National Repository of Grey Literature 105 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Study of the influence of alloying elements on the solubility of titanium in magnesium
Staněk, Jan ; Buchtík, Martin (referee) ; Březina, Matěj (advisor)
This master’s thesis deals with the study of the influence of aluminium and zinc on the solubility of titanium in magnesium. The theoretical part summarizes the basic knowledge about magnesium and magnesium alloys with a focus on systems containing aluminium, zinc and titanium. It also describes powder metallurgy technology, specifically the preparation, compaction and sintering of metal powders. The theoretical part ends with literature review on the current research of ternary and quaternary magnesium alloys. The experimental part focuses on the preparation of magnesium materials alloyed with titanium, zinc and aluminium by powder metallurgy and the basic structural and mechanical characterisation of the prepared materials. The effect of alloying elements and temperature on the solubility of titanium particles in magnesium was investigated. It was found that the main condition for the dissolution of titanium in magnesium is the temperature of 800 °C and the presence of aluminium, which initiates the reaction by forming intermetallic compounds with titanium. After incorporation of titanium into the material structure, new intermetallic compounds were formed with all elements not previously described in the literature, in addition to the structures described.
Research on the content of risk elements in the material of PET bottles
Kryštofová, Petra ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
This thesis deals with the research of the content of risk elements in the material of rPET (recycled polyethylene terephthalate), supplied from various countries, and the study of different factors (type of liquid, temperature) on the migration of antimony from this material. The recycling process has the potential to increase the content of unwanted substances and promote the formation of degradation products of chemical additives and by-products of polymerization, thus contributing to higher migration of these substances into food or food simulants [1]. The supplied rPET samples were subjected to total decomposition in an environment of concentrated sulfuric and nitric acid under the influence of microwave radiation prior to analysis. Prepared samples were analyzed by atomic absorption spectroscopy (AAS) techniques. The contents of Sb and Zn were determined by flame atomic absorption spectrometry (FAAS), and the concentrations of Pb, Cu, Zn, Cd, Cr, and Ni were determined by electrothermal atomic absorption spectrometry (ETAAS). Additionally, the concentrations of Sb were determined by this method in migration experiments. This thesis builds upon the author's bachelor's thesis, which included pilot experiments.
Význam konzumace rybího masa v prevalenci skrytého hladu u dětí: komparace vybraných zemí Latinské Ameriky a Afriky
Rajchmanová, Jana
This thesis is primarily focused on the impact of fish meat supply on the prevalence of hidden hunger in children under 5 years of age in selected countries from Africa and Latin America. The aim of the thesis was to test the hypothesis that there is an inverse realtionship between fish meat supply and the prevalence of indicators representing the prevalence of hidden hunger. As the prevalence of hidden hunger is influenced by many factors, the analytical part of the thesis also included an analysis of the effect of total calorie intake and protein intake. Correlations were performed for each selected country from Africa and Latin America separately, and then also as an average of selected countries from both regions. Trends in dietary intake of each micronutrient in the selected countries were also monitored. An inverse realtionship was found between fish meat supply and the prevalence of hidden hunger, as well as between total energy intake and the prevalence of hidden hunger, and between protein supply and the prevalence of hidden hunger. For selected countries in the African region, total calorie supply had the greatest effect on the prevalence of hidden hunger, followed by protein supply and finally fish meat supply. For the selected countries from the Latin American region, protein supply, followed by total calorie supply, and finally fish meat supply had the greatest impact on the reduction of hidden hunger.
Využití zinkových povlaků pro antikorozní ochranu ocelových součástí
Straka, Dominik
This Bachelor thesis „Use of zinc coats for anticorrosive protection of steel components“ characterizes corrosion and its effect on steel materials when being in a corrosive environment. Moreover, it categorizes corrosion and defines various methods of how steel materials can be protected against it. Special focus is given to protection using metal coats with lower electrode potential than Fe. Furthermore, this thesis determines particular methods of how to create metal coats depending on the type of material. Especially, the use of zinc applied by the hot-dipped and galvanic method is discussed. Quick laboratory tests are identified as a suitable method in order to evaluate the quality and resistance of created coats. Finally, lifespan and corrosive resistance of each coat are assessed considering the environment in which these coats are exposed.
The impact of synthetic chelators from the group of 4-acylpyrazole-5-ones on alcohol dehydrogenase
Sobolová, Zuzana ; Mladěnka, Přemysl (advisor) ; Jirkovský, Eduard (referee)
Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology & Toxicology Student: Zuzana Sobolová Supervisor: Prof. Přemysl Mladěnka, Pharm.D., Ph.D. Consultant: Marcel Hrubša, MS.c. Title of diploma thesis: The impact of synthetic chelators from the group of 4-acylpyrazole-5-ones on alcohol dehydrogenase Inhibitors of alcohol dehydrogenase play a key role in the treatment of poisoning caused by methanol, ethanol, ethylene glycol, and their toxic metabolites. Such treatment can therefore be considered as life-saving. In clinical practice, a single substance, fomepizole, is used. This thesis is aimed at investigation of the effect of eleven experimental chelators from the 4- acylpyrazol-5-ones group on equine and yeast alcohol dehydrogenases, and the possible definition of structural features that would be the most suitable for interaction with this enzyme. Due to the ability of these substances to chelate zinc ions, it is believed that they could inhibit an enzyme that has a zinc molecule in the structure. The measurement itself is based on principle of increase in absorbance during the enzymatic reaction, which is caused by the formation of NADH. This measurement is relatively simple, efficient and, due to used kinetic method, also less susceptible to be affected by...
Determination of selected metals in soils and mushrooms in the vicinity of the D1 highway.
The aim of the bachelor thesis was to determine the concentrations of heavy metals in edible mushroom samples and underlying soils. The elements measured were mainly copper, iron and zinc, followed by manganese, strontium and rubidium. The literature search contains brief information on each element and their content in soils and fruiting bodies of mushrooms in other studies. The theoretical part also includes chapters on fungi, soils and their contamination, the effect of vehicular traffic on the heavy metal content of soils and the used analytical method, which was atomic absorption spectrometry. For the practical part, 24 samples of eight different species of edible mushrooms were collected in the autumn of 2020 and 2021 in the vicinity of the D1 motorway. As part of the collection, the soil beneath the mushroom was also sampled to a depth of approximately 15 cm. The samples were first perfectly dried, then processed by microwave digestion, and finally analysed by AAS. All work was carried out in the laboratories of the Department of Applied Chemistry, Faculty of Agriculture and Technology, University of South Bohemia in České Budějovice. The results of the measurements were tabulated and processed statistically and graphically. Finally, they were evaluated in a discussion. The analysis showed that birch and birch goosefoot accumulate the least heavy metals in their fruiting bodies. The spruce budworm, the pink toadflax, the celandine and the brown mushroom accumulate metals on a large scale. In total, 4.2-45 dry weight Cu, 97,4-4166 Fe, 52,1-338,7 Zn, 3-61,4 Mn, 1,3-7 Sr and 7,7-300,9 Rb were measured in mushrooms. In soils, the values were as follows: 5,2-78,6 Cu, 2 965-41 983 Fe, 25,8- 174,2 Zn, 49,7-1 868 Mn, 6,2-25,2 Sr and 12,2-114,5 Rb in dry weight. These results show that strontium was the least represented heavy metal studied and iron was the most represented.
Mikroelementy a imunitní systém
HODAN, Lukáš
The immune system is an example of the body's ability to maintain its homeostasis and adaptability to external and internal environments. Microelements are an essential part of the proper functioning of the immune system. Quarantine can be as harmful as an excess of individual elements. The presented bachelor thesis deals with the immune system, especially the influence of microelements on its proper function. The individual chapters describe cells, molecules, organs and abnormalities of improper development. A significant part is devoted to microelements, occurrence, absorption, transport, influence on the immune system, deficiency and toxicity and their consequences.
The content of the micronutrients in consumer eggs
The aim of the diploma work was to analyticly verify the actual status of the micronutrients (iodine, copper, zinc and manganese) in consumer eggs. The results of the research gives information about the content of the observed micronutrients in egg yolk and the importance of eggs as a source of these micronutrients for the nutrition of people. The eggs came from 13 small flocks and 7 large flocks in both 2007 and 2008. The average content of iodine in fresh matter of yolk of the eggs from the large flocks in 2007 was 1285,2 {$\pm$} 861,6 {$\mu$}g{$\bullet$}kg-1, zinc 63,71 {$\pm$} 31,08 mg{$\bullet$}kg-1, copper 7,42 {$\pm$} 4,88 mg{$\bullet$}kg-1 and manganese 1,02 {$\pm$} 0,84 mg{$\bullet$}kg-1. The average content of iodine in fresh matter of yolk of the eggs from the small flocks in 2007 was 387,1 {$\pm$} 214,3 {$\mu$}g{$\bullet$}kg-1, Cu 10,90 {$\pm$} 5,28 mg{$\bullet$}kg-1, Zn 73,54 {$\pm$} 44,33 mg{$\bullet$}kg-1 a Mn 1,28 {$\pm$} 0,75 mg{$\bullet$}kg-1. In 2008 the average concentration of iodine in fresh matter of yolk of the eggs from the large flocks was 1071,9 {$\pm$} 543,9 {$\mu$}g{$\bullet$}kg-1, Cu 20,63 {$\pm$} 8,85 mg{$\bullet$}kg-1, Zn 29,59 {$\pm$} 8,67 mg{$\bullet$}kg-1 a Mn 1,42 {$\pm$} 0,62 mg{$\bullet$}kg-1. In 2008 the average concentration of iodine in fresh matter of yolk of the eggs from the small flocks was 340,7 {$\pm$} 330,6 {$\mu$}g{$\bullet$}kg-1, Cu 17,95 {$\pm$} 6,19 mg{$\bullet$}kg-1, Zn 33,10 {$\pm$} 7,97 mg{$\bullet$}kg-1 and Mn 1,22 {$\pm$} 0,54 mg{$\bullet$}kg-1. The Eggs from the large flocks cover 6,8 {--} 13,5% of the daily iodine requirement in adults, 13 {--} 17,3% of copper, only 2,5 {--} 3,1% of zinc and 0,4 {--} 1,1% of manganese. The gained results imply that only the content of iodine in the egg yolk is evidently affected by the intake of it in the feeding rations, the intensity of the egg production and the stage of the laying cycle. The stated relations were not definite with the other elements. The concentration of iodine in the egg yolk was assessed spectrophotometrically by the method of Sandell {--} Kolthoff, modified by Bednář et al., (1964). The content of zinc, manganese and copper in the egg yolk were assessed by the method of atomic absorption spectroscopy (AAS).
Application of a commercial multimode sample introduction system as a generator of volatile compounds
Hadbavníková, Alexandra ; Nováková, Eliška (advisor) ; Červený, Václav (referee)
EN The main goal of this thesis was the determination of zinc using a commercial multimode sample introduction system (MSIS) as a generator of volatile compounds with inductively coupled plasma mass spectrometer as detector. The generation of volatile compounds took place using sodium borohydride in an acid environment. In the first step of the experiment, the following parameters affecting the generation of volatile compounds were optimized: acid selection, acid concentration, sodium hydroxide concentration, mass concentration of sodium borohydride, mass concentration of 8-hydroxyquinoline, volume of the injection loop and flow rates of sample, carrier gas and hydrogen. Subsequently, figures of merit of the method were determined under optimal conditions. The limit of detection was 2.8 μg·dm-3 and the limit of quantification was 9.3 μg·dm-3 . Generation efficiency of the volatile zinc compound was determined as 3.7 %, which is the highest efficiency yet achieved for this element and generation system in this laboratory. Interference studies did not demonstrate the ability of any of the tested hydride-forming or transition elements to act as a modifier increasing the generation efficiency, but at the same time, none of the investigated elements proved to be a significant interferent. Key words...

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