Ústav fyzikální a spotřební chemie
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- ItemComprehensive Study of Stereolithography and Digital Light Processing Printing of Zirconia Photosensitive Suspensions(Multidisciplinary Digital Publishing Institute, 2024-11-04) Sokola, Patrik; Ptáček, Petr; Bafti, Arijeta; Panžić, Ivana; Mandić, Vilko; Blahut, Jan; Kalina, MichalZirconia ceramics are used in a wide range of applications, including dental restorations, bioimplants, and fuel cells, due to their accessibility, biocompatibility, chemical resistance, and favorable mechanical properties. Following the development of 3D printing technologies, it is possible to rapidly print zirconia-based objects with high precision using stereolithography (SLA) and digital light processing (DLP) techniques. The advantages of these techniques include the ability to print multiple objects simultaneously on the printing platform. To align with the quality standards, it is necessary to focus on optimizing processing factors such as the viscosity of the suspension and particle size, as well as the prevention of particle agglomeration and sedimentation during printing, comprising the choice of a suitable debinding and sintering mode. The presented review provides a detailed overview of the recent trends in preparing routes for zirconium oxide bodies; from preparing the suspension through printing and sintering to characterizing mechanical properties. Additionally, the review offers insight into applications of zirconium-based ceramics.
- ItemAgarose Hydrogels Enriched by Humic Acids as a Functional Model for the Transport of Pharmaceuticals in Nature Systems(MDPI, 2024-12-16) Klučáková, Martina; Závodská, PetraThe presence of pharmaceuticals in nature systems poses a threat to the environment, plants, animals, and, last but not least, human health. Their transport in soils, waters, and sediments plays important roles in the toxicity and bioavailability of pharmaceuticals. The mobility of pharmaceuticals can be affected by their interactions with organic matter and other soil and water constituents. In this study, a model agarose hydrogel enriched by humic acid as a representative of organic matter is used as a transport medium for pharmaceuticals. Sulphapyridine (as a representative of sulphonamide antibiotics) and diclofenac (as a representative of widely used non-steroidal anti-inflammatory drugs) were chosen for experiments in diffusion cells. Pharmaceuticals were passed through the hydrogel from the donor solution to the acceptor compartment and could interact with humic acids incorporated in the hydrogel. The lag time was prolonged if the hydrogel was enriched by humic acids from 134 to 390 s for sulphapyridine and from 323 to 606 s for diclofenac. Similarly, the incorporation of humic acids in the hydrogel resulted in a decrease in the determined diffusion coefficients. The decrease was stronger in the first stage of the experiment when diffusing particles could interact with vacant binding sites.
- ItemSoil organic matter interactions along the elevation gradient of the James Ross Island (Antarctica)(European Geoscience Union, 2024-11-19) Vlček, Vítězslav; Juřička, David; Valtera, Martin; Dvořáčková, Helena; Štulc, Vojtěch; Bednaříková, Michaela; Šimečková, Jana; Váczi, Peter; Pohanka, Miroslav; Kapler, Pavel; Barták, Miloš; Enev, VojtěchAround half of the Earth's soil organic carbon (SOC) is presently stored in the Northern Hemisphere permafrost region. In polar permafrost regions, low temperatures particularly inhibit both the production and biodegradation of organic matter. Under such conditions, abiotic factors such as mesoclimate, pedogenic substrate or altitude are thought to be more important for soil development than biological factors. In Antarctica, biological factors are generally underestimated in soil development due to the rare occurrence of higher plants and the short time since deglaciation. In this study, we aim to assess the relationship between SOC and other soil properties related to the pedogenic factors or properties. Nine plots were investigated along the altitudinal gradient from 10 to 320 m in the deglaciated area of James Ross Island (Ulu Peninsula) using a parallel tea-bag decomposition experiment. SOC contents showed a positive correlation with the content of easily extractable glomalin-related soil protein (EE-GRSP; Spearman r = 0.733, P = 0.031) and the soil buffering capacity (expressed as pH; Spearman r = 0.817, P = 0.011). The soil-available P was negatively correlated with altitude (Spearman r = -0.711, P = 0.032), and the exchangeable Mg was negatively correlated with the rock fragment content (Spearman r = -0.683, P = 0.050). No correlation was found between the available mineral nutrients (P, K, Ca and Mg) and SOC or GRSP. This may be a consequence of the inhibition of biologically mediated nutrient cycling in the soil. Therefore, the main factor influencing nutrient availability in these soils does not seem to the biotic environment; rather, the main impact appears to stem from the abiotic environment influencing the mesoclimate (altitude) or the level of weathering (rock content). Incubation in tea bags for 45 d resulted in the consumption and translocation of more labile polyphenolic and water-extractable organic matter, along with changes in the C content (increase of up to +0.53 % or decrease of up to -1.31 % C) and a decrease in the C:N ratio (from 12.5 to 7.1-10.2), probably due to microbial respiration and an increase in the abundance of nitrogen-binding microorganisms. Our findings suggest that one of the main variables influencing the SOC/GRSP content is not the altitude or coarse-fraction content (for which a correlation with SOC/GRSP was not found); rather, we suspect effects from other factors that are difficult to quantify, such as the availability of liquid water.
- ItemEffect of Silk Fibroin on the Mechanical and Transport Properties of Agarose Hydrogels(MDPI, 2024-09-24) Richterová, Veronika; Pekař, MiloslavIn this work, the effect of incorporating silk fibroin, a fibrous biocompatible protein, into physically cross-linked agarose hydrogels was investigated as a simple model study to examine how supramolecular fibrous structures influence the properties of the hydrogels. The rheological and transport properties were studied. Fibroin did not change the general viscoelastic properties of the investigated hydrogels but changed the viscoelastic moduli values and also the mesh size, as calculated from rheometry data. Fibroin influenced the mechanical properties depending on its concentration: at lower concentrations, it increased the mesh size, while at higher concentrations, it acted as a filler, decreasing the mesh size. Similarly, the storage and loss moduli were affected, either increasing or decreasing based on the fibroin concentration. The fibroin effect on the diffusion of two dyes differing in their charge was the result of a combination of structural effects, responsible also for changes in the rheological properties, and a result of electrostatic interactions between the charged groups. For positively charged methylene blue, low fibroin concentrations accelerated diffusion, while higher concentrations slowed it by filling network vacancies. In contrast, for negatively charged eosin-B, fibroin strongly impeded diffusion at all concentrations due to electrostatic repulsion, leading to its accumulation at the hydrogel interface. The findings of this work may contribute to an understanding of the behavior of the extracellular matrix or soft tissues as well as to the development of the tailored design of hydrogel materials.
- ItemThe Effect of Biochar Particle Size on the Leaching of Organic Molecules and Macro- and Microelements(MDPI, 2024-10-11) Bačovská, Šárka; Mravcová, Ludmila; Pořízka, Jaromír; Kubíková, Leona; Kalina, MichalBiochar is a carbon-rich material that has recently received attention due to its increasing agronomical potential. The agricultural utilization of biochar relates to its potential to act in the soil as a soil conditioner; nevertheless, complex information on the direct dependence of biochar’s physical properties (texture, particle size) and corresponding leaching and availability of organic molecules (e.g., the polycyclic and heterocyclic organic compounds) and inorganic mineral salts (based on micro- and macroelements) is still inconsistent. Multi-elemental analysis by using inductively coupled plasma atomic emission spectroscopy (ICP-OES) was used to assess the information on the contents and availability of macro- and microelements in studied commercial biochar samples. The results showed a statistically significant indirect relation between an increase in the size fraction of biochar and the content of aqueous-extractable K and Na and the direct relation with the aqueous-extractable Ca, Mg, and P. Compared to the macroelements, the detected contents of aqueous-extractable microelements were almost three orders lower, and the dependence on fraction size was not consistent or statistically significant. In addition, gas chromatography (GC) coupled with mass spectroscopy (MS) was further used to reveal the concentrations of available polycyclic aromatic and heterocyclic compounds in biochar samples. The detected concentrations of these types of organic compounds were far below the certified limits, and a statistically significant indirect correlation with particle size was also observed for all the studied biochar samples. The proposed methodological concept could provide the necessary insights into the description of biochar mineral content and its connection to biochar texture, the physicochemical properties, and the potential of biochar to release nutrients into the soil. These findings could help in the further assessment of biochar as a soil conditioner in modern agriculture.