The first topic of this thesis is a mixed radix-16/8/4/2 64b/32b integer divider which uses a variety of techniques, including operand scaling, table partitioning, and table sharing, to increase performance without paying the cost of increasing complexity. The second topic is a noise immune address transition detector¡]ATD¡^circuit. We employ a simple feedback loop to stabilize the generated CS¡]chip select¡^signal and two delay cells to dynamically adjust the width of the CS strobe.

Title from PDF of title page (University of Missouri--Columbia, viewed on March 17, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Matthew E. Gompper. Vita. Includes bibliographical references.

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Carvone is a flavor and fragrance compound that is prominent in nature and is found in the essential oils of many plants. Carvone exists as two enantiomers, (R)-(-)-carvone which has a spearmint aroma and (S)-(+)-carvone which has a caraway aroma and can be used in a variety of applications: as a common food additive, as an antimicrobial/antifungal agent and as a potato sprout inhibitor. Carvone is currently produced by the extraction of essential oils from plants where the yield and quality of the extracted oil depends largely on successful agricultural production of dill, spearmint and caraway plants. Biotechnological production can offer a constant supply of carvone that is independent of several agricultural limitations. In this study, it was confirmed that the substrate and product of the microbial biotransformation of trans-carveol to (R)-(-)-carvone by Rhodococcus erythropolis DCL14 can be inhibitory to the cells at high concentrations. As such, a two phase partitioning bioreactor was employed where the function of the second phase (immiscible organic solvent or solid polymer beads) was to partition the inhibitory substrate into the aqueous phase at a rate governed by the metabolic demand of the cells and uptake the inhibitory product as it accumulated in the aqueous phase. Rational selection strategies were employed when determining the appropriate organic solvent and solid polymer to be used as the second phase. The performance of the reactor was evaluated based on volumetric productivity, length of biotransformation and total volume of substrate added to the reactor. The most successful reactor configuration was one in which styrene/butadiene copolymer beads were used as a second phase in the reactor and the fermentation medium was continuously circulated through an external extraction column packed with Hytrel® 8206 polymer beads. The volumetric productivity, length of biotransformation and total volume of substrate added to this reactor were 99 mg/L.h, 48.75 h and 35 mL, respectively whereas in the single phase benchmark reactor the performance indicators were only 31 mg/L.h, 15.25 h and 5 mL, respectively. These results clearly show the advantage of employing a partitioning bioreactor configuration for the biotechnological production of high value chemical species that exhibit cytotoxicity. / Thesis (Master, Chemical Engineering) -- Queen's University, 2008-01-24 10:20:09.589

Lazy replication with snapshot isolation (SI) has emerged as a popular choice for distributed databases. However, lazy replication requires the execution of update transactions at one (master) site so that it is relatively easy for a total SI order to be determined for consistent installation of updates in the lazily replicated system. We propose a set of techniques that support update transaction execution over multiple partitioned sites, thereby allowing the master to scale. Our techniques determine a total SI order for update transactions over multiple master sites without requiring global coordination in the distributed system, and ensure that updates are installed in this order at all sites to provide consistent and scalable replication with SI. We have built our techniques into PostgreSQL and demonstrate their effectiveness through experimental evaluation.

Social networks are large graphs which require multiple servers to store and manage them. Providing performant scalable systems that store these graphs through partitioning them into subgraphs is an important issue. In such systems each partition is hosted by a server to satisfy multiple objectives. These objectives include balancing server loads, reducing remote traversals (number of edges cut), and adapting the partitioning to changes in the structure of the graph in the face of changing workloads. To address these issues, a dynamic repartitioning algorithm is required to modify an existing partitioning to maintain good quality partitions. Such a repartitioner should not impose a significant overhead to the system. This thesis introduces a greedy repartitioner, which dynamically modifies a partitioning using a small amount of resources. In contrast to the existing repartitioning algorithms, the greedy repartitioner is performant (in terms of time and memory), making it suitable for implementing and using it in a real system. The greedy repartitioner is integrated into DistNeo4j, which is designed as an extension of the open source Neo4j graph database system, to support workloads over partitioned graph data distributed over multiple servers. Using real-world data sets, this thesis shows that DistNeo4j leverages the greedy repartitioner to maintain high quality partitions and provides a 2 to 3 times performance improvement over the de-facto hash-based partitioning.

This thesis investigated polymer properties for their application as extractants in two-phase partitioning bioreactors (TPPBs), which are intended to remove inhibitory fermentation products as they are produced. Three applications of polymer TPPB extractants were studied, followed by an investigation into poly(ether)-based polymers’ affinity toward representative target molecules, to identify properties which confer improved extraction performance. The first investigation aimed to replace a liquid extractant (silicone oil) using a block copolymer, Hytrel® 8206, in the biotransformation of indene to cis-(1S,2R)-indandiol, a chiral pharmaceutical intermediate, by Pseudomonas putida ATCC55687. The polymer simultaneously delivered substrate and removed the product and by-products to alleviate inhibition, improving operability and productivity relative to silicone oil, which could only deliver substrate. Subsequently, soft segment composition and proportion were varied in different block copolymers to selectively extract product or by-product(s) from the same biotransformation, altering the cells’ production profile. This demonstrated selective polymer extraction to help direct substrate utilization toward the product rather than by-product(s) in complex biotransformations. The next study was on absorptive extraction of a hydrophilic target molecule, 4-valerolactone, produced by recombinant Pseudomonas putida KT2440, featuring an equilibrium-limited final step. The aim was to demonstrate the first application of equilibrium-pulling using selective product absorption, improving production by 30%. Furthermore, this study showed that limited polymer water absorption is helpful to aid in extraction of hydrophilic target molecules, but high polymer water content compromises selectivity, diminishing the equilibrium-pulling effect. Finally, the effects of soft block proportion, molecular weight, and chain-end composition on affinity toward representative target molecules, carveol and carvone, were studied using commercial block copolymers and their representative homopolymer components. Target molecule affinity improved at low molecular weights in the absence of polar homopolymer end-groups. End-group polarity had an effect whose direction depended on the polarity of the target molecule, improving affinity toward a third, polar target molecule, 4-valerolactone, thereby providing a means to tailor selectivity. Crystallinity and hard segment proportion were both found to reduce uptake. This work has provided insights into the selection of polymeric TPPB absorbents by identifying polymer properties which improve affinity and selectivity toward different fermentation target molecules, especially relatively hydrophilic ones. The future design of purpose-built polymer extractants will benefit from considering these findings. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2014-01-17 13:43:54.818

Diverse fish species consume fruits and seeds in the Neotropics, in particular in the lowland reaches of large rivers, such as the Amazon, Orinoco, and Parana in South America. Floodplains of the Amazon River and its lowland tributaries are characterized by marked hydrological seasonality and diverse assemblages of frugivorous fishes, including closely related and morphologically similar species of several characiform families. Here, I investigated whether or not these fishes are capable of detecting fluctuations in food availability and if they are, how they adjust their feeding strategies. I tested predictions of optimal foraging, limiting similarity and resource partitioning theories with regard to expansion or compression of niche breadth and reduction in trophic niche overlap among species in relation with fluctuations in the availability of alternative food resources. I monitored fruiting phenology patterns to assess food availability and conducted intensive fishing during the high-, falling-, and low-water seasons in an oligotrophic river and an adjacent oxbow lake in the Colombian Amazon. I combined analysis of stomach contents and stable isotope ratios to evaluate dietary patterns, niche breadth, and niche overlap. Diets of six characiform fish species (Brycon falcatus, B. melanopterus, Myloplus asterias, M. rubripinnis, and M. torquatus) changed in a manner that indicated responses to fluctuations in food availability. Feeding strategies during the peak of the flood pulse were consistent with predictions of optimal foraging theory. During times of high fruit abundance, fish preferentially consumed items to which their phenotype is best adapted, maximizing net energy gain and enhancing fitness. As the flood pulse subsided and the availability of forest food resources was reduced in aquatic habitats, there was not a consistent pattern of diet breadth expansion or compression, even though diet shifts occurred, suggesting interspecific differences in foraging efficiencies. Analyses of diets and isotopic ratios revealed a general pattern of increased dietary segregation as the water level receded. Although there never was complete niche segregation among these fishes, these dietary changes effectively reduced interspecific niche overlap. Implications of these results and contribution of allochthonous food resources to diversity maintenance of floodplain fishes are discussed.

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