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STRAIN ENGINEERING OF THE ELECTRONIC STRUCTURE OF 2D MATERIALS
del Corro, Elena ; Peňa-Alvarez, M. ; Morales-García, A. ; Bouša, Milan ; Řáhová, Jaroslava ; Kavan, Ladislav ; Kalbáč, Martin ; Frank, Otakar
The research on graphene has attracted much attention since its first successful preparation in 2004. It possesses many unique properties, such as an extreme stiffness and strength, high electron mobility, ballistic transport even at room temperature, superior thermal conductivity and many others. The affection for graphene was followed swiftly by a keen interest in other two dimensional materials like transition metal dichalcogenides. As has been predicted and in part proven experimentally, the electronic properties of these materials can be modified by various means. The most common ones include covalent or non-covalent chemistry, electrochemical, gate or atomic doping, or quantum confinement. None of these methods has proven universal enough in terms of the devices' characteristics or scalability. However, another approach is known mechanical strain/stress, but experiments in that direction are scarce, in spite of their high promises.\nThe primary challenge consists in the understanding of the mechanical properties of 2D materials and in the ability to quantify the lattice deformation. Several techniques can be then used to apply strain to the specimens and thus to induce changes in their electronic structure. We will review their basic concepts and some of the examples so far documented experimentally and/or theoretically.
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Satisfaction of women in labour with nursing care during childbirth.
KLÍMOVÁ, Magdaléna
This dissertation investigates the level of satisfaction among expectant mothers with the care services provided during childbirth. Satisfaction reflects a subjective perception of an expectant mother in meeting her needs during childbirth. The feeling of satisfaction is very personal, however, evaluation of the care provided needs to be determined and not ignored. It is important for expectant mothers that the health care professionals present as empathic, friendly, co-operative, and tactful.Theoretical part was developed from evidence-based literature and available findings related to this problematic. There is a description of a childbirth process including a midwife's role during the individual stages of childbirth and options for pain management. Other chapters focus on midwife's approach toward an expectant mother and factors which influence the level of satisfaction during childbirth. Dissertation's aim was to determine whether the expectant mothers were more satisfied in smaller maternity departments, and to evaluate the way a midwife may influence the mother's satisfaction. There were two hypotheses stated and verified by a statistical testing. Hypothesis No. 1: Expectant mothers are more satisfied in smaller maternity departments than larger ones. Hypothesis No. 2: The level of satisfaction is influenced by midwife's empathic approach. Practical part focused mainly on a midwife's approach toward expectant mother. A quantitative research was implemented in form of questionnaires. The research sample constituted of expectant mothers from four postpartum departments in the Czech Republic. In total the sample included 215 expectant mothers, 109 from smaller facilities and 106 from larger maternity departments. In terms of the overall level of satisfaction with their midwife during the childbirth process, 89% of expectant mothers from smaller maternity departments and 83% of expectant mothers from larger departments stated they were satisfied. Conversely, 11% of respondents from smaller facilities and 17% of respondents from larger facilities were dissatisfied. Based on research analysis comparing the level of satisfaction of expectant mothers from smaller and larger maternity departments the hypothesis no. 1 "Expectant mothers are more satisfied in smaller maternity departments than the larger ones" did not show as statistically significant and was rejected. Nonetheless, the questionnaire responses clearly showed that empathic approach of a midwife influenced expectant mother's satisfaction. Statistical testing demonstrated a significant correlation between an expectant mother's satisfaction and empathic approach of a midwife. The second hypothesis "The level of satisfaction is influenced by midwife's empathic approach" was accepted.The research findings may serve as a guiding material for the midwives in order to provide a high quality care to expectant mothers during the childbirth process. They may also be utilised by future midwives who are in undergraduate preparation for the profession, or those professionals who contribute in any way during the childbirth process. Additionally, the research findings may be presented at conferences designated for midwives.
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Study of dielectrical properties of organic material thin films
Pospíšil, Jan ; Boušek, Jaroslav (referee) ; Mikula, Milan (referee) ; Zmeškal, Oldřich (advisor)
The dissertation is focused on the study of electric and especially dielectric properties of thin film organic materials with their huge potential for optoelectronics and other industrial sectors. The theoretical part deals with the use of organic materials in organic photovoltaic cells, the methods of deposition techniques and characterization. The theoretical knowledge of the dielectric spectroscopy, including methods for determining the physical properties and evaluation of experimental data are also described. The experimental part is devoted to the study of small molecule organic solar cells with bulk heterojunction composed of electron donor molecule of DPP(TBFu)2 and electron acceptor fullerene derivatives, such as PC60BM, PC70BM and TC60BM. The experimental part is divided into two main parts. The first part deals with the study of processes occurring at the interface between the active layer and the contact; the second part is focused on transport processes inside the structure of photovoltaic cells and also contains a study of perovskite solar cells.
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Noise, Transport and Structural Properties of High Energy Radiation Detectors Based on CdTe
Šik, Ondřej ; Lazar, Josef (referee) ; Navrátil, Vladislav (referee) ; Grmela, Lubomír (advisor)
Poptávka ze strany vesmírného výzkumu, zdravotnictví a bezpečnostního průmyslu způsobila v posledních letech zvýšený zájem o vývoj materiálů pro detekci a zobrazování vysokoenergetického záření. CdTe a jeho slitina CdZnTe. jsou polovodiče umožnují detekci záření o energiích v rozsahu 10 keV až 500 keV. Šířka zakázaného pásma u CdTe / CdZnTe je 1.46 -1.6 eV, což umožňuje produkci krystalů o vysoké rezistivitě (10^10-10^11 cm), která je dostačující pro použití CdTe / CdZnTe při pokojové teplotě. V mé práci byly zkoumány detektory CdTe/CdZnTe v různých stádiích jejich poruchovosti. Byly použity velmi kvalitní spektroskopické detektory, materiál s nižší rezistivitou a výraznou polarizací, detektory s asymetrií elektrických parametrů kontaktů a teplotně degenerované vzorky. Z výsledků analýzy nízkofrekvenčního šumu je patrný obecný závěr, že zvýšená koncentrace defektů způsobí změnu povahy původně monotónního spektra typu 1/f na spektrum s výrazným vlivem generačně-rekombinačních procesů. Další výrazná vlastnost degenerovaných detektorů a detektorů nižší kvality je nárůst spektrální hustoty šumu typu 1/f se vzrůstajícím napájecím napětí se směrnicí výrazně vyšší než 2. Strukturální a chemické analýzy poukázaly, že teplotní generace detektorů způsobuje difuzi kovu použitého při kontaktování a stopových prvků hlouběji do objemu krystalu. Část mé práce je věnována modifikaci povrchu svazkem argonových iontů a jejímu vlivu na chemické složení a morfologii povrchu.
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The use of (nano)oxides for metal and metalloid stabilization in contaminated soils
Michálková, Zuzana ; Komárek, Michael (advisor) ; Luke, Luke (referee)
The main objective of the thesis was to evaluate the potential of selected Mn and Fe (nano)oxides for the stabilization of metals and metalloids in contaminated soils. The research was focused basically on three materials - commercial nanomaghemite (Fe III), nanomagnetite (Fe II,III) and a synthetic amorphous Mn oxide (AMO). The main aim of the work was to provide a complex view on the chosen stabilizing amendments regarding not just their direct influence on contaminants mobility and stabilization mechanisms, but also their stability and alterations in soil conditions together with influence on soil microorganisms and higher plants. Firstly, adsorption properties of the tested materials towards Cd, Cu, Pb and As were investigated. In this context, the most effective material showed to be the AMO reaching one to two orders of magnitude higher adsorption capacities than Fe III and Fe II,III under given experimental conditions. Interestingly, the rate of As(V) adsorption onto AMO was increasing with increasing pH as a result of high pHzpc of the AMO (8.1) and significant dissolution of this phase at lower pH values. As a next step, the influence of (nano)oxides on metal(loid)s mobility and other physico-chemical soil characteristics after application to contaminated soil was examined. Again, the AMO proved to be the most efficient in reducing mobile pools of Cd, Cu, Pb, Zn and As. On the other hand, Fe III and Fe II,III addition had generally less significant effects on contaminants mobility. AMO application further resulted in an increase of soil pH connected with AMO dissolution and unwanted decomposition of soil organic matter. When (nano)oxides alterations in soil conditions were observed, MnCO3 coatings were identified on AMO surface while no significant changes were recorded for Fe III and Fe II,III. As the MnCO3 formation was connected with increased AMO stability, AMO particles synthetically covered with MnCO3 coating (denoted as SM AMO) were prepared. Although the SM-AMO had a lower mass loss in soil than pure AMO, the stabilizing efficiency was almost the same for both materials. The differences in surface composition of both materials were decreasing with time as MnCO3 naturally precipitated on the AMO surface in soils while the SM AMO coating was gradually dissolving. When investigating the effect on soil microbiota, AMO efficiently promoted soil microbial activity while no significant changes were observed in the case of Fe III and Fe II,III. The AMO was also able to reduce the uptake of Cd, Pb and Zn by sunflower (Helianthus annuus L.), eliminate Zn phytotoxicity symptoms and increase biomass yield. On the other hand, toxic levels of Mn released from the AMO in an acidic soil were found in sunflower tissues. AMO application is thus recommended for contaminated neutral or slightly alkaline pH with a higher cation exchange capacity in order to avoid unwanted release of Mn. Finally, various types of AMO-biochar composite sorbents were recently prepared and field experiment focused on stabilization of Cd, Pb, Zn and As using studied materials is currently under preparation. The combined results from the thesis highlight the importance of a complex experimental approach dealing with all parts of the contaminated soil environment in order to obtain complete information about the efficiency and usefulness of any newly developed stabilizing amendment.
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The overview and the evaluation of the technical specifications of transparent materials for the production of composite wood panels
Holub, Jan ; Böhm, Martin (advisor) ; Arnetová, Karolína (referee)
Work includes: general introduction to the components of the wood-based panels with a transparent layer, the history of their production. It includes requirements for individual components of composite wood panels and requirements for wood and other wood-based materials, which serve as reinforcement. Also mentions claims potting material, which serves as a matrix.
It includes a description of the technology of wood-based panels with a transparent layer. This paper introduces the most commonly used material serving as a matrix, their distinctive characteristics essential for the production of composite plates. Compares parameters resins based on polyester, polyurethane and epoxy resins and analyzes the choice of a suitable material for producing a composite board based on user requirements. Part of this work is to design materials for the manufacture of composite board with controlled light distribution.
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Evaluation of selected properties of mineral fibers-based board, including the design of suitable purposes of its application
Sýkora, Radim ; Böhm, Martin (advisor) ; Múčka, Martin (referee)
This thesis evaluates properties of board based on mineral fibers. In first part of the thesis is conducted analysis of the literature, where are described materials based on basalt fibers. Here is also explained production of basalt fiber and its practical applications. Sandwich materials and materials with great fire resistance based on wood are also looked into. Following part describes options of aplication of materials with great fire resistance and mechanical a physical properties of materials based on wood.
Second part of the thesis lays out methodical approach to individual performed mechanical and physical tests. Characteristic of examined material is included. The last part deals with test results, comparing results with other selected materials, debating results and proposing possible applications of examined basalt board. With use of found data is evaluated suitability of the material for use for construction of sandwich panel.
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