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Hodnocení bobtnavosti dehydratovaných produktů
Kadlec, Lukáš
The diploma thesis was elaborated at the Institute of Post-Harvest Technology of Horticultural Products of the Faculty of Horticulture of Mendel University in Brno in 2019/2020. The theoretical part is devoted to water activity in food, drying of fruits and vegetables, lyophilization, swelling of dehydrated products and their substance composition. In the experimental part, water activity, dry matter and rehydration dynamics and the achieved humidity were determined for various samples of fruits and vegetables obtained by different drying methods.
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Optimisation of polyethylene glycol hydrogels preparation by polymerisation and their subsequent characterisation
Fornůsek, Jakub ; Trudičová, Monika (referee) ; Smilek, Jiří (advisor)
The goal of this bachelor’s thesis was the optimization of the preparation of polyethyleneglycol hydrogels by radical polymerization and their subsequent characterization by the means of rheometry, swelling experiments and examination of transport properties through the absorption of an active substance and its subsequent desorption. To examine these hydrogels, UV photopolymerization was chosen due to its simplicity and reproducibility. As part of the optimalization, hydrogels were prepared under varying conditions and then characterised by the previously mentioned methods. The effect of the presence of the cross-linking agent ethylenglycol dimethacrylate on the properties of the resulting hydrogels was also investigated. These examined gels represent a new type of chemically cross-linked hydrogels, which are part of a basic research project applications by GAČR. From rheometric measurements, it was confirmed that a higher molecular weight of the measured sample corresponded to lower values of viscoelastic moduli. The effect of the cross-linking agent on these values was negligible. The mesh density played a significant role in swelling and transport experiments. As its value increased, the swelling capacity of the hydrogel decreased and therefore a smaller amount of water was absorbed. The presence of the cross-linking agent was also noticeable, as it contributed to a creation of higher density polymer networks.
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Hybrid gellan hydrogels
Borovský, Martin ; Přibyl, Jiří (referee) ; Krouská, Jitka (advisor)
The subject of this bachelor thesis was the preparation of hybrid gellan hydrogels based on the combination of physical crosslinking and ionic interaction of the functional groups of gellan with multivalent ions of selected metals. These materials were subsequently characterized by analysis on their mechanical properties, ability to swell in aquatic environment, and by studying of their rate of drying using drying scales. The results of the study indicate that hybrid crosslinked hydrogel networks provide better mechanical properties, thus these hydrogels have high application potential. From the obtained data it was found that hydrogels with the addition of multivalent ions exhibit a higher degree of crosslinking of their hydrogel network, which positively affects the resulting properties of the hydrogels. By using different types of ions at variable concentrations, the hydrogels with a wide range of properties can be prepared. In conclusion, the experimental findings are summarized and an overview of the influence of multivalent ions on the mechanical properties of hydrogels is provided.
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The use of vacuum compression therapy on patients after knee surgery
BUŠEK, Matěj
In this bachelor thesis the main topic is the effect of vacuum compression therapy in patients after knee surgery. First, the basic anatomy of the knee joint was described, summarizing the structures that, when damaged, are indications for knee surgery. Next, the possibilities of knee joint damage as well as knee joint surgery options were described. As this bachelor thesis came from a spa setting and one of the main objectives was to investigate the use of vacuum compression therapy in a comprehensive spa treatment system, spa treatment options for patients after knee surgery were also described. In its practical part, the research population of five probands who were prescribed vacuum-compression therapy in their set of treatments was examined. With these probands, their knee joint development during the spa treatment was subsequently investigated using entry and exit aspect and palpation, goniometric measurements and somatometry. Also, one of the outcome factors of this undergraduate thesis was the subjective view of this issue and this was obtained through a semi-structured interview. A total of 5 probands participated in this research for this Bachelor's thesis. All of them had experienced vacuum compression therapy for the first time and therefore the semi-structured interview output made sense and therefore the probands' responses were not influenced by their previous experience of this form of physical therapy. Exit examinations concluded that their condition had improved, both in range of motion of the knee joint and in the length of the knee joint circumference, which indicated improved swelling rates, as confirmed by the facet and palpation examinations. At the same time, through interviews, a positive perception of vacuum compression therapy was found by patients who underwent this therapy. The majority of them reported a positive attitude towards the therapies they had undergone and also felt that their health status had improved after all applications of vacuum-compression therapy.
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Transport and mechanical properties of hybrid hydrogel networks based on gellan
Sokolínský, Jan ; Pekař, Miloslav (referee) ; Kalina, Michal (advisor)
This diploma thesis deals with the characterization of the mechanical and transport properties of gellan based hybrid hydrogels. As part of this work, the process of optimizing the preparation of gellan-poly(vinylalcohol) IPN hydrogel was first studied with an emphasis on the repeatability of the preparation due to the preservation of mechanical properties of the hydrogel. Then, both on the gellan hydrogels themselves and on selected IPN compositions, the effect of various additives was studied (specifically, the effect of the addition of a plasticizer and the effect of cross-linking by polyvalent ions). Based on these tests, a set of samples was selected, on which dynamic mechanical analysis, swelling and drying experiments were additionally measured. At the end of this diploma thesis, the transport properties of selected hydrogel compositions were also studied. The tests conducted in this thesis revealed that both the formation of a dual network and the addition of the mentioned additives allow us to influence the studied properties.
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Characterization of hydrogels based on photocross-linked derivative of hyaluronan
Hekrlová, Veronika ; Smilek, Jiří (referee) ; Klučáková, Martina (advisor)
This bachelor thesis focuses on characterization of hydrogels based on photocross-linked Tyramine-modified hyaluronan (HA-Tyr). In the first part of the work, swelling of gels in saline and porcine plasma was examined, in which the hydrogels swell significantly less. The second part of the thesis is focused on rheology. First, dependence of the apparent viscosity of precursor solutions on shear rate was tested. The apparent viscosity increases with the concentration of derivative and Mw. This trend can also be observed when measuring viscoelastic properties (the elastic modulus) in oscillation mode (strain sweep test). The elastic modulus can also be affected by using a higher concentration of the photoinitiator riboflavin (RF), higher radiation intensity or by longer exposure times, although the material can be degraded. The work also includes an ATP bioluminescence method cytotoxicity test, which proved that the methods used are safe for in situ application.
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Preparation and characterization of novel application forms of humic substances in combination with water sorbents
Nováčková, Táňa ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
This bachelor’s thesis discusses an applicability of hydrogel forms-based composite materials of humic acids and commercial water sorbent. According to the literature review, methods of incorporation of humic acids into commercial sorbents of water under various conditions and the resulting materials were subsequently characterized. In the characterization, major attention was paid to the determination of the water content and the swelling characteristics. Preparation of the composite materials was directed to use their sorption abilities and ability to control the release of humic substances in agriculture.
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Biodegradable polyurethanes based on poly(ethylene glycol)
Kupka, Vojtěch ; Žídek, Jan (referee) ; Vojtová, Lucy (advisor)
Predložená diplomová práce se zabývá syntézou biodegradabilních polyuretanu (bio-PU) na bázi polyethylenglykolu (PEG-u) a polykaprolaktonu (PCL) pro využití k medicínským úcelum. Cílem práce bylo vyvinout metodiku prípravy elastomerního polyuretanu, ze kterého by se dal v budoucnu pripravit skafold (nosic bunek) použitelný v tkánovém inženýrství pro humánní regenerativní medicínu. Teoretická cást práce shrnuje informace o materiálech využitelných pro zamýšlenou aplikaci. Zahrnuty jsou také techniky prípravy skafoldu, jejich biokompatibilita a charakterizace vlastností výsledného materiálu. Praktická cást je pak zamerena na navržení vhodné metodiky pro prípravu funkcních vzorku obsahujících PEG, PCL, hexamethylen-diisokyanát (HMDI) a ethylhexanoát cínatý jako katalyzátor. U pripravených vzorku byl zjištován vliv jejich složení (predevším ruzný obsah a molekulová hmotnost PEG-u) na botnání a hydrolytickou stabilitu spolecne s testováním mechanických vlastností, sledováním kinetiky sítování a stanovením stupne konverze. Morfologie vzorku byla sledována pomocí optické mikroskopie, chemické složení bylo potvrzeno infracervenou spektroskopií a tepelné vlastnosti byly urceny diferencní kompenzacní kalorimetrií. Vývoj v metodice prípravy ukázal, že je nezbytné odstranit pred syntézou z výchozích látek veškeré necistoty, predevším vodu a kyslík, jinak vznikaly nedokonale zreagované vzorky s velkým obsahem póru ruzných velikostí. Syntéza všech vzorku probíhala pod dusíkovou atmosférou ve dvou krocích, kdy v prvním se pouze homogenizovaly oba polyoly (PEG i PCL) na vakuové lince pri 130 °C a ve druhém pak vznikaly výsledné bio-PU za pridání HMDI pri 65 °C v inertní atmosfére manipulacního boxu. Vzorky pak byly dopolymerovány ve forme pri 65 °C pod dobu 48 hodin v sušárne. Ruzné fyzikální podmínky metodiky vedly k príprave jak nepruhledných bílých filmu, tak i vzorku s viditelnou separací fází až po flexibilní transparentní filmy. Pozorování optickým mikroskopem vzorku s fázovou separací prokázalo prítomnost sférolitické struktury krystalické fáze PCL v amorfní fázi matrice PEG-u. Sledování kinetiky sítování pomocí soxhletovy extrakce potvrdilo maximální konverzi polymerace (96 %) již za 4 h dopolymerování v sušárne. Testování zkouškou v tahu ukázalo, že výrazný vliv na pevnost v tahu má isokyanátový index (pomer NCO/OH skupin). Molekulová hmotnost PEG-u ovlivnovala pevnost v tahu jen u vzorku zcela zesítovaných. Merení botnání vzorku ve vode prokázalo, že s rustem molekulové hmotnosti PEG-u roste i obsah vody (od cca 28 až po 58 hm.%) ve vzorcích. Také degradace filmu ve vode pri 37 °C probíhala dle predpokladu rychleji u vzorku s vyšší molekulovou hmotností PEG-u. V predložené diplomové práci bylo potvrzeno, že množstvím a molekulovou hmotností polyethylenglykolu je možné rídit hydrolytickou stabilitu výsledných biodegradabilních polyuretanových elastomeru.
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Nuclear Fuel and its Behavior during Burn-up
Matocha, Vítězslav ; Foral, Štěpán (referee) ; Katovský, Karel (advisor)
The point of this bachelor’s thesis is to characterize different types of nuclear fuels and their behaviour during the process of burning-up. Futher, basic types of nuclear reactors are mentioned, as well as their history and different kinds of nuclear fuels used in these reactors. Then there are pieces of information about fuel cycles and fuel burning-up. Furthermore, the thesis concentrates on the changes, which happen in the nuclear fuel during the process of burning-up, such as swelling and cracking. In its other parts, this bachelor’s thesis deals with fission products, mainly gas fission products are mentioned here. At the end of this thesis, a simple model of nuclear fuel burning-up is created. This model follows concentration of izotopes of uranium and plutonium during fuel burning-up.
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