Matching Items (5)
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- All Subjects: Genetics
- All Subjects: Space Debris
- Creators: Foy, Joseph
Description
Orbiting space debris is an active issue that affects the capability of space launch for future satellites, probes, and space shuttles, and it will become a nearly insurmountable problem without action. Debris of varying sizes and speeds orbit the Earth at a range of heights above the atmosphere and need to be removed to avoid damage to crucial equipment of active orbiting satellites including the International Space Station. Finding a feasible solution to space debris removal requires that several facets be covered to become a reality; these include being aware of the problem in magnitude and source. This literature assessment covers the magnitude of space debris in low-earth and geosynchronous orbit as well as collision events which have increased the amount of space debris. There have been efforts made by several space agencies to control the amount of space debris added to orbit by current and future launches over the last decade \u2014 serving as a temporary fix before removal can be executed. This paper explores known removal efforts through mitigation, projects conceived and tested by DARPA, related space policies and laws, CubeSat technology, and the cataloguing of known space debris. To make space debris removal a reality, roadblocks need to be removed to acquire permission from states or countries for space missions. For example, these restrictions are in place to protect the assets of several countries and organizations. Guidelines set to curb the growth of space debris fail to prevent the growth due to the restrictions for ownership rights making them not as effective. This paper covers space policy and laws, the economy, satellite ownership, international conflict, status of space debris, and the overall feasibility of space debris removal. It will then discuss currently proposed solutions for the removal of space debris. Finally, this paper attempts to weight the advantages and disadvantages of the idea that space debris removal should include the opportunity to recycle materials. For example, defunct satellites and other discarded space crafts could be used for future launches. It will conclude with a personal exploration of what materials can be recycled, what chemical processes can be used to break down materials, and how to combine recycling and chemical processes for space-based recycling stations between Earth and the moon. The overall question that drives the search for making space debris removal a reality is whether it is feasible in multiple areas including technologically, legally, monetarily, and physically.
ContributorsBreden, Elizabeth Catherine (Author) / Foy, Joseph (Thesis director) / Thoesen, Andrew (Committee member) / Maximon, Leonard (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
This study focused on the connection between the EnvZ/OmpR two-component regulatory system and the iron homeostasis system in Escherichia coli, specifically how a mutant form of EnvZ11/OmpR is able to reduce the expression of fepA::lacZ, a reporter gene fusion in E. coli. FepA is one of several outer membrane siderophore receptors that allow extracellular siderophores bound to iron to enter the cells to power various biological processes. Previous studies have shown that in E. coli cells that expressed a mutant allele of envZ, called envZ11, which led to altered expression of various iron genes including down regulation of fepA::lacZ. The wild type EnvZ/OmpR system is not considered to regulate iron genes, but because these envz11 strains had downregulated fepA::lacZ, this study was undertaken to understand the connection and mechanisms of this downregulation. A large number of Lac+ revertants were obtained from the B32-2483 strain (envz11 and fepA::lacZ) and 7 Lac+ revertants that had reversion mutations not directly correcting the envZ11 allele were further characterized. With P1 phage transduction genetic mapping that involved moving a kanamycin resistance marker linked to fepA::lacZ, two Lac+ revertants were found to have their reversion mutations in the fepA promoter region, while the other five revertants had their mutations mapping outside the fepA region. These two revertants underwent DNA sequencing and found to carry two different single base pair mutations in two different locations of the fepA promoter region. Each one is in the Fur repressor binding region, but one also may have affected the Shine-Dalgarno region involved in translation initiation. All 7 reveratants underwent beta-galactosidase assays to measure fepA::lacZ expression. The two revertants that had mutations in the fepA promoter region had significantly increased fepA activity, with the revertant with the Shine-Dalgarno mutation having the most elevated fepA expression. The other 5 revertants that did not map in the fepA region had fepA expression elevated to the same level as that found in the wild type EnvZ/OmpR background. The data suggest that the negative effect of envZ11 can be overcome by multiple mechanisms, including directly correcting the envZ11 allele or changing the fepA promoter region.
ContributorsKalinkin, Victor Arkady (Co-author) / Misra, Rajeev (Co-author, Thesis director) / Mason, Hugh (Committee member) / Foy, Joseph (Committee member) / Biomedical Informatics Program (Contributor) / School of Life Sciences (Contributor) / W. P. Carey School of Business (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The interaction between England and Scotland is complicated and continually changing. Scottish writer Sir Walter Scott examines this long-standing relationship through his various writings. Scott conveys a presence that is both acutely aware of the damages enacted upon Scotland by various English political efforts, and sensitive to the delicate relationship that the two regions had begun to form during his lifetime. Through a critical analysis of Scott's novel, Rob Roy, one can see the various strategies Scott used to balance the need to address prior controversies within the relationship, and the petition to move beyond the prior conflict and develop a mutual understanding of each culture. Through this, Scott is able to regenerate a sense of Scottish nationalism for his people, and encourage improved relations within the British Isles.
ContributorsChotena, Chelsea (Author) / Facinelli, Diane (Thesis director) / Foy, Joseph (Committee member) / White, Julianne (Committee member) / Barrett, The Honors College (Contributor)
Created2013-05
Description
Gle1 is an mRNP export mediator with major activity localized to the nuclear pore complex in eukaryotic cells. The protein's high preservation across vast phylogenetic distances allows us to approximate research on the properties of yeast Gle1 (yGle1) with those of human Gle1 (hGle1). Research at Vanderbilt University in 2016, which provides the research basis of this thesis, suggests that the coiled-coil domain of yGle1 is best crystallized in dicationic aqueous conditions of pH ~8.0 and 10\u201420% PEG 8000. Further exploration of crystallizable microconditions revealed a favorability toward lower pH and lower PEG concentration. Following the discovery of the protein's native crystallography conditions, a comprehensive meta-analysis of scientific literature on Gle1 was conducted on the association of Gle1 mutations with neuron disease.
ContributorsGaetano, Philip Pasquale (Author) / Foy, Joseph (Thesis director) / Dawson, T. Renee (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
This thesis seeks to examine shortcomings in space law by focusing on two interconnected aspects: privatization and space debris. The aspects of privatization and space debris will be examined under the context of the Outer Space Treaty (OST) and other relevant legal instruments. Privatization and space debris are two current challenges that the OST fails to regulate efficiently. While the OST was being drafted, the international community did not foresee problems such as privatization and space debris. This is significant because we are witnessing an increase in privatization of space activities and corporations as well as a massive accumulation of dangerous space debris. While the OST grants states the power to regulate private space companies and the accretion of space debris, national laws rarely align with the OST, leading to the abuse of international space laws. We will make recommendations at the end of the thesis in an effort to revise the use of soft language in the OST to attune national laws with international laws as well as address the growing ambiguity surrounding privatization and space debris.
ContributorsSimper, Elizabeth Mary (Co-author) / Simper, Elizabeth (Co-author) / Ziglin, Kathryn (Co-author) / Iheduru, Okechukwu (Thesis director) / Foy, Joseph (Committee member) / School of Politics and Global Studies (Contributor, Contributor, Contributor) / School of Human Evolution & Social Change (Contributor) / Department of Management and Entrepreneurship (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05