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Involvement of vibrational spectroscopy in the study on interactions of natural organic matter with model environmental pollutants.
Stehlíková, Kristína ; Enev, Vojtěch (referee) ; Sedláček, Petr (advisor)
The main objective of this diploma thesis was to verify the potential of using advanced infrared spectra processing techniques – specifically the principal component analysis (PCA) – in order to monitor the interaction of natural organic matter with organic pollutants. Natural organic matter was represented by standard IHSS Leonardite humic acid, while the aromatic dyes methylene blue and Rhodamine 6G and the aliphatic substance Septonex were chosen as representatives of organic ions. Their interactions were monitored using Fourier-transform infrared spectroscopy, the use of which for this purpose was verified in my bachelor's thesis. Principal component analysis was finally applied to the obtained infrared spectra of the formed complexes and prepared blank samples, which helped to reveal spectral changes at first glance unrecognizable in the spectra themselves. It was found out that the most likely mechanism of humic acid interaction with aromatic pollutants is a - interaction, while the electrostatic nature of the interaction is assumed for the binding of aliphatic substances.
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Involvement of various gelation strategies in development of next-generation bioinnoculants
Krýslová, Jana ; Smilek, Jiří (referee) ; Sedláček, Petr (advisor)
This diploma thesis deals with the investigation cross-linking approaches of the bacterium Azotobacter vinelandii, which belongs to the PGPR group and is capable of producing alginate extracellularly. This crosslinking concept represents a novel approach to development of bioinoculants based on the PGPR. The first part is dedicated to investigating the effect of oxygen on the gelation of bacterial cultures itself. Experimentally, it was found that bacterial cultures in a total volume of 50 and 100 ml in 250 ml Erlenmeyer flasks showed spontaneous gelation already during the cultivation process, while the formed gels were measured rheometrically and showed values of const. complex modulus 0,026 kPa and 0,030 kPa. With a bacterial culture in a total volume of 150 ml, spontaneous cross-linking itself did not occur. In addition to gelation testing, the content of PHB and extracellular alginate and its molecular weight were determined in the bacterial cultures using size exclusion chromatography with multi-angle light scattering (SEC-MALS) and the mechanical properties of the resulting gels using rheometry. Cross-linking of bacterial cultures took place mainly with the use of CaCl2 as a cross-linking agent, but various alternative methods of gelation were tested as well (by means of polyvalent ions, weak organic acids, precipitants such as DMSO, emulsion gelation). The effect of glucono-D-lactone (GDL) as a gelling agent based on a slow release of crosslinking ions from their insoluble form was also tested. The strongest gels were formed by the addition of polyvalent ions (they ranged in the value of the complex modulus of 10 kPa, in the case of the use of weak acids and DMSO, the gels ranged in the value of the complex modules in the range of 1 to 10 kPa. The addition of GDL did not create gels immediately, but delayed, and gelation was observed in time.The formed gel ranged in value up to 1 kPa.
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Wartime economic headquarters in Cisleithania (1914-1918)
Sedláček, Petr ; Kubů, Eduard (advisor) ; Štolleová, Barbora (referee) ; Jemelka, Martin (referee)
The dissertation deals with the topic of Wartime Economic Headquarters in the time span of the First World War in Cisleithania; these organisations are understood primarily as institutions authorized with the administration of goods and foodstuffs in short supply. Firstly, the thesis evaluates and defines the position of the Wartime Economic Headquarters in the system of the Cisleitanian war economy, offers their classification based on their roles and forms and it offers their overview. In the three individual studies the thesis deals in detail with the chosen Wartime Economic Headquarters - The Wartime Grain Agency, The Central Sugar Agency, and the organizations active in the field of the cotton industry - The Central Cotton Agency, and The Wartime Union of Cotton Industry. Based on a thorough analysis of wartime legislation, the thesis specifies the tasks and role of each closely analyzed organization in the framework of governmental regulation. It follows the chosen organizational forms of the respective organizations, including the persons in charge and it evaluates the profitability of those organizations. Above all, the thesis deals with the ways, in which the said organisations took part in performing of the state regulations of the individual branches. Moreover, the thesis puts a closer...
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Transport Properties of Gellan Hydrogels
Sokolínský, Jan ; Sedláček, Petr (referee) ; Kalina, Michal (advisor)
This bachelor thesis deals with the characterization of mechanical and transport properties of gellan based hydrogel systems. As gellan gum is a biopolymer, hydrogels based on this biopolymer are suitable candidates for use in the pharmaceutical industry and medical applications. The characterization of mechanical properties was realized by rheological analysis and by drying scales, transport properties were characterized by diffusion experiments in combination with the detection using UV-VIS spectrometry. The result of this work is a comparation and commentary of the measured data, in order to provide an overview of the properties of physical gellan gum hydrogels. It was found out that by changing the concentration of the biopolymer and by a suitable selection of the dispersion medium, transport, and mechanical properties of the physical gellan gum hydrogels can be modified.
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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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Utilization of physico-chemical and spectroscopical methods in study on microbial extremofiles
Dobešová, Kateřina ; Enev, Vojtěch (referee) ; Sedláček, Petr (advisor)
The aim of this bachelor thesis is the determination od polyhydroxyalkanoates in the cells of extremophille bacterie, preformed by several methods. The chosen bacterium was Schlegelella thermodepolymerans DSM 15 344 Thermogravimetric analysis, infrared spectroscopy with Fourier transformation, and Raman spectroscopy were used in this thesis. The TGA method was used for the determination of extracellular and intracellular water in samples. The FTIR method was used in order to observe the amount od PHA, but aslo to observe the physical properties of the polymer in the sample, specifically to determine either amorphous or crystalline featuers of this polymer. Raman spectroscopy was used in oder to confirm the presence of PHA in the samples. All results e´were compared eith the results accomplished by gas chromatografy.
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Use of copolymer polyhydroxyalkanoates in development of intelligent packaging
Kreuzerová, Monika ; Kalina, Michal (referee) ; Sedláček, Petr (advisor)
This bachelor thesis deals with the preparation and characterization of copolymers P(3HB-co-4HB). The theoretical part discusses polyhydroxyalcanolates (PHA), where their structure, properties and synthesis are described and subsequently the selected copolymers, which contain monomeric units 3HB, are listed. Furthermore, the review part is processed for the current state of the issue, which states the use of copolymers PHA and current research work on the incorporation of active substances into copolymers. The aim of this work was to characterize and compare the created P(3HB) and P(3HB-co-4HB) foils with a 4HB monomeric unit of 65,25 % and 43,61 % and subsequently determine the potential of foil usability as intelligent packaging materials. First, PHA were subjected to gas chromatography, SEC-MALS, FTIR and DSC analysis. In the second part of the thesis, the permeability of foils to water vapor and the release of model active substances from PHA foils was studied. For this purpose, two active substances (curcumin and salicylic acid) were selected, which were incorporated into a film of homopolymer P(3HB) and two copolymers with a proportion of 4HB of 65,25 % and 43,61 %. In foils prepared from copolymers, the active substances diffusion was faster than in P(3HB). Within the copolymers, P(3HB-co-43,61%4HB) released substances at a higher speed, due to the greater crystallinity of a copolymer containing 65,25 % 4HB.
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Coated slow-release fertilizers based on PHB
Bobková, Magdalena ; Sedláček, Petr (referee) ; Kontárová, Soňa (advisor)
This bachelor thesis deals with the preparation, characterization and optimization of slow-release fertilizers coated with a solution of poly-3-hydroxybutyrate in dioxolane. First, manual formulations of fertilizers consisting of different ratios of urea and poly-3-hydroxybutyrate were prepared and coated, which were studied for the release of urea in the water environment. Most of the formulations released only about 50 % of the fertilizer after two months, so the potential for their use as slow-release fertilizers was proved. Furthermore, pellets with different ratios of urea and poly-3-hydroxybutyrate were also prepared using a quarter-operation pelletizer and coated in a coating drum. The pellets were studied in water and soil environments and certain mixtures in field tests. The delayed release of urea was also confirmed, and their ability to adequately nourish the plants was proved. The formulation consisting of 80 % urea and 20 % biodegradable poly-3-hydroxybutyrate in the matrix, in which 50 % of the fertilizer was released in water after 44 days, was chosen as the most promising one. In the soil environment, a slower nitrogen release was also confirmed for this formulation, and at the same time, a positive effect on the weight development of the above-ground parts of the plants and on the chlorophyll content in the leaves was observed in all formulations of the coated fertilizers.
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Self-encapsulation of Plant Growth Promoting Rhizobacteria as a way towards new generation of bioinoculants
Gašparová, Dominika ; Obruča, Stanislav (referee) ; Sedláček, Petr (advisor)
This bachelor thesis focuses on Plant Growth-Promoting Rhizobacteria that can be used as a suitable ecological alternative to conventional fertilizers. However, most of today's approaches to incorporating PGPR into the process of soil fertilization are convoluted and costly. Crosslinking of alginate self-produced by PGPR offers a new possibility of plantgrowth- promoting bacteria encapsulation. The aim of this thesis consists of preparing gel matrices with incorporated bacteria, followed by testing the bacteria's viability and quantity. Firstly, experiments were carried out to determine various properties of gels produced by the chosen representative bacteria Azotobacter vinelandii. These properties include the molecular weight of alginate (with the highest molecular weight of strain CCM 289 (329,78± 6,8) kDa), the alginate's amount in the gel, the content of PHB (34%-44% CDW), and the gel's overall rheological properties. The complex modulus (as a representation of rheological properties) of the firmest gel reached the value of 13,34 kPa. The bacteria content was examined by flow cytometry, the CFU method, and spectrophotometry. The viability of bacteria was determined by analyzing the fluorescence intensity via fluorescent dyes (propidium iodide, fluorescein diacetate, rhodamine 123, calcein AM), then by using the CFU method, and also via the plate method. Furthermore, the effects of various factors such as different pH levels (pH 3, 7, and 10) or adding the specific alginatedegrading enzyme alginase were also examined. Releasing of the bacteria was observed over the course of seven days using flow cytometry and the CFU method. The plate method proved the bacteria's survival after gelation and without any source of carbon. The largest disintegration of gels occurred in acidic pH. Moreover, the effect of alginase on crosslinked bacterial gels and synthetic alginate were very similar. The survival of bacterial cultures in gel and their continuous release are significant findings in the development of novel bioinoculants based on this new concept.
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Microrheology modeling with COMSOL Multiphysics package
Koláček, Jakub ; Sedláček, Petr (referee) ; Pekař, Miloslav (advisor)
This bachelor thesis focuses on modeling Brownian motion using the COMSOL Multiphysics package and its Particle Tracing module. The aim of the work is to design and create elementary models that will be able to suitably simulate the movement of microparticles in viscous and viscoelastic environments, which can later be used for modeling passive microrheology. Within this work, Matlab scripts were created for the calculation of MSD from the simulation results, validation of the viscous model was performed on experimental data and elementary models for the simulation of the viscoelastic environment were also designed. Two different approaches were chosen for the design of these models, namely the use of rigid obstacles under the assumption of a discrete environment and a mathematical model assuming continuous environment. Data from the viscous model showed good agreement with the experimental results. The results of viscoelastic simulations are presented, and further possible development of these models is discussed. The continuous mathematical model is considered closest to modeling viscoelastic behavior because of a characteristic curvature that was observed in the evaluation of MSD.
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