Deep learning for improving non-destructive grain mapping in 3D

Laboratory X-ray diffraction contrast tomography (LabDCT) is a novel imaging technique for non-destructive 3D characterization of grain structures. An accurate grain reconstruction critically relies on precise segmentation of diffraction spots in the LabDCT images. The conventional method utilizing various filters generally satisfies segmentation of sharp spots in the images, thereby serving as a standard routine, but it also very often leads to over or under segmentation of spots, especially those with low signal-to-noise ratios and/or small sizes. The standard routine also requires a fine tuning of the filtering parameters. To overcome these challenges, a deep learning neural network is presented to efficiently and accurately clean the background noise, thereby easing the spot segmentation. The deep learning network is first trained with input images, synthesized using a forward simulation model for LabDCT in combination with a generic approach to extract features of experimental backgrounds. Then, the network is applied to remove the background noise from experimental images measured under different geometrical conditions for different samples. Comparisons of both processed images and grain reconstructions show that the deep learning method outperforms the standard routine, demonstrating significantly better grain mapping.

Improved grain mapping by laboratory X-ray diffraction contrast tomography

Laboratory diffraction contrast tomography (LabDCT) is a novel technique for non-destructive imaging of the grain structure within polycrystalline samples. To further broaden the use of this technique to a wider range of materials, both the spatial resolution and detection limit achieved in the commonly used Laue focusing geometry have to be improved. In this work, the possibility of improving both grain indexing and shape reconstruction was investigated by increasing the sample-to-detector distance to facilitate geometrical magnification of diffraction spots in the LabDCT projections. LabDCT grain reconstructions of a fully recrystallized iron sample, obtained in the conventional Laue focusing geometry and in a magnified geometry, are compared to one characterized by synchrotron X-ray diffraction contrast tomography, with the latter serving as the ground truth. It is shown that grain indexing can be significantly improved in the magnified geometry. It is also found that the magnified geometry improves the spatial resolution and the accuracy of the reconstructed grain shapes. The improvement is shown to be more evident for grains smaller than 40 µm than for larger grains. The underlying reasons are clarified by comparing spot features for different LabDCT datasets using a forward simulation tool.

A flexible and standalone forward simulation model for laboratory X-ray diffraction contrast tomography

Laboratory X-ray diffraction contrast tomography (LabDCT) has recently been developed as a powerful technique for non-destructive mapping of grain microstructures in bulk materials. As the grain reconstruction relies on segmentation of diffraction spots, it is essential to understand the physics of the diffraction process and resolve all the spot features in detail. To this aim, a flexible and standalone forward simulation model has been developed to compute the diffraction projections from polycrystalline samples with any crystal structure. The accuracy of the forward simulation model is demonstrated by good agreements in grain orientations, boundary positions and shapes between a virtual input structure and that reconstructed based on the forward simulated diffraction projections of the input structure. Further experimental verification is made by comparisons of diffraction spots between simulations and experiments for a partially recrystallized Al sample, where a satisfactory agreement is found for the spot positions, sizes and intensities. Finally, applications of this model to analyze specific spot features are presented.

Gas-Liquid Chromatographic Method for the Analysis of Microencapsulated Ethyl Parathion and Methyl Parathion Insecticides: Collaborative Study

The determination of ethyl parathion in Penncap-E insecticide was studied collaboratively by 14 laboratories. The assay of methyl parathion in Penncap-M insecticide was studied by 8 laboratories. The original method which was adopted official first action for methyl parathion specified dimethoate, which is currently classified as a suspected carcinogen, as the internal standard. The current collaborative efforts were conducted as a supplemental study to evaluate the performance of the new internal standard, bis-2-methoxyethyl phthalate, and to test the gas-liquid chromatographic method for microencapsulated ethyl parathion (internal standard, dibutyl phthalate). The method uses essentially the same grinding and extraction with acetonitrile as the original study. At the 20% methyl parathion level, the standard deviation within laboratories was 0.186%, and among laboratories, 0.737%. Two formulations of ethyl parathion at approximately 16 and 24% were analyzed in replicate on 2 days by the same analyst, and provided excellent agreement within laboratories as well as among laboratories. The standard deviation (pooled) within laboratories was 0.284% and among laboratories, 0.518%. The method has been adopted as official first action.

Boundary migration in a 3D deformed microstructure inside an opaque sample

How boundaries surrounding recrystallization grains migrate through the 3D network of dislocation boundaries in deformed crystalline materials is unknown and critical for the resulting recrystallized crystalline materials. Using X-ray Laue diffraction microscopy, we show for the first time the migration pattern of a typical recrystallization boundary through a well-characterized deformation matrix. The data provide a unique possibility to investigate effects of both boundary misorientation and plane normal on the migration, information which cannot be accessed with any other techniques. The results show that neither of these two parameters can explain the observed migration behavior. Instead we suggest that the subdivision of the deformed microstructure ahead of the boundary plays the dominant role. The present experimental observations challenge the assumptions of existing recrystallization theories, and set the stage for determination of mobilities of recrystallization boundaries.

A method to characterize the roughness of 2-D line features: recrystallization boundaries

A method is presented, which allows quantification of the roughness of nonplanar boundaries of objects for which the neutral plane is not known. The method provides quantitative descriptions of both the local and global characteristics. How the method can be used to estimate the sizes of rough features and local curvatures is also presented. The potential of the method is illustrated by quantification of the roughness of two recrystallization boundaries in a pure Al specimen characterized by scanning electron microscopy.

Plastic Deformation and Recrystallization Studied by the 3-D x-ray Microscope

A newly developed synchrotron instrument – the so-called 3D X-ray microscope – is presented. The instrument is placed at the Materials Science beamline at ESRF and dedicated to local μm scale structural characterization within bulk materials. In this paper, emphasis is on in situ studies of thermomechanical processing. The potential of the instrument for characterization of single nuclei and grains is described and discussed based on both first results and planned experiments.

Watching the growth of bulk grains during recrystallization of deformed metals

We observed the in situ growth of a grain during recrystallization in the bulk of a deformed sample. We used the three-dimensional x-ray diffraction microscope located at the European Synchrotron Radiation Facility in Grenoble, France. The results showed a very heterogeneous growth pattern, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical characterization of microstructures. For recrystallization, the in situ method includes direct measurements of nucleation and boundary migration through a deformed matrix.

Three-dimensional maps of grain boundaries and the stress state of individual grains in polycrystals and powders

A fast and non-destructive method for generating three-dimensional maps of the grain boundaries in undeformed polycrystals is presented. The method relies on tracking of micro-focused high-energy X-rays. It is verified by comparing an electron microscopy map of the orientations on the 2.5 × 2.5 mm surface of an aluminium polycrystal with tracking data produced at the 3DXRD microscope at the European Synchrotron Radiation Facility. The average difference in grain boundary position between the two techniques is 26 µm, comparable with the spatial resolution of the 3DXRD microscope. As another extension of the tracking concept, algorithms for determining the stress state of the individual grains are derived. As a case study, 3DXRD results are presented for the tensile deformation of a copper specimen. The strain tensor for one embedded grain is determined as a function of load. The accuracy on the strain is Δ∊ ≃ 10−4.

Efficient method for determining the glycyrrhizin content of fresh and dried roots, and root extracts, of Glycyrrhiza species

A reliable and efficient method suitable for the selective analysis of the glycyrrhizin content of fresh and dried roots of Glycyrrhiza species and of root extracts is described. The method was optimised for recovery and analysis of glycyrrhizin after conversion to its aglycone, 18 beta-glycyrrhetinic acid. The reversed-phase HPLC system was developed using a sterically protected C8 column that allowed UV detection of the aglycone at 254 mm without interference from co-occurring components. The average recovery through the method was determined at 83%, with a range of 65-99%. Analysis of 150 dried root samples gave levels of glycyrrhizin consistent with earlier reported values. A comparison of post-harvest treatment conditions. showed that the drying of root samples at up to 65 degrees C did not result in any measurable reduction in glycyrrhizin.

Application of high-energy synchrotron radiation for texture studies

A novel experimental technique that employs high-energy synchrotron radiation is used for the investigation of through-thickness texture gradients in two aluminium plates, cold-rolled 40% with either intermediate or small draughts. In these two plates, crystallographic textures are inspected in a large number of layers. Texture maps of pole densities throughout the sample thickness are presented. A texture of the rolling type is developed through the plate thickness after intermediate draught rolling. Pronounced inhomogeneities associated with the shear texture are observed in the sample rolled with small draughts. For selected layers, direct pole figures are compared with those obtained by traditional low-energy X-ray diffraction and by the electron backscattering pattern technique using a scanning electron microscope. A good qualitative agreement between textures measured using the three different techniques is obtained. Experimental aspects and potentials of the new technique are discussed.

Applications of high-energy synchrotron radiation for structural studies of polycrystalline materials

The large penetration power of high-energy X-rays (>60 keV) raises interesting prospects for new types of structural characterizations of polycrystalline materials. It becomes possible in a non-destructive manner to perform local studies, within the bulk of the material, of the fundamental materials physics properties: grain orientations, strain, dislocation densities etc. In favourable cases these properties may be mapped in three dimensions with a spatial resolution that matches the dimensions of the individual grains. Imbedded volumes and interfaces become accessible. Moreover, the high energies allow better in-situ studies of samples in complicated environments (industrial process optimization). General techniques for research in this energy range have been developed using broad-band angle-dispersive methods, on-line two-dimensional detectors and conical slits. Characterizations have been made at the level of the individual grains and grain boundaries as well as on ensembles of grains. The spatial resolution is presently of the order of 10-100 micom. Four examples of applications are presented along with an outlook.

Sertl shelf arthroplasty (BOP procedure) in the treatment of canine hip dysplasia

The BOP/Sertl shelf arthroplasty procedure is not difficult or lengthy. It uses minimal metallic fixation. It is quite physiological with minimal morbidity because there is no change in the bony anatomic pelvis except to create an extension of the lateral rim of the acetabulum. The animal is able to walk the day after surgery. The procedure can be performed bilaterally the same day, thus creating good bony stability and decreasing stretching of the joint capsule, which in turn prevents further subluxation and pain in the hip joint. The aim of this procedure is to return the animal to a satisfactory lifestyle through an effective but less complicated surgical procedure as compared to other available options. This procedure is straightforward and can be done by a surgeon who is familiar with orthopedic surgical techniques and has been trained in this procedure. To date, more than 150 veterinarians have had hands-on training to perform this operation. We are not claiming that this procedure is a cure for CHD; rather, it is a procedure that dramatically slows down the progress of this malady and allows the dog to lead a more normal lifestyle and avoids euthanasia. After 51 months, our study of 200 hips has had a success rate of 99% on the animals available for follow-up as evidenced by returning those animals to a satisfactory lifestyle with stable hips.

Reduction of pulsed gradient settling time in the superconducting magnet of a magnetic resonance instrument

The implementation of electronic compensation for eddy currents to reduce the gradient settling times on a superconducting magnet is described. Field plots inside the magnet indicate the importance of assessing the field changes at several positions in the magnet. The effect of an asymmetry between the gradient coil system and the cryostat is demonstrated. A modified compensation circuit is described to overcome this mechanical asymmetry.

Magnetic resonance imaging of experimental mumps meningoencephalitis in suckling hamsters

Mumps virus-infected and normal newborn hamster brains were imaged with magnetic resonance (MR) within 24 h after birth and serially scanned. Hydrocephalus developed explosively on Day 6 postinfection and progressed until death occurred soon after Day 10. This study demonstrates the utility of MR in the investigation of experimental viral encephalitis in very small laboratory animals.

Pulse sequence design for volume selective excitation in magnetic resonance

The design of a pulse sequence for volume localization in magnetic resonance spectroscopy is described in detail. The sequence is based on the volume selective excitation technique (VSE) proposed by Aue et al. [J. Magn. Reson. 56, 350 (1984)] and overcomes the high rf power requirements of VSE. The implications of various design stages are demonstrated experimentally and by computer simulations.