An orientation-space super sampling technique for six-dimensional diffraction contrast tomography

Diffraction contrast tomography (DCT) is an X-ray full-field imaging technique that allows for the non-destructive three-dimensional investigation of polycrystalline materials and the determination of the physical and morphological properties of their crystallographic domains, called grains. This task is considered more and more challenging with the increasing intra-granular deformation, also known as orientation-spread. The recent introduction of a sixdimensional reconstruction framework in DCT (6D-DCT) has proven to be able to address the intra-granular crystal orientation for moderately deformed materials. The approach used in 6D-DCT, which is an extended sampling of the six-dimensional combined position-orientation space, has a linear scaling between the number of sampled orientations, which determine the orientation-space resolution of the problem, and computer memory usage. As a result, the reconstruction of more deformed materials is limited by their high resource requirements from a memory and computational point of view, which can easily become too demanding for the currently available computer technologies. In this article we propose a super-sampling method for the orientation-space representation of the six-dimensional DCT framework that enables the reconstruction of more deformed cases by r

Efficient passive network description of IC conducted emission models for model reduction

This article adresses the model reduction of IC conducted emission models. A method to efficiently deal with the high number of independent sources in IC conducted emission models, which are a strong limitation for model order reduction, is presented. A network alteration is proposed, which allows for a much higher model reduction than standard approaches. The system of the altered network can be more efficiently reduced with standard model order reduction algorithms in order to speed up frequency-simulations. Synthesising the reduced system into a passive electrical network enables fast time-simulations to be made with circuit simulators. The whole procedure is validated by reducing an example of an IC conducted emission model of an 32 Bit microcontroller.BMBF/01M 3169 ABMBF/01M 3169 DBMBF/01M 3169

Model order reduction of linear time invariant systems

This paper addresses issues related to the order reduction of systems with multiple input/output ports. The order reduction is divided up into two steps. The first step is the standard order reduction method based on the multipoint approximation of system matrices by applying Krylov subspace. The second step is based on the rejection of the weak part of a system. To recognise the weak system part, Lyapunov equations are used. Thus, this paper introduces efficient solutions of the Lyapunov equations for port to port subsystems.BMBF/01 M 3169

X-ray orientation microscopy using topo-tomography and multi-mode diffraction contrast tomography

Polycrystal orientation mapping techniques based on full-field acquisition schemes like X-ray Diffraction Contrast Tomography and certain other variants of 3D X-ray Diffraction or near-field High Energy Diffraction Microscopy enable time efficient mapping of 3D grain microstructures. The spatial resolution obtained with this class of monochromatic beam X-ray diffraction imaging approaches remains typically below the ultimate spatial resolution achievable with X-ray imaging detectors. Introducing a generalised reconstruction framework enabling the combination of acquisitions with different detector pixel size and sample tilt settings provide a pathway towards 3D orientation mapping with a spatial resolution approaching the one of state of the art X-ray imaging detector systems

Monitoring grain boundary migration during recrystallisation using topotomography

International audienceThe growth of a single grain during recrystallisation into a mildly deformed {001}100 oriented single crystal has been monitored by synchrotron radiation using the topotomo technique. The formation and migration of individual facets is analysed using a new method which measures distances between grain boundary segments at different time steps along parallel lines normal to the facet plane. One facet is shown to move with a constant rate, while it remains planar and keeps the same boundary plane orientation. The formation of another facet, which is analysed in detail, reveals that first a planar boundary with a different orientation forms before it changes its boundary plane orientation into that of the final facet. It is argued that the local microstructural configuration in front of moving grain boundaries has a considerable influence on the kinetics of individual boundary segments and facets

Dark-field X-ray microscopy for multiscale structural characterization

Many physical and mechanical properties of crystalline materials depend strongly on their internal structure, which is typically organized into grains and domains on several length scales. Here we present dark-field X-ray microscopy; a non-destructive microscopy technique for the three-dimensional mapping of orientations and stresses on lengths scales from 100 nm to 1 mm within embedded sampling volumes. The technique, which allows ‘zooming’ in and out in both direct and angular space, is demonstrated by an annealing study of plastically deformed aluminium. Facilitating the direct study of the interactions between crystalline elements is a key step towards the formulation and validation of multiscale models that account for the entire heterogeneity of a material. Furthermore, dark-field X-ray microscopy is well suited to applied topics, where the structural evolution of internal nanoscale elements (for example, positioned at interfaces) is crucial to the performance and lifetime of macro-scale devices and components thereof

Three-dimensional full-field X-ray orientation microscopy

International audienceA previously introduced mathematical framework for full-field X-ray orientation microscopy is for the first time applied to experimental near-field diffraction data acquired from a polycrystalline sample. Grain by grain tomographic reconstructions using convex optimization and prior knowledge are carried out in a six-dimensional representation of position-orientation space, used for modelling the inverse problem of X-ray orientation imaging. From the 6D reconstruction output we derive 3D orientation maps, which are then assembled into a common sample volume. The obtained 3D orientation map is compared to an EBSD surface map and local misorientations, as well as remaining discrepancies in grain boundary positions are quantified. The new approach replaces the single orientation reconstruction scheme behind X-ray diffraction contrast tomography and extends the applicability of this diffraction imaging technique to material micro-structures exhibiting sub-grains and/or intra-granular orientation spreads of up to a few degrees. As demonstrated on textured sub-regions of the sample, the new framework can be extended to operate on experimental raw data, thereby bypassing the concept of orientation indexation based on diffraction spot peak positions. This new method enables fast, three-dimensional characterization with isotropic spatial resolution, suitable for time-lapse observations of grain microstructures evolving as a function of applied strain or temperature

4D characterization of metals by 3DXRD

31st Riso International Symposium on Materials Science, Roskilde, DENMARK, SEP 06-10, 2010International audienceThe status of 3DXRD microscopy is reviewed, with a special view to applications in metallurgy. Various approaches are compared in terms of perfounance. In addition several recent advances are presented, such as a 3D grain map with an unprecedented spatial resolution of 500 nm, first results from the commissioning of a novel 3D detector set-up and a validation of the box-scan procedure

Association between Antibodies to the MR 67,000 Isoform of Glutamate Decarboxylase (GAD) and Type 1 (Insulin-Dependent) Diabetes Mellitus with Coexisting Autoimmune Polyendocrine Syndrome Type II

By using an immunoprecipitation assay, we analysed reactivity of autoantibodies to human recombinant GAD65 and GAD67 in sera from patients with autoimmune polyendocrine syndrome Type II (APS II) with and without Type 1 (insulin-dependent) diabetes mellitus (IDDM) compared to patients with organ-specific autoimmunity. Overall antibodies to GAD65 were correlated with IDDM in all study groups, whereas GAD67 antibodies were associated with IDDM when APS II coexists. Antibodies to GAD65 and GAD67 were detected in 13 (44.8%) and 7 (24.1%) out of 29 APS II patients with IDDM, but in only 4 (13.8%) and 2 (6.9%) out of 29 APS II patients without IDDM, respectively (p < 0.05). In short-standing IDDM (< 1 year), antibodies to GAD67 were significantly more frequent in patients with APS II (5 of 9 [55.6%] subjects) compared to matched diabetic patients without coexisting polyendocrinopathy (1 of 18 [5.6%] subjects) (p < 0.02). The levels of GAD65 (142 ± 90 AU) and GAD67 antibodies (178 ± 95 AU) were significantly higher in patients with polyglandular disease than in patients with isolated IDDM (91 ± 85 AU and 93 ± 57 AU) (p < 0.02). Interestingly, all 11 GAD67 antibody positive subjects also had GAD65 antibodies (p < 0.0001), and in 10 of 11 anti-GAD67 positive sera the GAD67 antibodies could be blocked by either GAD67 or GAD65, suggesting the presence of cross-reactive autoantibodies. No correlation was observed between GAD antibodies and age, sex or any particular associated autoimmune disease, besides IDDM. GAD antibodies were present in only 1 of 6 (16.7%) patients with APS Type I, in 1 of 26 (3.9%) patients with autoimmune thyroid disease but in none of the patients with Addison's disease (n = 16), pernicious anaemia (n = 7) or normal controls (n = 50). Our data suggest distinct antibody specificities reactive to GAD isoforms in APS II and IDDM, which might reflect different mechanisms of autoimmune response in IDDM with coexisting autoimmune polyendocrine autoimmunity

Creating ecologically sound buildings by integrating ecology, architecture and computational design

1. Research is revealing an increasing number of positive effects of nature for humans. At the same time, biodiversity in cities, where most humans live, is often low or in decline. Tangible solutions are needed to increase urban biodiversity. 2. Architecture is a key discipline that has considerable influence on the built-up area of cities, thereby influencing urban biodiversity. In general, architects do not design for biodiversity. Conversely, urban conservation planning generally focuses on the limited space free of buildings and does not embrace architecture as an important discipline for the creation of urban green infrastructure. 3. In this paper, we argue that the promotion of biodiversity needs to become a key driving force of architectural design. This requires a new multi-species design paradigm that considers both human and non-human needs. Such a design approach needs to maintain the standards of the architectural profession, including the aim to increase the well-being of humans in buildings. Yet, it also needs to add other stakeholders, organisms such as animals, plants and even microbiota. New buildings designed for humans and other inhabitants can then increase biodiversity in cities and also increase the benefits that humans can derive from close proximity to nature. 4. We review the challenges that this new design approach poses for both architecture and ecology and show that multi-species-design goes beyond existing approaches in architecture and ecology. The new design approach needs to make ecological knowledge available to the architectural design process, enabling practitioners to find architectural solutions that can facilitate synergies from a multi-species perspective. 5. We propose that a first step in creating such a multi-species habitat is the design of buildings with an ecolope, a multi criteria-designed building envelope that takes into account the needs of diverse organisms. Because there is no framework to design such an ecolope, we illustrate how multi-species design needs to draw on knowledge from ecology, as well as architecture, and design computation. 6. We discuss how architectures designed via a multi-species approach can be an important step in establishing beneficial human-nature relationships in cities, and contribute to human well-being and biodiversity conservation.Read the free Plain Language Summary for this article on the Journal blog