Acoustic emission signal processing framework to identify fracture in aluminum alloys

Acoustic emission (AE) is a common nondestructive evaluation tool that has been used to monitor fracture in materials and structures. The direct connection between AE events and their source, however, is difficult because of material, geometry and sensor contributions to the recorded signals. Moreover, the recorded AE activity is affected by several noise sources which further complicate the identification process. This article uses a combination of in situ experiments inside the scanning electron microscope to observe fracture in an aluminum alloy at the time and scale it occurs and a novel AE signal processing framework to identify characteristics that correlate with fracture events. Specifically, a signal processing method is designed to cluster AE activity based on the selection of a subset of features objectively identified by examining their correlation and variance. The identified clusters are then compared to both mechanical and in situ observed microstructural damage. Results from a set of nanoindentation tests as well as a carefully designed computational model are also presented to validate the conclusions drawn from signal processing

Optimization of acoustic emission data clustering by a genetic algorithm method

cited By 18International audienceThe segmentation of acoustic emission data collected during mechanical tests is one of the current challenges to allow further analysis of damaged materials. Among the existing clustering methods, one of the most widely used is the k-means algorithm. In this paper, a genetic algorithm-based approach is presented. Data sets derived from experimental AE data are processed to highlight the contributions of the new algorithm. Its superiority over the k-means algorithm is demonstrated for several data sets, and especially when a cluster is significantly smaller than the others, or very far and thus behaves as a group of outliers or if the clusters have very different sizes. This method allows the better clustering of AE data even on complex data sets. © Springer Science+Business Media, LLC 2012

Microcracking of high zirconia refractories after t→m phase transition during cooling: An EBSD study

High zirconia refractories are composed of a zirconia skeleton surrounded by an intergranular glassy phase. In these materials, zirconia undergoes up to two successive phase transitions during the manufacturing process, c → t then t → m. This leads, after complete cooling, to the formation of microcracks. Preliminary observations have enabled to identify the mechanism mostly responsible for the observed microcracking. In particular, SEM imaging emphasizes the link between the positions of cracks and the presence of distinct crystallographic domains. Thus, our work focuses on the arrangement of the monoclinic and tetragonal domains in zirconia dendrites. The assessment by XRD of the thermal expansion coefficients of zirconia at the lattice scale and the analysis of EBSD maps show that cracking is produced by the thermal expansion mismatch between groups of crystallographic variants. The further reconstruction of both cubic and tetragonal - in the case of a presence of monoclinic zirconia at room temperature - parent grains enables to determine the impact of each transition on the final microstructure and the generated microcracking. © 2011 Elsevier Ltd

Study of damage of high zirconia fused-cast refractories by measurement of Young's modulus

cited By 7International audienc

Reconstruction of the cubic and tetragonal oarent grains from electron backscatter diffraction maps of monoclinic zirconia

Monoclinic zirconia results from cubic→tetragonal→monoclinic phase transformations occurring at high temperature. Electron backscatter diffraction maps of monoclinic zirconia in fused-cast refractories have been treated with new crystallographic computer programs. The correct orientation relationships between the three phases have been identified among those proposed in the literature, the tetragonal and cubic parent grains have been automatically reconstructed, and the variants have been indexed. This example illustrates the possibilities of automatic crystallographic reconstruction software to study complex phase transition materials. © 2010 The American Ceramic Society

Nuclear Trafficking of the Rabies Virus Interferon Antagonist P-Protein Is Regulated by an Importin-Binding Nuclear Localization Sequence in the C-Terminal Domain

<div><p>Rabies virus P-protein is expressed as five isoforms (P1-P5) which undergo nucleocytoplasmic trafficking important to roles in immune evasion. Although nuclear import of P3 is known to be mediated by an importin (IMP)-recognised nuclear localization sequence in the N-terminal region (N-NLS), the mechanisms underlying nuclear import of other P isoforms in which the N-NLS is inactive or has been deleted have remained unresolved. Based on the previous observation that mutation of basic residues K214/R260 of the P-protein C-terminal domain (P-CTD) can result in nuclear exclusion of P3, we used live cell imaging, protein interaction analysis and <i>in vitro</i> nuclear transport assays to examine in detail the nuclear trafficking properties of this domain. We find that the effect of mutation of K214/R260 on P3 is largely dependent on nuclear export, suggesting that nuclear exclusion of mutated P3 involves the P-CTD-localized nuclear export sequence (C-NES). However, assays using cells in which nuclear export is pharmacologically inhibited indicate that these mutations significantly inhibit P3 nuclear accumulation and, importantly, prevent nuclear accumulation of P1, suggestive of effects on NLS-mediated import activity in these isoforms. Consistent with this, molecular binding and transport assays indicate that the P-CTD mediates IMPα2/IMPβ1-dependent nuclear import by conferring direct binding to the IMPα2/IMPβ1 heterodimer, as well as to a truncated form of IMPα2 lacking the IMPβ-binding autoinhibitory domain (ΔIBB-IMPα2), and IMPβ1 alone. These properties are all dependent on K214 and R260. This provides the first evidence that P-CTD contains a genuine IMP-binding NLS, and establishes the mechanism by which P-protein isoforms other than P3 can be imported to the nucleus. These data underpin a refined model for P-protein trafficking that involves the concerted action of multiple NESs and IMP-binding NLSs, and highlight the intricate regulation of P-protein subcellular localization, consistent with important roles in infection.</p></div

Domain structure of RABV P-protein.

<p>P-protein is shown schematically with key domains/sequences indicated; residue positions are indicated by italicized numbering. The RABV P gene encodes full length P1 (residues 1–297) and N-terminally truncated isoforms P2-P5 (expressed <i>via</i> ribosomal leaky scanning that initiates translation from internal in-frame AUG codons corresponding to methionines M20, M53, M69 and M83 of P1 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref013" target="_blank">13</a>]). P1 alone contains residues 1–19 that are required for association with the viral L-protein so that P1 can act as the polymerase cofactor [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref018" target="_blank">18</a>]. All P-protein isoforms contain the CTD which incorporates the binding sites for viral genome–associated N-protein (N-RNA), [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref017" target="_blank">17</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref023" target="_blank">23</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref025" target="_blank">25</a>] and STAT1 (black boxes) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref011" target="_blank">11</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref019" target="_blank">19</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref026" target="_blank">26</a>]. P-protein interaction with EXPs and IMPs is mediated through two CRM-1-binding NESs (yellow boxes) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref027" target="_blank">27</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref028" target="_blank">28</a>] and two IMPα/β-binding NLSs (blue boxes, described elsewhere [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref009" target="_blank">9</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref027" target="_blank">27</a>] and in this study), located in both the NTR and CTD. A third potential NES has been suggested to exist within NTR residues 53–174 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref009" target="_blank">9</a>]. The NTR-localized N-NLS is activated in P3 due to truncation of residues 1–52, which also truncates/deactivates the N-NES [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref009" target="_blank">9</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref027" target="_blank">27</a>]. The P-CTD localized C-NLS, which includes key residues K214/R260 (blue boxes) of a positively charged patch on the surface of the CTD, is characterized in this study; the positive patch has also been implicated in binding to N-RNA [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref019" target="_blank">19</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref024" target="_blank">24</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref029" target="_blank">29</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref031" target="_blank">31</a>], suggesting that the N-RNA-binding site overlaps with the C-NLS [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref024" target="_blank">24</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref025" target="_blank">25</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref027" target="_blank">27</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.ref028" target="_blank">28</a>]. The nucleocytoplasmic (Nuc/Cyt) localisation of each isoform is indicated (cytoplasmic (C), nuclear (N), diffuse (N/C)).</p

P-CTD mediates nuclear import of GFP dependent on IMPα2 and IMPβ1.

<p>Nuclear import of purified GFP-P-CTD and GFP-T-ag NLS was analyzed as described in the legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.g004" target="_blank">Fig 4</a> except that exogenous cytosol was pre-incubated (15 min) with the indicated antibodies. (A) CLSM images following 30 min incubation of GFP-P-CTD and GFP-T-ag NLS in the presence of the indicated antibody are shown. (B) Images such as those in A were analyzed to determine the F_n/c as described in the legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150477#pone.0150477.g002" target="_blank">Fig 2</a> (mean ± S.E.M., n ≥ 3 nuclei for each time point; data are from a single assay typical of three separate assays). Curve fitting used GraphPad Prism 6 (one-phase association).</p