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Influence of environmental conditions on the modulus of elasticity of concrete
Peřina, Tomáš ; Novosad, Petr (referee) ; Křížová, Klára (advisor)
Increasingly, the modulus of elasticity of concrete is at the forefront of interest. In the past, it has been neglected to some reason and not taken into due consideration. The theoretical part of the bachelor thesis is to study of factors influencing the static modulus of elasticity in compression. The practical part is focused on monitoring the modulus of elasticity of concrete, based on the different type of the environment stored test specimens. Concrete will be stored outdoor in the water and in the laboratory environment conditions. Designed concrete mixes will be primarily different with the used of type of admixtures but also with type of cement. The result values will be compared on the dependence of environmental conditions of the test specimens.
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The effect of real condition of a rail on friction between the wheel and rail
Škubna, Michal ; Hajžman, Michal (referee) ; Omasta, Milan (advisor)
The aim of this master’s thesis is to determine the influence of the friction layer formation conditions on the rail surface on the coefficient of adhesion. Currently, laboratory studies of adhesion are carried out on simplified contact models using tribometers in a two-disc device configuration or in a ball-to-disc configuration, which does not correspond to the real behavior of the wheel-rail interface. The experiments described in this work were carried out in a laboratory environment on a sample of a real rail using a tribometer to achieve variable slip. This made it possible to measure the entire traction curves for the specific rail surface condition. Several experiments were carried out to determine the influence of climatic conditions – especially relative humidity and the effect of water on the development and composition of friction layers naturally formed on the rail. To do this, several procedures were used to achieve the individual friction layers. In addition to the influence of climatic conditions, the influence of simulated passages of rolling stock using a contact simulator was also implemented. The output of the thesis is a draft article describing the methods of preparation of friction layers and the results achieved.
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Seasonality and weather conditions jointly drive flight activity patterns of aquatic and terrestrial chironomids
VEBROVÁ, Lucie
Dispersal by flight is crucial for long-term survival of organisms inhabiting dynamic environments, especially small standing waters. Surprisingly, flight activity of the most abundant macroinvertebrate group in standing freshwater habitats, the Chironomidae, has rarely been studied, leaving a gap in our understanding of the environmental drivers of their dispersal activity. The goal of this study was to investigate flight activity of adult chironomids on diel and seasonal timescales in sandpit pools in the Czech Republic. We show that aquatic and terrestrial chironomids use partly alternating time windows for their flight and partly differ in their responses to weather conditions. We also compare our results to previous studies that analysed the impact of weather conditions on flight activity of aquatic insects.
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Svalbard reindeer and its interaction with extreme polar environment
KAVANOVÁ, Veronika
Two distinct populations of Svalbard reindeer are compared based on their antler parameters. Relative antler size and number of tines are supposed to reflect well environmental conditions of the sedentary population within the growing season. Both studied populations are well spatially isolated due to high mountain ridges, glaciers and fjords. The population in Petuniabukta occupies sparsely vegetated region with harsh climatic conditions, whereas Skansbukta represents area with continuous tundra vegetation, milder climatic conditions and consequently also longer vegetation season. These environmental factors probably lead to significant differences in relative antler size and number of tines. Skansbukta population has larger relative antler size and higher number of tines than the population in Petuniabukta.
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The efect of environmental variables on diversity of lichen photobionts
Červenková, Tereza ; Škaloud, Pavel (advisor) ; Peksa, Ondřej (referee)
Lichens represent a synergistic combination of at least two organisms, a heterotrophic fungus and a photosynthetic alga or a cyanobacterium. This association has resulted in a symbiotic organism, which is well tolerant to environmental influences. In fact, symbiotic relationship provides mutual benefit for both organisms. It is generally well known that the fungal partners of lichens are far less sensitive to environmental conditions, such as the temperature, altitude, rainfall or the type and composition of the substrate, in comparison to their algal partners. Therefore, lichen forming fungi have much wider ecological valences than the photobionts interacting with them. Indeed, most of the photosyntetic genera and species are adapted only to certain environmental conditions. For this reason, the symbiotic algae and cyanobacteria probably play a major role during the initial lichen formation on the site. This thesis focuses on the adaptability of photoautotrophic symbionts of lichens, coccoid green algae and cyanobacteria, to environmental conditions. Ecological diversification of photobionts has a direct impact on their genetic differentiation and thus to differentiate lichen species themselves. Unfortunately, in many studies the authors mostly dealt with the diversity of macroscopic symbiotic...
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Biology of epiphytic bryophytes: methods of study
Reitschmiedová, Erika ; Soldán, Zdeněk (advisor) ; Novozámská, Eva (referee)
This thesis is aimed to provide basic description and summary of methods used to study biology/ecology of bryophytes, especially epiphytes. Described methods include study of mosses and liverworts; hornworts are not included due to the fact that their epiphytic form is not known. There are five chapters in this thesis, all of them are primarily focused on description of basic or most useful methods for studying phenology, growth, bioindication and environmental conditions, e.g. light and water relationship measurement as well as bark pH measurement. The last one, "Forms and Strategies", is only terminological and it includes terms of life and growth forms and life strategy which are used in studying colonies of bryophytes.
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Predicting light use efficiency using optical vegetation indices at various time scales and environmental conditions
Kováč, Daniel ; Ač, Alexander ; Veselovská, Petra ; Dreveňáková, Petra ; Rapantová, Barbora ; Klem, Karel
This study presents data points acquired during 2 years of measuring optical properties and gas-exchange\ncharacteristics of European beech (Fagus sylvatica) and Norway spruce (Picea abies) tree species in controlled\nenvironments. The observed statistical relationships between 105 pairs of selected optical parameters\n(i.e. photochemical reflectance index [PRI], ΔPRI, and normalized difference between wavebands R690\nand R630 [where R is a reflectance at a subscripted wavelength]) and light use efficiency (LUE) were considered\nat assumed different canopy leaf area index, changing pigments stoichiometrics, and daily changing\ndynamics of environmental conditions. Our measurements suggested that consistency of the LUE estimation\nusing PRI may be disrupted by acclimation responses of plants that reduce energetic carriers for\nuse in photosynthetic CO2 uptake and the xanthophyll cycle. Also, a changing chlorophylls-to-carotenoids\nratio tends to interrupt the PRI–LUE relationship. ΔPRI showed sensitivity to leaf area index of the measured\ntrees that complicated leaf-level estimation of LUE. The most consistent assessment of LUE was\nachieved using the chlorophyll fluorescence detecting ratio (R690 – R630)/(R690 + R630).
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The importance of enviromental conditions on plant-invertebrate herbivore interactions
Kuglerová, Marcela ; Münzbergová, Zuzana (advisor) ; Skuhrovec, Jiří (referee)
Plants and herbivores influence each other for more than million years. Most studies are focused on interspecific variability in herbivory intensity, but little i known about intraspecific variability and what controls it. Environmental conditions can determine intraspecific variation. Goal of this thesis is to examine importance of environmental conditions and interspecific variation for invertebrate herbivory preferences. Plant material that was used in experiments comes from several species from subfamily Carduoideae. Preferences of invertebrate herbivores are tested in food-choice experiments. Plastic arenas are made for these experiments, in which leaves are put in small tubes that are placed along the periphery. After herbivores are placed in to arena, arena is covered by net to ensure that herbivores can't escape. Plant material for experiments was grown in experimental garden and was also brought from field. Plants from garden differ in productivity of soil and water regime. In experiments with field material, plant leaves were collected from eight localities, four fields and four grasslands. Leaves were scanted before and after each experiment. Scans were processed and the amount of consumed leaf tissue was determined. For plant characteristics I measured plant functional traits, specific...
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Influence of environmental conditions on the modulus of elasticity of concrete
Peřina, Tomáš ; Novosad, Petr (referee) ; Křížová, Klára (advisor)
Increasingly, the modulus of elasticity of concrete is at the forefront of interest. In the past, it has been neglected to some reason and not taken into due consideration. The theoretical part of the bachelor thesis is to study of factors influencing the static modulus of elasticity in compression. The practical part is focused on monitoring the modulus of elasticity of concrete, based on the different type of the environment stored test specimens. Concrete will be stored outdoor in the water and in the laboratory environment conditions. Designed concrete mixes will be primarily different with the used of type of admixtures but also with type of cement. The result values will be compared on the dependence of environmental conditions of the test specimens.
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The efect of environmental variables on diversity of lichen photobionts
Červenková, Tereza ; Škaloud, Pavel (advisor) ; Peksa, Ondřej (referee)
Lichens represent a synergistic combination of at least two organisms, a heterotrophic fungus and a photosynthetic alga or a cyanobacterium. This association has resulted in a symbiotic organism, which is well tolerant to environmental influences. In fact, symbiotic relationship provides mutual benefit for both organisms. It is generally well known that the fungal partners of lichens are far less sensitive to environmental conditions, such as the temperature, altitude, rainfall or the type and composition of the substrate, in comparison to their algal partners. Therefore, lichen forming fungi have much wider ecological valences than the photobionts interacting with them. Indeed, most of the photosyntetic genera and species are adapted only to certain environmental conditions. For this reason, the symbiotic algae and cyanobacteria probably play a major role during the initial lichen formation on the site. This thesis focuses on the adaptability of photoautotrophic symbionts of lichens, coccoid green algae and cyanobacteria, to environmental conditions. Ecological diversification of photobionts has a direct impact on their genetic differentiation and thus to differentiate lichen species themselves. Unfortunately, in many studies the authors mostly dealt with the diversity of macroscopic symbiotic...
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