National Repository of Grey Literature 310 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Utilization of novel strategies of alginate crosslinking in the development of next-generation bioinoculants
Gašparová, Dominika ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
Tato diplomová práce se zaměřuje na různé strategie síťování alginátu, s cílem posunout vpřed vývoj bioinokulantů nové generace. Zkoumání různých strategií gelování se aplikuje na pět komerčně dostupných alginátů a izolovaný bakteriální alginát. Experimenty zahrnující přípravu alginátového makrogelu sloužily ke stanovení výskytu a kvality síťování, které byly analyzovány amplitudovými testy. Výběr vhodných síťovacích činidel a stanovení jejich optimálních koncentrací byly klíčovými cíli. Síťovací činidla, která byla vybrána jako vhodná pro makro- i mikroenkapsulační procesy, byly ty obsahující chlorid zinečnatý, chlorid hlinitý, chlorid barnatý, síran vápenatý a chlorid železitý. Optimální podmínky síťování byly stanoveny při teplotě 7~°C a optimální délka doby síťování v rozmezí od 30 do 120 minut. Byly provedeny komparativní analýzy šesti vybraných síťovacích činidel a to prostřednictvím analýzy mechanických vlastností skrz squeeze test, termogravimetrickou analýzou, botnáním gelu a obrazovou analýzou. Síťování barnatým síťovacím činidlem prokázalo slibné výsledky při zachování obsahu vody během rehydratace, zatímco sítování zinečnatým síťovacím činidlem dosáhlo nejvyššího obsahu sušiny. Obrazová analýza odhalila menší gelové perly tvořené síťovacími činidly s obsahem hliníku a barya, což naznačuje jejich účinnost. Mikroenkapsulované gelové perly, zejména ty síťované s baryem, prokázaly potenciál díky jejich menší velikosti. Vrcholem pokusů bylo síťování bakteriální kultury, kde hliníková a barnatá síťovací činidla dosahovala nejmenších gelových perel. Obzvlášť síťování barnatým činidlem dosahovalo nejmenších velikostí s nejmenší odchylkou, indikujíc jeho efektivitu.
Computer modeling of diffusional transport in hydrogel
Koláček, Jakub ; Sedláček, Petr (referee) ; Pekař, Miloslav (advisor)
This thesis focuses on the design of models applicable to the simulation of particle motion in a viscoelastic environment in COMSOL Multiphysics. Two approaches have been chosen for the design of these models: the first is the design of a geometry representing the porous structure of hydrogels and the second is the implementation of viscoelasticity using the mathematical concept of a continuous environment. Two elementary geometrical models are presented in this work – a three-dimensional periodic lattice and a spherical volume model. Furthermore, the possibilities of implementing the generalized Langevin equation in COMSOL Multiphysics are explored by using the interface for custom partial differential equations, by adding an auxiliary dependent variable, or by defining a custom external function written in the C language. The proposed geometric models did not prove to be suitable for the simulation of viscoelastic environment. An implementation using an external function seems to be the most promising, as it offers the most customization possibilities, and its implementation reflects the theoretical foundations. The thesis also includes a custom add-in written for COMSOL Multiphysics to facilitate the evaluation of simulation data and a modified Python script to calculate the complex shear modulus from MSD data.
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.
Hydrogels modified by amphiphilic structures
Heger, Richard ; Sedlařík, Vladimír (referee) ; Kráčalík, Milan (referee) ; Pekař, Miloslav (advisor)
The submitted dissertation deals with the influence of amphiphilic structures on hydrogel properties. Additions of various amphiphilic substances associated with the formation of highly ordered structures affect the mechanical, transport and structural properties of hydrogels. The main inspiration for this type of work was living tissue, more precisely the extracellular matrix, which is often mimicked by hydrocolloids, and its high orderliness is responsible for its unique properties. The knowledge obtained from this tissue was applied to the hydrogel systems studied in this work. Various cross-linked hydrogel matrices (physically cross-linked agarose and gelatin, ionically cross-linked alginate and chemically cross-linked mixture of polyvinyl alcohol and chitosan) were suitable representatives for this work. These hydrogel systems were modified by the addition of various amphiphilic substances. The human body’s own phospholipid, lecithin, or variously charged more classic surfactants (CTAB, SDS and Triton X-100). Experimentally, this work is divided into three areas, the study of mechanical properties using rheology, the description of transport properties via release and flow experiments using various model drugs (rhodamine 6G, eosin B, amido black 10B, methylene blue and riboflavin), and morphological characterization using SEM. The characterization of hydrogel systems was supported by other techniques used in this work, such as drying and swelling experiments or gas sorption.
Hyaluronan micro- and nanoparticles
Mourycová, Jana ; Marián, Lehocký (referee) ; Pekař, Miloslav (advisor)
The aim of this thesis was to prepare hyaluronic acid micro- and nanoparticles based on electrostatic interactions with oppositely charged molecules. Following parameters were monitored: correlation function behavior, the particle size and zeta potential value. At the beginning, it was necessary to study the behavior of hyaluronan in solution by dynamic light scattering measurement. Micro- and nanoparticles were prepared by mixing different volume ratios of negatively charged hyaluronan and positively charged polyarginine or cetyltrimethylammonium bromide. Micro- and nanoparticles were prepared in aqueous solution as well as in 0,15 M sodium chloride solution (physiological solution). In the case of the hyaluronan solution a polydisperse character of hyaluronan was detected. It was found that the dissolution of hyaluronan in the physiological solution gives us the smaller particle size in opposite to particle size obtained from the same concentrations of hyaluronan dissolved in water. Furthermore, it was found that systems composed of hyaluronan and polyarginine create particle size of about 100 nm. Whereas systems consisting of cetyltrimethylaminoum bromide and hyaluronan form larger particles, in units of hundreds of nanometers, the particle size in physiological solution were smaller than the same systems dissolved in aqueous solution.
Hydrogels with incorporated vesicular systems
Kalendová, Lucie ; Pekař, Miloslav (referee) ; Venerová, Tereza (advisor)
This bachelor thesis deals with the incorporation of vesicular systems into polysaccharide – based hydrogels. The chosen vesicular systems were Ion Pair Amphiphile vesicles (IPA), which consist of cetrimethylammonium bromide, sodium dodecyl sulfate, dioctadecyldimethylammonium chloride and cholesterol. The work is divided into two parts. In the first part, interactions between IPA vesicles and sodium hyaluronan and interactions between IPA vesicles and sodium polystyrene sulfonate were studied. Even though interactions occured, it was not possible to prepare a hydrogel based on these interactions. The second part of this work deals with incorporation of IPA vesicles into an agarose – based gel when heated. Particles of two different concentrations (1 mmol·l1 and 2 mmol·l1) were used. The effect of the IPA particles on the properties of the gel was observed with rheological measurements. The results showed that the gel with incorporated particles has a longer linear viscoelastic region and that there were no interactions between the IPA particles and the gel. The particles only fill the gaps of the gel network. Different behaviour within the gels with different concentrations of IPA vesicles was not observed.
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.
Hyaluronan effect on transdermal penetration of selected pharmaceutical substances
Ureš, Tomáš ; Sedláček, Petr (referee) ; Pekař, Miloslav (advisor)
This work deals with the transmittance of a family of non-steroidal anti-inflammatory drugs across biological membranes in combination with the use of hyaluronan. Hyaluronic acid (hyaluronan, HYA) is a linear polysaccharide formed from disacharide units containing N-acetyl-D-glucosamine and glucuronic acid. HYA is present in almost all biological fluids and tissues, so there is an assumption that could affect the penetration of substances through the skin. Standards were prepared by anti-inflammatory drugs in admixture with various concentrations hyaluronan and subsequently measured transmittance of such substances through the skin. Standards were applied to the skin obtained from pig auricle. The drug content was determined by HPLC.
Preparation, characterization of trimethylchitosan and verification of its interaction ability with regards to variable charged ionic compounds
Bayerová, Zuzana ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
The aim of this thesis is to study the interactions of trimethylchitosan with oppositely charged substances with regard to its potential biomedical use. A substantial step before the study of interactions was a successful synthesis of trimethylchitosan, which was subsequently confirmed by characterization of the final synthesis product using physico-chemical methods (infrared spectroscopy, elemental analysis, nuclear magnetic resonance). The result product was subjected to negatively charged interactions such as sodium dodecyl sulphate as a representative of the ionic surfactant, alginate as a natural polysaccharide representative and Chicago Blue as a representative of the anionic dye. The ability to interact with sodium dodecyl sulfate and alginate was demonstrated by the formation of hydrogels, which were subsequently characterized by mechanical viscosity tests using rheometric properties. The positive affinity of trimethylchitosan for organic dyes has been investigated in agarose-based support hydrogel matrices for changes in transport and barrier properties.
Genesis of new ultra-fine particles of milling stock in the course of the mill exposure.
Kejík, Pavel ; Pekař, Miloslav (referee) ; Svěrák, Tomáš (advisor)
This work deals with the study of limestone and corundum dry milling using attritor-type stirred mill in a batch mode. There were stearin and polyethylene glycol used as surfactants and spherical shaped steel grinding elements used for the experimental part of the work. The main idea was to examine behavior of the selected grinding stock type within a long-term grinding forces exposure in selected conditions of ultrafine dry milling leading up to the submicron area. Characterization of samples was performed by laser granulometry, X-ray powder diffraction analysis, flame atomic absorption spectroscopy, objective color determination and electrokinetic potential measurement. Experimetaly measured data implies that in all cases there was a re-agglomeration of the grinding stock particles occurring, although in different stages of the disintegration process and in mutually various degree. The analysis results denote that a larger erosion of the crystal structures with the associated increase of the amorphous phase in the submicron particle size took place in the grinding stock.

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See also: similar author names
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9 Pekař, Martin
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