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Flow properties of coolants for metal cutting
Blašková, Daniela ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
The flow properties of two types of operating and clean coolants (A and B) were measured, both used in metalworking. Four samples of both operating liquids were sampled from the process monthly (from the beginning to the end of its use). All liquids were measured at 25 °C with an oil emulsion content of 4%. In addition, flow curves of pure cooling emulsions with concentration of coolant 2, 4, 6 and 8% were measured at 30, 35, 40, 45 and 50 °C. Rheological measurement was performed at geometry of concentric cylinders. Microbial activity and content of additives (Thermogravimetry) was determined in operating liquid A. Both operating liquids exhibited non-Newtonian behavior. Viscosity increased with the shear rate (10–100 s-1) and impurity level. Although the amount of impurity was approximately the same in both liquids, viscosity varied. For pure liquids, the viscosity increased with increasing concentration and decreased with increasing temperature, except for liquid A with concentration of coolants 6 and 8%, which, depending on the temperature, exhibited both shear thinning, shear thickening and Newtonian behavior. The results shown that impurity level of operating liquids has only minor effect on viscosity and flow properties, but it had an effect on cooling effect. Impurities diluted operating liquids, partial decomposition of the oil component may occur, but in particular, microbial activity causes skin problems of staff. Recommended is to introduce a specific control test for the presence of bacteria.
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Vliv vybraných leguminóz na mikrobiální aktivity půdy
HODAN, Lukáš
The presented diploma thesis presents an evaluation of the results of the influence of selected legumes on soil microbial activity. The literature review includes a description of legumes in sowing procedures, a description of the spectrum and representatives of the soil microbial community, the main features of soil microbial activity and methods of measuring this activity. The conclusions were preceded by a small-plot experiment on a plot of land managed in an organic farming regime, from which soil basal respiration, as the main parameter of soil microbial activity, was investigated in the laboratory with mixed samples, and further quantification of the total number of microorganisms by the cultivation method.
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Influence of bioplastic biodegradation on soil properties
Stanislavová, Veronika ; Zlámalová Gargošová, Helena (referee) ; Kučerík, Jiří (advisor)
Biodegradabilné polyméry sa na trhu stávajú čoraz populárnejšími, a to najmä v poľnohospodárstve, kde sa vďaka svojim priaznivým vlastnostiam používajú ako nátery a mulčovacie fólie. V tejto štúdii bol skúmaný vplyv poly-3-hydroxybutyrátu (P3HB), vnútrobunkového bakteriálneho polyméru, na rôzne vlastnosti pôdy vrátane fyzikálnych, chemických a biologických parametrov s cieľom posúdiť jeho potenciálne využitie v poľnohospodárstve. Výsledky ukázali, že P3HB mal negatívny vplyv na obsah sušiny v pôde, nadzemnú biomasu a spôsobil mierne zníženie pH pôdy. Okrem toho sa aktivita vybraných enzýmov výrazne zvýšila, keď sa P3HB aplikoval samostatne alebo došlo k ešte väčšiemu nárastu v kombinácií s niektorými pôdnymi doplnkami. Výsledky sa líšili v závislosti od použitého pôdneho doplnku. Účinky boli buď negatívne, neutrálne alebo pozitívne. Na posúdenie miery biodegradácie P3HB, vplyvu P3HB na organickú hmotu a zadržiavanie vody sa použila termogravimetrická analýza. Bolo preukázané, že prítomnosť organických doplnkov ovplyvnila rýchlosť degradácie P3HB a iných organických látok v pôde. Okrem toho aplikácia P3HB do pôdy viedla k inhibícii rastu rastlín (Zea mays L.). Pridanie zmien do pôdy pred aplikáciou P3HB tento účinok zlepšilo len okrajovo. Dospelo sa k záveru, že biodegradácia P3HB podporovala mikrobiálnu aktivitu, čo mohlo v konečnom dôsledku negatívne ovplyvniť dostupnosť esenciálnych živín v pôde. Okrem toho výsledky z termogravimetrickej analýzy naznačujú, že kombinácia P3HB a biouhlia by mohla prispieť k lepšiemu zadržiavania vody v pôde.
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Vliv aplikovaného biouhlu na biologickou aktivitu půdy a růst vybrané zemědělské plodiny
Řezníček, David
In recent years, biochar has been extensively studied for its potential to significantly increase some of the soil characteristics and its ability to mitigate the effects of ongo-ing climate change through carbon sequestration. One of the most discussed issues regarding biochar is its impact on soil biological activity and crop growth. Therefore, we conducted a pot experiment with a model crop of barley (Hordeum vulgare). Soil samples were taken during the experiment to determine basal respiration (BR), substrate-induced respiration (SIR) and nitrous oxide (N2O) production. These values indicate biological activity of the soil. Ion exchange discs were placed under the pots to determine the amount of mineral nitrogen leached. In addition, nets with model cellulose were placed to the soil to determine the activity of decomposers. At the end of the experiment, parameters of plants growth were determined. The positive effect of biochar, which underwent a composting process, was observed only in the case with simultaneously applied mineral nitrogen. However, without applied mineral N, this positive effect did not occur, and the effect of the biochar was in some cases negative. If mineral nitrogen was applied, we observed an increased leakage from the system. The supply of organic matter (compost, biochar) has led to a reduction in these losses of mineral nitrogen from the agroecosystem. Measurement of basal and substrate-induced respiration confirmed an assumption that soils with sufficient organic matter content has a stable and well-developed active community of microorganisms, evenly supplied with the main biogenic nutrients.
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Genetic potential for methane metabolism in the Greenland subglacial ecosystem
Rybár, Marek ; Stibal, Marek (advisor) ; Šabacká, Marie (referee)
Subglacial environments, located at the interface of glacier ice and bedrock, represent one of the major ecosystems associated with glaciers and ice sheets. This environment contains liquid water and underlying sediment with large amounts of organic matter overridden during periods of ice advance. Large areas of subglacial sediment are exposed annually by glacier melting and retreat, which affects the subglacial carbon stores and may significantly impact regional carbon fluxes. Due to the widespread anoxia at glacier beds, subglacial environments are potential producers and reservoirs of methane that can be released into the atmosphere as a consequence of glacial retreat. While the presence of methanogens and methane oxidisers has been shown based on 16S rRNA gene data, no data on the functional genetic potential for methane metabolism currently exist. In this study, the first subglacial metagenomes obtained from subglacial sediment exported from beneath the Greenland ice sheet by a meltwater river were used to characterize the metabolic potential for methane metabolism by the identification and quantification of genes involved in methane production and consumption. Functional genes of potential syntrophic pathways were also investigated. Functional genes of methanogenesis/anaerobic oxidation of methane and...
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Flow properties of coolants for metal cutting
Blašková, Daniela ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
The flow properties of two types of operating and clean coolants (A and B) were measured, both used in metalworking. Four samples of both operating liquids were sampled from the process monthly (from the beginning to the end of its use). All liquids were measured at 25 °C with an oil emulsion content of 4%. In addition, flow curves of pure cooling emulsions with concentration of coolant 2, 4, 6 and 8% were measured at 30, 35, 40, 45 and 50 °C. Rheological measurement was performed at geometry of concentric cylinders. Microbial activity and content of additives (Thermogravimetry) was determined in operating liquid A. Both operating liquids exhibited non-Newtonian behavior. Viscosity increased with the shear rate (10–100 s-1) and impurity level. Although the amount of impurity was approximately the same in both liquids, viscosity varied. For pure liquids, the viscosity increased with increasing concentration and decreased with increasing temperature, except for liquid A with concentration of coolants 6 and 8%, which, depending on the temperature, exhibited both shear thinning, shear thickening and Newtonian behavior. The results shown that impurity level of operating liquids has only minor effect on viscosity and flow properties, but it had an effect on cooling effect. Impurities diluted operating liquids, partial decomposition of the oil component may occur, but in particular, microbial activity causes skin problems of staff. Recommended is to introduce a specific control test for the presence of bacteria.
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Microbial communities and carbon cycling in subglacial ecosystems and their analogues
Rybár, Marek ; Stibal, Marek (advisor) ; Řeháková, Klára (referee)
Subglacial environments are located at the interface of glacier ice and bedrock. They represent one of the major ecosystems associated with glaciers and ice sheets. They contain liquid water and fine material including organic matter, accumulated during periods of glacier advance. It is well established that there are active microbial communities residing in these environments, which are adapted to living in extreme conditions. Subglacial ecosystems are mostly isolated from the atmosphere and thus their oxygen content is usually very low. Therefore, the organisms residing in these environments often employ anaerobic/anoxic strategies to ensure their survival. However, knowledge of these communities is limited due to practical constrains associated with subglacial ecology and biogeochemistry research. The activity of microorganisms beneath glaciers significantly influences carbon cycling. In recent years, this ecosystem is dynamically changing and may have important impact on regional and global carbon cycle. Therefore, it is important to better understand this ecosystem. This thesis summarizes recent knowledge of microbial communities and carbon cycling in this ecosystem and discusses suitable analogues, which could help us understand the fascinating subglacial ecosystem and formulate future research...
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Microbial activity of deep subsurphace miocen sediments near Soklov
Galertová, Renata ; Frouz, Jan (advisor) ; Kryštůfek, Václav (referee)
In my diploma thesis I observed microbial activity in Miocene sediments collected at two different depths - 30 and 150 meters - in the "Družba" open-mine pit, which is located in Sokolov Brown Coal Basin. There were three different types of sediment: lamellar, amorphous and transitional. Samples were obtained under sterile conditions and following treatments were applied to the transitional sediment: addition of glucose, wetting and freezing. The aim of my study was to observe the activity of the original microflora at various depths and the impact of environmental factors that can affect the quarried claystones after being put on heaps. Microbial activity was evaluated by measuring released CO2 (titration). Obtained values of microbial activity did not show any differences between the respiration of sediments of different ages (depths), but differences between different types of sediments were significant, the highest values were found in lamellar sediment. Affection of samples then showed biota activity response suggesting that microbial communities at lower depths are limited by nutrients. Because the application of glucose did not show any noteworthy effect, we can assume that these communities are specialize on present fossil organic matter they are able to decompose, which is important especially in...
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Diversity of the soil microbial community and its functional aspects in man-influenced environments
CHROŇÁKOVÁ, Alica
Diversity of the soil microbial community and its functional aspects were investigated in man-influenced environments, such as colliery spoil heaps in post mining sites and upland pasture used for outdoor cattle husbandry. The study was based on the cultivation of bacteria and streptomycetes as well as culture-independent approaches. Cultivated bacteria and streptomycetes were characterized by phenotypic and genotypic means. The culture-independent approaches were based on an analysis of environmental DNA in terms of both qualitative and quantitative parameters.
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