National Repository of Grey Literature 161 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Membrane modeling in microfludic chip
Konečná, Tereza ; Pekař, Miloslav (referee) ; Venerová, Tereza (advisor)
This work focuses on microfluidic chips suitable for modeling phospholipid membranes, their design, and possible applications. It also provides a more detailed specification of selected techniques for creating membranes on a chip. The experimental part deals with the production of chips from polydimethylsiloxane, the optimization of infusing of solutions into the chip, and the formation of membranes inside microfluidic channels using the selected model phospholipid – asolectin. The entire process of membrane modeling was visualized using optical and fluorescence microscopy. In conclusion, the success of the developed method is evaluated, including the suitability of asolectin for the formation of model membranes, and solutions to existing problems are proposed.
Modeling controlled release
Čelková, Ivana ; Smilek, Jiří (referee) ; Pekař, Miloslav (advisor)
This bachelor's thesis is focused on the controlled release of drugs from hydrogels and the subsequent simulation of this process using the COMSOL Multiphysics computing platform. The aim of the work is to propose a simple model describing the release from the hydrogel structure, to study the effect of diffusion coefficient and to perform simulations on this model and evaluate the results related to controlled release. As part of the thesis, two models were created to investigate the release of particles from the hydrogel. Simulations of this process were carried out for three selected diffusion coefficients (110-9, 110-10, 110-11 m2s-1) and were subsequently discussed in terms of the influence on the speed of particle transport. Two procedures were chosen to determine the total concentration of the released substance in vicinity of the hydrogel, i.e. using the integration of the area of the aqueous environment (in a two-dimensional model) and monitoring the flow of particles through the phase interface of the hydrogel and the aqueous environment.
Modeling diffusion in hydrogels
Vrána, Matouš ; Sedláček, Petr (referee) ; Pekař, Miloslav (advisor)
This bachelor thesis is focused on basic knowledge about hydrogels and their potential uses, Brownian motion in hydrogels and it’s connection with diffusion and the possible modeling in COMSOL Multiphysics with the help of Particle Tracing Module. The aim of this work is to propose adjustments to a model given from COMSOL Application Library that could lead to a functional simple model true to the viscoelastic properties of the environment. Those were controlled through a given script for calculation of MSD in Matlab. The original model was adjusted with the help of rigid obstacles blocking particle transport. Second, rectangular model was also created, where the particle movement had been observed through created channels.
Preparation and characterization of triple-IPA for the formation of vesicular systems
Novotná, Ludmila ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
This thesis deals with the preparation and characterization of vesicular systems consisting of triple-IPA (ion pair amphiphile with three hydrophobic chains). For the preparation of tripleIPA were used double-chain cationic surfactants dimethyldimyristylammonium bromide (DMSAB), dimethyldipalmitylammonium bromide (DPAB), dimethyldioctadecylammonium bromide (DODAB) and dimethyldioctadecylammonium chloride (DODAC) and the singlechain anionic surfactant sodium dodecyl sulfate (SDS). Among the cationic surfactants, DMSAB and DPAB were selected to be studied more thoroughly. Triple-IPAs were prepared by mixing solutions of oppositely charged surfactants in equimolar ratio, and the resulting triple-IPA precipitate was filtered and dried. From the obtained powder, vesicular systems were prepared by rehydration and sonication. Cholesterol and cationic surfactants, from which the triple-IPAs were prepared, were used to stabilize the cationic vesicles. The properties of the vesicular systems were evaluated by dynamic and electrophoretic light scattering measurements and turbidimetry. The dispersion solutions with the addition of cholesterol were less turbid; therefore, it can be assumed that they supported the formation of cationic vesicles. The optimum cholesterol content is 20 mol. %. At this concentration, the effect of cholesterol on vesicle membrane reorganization becomes apparent and the cationic system remains monodisperse. A positive zeta potential in the stable region was determined for all prepared solutions, which was further increased by the addition of a positive surfactant. The most suitable cationic surfactant for the preparation of triple-IPA is DPAB, which is easy to work with, produces the most monodisperse systems and has the lowest measurement uncertainties.
Lignite degradation in soil environment
Vybíralová, Natálie ; Salaš, Petr (referee) ; Pekař, Miloslav (advisor)
This Master‘s thesis deals with the topic of coal and, more precisely South Moravian lignite. Lignite was degraded by using biological and chemical methods, which included oxidation of lignite with hydrogen peroxide. Special attention was paid to the degradation of lignite in the soil environment, where the simulation of natural fields conditions took place for 6 months. Furthermore, a simulation of root exudates was carried out using organic acids, which occur naturally in the soil environment and directly affect life in the soil and around the roots of the plant. Lignite degradation was also performed using a cultured bacterial solution and then using a commercially available horticultural products to increase the activity of soil microorganisms and promote growth.
Development and experimental evaluation of bioactivity of the next-generation bioinnoculants
Súkeník, Martin ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
This diploma thesis aimed to characterize specific mechanisms of biological activity in plant growth-promoting rhizobacteria (PGPR) commonly found in the rhizosphere of plants and to study the effects of liquid and gel application of PGPR bioinoculants on plants in a controlled environment. An original concept of self-encapsulation via cross-linking of alginate directly produced during their culturing was proposed for the preparation of gel bioinoculants based on these PGPRs. To validate the efficacy of this concept, all selected strains had to be subjected to gelation experiments with the crosslinking agent CaCl2 2 wt. % under alginate gel formation. Three specific strains of Azotobacter vinelandii DSM 87, DSM 720 and CCM 289 were selected for the preparation and characterization of the bioinoculants. The material properties of the formed gels were characterized by oscillatory rheometry (amplitude test). All strains were subjected to gravimetric determination of alginate and biomass concentrations. Flow cytometry with fluorescent probe PI, DAPI and SYTOX™ Green was used to verify cell viability immediately after culturing. Furthermore, the drying of gels was performed using a lyophilizer, where the lyophilized gel was used in swelling experiments followed by drying. To verify the biological activity of the bioinoculants, the ability of all strains to dissolve and utilize phosphate from the agar medium was qualitatively verified. Furthermore, the production of indole-3-acetic acid was spectrophotometrically verified for all strains. The production of siderophores was also verified qualitatively and quantitatively. Cultivation pilot experiments on the lettuce (Lactuca sativa) plant were performed with the addition of both liquid and gel carrier PGPR compositions; as a negative control, the plant was left without the addition of carrier PGPR composition. The results from the pilot growth experiment showed a positive growth effect of both gel and liquid PGPR composition on the plants. At the end of the growing experiment, higher leaf and root system lengths were recorded after the application of both forms of PGPR to the soil, specifically, the average leaf length with the addition of gel carrier PGPR composition was 4.3±1.0 cm and 4.3±1.2 cm for the gel carrier PGPR composition, and the average root system length was 18.3±5.2 cm and 17.4±6.0 cm, respectively. The dry weight per plant grown with the addition of liquid and gel PGPR was the same 0.19±0.07 g. The highest content of chlorophyll a, chlorophyll b and carotenoids in the leaves was spectrophotometrically detected in plants grown with the addition of liquid PGPR composition, specifically chlorophyll a was found to be 6±1 µg/ml, chlorophyll b 7±2 µg/ml and carotenoids 3.6±0.5 µg/ml. The diversity of soil microbiomes collected from the soil without the addition of PGPR composition, with the addition of liquid PGPR composition and with the addition of gel PGPR composition was analysed using BIOLOG EcoPlate™ plates. The diversity of the microbiome was evaluated using the average well colour development, i.e., the AWCD parameter, and the Shannon diversity index, H'. The highest utilization of the widest number of carbon sources on the plate was recorded for the soil microbiome with the addition of the gel PGPR composition. The aforementioned soil microbiome also showed the highest value of the H' index.
The long-term stability and properties of a skin cream with addition of liposomes
Müllerová, Kristýna ; Pekař, Miloslav (referee) ; Enev, Vojtěch (advisor)
The aim of the thesis was to design a formulation and subsequently prepare a native skin cream and skin creams enriched with liposomal particles with encapsulated vitamin E. After preparation of the skin creams, their stability and rheological properties were studied at given time intervals during storage for 12 weeks. The stability of the prepared samples was determined using a LUMiSizer analytical centrifuge with STEP-Technology. Among the rheological properties, changes in the rate of structure recovery of the formulations were monitored, as well as changes in zero and infinite viscosity, which can be presented as changes in viscosity during product storage and changes in viscosity during application and spreading on the skin. All stability and rheological tests were performed for a temperature of 25 °C, which also corresponded to the storage temperature, and for a temperature of 37 °C, which approximately corresponds to the human body temperature. According to the results, the sample without the addition of liposomes showed the highest stability and the skin cream with the addition of 10 wt.% liposomes at 1 week of age showed the best spreadability. Next, the characterization of liposomal particles was performed. Finally, a sensory analysis was performed where the evaluators compared the fresh native skin cream, the native skin cream at 12 weeks of age, the fresh skin cream with the highest liposome content and the skin cream with the highest liposomal particle content at 12 weeks of age.
Hydrogels and nerve tissue engineering
Šindel, Matej ; Mravec, Filip (referee) ; Pekař, Miloslav (advisor)
Master’s thesis deals with hydrogels suitable for neural tissue engineering. The thesis consists of a literature research with focus on understanding the parts of the neural system, the principles of used techniques and the requirements of the neural system for materials with potential to be used in neural tissue engineering. Then the thesis continues to the experimental part, where a simple model, created from agarose with linear channel filled with collagen mass, was designed. The individual materials used in model are prepared by various methods and then are tested. Testing includes verifying their ability or inability to fulfill the required functions. Ended by evaluating their potential of further use in more complex prototypes.
Microfludic chip development for phospholipid membrane modeling
Haluzová, Kateřina ; Pekař, Miloslav (referee) ; Venerová, Tereza (advisor)
The diploma thesis deals with the issue of phospholipid membranes and their modeling in a microfluidic environment. It describes the composition and its effect on the structure of cell membranes and defines a mathematical-physical model for characterizing the environment in microfluidic channels. Experimental part describes the production of a microfluidic chip and equipment required for reliable formation of membranes formed by L--phosphatidylcholine dissolved in hexadecane. The main emphasis is then placed on optimizing the conditions for the formation of this specific membrane model observed under a fluorescence microscope. We have succeeded in proving the correctness of the mathematical model and in partially describing the conditions under which the membrane is formed despite a large number of complications described in more detail in the discussion of this thesis.
Effect of different type and crosslinking density of polyethylene glycol hydrogels on transport and sorption properties
Janáková, Kristýna ; Pekař, Miloslav (referee) ; Krouská, Jitka (advisor)
The main goal of this work was to study the transport and sorption properties of polyethylene glycol (PEG) hydrogels with different types and densities of cross-linking. Before characterizing these properties it was necessary to optimize the preparation of selected hydrogels including the study of mechanical properties using rheological measurements. A significant part of the work, therefore, consists of the optimization of PEGDA-thiol hydrogels created from 4-arm polyethylene glycol-thiol (PEG-4SH) and polyethylene glycol diacrylate PEGDA by step-growth polymerization. To compare the transport and sorption properties of another type of crosslinking, PEGDA hydrogels were prepared using radical polymerization. In the transport experiments, the sorption and desorption of the Rhodamine 6G dye were monitored using free diffusion. Molecular absorption spectrometry (UV/VIS) was used to characterize the course of these experiments. The structure of these gels was compared using scanning electron microscopy.

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