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Hydration of biopolymers
Šméralová, Ester ; Smilková, Marcela (referee) ; Klučáková, Martina (advisor)
Presented bachelor's thesis focuses on the study of hydration of selected biopolymers – humic acids, chitosan, hyaluronic acid (low molecular weight and high molecular weight) and dextran. Thermogravimetric analysis TGA is used t determine the original moisture content of the samples. Two calorimetric methods were used for subsequent observations of changes in their chemical and mechanical properties in the presence of water – differential scanning calorimetry DSC and perfusion calorimetry.
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Transport of humic substances through plant cuticle
Smilková, Marcela ; Salaš, Petr (referee) ; Weidlich, Tomáš (referee) ; Klučáková, Martina (advisor)
Doctoral Thesis is aimed on the transport of liquid preparations chemically based on potassium lignohumate through plant cuticles commonly utilized in agricultural applications. Firstly, the thesis deals with optimization and correct mathematical description of diffusion experiments. Transport (diffusion) experiments have been realized in model hydrogel media based on linear polysaccharide – chemically inert agarose. Diffusion experiments have been realized by two independent approaches (diffusion models) – free diffusion of lignohumate in hydrogel and diffusion pair (hydrogel-hydrogel), where one of these was enriched by lignohumate in contrast with the second one. Plant cuticle, as the major barrier on the leaves, isolated from Prunus laurocerasus, was used as porous membrane in diffusion experiments. The main aim of Ph.D. thesis was the characterization of barrier properties of cuticles, which are the most limiting barrier regulating the transport of lignohumate in/out the leaves during foliar fertilization. These experimental problems have been solved by diffusion experiments and by their proper mathematical description, especially by the determination of fundamental diffusion parameters such as effective diffusion coefficients. These parameters have been used for the modelling of concentration profiles in hydrogels and comparison with experimental data. Significant part of thesis is aimed on the determination of physico-chemical properties of plant cuticles and hydrogels matrixes utilized as model diffusion environment. These characteristics are subsequently correlated with transport (diffusion) parameters. Plant cuticles have been isolated from Prunus laurocerasus leaves and then were characterized by relevant instrumentation notably with respect to their structure and penetration through of lignohumate. Hydrogels have been characterized with respect to mechanical (viscoelastic) (rheology), morphological e.g. porosimetry) and structural (scanning electron microscopy) properties. Mentioned properties have direct link to transport processes ongoing in these materials. Next part of doctoral thesis is aimed on the proper and correct interpretation of experimental results obtained from glass-house experiments. During these experiments, hydrogels based on superabsorbent polymers developed on Faculty of Chemistry, Brno University of Technology, have been used together with commercial preparation – potassium lignohumate kindly provided by co-working commercial subject – Amagro s.r.o. The main aim was the application of lignohumate directly on plants through root system. Results of these experiments should confirm the positive effect on plant growth as well as their positive development. Results obtained from transport/diffusion experiments confirm that the penetration of active compounds (lignohumate) is more efficient in comparison with adaxial cuticles. The kinetics of lignohumate transport is faster for abaxial cuticles. From superabsorbent experiments it is obvious that these play significant role in growth and development of plant and simultaneously positively contribute to creation of suitable conditions for proper microbiological and bacterial activity, which is essential for health soil.
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Interactions of metal ions with humic substances
Obručová, Kateřina ; Smilková, Marcela (referee) ; Klučáková, Martina (advisor)
This bachelor thesis is focused on humic substances, especially fulvic and humic acids. It deals with their genesis and subsequent extraction from nature materials. There are described not only physical and chemicals properties, structure of humic and fulvic acid, but also their reactivity. There is also described the method od isothermal titration calorimetry, which was subsequently used to study of interaction fulvic acid with selected metal ions (Cu2+, Ca2+, Mg2+). From the resulting titration data were determined values of reaction enthalpy, which was then compared with model complexes. From the resulting graphs, it was possible to determine when the reaction reached its maximum, the state when all the binding sites were full. Heat values were determined for this condition.
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Usage of physical-chemical methods for the study of interaction of humic substances with the plant cutisles
Rampáčková, Eliška ; Sedláček, Petr (referee) ; Smilková, Marcela (advisor)
This bachelor’s thesis deals with the study of interaction (or binding or adsorption) of plant cuticle with potassium lignohumate, as a liquid agriculture product used in the field of foliar fertilization, which belongs to the most used agronomic applications in general. The studied materials became the plant cuticle, which forms upper part of plants and potassium lignohumate (commercially Lignohumate), which is widely used thanks to its properties, which allow to increase the quality, growth and profitability of the crops. The aim of this bachelor’s thesis was to investigate the binding of compounds to plant cuticles, useful methods for this field of research and the use of thermal methods (precisely isothermal microcalorimetry and thermogravimetry). The next step was to use this instrumentation as a physicochemical method for assessing the ability of Lignohumate to bind to plant cuticles.
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Diffusion characterization of hydrogels at microscopic level
Uher, Tadeáš ; Smilková, Marcela (referee) ; Sedláček, Petr (advisor)
This Bachelor’s thesis deals with study of diffusion in gels on microscopic level. The method of fluorescence correlation spectroscopy is used for the study of diffusion and this method is based on monitoring the diffusion coefficients in a confocal volume of studied substance. As fluorescence probe is used organic pigment called Rhodamin 6G and diffusion experiments are realized in hydrogel matrix, whose medium forms thermoreversible linear polycarbohydrate – agarose, with addition of reactive component – biopolymer called sodium polystyrenesulphate in certain concentrations. The purpose of the thesis is to research the impacts of interaction between diffusing pigment and specific type of hydrogel. The change of final diffusion coefficient is observed. It is assumed, that sodium polystyrenesulphate influences the diffusion of fluorophore (Rhodamin 6G) in agarose hydrogel.
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Hydration of biopolymers
Šméralová, Ester ; Smilková, Marcela (referee) ; Klučáková, Martina (advisor)
Presented bachelor's thesis focuses on the study of hydration of selected biopolymers – humic acids, chitosan, hyaluronic acid (low molecular weight and high molecular weight) and dextran. Thermogravimetric analysis TGA is used t determine the original moisture content of the samples. Two calorimetric methods were used for subsequent observations of changes in their chemical and mechanical properties in the presence of water – differential scanning calorimetry DSC and perfusion calorimetry.
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Preparation and characterization of cosmetic emulsion with addition of active compounds
Zinkovska, Natalia ; Smilková, Marcela (referee) ; Smilek, Jiří (advisor)
In the theoretical part, this bachelor’s thesis focuses on the overview of the basic characteristics and properties of the emulsion. Great attention is paid to choosing the type of emulsifier and the calculation hydrophilic-lipophilic balance. The mechanisms andcauses of instability of emulsions and their possible prevention and methods of stabilization are analyzed. The present state of the problem aimed to the analysis of existing methods for determination of emulsion stability and their use in practice is also part of this thesis. The experimental part of the work is primarily focused on the preparation of O/W cosmetic emulsions with additive of active substances such as UV absorbers. To characterize the prepared samples, pH values were measured and viscosities determined. The stability of the emulsion was carried out using an analytical centrifuge, and these results were further correlated with the standard gravitational stability tests (change of storage temperature of the formulation) according to the SÚKL methodical guidelines (REG-49, REG 51), which are the Czech version of the 75/318 /: Stability tests on active ingredients and finished products. Methods of preparation and composition of individual samples are described, which is further correlated with the stated characteristics of prepared creams.
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Soil hydrogels based on the principle of controlled release
Macuráková, Viktória ; Smilková, Marcela (referee) ; Kratochvílová, Romana (advisor)
This bachelor thesis is focused on soil hydrogels, which operate on the principle of controlled release. The aim of the research was on the release of substances, and the practical use of hydrogels in agricultural practice. At work, we focused on the effect of humic substances and the quantities of the substances of the fertilizer NPK of hydrogel. Querying this data will use a variety of methods such as pH-metry, conductometry, spectrophotometry and chromatography and knowledge not only of the analysis but also the macromolecular chemistry. Experiment it was found that the content of sodium lignohumate does not affect the rate of release of potassium and phosphorus into the soil. Hydrogel which is located above the quantity of NPK fertilizer and a certain number of lignohumate released from its structures much larger amounts of ions such as Hydrogel without fertilizer NPK with approximately the same amount of lignohumate
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