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Selected AbstractsEffect of light source and time on the polymerization of resin cement through ceramic veneersJOURNAL OF PROSTHODONTICS, Issue 3 2001Flavio H. Rasetto Odont Purpose The purpose of this study was to evaluate the efficiency of 3 different light sources to polymerize a light curing resin cement beneath 3 types of porcelain veneer materials. Materials and Methods A conventional halogen light, a plasma arc light, and a high intensity halogen light were used to polymerize resin cement (Variolink II; Ivoclar North America Inc, Amherst, NY) through disks of veneer materials. Equal diameter and thickness disks of feldspathic porcelain (Ceramco II; Ceramco Inc, Burlington, NJ), pressable ceramic (IPS Empress; Ivoclar North America Inc), and aluminous porcelain (Vitadur Alpha; Vident Inc, Brea, CA) were used as an interface between the curing light tips and the light polymerized resin cement. The resin cement/veneer combinations were exposed to 4 different photopolymerization time protocols of 5 seconds, 10 seconds, 15 seconds, and 20 seconds for high intensity light units (Apollo 95E [Dental Medical Diagnostic Systems Inc, Westlake Village, CA] and Kreativ 2000 [Kreativ Inc, San Diego, CA]), and 20 seconds, 40 seconds, 60 seconds, and 80 seconds for conventional halogen light (Optilux; Demetron Research Inc, Danbury, CT). A surface hardness test (Knoop indenter) was used to determine the level of photopolymerization of the resin through the ceramic materials with each of the light sources. The data were analyzed by one-way analysis of variance and a post-hoc Scheffe test (p < .05). Results The data indicates that the Variolink II Knoop Hardness Number values vary with the light source, the veneer material, and the polymerization time. For a given light and veneer material, Knoop Hardness Number increases with longer polymerization times. The Kreativ light showed statistically significant differences (p < .05) between all test polymerization times. Use of this light required a polymerization time of greater than 20 seconds to reach maximum resin cement hardness. For samples polymerized with the Apollo light, there were statistically significant (p < .05) differences in surface hardness between samples polymerized at all times, except for the 15-second and 20-second times. Samples polymerized with the halogen light showed no statistically significant (p < .05) differences in hardness between polymerization times of 60 seconds and 80 seconds. Conclusions High intensity curing lights achieve adequate polymerization of resin cements through veneers in a markedly shorter time period than the conventional halogen light. However, the data in this report indicate that a minimum exposure time of 15 seconds with the Kreativ light and 10 seconds with the Apollo 95E light should be used to polymerize the Variolink II resin, regardless of the composition of the veneer. Conventional halogen lights required a correspondingly greater polymerization time of 60 seconds. [source] COMPETITION FOR MARKET SHARE OR FOR MARKET SIZE: OLIGOPOLISTIC EQUILIBRIA WITH VARYING COMPETITIVE TOUGHNESS,INTERNATIONAL ECONOMIC REVIEW, Issue 3 2007Claude D'Aspremont For an industry producing a composite commodity, we propose a comprehensive concept of oligopolistic equilibrium, allowing for a parameterized continuum of regimes varying in competitive toughness. Each firm sets simultaneously its price and its quantity under two constraints, relative to its market share and to market size. The price and the quantity equilibrium outcomes always belong to the set of oligopolistic equilibria. When firms are identical and we let their number increase, any sequence of symmetric oligopolistic equilibria converges to the monopolistic competition outcome. Further results are derived in the symmetric CES case, concerning in particular the collusive solution enforceability. [source] Postnatal maturation of Na+, K+, 2Cl, cotransporter expression and inhibitory synaptogenesis in the rat hippocampus: an immunocytochemical analysisEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2002Serge Marty Abstract GABA, a major inhibitory neurotransmitter, depolarizes hippocampal pyramidal neurons during the first postnatal week. These depolarizations result from an efflux of Cl, through GABAA -gated anion channels. The outward Cl, gradient that provides the driving force for Cl, efflux might be generated and maintained by the Na+, K+, 2Cl, cotransporter (NKCC) that keeps intracellular Cl, concentration above electrochemical equilibrium. The developmental pattern of expression of the cotransporter in the hippocampus is not known. We studied the postnatal distribution pattern of NKCC in the hippocampus using a monoclonal antibody (T4) against a conserved epitope in the C-terminus of the cotransporter molecule. We also examined the temporal relationships between the developmental pattern of NKCC expression and the formation of perisomatic GABAergic synapses. This study was aimed at determining, with antivesicular inhibitory amino acid transporter (VIAAT) antibodies, whether perisomatic GABAergic synapses are formed preferentially at the time when GABA is depolarizing. During the first postnatal week, NKCC immunolabelling was restricted to cell bodies in the pyramidal cell layer and in the strata oriens and radiatum. In contrast, at postnatal day 21 (P21) and in adult animals little or no labelling occurred in cell bodies; instead, a prominent dendritic labelling appeared in both pyramidal and nonpyramidal neurons. The ultrastructural immunogold study in P21 rat hippocampi corroborated the light-microscopy results. In addition, this study revealed that a portion of the silver-intensified colloidal gold particles were located on neuronal plasmalemma, as expected for a functional cotransporter. The formation of inhibitory synapses on perikarya of the pyramidal cell layer was a late process. The density of VIAAT-immunoreactive puncta in the stratum pyramidale at P21 reached four times the P7 value in CA3, and six times the P7 value in CA1. Electron microscopy revealed that the number of synapses per neuronal perikaryal profile in the stratum pyramidale of the CA3 area at P21 was three times higher than at P7, even if a concomitant 20% increase in the area of these neuronal perikaryal profiles occurred. It is concluded that, in hippocampal pyramidal cells, there is a developmental shift in the NKCC localization from a predominantly somatic to a predominantly dendritic location. The presence of NKCC during the first postnatal week is consistent with the hypothesis that this transporter might be involved in the depolarizing effects of GABA. The depolarizing effects of GABA may not be required for the establishment of the majority of GABAergic synapses in the stratum pyramidale, because their number increases after the first postnatal week, when GABA action becomes hyperpolarizing. [source] Determination of genomic copy number with quantitative microsphere hybridization,,HUMAN MUTATION, Issue 4 2006Heather L. Newkirk Abstract We developed a novel quantitative microsphere suspension hybridization (QMH) assay for determination of genomic copy number by flow cytometry. Single copy (sc) products ranging in length from 62 to 2,304 nucleotides [Rogan et al., 2001; Knoll and Rogan, 2004] from ABL1 (chromosome 9q34), TEKT3 (17p12), PMP22 (17p12), and HOXB1 (17q21) were conjugated to spectrally distinct polystyrene microspheres. These conjugated probes were used in multiplex hybridization to detect homologous target sequences in biotinylated genomic DNA extracted from fixed cell pellets obtained for cytogenetic studies. Hybridized targets were bound to phycoerythrin-labeled streptavidin; then the spectral emissions of both target and conjugated microsphere were codetected by flow cytometry. Prior amplification of locus-specific target DNA was not required because sc probes provide adequate specificity and sensitivity for accurate copy number determination. Copy number differences were distinguishable by comparing the mean fluorescence intensities (MFI) of test probes with a biallelic reference probe in genomic DNA of patient samples and abnormal cell lines. Concerted 5, ABL1 deletions in patient samples with a chromosome 9;22 translocation and chronic myelogenous leukemia were confirmed by comparison of the mean fluorescence intensities of ABL1 test probes with a HOXB1 reference probe. The relative intensities of the ABL1 probes were reduced to 0.59±0.02 &!ndash;fold in three different deletion patients and increased 1.42±0.01 &!ndash;fold in three trisomic 9 cell lines. TEKT3 and PMP22 probes detected proportionate copy number increases in five patients with Charcot-Marie-Tooth Type 1a disease and chromosome 17p12 duplications. Thus, the assay is capable of distinguishing one allele and three alleles from a biallelic reference sequence, regardless of chromosomal context. Hum Mutat 27(4), 376,386, 2006. © 2006 Wiley-Liss, Inc. [source] Flow characteristics of a cold helium arc-jet plasma along open field linesIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2009Kazuyuki Yoshida Member Abstract We experimentally study plasma parameters including ion acoustic Mach number of expanding cold helium plasma jet with an electron temperature of less than 1 eV flowing along open field lines. It is experimentally found that the ion Mach number increases from 1 to 3, and that the plasma potential decreases by about 1 V. We discuss the experimental results based on a quasi one-dimensional flow model in which the plasma is assumed to be quasi-neutral and in a state of thermodynamic equilibrium. Our model describes the ion acceleration, the axial profiles of the potential drop, and the electron temperature/density. The model also shows that the helium ions are accelerated both by the electric field and by the increasing cross-sectional area of the transonic flow. After the ion acceleration, the ion Mach number decreases and the electron temperature increases. These phenomena are discussed in terms of a shock wave. It is noted that the electron density decreases even in the shock wave. This is discussed in terms of rapid recombination because of the low electron temperature. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Mobility of shear thinning viscous drops in a shear Newtonian carrying flow using DR-BEMINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009M. Giraldo Abstract The study of drop behaviour has attracted great interest in the last years due to its importance in different industrial and biological systems. Most available works focus on Newtonian drops, excluding some very important applications such as polymer mixing. Simulations of non-Newtonian drops have had only limited study, mostly in time-dependent rheologies or simple flow cases. This work presents a boundary-only formulation based on the dual reciprocity method to model the motion and deformation of non-Newtonian shear thinning drops due to a shear Newtonian unbounded carrying flow. Pair-wise interactions at low Reynolds number between two viscous shear thinning non-Newtonian drops are numerically simulated in order to obtain mobility magnitudes under linear shear flow of different strengths. Separation of the drops in the direction perpendicular to the imposed flow field at high capillary number (small surface tension) and low viscosity ratio was favoured by shear thinning, increasing in magnitude as the capillary number increases and the viscous ratio decreases. Higher values of this separation occur at higher values of the viscosity ratio when compared with the case of Newtonian drops. In order to obtain a good physical description of the non-Newtonian drop behaviour, while maintaining good computational performance, the non-Newtonian viscosity is made to obey the truncated power law model. Copyright © 2008 John Wiley & Sons, Ltd. [source] Numerical solutions of 2-D steady incompressible driven cavity flow at high Reynolds numbersINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2005E. Erturk Abstract Numerical calculations of the 2-D steady incompressible driven cavity flow are presented. The Navier,Stokes equations in streamfunction and vorticity formulation are solved numerically using a fine uniform grid mesh of 601 × 601. The steady driven cavity flow solutions are computed for Re , 21 000 with a maximum absolute residuals of the governing equations that were less than 10,10. A new quaternary vortex at the bottom left corner and a new tertiary vortex at the top left corner of the cavity are observed in the flow field as the Reynolds number increases. Detailed results are presented and comparisons are made with benchmark solutions found in the literature. Copyright © 2005 John Wiley & Sons, Ltd. [source] Dispersion and stability analyses of the linearized two-dimensional shallow water equations in boundary-fitted co-ordinatesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2003S. Sankaranarayanan Abstract In the present investigation, a Fourier analysis is used to study the phase and group speeds of a linearized, two-dimensional shallow water equations, in a non-orthogonal boundary-fitted co-ordinate system. The phase and group speeds for the spatially discretized equations, using the second-order scheme in an Arakawa C grid, are calculated for grids with varying degrees of non-orthogonality and compared with those obtained from the continuous case. The spatially discrete system is seen to be slightly dispersive, with the degree of dispersivity increasing with an decrease in the grid non-orthogonality angle or decrease in grid resolution and this is in agreement with the conclusions reached by Sankaranarayanan and Spaulding (J. Comput. Phys., 2003; 184: 299,320). The stability condition for the non-orthogonal case is satisfied even when the grid non-orthogonality angle, is as low as 30° for the Crank Nicolson and three-time level schemes. A two-dimensional wave deformation analysis, based on complex propagation factor developed by Leendertse (Report RM-5294-PR, The Rand Corp., Santa Monica, CA, 1967), is used to estimate the amplitude and phase errors of the two-time level Crank,Nicolson scheme. There is no dissipation in the amplitude of the solution. However, the phase error is found to increase, as the grid angle decreases for a constant Courant number, and increases as Courant number increases. Copyright © 2003 John Wiley & Sons, Ltd. [source] Transition from vortex to wall driven turbulence production in the Taylor,Couette system with a rotating inner cylinderINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2002W. M. J. Batten Abstract Axisymmetrically stable turbulent Taylor vortices between two concentric cylinders are studied with respect to the transition from vortex to wall driven turbulent production. The outer cylinder is stationary and the inner cylinder rotates. A low Reynolds number turbulence model using the k - , formulation, facilitates an analysis of the velocity gradients in the Taylor,Couette flow. For a fixed inner radius, three radius ratios 0.734, 0.941 and 0.985 are employed to identify the Reynolds number range at which this transition occurs. At relatively low Reynolds numbers, turbulent production is shown to be dominated by the outflowing boundary of the Taylor vortex. As the Reynolds number increases, shear driven turbulence (due to the rotating cylinder) becomes the dominating factor. For relatively small gaps turbulent flow is shown to occur at Taylor numbers lower than previously reported. Copyright © 2002 John Wiley & Sons, Ltd. [source] Jordan's and other ecogeographical rules, and the vertebral number in fishesJOURNAL OF BIOGEOGRAPHY, Issue 3 2008R. M. McDowall Abstract Aim, To explore variation in the number of vertebrae in fishes in the context of Jordan's rule and other ecogeographical rules. Location, Global. Methods, The study is based on literature review. Results, The number of vertebrae varies very widely across the diversity of fishes. Jordan's rule states that vertebral number increases with latitude, and this is widely attributed to ambient temperatures during ontogeny of individual fishes. However, the number of vertebrae may depend on both the ontogenetic environment and inheritance. Diverse other aspects of fish development and ecology are suggested as influencing vertebral number, including fish size, phyletic position, body shape and swimming mode. Main conclusions, The number of different factors that influence the number of vertebrae in fishes makes for highly complex patterns of variation, and means that unravelling causes is difficult. The question needs to be addressed at the population/species/species group scale; moreover, the lack of discrimination between environmental and inherited causes of variation adds to the complexity. [source] Organic,Inorganic Interactions in Poly(trimethylene carbonate),Titania HybridsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2009Elisa Cortecchia Abstract Polycarbonate,titania hybrids have been synthesized by a sol,gel reaction, starting from poly(trimethylene carbonate) (PTMC) and titanium isoproproxide in different ratios. PTMC with a given chain length was obtained by ring opening polymerization. FT-IR spectra reveal the presence of TiOC covalent bonds between organic and inorganic phases, and their number increases with increasing inorganic phase content. Solvent extractions show that hybrid soluble fraction contains low PTMC chains with isopropoxide ends, which suggests that TiOC bond formation is mainly promoted by transesterification reactions of isopropyl alcohol onto the polymer chain, catalyzed by Ti compounds. Hybrid thermal properties reflect the combined effect of the decrease of PTMC molecular weight and of bond formation between PTMC and the inorganic network. The nanometric dimension of the TiO2 domains, confirmed by atomic force microscopy, provides optically transparent hybrids. [source] PLASTICITY IN QUEEN NUMBER AND SOCIAL STRUCTURE IN THE INVASIVE ARGENTINE ANT (LINEPITHEMA HUMILE)EVOLUTION, Issue 10 2002Krista K. Ingram Abstract., In many polygynous social insect societies, ecological factors such as habitat saturation promote high queen numbers by increasing the cost of solitary breeding. If polygyny is associated with constrained environments, queen number in colonies of invasive social insects should increase as saturation of their new habitat increases. Here I describe the variation in queen number, nestmate relatedness, and nest size along a gradient of time since colonization in an invading population of Argentine ants (Linepithema humile) in Haleakala, Hawaii. Nest densities in this population increase with distance from the leading edge of the invasion, reaching a stable density plateau approximately 80 m from the edge (> 2 years after colonization). Although the number of queens per nest in Haleakala is generally lower than previously reported for Argentine ants, there is significant variation in queen number across this population. Both the observed and effective queen numbers increase across the density gradient, and nests in the center of the population contain queen numbers three to nine times higher than those on the edge of the invasion. The number of workers per nest is correlated with queen number, and nests in the center are six times larger than nests at the edge. Microsatellite analysis of relatedness among nestmates reveals that all nests in the Haleakala population are characterized by low relatedness and have evidence of multiple reproducing queens. Relatedness values are significantly lower in nests in the center of the population, indicating that the number of reproducing queens is greater in areas of high nest density. The variation in queen number and nestmate relatedness in this study is consistent with expectations based on changes in ecological constraints during the invasion of a new habitat, suggesting that the social structure of Argentine ant populations is strongly influenced by ecological factors. Flexibility in social structure may facilitate persistence in variable environments and may also confer significant advantages to a species when introduced into new areas. [source] Undirected motility of filamentous cyanobacteria produces reticulate matsGEOBIOLOGY, Issue 3 2010R. N. SHEPARD The roles of biology in the morphogenesis of microbial mats and stromatolites remain enigmatic due to the vast array of physical and chemical influences on morphology. However, certain microbial behaviors produce complex morphological features that can be directly attributed to motility patterns. Specifically, laboratory experiments with a strain of the cyanobacteria Pseudanabaena demonstrate that distinctive morphologies arise from the undirected gliding and colliding of filaments. When filamentous cells collide, they align and clump, producing intersecting ridges surrounding areas with low cell density, i.e. reticulate structures. Cell motility is essential for the development of reticulates and associated structures: filaments organize into reticulates faster than cell division and growth, and conditions that inhibit motility also inhibit reticulate formation. Cell density of the inoculum affects the frequency of cell,cell collisions, and thus the time required for biofilm organization into reticulate structures. This also affects the specific geometry of the reticulates. These patterns are propagated into larger structures as cyanobacterial cell numbers increase and cells remain motile. Thus, cell motility is important for templating and maintaining the morphology of these microbial communities, demonstrating a direct link between a microbial behavior and a community morphology. Reticulate geometries have been identified in natural microbial mats as well as in the fossil record, and these structures can be attributed to the motility of filamentous bacteria. [source] | |||||||||||||