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Uniform Layer (uniform + layer)
Selected AbstractsHVPE Growth of GaN on a GaN Templated (111) Si SubstratePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003Y. Honda Abstract The hydride vapor phase epitaxial (HVPE) growth of GaN was attempted on a (111) Si substrate. In order to suppress the chemical reaction of the Si at high temperatures, the surface of the substrate was covered by a thin SiO2 film or GaN pyramids which were grown by selective metalorganic vapor phase epitaxy (MOVPE). The GaN pyramids served as the seeds for the following HVPE growth of GaN. Uniform layer of 12 ,m thick wurtzite GaN was achieved successfully. The full width at half maximum (FWHM) of (0004) X-ray rocking curve was 450 arcsec. The cathode luminescence (CL) spectra at 4.2 K exhibited a strong band edge emission peak of which FWHM was as broad as 30.3 meV. [source] Solvent-Assisted Decal Transfer Lithography by Oxygen-Plasma Bonding and Anisotropic SwellingADVANCED MATERIALS, Issue 22 2010Pilnam Kim Solvent-assisted decal transfer lithography (DTL) enables the formation of well-defined micro-/nanostructures over a large area (,4 in. wafer) by combining irreversible oxygen bonding and anisotropic swelling of poly(dimethoxylsiloxane) (PDMS). Such swelling-induced stress gradient allows for cohesion failure of the skin layer upon removal of the stamp, leaving behind a highly uniform layer (,100,nm). [source] Assessing the impact of the hydraulic properties of a crusted soil on overland flow modelling at the field scaleHYDROLOGICAL PROCESSES, Issue 8 2006Nanée Chahinian Abstract Soil surface crusts are widely reported to favour Hortonian runoff, but are not explicitly represented in most rainfall-runoff models. The aim of this paper is to assess the impact of soil surface crusts on infiltration and runoff modelling at two spatial scales, i.e. the local scale and the plot scale. At the local scale, two separate single ring infiltration experiments are undertaken. The first is performed on the undisturbed soil, whereas the second is done after removal of the soil surface crust. The HYDRUS 2D two-dimensional vertical infiltration model is then used in an inverse modelling approach, first to estimate the soil hydraulic properties of the crust and the subsoil, and then the effective hydraulic properties of the soil represented as a single uniform layer. The results show that the crust hydraulic conductivity is 10 times lower than that of the subsoil, thus illustrating the limiting role the crust has on infiltration. Moving up to the plot scale, a rainfall-runoff model coupling the Richards equation to a transfer function is used to simulate Hortonian overland flow hydrographs. The previously calculated hydraulic properties are used, and a comparison is undertaken between a single-layer and a double-layer representation of the crusted soil. The results of the rainfall-runoff model show that the soil hydraulic properties calculated at the local scale give acceptable results when used to model runoff at the plot scale directly, without any numerical calibration. Also, at the plot scale, no clear improvement of the results can be seen when using a double-layer representation of the soil in comparison with a single homogeneous layer. This is due to the hydrological characteristics of Hortonian runoff, which is triggered by a rainfall intensity exceeding the saturated hydraulic conductivity of the soil surface. Consequently, the rainfall-runoff model is more sensitive to rainfall than to the subsoil's hydrodynamic properties. Therefore, the use of a double-layer soil model to represent runoff on a crusted soil does not seem necessary, as the increase of precision in the soil discretization is not justified by a better performance of the model. Copyright © 2005 John Wiley & Sons, Ltd. [source] A comparison of spreader penetration depth and load required during lateral condensation in teeth prepared using various root canal preparation techniquesINTERNATIONAL ENDODONTIC JOURNAL, Issue 8 2005S. F. Dulaimi Abstract Aim, To compare the influence of various root canal preparation techniques on spreader penetration depth and load required during lateral condensation with gutta-percha and sealer. Methodology, Eighty extracted human teeth with single and straight canals were used. Twenty teeth were instrumented using one of four root canal preparation techniques. The four preparation techniques were: step-back technique without Gates-Glidden drills, step-back technique with Gates-Glidden drills, crown-down pressureless technique and hybrid technique (step-down/step-back). After root canal preparation had been completed a simulated periodontal ligament was fabricated from a uniform layer of silicone impression material. The roots were then mounted in an acrylic resin to simulate the physical condition found in tooth socket. A standardized stainless steel hand spreader of the same size as the master apical file was mounted in an Instron testing machine and lateral compaction with gutta-percha and sealer was performed. The load value was recorded from the Instron testing machine. The spreader penetration depths were measured with an endodontic ruler. The data obtained were analysed statistically using anova and Student's t -tests. Results, No significant difference in initial spreader load needed to condense the master cone was found amongst the four canal preparation techniques (P > 0.05). The step-back technique with Gates-Glidden drills and the hybrid technique demonstrated the least difference between the initial spreader penetration and the working length (mean 1.925 and 2.25 mm, respectively). The step-back technique without Gates-Glidden drills and the crown-down pressureless technique had the greatest difference between initial spreader penetration and the working length (mean 4.425 and 4.75 mm, respectively). Conclusion, The flare created by canal preparation affected spreader penetration depth, but had no effect on the spreader load. [source] Carbon Nanofibers Uniformly Grown on ,-Alumina Washcoated Cordierite Monoliths,ADVANCED MATERIALS, Issue 12 2006E. García-Bordejé A uniform layer of carbon nanofibers is grown on a cordierite monolith by first coating the monolith with a thin layer of ,-alumina. The nanofibers form a thick, uniform layer on the monolith walls as shown in the figure, leading to the formation of a mesoporous and mechanically robust composite. The absence of microporosity in the composite and the ability to tune the thickness of the nanofiber layer suggests that these nanofibers/monolith composites may be useful as catalyst supports for liquid-phase catalytic reactions. [source] Protective effect of Copalite surface coating on mercury release from dental amalgam following treatment with carbamide peroxideDENTAL TRAUMATOLOGY, Issue 3 2000I. Rotstein Abstract , The effect of Copalite coating on mercury release from dental amalgam following treatment with 10%, 20%, 30% and 40% carbamide peroxide was assessed in vitro, using a cold-vapour atomic absorption Mercury Analyzer System. Eighty samples of dental amalgam were automatically mixed in a dental amalgamator and condensed into silicon embedding molds. Forty amalgam samples were coated with three uniform layers of Copalite intermediary varnish and the other 40 samples were left uncoated. The coated and non-coated amalgam samples were exposed for 24 h to 10%, 20%, 30% or 40% carbamide peroxide preparations and compared with samples exposed to phosphate buffer. In the non-coated samples a significant increase of mercury concentration in solution was found following exposure to all carbamide peroxide preparations tested. Mercury concentration was directly related to carbamide peroxide concentration. In the Copalite-coated samples, significantly lower concentrations of mercury in solution were found as compared to the non-coated samples (P<0.01). In conclusion, exposure of amalgam restorations to 10%,40% carbamide peroxide-based bleaching agents increased the mercury release. Pre-coating of the external amalgam surfaces with Copalite significantly reduced the release of mercury. [source] | ||||||||||