Pokročilé instrumentace a metody pro charakterizace materiálů

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Automated detection of element-specific features in LIBS spectra
(ROYAL SOC CHEMISTRY, 2024-11-27) Gajarská, Zuzana; Faruzelová, Anna; Képeš, Erik; Prochazka, David; Pořízka, Pavel; Kaiser, Jozef; Lohninger, Hans; Limbeck, Andreas
This work introduces a novel semi-automatic approach to identify elemental lines in spectra obtained via laser-induced breakdown spectroscopy (LIBS). The algorithm is based on unique spectral fingerprints of individual elements that are configured into comb-like filters. The element-specific filters are then correlated with measured spectra for semi-supervised qualitative analysis of samples. Spectral variations are accommodated by adjusting the micro-parameters of the comb filter. This step ensures accurate results despite minor deviations from the instrument's ideal calibration due to instrumental fluctuations, e.g., drift in spectral calibration or line broadening. Additionally, the algorithm can autonomously detect spectral interference regions, aiding the analyst in verifying spectral lines where such interference may occur. The paper presents a comprehensive overview of the algorithm and discusses the main concepts, parameters, optimization steps, and limitations using Echelle spectra of two standard reference materials with different complexity: borosilicate glass (NIST 1411) and low-alloyed steel (SUS1R). Furthermore, the transferability of the approach to different scenarios and real-life applications is demonstrated using a single-channel Czerny-Turner spectrum of an amalgam filling extracted from a hyperspectral image of a human tooth. A demo of the algorithm is publicly available for non-commercial purposes.
Computed tomographic visualisation and 2D/3D microscopic evaluation of soil macro- and micromorphology
(CZECH ACADEMY AGRICULTURAL SCIENCES, 2024-10-13) Pospíšilová, Ľubica; Plíšková, Jana; Jaques, Victory; Zikmund, Tomáš; Sedlák, Luboš; Eichmeier, Aleš; Klement, Aleš; Kodešová, Radka; Borůvka, Luboš; Kaiser, Jozef; Menšík, Ladislav
Soil organic matter and pores distribution within aggregates were studied using X-ray computed tomography (XCT; Nikon XT H 225ST and GE Phoenix L240) and advanced 2D/3D measurements by the digital Keyence VHX-6000 microscope (Japan). A new methodological approach with computed tomography involvement for studying the spatial arrangement of pores, porosity, and soil morphology is presented. Changes in studied parameters are documented along the transect of intensively used Haplic Chernozem. Soil disturbance due to erosion and colluvial soil profile formation is reported. Moreover, soil organic matter quality and aggregate stability were evaluated. Obtained results showed statistically significant differences between the control and eroded sites and between eroded and accumulated sites. The correlation coefficients were the highest for soil organic carbon (SOC) and humic substances C-HS (r = 0.805) and C-HS and C-HA/C-FA (r = 0.764). The highest porosity, aggregates stability and coefficients stability were confirmed on the eroded site. The computed tomography measurements also document the high disturbance of Haplic Chernozem on the control site and the newly formed profile of Colluvisol. Despite excellent complementary technique further research is necessary to improve micro-XCT resolution and capacity for the soil micromorphological study.
Statistical behaviour of laser-induced plasma and its complementary characteristic signals
(Royal Society of Chemistry, 2024-09-04) Buday, Jakub; Holub, Daniel; Pořízka, Pavel; Kaiser, Jozef
In this work, we present a study aimed at the statistical distribution of characteristic signals of laser-induced plasmas. This work mainly focuses on observing statistical distribution for repetitive measurement of spectra, plasma plume imaging, and sound intensity. These were captured by using various laser irradiances, spanning between 1.72 and 6.25 GW cm2 for a 266 nm laser. Their distributions were fitted by Gaussian, generalized extreme value (GEV), and Burr distributions, as typical representation models used in LIBS. These were compared using the Kolmogorov–Smirnov (KS) test by its null hypothesis on whether these models are suitable or fail to describe the statistical distribution of the data. The behavior of the data distribution has shown a certain connection to the plasma plume temperature. This was observed for all the used ablation energies. Performances of the statistical models were further compared in the outlier filtering process, where the relative standard deviation of the filtered data was observed. The results presented in this work suggest that an appropriate selection of a statistical model for the data representation can lead to an improvement in the LIBS performance.
Resolution Enhancement by Variable Zoom Trajectory in X-Ray Computed Tomography
(SPRINGER/PLENUM PUBLISHERS, 2024-09-01) Blažek, Pavel; Suppes, Alexander; Wolfschläger, Dominik; Zikmund, Tomáš; Kaiser, Jozef; Schmitt, Robert H.
Flat objects like electronic boards are challenging samples for high-resolution X-ray computed tomography scanning because their largest dimension significantly limits the magnification using circular trajectory scans. One way to improve spatial resolution for such samples is to utilize variable zoom trajectory. During variable zoom trajectory scanning, the source-to-object distance changes during the 360 degrees rotation to maximize the magnification in the projections. Here, we propose an automatic variable zoom trajectory generation algorithm for arbitrary object and region of interest (ROI). We analyze how such a trajectory can enhance resolution in different cases and how isotropic is the resolution in the reconstructed volume. We demonstrate that the resolution can be improved without destroying the sample. However, the improvement is manifested mainly in directions in which we achieved the highest magnification in the projection.
Technology and provenience of the oldest pottery in the northern Pannonian Basin indicates its affiliation to hunter-gatherers
(Springer Nature, 2024-08-20) Petřík, Jan; Slavíček, Karel; Adameková, Katarína; Jaques, Victory; Košťál, Martin; Tóth, Peter; Petr, Libor; Všianský, Dalibor; Zikmund, Tomáš; Kaiser, Jozef; Bátora, Jozef; Bickle, Penny
Consensus holds that pottery technology came to Central Europe from the Northern Balkans with independent pottery traditions existing concurrently in Eastern Europe. An unusual grass-tempered pottery dating back to around 5800 cal BC found in lake sediments at Santovka, Slovakia, predated the earliest known Neolithic pottery in the region (similar to 5500 cal BC), suggesting unexplored narratives of pottery introduction. Analyses of the pottery's technology, origin, and grass temper shedding light on ceramic traditions' spread can unveil mobility patterns and community lifestyles. Our findings indicate a non-local provenance, low temperature firing, Festugc sp. grass temper and unique rectangular or cylindrical vessel shapes which align with Eastern European hunter-gatherer practices. Moreover, the pottery style and technology have no analogies in the contemporary Danubian pottery traditions and have more similarities to those of the Eastern traditions. The pottery's raw materials likely originated from distant areas, indicating extensive territorial access for its creators. Our findings imply late Mesolithic hunter-gatherers as the probable artisans and with implications for the site's significance in the late Mesolithic landscape.

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