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Diffusion of organic molecules in the hydrogel environment
Holubová, Anna ; Sedláček, Petr (referee) ; Mravec, Filip (advisor)
This diploma thesis deals with study of hydrogels formed by phase separation of hyaluronan with oppositely charged surfactants cetyltrimethylammonium bromide (CTAB) and Septonex. It follows the bachelor thesis and extends the knowledge about the detailed characterisation of the inner environment of the hydrogel by determining the diffusion behaviour of the fluorescent probes Atto 488 and Nile Red using fluorescence correlation spectroscopy (FCS) technique and its modified version dual-focus fluorescence correlation spectroscopy (2f-FCS). Compared results showed that both methods show similar values and probes specifically interact with CTAB but Atto 488 shows only weak interaction with Septonex compared to Nile Red. Additionally, these interactions were not affected by the molecular weight of hyaluronan. In conclusion, it was recommended to measure this type of hydrogel in a small depth of gel using a conventional method.
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Functional technical materials modified by lignin isolated from winery by-products
Chovanec, Martin ; Sedláček, Petr (referee) ; Kovalčík, Adriána (advisor)
In this thesis, the possibility of producing composites of epoxy resin and lignin isolated from grape skins was examined. The motivation was to reduce the amount of bisphenol A, which is nowadays used to produce most of the epoxy resins and is the main environmental pollutant. The composites were prepared by mixing commercial bisphenol A diglycidylether (DGEBA) with lignin samples. In this work, the sodium hydroxide pulping method in a hydrothermal autoclave was used to isolate lignin. The content of reducing sugars, lignin, and fatty acids in the sample of grape skins was determined and the chemical composition was determined by Fourier transform infrared spectroscopy (FT-IR). The chemical and thermal properties of isolated soda lignin were compared with commercial Kraft lignin and analyzed by elemental analysis, FT-IR, thermogravimetric analysis, and ash content determination. Epoxidized lignin was prepared by three methods, which were compared based on yield, epoxide equivalent, and chemical composition. Samples of unmodified soda lignin and epoxidized soda and Kraft lignins were selected for the preparation of epoxy composites. Experiments have shown that isolated soda lignin was not suitable for the addition to epoxy resins, unlike Kraft lignin. Thermal and viscoelastic properties of the prepared composites with a homogeneous structure were analyzed. It was found that the epoxy composites with added epoxidized Kraft lignin showed lower material stiffness and the glass transition temperature was significantly shifted to lower temperatures.
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Corelation of transport and viscoelastic properties of hydrogels with diffusion gradient
Ščotková, Romana ; Sedláček, Petr (referee) ; Smilek, Jiří (advisor)
The aim of the presented bachelor thesis was to prepare hydrogels with diffusion gradient and to demonstrate the gradient structure of hydrogels in terms of viscoelastic and transport properties. With regard to potential biomedical applications, the cationic polysaccharide chitosan was selected for the preparation, especially for its antimicrobial and biocompatible properties. The resulting gradient hydrogels were subsequently characterized by oscillation tests to observe the differences using different concentrations and molecular weights of chitosan, crosslinking agent concentrations, dispersion environments for chitosan dissolution, and different gel crosslinking times. The samples were also subjected to drying experiments to confirm the gradient structure formed. The ability of the hydrogels to transport the active species was confirmed by visually evaluating the permeation of the anionic dye (bromothymol blue) during the gelation process. From the results obtained during the experimental part of the bachelor thesis it can be concluded that the viscoelastic properties of hydrogels can be modified by changing selected parameters during the preparation itself. It was also confirmed the assumption that with better mechanical properties of hydrogels there is a deterioration of transport properties. By controlled diffusion method, it was possible to prepare a hydrogel with a gradual gradient of crosslinking density, thus modifying the viscoelastic and transport properties.
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Structural characterization of hydrogels at macroscopic and microscopic level
Kropáčková, Šárka ; Trudičová, Monika (referee) ; Sedláček, Petr (advisor)
This Bachelor´s thesis deals with study of use several methods for structural analysis of hydrogels. The aim was testing selected method to study structure of these gels. Agarose hydrogels were selected as model systems for their easy preparation and wide use. In this work the oscillatory rheology method was used to study the structure. Strain-sweep and time-sweep tests were performed. These tests were performed in a linear viscoelastic region, in the cross-over area and beyond the cross-over area. It was found that in linear viscoelastic region, the deformation causes the non-covalent bonds and the structure of the gel to break through. Consequently there is relaxation of the polymeric site and increase in elasticity. In cross-over area and beyond cross-over gels does not relax. The gels behave like a fluid.
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Utilization of spectroscopy in study on stress-resistance of bacteria on the sigle-cell level
Köbölová, Klaudia ; Venerová, Tereza (referee) ; Sedláček, Petr (advisor)
This diploma thesis deals with the possibilities of stress resistance analysis of the Cupriavidus necator H16 and PHB-4 bacterial cells by spectroscopic methods and by testing the suitability of acridine orange as a viable dye. Based on research in literature, suitable analytical methods have been proposed, namely flow cytometer and fluorescence microscope. The first part of the experimental work was focused on the fluorescence microscope, which confirmed the basic character of acridine orange. Three stress factors, 50% and 70% ethanol, and acidic pH (pH = 1) were selected for viability monitoring. The bacteria fluoresced with green color after exposure to ethanol and red spots were found next to the cells, indicating their loss of integrity. In an acidic environment, the bacteria fluoresced red because of a partial DNA breakdown. The results were verified by the combination of propidium iodide with SYTO9 and the acridine orange suitability proved to be useful in this method. Image records were processed using image analysis. In the second part, acridine orange was used to monitor fluorescence using a flow cytometer. The result of the measurement was fluorescence expressed as histograms for individual channels, where fluorescence was characterized by median and mean intensity. By comparing the methods used, the acridine orange appears to be a more suitable fluorescent dye for the microscope than for a flow cytometer in which it was more difficult to obtain cell viability information. In the last part of the experimental work interesting photophysical properties of acridine orange were investigated.
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Utilization of thermal analysis in the study on effects of microbial inhibitors
Bošeľová, Miriam ; Obruča, Stanislav (referee) ; Sedláček, Petr (advisor)
This diploma thesis deals with the use of thermal analysis in the study on effects of microbial inhibitors. The main aim of this work was to determine the utilization of the method, which is mainly used in different fields of science and research. Three bacterial strains: Cupriavidus necator H16, its mutant strain Cupriavidus necator PHB-4 and Halomonas halophila, were used as model microorganisms. The inhibitory effect of levulinic acid on growth and metabolic activity was monitored by microcalorimetry. It was found that bacteria were able to adapt to levulinic acid to a certain concentration - Cupriavidus necator to 5 g/l and Halomonas halophila to 2 g/l. The thermal analysis results were compared to a conventional method, which is commonly used to study the growth of microorganisms.
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Interactions of soil organic matter with pollutants studied by microcalorimetric techniques
Macuráková, Viktória ; Sedláček, Petr (referee) ; Smilek, Jiří (advisor)
This diploma thesis dealt with the study of interactions of soil organic matter, specifically humic acids with a pollutant, where the surfactant Septonex was used. Humic acids were isolated from two different soils in the work, namely black earth and cambium. The theoretical part describes the formation of humic acids as such, their possible interactions with substances and the characterization of surfactants. The experimental part is devoted to the characteristics of humic acids using elemental analysis, thermogravimetry and then the most important part of the thesis, namely the monitoring of interactions using isothermal titration calorimetry. The experiment showed that the sample of isolated black earth at the surfactant concentration of 0,075 moldm3 had the best interaction with the surfactant.
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Security of Trapdoor Permutations under Preimage Leakage
Sedláček, Petr ; Hubáček, Pavel (advisor) ; Göloglu, Faruk (referee)
This thesis explores preimage leakage-resilient trapdoor permutations (PLR-TDPs) and their applications in proofs of storage replication and incompressible encodings. The thesis consists of three chapters covering the trapdoor permutations, formal definition of PLR-TDPs, and analysis of security properties of PLR-TDPs. The first chapter provides an overview of trapdoor permutations (TDPs), their def- initions, and applications in proofs of storage replication. Our results are presented in the second and third chapters. The second chapter formally defines PLR-TDPs and demonstrates their use by constructing a simple incompressible encoding in the random oracle model. The third chapter focuses on the existence of PLR-TDPs. It demonstrates the strong preimage leakage-resilience of fully random TDPs in an idealized model. We are the first to provide a partial formal justification for the conjecture of the preimage leakage-resilience of practical TDPs, such as RSA or Rabin permutations.
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Material flow concept of a production line supply
Sedláček, Petr ; Dorušáková, Kamila (referee) ; Zeizinger, Lukáš (advisor)
The content of this thesis is a research analysis of individual concepts in the field of corporate logistics with an emphasis on intra-company transport. In the practical part, the current state of the production line loading is evaluated and new variants of line supply are made on the of the given parameters. The work also includes the creation of simulation models of all variants in the Plant Simulation program and conclusions are drawn based on the data obtained.
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