Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2010. / Committee Chair: Ellery Ingall; Committee Member: Irina Sokolik; Committee Member: Josef Dufek. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Group II introns are a class of mobile ribozymes found in bacteria and eukaryotic organelles that self-splice from precursor RNAs. The resulting lariat intron RNA can then insert into new genomic DNA sites through a reverse splicing reaction. Collectively, this process of intron mobility is termed “retrohoming.” Mobile group II introns encode a reverse transcriptase (RT) that stabilizes the catalytically active form of the intron RNA for both the forward and reverse splicing reactions and also converts the integrated intron RNA into DNA. This work aims to elucidate the structure of bacterial group II intron-encoded RTs and ultimately determine how they function in intron mobility. Although efforts to crystallize group II introns RTs have been unsuccessful, small angle X-ray scattering studies in conjunction with homology modeling have provided new insights into the structure and function of these enzymes. / text

Reverse Mortgage Programme (“RMP”) was launched in Hong Kong on 11th July 2011. It aims to help the elderly to improve the living standard. Since the aging population is getting serious and the lack of comprehensive retirement protection scheme in Hong Kong, a big potential market for reverse mortgage is given which is anticipated that the eligible elderly should eagerly participate to the programme. However, the statistic from the Hong Kong Mortgage Corporation (“HKMC”) showing that the participation rate of RMP is surprisingly low. Up to 31st May 2014, only 624numbers of applications were recorded. In order to boost the participation rate, this dissertation has conducted a study to identify the reason(s) of low participation rate and explore the possible way(s)to enhance the RMP. In order to achieve the aim of the study, a questionnaire survey was conducted to investigate the consumer’s perception to RMP. It divided consumer’s perception into consumer’s awareness and consumer’s motivation. High awareness but low understanding to RMP was found according to the results of survey. Meanwhile, low consumer’s motivation to RMP was found and the complicated programme content and legacy concern are the major factors influencing the consumer’s motivation. Nevertheless, there still a long way to go for the RMP in Hong Kong. To enhance the performance of RMP, it is recommended to promote it by different means of media and focus it to the elderly without children. Further studies would be needed to assess the effectiveness of the approaches in the recommendation. / published_or_final_version / Housing Management / Master / Master of Housing Management

The Lactococcus lactis Ll.LtrB group II intron encodes a reverse transcriptase (LtrA protein), which binds the intron RNA to promote RNA splicing and intron mobility. Mobility occurs by intron RNA reverse splicing directly into a DNA strand and reverse transcription by LtrA. I used LtrA-GFP fusions and immunofluorescence microscopy to show that LtrA localizes to the cellular poles in both Escherichia coli and L. lactis. This polar localization occurs with or without co-expression of the intron RNA, is observed over a wide range of cellular growth rates and expression levels, and is independent of replication origin function. The same localization pattern was found for three non-overlapping LtrA subsegments, reflecting dependence on common redundant signals and/or protein physiochemical properties. When coexpressed in E. coli, LtrA interferes with the polar localization of the Shigella IcsA protein, which mediates polarized actin tail assembly, suggesting competition for a common localization determinant. In E. coli, the Ll.LtrB intron inserts preferentially into the chromosomal ori and ter regions, which are pole localized during much of the cell cycle. Thus, the polar localization of LtrA could account for the preferential insertion of the Ll.LtrB intron in these regions. I established a high throughput method using cellular array and automated fluorescence microscopy for screening transposon-induced mutants, and identified five E. coli genes (gppA, uhpT, wcaK, ynbC, and zntR) in which disruptions result in increased proportion of cells having diffuse LtrA distribution. This altered localization is correlated with a more uniform distribution of Ll.LtrB insertion sites throughout the E. coli genome. Finally, I find that altered LtrA localization in all five disruptants is correlated with accumulation and more diffuse intracellular distribution of polyphosphate, and that a ppx disruptant, which also results in polyphosphate accumulation, shows similar LtrA mislocalization. These findings may reflect interaction between LtrA and intracellular polyphosphate. My findings support the hypothesis that the intracellular localization of LtrA is a major determinant of Ll.LtrB insertion site preference in the E. coli genome. Further, they show that alterations in polyphosphate metabolism can lead to protein mislocalization, and suggest that polyphosphate is an important factor affecting intracellular protein localization.

Not available / text

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

No description available.

In spite of abundant water resources, world is suffering from the scarcity of usable water. Seawater Reverse Osmosis (SWRO) desalination technology using polymeric membranes has been recognized as a key solution to water scarcity problem. However, economic sustainability of this advanced technology is adversely impacted by the membrane fouling problem. Fouling of RO membranes is a highly studied phenomenon. However, literature is found to be lacking a detailed study on kinetic and dynamic aspects of SWRO membrane fouling. The factors that impact the fouling dynamics, i.e., pretreatment and water quality were also not adequately studied at full–scale of operation. Our experimental protocol was designed to systematically explore these fouling aspects with the objective to improve the understanding of SWRO membrane fouling mechanisms. An approach with multiple analytical techniques was developed for fouling characterization. In addition to the fouling layer characterization, feed water quality was also analysed to assess its fouling potential. Study of SWRO membrane fouling dynamics and kinetics revealed variations in relative abundance of chemical and microbial constituents of the fouling layer, over operating time. Aromatic substances, most likely humic–like substances, were observed at relatively high abundance in the initial fouling layer, followed by progressive increase in relative abundances of proteins and polysaccharides. Microbial population grown on all membranes was dominated by specific groups/species belonging to different classes of Proteobacteria phylum; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age and with the position of membrane element in RO vessel. Our results demonstrated that source water quality can significantly impact the RO membrane fouling scenarios. Moreover, the major role of chlorination in the SWRO membrane fouling was highlighted. It was found that intermittent mode of chlorination is better than continuous mode of chlorination of seawater, as anti–biofouling strategy. It was also confirmed that significant biofilm development was inevitable even with the use of chlorine to disinfect SWRO membranes. Our findings on the dynamic patterns of SWRO membrane fouling should help in further elaborating research projects focusing on the development of better strategies to minimize this troublesome phenomenon.

Central Arizona Project water was treated using slow sand filtration (SSF) and reverse osmosis (RO) in series. Additional desalination water was recovered from RO brine using the vibratory shear-enhanced processing (VSEP®; New Logic, Inc.). SSF removed 90% of the turbidity in raw CAP water. SSF decreased total organic carbon by almost 20%. After a little more than a year of continuous operation, performance of the RO system declined noticeably, as indicated by a rapid decrease in membrane permeation coefficient and an increase in salt flux. Foulant scrapings contained both clay material and large amounts of unidentified organics. Alternative hypotheses regarding major sources of membrane foulants are discussed in this study.Water lost as brine was reduced from 20% to 2-4% via post-RO VSEP treatment. Estimated costs were compared to those of a no-VSEP option in which disposal of the entire RO brine flow was required. The total annualized cost of brine treatment was fairly insensitive to recovery during VSEP treatment in the range 80-90%, and the period of VSEP operation between cleanings in the range 25-40 hrs. These values define a fairly broad window for near optimal VSEP operation under the conditions of the study. The cost of VSEP treatment to minimize brine loss was estimated at $394- $430 per acre foot ($1.21 - $1.32 per 1000 gal) of 15 MGD CAP water treated. For a hypothetical 3 MGD RO brine flow, the use of VSEP to recover water and reduce the volume of brine for disposal results in a savings of more than $5M/year relative to the no-VSEP brine disposal alternative.

Autonomic Computing is an approach to designing systems that are capable of self-management. Fundamental to the autonomic ideal is a software's awareness of and ability to tune parameters that affect metrics like performance and security. Traditionally, these parameters are tuned by human experts with extensive knowledge of parameter names and effects---existing software was not designed to be self-tuning. Efforts to automate the isolation and tuning of parameters have yielded encouraging results. However, the parameters are identified manually. This thesis proposes the adaptation of reverse engineering techniques for automating the recovery of software tuning parameters. Tuning parameters from several industrially relevant applications are studied for patterns of use. These patterns are used to classify the parameters into a taxonomy, and to develop a metamodel of the source code elements and relationships needed to express them. An extractor is then built to obtain instances of the relationships from source code. The relationships are represented as graphs, which are manipulated and queried for instances of tuning parameter patterns. The recovery is implemented as a tool for finding tuning parameters in applications. Experimental results show that the approach is effective at recovering documented tuning parameters, as well as other undocumented ones. The results also indicate that the tuning parameter patterns are not specific to a particular application, or application domain. / Thesis (Master, Computing) -- Queen's University, 2008-06-28 19:36:43.291