| 1. |
- Dong, Yan, et al.
(författare)
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Atom Probe Tomography Interlaboratory Study on Clustering Analysis in Experimental Data Using the Maximum Separation Distance Approach
- 2019
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Ingår i: Microscopy and Microanalysis. - 1435-8115 .- 1431-9276. ; 25:2, s. 356-366
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Tidskriftsartikel (refereegranskat)abstract
- We summarize the findings from an interlaboratory study conducted between ten international research groups and investigate the use of the commonly used maximum separation distance and local concentration thresholding methods for solute clustering quantification. The study objectives are: to bring clarity to the range of applicability of the methods; identify existing and/or needed modifications; and interpretation of past published data. Participants collected experimental data from a proton-irradiated 304 stainless steel and analyzed Cu-rich and Ni-Si rich clusters. The datasets were also analyzed by one researcher to clarify variability originating from different operators. The Cu distribution fulfills the ideal requirements of the maximum separation method (MSM), namely a dilute matrix Cu concentration and concentrated Cu clusters. This enabled a relatively tight distribution of the cluster number density among the participants. By contrast, the group analysis of the Ni-Si rich clusters by the MSM was complicated by a high Ni matrix concentration and by the presence of Si-decorated dislocations, leading to larger variability among researchers. While local concentration filtering could, in principle, tighten the results, the cluster identification step inevitably maintained a high scatter. Recommendations regarding reporting, selection of analysis method, and expected variability when interpreting published data are discussed.
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| 2. |
- Marquis, Emmanuelle A., et al.
(författare)
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On the use of density-based algorithms for the analysis of solute clustering in atom probe tomography data
- 2019
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Ingår i: Minerals, Metals and Materials Series. - Cham : Springer International Publishing. - 2367-1696 .- 2367-1181. ; Part F11, s. 2097-2113
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Konferensbidrag (refereegranskat)abstract
- Because atom probe tomography (APT) provides three-dimensional reconstructions of small volumes by resolving atomic chemical identities and positions, it is uniquely suited to analyze solute clustering phenomena in materials. A number of approaches have been developed to extract clustering information from the 3D reconstructed dataset, and numerous reports can be found applying these methods to a wide variety of materials questions. However, results from clustering analyses can differ significantly from one report to another, even when performed on similar microstructures, raising questions about the reliability of APT to quantitatively describe solute clustering. In addition, analysis details are often not provided, preventing independent confirmation of the results. With the number of APT research groups growing quickly, the APT community recognizes the need for educating new users about common methods and artefacts, and for developing analysis and data reporting protocols that address issues of reproducibility, errors, and variability. To this end, a round robin experiment was organized among ten different international institutions. The goal is to provide a consistent framework for the analysis of irradiated stainless steels using APT. Through the development of more reliable and reproducible data analysis and through communication, this project also aims to advance the understanding between irradiated microstructure and materials performance by providing more complete quantitative microstructural input for modeling. The results, methods, and findings of this round robin will also apply to other clustering phenomena studied using APT, beyond the theme of radiation damage.
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| 3. |
- Takata, Tohru, et al.
(författare)
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Presence of both heterogeneous vancomycin-intermediate resistance and beta-lactam antibiotic-induced vancomycin resistance phenotypes is associated with the outcome in methicillin-resistant Staphylococcus aureus bloodstream infection
- 2013
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 45:3, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although the individual expression of heterogeneous vancomycin-intermediate resistance (hVISA) and beta-lactam antibiotic-induced vancomycin resistance (BIVR) phenotypes has been associated with treatment failure and recurrence in methicillin-resistant Staphylococcus aureus (MRSA) infections, the effect of the co-expression of these phenotypic profiles on clinical outcome has not been fully elucidated. The aim of this study was to determine the impact of the combination of hVISA and BIVR phenotypes on the clinical outcome in MRSA bacteremia. Methods: One hundred and sixty-two MRSA blood isolates from a 21-y period, 1987-2007, were randomly selected. Screening for hVISA was done by the macromethod Etest and confirmed by population analysis profiles. BIVR was identified using Mu3 agar containing 4 mu g/ml of vancomycin. Results: Thirty (18.5%) and 39 (24.1%) of the 162 MRSA blood isolates were positive for the hVISA and BIVR phenotypes, respectively. Eighteen (11.1%) isolates possessed both hVISA and BIVR phenotypes (hVISA(+)/BIVR(+)). In a subset of patients who received initial treatment with glycopeptides, only the patients whose isolates were hVISA(+)/BIVR(+) displayed a significantly higher mortality rate in comparison to those with non-hVISA(+)/BIVR(+) (80.0% vs 31.3%, p = 0.004). The presence of both hVISA and BIVR phenotypes was a predictor of mortality using a logistic regression analysis (p = 0.025). Conclusions: The combined phenotype of hVISA and BIVR was associated with a higher probability of mortality in patients with MRSA bacteremia. Further prospective studies are warranted to delineate the clinical significance of the combined phenotype of hVISA and BIVR.
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