Pokročilé instrumentace a metody pro charakterizace materiálů

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Assessing the ecological consequences of biodegradable plastics: Acute, chronic and multigenerational impacts of poly-3-hydroxybutyrate microplastics on freshwater invertebrate Daphnia magna
(CELL PRESS, 2024-08-30) Procházková, Petra; Kalčíková, Gabriela; Maršálková, Eliška; Brtnický, Martin; Zlámalová Gargošová, Helena; Kučerík, Jiří
Microplastics, pervasive contaminants in freshwater ecosystems, have raised ecological concerns. Efforts are underway to substitute conventional plastics with biodegradable alternatives that should be more easily decomposed in the environment. However, the biodegradation of these alternatives depends on specific conditions such as temperature, humidity, pH, and microorganisms, which are not always met. Consequently, these biodegradable alternatives can also fragment and generate microplastics, which can be ingested and affect biota. In this study, we investigated the acute, chronic, and multigenerational effects of two fractions (particles <63 mu m and particles <125 mu m) of biodegradable poly-3-hydroxybutyrate (P3HB) at varying concentrations on the inhibition, mortality, reproduction activity, and growth of the freshwater invertebrate Daphnia magna. No acute effects were observed for either size fraction. However, during chronic and multigenerational experiments, an increase in the concentration of P3HB microplastics corresponded with increased mortality, reduced reproductive activity, and slower growth among the mother organisms. Given the important role of D. magna in the food chain, these findings suggest that biodegradable microplastics may indeed negatively affect freshwater ecosystems.
Advancing microplastic detection in zebrafish with micro computed tomography: A novel approach to revealing microplastic distribution in organisms
(Elsevier, 2025-05-05) Parobková, Viktória; Maleček, Lukáš; Zemek, Marek; Kalčíková, Gabriela; Vykypělová, Michaela; Buchtová, Marcela; Adamovský, Ondřej; Zikmund, Tomáš; Kaiser, Jozef
The analysis of microplastics with current spectroscopic and pyrolytic methods is reaching its limits, especially with regard to detailed spatial distribution in biological tissues. This limitation hampers a comprehensive understanding of the effects of microplastics on organisms. Therefore, there is a pressing need to expand the analytical approaches to study microplastics in biota. In this context, the aim of this study was to test the applicability of non-destructive 3D imaging using X-ray micro-computed tomography (microCT) for the detection of microplastics in fish. Zebrafish (Danio rerio) were gavaged with polyethylene spherical microplastics (30-110 mu m) and the distribution of microplastics in the gut was investigated using microCT. The results showed that the particle size distribution determined by microCT closely matched the data from conventional laser diffraction analysis. In addition, microCT was able to detect microplastics in spiked fish tissue and provide precise localization data by tracing particles of known type and shape. MicroCT offers a novel approach for tracking microplastics in organisms and enables accurate sizing without compromising the integrity of the tissue under investigation. It therefore represents a valuable addition to spectroscopic methods, which are widely used for the detection of microplastics based on their chemical composition but do not provide data on their spatial distribution.
Laser-induced breakdown spectroscopy in space applications: Review and prospects
(Elsevier, 2024-12-01) Saeidfirouzeh, Homa; Kubelík, Petr; Laitl, Vojtěch; Křivková, Anna; Vrábel, Jakub; Rammelkamp, Kristin; Schröder, Susanne; Gornushkin, Igor; Képeš, Erik; Žabka, Ján; Ferus, Martin; Pořízka, Pavel; Kaiser, Jozef
This review describes the principles and summarizes the challenges of analytical methods based on optical emission spectroscopy (OES) in space applications, with a particular focus on Laser-Induced Breakdown Spectroscopy (LIBS). Over the past decade, LIBS has emerged as a powerful analytical technique for space exploration and In-Situ Resource Utilization (ISRU) of celestial bodies. Its implementation has been suggested for various segments of the Space Resources Value Chain, including prospecting, mining, and beneficiation. Current missions to Mars, including the ChemCam instrument on the Curiosity rover, the SuperCam on the Perseverance rover, and the MarSCoDe on the Zhurong rover, are considered flagship applications of LIBS. Despite neither the Pragyan rover nor the Vikram lander waking from the lunar night, the success of the Chandrayaan-3 mission marks another milestone in the development of LIBS instruments, with further missions, including commercial ones, anticipated. This paper reviews the deployment of LIBS payloads on Mars rovers, upcoming missions prospecting the Moon and asteroids, and LIBS analysis of meteorites. Additionally, it highlights the importance of data processing specific to space applications, emphasizing recent trends in transfer learning. Furthermore, LIBS combined with other spectroscopic techniques (e.g., Raman Spectroscopy, Mass Spectrometry, and Fourier-Transform Infrared Spectroscopy) represents an intriguing platform with comprehensive analytical capabilities. The review concludes by emphasizing the significance of LIBS-based contributions in advancing our understanding of celestial bodies and paving the way for future space exploration endeavors.
Microstructural study of AZ91C magnesium alloy castings produced by investment casting in as-cast state and after heat treatment
(Tanger Ltd., 2019-05-24) Dyčka, Martin; Dyčková, Lucie; Gejdoš, Pavel; Juliš, Martin
In this article, the microstructure of AZ91C magnesium alloy castings produced by investment casting was investigated. Castings were studied in as-cast state and after T4 and T6 heat treatment. The identification of all phases in microstructure was carried out using a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) analysis. The influence of cooling rate after casting, temperature of solution annealing, temperature of artificial aging and cooling rate after heat treatment on the microstructural characteristics such as secondary dendrite arm spacing (SDAS) or grain size was studied. The SDAS analyses were carried out using a light microscopy with the subsequent image analysis. Except of Mg-Al solid solution and Mg17Al12 precipitates, the microstructure contains other phases based on Mg-Si and (Al,Si)-Mn in globular or needle morphology. The SDAS in as-cast state was measured and was of tens of micrometers, but after T4 heat treatment, the gran size exceeded 100 µm and the Mg17Al12 phase was still undissolved along the grain boundaries in samples with thicker wall dimension. After T6 heat treatment, continuous and discontinuous precipitates of Mg17Al12 phase were formed, most of them were nearby the grain boundaries proving the inhomogeneous distribution of Al atoms in solid solution after T4 heat treatment.
Calcareous nannofossil assemblage in paintings chalk ground for provenance analysis: three original paintings compared to european source materials
(Springer Nature, 2023-07-07) Jaques, Victory; Holcová, Katarína
Chalk has been used since Antiquity for various purposes, and since Gothic for preparatory layers of painted cultural heritage objects. Several materials are called chalk in Cultural Heritage, but this work especially focuses on chalk composed of calcareous nannofossils (up to 98%). These are fossil remains of photoautotrophic algae generally smaller than 30 & mu;m. They are mainly visible as platelets of various shapes under a cross-polarised or scanning electron microscope. The provenance of chalk can be determined using calcareous nannofossils due to their well-known paleobiogeographic localities. They are already used as proxies since the 90s in Cultural Heritage, but rarely for paintings. In this work, 6 chalk historical mining areas were chosen: Germany (Ruegen), France (Champagne, Meudon), Belgium (Mons), England (Norfolk) and Italy (Bologna). Natural and processed chalk were used as reference materials and compared to 3 original paintings. The difference between the chalks calcareous nannofossil assemblages was shown using multivariate statistical analysis based on species relative abundance. Marker nannofossil species were defined for each chalk locality. One painting material could not be originated due to the preservation of its nannofossils assemblage, but the origins of the rock chalk material from the two other paintings could be geographically located in France.

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