CU Scholar Institutional Repository

    Good Neighbor Renditions and the Enemy Alien: The Latin American Civilian Internees of World War II and the Integrity of the Good Neighbor Policy

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    This paper concerns a series of “renditions” of ethnically Japanese, German and Italian internees from their countries of residency in Latin America to the custody of the United States during the Second World War which were enacted through the framework of the Good Neighbor Policy. Despite many revisionist popular and scholarly contentions that the Good Neighbor Policy was an inauthentic application of the rhetoric that it aspired to, which traditionally cast the United States’ relations with Latin America as characterized by an attitude of respectful rapprochement premised on mutual recognition of autonomy, this paper instead uses the case of the “renditions” to argue that Latin America’s diplomatic influence was at least on par with that of the United States during the Good Neighbor Policy, even under the stresses of wartime conditions. However, I also argue that the mutual influence that the Good Neighbor Policy afforded to the United States and Latin America in the context of the “renditions” did not universally benefit Latin American civilians, such as those internees held as a consequence of these policies

    Modified DNA Aptamer Affinity Reagents for the Detection of Protein Tuberculosis Biomarkers in Urine

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    In 2015 the World Health Organization (WHO) determined that tuberculosis (TB) was the world’s most fatal infectious disease. Furthermore, Doctors Without Boarders (DWOB) published reports indicating that incidents of multi-drug resistant strains of TB (MDR-TB) infection have become rampant in resource-limited parts of the world. DWOB attributes the rapid increase in MDR-TB in part to a lack of accurate diagnostic techniques. The Feldheim group has been working towards developing aptamers to function as capture reagents in a new diagnostic platform for the detection of TB biomarkers in patient urine. Utilizing the SELEX process, an evolved pool of modified DNA aptamers were generated for the protein TB biomarker, MT2462, which is found in the urine of patients with active TB disease. Analysis of the evolved aptamer pool has revealed several aptamer sequences that could function as binders to MT2462. Specifically, an aptamer termed SEQ1, was selected for analysis. Determination of the aptamer affinity and specificity of SEQ1 for MT2462 will then create the potential for this sequence to be utilized in the development of a new diagnostic for TB

    Invalidating Transactions: Optimizations, Theory, Guarantees, and Unification

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    Transactional memory (TM) is a modern concurrency control paradigm that reduces the difficulty of parallel programming. TM also reduces some unnecessary program serialization by allowing operations from different critical sections, called transactions, to execute concurrently. Although allowing transactions to execute concurrently can increase throughput, care is needed to avoid memory access conflicts between transactions that can lead to incorrect program states. To prevent such incorrect program states, TM systems identify conflicts between transactions before such illegal states become part of the visible program state. To do this, when two or more transactions conflict, the TM stalls or rolls back some number of transactions to ensure the program state remains serializable, the main correctness criterion for TM systems. The process of identifying when transactions conflict is called conflict detection and is a significant source of overhead. To improve the performance of TM, researchers have found optimizations that reduce the cost of conflict detection. However, many of these TMs perform one aspect of conflict detection in the same manner. That is, they perform commit-time validation, where a transaction is analyzed for conflicts with previously committed transactions during its commit phase. While commit-time validation has certain benefits, it also has drawbacks that make it a suboptimal conflict detection strategy for certain environments. In this work we present a conflict detection strategy called full invalidation where the TM resolves all conflicts between a given transaction and all other active transactions before the given transaction commits. Full invalidation has a number of advantages over validation such as improved performance, enforceable execution guarantees, reduced conflict speculation, reduced conflict analysis space and time overhead, and simplified integration of optimistic and pessimistic concurrency control. We analyze full invalidation in the following ways. First, we compare and contrast InvalSTM, a software transactional memory (STM) that implements full invalidation, against TL2, a state-of-the-art STM that uses commit-time validation. Next we present a new theoretical model for TM systems and use the model to prove that histories accepted by a full invalidation system are both conflict and view serializable. We then demonstrate that a full invalidation STM is notably more efficient (by upwards of 100x) than a commit-time validation STM for programs where transactional priority must be respected. Last, we show that a full invalidation STM can reduce the TM implementation complexity and the TM operational overhead when using optimistic (transactions) and pessimistic (locks) critical sections in the same program

    Effective Instructional Approaches in a Large Introductory Biology Classroom: A Research Review and Illustrative Case Study

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    International students continue to outperform U.S. students in Science, Technology, Engineering, and Mathematics (STEM), while U.S. students increasingly leave these high-demand areas. To improve STEM performance and to alleviate STEM fatigue and attrition, researchers from several disciplines have been conducting studies to determine the most effective and efficient instructional and organizational practices in these courses. This thesis identifies best practices in structuring a STEM course to promote transformation to comprehension-based learning, while fostering student success. Best practices fall within three clusters: (a) structuring a course; (b) focusing on how to teach; and (c) assessing student performance. An illustrative case study in a large introductory biology classroom is highlighted as each cluster is described. Further, recommendations are provided related to effective instructional practices to be used in STEM classes. This combined research review and case study aims to provide new or inquiring instructors with the evidence-based strategies they may need to help reduce STEM fatigue and attrition in their classes

    Improving Palladium Catalysis with Self-Assembled Monolayers

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    Improving selectivity in catalytic systems is of primary interest to a number of fields. One means of achieving selectivity is through the use of promoters, or deposited materials that improve catalytic properties. Here, we present the modification of palladium surfaces with self-assembled monolayers (SAMs) formed from thiols. SAM coatings are employed in two systems: metal-insulator-semiconductor (MIS) sensors and supported palladium catalysts. On MIS sensors, modification with alkanethiol SAMs results in enhanced sensitivity to acetylene. Excellent selectivity for acetylene over ethylene is also observed. The functionalized sensors would serve as excellent acetylene detectors in a variety of applications including the detection of fault gases in transformers and detecting trace acetylene in ethylene production plants. Supported palladium catalysts were modified with SAM coatings for the selective reduction of 1-epoxy-3-butene (EpB) to 1-epoxybutane. Aside from having significant relevance for the production of value added chemicals, this reaction serves as an excellent probe for the conversion of unsaturated oxygenates derived from biomass and it is difficult to achieve high selectivity over conventional catalysts. Experiments probing the mechanism for the enhancement observed in sensors and catalysts showed increasing order of the SAM coating results in increasing sensor response or catalyst activity. By varying the chemical composition of the thiols used to create SAMs and by comparing these coatings to surface sulfur, we uncovered that surface sulfur is largely responsible for the enhancement of these devices. However, the hydrocarbon tails of thiols play an important role in controlling surface order. The reaction of EpB on coated and uncoated palladium surfaces was studied in more detail using temperature programmed desorption and high resolution electron energy loss spectroscopy on model systems in ultra-high vacuum. These experiments showed that on clean palladium, EpB ring opens to form an aldehyde-like intermediate; however, on surfaces coated with SAMs no ring opening is observed. Comparing the desorption energy of EpB to similar molecules suggests it binds through its olefin functionality, and comparing the desorption spectra at different surface coverages on coated surfaces suggests less well-ordered self-assembled monolayers decrease activity by preventing adsorption in active sites

    The Informal Recycler in Shanghai: Mobility, Migration and Citizenship

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    As social and economic realities shift in China\u27s post-reform era, increasing instability for the country\u27s hundreds of millions of migrant workers. The recent, dramatic growth of informal markets for recyclable waste represents a valuable opportunity for geographers to reinterpret how migrant labor is transforming urban identities. This thesis argues for a grounded study of informal recycling in Shanghai, now the world\u27s largest receiving port for recyclables as well as hundreds of thousands of domestic migrants. Perhaps more than any other class in the Chinese labor forces, migrant workers participating in informal urban markets face myriad social and economic challenges. Yet despite conflicting discourses on the value and culture of waste, participation in informal recycling offers a constitutive social role, in contrast to conventional ideas of marginalized urban subsistence activity

    Improving Security and Performance in Low Latency Anonymous Networks

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    Conventional wisdom dictates that the level of anonymity offered by low latency anonymity networks increases as the user base grows. However, the most significant obstacle to increased adoption of such systems is that their security and performance properties are perceived to be weak. In an effort to help foster adoption, this dissertation aims to better understand and improve security, anonymity, and performance in low latency anonymous communication systems. To better understand the security and performance properties of a popular low latency anonymity network, we characterize Tor, focusing on its application protocol distribution, geopolitical client and router distributions, and performance. For instance, we observe that peer-to-peer file sharing protocols use an unfair portion of the network’s scarce bandwidth. To reduce the congestion produced by bulk downloaders in networks such as Tor, we design, implement, and analyze an anonymizing network tailored specifically for the BitTorrent peer-to-peer file sharing protocol. We next analyze Tor’s security and anonymity properties and empirically show that Tor is vulnerable to practical end-to-end traffic correlation attacks launched by relatively weak adversaries that inflate their bandwidth claims to attract traffic and thereby compromise key positions on clients’ paths. We also explore the security and performance trade-offs that revolve around path length design decisions and we show that shorter paths offer performance benefits and provide increased resilience to certain attacks. Finally, we discover a source of performance degradation in Tor that results from poor congestion and flow control. To improve Tor’s performance and grow its user base, we offer a fresh approach to congestion and flow control inspired by techniques from IP and ATM networks

    Stiffness Analysis of the Tethered Coulomb Structure Concept and Application

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    This thesis investigates the Tethered Coulomb Structure (TCS) concept and its operating regime for creating large space structures and for providing satellite situational awareness. A TCS consists of a three-dimensional tethered spacecraft formation that uses electrostatic forces to repel the spacecraft and inflate the formation to a semi-rigid structure. The influential force modeling and equations of motion are given. Numerical simulations of a two-node TCS show that TCS systems have the greatest translational and rotational stiffness when the nodes have high voltage, low separation distance and low mass. Single tether two node TCS at 30 kV with 5 m separation are shown to withstand up to 50 deg/min initial rotations before reaching an entangled state. Multiple tether TCS simulations demonstrate that additional tethers between TCS nodes provides full three-dimensional stiffness and reduces the maximum absolute rotation for the system due to an initial perturbation. Using a double- or triple-tether TCS increases the maximum allowable initial rotation by 40-60%. Orbital perturbations, differential gravity and solar radiation pressure, are examined and it is demonstrated that both can be considered negligible for this study. A TCS configuration where one small spacecraft is tethered to a large spacecraft in orbit is presented. Simulations using a simple attitude control law show that a TCS in this configuration can be used to hold the smaller craft at a relatively fixed arbitrary position and rotation relative to the larger craft. Using multiple tethers for this configuration allows for separation distances of up to 10 m with less than 5 deg and 1 cm relative rotation and translation, respectively

    Atomic Layer Deposition for Improved Electrochemical Stability for Lithium Ion Batteries

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    The dwindling supply of fossil fuels and the harmful green house gases which they produce have driven research towards developing a reliable and safe solution. Alternative forms of transportation, such as hybrid electric, plug-in hybrid electric and all electric vehicles in turn have recently received vast consumer attention. Lithium ion batteries (LIBs) are seen as the most promising option in HEVs and PHEVs. However, while prevalent in watches, computers and phones, significant improvements in both energy density and rate capability need to be achieved before LIBs are suitable for vehicular applications. Decades of research has yielded a range of anode and cathode materials that exhibit higher capacity and better rate capability than the traditional graphite and LiCoO2 found in commercial batteries. Unfortunately due to material pulverization and electrode/electrolyte interfacial reactions high performance materials are often plagued with poor capacity retention and material degradation. Surprisingly, many of the issues accompanying high performance materials can be suppressed by the application of as little as 8 angstroms of Al2O3 on the surface. Ultrathin, conformal, ceramic passivating layers are grown using a thin _lm technique called Atomic Layer Deposition (ALD). Self-limiting and easily tailored, ALD is a superior coating method compared to the more common wet-chemical methods such as sol-gel. Conformal ALD is applied to commercially common materials (graphite, LiCoO2), as well as high energy density alternatives (MoO3, Li(Ni1/3 Mn1/3 Co1/3)O2). It will be shown that the ALD coating protects high surface area state-of-the-art nanoparticles from decomposition and protects electrode surfaces from HF attack and dissolution even up to 5.0 V. In addition to extending overall electrochemical cycling stability, ALD will be shown to minimize hazards and risks, such as thermal runaway, by preventing unwanted side reactions with the organic liquid electrolyte. ALD is a simple, non-toxic and effective method for the implementation of LIBs in high power applications

    Biaxial mechanical characterization and microstructure-driven modeling of elastic pulmonary artery walls of large mammals under hypertensive conditions

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    Pulmonary Hypertension (PH) is a disease of the pulmonary vasculature which causes right heart failure. It is known that PH causes significant remodeling of the pulmonary arterial vasculature, but the effects of this remodeling are not well-understood. In addition, there is a dearth of research in large mammals for PH. Modeling of the arteries is also important in the simulation of deformation due to blood flow. Current models either do not reflect the microstructure, or are too complex for clinical use. This work presents mechanical characterization and analysis of the artery wall, in addition to a constitutive model driven by the microstructure of the artery. In this work, mechanical characterization of the artery wall is performed via multiaxial deformation using a custom-fabricated planar biaxial tester. This test device provides higher fidelity than the standard uniaxial tests. Using the data gathered from the biaxial tester, trends in aspects of the mechanical behavior due to PH can be elucidated. Specifically, in this work, the anisotropy of the elastin protein network has been quantified, with the circumferential direction being 1.4x stiffer than the longitudinal direction. In addition to this new finding, PH has been shown to slightly decrease the anisotropy of the pulmonary artery trunk. A new microstructurally-based constitutive model for the artery wall was developed to reflect this finding. This model uses decoupled anisotropy for the elastin and collagen networks, reflecting the true behavior of the artery wall. The model uses a sinusoidal elastic beam to model the collagen fibers, reflecting the microstructure. This microstructural basis is then verified through histology and correlation of material parameters to histological images. Using information from this data, prospective future analysis of mechanical behavior will be proposed
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