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Propagation of inclined cracks to the interface of ceramic laminates
Novotná, Lenka ; Trunec, Martin (referee) ; Chlup, Zdeněk (advisor)
Composite materials with laminated structure provide advantages which are utilised during component design. Low density, temperature and chemical stability are the profitable properties predetermining application of ceramic laminates. The main obstacle for wide spread of ceramic materials is their inherent brittleness. Therefore, in this thesis, the crack propagation in ceramics laminates has been extensively studied. Laminated structures with various volume fractions of components (alumina and zirconia) were prepared by electrophoretic deposition. Evaluation of crack propagation through the interface and determination of basic mechanical properties was conducted on the basis of extensive literature search. Crack deflection originated in both presence of internal stresses and differences in elastic modulus during the crack interface passing was monitored. A special type of specimen geometry was employed with the aim to set arbitrary angle between crack and interface. It was experimentally found that the degree of crack deflection is dependent on entering angle and volume fraction of components. Higher crack deflection was already found in the bulk of the test piece comparing to the test piece surface. The 3D fracture surface reconstruction generated using laser confocal microscopy was used in this detailed crack propagation study. Further basic elastic and strength characteristics of laminates were determined and compared to those obtained from monolithic materials. The validity of the mix rule for elastic characteristics was confirmed by comparing of elastics modulus. The most reliable method for elastic modulus determination was marked the dynamic resonance method due to low scatter and consistency in measurement. The flexural strength of all laminates tends to be close to the flexural strength of the weakest component. Therefore the mix rule is not applicable for flexural strength estimation on the contrary of elastic characteristics. The change of component volume fraction leads only to change of flexural strength scatter. Thanks to gained knowledge about crack propagation and basic characteristic determination will be possible to design ceramic laminates more efficiently for given needs of application.
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Bioceramic Materials and Their Biocopatibility with Bone Tissues
Novotná, Lenka ; Trunec, Martin (referee) ; Cihlář, Jaroslav (advisor)
The thesis concerns the study of ceramic coatings of zirconia nanoparticles deposited on alumina, zirconia and glass substrates by ultrasonic spraying. The quality of deposits was investigated in dependence on the type of substrate (composition, temperature, roughness) and concentration of ceramic suspension. The best results were received by the deposition of suspension of low concentration on rough substrates at low temperatures. The biocompatibility was tested in vitro. Good cytocompatibility of ceramics with nanostructure coatings was found.
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Study of bioceramic materials for dental applications
Lokvenc, Martin ; Matoušek, Aleš (referee) ; Novotná, Lenka (advisor)
This thesis deals with bioceramics used in dentistry. The biocompatibility, which is the characteristic property of biomaterials, is described in the opening chapter of the thesis. Advantages and disadvantages of advanced ceramics are also discussed. The main attention was paid particularly to the dental bioceramics, which can be divided according to different criteria. The used classification was based on microstructure, which significantly influences behaviour and properties of biomaterials. The ceramic is viewed as a composite material, where the glass matrix is filled with different amount of crystal phase. The thesis also includes the use of the individual types of bioceramics for the manufacture of dental restorations.
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Creating and testing bioluminescence sensors for cytokinins in Arabidopsis thaliana
Novotná, Lenka ; Petrášek, Jan (advisor) ; Vosolsobě, Stanislav (referee)
Advances in microscopy and the sensitivity of novel biosensors have enabled the development of new methods for monitoring phytohormones with low invasiveness and relatively high resolution, providing greater insight into phytohormone function in plants. Genetically encoded indirect biosensors for cytokinins, one of the main plant hormones, are widely used for the tracking of dynamic changes in their levels during plant development and growth. The cytokinin-sensitive synthetic promoters used as cytokinin biosensors are being continuously improved, providing better insight into cytokinin function. However, the reporter systems used for the visualizations are either based on the enzymatic reaction producing colour or on the usage of fluorescence proteins. Luminescence-based biosensors are often used to visualize signaling outputs of plant hormones, but they are based on exogenous addition of luciferin substrate. Therefore, in this thesis, I have introduced a new technique for the generation of cytokinin signaling output sensors based on autonomous bioluminescence. This autonomous bioluminescence represents a non-invasive technique that depends on the expression of the whole autonomous bioluminescence system from fungi Neonothopanus nambi, in particular, the caffeic acid cycle with the fungal...
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Development of photosensitive ceramic suspensions for 3D printing of porous bioscaffolds
Ravasová, Michaela ; Novotná, Lenka (referee) ; Částková, Klára (advisor)
The aim of the diploma thesis is the development of light-sensitive ceramic suspensions for the creation of porous bioscaffolds using 3D printing. The suspensions were based on aluminum oxide in the first phase and, in the second phase of the experimental part, on calcium phosphate. The theoretical part of the thesis focuses on describing human bone and the properties of bioscaffolds, providing an overview of biomaterials and methods for preparing porous bioceramics, along with a summary of previous results achieved by other scientific groups in the field. The experimental part describes the development of the suspensions. The influence of monomers, photoinitiators, dispersants, and ceramic powders on the properties of the suspensions and their photopolymerization ability was observed. By optimizing the suspensions, a suitable composition for 3D printing of scaffolds from aluminum oxide was achieved. The amount of dispersant and ceramic powder was determined based on rheological measurements, and the ratio of monomers and initiator content was adjusted according to gelation tests, where the dependence of resin polymerization on the illumination time was monitored. The suspensions were subsequently printed and sintered. The microstructure of the sintered bodies was characterized with a focus on defects specific to the debinding process. After creating a suspension suitable for 3D printing from aluminum oxide, the same procedure was applied to develop suspensions based on calcium phosphates. The outcome of the diploma thesis is a suspension based on aluminum oxide or tricalcium phosphate prepared from a mixture of di- and tetrafunctional acrylates in a weight ratio of 1:1, with 73-77 wt.% or 65 wt.% powder filling and 2 wt.% or 3 wt.% dispersant. The suspension is suitable for stereolithographic 3D printing of thin-walled bodies for biomedical applications.
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Bioceramic materials bioactivity testing via simulated body fluid
Holbusová, Eva ; Novotná, Lenka (referee) ; Salamon, David (advisor)
These days, there is a possibility of joint replacement implantation, more common dental implants, or regeneration of bone fractures using bone graft replacements is more accessible than in history. Bioceramic materials are used for these purposes. Bioceramics is a non-toxic ceramic material. It is characterized by its bioactivity and biocompatibility. Bioactivity testing of bioceramics is performed using simulated body fluid (SBF). In addition, the change in the concentration of calcium ions was investigated during the testing. The aim of the work was to determine whether the concentration of calcium ions changes between bioceramics and SBF. Bioceramic samples were prepared by two methods, namely freeze-casting and cold isostatic pressing. What was soaked in c-SBF was prepared according to Kokubo. The analysis of SBF was performed using a colorimetric method with a reagent of Murexide solution and reagent KIT. The concentration of calcium ions in the SBF after soaking samples in a testing cycle 0, 3, 7, 14, and 21 days was measured using a UV/VIS spectrophotometer. In addition, X-ray diffractometry was used to determine the phase composition of the material before soaking in SBF. The change in calcium ion concentration during the test cycle in the bioceramic – SBF system was confirmed with UV/VIS spectrophotometry. The most significant increase in concentration was recorded on the third day of soaking. The assumption of an apatite layer formation on the soaked bioceramic samples was supported by a change in the concentration of calcium ions SBF and the change in weight of the material after soaking. It was found that using indirect colorimetric determination delivered better results when the Murexide indicator was used instead of KIT.
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Public health insurance and its new legislative conception in the Czech legal order
Novotná, Lenka ; Císařová, Dagmar (advisor) ; Sovová, Olga (referee)
This thesis is focused on current public health insurance system in Czech Republic and its possible future changes according to the proposals of the present government. The term "public health insurance" does not necessarily imply that the system is administered by public body (or bodies); it rather refers to the fact that the health insurance scheme in Czech Republic is designed to be a social and mandatory system based on solidarity of insured and plurality of health insurers. All members of the system are regularly contributing according to their possibilities. Their contribution is monthly redistributed among health insurance companies according to the risk adjustment scheme. That ensures that the health insurers get more money for diseased insured and so they don't have motivation to risk selection. As a result, all diseased should be getting every health care they need. Such systems are also often called statutory health insurance schemes. Nowadays, Czech Republic faces several problems related to this area. Czech health insurers are owned neither by the state, nor by anyone else. That brings a lot of uncertainty into the system, because there is no one responsible for the economic results of health insurance companies. As a result of that, a huge amount of financial resources is spent needlessly. On...
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Basal stimulation
Novotná, Lenka ; Schneiderová, Michaela (advisor) ; Kupečková, Ivana (referee) ; Juřeníková, Petra (referee)
The paper deals with the sence of a basal stimulation. It's composed of a theoretical part and a practical one. In the theoretical part there is global information about basal stimulation, its components and development. The paper is directed on positioning and the main accent is on the nest position. The influence on psychical and physical perception is included too. Explored group is composed of healthy persons and patients who are suffering from stroke and are hospitalizated on the Neurological clinic. In the practical part there is research that in praxis explores how do people react in the nest position. All of them expressed their feelings by drawing a picture with comentary.
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