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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Relationships between water quality, species composition, biodiversity and ecosystem function in lakes and flooded pits exposed to uranium mining activities in Northern Saskatechewan

Helps, Devin Murray 25 May 2009 (has links)
Uranium mining activities have the potential to impact aquatic systems through mine drainage (runoff) and the release of treated effluent into nearby watersheds. Such anthropogenic exposure can lead to elevated concentrations of metals and major ions, which may impact aquatic biota. Previous studies have looked at the effects of water quality on aquatic biota within flooded pit lakes and natural lakes that have been exposed to various mechanisms of mining exposure. However, the literature often only examines the effects of a limited number of contaminants on a limited number of species. Researchers have rarely looked at the effects of multiple contaminants on species composition, biodiversity and ecosystem function in aquatic systems. This study uses a multivariate approach to look for relationships between water quality (24 variables), plankton species composition and abundance, biodiversity (richness and evenness) and ecosystem function among lakes exposed to mining activities (n = 18) and non-exposed reference lakes (n = 8). Lake water quality data was used to cluster lakes into groups. Lake groups were then overlain onto multivariate ordinations derived from species composition-abundance data to determine if species composition was related to water quality. Ecosystem function variables included planktonic phosphorus cycling and planktonic respiration. The classified lake groups clustered well on ordinations derived from species composition-abundance data suggesting that relationships exist between water quality and plankton species composition. However, ecosystem function was similar among the majority of lakes and flooded pits despite differences in species richness, species composition and species abundance. Only a small number of aquatic systems had ecosystem function properties that were different from the majority of lakes and pits. These systems had the greatest concentrations of contaminants and had very low biodiversity (richness and evenness) compared to the other systems. Despite having differences in plankton species composition and species richness, all lake groups were functionally similar. This suggests that functional redundancy in species composition may be present in the majority of lakes and pits in such a way that ecosystem function is maintained.
22

Möjlig bronsåldersboplats? : en undersökning av platser från bronsåldern på Gotland / Possible Bronze Age Settlement? : a study of places from Bronze Age on Gotland

Sardén Johansson, Erika January 2010 (has links)
There are none known Bronze Age settlement on Gotland, although there are severalexcavation reports that mention that they have found a probable Bronze Age settlement. In the excavation that have been done in the study areas, there are Bronze Age dated hearths, cooking pits and post holes. These study areas have been investigated if they might be possible Bronze Age settlements. This paper discusses about the criteria of settlements and also investigate if the study areas meet those criterias. There are many different criteria for settlement but only the criteria of FMIS are used in the study. There are also different criteria for hearths and cooking pits, what separates them from each other. There have been measures on the distance between different landscape variables in the study areas to see if there are any differences or similarities between the different study areas.
23

Grain storage methods and their effects on Sorghum grain quality in Hararghe, Ethiopia /

Dejene, Mashilla, January 2004 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 4 uppsatser.
24

Generic guidelines for rehabilitation of borrow pits on linear pipeline projects

Beukes, Werner 10 March 2010 (has links)
M.Sc. / This study focuses on the rehabilitation of borrow pits on linear pipeline projects. In the past there have been many attempts to rehabilitate borrow pits to an ecological acceptable manner. Recently legislation has become more stringent regarding mine closure and rehabilitation. With the introduction of the new Mineral and Petroleum Development Act (MPRDA 28 of 2002), there has been an increase of awareness towards the immediate environment. As this project was a challenge in itself, there were no clear and concise methods in the Act that provide guidelines for final rehabilitation. Normally borrow pits as used on road concessions for material sourcing is left as different landforms like before excavation. The main reason for this is that materials are removed from the pits and not replaced, resulting in areas that are usually lower than their original ground levels. Some unwanted screened material will return to these borrow pits but will not complement what the original level should be. These borrow pits are usually clearly visible as low lying areas filled with water alongside roads. The Vaal River Eastern Subsection Augmentation Project (VRESAP) pipeline borrow pits were unique in the sense that not only material from screening activities were replaced, but also material excavated from the trench were replaced into the borrow pits. What makes this study unique is the fact that an opportunity was presented and clearly stipulated by the standard environmental management plan (SEMP) that borrow pits had to be filled back to their original ground levels or an acceptable level agreed on by the landowner. With this unique project, unique problems arose causing excess material amounting to 327 700 m³, available from the pipeline cavity. External spoil areas had to be promulgated and managed as part of site. This study through its various elements addresses some of the main problems encountered on VRESAP by looking at soil analysis, monitoring regimes, pre and post land use and other mechanisms from literature studies used on similar projects in the mining industry. vii The study also provides recommendations to the reader for future pipeline developments as well as conclusions made by the author. The recommendations made, include ways of rehabilitation planning through trials and errors made on site. Various conclusions were made that would substantiate this study in perspective to user-friendly and practical approaches.
25

Katalog obratlovčí fauny z pleistocénních lokalit na území Prahy / The catalogue of the mammalian fauna of pleistocenne localities in Prague area

Havlová, Tereza January 2014 (has links)
More than a hundred sites were in Prague in the past, where skeletal remains of Pleistocene mammals had been found. Most of these sites were brickyards or sand pits. These pits were in operation during the second half of the 19th century and first half of the 20th century. Many awards were found during construction works as well. Most of researchers attended only several most famous sites at the time of the findings. The catalog summarizes the basic known information about majority of Prague localities and includes a list of taxa wich were found there. Key words: Prague, locality, mammals, Pleistocene, brickyards, sand pits
26

Evaluating the Potential for Atmospheric Corrosion of 304 Stainless Steel Used for Dry Storage of Spent Nuclear Fuel

Weirich, Timothy Douglas 24 October 2019 (has links)
No description available.
27

Evaluation of the test procedure for a Rubber Balloon Soil Densitometer

Ahmed, Mohammad Minhajur January 2021 (has links)
A Rubber Balloon Soil Densitometer is one of the essential apparatuses in Geotechnical Engineering to measure the in-place volume of compacted soil to calculate the soil density. In 2019, some renowned institutions and organizations, Vattenfall, Luleå University of Technology, Uppsala University, Lund University, and HydroResearch AB, were involved in a research project. As a part of that research project, a small earth-rockfill dam was built in Älvkarleby, Vattenfall. During the construction of the experimental dam, to test the sufficiency of the degree of compaction in the core layers, the Rubber Balloon Soil Densitometer of the German company called Headquarters of Magdeburger Prüfgerätebau GmbH, in short HMP, was used. However, it was suspected that some of the HMP densitometer test results showed measured volumes of the excavated holes lower than the expectation. Hence, it aroused the necessity to check the correctness of the balloon test apparatus and its test procedure. This thesis topic aims to fulfill that necessity. The objective of this research is to determine whether the volumetric measurements achieved by this apparatus are accurate. If the volumes measured by this apparatus are inaccurate, it is crucial to find the reasons behind the inaccuracy. It is also essential to determine the inaccuracy causes and pursue the solution to obtain precision in volumetric measurement. This thesis topic is vital for engineers and researchers of civil engineering and other departments because concluding the research would help collect better soil density data using an HMP Rubber Balloon Soil Densitometer and other similar densitometers. All the laboratory works of this thesis were conducted at the Soil Laboratory of Luleå University of Technology. At the beginning of the laboratory work, a pit was excavated in a compacted mixed fine-grained silty sand type of soil inside a bucket to conduct a densitometer test. The actual volume of this pit was determined using the water replacement method. The HMP densitometer measured a volume of this pit smaller than its actual volume. Then, the apparatus itself was tested to evaluate its function. It was found that the plexiglass cylinder has different inner circular cross-sectional areas at different heights, which do not match the inner circular cross-sectional area mentioned in the HMP sticker on the plexiglass. As time passes, slight deformation of a plexiglass cylinder is normal and can happen because of temperature, applied pressure, and repetitive usage. The precision in percentage from the actual volume of a pit indicates the stuck air between the pit surface and the rubber balloon during a densitometer test. For engineering purposes, a precision in percentage smaller than one percent can be considered reasonable. The results showed that the actual volume of a pit should be at least around one liter to achieve precision in percentage from the actual volume of the pit smaller than about one percent. Additionally, pits with larger actual volumes have smaller precision in percentages from the actual volumes of the pits. The imperfection of the plexiglass cylinder has a lesser influence on larger pits during a densitometer test. Compacted coarse-grained soil can absorb the stuck air during a densitometer test because of having a sufficient quantity of pores. However, compacted fine-grained soil is so airtight that the soil can not absorb the stuck air. Transparent bowls and non-transparent bowls and a bucket were considered artificial pits of different sizes and shapes in compacted fine-grained soil, and densitometer tests were conducted with them. The results showed that the extended Ucsan bowl had the appropriate shape and size among these artificial pits. Because the average percentage of stuck air inside it was the smallest. However, the topmost diameter of an artificial pit or a real pit should be the same as the inner diameter of the metal ring of the HMP apparatus. Putting two stripes of industrial cleaning cloth perpendicularly inside an artificial or a real pit during a densitometer test was considered a solution to the stuck air problem. After applying this solution for the densitometer tests with all the artificial pits, the results showed that a real pit's appropriate shape and size with this solution should be similar to the extended Ucsan bowl. This was proved at the end of the laboratory work when a pit was excavated through the metal ring of the apparatus in a compacted mixed fine-grained silty sand type of soil inside a bucket to conduct densitometer tests. This pit was given a shape and size similar to the extended Ucsan bowl during excavation. This time, two industrial cleaning cloth stripes were placed perpendicularly inside the pit before the tests. The results showed that almost all the stuck air could be dissipated during a densitometer test by placing two stripes of industrial cleaning cloth perpendicularly inside a pit with a shape and size similar to the Ucsan bowl. During laboratory work, the HMP apparatus continuously measured volumes smaller than the actual volumes in all the densitometer tests.
28

Application of lipid biomarker analysis to evaluate the function of "slab-lined pits" in Arctic Norway

Heron, Carl P., Nilsen, G., Stern, Ben, Craig, O.E., Nordby, C.C. January 2010 (has links)
No / Gas chromatography–mass spectrometry (GC–MS) and bulk carbon isotope determinations have been performed on samples (‘cemented organic residues’, charcoal, sediment and fire-cracked rock) excavated from 12 slab-lined pits from various locations in Arctic Norway to test the premise that these archaeological features were used for the extraction of oil from the blubber of marine mammals, such as seal, whale and walrus. A wide range of lipid compound classes were detected especially in the cemented organic residues and in the charcoal samples. The presence of long-chain unsaturated and isoprenoid fatty acids together with oxidation and thermal alteration products of unsaturated acids such as dicarboxylic acids, dihydroxyfatty acids and ω-(o-alkylphenyl)alkanoic acids suggests that these features were used for marine oil extraction at elevated temperatures. Notably the location of the hydroxyl groups in the dihydroxyfatty acids provides a record of the positional isomer of the precursor fatty acid and allows confirmation that 11-docosenoic (cetoleic) acid, the most abundant C22:1 isomer in marine oil, was a major component of the original lipid. Further information was provided by the presence of long-chain fatty acyl moieties in surviving triacylglycerols and the presence of cholesterol. A fungal metabolite, mycose (trehalose), was found in all samples apart from a fire-cracked rock and points to microbiological activity in the pits. Bulk isotope analysis conducted on the ‘cemented organic residues’ is consistent with modern reference samples of blubber and oil from seal and whale. These data provide clear analytical evidence of the function of slab-lined pits in the archaeological record and suggest widespread exploitation of marine mammals for producing oil for heating, lighting and myriad other uses in the past.
29

Arran pitchstone (Scottish volcanic glass: new dating evidence

Ballin, T.B. January 2015 (has links)
Yes / In the present paper, the author offers new absolute and contextual dating evidence for Scottish archaeological pitchstone. Much archaeological pitchstone from the Scottish mainland is recovered from unsealed contexts of multi-period or palimpsest sites, and pitchstone artefacts from radiocarbon-dated pits therefore provide important dating evidence for this material group and its associated exchange network. In Scotland, all archaeological pitchstone derives from outcrops on the Isle of Arran, in the Firth of Clyde, and on the source island pitchstone-bearing assemblages include diagnostic types from the Mesolithic, Neolithic and Early Bronze Age period. Off Arran, pitchstone-bearing assemblages never include Mesolithic types, such as microliths, suggesting a post Mesolithic date. This suggestion is supported by worked pitchstone from radiocarbon-dated pits, where all presently available dates indicate that, on the Scottish mainland, Arran pitchstone was traded and used after the Mesolithic period, and in particular during the Early Neolithic period.
30

Avaliação in vitro e in situ da eficácia de diferentes lasers no aumento da resistência ácida do esmalte em regiões de sulcos e fissuras / In vitro and in situ assessment of lasers to increase enamel acid resistance on the pits and fissures surface.

Afonso, Alessandra Marques Corrêa 03 December 2009 (has links)
O objetivo desse estudo foi avaliar in vitro e in situ a efetividade de irradiação dos lasers Er:YAG, Nd:YAG e CO2 no aumento da resistência ácida do esmalte em regiões de sulcos e fissuras. Para o estudo in vitro foram utilizados molares humanos em fragmentos da porção oclusal de 8mmx4mm divididos em 3 grupos de acordo com o tipo de tratamento : Grupo 1 - Er:YAG; Grupo 2 - Nd:YAG; Grupo 3 - CO2 (n=15). O tratamento de superfície foi feito apenas em metade da área do fragmento, sendo que a outra metade foi considerada controle. As áreas expostas ao desafio cariogênico (14mm2) foram submetidas a ciclagens de pH. Para o testede microdureza os espécimes foram seccionados ao meio e a parede da secção é que sofreu o teste, a outra metade foi utilizada para análise em microscopia de luz polarizada para a medição da área da lesão de desmineralização e análise em MEV para verificar as alterações na morfologia do tecido dentário. As análises dos dados de microdureza (HKN) e área das lesões (mm2) foram feitas com o teste de Wilcoxon para a comparação interna de cada grupo com o seu controle e a comparação entre os grupos utilizou ANOVA para as áreas das lesões e Kruskal Wallis para a microdureza (&alpha; = 5%). Foi observada apenas diferença estatística significante para as amostras do grupo irradiado com laser CO2 entre as partes controle e experimental. Os demais grupos não apresentaram diferença estatisticamente significante com sua área controle. Na análise das medidas de lesão foram observadas diferença estatística significante para as amostras do grupo irradiado com os lasers CO2 e Nd:YAG com suas partes controles, sendo as medidas de área de lesão apresentadas pela área irradiada inferiores a área controle. Na análise em MEV o grupo irradiado com laser CO2 mostrou ausência de exposição dos prismas de esmalte e modificação de superfície na área irradiada. Para o estudo in situ foram utilizados molares humanos em fragmentos da porção oclusal de 4mmx4mm tratados com os 3 diferentes tipos de laser: Grupo 1 - controle (sem tratamento); Grupo 2 - Er:YAG; Grupo 3 - Nd:YAG; Grupo 4 - CO2 (n=15). Os espécimes foram adaptados a um dispositivo intrabucal que foi utilizado pelos voluntários durante 14 dias. Para o desafio cariogênico gotejou-se solução de sacarose 20% sobre os espécimes. Assim como no estudo in vitro, foram realizados o teste de microdureza, análise em microscópio de luz polarizada e análise em MEV. Para a análise dos dados de microdureza (HKN) foi utilizada ANOVA e teste de Fisher LSD (&alpha;= 5%). Foi observada diferença estatística significante para as amostras do grupo irradiado com laser CO2 e Nd:YAG, que apresentaram maiores valores de microdureza do que o grupo controle e não foram diferentes estatisticamente entre si. Os valores de microdureza observados em profundidade foram maiores proporcionalmente a distância da superfície, ou seja, 20&micro;m <30&micro;m <40&micro;m <50&micro;m. Na análise em microscopia de luz polarizada a análise foi feita com teste de Wilcoxon e todos os grupos apresentaram semelhança estatística. Considerando os resultados obtidos nos dois estudo pode-se concluir que os lasers CO2 e Nd:YAG foram capazes de promover aumento de resistência ácida no esmalte dental localizado nas superfície de sulcos e fissuras. / The aim of this study was to assess in vitro and in situ the lasers Er:YAG, Nd:YAG e CO2 in preventing enamel demineralization on the pits and fissures surface. For the in vitro study 45 occlusal enamel blocks were randomly divided into 3 groups in according with the treatment: G1 - Er:YAG; G2 - Nd:YAG; G3 - CO2. Treatments were made only on a half of the specimen and the remaining part was considered as a control. The samples were submitted to an in vitro pH cycles. For the microhardness test the specimens were seccioned in the middle and the seccioned wall received the test. The other halves were analyzed using polarized light microscopy for the measurement of the caries-lesion areas and morphological SEM analyses. Wilcoxon test were performed for the statistical analysis of the data obtained from the microhardness test (KHN) and caries-lesion area measurements (mm2) (&alpha;= 5%) when each groups was compared with its control. Variance analysis were performed for the difference in means of microhardness data and Kruskal Wallis test were performed for the difference in means of caries-lesion area measurements (&alpha;= 5%). For the microhardness data the G3 was statically different from its control area and the others groups presented statistical similarity among the experimental and control areas. For the caries-lesion area measurements statistical difference was observed for the groups G2 and G3 presenting smaller caries-lesion area when compared with their respective control areas. In the SEM analysis the G3 showed uniform surface without enamel-prism exposure. For the in situ study 60 occlusal enamel blocks were randomly divided into 4 groups in according with the treatment: G1 - Control (no treatment); G2 - Er:YAG; G3 - Nd:YAG; G4 - CO2 (n=15). The specimens were fixed in intra oral appliances and worn by the volunteers for 14d. Sucrose solution (20%) was applied to each specimen 6 times/d. As the in vitro study the samples were removed, sectioned and examined for microhardness, caries-lesion area measurements on the polarized light microcopy and morphological analyses on SEM. Variance analysis and the Fisher test were performed for the statistical analysis of the data obtained from the microhardness test (KHN) (&alpha;= 5%). The control group was statically different from G3 and G4, which present higher microhardness values and were statistical similar between them. The data of microhardness from the depth of surface were greater in proportion of distance from the surface, as 20&micro;m <30&micro;m <40&micro;m <50&micro;m. Wilcoxon test were performed for the statistical analysis of the data obtained from the caries-lesion area measurements (mm2) (= 5%) and all the groups were statically similar. Considering the results obtained from the both of studies can be concluded that the laser CO2 and Nd:YAG were able to increase the enamel acid resistance on the surface of pits and fissures.

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