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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.
1

Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden

Roopnarain, Sherissa January 2013 (has links)
The Alnö Complex is a Late Precambrian alkaline and carbonatite intrusion (c. 30km2) into Early Proterozoic country rock that extends from the north east, to the north western shoulder of Alnö Island. Carbonatites are rare among volcanic provinces, with Oldoinyo Lengai of northern Tanzania being the only active carbonatite volcano in the world today. The high carbonate mineral volumes and rare earth element (REE) concentrations of carbonatites, in combination with the intrusive-extrusive nature of their suites contribute to the rarity of these rocks. Carbonatites, through their peculiar petrological and geochemical compositions, provide vital insights to the composition and condition of the Earth’s mantle. The genesis of the Alnö carbonatites and their relation to other lithological units at the complex is however, only partially understood. This stems from the epistemological division of carbonatites as having either a ‘magmatic’ or ‘reactive’ origin. This study focuses on sampled carbonatites from the Alnö Complex, employing an oxygen and carbon isotope approach on their native calcite, complemented with petrological and mineralogical methods in order to constrain petrogenesis. As a reference, oxygen and carbon isotope data of calcite from an earlier Alnö investigation as well as from an array of data from comparative alkaline complexes elsewhere are also discussed. The combined data and the derived findings support a scenario that is consistent with the ‘magmatic’ model wherein carbonatites have a primary mantle-derived origin, and prospectively stem from a parent magma akin to that of Oldoinyo Lengai, but have experienced a degree of silicate and sedimentary assimilation. The extraction of the Alnö carbonatites for their rare earth metals is a looming possibility due to the current volatility in the rare earth market. The risks and opportunities involved in this kind of natural resource extraction provide a context wherein sustainable development paradigms can be applied. The capacity of the Alnö environment to withstand the impact of development in the mining sector is discussed through a perspective of establishing a quarry, and quarry-related methods for rare earth extraction.
2

Digital Education Resource Mining for Decision Support

AL Fanah, Muna M.S. January 2021 (has links)
Nowadays education becomes a competitive and challenging domain, both na­tionally and internationally in terms of quality, visibility, experience of aca­demic delivery affecting institutions, applicants, regulatory bodies. Currently data becomes more available for the general and public use, and plays also an increasingly significant role in decision support for education topics. For example, world university rankings (WUR) such as Quacquarelli Symonds (QS), Central World University Rankings (CWUR), Times Higher Education (Times) and national university rankings (e.g. the Guardian newspaper Best UK Universities and the Complete University Guide league tables) have published their data for many years now and are increasingly used in such decision making processes by institutions and general public.
3

Electrochemical Microwell Plate to Study Electroactive Microorganisms in Parallel and Real-Time

Kuchenbuch, Anne, Frank, Ronny, Ramos, José Vazquez, Jahnke, Heinz-Georg, Harnisch, Falk 03 April 2023 (has links)
Microbial resource mining of electroactive microorganism (EAM) is currently methodically hampered due to unavailable electrochemical screening tools. Here, we introduce an electrochemical microwell plate (ec-MP) composed of a 96 electrochemical deepwell plate and a recently developed 96-channel multipotentiostat. Using the ec-MP we investigated the electrochemical and metabolic properties of the EAM models Shewanella oneidensis and Geobacter sulfurreducens with acetate and lactate as electron donor combined with an individual genetic analysis of each well. Electrochemical cultivation of pure cultures achieved maximumcurrent densities (jmax) and coulombic efficiencies (CE) that were well in line with literature data. The co-cultivation of S. oneidensis and G. sulfurreducens led to an increased current density of jmax of 88.57 ± 14.04 μA cm−2 (lactate) and jmax of 99.36 ± 19.12 μA cm−2 (lactate and acetate). Further, a decreased time period of reaching jmax and biphasic current production was revealed and the microbial electrochemical performance could be linked to the shift in the relative abundance.
4

Making Space Exploration Sustainable: A Quantitative Assessment of Valuable Elements for Implementation of In-Situ Utilisation of Lunar Resources

Klaus, Bella January 2022 (has links)
Exploring the Solar System is an ongoing process of humanity that cannot be stopped. It requires large amounts of resources to explore space, which need to be acquired from somewhere. Resources mined on Earth cannot be diverted from vital productions on Earth as those required for energy systems transition and developing a sustainable society. With an ever-increasing demand of resources on Earth, resource extraction needs to be increased and diverted to avoid resource depletion. One such diversion is resource extraction from terrestrial bodies other than Earth, such as asteroids, meteorites, and the Moon. This thesis looks at the resources present on the Moon by compiling a chemical database which is then fed to mathematical models aimed to compare historical trends of Earth mining operations and prospected trends from lunar resources. Such approach is expected to establish if lunar mining is viable. The results are discussed in a larger context of how lunar resources can be used for in-situ resource utilization for solar system exploration, as well as questions regarding space law and possible colonialization.

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