2,007 research outputs found

    Retail Bottle Pricing at the Border: Evidence of Cross-Border Shopping, Fraudulent Redemptions, and Use Tax Evasion

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    This paper examines the pattern of retail prices for deposit eligible goods near Michigan’s borders. Michigan’s unique bottle redemption system and lower sales tax generate incentives for various potentially illegal household responses. Such incentives and behavior should be capitalized in the prices of affected goods. I empirically quantify the spatial price effects and find patterns consistent with theoretical predictions. Michigan’s border prices are higher (lower) for goods with higher (lower) per unit costs by up to 38%. Price-distance trends reflect the waning of these effects away from the border

    CO2 Flooding in Chalk Reservoirs

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    The potential of on-chip photonics is limited by the difficulty in coupling light from optical fibers to on-chip waveguides. Specifically, 3rd-order nonlinear on-chip photonics usually requires high optical power. Hence the first major focus of this research is to design high-efficiency edge couplers. To achieve this goal, loss mechanisms of basic inverse taper couplers are analyzed and experimentally verified. Then a cantilever-encapsulated inverse taper is demonstrated to further lower coupling loss compared to basic inverse tapers. Nonetheless, both couplers are designed to couple with lensed fibers. Hence for flat fibers with larger mode-field-diameter (MFD), a novel sub-wavelength grating based edge coupler is proposed and experimentally demonstrated to have 1.9dB/facet loss. Eventually a silicon multi-section taper with intermediate SU-8 waveguide cladding is proposed for flat fibers with even larger MFD and experimentally verified. Based on the result several suggestions are proposed for further improvement

    Mass Spectrometry-based Structural Proteomics: Methodology and Application of Fast Photochemical Oxidation of Proteins (FPOP)

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    The dissertation will be solely focused on using mass spectrometry to characterize protein high order structures (HOS), it emphasizes the use of hydroxyl radical footprinting (FPOP) coupled to bottom-up MS approach. A detailed background information about FPOP, and the corresponding method developments as well as applications will be covered. The first chapter will be a comprehensive review regarding the FPOP. Following this, chapter 2, 3, and 4 will be focused on the method developments. Chapter 2 describes an isotope dilution GC-MS method to quantitate OH radicals in FPOP; chapter 3 describes the incorporation of Leu-enkephalin as reporter peptide for a more quantitative FPOP platform; and chapter 4 introduces how R-programming can facilitate the MS-based structural proteomics. After this, chapter 5, 6, and 7 are mainly about the applications of FPOP to characterize the proteins. Chapter 5 talks about using FPOP to localize the dimer dissociation and local unfolding of G93A SOD1; chapter 6 describes how FPOP can be used to characterize an intrinsically disordered tail of EGF receptor protein; and chapter 7 demonstrates the feasibility of a marriage of FPOP and Nanodiscs to study the membrane-associated KRAS protein

    Practical Control-Flow Integrity

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    Control-Flow Integrity (CFI) is effective at defending against prevalent control-flow hijacking attacks. CFI extracts a control-flow graph (CFG) for a given program and instruments the program to respect the CFG. Specifically, checks are inserted before indirect branch instructions. Before these instructions are executed during runtime, the checks consult the CFG to ensure that the indirect branch is allowed to reach the intended target. Hence, any sort of control-flow hijacking would be prevented.However, CFI traditionally suffered from several problems that thwarted its practicality. The first problem is about precise CFG generation. CFI’s security squarely relies on the CFG, therefore the more precise the CFG is, the more security CFI improves, but precise CFG generation was considered hard. The second problem is modularity, or support for dynamic linking. When two CFI modules are linked together dynamically, their CFGs also need to be merged. However, the merge process has to be thread-safe to avoid concurrency issues. The third problem is efficiency. CFI instrumentation adds extra instructions to programs, so it is critical to minimize the performance impact of the CFI checks. Fourth, interoperability is required for CFI solutions to enable gradual adoption in practice, which means that CFI-instrumented modules can be linked with uninstrumented modules without breaking the program.In this dissertation, we propose several practical solutions to the above problems. To generate a precise CFG, we compile the program being protected using a modified compilation toolchain, which can propagate source-level information such as type information to the binary level. At runtime, such information is gathered to generate a relatively precise CFG. On top of this CFG, we further instrument the code so that only if a function’s address is dynamically taken can it be reachable. This approach results in lazily computed per-input CFGs, which provide better precision. To address modularity, we design a lightweight Software Transactional Memory (STM) algorithm to synchronize accesses to the CFG’s data structure at runtime. To minimize the performance overhead, we optimize the CFG representation and access operations so that no heavy buslockinginstructions are needed. For interoperability, we consider addresses in uninstrumented modules as special targets and make the CFI instrumentation aware of them. Finally, we propose a new architecture for Just-In-Time compilers to adopt our proposed CFI schemes
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