Analysis of Weighted Fraction of Length for Interfacial Gap in Cervical Composite Restorations as a Function of the Number of B-Scans of OCT Volume Scans

In dental research, the morphometric assessment of restorations is a challenge. This also applies to the assessment of the length of interfacial adhesive defects in composite restorations as a measure of tooth-restoration bond failure. The determined mean fractions of interfacial gap length on enamel and dentin interfaces deviate from the true means (N → ∞), depending on the number (Ni) of object layers assessed. Cervical composite restorations were imaged with spectral domain optical coherence tomography (SD-OCT). The mean fractions of interfacial gap length on enamel and dentin were determined for an increasing number of OCT cross-sectional images (B-scans) per restoration and were graphically displayed as a function of the number of B-scans. As the number of B-scans increased, the calculated object means approached a range of ±2.5%. This analysis is appropriate for displaying the relationship between the determined mean fraction of interfacial gap length at the enamel/dentin-restoration interface and the number of B-scans

Assessment of the Axial Resolution of a Compact Gamma Camera with Coded Aperture Collimator

Purpose: Handheld gamma cameras with coded aperture collimators are under investigation for intraoperative imaging in nuclear medicine. Coded apertures are a promising collimation technique for applications such as lymph node localization due to their high sensitivity and the possibility of 3D imaging. We evaluated the axial resolution and computational performance of two reconstruction methods. Methods: An experimental gamma camera was set up consisting of the pixelated semiconductor detector Timepix3 and MURA mask of rank $31$ with round holes of $0.08$mm in diameter in a $0.11$mm thick Tungsten sheet. A set of measurements was taken where a point-like gamma source was placed centrally at $21$ different positions within the range of $12$ to $100$mm. For each source position, the detector image was reconstructed in $0.5$mm steps around the true source position, resulting in an image stack. The axial resolution was assessed by the full width at half maximum (FWHM) of the contrast-to-noise ratio (CNR) profile along the z-axis of the stack. Two reconstruction methods were compared: MURA Decoding and a 3D maximum likelihood expectation maximization algorithm (3D-MLEM). Results: While taking $4{,}400$ times longer in computation, 3D-MLEM yielded a smaller axial FWHM and a higher CNR. The axial resolution degraded from $5.3$mm and $1.8$mm at $12$mm to $42.2$mm and $13.5$mm at $100$mm for MURA Decoding and 3D-MLEM respectively. Conclusion: Our results show that the coded aperture enables the depth estimation of single point-like sources in the near field. Here, 3D-MLEM offered a better axial resolution but was computationally much slower than MURA Decoding, whose reconstruction time is compatible with real-time imaging

Generation of subdivision : hierarchies for efficient occlusion culling of large polygonal models

Veröffentlichung des Wilhelm-Schickard-Institut für Informatik Universität Tübinge

OpenGL-assisted Visibility Queries of Large Polygonal Models

Veröffentlichung des Wilhelm-Schickard-Institut für Informatik Universität Tübinge

Corrosion behaviour of FE and NI-based alloys in solar salt and corrosion mitigation strategies via protective coatings

ABSTRACT: This study investigated the corrosion behaviour of commercial and model Fe- and Ni-based alloys in solar salt at 600°C. The thermal decomposition of nitrate salts led to an increasing concentration of oxidizing agents in the salt melt and thus to a higher corrosion rate. For Fe-based alloys, the oxide scales contained a Na- and Fe-rich outer layer, followed by an inner Cr-rich layer and nitridation as well as Cr-depletion was observed at the scale/metal interface. Furthermore, higher extent of chloride impurities in solar salt, led to a significantly higher corrosion rate for ferritic-martensitic alloys. For Ni-based alloys, the formation of a duplex scale consisting of a NiO outer and Ni-Cr spinel layer showed protective character during isothermal exposure; however even for Ni-based alloys, Cr was detected in the salt melt, which showed evidence for its dissolution in the melt as toxic hexavalent Cr. Diffusion aluminide and electroless Ni-P coatings deposited on cost-efficient ferriticmartensitic alloys led to formation of protective oxide scales and hindered the Cr-dissolution into the salt melt.info:eu-repo/semantics/publishedVersio