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Metabolic and biophysical characterization of bacterial cells capable of PHA accumulation
Slaninová, Eva ; Lehocký, Marián (referee) ; Doškař, Jiří (referee) ; Chodak, Ivan (referee) ; Obruča, Stanislav (advisor)
This thesis deals with the characterization of bacterial cells capable of polyhydroxyalkanoates (PHA) accumulation. The dissertation thesis is written in the form of a discussed published publications which are attached to the thesis as appendixes. The work develops a study of the current topic of the protective functions of PHA and clarifies protective mechanisms against selected stressors. Firstly, we focused on the protective effects of PHA granules against UV radiation and osmotic stress, specifically hypotonic conditions. In the case of UV exposition, the cells protected themselves by scattering UV radiation on the intracellular granules protecting especially nucleoid. When exposed to osmotic stress, the amorphous state of PHA granules is very important since it is capable of stabilization of cell membranes under hypertonic stress, afterwards, bacterial cells can maintain their integrity during the subsequent hypotonic challenge. In general, the amorphous state of PHA granules is key to ensure the proper biological functions of PHA whether as storage or protective polymer. Therefore, in the next part of this work, we focused on the core of the stabilization mechanism that protects native PHA granules from crystallization and thus the intracellular polymer maintains in a thermodynamically unfavorable amorphous phase state. Based on experimental work, we applied selected stresses because we proposed a new model of stabilization of the amorphous state of PHA granules in vivo. It consists of two mechanisms, where small volumes of PHA granules reduce the rates of crystallization and at the same time the water present in the granules plays the role of a low molecular plasticizer. Due to the metabolic apparatus of bacterial cells, PHA are simultaneously synthesized and degraded which leads to an increment of intracellular concentration of monomers that also figure in the protective effect of PHA. In this context, we aimed at the description of the mechanism of cryoprotective effects of 3-hydroxybutyrate, the monomer of the most common of PHA, poly(3-hydroxybutyrate). Hence, we constructed an equilibrium and non-equilibrium phase diagram of the 3HB-water system to prove that 3HB is a very effective cryoprotectant. This fundamental understanding of the protective properties of PHA monomers could be also used in the food industry or cryopreservation of biological samples.
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Hydrogels hyaluronan-surfactant: phase diagram
Gruberová, Eliška ; Hurčíková, Andrea (referee) ; Pekař, Miloslav (advisor)
This bachelor’s thesis deals with phase separation of the hyaluronan-cationic surfactant system in a model physiological solution of 0,15 M NaCl resulting in gel formation. The most widely used concentrations of hyaluronan and a wide range of surfactant concentrations was used to form the gel. We have investigated under which conditions the greatest amount of compacted gel was produced. It has been found that phase separation occurs over the entire concentration range. The largest amount of gel was formed at the highest concentration of both hyaluronan and surfactant. The results were plotted in well-arranged graphs. A hydrophobic colorant was used to indicate the presence of micellar formations and the results were depicted in a schematic phase diagram.
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Immiscible alloy based on Fe-Cu system
Semerák, Petr ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The aim of this work is the preparation of FeCuMn alloy in equimolar composition by melting and the analysis of the resulting microstructure. The theoretical part of the work deals with miscibility and the use of immiscible systems in practical applications. Furthermore, the influence of cooling rate and the effect of the ratio of the components of the immiscible Fe-Cu system on the resulting microstructure are described. The practical part of the work presents the microstructure of FeCuMn alloy, which was prepared by melting in an induction furnace under a protective atmosphere of argon. Furthermore, the practical part deals with the chemical composition of the individual phases and the shape of the resulting phases. For the FeCuMn alloy, the melting temperature of the phases is analysed, the material is also deformed, and the hardness of the deformed and undeformed material is evaluated. In the subsequent discussion, the results from the experimental part are related to published experimental results by other authors.
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Phase equilibrium curve of gas mixtures
Fúdor, Vlastimil ; Habán, Vladimír (referee) ; Himr, Daniel (advisor)
This thesis is focused on the construction phase diagrams of various gas mixtures. The properties of real gas mixtures are modeled by two equations of state. The simpler one is the Peng-Robinson equation of state. The more complex and accurate equation of state is the GERG-2004. Two methods are used to construct the phase diagram namely the successive substitution method and the Newton method. The numerical procedure has been developed in Python programming language. A zip archive of the developed program is an integral part of the thesis. This program solves gas mixtures consisting of nitrogen, carbon dioxide, methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, n-heptane.
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Structural changes in intermetallic compounds
Doležal, Petr ; Prchal, Jiří (advisor) ; Daniš, Stanislav (referee)
This diploma thesis is focused on the study of the structural phase transitions in intermetallic compounds LaPd2(Al,Ga)2 by low-temperature x-ray powder diffraction and macroscopic measurements on single crystals. The results obtained from powder diffraction at room temperature confirm that the compounds crystallize in tetragonal CaBe2Ge2 structure type (space group P4/nmm). At low temperature all the compounds undergo the same structural phase transition by lowering the symmetry to the orthorhombic space group Cmma. Although the structural transformation is of first order, the transition is not-manifested in step-like change of the phase at a certain temperature, but occurs in a broader temperature interval. In this interval the different phases coexist and transform gradually from high- to low- temperature phase. After application of hydrostatic pressure the structural transition is shifted to higher temperatures. Despite that the low temperature structures are of the same type, there is a difference between compounds containing Ga and Al in the discontinuity of the lattice parameters resulting in a distinct anomaly in electrical resistivity. In pressures >0.6 GPa this characteristic anomaly on single crystalline CePd2Al2 is changed, indicating a pressure- induced change of the low-temperature...
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Structural changes in intermetallic compounds
Doležal, Petr ; Prchal, Jiří (advisor)
This diploma thesis is focused on the study of the structural phase transitions in intermetallic compounds LaPd2(Al,Ga)2 by low-temperature x-ray powder diffraction and macroscopic measurements on single crystals. The results obtained from powder diffraction at room temperature confirm that the compounds crystallize in tetragonal CaBe2Ge2 structure type (space group P4/nmm). At low temperature all the compounds undergo the same structural phase transition by lowering the symmetry to the orthorhombic space group Cmma. Although the structural transformation is of first order, the transition is not-manifested in step-like change of the phase at a certain temperature, but occurs in a broader temperature interval. In this interval the different phases coexist and transform gradually from high- to low- temperature phase. After application of hydrostatic pressure the structural transition is shifted to higher temperatures. Despite that the low temperature structures are of the same type, there is a difference between compounds containing Ga and Al in the discontinuity of the lattice parameters resulting in a distinct anomaly in electrical resistivity. In pressures >0.6 GPa this characteristic anomaly on single crystalline CePd2Al2 is changed, indicating a pressure- induced change of the low-temperature...
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Metabolic and biophysical characterization of bacterial cells capable of PHA accumulation
Slaninová, Eva ; Lehocký, Marián (referee) ; Doškař, Jiří (referee) ; Chodak, Ivan (referee) ; Obruča, Stanislav (advisor)
This thesis deals with the characterization of bacterial cells capable of polyhydroxyalkanoates (PHA) accumulation. The dissertation thesis is written in the form of a discussed published publications which are attached to the thesis as appendixes. The work develops a study of the current topic of the protective functions of PHA and clarifies protective mechanisms against selected stressors. Firstly, we focused on the protective effects of PHA granules against UV radiation and osmotic stress, specifically hypotonic conditions. In the case of UV exposition, the cells protected themselves by scattering UV radiation on the intracellular granules protecting especially nucleoid. When exposed to osmotic stress, the amorphous state of PHA granules is very important since it is capable of stabilization of cell membranes under hypertonic stress, afterwards, bacterial cells can maintain their integrity during the subsequent hypotonic challenge. In general, the amorphous state of PHA granules is key to ensure the proper biological functions of PHA whether as storage or protective polymer. Therefore, in the next part of this work, we focused on the core of the stabilization mechanism that protects native PHA granules from crystallization and thus the intracellular polymer maintains in a thermodynamically unfavorable amorphous phase state. Based on experimental work, we applied selected stresses because we proposed a new model of stabilization of the amorphous state of PHA granules in vivo. It consists of two mechanisms, where small volumes of PHA granules reduce the rates of crystallization and at the same time the water present in the granules plays the role of a low molecular plasticizer. Due to the metabolic apparatus of bacterial cells, PHA are simultaneously synthesized and degraded which leads to an increment of intracellular concentration of monomers that also figure in the protective effect of PHA. In this context, we aimed at the description of the mechanism of cryoprotective effects of 3-hydroxybutyrate, the monomer of the most common of PHA, poly(3-hydroxybutyrate). Hence, we constructed an equilibrium and non-equilibrium phase diagram of the 3HB-water system to prove that 3HB is a very effective cryoprotectant. This fundamental understanding of the protective properties of PHA monomers could be also used in the food industry or cryopreservation of biological samples.
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Thermal and microstructure analysis of binary eutectic system
Bielková, Kateřina ; Klepárníková, Eliška (referee) ; Adam, Ondřej (advisor)
This bachelor thesis deals with the analysis and verification of binary diagram of the Sn-Bi system. The theoretical segment of the thesis describes the common phase transformations and methods of their research, especially thermal analysis. The experimental part is focused on the analysis of six samples (four alloys and two pure metals). Analyses were performed by differential scanning calorimetry (DSC) and scanning electron microscope. The measured data were compared with the given binary diagram, with which it corresponds relatively well.
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The analysis of Cu-Sn-Sb ternary alloy
Kučera, Jan ; Doubrava, Marek (referee) ; Jan, Vít (advisor)
This bacholor thesis deals with substituting silver-based material, currently used for experimental semi-liquid extrusion. The proposed material is from the Cu-Sb-Sn system. The theoretical part of the work deals with soldering and phase diagrams. The experimental part is devoted to the analysis of three proposed alloys from the Cu-Sb-Sn system, their structural and mechanical properties. Thermal analyzes of the alloys were performed using differential scanning calorimetry (DSC), the microstructure using a light microscope and a scanning electron microscope, and a hardness tester was also used to determine the hardness. The results are summarized in the discussion.
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The analysis of Fe-Cr-Ti binary alloys
Lauš, Lukáš ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The aim of this bachelor thesis is the preparation of high volume ratio of intermediate phases in the microstructure of Ti-Fe, Fe-Cr, Ti-Cr. The bibliographic introduction includes basic information about phase equilibrium diagrams. It also includes phases in metal systems and the binary diagrams of the prepared alloys. The experimental part deals with the analysis of the alloy phases. The experimental part also deals with determination of alloys microstructure parts using calculated pseudobinary diagrams. It has been found, that although prepared from pure stock materials, the produced alloys were not binary and contained 0,6–1,4 at. % Si. Intermediate phases were found in Ti-Fe and Ti-Cr alloys. According to the calculated diagrams comparison, all of the prepared alloys were not in equilibrium.
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