National Repository of Grey Literature 38 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Solubilization in catanionic surfactant systems
Konečná, Anna ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with the solubilization of hydrophobic dyes in systems of positively charged catanionic vesicles. The aim of the work was to determine their solubilization capacity. Vesicular systems were prepared from oppositely charged surfactants CTAB and SDS. To increase the stability of the vesicles, cholesterol and the positively charged double-chain surfactant DODAC were added to their structure. DODAC also gave the system a positive charge. To determine the solubilization capacity, the dyes 1-Naphthol, Sudan Red G and Oil Red O were used. For sample preparation two methods were used, spontaneous and direct solubilization. The measurement was performed after 1, 2, 3 and 7 days from the preparation of the samples by UV-VIS spectrophotometry. The solubilization capacity was determined from the measured absorbance by calculation from the calibration curves. The results indicate that direct solubilization is slightly more effective than spontaneous solubilization. Of the selected dyes, 1-Naphthol is the substance with the smallest molecule, and therefore it seems to be 100% solubilized in the vesicle system.
Microcalorimetric study of interactions between hyaluronan and catanionic vesicular systems
Mach, Jakub ; Pekař, Miloslav (referee) ; Krouská, Jitka (advisor)
Properties of surfactants in water, interactions between oppositely charged surfactants and interactions in system containing didecyldimethylammonium chloride (DDAC), hyaluronan and ion pair amphiphile (IPA) have been studied using isothermal titration calorimetry. For the study of properties of surfactants in water and their mutual interactions, two cationic surfactants have been chosen, namely cetyl trimethylammonium bromide (CTAB) and carbethopendecinium bromide (Septonex), and an anionic surfactant sodium dodecyl sulfate (SDS). For hyaluronan, a molecular weight of 250 450 has been chosen. Critical micelle concentration of the chosen surfactants and enthalpy of the investigated interactions have been determined using the TAM III calorimeter. To prove the interactions in system containing hyaluronan, DDAC and IPA and to determine enthalpy the Microcal PEAQ-ITC calorimeter has been used.
Preparation and characterization of magnetorheological suspensions with high sedimentation stability
Oharek, Lukáš ; Krouská, Jitka (referee) ; Smilek, Jiří (advisor)
The introduced diploma thesis focuses on the preparation of magnetorheological suspensions with high sedimentation stability. The theoretical part generally describes these suspensions and their properties, it also focuses on the possibilities of improving sedimentation stability, for example by modifying the surface of the particles or adding additives. A research based on the topic of preparation of sedimentation stable magnetorheological suspensions was also carried out. The experimental part focuses on two types of magnetorheological suspensions. The first type of suspension consisted of a water-in-oil emulsion and carbonyl iron particles that were modified by chemisorption of the surfactant Tween 80. Another type of suspension contained thixotropic organoclay along with untreated iron particles. In both types of magnetorheological suspensions, the process of their preparation was optimized, together with the composition of carrier fluids for the preparation of the most sedimentation-stable magnetorheological suspension. The measurement of sedimentation stability by a dispersion analyser confirmed the positive effect of particle modification and the addition of thixotropic agent on the sedimentation stability of suspensions.
Study on interaction of humic substances with surface active agents
Bělušová, Anna ; Krouská, Jitka (referee) ; Smilek, Jiří (advisor)
This bachelor thesis deals with the study of interactions between humic acids (HK), as the main component of soil organic matter, and model pollutants in the form of surfactants through unconventional and original combination of dialysis and diffusion techniques. Since dialysis techniques are rarely used for the interaction of humic substances with surfactants study, it was necessary to optimize methods for determining of ionic surfactants (cationic Septonex and anionic sodium dodecylsulfate were selected as representatives) prior to begining of own experiments, using a method based on the color ion pair creation between a surfactant and a counter-charged dye, followed by this pair extraction into an organic solvent. Diffusion cell dialysis experiments were performed with cationic surfactant Septonex, which was expected to interact positively with humic acids relative to its charge. As humic acids representatives, the standards of these substances provided by the International Society for Humic Substances (IHSS) were selected, namely humic acids (IHSS HK) isolated from Leonardite (1S104H). One of this bachelor thesis aims was to verify the effect of carboxylic functional acids on reactivity and barrier abilities of humic acids. For this reason, these standards have been modified by the selective methylation of carboxyl groups which no longer participate in the interaction with surfactants. Already from the first experiments there was a noticeable decrease in the concentration of Septonex over time – it means its transition through the dialysis membrane to humic acids, which indicates a positive affinity of humic acids to Septonex. The extent of these interactions was assessed through the apparent interactions parameter app through which the assumption that IHSS HK reacted with Septonex more than their methylated form of MIHSS HK was verified.
Interaction of trimethylchitosan with Niaproof surfactant
Zbořilová, Hana ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This thesis is focused on the study of interaction of the polycation N,N,N-trimethylchitosan (TMC) with the anionic surfactant Niaproof® 4 in water and physiological saline solution. Due to the commercial unavailability of N,N,N-trimethylchitosan, the polymer was first synthesized from chitosan, followed by NMR and FTIR characterization. Before the study of the system polycation–anionic surfactant itself, the behavior of the anionic surfactant Niaproof® 4 in aqueous solution and physiological saline solution was explored. The micellization of the surfactant Niaproof® 4 and the aggregation of TMC–Niaproof® 4 system were observed by fluorescence spectroscopy using the fluorescence probe pyrene. Values of critical micelle and critical aggregation concentration were determined on the basis of measurements. It was confirmed that presence of the sodium chloride supports the micellization by increasing the ionic strength of the solution, which leads to decrease of CMC in physiological saline solution. The interaction of TMC–Niaproof® 4 occurs at lower concentration then CMC in both aqueous and physiological environments. Phase separation occurs at higher concentrations of the surfactant leading to stabilization of the system.
Hydrogels with incorporated enzymes
Geistová, Karolína ; Krouská, Jitka (referee) ; Mravec, Filip (advisor)
This bachelor thesis deals with the study of incorporation of enzymes into phase separated hydrogels. The aim of this work is to determine the enzyme activity in phase separated gels. Gels were prepared by the dry-way based on the interaction of negatively charged polyelectrolyte (hyaluronan) with positively charged surfactant (Septonex). Two enzymes, bromelain and collagenase, were incorporated into the hydrogels. To determine enzyme activity, the modified albumin protein with bound sulfanilamide group (azoalbumin) was used as a substrate. The enzyme activity of the enzyme itself, the enzyme activity affected by one of the two components of the system as well as the activity of the enzyme directly in the hydrogel was determined on UV-VIS spectrophotometry. The enzyme was found to be incorporated in the hydrogel. Furthermore, a significant effect of the positively charged surfactant on the enzyme activity was detected in phase-separated hydrogels.
The use of microcalorimetric methods in the study of the protective effects of chemical chaperons
Bohunská, Miroslava ; Pekař, Miloslav (referee) ; Krouská, Jitka (advisor)
This bachelor thesis deals with the study of protective substances against denaturation processes, called chemical chaperones. The theoretical part describes the general characteristics of proteins, description of selected chaperones and methods of differential scanning calorimetry. In the experimental part, the protective effects of four potential protective agents - trehalose, guanidine hydrochloride, 3-hydroxybutyrate and hydroxyectoine - were investigated on the lysozyme model protein. The protective effects of the individual substances were examined by differential scanning calorimetry (DSC), which determined the denaturation temperature of lysozyme in the presence of preservatives. Of all the chemical chaperones examined, the highest protective effect was observed with 3-hydroxybutyrate, which shifted the denaturation temperature to higher levels, and guanidine hydrochloride, which on the other hand lowered the denaturation temperature. At the same time, a reversible denaturation process was found in some substances, which was the most intense in GuHCl.
Adsorption of microbial cells on model biological surfaces
Mikušová, Janka ; Krouská, Jitka (referee) ; Sedláček, Petr (advisor)
The aim of this bachelor thesis is creating sorption surface suitable for studying adsorption bacterial strain Lactobacillus rhamnosus, as representative probiotic bacterial strain. Included in the experimental part of this thesis was the process of creating sorption surface, according to the designed and especially optimized method. Optimization method comprised of preparing sorbent with sorption surface including mucin, on which was the bacterial strain Lactobacillus rhamnosus bound to, using specific interaction. UV-VIS spectrophotometry was utilized in the optimization of the sorption surface preparation for monitoring losses of mucin in solution that happens during the bondation on used substrate. Designed sorption surfaces were subjected to various physical-chemical analyses, which roles were displaying and characterisation of surface and confirming the presence of mucin. One of the major components, in the process of observing and characterization of changes in surface structure of the sorption surface, was infrared spectroscopy with Fourier transformation. Scanning electron microscopy was used for more detailed observation of the surface structure, created by adhesive interactions, which participate in probiotic bacteria adhesion. Finally, the created surfaces were used in pilot experiment, during which, the kinetics in growing bacterial culture with and without the presence of sorbent using microcalorimetry were observed. Designed sorbent appears to be a suitable mediator for detailed characterisation of bacterial adhesion, which is the first step in creating bacterial biofilm.
Stability evaluation of cosmetic dispersions using centrifugal analyser
Procházková, Michaela ; Krouská, Jitka (referee) ; Pekař, Miloslav (advisor)
This bachelor thesis is focused on the evaluation of stability of cosmetics emulsions prepared from ingredients commonly available in laboratory and compared to the stability of commercially available body lotions. In the theoretical part cosmetics emulsion and methods used to stability measurements were described. Experimental part of this work at first describes the preparation of the emulsions. Furthermore, the stability of prepared emulsion was compared to commercially available ones using the centrifugal analyser LUMiSizer. In conclusion, the test results obtained from analyser LUMiSizer have showed the stability of the commercial emulsions and two prepared samples.
Influence of metal ions on microorganization of humic substances
Odehnalová, Nikola ; Krouská, Jitka (referee) ; Klučáková, Martina (advisor)
This bachelor thesis is focused on the study of influence of metal ions on microorganization of humic substances. This issue was studied on a sample od fulvic acid. Solution of cocentration 1 g/l was prepared from this sample. This solution was ten titrate with solutions of copper, calcium and magnesium ions. For this purpose, methods of dinamic and electrophoretic light scattering were used. The results obtained by these methods show that the solution of fulvic acid is the most made by associated molecules of fulvic acid. The size of molecules became larger and larger during titrations. Copper was sorpted the most.

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