The field of decision making has largely focused on the influence of contextual factors on risk tolerance. Much work has focused on how the problem itself is presented, in hopes of understanding the circumstances under which individuals may be helped in areas of long-term investment and planning through encouragement of greater risk tolerance. Specifically, when making financial decisions, it has been suggested that by presenting individual decisions in groups (Gneezy & Potters, 1997), or by presenting feedback less frequently (Thaler et al, 1997), participants are able to process individual problems in a holistic manner, which encourages risk tolerance when deciding. This literature has typically made claims that these effects are dependent on how the problem is presented. However, evidence for the benefits of “broadly bracketed” problems often relies as much on the presentation of aggregated outcomes as it relies on the grouping of problems. The purpose of this thesis was to further examine whether bracketing effects might be attributable to manipulations of problem framing or outcome framing. In addition, it has been suggested that perhaps individuals who differ in processing styles might respond differentially to framing effects in general (Frederick, 2005). That is, perhaps individuals who are more intuitive decision makers might be more susceptible to context-based changes, and so might show larger framing effects. Deliberative decision makers, on the other hand, might overcome these framing effects by reflecting on, or actively “reframing”, the problem. A secondary purpose of this thesis was thus to investigate individual differences in the magnitude of the bracketing effect on risk tolerance. In Experiment 1, problem and outcome bracketing were examined in the domain of discrete choices, while in Experiment 2, bracketing was examined with continuous iv investments. Results suggest that when investment opportunities are identical, problem framing encourages long-term risk tolerance. However, when choices are somewhat different from one another, as is often the case in real-world investment situations, outcome information is critical to encouraging long-term risk tolerance. Together, results suggest a critical reevaluation of the bracketing hypothesis and its application to long-term investment.

We address two problems dealing with fault-tolerant communication in networks. The first one is designing a distributed storage protocol tolerant to Byzantine failure of servers. The protocol implements a multi-writer multi-reader register which satisfies a weaker consistency condition called MWReg. Most of the earlier work gives multiwriter implementations by simulating m copies of a single-writer protocol where m is the number of writers. Our solution gives a direct multi-writer implementation and thus has bounded message and time complexity independent of the number of writers. We have simulated the complete protocol to test its performance and also proved its correctness theoretically. The second problem we address is of providing a reliable communication link between two nodes in a network. We present a capacity reservation algorithm in the case for upper bounds on edge capacities and costs associated with using per unit capacity on any edge. We give a flow based approximation algorithm with cost at most four times optimal. To conclude, we design a distributed storage protocol and a capacity reservation algorithm which are tolerant to network failures.

Field studies were conducted during the 2003 and 2004 growing seasons to: 1) evaluate the control of silverleaf nightshade and western ragweed, and (2) assess the forage tolerance of Coastal and Tifton 85 bermudagrass hybrids using tank mix combinations of diflufenzopyr. Herbicides that were evaluated in each study included picloram, multiple rates of picloram with diflufenzopyr, triclopyr, triclopyr with diflufenzopyr, dicamba + diflufenzopyr, and diflufenzopyr alone. Visual ratings were taken on the weed control experiments approximately 30, 60 and 90 days after treatment. Phytotoxicity ratings were taken prior to each harvest of the Coastal and Tifton 85 varieties to determine influence of each herbicide treatment. Each bermudagrass variety was harvested twice during each growing season to determine dry matter yield and quality. Forage quality, including crude protein, acid detergent fiber, and neutral detergent fiber, was assessed using near infrared reflectance spectroscopy. Adding diflufenzopyr to triclopyr did not consistently increase control of silverleaf nightshade or western ragweed. In general, picloram + diflufenzopyr and picloram applied alone provided the greatest control of both species at the highest rate of picloram. Increased efficacy was more evident from the addition of diflufenzopyr to picloram in 2004 on western ragweed. By the final ratings in both experimental years, dicamba + diflufenzopyr provided no more than 76% control of either species. Both forage varieties showed significant variability in phytotoxicity between years. Although observed levels of growth reduction were relatively high at the first harvest in 2003, no treatment exceeded a 10% growth reduction by the second harvest for either forage variety. In addition, the only significant reduction in dry matter yield occurred at the first harvest of Coastal in 2003 from picloram + diflufenzopyr applied at the highest rate.

The fungus Ceratocystis fagacearum (Bretz) Hunt causes the vascular disease of oak wilt and has been decimating live oaks (Quercus virginiana Mill. and Quercus fusiformis Small.) and red oaks (Quercus texana Small and Quercus marilandica Muenchh.) in Texas. The purpose of this research was to test the hypotheses that live oaks have heritable tolerance to oak wilt, and that allozyme markers are associated with this tolerance. One-year-old half-sib and two-year-old clonal progeny of live oaks (Q. fusiformis) were grown from acorns and ramets from a disease center and then challenged with C. fagacearum. Allozyme analyses were used to compare the pre- and post-epidemic populations in two natural disease centers to search for alleles associated with survivability and decreased crown loss. Half-sib and clonal challenge tests supported the hypothesis that heritable tolerance to the pathogen occurs in live oaks. The progeny tolerances seen in half-sib and clonal groups did not correlate with parental tree performance. This finding suggests that the tolerance of one-year-old seedlings in the greenhouse setting is not a good predictor of how mature trees will do in a natural setting. Seedlings may not be a good model for testing tolerance to a pathogen. The ability to survive this vascular pathogen is containment, and seedlings may be too small to test this type of tolerance. The clonal groups from post-epidemic trees performed better than the seedlings. They may have an increased resistance because they are mature or they may have a postdisease immunity. No significant allele frequencies between pre- and post-epidemic trees were consistent among sites or with previous research. The different disease sites had remarkably similar allele frequencies which indicate high levels of gene flow among sites. Both sites were found to contain significant numbers of clones, but the Izoro site had significantly larger clonal groups. Sites were in Hardy-Weinberg equilibrium which indicates substantial sexual reproduction and not just clonal reproduction is taking place. Several cases of linkage disequilibrium occurred at the Izoro site, but population structure was responsible in all but one case.

We examine the tolerance of dining philosopher algorithms subject to process crash faults in arbitrary conflict graphs. This classic problem is unsolvable in asynchronous message-passing systems subject to even a single crash fault. By contrast, dining can be solved in synchronous systems capable of implementing the perfect failure detector P (from the Chandra-Toueg hierarchy). We show that dining is also solvable in weaker timing models using a combination of the trusting detector T and the strong detector S; Our approach extends and composes two currents of previous research. First, we define a parametric generalization of Lynch’s classic algorithm for hierarchical resource allocation. Our construction converts any mutual exclusion algorithm into a valid dining algorithm. Second, we consider the fault-tolerant mutual exclusion algorithm (FTME) of Delporte-Gallet, et al., which uses T and the strong detector S to mask crash faults in any environment. We instantiate our dining construction with FTME, and prove that the resulting dining algorithm guarantees masking tolerance to crash faults. Our contribution (1) defines a new construction for transforming mutual exclusion algorithms into dining algorithms, and (2) demonstrates a better upper-bound on the fault-detection capabilities necessary to mask crash faults in dining philosophers.

Thesis (Ph. D.)--University of Chicago, Divinity School, 2002. / Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on Dec. 14, 2009). Includes bibliographical references (p. 74-76).

For the last 40 years, the systems community has invested a lot of effort in designing techniques for building fault tolerant distributed systems and services. This effort has produced a massive list of results: the literature describes how to design replication protocols that tolerate a wide range of failures (from simple crashes to malicious "Byzantine" failures) in a wide range of settings (e.g. synchronous or asynchronous communication, with or without stable storage), optimizing various metrics (e.g. number of messages, latency, throughput). These techniques have their roots in ideas, such as the abstraction of State Machine Replication and the Paxos protocol, that were conceived when computing was very different than it is today: computers had a single core; all processing was done using a single thread of control, handling requests sequentially; and a collection of 20 nodes was considered a large distributed system. In the last decade, however, computing has gone through some major paradigm shifts, with the advent of multicore architectures and large cloud infrastructures. This dissertation explains how these profound changes impact the practical usefulness of traditional fault tolerant techniques and proposes new ways to architect these solutions to fit the new paradigms. / text

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