in Multilayer Aquifers Using AnAqSim.

    PubMed

    Fitts, Charles R; Godwin, Joshua; Feiner, Kathleen; McLane, Charles; Mullendore, Seth

    2015-01-01

    This paper presents the analytic element modeling approach implemented in the software AnAqSim for simulating steady groundwater flow with a sharp fresh-salt interface in multilayer (three-dimensional) aquifer systems. Compared with numerical methods for variable-density interface modeling, this approach allows quick model construction and can yield useful guidance about the three-dimensional configuration of an interface even at a large scale. The approach employs subdomains and multiple layers as outlined by Fitts (2010) with the addition of discharge potentials for shallow interface flow (Strack 1989). The following simplifying assumptions are made: steady flow, a sharp interface between fresh- and salt water, static salt water, and no resistance to vertical flow and hydrostatic heads within each fresh water layer. A key component of this approach is a transition to a thin fixed minimum fresh water thickness mode when the fresh water thickness approaches zero. This allows the solution to converge and determine the steady interface position without a long transient simulation. The approach is checked against the widely used numerical codes SEAWAT and SWI/MODFLOW and a hypothetical application of the method to a coastal wellfield is presented.

  17. Irreducibility of multilayer network dynamics: the case of the voter model

    NASA Astrophysics Data System (ADS)

    Diakonova, Marina; Nicosia, Vincenzo; Latora, Vito; San Miguel, Maxi

    2016-02-01

    We address the issue of the reducibility of the dynamics on a multilayer network to an equivalent process on an aggregated single-layer network. As a typical example of models for opinion formation in social networks, we implement the voter model on a two-layer multiplex network, and we study its dynamics as a function of two control parameters, namely the fraction of edges simultaneously existing in both layers of the network (edge overlap), and the fraction of nodes participating in both layers (interlayer connectivity or degree of multiplexity). We compute the asymptotic value of the number of active links (interface density) in the thermodynamic limit, and the time to reach an absorbing state for finite systems, and we compare the numerical results with the analytical predictions on equivalent single-layer networks obtained through various possible aggregation procedures. We find a large region of parameters where the interface density of large multiplexes gives systematic deviations from that of the aggregates. We show that neither of the standard unweighted aggregation procedures is able to capture the highly nonlinear increase in the lifetime of a finite size multiplex at small interlayer connectivity. These results indicate that multiplexity should be appropriately taken into account when studying voter model dynamics, and that, in general, single-layer approximations might be not accurate enough to properly understand processes occurring on multiplex networks, since they might flatten out relevant dynamical details.

  18. Multilayered 3D Lidar image construction using spatial models in a Bayesian framework.

    PubMed

    Hernandez-Marin, Sergio; Wallace, Andrew M; Gibson, Gavin J

    2008-06-01

    Standard 3D imaging systems process only a single return at each pixel from an assumed single opaque surface. However, there are situations when the laser return consists of multiple peaks due to the footprint of the beam impinging on a target with surfaces distributed in depth or with semi-transparent surfaces. If all these returns are processed, a more informative multi-layered 3D image is created. We propose a unified theory of pixel processing for Lidar data using a Bayesian approach that incorporates spatial constraints through a Markov Random Field with a Potts prior model. This allows us to model uncertainty about the underlying spatial process. To palliate some inherent deficiencies of this prior model, we also introduce two proposal distributions, one based on spatial mode jumping, the other on a spatial birth/death process. The different parameters of the several returns are estimated using reversible jump Markov chain Monte Carlo (RJMCMC) techniques in combination with an adaptive strategy of delayed rejection to improve the estimates of the parameters. PMID:18421108

  19. Modeling Dental Health Care Workers' Risk of Occupational Infection from Bloodborne Pathogens.

    ERIC Educational Resources Information Center

    Capilouto, Eli; And Others

    1990-01-01

    The brief paper offers a model which permits quantification of the dental health care workers' risk of occupationally acquiring infection from bloodborne pathogens such as human immunodeficiency virus and hepatitis B virus. The model incorporates five parameters such as the probability that any individual patient is infected and number of patients…

  20. Synthetic, Multi-Layer, Self-Oscillating Vocal Fold Model Fabrication

    PubMed Central

    Murray, Preston R.; Thomson, Scott L.

    2011-01-01

    , however, have either been homogenous (one-layer models) or have been fabricated using two materials of differing stiffness (two-layer models). This approach does not allow for representation of the actual multi-layer structure of the human vocal folds 1 that plays a central role in governing vocal fold flow-induced vibratory response. Consequently, one- and two-layer synthetic vocal fold models have exhibited disadvantages 3,6,8 such as higher onset pressures than what are typical for human phonation (onset pressure is the minimum lung pressure required to initiate vibration), unnaturally large inferior-superior motion, and lack of a "mucosal wave" (a vertically-traveling wave that is characteristic of healthy human vocal fold vibration). In this paper, fabrication of a model with multiple layers of differing material properties is described. The model layers simulate the multi-layer structure of the human vocal folds, including epithelium, superficial lamina propria (SLP), intermediate and deep lamina propria (i.e., ligament; a fiber is included for anterior-posterior stiffness), and muscle (i.e., body) layers 1. Results are included that show that the model exhibits improved vibratory characteristics over prior one- and two-layer synthetic models, including onset pressure closer to human onset pressure, reduced inferior-superior motion, and evidence of a mucosal wave. PMID:22157812

  1. Synthetic, multi-layer, self-oscillating vocal fold model fabrication.

    PubMed

    Murray, Preston R; Thomson, Scott L

    2011-01-01

    been homogenous (one-layer models) or have been fabricated using two materials of differing stiffness (two-layer models). This approach does not allow for representation of the actual multi-layer structure of the human vocal folds that plays a central role in governing vocal fold flow-induced vibratory response. Consequently, one- and two-layer synthetic vocal fold models have exhibited disadvantages such as higher onset pressures than what are typical for human phonation (onset pressure is the minimum lung pressure required to initiate vibration), unnaturally large inferior-superior motion, and lack of a "mucosal wave" (a vertically-traveling wave that is characteristic of healthy human vocal fold vibration). In this paper, fabrication of a model with multiple layers of differing material properties is described. The model layers simulate the multi-layer structure of the human vocal folds, including epithelium, superficial lamina propria (SLP), intermediate and deep lamina propria (i.e., ligament; a fiber is included for anterior-posterior stiffness), and muscle (i.e., body) layers. Results are included that show that the model exhibits improved vibratory characteristics over prior one- and two-layer synthetic models, including onset pressure closer to human onset pressure, reduced inferior-superior motion, and evidence of a mucosal wave.

  2. Multilayer in-place learning networks for modeling functional layers in the laminar cortex.

    PubMed

    Weng, Juyang; Luwang, Tianyu; Lu, Hong; Xue, Xiangyang

    2008-01-01

    Currently, there is a lack of general-purpose in-place learning networks that model feature layers in the cortex. By "general-purpose" we mean a general yet adaptive high-dimensional function approximator. In-place learning is a biological concept rooted in the genomic equivalence principle, meaning that each neuron is fully responsible for its own learning in its environment and there is no need for an external learner. Presented in this paper is the Multilayer In-place Learning Network (MILN) for this ambitious goal. Computationally, in-place learning provides unusually efficient learning algorithms whose simplicity, low computational complexity, and generality are set apart from typical conventional learning algorithms. Based on the neuroscience literature, we model the layer 4 and layer 2/3 as the feature layers in the 6-layer laminar cortex, with layer 4 using unsupervised learning and layer 2/3 using supervised learning. As a necessary requirement for autonomous mental development, MILN generates invariant neurons in different layers, with increasing invariance from earlier to later layers and the total invariance in the last motor layer. Such self-generated invariant representation is enabled mainly by descending (top-down) connections. The self-generated invariant representation is used as intermediate representations for learning later tasks in open-ended development. PMID:18314307

  3. Examining the impact of multi-layer graphene using cellular and amphibian models

    NASA Astrophysics Data System (ADS)

    Muzi, Laura; Mouchet, Florence; Cadarsi, Stéphanie; Janowska, Izabela; Russier, Julie; Ménard-Moyon, Cécilia; Risuleo, Gianfranco; Soula, Brigitte; Galibert, Anne-Marie; Flahaut, Emmanuel; Pinelli, Eric; Gauthier, Laury; Bianco, Alberto

    2016-06-01

    In the last few years, graphene has been defined as the revolutionary material showing an incredible expansion in industrial applications. Different graphene forms have been applied in several contexts, spreading from energy technologies and electronics to food and agriculture technologies. Graphene showed promises also in the biomedical field. Hopeful results have been already obtained in diagnostic, drug delivery, tissue regeneration and photothermal cancer ablation. In view of the enormous development of graphene-based technologies, a careful assessment of its impact on health and environment is demanded. It is evident how investigating the graphene toxicity is of fundamental importance in the context of medical purposes. On the other hand, the nanomaterial present in the environment, likely to be generated all along the industrial life-cycle, may have harmful effects on living organisms. In the present work, an important contribution on the impact of multi-layer graphene (MLG) on health and environment is given by using a multifaceted approach. For the first purpose, the effect of the material on two mammalian cell models was assessed. Key cytotoxicity parameters were considered such as cell viability and inflammatory response induction. This was combined with an evaluation of MLG toxicity towards Xenopus laevis, used as both in vivo and environmental model organism.

  4. Spectroscopic investigation of the wettability of multilayer graphene using highly ordered pyrolytic graphite as a model material.

    PubMed

    Ashraf, Ali; Wu, Yanbin; Wang, Michael C; Aluru, Narayana R; Dastgheib, Seyed A; Nam, SungWoo

    2014-11-01

    We report the intrinsic water contact angle (WCA) of multilayer graphene, explore different methods of cleaning multilayer graphene, and evaluate the efficiency of those methods on the basis of spectroscopic analysis. Highly ordered pyrolytic graphite (HOPG) was used as a model material system to study the wettability of the multilayer graphene surface by WCA measurements. A WCA value of 45° ± 3° was measured for a clean HOPG surface, which can serve as the intrinsic WCA for multilayer graphene. A 1 min plasma treatment (100 W) decreased the WCA to 6°, owing to the creation of surface defects and functionalization by oxygen-containing groups. Molecular dynamics simulations of water droplets on the HOPG surface with or without the oxygen-containing defect sites confirmed the experimental results. Heat treatment at near atmospheric pressure and wet chemical cleaning methods using hydrofluoric acid and chloroform did not change the WCA significantly. Low-pressure, high-temperature annealing under argon and hydrogen reduced the WCA to 54°, close to the intrinsic WCA of HOPG. Raman spectroscopy and atomic force microscopy did not show any significant change for the HOPG surface after this treatment, confirming low-pressure, high-temperature annealing as an effective technique to clean multilayer graphene without damaging the surface. Time-of-flight secondary ion mass spectrometry indicated the existence of hydrocarbon species on the surface of the HOPG sample that was exposed to air for <5 min and the absence of these impurities in the bulk. X-ray photoelectron spectroscopy analyses of the sample surfaces after the different cleaning techniques were performed to correlate the WCA to the surface chemistry. X-ray photoelectron spectroscopy results revealed that the WCA value changed drastically, depending on the amounts of oxygen-containing and hydrocarbon-containing groups on the surface.

  5. Anisotropic constitutive model incorporating multiple damage mechanisms for multiscale simulation of dental enamel.

    PubMed

    Ma, Songyun; Scheider, Ingo; Bargmann, Swantje

    2016-09-01

    An anisotropic constitutive model is proposed in the framework of finite deformation to capture several damage mechanisms occurring in the microstructure of dental enamel, a hierarchical bio-composite. It provides the basis for a homogenization approach for an efficient multiscale (in this case: multiple hierarchy levels) investigation of the deformation and damage behavior. The influence of tension-compression asymmetry and fiber-matrix interaction on the nonlinear deformation behavior of dental enamel is studied by 3D micromechanical simulations under different loading conditions and fiber lengths. The complex deformation behavior and the characteristics and interaction of three damage mechanisms in the damage process of enamel are well captured. The proposed constitutive model incorporating anisotropic damage is applied to the first hierarchical level of dental enamel and validated by experimental results. The effect of the fiber orientation on the damage behavior and compressive strength is studied by comparing micro-pillar experiments of dental enamel at the first hierarchical level in multiple directions of fiber orientation. A very good agreement between computational and experimental results is found for the damage evolution process of dental enamel.

  6. Anisotropic constitutive model incorporating multiple damage mechanisms for multiscale simulation of dental enamel.

    PubMed

    Ma, Songyun; Scheider, Ingo; Bargmann, Swantje

    2016-09-01

    An anisotropic constitutive model is proposed in the framework of finite deformation to capture several damage mechanisms occurring in the microstructure of dental enamel, a hierarchical bio-composite. It provides the basis for a homogenization approach for an efficient multiscale (in this case: multiple hierarchy levels) investigation of the deformation and damage behavior. The influence of tension-compression asymmetry and fiber-matrix interaction on the nonlinear deformation behavior of dental enamel is studied by 3D micromechanical simulations under different loading conditions and fiber lengths. The complex deformation behavior and the characteristics and interaction of three damage mechanisms in the damage process of enamel are well captured. The proposed constitutive model incorporating anisotropic damage is applied to the first hierarchical level of dental enamel and validated by experimental results. The effect of the fiber orientation on the damage behavior and compressive strength is studied by comparing micro-pillar experiments of dental enamel at the first hierarchical level in multiple directions of fiber orientation. A very good agreement between computational and experimental results is found for the damage evolution process of dental enamel. PMID:27294283

  7. Recent Advances in Modeling Stress Distributions in Multilayers Subjected to Biaxial Flexure Tests

    SciTech Connect

    Hsueh, Chun-Hway; Luttrell, Claire Roberta

    2007-01-01

    Although biaxial flexure tests have been used extensively to measure the strength of brittle materials, the tests and analyses have been limited to materials of uniform properties. Despite the increasing applications of multilayered structures, characterization of their strengths using biaxial flexure tests has been difficult because the analytical description of the strength-fracture load relation for multilayers subjected to biaxial flexure tests is unavailable. The newly derived closed-form solutions for the elastic stress distributions in multilayered discs subjected to ring-on-ring tests are summarized here. These solutions are obtained by (i) finding the correlation between monolayered and multilayered discs subjected to biaxial bending moment and (ii) conversion from the existing solutions for monolayers. Using this methodology, the closed-form solutions for multilayers subjected to other biaxial flexure tests can also be obtained. Finite element results for ring-on-rings tests performed on (i) porcelain/zirconia bilayered discs and (ii) solid oxide fuel cells trilayered discs are also presented to validate the closed-form solutions. The closed-form solutions hence provide a basis for evaluating biaxial strength of multilayers using biaxial flexure tests.

  8. A ceramic damage model for analyses of multi-layered ceramic-core sandwich panels under blast wave pressure loading

    NASA Astrophysics Data System (ADS)

    Lee, Keejoo

    2005-11-01

    A damage model for ceramic materials is developed and incorporated into the geometrically nonlinear solid shell element formulation for dynamic analyses of multi-layered ceramic armor panels under blast wave pressure loading. The damage model takes into account material behaviors observed from multi-axial dynamic tests on Aluminum Nitride (AlN) ceramic. The ceramic fails in a brittle or gradual fashion, depending upon the hydrostatic pressure and applied strain-rate. In the model, the gradual failure is represented by two states: the initial and final failure states. These states are described by two separate failure surfaces that are pressure-dependent and strain-rate-dependent. A scalar damage parameter is defined via using the two failure surfaces, based on the assumption that the local stress state determines material damage and its level. In addition, the damage model accounts for the effect of existing material damage on the new damage. The multi-layered armor panel of interest is comprised of an AlN-core sandwich with unidirectional composite skins and a woven composite back-plate. To accommodate the material damage effect of composite layers, a composite failure model in the open literature is adopted and modified into two separate failure models to address different failure mechanisms of the unidirectional and woven composites. In addition, the effect of strain-rates on the material strengths is incorporated into the composite failure models. For finite element modeling, multiple eighteen-node elements are used in the thickness direction to properly describe mechanics of the multi-layered panel. Dynamic analyses of a multi-layered armor panel are conducted under blast wave pressure loadings. The resulting dynamic responses of the panel demonstrate that dynamic analyses that do not take into account material damage and failure significantly under-predict the peak displacement. The under-prediction becomes more pronounced as the blast load level increases

  9. Modeling and finite element analysis of the nonstationary action on a multi-layer poroelastic seam with nonlinear geomechanical properties

    SciTech Connect

    Nasedkina, A.A.; Nasedkin, A.V.; Iovane, G.

    2009-07-15

    The paper discusses modeling of a multi-layer coal seam under hydrodynamic action based on the coupled equations of poroelasticity and filtration with the nonlinear relationship of permeability and porous pressure. The calculations by the finite element method use correspondence between the poroelasticity and thermoelasticity equations. The influence of input data on the size of a degassing hole area is analyzed for the couple problem and pure filtration problem.

  10. Dynamics of multilayer, multidisc viscoelastic rotor - An operator based higher order classical model

    NASA Astrophysics Data System (ADS)

    Roy, H.; Chandraker, S.; Dutt, J. K.; Roy, T.

    2016-05-01

    Inherent material damping plays a very significant role on dynamic behaviour of rotors. The material damping in a spinning rotor produces a tangential force along the whirl direction and its magnitude being proportional to spin speed. After certain value of spin speed, decided by the characteristic of the system, the tangential force becomes strong enough to throw the rotor centre out of the whirl orbit by inflating it progressively. This leads to destabilization of the system and corresponding speed is known as stability limit of spin speed. Stability limit of spin speed for Jeffcott rotor, by using viscous form of material damping model is straight forward and has been reported by several researchers, however the same analysis for viscoelastic material characteristics is not reported much. This analysis is very relevant for industrial requirements to replace bulky and heavy metal rotor by light but strong rotors. This is achieved either by reinforcing fibre or multi layering arrangements. Both of which are represented by viscoelastic constitutive behaviour. This paper gives mathematical derivation of equations of motion for multi-disc, multi-layered rotor-shaft-system. Both lumped mass and discretized approach (finite element) are presented here mathematically and numerical simulation results are compared. The lumped mass approach gives a concise yet acceptable accuracy of the results.

  11. Model independent x-ray standing wave analysis of periodic multilayer structures

    SciTech Connect

    Yakunin, S. N.; Pashaev, E. M.; Subbotin, I. A.; Makhotkin, I. A.; Kruijs, R. W. E. van de; Zoethout, E.; Chuev, M. A.; Louis, E.; Seregin, S. Yu.; Novikov, D. V.; Bijkerk, F.; Kovalchuk, M. V.

    2014-04-07

    We present a model independent approach for the analysis of X-ray fluorescence yield modulated by an X-ray standing wave (XSW), that allow a fast reconstruction of the atomic distribution function inside a sample without fitting procedure. The approach is based on the direct regularized solution of the system of linear equations that characterizes the fluorescence yield. The suggested technique was optimized for, but not limited to, the analysis of periodic layered structures where the XSW is formed under Bragg conditions. The developed approach was applied to the reconstruction of the atomic distribution function for LaN/BN multilayers with 50 periods of 43 Å thick layers. The object is especially difficult to analyze with traditional methods, as the estimated thickness of the interface region between the constituent materials is comparable to the individual layer thicknesses. However, using the suggested technique, it was possible to reconstruct width of the La atomic distribution showing that the La atoms stay localized within the LaN layers and interfaces and do not diffuse into the BN layer. The analysis of the reconstructed profiles showed that the positions of the center of the atomic distribution function can be estimated with an accuracy of 1 Å.

  12. A model-based, Bayesian characterization of subsurface corrosion parameters in composite multi-layered structures

    NASA Astrophysics Data System (ADS)

    Reed, Heather; Hoppe, Wally

    2016-02-01

    Thermographic NDE approaches to detect subsurface corrosion defects of multi-layered structures with composite top layers have proven difficult due to the fact that the thermal conductivity of composite materials is larger in lateral directions (the plane parallel to the surface) than in the through-thickness directions. This causes heat to dissipate faster laterally than through the thickness when a heat source is applied to the surface of the structure, making it difficult for subsurface damage effects to manifest on the surface, where the heat source and inspection typically occur. To address this, a heat induction approach is presented that excites the damaged, metallic bottom layer directly by Joule heating, resulting in more observable damage effects on the surface than what could be expected for traditional thermographic methods on this type of structure. To characterize the subsurface damage parameters (defect location, diameter, and depth), Bayesian inversion of numerically-simulated noisy data, using a high-fidelity, coupled electromagnetic-heat transfer model is employed. Stochastic estimation methods such as Markov chain Monte Carlo (MCMC) allow for quantification of uncertainty surrounding the damage parameters, which is important as this directly translates into uncertainty surrounding the component reliability. However, because thousands of high-fidelity finite element models are computationally costly to evaluate, as is typical in most MCMC methods, the use of Bayesian inversion is rarely feasible in real-time. To address this, a projection-based reduced order modeling (ROM) tracking and interpolation scheme is formulated within the MCMC sampling method for the multi-physics problem, resulting in significant speedup of solution time with little loss of accuracy, enabling near-real time stochastic estimation of damage.

  13. JERM model of care: an in-principle model for dental health policy.

    PubMed

    Lam, Raymond; Kruger, Estie; Tennant, Marc

    2014-01-01

    Oral diseases are the most prevalent conditions in the community. Their economic burden is high and their impact on quality of life is profound. There is an increasing body of evidence indicating that oral diseases have wider implications beyond the confines of the mouth. The importance of oral health has not been unnoticed by the government. The Commonwealth (Federal) government under the Howard-led Coalition in 2004 had broken tradition by placing dentistry in its universal health insurance scheme, Medicare. Known as the Chronic Disease Dental Scheme (CDDS), the program aimed to manage patients with chronic conditions as part of the Enhanced Primary Care initiative. This scheme was a landmark policy for several reasons. Besides being the first major dental policy under Medicare, the program proved to be the most expensive and controversial. Unfortunately, cost containment and problems with service provision led to its cessation in 2012 by the Gillard Labor Government. Despite being seen as a failure, the CDDS provided a unique opportunity to assess national policy in practice. By analysing the policy-relevant effects of the CDDS, important lessons can be learnt for policy development. This paper discusses these lessons and has formulated a set of principles recommended for effective oral health policy. The JERM model represents the principles of a justified, economical and research-based model of care. PMID:23927886

  14. JERM model of care: an in-principle model for dental health policy.

    PubMed

    Lam, Raymond; Kruger, Estie; Tennant, Marc

    2014-01-01

    Oral diseases are the most prevalent conditions in the community. Their economic burden is high and their impact on quality of life is profound. There is an increasing body of evidence indicating that oral diseases have wider implications beyond the confines of the mouth. The importance of oral health has not been unnoticed by the government. The Commonwealth (Federal) government under the Howard-led Coalition in 2004 had broken tradition by placing dentistry in its universal health insurance scheme, Medicare. Known as the Chronic Disease Dental Scheme (CDDS), the program aimed to manage patients with chronic conditions as part of the Enhanced Primary Care initiative. This scheme was a landmark policy for several reasons. Besides being the first major dental policy under Medicare, the program proved to be the most expensive and controversial. Unfortunately, cost containment and problems with service provision led to its cessation in 2012 by the Gillard Labor Government. Despite being seen as a failure, the CDDS provided a unique opportunity to assess national policy in practice. By analysing the policy-relevant effects of the CDDS, important lessons can be learnt for policy development. This paper discusses these lessons and has formulated a set of principles recommended for effective oral health policy. The JERM model represents the principles of a justified, economical and research-based model of care.

  15. International Oral Care: a proposed model for the humanitarian dental missions.

    PubMed

    Marrelli, Massimo; Panaia, Vincenzo; Marrelli, Doriana; Tatullo, Marco

    2014-09-01

    The creation of a good "field hospital" operating in the humanitarian missions has ever been the main aim to reach in any humanitarian missions. The Authors want to propose a model for all the humanitarian dental missions, so to standardize the activities and to make the results predictable in all the missions: this model has been named "International Oral Care" project. In the light of the experiences in the previous humanitarian missions, we have developed and standardized a protocol that provides a complex organizational planning for each phase of the mission. Our strengths are the "Dental-Marquee", the"Dental-Ambulance", the "Dental-Roulotte" and a well-tested operative workflow. In the last 3 years of activity on the field, International Oral Care has achieved an increase of treated patients, certainly consequential to the increase of operators on the field, but also due to the optimization of internal processes and the improvement of organizational structures. IOC has achieved in recent years an organization optimized and highly predictable: this makes it a model for humanitarian missions in the field of dentistry, a model that could be adopted also by international NGOs operating in war zones, or in the major natural disasters.

  16. An Articulation Model in Dental Assisting for the Commonwealth of Pennsylvania. A Continuation.

    ERIC Educational Resources Information Center

    Sylves, Jane M.; Boody, Sandra

    A curriculum development project was conducted to generate additional competency-based modules to be used within the articulation model for Pennsylvania dental assisting programs, established in 1988. Project activities included reviewing, modifying, and providing parallel competency-based structure for the courses at the A.W. Beattie Technical…

  17. Dental Amalgam

    MedlinePlus

    ... Products and Medical Procedures Dental Devices Dental Amalgam Dental Amalgam Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Dental amalgam is a dental filling material which is ...

  18. A Fully Self-consistent Multi-layered Model of Jupiter

    NASA Astrophysics Data System (ADS)

    Kong, Dali; Zhang, Keke; Schubert, Gerald

    2016-08-01

    We construct a three-dimensional, fully self-consistent, multi-layered, non-spheroidal model of Jupiter consisting of an inner core, a metallic electrically conducting dynamo region, and an outer molecular electrically insulating envelope. We assume that the Jovian zonal winds are on cylinders parallel to the rotation axis but, due to the effect of magnetic braking, are confined within the outer molecular envelope. We also assume that the location of the molecular-metallic interface is characterized by its equatorial radius {{HR}}e, where R e is the equatorial radius of Jupiter at the 1 bar pressure level and H is treated as a parameter of the model. We solve the relevant mathematical problem via a perturbation approach. The leading-order problem determines the density, size, and shape of the inner core, the irregular shape of the 1 bar pressure level, and the internal structure of Jupiter that accounts for the full effect of rotational distortion, but without the influence of the zonal winds; the next-order problem determines the variation of the gravitational field solely caused by the effect of the zonal winds on the rotationally distorted non-spheroidal Jupiter. The leading-order solution produces the known mass, the known equatorial and polar radii, and the known zonal gravitational coefficient J 2 of Jupiter within their error bars; it also yields the coefficients J 4 and J 6 within about 5% accuracy, the core equatorial radius 0.09{R}e and the core density {ρ }c=2.0× {10}4 {{kg}} {{{m}}}-3 corresponding to 3.73 Earth masses; the next-order solution yields the wind-induced variation of the zonal gravitational coefficients of Jupiter.

  19. Multilayer Perceptron applied to Data Assimilation for the Global FSU Atmospheric Model

    NASA Astrophysics Data System (ADS)

    Cocke, S.; Cintra, R. S.; Campos Velho, H. F.

    2015-12-01

    The better quality of forecasts is given the more accurate of the initial conditions. Data assimilation (DA) is the process by which short-forecast and observations are combined to obtain an accurate representation of the state of the modeled system, e.g. is a technique to generate an initial condition to a weather forecasts. This paper shows the results of a DA technique using artificial neural networks (NN) to obtain the analysis to the atmospheric model for the Florida State University. The Local Ensemble Transform Kalman filter (LETKF) is implemented with Florida State University Global Spectral Model (FSUGSM). The ANN data assimilation is made to emulate the initial condition from LETKF to run the FSUGSM. LETKF is a version of Kalman filter with Monte-Carlo ensembles of short-term forecasts to solve the data assimilation problem. The model FSUGSM is a multilevel spectral primitive equation model with vertical sigma coordinates, at resolution T63L27. The data assimilation experiments are based in simulated observations data and FSUGSM 6-hours forecasts. For the NN data assimilation, we use Multilayer Perceptron (MLP) with supervised training algorithm where NN receives input vectors with their corresponding response from LETKF data assimilation. The surface pressure, absolute temperature, zonal component wind, meridional component wind and humidity results are presented. A self-configuration method finds the optimal NN and configures a set of 52 MLPs to DA experiment, referred as MLP-DA. A methodology developed with self-configuration using a meta-heuristic called the Multiple Particle Collision Algorithm to compute the optimal topology for NN. The MLP presents four input nodes, two nodes coordinates vector, one for the 6-hours forecast vector and one node for observation vector; one output node for the analysis vector results. The vector represents the values for one grid model point. The ANNs were trained with data from each month of 2001, 2002, and 2003. The

  20. Multiscale Simulation and Modeling of Multilayer Heteroepitactic Growth of C60 on Pentacene.

    PubMed

    Acevedo, Yaset M; Cantrell, Rebecca A; Berard, Philip G; Koch, Donald L; Clancy, Paulette

    2016-03-29

    We apply multiscale methods to describe the strained growth of multiple layers of C60 on a thin film of pentacene. We study this growth in the presence of a monolayer pentacene step to compare our simulations to recent experimental studies by Breuer and Witte of submonolayer growth in the presence of monolayer steps. The molecular-level details of this organic semiconductor interface have ramifications on the macroscale structural and electronic behavior of this system and allow us to describe several unexplained experimental observations for this system. The growth of a C60 thin film on a pentacene surface is complicated by the differing crystal habits of the two component species, leading to heteroepitactical growth. In order to probe this growth, we use three computational methods that offer different approaches to coarse-graining the system and differing degrees of computational efficiency. We present a new, efficient reaction-diffusion continuum model for 2D systems whose results compare well with mesoscale kinetic Monte Carlo (KMC) results for submonolayer growth. KMC extends our ability to simulate multiple layers but requires a library of predefined rates for event transitions. Coarse-grained molecular dynamics (CGMD) circumvents KMC's need for predefined lattices, allowing defects and grain boundaries to provide a more realistic thin film morphology. For multilayer growth, in this particularly suitable candidate for coarse-graining, CGMD is a preferable approach to KMC. Combining the results from these three methods, we show that the lattice strain induced by heteroepitactical growth promotes 3D growth and the creation of defects in the first monolayer. The CGMD results are consistent with experimental results on the same system by Conrad et al. and by Breuer and Witte in which C60 aggregates change from a 2D structure at low temperature to 3D clusters along the pentacene step edges at higher temperatures.

  1. Organic overlayer model of a dental composite analyzed by laser desorption postionization mass spectrometry and photoemission.

    PubMed

    Zhou, Manshui; Wu, Chunping; Edirisinghe, Praneeth D; Drummond, James L; Hanley, Luke

    2006-04-01

    Some dental composites consist of a polymerizable resin matrix bound to glass filler particles by silane coupling agents. The resin in these composites includes bisphenol A diglycidyl methacrylate (Bis-GMA) as well as other organic components. Silane coupling agents such as 3-(trimethoxysilyl) propyl methacrylate (MPS) have been used to improve the mechanical properties of the dental composites by forming a covalent bond between the glass filler particles and the resin. These resin-glass composites undergo material property changes during exposure to the oral environment, but degradation studies of the commercial composites are severely limited by their chemical complexity. A simplified model of the dental composite has been developed, which captures the essential chemical characteristics of the filler particle-silane-resin interface. This model system consists of the resin matrix compound Bis-GMA covalently bound via a methacryloyl overlayer to amorphous silicon oxide (SiO2) surface via a siloxane bond. Scanning electron microscopy shows the porous characteristic and elemental composition of the SiO2 film, which approximately mimics that of the glass filler particles used in dental composites. LDPI MS and XPS verify the chemistry and morphology of the Bis-GMA-methacryloyl overlayer. Preliminary results demonstrate that LDPI MS will be able to follow the chemical processes resulting from aging Bis-GMA-methacryloyl overlayers aged in water, artificial saliva, or other aging solutions.

  2. Implementation of a 3d numerical model of a folded multilayer carbonate aquifer

    NASA Astrophysics Data System (ADS)

    Di Salvo, Cristina; Guyennon, Nicolas; Romano, Emanuele; Bruna Petrangeli, Anna; Preziosi, Elisabetta

    2016-04-01

    The main objective of this research is to present a case study of the numerical model implementation of a complex carbonate, structurally folded aquifer, with a finite difference, porous equivalent model. The case study aquifer (which extends over 235 km2 in the Apennine chain, Central Italy) provides a long term average of 3.5 m3/s of good quality groundwater to the surface river network, sustaining the minimum vital flow, and it is planned to be exploited in the next years for public water supply. In the downstream part of the river in the study area, a "Site of Community Importance" include the Nera River for its valuable aquatic fauna. However, the possible negative effects of the foreseen exploitation on groundwater dependent ecosystems are a great concern and model grounded scenarios are needed. This multilayer aquifer was conceptualized as five hydrostratigraphic units: three main aquifers (the uppermost unconfined, the central and the deepest partly confined), are separated by two locally discontinuous aquitards. The Nera river cuts through the two upper aquifers and acts as the main natural sink for groundwater. An equivalent porous medium approach was chosen. The complex tectonic structure of the aquifer requires several steps in defining the conceptual model; the presence of strongly dipping layers with very heterogeneous hydraulic conductivity, results in different thicknesses of saturated portions. Aquifers can have both unconfined or confined zones; drying and rewetting must be allowed when considering recharge/discharge cycles. All these characteristics can be included in the conceptual and numerical model; however, being the number of flow and head target scarce, the over-parametrization of the model must be avoided. Following the principle of parsimony, three steady state numerical models were developed, starting from a simple model, and then adding complexity: 2D (single layer), QUASI -3D (with leackage term simulating flow through aquitards) and

  3. Mathematical modeling to predict the sub-bandage pressure on a conical limb for multi-layer bandaging.

    PubMed

    Sikka, M P; Ghosh, S; Mukhopadhyay, A

    2016-09-01

    The effectiveness of the compression treatment by a medical compression bandage is dependent on the pressure generated at the interface between the bandage and the skin. This pressure is called interface pressure or sub-bandage pressure. The performance of a bandage depends upon the level of interface pressure applied by the bandage and the sustenance of this pressure over time. The interface pressure exerted by the bandage depends on several other factors like limb shape or size, application technique, physical and structural properties of the bandage, physical activities taken by the patient, etc. The current understanding of how bandages apply pressure to a limb is based on the Law of Laplace, which states that tension in the walls of a container is dependent on both the pressure of the container's content and its radius. This concept was translated mathematically into equation relating pressure to tension and radius by Thomas. In addition, a modified equation was generated by multiplying the model with a constant that represents the number of bandage layers in order to use the model to estimate the pressure applied by multi-layer bandages. This simple multiplication adjustment was questioned by researchers. They had doubts about the model validity and whether it can be used to predict the sub-bandage pressure applied by pressure garments. One of the questions that were raised regarding the bandage thickness affecting the sub-bandage pressure has been recently explored by Al Khaburi where he used the thin and thick cylinder shell theory to study the effect of Multi Component Bandage's (MCB) thickness on the sub-bandage pressure. The model by Al Khaburi and the earlier models developed for pressure prediction are all based on calculations considering the cylindrical limb shapes although the human limb normally is wider at the calf and reduces in circumference towards the ankle. So in our approach, the bandage is assumed to take a conical shape during application

  4. First Principles Modeling of Metal/Ceramic Multilayer Nano-heterostructures.

    SciTech Connect

    Yadav, Satyesh K.; Wang, Jian; Misra, Amit; Liu, Xiang-Yang; Ramprasad, Ramamurthy

    2012-07-31

    Nanoscaled multilayer films composed of metals and ceramics have been explored for their potential applications as ductile, yet strong, materials. It is believed that at the nanoscale, the interfaces between the two materials constituting the multilayer assume an increasingly important role in determining the properties, as they comprise a more significant volume fraction of the multilayer with decreasing layer thickness. In this ab initio work, density functional theory was used to calculate the ideal shear strengths of pure Al, pure TiN, the Al/TiN interfacial region, and Al/TiN multilayers. The ideal shear strength of the Al/TiN interface was found to vary from very low (on the order of the ideal shear strength of Al) to very high (on the order of the ideal shear strength of TiN), depending on whether the TiN at the interface was Ti- or N-terminated, respectively. The results suggest that the shear properties of Al/TiN depend strongly on the chemistry of the interface, Al:N versus Al:Ti terminations. Nevertheless, for the Al/TiN multilayers, the ideal shear strength was limited by shear in the Al layer away from the interface, even when the individual layer thickness is less than a nanometer. Further we found an unusual structural rotation of bulk single-crystal Al under uniaxial compressive strains. It was found that under strains either along the <11-2> or the <111> directions, beyond a critical stress of about 13 GPa, the Al crystal can rotate through shear in the Shockley partial direction (i.e.,<11-2>) on the {l_brace}111{r_brace} plane, in an attempt to relieve internal stresses. This phenomenon reveals a possible mechanism leading to the onset of homogeneous dislocation nucleation in Al under high uniaxial compressions.

  5. 3-dimensional orthodontics visualization system with dental study models and orthopantomograms

    NASA Astrophysics Data System (ADS)

    Zhang, Hua; Ong, S. H.; Foong, K. W. C.; Dhar, T.

    2005-04-01

    The aim of this study is to develop a system that provides 3-dimensional visualization of orthodontic treatments. Dental plaster models and corresponding orthopantomogram (dental panoramic tomogram) are first digitized and fed into the system. A semi-auto segmentation technique is applied to the plaster models to detect the dental arches, tooth interstices and gum margins, which are used to extract individual crown models. 3-dimensional representation of roots, generated by deforming generic tooth models with orthopantomogram using radial basis functions, is attached to corresponding crowns to enable visualization of complete teeth. An optional algorithm to close the gaps between deformed roots and actual crowns by using multi-quadratic radial basis functions is also presented, which is capable of generating smooth mesh representation of complete 3-dimensional teeth. User interface is carefully designed to achieve a flexible system with as much user friendliness as possible. Manual calibration and correction is possible throughout the data processing steps to compensate occasional misbehaviors of automatic procedures. By allowing the users to move and re-arrange individual teeth (with their roots) on a full dentition, this orthodontic visualization system provides an easy and accurate way of simulation and planning of orthodontic treatment. Its capability of presenting 3-dimensional root information with only study models and orthopantomogram is especially useful for patients who do not undergo CT scanning, which is not a routine procedure in most orthodontic cases.

  6. Using a multi-layered transducer model to estimate the properties of paraffin wax deposited on steel.

    PubMed

    Rommetveit, Tarjei; Johansen, Tonni F; Johnsen, Roy

    2011-01-01

    When using ultrasound for detecting low impedance materials on the surface of high impedance materials, a major challenge is the contrast difference between the strong reverberations from the high impedance material and the weak echoes received from the low impedance material. The purpose of this work is to present the theoretical and experimental validation of an ultrasonic methodology for estimating the acoustical properties of paraffin wax on the surface of steel. The method is based on modeling and inversion of the complete electro-acoustic channel from the transmitted voltage over the active piezoelectric element, to the received voltage resulting from the acoustic reverberations in the multilayered structure. In the current work, two conceptually different models of the same multi-layer transducer structure attached to steel is developed and compared with measurements. A method is then suggested for suppressing the strong reverberations in steel, hence isolating the wax signals. This contrast enhancement method is fitted to the model of the structure, facilitating parameter inversion from the wax layer. The results show that the models agree well with measurements and that up to three parameters (travel time, impedance and attenuation) can be inverted from the wax simultaneously. Hence, given one of the three parameters, density, sound speed or thickness, the other two can be estimated in addition to the attenuation.

  7. Evaluation of a Local Anesthesia Simulation Model with Dental Students as Novice Clinicians.

    PubMed

    Lee, Jessica S; Graham, Roseanna; Bassiur, Jennifer P; Lichtenthal, Richard M

    2015-12-01

    The aim of this study was to evaluate the use of a local anesthesia (LA) simulation model in a facilitated small group setting before dental students administered an inferior alveolar nerve block (IANB) for the first time. For this pilot study, 60 dental students transitioning from preclinical to clinical education were randomly assigned to either an experimental group (N=30) that participated in a small group session using the simulation model or a control group (N=30). After administering local anesthesia for the first time, students in both groups were given questionnaires regarding levels of preparedness and confidence when administering an IANB and level of anesthesia effectiveness and pain when receiving an IANB. Students in the experimental group exhibited a positive difference on all six questions regarding preparedness and confidence when administering LA to another student. One of these six questions ("I was prepared in administering local anesthesia for the first time") showed a statistically significant difference (p<0.05). Students who received LA from students who practiced on the simulation model also experienced fewer post-injection complications one day after receiving the IANB, including a statistically significant reduction in trismus. No statistically significant difference was found in level of effectiveness of the IANB or perceived levels of pain between the two groups. The results of this pilot study suggest that using a local anesthesia simulation model may be beneficial in increasing a dental student's level of comfort prior to administering local anesthesia for the first time.

  8. Effects of prepolymerized particle size and polymerization kinetics on volumetric shrinkage of dental modeling resins.

    PubMed

    Kwon, Tae-Yub; Ha, Jung-Yun; Chun, Ju-Na; Son, Jun Sik; Kim, Kyo-Han

    2014-01-01

    Dental modeling resins have been developed for use in areas where highly precise resin structures are needed. The manufacturers claim that these polymethyl methacrylate/methyl methacrylate (PMMA/MMA) resins show little or no shrinkage after polymerization. This study examined the polymerization shrinkage of five dental modeling resins as well as one temporary PMMA/MMA resin (control). The morphology and the particle size of the prepolymerized PMMA powders were investigated by scanning electron microscopy and laser diffraction particle size analysis, respectively. Linear polymerization shrinkage strains of the resins were monitored for 20 minutes using a custom-made linometer, and the final values (at 20 minutes) were converted into volumetric shrinkages. The final volumetric shrinkage values for the modeling resins were statistically similar (P > 0.05) or significantly larger (P < 0.05) than that of the control resin and were related to the polymerization kinetics (P < 0.05) rather than the PMMA bead size (P = 0.335). Therefore, the optimal control of the polymerization kinetics seems to be more important for producing high-precision resin structures rather than the use of dental modeling resins.

  9. Implementation of a flipped classroom educational model in a predoctoral dental course.

    PubMed

    Park, Sang E; Howell, T Howard

    2015-05-01

    This article describes the development and implementation of a flipped classroom model to promote student-centered learning as part of a predoctoral dental course. This model redesigns the traditional lecture-style classroom into a blended learning model that combines active learning pedagogy with instructional technology and "flips" the sequence so that students use online resources to learn content ahead of class and then use class time for discussion. The dental anatomy portion of a second-year DMD course at Harvard School of Dental Medicine was redesigned using the flipped classroom model. The 36 students in the course viewed online materials before class; then, during class, small groups of students participated in peer teaching and team discussions based on learning objectives under the supervision of faculty. The utilization of pre- and post-class quizzes as well as peer assessments were critical motivating factors that likely contributed to the increase in student participation in class and helped place learning accountability on the students. Student feedback from a survey after the experience was generally positive with regard to the collaborative and interactive aspects of this form of blended learning. PMID:25941150

  10. Effects of Prepolymerized Particle Size and Polymerization Kinetics on Volumetric Shrinkage of Dental Modeling Resins

    PubMed Central

    Ha, Jung-Yun; Chun, Ju-Na; Son, Jun Sik; Kim, Kyo-Han

    2014-01-01

    Dental modeling resins have been developed for use in areas where highly precise resin structures are needed. The manufacturers claim that these polymethyl methacrylate/methyl methacrylate (PMMA/MMA) resins show little or no shrinkage after polymerization. This study examined the polymerization shrinkage of five dental modeling resins as well as one temporary PMMA/MMA resin (control). The morphology and the particle size of the prepolymerized PMMA powders were investigated by scanning electron microscopy and laser diffraction particle size analysis, respectively. Linear polymerization shrinkage strains of the resins were monitored for 20 minutes using a custom-made linometer, and the final values (at 20 minutes) were converted into volumetric shrinkages. The final volumetric shrinkage values for the modeling resins were statistically similar (P > 0.05) or significantly larger (P < 0.05) than that of the control resin and were related to the polymerization kinetics (P < 0.05) rather than the PMMA bead size (P = 0.335). Therefore, the optimal control of the polymerization kinetics seems to be more important for producing high-precision resin structures rather than the use of dental modeling resins. PMID:24779020

  11. Implementation of a flipped classroom educational model in a predoctoral dental course.

    PubMed

    Park, Sang E; Howell, T Howard

    2015-05-01

    This article describes the development and implementation of a flipped classroom model to promote student-centered learning as part of a predoctoral dental course. This model redesigns the traditional lecture-style classroom into a blended learning model that combines active learning pedagogy with instructional technology and "flips" the sequence so that students use online resources to learn content ahead of class and then use class time for discussion. The dental anatomy portion of a second-year DMD course at Harvard School of Dental Medicine was redesigned using the flipped classroom model. The 36 students in the course viewed online materials before class; then, during class, small groups of students participated in peer teaching and team discussions based on learning objectives under the supervision of faculty. The utilization of pre- and post-class quizzes as well as peer assessments were critical motivating factors that likely contributed to the increase in student participation in class and helped place learning accountability on the students. Student feedback from a survey after the experience was generally positive with regard to the collaborative and interactive aspects of this form of blended learning.

  12. Modelling ice layer formation using a preferential flow formulation in the physics based multi-layer SNOWPACK model

    NASA Astrophysics Data System (ADS)

    Wever, Nander; Würzer, Sebastian; Fierz, Charles; Lehning, Michael

    2016-04-01

    For physics based snow cover models, simulating the formation of dense ice layers inside the snowpack has been a long time challenge. In spite of their small vertical extend, the presence of ice lenses inside the snowpack can have a profound impact on vapor, heat and liquid water flow. These effects may ultimately influence processes on larger scales when, for example, looking at hydrological processes or wet snow avalanche formation. Also microwave emission signals from the snowpack are strongly influenced by the presence of ice layers. Recent laboratory experiments and modelling techniques of liquid water flow in snow have advanced the understanding of liquid water flow in snow, in particular the formation of preferential flow paths. We present a modelling approach in the one-dimensional, multi-layer snow cover model SNOWPACK for preferential flow that is based on a dual-domain approach (i.e., separation into a matrix flow and a preferential flow domain) and solving Richards equation for both. In recently published laboratory experiments, water ponding inside the snowpack has been identified to initiate preferential flow. Those studies also quantified the part of the snowpack involved in preferential flow as a function of grain size. By combining these concepts with an empirical function to determine refreezing of preferential flow water inside the snowpack, we are able to simulate preferential water flow in the model. We found that preferential flow paths arriving at a layer transition in the snowpack may lead to ponding conditions. Subsequent refreezing then may form dense ice layers (>700 kg/m3). We compare the simulations to 14 years of biweekly snow profiles made at the Weissfluhjoch study plot at 2540m altitude in the Eastern Swiss Alps. We show that we are able to reproduce several ice lenses that were observed in the field, whereas some profiles remain challenging to simulate.

  13. SSIC model: A multi-layer model for intervention of online rumors spreading

    NASA Astrophysics Data System (ADS)

    Tian, Ru-Ya; Zhang, Xue-Fu; Liu, Yi-Jun

    2015-06-01

    SIR model is a classical model to simulate rumor spreading, while the supernetwork is an effective tool for modeling complex systems. Based on the Opinion SuperNetwork involving Social Sub-network, Environmental Sub-network, Psychological Sub-network, and Viewpoint Sub-network, drawing from the modeling idea of SIR model, this paper designs super SIC model (SSIC model) and its evolution rules, and also analyzes intervention effects on public opinion of four elements of supernetwork, which are opinion agent, opinion environment, agent's psychology and viewpoint. Studies show that, the SSIC model based on supernetwork has effective intervention effects on rumor spreading. It is worth noting that (i) identifying rumor spreaders in Social Sub-network and isolating them can achieve desired intervention results, (ii) improving environmental information transparency so that the public knows as much information as possible to reduce the rumors is a feasible way to intervene, (iii) persuading wavering neutrals has better intervention effects than clarifying rumors already spread everywhere, so rumors should be intervened in properly in time by psychology counseling.

  14. Possibility of reconstruction of dental plaster cast from 3D digital study models

    PubMed Central

    2013-01-01

    Objectives To compare traditional plaster casts, digital models and 3D printed copies of dental plaster casts based on various criteria. To determine whether 3D printed copies obtained using open source system RepRap can replace traditional plaster casts in dental practice. To compare and contrast the qualities of two possible 3D printing options – open source system RepRap and commercially available 3D printing. Design and settings A method comparison study on 10 dental plaster casts from the Orthodontic department, Department of Stomatology, 2nd medical Faulty, Charles University Prague, Czech Republic. Material and methods Each of 10 plaster casts were scanned by inEos Blue scanner and the printed on 3D printer RepRap [10 models] and ProJet HD3000 3D printer [1 model]. Linear measurements between selected points on the dental arches of upper and lower jaws on plaster casts and its 3D copy were recorded and statistically analyzed. Results 3D printed copies have many advantages over traditional plaster casts. The precision and accuracy of the RepRap 3D printed copies of plaster casts were confirmed based on the statistical analysis. Although the commercially available 3D printing enables to print more details than the RepRap system, it is expensive and for the purpose of clinical use can be replaced by the cheaper prints obtained from RepRap printed copies. Conclusions Scanning of the traditional plaster casts to obtain a digital model offers a pragmatic approach. The scans can subsequently be used as a template to print the plaster casts as required. Using 3D printers can replace traditional plaster casts primarily due to their accuracy and price. PMID:23721330

  15. Climate warming due to increasing atmospheric CO2 - Simulations with a multilayer coupled atmosphere-ocean seasonal energy balance model

    NASA Technical Reports Server (NTRS)

    Li, Peng; Chou, Ming-Dah; Arking, Albert

    1987-01-01

    The transient response of the climate to increasing CO2 is studied using a modified version of the multilayer energy balance model of Peng et al. (1982). The main characteristics of the model are described. Latitudinal and seasonal distributions of planetary albedo, latitude-time distributions of zonal mean temperatures, and latitudinal distributions of evaporation, water vapor transport, and snow cover generated from the model and derived from actual observations are analyzed and compared. It is observed that in response to an atmospheric doubling of CO2, the model reaches within 1/e of the equilibrium response of global mean surface temperature in 9-35 years for the probable range of vertical heat diffusivity in the ocean. For CO2 increases projected by the National Research Council (1983), the model's transient response in annually and globally averaged surface temperatures is 60-75 percent of the corresponding equilibrium response, and the disequilibrium increases with increasing heat diffusivity of the ocean.

  16. Modelling ultrasonic array signals in multilayer anisotropic materials using the angular spectrum decomposition of plane wave responses

    NASA Astrophysics Data System (ADS)

    Humeida, Yousif; Pinfield, Valerie J.; Challis, Richard E.

    2013-08-01

    Ultrasonic arrays have seen increasing use for the characterisation of composite materials. In this paper, ultrasonic wave propagation in multilayer anisotropic materials has been modelled using plane wave and angular spectrum decomposition techniques. Different matrix techniques, such as the stiffness matrix method and the transfer matrix method, are used to calculate the reflection and transmission coefficients of ultrasonic plane waves in the considered media. Then, an angular decomposition technique is used to derive the bounded beams from finite-width ultrasonic array elements from the plane wave responses calculated earlier. This model is considered to be an analytical exact solution for the problem; hence the diffraction of waves in such composite materials can be calculated for different incident angles for a very wide range of frequencies. This model is validated against experimental measurements using the Full-Matrix Capture (FMC) of array data in both a homogeneous isotropic material, i.e. aluminium, and an inhomogeneous multilayer anisotropic material, i.e. a carbon fibre reinforced composite.

  17. Evaluation of an integrative model for professional development and research in a dental curriculum.

    PubMed

    Ditmyer, Marcia M; Mobley, Connie C; Davenport, William D

    2014-03-01

    The purpose of this project was to evaluate a Research, Professional Development, and Critical Thinking Integrative Model developed for use in a dental curriculum. This article outlines strategies used in developing a competency-based pedagogical model designed to provide a tailored student learning environment with objective, measurable, and calibrated assessment outcomes. The theoretical model integrated elements of critical thinking, professionalism, and evidence-based dentistry across dental school disciplines; implementation was based on consensus of dental faculty and student representatives about course content, faculty allocation, and curriculum alignment. Changes introduced included the following: 1) conversion and integration of previously siloed course content taught in Years 1 and 2 to sequential two-year combined courses; 2) reduction of course and content redundancies; 3) delivery of courses by teams of faculty members in biomedical, behavioral, and clinical sciences; and 4) reduction of total curriculum credit/contact hours from 13.5 (201 contact hours) to 5.0 (60 contact hours), allowing the Curriculum Committee to accommodate additional courses. These changes resulted in improvement in student satisfaction. PMID:24609339

  18. Evaluation of an integrative model for professional development and research in a dental curriculum.

    PubMed

    Ditmyer, Marcia M; Mobley, Connie C; Davenport, William D

    2014-03-01

    The purpose of this project was to evaluate a Research, Professional Development, and Critical Thinking Integrative Model developed for use in a dental curriculum. This article outlines strategies used in developing a competency-based pedagogical model designed to provide a tailored student learning environment with objective, measurable, and calibrated assessment outcomes. The theoretical model integrated elements of critical thinking, professionalism, and evidence-based dentistry across dental school disciplines; implementation was based on consensus of dental faculty and student representatives about course content, faculty allocation, and curriculum alignment. Changes introduced included the following: 1) conversion and integration of previously siloed course content taught in Years 1 and 2 to sequential two-year combined courses; 2) reduction of course and content redundancies; 3) delivery of courses by teams of faculty members in biomedical, behavioral, and clinical sciences; and 4) reduction of total curriculum credit/contact hours from 13.5 (201 contact hours) to 5.0 (60 contact hours), allowing the Curriculum Committee to accommodate additional courses. These changes resulted in improvement in student satisfaction.

  19. APPRAISAL OF ACCESS TO DENTAL SERVICES IN SOUTH EAST OF IRAN USING FIVE AS MODEL

    PubMed Central

    Moosazadeh, Mahmood; Amiresmaili, Mohammadreza; Karimi, Sara; Arabpoor, Mahboobeh; Afshari, Mahdi

    2016-01-01

    Background: Access to dental services not only refers to utilization but also to the extent by which the utilization is judged according to professional norms. This study aimed to study the access to dental services using the Five As model. Methods: This cross sectional study was conducted in southeast of Iran. A sample of 400 subjects participated in the study according to a multistage sampling method. A questionnaire was used for data collection. Data were analyzed using independent T test, ANOVA and multivariate linear regression models by means of SPSS V.20 software. Findings: Affordability, availability, accessibility, accommodation and acceptability mean scores were 58.2±12.2, 53.9±12.9, 59.4±15.7, 60.2±8.6, 70±11.5 and 60.3±7.4 respectively. According to multivariate linear regression models, there was significant associations between affordability and age, education level, having basic insurance and family income. Moreover, total accessibility was significantly correlated with education and monthly family income. Conclusion: This study showed that access to dental services was at the moderate level among the studied population. It also revealed that age, basic insurance coverage, family income and level of education, are determinants of this accessibility. PMID:27482161

  20. Improved classification and visualization of healthy and pathological hard dental tissues by modeling specular reflections in NIR hyperspectral images

    NASA Astrophysics Data System (ADS)

    Usenik, Peter; Bürmen, Miran; Fidler, Aleš; Pernuš, Franjo; Likar, Boštjan

    2012-03-01

    Despite major improvements in dental healthcare and technology, dental caries remains one of the most prevalent chronic diseases of modern society. The initial stages of dental caries are characterized by demineralization of enamel crystals, commonly known as white spots, which are difficult to diagnose. Near-infrared (NIR) hyperspectral imaging is a new promising technique for early detection of demineralization which can classify healthy and pathological dental tissues. However, due to non-ideal illumination of the tooth surface the hyperspectral images can exhibit specular reflections, in particular around the edges and the ridges of the teeth. These reflections significantly affect the performance of automated classification and visualization methods. Cross polarized imaging setup can effectively remove the specular reflections, however is due to the complexity and other imaging setup limitations not always possible. In this paper, we propose an alternative approach based on modeling the specular reflections of hard dental tissues, which significantly improves the classification accuracy in the presence of specular reflections. The method was evaluated on five extracted human teeth with corresponding gold standard for 6 different healthy and pathological hard dental tissues including enamel, dentin, calculus, dentin caries, enamel caries and demineralized regions. Principal component analysis (PCA) was used for multivariate local modeling of healthy and pathological dental tissues. The classification was performed by employing multiple discriminant analysis. Based on the obtained results we believe the proposed method can be considered as an effective alternative to the complex cross polarized imaging setups.

  1. Comparison of dimensional accuracy of digital dental models produced from scanned impressions and scanned stone casts

    NASA Astrophysics Data System (ADS)

    Subeihi, Haitham

    Introduction: Digital models of dental arches play a more and more important role in dentistry. A digital dental model can be generated by directly scanning intraoral structures, by scanning a conventional impression of oral structures or by scanning a stone cast poured from the conventional impression. An accurate digital scan model is a fundamental part for the fabrication of dental restorations. Aims: 1. To compare the dimensional accuracy of digital dental models produced by scanning of impressions versus scanning of stone casts. 2. To compare the dimensional accuracy of digital dental models produced by scanning of impressions made of three different materials (polyvinyl siloxane, polyether or vinyl polyether silicone). Methods and Materials: This laboratory study included taking addition silicone, polyether and vinyl polyether silicone impressions from an epoxy reference model that was created from an original typodont. Teeth number 28 and 30 on the typodont with a missing tooth number 29 were prepared for a metal-ceramic three-unit fixed dental prosthesis with tooth #29 being a pontic. After tooth preparation, an epoxy resin reference model was fabricated by duplicating the typodont quadrant that included the tooth preparations. From this reference model 12 polyvinyl siloxane impressions, 12 polyether impressions and 12 vinyl polyether silicone impressions were made. All 36 impressions were scanned before pouring them with dental stone. The 36 dental stone casts were, in turn, scanned to produce digital models. A reference digital model was made by scanning the reference model. Six groups of digital models were produced. Three groups were made by scanning of the impressions obtained with the three different materials, the other three groups involved the scanning of the dental casts that resulted from pouring the impressions made with the three different materials. Groups of digital models were compared using Root Mean

  2. Analytical modeling of drug dynamics induced by eluting stents in the coronary multi-layered curved domain.

    PubMed

    d'Errico, Michele; Sammarco, Paolo; Vairo, Giuseppe

    2015-09-01

    Pharmacokinetics induced by drug eluting stents (DES) in coronary walls is modeled by means of a one-dimensional multi-layered model, accounting for vessel curvature and non-homogeneous properties of the arterial tissues. The model includes diffusion mechanisms, advection effects related to plasma filtration through the walls, and bio-chemical drug reactions. A non-classical Sturm-Liouville problem with discontinuous coefficients is derived, whose closed-form analytical solution is obtained via an eigenfunction expansion. Soundness and consistency of the proposed approach are shown by numerical computations based on possible clinical treatments involving both hydrophilic and hydrophobic drugs. The influence of the main model parameters on drug delivery mechanisms is analyzed, highlighting the effects induced by vessel curvature and yielding comparative indications and useful insights into the concurring mechanisms governing the pharmacokinetics. PMID:26162517

  3. Sound transmission modeling of advanced multilayered composite structures using enhanced T-matrices for two-phase materials

    NASA Astrophysics Data System (ADS)

    Woodcock, Roland L.; Bryant, Rebecca S.

    2005-09-01

    Advanced composite structures have been used for many years in the aerospace industry. When designing multilayered structures special attention must be paid to the bonding techniques since the interface conditions have a direct effect on the mechanical coupling between the individual layers. Previous studies have shown the overall acoustical performance such as transmission loss and surface absorption to be sensitive to this structural path mainly in the lower frequency range. The state of the art shows that a comprehensive model is still lacking in the framework of the transfer matrix Method. The present paper proposes a new analytical modeling approach to tackle systems with stiffeners in the low-frequency range. This technique is based on the so-called Series-Parallel network of the transmission line theory in the framework of the classical electro-acoustical analogies. The simulations show that in the typical case of a double plate with stiffeners, with regards to transmission loss the design change due to the mechanical path is captured and the increase of the overall stiffness of the system shifts the resonance to the higher frequencies. The other important acoustical properties of multilayered systems will be highlighted during the presentation with regards to optimizing the overall acoustical performance.

  4. Modeling the electromechanical impedance technique for the assessment of dental implant stability.

    PubMed

    LaMalfa Ribolla, Emma; Rizzo, Piervincenzo

    2015-07-16

    We simulated the electromechanical impedance (EMI) technique to assess the stability of dental implants. The technique consists of bonding a piezoelectric transducer to the element to be monitored. When subjected to an electric field, the transducer induces structural excitations which, in turn, affect the transducer's electrical admittance. As the structural vibrations depend on the mechanical impedance of the element, the measurement of the transducer's admittance can be exploited to assess the element's health. In the study presented in this paper, we created a 3D finite element model to mimic a transducer bonded to the abutment of a dental implant placed in a host bone site. We simulated the healing that occurs after surgery by changing Young's modulus of the bone-implant interface. The results show that as Young's modulus of the interface increases, i.e. as the mechanical interlock of the implant within the bone is achieved, the electromechanical characteristic of the transducer changes. The model and the findings of this numerical study may be used in the future to predict and interpret experimental data, and to develop a robust and cost-effective method for the assessment of primary and secondary dental implant stability. PMID:26070645

  5. A BAYESIAN HIERARCHICAL SPATIAL MODEL FOR DENTAL CARIES ASSESSMENT USING NON-GAUSSIAN MARKOV RANDOM FIELDS

    PubMed Central

    Jin, Ick Hoon; Yuan, Ying; Bandyopadhyay, Dipankar

    2016-01-01

    Research in dental caries generates data with two levels of hierarchy: that of a tooth overall and that of the different surfaces of the tooth. The outcomes often exhibit spatial referencing among neighboring teeth and surfaces, i.e., the disease status of a tooth or surface might be influenced by the status of a set of proximal teeth/surfaces. Assessments of dental caries (tooth decay) at the tooth level yield binary outcomes indicating the presence/absence of teeth, and trinary outcomes at the surface level indicating healthy, decayed, or filled surfaces. The presence of these mixed discrete responses complicates the data analysis under a unified framework. To mitigate complications, we develop a Bayesian two-level hierarchical model under suitable (spatial) Markov random field assumptions that accommodates the natural hierarchy within the mixed responses. At the first level, we utilize an autologistic model to accommodate the spatial dependence for the tooth-level binary outcomes. For the second level and conditioned on a tooth being non-missing, we utilize a Potts model to accommodate the spatial referencing for the surface-level trinary outcomes. The regression models at both levels were controlled for plausible covariates (risk factors) of caries, and remain connected through shared parameters. To tackle the computational challenges in our Bayesian estimation scheme caused due to the doubly-intractable normalizing constant, we employ a double Metropolis-Hastings sampler. We compare and contrast our model performances to the standard non-spatial (naive) model using a small simulation study, and illustrate via an application to a clinical dataset on dental caries. PMID:27807470

  6. Aspects of Integrating Functional Electroceramic Material in Multilayer Thin Films for Image Sensing: Modeling and Experiment

    NASA Astrophysics Data System (ADS)

    Matin, M. A.; Oishi, K.; Katsuta, A.; Akai, D.; Sawada, K.; Ishida, M.

    2015-07-01

    Using combined experimental and simulation techniques, this study addresses the critical stress for peeling off crucial layer(s) in multilayered epitaxial functional thin films on n-Si(001) substrate. The thickness of platinum (Pt) and PZT thin films was varied from 22 nm to 142 nm and 90 nm to 450 nm, respectively. Residual stresses were measured by analyzing captured fringes using Newton's rings technique. Advanced finite element computation was next conducted to predict the evolution of residual stresses. Induced stresses in Pt thin film were found to be decreased with decreasing the thickness of film from 72 nm to 40 nm. In contrast, stresses are shown to be decreased with increasing the thickness of PZT film from 240 nm to 450 nm. The design of the pyroelectric multilayered sensors was thus optimized employing finite element (FE) simulation. Computed stresses were found to correlate well with that observed in experiments. FE simulations can thus be used as a tool to a priori predict the evolution of residual stresses, which may allow a fail-safe design before the fabrication of pyroelectric image sensors.

  7. Fabrication and characterization of a multilayered optical tissue model with embedded scattering microspheres in polymeric materials.

    PubMed

    Chang, Robert C; Johnson, Peter; Stafford, Christopher M; Hwang, Jeeseong

    2012-06-01

    We report on a novel fabrication approach to build multilayered optical tissue phantoms that serve as independently validated test targets for axial resolution and contrast in scattering measurements by depth-resolving optical coherent tomography (OCT) with general applicability to a variety of three-dimensional optical sectioning platforms. We implement a combinatorial bottom-up approach to prepare monolayers of light-scattering microspheres with interspersed layers of transparent polymer. A dense monolayer assembly of monodispersed microspheres is achieved via a combined methodology of polyelectrolyte multilayers (PEMs) for particle-substrate binding and convective particle flux for two-dimensional crystal array formation on a glass substrate. Modifications of key parameters in the layer-by-layer polyelectrolyte deposition approach are applied to optimize particle monolayer transfer from a glass substrate into an elastomer while preserving the relative axial positioning in the particle monolayer. Varying the dimensions of the scattering microspheres and the thickness of the intervening transparent polymer layers enables different spatial frequencies to be realized in the transverse dimension of the solid phantoms. Step-wise determination of the phantom dimensions is performed independently of the optical system under test to enable precise spatial calibration, independent validation, and quantitative dimensional measurements.

  8. Matrix approach for modeling of emission from multilayer spin-polarized light-emitting diodes and lasers

    NASA Astrophysics Data System (ADS)

    Fördös, Tibor; Postava, Kamil; Jaffrès, Henri; Pištora, Jaromír

    2014-06-01

    Spin-polarized light sources such as the spin-polarized light-emitting diodes (spin-LEDs) and spin-polarized lasers (spin-lasers) are prospective devices in which the radiative recombination of spin-polarized carriers results in emission of circularly polarized photons. The main goal of this article is to model emitted radiation and its polarization properties from spin-LED and spin-controlled vertical-cavity surface-emitting laser (spin-VCSEL) solid-state structures. A novel approach based on 4 × 4 transfer matrix formalism is derived for modeling of the interaction of light with matter in active media of resonant multilayer anisotropic structure and enables magneto-optical effects. Quantum transitions, which result in photon emission, are described using general Jones source vectors.

  9. Full-wave model and numerical study of electromagnetic plane wave scattering by multilayered, fiber-based periodic composites

    NASA Astrophysics Data System (ADS)

    Li, C. Y.; Lesselier, D.; Zhong, Y.

    2015-07-01

    The present work aims at building up a full-wave computational model of electromagnetic nondestructive testing of composite materials produced by stacking up dielectric slabs one over the other. In each such dielectric slab, a periodic array of infinite cylindrical fibers is embedded. Electromagnetic scattering of such a multilayered, fiber-based periodic composite is investigated here for an obliquely incident plane wave, the plane of incidence of which differs from the plane orthogonal to the fibers' axes. Full-wave field representations are given first by multipole and plane wave expansions. Mode matching at boundaries between layers then yields the propagating matrices, which are applied to connect reflection and transmission coefficients of the longitudinal field components. Power reflection and transmission coefficients are obtained from time-averaged Poynting vectors. Numerical experiments with comparisons with known results illustrate the accuracy of the model proposed.

  10. Characterization of thin-film multilayers using magnetization curves and modeling of low-angle X-ray diffraction data

    SciTech Connect

    Lane, M.; Chaiken, A.; Michel, R.P.

    1994-12-01

    We have characterized thin-film multilayers grown by ion-beam sputtering using magnetization curves and modeling of low-angle x-ray diffraction data. In our films, we use ferromagnetic layer = Co, Fe, and NiFe and spacer layer = Si, Ge, FeSi{sub 2}, and CoSi{sub 2}. We have studied the effects of (1) deposition conditions; (2) thickness of layers; (3) different layer materials; and (4) annealing. We find higher magnetization in films grown at 1000V rather than 500V and in films with spacer layers of 50{angstrom} rather than 100{angstrom}. We find higher coercivity in films with cobalt grown on germanium rather than silicon, metal grown on gold underlayers rather than on glass substrates, and when using thinner spacer layers. Finally, modeling reveals that films grown with disilicide layers are more thermally stable than films grown with silicon spacer layers.

  11. Influence of core design, production technique, and material selection on fracture behavior of yttria-stabilized tetragonal zirconia polycrystal fixed dental prostheses produced using different multilayer techniques: split-file, over-pressing, and manually built-up veneers

    PubMed Central

    Mahmood, Deyar Jallal Hadi; Linderoth, Ewa H; Wennerberg, Ann; Vult Von Steyern, Per

    2016-01-01

    Aim To investigate and compare the fracture strength and fracture mode in eleven groups of currently, the most commonly used multilayer three-unit all-ceramic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) fixed dental prostheses (FDPs) with respect to the choice of core material, veneering material area, manufacturing technique, design of connectors, and radii of curvature of FDP cores. Materials and methods A total of 110 three-unit Y-TZP FDP cores with one intermediate pontic were made. The FDP cores in groups 1–7 were made with a split-file design, veneered with manually built-up porcelain, computer-aided design-on veneers, and over-pressed veneers. Groups 8–11 consisted of FDPs with a state-of-the-art design, veneered with manually built-up porcelain. All the FDP cores were subjected to simulated aging and finally loaded to fracture. Results There was a significant difference (P<0.05) between the core designs, but not between the different types of Y-TZP materials. The split-file designs with VITABLOCS® (1,806±165 N) and e.max® ZirPress (1,854±115 N) and the state-of-the-art design with VITA VM® 9 (1,849±150 N) demonstrated the highest mean fracture values. Conclusion The shape of a split-file designed all-ceramic reconstruction calls for a different dimension protocol, compared to traditionally shaped ones, as the split-file design leads to sharp approximal indentations acting as fractural impressions, thus decreasing the overall strength. The design of a framework is a crucial factor for the load bearing capacity of an all-ceramic FDP. The state-of-the-art design is preferable since the split-file designed cores call for a cross-sectional connector area at least 42% larger, to have the same load bearing capacity as the state-of-the-art designed cores. All veneering materials and techniques tested in the study, split-file, over-press, built-up porcelains, and glass–ceramics are, with a great safety margin, sufficient for clinical use

  12. Ultrasonic NDE of Multilayered Structures

    SciTech Connect

    Quarry, M J; Fisher, K A; Lehman, S K

    2005-02-14

    This project developed ultrasonic nondestructive evaluation techniques based on guided and bulk waves in multilayered structures using arrays. First, a guided wave technique was developed by preferentially exciting dominant modes with energy in the layer of interest via an ultrasonic array. Second, a bulk wave technique uses Fermat's principle of least time as well as wave-based properties to reconstruct array data and image the multilayered structure. The guided wave technique enables the inspection of inaccessible areas of a multilayered structure without disassembling it. Guided waves propagate using the multilayer as a waveguide into the inaccessible areas from an accessible position. Inspecting multi-layered structures with a guided wave relies on exciting modes with sufficient energy in the layer of interest. Multilayered structures are modeled to determine the possible modes and their distribution of energy across the thickness. Suitable modes were determined and excited by designing arrays with the proper element spacing and frequency. Bulk wave imaging algorithms were developed to overcome the difficulties of multiple reflections and refractions at interfaces. Reconstruction algorithms were developed to detect and localize flaws. A bent-ray algorithm incorporates Fermat's principle to correct time delays in the ultrasonic data that result from the difference in wave speeds in each layer and refractions at the interfaces. A planar wave-based algorithm was developed using the Green function for the multilayer structure to enhance focusing on reception for improved imaging.

  13. pH Landscapes in a Novel Five-Species Model of Early Dental Biofilm

    PubMed Central

    Schlafer, Sebastian; Raarup, Merete K.; Meyer, Rikke L.; Sutherland, Duncan S.; Dige, Irene; Nyengaard, Jens R.; Nyvad, Bente

    2011-01-01

    Background Despite continued preventive efforts, dental caries remains the most common disease of man. Organic acids produced by microorganisms in dental plaque play a crucial role for the development of carious lesions. During early stages of the pathogenetic process, repeated pH drops induce changes in microbial composition and favour the establishment of an increasingly acidogenic and aciduric microflora. The complex structure of dental biofilms, allowing for a multitude of different ecological environments in close proximity, remains largely unexplored. In this study, we designed a laboratory biofilm model that mimics the bacterial community present during early acidogenic stages of the caries process. We then performed a time-resolved microscopic analysis of the extracellular pH landscape at the interface between bacterial biofilm and underlying substrate. Methodology/Principal Findings Strains of Streptococcus oralis, Streptococcus sanguinis, Streptococcus mitis, Streptococcus downei and Actinomyces naeslundii were employed in the model. Biofilms were grown in flow channels that allowed for direct microscopic analysis of the biofilms in situ. The architecture and composition of the biofilms were analysed using fluorescence in situ hybridization and confocal laser scanning microscopy. Both biofilm structure and composition were highly reproducible and showed similarity to in-vivo-grown dental plaque. We employed the pH-sensitive ratiometric probe C-SNARF-4 to perform real-time microscopic analyses of the biofilm pH in response to salivary solutions containing glucose. Anaerobic glycolysis in the model biofilms created a mildly acidic environment. Decrease in pH in different areas of the biofilms varied, and distinct extracellular pH-microenvironments were conserved over several hours. Conclusions/Significance The designed biofilm model represents a promising tool to determine the effect of potential therapeutic agents on biofilm growth, composition and

  14. Teaching dental students how to deliver bad news: S-P-I-K-E-S model.

    PubMed

    Curtin, Sharon; McConnell, Mary

    2012-03-01

    Delivering bad news has traditionally been associated with life-threatening illness, the imminence of death, or communicating about the death of a loved one to a family member. The delivery of bad news in dentistry is rarely about life-threatening circumstances. However, the impact of the bad news such as the loss of an anterior tooth can be devastating for the patient. This article outlines the S-P-I-K-E-S protocol and discusses the teaching aims and methodology in applying the model in an undergraduate dental program in Ireland. PMID:22383606

  15. A Multi-Layered Computational Model of Coupled Elastin Degradation, Vasoactive Dysfunction, and Collagenous Stiffening in Aortic Aging

    PubMed Central

    Valentín, A.; Humphrey, J.D.; Holzapfel, G.A.

    2011-01-01

    Arterial responses to diverse pathologies and insults likely occur via similar mechanisms. For example, many studies suggest that the natural process of aging and isolated systolic hypertension share many characteristics in arteries, including loss of functional elastin, decreased smooth muscle tone, and altered rates of deposition and/or cross-linking of fibrillar collagen. Our aim is to show computationally how these coupled effects can impact evolving aortic geometry and mechanical behavior. Employing a thick-walled, multi-layered constrained mixture model, we suggest that a coupled loss of elastin and vasoactive function are fundamental mechanisms by which aortic aging occurs. Moreover, it is suggested that collagenous stiffening, although itself generally an undesirable process, can play a key role in attenuating excessive dilatation, perhaps including the enlargement of abdominal aortic aneurysms. PMID:21380570

  16. Perceived Stress Latent Factors and the Burnout Subtypes: A Structural Model in Dental Students

    PubMed Central

    Montero-Marín, Jesús; Piva Demarzo, Marcelo Marcos; Stapinski, Lexine; Gili, Margarita; García-Campayo, Javier

    2014-01-01

    Background Students of health-professions suffer high levels of stress and burnout. The aim of the present study was to evaluate the relationship between perceived stress latent factors (‘tenseness’ and ‘frustration’) and the features (‘overload’, ‘lack of development’ and ‘neglect’) of the three burnout subtypes (‘frenetic’, ‘under-challenged’ and ‘worn-out’, respectively), in a sample of Spanish dental students. Methods The study employed a cross-sectional design. A sample of Spanish dental students (n = 314) completed the ‘Perceived Stress Questionnaire’ and the ‘Burnout Clinical Subtype Questionnaire Student Survey’. The associations among variables were observed by means of structural equation modelling using the unweighted least squares method from polychoric correlations. Results Strong associations among perceived stress factors and the burnout characteristics were observed, although a distinct pattern of relations was observed for each burnout subtype. The ‘overload’ was moderately and positively associated with both ‘tenseness’ (0.45), and ‘frustration’ (0.38) dimensions of perceived stress; the ‘lack of development’ was positively associated with the ‘frustration’ dimension (0.72), but negatively associated with ‘tenseness’ (−0.69); the ‘neglect’ showed a weaker positive associated with ‘frustration’ (0.41), and a small negative association with ‘tenseness’ (−0.20). The model was a very good fit to the data (GFI  =  0.96; RSMR  =  0.07; AGFI = 0.96; NFI = 0.95; RFI = 0.95). Conclusions The stress factors of ‘frustration’ and ‘tenseness’ seems to be related in a distinct way to the burnout subtypes in Spanish dental students. This finding suggests that intervention programs specifically tailored to these subtypes may be a promising future direction. PMID:24927260

  17. A comparative study of the effect of probiotics on cariogenic biofilm model for preventing dental caries.

    PubMed

    Lee, Sung-Hoon; Kim, Young-Jae

    2014-08-01

    Dental caries is induced by oral biofilm containing Streptococcus mutans. Probiotic bacteria were mainly studied for effect on the gastrointestinal tract and have been known to promote human health. However, the information of probiotics for oral health has been lack yet. In this study, we investigated influence of various probiotics on oral bacteria or cariogenic biofilm and evaluated candidate probiotics for dental caries among them. The antimicrobial activity of the spent culture medium of probiotics for oral streptococci was performed. Probiotics were added during the biofilm formation with salivary bacteria including S. mutans. The oral biofilms were stained with a fluorescent dye and observed using the confocal laser scanning microscope. To count bacteria in the biofilm, the bacteria were plated on MSB and BHI agar plates after disrupting the biofilm and cultivated. Glucosyltransferases (gtfs) expression of S. mutans and integration of lactobacilli into the biofilm were evaluated by real-time RT-PCR. Among probiotics, Lactobacillus species strongly inhibited growth of oral streptococci. Moreover, Lactobacillus species strongly inhibited formation of cariogenic biofilm model. The expression of gtfs was significantly reduced by Lactobacillus rhamnosus. The integration of L. rhamnosus into the biofilm model did not exhibit. However, L. acidophilus and L casei integrated into the biofilm model. These results suggest that L. rhamnosus may inhibit oral biofilm formation by decreasing glucan production of S. mutans and antibacterial activity and did not integrate into oral biofilm, which can be a candidate for caries prevention strategy.

  18. Dental Sealants

    MedlinePlus

    ... Data & Statistics > Find Data by Topic > Dental Sealants Dental Sealants Main Content Dental sealants are thin plastic coatings that protect the chewing surfaces of children’s back teeth from tooth decay. Overall, the prevalence of sealants ...

  19. Modeling multi-layer effects in passive microwave remote sensing of dry snow using Dense Media Radiative Transfer Theory (DMRT) based on quasicrystalline approximation

    USGS Publications Warehouse

    Liang, D.; Xu, X.; Tsang, L.; Andreadis, K.M.; Josberger, E.G.

    2008-01-01

    The Dense Media Radiative Transfer theory (DMRT) of Quasicrystalline Approximation of Mie scattering by sticky particles is used to study the multiple scattering effects in layered snow in microwave remote sensing. Results are illustrated for various snow profile characteristics. Polarization differences and frequency dependences of multilayer snow model are significantly different from that of the single-layer snow model. Comparisons are also made with CLPX data using snow parameters as given by the VIC model. ?? 2007 IEEE.

  20. 77 FR 20648 - Certain Digital Models, Digital Data, and Treatment Plans for Use in Making Incremental Dental...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-05

    ... COMMISSION Certain Digital Models, Digital Data, and Treatment Plans for Use in Making Incremental Dental Positioning Adjustment Appliances, the Appliances Made Therefrom, and Methods of Making the Same; Institution... of certain digital models, digital data, and treatment plans for use in making incremental...

  1. A dynamic model of the fate of organic chemicals in a multilayered air/soil system: development and illustrative application.

    PubMed

    Ghirardello, Davide; Morselli, Melissa; Semplice, Matteo; Di Guardo, Antonio

    2010-12-01

    A new site-specific, dynamic model (SoilPlus) was developed to simulate the fate of nonionized organic chemicals in the air/litter/soil system; key features of the model are the double-layered air compartment interacting dynamically with multilayered litter and soil compartments, with seasonal dissolved organic carbon (DOC) fluxes. The model describes the soil environment calculating separate mass balances for water, chemical, and organic matter. SoilPlus underwent a process of benchmarking and evaluation in order to reach a satisfying confirmation of its predictive capability. Several simulations were performed to estimate the role of litter and DOC in affecting the fate of a model contaminant for POPs (hexachlorobenzene). The model shows that litter can behave as a buffer in the process of transferring hexachlorobenzene from air to the mineral soil and as a trap when hexachlorobenzene tends to move from a contaminated field toward clean air. DOC seems to behave as a leaching-enhancer in certain climatic conditions (heavy rainfall, high DOC concentrations), but it does not appear to move significant amounts of HCB in a year calculation. PMID:21053937

  2. Modeling Hydrogeological and Geomenchanical Processes Related toCO2 Injection in a Faulted Multilayer System

    SciTech Connect

    Rutqvist, Jonny; Birkholzer, Jens; Tsang, Chin-Fu

    2006-01-01

    This paper presents a numerical study of coupled hydrological and geomechanical processes during a deep underground injection of supercritical CO{sub 2} in a hypothetical brine aquifer. We consider a multilayer system in which the injection zone is situated below a sequence of caprock and aquifer layers that are intersected by a vertical fault zone. The fault zone consists of highly fractured shale across the first caprock layers that are located just above the injection zone. Initially, the fractured shale zones are considered sealed with minerals, but we allow fractures (and the fractured zones) to open as a result of injection induced reductions in effective stresses. Our results indicate that even when assuming a very sensitive relationship between effective stress and fractured-zone permeability, the injection-induced changes in permeability across are only moderate with largest changes occurring in the first caprock layer, just above the injection zone. As a result, the upward leakage rate remains relatively small and therefore changes in fluid pressure and hydromechanical effects in overlying zones are also relatively small for the case studied in this paper.

  3. Dental Procedures.

    PubMed

    Ramponi, Denise R

    2016-01-01

    Dental problems are a common complaint in emergency departments in the United States. There are a wide variety of dental issues addressed in emergency department visits such as dental caries, loose teeth, dental trauma, gingival infections, and dry socket syndrome. Review of the most common dental blocks and dental procedures will allow the practitioner the opportunity to make the patient more comfortable and reduce the amount of analgesia the patient will need upon discharge. Familiarity with the dental equipment, tooth, and mouth anatomy will help prepare the practitioner for to perform these dental procedures. PMID:27482994

  4. Magnetic multilayer structure

    DOEpatents

    Herget, Philipp; O'Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang; Webb, Bucknell C.

    2016-07-05

    A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.

  5. Use of the generalized linear models in data related to dental caries index.

    PubMed

    Javali, S B; Pandit, Parameshwar V

    2007-01-01

    The aim of this study is to encourage and initiate the application of generalized linear models (GLMs) in the analysis of the covariates of decayed, missing, and filled teeth (DMFT) index data, which is not necessarily normally distributed. GLMs can be performed assuming underlying many distributions; in fact Poisson distribution with log built-in link function and binomial distribution with Logit and Probit built-in link functions are considered. The Poisson model is used for modeling the DMFT index data and the Logit and Probit models are employed to model the dichotomous outcome of DMFT = 0 and DMFT not equal to 0 (caries free/caries present). The data comprised 7188 subjects aged 18-30 years from the study on the oral health status of Karnataka state conducted by SDM College of Dental Sciences and Hospital, Dharwad, Karnataka, India. The Poisson model and binomial models (Logit and Probit) displayed dissimilarity in the outcome of results at 5% level of significance ( P <0.05). The binomial models were a poor fit, whereas the Poisson model showed a good fit for the DMFT index data. Therefore, a suitable modeling approach for DMFT index data is to use a Poisson model for the DMFT response and a binomial model for the caries free and caries present (DMFT = 0 and DMFT not equal to 0). These GLMs allow separate estimation of those covariates which influence the magnitude of caries. PMID:17938491

  6. Biomechanical model produced from light-activated dental composite resins: a holographic analysis

    NASA Astrophysics Data System (ADS)

    Pantelić, Dejan; Vasiljević, Darko; Blažić, Larisa; Savić-Šević, Svetlana; Murić, Branka; Nikolić, Marko

    2013-11-01

    Light-activated dental composites, commonly applied in dentistry, can be used as excellent material for producing biomechanical models. They can be cast in almost any shape in an appropriate silicone mold and quickly solidified by irradiation with light in the blue part of the spectrum. In that way, it is possible to obtain any number of nearly identical casts. The models can be used to study the behavior of arbitrary structure under mechanical loads. To test the technique, a simple mechanical model of the tooth with a mesio-occluso-distal cavity was manufactured. Composite resin restoration was placed inside the cavity and light cured. Real-time holographic interferometry was used to analyze the contraction of the composite resin and its effect on the surrounding material. The results obtained in the holographic experiment were in good agreement with those obtained using the finite element method.

  7. Optimization of microCT data processing for modelling of dental structures in orthodontic studies.

    PubMed

    Viecilli, R; Katona, T; Roberts, W

    2007-08-01

    Dental studies evaluating microCT output often examine resolution as a parameter that affects the data, but many other factors can influence image quality. The objective of this paper is to present the issues involved with the optimization of microCT data acquisition and processing for two biomechanical animal models. The first model evaluates surface and volumetric changes in root structure after in vitro fatigue loading of dog incisors. The second evaluates the in vivo morphometric bone and tooth responses to application of orthodontic force in inbred and transgenic mice. This type of data required specific magnification and noise control microCT settings to segment and render objects with acceptable definition. The proposed procedures enabled high definition rendering of changes in tooth and bone morphology in orthodontic studies. They also allowed for the construction of solid models for finite element analyses. PMID:17671859

  8. Self-efficacy and oral hygiene beliefs about toothbrushing in dental patients: a model-guided study.

    PubMed

    Anagnostopoulos, Fotios; Buchanan, Heather; Frousiounioti, Sofia; Niakas, Dimitris; Potamianos, Gregory

    2011-10-01

    Building on previous research on psychosocial variables associated with oral hygiene behavior, this study examined the ability of Health Belief Model variables (perceived benefits, barriers, susceptibility, severity) and self-efficacy beliefs about toothbrushing to inform prevalence of dental caries and toothbrushing frequency. To accomplish this goal, a sample of 125 dental patients completed self-report questionnaires and provided data on demographic and behavioral factors. A path analysis model with manifest variables was tested. Oral hygiene beliefs emerged as a multidimensional construct. Results suggested that stronger self-efficacy beliefs (β = .81) and greater perceived severity of oral diseases (β = .18) were related to increased toothbrushing frequency, which in turn was associated with better oral health status, as indicated by the total number of decayed, missing, and filled teeth due to dental caries (β = -.39). Possible strategies for improving oral health are discussed.

  9. Adaptive Weibull Multiplicative Model and Multilayer Perceptron neural networks for dark-spot detection from SAR imagery.

    PubMed

    Taravat, Alireza; Oppelt, Natascha

    2014-12-02

    Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. Dark formation detection is the first and critical stage in oil-spill detection procedures. In this paper, a novel approach for automated dark-spot detection in SAR imagery is presented. A new approach from the combination of adaptive Weibull Multiplicative Model (WMM) and MultiLayer Perceptron (MLP) neural networks is proposed to differentiate between dark spots and the background. The results have been compared with the results of a model combining non-adaptive WMM and pulse coupled neural networks. The presented approach overcomes the non-adaptive WMM filter setting parameters by developing an adaptive WMM model which is a step ahead towards a full automatic dark spot detection. The proposed approach was tested on 60 ENVISAT and ERS2 images which contained dark spots. For the overall dataset, an average accuracy of 94.65% was obtained. Our experimental results demonstrate that the proposed approach is very robust and effective where the non-adaptive WMM & pulse coupled neural network (PCNN) model generates poor accuracies.

  10. Adaptive Weibull Multiplicative Model and Multilayer Perceptron Neural Networks for Dark-Spot Detection from SAR Imagery

    PubMed Central

    Taravat, Alireza; Oppelt, Natascha

    2014-01-01

    Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. Dark formation detection is the first and critical stage in oil-spill detection procedures. In this paper, a novel approach for automated dark-spot detection in SAR imagery is presented. A new approach from the combination of adaptive Weibull Multiplicative Model (WMM) and MultiLayer Perceptron (MLP) neural networks is proposed to differentiate between dark spots and the background. The results have been compared with the results of a model combining non-adaptive WMM and pulse coupled neural networks. The presented approach overcomes the non-adaptive WMM filter setting parameters by developing an adaptive WMM model which is a step ahead towards a full automatic dark spot detection. The proposed approach was tested on 60 ENVISAT and ERS2 images which contained dark spots. For the overall dataset, an average accuracy of 94.65% was obtained. Our experimental results demonstrate that the proposed approach is very robust and effective where the non-adaptive WMM & pulse coupled neural network (PCNN) model generates poor accuracies. PMID:25474376

  11. Experimental model to measure the increase of dental pulp temperature in vivo during laser application

    NASA Astrophysics Data System (ADS)

    Nicola, Ester M. D.; Junqueira, Silvio L. M.; Busato, Mara S.

    1994-09-01

    Carbon dioxide laser has been used in dental surgery. The existence of healthy teeth, which have pulp vitality needing to be preserved, is observed in a great number of cases. In this work we describe an experimental model which provides the measurement of temperature in pulp chamber `in vivo,' during oral surgeries in which the CO2 laser beam is applied to gingival tissue. The problems met during the search for the best way to place the thermal probe regarding the diameter and depth of pulp chamber and the thickness of the tissue layer formed by gum and maxillary bone are discussed. We use a thermocouple placed in the pulp chamber of superior canine teeth in dogs. After that, the probe was also placed between gum and dental root. Since the temperature at gingival surface was known, it was easy to determine the rise in temperature at pulp chamber and also to observe the thermal gradient from gum to tissue to bone, thus avoiding pulp damage during laser applications.

  12. Modeling dental composite shrinkage by digital image correlation and finite element methods

    NASA Astrophysics Data System (ADS)

    Chen, Terry Yuan-Fang; Huang, Pin-Sheng; Chuang, Shu-Fen

    2014-10-01

    Dental composites are light-curable resin-based materials with an inherent defect of polymerization shrinkage which may cause tooth deflection and debonding of restorations. This study aimed to combine digital image correlation (DIC) and finite element analysis (FEA) to model the shrinkage behaviors under different light curing regimens. Extracted human molars were prepared with proximal cavities for composite restorations, and then divided into three groups to receive different light curing protocols: regular intensity, low intensity, and step-curing consisting of low and high intensities. For each tooth, the composite fillings were consecutively placed under both unbonded and bonded conditions. At first, the shrinkage of the unbonded restorations was analyzed by DIC and adopted as the setting of FEA. The simulated shrinkage behaviors obtained from FEA were further validated by the measurements in the bonded cases. The results showed that different light curing regimens affected the shrinkage in unbonded restorations, with regular intensity showing the greatest shrinkage strain on the top surface. The shrinkage centers in the bonded cases were located closer to the cavity floor than those in the unbonded cases, and were less affected by curing regimens. The FEA results showed that the stress was modulated by the accumulated light energy density, while step-curing may alleviate the tensile stress along the cavity walls. In this study, DIC provides a complete description of the polymerization shrinkage behaviors of dental composites, which may facilitate the stress analysis in the numerical investigation.

  13. Framework for e-learning assessment in dental education: a global model for the future.

    PubMed

    Arevalo, Carolina R; Bayne, Stephen C; Beeley, Josie A; Brayshaw, Christine J; Cox, Margaret J; Donaldson, Nora H; Elson, Bruce S; Grayden, Sharon K; Hatzipanagos, Stylianos; Johnson, Lynn A; Reynolds, Patricia A; Schönwetter, Dieter J

    2013-05-01

    The framework presented in this article demonstrates strategies for a global approach to e-curricula in dental education by considering a collection of outcome assessment tools. By combining the outcomes for overall assessment, a global model for a pilot project that applies e-assessment tools to virtual learning environments (VLE), including haptics, is presented. Assessment strategies from two projects, HapTEL (Haptics in Technology Enhanced Learning) and UDENTE (Universal Dental E-learning), act as case-user studies that have helped develop the proposed global framework. They incorporate additional assessment tools and include evaluations from questionnaires and stakeholders' focus groups. These measure each of the factors affecting the classical teaching/learning theory framework as defined by Entwistle in a standardized manner. A mathematical combinatorial approach is proposed to join these results together as a global assessment. With the use of haptic-based simulation learning, exercises for tooth preparation assessing enamel and dentine were compared to plastic teeth in manikins. Equivalence for student performance for haptic versus traditional preparation methods was established, thus establishing the validity of the haptic solution for performing these exercises. Further data collected from HapTEL are still being analyzed, and pilots are being conducted to validate the proposed test measures. Initial results have been encouraging, but clearly the need persists to develop additional e-assessment methods for new learning domains.

  14. Kinetic Monte Carlo modeling of the efficiency roll-off in a multilayer white organic light-emitting device

    NASA Astrophysics Data System (ADS)

    Mesta, M.; van Eersel, H.; Coehoorn, R.; Bobbert, P. A.

    2016-03-01

    Triplet-triplet annihilation (TTA) and triplet-polaron quenching (TPQ) in organic light-emitting devices (OLEDs) lead to a roll-off of the internal quantum efficiency (IQE) with increasing current density J. We employ a kinetic Monte Carlo modeling study to analyze the measured IQE and color balance as a function of J in a multilayer hybrid white OLED that combines fluorescent blue with phosphorescent green and red emission. We investigate two models for TTA and TPQ involving the phosphorescent green and red emitters: short-range nearest-neighbor quenching and long-range Förster-type quenching. Short-range quenching predicts roll-off to occur at much higher J than measured. Taking long-range quenching with Förster radii for TTA and TPQ equal to twice the Förster radii for exciton transfer leads to a fair description of the measured IQE-J curve, with the major contribution to the roll-off coming from TPQ. The measured decrease of the ratio of phosphorescent to fluorescent component of the emitted light with increasing J is correctly predicted. A proper description of the J-dependence of the ratio of red and green phosphorescent emission needs further model refinements.

  15. Prediction of Corrosion Resistance of Some Dental Metallic Materials with an Adaptive Regression Model

    NASA Astrophysics Data System (ADS)

    Chelariu, Romeu; Suditu, Gabriel Dan; Mareci, Daniel; Bolat, Georgiana; Cimpoesu, Nicanor; Leon, Florin; Curteanu, Silvia

    2015-04-01

    The aim of this study is to investigate the electrochemical behavior of some dental metallic materials in artificial saliva for different pH (5.6 and 3.4), NaF content (500 ppm, 1000 ppm, and 2000 ppm), and with albumin protein addition (0.6 wt.%) for pH 3.4. The corrosion resistance of the alloys was quantitatively evaluated by polarization resistance, estimated by electrochemical impedance spectroscopy method. An adaptive k-nearest-neighbor regression method was applied for evaluating the corrosion resistance of the alloys by simulation, depending on the operation conditions. The predictions provided by the model are useful for experimental practice, as they can replace or, at least, help to plan the experiments. The accurate results obtained prove that the developed model is reliable and efficient.

  16. Estimation of snow water equivalent using a radiance assimilation scheme with a multi-layered snow physical model

    NASA Astrophysics Data System (ADS)

    Mounirou Toure, Ally

    The feasibility of a radiance assimilation using a multi-layered snow physical model to estimate snow physical parameters is studied. The work is divided in five parts. The first two chapters are dedicated to the literature review. In the third chapter, experimental work was conducted in the alpine snow to estimate snow correlation (for microwave emission modelling) using near-infrared digital photography. We made microwave radiometric and near-infrared reflectance measurements of snow slabs under different experimental conditions. We used an empirical relation to link near-infrared reflectance of snow to the specific surface area (SSA), and converted the SSA into the correlation length. From the measurements of snow radiances at 21 and 35 GHz, we derived the microwave scattering coefficient by inverting two coupled radiative transfer models (RTM) (the sandwich and six-flux model). The correlation lengths found are in the same range as those determined in the literature using cold laboratory work. The technique shows great potential in the determination of the snow correlation length under field conditions. In the fourth chapter, the performance of the ensemble Kalman filter (EnKF) for snow water equivalent (SWE) estimation is assessed by assimilating synthetic microwave observations at Ground Based Microwave Radiometer (GBMR-7) frequencies (18.7, 23.8, 36.5, 89 vertical and horizontal polarization) into a snow physics model, CROCUS. CROCUS has a realistic stratigraphic and ice layer modelling scheme. This work builds on previous methods that used snow physics model with limited number of layers. Data assimilation methods require accurate predictions of the brightness temperature (Tb) emitted by the snowpack. It has been shown that the accuracy of RTMs is sensitive to the stratigraphic representation of the snowpack. However, as the stratigraphic fidelity increases, the number of layers increases, as does the number of state variables estimated in the assimilation

  17. Oral health in Brazil: the challenges for dental health care models.

    PubMed

    Chaves, Sônia Cristina Lima

    2012-01-01

    This paper discusses adult oral health in Brazil according to three perspectives: 1) the available epidemiological evidence about the population's oral-health-related epidemiological situation, especially adults and the elderly population, in relation to two high prevalence oral injuries (dental caries and tooth loss), 2) the main health care models for dealing with this situation, by analyzing the related historical processes in order to reveal the likely social, political and epidemiological implications of the different models, and 3) lastly, the possible challenges to Brazilian dentistry or collective oral health in overcoming these obstacles. The main results of the study indicate that, from an epidemiological point of view, Brazil is undergoing a transition in dental caries and tooth loss, which is not yet reflected in the profile of the elderly, but which is tentatively evidenced in young adults. Tooth loss remains high. Certain aspects of society's economic and political superstructure have an important impact on oral health indicators and existing inequalities. Oral health care models have a relative importance and must not be neglected. Vestiges of ideological movements, like preventive medicine, may explain the current impasse in collective oral health practices, such as the preeminence of Finalized Treatment (FT) in clinics and of preventive care in schools fostered by community-based programs. It is therefore important to develop conceptual, theoretical reflections and to increase the objects of intervention, their purposes and their modus operandi. The practice of dentistry according to these alternative models is still being constructed. New studies related to the different formats of these new practices are recommended.

  18. A cone-beam CT based technique to augment the 3D virtual skull model with a detailed dental surface.

    PubMed

    Swennen, G R J; Mommaerts, M Y; Abeloos, J; De Clercq, C; Lamoral, P; Neyt, N; Casselman, J; Schutyser, F

    2009-01-01

    Cone-beam computed tomography (CBCT) is used for maxillofacial imaging. 3D virtual planning of orthognathic and facial orthomorphic surgery requires detailed visualisation of the interocclusal relationship. This study aimed to introduce and evaluate the use of a double CBCT scan procedure with a modified wax bite wafer to augment the 3D virtual skull model with a detailed dental surface. The impressions of the dental arches and the wax bite wafer were scanned for ten patient separately using a high resolution standardized CBCT scanning protocol. Surface-based rigid registration using ICP (iterative closest points) was used to fit the virtual models on the wax bite wafer. Automatic rigid point-based registration of the wax bite wafer on the patient scan was performed to implement the digital virtual dental arches into the patient's skull model. Probability error histograms showed errors of < or =0.22 mm (25% percentile), < or =0.44 mm (50% percentile) and < or =1.09 mm (90% percentile) for ICP surface matching. The mean registration error for automatic point-based rigid registration was 0.18+/-0.10 mm (range 0.13-0.26 mm). The results show the potential for a double CBCT scan procedure with a modified wax bite wafer to set-up a 3D virtual augmented model of the skull with detailed dental surface.

  19. 78 FR 29157 - Certain Digital Models, Digital Data, and Treatment Plans for Use, in Making Incremental Dental...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-17

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Digital Models, Digital Data, and Treatment Plans for Use, in Making Incremental Dental Positioning Adjustment Appliances Made Therefrom, and Methods of Making the Same Investigation No. 337-...

  20. Toward an Innovative, Basic Program Model for the Improvement of Professional Instruction in Dental Education: A Review of the Literature.

    ERIC Educational Resources Information Center

    Wulf, Kathleen M.; And Others

    1980-01-01

    An analysis of the massive amount of literature pertaining to the improvement of professional instruction in dental education resulted in the formation of a comprehensive model of 10 categories, including Delphi technique; systems approach; agencies; workshops; multi-media, self-instruction; evaluation paradigms, measurement, courses, and…

  1. The structure of observed learning outcome (SOLO) taxonomy: a model to promote dental students' learning.

    PubMed

    Lucander, H; Bondemark, L; Brown, G; Knutsson, K

    2010-08-01

    Selective memorising of isolated facts or reproducing what is thought to be required - the surface approach to learning - is not the desired outcome for a dental student or a dentist in practice. The preferred outcome is a deep approach as defined by an intention to seek understanding, develop expertise and relate information and knowledge into a coherent whole. The aim of this study was to investigate whether the structure of observed learning outcome (SOLO) taxonomy could be used as a model to assist and promote the dental students to develop a deep approach to learning assessed as learning outcomes in a summative assessment. Thirty-two students, participating in course eight in 2007 at the Faculty of Odontology at Malmö University, were introduced to the SOLO taxonomy and constituted the test group. The control group consisted of 35 students participating in course eight in 2006. The effect of the introduction was measured by evaluating responses to a question in the summative assessment by using the SOLO taxonomy. The evaluators consisted of two teachers who performed the assessment of learning outcomes independently and separately on the coded material. The SOLO taxonomy as a model for learning was found to improve the quality of learning. Compared to the control group significantly more strings and structured relations between these strings were present in the test group after the SOLO taxonomy had been introduced (P < 0.01, one tailed test for both results). The SOLO taxonomy is recommended as a model for promoting and developing a deeper approach to learning in dentistry.

  2. Multi-layer model vs. single-layer model for N and P doped poly layers in etch bias modeling

    NASA Astrophysics Data System (ADS)

    Li, Jianliang; Vidal-Russell, Ezequiel; Beale, Daniel; Wang, Chunqing; Melvin, Lawrence S., III

    2010-09-01

    In modern photolithography, ever smaller critical dimension (CD) budgets require tighter control over the entire process, demanding more accurate practice of optical proximity correction (OPC). In last decade, the model based OPC (MBOPC) has outpaced the rule based OPC (RBOPC) and become widely adopted in semiconductor industry. During the MBOPC process, the physical models are called to compute the signal values at the evaluation points and the design patterns are perturbed such that the final model contours are as close to the targets as possible. It has been demonstrated that in addition to simulating the optics and resist effects, the physical models must accommodate the pattern distortion due to etch process as well. While the etch process may be lumped with optics and resist processes into one model for the 65nm and above nodes, it can no longer be treated as small perturbations on photolithographic effects for more advanced nodes and it is highly desired to build a physics-based etch model formulations that differ from the conventional convolution-based process models used to simulate the optical and resist effect. Our previous studies proposed a novel non-linear etch modeling object in combination with conventional convolution kernels, which simulates the non-optics and non-resist proximity effect successfully. This study examines further the non-linear etch modeling method by checking the different behaviors of N and p doped layers which physically have different etching rates and should be represented differently in etch modeling. The experimental results indicate that the fitting accuracy is significantly improved when the data points are split into N and P groups and calibrated separately. The N and P layer etch models are used in staged MBOPCs and the results are compared with single-layer model as well.

  3. Study on x-ray multilayer monochromator

    NASA Astrophysics Data System (ADS)

    Zhou, Changxin; Li, Mao-Lian; Miao, Tongqun; Lu, Xilin; Ma, Lie; An, Qingxiang; Liang, Guoli

    1993-01-01

    At present natural crystal TLAP used usually is replaced by artificial coated with multilayer for X-ray fluorescence (XRF) spectral analysis. X-ray multilayer monochromator can be used for analyzing light elements such as F, Na, Mg etc. Diffraction intensity of the multilayer component is 5 times higher than that of TLAP. This paper describes operating principle, Fabrication method and technique of the X-ray multilayer monochromator and the components are used Model 3080 E sequential X-ray fluorescence spectroscope. The multilayer diffraction components are fabricated by means of coating alternatively multilayer with high and low electron density elements on single crystal silicon substrate by vapor deposition or sputtering. Gap between multilayers is d to be equivalent to lattice constant of crystal. Sample is excited to emit fluorescence with multi-wavelength when X-ray beam illuminates surface of the sample. Fluorescence emitted passes through collimator and incidences on multilayer diffraction component to be diffracted into various wavelengths which are corresponding some angles. Contents of elements in samples can be detected according to Bragg diffraction principle. Key technologies fabricating multilayer diffraction components are how to polish super-smooth surface substrate and to control d value of thickness of multilayer. Roughness of Si(111) substrate polished by us is up to 0.1 nm RMS. Gap d 2.5 nm between multilayers. It is very difficult to realize specification as mentioned above. Thicknesses of layers are controlled by quartz piezoelectric crystal and their monitor controlling errors is about 0.34 nm RMS. Ion sputtering device is adopted to improve surface finish and construct specialty of the layers. Finally we have developed multilayer diffraction components which have been used to analyze F, Na and Mg etc. by X-ray fluorescence spectroscope.

  4. Bayesian dynamic regression models for interval censored survival data with application to children dental health.

    PubMed

    Wang, Xiaojing; Chen, Ming-Hui; Yan, Jun

    2013-07-01

    Cox models with time-varying coefficients offer great flexibility in capturing the temporal dynamics of covariate effects on event times, which could be hidden from a Cox proportional hazards model. Methodology development for varying coefficient Cox models, however, has been largely limited to right censored data; only limited work on interval censored data has been done. In most existing methods for varying coefficient models, analysts need to specify which covariate coefficients are time-varying and which are not at the time of fitting. We propose a dynamic Cox regression model for interval censored data in a Bayesian framework, where the coefficient curves are piecewise constant but the number of pieces and the jump points are covariate specific and estimated from the data. The model automatically determines the extent to which the temporal dynamics is needed for each covariate, resulting in smoother and more stable curve estimates. The posterior computation is carried out via an efficient reversible jump Markov chain Monte Carlo algorithm. Inference of each coefficient is based on an average of models with different number of pieces and jump points. A simulation study with three covariates, each with a coefficient of different degree in temporal dynamics, confirmed that the dynamic model is preferred to the existing time-varying model in terms of model comparison criteria through conditional predictive ordinate. When applied to a dental health data of children with age between 7 and 12 years, the dynamic model reveals that the relative risk of emergence of permanent tooth 24 between children with and without an infected primary predecessor is the highest at around age 7.5, and that it gradually reduces to one after age 11. These findings were not seen from the existing studies with Cox proportional hazards models. PMID:23389549

  5. Homology modeling and virtual screening of inhibitors against TEM- and SHV-type-resistant mutants: A multilayer filtering approach.

    PubMed

    Baig, Mohammad H; Balaramnavar, Vishal M; Wadhwa, Gulshan; Khan, Asad U

    2015-01-01

    TEM and SHV are class-A-type β-lactamases commonly found in Escherichia coli and Klebsiella pneumoniae. Previous studies reported S130G and K234R mutations in SHVs to be 41- and 10-fold more resistant toward clavulanic acid than SHV-1, respectively, whereas TEM S130G and R244S also showed the same level of resistance. These selected mutants confer higher level of resistance against clavulanic acid. They also show little susceptibility against other commercially available β-lactamase inhibitors. In this study, we have used docking-based virtual screening approach in order to screen potential inhibitors against some of the major resistant mutants of SHV and TEM types β-lactamase. Two different inhibitor-resistant mutants from SHV and TEM were selected. Moreover, we have retained the active site water molecules within each enzyme. Active site water molecules were placed within modeled structure of the mutant whose structure was unavailable with protein databank. The novelty of this work lies in the use of multilayer virtual screening approach for the prediction of best and accurate results. We are reporting five inhibitors on the basis of their efficacy against all the selected resistant mutants. These inhibitors were selected on the basis of their binding efficacies and pharmacophore features.

  6. Time series modeling with pruned multi-layer perceptron and 2-stage damped least-squares method

    NASA Astrophysics Data System (ADS)

    Voyant, Cyril; Tamas, Wani; Paoli, Christophe; Balu, Aurélia; Muselli, Marc; Nivet, Marie-Laure; Notton, Gilles

    2014-03-01

    A Multi-Layer Perceptron (MLP) defines a family of artificial neural networks often used in TS modeling and forecasting. Because of its "black box" aspect, many researchers refuse to use it. Moreover, the optimization (often based on the exhaustive approach where "all" configurations are tested) and learning phases of this artificial intelligence tool (often based on the Levenberg-Marquardt algorithm; LMA) are weaknesses of this approach (exhaustively and local minima). These two tasks must be repeated depending on the knowledge of each new problem studied, making the process, long, laborious and not systematically robust. In this paper a pruning process is proposed. This method allows, during the training phase, to carry out an inputs selecting method activating (or not) inter-nodes connections in order to verify if forecasting is improved. We propose to use iteratively the popular damped least-squares method to activate inputs and neurons. A first pass is applied to 10% of the learning sample to determine weights significantly different from 0 and delete other. Then a classical batch process based on LMA is used with the new MLP. The validation is done using 25 measured meteorological TS and cross-comparing the prediction results of the classical LMA and the 2-stage LMA.

  7. Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model ADCHAM

    SciTech Connect

    Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, Ditte; Rusanen, A.; Boy, Michael; Swietlicki, E.; Svenningsson, Birgitta; Zelenyuk, Alla; Pagels, J.

    2014-08-11

    We have developed the novel Aerosol Dynamics, gas- and particle- phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas phase Master Chemical Mechanism version 3.2, an aerosol dynamics and particle phase chemistry module (which considers acid catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study: 1) the mass transfer limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), 2) the slow and almost particle size independent evaporation of α-pinene secondary organic aerosol (SOA) particles, and 3) the influence of chamber wall effects on the observed SOA formation in smog chambers.

  8. Dental arch changes associated with rapid maxillary expansion: A retrospective model analysis study

    PubMed Central

    D’Souza, Ivor M; Kumar, H. C. Kiran; Shetty, K. Sadashiva

    2015-01-01

    Introduction: Transverse deficiency of the maxilla is a common clinical problem in orthodontics and dentofacial orthopedics. Transverse maxillary deficiency, isolated or associated with other dentofacial deformities, results in esthetic and functional impairment giving rise to several clinical manifestations such as asymmetrical facial growth, positional and functional mandibular deviations, altered dentofacial esthetics, adverse periodontal responses, unstable dental tipping, and other functional problems. Orthopedic maxillary expansion is the preferred treatment approach to increase the maxillary transverse dimension in young patients by splitting of the mid palatal suture. This orthopedic procedure has lately been subject of renewed interest in orthodontic treatment mechanics because of its potential for increasing arch perimeter to alleviate crowding in the maxillary arch without adversely affecting facial profile. Hence, the present investigation was conducted to establish a correlation between transverse expansion and changes in the arch perimeter, arch width and arch length. Methods: For this purpose, 10 subjects (five males, five females) were selected who had been treated by rapid maxillary expansion (RME) using hyrax rapid palatal expander followed by fixed mechanotherapy (PEA). Pretreatment (T1), postexpansion (T2), and posttreatment (T3) dental models were compared for dental changes brought about by RME treatment and its stability at the end of fixed mechanotherapy. After model measurements were made, the changes between T1–T2, T2–T3 and T1–T3 were determined for each patient. The mean difference between T1–T2, T2–T3 and T1–T3 were compared to assess the effects of RME on dental arch measurements. Results are expressed as mean ± standard deviation and are compared by repeated measures analysis of variance followed by a post-hoc test. Arch perimeter changes are correlated with changes in arch widths at the canine, premolar and molar regions

  9. History of dental hygiene research.

    PubMed

    Bowen, Denise M

    2013-01-01

    Dental hygiene is defined as the science and practice of the recognition, treatment and prevention of oral diseases. The history of dental hygiene research is considered in the context of the development of the discipline and an emerging infrastructure. Research-related events supporting the growth and maturation of the profession are considered from the early years to the most recent. The benefits of preventive oral health services provided by dental hygienists have been supported by research, and the practice of dental hygiene has expanded as a result of research findings since its inception 100 years ago. Dental hygienists' engagement in research, however, did not begin until the 1960s as research associates or administrators, primarily with dental researchers as primary investigators. The Journal of Dental Hygiene (JDH) has provided information for dental hygiene practice since 1927, and has been the primary venue for dissemination of dental hygiene research since 1945. Graduate education in dental hygiene at the master's degree level and the work of early dental hygiene researchers led to the first conference on dental hygiene research in 1982. Over 30 years later, dental hygiene has established a meta-paradigm and defined conceptual models, built an initial infrastructure to support research endeavors and contributed much to the development of dental hygiene as a unique discipline. A doctoral degree in the discipline, continued theory-based research, initiatives to foster collaborations between dental hygiene and other researchers and enhanced capabilities to attract funding to support large scale studies are goals that must be attained through the efforts of future researchers to address the needs for additional development in the discipline of dental hygiene. Dental hygiene research supports the growing discipline and its value to society. PMID:24046337

  10. History of dental hygiene research.

    PubMed

    Bowen, Denise M

    2013-01-01

    Dental hygiene is defined as the science and practice of the recognition, treatment and prevention of oral diseases. The history of dental hygiene research is considered in the context of the development of the discipline and an emerging infrastructure. Research-related events supporting the growth and maturation of the profession are considered from the early years to the most recent. The benefits of preventive oral health services provided by dental hygienists have been supported by research, and the practice of dental hygiene has expanded as a result of research findings since its inception 100 years ago. Dental hygienists' engagement in research, however, did not begin until the 1960s as research associates or administrators, primarily with dental researchers as primary investigators. The Journal of Dental Hygiene (JDH) has provided information for dental hygiene practice since 1927, and has been the primary venue for dissemination of dental hygiene research since 1945. Graduate education in dental hygiene at the master's degree level and the work of early dental hygiene researchers led to the first conference on dental hygiene research in 1982. Over 30 years later, dental hygiene has established a meta-paradigm and defined conceptual models, built an initial infrastructure to support research endeavors and contributed much to the development of dental hygiene as a unique discipline. A doctoral degree in the discipline, continued theory-based research, initiatives to foster collaborations between dental hygiene and other researchers and enhanced capabilities to attract funding to support large scale studies are goals that must be attained through the efforts of future researchers to address the needs for additional development in the discipline of dental hygiene. Dental hygiene research supports the growing discipline and its value to society.

  11. Synchronous chaos and broad band gamma rhythm in a minimal multi-layer model of primary visual cortex.

    PubMed

    Battaglia, Demian; Hansel, David

    2011-10-01

    Visually induced neuronal activity in V1 displays a marked gamma-band component which is modulated by stimulus properties. It has been argued that synchronized oscillations contribute to these gamma-band activity. However, analysis of Local Field Potentials (LFPs) across different experiments reveals considerable diversity in the degree of oscillatory behavior of this induced activity. Contrast-dependent power enhancements can indeed occur over a broad band in the gamma frequency range and spectral peaks may not arise at all. Furthermore, even when oscillations are observed, they undergo temporal decorrelation over very few cycles. This is not easily accounted for in previous network modeling of gamma oscillations. We argue here that interactions between cortical layers can be responsible for this fast decorrelation. We study a model of a V1 hypercolumn, embedding a simplified description of the multi-layered structure of the cortex. When the stimulus contrast is low, the induced activity is only weakly synchronous and the network resonates transiently without developing collective oscillations. When the contrast is high, on the other hand, the induced activity undergoes synchronous oscillations with an irregular spatiotemporal structure expressing a synchronous chaotic state. As a consequence the population activity undergoes fast temporal decorrelation, with concomitant rapid damping of the oscillations in LFPs autocorrelograms and peak broadening in LFPs power spectra. We show that the strength of the inter-layer coupling crucially affects this spatiotemporal structure. We predict that layer VI inactivation should induce global changes in the spectral properties of induced LFPs, reflecting their slower temporal decorrelation in the absence of inter-layer feedback. Finally, we argue that the mechanism underlying the emergence of synchronous chaos in our model is in fact very general. It stems from the fact that gamma oscillations induced by local delayed

  12. Convergent methods assessing bone growth in an experimental model at dental implants in the minipig.

    PubMed

    Friedmann, Anton; Friedmann, Asisa; Grize, Leticia; Obrecht, Marcel; Dard, Michel

    2014-05-01

    Implant dentistry demonstrated its reliability in treating successfully an increased amount of patients with dental implants exhibiting hydrophilic (modSLA) or non-hydrophilic (SLA) surfaces. Objectives of this minipig study consisted in assessing bone regeneration at both types of dental implants in a new experimental model (lateral bone defects) by implementing a convergent analysis approach combining histology and contact radiography. In six adult female minipigs standardized acute alveolar defects were created, then receiving two implants in the mandibles bilaterally (modSLA and SLA, one of each combined with Guided Bone Regeneration). Animals were sacrificed after 28 days of healing. Mid-crestal specimen were analyzed assessing missing BIC to implant shoulder (fBIC); vertical bone growth upon implant surface, bone:tissue ratio and grafting material area occupied by material remnants for GBR sites. Values obtained from both analyses were compared and statistical correlations scrutinized. Although dimensions of mean differences and adjusted means given by radiographic method were lower than histological ones, comparison of different implants yielded similar results. Statistical analyses of correlation and concordance coefficients used to evaluate radiological method of measurement showed high level of concordance (concordance coefficient=0.912 and correlation coefficient=0.939) for fBIC. Similar results were observed for vertical new bone and for remnants of graft. Discrepancies for new bone and for mineralized tissue resulted in concordance coefficient of 0.182 and 0.054. The results indicate that contact X-rays can be used for morphometric assessments regarding defect fill; however, histological staining remains beneficial if greater resolution for distinguishing qualitative differences in the tissues is required. PMID:24656913

  13. Cariogenic effects of probiotic Lactobacillus rhamnosus GG in a dental biofilm model.

    PubMed

    Schwendicke, F; Dörfer, C; Kneist, S; Meyer-Lueckel, H; Paris, S

    2014-01-01

    Probiotic bacteria have been suggested to inhibit Streptococcus mutans (SM) and thus prevent dental caries. However, supporting evidence is weak and probiotic species might be cariogenic themselves. Thus, we compared and combined the probiotic Lactobacillus rhamnosus GG (LGG) with SM and analysed the resulting mineral loss (ΔZ) in dental tissues. We simulated three biofilm compositions (SM, LGG, SM × LGG), two lesion sites (smooth enamel, dentin cavity) and two nutrition supply frequencies (twice/day, 6 times/day) in a multi-station, continuous-culture biofilm model. A total of 240 bovine enamel and dentin samples were cut, polished and embedded. All experimental procedures were performed in independent duplicates, with 10 samples being allocated to each group for each experiment (final sample size n = 20/group). Biofilms were cultured on the specimens and supplied with 2% sucrose medium and artificial saliva in consecutive pulses. After 10 days, ΔZ and bacterial numbers were assessed. SM × LGG biofilms caused significantly increased ΔZ compared with SM or LGG biofilms (p < 0.01, Mann-Whitney test), and ΔZ was significantly increased in dentin cavities compared with smooth enamel lesions (p < 0.01). Bacterial numbers did not significantly differ between biofilms of different species (p > 0.05, ANOVA). Frequent nutrition supply significantly increased bacterial numbers (p < 0.01). Biofilms in dentin cavities compared to smooth enamel harboured significantly more bacteria (p < 0.05). LGG induced mineral loss especially in dentin cavities and under highly cariogenic conditions. LGG did not have inhibitory effects on SM, but rather contributed to the caries process in vitro.

  14. Damage modeling of small-scale experiments on dental enamel with hierarchical microstructure.

    PubMed

    Scheider, I; Xiao, T; Yilmaz, E; Schneider, G A; Huber, N; Bargmann, S

    2015-03-01

    Dental enamel is a highly anisotropic and heterogeneous material, which exhibits an optimal reliability with respect to the various loads occurring over years. In this work, enamel's microstructure of parallel aligned rods of mineral fibers is modeled and mechanical properties are evaluated in terms of strength and toughness with the help of a multiscale modeling method. The established model is validated by comparing it with the stress-strain curves identified by microcantilever beam experiments extracted from these rods. Moreover, in order to gain further insight in the damage-tolerant behavior of enamel, the size of crystallites below which the structure becomes insensitive to flaws is studied by a microstructural finite element model. The assumption regarding the fiber strength is verified by a numerical study leading to accordance of fiber size and flaw tolerance size, and the debonding strength is estimated by optimizing the failure behavior of the microstructure on the hierarchical level above the individual fibers. Based on these well-grounded properties, the material behavior is predicted well by homogenization of a representative unit cell including damage, taking imperfections (like microcracks in the present case) into account.

  15. Flaw detection in multi-layer, multi-material composites by resonance imaging: Utilizing Air-coupled Ultrasonics and Finite Element Modeling

    NASA Astrophysics Data System (ADS)

    Livings, Richard Andrew

    2011-12-01

    Ceramic tiles are the main ingredient of a multi-material, multi-layered composite being considered for the modernization of tank armors. The high stiffness, low attenuation, and precise dimensions of these uniform tiles make them remarkable resonators when driven to vibrate. Defects in the tile, during manufacture or after usage, are expected to change the resonance frequencies and resonance images of the tile. The comparison of the resonance frequencies and resonance images of a pristine tile/lay-up to a defective tile/lay-up will thus be a quantitative damage metric. By examining the vibrational behavior of these tiles and the composite lay-up with Finite Element Modeling and analytical plate vibration equations, the development of a new Nondestructive Evaluation technique is possible. This study examines the development of the Air-Coupled Ultrasonic Resonance Imaging technique as applied to a hexagonal ceramic tile and a multi-material, multi-layered composite.

  16. Vadose Zone Contaminant Migration Multi-Layer Model Software (Version 4.0)

    2009-08-12

    The Version 4.0 model is designed to improve functionality and addresses a greater range of unsaturated zone scenarios than previous versions. The additional flexibility is accomplished in the model by including user-defined hydraulic layer functions and hydraulic parameters.

  17. Shape, zonal winds and gravitational field of Jupiter: a fully self-consistent, multi-layered model

    NASA Astrophysics Data System (ADS)

    Schubert, Gerald; Kong, Dali; Zhang, Keke

    2016-10-01

    We construct a three-dimensional, finite-element, fully self-consistent, multi-layered,non-spheroidal model of Jupiter consisting of an inner core, a metallic electrically conducting dynamo region and an outer molecular electrically insulating envelope. We assume that the Jovian zonal winds are on cylinders parallel to the rotation axis but, due to the effect of magnetic braking, are confined within the outer molecular envelope. Two related calculations are carried out. The first provides an accurate description of the shape and internal density profile of Jupiter; the effect of rotational distortion is not treated as a small perturbation on a spherically symmetric state. This calculation determines the density, size and shape of the inner core, the irregular shape of the 1-bar pressure level, and the internal structure of Jupiter; the full effect of rotational distortion, without the influence of the zonal winds, is accounted for. Our multi-layered model is able to produce the known mass, the known equatorial and polar radii, and the known zonal gravitational coefficient J2 of Jupiter within their error bars; it also yields the coefficients J4 and J6 within about 5% accuracy, and the core equatorial radius 0.09RJ containing 3.73 Earth masses.The second calculation determines the variation of the gravitational field caused solely by the effect of the zonal winds on the rotationally distorted non-spheroidal Jupiter. Four different cases, ranging from a deep wind profile to a very shallow profile, are considered and implications for accurate interpretation of the zonal gravitational coefficients expected from the Juno mission are discussed.

  18. Comparison of measured reactive trace gas profiles with a multi-layer canopy chemical exchange model in an Amazonian rainforest

    NASA Astrophysics Data System (ADS)

    Wolff, Stefan; Ganzeveld, Laurens; Tsokankunku, Anywhere; Pöhlker, Christopher; de Abreu Sá, Leonardo Deane; Ocimar Manzi, Antonio; Souza, Rodrigo; Trebs, Ivonne; Sörgel, Matthias

    2016-04-01

    In 2011, an 80 m high walk up tower for atmospheric research was erected at the ATTO (Amazon Tall Tower Observatory) site (02°08'38.8''S, 58°59'59.5''W) in the remote Amazonian rainforest. The nearly pristine environment allows biosphere-atmosphere studies within an ecosystem far away from large anthropogenic emission sources. Since April 2012 vertical mixing ratio profiles of H2O, CO2 and O3 were measured at 8 different heights between 0.05 m and 79.3 m. During five intensive campaigns (Oct-Dec 2012, Oct-Nov 2013, Mar 2014, Aug-Sep 2014, Oct-Dec 2015) nitric oxide (NO) and nitrogen dioxide (NO2) were also measured. We applied the Multi-layer Canopy Chemical Exchange Model - MLC-CHEM to support the analysis of the observed profiles of NOx and O3. This includes inferring bi-directional surface-atmosphere exchange fluxes as well as the role of the canopy interactions between the emissions, dry deposition, chemistry and turbulent transport of trace gases. During our investigation of diurnal and seasonal differences between model and measurements, we conducted a set of sensitivity studies to analyse the effects of changes in NOx-soil emissions, in-canopy turbulence and resistances for O3 and NO2 uptake on wet surfaces. These analyses suggest some modification in the representation of some of the poorly constrained canopy processes resulting in a significantly better comparison between the simulated and measured exchange fluxes and concentrations.

  19. Fostering dental faculty collaboration with an evidence-based decision making model designed for curricular change.

    PubMed

    Stafford, Gary L

    2014-03-01

    This article introduces an innovative decision making model for adapting evidence-based practice to the specific needs of a department in a dental school. The design encourages suggestions for curricular change directly from the faculty members, while providing a mechanism that allows them to actively participate in the process through the use of evidence-based principles and practice. The nucleus of this model is an Advisory Council comprised of nine full-time departmental faculty members who, when charged, act as independent task force leaders who recruit other faculty members and lead small teams that investigate suggestions for curricular change. Following an accelerated investigative process, recommendations to the Advisory Council are made; if approved, these changes are integrated into the curriculum. The incorporation of an interdisciplinary Advisory Council of key departmental faculty members structured to investigate questions or concerns posed by students, administrators, or other faculty members through the use of evidence-based methodologies has proved to be a successful management tool. Well received by the participants, this model has the potential to further develop and calibrate the school's faculty, increase the timeliness of the decision making process, and lessen the time required to incorporate a proposed change into the curriculum. PMID:24609337

  20. Hydroxyapatite induces spontaneous polymerization of model self-etch dental adhesives.

    PubMed

    Zhang, Ying; Wu, Ningjing; Bai, Xinyan; Xu, Changqi; Liu, Yi; Wang, Yong

    2013-10-01

    The objective of this study is to report for the first time the spontaneous polymerization phenomenon of self-etch dental adhesives induced by hydroxylapatite (HAp). Model self-etch adhesives were prepared by using a monomer mixture of bis[2-(methacryloyloxy)ethyl] phosphate (2MP) with 2-hydroxyethyl methacrylate (HEMA). The initiator system consisted of camphorquinone (CQ, 0.022 mmol/g) and ethyl 4-dimethylaminobenzoate (4E, 0.022-0.088 mmol/g). HAp (2-8 wt.%) was added to the neat model adhesive. In a dark environment, the polymerization was monitored in-situ using ATR/FT-IR, and the mechanical properties of the polymerized adhesives were evaluated using nanoindentation technique. Results indicated that spontaneous polymerization was not observed in the absence of HAp. However, as different amounts of HAp were incorporated into the adhesives, spontaneous polymerization was induced. Higher HAp content led to higher degree of conversion (DC), higher rate of polymerization (RP) and shorter induction period (IP). In addition, higher 4E content also elevated DC and RP and reduced IP of the adhesives. Nanoindentation result suggested that the Young's modulus of the polymerized adhesives showed similar dependence on HAp and 4E contents. In summary, interaction with HAp could induce spontaneous polymerization of the model self-etch adhesives. This result provides important information for understanding the initiation mechanism of the self-etch adhesives, and may be of clinical significance to strengthen the adhesive/dentin interface based on the finding.

  1. Dental Hygienists

    MedlinePlus

    ... anatomy, patient management, and periodontics, which is the study of gum disease. High school students interested in becoming dental hygienists should take courses in biology, chemistry, and math. Most dental hygiene programs also require applicants to have completed at ...

  2. Dental sealants

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000779.htm Dental sealants To use the sharing features on this ... case a sealant needs to be replaced. How Dental Sealants Are Applied Your dentist applies sealants on ...

  3. Finite element modeling of dental restoration through multi-material laser densification

    NASA Astrophysics Data System (ADS)

    Dai, Kun

    To provide guidance for intelligent selection of various parameters in the Multi-Material Laser Densification (MMLD) process for dental restorations, finite element modeling (FEM) has been carried out to investigate the MMLD process. These modeling investigations include the thermal analysis of the nominal surface temperature that should be adopted during experiments in order to achieve the desired microstructure; the effects of the volume shrinkage due to transformation from a powder compact to dense liquid on the temperature distribution and the size of the transformation zone; the evolution of transient temperature, transient stresses, residual stresses and distortions; and the effects of laser processing conditions, such as fabrication sequences, laser scanning patterns, component sizes, preheating temperatures, laser scanning rates, initial porosities, and thicknesses of each powder layer, on the final quality of the component fabricated via the MMLD process. The simulation results are compared with the experiments. It is found that the predicted temperature distribution matches the experiments very well. The nominal surface temperature applied on the dental porcelain body should be below 1273 K to prevent the forming of the un-desired microstructure (i.e., a leucite-free glassy phase). The simplified models that do not include the volume shrinkage effect provide good estimations of the temperature field and the size of the laser-densified body, although the shape of the laser-densified body predicted is different from that obtained in the experiment. It is also fount that warping and residual thermal stresses of the laser-densified component are more sensitive to the chamber preheating temperature and the thickness of each powder layer than to the laser scanning rate and the initial porosity of the powder layer. The major mechanism responsible for these phenomena is identified to be related to the change of the temperature gradient induced by these laser

  4. Multilayer sea ice in the Arctic - Model- and satellite-derived

    NASA Technical Reports Server (NTRS)

    Walsh, John E.; Zwally, H. Jay

    1990-01-01

    The behavior of sea ice is a strong function of ice strength which, in the central Arctic, depends on the relative fractions of multiyear and first-year ice coverage. A dynamic-thermodynamic sea ice model has been configured to include both multiyear and first-year ice. The model has been run for a 7-year period, 1979-1985, for which a satellite microwave record of multiyear sea ice coverage is available. The simulated concentrations of multiyear ice are slightly higher than the satellite-derived concentrations, although the total coverage of simulated multiyear ice agrees well with the satellite-derived coverage. Both the simulated and the satellite-derived coverages in the early 1980s show large interannual variations that represent potentially large perturbations in the mass balance of Arctic pack ice. These fluctuations are generally consistent in the model and satellite data, and they are generally consistent with year-to-year differences in the large-scale wind forcing. In at least some cases the wintertime distribution of multiyear ice is influenced by the pattern of ice drift as far back as the previous summer. The late December coverage of multiyear ice in the Alaskan region appears to foreshadow summer ice conditions in the same region. The short-term response to an intense synoptic system is considerably larger in the satellite data than in the model results.

  5. Electromagnetic absorption in a multilayered slab model of tissue under near-field exposure conditions.

    PubMed

    Chatterjee, I; Hagmann, M J; Gandhi, O P

    1980-01-01

    The electromagnetic energy deposited in a semi-infinite slab model consisting of skin, fat, and muscle layers is calculated for both plane-wave and near-field exposures. The plane-wave spectrum (PWS) approach is used to calculate the energy deposited in the model by fields present due to leakage from equipment using electromagnetic energy. This analysis applies to near-field exposures where coupling of the target to the leakage source can be neglected. Calculations were made for 2,450 MHz, at which frequency the layered slab adequately models flat regions of the human body. Resonant absorption due to layering is examined as a function of the skin and fat thicknesses for plane-wave exposure and as a function of the physical extent of the near-field distribution. Calculations show that for fields that are nearly constant over at least a free-space wavelength, the energy deposition (for skin, fat, and muscle combination that gives resonant absorption) is equal to or less than that resulting from plane-wave exposure, but is appreciably greater than that obtained for a homogeneous muscle slab model.

  6. Electromagnetic absorption in a multilayered slab model of tissue under near-field exposure conditions

    SciTech Connect

    Chatterjee, I.; Hagmann, M.J.; Gandhi, O.P.

    1980-01-01

    The electromagnetic energy deposited in a semi-infinite slab model consisting of skin, fat, and muscle layers is calculated for both plane-wave and near-field exposures. The plane-wave spectrum (PWS) approach is used to calculate the energy deposited in the model by fields present due to leakage from equipment using electromagnetic energy. This analysis applies to near-field exposures where coupling of the target to the leakage source can be neglected. Calculations were made for 2,450 MHz, at which frequency the layered slab adequately models flat regions of the human body. Resonant absorption due to layering is examined as a function of the skin and fat thicknesses for plane-wave exposure and as a function of the physical extent of the near-field distribution. Calculations show that for fields that are nearly constant over at least a free-space wavelength, the energy deposition (for skin, fat, and muscle combination that gives resonant absorption) is equal to or less than that resulting from plane-wave exposure, but is appreciably greater than that obtained for a homogeneous muscle slab model.

  7. Nonlinear continuum growth model of multiscale reliefs as applied to rigorous analysis of multilayer short-wave scattering intensity. I. Gratings

    PubMed Central

    Goray, Leonid; Lubov, Maxim

    2013-01-01

    It is shown that taking into proper account certain terms in the nonlinear continuum equation of thin-film growth makes it applicable to the simulation of the surface of multilayer gratings with large boundary profile heights and/or gradient jumps. The proposed model describes smoothing and displacement of Mo/Si and Al/Zr boundaries of gratings grown on Si substrates with a blazed groove profile by magnetron sputtering and ion-beam deposition. Computer simulation of the growth of multilayer Mo/Si and Al/Zr gratings has been conducted. Absolute diffraction efficiencies of Mo/Si and Al/Zr gratings in the extreme UV range have been found within the framework of boundary integral equations applied to the calculated boundary profiles. It has been demonstrated that the integrated approach to the calculation of boundary profiles and of the intensity of short-wave scattering by multilayer gratings developed here opens up a way to perform studies comparable in accuracy to measurements with synchrotron radiation, at least for known materials and growth techniques. PMID:24046500

  8. Nonlinear continuum growth model of multiscale reliefs as applied to rigorous analysis of multilayer short-wave scattering intensity. I. Gratings.

    PubMed

    Goray, Leonid; Lubov, Maxim

    2013-08-01

    It is shown that taking into proper account certain terms in the nonlinear continuum equation of thin-film growth makes it applicable to the simulation of the surface of multilayer gratings with large boundary profile heights and/or gradient jumps. The proposed model describes smoothing and displacement of Mo/Si and Al/Zr boundaries of gratings grown on Si substrates with a blazed groove profile by magnetron sputtering and ion-beam deposition. Computer simulation of the growth of multilayer Mo/Si and Al/Zr gratings has been conducted. Absolute diffraction efficiencies of Mo/Si and Al/Zr gratings in the extreme UV range have been found within the framework of boundary integral equations applied to the calculated boundary profiles. It has been demonstrated that the integrated approach to the calculation of boundary profiles and of the intensity of short-wave scattering by multilayer gratings developed here opens up a way to perform studies comparable in accuracy to measurements with synchrotron radiation, at least for known materials and growth techniques. PMID:24046500

  9. Tissue prolapse and stresses in stented coronary arteries: A computer model for multi-layer atherosclerotic plaque.

    PubMed

    Hajiali, Zuned; Dabagh, Mahsa; Debusschere, Nic; De Beule, Matthieu; Jalali, Payman

    2015-11-01

    Among the many factors influencing the effectiveness of cardiovascular stents, tissue prolapse indicates the potential of a stent to cause restenosis. The deflection of the arterial wall between the struts of the stent and the tissue is known as a prolapse or draping. The prolapse is associated with injury and damage to the vessel wall due to the high stresses generated around the stent when it expands. The current study investigates the impact of stenosis severity and plaque morphology on prolapse in stented coronary arteries. A finite element method is applied for the stent, plaque, and artery set to quantify the tissue prolapse and the corresponding stresses in stenosed coronary arteries. The variable size of atherosclerotic plaques is considered. A plaque is modelled as a multi-layered medium with different thicknesses attached to the single layer of an arterial wall. The results reveal that the tissue prolapse is influenced by the degree of stenosis severity and the thickness of the plaque layers. Stresses are observed to be significantly different between the plaque layers and the arterial wall tissue. Higher stresses are concentrated in fibrosis layer of the plaque (the harder core), while lower stresses are observed in necrotic core (the softer core) and the arterial wall layer. Moreover, the morphology of the plaque regulates the magnitude and distribution of the stress. The fibrous cap between the necrotic core and the endothelium constitutes the most influential layer to alter the stresses. In addition, the thickness of the necrotic core and the stenosis severity affect the stresses. This study reveals that the morphology of atherosclerotic plaques needs to be considered a key parameter in designing coronary stents.

  10. Theoretical model for thin ferroelectric films and the multilayer structures based on them

    SciTech Connect

    Starkov, A. S. Pakhomov, O. V.; Starkov, I. A.

    2013-06-15

    A modified Weiss mean-field theory is used to study the dependence of the properties of a thin ferroelectric film on its thickness. The possibility of introducing gradient terms into the thermodynamic potential is analyzed using the calculus of variations. An integral equation is introduced to generalize the well-known Langevin equation to the case of the boundaries of a ferroelectric. An analysis of this equation leads to the existence of a transition layer at the interface between ferroelectrics or a ferroelectric and a dielectric. The permittivity of this layer is shown to depend on the electric field direction even if the ferroelectrics in contact are homogeneous. The results obtained in terms of the Weiss model are compared with the results of the models based on the correlation effect and the presence of a dielectric layer at the boundary of a ferroelectric and with experimental data.

  11. Computer modelling of aluminum-gallium arsenide/gallium arsenide multilayer photovoltaics. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Wagner, Michael Broderick

    1987-01-01

    The modeled cascade cells offer an alternative to conventional series cascade designs that require a monolithic intercell ohmic contact. Selective electrodes provide a simple means of fabricating three-terminal devices, which can be configured in complementary pairs to circumvent the attendant losses and fabrication complexities of intercell ohmic contacts. Moreover, selective electrodes allow incorporation of additional layers in the upper subcell which can improve spectral response and increase radiation tolerance. Realistic simulations of such cells operating under one-sun AMO conditions show that the seven-layer structure is optimum from the standpoint of beginning-of-life efficiency and radiation tolerance. Projected efficiencies exceed 26 percent. Under higher concentration factors, it should be possible to achieve efficiencies beyond 30 percent. However, to simulate operation at high concentration will require a model for resistive losses. Overall, these devices appear to be a promising contender for future space applications.

  12. Multilayer limb quasi-static electromagnetic modeling with experiments for Galvanic coupling type IBC.

    PubMed

    Pun, S H; Gao, Y M; Mou, P A; Mak, P U; Vai, M I; Du, M

    2010-01-01

    Intra-body communication (IBC) is a new, emerging, short-range and human body based communication methodology. It is a technique to network various devices on human body, by utilizing the conducting properties of human tissues. For currently fast developed Body area network(BAN)/Body sensor network(BSN), IBC is believed to have advantages in power consumption, electromagnetic radiation, interference from external electromagnetic noise, security, and restriction in spectrum resource. In this article, the authors propose an improved mathematical model, which includes both electrical properties and proportion of human tissues, for IBC on a human limb. By solving the mathematical model analytically on four-layer system (skin, fat, muscle, and bone) and conducting in-vivo experiment, a comparison has been conducted.

  13. An analytical model for predicting LNAPL distribution and recovery from multi-layered soils.

    PubMed

    Jeong, Jaehak; Charbeneau, Randall J

    2014-01-01

    An analytical model was developed for estimating the distribution and recovery of light nonaqueous phase liquids (LNAPL) in heterogeneous aquifers. Various scenarios of LNAPL recovery may be simulated using LDRM for LNAPL recovery systems such as skimmer wells, water-enhanced wells, air-enhanced wells, and trenches from heterogeneous aquifers. LDRM uses multiple horizontal soil layers to model a heterogeneous aquifer. Up to three soil layers may be configured with unique soil properties for each layer. Simulation results suggest that LNAPL distribution and its recovery volume are highly affected by soil properties. In sandy soils LNAPL can be highly mobile and the recovery efficiency can be high. In contrast, even at high LNAPL saturations, LNAPL mobility is typically low in fine-grained soils. This characteristic of LNAPL with respect to soil texture has to be carefully accounted for in the model to better predict the recovery of LNAPL from heterogeneous soils. The impact of vertical hydraulic gradient in fine grain zone was assessed. A sensitivity analysis suggests that the formation LNAPL volume can be significantly affected by a downward vertical hydraulic gradient if the magnitude is near a critical amount (=ρr-1). Sensitivity of input parameters with respect to LNAPL formation in soils and LNAPL recovery volume were identified through a sensitivity analysis. The performance of LDRM on predicting the distribution and recovery of LNAP was reasonably accurate for a short-term analysis as demonstrated in a case study. However, further validation is needed to ascertain the model's performance in long-term simulations. PMID:24262305

  14. An analytical model for predicting LNAPL distribution and recovery from multi-layered soils.

    PubMed

    Jeong, Jaehak; Charbeneau, Randall J

    2014-01-01

    An analytical model was developed for estimating the distribution and recovery of light nonaqueous phase liquids (LNAPL) in heterogeneous aquifers. Various scenarios of LNAPL recovery may be simulated using LDRM for LNAPL recovery systems such as skimmer wells, water-enhanced wells, air-enhanced wells, and trenches from heterogeneous aquifers. LDRM uses multiple horizontal soil layers to model a heterogeneous aquifer. Up to three soil layers may be configured with unique soil properties for each layer. Simulation results suggest that LNAPL distribution and its recovery volume are highly affected by soil properties. In sandy soils LNAPL can be highly mobile and the recovery efficiency can be high. In contrast, even at high LNAPL saturations, LNAPL mobility is typically low in fine-grained soils. This characteristic of LNAPL with respect to soil texture has to be carefully accounted for in the model to better predict the recovery of LNAPL from heterogeneous soils. The impact of vertical hydraulic gradient in fine grain zone was assessed. A sensitivity analysis suggests that the formation LNAPL volume can be significantly affected by a downward vertical hydraulic gradient if the magnitude is near a critical amount (=ρr-1). Sensitivity of input parameters with respect to LNAPL formation in soils and LNAPL recovery volume were identified through a sensitivity analysis. The performance of LDRM on predicting the distribution and recovery of LNAP was reasonably accurate for a short-term analysis as demonstrated in a case study. However, further validation is needed to ascertain the model's performance in long-term simulations.

  15. A multilayer micromechanical model of the cuticle of Curculio longinasus Chittenden, 1927 (Coleoptera: Curculionidae).

    PubMed

    Andrew Jansen, M; Singh, Sudhanshu S; Chawla, Nikhilesh; Franz, Nico M

    2016-08-01

    Curculio longinasus Chittenden, 1927 (Coleoptera: Curculionidae), is a weevil species common throughout the southwestern United States that uses its rostrum - a very slender, curved, beak-like projection of the head - to excavate tunnels in plant organs (such as acorns) for egg laying (oviposition). Once the apical portion of the rostrum has been inserted into the preferred substrate for oviposition, the female begins rotating around the perimeter of the hole, elevating her head by extending the fore-legs, and rotating the head in place in a drilling motion. This action causes significant elastic deformation of the rostrum, which will bend until it becomes completely straight. To better understand the mechanical behavior of the cuticle as it undergoes deformation during the preparation of oviposition sites, we develop a comprehensive micro/macro model of the micromechanical structure and properties of the cuticle, spanning across all cuticular regions, and reliably mirroring the resultant macroscale properties of the cuticle. Our modeling approach relies on the use of multi-scale, hierarchical biomaterial representation, and employs various micromechanical schemata - e.g., Mori-Tanaka, effective field, and Maxwell - to calculate the homogenized properties of representative volume elements at each level in the hierarchy. We describe the configuration and behavior of this model in detail, and discuss the theoretical implications and limitations of this approach with emphasis on future biomechanical and comparative evolutionary research. Our detailed account of this approach can thereby serve as a methodological template for exploring the biomechanical behavior of new insect structures. PMID:27189867

  16. SENCA: A Multilayered Codon Model to Study the Origins and Dynamics of Codon Usage

    PubMed Central

    Pouyet, Fanny; Bailly-Bechet, Marc; Mouchiroud, Dominique; Guéguen, Laurent

    2016-01-01

    Gene sequences are the target of evolution operating at different levels, including the nucleotide, codon, and amino acid levels. Disentangling the impact of those different levels on gene sequences requires developing a probabilistic model with three layers. Here we present SENCA (site evolution of nucleotides, codons, and amino acids), a codon substitution model that separately describes 1) nucleotide processes which apply on all sites of a sequence such as the mutational bias, 2) preferences between synonymous codons, and 3) preferences among amino acids. We argue that most synonymous substitutions are not neutral and that SENCA provides more accurate estimates of selection compared with more classical codon sequence models. We study the forces that drive the genomic content evolution, intraspecifically in the core genome of 21 prokaryotes and interspecifically for five Enterobacteria. We retrieve the existence of a universal mutational bias toward AT, and that taking into account selection on synonymous codon usage has consequences on the measurement of selection on nonsynonymous substitutions. We also confirm that codon usage bias is mostly driven by selection on preferred codons. We propose new summary statistics to measure the relative importance of the different evolutionary processes acting on sequences. PMID:27401173

  17. SENCA: A Multilayered Codon Model to Study the Origins and Dynamics of Codon Usage.

    PubMed

    Pouyet, Fanny; Bailly-Bechet, Marc; Mouchiroud, Dominique; Guéguen, Laurent

    2016-01-01

    Gene sequences are the target of evolution operating at different levels, including the nucleotide, codon, and amino acid levels. Disentangling the impact of those different levels on gene sequences requires developing a probabilistic model with three layers. Here we present SENCA (site evolution of nucleotides, codons, and amino acids), a codon substitution model that separately describes 1) nucleotide processes which apply on all sites of a sequence such as the mutational bias, 2) preferences between synonymous codons, and 3) preferences among amino acids. We argue that most synonymous substitutions are not neutral and that SENCA provides more accurate estimates of selection compared with more classical codon sequence models. We study the forces that drive the genomic content evolution, intraspecifically in the core genome of 21 prokaryotes and interspecifically for five Enterobacteria. We retrieve the existence of a universal mutational bias toward AT, and that taking into account selection on synonymous codon usage has consequences on the measurement of selection on nonsynonymous substitutions. We also confirm that codon usage bias is mostly driven by selection on preferred codons. We propose new summary statistics to measure the relative importance of the different evolutionary processes acting on sequences.

  18. SENCA: A Multilayered Codon Model to Study the Origins and Dynamics of Codon Usage.

    PubMed

    Pouyet, Fanny; Bailly-Bechet, Marc; Mouchiroud, Dominique; Guéguen, Laurent

    2016-01-01

    Gene sequences are the target of evolution operating at different levels, including the nucleotide, codon, and amino acid levels. Disentangling the impact of those different levels on gene sequences requires developing a probabilistic model with three layers. Here we present SENCA (site evolution of nucleotides, codons, and amino acids), a codon substitution model that separately describes 1) nucleotide processes which apply on all sites of a sequence such as the mutational bias, 2) preferences between synonymous codons, and 3) preferences among amino acids. We argue that most synonymous substitutions are not neutral and that SENCA provides more accurate estimates of selection compared with more classical codon sequence models. We study the forces that drive the genomic content evolution, intraspecifically in the core genome of 21 prokaryotes and interspecifically for five Enterobacteria. We retrieve the existence of a universal mutational bias toward AT, and that taking into account selection on synonymous codon usage has consequences on the measurement of selection on nonsynonymous substitutions. We also confirm that codon usage bias is mostly driven by selection on preferred codons. We propose new summary statistics to measure the relative importance of the different evolutionary processes acting on sequences. PMID:27401173

  19. Mesoscopic modeling of the response of human dental enamel to mid-infrared radiation

    NASA Astrophysics Data System (ADS)

    Vila Verde, Ana; Ramos, Marta; Stoneham, A. M.

    2006-03-01

    Ablation of human dental enamel, a composite biomaterial with water pores, is of significant importance in minimally invasive laser dentistry but progress in the area is hampered by the lack of optimal laser parameters. We use mesoscopic finite element models of this material to study its response to mid-infrared radiation. Our results indicate that the cost-effective, off-the-shelf CO2 laser at λ = 10.6 μm may in fact ablate enamel precisely, reproducibly and with limited unwanted side effects such as cracking or heating, provided that a pulse duration of 10 μs is used. Furthermore, our results also indicate that the Er:YAG laser (λ = 2.94 μm), currently popular for laser dentistry, may in fact cause unwanted deep cracking in the enamel when regions with unusually high water content are irradiated, and also provide an explanation for the large range of ablation threshold values observed for this material. The model may be easily adapted to study the response of any composite material to infrared radiation and thus may be useful for the scientific community.

  20. Craniofacial and Dental Defects in the Col1a1Jrt/+ Mouse Model of Osteogenesis Imperfecta.

    PubMed

    Eimar, H; Tamimi, F; Retrouvey, J-M; Rauch, F; Aubin, J E; McKee, M D

    2016-07-01

    Certain mutations in the COL1A1 and COL1A2 genes produce clinical symptoms of both osteogenesis imperfecta (OI) and Ehlers-Danlos syndrome (EDS) that include abnormal craniofacial growth, dental malocclusion, and dentinogenesis imperfecta. A mouse model (Col1a1(Jrt)/+) was recently developed that had a skeletal phenotype and other features consistent with moderate-to-severe OI and also with EDS. The craniofacial phenotype of 4- and 20-wk-old Col1a1(Jrt)/+ mice and wild-type littermates was assessed by micro-computed tomography (µCT) and morphometry. Teeth and the periodontal ligament compartment were analyzed by µCT, light microscopy/histomorphometry, and electron microscopy. Over time, at 20 wk, Col1a1(Jrt)/+ mice developed smaller heads, a shortened anterior cranial base, class III occlusion, and a mandibular side shift with shorter morphology in the masticatory region (maxilla and mandible). Col1a1(Jrt)/+ mice also had changes in the periodontal compartment and abnormalities in the dentin matrix and mineralization. These findings validate Col1a1(Jrt)/+ mice as a model for OI and EDS in humans. PMID:26951553

  1. Verification of the multi-layer SNOWPACK model with different water transport schemes

    NASA Astrophysics Data System (ADS)

    Wever, N.; Schmid, L.; Heilig, A.; Eisen, O.; Fierz, C.; Lehning, M.

    2015-12-01

    The widely used detailed SNOWPACK model has undergone constant development over the years. A notable recent extension is the introduction of a Richards equation (RE) solver as an alternative for the bucket-type approach for describing water transport in the snow and soil layers. In addition, continuous updates of snow settling and new snow density parameterizations have changed model behavior. This study presents a detailed evaluation of model performance against a comprehensive multiyear data set from Weissfluhjoch near Davos, Switzerland. The data set is collected by automatic meteorological and snowpack measurements and manual snow profiles. During the main winter season, snow height (RMSE: < 4.2 cm), snow water equivalent (SWE, RMSE: < 40 mm w.e.), snow temperature distributions (typical deviation with measurements: < 1.0 °C) and snow density (typical deviation with observations: < 50 kg m-3) as well as their temporal evolution are well simulated in the model and the influence of the two water transport schemes is small. The RE approach reproduces internal differences over capillary barriers but fails to predict enough grain growth since the growth routines have been calibrated using the bucket scheme in the original SNOWPACK model. However, the agreement in both density and grain size is sufficient to parameterize the hydraulic properties successfully. In the melt season, a pronounced underestimation of typically 200 mm w.e. in SWE is found. The discrepancies between the simulations and the field data are generally larger than the differences between the two water transport schemes. Nevertheless, the detailed comparison of the internal snowpack structure shows that the timing of internal temperature and water dynamics is adequately and better represented with the new RE approach when compared to the conventional bucket scheme. On the contrary, the progress of the meltwater front in the snowpack as detected by radar and the temporal evolution of the vertical

  2. A new method for the integration of digital dental models and cone-beam computed tomography images.

    PubMed

    Lin, Hsiu-Hsia; Chiang, Wen-Chung; Lo, Lun-Jou; Wang, Chien-Hsuan

    2013-01-01

    This study introduces a regional-surface-based registration without markers for integration of laser-scanned dental images into maxillofacial cone-beam computed tomography (CBCT) images. The method just needs to manually select three similar areas without artifact on the digital dental image and CBCT image, and then the process is automatically complete the fusion (superimposition) of maxillofacial model and the digital dental model. Then the differences such as mean error and root-mean-square (RMS) error are automatically computed between the 2 images according to the selected surfaces and expressed in a color scale. Experimental results show that the mean errors between the 2 models at the integrated model range from 0.15 mm to 0.45 mm and the RMS errors range 0.18 mm to 0.49 mm. The numbers are similar to the results of previous methods and reach a desirable error. Moreover, it is robust feasibility for especially serious artifacts CBT images. It is worth mentioning that all measurements of intra-operator reproducibility and inter-operator reliability are excellent. PMID:24110191

  3. Application of third molar development and eruption models in estimating dental age in Malay sub-adults.

    PubMed

    Mohd Yusof, Mohd Yusmiaidil Putera; Cauwels, Rita; Deschepper, Ellen; Martens, Luc

    2015-08-01

    The third molar development (TMD) has been widely utilized as one of the radiographic method for dental age estimation. By using the same radiograph of the same individual, third molar eruption (TME) information can be incorporated to the TMD regression model. This study aims to evaluate the performance of dental age estimation in individual method models and the combined model (TMD and TME) based on the classic regressions of multiple linear and principal component analysis. A sample of 705 digital panoramic radiographs of Malay sub-adults aged between 14.1 and 23.8 years was collected. The techniques described by Gleiser and Hunt (modified by Kohler) and Olze were employed to stage the TMD and TME, respectively. The data was divided to develop three respective models based on the two regressions of multiple linear and principal component analysis. The trained models were then validated on the test sample and the accuracy of age prediction was compared between each model. The coefficient of determination (R²) and root mean square error (RMSE) were calculated. In both genders, adjusted R² yielded an increment in the linear regressions of combined model as compared to the individual models. The overall decrease in RMSE was detected in combined model as compared to TMD (0.03-0.06) and TME (0.2-0.8). In principal component regression, low value of adjusted R(2) and high RMSE except in male were exhibited in combined model. Dental age estimation is better predicted using combined model in multiple linear regression models. PMID:26165657

  4. Application of third molar development and eruption models in estimating dental age in Malay sub-adults.

    PubMed

    Mohd Yusof, Mohd Yusmiaidil Putera; Cauwels, Rita; Deschepper, Ellen; Martens, Luc

    2015-08-01

    The third molar development (TMD) has been widely utilized as one of the radiographic method for dental age estimation. By using the same radiograph of the same individual, third molar eruption (TME) information can be incorporated to the TMD regression model. This study aims to evaluate the performance of dental age estimation in individual method models and the combined model (TMD and TME) based on the classic regressions of multiple linear and principal component analysis. A sample of 705 digital panoramic radiographs of Malay sub-adults aged between 14.1 and 23.8 years was collected. The techniques described by Gleiser and Hunt (modified by Kohler) and Olze were employed to stage the TMD and TME, respectively. The data was divided to develop three respective models based on the two regressions of multiple linear and principal component analysis. The trained models were then validated on the test sample and the accuracy of age prediction was compared between each model. The coefficient of determination (R²) and root mean square error (RMSE) were calculated. In both genders, adjusted R² yielded an increment in the linear regressions of combined model as compared to the individual models. The overall decrease in RMSE was detected in combined model as compared to TMD (0.03-0.06) and TME (0.2-0.8). In principal component regression, low value of adjusted R(2) and high RMSE except in male were exhibited in combined model. Dental age estimation is better predicted using combined model in multiple linear regression models.

  5. Reducing child uncooperative behavior during dental treatment through modeling and reinforcement.

    PubMed

    Stokes, T F; Kennedy, S H

    1980-01-01

    The uncooperative behavior of grade-school children during dental treatment was examined. Forty children enrolled in a government dental program were observed during treatment conditions involving instructions concerning the appropriate behavior required by the dental practitioner, description of the objective procedures and subjective experience the child could expect, praise for appropriate behavior, and a colorful stamp for coming to the clinic. Eight of these children whose behavior was still too disruptive for effective dentistry were formally introduced to additional intervention procedures of tangible consequences for cooperative behavior, and observation of peers and by peers during actual dental treatment. Within a multiple baseline design, the intervention conditions were effective in decreasing the children's uncooperative behavior to acceptable levels.

  6. Modelling of pain intensity and informative dropout in a dental pain model after naproxcinod, naproxen and placebo administration

    PubMed Central

    Björnsson, Marcus A; Simonsson, Ulrika S H

    2011-01-01

    AIMS To describe pain intensity (PI) measured on a visual analogue scale (VAS) and dropout due to request for rescue medication after administration of naproxcinod, naproxen or placebo in 242 patients after wisdom tooth removal. METHODS Non-linear mixed effects modelling was used to describe the plasma concentrations of naproxen, either formed from naproxcinod or from naproxen itself, and their relationship to PI and dropout. Goodness of fit was assessed by simultaneous simulations of PI and dropout. RESULTS Baseline PI for the typical patient was 52.7 mm. The PI was influenced by placebo effects, using an exponential model, and by naproxen concentrations using a sigmoid Emax model. Typical maximal placebo effect was a decrease in PI by 20.2%, with an onset rate constant of 0.237 h−1. EC50 was 0.135 µmol l−1. A Weibull time-to-event model was used for the dropout, where the hazard was dependent on the predicted PI and by the PI at baseline. Since the dropout was not at random, it was necessary to include the simulated dropout in visual predictive checks (VPC) of PI. CONCLUSIONS This model describes the relationship between drug effects, PI and the likelihood of dropout after naproxcinod, naproxen and placebo administration. The model provides an opportunity to describe the effects of other doses or formulations, after dental extraction. VPC created by simultaneous simulations of PI and dropout provides a good way of assessing the goodness of fit when there is informative dropout. PMID:21272053

  7. A Multilayered Box Model for Calculating Preliminary RemediationGoals in Soil Screening

    SciTech Connect

    Shan, Chao; Javandel, Iraj

    2004-05-21

    In the process of screening a soil against a certain contaminant, we define the health-risk based preliminary remediation goal (PRG) as the contaminant concentration above which some remedial action may be required. PRG is thus the first standard (or guidance) for judging a site. An over-estimated PRG (a too-large value) may cause us to miss some contaminated sites that can threaten human health and the environment. An under-estimated PRG (a too-small value), on the other hand, may lead to unnecessary cleanup and waste tremendous resources. The PRGs for soils are often calculated on the assumption that the contaminant concentration in soil does not change with time. However, that concentration usually decreases with time as a result of different chemical and transport mechanisms. The static assumption thus exaggerates the long-term exposure dose and results in a too-small PRG. We present a box model that considers all important transport processes and obeys the law of mass conservation. We can use the model as a tool to estimate the transient contaminant concentrations in air, soil and groundwater. Using these concentrations in conjunction with appropriate health risk parameters, we may estimate the PRGs for different contaminants. As an example, we calculated the tritium PRG for residential soils. The result is quite different from, but within the range of, the two versions of the corresponding PRG previously recommended by the U.S. EPA.

  8. Understanding geometric instabilities in thin films via a multi-layer model.

    PubMed

    Lejeune, Emma; Javili, Ali; Linder, Christian

    2016-01-21

    When a thin stiff film adhered to a compliant substrate is subject to compressive stresses, the film will experience a geometric instability and buckle out of plane. For high film/substrate stiffness ratios with relatively low levels of strain, the primary mode of instability will either be wrinkling or buckling delamination depending on the material and geometric properties of the system. Previous works approach these systems by treating the film and substrate as homogenous layers, either consistently perfectly attached, or perfectly unattached at interfacial flaws. However, this approach neglects systems where the film and substrate are uniformly weakly attached or where interfacial layers due to surface modifications in either the film or substrate are present. Here we demonstrate a method for accounting for these additional thin surface layers via an analytical solution verified by numerical results. The main outcome of this work is an improved understanding of how these layers influence global behavior. We demonstrate the utility of our model with applications ranging from buckling based metrology in ultrathin films, to an improved understanding of the formation of a novel surface in carbon nanotube bio-interface films. Moving forward, this model can be used to interpret experimental results, particularly for systems which deviate from traditional behavior, and aid in the evaluation and design of future film/substrate systems.

  9. A Case Study of Using a Multilayered Thermodynamical Snow Model for Radiance Assimilation

    NASA Technical Reports Server (NTRS)

    Toure, Ally M.; Goita, Kalifa; Royer, Alain; Kim, Edward J.; Durand, Michael; Margulis, Steven A.; Lu, Huizhong

    2011-01-01

    A microwave radiance assimilation (RA) scheme for the retrieval of snow physical state variables requires a snowpack physical model (SM) coupled to a radiative transfer model. In order to assimilate microwave brightness temperatures (Tbs) at horizontal polarization (h-pol), an SM capable of resolving melt-refreeze crusts is required. To date, it has not been shown whether an RA scheme is tractable with the large number of state variables present in such an SM or whether melt-refreeze crust densities can be estimated. In this paper, an RA scheme is presented using the CROCUS SM which is capable of resolving melt-refreeze crusts. We assimilated both vertical (v) and horizontal (h) Tbs at 18.7 and 36.5 GHz. We found that assimilating Tb at both h-pol and vertical polarization (v-pol) into CROCUS dramatically improved snow depth estimates, with a bias of 1.4 cm compared to-7.3 cm reported by previous studies. Assimilation of both h-pol and v-pol led to more accurate results than assimilation of v-pol alone. The snow water equivalent (SWE) bias of the RA scheme was 0.4 cm, while the bias of the SWE estimated by an empirical retrieval algorithm was -2.9 cm. Characterization of melt-refreeze crusts via an RA scheme is demonstrated here for the first time; the RA scheme correctly identified the location of melt-refreeze crusts observed in situ.

  10. Dental OCT

    NASA Astrophysics Data System (ADS)

    Colston, Bill W.; Sathyam, Ujwal S.; Dasilva, Luiz B.; Everett, Matthew J.; Stroeve, Pieter; Otis, L. L.

    1998-09-01

    We present here the first in vivo optical coherence tomography (OCT) images of human dental tissue. A novel dental optical coherence tomography system has been developed. This system incorporates the interferometer sample arm and transverse scanning optics into a handpiece that can be used intraorally to image human dental tissues. The average imaging depth of this system varied from 3 mm in hard tissues to 1.5 mm in soft tissues. We discuss the application of this imaging system for dentistry and illustrate the potential of our dental OCT system for diagnosis of periodontal disease, detection of caries, and evaluation of dental restorations.

  11. Multivariate Geostatistical Analysis of Uncertainty for the Hydrodynamic Model of a Geological Trap for Carbon Dioxide Storage. Case study: Multilayered Geological Structure Vest Valcele, ROMANIA

    NASA Astrophysics Data System (ADS)

    Scradeanu, D.; Pagnejer, M.

    2012-04-01

    The purpose of the works is to evaluate the uncertainty of the hydrodynamic model for a multilayered geological structure, a potential trap for carbon dioxide storage. The hydrodynamic model is based on a conceptual model of the multilayered hydrostructure with three components: 1) spatial model; 2) parametric model and 3) energy model. The necessary data to achieve the three components of the conceptual model are obtained from: 240 boreholes explored by geophysical logging and seismic investigation, for the first two components, and an experimental water injection test for the last one. The hydrodinamic model is a finite difference numerical model based on a 3D stratigraphic model with nine stratigraphic units (Badenian and Oligocene) and a 3D multiparameter model (porosity, permeability, hydraulic conductivity, storage coefficient, leakage etc.). The uncertainty of the two 3D models was evaluated using multivariate geostatistical tools: a)cross-semivariogram for structural analysis, especially the study of anisotropy and b)cokriging to reduce estimation variances in a specific situation where is a cross-correlation between a variable and one or more variables that are undersampled. It has been identified important differences between univariate and bivariate anisotropy. The minimised uncertainty of the parametric model (by cokriging) was transferred to hydrodynamic model. The uncertainty distribution of the pressures generated by the water injection test has been additional filtered by the sensitivity of the numerical model. The obtained relative errors of the pressure distribution in the hydrodynamic model are 15-20%. The scientific research was performed in the frame of the European FP7 project "A multiple space and time scale approach for the quantification of deep saline formation for CO2 storage(MUSTANG)".

  12. Chemical or microbiological models of secondary caries development around different dental restorative materials.

    PubMed

    Lobo, Maristela M; Gonçalves, Reginaldo B; Ambrosano, Gláucia Maria B; Pimenta, Luiz André F

    2005-08-01

    This study evaluated artificial secondary caries around restorative materials, induced by means of chemical or microbiological models. The following materials were used randomly to restore 130 dental blocks: (1) zinc-oxide eugenol-free temporary filling: Coltosol (Coltène/Whaledent Inc.; n = 30), (2) silver amalgam: Permite C (SDI Limited, n = 20), (3) composite resin: Filtek Z250 (3M ESPE; n = 20), (4) glass-ionomer cement: Fuji II (GC America Inc.; n = 20), (5) resin-modified glass ionomer: Vitremer (3M ESPE; n = 20), and (6) polyacid modified resin: Dyract AP (Dentsply; n = 20). Ten specimens of Group 1 were kept in humidity, and had no carious formation (NC). Ten specimens of each group were submitted to pH cycling (CG, n = 60), and the others were immersed in a medium containing Streptococcus mutans and sucrose (BG, n = 60). Mineral content was determined by microhardness assessment, and lesion depth was measured in polarized light photomicrographs. In the chemical model (CG), mineral content values in the vicinities of restoration were high for Groups 5 (75.7 +/- 11.9), 4 (70.8 +/- 14.2), and NC (95.4 +/- 3.8); intermediate for Groups 1 (55.8 +/- 18.5), 6 (45.6 +/- 11.0), and 2 (44.3 +/- 11.2); and reduced for Group 3 (34.7 +/- 9.7). In the microbiological model (BG), results were similar to CG, although there was less demineralization. The highest lesion depths were found for Groups 3 (182.3 +/- 33.2) in CG and 6 (126.5 +/- 42.8) in BG, when compared to Group 5 (114.6 +/- 26.0 and 56.2 +/- 33.2, respectively). In both models of caries induction, ionomeric materials showed a superior cariostatic effect when compared to the other restorative materials.

  13. Nanostructured assemblies for dental application.

    PubMed

    Fioretti, Florence; Mendoza-Palomares, Carlos; Helms, Marie; Al Alam, Denise; Richert, Ludovic; Arntz, Youri; Rinckenbach, Simon; Garnier, Fabien; Haïkel, Youssef; Gangloff, Sophie C; Benkirane-Jessel, Nadia

    2010-06-22

    Millions of teeth are saved each year by root canal therapy. Although current treatment modalities offer high levels of success for many conditions, an ideal form of therapy might consist of regenerative approaches in which diseased or necrotic pulp tissues are removed and replaced with healthy pulp tissue to revitalize teeth. Melanocortin peptides (alpha-MSH) possess anti-inflammatory properties in many acute and chronic inflammatory models. Our recent studies have shown that alpha-MSH covalently coupled to poly-l-glutamic acid (PGA-alpha-MSH) retains anti-inflammatory properties on rat monocytes. This study aimed to define the effects of PGA-alpha-MSH on dental pulp fibroblasts. Lipopolysaccharide (LPS)-stimulated fibroblasts incubated with PGA-alpha-MSH showed an early time-dependent inhibition of TNF-alpha, a late induction of IL-10, and no effect on IL-8 secretion. However, in the absence of LPS, PGA-alpha-MSH induced IL-8 secretion and proliferation of pulp fibroblasts, whereas free alpha-MSH inhibited this proliferation. Thus, PGA-alpha-MSH has potential effects in promoting human pulp fibroblast adhesion and cell proliferation. It can also reduce the inflammatory state of LPS-stimulated pulp fibroblasts observed in gram-negative bacterial infections. These effects suggest a novel use of PGA-alpha-MSH as an anti-inflammatory agent in the treatment of endodontic lesions. To better understand these results, we have also used the multilayered polyelectrolyte films as a reservoir for PGA-alpha-MSH by using not only PLL (poly-l-lysine) but also the Dendri Graft poly-l-lysines (DGL(G4)) to be able to adsorb more PGA-alpha-MSH. Our results indicated clearly that, by using PGA-alpha-MSH, we increase not only the viability of cells but also the proliferation. We have also analyzed at the nanoscale by atomic force microscopy these nanostructured architectures and shown an increase of thickness and roughness in the presence of PGA-alpha-MSH incorporated into the

  14. Associative Account of Self-Cognition: Extended Forward Model and Multi-Layer Structure

    PubMed Central

    Sugiura, Motoaki

    2013-01-01

    The neural correlates of “self” identified by neuroimaging studies differ depending on which aspects of self are addressed. Here, three categories of self are proposed based on neuroimaging findings and an evaluation of the likely underlying cognitive processes. The physical self, representing self-agency of action, body-ownership, and bodily self-recognition, is supported by the sensory and motor association cortices located primarily in the right hemisphere. The interpersonal self, representing the attention or intentions of others directed at the self, is supported by several amodal association cortices in the dorsomedial frontal and lateral posterior cortices. The social self, representing the self as a collection of context-dependent social-values, is supported by the ventral aspect of the medial prefrontal cortex and the posterior cingulate cortex. Despite differences in the underlying cognitive processes and neural substrates, all three categories of self are likely to share the computational characteristics of the forward model, which is underpinned by internal schema or learned associations between one’s behavioral output and the consequential input. Additionally, these three categories exist within a hierarchical layer structure based on developmental processes that updates the schema through the attribution of prediction error. In this account, most of the association cortices critically contribute to some aspect of the self through associative learning while the primary regions involved shift from the lateral to the medial cortices in a sequence from the physical to the interpersonal to the social self. PMID:24009578

  15. Numerical modelling of tooth enamel subsurface lesion formation induced by dental plaque.

    PubMed

    Ilie, O; van Turnhout, A G; van Loosdrecht, M C M; Picioreanu, C

    2014-01-01

    Using a one-dimensional mathematical model that couples tooth demineralisation and remineralisation with metabolic processes occurring in the dental plaque, two mechanisms for subsurface lesion formation were evaluated. It was found that a subsurface lesion can develop only as the result of alternating periods of demineralisation (acid attack during sugar consumption) and remineralisation (resting period) in tooth enamel with uniform mineral composition. It was also shown that a minimum plaque thickness that can induce an enamel lesion exists. The subsurface lesion formation can also be explained by assuming the existence of a fluoride-containing layer at the tooth surface that decreases enamel solubility. A nearly constant thickness of the surface layer was obtained with both proposed mechanisms. Sensitivity analysis showed that surface layer formation is strongly dependent on the length of remineralisation and demineralisation cycles. The restoration period is very important and the numerical simulations support the observation that often consumption of sugars is a key factor in caries formation. The calculated profiles of mineral content in enamel are similar to those observed experimentally. Most probably, both studied mechanisms interact in vivo in the process of caries development, but the simplest explanation for subsurface lesion formation remains the alternation between demineralisation and remineralisation cycles without any pre-imposed gradients.

  16. Finite-element modeling method for the study of dielectric relaxation at high frequencies of heterostructures made of multilayered particle

    NASA Astrophysics Data System (ADS)

    Fourn, Cédric; Lasquellec, Sophie; Brosseau, Christian

    2007-12-01

    There has been much recent interest in how morphological descriptors may affect the electromagnetic wave transport in particulate composite mediums. In this work, we present results of finite-element simulations that model the permittivity of two-dimensional (or cross sections of infinite three-dimensional parallel, infinitely long, identical, circular cylinders, where the properties and characteristics are invariant along the perpendicular cross-sectional plane) three-phase heterostructures made of a multilayered discoidal particle. While strictly valid only in a direct current situation, our analysis can be extended to treat electric fields that oscillate with time provided that the wavelengths and attenuation lengths associated with the fields are much larger than the microstructure dimension in order that the homogeneous (effective medium) representation of the composite structure makes sense. From simulations over a range of parameters, our analysis evaluates the effect of the surface fraction of inclusion, the conductivity, and thickness (relative to the particle radius) of the particle conductive coating on the effective complex permittivity of isotropic heterostructures in which the filler particles have a core-shell structure. Four main effects are found. First, the importance of the surface fraction of inclusion on the effective complex permittivity at high frequencies (from microwave to infrared) is illustrated over a broad range of coating thicknesses and conductivities. Second, the encapsulation phase (metallic coating) conductivity is identified as the key property controlling the dielectric relaxation due to interfacial polarization. Third, a simple parametrization of the high-frequency effective permittivity spectrum allowed us to obtain a reliable modelization of the Debye-type relaxation processes. From the least-squares fit of the effective complex permittivity data, we extract information on these relaxation processes, i.e., relaxation

  17. The role of mesoscopic modelling in understanding the response of dental enamel to mid-infrared radiation

    NASA Astrophysics Data System (ADS)

    Vila Verde, A.; Ramos, M. M. D.; Stoneham, A. M.

    2007-05-01

    Human dental enamel has a porous mesostructure at the nanometre to micrometre scales that affects its thermal and mechanical properties relevant to laser treatment. We exploit finite-element models to investigate the response of this mesostructured enamel to mid-infrared lasers (CO2 at 10.6 µm and Er:YAG at 2.94 µm). Our models might easily be adapted to investigate ablation of other brittle composite materials. The studies clarify the role of pore water in ablation, and lead to an understanding of the different responses of enamel to CO2 and Er:YAG lasers, even though enamel has very similar average properties at the two wavelengths. We are able to suggest effective operating parameters for dental laser ablation, which should aid the introduction of minimally-invasive laser dentistry. In particular, our results indicate that, if pulses of ap10 µs are used, the CO2 laser can ablate dental enamel without melting, and with minimal damage to the pulp of the tooth. Our results also suggest that pulses with 0.1-1 µs duration can induce high stress transients which may cause unwanted cracking.

  18. 3D-FE analysis of functionally graded structured dental posts.

    PubMed

    Abu Kasim, Noor H; Madfa, Ahmed A; Hamdi, Mohd; Rahbari, Ghahnavyeh R

    2011-01-01

    This study aimed to compare the biomechanical behaviour of functionally graded structured posts (FGSPs) and homogenous-type posts in simulated models of a maxillary central incisor. Two models of FGSPs consisting of a multilayer xTi-yHA composite design, where zirconia and alumina was added as the first layer for models A and B respectively were compared to homogenous zirconia post (model C) and a titanium post (model D). The amount of Ti and HA in the FGSP models was varied in gradations. 3D-FEA was performed on all models and stress distributions were investigated along the dental post. In addition, interface stresses between the posts and their surrounding structures were investigated under vertical, oblique, and horizontal loadings. Strain distribution along the post-dentine interface was also investigated. The results showed that FGSPs models, A and B demonstrated better stress distribution than models C and D, indicating that dental posts with multilayered structure dissipate localized and interfacial stress and strain more efficiently than homogenous-type posts. PMID:22123011

  19. Spherical cloaking with homogeneous isotropic multilayered structures

    NASA Astrophysics Data System (ADS)

    Qiu, Cheng-Wei; Hu, Li; Xu, Xiaofei; Feng, Yijun

    2009-04-01

    We propose a practical realization of electromagnetic spherical cloaking by layered structure of homogeneous isotropic materials. By mimicking the classic anisotropic cloak by many alternating thin layers of isotropic dielectrics, the permittivity and permeability in each isotropic layer can be properly determined by effective medium theory in order to achieve invisibility. The model greatly facilitates modeling by Mie theory and realization by multilayer coating of dielectrics. Eigenmode analysis is also presented to provide insights of the discretization in multilayers.

  20. Spherical cloaking with homogeneous isotropic multilayered structures.

    PubMed

    Qiu, Cheng-Wei; Hu, Li; Xu, Xiaofei; Feng, Yijun

    2009-04-01

    We propose a practical realization of electromagnetic spherical cloaking by layered structure of homogeneous isotropic materials. By mimicking the classic anisotropic cloak by many alternating thin layers of isotropic dielectrics, the permittivity and permeability in each isotropic layer can be properly determined by effective medium theory in order to achieve invisibility. The model greatly facilitates modeling by Mie theory and realization by multilayer coating of dielectrics. Eigenmode analysis is also presented to provide insights of the discretization in multilayers. PMID:19518392

  1. Multilayer Insulation Material Guidelines

    NASA Technical Reports Server (NTRS)

    Finckenor, M. M.; Dooling, D.

    1999-01-01

    Multilayer Insulation Material Guidelines provides data on multilayer insulation materials used by previous spacecraft such as Spacelab and the Long-Duration Exposure Facility and outlines other concerns. The data presented in the document are presented for information only. They can be used as guidelines for multilayer insulation design for future spacecraft provided the thermal requirements of each new design and the environmental effects on these materials are taken into account.

  2. Periodontal and dental effects of surgically assisted rapid maxillary expansion, assessed by using digital study models

    PubMed Central

    Siqueira, Danilo Furquim; Cardoso, Mauricio de Almeida; Capelozza, Leopoldino; Goldenberg, Dov Charles; Fernandes, Mariana dos Santos

    2015-01-01

    OBJECTIVE: The present study assessed the maxillary dental arch changes produced by surgically assisted rapid maxillary expansion (SARME). METHODS: Dental casts from 18 patients (mean age of 23.3 years) were obtained at treatment onset (T1), three months after SARME (T2) and 6 months after expansion (T3). The casts were scanned in a 3D scanner (D-250, 3Shape, Copenhagen, Denmark). Maxillary dental arch width, dental crown tipping and height were measured and assessed by ANOVA and Tukey's test. RESULTS: Increased transversal widths from T1 and T2 and the maintenance of these values from T2 and T3 were observed. Buccal teeth tipping also showed statistically significant differences, with an increase in all teeth from T1 to T2 and a decrease from T2 to T3. No statistically significant difference was found for dental crown height, except for left first and second molars, although clinically irrelevant. CONCLUSION: SARME proved to be an effective and stable procedure, with minimum periodontal hazards. PMID:26154457

  3. Exact solution of multilayered piezoelectric diaphragms.

    PubMed

    Yao, Linquan; Lu, Li; Wang, Zhihong; Zhu, Weiguang; Dai, Ying

    2003-10-01

    This paper investigates dynamic behavior of multilayered piezoelectric diaphragms that are simplified as laminated plates. The validity of the dynamic analysis based on the simplified clamped multilayered plate model has first been studied using ANSYS finite element (FE)-codes. The simplified, clamped, multilayered plate model has been verified to be a reasonable one in comparison with the exact model. Subsequently, the frequency characteristics of clamped rectangular piezoelectric laminated plates were further analytically investigated. Using the classical laminated plate theory, mechanical, electrical, and electromechanical characteristics of the multilayered piezoelectric diaphragms were studied. For ease of calculation, the dimensionless method was adopted. Furthermore, numerical analysis was carried out using the Rayleigh-Ritz method. Influence of dimensions of the laminar diaphragm on nature frequencies also was studied. The thickness ratio of the PZT layer to the total thickness of the laminar diaphragm has been optimized to obtain the largest deflection.

  4. A comparison of the clinical and experimental characteristics of four acute surgical pain models: dental extraction, bunionectomy, joint replacement, and soft tissue surgery.

    PubMed

    Singla, Neil K; Desjardins, Paul J; Chang, Phoebe D

    2014-03-01

    When a clinical trial of an analgesic produces a negative finding, it is important to consider the influence (if any) of experimental error on the validity of that result. Although efforts to identify and minimize experimental error in chronic pain investigations have begun in earnest, less work has been performed on the optimization of acute pain methodology. Of the acute surgical pain methodology articles that have been published over the last decade, almost all focus on either the dental or bunion model. Analgesics are typically evaluated in a variety of surgical models that eventually include hospital-based models (eg, joint replacement and soft tissue surgery). Every surgical procedure has unique clinical characteristics that must be considered to optimize study design and conduct. Much of the methodological knowledge garnered from bunion and dental studies is applicable to other surgical models, but some extrapolations are hazardous. The purposes of this review were (1) to qualitatively describe the clinical and experimental characteristics of the 4 classic surgical models: dental extraction, bunionectomy, joint replacement, and soft tissue surgery; and (2) to quantitatively compare the models by analyzing 3 factors: effect size, enrollment rate, and demographics. We found that the dental extraction and bunionectomy models had higher assay sensitivity than the joint replacement and soft tissue surgery models. It is probable that this finding is secondary to the superior experimental conditions under which the dental and bunion models are executed (utilization of few centers that have the ability to reduce surgical, anesthetic, and postoperative confounders).

  5. Quantitative analysis of electron energy loss spectra and modelling of optical properties of multilayer systems for extreme ultraviolet radiation regime

    SciTech Connect

    Gusenleitner, S.; Hauschild, D.; Reinert, F.; Handick, E.

    2014-03-28

    Ruthenium capped multilayer coatings for use in the extreme ultraviolet (EUV) radiation regime have manifold applications in science and industry. Although the Ru cap shall protect the reflecting multilayers, the surface of the heterostructures suffers from contamination issues and surface degradation. In order to get a better understanding of the effects of these impurities on the optical parameters, reflection electron energy loss spectroscopy (REELS) measurements of contaminated and H cleaned Ru multilayer coatings were taken at various primary electron beam energies. Experiments conducted at low primary beam energies between 100 eV and 1000 eV are very surface sensitive due to the short inelastic mean free path of the electrons in this energy range. Therefore, influences of the surface condition on the above mentioned characteristics can be appraised. In this paper, it can be shown that carbon and oxide impurities on the mirror surface decrease the transmission of the Ru cap by about 0.75% and the overall reflectance of the device is impaired as the main share of the non-transmitted EUV light is absorbed in the contamination layer.

  6. Fabrication of multilayer nanowires

    NASA Astrophysics Data System (ADS)

    Kaur, Jasveer; Singh, Avtar; Kumar, Davinder; Thakur, Anup; Kaur, Raminder

    2016-05-01

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  7. Effect of salivary pellicle on antibacterial activity of novel antibacterial dental adhesives using a dental plaque microcosm biofilm model

    PubMed Central

    Li, Fang; Weir, Michael D.; Fouad, Ashraf F.; Xu, Hockin H.K.

    2014-01-01

    Objectives Antibacterial primer and adhesive are promising to inhibit biofilms and caries. Since restorations in vivo are exposed to saliva, one concern is the attenuation of antibacterial activity due to salivary pellicles. The objective of this study was to investigate the effects of salivary pellicles on bonding agents containing a new monomer dimethylaminododecyl methacrylate (DMADDM) or nanoparticles of silver (NAg) against biofilms for the first time. Methods DMADDM and NAg were synthesized and incorporated into Scotchbond Multi-Purpose adhesive and primer. Specimens were either coated or not coated with salivary pellicles. A microcosm biofilm model was used with mixed saliva from ten donors. Two types of culture medium were used: an artificial saliva medium (McBain), and Brain Heart Infusion (BHI) medium without salivary proteins. Metabolic activity, colony-forming units (CFU), and lactic acid production of plaque microcosm biofilms were measured (n = 6). Results Bonding agents containing DMADDM and NAg greatly inhibited biofilm activities, even with salivary pellicles. When using BHI, the pre-coating of salivary pellicles on resin surfaces significantly decreased the antibacterial effect (p < 0.05). When using artificial saliva medium, pre-coating of salivary pellicles on resin did not decrease the antibacterial effect. These results suggest that artificial saliva yielded medium-derived pellicles on resin surfaces, which provided attenuating effects on biofilms similar to salivary pellicles. Compared with the commercial control, the DMADDM-containing bonding agent reduced biofilm CFU by about two orders of magnitude. Significance Novel DMADDM- and NAg-containing bonding agents substantially reduced biofilm growth even with salivary pellicle coating on surfaces, indicating a promising usage in saliva-rich environment. DMADDM and NAg may be useful in a wide range of primers, adhesives and other restoratives to achieve antibacterial and anti

  8. Bi-directional homogenization equivalent modeling for the prediction of thermo-mechanical properties of a multi-layered printed circuit board (PCB)

    NASA Astrophysics Data System (ADS)

    Joo, Sung-Jun; Park, Buhm; Kim, Do-Hyoung; Kwak, Dong-Ok; Park, Junhong; Kim, Hak-Sung

    2016-04-01

    Warpage of multi-layered printed circuit boards (PCB) during the reflow process is a serious problem which affects the reliability of solder ball connections between the PCB and the mounted semi-conductor packages in electronic devices. It is essential to predict the warpage of the PCB accurately; however, the complicated copper patterns in multi-layered PCBs render a full modeling analysis impossible due to the excessive computing time required. To overcome this problem, we have developed analytical equations of three Cu patterns (line, square, and grid) for the application of thermo-mechanical properties simply by equivalent modeling of Cu patterns. In the proposed equations, the effect of thermo-viscoelastic properties as well as the influence of surrounding layers such as woven glass fabric/BT (bismaleimide triazine), composite laminate (BT core), and photoimageable solder resist (PSR) were considered. To verify the developed equations, vibration tests based on the wave propagation approach were performed at various temperatures. Good agreement was observed between the equivalent model and the experimental results.

  9. Approximate Formula of Peak Frequency of H/V Ratio Curve in Multilayered Model and Its Use in H/V Ratio Technique

    NASA Astrophysics Data System (ADS)

    Tuan, Tran Thanh; Vinh, Pham Chi; Malischewsky, P.; Aoudia, Abdelkrim

    2016-02-01

    The main peak frequency of the Horizontal-to-Vertical (H/V) ratio curve is the key factor used in the H/V ratio technique since the resonance frequency of the transmission response of the site is estimated from this frequency. However, there has not been explicit formula of the main peak frequency of the H/V ratio curve in multilayered models. In the present study, an approximate explicit equation of the peak frequency of H/V ratio is derived for the multilayered models of high impedance contrast between the half-space and surface layers. This approximate equation is then generalized for model of an functionally graded material (FGM) layer over half-space. Then, the approximate equation is used to obtain an explicit approximate formula of the main peak frequency of H/V ratio curve. The principle formula of H/V ratio technique is used along with the obtained approximate formula of the main peak frequency to formulate a new average formula of the shear-wave velocity of a composite layer composed of an arbitrary number of horizontal, homogeneous layers. The new average formula is shown to be more suitable in the use of H/V ratio technique than the currently used ones in the sense that it takes into account the effect of the mass density and the position of sublayers. Finally, some numerical calculation to illustrate the application of the peak formula and the new average formula of shear-wave velocity is presented.

  10. Theoretical models of mercury dissolution from dental amalgams in neutral and acidic flows

    NASA Astrophysics Data System (ADS)

    Keanini, Russell G.; Ferracane, Jack L.; Okabe, Toru

    2001-06-01

    This article reports an experimental and theoretical investigation of mercury dissolution from dental amalgams immersed in neutral (noncorrosive) and acidic (corrosive) flows. Atomic absorption spectrophotometric measurements of Hg loss indicate that in neutral flow, surface oxide films formed in air prior to immersion persist and effectively suppress significant mercury release. In acidic (pH 1) flows, by contrast, oxide films are unstable and dissolve; depending on the amalgam’s material composition, particularly its copper content, two distinct mercury release mechanisms are initiated. In low copper amalgam, high initial mercury release rates are observed and appear to reflect preferential mercury dissolution from unstable Sn8Hg ( γ 2) grains within the amalgam matrix. In high copper amalgam, mercury release rates are initially low, but increase with time. Microscopic examination suggests that this feature reflects corrosion of copper from grains of Cu6Sn5 ( η') and consequent exposure of Ag2Hg3 ( γ 1) grains; the latter serve as internal mercury release sites and become more numerous as corrosion proceeds. Three theoretical models are proposed in order to explain observed dissolution characteristics. Model I, applicable to high and low copper amalgams in neutral flow, assumes that mercury dissolution is mediated by solid diffusion within the amalgam, and that a thin oxide film persists on the amalgam’s surface and lumps diffusive in-film transport into an effective convective boundary condition. Model II, applicable to low copper amalgam in acidic flow, assumes that the amalgam’s external oxide film dissolves on a short time scale relative to the experimental observation period; it neglects corrosive suppression of mercury transport. Model III, applicable to high copper amalgam in acidic flow, assumes that internal mercury release sites are created by corrosion of copper in η' grains and that corrosion proceeds via an oxidation-reduction reaction

  11. Dental Implants

    MedlinePlus

    ... Procedures Dental Implants Dentures Direct Bonding Implants versus Bridges Orthodontics and Aligners Periodontal Plastic Surgery Porcelain Crowns Porcelain Fixed Bridges Porcelain Veneers Repairing Chipped Teeth Teeth Whitening Tooth- ...

  12. A statistical modeling approach to computer-aided quantification of dental biofilm.

    PubMed

    Mansoor, Awais; Patsekin, Valery; Scherl, Dale; Robinson, J Paul; Rajwa, Bartlomiej

    2015-01-01

    Biofilm is a formation of microbial material on tooth substrata. Several methods to quantify dental biofilm coverage have recently been reported in the literature, but at best they provide a semiautomated approach to quantification with significant input from a human grader that comes with the grader's bias of what is foreground, background, biofilm, and tooth. Additionally,human assessment indices limit the resolution of the quantification scale; most commercial scales use five levels of quantification for biofilm coverage (0%, 25%, 50%, 75%, and 100%). On the other hand, current state-of-the-art techniques in automatic plaque quantification fail to make their way into practical applications owing to their inability to incorporate human input to handle misclassifications. This paper proposes a new interactive method for biofilm quantification in Quantitative light-induced fluorescence(QLF) images of canine teeth that is independent of the perceptual bias of the grader. The method partitions a QLF image into segments of uniform texture and intensity called superpixels; every superpixel is statistically modeled as a realization of a single 2-D Gaussian Markov random field (GMRF) whose parameters are estimated; the superpixel is then assigned to one of three classes (background, biofilm, tooth substratum) based on the training set of data. The quantification results show a high degree of consistency and precision. At the same time, the proposed method gives pathologists full control to postprocess the automatic quantification by flipping misclassified superpixels to a different state (background,tooth, biofilm) with a single click, providing greater usability than simply marking the boundaries of biofilm and tooth as done by current state-of-the-art methods.

  13. Quantifying spatio-temporal stream-aquifer water exchanges along a multi-layer aquifer system using LOMOS and hydro-thermo modelling

    NASA Astrophysics Data System (ADS)

    Mouhri, Amer; flipo, Nicolas; Rejiba, Fayçal; Bodet, Ludovic; Jost, Anne; Goblet, Patrick

    2014-05-01

    The aim of this work is to understand the spatial and temporal variability of stream-aquifer water exchanges along a 6 km-stream network in a multi-layer aquifer system using both LOcal MOnitoring Stations (LOMOSs) coupled with the optimization of a hydro-thermo model per LOMOS. With an area of 45 km2, the Orgeval experimental basin is located 70 km east from Paris. It drains a multi-layer aquifer system, which is composed of two main geological formations: the Oligocene (upper aquifer unit) and the Eocene (lower aquifer unit). These two aquifer units are separated by a clayey aquitard. The connectivity status between streams and aquifer units has been evaluated using near surface geophysical investigations as well as drill cores. Five LOMOSs of the stream-aquifer exchanges have been deployed along the stream-network to monitor stream-aquifer exchanges over years, based on continuous pressure and temperature measurements (15 min-time step). Each LOMOS is composed of one or two shallow piezometers located 2 to 3 m away from the river edge; one surface water monitoring system; two hyporheic zone temperature profiles located close to each river bank. The five LOMOSs are distributed in two upstream, two intermediate, and one downstream site. The two upstream sites are connected to the upper aquifer unit, and the downstream one is connected to the lower aquifer unit. The 2012-April - 2013-december period of hydrological data are hereafter analyzed. We first focus on the spatial distribution of the stream-aquifer exchanges along the multi-layer aquifer system during the low flow period. Results display an upstream-downstream functional gradient, with upstream gaining stream and downstream losing stream. This spatial distribution is due to the multi-layer nature of the aquifer system, whose lower aquifer unit is depleted. Then it appears that the downstream losing streams temporally switch into gaining ones during extreme hydrological events, while the upstream streams

  14. Virtual model surgery and wafer fabrication using 2-dimensional cephalograms, 3-dimensional virtual dental models, and stereolithographic technology.

    PubMed

    Choi, Jin-Young; Hwang, Jong-Min; Baek, Seung-Hak

    2012-02-01

    Although several 3-dimensional virtual model surgery (3D-VMS) programs have been introduced to reduce time-consuming manual laboratory steps and potential errors, these programs still require 3D-computed tomography (3D-CT) data and involve complex computerized maneuvers. Because it is difficult to take 3D-CTs for all cases, a new VMS program using 2D lateral and posteroanterior cephalograms and 3D virtual dental models (2.5D-VMS program; 3Txer version 2.5, Orapix, Seoul, Korea) has recently been introduced. The purposes of this article were to present the methodology of the 2.5D-VMS program and to verify the accuracy of intermediate surgical wafers fabricated with the stereolithographic technique. Two cases successfully treated using the 2.5D-VMS program are presented. There was no significant difference in the position of upper dentition after surgical movement between 2.5D-VMS and 3D-VMS in 18 samples (less than 0.10 mm, P > .05, Wilcoxon-signed rank test). The 2.5D-VMS can be regarded as an effective alternative for 3D-VMS for cases in which 3D-CT data are not available.

  15. Dental peculiarities in the silvery mole-rat: an original model for studying the evolutionary and biological origins of continuous dental generation in mammals

    PubMed Central

    Šumbera, Radim

    2015-01-01

    Unravelling the evolutionary and developmental mechanisms that have impacted the mammalian dentition, since more than 200 Ma, is an intricate issue. Interestingly, a few mammal species, including the silvery mole-rat Heliophobius argenteocinereus, are able to replace their dentition by the addition of supernumerary molars at the back of jaw migrating then toward the front. The aim here was to demonstrate the potential interest of further studying this rodent in order to better understand the origins of continuous dental replacement in mammals, which could also provide interesting data concerning the evolution of limited dental generation occurring in first mammals. In the present study, we described the main stages of the dental eruptive sequence in the silvery mole-rat and the associated characteristics of horizontal replacement using X-ray microtomography. This was coupled to the investigation of other African mole-rats which have no dental replacement. This method permitted to establish evidence that the initial development of the dentition in Heliophobius is comparable to what it is observed in most of African mole-rats. This rodent first has premolars, but then identical additional molars, a mechanism convergent to manatees and the pygmy rock-wallaby. Evidence of continuous replacement and strong dental dynamics were also illustrated in Heliophobius, and stressed the need to deeply investigate these aspects for evolutionary, functional and developmental purposes. We also noticed that two groups of extinct non-mammalian synapsids convergently acquired this dental mechanism, but in a way differing from extant mammals. The discussion on the diverse evolutionary origins of horizontal dental replacement put emphasis on the necessity of focusing on biological parameters potentially involved in both continuous and limited developments of teeth in mammals. In that context, the silvery mole-rat could appear as the most appropriate candidate to do so. PMID:26401449

  16. Dental peculiarities in the silvery mole-rat: an original model for studying the evolutionary and biological origins of continuous dental generation in mammals.

    PubMed

    Gomes Rodrigues, Helder; Šumbera, Radim

    2015-01-01

    Unravelling the evolutionary and developmental mechanisms that have impacted the mammalian dentition, since more than 200 Ma, is an intricate issue. Interestingly, a few mammal species, including the silvery mole-rat Heliophobius argenteocinereus, are able to replace their dentition by the addition of supernumerary molars at the back of jaw migrating then toward the front. The aim here was to demonstrate the potential interest of further studying this rodent in order to better understand the origins of continuous dental replacement in mammals, which could also provide interesting data concerning the evolution of limited dental generation occurring in first mammals. In the present study, we described the main stages of the dental eruptive sequence in the silvery mole-rat and the associated characteristics of horizontal replacement using X-ray microtomography. This was coupled to the investigation of other African mole-rats which have no dental replacement. This method permitted to establish evidence that the initial development of the dentition in Heliophobius is comparable to what it is observed in most of African mole-rats. This rodent first has premolars, but then identical additional molars, a mechanism convergent to manatees and the pygmy rock-wallaby. Evidence of continuous replacement and strong dental dynamics were also illustrated in Heliophobius, and stressed the need to deeply investigate these aspects for evolutionary, functional and developmental purposes. We also noticed that two groups of extinct non-mammalian synapsids convergently acquired this dental mechanism, but in a way differing from extant mammals. The discussion on the diverse evolutionary origins of horizontal dental replacement put emphasis on the necessity of focusing on biological parameters potentially involved in both continuous and limited developments of teeth in mammals. In that context, the silvery mole-rat could appear as the most appropriate candidate to do so. PMID:26401449

  17. Dental mesenchymal stem cells.

    PubMed

    Sharpe, Paul T

    2016-07-01

    Mammalian teeth harbour mesenchymal stem cells (MSCs), which contribute to tooth growth and repair. These dental MSCs possess many in vitro features of bone marrow-derived MSCs, including clonogenicity, expression of certain markers, and following stimulation, differentiation into cells that have the characteristics of osteoblasts, chondrocytes and adipocytes. Teeth and their support tissues provide not only an easily accessible source of MSCs but also a tractable model system to study their function and properties in vivo In addition, the accessibility of teeth together with their clinical relevance provides a valuable opportunity to test stem cell-based treatments for dental disorders. This Review outlines some recent discoveries in dental MSC function and behaviour and discusses how these and other advances are paving the way for the development of new biologically based dental therapies. PMID:27381225

  18. Developing Teaching Expertise in Dental Education

    ERIC Educational Resources Information Center

    Lyon, Lucinda J.

    2009-01-01

    This exploratory study was designed to develop a baseline model of expertise in dental education utilizing the Dreyfus and Dreyfus continuum of skill acquisition. The goal was the development of a baseline model of expertise, which will contribute to the body of knowledge about dental faculty skill acquisition and may enable dental schools to…

  19. Dynamic Systems (Complexity) theory as a new conceptual model for researching PBL in dental education.

    PubMed

    Townsend, G C; Kim, M; Sankey, D

    2012-02-01

    Although problem-based learning (PBL) was introduced into dental education some 20 years ago, there have been relatively few well-designed studies carried out to clarify whether, how or why it works in a dental context. This paper introduces the Dynamic Systems (Complexity) theory as a new and potentially productive theoretical framework for researching PBL in dental education. This framework emphasises the importance of emergent self-organisation, perception and brain plasticity in learning. In this paper, a brief overview of the history of PBL in dentistry is presented and then the fundamentals of a Dynamic Systems Approach (DSA) are explained, drawing on two recently published papers advocating the DSA in medical education and teacher education. We focus on three key points related to this new approach: emergent self-organisation rather than simple construction of knowledge; the notion that perception drives the learning process; and the brain as the substrate of all learning. The paper also suggests how the DSA can help us move forward, both in terms of the future application of PBL in dental education and also in relation to posing new types of research questions. PMID:22251326

  20. Dynamic Systems (Complexity) theory as a new conceptual model for researching PBL in dental education.

    PubMed

    Townsend, G C; Kim, M; Sankey, D

    2012-02-01

    Although problem-based learning (PBL) was introduced into dental education some 20 years ago, there have been relatively few well-designed studies carried out to clarify whether, how or why it works in a dental context. This paper introduces the Dynamic Systems (Complexity) theory as a new and potentially productive theoretical framework for researching PBL in dental education. This framework emphasises the importance of emergent self-organisation, perception and brain plasticity in learning. In this paper, a brief overview of the history of PBL in dentistry is presented and then the fundamentals of a Dynamic Systems Approach (DSA) are explained, drawing on two recently published papers advocating the DSA in medical education and teacher education. We focus on three key points related to this new approach: emergent self-organisation rather than simple construction of knowledge; the notion that perception drives the learning process; and the brain as the substrate of all learning. The paper also suggests how the DSA can help us move forward, both in terms of the future application of PBL in dental education and also in relation to posing new types of research questions.

  1. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. Part II: Multi-layered cloud

    SciTech Connect

    Morrison, H; McCoy, R B; Klein, S A; Xie, S; Luo, Y; Avramov, A; Chen, M; Cole, J; Falk, M; Foster, M; Genio, A D; Harrington, J; Hoose, C; Khairoutdinov, M; Larson, V; Liu, X; McFarquhar, G; Poellot, M; Shipway, B; Shupe, M; Sud, Y; Turner, D; Veron, D; Walker, G; Wang, Z; Wolf, A; Xu, K; Yang, F; Zhang, G

    2008-02-27

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a deep, multi-layered, mixed-phase cloud system observed during the ARM Mixed-Phase Arctic Cloud Experiment. This cloud system was associated with strong surface turbulent sensible and latent heat fluxes as cold air flowed over the open Arctic Ocean, combined with a low pressure system that supplied moisture at mid-level. The simulations, performed by 13 single-column and 4 cloud-resolving models, generally overestimate the liquid water path and strongly underestimate the ice water path, although there is a large spread among the models. This finding is in contrast with results for the single-layer, low-level mixed-phase stratocumulus case in Part I of this study, as well as previous studies of shallow mixed-phase Arctic clouds, that showed an underprediction of liquid water path. The overestimate of liquid water path and underestimate of ice water path occur primarily when deeper mixed-phase clouds extending into the mid-troposphere were observed. These results suggest important differences in the ability of models to simulate Arctic mixed-phase clouds that are deep and multi-layered versus shallow and single-layered. In general, models with a more sophisticated, two-moment treatment of the cloud microphysics produce a somewhat smaller liquid water path that is closer to observations. The cloud-resolving models tend to produce a larger cloud fraction than the single-column models. The liquid water path and especially the cloud fraction have a large impact on the cloud radiative forcing at the surface, which is dominated by the longwave flux for this case.

  2. Numerical modelling of GPR ground-matching enhancement by a chirped multilayer structure - output of cooperation within COST Action TU1208

    NASA Astrophysics Data System (ADS)

    Baghdasaryan, Hovik V.; Knyazyan, Tamara M.; Hovhannisyan, Tamara. T.; Marciniak, Marian; Pajewski, Lara

    2016-04-01

    As is well know, Ground Penetrating Radar (GPR) is an electromagnetic technique for the detection and imaging of buried objects, with resolution ranging from centimeters to few meters [1, 2]. Though this technique is mature enough and different types of GPR devices are already in use, some problems are still waiting for their solution [3]. One of them is to achieve a better matching of transmitting GPR antenna to the ground, that will increase the signal penetration depth and the signal/noise ratio at the receiving end. In the current work, a full-wave electromagnetic modelling of the interaction of a plane wave with a chirped multilayered structure on the ground is performed, via numerical simulation. The method of single expression is used, which is a suitable technique for multi-boundary problems solution [4, 5]. The considered multilayer consists of two different dielectric slabs of low and high permittivity, where the highest value of permittivity doesn't exceed the permittivity of the ground. The losses in the ground are suitably taken into account. Two types of multilayers are analysed. Numerical results are obtained for the reflectance from the structure, as well as for the distributions of electric field components and power flow density in both the considered structures and the ground. The obtained results indicate that, for a better matching with the ground, the layer closer to the ground should be the high-permittivity one. Acknowledgement This work benefited from networking activities carried out within the EU funded COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar" (www.GPRadar.eu, www.cost.eu). Part of this work was developed during the Short-Term Scientific Mission COST-STSM-TU1208-25016, carried out by Prof. Baghdasaryan in the National Institute of Telecommunications in Warsaw, Poland. References [1] H. M. Jol. Ground Penetrating Radar: Theory and Applications. Elsevier, 2009. 509 pp. [2] R. Persico. Introduction to

  3. Dental Hygienist.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document, which is designed for use in developing a tech prep competency profile for the occupation of dental hygienist, lists technical competencies and competency builders for 13 units pertinent to the health technologies cluster in general and 9 units specific to the occupation of dental hygienist. The following skill areas are covered in…

  4. Predicting dental avoidance among dentally fearful Australian adults.

    PubMed

    Armfield, Jason M

    2013-06-01

    Dental fear is related to poorer oral health outcomes, and this might be explained by the less frequent dental visiting of many fearful people. The objectives of this study were to investigate differences between dentally fearful people who regularly attend the dentist and fearful people who infrequently visit the dentist. A random sample of 1,082 Australians ≥ 15 yr of age completed a mailed questionnaire (response rate = 71.6%), and 191 dentate, high-fear adults (≥ 18 yr of age) were selected for further analysis. Dental avoidance was recorded if a person was currently avoiding or delaying dental care and if he/she had not been to a dentist in the previous 2 yr. Among the selected dentally fearful adults, dental avoidance was predicted by smoking status, toothbrushing frequency, coping strategy use, perceptions of dental visits as uncontrollable and unpredictable, and by anxiety relating to numbness, not knowing what the dentist is going to do, and cost. In a multivariate logistic regression model, smoking, toothbrushing, coping, and anxiety about numbness and cost remained as statistically significant predictors, with the model accounting for 30% of the variance. While several variables were associated with dental avoidance among fearful adults, the nature and causal directions of these associations remain to be established.

  5. An Ex Vivo Model in Human Femoral Heads for Histopathological Study and Resonance Frequency Analysis of Dental Implant Primary Stability

    PubMed Central

    Hernández-Cortés, Pedro; Galindo-Moreno, Pablo; Catena, Andrés; Ortega-Oller, Inmaculada; Salas-Pérez, José; Gómez-Sánchez, Rafael; Aguilar, Mariano; Aguilar, David

    2014-01-01

    Objective. This study was designed to explore relationships of resonance frequency analysis (RFA)—assessed implant stability (ISQ values) with bone morphometric parameters and bone quality in an ex vivo model of dental implants placed in human femoral heads and to evaluate the usefulness of this model for dental implant studies. Material and Methods. This ex vivo study included femoral heads from 17 patients undergoing surgery for femoral neck fracture due to osteoporosis (OP) (n = 7) or for total prosthesis joint replacement due to severe hip osteoarthrosis (OA) (n = 10). Sixty 4.5 × 13 mm Dentsply Astra implants were placed, followed by RFA. CD44 immunohistochemical analysis for osteocytes was also carried out. Results. As expected, the analysis yielded significant effects of femoral head type (OA versus OA) (P < 0.001), but not of the implants (P = 0.455) or of the interaction of the two factors (P = 0.848). Bonferroni post hoc comparisons showed a lower mean ISQ for implants in decalcified (50.33 ± 2.92) heads than in fresh (66.93 ± 1.10) or fixated (70.77 ± 1.32) heads (both P < 0.001). The ISQ score (fresh) was significantly higher for those in OA (73.52 ± 1.92) versus OP (67.13 ± 1.09) heads. However, mixed linear analysis showed no significant association between ISQ scores and morphologic or histomorphometric results (P > 0.5 in all cases), and no significant differences in ISQ values were found as a function of the length or area of the cortical layer (both P > 0.08). Conclusion. Although RFA-determined ISQ values are not correlated with morphometric parameters, they can discriminate bone quality (OP versus OA). This ex vivo model is useful for dental implant studies. PMID:24995307

  6. Modelling and simulation of low-density lipoprotein transport through multi-layered wall of an anatomically realistic carotid artery bifurcation

    PubMed Central

    Kenjereš, Saša; de Loor, Alexander

    2014-01-01

    A high concentration of low-density lipoprotein (LDL) is recognized as one of the principal risk factors for development of atherosclerosis. This paper reports on modelling and simulations of the coupled mass (LDL concentration) and momentum transport through the arterial lumen and the multi-layered arterial wall of an anatomically realistic carotid bifurcation. The mathematical model includes equations for conservation of mass, momentum and concentration, which take into account a porous layer structure, the biological membranes and reactive source/sink terms in different layers of the arterial wall, as proposed in Yang & Vafai (2006). A four-layer wall model of an arterial wall with constant thickness is introduced and initially tested on a simple cylinder geometry where realistic layer properties are specified. Comparative assessment with previously published results demonstrated proper implementation of the mathematical model. Excellent agreement for the velocity and LDL concentration distributions in the arterial lumen and in the artery wall are obtained. Then, an anatomically realistic carotid artery bifurcation is studied. This is the main novelty of the presented research. We find a strong dependence between underlying blood flow pattern (and consequently the wall shear stress distributions) and the uptake of the LDL concentration in the artery wall. The radial dependency of interactions between the diffusion, convection and chemical reactions within the multi-layered artery wall is crucial for accurate predictions of the LDL concentration in the media. It is shown that a four-layer wall model produced qualitatively good agreement with the experimental results of Meyer et al. (1996) in predicting levels of LDL within the media of a rabbit aorta under identical transmural pressure conditions. Finally, it is demonstrated that the adopted model represents a good initial platform for future numerical investigations of the initial stage of atherosclerosis for

  7. Dental Implants.

    PubMed

    Zohrabian, Vahe M; Sonick, Michael; Hwang, Debby; Abrahams, James J

    2015-10-01

    Dental implants restore function to near normal in partially or completely edentulous patients. A root-form implant is the most frequently used type of dental implant today. The basis for dental implants is osseointegration, in which osteoblasts grow and directly integrate with the surface of titanium posts surgically embedded into the jaw. Radiologic assessment is critical in the preoperative evaluation of the dental implant patient, as the exact height, width, and contour of the alveolar ridge must be determined. Moreover, the precise locations of the maxillary sinuses and mandibular canals, as well as their relationships to the site of implant surgery must be ascertained. As such, radiologists must be familiar with implant design and surgical placement, as well as augmentation procedures utilized in those patients with insufficient bone in the maxilla and mandible to support dental implants.

  8. A multilayered sharp interface model of coupled freshwater and saltwater flow in coastal systems: model development and application

    USGS Publications Warehouse

    Essaid, H.I.

    1990-01-01

    The model allows for regional simulation of coastal groundwater conditions, including the effects of saltwater dynamics on the freshwater system. Vertically integrated freshwater and saltwater flow equations incorporating the interface boundary condition are solved within each aquifer. Leakage through confining layers is calculated by Darcy's law, accounting for density differences across the layer. The locations of the interface tip and toe, within grid blocks, are tracked by linearly extrapolating the position of the interface. The model has been verified using available analytical solutions and experimental results and applied to the Soquel-Aptos basin, Santa Cruz County, California. -from Author

  9. Modeling and Validation of Multilayer Poly(Lactide-Co-Glycolide) Scaffolds for In Vitro Directed Differentiation of Juxtaposed Cartilage and Bone

    PubMed Central

    Huang, George X.; Arany, Praveen R.

    2015-01-01

    Polymeric scaffolds, which release growth factors in a temporally controlled manner, have successfully directed the differentiation of stem cells into monolithic tissues of a single lineage. However, engineering precise boundaries in multilineage functional tissues, such as the juxtaposed cartilaginous and osseous tissue present in articulated joints, often remains a challenge. This work demonstrates a precise materials system for in vitro reconstruction of the three-dimensional architecture of these types of human tissues. Multilayer poly(lactide-co-glycolide) (PLG) scaffolds were used to produce spatiotemporal gradients to direct the differentiation of an initially uniform population of mesenchymal stem cells (MSCs) into juxtaposed cartilage and bone. Specifically, growth factors (chondrogenic transforming growth factor-β3 and osteogenic bone morphogenetic protein-4) and their neutralizing antibodies were incorporated within distinct layers of the PLG scaffolds to create spatially segregated morphogen fields within the scaffold volume. The multilayer PLG scaffold designs were optimized by mathematical modeling, and generation of spatially segregated morphogen gradients was validated by assessing activity of luciferase reporter cell lines responsive to each growth factor. Scaffolds seeded with MSCs demonstrated production of juxtaposed cartilage and bone, as evaluated by biochemical staining and western blotting for tissue-specific matrix proteins. This work demonstrates a significant advance for the engineering of implantable constructs comprising tissues of multiple lineages, with potential applications in orthopedic regenerative medicine. PMID:25923238

  10. Mobile and Portable Dental Services Catering to the Basic Oral Health Needs of the Underserved Population in Developing Countries: A Proposed Model

    PubMed Central

    Ganavadiya, R; Chandrashekar, BR; Goel, P; Hongal, SG; Jain, M

    2014-01-01

    (adding each of these terms in a sequential order). Based on the review of the programs successfully implemented in developed countries, we propose a model to cater to the basic oral health needs of an extensive underserved population in India that may be pilot tested. The increasing dental manpower can best be utilized for the promotion of oral health through mobile and portable dental services. The professional dental organizations should have a strong motive to translate this into reality. PMID:24971198

  11. Mobile and portable dental services catering to the basic oral health needs of the underserved population in developing countries: a proposed model.

    PubMed

    Ganavadiya, R; Chandrashekar, Br; Goel, P; Hongal, Sg; Jain, M

    2014-05-01

    (adding each of these terms in a sequential order). Based on the review of the programs successfully implemented in developed countries, we propose a model to cater to the basic oral health needs of an extensive underserved population in India that may be pilot tested. The increasing dental manpower can best be utilized for the promotion of oral health through mobile and portable dental services. The professional dental organizations should have a strong motive to translate this into reality.

  12. Dental arch asymmetry

    PubMed Central

    Al-Zubair, Nabil Muhsen

    2014-01-01

    Objective: This study was conducted to assess the dental arch asymmetry in a Yemeni sample aged (18-25) years. Materials and Methods: The investigation involved clinical examination of 1479 adults; only 253 (129 females, 124 males) out of the total sample were selected to fulfill the criteria for the study sample. Study models were constructed and evaluated to measure mandibular arch dimensions. Three linear distances were utilized on each side on the dental arch: Incisal-canine distance, canine-molar distance and incisal-molar distance, which represent the dental arch segmental measurements. Results: When applying “t-test” at P < 0.05, no significant differences were found between the right and left canine-molar, incisal-canine and incisal-molar distances in both dental arches for both sexes. The greater variation (0.30 mm) was observed between right and left canine-molar distance in the maxillary dental arch in male and the smaller (0.04 mm) in the mandibular dental arch between the right and left canine-molar distance in females. Conclusion: The findings of the present study revealed a symmetrical pattern of dental arches, since the right and left sides showed no statistically significant difference. In general, it can be observed that the measurements related to the central incisors and canines have the widest range of reading and give the impression that the location of central incisor and canines to each other and to other teeth is the strongest factor in determining the dental arch asymmetry. PMID:24966774

  13. Oral health care for children in countries using dental therapists in public, school-based programs, contrasted with that of the United States, using dentists in a private practice model.

    PubMed

    Mathu-Muju, Kavita R; Friedman, Jay W; Nash, David A

    2013-09-01

    The United States faces a significant problem with access to oral health care, particularly for children. More than 50 countries have developed an alternative dental provider, a dental therapist, practicing in public, school-based programs, to address children's access to care. This delivery model has been demonstrated to improve access to care and oral health outcomes while providing quality care economically. We summarize elements of a recent major review of the global literature on the use of dental therapists, "A Review of the Global Literature on Dental Therapists: In the Context of the Movement to Add Dental Therapists to the Oral Health Workforce in the United States." We contrast the success of a school-based model of caring for children by dental therapists with that of the US model of dentists providing care for children in private practices.

  14. Coinsurance effects on dental prices.

    PubMed

    Grembowski, D; Conrad, D A

    1986-01-01

    For many Americans the cost of dental services represents a barrier to receiving regular dental care and maintaining proper oral health. The recent growth of the dental insurance industry, however, may partly offset this price barrier among insureds. Our purpose is to examine the relationship between coinsurance and dental prices for 16 dental services among a sample of Pennsylvania Blue Shield (PBS) adult insureds. The dependent price measure is the annual average gross price paid for 16 specific preventive, restorative, periodontic, endodontic, prosthodontic, and surgical dental services. Independent variables in the price model include the insured's age, education, coinsurance rates, time costs, market area, non-wage income, oral health status, area dentist-population ratio and usual source of care. Data sources are 1980 PBS claims and coinsurance rate data and a mail survey of sampled insureds. OLS regression analysis reveals that the model's independent variables explain little dental price variation. No variable is consistently significant across services, but market area, coinsurance rates, and time costs alternately dominate across equations. These results suggest that, among adult insureds, coinsurance and time costs influence dental fees in a minority of dental services. Insurance reduces the patient's sensitivity to money price, and non-price factors correspondingly seem to become more important in patient search.

  15. Modeling of gamma ray energy-absorption buildup factors for thermoluminescent dosimetric materials using multilayer perceptron neural network: A comparative study

    NASA Astrophysics Data System (ADS)

    Kucuk, Nil; Manohara, S. R.; Hanagodimath, S. M.; Gerward, L.

    2013-05-01

    In this work, multilayered perceptron neural networks (MLPNNs) were presented for the computation of the gamma-ray energy absorption buildup factors (BA) of seven thermoluminescent dosimetric (TLD) materials [LiF, BeO, Na2B4O7, CaSO4, Li2B4O7, KMgF3, Ca3(PO4)2] in the energy region 0.015-15 MeV, and for penetration depths up to 10 mfp (mean-free-path). The MLPNNs have been trained by a Levenberg-Marquardt learning algorithm. The developed model is in 99% agreement with the ANSI/ANS-6.4.3 standard data set. Furthermore, the model is fast and does not require tremendous computational efforts. The estimated BA data for TLD materials have been given with penetration depth and incident photon energy as comparative to the results of the interpolation method using the Geometrical Progression (G-P) fitting formula.

  16. Puerto Rico Experimental Model Dental Auxiliary Training Program. The Comprehensive Report, October 22, 1976-February 24, 1980.

    ERIC Educational Resources Information Center

    Puerto Rico Univ., San Juan. School of Dentistry.

    The Dental Auxiliary Department of the University of Puerto Rico designed a career option dental auxiliary training program which is a step ladder program with three exit points over a period of two academic years. The first option is a six-month track to train a traditional chairside dental auxiliary. The second option is a nine-month track to…

  17. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

    1999-01-01

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

  18. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, M.D.; Britten, J.A.; Nguyen, H.T.; Boyd, R.; Shore, B.W.

    1999-05-25

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described. 7 figs.

  19. Enzyme replacement therapy prevents dental defects in a model of hypophosphatasia.

    PubMed

    McKee, M D; Nakano, Y; Masica, D L; Gray, J J; Lemire, I; Heft, R; Whyte, M P; Crine, P; Millán, J L

    2011-04-01

    Hypophosphatasia (HPP) occurs from loss-of-function mutation in the tissue-non-specific alkaline phosphatase (TNALP) gene, resulting in extracellular pyrophosphate accumulation that inhibits skeletal and dental mineralization. TNALP-null mice (Akp2(-/-)) phenocopy human infantile hypophosphatasia; they develop rickets at 1 week of age, and die before being weaned, having severe skeletal and dental hypomineralization and episodes of apnea and vitamin B(6)-responsive seizures. Delay and defects in dentin mineralization, together with a deficiency in acellular cementum, are characteristic. We report the prevention of these dental abnormalities in Akp2(-/-) mice receiving treatment from birth with daily injections of a mineral-targeting, human TNALP (sALP-FcD(10)). sALP-FcD(10) prevented hypomineralization of alveolar bone, dentin, and cementum as assessed by micro-computed tomography and histology. Osteopontin--a marker of acellular cementum--was immuno-localized along root surfaces, confirming that acellular cementum, typically missing or reduced in Akp2(-/-) mice, formed normally. Our findings provide insight concerning how acellular cementum is formed on tooth surfaces to effect periodontal ligament attachment to retain teeth in their osseous alveolar sockets. Furthermore, they provide evidence that this enzyme-replacement therapy, applied early in post-natal life--where the majority of tooth root development occurs, including acellular cementum formation--could prevent the accelerated tooth loss seen in individuals with HPP. PMID:21212313

  20. A model for cultivating dental hygiene faculty development within a community of practice.

    PubMed

    Tax, Cara L; Doucette, Heather; Neish, Nancy R; Maillet, J Peggy

    2012-03-01

    There is a need to explore approaches in faculty development that will foster change in actual teaching practices. The literature suggests that there should be more deliberate use of theory in faculty development research. This study addressed this gap in the literature by exploring social learning theory in the context of communities of practice and applying this theory to a dental hygiene faculty development program. The purpose of the study was to determine if participation in a community of practice helped dental hygiene clinical instructors implement new teaching strategies by providing ongoing support for their learning. In addition, the study explored whether the level of participation in the community changed over time. A retrospective self-assessment questionnaire consisting of four open-ended questions was administered to a group of clinical dental hygiene instructors at the end of the 2010 academic year. The narrative data were analyzed thematically using qualitative methodology. The results indicated that participation in the community of practice helped clinical instructors make effective changes in their teaching practices by optimizing social learning opportunities. The responses also revealed that instructors became more comfortable participating in discussions as they identified with other members of this unique community. PMID:22383599

  1. Dental OCT

    NASA Astrophysics Data System (ADS)

    Wilder-Smith, Petra; Otis, Linda; Zhang, Jun; Chen, Zhongping

    This chapter describes the applications of OCT for imaging in vivo dental and oral tissue. The oral cavity is a diverse environment that includes oral mucosa, gingival tissues, teeth and their supporting structures. Because OCT can image both hard and soft tissues of the oral cavity at high resolution, it offers the unique capacity to identity dental disease before destructive changes have progressed. OCT images depict clinically important anatomical features such as the location of soft tissue attachments, morphological changes in gingival tissue, tooth decay, enamel thickness and decay, as well as the structural integrity of dental restorations. OCT imaging allows for earlier intervention than is possible with current diagnostic modalities.

  2. Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multi-layer model ADCHAM

    NASA Astrophysics Data System (ADS)

    Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, D.; Rusanen, A.; Boy, M.; Swietlicki, E.; Svenningsson, B.; Zelenyuk, A.; Pagels, J.

    2014-01-01

    We have developed the novel Aerosol Dynamics, gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas phase Master Chemical Mechanism version 3.2, an aerosol dynamics and particle phase chemistry module (which considers acid catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study: (1) the mass transfer limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), (2) the slow and almost particle size independent evaporation of α-pinene secondary organic aerosol (SOA) particles, and (3) the influence of chamber wall effects on the observed SOA formation in smog chambers. ADCHAM is able to capture the observed α-pinene SOA mass increase in the presence of NH3(g). Organic salts of ammonium and carboxylic acids predominantly form during the early stage of SOA formation. These salts contribute substantially to the initial growth of the homogeneously nucleated particles. The model simulations of evaporating α-pinene SOA particles support the recent experimental findings that these particles have a semi-solid tar like amorphous phase state. ADCHAM is able to reproduce the main features of the observed slow evaporation rates if low-volatility and viscous oligomerized SOA material accumulates in the particle surface layer upon evaporation. The evaporation rate is mainly governed by the reversible decomposition of oligomers back to monomers. Finally, we demonstrate that the mass transfer limited uptake of condensable organic compounds onto wall deposited particles or directly onto the Teflon chamber walls of smog chambers can have profound influence on the

  3. Ethical decisions in dental treatment planning using the Ozar model: a descriptive study of fifty-two consecutive patients.

    PubMed

    Schuman, N J; Turner, J E

    1997-01-01

    Chairside dental ethics necessitates special consideration by the faculty member-dentist, the dental student, and the patient. The patient must always be aware of treatment options, in addition to learning the health status of the oral hard and soft tissues, costs, and time to be involved to accomplish proposed treatment. What may seem like a burden to an individual practitioner is actually only the necessities incurred by any self governing profession. Fifty-two consecutive dental patients had their cases reviewed for the ethical behavior of the dentist-practitioner, student, and patient. Categories reviewed were informed consent (100%), agreement, compromise, economic issues, conflict, and institutional issues. The results were: 1. Agreement: 17 cases, 2. Compromise: 21 cases, 3. Economic Issues: 4 cases, 4. Conflict: 6 cases, and 5. Institutional Issues: 4 cases. Fourteen percent of all patients were minors. Ninety percent of the patients were treated. Of those 10% not treated, five percent were for medical reasons, and five percent of the patients refused treatment. These results were placed in the Ozar Model 9 and were categorized as follows: 1. Appropriate pain free oral function: 22 cases, 2. Patient Autonomy: 14 cases, 3. Life and health: 9 cases, 4. Preferred practice values: 6 cases, and 5. Other external considerations: 1 case. This template demonstrated appropriate ethical behavior on the part of dentists, students, and patients, especially with a 90% treatment group, and only 5% refusing treatment. The 52 consecutive patients were characteristic of the University of Tennessee's overall patient pool. No identifiable differences were found between patients regardless of gender, age, or race.

  4. The use of in vitro model systems to study dental biofilms associated with caries: a short review

    PubMed Central

    Salli, Krista M.; Ouwehand, Arthur C.

    2015-01-01

    A dental biofilm forms a distinct environment where microorganisms live in a matrix of extracellular polysaccharides. The biofilm favors certain bacteria and creates a habitat that functions differently compared to planktonic bacteria. Reproducible model systems which help to address various questions related to biofilm formation, the process of caries development, and its prevention are needed and are continuously developed. Recent research using both batch culture, continuous culture and flow cells in caries biofilm formation is presented. The development of new techniques and equipment has led to a deeper understanding of how caries biofilms function. Biofilm models have also been used in the development of materials inhibiting secondary caries. This short review summarizes available models to study these questions. PMID:25740099

  5. Dental Support Organizations.

    PubMed

    Dufurrena, Quinn

    2015-01-01

    The Association of Dental Support Organizations is a recently formed association of 33 companies representing a range of management and support services for dental practices. These organizations do not engage in the practice of dentistry, although in some cases they operate as holding companies for practices that do, thus separating the legal responsibility of providing treatment from the management and flow of funds. This report summarizes some of the recent trends in oral health care and dentists' practice patterns that are prompting the increased prevalence of this model. The general functioning of the DSO model is described, including some common variations, and the core values of ADSO are featured. PMID:26455048

  6. Dental Fluorosis

    MedlinePlus

    ... when children regularly consume fluoride during the teeth-forming years, age 8 and younger. Most dental fluorosis ... over a long period when the teeth are forming under the gums. Only children aged 8 years ...

  7. Disparities in unmet dental need and dental care received by pregnant women in Maryland.

    PubMed

    Singhal, Astha; Chattopadhyay, Amit; Garcia, A Isabel; Adams, Amy B; Cheng, Diana

    2014-09-01

    To examine prenatal dental care needs, utilization and oral health counseling among Maryland women who delivered a live infant during 2001-2003 and identify the factors associated with having a dental visit and having an unmet dental need during pregnancy. Pregnancy Risk Assessment Monitoring System is an ongoing population based surveillance system that collects information of women's attitudes and experiences before, during, and shortly after pregnancy. Logistic regression was used to model dental visits and unmet dental need using predictor variables for Maryland 2001-2003 births. Less than half of all women reported having a dental visit and receiving oral health advice during pregnancy. Twenty-five percent of women reported a need for dental care, of which 33 % did not receive dental care despite their perceived need. Multivariate modeling revealed that racial minorities, women who were not married and those with annual income <$40,000 were least likely to have a dental visit. Women who were not married, had low annual income, were older than 40 years of age, had an unintended pregnancy and received prenatal care later than desired were most likely to have an unmet dental need during pregnancy. Despite reported needs and existing recommendations to include oral health as a component of prenatal care, less than half of pregnant women have a dental visit during their pregnancy. One-third of women with a dental problem did not have a dental visit highlighting the unmet need for dental care during pregnancy.

  8. Integrating critical thinking and evidence-based dentistry across a four-year dental curriculum: a model for independent learning.

    PubMed

    Marshall, Teresa A; Straub-Morarend, Cheryl L; Handoo, Nidhi; Solow, Catherine M; Cunningham-Ford, Marsha A; Finkelstein, Michael W

    2014-03-01

    Introducing critical thinking and evidence-based dentistry (EBD) content into an established dental curriculum can be a difficult and challenging process. Over the past three years, the University of Iowa College of Dentistry has developed and implemented a progressive four-year integrated critical thinking and EBD curriculum. The objective of this article is to describe the development and implementation process to make it available as a model for other dental schools contemplating introduction of critical thinking and EBD into their curricula. The newly designed curriculum built upon an existing problem-based learning foundation, which introduces critical thinking and the scientific literature in the D1 year, in order to expose students to the rationale and resources for practicing EBD in the D2 and D3 years and provide opportunities to practice critical thinking and apply the EBD five-step process in the D2, D3, and D4 years. All curricular content is online, and D3 and D4 EBD activities are integrated within existing clinical responsibilities. The curricular content, student resources, and student activities are described.

  9. Weibull models of fracture strengths and fatigue behavior of dental resins in flexure and shear.

    PubMed

    Baran, G R; McCool, J I; Paul, D; Boberick, K; Wunder, S

    1998-01-01

    In estimating lifetimes of dental restorative materials, it is useful to have available data on the fatigue behavior of these materials. Current efforts at estimation include several untested assumptions related to the equivalence of flaw distributions sampled by shear, tensile, and compressive stresses. Environmental influences on material properties are not accounted for, and it is unclear if fatigue limits exist. In this study, the shear and flexural strengths of three resins used as matrices in dental restorative composite materials were characterized by Weibull parameters. It was found that shear strengths were lower than flexural strengths, liquid sorption had a profound effect on characteristic strengths, and the Weibull shape parameter obtained from shear data differed for some materials from that obtained in flexure. In shear and flexural fatigue, a power law relationship applied for up to 250,000 cycles; no fatigue limits were found, and the data thus imply only one flaw population is responsible for failure. Again, liquid sorption adversely affected strength levels in most materials (decreasing shear strengths and flexural strengths by factors of 2-3) and to a greater extent than did the degree of cure or material chemistry.

  10. Utilization of dental care: An Indian outlook

    PubMed Central

    Gambhir, Ramandeep Singh; Brar, Prabhleen; Singh, Gurminder; Sofat, Anjali; Kakar, Heena

    2013-01-01

    Oral health has a significant impact on the quality of life, appearance, and self-esteem of the people. Preventive dental visits help in the early detection and treatment of oral diseases. Dental care utilization can be defined as the percentage of the population who access dental services over a specified period of time. There are reports that dental patients only visit the dentist when in pain and never bother to return for follow-up in most cases. To improve oral health outcomes an adequate knowledge of the way the individuals use health services and the factors predictive of this behavior is essential. The interest in developing models explaining the utilization of dental services has increased; issues like dental anxiety, price, income, the distance a person had to travel to get care, and preference for preservation of teeth are treated as barriers in regular dental care. Published materials which pertain to the use of dental services by Indian population have been reviewed and analyzed in depth in the present study. Dental surgeons and dental health workers have to play an adequate role in facilitating public enlightenment that people may appreciate the need for regular dental care and make adequate and proper use of the available dental care facilities. PMID:24082719

  11. Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model ADCHAM

    NASA Astrophysics Data System (ADS)

    Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, D.; Rusanen, A.; Boy, M.; Swietlicki, E.; Svenningsson, B.; Zelenyuk, A.; Pagels, J.

    2014-08-01

    We have developed the novel Aerosol Dynamics, gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas-phase Master Chemical Mechanism version 3.2 (MCMv3.2), an aerosol dynamics and particle-phase chemistry module (which considers acid-catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion-limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study (1) the evaporation of liquid dioctyl phthalate (DOP) particles, (2) the slow and almost particle-size-independent evaporation of α-pinene ozonolysis secondary organic aerosol (SOA) particles, (3) the mass-transfer-limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), and (4) the influence of chamber wall effects on the observed SOA formation in smog chambers. ADCHAM is able to capture the observed α-pinene SOA mass increase in the presence of NH3(g). Organic salts of ammonium and carboxylic acids predominantly form during the early stage of SOA formation. In the smog chamber experiments, these salts contribute substantially to the initial growth of the homogeneously nucleated particles. The model simulations of evaporating α-pinene SOA particles support the recent experimental findings that these particles have a semi-solid tar-like amorphous-phase state. ADCHAM is able to reproduce the main features of the observed slow evaporation rates if the concentration of low-volatility and viscous oligomerized SOA material at the particle surface increases upon evaporation. The evaporation rate is mainly governed by the reversible decomposition of oligomers back to monomers. Finally, we demonstrate that the mass-transfer-limited uptake of condensable organic compounds

  12. Dental Calculus Arrest of Dental Caries

    PubMed Central

    Keyes, Paul H.; Rams, Thomas E.

    2016-01-01

    Background An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human teeth for the presence and location of dental caries, dental calculus, and dental plaque biofilms. Materials and methods A total of 1,200 teeth were preserved in 10% buffered formal saline, and viewed while moist by a single experienced examiner using a research stereomicroscope at 15-25× magnification. Representative teeth were sectioned and photographed, and their dental plaque biofilms subjected to gram-stain examination with light microscopy at 100× magnification. Results Dental calculus was observed on 1,140 (95%) of the extracted human teeth, and no dental carious lesions were found underlying dental calculus-covered surfaces on 1,139 of these teeth. However, dental calculus arrest of dental caries was found on one (0.54%) of 187 evaluated teeth that presented with unrestored proximal enamel caries. On the distal surface of a maxillary premolar tooth, dental calculus mineralization filled the outer surface cavitation of an incipient dental caries lesion. The dental calculus-covered carious lesion extended only slightly into enamel, and exhibited a brown pigmentation characteristic of inactive or arrested dental caries. In contrast, the tooth's mesial surface, without a superficial layer of dental calculus, had a large carious lesion going through enamel and deep into dentin. Conclusions These observations further document the potential protective effects of dental calculus mineralization against dental caries. PMID:27446993

  13. Using multi-year data to evaluate performance of one-layer and multi-layer models in snow hydrology: an example from Col De Porte

    NASA Astrophysics Data System (ADS)

    Avanzi, Francesco; De Michele, Carlo; Morin, Samuel; Carmagnola, Carlo Maria; Ghezzi, Antonio; Lejeune, Yves

    2016-04-01

    Snow mass dynamics prediction represents an important task for snow hydrologists, since snow on the ground influences local/global water availability and streamflow timing and amount. Different modeling tools have been formulated for decades to predict snowmelt runoff dynamics and therefore to integrate snow mass dynamics in watershed hydrology modeling. Typical variables of interest include snow depth, snow bulk density, snow water equivalent (SWE) and snowmelt runoff. All these variables have been monitored at several locations worldwide for several decades in order to evaluate model performance. As a result, several multi-year datasets are now available to perform extensive evaluation tests. In this presentation, we report an example of these evaluations by discussing the performance of two models of different complexity in reproducing observed data of snow dynamics at a site in French Alps (Col De Porte, 1325 m AMSL), where 18 continuous-time years of observations are available. We consider Crocus as an example of multi-layer physically-based complex models and HyS (De Michele et al. 2013) as an example of a one-layer temperature-index models. Using multi-year data allows us to compare models performance over long periods of time, thus considering different climatic and snow conditions. Moreover, the use of continuous-time data allows to evaluate models performance at different temporal resolutions. De Michele, C., Avanzi, F., Ghezzi, A., and Jommi, C.: Investigating the dynamics of bulk snow density in dry and wet conditions using a one-dimensional model, The Cryosphere, 7, 433-444, doi:10.5194/tc-7-433-2013, 2013.

  14. Multilayer silicene: clear evidence

    NASA Astrophysics Data System (ADS)

    De Padova, Paola; Generosi, Amanda; Paci, Barbara; Ottaviani, Carlo; Quaresima, Claudio; Olivieri, Bruno; Salomon, Eric; Angot, Thierry; Le Lay, Guy

    2016-09-01

    One year after the publication of the seminal paper on monolayer 3 × 3 reconstructed silicene grown on a silver (111) substrate, evidence of the synthesis of epitaxial √3 × √3 reconstructed multilayer silicene hosting Dirac fermions was presented. Although a general consensus was immediately reached in the former case, in the latter, the mere existence of multilayer silicene was questioned and strongly debated. Here, we demonstrate by means of a comprehensive x-ray crystallographic study that multilayer silicene is effectively realized upon growth at rather low growth temperatures (∼200 °C), while three-dimensional growth of silicon crystallites takes place at higher temperatures, (∼300 °C). This transition to bulk-like silicon perfectly explains the various data presented and discussed in the literature and solves their conflicting interpretations.

  15. Multilayered Graphene in Microwaves

    NASA Astrophysics Data System (ADS)

    Kuzhir, P.; Volynets, N.; Maksimenko, S.; Kaplas, T.; Svirko, Yu.

    2013-05-01

    We report on the experimental study of electromagnetic (EM) properties of multilayered graphene in Ka-band synthesized by catalytic chemical vapor deposition (CVD) process in between nanometrically thin Cu catalyst film and dielectric (SiO2) substrate. The quality of the produced multilayered graphene samples were monitored by Raman spectroscopy. The thickness of graphene films was controlled by atomic force microscopy (AFM) and was found to be a few nanometers (up to 5 nm). We discovered, that the fabricated graphene provided remarkably high EM shielding efficiency caused by absorption losses at the level of 35-43% of incident power. Being highly conductive at room temperature, multi-layer graphene emerges as a promising material for manufacturing ultrathin microwave coatings to be used in aerospace applications.

  16. Control of Multilayer Networks

    PubMed Central

    Menichetti, Giulia; Dall’Asta, Luca; Bianconi, Ginestra

    2016-01-01

    The controllability of a network is a theoretical problem of relevance in a variety of contexts ranging from financial markets to the brain. Until now, network controllability has been characterized only on isolated networks, while the vast majority of complex systems are formed by multilayer networks. Here we build a theoretical framework for the linear controllability of multilayer networks by mapping the problem into a combinatorial matching problem. We found that correlating the external signals in the different layers can significantly reduce the multiplex network robustness to node removal, as it can be seen in conjunction with a hybrid phase transition occurring in interacting Poisson networks. Moreover we observe that multilayer networks can stabilize the fully controllable multiplex network configuration that can be stable also when the full controllability of the single network is not stable. PMID:26869210

  17. Protective effect of chitosan oligosaccharide lactate against DNA double-strand breaks induced by a model methacrylate dental adhesive

    PubMed Central

    Szczepanska, Joanna; Pawlowska, Elzbieta; Synowiec, Ewelina; Czarny, Piotr; Rekas, Marek; Blasiak, Janusz; Szaflik, Jacek Pawel

    2011-01-01

    Summary Background Monomers of methacrylates used in restorative dentistry have been recently reported to induce DNA double-strand breaks (DSBs) in human gingival fibroblasts (HGFs) in vitro. Because such monomers may penetrate the pulp and oral cavity due to the incompleteness of polymerization and polymer degradation, they may induce a similar effect in vivo. DSBs are the most serious type of DNA damage and if misrepaired or not repaired may lead to mutation, cancer transformation and cell death. Therefore, the protection against DSBs induced by methacrylate monomers released from dental restorations is imperative. Material/Methods We examined the protective action of chitosan oligosaccharide lactate (ChOL) against cytotoxic and genotoxic effects induced by monomers of the model adhesive consisting of 55% bisphenol A-diglycidyl dimethacrylate (Bis-GMA) and 45% 2-hydroxyethyl methacrylate (HEMA). We evaluated the extent of DSBs by the neutral comet assay and the phosphorylation of the H2AX histone test. Results ChOL increased the viability of HGFs exposed to Bis-GMA/HEMA as assessed by flow cytometry. ChOL decreased the extent of DSBs induced by Bis-GMA/HEMA as evaluated by neutral comet assay and phosphorylation of the H2AX histone. ChOL did not change mechanical properties of the model adhesive, as checked by the shear bond test. Scanning electron microscopy revealed a better sealing of the dentinal microtubules in the presence of ChOL, which may protect pulp cells against the harmful action of the monomers. Conclusions ChOL can be considered as an additive to methacrylate-based dental materials to prevent DSBs induction, but further studies are needed on its formulation with the methacrylates. PMID:21804456

  18. A simple theoretical model of heat and moisture transport in multi-layer garments in cool ambient air.

    PubMed

    Wissler, Eugene H; Havenith, George

    2009-03-01

    Overall resistances for heat and vapor transport in a multilayer garment depend on the properties of individual layers and the thickness of any air space between layers. Under uncomplicated, steady-state conditions, thermal and mass fluxes are uniform within the garment, and the rate of transport is simply computed as the overall temperature or water concentration difference divided by the appropriate resistance. However, that simple computation is not valid under cool ambient conditions when the vapor permeability of the garment is low, and condensation occurs within the garment. Several recent studies have measured heat and vapor transport when condensation occurs within the garment (Richards et al. in Report on Project ThermProject, Contract No. G6RD-CT-2002-00846, 2002; Havenith et al. in J Appl Physiol 104:142-149, 2008). In addition to measuring cooling rates for ensembles when the skin was either wet or dry, both studies employed a flat-plate apparatus to measure resistances of individual layers. Those data provide information required to define the properties of an ensemble in terms of its individual layers. We have extended the work of previous investigators by developing a rather simple technique for analyzing heat and water vapor transport when condensation occurs within a garment. Computed results agree well with experimental results reported by Richards et al. (Report on Project ThermProject, Contract No. G6RD-CT-2002-00846, 2002) and Havenith et al. (J Appl Physiol 104:142-149, 2008). We discuss application of the method to human subjects for whom the rate of sweat secretion, instead of the partial pressure of water on the skin, is specified. Analysis of a more complicated five-layer system studied by Yoo and Kim (Text Res J 78:189-197, 2008) required an iterative computation based on principles defined in this paper. PMID:19125281

  19. Development of three-dimensional patient face model that enables real-time collision detection and cutting operation for a dental simulator.

    PubMed

    Yamaguchi, Satoshi; Yamada, Yuya; Yoshida, Yoshinori; Noborio, Hiroshi; Imazato, Satoshi

    2012-01-01

    The virtual reality (VR) simulator is a useful tool to develop dental hand skill. However, VR simulations with reactions of patients have limited computational time to reproduce a face model. Our aim was to develop a patient face model that enables real-time collision detection and cutting operation by using stereolithography (STL) and deterministic finite automaton (DFA) data files. We evaluated dependence of computational cost and constructed the patient face model using the optimum condition for combining STL and DFA data files, and assessed the computational costs for operation in do-nothing, collision, cutting, and combination of collision and cutting. The face model was successfully constructed with low computational costs of 11.3, 18.3, 30.3, and 33.5 ms for do-nothing, collision, cutting, and collision and cutting, respectively. The patient face model could be useful for developing dental hand skill with VR. PMID:23207214

  20. Multilayer adsorption by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Molina-Mateo, J.; Salmerón Sánchez, M.; Monleón Pradas, M.; Torregrosa Cabanilles, C.

    2012-10-01

    Adsorption phenomena are characterized by models that include free parameters trying to reproduce experimental results. In order to understand the relationship between the model parameters and the material properties, the adsorption of small molecules on a crystalline plane surface has been simulated using the bond fluctuation model. A direct comparison between the Guggenheim-Anderson-de Boer (GAB) model for multilayer adsorption and computer simulations allowed us to establish correlations between the adsorption model parameters and the simulated interaction potentials.

  1. Simulation of Surface Energy Fluxes and Snow Interception Using a Higher Order Closure Multi-Layer Soil-Vegetation-Atmospheric Model: The Effect of Canopy Shape and Structure

    NASA Astrophysics Data System (ADS)

    McGowan, L. E.; Dahlke, H. E.; Paw U, K. T.

    2015-12-01

    Snow cover is a critical driver of the Earth's surface energy budget, climate change, and water resources. Variations in snow cover not only affect the energy budget of the land surface but also represent a major water supply source. In California, US estimates of snow depth, extent, and melt in the Sierra Nevada are critical to estimating the amount of water available for both California agriculture and urban users. However, accurate estimates of snow cover and snow melt processes in forested area still remain a challenge. Canopy structure influences the vertical and spatiotemporal distribution of snow, and therefore ultimately determines the degree and extent by which snow alters both the surface energy balance and water availability in forested regions. In this study we use the Advanced Canopy-Atmosphere-Soil algorithm (ACASA), a multi-layer soil-vegetation-atmosphere numerical model, to simulate the effect of different snow-covered canopy structures on the energy budget, and temperature and other scalar profiles within different forest types in the Sierra Nevada, California. ACASA incorporates a higher order turbulence closure scheme which allows the detailed simulation of turbulent fluxes of heat and water vapor as well as the CO2 exchange of several layers within the canopy. As such ACASA can capture the counter gradient fluxes within canopies that may occur frequently, but are typically unaccounted for, in most snow hydrology models. Six different canopy types were modeled ranging from coniferous forests (e.g. most biomass near the ground) to top-heavy (e.g. most biomass near the top of the crown) deciduous forests to multi-layered forest canopies (e.g. mixture of young and mature trees). Preliminary results indicate that the canopy shape and structure associated with different canopy types fundamentally influence the vertical scalar profiles (including those of temperature, moisture, and wind speed) in the canopy and thus alter the interception and snow

  2. The use of dental services for children: implications of the 2010 dental reform in Israel.

    PubMed

    Shahrabani, Shosh; Benzion, Uri; Machnes, Yaffa; Gal, Assaf

    2015-02-01

    Routine dental examinations for children are important for early diagnosis and treatment of dental problems. The level of dental morbidity among Israeli children is higher than the global average. A July 2010 reform of Israel's National Health Insurance Law gradually offers free dental services for children up to age 12. The study examines the use of dental services for children and the factors affecting mothers' decision to take their children for routine checkups. In addition, the study examines the impact of the reform on dental checkups for children in various populations groups. A national representative sample comprising 618 mothers of children aged 5-18 was surveyed by telephone. The survey integrated the principles of the health beliefs model and socio-demographic characteristics. The results show that mothers' decision to take their children for dental checkups is affected by their socio-demographic status and by their health beliefs with respect to dental health. After the reform, the frequency of children's dental checkups significantly increased among vulnerable populations. Therefore, the reform has helped reduce gaps in Israeli society regarding children's dental health. Raising families' awareness of the reform and of the importance of dental health care together with expanding national distribution of approved dental clinics can increase the frequency of dental checkups among children in Israel.

  3. Unfolding single- and multilayers

    NASA Astrophysics Data System (ADS)

    Llorens, Maria-Gema; Bons, Paul D.; Griera, Albert; Gomez-Rivas, Enrique

    2014-05-01

    When planar structures (e.g. sedimentary layers, veins, dykes, cleavages, etc.) are subjected to deformation, they have about equal chances to be shortened or stretched. The most common shortening and stretching structures are folds and boudinage, respectively. However, boudinage requires additional deformation mechanisms apart from viscous flow, like formation of fractures or strain localization. When folded layers are subjected to extension, they could potentially unfold back to straight layers. Although probably not uncommon, this would be difficult to recognize. Open questions are whether folded layers can unfold, what determines their mechanical behaviour and how we can recognize them in the field. In order to approach these questions, we present a series of numerical experiments that simulate stretching of previously folded single- and multi-layers in simple shear, using the two dimensional numerical modelling platform ELLE, including the finite element module BASIL that calculates viscous deformation. We investigate the parameters that affect a fold train once it rotates into the extensional field. The results show that the unfolding process strongly depends on the viscosity contrast between the layer and matrix (Llorens et al., 2013). Layers do not completely unfold when they experience softening before or during the stretching process or when other neighbouring competent layers prevent them from unfolding. The foliation refraction patterns are the main indicators of unfolded folds. Additionally, intrafolial folds and cusp-like folds adjacent to straight layers, as well as variations in fold amplitudes and limb lengths of irregular folds can also be used as indicators of stretching of a layer after shortening and folding. References: Llorens, M-.G., Bons, P.D., Griera, A. and Gomez-Rivas, E. 2013. When do folds unfold during progressive shear?. Geology, 41, 563-566.

  4. Dental Assistant.

    ERIC Educational Resources Information Center

    Michigan State Univ., East Lansing. Coll. of Agriculture and Natural Resources Education Inst.

    This curriculum guide, developed for use in dental assistant education programs in Michigan, describes a task-based curriculum that can help a teacher to develop a classroom management system where students learn by doing. It is based on task analysis and reflects the skills, knowledge, and attitudes that employers expect entry-level dental…

  5. An efficient model to predict guided wave radiation by finite-sized sources in multilayered anisotropic plates with account of caustics

    NASA Astrophysics Data System (ADS)

    Stévenin, M.; Lhémery, A.; Grondel, S.

    2016-01-01

    Elastic guided waves (GW) are used in various non-destructive testing (NDT) methods to inspect plate-like structures, generated by finite-sized transducers. Thanks to GW long range propagation, using a few transducers at permanent positions can provide a full coverage of the plate. Transducer diffraction effects take place, leading to complex radiated fields. Optimizing transducers positioning makes it necessary to accurately predict the GW field radiated by a transducer. Fraunhofer-like approximations applied to GW in isotropic homogeneous plates lead to fast and accurate field computation but can fail when applied to multi-layered anisotropic composite plates, as shown by some examples given. Here, a model is proposed for composite plates, based on the computation of the approximate Green's tensor describing modal propagation from a source point, with account of caustics typically seen when strong anisotropy is concerned. Modal solutions are otherwise obtained by the Semi-Analytic Finite Element method. Transducer diffraction effects are accounted for by means of an angular integration over the transducer surface as seen from the calculation point, that is, over energy paths involved, which are mode-dependent. The model is validated by comparing its predictions with those computed by means of a full convolution integration of the Green's tensor with the source over transducer surface. Examples given concern disk and rectangular shaped transducers commonly used in NDT.

  6. A structural model for multi-layered ceramic cylinders and its application to silicon carbide cladding of light water reactor fuel

    NASA Astrophysics Data System (ADS)

    Lee, Youho; Kazimi, Mujid S.

    2015-03-01

    A thermo-mechanical model for stress distribution and Weibull statistical fracture of a multi-layered SiC cladding for LWR fuel is developed. The model is validated by comparing its results to those of the Finite Element Analysis (FEA) code ANSYS. In steady-state operation, the temperature sensitive swelling may lead to undesirable tensile stresses which is anticipated to challenge the structural integrity of the fission-gas retaining inner layer of CVD-SiC monolith in a triple layer design with the composite being the middle layer. The stress distribution is sensitive to potential differences in the swelling of the monolith from that of the composite layer. The sensitivity is discussed in this work. A double-layered SiC cladding that employs the inner SiCf /SiC composite layer, and the outer CVD-SiC layer has also been analyzed. This SiC cladding design significantly reduces failure probability as it appropriately allocates peak tensile stresses in the inner composite while significantly reducing tensile stress levels of the CVD-SiC monolith.

  7. Dental biometrics: alignment and matching of dental radiographs.

    PubMed

    Chen, Hong; Jain, Anil K

    2005-08-01

    Dental biometrics utilizes dental radiographs for human identification. The dental radiographs provide information about teeth, including tooth contours, elative positions of neighboring teeth, and shapes of the dental work (e.g., crowns, fillings, and bridges). The proposed system has two main stages: feature extraction and matching. The feature extraction stage uses anisotropic diffusion to enhance the images and a Mixture of Gaussians model to segment the dental work. The matching stage has three sequential steps: tooth-level matching, computation of image distances, and subject identification. In the tooth-level matching step, tooth contours are matched using a shape registration method, and the dental work is matched on overlapping areas. The distance between the tooth contours and the distance between the dental work are then combined using posterior probabilities. In the second step, the tooth correspondences between the given query (postmortem) radiograph and the database (antemortem) radiograph are established. A distance based on the corresponding teeth is then used to measure the similarity between the two radiographs. Finally, all the distances between the given postmortem radiographs and the antemortem radiographs that provide candidate identities are combined to establish the identity of the subject associated with the postmortem radiographs.

  8. Point-based superimposition of a digital dental model on to a three-dimensional computed tomographic skull: an accuracy study in vitro.

    PubMed

    Lin, X; Chen, T; Liu, J; Jiang, T; Yu, D; Shen, S G F

    2015-01-01

    We investigated the accuracy of point-based superimposition of a digital dental model on to a 3-dimensional computed tomographic (CT) skull with intact dentition. The physical model was scanned by CT to give a virtual skull model, and a plaster dental model was taken and laser-scanned to give a digital dental model. Three different background investigators were recruited and calibrated to make the point-based superimposition, and afterwards were asked to repeat 5 superimpositions each. Five bone-to-tooth measurements for the maxilla and 6 for the mandible were selected to indicate the relation of teeth to skull. Repeated measures were made on the physical model to act as a control group, and on the virtual model to act as the test group. The absolute agreement intra-class correlation coefficient (ICC) was used to assess the intra/inter-investigator reliability; Bland-Altman analysis was used to calculate the general differences, limits of agreement, and precision ranges of the estimated limits. Inter/intra-investigator reliability was excellent with ICC varying from 0.986 to 1; Bland-Altman analysis indicated that general difference was 0.01 (0.25)mm, the upper limit of agreement was 0.50mm and the lower limit -0.47 mm, and the precision range for the upper limit was 0.43 mm to 0.57 mm and for the lower limit -0.54 mm to -0.40 mm. Clinically acceptable accuracy can be achieved using a direct point-based method to superimpose a digital dental model on to a 3-dimensional CT skull.

  9. Dental Training Films.

    ERIC Educational Resources Information Center

    Veterans Administration Medical Center, Washington, DC.

    This dental training films catalog is organized into two sections. Section I is a category listing of the films by number and title, indexed according to generalized headings; categories are as follow: anatomy, articulator systems, complete dentures, dental assisting, dental laboratory technology, dental materials, dental office emergencies,…

  10. Oral Lactobacilli and Dental Caries: A Model for Niche Adaptation in Humans.

    PubMed

    Caufield, P W; Schön, C N; Saraithong, P; Li, Y; Argimón, S

    2015-09-01

    Lactobacilli have been associated with dental caries for over a century. Here, we review the pertinent literature along with findings from our own study to formulate a working hypothesis about the natural history and role of lactobacilli. Unlike most indigenous microbes that stably colonize a host, lactobacilli appear to be planktonic, opportunistic settlers that can gather and multiply only in certain restrictive niches of the host, at least within the oral cavity. We postulate that the following essential requirements are necessary for sustained colonization of lactobacilli in humans: 1) a stagnant, retentive niche that is mostly anaerobic; 2) a low pH milieu; and 3) ready access to carbohydrates. Three sites on the human body meet these specifications: caries lesions, the stomach, and the vagina. Only a handful of Lactobacillus species is found in caries lesions, but they are largely absent in caries-free children. Lactobacilli present in caries lesions represent both a major contributor to caries progression and a major reservoir to the gastrointestinal (GI) tract. We extend the assertion from other investigators that lactobacilli found in the GI tract originate in the oral cavity by proposing that lactobacilli in the oral cavity arise from caries lesions. This, in turn, leads us to reflect on the health implications of the lactobacilli in the mouth and downstream GI and to ponder whether these or any of the Lactobacillus species are truly indigenous to the human GI tract or the oral cavity.

  11. To explore and develop a model to maintain and build upon a dental clinic open for all in developing regions, with a primary focus on India

    PubMed Central

    Sugandhi, Ayushi; Mangal, Brijesh; Mishra, Amit Kumar; Sethia, Bhavna

    2014-01-01

    AIM: To study a service model that enables a clinic to be open to all members of the community, irrespective of their ability to pay. METHODS: Sampling methodology was used to gather information in two phases, with the city of Indore as the target region. In the first phase, dental professionals were surveyed to gather the cost of the facility, land and equipment and the cost of sustaining the practice. In the second phase, the residents of Indore were surveyed to collect information regarding their oral health problems and their expenditure for the same. Assessing the current situation, the questions to answer are related to the issues of dental health care access problems and the resources required, human and financial. RESULTS: (1) People younger than 20 years of age form a large proportion (43%) of the population of the city and also a large proportion (54%) of people who visit dental clinics; (2) Dental caries are commonly found in the population younger than 20 years of age and mobile teeth in those older than 50 years of age; (3) Dental caries and mobile teeth are almost equally found in people of the age group 20-50 years old; (4) A significantly large proportion of those older than 50 years old have had all their teeth extracted; and (5) A significantly large proportion of the 20-30 years of age group has had no teeth extracted. CONCLUSION: The model which we propose works well for low income patients; however, it places a lot of extra burden on the higher income group. A lot of effort can be put into generating revenue from other sources, including events and donations. PMID:25232547

  12. Evaluating the performance of land surface model ORCHIDEE-CAN v1.0 on water and energy flux estimation with a single- and multi-layer energy budget scheme

    NASA Astrophysics Data System (ADS)

    Chen, Yiying; Ryder, James; Bastrikov, Vladislav; McGrath, Matthew J.; Naudts, Kim; Otto, Juliane; Ottlé, Catherine; Peylin, Philippe; Polcher, Jan; Valade, Aude; Black, Andrew; Elbers, Jan A.; Moors, Eddy; Foken, Thomas; van Gorsel, Eva; Haverd, Vanessa; Heinesch, Bernard; Tiedemann, Frank; Knohl, Alexander; Launiainen, Samuli; Loustau, Denis; Ogée, Jérôme; Vessala, Timo; Luyssaert, Sebastiaan

    2016-09-01

    Canopy structure is one of the most important vegetation characteristics for land-atmosphere interactions, as it determines the energy and scalar exchanges between the land surface and the overlying air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget in the ORCHIDEE-CAN v1.0 land surface model (Organising Carbon and Hydrology In Dynamic Ecosystems - CANopy), which simulates canopy structure and can be coupled to an atmospheric model using an implicit coupling procedure. We aim to provide a set of acceptable parameter values for a range of forest types. Top-canopy and sub-canopy flux observations from eight sites were collected in order to conduct this evaluation. The sites crossed climate zones from temperate to boreal and the vegetation types included deciduous, evergreen broad-leaved and evergreen needle-leaved forest with a maximum leaf area index (LAI; all-sided) ranging from 3.5 to 7.0. The parametrization approach proposed in this study was based on three selected physical processes - namely the diffusion, advection, and turbulent mixing within the canopy. Short-term sub-canopy observations and long-term surface fluxes were used to calibrate the parameters in the sub-canopy radiation, turbulence, and resistance modules with an automatic tuning process. The multi-layer model was found to capture the dynamics of sub-canopy turbulence, temperature, and energy fluxes. The performance of the new multi-layer model was further compared against the existing single-layer model. Although the multi-layer model simulation results showed few or no improvements to both the nighttime energy balance and energy partitioning during winter compared with a single-layer model simulation, the increased model complexity does provide a more detailed description of the canopy micrometeorology of various forest types. The multi-layer model links to potential future environmental and ecological studies such as the assessment of in

  13. Piezoelectric polymer multilayer on flexible substrate for energy harvesting.

    PubMed

    Zhang, Lei; Oh, Sharon Roslyn; Wong, Ting Chong; Tan, Chin Yaw; Yao, Kui

    2013-09-01

    A piezoelectric polymer multilayer structure formed on a flexible substrate is investigated for mechanical energy harvesting under bending mode. Analytical and numerical models are developed to clarify the effect of material parameters critical to the energy harvesting performance of the bending multilayer structure. It is shown that the maximum power is proportional to the square of the piezoelectric stress coefficient and the inverse of dielectric permittivity of the piezoelectric polymer. It is further found that a piezoelectric multilayer with thinner electrodes can generate more electric energy in bending mode. The effect of improved impedance matching in the multilayer polymer on energy output is remarkable. Comparisons between piezoelectric ceramic multilayers and polymer multilayers on flexible substrate are discussed. The fabrication of a P(VDF-TrFE) multilayer structure with a thin Al electrode layer is experimentally demonstrated by a scalable dip-coating process on a flexible aluminum substrate. The results indicate that it is feasible to produce a piezoelectric polymer multilayer structure on flexible substrate for harvesting mechanical energy applicable for many low-power electronics.

  14. Piezoelectric polymer multilayer on flexible substrate for energy harvesting.

    PubMed

    Zhang, Lei; Oh, Sharon Roslyn; Wong, Ting Chong; Tan, Chin Yaw; Yao, Kui

    2013-09-01

    A piezoelectric polymer multilayer structure formed on a flexible substrate is investigated for mechanical energy harvesting under bending mode. Analytical and numerical models are developed to clarify the effect of material parameters critical to the energy harvesting performance of the bending multilayer structure. It is shown that the maximum power is proportional to the square of the piezoelectric stress coefficient and the inverse of dielectric permittivity of the piezoelectric polymer. It is further found that a piezoelectric multilayer with thinner electrodes can generate more electric energy in bending mode. The effect of improved impedance matching in the multilayer polymer on energy output is remarkable. Comparisons between piezoelectric ceramic multilayers and polymer multilayers on flexible substrate are discussed. The fabrication of a P(VDF-TrFE) multilayer structure with a thin Al electrode layer is experimentally demonstrated by a scalable dip-coating process on a flexible aluminum substrate. The results indicate that it is feasible to produce a piezoelectric polymer multilayer structure on flexible substrate for harvesting mechanical energy applicable for many low-power electronics. PMID:24658732

  15. Non-Lethal Control of the Cariogenic Potential of an Agent-Based Model for Dental Plaque

    PubMed Central

    Head, David A.; Marsh, Phil D.; Devine, Deirdre A.

    2014-01-01

    Dental caries or tooth decay is a prevalent global disease whose causative agent is the oral biofilm known as plaque. According to the ecological plaque hypothesis, this biofilm becomes pathogenic when external challenges drive it towards a state with a high proportion of acid-producing bacteria. Determining which factors control biofilm composition is therefore desirable when developing novel clinical treatments to combat caries, but is also challenging due to the system complexity and the existence of multiple bacterial species performing similar functions. Here we employ agent-based mathematical modelling to simulate a biofilm consisting of two competing, distinct types of bacterial populations, each parameterised by their nutrient uptake and aciduricity, periodically subjected to an acid challenge resulting from the metabolism of dietary carbohydrates. It was found that one population was progressively eliminated from the system to give either a benign or a pathogenic biofilm, with a tipping point between these two fates depending on a multiplicity of factors relating to microbial physiology and biofilm geometry. Parameter sensitivity was quantified by individually varying the model parameters against putative experimental measures, suggesting non-lethal interventions that can favourably modulate biofilm composition. We discuss how the same parameter sensitivity data can be used to guide the design of validation experiments, and argue for the benefits of in silico modelling in providing an additional predictive capability upstream from in vitro experiments. PMID:25144538

  16. Non-lethal control of the cariogenic potential of an agent-based model for dental plaque.

    PubMed

    Head, David A; Marsh, Phil D; Devine, Deirdre A

    2014-01-01

    Dental caries or tooth decay is a prevalent global disease whose causative agent is the oral biofilm known as plaque. According to the ecological plaque hypothesis, this biofilm becomes pathogenic when external challenges drive it towards a state with a high proportion of acid-producing bacteria. Determining which factors control biofilm composition is therefore desirable when developing novel clinical treatments to combat caries, but is also challenging due to the system complexity and the existence of multiple bacterial species performing similar functions. Here we employ agent-based mathematical modelling to simulate a biofilm consisting of two competing, distinct types of bacterial populations, each parameterised by their nutrient uptake and aciduricity, periodically subjected to an acid challenge resulting from the metabolism of dietary carbohydrates. It was found that one population was progressively eliminated from the system to give either a benign or a pathogenic biofilm, with a tipping point between these two fates depending on a multiplicity of factors relating to microbial physiology and biofilm geometry. Parameter sensitivity was quantified by individually varying the model parameters against putative experimental measures, suggesting non-lethal interventions that can favourably modulate biofilm composition. We discuss how the same parameter sensitivity data can be used to guide the design of validation experiments, and argue for the benefits of in silico modelling in providing an additional predictive capability upstream from in vitro experiments. PMID:25144538

  17. The Development of Dental Anesthesiology As a Discipline and Its Role As a Model of Interdisciplinary Collaboration.

    PubMed

    Giovannitti, Joseph A; Montandon, Richard J; Herlich, Andrew

    2016-08-01

    The majority of dental procedures can be performed with an awake patient and the use of a local anesthetic, but when deep sedation and general anesthesia are needed, they typically are provided by those dentists with advanced training in anesthesiology, i.e., oral and maxillofacial surgeons and dentist anesthesiologists. Dental anesthesiology began with the discovery of anesthesia by a dentist in 1844 and has been recognized as a separate discipline in dentistry for nearly 70 years. Training over this time evolved from apprenticeships to one-year training programs, and in 2007, the Commission on Dental Accreditation (CODA) began accrediting two-year dental anesthesiology training programs. Since 2015, in recognition of the increasing complexity of the discipline, training has required three years of postgraduate study. The number of dentist anesthesiologists has grown with the increasing demand for anesthesia services by both the public and the profession. However, the present number of dentist anesthesiologists is not sufficient to meet the demand, so additional programs and growth in current programs are needed. Another valuable aspect of this discipline is its role as a positive example of interdepartmental collaboration since dental anesthesiology faculty, as members of a support discipline, typically work across many of the other departments in a dental school. This article reviews the history of the discipline, describes the educational goals and CODA standards for dental anesthesiology programs, using one program as an example, and discusses the needs and challenges that will shape the discipline's development in the future. PMID:27480705

  18. The Development of Dental Anesthesiology As a Discipline and Its Role As a Model of Interdisciplinary Collaboration.

    PubMed

    Giovannitti, Joseph A; Montandon, Richard J; Herlich, Andrew

    2016-08-01

    The majority of dental procedures can be performed with an awake patient and the use of a local anesthetic, but when deep sedation and general anesthesia are needed, they typically are provided by those dentists with advanced training in anesthesiology, i.e., oral and maxillofacial surgeons and dentist anesthesiologists. Dental anesthesiology began with the discovery of anesthesia by a dentist in 1844 and has been recognized as a separate discipline in dentistry for nearly 70 years. Training over this time evolved from apprenticeships to one-year training programs, and in 2007, the Commission on Dental Accreditation (CODA) began accrediting two-year dental anesthesiology training programs. Since 2015, in recognition of the increasing complexity of the discipline, training has required three years of postgraduate study. The number of dentist anesthesiologists has grown with the increasing demand for anesthesia services by both the public and the profession. However, the present number of dentist anesthesiologists is not sufficient to meet the demand, so additional programs and growth in current programs are needed. Another valuable aspect of this discipline is its role as a positive example of interdepartmental collaboration since dental anesthesiology faculty, as members of a support discipline, typically work across many of the other departments in a dental school. This article reviews the history of the discipline, describes the educational goals and CODA standards for dental anesthesiology programs, using one program as an example, and discusses the needs and challenges that will shape the discipline's development in the future.

  19. Laser beam induced nanoscale spot through nonlinear “thick” samples: A multi-layer thin lens self-focusing model

    SciTech Connect

    Wei, Jingsong; Yan, Hui

    2014-08-14

    Self-focusing is a well-researched phenomenon. Nanoscale spots can be achieved through self-focusing, which is an alternative method for achieving high-density data storage, high-resolution light imaging, and maskless nanolithography. Several research groups have observed that self-focusing spots can be reduced to nanoscale levels via incident laser power manipulation. Self-focusing spots can be analyzed by solving the nonlinear Schrödinger equation and the finite difference time domain method. However, both procedures are complex and time-consuming. In the present work, a multi-layer thin-lens self-focusing model that considers diffraction effects and changes of refractive index along the radial and film thickness directions is proposed to analyze the self-focusing behavior and traveling process of light beams intuitively. The self-focusing behaviors of As{sub 2}S{sub 3} are simulated, and results show that a nanoscale self-focusing spot with a radius of about 0.12 μm can be formed at the bottom of nonlinear sample when the incident laser power exceeds 4.25 mW. Our findings are basically consistent with experimental reports and provide a good method for analyzing and understanding the self-focusing process. An appropriate application schematic design is also provided.

  20. Temperature profile retrieval in axisymmetric combustion plumes using multilayer perceptron modeling and spectral feature selection in the infrared CO2 emission band.

    PubMed

    García-Cuesta, Esteban; de Castro, Antonio J; Galván, Inés M; López, Fernando

    2014-01-01

    In this work, a methodology based on the combined use of a multilayer perceptron model fed using selected spectral information is presented to invert the radiative transfer equation (RTE) and to recover the spatial temperature profile inside an axisymmetric flame. The spectral information is provided by the measurement of the infrared CO2 emission band in the 3-5 μm spectral region. A guided spectral feature selection was carried out using a joint criterion of principal component analysis and a priori physical knowledge of the radiative problem. After applying this guided feature selection, a subset of 17 wavenumbers was selected. The proposed methodology was applied over synthetic scenarios. Also, an experimental validation was carried out by measuring the spectral emission of the exhaust hot gas plume in a microjet engine with a Fourier transform-based spectroradiometer. Temperatures retrieved using the proposed methodology were compared with classical thermocouple measurements, showing a good agreement between them. Results obtained using the proposed methodology are very promising and can encourage the use of sensor systems based on the spectral measurement of the CO2 emission band in the 3-5 μm spectral window to monitor combustion processes in a nonintrusive way.

  1. Efficacy of disintegrating aspirin in two different models for acute mild-to-moderate pain: sore throat pain and dental pain.

    PubMed

    Voelker, M; Schachtel, B P; Cooper, S A; Gatoulis, S C

    2016-02-01

    A recently developed fast-release aspirin tablet formulation has been evaluated in two different pain models. The dental impaction pain model and the sore throat pain model are widely used for assessing analgesia, including acute mild-to-moderate pain. Both studies were double-blind, randomized, parallel group and compared a single dose of 1000 mg aspirin with 1000 mg paracetamol and with placebo and investigated the onset and overall time course of pain relief. Speed of onset was measured by the double-stopwatch method for time to meaningful pain relief and time to first perceptible pain relief. Pain intensity and pain relief were rated subjectively over a 6-h (dental pain) and 2-h (sore throat pain) time period. In both models fast-release aspirin and commercial paracetamol were statistically significantly different from placebo for onset of action, summed pain intensity differences and total pain relief. Meaningful pain relief was achieved within a median of 42.3 and 42.9 min for aspirin and paracetamol, respectively, in the dental pain model. The corresponding numbers in sore throat pain were 48.0 and 40.4 min. All treatments in both studies were safe and well tolerated. No serious adverse events were reported and no subject was discontinued due to an adverse event. Overall the two studies clearly demonstrated efficacy over placebo in the two pain models and a comparable efficacy and safety profile between aspirin and an equivalent dose of paracetamol under the conditions of acute dental pain and acute sore throat pain. Trial registration These trials were registered with ClinicalTrials.gov, registration number: NCT01420094, registration date: July 27, 2011 and registration number: NCT01453400, registration date: October 13, 2011. PMID:26603742

  2. Efficacy of disintegrating aspirin in two different models for acute mild-to-moderate pain: sore throat pain and dental pain.

    PubMed

    Voelker, M; Schachtel, B P; Cooper, S A; Gatoulis, S C

    2016-02-01

    A recently developed fast-release aspirin tablet formulation has been evaluated in two different pain models. The dental impaction pain model and the sore throat pain model are widely used for assessing analgesia, including acute mild-to-moderate pain. Both studies were double-blind, randomized, parallel group and compared a single dose of 1000 mg aspirin with 1000 mg paracetamol and with placebo and investigated the onset and overall time course of pain relief. Speed of onset was measured by the double-stopwatch method for time to meaningful pain relief and time to first perceptible pain relief. Pain intensity and pain relief were rated subjectively over a 6-h (dental pain) and 2-h (sore throat pain) time period. In both models fast-release aspirin and commercial paracetamol were statistically significantly different from placebo for onset of action, summed pain intensity differences and total pain relief. Meaningful pain relief was achieved within a median of 42.3 and 42.9 min for aspirin and paracetamol, respectively, in the dental pain model. The corresponding numbers in sore throat pain were 48.0 and 40.4 min. All treatments in both studies were safe and well tolerated. No serious adverse events were reported and no subject was discontinued due to an adverse event. Overall the two studies clearly demonstrated efficacy over placebo in the two pain models and a comparable efficacy and safety profile between aspirin and an equivalent dose of paracetamol under the conditions of acute dental pain and acute sore throat pain. Trial registration These trials were registered with ClinicalTrials.gov, registration number: NCT01420094, registration date: July 27, 2011 and registration number: NCT01453400, registration date: October 13, 2011.

  3. Dental practice in Paris.

    PubMed

    Baron, Pierre

    2003-01-01

    This describes dental practice and the availability of dental patent remedies in Paris. Accounts of legal disputes, from original sources, illustrate the status and social history of some of the most wealthy dental practitioners in Paris during the Revolution.

  4. American Dental Association

    MedlinePlus

    ... Public Prevention Summit ADA Find-a-Dentist Health Literacy in Dentistry Volunteer Efforts Dental Benefit Plan Information ... on Sleep Bruxism Rethinking Dental Insurance Oral Health Literacy's Role in Missed Appointments Dental Implant Failure Rate ...

  5. Validity of Intraoral Scans Compared with Plaster Models: An In-Vivo Comparison of Dental Measurements and 3D Surface Analysis

    PubMed Central

    2016-01-01

    Purpose Dental measurements have been commonly taken from plaster dental models obtained from alginate impressions can. Through the use of an intraoral scanner, digital impressions now acquire the information directly from the mouth. The purpose of this study was to determine the validity of the intraoral scans compared to plaster models. Materials and Methods Two types of dental models (intraoral scan and plaster model) of 20 subjects were included in this study. The subjects had impressions taken of their teeth and made as plaster model. In addition, their mouths were scanned with the intraoral scanner and the scans were converted into digital models. Eight transverse and 16 anteroposterior measurements, 24 tooth heights and widths were recorded on the plaster models with a digital caliper and on the intraoral scan with 3D reverse engineering software. For 3D surface analysis, the two models were superimposed by using best-fit algorithm. The average differences between the two models at all points on the surfaces were computed. Paired t-test and Bland-Altman plot were used to determine the validity of measurements from the intraoral scan compared to those from the plaster model. Results There were no significant differences between the plaster models and intraoral scans, except for one measurement of lower intermolar width. The Bland-Altman plots of all measurements showed that differences between the two models were within the limits of agreement. The average surface difference between the two models was within 0.10 mm. Conclusions The results of the present study indicate that the intraoral scans are clinically acceptable for diagnosis and treatment planning in dentistry and can be used in place of plaster models. PMID:27304976

  6. Impact on multilayered composite plates

    NASA Technical Reports Server (NTRS)

    Kim, B. S.; Moon, F. C.

    1977-01-01

    Stress wave propagation in a multilayer composite plate due to impact was examined by means of the anisotropic elasticity theory. The plate was modelled as a number of identical anisotropic layers and the approximate plate theory of Mindlin was then applied to each layer to obtain a set of difference-differential equations of motion. Dispersion relations for harmonic waves and correction factors were found. The governing equations were reduced to difference equations via integral transforms. With given impact boundary conditions these equations were solved for an arbitrary number of layers in the plate and the transient propagation of waves was calculated by means of a Fast Fourier Transform algorithm. The multilayered plate problem was extended to examine the effect of damping layers present between two elastic layers. A reduction of the interlaminar normal stress was significant when the thickness of damping layer was increased but the effect was mostly due to the softness of the damping layer. Finally, the problem of a composite plate with a crack on the interlaminar boundary was formulated.

  7. Correction of dental artifacts within the anatomical surface in PET/MRI using active shape models and k-nearest-neighbors

    NASA Astrophysics Data System (ADS)

    Ladefoged, Claes N.; Andersen, Flemming L.; Keller, Sune H.; Beyer, Thomas; Højgaard, Liselotte; Lauze, François

    2014-03-01

    In combined PET/MR, attenuation correction (AC) is performed indirectly based on the available MR image information. Metal implant-induced susceptibility artifacts and subsequent signal voids challenge MR-based AC. Several papers acknowledge the problem in PET attenuation correction when dental artifacts are ignored, but none of them attempts to solve the problem. We propose a clinically feasible correction method which combines Active Shape Models (ASM) and k- Nearest-Neighbors (kNN) into a simple approach which finds and corrects the dental artifacts within the surface boundaries of the patient anatomy. ASM is used to locate a number of landmarks in the T1-weighted MR-image of a new patient. We calculate a vector of offsets from each voxel within a signal void to each of the landmarks. We then use kNN to classify each voxel as belonging to an artifact or an actual signal void using this offset vector, and fill the artifact voxels with a value representing soft tissue. We tested the method using fourteen patients without artifacts, and eighteen patients with dental artifacts of varying sizes within the anatomical surface of the head/neck region. Though the method wrongly filled a small volume in the bottom part of a maxillary sinus in two patients without any artifacts, due to their abnormal location, it succeeded in filling all dental artifact regions in all patients. In conclusion, we propose a method, which combines ASM and kNN into a simple approach which, as the results show, succeeds to find and correct the dental artifacts within the anatomical surface.

  8. Accuracy and precision of polyurethane dental arch models fabricated using a three-dimensional subtractive rapid prototyping method with an intraoral scanning technique

    PubMed Central

    Kim, Jae-Hong; Kim, Ki-Baek; Kim, Woong-Chul; Kim, Ji-Hwan

    2014-01-01

    Objective This study aimed to evaluate the accuracy and precision of polyurethane (PUT) dental arch models fabricated using a three-dimensional (3D) subtractive rapid prototyping (RP) method with an intraoral scanning technique by comparing linear measurements obtained from PUT models and conventional plaster models. Methods Ten plaster models were duplicated using a selected standard master model and conventional impression, and 10 PUT models were duplicated using the 3D subtractive RP technique with an oral scanner. Six linear measurements were evaluated in terms of x, y, and z-axes using a non-contact white light scanner. Accuracy was assessed using mean differences between two measurements, and precision was examined using four quantitative methods and the Bland-Altman graphical method. Repeatability was evaluated in terms of intra-examiner variability, and reproducibility was assessed in terms of inter-examiner and inter-method variability. Results The mean difference between plaster models and PUT models ranged from 0.07 mm to 0.33 mm. Relative measurement errors ranged from 2.2% to 7.6% and intraclass correlation coefficients ranged from 0.93 to 0.96, when comparing plaster models and PUT models. The Bland-Altman plot showed good agreement. Conclusions The accuracy and precision of PUT dental models for evaluating the performance of oral scanner and subtractive RP technology was acceptable. Because of the recent improvements in block material and computerized numeric control milling machines, the subtractive RP method may be a good choice for dental arch models. PMID:24696823

  9. Integrating Social Activity Theory and Critical Discourse Analysis: A Multilayered Methodological Model for Examining Knowledge Mediation in Mentoring

    ERIC Educational Resources Information Center

    Becher, Ayelet; Orland-Barak, Lily

    2016-01-01

    This study suggests an integrative qualitative methodological framework for capturing complexity in mentoring activity. Specifically, the model examines how historical developments of a discipline direct mentors' mediation of professional knowledge through the language that they use. The model integrates social activity theory and a framework of…

  10. Dental students--dental advocates.

    PubMed

    Bensch, Brittany

    2010-01-01

    Student advocacy and involvement in the political process is built into the structure of the American Student Dental Association (ASDA), especially in its Legislative Grassroots Network and an internal communication network among students to ensure political awareness. Students are concerned with such issues as a universally accepted, non-patient-based licensure process, mid-level providers, loan availability and tax deductibility, financial support for schools, and service early in one's professional career (giving forward rather than giving back). Through collaboration with the American Dental Education Association and with many state associations, students participate in lobbying, awareness campaigns, and behind the scenes as legislative aids. Although students share the same love for the profession that animates established practitioners, they are perceived by legislators as being different. Students are involved in the legislative process because it represents their future.

  11. Dental students--dental advocates.

    PubMed

    Bensch, Brittany

    2010-01-01

    Student advocacy and involvement in the political process is built into the structure of the American Student Dental Association (ASDA), especially in its Legislative Grassroots Network and an internal communication network among students to ensure political awareness. Students are concerned with such issues as a universally accepted, non-patient-based licensure process, mid-level providers, loan availability and tax deductibility, financial support for schools, and service early in one's professional career (giving forward rather than giving back). Through collaboration with the American Dental Education Association and with many state associations, students participate in lobbying, awareness campaigns, and behind the scenes as legislative aids. Although students share the same love for the profession that animates established practitioners, they are perceived by legislators as being different. Students are involved in the legislative process because it represents their future. PMID:21314046

  12. The relationship between dental anxiety and dental decay experience in antenatal mothers.

    PubMed

    Esa, Rashidah; Savithri, Vengadasalam; Humphris, Gerry; Freeman, Ruth

    2010-02-01

    The aim of this study was to investigate the relationship between dental anxiety and dental decay experience among antenatal mothers attending Maternal and Child Health clinics in Malaysia. A cross-sectional study was conducted on a consecutive sample of 407 antenatal mothers in Seremban, Malaysia. The questionnaire consisted of participants' demographic profile and the Dental Fear Survey. The D(3cv)MFS was employed as the outcome measure and was assessed by a single examiner (intraclass correlation = 0.98). A structural equation model was designed to inspect the relationship between dental anxiety and dental decay experience. The mean Dental Fear Survey score for all participants was 35.1 [95% confidence interval (34.0, 36.3)]. The mean D(3cv)MFS score was 10.8 [95% confidence interval (9.5, 12.1)]. Participants from low socio-economic status groups had significantly higher D(3cv)MFS counts than those from high socio-economic status groups. The path model with dental anxiety and socio-economic status as predictors of D(3cv)MFS showed satisfactory fit. The correlation between dental anxiety and dental decay experience was 0.30 (standardized estimate), indicating a positive association. Socio-economic status was also statistically significantly associated with the D(3cv)MFS count (beta = 0.19). This study presented robust evidence for the significant relationship between dental anxiety and dental decay experience in antenatal mothers. PMID:20156266

  13. The relationship between dental anxiety and dental decay experience in antenatal mothers.

    PubMed

    Esa, Rashidah; Savithri, Vengadasalam; Humphris, Gerry; Freeman, Ruth

    2010-02-01

    The aim of this study was to investigate the relationship between dental anxiety and dental decay experience among antenatal mothers attending Maternal and Child Health clinics in Malaysia. A cross-sectional study was conducted on a consecutive sample of 407 antenatal mothers in Seremban, Malaysia. The questionnaire consisted of participants' demographic profile and the Dental Fear Survey. The D(3cv)MFS was employed as the outcome measure and was assessed by a single examiner (intraclass correlation = 0.98). A structural equation model was designed to inspect the relationship between dental anxiety and dental decay experience. The mean Dental Fear Survey score for all participants was 35.1 [95% confidence interval (34.0, 36.3)]. The mean D(3cv)MFS score was 10.8 [95% confidence interval (9.5, 12.1)]. Participants from low socio-economic status groups had significantly higher D(3cv)MFS counts than those from high socio-economic status groups. The path model with dental anxiety and socio-economic status as predictors of D(3cv)MFS showed satisfactory fit. The correlation between dental anxiety and dental decay experience was 0.30 (standardized estimate), indicating a positive association. Socio-economic status was also statistically significantly associated with the D(3cv)MFS count (beta = 0.19). This study presented robust evidence for the significant relationship between dental anxiety and dental decay experience in antenatal mothers.

  14. Simulation of Seasonal Snow Microwave TB Using Coupled Multi-Layered Snow Evolution and Microwave Emission Models

    NASA Technical Reports Server (NTRS)

    Brucker, Ludovic; Royer, Alain; Picard, Ghislain; Langlois, Alex; Fily, Michel

    2014-01-01

    The accurate quantification of SWE has important societal benefits, including improving domestic and agricultural water planning, flood forecasting and electric power generation. However, passive-microwave SWE algorithms suffer from variations in TB due to snow metamorphism, difficult to distinguish from those due to SWE variations. Coupled snow evolution-emission models are able to predict snow metamorphism, allowing us to account for emissivity changes. They can also be used to identify weaknesses in the snow evolution model. Moreover, thoroughly evaluating coupled models is a contribution toward the assimilation of TB, which leads to a significant increase in the accuracy of SWE estimates.

  15. Multi-Layer, Sharp-Interface Models of Pore Pressure Buildup within the Illinois Basin due to Basin-Wide CO2 Injection

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Person, M. A.; Gable, C. W.; Celia, M. A.; Nordbotten, J. M.; Bandilla, K.; Elliot, T. R.; Rupp, J.; Ellett, K. M.; Bowen, B.; Pickett, W.; Woolsey, E. E.

    2011-12-01

    We recently developed and applied a new parallel, multi-layer, finite-element model to the Illinois Basin in order to assess the spatial extent and magnitude of pore pressure increases resulting from the annual projected injection of 100 million metric tons of CO2. One focus of this work is to assess the potential for inducing a seismic event associated with low effective stress conditions around CO2 injection wells in the southern Illinois Basin where Mt Simon permeability is relatively low (< 50 mD). We used a sharp-interface formulation to represent a CO2, freshwater, and brine transport within each layer. A simple parallelization scheme was used in which fluid transport in each layer is solved on a separate processor. The layers are linked at the after each time step through vertical fluxes of fresh and saline water across their respective confining units. This model was validated, in part, by comparison to computed pore pressure distributions from a published 8-layer test case. Our Illinois Basin model represents spatial variations in porosity using a modified form of Athy's law. Permeability is logarithmically related to porosity so that permeability. Principal reservoirs represented in our model include the Mt. Simon Formation, the Knox Dolomite, Ordovician carbonates, Silurian-Devonian and Mississippian-Pennsylvanian sandstone/carbonates units. Key confining unit represented include the Eau Claire, Maquoketa, and New Albany Shales. A limited number of low-permeability faults were also included in the model. The permeability of fault elements were set to between 10-100 times lower than surrounding sediments. We calibrated our model using historical freshwater pumping data from the Chicago area (128 million gallons per day of H2O) as well as the salinity distribution across the Illinois Basin. We found that incorporating a stream network which included the Rock River near Chicago was important in reproducing pre-development head patterns in the Cambro

  16. Exploration of complex multilayer film growth morphologies: STM analysis and predictive atomistic modeling for Ag on Ag(111)

    SciTech Connect

    Li, Maozhi; Chung, P.W.; Cox, E.; Jenks, C.J.; Thiel, P.A.; Evans, J.W.

    2008-01-03

    Scanning tunneling microscopy studies are integrated with development of a realistic atomistic model to both characterize and elucidate the complex mounded morphologies formed by deposition of Ag on Ag(111) at 150 and 180 K. Threefold symmetric lateral shapes of islands and mounds are shown to reflect the influence of a nonuniform step edge barrier inhibiting interlayer transport. Modeling of structure at the mound peaks leads to a sensitive estimate of the magnitude of this large barrier.

  17. Evaluation of a dental floss containing soluble pyrophosphate on calculus formation using a short-term clinical model.

    PubMed

    Kleber, C J; Putt, M S; Milleman, J L; Harris, M

    1998-01-01

    This clinical study compared the effect of a dental floss containing 0.25 mg tetrasodium pyrophosphate per cm and a placebo floss on supragingival calculus formation using a 6-week, partial-mouth toothshield model. The six lower anterior teeth were scaled and polished before each 2-week period (i.e., pre-trial, washout, trial). During both the pre-trial and trial periods, subjects brushed twice daily with a non-tartar control dentifrice, while a toothshield protected the six test teeth from brushing. After rinsing with water and removing the shield, they flossed the test teeth. All subjects used placebo floss during the pre-trial period in order to determine the baseline Volpe-Manhold Index (VMI) calculus formation scores, which were used to balance groups for the trial period. During the trial period, one group used the placebo floss, while the second group used the pyrophosphate floss. The final results demonstrated that the pyrophosphate floss significantly inhibited calculus formation between teeth (mesial-distal scores) by 21%, and on labial surfaces by 37% relative to the placebo floss.

  18. Analyzing Patients' Values by Applying Cluster Analysis and LRFM Model in a Pediatric Dental Clinic in Taiwan

    PubMed Central

    Lin, Shih-Yen; Liu, Chih-Wei

    2014-01-01

    This study combines cluster analysis and LRFM (length, recency, frequency, and monetary) model in a pediatric dental clinic in Taiwan to analyze patients' values. A two-stage approach by self-organizing maps and K-means method is applied to segment 1,462 patients into twelve clusters. The average values of L, R, and F excluding monetary covered by national health insurance program are computed for each cluster. In addition, customer value matrix is used to analyze customer values of twelve clusters in terms of frequency and monetary. Customer relationship matrix considering length and recency is also applied to classify different types of customers from these twelve clusters. The results show that three clusters can be classified into loyal patients with L, R, and F values greater than the respective average L, R, and F values, while three clusters can be viewed as lost patients without any variable above the average values of L, R, and F. When different types of patients are identified, marketing strategies can be designed to meet different patients' needs. PMID:25045741

  19. Chipping fracture resistance of dental CAD/CAM restorative materials: Part 2. Phenomenological model and the effect of indenter type

    PubMed Central

    Quinn, G.D.; Giuseppetti, A.A.; Hoffman, K.H.

    2014-01-01

    The edge chipping resistances of six CAD/CAM dental restoration materials are analyzed and correlated to other mechanical properties. A new quadratic relationship that is based on a phenomenological model is presented. Objective The purpose of this study was to further analyze the edge chipping resistance of the brittle materials evaluated in Part 1. One objective was to determine why some force-distance trends were linear and others were nonlinear. A second objective was to account for differences in chipping resistance with indenter type. Methods Edge chipping experiments were conducted with different indenters, including some custom-made sharp conical indenters. A new force – distance quadratic expression was correlated to the data and compared to the linear and power law trends. Results The new quadratic function was an excellent fit in every instance. It can account for why some materials can be fit by a linear trend, while others can be fit by the power law trend. The effects of indenter type are accounted for variations in crack initiation and by the wedging stresses once an indentation hole is created. Significance The new quadratic force – edge distance function can be used with edge chipping data for all brittle materials, not just those evaluated in this study. The data trends vary from linear to nonlinear depending upon the material’s hardness, fracture toughness, and elastic modulus. PMID:24685179

  20. Analyzing patients' values by applying cluster analysis and LRFM model in a pediatric dental clinic in Taiwan.

    PubMed

    Wu, Hsin-Hung; Lin, Shih-Yen; Liu, Chih-Wei

    2014-01-01

    This study combines cluster analysis and LRFM (length, recency, frequency, and monetary) model in a pediatric dental clinic in Taiwan to analyze patients' values. A two-stage approach by self-organizing maps and K-means method is applied to segment 1,462 patients into twelve clusters. The average values of L, R, and F excluding monetary covered by national health insurance program are computed for each cluster. In addition, customer value matrix is used to analyze customer values of twelve clusters in terms of frequency and monetary. Customer relationship matrix considering length and recency is also applied to classify different types of customers from these twelve clusters. The results show that three clusters can be classified into loyal patients with L, R, and F values greater than the respective average L, R, and F values, while three clusters can be viewed as lost patients without any variable above the average values of L, R, and F. When different types of patients are identified, marketing strategies can be designed to meet different patients' needs. PMID:25045741

  1. Monte Carlo simulation of in vivo Raman spectral measurements of human skin with a multi-layered tissue optical model.

    PubMed

    Wang, Shuang; Zhao, Jianhua; Lui, Harvey; He, Qingli; Bai, Jintao; Zeng, Haishan

    2014-09-01

    Raman photon generation inside human skin and escaping to skin surface were modeled in an eight-layered skin optical model. Intrinsic Raman spectra of different skin layers were determined by microscopy measurements of excised skin tissue sections. Monte Carlo simulation was used to study the excitation light distribution and intrinsic Raman signal distortion caused by tissue reabsorption and scattering during in vivo measurements. The simulation results demonstrated how different skin layers contributed to the observed in vivo Raman spectrum. Using the strongest Raman peak at 1445 cm(-1) as an example, the simulation suggested that the integrated contributions of the stratum corneum layer is 1.3%, the epidermis layer 28%, the dermis layer 70%, and the subcutaneous fat layer 1.1%. Reasonably good matching between the calculated spectrum and the measured in vivo Raman spectra was achieved, thus demonstrated great utility of our modeling method and approaches for help understanding the clinical measurements.

  2. Explicit Finite Element Modeling of Multilayer Composite Fabric for Gas Turbine Engine Containment Systems. Part 2; Ballistic Impact Testing

    NASA Technical Reports Server (NTRS)

    Pereira, J. M.; Revilock, D. M.

    2004-01-01

    Under the Federal Aviation Administration's Airworthiness Assurance Center of Excellence and the Aircraft Catastrophic Failure Prevention Program, National Aeronautics and Space Administration Glenn Research Center collaborated with Arizona State University, Honeywell Engines, Systems and Services, and SRI International to develop improved computational models for designing fabric-based engine containment systems. In the study described in this report, ballistic impact tests were conducted on layered dry fabric rings to provide impact response data for calibrating and verifying the improved numerical models. This report provides data on projectile velocity, impact and residual energy, and fabric deformation for a number of different test conditions.

  3. Status and limitations of multilayer x-ray interference structures

    SciTech Connect

    Kortright, J.B.

    1996-03-01

    Trends in the performance of x-ray multilayer interference structures with periods ranging from 9 to 130 {angstrom} are reviewed. Analysis of near-normal incidence reflectance data vs photon energy reveals that the effective interface with {sigma} in a static Debye-Waller model, describing interdiffusion and roughness, decreases as the multilayer period decreases, and reaches a lower limit of roughly 2 {angstrom}. Specular reflectance and diffuse scattering from uncoated and multilayer-coated substrates having different roughness suggest that this lower limit results largely from substrate roughness. The increase in interface width with period thus results from increasing roughness of interdiffusion as the layer thickness increases.

  4. Size dependent gold nanoparticle interaction at nano-micro interface using both monolayer and multilayer (tissue-like) cell models

    NASA Astrophysics Data System (ADS)

    Yohan, Darren; Yang, Celina; Lu, Xiaofeng; Chithrani, Devika B.

    2016-03-01

    Gold nanoparticles (GNPs) can be used as a model NP system to improve the interface between nanotechnology and medicine since their size and surface properties can be tailored easily. GNPs are being used as radiation dose enhancers and as drug carriers in cancer research. Hence, it is important to know the optimum NP size for uptake not only at monolayer level but also at tissue level. Once GNPs leave tumor vasculature, they enter the tumor tissue. Success of any therapeutic technique using NPs depends on how well NPs penetrate the tumor tissue and reach individual tumor cells. In this work, multicellular layers (MCLs) were grown to model the post-vascular tumor environment. GNPs of 20 nm and 50 nm diameters were used to elucidate the effects of size on the GNP penetration and distribution dynamics. Larger NPs (50 nm) were better at monolayer level, but smaller NPs (20 nm) were at tissue level. The MCLs exhibited a much more extensive extracellular matrix (ECM) than monolayer cell cultures. This increased ECM created a barrier for NP transport and ECM was also dependent on the tumor cell lines. Smaller NPs penetrated better compared to larger NPs. Transport of NPs was better in MDA-MB231 vs MCF-7. This MCL model tissue structures are better tools to optimize NP transport through tissue before using them in animal models. Based on our study, we believe that smaller NPs are better for improved outcome in future cancer therapeutics.

  5. Parity & untreated dental caries in US women.

    PubMed

    Russell, S L; Ickovics, J R; Yaffee, R A

    2010-10-01

    While parity (number of children) reportedly is related to tooth loss, the relationship between parity and dental caries has not been extensively investigated. We used path analysis to test a theoretical model that specified that parity influences dental caries levels through dental care, psycho- social factors, and dental health damaging behaviors in 2635 women selected from the NHANES III dataset. We found that while increased parity was not associated with a greater level of total caries (DFS), parity was related to untreated dental caries (DS). The mechanisms by which parity is related to caries, however, remain undefined. Further investigation is warranted to determine if disparities in dental caries among women are due to differences in parity and the likely changes that parallel these reproductive choices.

  6. Modeling of the wafer bow in GaN-on-Si epiwafers employing GaN/AlN multilayer buffer structures

    NASA Astrophysics Data System (ADS)

    Miyoshi, Makoto; Watanabe, Arata; Egawa, Takashi

    2016-10-01

    We built a calculation model for the wafer bow in GaN-on-Si epiwafers employing GaN/AlN multilayer (ML) buffer structures by extending Stoney’s equation. The calculated bow and the derived strain in the epilayers were almost consistent with experimental results. The calculation quantitatively revealed that the ML buffers introduced an in-plane compressive stress in the epitaxial structures. Also, relationships between the epiwafer bow and the stress in the respective layers became clear to a certain extent. For instance, when considering the case where periodic structures with 20 nm thick GaN/5 nm thick AlN pairs were grown as ML buffers on 4-in.-diameter and 525 μm thick Si (111) substrates at a growth temperature (T g) of 1125 °C, the stress in the MLs was derived to be 2.18 GPa in the in-plane compressive direction in the GaN layers and 5.89 GPa in the in-plane tensile direction in the AlN layers at T g. Although magnitude of the in-plane stress in the GaN layers is obviously smaller than that in the AlN layers, the restoring force generated in the GaN layers becomes larger than that in the AlN layers, because the force is in proportion to the layer thickness rather than to just the stress. As a consequence, the generated stress in the MLs was considered to produce enough force to suppress the epiwafer bow. The calculation also demonstrated that GaN epilayers on GaN/AlN MLs were strained in the in-plane compressive direction at T g and almost strain-free at room temperature.

  7. Surface footprint from initial Chernobyl release as indicated by the meso-alpha MLAM (Multi-Layer Air Mass) model

    SciTech Connect

    Davis, W.E.; Olsen, A.R.; Didier, B.T.; Tucker, P.E.; Damschen, D.W.

    1989-12-01

    This document reports the results of dose calculations from the Chernobyl reactor accident in April 1986. The calculations were completed in 1987. The results are now being published to disseminate the information to an audience of potential users. This study's objective was to model the transport path of materials released during April 26 and 27, the first 48 hours of the accident. 5 refs., 15 figs.

  8. Haptic feedback for multilayer cutting.

    PubMed

    Rianto, Sugeng; Li, Ling; Hartley, Bruce

    2008-01-01

    An approach in effectively estimating the force feedback for a tactile haptic based on multi-proxy rendering for 3D surface cuttings for a virtual surgery simulation is described in this paper. The force-models representing haptic force-feedback are approximated using D'Alembert's principle in the mechanic case of spring-damper-stiffness interaction of the surfaces. We also propose a combination between mesh refinement and adaptive re-meshing to create a progressive cutting over the layering surfaces. Experimental results prove that the physical interaction to create cutting paths over the multilayer surfaces can be deliver smoothly with haptic in real time with 3D visual stereo on a PC.

  9. Retrieval and classification of dental research articles.

    PubMed

    Bartling, W C; Schleyer, T K; Visweswaran, S

    2003-12-01

    Successful retrieval of a corpus of literature on a broad topic can be difficult. This study demonstrates a method to retrieve the dental and craniofacial research literature. We explored MeSH manually for dental or craniofacial indexing terms. MEDLINE was searched using these terms, and a random sample of references was extracted from the resulting set. Sixteen dental research experts categorized these articles, reading only the title and abstract, as either: (1) dental research, (2) dental non-research, (3) non-dental, or (4) not sure. Identify Patient Sets (IPS), a probabilistic text classifier, created models, based on the presence or absence of words or UMLS phrases, that distinguished dental research articles from all others. These models were applied to a test set with different inputs for each article: (1) title and abstract only, (2) MeSH terms only, or (3) both. By title and abstract only, IPS correctly classified 64% of all dental research articles present in the test set. The percentage of correctly classified dental research articles in this retrieved set was 71%. MeSH term inclusion decreased performance. Computer programs that use text input to categorize articles may aid in retrieval of a broad corpus of literature better than indexing terms or key words alone.

  10. Weaker dental enamel explains dental decay.

    PubMed

    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution.

  11. 1D-Var multilayer assimilation of X-band SAR data into a detailed snowpack model

    NASA Astrophysics Data System (ADS)

    Phan, X. V.; Ferro-Famil, L.; Gay, M.; Durand, Y.; Dumont, M.; Morin, S.; Allain, S.; D'Urso, G.; Girard, A.

    2014-10-01

    The structure and physical properties of a snowpack and their temporal evolution may be simulated using meteorological data and a snow metamorphism model. Such an approach may meet limitations related to potential divergences and accumulated errors, to a limited spatial resolution, to wind or topography-induced local modulations of the physical properties of a snow cover, etc. Exogenous data are then required in order to constrain the simulator and improve its performance over time. Synthetic-aperture radars (SARs) and, in particular, recent sensors provide reflectivity maps of snow-covered environments with high temporal and spatial resolutions. The radiometric properties of a snowpack measured at sufficiently high carrier frequencies are known to be tightly related to some of its main physical parameters, like its depth, snow grain size and density. SAR acquisitions may then be used, together with an electromagnetic backscattering model (EBM) able to simulate the reflectivity of a snowpack from a set of physical descriptors, in order to constrain a physical snowpack model. In this study, we introduce a variational data assimilation scheme coupling TerraSAR-X radiometric data into the snowpack evolution model Crocus. The physical properties of a snowpack, such as snow density and optical diameter of each layer, are simulated by Crocus, fed by the local reanalysis of meteorological data (SAFRAN) at a French Alpine location. These snowpack properties are used as inputs of an EBM based on dense media radiative transfer (DMRT) theory, which simulates the total backscattering coefficient of a dry snow medium at X and higher frequency bands. After evaluating the sensitivity of the EBM to snowpack parameters, a 1D-Var data assimilation scheme is implemented in order to minimize the discrepancies between EBM simulations and observations obtained from TerraSAR-X acquisitions by modifying the physical parameters of the Crocus-simulated snowpack. The algorithm then re

  12. Dental education in Colombia

    PubMed Central

    Jaramillo, Jorge A.; Pulido, Jairo H. Ternera; Núñez, Jaime A. Castro; Bird, William F.; Komabayashi, Takashi

    2014-01-01

    This article describes Colombia's development of formal dentistry, its dental school system, curriculum, and dental licensure, and current issues in oral health care. In 1969, there were only 4 dental schools in Colombia; at this writing there are 21. Five dental schools are public and the other 16 are private. Nearly all classes are conducted in Spanish. Undergraduate pre-dental coursework is not a prerequisite for dental school in Colombia. To obtain licensure, Colombian dental students must complete 5 years of study in dental school, earn a diploma, and work for the government for 1 year. There are approximately 41,400 dentists in Colombia, and the number is increasing quickly. However, the unemployment rate among dentists is very high, even though graduation from dental school is extremely difficult. Although the 1,100:1 ratio of citizens to dentists is considered satisfactory, access to dental care is limited due to the high rate of poverty. PMID:20339245

  13. Coupled DDD-FEM modeling on the mechanical behavior of microlayered metallic multilayer film at elevated temperature

    NASA Astrophysics Data System (ADS)

    Huang, Minsheng; Li, Zhenhuan

    2015-12-01

    To investigate the mechanical behavior of the microlayered metallic thin films (MMMFs) at elevated temperature, an enhanced discrete-continuous model (DCM), which couples rather than superposes the two-dimensional climb/glide-enabled discrete dislocation dynamics (2D-DDD) with the linearly elastic finite element method (FEM), is developed in this study. In the present coupling scheme, two especial treatments are made. One is to solve how the plastic strain captured by the DDD module is transferred properly to the FEM module as an eigen-strain; the other is to answer how the stress field computationally obtained by the FEM module is transferred accurately to the DDD module to drive those discrete dislocations moving correctly. With these two especial treatments, the interactions between adjacent dislocations and between dislocation pile-ups and inter-phase boundaries (IBs), which are crucial to the strengthening effect in MMMFs, are carefully taken into account. After verified by comparing the computationally predicted results with the theoretical solutions for a dislocation residing in a homogeneous material and nearby a bi-material interface, this 2D-DDD/FEM coupling scheme is used to model the tensile mechanical behaviors of MMMFs at elevated temperature. The strengthening mechanism of MMMFs and the layer thickness effect are studied in detail, with special attentions to the influence of dislocation climb on them.

  14. Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

    SciTech Connect

    London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M.; Neev, J.

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  15. Estimation of surface heat flux and temperature distributions in a multilayer tissue based on the hyperbolic model of heat conduction.

    PubMed

    Lee, Haw-Long; Chen, Wen-Lih; Chang, Win-Jin; Yang, Yu-Ching

    2015-01-01

    In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown time-dependent surface heat flux in a skin tissue, which is stratified into epidermis, dermis, and subcutaneous layers, from the temperature measurements taken within the medium. Subsequently, the temperature distributions in the tissue can be calculated as well. The concept of finite heat propagation velocity is applied to the modeling of the bioheat transfer problem. The inverse solutions will be justified based on the numerical experiments in which two different heat flux distributions are to be determined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors on the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent surface heat flux can be obtained for the test cases considered in this study.

  16. Atypical Forensic Dental Identifications.

    PubMed

    Cardoza, Anthony R; Wood, James D

    2015-06-01

    Forensic dental identification specialists are typically the last conventional option for postmortem identification. Forensic dental identification is most often accomplished by comparing radiographs of the decedent's teeth with the dental radiographs obtained from the dentist of the suspected victim. Unfortunately, antemortem dental radiographs are not always available. When presented with this challenge, the authors of this article have been successful in completing identifications using means other than dental radiographic comparison. PMID:26126345

  17. Atypical Forensic Dental Identifications.

    PubMed

    Cardoza, Anthony R; Wood, James D

    2015-06-01

    Forensic dental identification specialists are typically the last conventional option for postmortem identification. Forensic dental identification is most often accomplished by comparing radiographs of the decedent's teeth with the dental radiographs obtained from the dentist of the suspected victim. Unfortunately, antemortem dental radiographs are not always available. When presented with this challenge, the authors of this article have been successful in completing identifications using means other than dental radiographic comparison.

  18. Kinetic multi-layer model of the epithelial lining fluid (KM-ELF): Reactions of ozone and OH with antioxidants and surfactant molecules

    NASA Astrophysics Data System (ADS)

    Lakey, Pascale; Pöschl, Ulrich; Shiraiwa, Manabu

    2015-04-01

    Oxidants cause damage to biosurfaces such as the lung epithelium unless they are effectively scavenged. The respiratory tract is covered in a thin layer of fluid which extends from the nasal cavity to the alveoli and contain species that scavenge ozone and other incoming oxidants. The kinetic multi-layer model of the epithelial lining fluid (KM-ELF) has been developed in order to investigate the reactions of ozone and OH with antioxidants (ascorbate, uric acid, glutathione and α-tocopherol) and surfactant lipids and proteins within the epithelial lining fluid (ELF). The model incorporates different processes: gas phase diffusion, adsorption and desorption from the surface, bulk phase diffusion and known reactions at the surface and in the bulk. The ELF is split into many layers: a sorption layer, a surfactant layer, a near surface bulk layer and several bulk layers. Initial results using KM-ELF indicate that at ELF thicknesses of 80 nm and 1 × 10-4cm the ELF would become rapidly saturated with ozone with saturation occurring in less than a second. However, at an ELF thickness of 1 × 10-3cm concentration gradients were observed throughout the ELF and the presence of antioxidants reduced the O3 reaching the lung cells and tissues by 40% after 1 hour of exposure. In contrast, the antioxidants were efficient scavengers of OH radicals, although the large rate constants of OH reacting with the antioxidants resulted in the antioxidants decaying away rapidly. The chemical half-lives of the antioxidants and surface species were also calculated using KM-ELF as a function of O3 and OH concentration and ELF thickness. Finally, the pH dependence of the products of reactions between antioxidants and O3 were investigated. The KM-ELF model predicted that a harmful ascorbate ozonide product would increase from 1.4 × 1011cm-3at pH 7.4 to 1.1 × 1014 cm-3 at pH 4after 1 hour although a uric acid ozonide product would decrease from 2.0 × 1015cm-3to 5.9 × 1012cm-3.

  19. Process for manufacturing multilayer capacitors

    DOEpatents

    Lauf, Robert J.; Holcombe, Cressie E.; Dykes, Norman L.

    1996-01-01

    The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation.

  20. Process for manufacturing multilayer capacitors

    DOEpatents

    Lauf, R.J.; Holcombe, C.E.; Dykes, N.L.

    1996-01-02

    The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation. 4 figs.

  1. Study and modeling of the ironing process on a multi-layered polymer coated low-carbon steel

    NASA Astrophysics Data System (ADS)

    Selles Canto, Miguel Angel

    The ironing process is the most crucial step in the manufacture of cans. Sheet steel covered by three polymer layers can be used as the starting material, but this coating must neither break nor fail in any manner in order to be considered as a viable and effective alternative to traditional practice. During ironing, the deformations are severe and high pressures exist at the tool-workpiece interface. Thickness reductions inherent in ironing require a large amount of surface generation. Deterioration of the coating in this delicate operation might enable direct contact of the stored food or drink with the metal. As can be appreciated, the key to the use of polymer-coated steel sheets in the manufacture of cans lies in the survival of these layers during the ironing process. Another important issue is the roughness of the newly-generated surface, because it should be possible to decorate the can without any difficulty. Changing the traditional manufacture of metallic containers such as cans and using this new coated material permits great reduction in environmental contaminants produced as a result of avoiding the formation of Volatile Organic Compounds (VOCs) during the manufacture of the polymer layers. This reduction is even greater because of not using additional lubricants due to the self-lubricanting property of the solid polymer coating layers during the drawing process. These objectives, together with the improvement of the mechanical characteristics and the adhesion of the painting or decorative priming, are realized by the use of the proposed material. In the existing bibliography about ironing processes on coated materials, some authors propose the use of the Upper Bound Theorem for modeling the material behavior. The present research shows for the first time the modeling of the ironing process on a three-layer polymer coated material. In addition, it takes into account the cases in which successful ironing is produced and those in which ones the ironing

  2. Pain relief model for a COX-2 inhibitor in patients with postoperative dental pain

    PubMed Central

    Rohatagi, Shashank; Kastrissios, Helen; Sasahara, Kunihiro; Truitt, Kenneth; Moberly, James B; Wada, Russell; Salazar, Daniel E

    2008-01-01

    AIM To develop a pain relief model for a cyclooxygenase (COX)-2 inhibitor, CS-706, that permits prediction of doses for acute pain relief in Japanese and Western populations. METHODS A categorical response model was developed to describe the probability of pain relief (PR) over time for a Phase 2a study. Models were also developed to describe patient's use of rescue medication and onset of pain relief. RESULTS The placebo response was described by a first-order increase in PR that achieved a stable response after 4 h. The effect of CS-706 on PR was described using an Emax model; the plasma concentration of CS-706 producing 50% of the maximum response was estimated to be 87 ng ml−1, the median peak plasma concentration achieved after a 50-mg oral dose. The probability of rescue medication (REMD) decreased over time and was a function of the last observed PR score. This probability was < 16% for patients with a PR score ≥2. The probability of experiencing meaningful PR was 98% in patients who did not require REMD and 47% in those who required REMD. For patients who did not require REMD, the median onset time of meaningful pain relief (TMPR) decreased with increasing doses. In patients who required REMD, there was a saturable decline in TMPR, with the greatest improvement occurring from placebo to 50-mg doses. CONCLUSIONS The set of models developed permitted compilation of multiple dose–response curves for dose selection of CS-706 in Westerners and facilitated scaling of doses to a Japanese population. WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT Modelling and simulation are being increasingly used to support decision-making in new drug development.Novel modelling methods are required to capture the complexity of multiple end-points for a disease and to address questions such as dose selection in various populations.The focus of this study was to present a novel pain relief model to address such questions. WHAT THIS STUDY ADDS New contributions of this work to the

  3. Integration of Basic-Clinical Sciences, PBL, CBL, and IPE in U.S. Dental Schools' Curricula and a Proposed Integrated Curriculum Model for the Future.

    PubMed

    Elangovan, Satheesh; Venugopalan, Shankar Rengasamy; Srinivasan, Sreedevi; Karimbux, Nadeem Y; Weistroffer, Paula; Allareddy, Veerasathpurush

    2016-03-01

    The integration of basic and clinical sciences in dental curricula enhances the application of basic science principles to clinical decision making and improves students' critical thinking. The aim of this study was to define the characteristics of U.S. dental schools' curricula with regard to level of course integration and degree of incorporation of problem-based and case-based learning. A second aim was to propose a dental curriculum that supports effective integration of courses and addresses some of the concerns facing academic dentistry. A survey was sent to 58 academic deans in U.S. dental schools. The survey included questions about integrating courses in the schools' curricula and major changes in curricular structure or teaching pedagogy that respondents anticipated in the immediate future. A total of 31 schools responded to the survey, for a 53.4% response rate. The results showed that three-quarters of the responding schools still teach basic and clinical sciences separately, although 61.3% reported having an integrated curriculum. Among the responding schools, 16 had a PBL component integrated into their curricula (two had integrated PBL in all courses and 14 used a hybrid PBL approach). Two schools had CBL integrated in all courses, and ten had CBL integrated in >75% of courses. Only slightly more than half agreed that their curricula foster students' thinking "outside the box." Faculty shortages and lack of protected time and resources were the most frequent reasons given for a lack of integrated courses. The integrated model proposed in this article has the potential to provide a low stress environment for students and to address important issues like faculty shortages.

  4. Analytical modeling of Schumann resonance and ELF propagation parameters on Mars with a multi-layered ground

    NASA Astrophysics Data System (ADS)

    Kozakiewicz, Joanna; Kulak, Andrzej; Mlynarczyk, Janusz

    2015-11-01

    Two electrically conductive planetary spheres, the ionosphere and the ground, form a spherical waveguide. Within such a planetary cavity a phenomenon called Schumann resonance (SR) can occur. It is a resonance of extremely low frequency (ELF) electromagnetic waves. The resonance parameters are strongly related to the electromagnetic properties of the cavity. On Mars, as there is no liquid water at the planetary surface, the ground has a low conductivity. In such a situation, ELF waves penetrate into the planetary subsurface up to many kilometers depth. To examine the influence of low-conductivity grounds on ELF propagation, we have introduced a recently developed analytical method, which enables to estimate the propagation parameters and explicate their dependence of the ground properties. Since the presented model is fully analytical, it is computationally efficient and can be very useful in finding inverse solutions. To demonstrate the potential of the method, we present the relationship between individual ground properties and the parameters of Schumann resonance. The obtained results indicate that Martian exploration performed by one ELF station located at the planetary surface can reveal, along with the properties of the ionosphere, the existence of liquid water under the Martian surface.

  5. Heat Transfer in High Temperature Multilayer Insulation

    NASA Technical Reports Server (NTRS)

    Daryabeigi, Kamran; Miller, Steve D.; Cunnington, George R.

    2007-01-01

    High temperature multilayer insulations have been investigated as an effective component of thermal-protection systems for atmospheric re-entry of reusable launch vehicles. Heat transfer in multilayer insulations consisting of thin, gold-coated, ceramic reflective foils and Saffil(TradeMark) fibrous insulation spacers was studied both numerically and experimentally. A finite volume numerical thermal model using combined conduction (gaseous and solid) and radiation in porous media was developed. A two-flux model with anisotropic scattering was used for radiation heat transfer in the fibrous insulation spacers between the reflective foils. The thermal model was validated by comparison with effective thermal conductivity measurements in an apparatus based on ASTM standard C201. Measurements were performed at environmental pressures in the range from 1x10(exp -4) to 760 torr over the temperature range from 300 to 1300 K. Four multilayer samples with nominal densities of 48 kg/cu m were tested. The first sample was 13.3 mm thick and had four evenly spaced reflective foils. The other three samples were 26.6 mm thick and utilized either one, two, or four reflective foils, located near the hot boundary with nominal foil spacing of 1.7 mm. The validated thermal model was then used to study relevant design parameters, such as reflective foil spacing and location in the stack-up and coating of one or both sides of foils.

  6. SISGR - In situ characterization and modeling of formation reactions under extreme heating rates in nanostructured multilayer foils

    SciTech Connect

    Hufnagel, Todd C.

    2014-06-09

    Materials subjected to extreme conditions, such as very rapid heating, behave differently than materials under more ordinary conditions. In this program we examined the effect of rapid heating on solid-state chemical reactions in metallic materials. One primary goal was to develop experimental techniques capable of observing these reactions, which can occur at heating rates in excess of one million degrees Celsius per second. One approach that we used is x-ray diffraction performed using microfocused x-ray beams and very fast x-ray detectors. A second approach is the use of a pulsed electron source for dynamic transmission electron microscopy. With these techniques we were able to observe how the heating rate affects the chemical reaction, from which we were able to discern general principles about how these reactions proceed. A second thrust of this program was to develop computational tools to help us understand and predict the reactions. From atomic-scale simulations were learned about the interdiffusion between different metals at high heating rates, and about how new crystalline phases form. A second class of computational models allow us to predict the shape of the reaction front that occurs in these materials, and to connect our understanding of interdiffusion from the atomistic simulations to measurements made in the laboratory. Both the experimental and computational techniques developed in this program are expected to be broadly applicable to a wider range of scientific problems than the intermetallic solid-state reactions studied here. For example, we have already begun using the x-ray techniques to study how materials respond to mechanical deformation at very high rates.

  7. Magnetic metallic multilayers

    SciTech Connect

    Hood, R.Q.

    1994-04-01

    Utilizing self-consistent Hartree-Fock calculations, several aspects of multilayers and interfaces are explored: enhancement and reduction of the local magnetic moments, magnetic coupling at the interfaces, magnetic arrangements within each film and among non-neighboring films, global symmetry of the systems, frustration, orientation of the various moments with respect to an outside applied field, and magnetic-field induced transitions. Magnetoresistance of ferromagnetic-normal-metal multilayers is found by solving the Boltzmann equation. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by an external magnetic field. The calculation depends on (1) geometric parameters (thicknesses of layers), (2) intrinsic metal parameters (number of conduction electrons, magnetization, and effective masses in layers), (3) bulk sample properties (conductivity relaxation times), (4) interface scattering properties (diffuse scattering versus potential scattering at the interfaces, and (5) outer surface scattering properties (specular versus diffuse surface scattering). It is found that a large negative magnetoresistance requires considerable asymmetry in interface scattering for the two spin orientations. Features of the interfaces that may produce an asymmetrical spin-dependent scattering are studied: varying interfacial geometric random roughness with no lateral coherence, correlated (quasi-periodic) roughness, and varying chemical composition of the interfaces. The interplay between these aspects of the interfaces may enhance or suppress the magnetoresistance, depending on whether it increases or decreases the asymmetry in the spin-dependent scattering of the conduction electrons.

  8. Wrapped Multilayer Insulation

    NASA Technical Reports Server (NTRS)

    Dye, Scott A.

    2015-01-01

    New NASA vehicles, such as Earth Departure Stage (EDS), Orion, landers, and orbiting fuel depots, need improved cryogenic propellant transfer and storage for long-duration missions. Current cryogen feed line multilayer insulation (MLI) performance is 10 times worse per area than tank MLI insulation. During each launch, cryogenic piping loses approximately 150,000 gallons (equivalent to $300,000) in boil-off during transfer, chill down, and ground hold. Quest Product Development Corp., teaming with Ball Aerospace, developed an innovative advanced insulation system, Wrapped MLI (wMLI), to provide improved thermal insulation for cryogenic feed lines. wMLI is high-performance multilayer insulation designed for cryogenic piping. It uses Quest's innovative discrete-spacer technology to control layer spacing/ density and reduce heat leak. The Phase I project successfully designed, built, and tested a wMLI prototype with a measured heat leak 3.6X lower than spiral-wrapped conventional MLI widely used for piping insulation. A wMLI prototype had a heat leak of 7.3 W/m2, or 27 percent of the heat leak of conventional MLI (26.7 W/m2). The Phase II project is further developing wMLI technology with custom, molded polymer spacers and advancing the product toward commercialization via a rigorous testing program, including developing advanced vacuuminsulated pipe for ground support equipment.

  9. Wrapped Multilayer Insulation

    NASA Technical Reports Server (NTRS)

    Dye, Scott A.

    2015-01-01

    New NASA vehicles, such as Earth Departure Stage (EDS), Orion, landers, and orbiting fuel depots, need improved cryogenic propellant transfer and storage for long-duration missions. Current cryogen feed line multilayer insulation (MLI) performance is 10 times worse per area than tank MLI insulation. During each launch, cryogenic piping loses approximately 150,000 gallons (equivalent to $300,000) in boil-off during transfer, chill down, and ground hold. Quest Product Development Corp., teaming with Ball Aerospace, developed an innovative advanced insulation system, Wrapped MLI (wMLI), to provide improved thermal insulation for cryogenic feed lines. wMLI is high-performance multilayer insulation designed for cryogenic piping. It uses Quest's innovative discrete-spacer technology to control layer spacing/ density and reduce heat leak. The Phase I project successfully designed, built, and tested a wMLI prototype with a measured heat leak 3.6X lower than spiral-wrapped conventional MLI widely used for piping insulation. A wMLI prototype had a heat leak of 7.3 W/sq m, or 27 percent of the heat leak of conventional MLI (26.7 W/sq m). The Phase II project is further developing wMLI technology with custom, molded polymer spacers and advancing the product toward commercialization via a rigorous testing program, including developing advanced vacuuminsulated pipe for ground support equipment.

  10. Ultrahard Multilayer Coatings

    SciTech Connect

    Chrzan, D.C.; Dugger, M.; Follstaedt, D.M.; Friedman, Lawrence H.; Friedmann, T.A.; Knapp, J.A.; McCarty, K.F.; Medlin, D.L.; Mirkarimi, P.B.; Missert, N.; Newcomer, P.P.; Sullivan, J.P.; Tallant, D.R.

    1999-05-01

    We have developed a new multilayer a-tC material that is thick stress-free, adherent, low friction, and with hardness and stiffness near that of diamond. The new a-tC material is deposited by J pulsed-laser deposition (PLD) at room temperature, and fully stress-relieved by a short thermal anneal at 600°C. A thick multilayer is built up by repeated deposition and annealing steps. We measured 88 GPa hardness, 1100 GPa Young's modulus, and 0.1 friction coefficient (under high load). Significantly, these results are all well within the range reported for crystalline diamond. In fact, this material, if considered separate from crystalline diamond, is the 2nd hardest material known to man. Stress-free a-tC also has important advantages over thin film diamond; namely, it is smooth, processed at lower temperature, and can be grown on a much broader range of substrates. This breakthrough will enable a host of applications that we are actively pursuing in MEMs, sensors, LIGA, etc.

  11. An Analysis of Graduates from a Non-Traditional Model of Dental Hygiene Education

    ERIC Educational Resources Information Center

    Benitez, Hubert

    2013-01-01

    Prior studies document the need to increase the racial and ethnic diversity of the health care workforce. Different approaches to increase the diversity of the healthcare workforce include implementing bridge, transitional and academic enrichment programs; diversifying college admissions criteria; and developing models of education that enhance…

  12. Dental hyponatraemia.

    PubMed

    Simpson, R M

    2011-08-01

    A 14-year-old girl developed dental pain and was treated for acute infected pulpitis of her right upper lateral incisor with drilling and filling. The pain continued and was helped by analgesia, sucking ice cubes and drinking cold water. Forty-eight hours later, she became confused and disoriented. She started to vomit and complained of headache. Investigations revealed hyponatraemia with normal serum potassium levels and initially normal urinary sodium excretion. Over the next 24 hours, she passed 5.45 L of urine and her serum sodium rose from 125 to 143 mmol/L. Self-induced water intoxication has been described during drinking games and initiation ceremonies, but this would appear to an unusual cause. Conservative management proved successful in allowing this girl to recover without sequelae. PMID:21873727

  13. Toughening mechanisms in bioinspired multilayered materials

    PubMed Central

    Askarinejad, Sina; Rahbar, Nima

    2015-01-01

    Outstanding mechanical properties of biological multilayered materials are strongly influenced by nanoscale features in their structure. In this study, mechanical behaviour and toughening mechanisms of abalone nacre-inspired multilayered materials are explored. In nacre's structure, the organic matrix, pillars and the roughness of the aragonite platelets play important roles in its overall mechanical performance. A micromechanical model for multilayered biological materials is proposed to simulate their mechanical deformation and toughening mechanisms. The fundamental hypothesis of the model is the inclusion of nanoscale pillars with near theoretical strength (σth ~ E/30). It is also assumed that pillars and asperities confine the organic matrix to the proximity of the platelets, and, hence, increase their stiffness, since it has been previously shown that the organic matrix behaves more stiffly in the proximity of mineral platelets. The modelling results are in excellent agreement with the available experimental data for abalone nacre. The results demonstrate that the aragonite platelets, pillars and organic matrix synergistically affect the stiffness of nacre, and the pillars significantly contribute to the mechanical performance of nacre. It is also shown that the roughness induced interactions between the organic matrix and aragonite platelet, represented in the model by asperity elements, play a key role in strength and toughness of abalone nacre. The highly nonlinear behaviour of the proposed multilayered material is the result of distributed deformation in the nacre-like structure due to the existence of nano-asperities and nanopillars with near theoretical strength. Finally, tensile toughness is studied as a function of the components in the microstructure of nacre. PMID:25551150

  14. Toughening mechanisms in bioinspired multilayered materials.

    PubMed

    Askarinejad, Sina; Rahbar, Nima

    2015-01-01

    Outstanding mechanical properties of biological multilayered materials are strongly influenced by nanoscale features in their structure. In this study, mechanical behaviour and toughening mechanisms of abalone nacre-inspired multilayered materials are explored. In nacre's structure, the organic matrix, pillars and the roughness of the aragonite platelets play important roles in its overall mechanical performance. A micromechanical model for multilayered biological materials is proposed to simulate their mechanical deformation and toughening mechanisms. The fundamental hypothesis of the model is the inclusion of nanoscale pillars with near theoretical strength (σth ~ E/30). It is also assumed that pillars and asperities confine the organic matrix to the proximity of the platelets, and, hence, increase their stiffness, since it has been previously shown that the organic matrix behaves more stiffly in the proximity of mineral platelets. The modelling results are in excellent agreement with the available experimental data for abalone nacre. The results demonstrate that the aragonite platelets, pillars and organic matrix synergistically affect the stiffness of nacre, and the pillars significantly contribute to the mechanical performance of nacre. It is also shown that the roughness induced interactions between the organic matrix and aragonite platelet, represented in the model by asperity elements, play a key role in strength and toughness of abalone nacre. The highly nonlinear behaviour of the proposed multilayered material is the result of distributed deformation in the nacre-like structure due to the existence of nano-asperities and nanopillars with near theoretical strength. Finally, tensile toughness is studied as a function of the components in the microstructure of nacre.

  15. Toughening mechanisms in bioinspired multilayered materials.

    PubMed

    Askarinejad, Sina; Rahbar, Nima

    2015-01-01

    Outstanding mechanical properties of biological multilayered materials are strongly influenced by nanoscale features in their structure. In this study, mechanical behaviour and toughening mechanisms of abalone nacre-inspired multilayered materials are explored. In nacre's structure, the organic matrix, pillars and the roughness of the aragonite platelets play important roles in its overall mechanical performance. A micromechanical model for multilayered biological materials is proposed to simulate their mechanical deformation and toughening mechanisms. The fundamental hypothesis of the model is the inclusion of nanoscale pillars with near theoretical strength (σth ~ E/30). It is also assumed that pillars and asperities confine the organic matrix to the proximity of the platelets, and, hence, increase their stiffness, since it has been previously shown that the organic matrix behaves more stiffly in the proximity of mineral platelets. The modelling results are in excellent agreement with the available experimental data for abalone nacre. The results demonstrate that the aragonite platelets, pillars and organic matrix synergistically affect the stiffness of nacre, and the pillars significantly contribute to the mechanical performance of nacre. It is also shown that the roughness induced interactions between the organic matrix and aragonite platelet, represented in the model by asperity elements, play a key role in strength and toughness of abalone nacre. The highly nonlinear behaviour of the proposed multilayered material is the result of distributed deformation in the nacre-like structure due to the existence of nano-asperities and nanopillars with near theoretical strength. Finally, tensile toughness is studied as a function of the components in the microstructure of nacre. PMID:25551150

  16. The impact of additional dental providers in the dental labor market on the income of private practice dentists.

    PubMed

    Brown, Timothy T; Hong, Juliette S

    2012-03-01

    This study estimates the impact that the entrance of hypothetical allied dental professionals into the dental labor market may have on the earnings of currently practicing private practice dentists. A simulation model that uses the most reliable available data was constructed and finds that the introduction of hypothetical allied dental professionals into the competitive California dental labor market is likely to have relatively small effects on the earnings of the average dentist in California.

  17. Developing Multilayer Thin Film Strain Sensors With High Thermal Stability

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M., III

    2006-01-01

    A multilayer thin film strain sensor for large temperature range use is under development using a reactively-sputtered process. The sensor is capable of being fabricated in fine line widths utilizing the sacrificial-layer lift-off process that is used for micro-fabricated noble-metal sensors. Tantalum nitride films were optimized using reactive sputtering with an unbalanced magnetron source. A first approximation model of multilayer resistance and temperature coefficient of resistance was used to set the film thicknesses in the multilayer film sensor. Two multifunctional sensors were fabricated using multilayered films of tantalum nitride and palladium chromium, and tested for low temperature resistivity, TCR and strain response. The low temperature coefficient of resistance of the films will result in improved stability in thin film sensors for low to high temperature use.

  18. Characterization of Mo/Si multilayer growth on stepped topographies

    SciTech Connect

    Boogaard, A. J. R. vcan den; Louis, E.; Zoethout, E.; Goldberg, K. A.; Bijkerk, F.

    2011-08-31

    Mo/Si multilayer mirrors with nanoscale bilayer thicknesses have been deposited on stepped substrate topographies, using various deposition angles. The multilayer morphology at the stepedge region was studied by cross section transmission electron microscopy. A transition from a continuous- to columnar layer morphology is observed near the step-edge, as a function of the local angle of incidence of the deposition flux. Taking into account the corresponding kinetics and anisotropy in layer growth, a continuum model has been developed to give a detailed description of the height profiles of the individual continuous layers. Complementary optical characterization of the multilayer system using a microscope operating in the extreme ultraviolet wavelength range, revealed that the influence of the step-edge on the planar multilayer structure is restricted to a region within 300 nm from the step-edge.

  19. EUV-multilayers on grating-like topographies

    SciTech Connect

    van Boogaard, A. J. R.; Louis, E.; Goldberg, K. A.; Mochi, I.; Bijkerk, F.

    2010-03-12

    In this study, multilayer morphology near the key anomalies in grating-like structures, namely sharp step-edges and steep walls, are examined. Different deposition schemes are employed. Based on cross section TEM analysis an explanatory model describing the morphology of the successive layers is developed. A further insight into the periodicity and the general performance of the multilayer is obtained by EUV microscopy. The main distortions in multilayer structure and hence EUV performance are found to be restricted to a region within a few hundred nanometers from the anomalies, which is very small compared to the proposed grating period (50-100 {micro}m). These multilayer coated blazed gratings can thus be considered a viable option for spectral purity enhancement of EUV light sources.

  20. Multilayer Coextrusion Reveals Slip at Polymer-polymer Interfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Rui; Macosko, Christopher W.

    2000-03-01

    De Gennes (1992) suggested that loss of entanglement in the interfacial region between two incompatible polymers causes slip at interfaces. Goveas and Fredrickson (1998) developed a quantitative model for the lowering of interfacial viscosity. However, to date there appears to be no quantitative experimental evidence for interfacial slip. We coextruded polypropylene and polystyrene with closely matched viscosities into multilayers with 2,32 and 128 layers. Pressure drop of the coextruded multilayer melts through a slit die was measured. The data showed a 40reduction when the number of layers increased from 2 to 128, which indicates interfacial slip. The steady shear viscosity of the multilayer sample was also measured in parallel plates. When the shear stress was higher than a critical value, the viscosity of the multilayers was lower than either of the components. The interfacial viscosity was estimated, and 40 times reduction was observed. Diblock copolymer which spanned the interfaces was shown to able to suppress interfacial slip.

  1. Model-based vision system for automatic recognition of structures in dental radiographs

    NASA Astrophysics Data System (ADS)

    Acharya, Raj S.; Samarabandu, Jagath K.; Hausmann, E.; Allen, K. A.

    1991-07-01

    X-ray diagnosis of destructive periodontal disease requires assessing serial radiographs by an expert to determine the change in the distance between cemento-enamel junction (CEJ) and the bone crest. To achieve this without the subjectivity of a human expert, a knowledge based system is proposed to automatically locate the two landmarks which are the CEJ and the level of alveolar crest at its junction with the periodontal ligament space. This work is a part of an ongoing project to automatically measure the distance between CEJ and the bone crest along a line parallel to the axis of the tooth. The approach presented in this paper is based on identifying a prominent feature such as the tooth boundary using local edge detection and edge thresholding to establish a reference and then using model knowledge to process sub-regions in locating the landmarks. Segmentation techniques invoked around these regions consists of a neural-network like hierarchical refinement scheme together with local gradient extraction, multilevel thresholding and ridge tracking. Recognition accuracy is further improved by first locating the easily identifiable parts of the bone surface and the interface between the enamel and the dentine and then extending these boundaries towards the periodontal ligament space and the tooth boundary respectively. The system is realized as a collection of tools (or knowledge sources) for pre-processing, segmentation, primary and secondary feature detection and a control structure based on the blackboard model to coordinate the activities of these tools.

  2. Competition of fracture mechanisms in monolithic dental ceramics: flat model systems.

    PubMed

    Zhang, Yu; Kim, Jae-Won; Bhowmick, Sanjit; Thompson, Van P; Rekow, E Dianne

    2009-02-01

    Monolithic (single layer) glass-ceramic restorations often fail from chipping and fracture. Using blunt indentation of a model flat porcelain-like brittle layer bonded onto a dentin-like polymer support system, a variety of fatigue fracture modes has been identified and analyzed: outer cone, inner cone, and median cracks developing in the near-contact region at the occlusal surface; radial cracks developing at the internal cementation surface along the loading axis. Our findings indicate that monolithic glass-ceramic layers are vulnerable to both occlusal surface damage and cementation internal surface fracture. Clinical issues in the longevity of ceramic restorations are discussed in relation to biting force, physical properties of ceramic crowns and luting cement, and thicknesses of ceramic and cement layers.

  3. Competition of Fracture Mechanisms in Monolithic Dental Ceramics: Flat Model Systems

    PubMed Central

    Zhang, Yu; Kim, Jae-Won; Bhowmick, Sanjit; Thompson, Van P.; Rekow, E. Dianne

    2015-01-01

    Monolithic (single layer) glass-ceramic restorations often fail from chipping and fracture. Using blunt indentation of a model flat porcelain-like brittle layer bonded onto a dentin-like polymer support system, a variety of fatigue fracture modes has been identified and analyzed: outer cone, inner cone, and median cracks developing in the near-contact region at the occlusal surface; radial cracks developing at the internal cementation surface along the loading axis. Our findings indicate that monolithic glass-ceramic layers are vulnerable to both occlusal surface damage and cementation internal surface fracture. Clinical issues in the longevity of ceramic restorations are discussed in relation to biting force, physical properties of ceramic crowns and luting cement, and thicknesses of ceramic and cement layers. PMID:18478533

  4. Novel in-situ longitudinal model for the study of dentifrices on dental erosion-abrasion.

    PubMed

    Hara, Anderson T; Barlow, Ashley P; Eckert, George J; Zero, Domenick T

    2014-04-01

    A novel longitudinal erosion-abrasion in-situ model was proposed. In an exploratory test (phase 1) toothbrushing effect was investigated using a parallel design, whereas in the main study (phases 1 + 2), a crossover design tested the effect of fluoride dentifrice. In phase 1, 16 subjects (n = 5-6 subjects per group) wore partial dentures with enamel specimens for 28 d and adhered to one of the following treatment regimens: regimen A, erosion only; regimen B, erosion + toothbrushing with fluoride-containing dentifrice [1,100 ppm of fluoride as sodium fluoride (NaF)]; and regimen C, erosion + toothbrushing with placebo dentifrice (0 ppm fluoride). Erosion consisted of the exposure of specimens to grapefruit juice. In regimens B and C, toothbrushing was performed with the test dentifrices 5 min after erosion. For the main study a second phase was carried out in which subjects initially treated with regimen B were treated with regimen C, and vice versa (crossover, n = 11), repeating the same experimental protocol. Enamel wear was measured by optical profilometry at baseline and every 7 d thereafter. In the exploratory test (phase 1), no significant differences were observed among regimens at any of the study time-points. In the main study (phases 1 + 2), higher enamel wear was observed for regimen C than for regimen B. A significant trend was observed for the increase of enamel wear over time. Fluoridated dentifrice reduced the development of erosive-abrasive lesions. The proposed longitudinal model provided adequate responses for erosion-abrasion frequency and fluoride effects.

  5. Modeling the dental development of fossil hominins through the inhibitory cascade.

    PubMed

    Schroer, Kes; Wood, Bernard

    2015-02-01

    The inhibitory cascade is a mathematical model for interpreting the relative size of the occlusal surfaces of mammalian molars in terms of developmental mechanisms. The cascade is derived from experimental studies of mouse molars developed in culture, and has been tested and applied to the dentitions of rodents, ungulates, carnivores, and platyrrhines. Results from such applications have provided new information regarding the origins of plesiomorphic traits in mammalian clade and how derived morphologies may arise. In this study we apply the inhibitory cascade model to the postcanine dentition of a sample of Old World primates that includes fossil hominins. The results of this study suggest that the inhibitory cascade (i.e. M1 < M2 < M3 ) describes the relative sizes of the molar occlusal areas of Old World primates and is likely the plesiomorphic condition for this clade. Within that clade, whereas most Old World monkeys have a M1 < M2 < M3 pattern, most apes have a M1 < M2 ≈ M3 pattern. This modified cascade suggests that greater levels of inhibition (or less activation) are acting on the posterior molars of apes, thus facilitating the reduction of M3 s within the apes. With the exception of the baboon genus Papio, extant congeners typically share the same molar inhibitory cascade. The differences in the relative size relationships observed in the molar and premolar-molar cascades of the species included in the fossil hominin genus Paranthropus suggest that although large postcanine teeth are a shared derived trait within this genus, the developmental basis for postcanine megadontia may not be the same in these two Paranthropus taxa. Our results show that phenotypic characters such as postcanine megadontia may not reflect common development. PMID:25420453

  6. A multilayer sonic film

    NASA Astrophysics Data System (ADS)

    Munteanu, L.; Chiroiu, V.; Sireteanu, T.; Dumitriu, D.

    2015-10-01

    A non-periodic multilayer film was analyzed to show that, despite its non-periodicity, the film exhibits full band-gaps and localized modes at its interfaces, as well as in the sonic composites. The film consists of alternating layers of two different materials that follow a triadic Cantor sequence. The Cantor structure shows extremely low thresholds for subharmonic generation of ultrasonic waves, compared with homogeneous and periodic structures. The coupling between the extended-mode (phonon) and the localized-mode (fracton) vibration regimes explains the generation of full band-gaps, for which there are no propagating Lamb waves. The large enhancement of the nonlinear interaction results from a more favorable frequency and spatial matching of coupled modes. A full band-gap that excludes Love waves is also analyzed.

  7. Multilayer optical dielectric coating

    DOEpatents

    Emmett, John L.

    1990-01-01

    A highly damage resistant, multilayer, optical reflective coating includes alternating layers of doped and undoped dielectric material. The doping levels are low enough that there are no distinct interfaces between the doped and undoped layers so that the coating has properties nearly identical to the undoped material. The coating is fabricated at high temperature with plasma-assisted chemical vapor deposition techniques to eliminate defects, reduce energy-absorption sites, and maintain proper chemical stoichiometry. A number of differently-doped layer pairs, each layer having a thickness equal to one-quarter of a predetermined wavelength in the material are combined to form a narrowband reflective coating for a predetermined wavelength. Broadband reflectors are made by using a number of narrowband reflectors, each covering a portion of the broadband.

  8. Multilayer graphene condenser microphone

    NASA Astrophysics Data System (ADS)

    Todorović, Dejan; Matković, Aleksandar; Milićević, Marijana; Jovanović, Djordje; Gajić, Radoš; Salom, Iva; Spasenović, Marko

    2015-12-01

    Vibrating membranes are the cornerstone of acoustic technology, forming the backbone of modern loudspeakers and microphones. Acoustic performance of a condenser microphone is derived mainly from the membrane’s size, surface mass and achievable static tension. The widely studied and available nickel has been a dominant membrane material for professional microphones for several decades. In this paper we introduce multilayer graphene as a membrane material for condenser microphones. The graphene device outperforms a high end commercial nickel-based microphone over a significant part of the audio spectrum, with a larger than 10 dB enhancement of sensitivity. Our experimental results are supported with numerical simulations, which also show that a 300 layer thick graphene membrane under maximum tension would offer excellent extension of the frequency range, up to 1 MHz.

  9. Random walk centrality in interconnected multilayer networks

    NASA Astrophysics Data System (ADS)

    Solé-Ribalta, Albert; De Domenico, Manlio; Gómez, Sergio; Arenas, Alex

    2016-06-01

    Real-world complex systems exhibit multiple levels of relationships. In many cases they require to be modeled as interconnected multilayer networks, characterizing interactions of several types simultaneously. It is of crucial importance in many fields, from economics to biology and from urban planning to social sciences, to identify the most (or the less) influent nodes in a network using centrality measures. However, defining the centrality of actors in interconnected complex networks is not trivial. In this paper, we rely on the tensorial formalism recently proposed to characterize and investigate this kind of complex topologies, and extend two well known random walk centrality measures, the random walk betweenness and closeness centrality, to interconnected multilayer networks. For each of the measures we provide analytical expressions that completely agree with numerically results.

  10. CT segmentation of dental shapes by anatomy-driven reformation imaging and B-spline modelling.

    PubMed

    Barone, S; Paoli, A; Razionale, A V

    2016-06-01

    Dedicated imaging methods are among the most important tools of modern computer-aided medical applications. In the last few years, cone beam computed tomography (CBCT) has gained popularity in digital dentistry for 3D imaging of jawbones and teeth. However, the anatomy of a maxillofacial region complicates the assessment of tooth geometry and anatomical location when using standard orthogonal views of the CT data set. In particular, a tooth is defined by a sub-region, which cannot be easily separated from surrounding tissues by only considering pixel grey-intensity values. For this reason, an image enhancement is usually necessary in order to properly segment tooth geometries. In this paper, an anatomy-driven methodology to reconstruct individual 3D tooth anatomies by processing CBCT data is presented. The main concept is to generate a small set of multi-planar reformation images along significant views for each target tooth, driven by the individual anatomical geometry of a specific patient. The reformation images greatly enhance the clearness of the target tooth contours. A set of meaningful 2D tooth contours is extracted and used to automatically model the overall 3D tooth shape through a B-spline representation. The effectiveness of the methodology has been verified by comparing some anatomy-driven reconstructions of anterior and premolar teeth with those obtained by using standard tooth segmentation tools. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26418417

  11. Integrated Multilayer Insulation

    NASA Technical Reports Server (NTRS)

    Dye, Scott

    2009-01-01

    Integrated multilayer insulation (IMLI) is being developed as an improved alternative to conventional multilayer insulation (MLI), which is more than 50 years old. A typical conventional MLI blanket comprises between 10 and 120 metallized polymer films separated by polyester nets. MLI is the best thermal- insulation material for use in a vacuum, and is the insulation material of choice for spacecraft and cryogenic systems. However, conventional MLI has several disadvantages: It is difficult or impossible to maintain the desired value of gap distance between the film layers (and consequently, it is difficult or impossible to ensure consistent performance), and fabrication and installation are labor-intensive and difficult. The development of IMLI is intended to overcome these disadvantages to some extent and to offer some additional advantages over conventional MLI. The main difference between IMLI and conventional MLI lies in the method of maintaining the gaps between the film layers. In IMLI, the film layers are separated by what its developers call a micro-molded discrete matrix, which can be loosely characterized as consisting of arrays of highly engineered, small, lightweight, polymer (typically, thermoplastic) frames attached to, and placed between, the film layers. The term "micro-molded" refers to both the smallness of the frames and the fact that they are fabricated in a process that forms precise small features, described below, that are essential to attainment of the desired properties. The term "discrete" refers to the nature of the matrix as consisting of separate frames, in contradistinction to a unitary frame spanning entire volume of an insulation blanket.

  12. Dental Auxiliary Occupations. Interim Report.

    ERIC Educational Resources Information Center

    Kingston, Richard D.

    As part of a dental auxiliaries project, a Dental Auxiliary National Technical Advisory Committee was established, and its major undertaking was to assist in the development of a functional inventory for each of the three dental auxiliary occupations (dental assisting, dental hygiene, and dental laboratory technology). The analysis consisted of…

  13. Evolutionary games on multilayer networks: a colloquium

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Wang, Lin; Szolnoki, Attila; Perc, Matjaž

    2015-05-01

    Networks form the backbone of many complex systems, ranging from the Internet to human societies. Accordingly, not only is the range of our interactions limited and thus best described and modeled by networks, it is also a fact that the networks that are an integral part of such models are often interdependent or even interconnected. Networks of networks or multilayer networks are therefore a more apt description of social systems. This colloquium is devoted to evolutionary games on multilayer networks, and in particular to the evolution of cooperation as one of the main pillars of modern human societies. We first give an overview of the most significant conceptual differences between single-layer and multilayer networks, and we provide basic definitions and a classification of the most commonly used terms. Subsequently, we review fascinating and counterintuitive evolutionary outcomes that emerge due to different types of interdependencies between otherwise independent populations. The focus is on coupling through the utilities of players, through the flow of information, as well as through the popularity of different strategies on different network layers. The colloquium highlights the importance of pattern formation and collective behavior for the promotion of cooperation under adverse conditions, as well as the synergies between network science and evolutionary game theory.

  14. Symmetric scrolled packings of multilayered carbon nanoribbons

    NASA Astrophysics Data System (ADS)

    Savin, A. V.; Korznikova, E. A.; Lobzenko, I. P.; Baimova, Yu. A.; Dmitriev, S. V.

    2016-06-01

    Scrolled packings of single-layer and multilayer graphene can be used for the creation of supercapacitors, nanopumps, nanofilters, and other nanodevices. The full atomistic simulation of graphene scrolls is restricted to consideration of relatively small systems in small time intervals. To overcome this difficulty, a two-dimensional chain model making possible an efficient calculation of static and dynamic characteristics of nanoribbon scrolls with allowance for the longitudinal and bending stiffness of nanoribbons is proposed. The model is extended to the case of scrolls of multilayer graphene. Possible equilibrium states of symmetric scrolls of multilayer carbon nanotribbons rolled up so that all nanoribbons in the scroll are equivalent are found. Dependences of the number of coils, the inner and outer radii, lowest vibrational eigenfrequencies of rolled packages on the length L of nanoribbons are obtained. It is shown that the lowest vibrational eigenfrequency of a symmetric scroll decreases with a nanoribbon length proportionally to L -1. It is energetically unfavorable for too short nanoribbons to roll up, and their ground state is a stack of plane nanoribbons. With an increasing number k of layers, the nanoribbon length L necessary for creation of symmetric scrolls increases. For a sufficiently small number of layers k and a sufficiently large nanoribbon length L, the scrolled packing has the lowest energy as compared to that of stack of plane nanoribbons and folded structures. The results can be used for development of nanomaterials and nanodevices on the basis of graphene scrolled packings.

  15. Quantum Spin Hall phase in multilayer graphene

    NASA Astrophysics Data System (ADS)

    Garcia, Noel; Lado, Jose Luis; Fernandez-Rossier, Joaquin; Theory of Nanostructures Team

    2015-03-01

    We address the question of whether multilayer graphene systems are Quantum Spin Hall (QSH) insulators. Since interlayer coupling coples pz orbitals to s orbitals of different layers and Spin-Orbit (SO) couples pz orbitals with px and py of opposite spins, new spins mixing channels appear in the multilayer scenario that were not present in the monolayer. These new spin-mixing channels cast a doubt on the validity of the spin-conserving Kane-Mele model for multilayers and motivates our choice of a four orbital tight-binding model in the Slater-Koster approximation with intrinsic Spin-Orbit interaction. To completely determine if the QSH phase is present we calculate for different number of layers both the Z2 invariant for different stackings (only for inversion symmetric systems), and the density of states at the edge of semi-infinite graphene ribbon with armchair termination. We find that systems with even number of layers are normal insulators while systems with odd number of layers are QSH insulators, regardless of the stacking. We acknowledge financial support by Marie-Curie-ITN 607904-SPINOGRAPH.

  16. Micro-computed tomography (CT) based assessment of dental regenerative therapy in the canine mandible model

    NASA Astrophysics Data System (ADS)

    Khobragade, P.; Jain, A.; Setlur Nagesh, S. V.; Andreana, S.; Dziak, R.; Sunkara, S. K.; Sunkara, S.; Bednarek, D. R.; Rudin, S.; Ionita, C. N.

    2015-03-01

    High-resolution 3D bone-tissue structure measurements may provide information critical to the understanding of the bone regeneration processes and to the bone strength assessment. Tissue engineering studies rely on such nondestructive measurements to monitor bone graft regeneration area. In this study, we measured bone yield, fractal dimension and trabecular thickness through micro-CT slices for different grafts and controls. Eight canines underwent surgery to remove a bone volume (defect) in the canine's jaw at a total of 44 different locations. We kept 11 defects empty for control and filled the remaining ones with three regenerative materials; NanoGen (NG), a FDA-approved material (n=11), a novel NanoCalcium Sulfate (NCS) material (n=11) and NCS alginate (NCS+alg) material (n=11). After a minimum of four and eight weeks, the canines were sacrificed and the jaw samples were extracted. We used a custombuilt micro-CT system to acquire the data volume and developed software to measure the bone yield, fractal dimension and trabecular thickness. The software used a segmentation algorithm based on histograms derived from volumes of interest indicated by the operator. Using bone yield and fractal dimension as indices we are able to differentiate between the control and regenerative material (p<0.005). Regenerative material NCS showed an average 63.15% bone yield improvement over the control sample, NCS+alg showed 55.55% and NanoGen showed 37.5%. The bone regeneration process and quality of bone were dependent upon the position of defect and time period of healing. This study presents one of the first quantitative comparisons using non-destructive Micro-CT analysis for bone regenerative material in a large animal with a critical defect model. Our results indicate that Micro-CT measurement could be used to monitor invivo bone regeneration studies for greater regenerative process understanding.

  17. Reactive multilayers fabricated by vapor deposition. A critical review

    SciTech Connect

    Adams, D. P.

    2014-10-02

    The reactive multilayer thin films are a class of energetic materials that continue to attract attention for use in joining applications and as igniters. Generally composed of two reactants, these heterogeneous solids can be stimulated by an external source to promptly release stored chemical energy in a sudden emission of light and heat. In our critical review article, results from recent investigations of these materials are discussed. Discussion begins with a brief description of the vapor deposition techniques that provide accurate control of layer thickness and film composition. More than 50 reactive film compositions have been reported to date, with most multilayers fabricated by magnetron sputter deposition or electron-beam evaporation. In later sections, we review how multilayer ignition threshold, reaction rate, and total heat are tailored via thin film design. For example, planar multilayers with nanometer-scale periodicity exhibit rapid, self-sustained reactions with wavefront velocities up to 100 m/s. Numeric and analytical models have elucidated many of the fundamental processes that underlie propagating exothermic reactions while demonstrating how reaction rates vary with multilayer design. Recent, time-resolved diffraction and imaging studies have further revealed the phase transformations and the wavefront dynamics associated with propagating chemical reactions. Many reactive multilayers (e.g., Co/Al) form product phases that are consistent with published equilibrium phase diagrams, yet a few systems, such as Pt/Al, develop metastable products. The final section highlights current and emerging applications of reactive multilayers. Examples include reactive Ni(V)/Al and Pd/Al multilayers which have been developed for localized soldering of heat-sensitive components.

  18. Reactive multilayers fabricated by vapor deposition. A critical review

    DOE PAGES

    Adams, D. P.

    2014-10-02

    The reactive multilayer thin films are a class of energetic materials that continue to attract attention for use in joining applications and as igniters. Generally composed of two reactants, these heterogeneous solids can be stimulated by an external source to promptly release stored chemical energy in a sudden emission of light and heat. In our critical review article, results from recent investigations of these materials are discussed. Discussion begins with a brief description of the vapor deposition techniques that provide accurate control of layer thickness and film composition. More than 50 reactive film compositions have been reported to date, withmore » most multilayers fabricated by magnetron sputter deposition or electron-beam evaporation. In later sections, we review how multilayer ignition threshold, reaction rate, and total heat are tailored via thin film design. For example, planar multilayers with nanometer-scale periodicity exhibit rapid, self-sustained reactions with wavefront velocities up to 100 m/s. Numeric and analytical models have elucidated many of the fundamental processes that underlie propagating exothermic reactions while demonstrating how reaction rates vary with multilayer design. Recent, time-resolved diffraction and imaging studies have further revealed the phase transformations and the wavefront dynamics associated with propagating chemical reactions. Many reactive multilayers (e.g., Co/Al) form product phases that are consistent with published equilibrium phase diagrams, yet a few systems, such as Pt/Al, develop metastable products. The final section highlights current and emerging applications of reactive multilayers. Examples include reactive Ni(V)/Al and Pd/Al multilayers which have been developed for localized soldering of heat-sensitive components.« less

  19. Decomposition of the magnetoresistance of multilayers into ferromagneticand superparamagnetic contributions

    NASA Astrophysics Data System (ADS)

    Bakonyi, I.; Péter, L.; Rolik, Z.; Kiss-Szabó, K.; Kupay, Z.; Tóth, J.; Kiss, L. F.; Pádár, J.

    2004-08-01

    An analysis of both magnetic and magnetotransport properties is presented for electrodeposited multilayers prepared intentionally under conditions to make the superparamagnetic (SPM) magnetization contribution comparable to or larger than the ferromagnetic term. Based on a model elaborated for the giant magnetoresistance (GMR) of granular metals [N. Wiser, J. Magn. Magn. Mater. 159, 119 (1996); B. Hickey , Phys. Rev. B. 51, 667 (1995)], it is shown that in such multilayers both the magnetization and the GMR can be decomposed into ferromagnetric and superparamagnetic contributions where the latter term is described by a Langevin function. The size of the SPM regions estimated from the experimental data is in the nanoscale regime. It is believed that the method applied here gives a quantitative answer to the problem of the often observed nonsaturating behavior of GMR in multilayers. Electrodeposited multilayers are particularly prone to this feature although the occurrence of SPM regions is quite common in multilayers prepared by any technique. Therefore, this type of analysis should help better understanding of the factors influencing the GMR of multilayer films.

  20. Developmental delays and dental caries in low-income preschoolers in the USA: a pilot cross-sectional study and preliminary explanatory model

    PubMed Central

    2013-01-01

    Background Anecdotal evidence suggests that low-income preschoolers with developmental delays are at increased risk for dental caries and poor oral health, but there are no published studies based on empirical data. The purpose of this pilot study was two-fold: to examine the relationship between developmental delays and dental caries in low-income preschoolers and to present a preliminary explanatory model on the determinants of caries for enrollees in Head Start, a U.S. school readiness program for low-income preschool-aged children. Methods Data were collected on preschoolers ages 3–5 years at two Head Start centers in Washington, USA (N = 115). The predictor variable was developmental delay status (no/yes). The outcome variable was the prevalence of decayed, missing, and filled surfaces (dmfs) on primary teeth. We used multiple variable Poisson regression models to test the hypothesis that within a population of low-income preschoolers, those with developmental delays would have increased dmfs prevalence than those without developmental delays. Results Seventeen percent of preschoolers had a developmental delay and 51.3% of preschoolers had ≥1 dmfs. Preschoolers with developmental delays had a dmfs prevalence ratio that was 1.26 times as high as preschoolers without developmental delays (95% CI: 1.01, 1.58; P < .04). Other factors associated with increased dmfs prevalence ratios included: not having a dental home (P = .01); low caregiver education (P < .001); and living in a non-fluoridated community (P < .001). Conclusions Our pilot data suggest that developmental delays among low-income preschoolers are associated with increased primary tooth dmfs. Additional research is needed to further examine this relationship. Future interventions and policies should focus on caries prevention strategies within settings like Head Start classrooms that serve low-income preschool-aged children with additional targeted home- and community

  1. American Dental Education Association

    MedlinePlus

    ... Diversity and Inclusion ADEA Commission on Change and Innovation in Dental Education What is ADEA CCI? ADEA ... Education, 2016–2017 Beyond the Crossroads: Change and Innovation in Dental Education ADEA Guidelines for Ethical Academic ...

  2. Dental x-rays

    MedlinePlus

    X-ray - teeth; Radiograph - dental; Bitewings; Periapical film; Panoramic film; Digital image ... dentist's office. There are many types of dental x-rays. Some of them are: Bitewing. Shows the crown ...

  3. The effect of Filmed modeling on the anxious and cooperative behavior of 4-6 years old children during dental treatment: A randomized clinical trial study

    PubMed Central

    Paryab, Mehrsa; Arab, Zeinab

    2014-01-01

    Background: The aim of this study was to evaluate the effect of Filmed modeling in comparison with commonly used Tell-Show-Do technique (T.S.D) on the anxious and cooperative behavior of 4-6 years old children during dental practice. Materials and Methods: Forty six children aged 4-6 years were enrolled in this study and randomly allocated into two groups. Group I: At the first visit, the procedure of Tell-Show-Do, and at the second visit, the treatment procedures were performed by the dentist for the children. Group II: At the first visit, children watched a film consisting of the procedure of Tell-Show-Do performed on a child model. At the second visit, treatment procedures were performed. In both groups, during the treatment procedure, index of heart rate was measured and behaviors of children were recorded. The children's anxious and cooperative behaviors on the recordings were quantified according to Venham and Frankl rating scales, respectively. The data were compared between two groups using T-test method. All statistical references were made at 0.05. Results: There were no statistically significant differences in heart rate measures, clinical anxiety and cooperative behavior scores of children between the two groups (P = 0.6). Conclusion: Filmed modeling can be an efficient alternative method to Tell-Show-Do technique in pre-appointment preparation of the 4-6 years old children during dental treatment. PMID:25225565

  4. Using peer-assisted learning and role-playing to teach generic skills to dental students: the health care simulation model.

    PubMed

    El Tantawi, Maha M A; Abdelaziz, Hytham; AbdelRaheem, Amira S; Mahrous, Ahmed A

    2014-01-01

    Increasing importance is attached to teaching generic skills to undergraduate students in various disciplines. This article describes an extracurricular, student-led activity for teaching generic skills using the Model United Nations over three months. The activity used the Health Care Simulation Model (HCSM) with peer learning and role-playing to accomplish its objectives. An interview was used to select from undergraduate and postgraduate dental students at Alexandria University, Alexandria, Egypt, to develop a group of staff to act as peer teachers after receiving training (n=77). These peer teachers provided training for 123 undergraduate dental students to serve as delegates who acted as trainees or peer learners. At the end of the training sessions, a conference was held in which the students played the roles of delegates representing officials responsible for health care systems in ten countries. The students reported improvement in generic skills, enjoyed several aspects of the experience, and disliked other aspects of the model to a lesser extent. In multivariate analysis, perceived usefulness of the HCSM was significantly greater for staff than delegates and increased as self-reported improvement in knowledge of health care systems increased. This study suggests that innovative, student-centered educational methods can be effective for teaching generic skills and factual information.

  5. Using peer-assisted learning and role-playing to teach generic skills to dental students: the health care simulation model.

    PubMed

    El Tantawi, Maha M A; Abdelaziz, Hytham; AbdelRaheem, Amira S; Mahrous, Ahmed A

    2014-01-01

    Increasing importance is attached to teaching generic skills to undergraduate students in various disciplines. This article describes an extracurricular, student-led activity for teaching generic skills using the Model United Nations over three months. The activity used the Health Care Simulation Model (HCSM) with peer learning and role-playing to accomplish its objectives. An interview was used to select from undergraduate and postgraduate dental students at Alexandria University, Alexandria, Egypt, to develop a group of staff to act as peer teachers after receiving training (n=77). These peer teachers provided training for 123 undergraduate dental students to serve as delegates who acted as trainees or peer learners. At the end of the training sessions, a conference was held in which the students played the roles of delegates representing officials responsible for health care systems in ten countries. The students reported improvement in generic skills, enjoyed several aspects of the experience, and disliked other aspects of the model to a lesser extent. In multivariate analysis, perceived usefulness of the HCSM was significantly greater for staff than delegates and increased as self-reported improvement in knowledge of health care systems increased. This study suggests that innovative, student-centered educational methods can be effective for teaching generic skills and factual information. PMID:24385528

  6. Multilayer coatings on flexible substrates

    SciTech Connect

    Martin, P.M.; Affinito, J.D.; Gross, M.E.; Coronado, C.A.; Bennett, W.D.; Stewart, D.C.

    1995-04-01

    Thin-film optical and non-optical multilayer coatings are deposited onto flexible substrates using a vacuum web coater developed at Pacific Northwest Laboratory. The coater`s primary application is rapid prototyping of multilayer (1) polymer coatings, (2) polymer/metal coatings, (3) ceramic/metal coatings, and (4) hybrid polymer, ceramic, and metal coatings. The coater is fully automated and incorporates polymer evaporation and extrusion heads, high-rate magnetron sputtering cathodes, and e-beam evaporation sources. Polymer electrolytes are deposited by extrusion techniques. Flexible plastic, metal, and ceramic substrates can be coated using roll-to-roll or closed-loop configurations. Examples of multilayer optical coatings demonstrated to date are solar reflectors, heat mirrors, Fabry-Perot filters, and alpha particle sensors. Nonoptical coatings include multilayer magnetic metal/ceramic and lamellar composites.

  7. Controlling light with plasmonic multilayers

    NASA Astrophysics Data System (ADS)

    Orlov, Alexey A.; Zhukovsky, Sergei V.; Iorsh, Ivan V.; Belov, Pavel A.

    2014-06-01

    Recent years have seen a new wave of interest in layered media - namely, plasmonic multilayers - in several emerging applications ranging from transparent metals to hyperbolic metamaterials. In this paper, we review the optical properties of such subwavelength metal-dielectric multilayered metamaterials and describe their use for light manipulation at the nanoscale. While demonstrating the recently emphasized hallmark effect of hyperbolic dispersion, we put special emphasis to the comparison between multilayered hyperbolic metamaterials and more broadly defined plasmonic-multilayer metamaterials A number of fundamental electromagnetic effects unique to the latter are identified and demonstrated. Examples include the evolution of isofrequency contour shape from elliptical to hyperbolic, all-angle negative refraction, and nonlocality-induced optical birefringence. Analysis of the underlying physical causes, which are spatial dispersion and optical nonlocality, is also reviewed. These recent results are extremely promising for a number of applications ranging from nanolithography to optical cloaking.

  8. Multilayered Magnetic Gelatin Membrane Scaffolds

    PubMed Central

    Samal, Sangram K.; Goranov, Vitaly; Dash, Mamoni; Russo, Alessandro; Shelyakova, Tatiana; Graziosi, Patrizio; Lungaro, Lisa; Riminucci, Alberto; Uhlarz, Marc; Bañobre-López, Manuel; Rivas, Jose; Herrmannsdörfer, Thomas; Rajadas, Jayakumar; De Smedt, Stefaan; Braeckmans, Kevin; Kaplan, David L.; Dediu, V. Alek

    2016-01-01

    A versatile approach for the design and fabrication of multilayer magnetic scaffolds with tunable magnetic gradients is described. Multilayer magnetic gelatin membrane scaffolds with intrinsic magnetic gradients were designed to encapsulate magnetized bioagents under an externally applied magnetic field for use in magnetic-field-assisted tissue engineering. The temperature of the individual membranes increased up to 43.7 °C under an applied oscillating magnetic field for 70 s by magnetic hyperthermia, enabling the possibility of inducing a thermal gradient inside the final 3D multilayer magnetic scaffolds. On the basis of finite element method simulations, magnetic gelatin membranes with different concentrations of magnetic nanoparticles were assembled into 3D multilayered scaffolds. A magnetic-gradient-controlled distribution of magnetically labeled stem cells was demonstrated in vitro. This magnetic biomaterial–magnetic cell strategy can be expanded to a number of different magnetic biomaterials for various tissue engineering applications. PMID:26451743

  9. Joint detection of anatomical points on surface meshes and color images for visual registration of 3D dental models

    NASA Astrophysics Data System (ADS)

    Destrez, Raphaël.; Albouy-Kissi, Benjamin; Treuillet, Sylvie; Lucas, Yves

    2015-04-01

    Computer aided planning for orthodontic treatment requires knowing occlusion of separately scanned dental casts. A visual guided registration is conducted starting by extracting corresponding features in both photographs and 3D scans. To achieve this, dental neck and occlusion surface are firstly extracted by image segmentation and 3D curvature analysis. Then, an iterative registration process is conducted during which feature positions are refined, guided by previously found anatomic edges. The occlusal edge image detection is improved by an original algorithm which follows Canny's poorly detected edges using a priori knowledge of tooth shapes. Finally, the influence of feature extraction and position optimization is evaluated in terms of the quality of the induced registration. Best combination of feature detection and optimization leads to a positioning average error of 1.10 mm and 2.03°.

  10. Dental laser technology.

    PubMed

    Fasbinder, Dennis J

    2008-10-01

    Dental technology is rapidly affecting the treatment options available to patients. Dental lasers are an innovative technology for both hard- and soft-tissue treatment applications. The ability to recontour soft tissues efficiently and predictably with immediate hemostatsis and minimal postoperative sequelae is of value to both the dentist and the patient. This article reviews the principles of dental lasers, criteria to consider when selecting a dental laser, and some of their clinical applications.

  11. Multilayer thermal barrier coating systems

    DOEpatents

    Vance, Steven J.; Goedjen, John G.; Sabol, Stephen M.; Sloan, Kelly M.

    2000-01-01

    The present invention generally describes multilayer thermal barrier coating systems and methods of making the multilayer thermal barrier coating systems. The thermal barrier coating systems comprise a first ceramic layer, a second ceramic layer, a thermally grown oxide layer, a metallic bond coating layer and a substrate. The thermal barrier coating systems have improved high temperature thermal and chemical stability for use in gas turbine applications.

  12. Accreditation in Dental Hygiene.

    ERIC Educational Resources Information Center

    National Commission on Accrediting, Washington, DC.

    The Council on Dental Education cooperates with the American Dental Hygienists' Association in developing educational requirements for schools of dental hygiene. To be eligible for accreditation, schools must operate on a non-profit basis. A school applying for accreditation completes a previsitation questionnaire concerning its program. The…

  13. Dental records: An overview

    PubMed Central

    Charangowda, B K

    2010-01-01

    Dental records consist of documents related to the history of present illness, clinical examination, diagnosis, treatment done, and the prognosis. A thorough knowledge of dental records is essential for the practicing dentist, as it not only has a forensic application, but also a legal implication with respect to insurance and consumerism. This article reviews the importance of dental records in forensics. PMID:21189983

  14. Dental Manpower Fact Book.

    ERIC Educational Resources Information Center

    Ake, James N.; Johnson, Donald W.

    Statistical data on many aspects of dental and allied dental personnel supply, distribution, characteristics, and education and on certain other aspects of dental services are presented and discussed. The data on dentist supply show the national trend in the supply of active dentists since 1950 and the concurrent changes in dentist-to-population…

  15. Dental Laboratory Technology.

    ERIC Educational Resources Information Center

    Department of the Air Force, Washington, DC.

    The Air Force dental laboratory technology manual is designed as a basic training text as well as a reference source for dental laboratory technicians, a specialty occupation concerned with the design, fabrication, and repair of dental prostheses. Numerous instructive diagrams and photographs are included throughout the manual. The comprehensive…

  16. DENTAL SCHOOL PLANNING.

    ERIC Educational Resources Information Center

    GALAGAN, DONALD J.

    THIS DISCUSSION PRESENTS A COMPLETE PICTURE OF THE CURRENT STATE OF DENTAL EDUCATION WITH SUGGESTIONS FOR MEETING THE DEMANDS FOR DENTAL STAFF AND FACILITIES. THE AREAS INVESTIGATED ARE (1) OBJECTIVES IN DENTAL EDUCATION--COURSES, TEACHING MODES, INNOVATIONS IN CURRICULUM, COORDINATION OF BASIC AND CLINICAL INSTRUCTION, (2) FACILITY…

  17. Artificial multilayers and nanomagnetic materials

    PubMed Central

    SHINJO, Teruya

    2013-01-01

    The author has been actively engaged in research on nanomagnetic materials for about 50 years. Nanomagnetic materials are comprised of ferromagnetic systems for which the size and shape are controlled on a nanometer scale. Typical examples are ultrafine particles, ultrathin films, multilayered films and nano-patterned films. In this article, the following four areas of the author’s studies are described. (1) Mössbauer spectroscopic studies of nanomagnetic materials and interface magnetism. (2) Preparation and characterization of metallic multilayers with artificial superstructures. (3) Giant magnetoresistance (GMR) effect in magnetic multilayers. (4) Novel properties of nanostructured ferromagnetic thin films (dots and wires). A subject of particular interest in the author’s research was the artificially prepared multilayers consisting of metallic elements. The motivation to initiate the multilayer investigation is described and the physical properties observed in the artificial multilayers are introduced. The author’s research was initially in the field of pure physical science and gradually extended into applied science. His achievements are highly regarded not only from the fundamental point of view but also from the technological viewpoint. PMID:23391605

  18. Wrapped multilayer insulation for cryogenic piping

    NASA Astrophysics Data System (ADS)

    Dye, Scott; Kopelove, Alan; Mills, Gary L.

    2012-06-01

    Many cryogenic systems require thermal insulation on piping and tubing containing cryogenic fluids. The lowest heat leak is typically achieved with conventional multilayer insulation (MLI) wrapped around the tubing and contained in a vacuum. However, because of inherent insulation compression and its effect on conventional netting spacer MLI, MLI performance on piping and tubing is four to ten times worse than MLI on a cryogenic tank or flat surface. Wrapped Multilayer Insulation (WMLI) is a high performance multilayer insulation designed for cryogenic piping that uses an innovative discrete spacer technology to control layer spacing/density and reduce heat leak. This paper reports on the initial development of WMLI and its demonstration as a feasible technology. The WMLI design was estimated in thermal models to provide four times better thermal insulation than conventional MLI on cryogenic piping. A WMLI prototype was built and had a measured heat leak 37% of the heat leak of conventional MLI insulating tubing. Test results for WMLI are presented, and plans for continued development of this insulation are discussed.

  19. Surface energetics of freely suspended fluid molecular monolayer and multilayer smectic liquid crystal films

    PubMed Central

    Nguyen, Zoom Hoang; Park, Cheol Soo; Pang, Jinzhong; Clark, Noel A.

    2012-01-01

    A study of the surface energetics of the thinnest substrate-free liquid films, fluid molecular monolayer and multilayer smectic liquid crystal films suspended in air, is reported. In films having monolayer and multilayer domains, the monolayer areas contract, contrary to predictions from the van der Waals disjoining pressure of thin uniform slabs. This discrepancy is accounted for by modeling the environmental asymmetry of the surface layers in multilayer films, leading to the possibility that preferential end-for-end polar ordering of the rod shaped molecules can reduce the surface energy of multilayers relative to that of the monolayer, which is inherently symmetric. PMID:22826264

  20. Quality Assurance Decisions with Air Models: A Case Study of ImputatIon of Missing Input Data Using EPA's Multi-Layer Model

    EPA Science Inventory

    Abstract Environmental models are frequently used within regulatory and policy frameworks to estimate environmental metrics that are difficult or impossible to physically measure. As important decision tools, the uncertainty associated with the model outputs should impact their ...

  1. American Dental Association White Paper Targets Dental Care for the Underserved

    ERIC Educational Resources Information Center

    Berthold, Mark

    2005-01-01

    Reaffirming its leadership role toward better oral health for all Americans, the ADA has produced a white paper that also challenges policy-makers and the US to improve access to dental services. The white paper, "State and Community Models for Improving Access to Dental Care for the Underserved," was presented October 1 to the House of Delegates…

  2. Weaker dental enamel explains dental decay.

    PubMed

    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution. PMID:25885796

  3. Weaker Dental Enamel Explains Dental Decay

    PubMed Central

    Vieira, Alexandre R.; Gibson, Carolyn W.; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is “weaker” while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution. PMID:25885796

  4. Dental training and changes in oral health attitudes and behaviors in Istanbul dental students.

    PubMed

    Peker, Kadriye; Uysal, Omer; Bermek, Gülçin

    2010-09-01

    The aim of this study was to examine the changes that occur in the oral health attitudes and behaviors of dental students in Istanbul, Turkey, during their dental education. The Turkish version of the Hiroshima University-Dental Behavioral Inventory (HU-DBI) was distributed among 757 dental students at the Dental Faculty, Istanbul University. The response rate was 72 percent. Chi-square and logistic regression models were used for statistical analysis. The mean HU-DBI score of the clinical students was significantly higher than that of the preclinical students. Preclinical students significantly more often believed that it was impossible to prevent gum disease with toothbrushing alone and worried about the color of their teeth and bad breath. Most of them brushed their teeth with strong strokes, thought the condition of their teeth was getting worse despite daily toothbrushing, and would seek dental care only when symptoms arise. Clinical students more often used disclosing solutions to see how clean their teeth were and complained of bleeding gums. The variation in favorable oral health attitudes/behaviors appeared to reflect the students' educational training experience. The findings of this study highlight the relatively poor oral health behaviors of Turkish dental students, which should be improved by means of comprehensive programs that aim to promote their own dental hygiene practices and preventive oral health knowledge from the start of dental training. PMID:20837744

  5. Multilayer microfluidic PEGDA hydrogels.

    PubMed

    Cuchiara, Michael P; Allen, Alicia C B; Chen, Theodore M; Miller, Jordan S; West, Jennifer L

    2010-07-01

    Development of robust 3D tissue analogs in vitro is limited by passive, diffusional mass transport. Perfused microfluidic tissue engineering scaffolds hold the promise to improve mass transport limitations and promote the development of complex, metabolically dense, and clinically relevant tissues. We report a simple and robust multilayer replica molding technique in which poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) diacrylate (PEGDA) are serially replica molded to develop microfluidic PEGDA hydrogel networks embedded within independently fabricated PDMS housings. We demonstrate the ability to control solute-scaffold effective diffusivity as a function of solute molecular weight and hydrogel concentration. Within cell laden microfluidic hydrogels, we demonstrate increased cellular viability in perfused hydrogel systems compared to static controls. We observed a significant increase in cell viability at all time points greater than zero at distances up to 1 mm from the perfused channel. Knowledge of spatiotemporal mass transport and cell viability gradients provides useful engineering design parameters necessary to maximize overall scaffold viability and metabolic density. This work has applications in the development of hydrogels as in vitro diagnostics and ultimately as regenerative medicine based therapeutics.

  6. Multilayer graphene rubber nanocomposites

    NASA Astrophysics Data System (ADS)

    Schartel, Bernhard; Frasca, Daniele; Schulze, Dietmar; Wachtendorf, Volker; Krafft, Bernd; Morys, Michael; Böhning, Martin; Rybak, Thomas

    2016-05-01

    Multilayer Graphene (MLG), a nanoparticle with a specific surface of BET = 250 m2/g and thus made of only approximately 10 graphene sheets, is proposed as a nanofiller for rubbers. When homogenously dispersed, it works at low loadings enabling the replacement of carbon black (CB), increase in efficiency, or reduction in filler concentration. Actually the appropriate preparation yielded nanocomposites in which just 3 phr are sufficient to significantly improve the rheological, curing and mechanical properties of different rubbers, as shown for Chlorine-Isobutylene-Isoprene Rubber (CIIR), Nitrile-Butadiene Rubber (NBR), Natural Rubber (NR), and Styrene-Butadiene Rubber (SBR). A mere 3 phr of MLG tripled the Young's modulus of CIIR, an effect equivalent to 20 phr of carbon black. Similar equivalents are observed for MLG/CB mixtures. MLG reduces gas permeability, increases thermal and electrical conductivities, and retards fire behavior. The later shown by the reduction in heat release rate in the cone calorimeter. The higher the nanofiller concentration is (3 phr, 5 phr, and 10 phr was investigated), the greater the improvement in the properties of the nanocomposites. Moreover, the MLG nanocomposites improve stability of mechanical properties against weathering. An increase in UV-absorption as well as a pronounced radical scavenging are proposed and were proved experimentally. To sum up, MLG is interesting as a multifunctional nanofiller and seems to be quite ready for rubber development.

  7. The pregnant dental patient.

    PubMed

    Singh, Medha

    2012-01-01

    When dealing with a pregnant patient, the dental practitioner should keep in mind the various physiological changes that occur in the pregnant female and the potential effects on the fetus in using various types of local anesthesia. This article reviews the current considerations in the use of local anesthesia in the pregnant dental patient, and the safety of local anesthetics, their dosage, and any adverse effect on mother and fetus. It also discusses various dental procedures and the trimester during which they can be performed. Lastly, this article talks about the complications that can occur with a pregnant dental patient in the dental chair.

  8. Multilayer waveguide-grating filters.

    PubMed

    Wang, S S; Magnusson, R

    1995-05-10

    The properties of guided-mode resonance reflection filters constructed with multiple thin-film layers are addressed. Greatly improved filter characteristics are shown to follow by the incorporation of multiple homogeneous layers with the spatially modulated layer. Calculated results for single-layer, double-layer, and triple-layer filter structures are presented. Whereas good filter characteristics are obtainable with single layers that are half-resonance-wavelength thick, there remains a residual reflection in the sidebands unless the cover and the substrate permittivities are equal. With double-layer and triple-layer designs, extensive wavelength ranges with low sideband-reflectance values are shown to be possible without requiring equal cover and substrate permittivities. The antireflection properties of the layer stack can be understood if the modulated layer is modeled as a homogeneous layer characterized by its average relative permittivity. However, as the grating-modulation index increases, this approximation deteriorates. In particular it is found that, for a given high modulation index, the double-layer antireflection thin-film approximation fails, whereas for the same modulation in a triple-layer system it holds firmly. Multilayer designs can thus have significantly large filter passbands, as they may contain heavily modulated resonant gratings without corruption of the ideal filter characteristics.

  9. Description and Documentation of the Dental School Dental Delivery System.

    ERIC Educational Resources Information Center

    Chase, Rosen and Wallace, Inc., Alexandria, VA.

    A study was undertaken to describe and document the dental school dental delivery system using an integrated systems approach. In late 1976 and early 1977, a team of systems analysts and dental consultants visited three dental schools to observe the delivery of dental services and patient flow and to interview administrative staff and faculty.…

  10. Explicit Finite Element Modeling of Multilayer Composite Fabric for Gas Turbine Engine Containment Systems, Phase II. Part 3; Material Model Development and Simulation of Experiments

    NASA Technical Reports Server (NTRS)

    Simmons, J.; Erlich, D.; Shockey, D.

    2009-01-01

    A team consisting of Arizona State University, Honeywell Engines, Systems & Services, the National Aeronautics and Space Administration Glenn Research Center, and SRI International collaborated to develop computational models and verification testing for designing and evaluating turbine engine fan blade fabric containment structures. This research was conducted under the Federal Aviation Administration Airworthiness Assurance Center of Excellence and was sponsored by the Aircraft Catastrophic Failure Prevention Program. The research was directed toward improving the modeling of a turbine engine fabric containment structure for an engine blade-out containment demonstration test required for certification of aircraft engines. The research conducted in Phase II began a new level of capability to design and develop fan blade containment systems for turbine engines. Significant progress was made in three areas: (1) further development of the ballistic fabric model to increase confidence and robustness in the material models for the Kevlar(TradeName) and Zylon(TradeName) material models developed in Phase I, (2) the capability was improved for finite element modeling of multiple layers of fabric using multiple layers of shell elements, and (3) large-scale simulations were performed. This report concentrates on the material model development and simulations of the impact tests.

  11. Multilayer Cloud Detection with the MODIS Near-Infrared Water Vapor Absorption Band

    NASA Technical Reports Server (NTRS)

    Wind, Galina; Platnick, Steven; King, Michael D.; Hubanks, Paul A,; Pavolonis, Michael J.; Heidinger, Andrew K.; Yang, Ping; Baum, Bryan A.

    2009-01-01

    Data Collection 5 processing for the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the NASA Earth Observing System EOS Terra and Aqua spacecraft includes an algorithm for detecting multilayered clouds in daytime. The main objective of this algorithm is to detect multilayered cloud scenes, specifically optically thin ice cloud overlying a lower-level water cloud, that presents difficulties for retrieving cloud effective radius using single layer plane-parallel cloud models. The algorithm uses the MODIS 0.94 micron water vapor band along with CO2 bands to obtain two above-cloud precipitable water retrievals, the difference of which, in conjunction with additional tests, provides a map of where multilayered clouds might potentially exist. The presence of a multilayered cloud results in a large difference in retrievals of above-cloud properties between the CO2 and the 0.94 micron methods. In this paper the MODIS multilayered cloud algorithm is described, results of using the algorithm over example scenes are shown, and global statistics for multilayered clouds as observed by MODIS are discussed. A theoretical study of the algorithm behavior for simulated multilayered clouds is also given. Results are compared to two other comparable passive imager methods. A set of standard cloudy atmospheric profiles developed during the course of this investigation is also presented. The results lead to the conclusion that the MODIS multilayer cloud detection algorithm has some skill in identifying multilayered clouds with different thermodynamic phases

  12. Analysis of multilayer insulation between 80K and 300K

    SciTech Connect

    Augustynowicz, S.D.; Demko, J.A.; Datskov, V.I.

    1993-07-01

    A model has been developed that can be used to determine the temperature distribution and heat transfer through a multilayer insulation (MLI) blanket. Predictions from the model were compared with a series of temperature measurements made during laboratory experiments and during a test of five superconducting magnets (dipoles) installed in a string and tested at Fermi National Accelerator Laboratory, FNAL (ER Test).

  13. Optical approach in characterizing dental biomaterials

    NASA Astrophysics Data System (ADS)

    Demoli, Nazif; Vučić, Zlatko; Milat, Ognjen; Gladić, Jadranko; Lovrić, Davorin; Pandurić, Vlatko; Marović, Danijela; Moguš-Milanković, Andrea; Ristić, Mira; Čalogović, Marina; Tarle, Zrinka

    2013-04-01

    The purpose of this paper is to present the current activities of a research collaborative program between three institutions from Zagreb (School of Dental Medicine, Institute of Physics, and Institute Ruđer Bo\\vsković). Within the scope of this program, it is planned to investigate and find guidelines for the refinement of the properties of dental biomaterials (DBs) and of procedures in restorative dental medicine. It is also planned to identify and model the dominant mechanisms which control polymerization of DBs. The materials to be investigated include methacrylate based composite resins, new composite materials with amorphous calcium phosphate, silorane based composite resins, glass-ionomer cements, and giomer.

  14. Multilayer perceptron for nonlinear programming.

    SciTech Connect

    Reifman, J.; Feldman, E. E.; Reactor Analysis

    2002-08-01

    A new method for solving nonlinear programming problems within the framework of a multilayer neural network perceptron is proposed. The method employs the Penalty Function method to transform a constrained optimization problem into a sequence of unconstrained optimization problems and then solves the sequence of unconstrained optimizations of the transformed problem by training a series of multilayer perceptrons. The neural network formulation is represented in such a way that the multilayer perceptron prediction error to be minimized mimics the objective function of the unconstrained problem, and therefore, the minimization of the objective function for each unconstrained optimization is attained by training a single perceptron. The multilayer perceptron allows for the transformation of problems with two-sided bounding constraints on the decision variables x, e.g., a{<=}x{sub n}{<=}b, into equivalent optimization problems in which these constraints do not explicitly appear. Hence, when these are the only constraints in the problem, the transformed problem is constraint free (i.e., the transformed objective function contains no penalty terms) and is solved by training a multilayer perceptron only once. In addition, we present a new Penalty Function method for solving nonlinear programming problems that is parameter free and guarantees that feasible solutions are obtained when the optimal solution is on the boundary of the feasible region. Simulation results, including an example from operations research, illustrate the proposed methods.

  15. [Dental anatomy of dogs].

    PubMed

    Sarkisian, E G

    2014-12-01

    The aim of the research was to investigate dog teeth anatomy as animal model for study of etiopathogenesis of caries disease and physiological tooth wear in human. After examining the dog's dental system, following conclusions were drawn: the dog has 42 permanent teeth, which are distributed over the dental arches not equally, and so the upper dentition consists of 20, and the lower of 22 teeth. The largest are considered upper fourth premolar and lower first molars, which are called discordant teeth. Between discordant teeth and fangs a dog has an open bite, which is limited to the top and bottom conical crown premolar teeth. Thus, in the closed position of the jaws, behind this occlusion is limited by discordant teeth, just in contact are smaller in size two molars. Only large dog's molars in a valid comparison can be likened to human molars, which allows us to use them in an analog comparison between them with further study of the morphological features ensure durability short-crown teeth and their predisposition to caries.

  16. Ferromagnetic/Superconducting Multilayers

    NASA Astrophysics Data System (ADS)

    Bader, S. D.

    1998-03-01

    Although it is well known that magnetism influences superconductivity, the converse issue has been less well explored. Recent theoretical predictions for ferromagnetic/ superconducting/ ferromagnetic trilayers exhibiting interlayer magnetic coupling in the normal state indicate that the coupling should be suppressed below the superconducting transition temperature.(C.A. R. Sá de Melo, Phys. Rev. Lett. 79), 1933 (1997); O. Sipr, B.L. Györffy, J. Phys. Cond. Matt. 7, 5239 (1995). To realize such a situation, a requirement (when the magnetic layers are thick) is that the superconducting layer thickness must simultaneously be less than the range over which the magnetic interlayer coupling decays, but greater than the superconducting coherence length. This introduces serious materials constraints. The present work describes initial explorations of three sputtered multilayer systems in an attempt to observe coupling of the ferromagnetic layers across a superconducting spacer:((a) J.E. Mattson, R.M. Osgood III, C.D. Potter, C.H. Sowers, and S.D. Bader, J. Vac. Sci. Technol. A 15), 1774 (1997); (b) J.E. Mattson, C.D. Potter, M.J. Conover, C.H. Sowers, and S.D. Bader, Phys. Rev. B 55, 70 (1997), and (c) R.M. Osgood III, J.E. Pearson, C.H. Sowers, and S.D. Bader, submitted (1997). (a) Ni/Nb, (b) Fe_4N/NbN, and (c) GdN/NbN. In these systems we have retained thinner superconducting layers than had been achieved previously, but interlayer magnetic coupling is not observed even in the normal state. For Ni/Nb the interfacial Ni loses its moment, which also reduces the superconducting pair-breaking. GdN is an insulating ferromagnet, so itinerancy is sacrificed, and, probably as a result of this, no coupling is observed. Each system gives rise to interesting and anisotropic superconducting properties. Thus, although the goal remains elusive, our search highlights the challenges and opportunities.

  17. Effects of Early Dental Office Visits on Dental Caries Experience

    PubMed Central

    Rozier, R. Gary; Preisser, John S.; Stearns, Sally C.; Lee, Jessica Y.

    2014-01-01

    Objectives. We determined the association between timing of a first dentist office visit before age 5 years and dental disease in kindergarten. Methods. We used North Carolina Medicaid claims (1999–2006) linked to state oral health surveillance data to compare caries experience for kindergarten students (2005–2006) who had a visit before age 60 months (n = 11 394) to derive overall exposure effects from a zero-inflated negative binomial regression model. We repeated the analysis separately for children who had preventive and tertiary visits. Results. Children who had a visit at age 37 to 48 and 49 to 60 months had significantly less disease than children with a visit by age 24 months (incidence rate ratio [IRR] = 0.88; 95% confidence interval [CI] = 0.81, 0.95; IRR = 0.75; 95% CI = 0.69, 0.82, respectively). Disease status did not differ between children who had a tertiary visit by age 24 months and other children. Conclusions. Medicaid-enrolled children in our study followed an urgent care type of utilization, and access to dental care was limited. Children at high risk for dental disease should be given priority for a preventive dental visit before age 3 years. PMID:24134364

  18. Sectioning of multilayers to make a multilayer Laue lens

    SciTech Connect

    Kang, Hyon Chol; Stephenson, G. Brian; Liu Chian; Conley, Ray; Khachatryan, Ruben; Wieczorek, Michael; Macrander, Albert T.; Yan Hanfei; Maser, Joerg; Hiller, Jon; Koritala, Rachel

    2007-04-15

    We report a process to fabricate multilayer Laue lenses (MLL's) by sectioning and thinning multilayer films. This method can produce a linear zone plate structure with a very large ratio of zone depth to width (e.g., >1000), orders of magnitude larger than can be attained with photolithography. Consequently, MLL's are advantageous for efficient nanofocusing of hard x rays. MLL structures prepared by the technique reported here have been tested at an x-ray energy of 19.5 keV, and a diffraction-limited performance was observed. The present article reports the fabrication techniques that were used to make the MLL's.

  19. The Future of Dental Education.

    ERIC Educational Resources Information Center

    Simonsen, Richard J.

    1994-01-01

    The author, a representative of the American Dental Trade Association, identifies major challenges facing dental education in the areas of predoctoral dental education, postdoctoral dental education, and continuing dental education. Ten recommendations address preclinical and clinical courses, licensing examinations, mandatory continuing…

  20. Phase measurement of soft x-ray multilayer mirrors.

    PubMed

    de Rossi, Sébastien; Bourassin-Bouchet, Charles; Meltchakov, Evgueni; Giglia, Angelo; Nannarone, Stefano; Delmotte, Franck

    2015-10-01

    We propose a new model enabling the extraction of the phase of a multilayer mirror from photocurrent measurements in the soft x rays. In this range, the effects of the mean free path of the electrons inside the stack can no longer be neglected, which prevents the phase reconstruction by conventional photocurrent measurements. The new model takes into account this phenomenon and thus extends up to the x rays the applicability range of the technique. This approach has been validated through a numerical and experimental study of chromium/scandium multilayers used near 360 eV. To our knowledge, this work constitutes the first measurement of the phase of a multilayer mirror in the soft x-ray range. PMID:26421544