15,742 research outputs found

    High-contrast x-ray microtomography in dental research

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    © 2017 SPIE. X-ray microtomography (XMT) is a well-established technique in dental research. The technique has been used extensively to explore the complex morphology of the root canal system, and to qualitatively and quantitatively evaluate root canal instrumentation and filling efficacy in extracted teeth; enabling different techniques to be compared. Densitometric information can be used to identify and map demineralized tissue resulting from tooth decay (caries) and, in extracted teeth, the method can be used to evaluate different methods of excavation. More recently, high contrast XMT is being used to investigate the relationship between external insults to teeth and the pulpal reaction. When such insults occur, fluid may flow through dentinal tubules as a result of cracking or porosity in enamel. Over time, there is an increase in mineralization along the paths of the tubules from the pulp to the damaged region in enamel and this can be visualized using high contrast XMT. The scanner used for this employs time-delay integration to minimize the effects of detector inhomogeneity in order to greatly increase the upper limit on signal-to-noise ratio that can be achieved with long exposure times. When enamel cracks are present in extracted teeth, the presence of these pathways indicates that the cracking occurred prior to extraction. At high contrast, growth lines are occasionally seen in deciduous teeth which may have resulted from periods of maternal illness. Various other anomalies in mineralization resulting from trauma or genetic abnormalities can also be investigated using this technique

    New Dimensions in Catalysis Research with Hard X‐Ray Tomography

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    The structure and function of solid catalysts are inseparably linked at length scales from nm to cm and beyond. Hard X-ray tomography offers unique potential for spatially-resolved characterization by combining flexible spatial resolution with a range of chemical contrasts. However, the full capabilities of hard X-ray tomography have not been widely explored in the catalysis community. This review highlights modern advances in hard X-ray tomography using synchrotron radiation. Case studies from model to technical scale illustrate the bright future of X-ray tomography in catalysis research

    The potential of X-ray tomography for research on modified wood

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    This paper exemplifies the use of X-ray tomography hardware and accompanying software for research on modified wood. Structural details on different spatial scales as well as time-dependent phenomena can be visualized, also including quantification of these structural details and probable changes due to treatment. As such, the impact of hydrophobing agents can be studied both structurally as well as regarding the efficacy of their water repellence effect, the anatomical changes of heat treated wood can be visualised and quantified at cell wall level as well as the density changes caused by these treatments, etc. X-ray tomography as such is the pre-eminent tool of the future for wood scientists in general and wood modification researchers more specifically

    Pulmonary arterial remodeling revealed by microfocal x-ray tomography

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    Animal models and micro-CT imaging are useful for understanding the functional consequences of, and identifying the genes involved in, the remodeling of vascular structures that accompanies pulmonary vascular disease. Using a micro-CT scanner to image contrast-enhanced arteries in excised lungs from fawn hooded rats (a strain genetically susceptible to hypoxia induced pulmonary hypertension), we found that portions of the pulmonary arterial tree downstream from a given diameter were morphometrically indistinguishable. This \u27self-consistency\u27 property provided a means for summarizing the pulmonary arterial tree architecture and mechanical properties using a parameter vector obtained from measurements of the contiguous set of vessel segments comprising the longest (principal) pathway and its branches over a range of vascular pressures. This parameter vector was used to characterize the pulmonary vascular remodeling that occurred in rats exposed to a hypoxic (11.5% oxygen) environment and provided the input to a hemodynamic model relating structure to function. The major effect of the remodeling was a longitudinally (pulmonary artery to arterioles) uniform decrease in vessel distensibility that resulted in a 90% increase in arterial resistance. Despite the almost uniform change in vessel distensibility, over 50% of the resistance increase was attributable to vessels with unstressed diameters less than 125 microns

    Characterizing analogue caldera collapse with computerized X-ray tomography

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    Analogue models of caldera collapse were imaged by computerized X-ray tomography (μCT). Interval μCT radiography sequences document ‘2.5D’ surface and internal model deformation in an unprecedented way, and carry the potential for a better understanding of the kinematics of various volcano-tectonic processes, of which caldera collapse is a mere illustration. A semi-automatic subsidence velocity analysis was carried out on radiographs. The developed method is a step towards the quantitative documentation of volcano-tectonic modelling that would render data interpretations immediately comparable to monitoring data available from recent deformation at natural volcanoes