Non-destructive research on wooden musical instruments: from macroscale to submicron imaging with lab-based XCT systems

X-ray CT scanning is growing of age as a research tool and of essential importance in many disciplines, which is certainly true for the study of wood, given its inherent hierarchical structure. The study of wooden musical instruments is even more challenging since these objects need to be handled with care such that non-destructive imaging is vital. Moreover, the different dimensions of the musical instruments as well as the interest in assessment of the instruments at different scales necessitates flexible scanning modes and equipment. In the framework of COST Action FP1302 WoodMusick, a set of wooden musical instruments has been scanned at UGCT and part of them have been analysed to illustrate the potential of X-ray CT scanning in this field of research. By combining different lab-based systems, a wide range of instruments can be scanned, of which examples are given in this paper for violin and standard recorder. Examples of analysis of board and wall thickness for these instruments are given as well

A flexible and modular X-ray micro and sub-micron CT scanner for multi-resolution and interdisciplinary research

Several types of CT systems are commercially available, but they are typically focusing on one specific range of samples and are therefore limited in terms of resolution or sample size. They come in closed cabinets and have pre-defined acquisition routines. These restrictions are often limiting the experimental freedom necessary to apply X-ray tomography to its full extent as required when the technique is used in a very wide range of applications and imaging resolutions. UGCT has designed and built a modular micro/sub-micron CT scanner with maximal flexibility destined for multi-resolution imaging of samples from many research disciplines. Its dual source / dual detector design with eight motorized axes and in-house developed acquisition software offers the possibility to optimize acquisition depending on the type and size of sample under investigation

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

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

Contributions of X-ray CT to the characterization of natural building stones and their disintegration

This paper highlights the use of the high resolution scanner at the Centre for X-ray Tomography in Ghent, Belgium (UGCT), for the 3D quantitative evaluation of the disintegration of some French natural building stones. Rocks deteriorate when they are exposed to extreme weathering factors such as a combination of water and freeze-thaw cycles or high pressure. The results of those processes can be very diverse: from element migration to crust formation to the origination of micro-cracks. Thanks to its non-destructive character, high resolution computed tomography (CT) turned out to be an excellent monitoring tool as it contributes to the characterization of the internal structure of the natural building stone. X-ray CT also provides a better insight into the micro-structural durability properties of the building stone

Changing The Definition Of The Kilogram:Insights For Psychiatric Disease Classification

Attempts to improve fundamental definitions or classifications are not unique for psychiatry. In a 'hard science' such as metrology-the discipline of measurements in the natural sciences-a major definitional change has been proposed. In 2019, the kilogram will be redefined in terms of a constant of nature instead of a cylinder of platinum-iridium. In this article, we aim to better understand the reasons and procedures for changing definitions by studying the redefinition of the kilogram. In short, the case of the kilogram shows that 1) sometimes the rationale for a redefinition might be clear but the scientific discoveries are not available, and a vast research effort is needed to make progress, 2) progress can be made even in absence of gold standards by reference to the definitions' epistemic aims, and 3) definitions are unlikely to be final as future discoveries might lead to new definitions. These results support the current approach of ongoing, piecemeal revision of psychiatric disease classifications, and stress the importance of robust scientific evidence before changing definitions

The evaluation of Computed Tomography hard- and software tools for micropaleontologic studies on foraminifera

Foraminifera (Forams) are single-celled amoeba-like organisms in the sea, which build a tiny calcareous multi-chambered shell for protection. Their enormous abundance, great variation of shape through time and their presence in all marine deposits made these tiny microfossils the oil companies’ best friend by facilitating the detection of new oil wells. Besides the success of forams in the oil and gas industry, they are also a most powerful tool for reconstructing climate change in the past. The shell of a foraminifer is a tiny gold mine of information both geometrical as chemical. However, until recently the best information on this architecture was only obtained through imaging the outside of a shell with Scanning Electron Microscopy (SEM), giving no clues towards internal structures other than single snapshots through breaking a specimen apart. With X-ray computed tomography (CT) it is possible to overcome this problem and uncover a huge amount of geometrical information without destructing the samples. Using the last generation of micro-CT’s, called nano-CT, because of the sub-micron resolution, it is now possible to perform adequate imaging even on these tiny samples without needing huge facilities. In this research, a comparison is made between different X-ray sources and X-ray detectors and the resulting image resolution. Both sharpness, noise and contrast are very important parameters that will have important effects on the accuracy of the results and on the speed of data-processing. Combining this tomography technique with specific image processing software, called segmentation, it is possible to obtain a 3D virtual representation of the entire forams shell. This 3D virtual object can then be used for many purposes, from which automatic measurement of the chambers size is one of the most important ones. The segmentation process is a combination of several algorithms that are often used in CT evaluation, in this work an evaluation of those algorithms is presented. Difficulties arising when the forams shell is filled with material but it still remains possible to perform adequate segmentation. The void inside the shell corresponds to the chambers of the foram and the inter-chamber connections. Using automatic separation algorithms it is possible to obtain the shape of individual chambers. The results from the segmentation process can then be used to perform a multitude of analysis on each foram. Out of the shells geometry one can derive variations in shell thickness, shell density and shell porosity. Since the geometry of each individual chamber can be derived, it is possible to track chamber size variation for one foram or between two different forams, the difference in orientation and distance between the chambers. In this work the algorithms and procedures have been applied on two forams: A. Pseudouvigerina sp., a benthic foram that lived within the sediments at the seafloor. It dates from the earliest Paleocene, 65 Ma and was collected near Brazos River, Texas. B. Globigerinoides, a modern planktic foram, living in the upper part of the water comlumn in the open ocean. The test settled on the seafloor after death and was recently collected from the seafloor at 2900 m water depth at Nazca Ridge in the eastern Pacific Ocean. It was found that foram A consists of 15 chambers with a total volume of 1.8 x 106 µm³ and shows progressive growth of consecutive chambers (average of 1,5 magnification). After the large globular initial chamber, which indicates asexual reproduction, each chamber is slightly larger than the previous one. In the later stages the chambers develop lateral edges with a thickened margin, leading to a distinct triangular shape in cross section. Foram B on the other hand has a distinct trochospiral coil (like a snail), consisting of 16 chambers with a total volume of 91 x 106 µm³. The entire shell thickens with every successive chamber, so that the initial part of the test is embraced in a thick calcite crust. The chambers grow rapidly in size (average magnification of 2,24 ), which is typical for most planktic foraminifera. The globular shape aids in the buoyancy of the specimen for its planktic way of life

High spectral and spatial resolution X-ray transmission radiography and tomography using a Color X-ray Camera

High resolution X-ray radiography and computed tomography are excellent techniques for non-destructive characterization of an object under investigation at a spatial resolution in the micrometer range. However, as the image contrast depends on both chemical composition and material density, no chemical information is obtained from this data. Furthermore, lab-based measurements are affected by the polychromatic X-ray beam, which results in beam hardening effects. New types of X-ray detectors which provide spectral information on the measured X-ray beam can help to overcome these limitations. In this paper, an energy dispersive CCD detector with high spectral resolution is characterized for use in high resolution radiography and tomography, where a focus is put on the experimental conditions and requirements of both measurement techniques

Disintegration of sedimentary rocks used as building material: evaluation and quantification in 4D

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Potential of X-ray computed tomography for 3D anatomical analysis and microdensitometrical assessment in wood research with focus on wood modification

Studying structure and chemistry of wood and wood-based materials is the backbone of all wood research and many techniques are at hand to do so. A very valuable modality is X-ray computed tomography (CT), able to non-destructively probe the three-dimensional (3D) structure and composition. In this paper, we elaborate on the use of Nanowood, a flexible multi-resolution X-ray CT set-up developed at UGCT, the Ghent University Centre for X-ray Tomography. The technique has been used successfully in many different fields of wood science. It is illustrated how 3D structural and microdensitometrical data can be obtained using different scan set-ups and protocols. Its potential for the analysis of modified wood is exemplified, e.g. for the assessment of wood treated with hydrophobing agents, localisation of modification agents, pathway analysis related to functional tissues, dimensional changes due to thermal treatment, etc. Furthermore, monitoring of transient processes is a promising field of activity too