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Title: Recycling nursery runoff : understanding plant sensitivity to nutrients and residual pesticides
Creator: Poudyal, Shital
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Runoff generated from landscape nursery operations contains agrochemicals such as pesticides and fertilizers, which, if released off-site, may pollute the environment. Nursery producers are increasingly interested in alternatives to using freshwater for irrigation due to increased environmental awareness and reduced water availability. As a result, some progressive nursery growers are already adopting the Runoff generated from landscape nursery operations contains agrochemicals such...
Show moreRunoff generated from landscape nursery operations contains agrochemicals such as pesticides and fertilizers, which, if released off-site, may pollute the environment. Nursery producers are increasingly interested in alternatives to using freshwater for irrigation due to increased environmental awareness and reduced water availability. As a result, some progressive nursery growers are already adopting the Runoff generated from landscape nursery operations contains agrochemicals such as pesticides and fertilizers, which, if released off-site, may pollute the environment. Nursery producers are increasingly interested in alternatives to using freshwater for irrigation due to increased environmental awareness and reduced water availability. As a result, some progressive nursery growers are already adopting the practice of retaining and recycling nursery runoff water for irrigation. While retaining and recycling runoff may be a practical solution, growers' concerns about the potential negative impact of residual pesticides on crop growth and quality still impede its adoption. Therefore the objectives of my studies were to reduce the concentration of nutrients in runoff water and to evaluate the impact of irrigating with recycled runoff water on growth and physiology of nursery crops.The first study was to identify minimum phosphorus concentration required for the optimum morphological and physiological performance in three common woody ornamental taxa; Hydrangea quercifolia (Queen of hearts), Cornus obliqua (Redtwig dogwood) and Physocarpus opulifolius (Seward). The optimum phosphorus concentrations for growth and photosynthetic biochemistry ranged between 4 and 7 mg·L-1, depending on taxa. For the second study, I investigated the response of common landscape nursery plants to residual pesticide commonly found in nursery runoff. Hydrangea paniculata (Limelight), Cornus obliqua (Powell Gardens), Hosta (Gold Standard) were exposed to low residual concentrations of isoxaben, chlorpyrifos and oxyfluorfen, simulating irrigation with nursery runoff. Exposure to oxyfluorfen produced phytotoxicity symptoms (visual leaf damage), while chlorpyrifos and isoxaben did not produce phytotoxicity. Among the three taxa, H. paniculata was the most sensitive species, and C. obliqua was the most resistant. Therefore the effects of pesticides were pesticide-specific and taxa-specific. For the third study, I investigated whether phytotoxicity in response to residual herbicide exposure was dependent on the growth stage of plants. In this study, H. paniculata plants were exposed to a low residual concentration of oryzalin and oxyfluorfen at the various growth stages, starting shorty after bud-break. Residual herbicide exposure had more impact on growth and photosynthetic physiology at early growth stages; however, the recovery rate of those plants was also rapid. For my final study, I conducted three-year field research replicating an actual nursery grower practice of recycling nursery water. Six ornamental species were irrigated with recycled water obtained from a nursery bed receiving ten different pesticides. In addition, the efficacy of woodchip bioreactors to reduced pesticides in water was also tested. Results from this study established the possibility of using recycled water to irrigate ornamentals plants such as Hydrangea macrophylla (Let's dance blue jangles), Hydrangea paniculata (Limelight), Thuja occidentalis (American Pillar), Juniperus horizontalis (Blue rug), Hydrangea arborescens (Invincibelle Spirit II®) and Rosa sp. (Oso Easy Double Red®) without impacting the growth and physiology of those plants. Woodchips bioreactor was also found to be effective in remediating pesticides from water. The results of three greenhouse studies and a field study together provide new information on reducing the concentration of nutrients and pesticides in nursery runoff water and demonstrate the possibility of recycling nursery runoff. The findings of this dissertation are vital in solving the emerging problem of agrochemical pollution and water scarcity that is currently faced by nursery growers.
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Title: Reaction-based knock predictive modeling and model-based stochastic knock limit control of spark-ignition engines
Creator: Li, Ruixue
Date: 2020
Collection: Electronic Theses & Dissertations
Description: This dissertation studies the spark-ignition (SI) engine knock phenomenon, abnormal combustion due to the auto-ignition of end-gas ahead of the propagated flame front, resulting in the rapid chemical energy release with aggressive combustion, limiting the further improvement of thermal efficiency and even damaging the engine mechanically. A control-oriented combustion and pressure wave model with satisfactory accuracy and low computational effort is a necessity for the knock control strategy...
Show moreThis dissertation studies the spark-ignition (SI) engine knock phenomenon, abnormal combustion due to the auto-ignition of end-gas ahead of the propagated flame front, resulting in the rapid chemical energy release with aggressive combustion, limiting the further improvement of thermal efficiency and even damaging the engine mechanically. A control-oriented combustion and pressure wave model with satisfactory accuracy and low computational effort is a necessity for the knock control strategy design. This dissertation develops a control-oriented knock predictive model that includes a two-zone reaction-based combustion model and a pressure wave model. This knock predictive model is capable of accurately describing the combustion process of a spark-ignited engine and predict the in-cylinder pressure oscillations under knocking combustion in real-time. Based on this model, a feedforward and feedback stochastic knock limit control strategy is developed to reduce the knock cyclic variability and control the knock mean-intensity below a desired up bound while keeping spark timing as close to engine maximum brake torque (MBT) timing as possible. A control-oriented two-zone reaction-based model to accurately describe the combustion process of a SI engine is first developed. Instead of using the conventional pre-determined Wiebe-based combustion model, a two-step chemical reaction model is utilized to predict the combustion process along with important thermodynamic parameters such as the mass-fraction-burned, in-cylinder pressure, temperatures and individual species mass changes in both zones. Sensitivities of model parameters are analyzed during the model calibration process. As a result, one set of calibration parameters are used to predict combustion characteristics over all engine operating conditions studied in this paper, which is the major advantage of the proposed method. Also, the proposed modeling approach is capable of modeling the combustion process for real-time simulations. As the by-product of the model, engine knock can also be predicted based on the Arrhenius integral in the unburned zone, which is valuable for model-based knock control. The proposed combustion model is intensively validated using the experimental data with a peak relative prediction error of 6.2% for the in-cylinder pressure. Based on this validated combustion model, a control-oriented pressure wave model for SI engines is further developed. This model is capable of predicting the in-cylinder pressure oscillations under knocking combustion in real-time and can be used for the model-based knock prediction and control. A pressure wave equation including the knock deadening behavior is proposed, simplified, and used to calculate the pressure perturbations generated by the knocking combustion. The boundary and initial conditions at knock onset are analyzed and the analytic solution of the pressure wave equation is obtained. The model is calibrated and validated over two different engine operating conditions at knock limit. The chemical kinetic-based Arrhenius integral (ARI) and the KI20 are used as the evaluation methods for knock onset and intensity prediction, and the knock frequency is studied with a fast Fourier transform of the filtered in-cylinder pressure oscillations. Especially, the knock characteristics associated with gas mixture properties at intake valve closing is analyzed based on the experimental data and their effect to knock cycle-to-cycle variation is also studied for the proposed model. In addition, this dissertation studies the correlation between in-cylinder mixture temperature at intake valve closing and the engine knock, along with knock cyclic variability based on the knock predictive model. A strong correlation between the intake temperature and knock intensity has been obtained and validated based on the simulation investigation and experiment data obtained at knock limit. Therefore, a model-based feedforward and feedback stochastic knock limit control strategy is developed to reduce the knock cycle-to-cycle variability and maintain the knock mean-intensity within a desired up bound by controlling the spark timing as close to MBT timing as possible. The control performance is validated with the simulation results to show the capability of the model-based feedforward and feedback stochastic knock limit control in significantly reducing the knock cyclic variability and improving the knock intensity distribution for the best fuel economy.
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Title: Empowered or entitled to lead? : an evolutionary psychological perspective of how managers navigate structural empowerment
Creator: Lee, Hun Whee
Date: 2020
Collection: Electronic Theses & Dissertations
Description: With the recognition that traditional bureaucratic structures are less likely to respond effectively to volatile and complex business environments, the movement toward structural empowerment has been touted as one of the most significant changes in modern organizations. However, research to date has advanced opposing viewpoints on whether or not structural empowerment will psychologically empower managers and enhance group functioning. The aim of my dissertation is to provide a more nuanced...
Show moreWith the recognition that traditional bureaucratic structures are less likely to respond effectively to volatile and complex business environments, the movement toward structural empowerment has been touted as one of the most significant changes in modern organizations. However, research to date has advanced opposing viewpoints on whether or not structural empowerment will psychologically empower managers and enhance group functioning. The aim of my dissertation is to provide a more nuanced view of the downstream consequences of how managers navigate structural empowerment through the lens of evolutionary psychology. I developed a comprehensive model of how evolved motives for social influence--prestige and dominance--and situational constraints--resource scarcity and outcome interdependence--guide managers' cognition and behavior in the context of structural empowerment. To test my arguments, I utilized experimental (Study 1) and field survey (Study 2) methodologies. My dissertation contributes to the literature in three important ways: 1) I complement the predominant focus on the link between structural empowerment and psychological empowerment by providing accounts for an unintended consequence of structural empowerment, namely entitled managers; 2) my focus on managers' external resource acquisition and sharing as outcomes of structural empowerment expands conceptual boundaries of the role of leadership in the literature; and 3) my dissertation provides an example of how insights from evolutionary psychology can be leveraged to gain a better understanding of why managers do what they do within contemporary organizational structures.
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Title: Immunomodulation by small molecules for prevention or treatment of cancer
Creator: Zhang, Di (Graduate of Michigan State University)
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Cancer is the second leading cause of deaths worldwide. Lung cancer and breast cancer, specifically, are two of the most common cancers in the U.S. except skin cancer. With the increasing medical and economic burden of these diseases, developing effective cancer prevention and treatment strategies is important and urgent. Cancer is characterized by uncontrolled cell proliferation. Targeting the tumor cells directly to inhibit their growth and increase cell death has been the major focus of...
Show moreCancer is the second leading cause of deaths worldwide. Lung cancer and breast cancer, specifically, are two of the most common cancers in the U.S. except skin cancer. With the increasing medical and economic burden of these diseases, developing effective cancer prevention and treatment strategies is important and urgent. Cancer is characterized by uncontrolled cell proliferation. Targeting the tumor cells directly to inhibit their growth and increase cell death has been the major focus of cancer treatment since the last century. Cancer is also described as a wound that does not heal. Inflammation plays critical roles in cancer development and progression. The immune system is a powerful host defense mechanism against infections and diseases including cancer. However, tumor cells are able to edit and suppress the immune system to evade the immune attack. Targeting immune cells to unleash the power of immune surveillance has become a research priority. The recent breakthroughs in cancer immunotherapy have revolutionized the landscape of cancer treatment. As immunotherapy becomes the first line of therapy in cancer treatment, it is essential to understand how other drugs modulate the immune system, so that we can deliver more effective and less toxic combinations. In this thesis project, I focused on four therapeutic targets (bromodomain proteins, retinoid X receptors, Nrf2 transcription factors, poly (ADP-ribose) polymerase) and explored their effects on the immune cells. Small molecules targeting these proteins were tested in various preclinical mouse models in the context of either cancer prevention or treatment. My studies not only demonstrated enhanced efficacy and reduced toxicity with all four classes of compounds but also provided some novel insights into the immunomodulatory effects of these clinically relevant signaling pathways. This work is highly translational and could have direct impact on human patients.
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Title: Measurement of the charged current muon neutrino differential cross section on scintillator with zero pions in the final state with the T2K on/off-axis near detectors
Creator: Cudd, Andrew Bruce
Date: 2020
Collection: Electronic Theses & Dissertations
Description: The Tokai to Kamioka (T2K) is a long-baseline neutrino oscillation experiment in Japan producing precise measurements of neutrino oscillations and neutrino interactions with nuclear targets. T2K utilizes a muon (anti-)neutrino beam produced at the J-PARC proton accelerator facility which is measured at a suite of near detectors, ND280 and INGRID, and the far detector, Super-Kamiokande. One of the dominant systematic uncertainties for the oscillation analysis is from the uncertainty in...
Show moreThe Tokai to Kamioka (T2K) is a long-baseline neutrino oscillation experiment in Japan producing precise measurements of neutrino oscillations and neutrino interactions with nuclear targets. T2K utilizes a muon (anti-)neutrino beam produced at the J-PARC proton accelerator facility which is measured at a suite of near detectors, ND280 and INGRID, and the far detector, Super-Kamiokande. One of the dominant systematic uncertainties for the oscillation analysis is from the uncertainty in neutrino interaction modeling with complex nuclei, which will eventually become the limiting uncertainty for the next generation of neutrino oscillation experiments. Therefore measurements of neutrino cross sections on nuclear targets is essential for understanding how to model these complicated nuclear interactions. This thesis presents a novel neutrino cross section measurement utilizing both of the T2K near detectors, ND280 and INGRID, in a joint statistical fit. Because the T2K near detectors are exposed to neutrinos from the same beamline, the uncertainties in the neutrino flux prediction will be correlated. This fact combined with the different neutrino energy spectra seen at each detector will allow for some separation of flux and cross section effects, and presents an opportunity to study the neutrino cross section as a function of energy using the same neutrino beam. This analysis is the first cross section measurement on T2K to use samples from multiple detectors in the same beamline. This thesis presents a description of the statistical analysis framework, the event selection, the treatment of systematic uncertainties, and the extracted muon neutrino CC0pi double differential cross section in bins of muon kinematics for ND280 and INGRID, including the correlations between the detectors.
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Title: Online innovization : towards knowledge discovery and achieving faster convergence in multi-objective optimization
Creator: Gaur, Abhinav
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Ì0300nnovization'' is a task of learning common principles thatexist among some or all of the Pareto-optimal solutions in amulti-objective optimization problem. Except a few earlierstudies, most innovization related studies were performed onthe final non-dominated solutions found by an evolutionary multi-objective algorithm eithermanually or by using a machine learning method.Recent studies have shown that these principles can be learnedduring intermediate iterations of an optimization run...
Show moreÌ0300nnovization'' is a task of learning common principles thatexist among some or all of the Pareto-optimal solutions in amulti-objective optimization problem. Except a few earlierstudies, most innovization related studies were performed onthe final non-dominated solutions found by an evolutionary multi-objective algorithm eithermanually or by using a machine learning method.Recent studies have shown that these principles can be learnedduring intermediate iterations of an optimization run and simultaneously utilized in thesame optimization run to repair variables to achieve a fasterconvergence to the Pareto-optimal set. This is what we are calling as ò0300nline innovization'' as it is performed online during the run of an evolutionary multi-objective optimization algorithm. Special attention is paid to learning rules that are easier to interpret, such as short algebraic expressions, instead of complex decision trees or kernel based black box rules.We begin by showing how to learn fixed form rules that are encountered frequently in multi-objective optimization problems. We also show how can we learn free form rules, that are linear combination of non-linear terms, using a custom genetic programming algorithm. We show how can we use the concept of k0300nee' in PO set of solutions along with a custom dimensional penalty calculator to discard rules that may be overly complex, or inaccurate or just dimensionally incorrect. The results of rules learned using this custom genetic programming algorithm show that it is beneficial to let evolution learn the structure of rules while the constituent weights should be learned using some classical learning algorithm such as linear regression or linear support vector machines. When the rules are implicit functions of the problem variables, we use a computationally inexpensive way of repairing the variables by turning the problem of repairing the variable into a single variable golden section search.We show the proof of concept on test problems by learning fixed form rules among variables of the problem, which we then use during the same optimization run to repair variables. Different principleslearned during an optimization run can involve differentnumber of variables and/or variables that arecommon among a number of principles. Moreover, a preferenceorder for repairing variables may play an important role forproper convergence. Thus, when multiple principles exist, itis important to use a strategy that is most beneficial forrepairing evolving population of solutions.The above methods are applied to a mix of test problems and engineering design problems. The results are encouraging and strongly supportsthe use of innovization task in enhancing the convergence of an evolutionary multi-objective optimization algorithms. Moreover, the custom genetic program developed in this work can be a useful machine learning tool for practitioners to learn human interpretable rules in the form of algebraic expressions.
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Title: "My life is changed but the trust ain't there to trust somebody else" : experiences of recovery from intimate partner abuse of women of Mexican heritage in a mid-size city in Michigan
Creator: Palma-Ramirez, Evangelina
Date: 2020
Collection: Electronic Theses & Dissertations
Description: This exploratory qualitative study aimed to gain an understanding of the experiences of recovery from intimate partner abuse (IPA) of 17 women of Mexican heritage in a mid-size urban city in Michigan. IPA was defined as any type of physical, sexual, stalking, psychological harm or coercive control by a former intimate partner or spouse. Two aspects were explored: experiences of abuse and experiences of recovery from abuse. The study used a feminist theory and intersectionality perspective as...
Show moreThis exploratory qualitative study aimed to gain an understanding of the experiences of recovery from intimate partner abuse (IPA) of 17 women of Mexican heritage in a mid-size urban city in Michigan. IPA was defined as any type of physical, sexual, stalking, psychological harm or coercive control by a former intimate partner or spouse. Two aspects were explored: experiences of abuse and experiences of recovery from abuse. The study used a feminist theory and intersectionality perspective as a guiding framework to understand the experiences of women considering their contextual situation. Data were collected using a semi-structured questionnaire and analyzed using a constructivist grounded theory by Charmaz. The findings revealed that women understand their experiences of abuse as being connected to their early socialization about gender roles, history of child abuse, lack of sexual education, and the influence of the environment. Also, the participants revealed they experienced overlapping types of abuse: psychological, coercion, economic, physical, sexual, and stalking. Despite the negative impact of the abuse on participants' physical and mental health, findings showed that women were able to recover from the abuse and to move on with their lives. Data suggested that the recovery was a gradual ongoing process of physical and psychological healing. Participants identified empowering experiences that helped them in their recovery from IPA. Such empowering experiences included life-changing religious realizations, receiving services in Spanish, acquiring more education, receiving counseling services, and getting a job. Receiving social support from family and friends and having access to resources were identified as factors that aided in the recovery from IPA. However, some participants experienced limited access to such resources due to economic constraints, cultural beliefs about gender roles, and the impact of immigration policies.Lastly, findings revealed that experiences of recovery from IPA vary based on whether women decided to leave their partners or to remain with them. Implications for culturally sensitive interventions for Latinas of Mexican heritage are discussed as well as implications for future research on issues of recovery for this specific Latino subgroup.
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Title: Multi-band reconfigurable RFICs in Si-based technologies for a compact and adaptive RF front-end
Creator: Nawaz, Asad Ali
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Recent advances in the wireless communication market have led to the coexistence of several networks such as cellular network, personal area network (PAN), wireless local area network (WLAN), etc. along with several different air interfaces (802.11a, 802.11g, Bluetooth, wireless code division multiple access (WCDMA), etc.). Thus, all the wireless devices need to be compatible with the different communication standards while still keeping similar performance, smaller die area and lower power...
Show moreRecent advances in the wireless communication market have led to the coexistence of several networks such as cellular network, personal area network (PAN), wireless local area network (WLAN), etc. along with several different air interfaces (802.11a, 802.11g, Bluetooth, wireless code division multiple access (WCDMA), etc.). Thus, all the wireless devices need to be compatible with the different communication standards while still keeping similar performance, smaller die area and lower power consumption. The need to enable the "global roaming'' capability between a wide variety of networks operating at different frequencies calls for the development of reconfigurable radio-frequency integrated circuits (RFICs) which can achieve maximum hardware sharing between different standards and across various functions. The objective of this dissertation is to present novel topologies for RF components and blocks that can yield a Si-based frequency-agile RF front-end. The targeted applications for this work are 5G multi-band wireless communication and reconfigurable short/long range phased arrays for automobile radars. However, the concept of the proposed reconfigurable RF elements is generic in nature and can be applied to all emerging applications which require on-chip reconfigurability at microwave and mm-wave frequencies.To demonstrate the concept of a reconfigurable RF front end, a Ka/V band-switchable TRX amplifier is developed in 0.13um BiCMOS SiGe process and a 18-50 GHz receiver is developed in 45nm SOI CMOS process. Unlike the traditional approach for a multi-band radio - where the dedicated single band transceivers composed of fixed RF components are designed and multiplexed with the help of switches - the proposed idea utilizes the switches inside each RF block; thus, adding the reconfigurability inside each block and eliminating the need for separate front-ends. However, the catch in the latter approach is to maintain the RF performance while still being able to save the real estate and power consumption. The proposed Ka/V band-switchable TRX amplifier consists of a band-switchable LNA, a band-switchable PA, and integrated T/R switches which saves a lot of area. The band-switch functionality is realized using thin-film microstrip based shunt stubs with reverse saturated SiGe switches. Design techniques for switch loss reduction and size miniaturizations are presented. This work illustrates that with the optimization of switch loss, appropriate selection of each block between wideband or bandswitching topology and co-design of RF blocks, a highly integrated multi-band transceiver can be designed with the minimal degradation to the RF performance compared to state-of-the-art dedicated single band transceivers. To further explore reconfigurable transceivers, a direct quadrature down-conversion mixer first receiver with active channel select filters has been designed. The receiver supports 200MHz instantaneous RF bandwidth and can be reconfigured to receive any 200 MHz channel within 18-50 GHz frequency range. With the ever-evolving wireless standards like 4G/5G/6G, equipment manufacturers are required to add more functionality into the chips while still maintaining the backward compatibility with previous standards or fallback option to lower frequency bands. A low power, highly integrated, multi-band and multi-standard chipset has thus become a requisite in commercial products. The proposed concept of in-block reconfigurability and the presented design techniques to realize mm-wave frequency reconfigurable transceivers have a huge potential in this regard.
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Title: Use of administative claims data to design and emulate a clinical trial in acute stroke patients comparing rehabilitation at inpatient rehabilitation facilities to skilled nursing facilities
Creator: Simmonds, Kent P.
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Stroke affects nearly 800,000 people every year in the United States and is a leading cause of adult disability. After hospitalization half of stroke patients continue to require medical and rehabilitation services provided at inpatient rehabilitation facilities (IRFs) or skilled nursing facilities (SNFs). In general, IRFs provide time-intensive therapy for two to three weeks, while SNFs provide moderately intensive therapy for four- to five-weeks. There is substantial variation in the...
Show moreStroke affects nearly 800,000 people every year in the United States and is a leading cause of adult disability. After hospitalization half of stroke patients continue to require medical and rehabilitation services provided at inpatient rehabilitation facilities (IRFs) or skilled nursing facilities (SNFs). In general, IRFs provide time-intensive therapy for two to three weeks, while SNFs provide moderately intensive therapy for four- to five-weeks. There is substantial variation in the utilization of these alternative rehabilitation settings, but their relative comparative effectiveness remains uncertain. A randomized controlled trial (RCT) would provide an unbiased comparative effectiveness estimate, but the design of such a trial is complicated by several practical and ethical issues. The overarching purpose of this dissertation was to use Medicare claims data to inform the design and to emulate such a trial. In the first aim, we sought to identify patient and hospital level factors that were associated with IRF or SNF discharge and characterize the heterogeneity of hospital effects that influenced discharge to an IRF (vs. SNF). From a retrospective cohort of 145,894 stroke patients, we used multi-level multivariable models to identify several patient- and hospital- level factors that were independently associated with discharge setting. We also showed that hospitals contributed around a third of the variation in IRF (vs. SNF) discharge, but there was substantial variation in the effect that specific hospitals had on influencing IRF discharge. The second aim, was to identify a target trial population that optimized the explanatory-pragmatic balance of a subsequent RCT. To identify this population, we profiled hospitals based on their propensity to discharge stroke patients to IRFs (vs. SNFs) and inferred IRF and SNF referral networks for each hospital. The final target trial population included 44,950 patients (30.8% of the starting sample) who were treated at 441 hospitals (14.5%) and subsequently discharged to 745 IRFs (64.8%) and 5,974 SNFs (48.2%).The third aim was to emulate three alternate RCTs that compared patient outcomes at IRFs vs. SNFs. Trial #1 used the target trial population identified in Aim 2, while trials #2 and 3 excluded increasingly infrequently used IRFs and SNFs. Comparative effectiveness was estimated using a matched propensity score analysis. Overall, on a relative basis, patients treated at IRFs were between 18-35% more likely to be successfully discharged home (i.e., alive and at home for >30 days) and were between 11-15% less likely to die within one year of acute care discharge. The variation in the effect size estimates across the trials was driven by poorer outcomes among patients treated at infrequently used SNFs. Finally, we identified that a moderate sized unmeasured confounder would nullify the observed differences.In conclusion, we identified that referring hospitals are a major driver of IRF or SNF use, and that patients treated at IRFs had better outcomes (relative to SNF patients). However, our results were limited by the inability to adjust for potentially important unmeasured confounders. A pragmatic RCT would eliminate such biases and provide a more valid comparative effectiveness estimate of these two alternative rehabilitation settings.
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Title: Understanding free-carrier accumulation in semiconductor nanomaterials : plasmonic behavior, charge storage energetics, and quantum confinement resilience of colloidal indium nitride nanocrystals
Creator: Liu, Zhihui
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Heavily doped semiconductor nanocrystals (NCs) are promising materials that can reversibly and substantially store electrical charges. Indium nitride (InN) is a particularly interesting semiconductor material for studying charge storage processes. Colloidal InN NCs are spontaneously degenerately doped with carrier densities large enough to lead to strong localized surface plasmon resonances (LSPR) in the infrared (IR) part of the spectrum. Unfortunately, many fundamental quantities that...
Show moreHeavily doped semiconductor nanocrystals (NCs) are promising materials that can reversibly and substantially store electrical charges. Indium nitride (InN) is a particularly interesting semiconductor material for studying charge storage processes. Colloidal InN NCs are spontaneously degenerately doped with carrier densities large enough to lead to strong localized surface plasmon resonances (LSPR) in the infrared (IR) part of the spectrum. Unfortunately, many fundamental quantities that ultimately control the behavior of colloidal InN NCs are currently unknown. In this thesis, we focused on advancing our current understanding of the properties of colloidal InN NCs, with special emphasis on the quantification of free electron density, the LSPR behavior, the charge storage ability, the screening effect on phonon behaviors and few other important fundamental quantities such as the electron effective mass, Fermi level, conduction band (CB) edge potential and IR transition oscillator strength.To understand the LSPR behavior of InN NCs, we first evaluated the free carrier density with a direct, model-independent quantification. We found that the number of free electrons per as-prepared InN NC is directly proportional to the NC volume, such that the free electron density is a size-independent quantity. Furthermore, we demonstrated that free electrons in InN NCs can be reversibly extracted with redox species, which leads to a direct way to manipulate the LSPR. Importantly, the LSPR energy in InN NCs barely shifts with free electron density, a behavior strikingly at odds with what is typically observed in other semiconductor plasmonic systems. These unusual plasmonic signatures are shown to arise from the nonparabolicity of the CB dispersion, which leads to a change in the electron effective mass with the number of free electrons per NC, thus mitigating the shift of LSPR in InN NCs.Consequently, we estimated the charge storage capability of InN NCs by pinning the chemical potential of InN NCs to redox-active molecular species. These studies directly yielded precise information on the Fermi level and on the chemical capacitance of InN NCs, which allowed the CB edge potential of InN NCs to be quantitatively determined for the first time. Surprisingly, the CB edge in InN NCs hardly showed any sign of quantum confinement effects, even for NCs sizes that were clearly smaller than the excitonic Bohr radius of InN. This "resilience to quantum confinement" effect was shown to also arise from the same nonparabolic dispersion effects described above.In addition, the light harvesting ability of free electrons in InN NCs was evaluated by calculating the molar absorptivity per free electron. This value directly yielded the optical oscillator strength of LSPR. We found that optical oscillator strength (per free electron) is independent of NC.Finally, the effects of free electrons on lattice vibrations were also explored. We demonstrated that free electrons weakened the A1(LO) phonon mode by screening the Coulombic restoring force induced by the lattice distortion. The A1(LO) mode frequency red-shifted linearly with the increasing free electron density. This relationship provided a fast way to estimate free electron density of InN NCs by measuring Raman spectroscopy.
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Title: Development of structurally defined platforms for long-range biological electron transfer
Creator: Huang, Jingcheng (Graduate of Michigan State University)
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Electron transfer reactions are vital for life: they are the essential steps in all the major biological energy conservation pathways and the rate of electron transfer sometimes determines the fate of energy flow. While the rates of electron transfer over 1-2 nanometers in proteins can largely be described by well-known theories, it is not well understood how these processes scale to microscopic distances, for example, micrometer length microbial nanowires. Electron transfer reactions are...
Show moreElectron transfer reactions are vital for life: they are the essential steps in all the major biological energy conservation pathways and the rate of electron transfer sometimes determines the fate of energy flow. While the rates of electron transfer over 1-2 nanometers in proteins can largely be described by well-known theories, it is not well understood how these processes scale to microscopic distances, for example, micrometer length microbial nanowires. Electron transfer reactions are known to be highly sensitive to the chemical properties of the electron carriers and distances between carriers, yet, this information is not available for naturally occurring microbial nanowires. On the other hand, microbial nanowires have inspired the development of novel biological conductive materials and bioelectronics, although these biomimicking materials would significantly benefit from a higher degree of structural definition, which would greatly improve rational redesign.This dissertation work presents two distinct approaches for arranging electron carriers (heme) into structurally defined arrays that can facilitate electron transfer:1) A crystalline lattice of small tetraheme cytochromes that form a well-defined, three-dimensional network of closely spaced redox centers was used to demonstrate the multi-step electron hopping over a micrometer scale.2) A heme attachment strategy was developed that allows one to introduce redox active cofactor hemes into non-heme-binding proteins, while maintaining the proteins' original function. Adding hemes to a nanotube-forming self-assembling protein was used to demonstrate the potential of this strategy to form a structurally defined heme array.The first crystal approach provides detailed information about structure and electronic states which can be used as a platform for testing theories, while the second heme-attaching approach is an engineering platform that allows researchers to introduce redox properties into other well-studied proteins with minimal effort. These two approaches, from two perspectives, lay the foundation of building structurally defined architectures for the understanding of microbial nanowires and the application of biological long-range electron transfer materials.
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Title: ER stress sensor IRE1-alpha and its implications in progression of hepatocellular carcinoma
Creator: Oak, Amrita
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "The endoplasmic reticulum (ER) is the site for protein folding and maturation. ER stressors, both physiological and pharmacological, can result in activation of the unfolded protein response (UPR). Palmitate, a saturated fatty acid, is one such ER stressor and leads to induction of the UPR. This is primarily through the activation of Inositol Requiring Enzyme-1 (IRE1) leading to splicing of XBP1 mRNA. However, the mechanism of this activation is unclear. With the aid of a bimolecular...
Show more"The endoplasmic reticulum (ER) is the site for protein folding and maturation. ER stressors, both physiological and pharmacological, can result in activation of the unfolded protein response (UPR). Palmitate, a saturated fatty acid, is one such ER stressor and leads to induction of the UPR. This is primarily through the activation of Inositol Requiring Enzyme-1 (IRE1) leading to splicing of XBP1 mRNA. However, the mechanism of this activation is unclear. With the aid of a bimolecular fluorescence complementation (BiFC) assay, we identified two crucial residues on the transmembrane domain (TM) of IRE1, S450 and W457, that are drivers of palmitate mediated activation. Previous research from our group suggested that IRE1 also has binding sites for palmitate on its cytosolic domain (CD). However, IRE1-CD protein expressed in E. coli was over-phosphorylated which possibly affected its binding to PA. To investigate this, we developed a protocol for expression and purification of wild type and mutant IRE1-CD protein in insect Sf21 cells. A fluorescence polarization based binding assay was performed to determine whether palmitate binds to residues on the IRE1-CD protein. Previously our laboratory demonstrated that palmitate induced the migration of cancer cells as well as transcription factors (TF) involved in epithelial-to-mesenchymal transition (EMT). Here, we investigated the role of IRE1 activation on these processes. Using CRISPR gene editing to generate IRE1 knockouts in liver and breast cancer cell lines, we observed that IRE1 mediates the upregulation in EMT-TFs, a decrease in the expression of the desmoplakin (DSP) protein, and an increase in the migration of liver and breast cancer cells. DSP is a critical component of desmosomes, which function to maintain the structural integrity at adjacent cell-cell contacts.In addition to migration, the effect of XBP1 splicing on metabolism has not been studied. We found the activation of IRE1-XBP1 is accompanied by changes in the metabolic genes involved in glycolysis, fatty acid oxidation, gluconeogenesis, and ceramide metabolism, suggesting that some of the metabolic effects of palmitate are mediated through IRE1. These results could have implications on the development of chemotherapeutic strategies. This study paves the way for further investigations into the far-reaching effects of activation of the UPR on cell survival, metabolism, and chemo-tolerance."--Pages ii-iii.
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Title: Interpretable machine learning in plant genomes : studies in modeling and understanding complex biological systems
Creator: Azodi, Christina Brady
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Complex systems are ubiquitous in genetics and genomics. From the regulation of gene expression to the genetic basis of complex traits, we see that complex networks of diverse cellular molecules underpin the natural world. Driven by technological advances, today's researchers have access to large amounts of omics data from diverse species. At the same time, improvements in computer processing and algorithms have produced more powerful computational tools. Taken together, these advances mean...
Show moreComplex systems are ubiquitous in genetics and genomics. From the regulation of gene expression to the genetic basis of complex traits, we see that complex networks of diverse cellular molecules underpin the natural world. Driven by technological advances, today's researchers have access to large amounts of omics data from diverse species. At the same time, improvements in computer processing and algorithms have produced more powerful computational tools. Taken together, these advances mean that those working at the interface of data science and biology are poised to better model and understand complex biological systems. The research in this dissertation demonstrates how a data-driven approach can be used to better understand three complex systems: (1) transcriptional response to single and combined heat and drought stress in Arabidopsis thaliana, (2) the genetic basis of flowering time, a complex trait, in Zea mays, and (3) the social basis for opinions and beliefs about biotechnology products.To study the first system, we generated models of the cis-regulatory code from information about DNA sequence and additional omics levels using both classic machine learning and deep learning algorithms. We identified 1,061 putative cis-regulatory elements associated with different patterns of response to single and combined heat and drought stress and found that information about additional levels of regulation, especially chromatin accessibility and known transcription factor binding, improved our models of the cis-regulatory code. To study the second system, we generated phenotype prediction models for flowering time, height, and yield based on either genetic markers or transcript levels at the seedling stage. We found that, while genetic marker-based models performed better than transcript level-based models, models that integrated both types of data performed best. Furthermore, transcript-based models were more useful for finding genes known to be associated with flowering time, highlighting how using additional levels of omics data can improve our ability to understand the genetic basis of complex traits. Finally, to study the third system, we integrated 29 characteristics about a person (e.g. age, political ideology, education, values, environmental beliefs) into a machine learning model that would predict an individual's beliefs and opinions about five different types of biotechnology products (e.g. biofortification, biopharmaceuticals). While this approach was particularly usefully for identifying individuals that were broadly supportive of biotechnology, finding characteristics of individuals with negative or conditional (i.e. support product A, but not B) opinions was more challenging, highlighting the complexity of public opinions about biotechnology.
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Title: Mitochondrial function does not limit aerobic metabolism in type 2 diabetes : magnetic resonance studies in the Goto-Kakizaki rat
Creator: Lewis, Matthew T.
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Type 2 diabetes (T2D) is a growing health concern with nearly 400 million affected worldwide as of 2014 (418). T2D presents with hyperglycemia and insulin resistance resulting in increased risk for blindness, renal failure, nerve damage and premature death (10). Skeletal muscle is a major site for insulin resistance and is responsible for up to 80% of glucose uptake during euglycemic hyperinsulinemic clamps (89). Glucose uptake in skeletal muscle is driven by mitochondrial oxidative...
Show more"Type 2 diabetes (T2D) is a growing health concern with nearly 400 million affected worldwide as of 2014 (418). T2D presents with hyperglycemia and insulin resistance resulting in increased risk for blindness, renal failure, nerve damage and premature death (10). Skeletal muscle is a major site for insulin resistance and is responsible for up to 80% of glucose uptake during euglycemic hyperinsulinemic clamps (89). Glucose uptake in skeletal muscle is driven by mitochondrial oxidative phosphorylation (MOP) and for this reason mitochondrial dysfunction has been implicated in T2D (225). Mitochondrial function in this sense is defined as the capacity for skeletal muscle mitochondria to produce ATP. In the present document, skeletal muscle mitochondrial function and its limitations were studied utilizing the Goto-Kakizaki (GK) rat model of type 2 diabetes. Mitochondrial function was defined computationally demonstrating the relationship between the drivers of ATP production (ADP, Pi) and ATP production itself. Computational depiction of MOP allowed for a functional understanding of any changes in mitochondrial function. Quantification of mitochondrial function demonstrated deficits during high metabolic workloads in the GK rat. However, upon closer analysis utilizing both computational and in vitro techniques results suggested that metabolic deficits were due to limitations separate from mitochondrial dysfunction. Since MOP ATP production requires oxygen utilization by the mitochondria and oxygen supply to the mitochondria, oxygen deficits may present in the same fashion as dysfunctional mitochondria and thus the most logical explanation to target for dysregulation was a limitation in oxygen supply. For this reason, cardiovascular function was measured in the conscious GK rat utilizing an array of challenges. Results showed no deficits in skeletal muscle performance at low workloads consistent with measures of normal mitochondrial function. However, measures indicated a harder working heart along with cardiovascular disease risk factors that may cause blood flow limitations during high intensity workloads. Quantification of blood flow using the identical setup that measured mitochondrial function during hindlimb contraction showed reductions in blood flow that could limit MOP during high intensity workloads in the diabetic GK rat. Taken together this culmination of works suggests that mitochondrial dysfunction is not inherent to type 2 diabetes, but rather muscle metabolic deficits manifest from blunted oxygen supply. This result is crucial to advance therapeutic interventions in type 2 diabetes and similar experiments in humans may direct drug therapies away from targeting skeletal muscle mitochondria and towards improving skeletal muscle blood flow."--Pages ii-iii.
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Title: Genetic mapping of resistance to soybean sudden death syndrome and soybean oil quality
Creator: Collins, Paul Joseph
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Soybean (Glycine max) is the world's leading oilseed crop and is a critical source of protein for poultry and swine production. Soybean production is limited by many biotic factors including soybean sudden death syndrome (SDS) which is caused by a soil-borne fungal pathogen, Fusarium virguliforme. Effective management methods for soybean sudden death syndrome include long-term rotations, fluopyram seed treatment, and planting SDS resistant varieties. Host resistance to F. virguliforme is a...
Show more"Soybean (Glycine max) is the world's leading oilseed crop and is a critical source of protein for poultry and swine production. Soybean production is limited by many biotic factors including soybean sudden death syndrome (SDS) which is caused by a soil-borne fungal pathogen, Fusarium virguliforme. Effective management methods for soybean sudden death syndrome include long-term rotations, fluopyram seed treatment, and planting SDS resistant varieties. Host resistance to F. virguliforme is a quantitative resistance, as it is controlled by many genes, largely of small effect. To more efficiently breed SDS resistant soybean varieties, researchers have sought to identify the loci on the soybean genome responsible for SDS-resistance. Three recombinant inbred line (RIL) populations were evaluated for foliar SDS resistance at a naturally infested field site in Decatur, MI during the 2014 and 2015 growing seasons. These populations segregated for SDS resistance, as they were derived from a parent resistant to SDS and a parent susceptible to SDS. The parents and a subset of RILs from each population were genotyped with the SoySNP6K Illumina Infinium BeadChip. Linkage maps unique to each population were constructed using JoinMap ver. 2. Composite interval mapping was done using WinQTLCartographer (ver. 2.5). Six quantitative trait loci (QTL) were identified to be associated with SDS resistance. Three of the QTL associated with SDS resistance were identified across multiple years and/or populations. While biotic factors, such as SDS, work to limit soybean production, soybean quality factors, such as oil quality, can offer new production opportunities. Soybean oil is predominantly composed of five fatty acids: palmitic acid (11%), stearic acid (4%), oleic acid (25%), linoleic acid (52%), and linolenic acid (8%). While there is little variability in most commodity soybean varieties for fatty acid content, soybean breeders have been able to introduce oil quality traits into the soybean germplasm. Oil quality traits for soybean oil include high oleic acid content (>75%), low linolenic acid content (<3%), and low saturated fat content (palmitic + stearic < 8%). A RIL population was developed by crossing a high oleic acid, low linolenic acid, and low saturated fat content public variety (E16831) with a high yielding line with a commodity soybean fatty acid profile (E12076T). The parents, the RIL population, and bulked pools representing extreme phenotypes were genotyped with the SoySNP6K Illumina Infinium BeadChip, a linkage map was developed using JoinMap (v.2), and QTLs were detected using WinQTLCartographer (v 2.5). The study confirmed the effects of many known fatty acid biosynthesis genes including GmFAD2-1B, GmFAD3A, GmFAD3B, GMFAD3C, and GmFATB-1A. The study was also able to dissect possible strategies and limitations of marker assisted selection (MAS) for the development of soybean varieties with high oleic acid, low linolenic acid, and low saturated fat content."--Pages ii-iii.
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Title: Effect of suspect's gender on police use of physical force
Creator: Ishola, Oluwatobi Taiwo
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Police use of force has received much research attention as researchers attempt to explain various predictors of this phenomenon. This topic is of great interest to police practitioners, policy makers, researchers, scholars, and criminal justice students. Several studies have examined various predictors of this behavior, including officer education, race, experience, age, and sex. However, most of these studies focused on either the officers' or suspect's sex, while research on the interplay...
Show more"Police use of force has received much research attention as researchers attempt to explain various predictors of this phenomenon. This topic is of great interest to police practitioners, policy makers, researchers, scholars, and criminal justice students. Several studies have examined various predictors of this behavior, including officer education, race, experience, age, and sex. However, most of these studies focused on either the officers' or suspect's sex, while research on the interplay between suspect's sex and officer sex as a predictor of police use of force is lacking. Drawing on criminal threat theory and research on chivalry, this study will examine how the interplay between officer and suspect sex influences the likelihood and severity of police use of physical force. Further, given the influence of social norms on chivalry, the study will further investigate whether the presence of bystanders moderates the influence of officer and suspect sex on use of physical force. The study is based on data from the 1996-1997 (ICPSR 3172) study titled 'Understanding the use of force by and against the police in six jurisdictions in the United States'."--Page ii.
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Title: Interfacial challenges of all-solid-state Li-ion batteries : multi-scale computational approach
Creator: Tian, Hong-Kang
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "All-solid-state Li-ion batteries (ASSLB) with solid electrolytes (SEs) have enhanced safety and higher volumetric/gravimetric energy density than conventional Li-ion batteries with liquid electrolytes. However, the applications of ASSLB are still limited by the interfacial issues, such as Li dendrite growth through the SEs and the high SE/electrode interfacial resistance. This thesis developed a multi-scale computational approach, combining Density Functional Theory (DFT) calculation and...
Show more"All-solid-state Li-ion batteries (ASSLB) with solid electrolytes (SEs) have enhanced safety and higher volumetric/gravimetric energy density than conventional Li-ion batteries with liquid electrolytes. However, the applications of ASSLB are still limited by the interfacial issues, such as Li dendrite growth through the SEs and the high SE/electrode interfacial resistance. This thesis developed a multi-scale computational approach, combining Density Functional Theory (DFT) calculation and Finite Element Method (FEM), to investigate the interfacial challenges in ASSLB. The Li dendrite growth through pores in SEs and the resulting short-circuit limit the highest current density in ASSLB. The underlining mechanism of Li dendrite nucleation and growth in SEs is still unclear. A DFT model was developed to evaluate the electronic properties of the bulk and surface structures of different SEs. It was revealed that the reduced bandgap and trapped electrons on the pore and crack surfaces are the main reasons for Li dendrite to form. The DFT computed material properties were compared for different SEs, and it was found that the ranked Li dendrite resistance in these SEs, based on the surface electronic properties instead of mechanical properties, is consistent with a broad range of experimental observations. The DFT results also served as the input to a phase-field model, which predicted the formation of isolated Li dendrite that matched with experimental observations. Furthermore, materials design strategies were proposed based on the critical material properties that can resist Li dendrite growth in SEs.The physically imperfect contact at interfaces is formed during the fabrication process of ASSLB and gets worse during cycling, resulting in high interfacial resistance and damaging to the battery performance. A 1D FEM battery model was constructed to investigate the relationship between the contact area and the discharging performance. Furthermore, the multi-scale Persson's contact theory was applied to predict the necessary pressure to prevent ASSLB capacity degradation due to contact area loss during the cycling of ASSLB. Cracked SE and SE/electrode interfaces also increase the impedance in ASSLB. The mechanical degradation of ASSLB is expected to be more severe than that in traditional Li-ion batteries with liquid electrolytes, as the solid-electrolyte also imposes mechanical constraints on the deformation of electrodes. A coupled electrochemical-mechanical FEM model was developed to evaluate the stress development in ASSLB. Two sources of volume change, namely the expansion/shrinkage of electrodes due to lithium concentration change and the interphase formation at the SE/electrode interface due to the decomposition of SEs, were considered. The favorable SE decomposition reactions and the associated volume change were predicted by DFT calculations. It was found that the SE-decomposition induced stress can be much larger than the electrodes volume changes due to Li concentration change, up to tens of GPa, if there are no voids in ASSLB to release some induced-stress. This model can also be used to design 3D ASSLB architectures to minimize the stress generation in ASSLB."--Pages ii-iii.
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Title: Quantifying differences in otolith chemistry of Chinook salmon in Lake Michigan to determine natal origins
Creator: Maguffee, Alexander C.
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Previous research has indicated that a substantial amount of hatchery-reared Chinook salmon (Oncorhynchus tshawytscha) migrate from Lake Huron to Lake Michigan, likely due to greater foraging opportunities in Lake Michigan, indicating the potential for wild Chinook salmon to exhibit similar movement patterns. Thus, an increased priority has been placed on quantifying the movement of wild Chinook salmon from Lake Huron to Lake Michigan. The goal of this research was to determine the...
Show morePrevious research has indicated that a substantial amount of hatchery-reared Chinook salmon (Oncorhynchus tshawytscha) migrate from Lake Huron to Lake Michigan, likely due to greater foraging opportunities in Lake Michigan, indicating the potential for wild Chinook salmon to exhibit similar movement patterns. Thus, an increased priority has been placed on quantifying the movement of wild Chinook salmon from Lake Huron to Lake Michigan. The goal of this research was to determine the feasibility of quantifying inter-basin movement of wild Chinook salmon using otolith microchemistry techniques. Chinook salmon otolith pairs were extracted from juvenile and adult fish collected in 2015 and 2016 from tributaries in six predefined regions. Otoliths were analyzed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP MS) to determine trace metal concentrations, and various multivariate classification algorithms were evaluated for accuracy of classification. Juvenile data reclassified to their natal regions with classification success at a basin level comparable to previous Great Lakes otolith studies. Applying the juvenile-fit models to the adult data resulted in moderate success at a basin level. MANOVAs indicated significant differences in otolith microchemistry between juvenile year classes, and these differences negatively affected classification accuracy. These findings suggest that otolith microchemistry can be used to estimate wild Chinook salmon inter-basin movement, and that classification accuracy will be much higher if the model is developed from the same year class as the assessment sample.
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Title: Privilege-based decentralized data sharing
Creator: Zaghloul, Ehab
Date: 2020
Collection: Electronic Theses & Dissertations
Description: In this dissertation, cryptographic mechanism-based data sharing schemes are presented that address the challenges of dependence on third trusted parties to facilitate sensitive data sharing and censorship. This work is driven by the lack of elevated security and privacy countermeasures necessary for use with sensitive data that many third parties exhibit. Our proposed schemes transition from centralized to distributed models, thus alleviating trust on third parties to realize data owner...
Show moreIn this dissertation, cryptographic mechanism-based data sharing schemes are presented that address the challenges of dependence on third trusted parties to facilitate sensitive data sharing and censorship. This work is driven by the lack of elevated security and privacy countermeasures necessary for use with sensitive data that many third parties exhibit. Our proposed schemes transition from centralized to distributed models, thus alleviating trust on third parties to realize data owner sharing preferences.We first propose a secure Privilege-based Multilevel Organizational Data sharing (P-MOD) scheme that uses the cloud as a storage medium. P-MOD integrates a privilege-based access structure into an attribute-based encryption mechanism to facilitate sensitive data sharing in hierarchical settings. This structure allows data owners to share their sensitive data selectively among all levels of the hierarchy in a fine-grained manner. It also reduces computational complexity by minimizing the overall cryptographic operations. Following the development of P-MOD, we wished to gain a better understanding of distributed systems in an effort to eliminate the need to trust third parties. Therefore, we conducted a comprehensive study of the first system to adopt blockchain, Bitcoin. In this study, we aimed to identify the security points of weakness of these distributed systems. We delved deeply into one of the major security threats, double-spending attacks, by performing two thorough probability analyses of its likelihood of success. Next, we conducted a probability of success versus profitability analysis of double-spending attacks to investigate the trade-offs between waiting time before accepting a transaction and the profitability of these attacks.Motivated by our study of blockchain and the underlying foundation of distributed peer-to-peer (P2P) networks, we developed a distributed Multilevel Attribute-based EMR management (d-MABE) scheme based on our groundwork of P-MOD. The d-MABE scheme incorporates smart contracts deployed and executed over the blockchain to ensure the data sharing preferences of the data owners are maintained. It also replaces the cloud storage with a distributed storage system that is managed by a P2P network to improve the reliability of retrieving data when requested. Using electronic medical records (EMR) as a use-case, our goal is to demonstrate the benefits of alleviating dependence on the electronic record-generating institutions and thus granting data owners (patients) control of their sensitive data in a distributed manner.To further expand our research and reflect its applicability to a wider domain space, we proposed a blockchain-based distributed Coercion-Resistant and Anonymous Mobile Electronic (d-CRAME) voting scheme. The proposed scheme is secure and preserves voter privacy through secure multi-party computations performed by parties of differing allegiances. It also leverages a blockchain running smart contracts as a publicly accessible and tamper-resistant bulletin board to permanently store votes and prevent double-voting. Using voting as an application, our goal is to demonstrate the potential and feasibility of designing a distributed and remote voting scheme for large-scale elections, thus increasing voter turnout and accuracy in the decision-making process.
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Title: Insights into the photophysical reaction coordinate of 1st row transition metal chromophores from vibrational coherences
Creator: Paulus, Bryan Christopher
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Controlling the processes which occur following absorption of photon is beneficial for any conceivable application which seeks to convert light into chemical potential. Transition metal chromophores often undergo ultrafast photoinduced transformations which involve significant nuclear motion. This intricate relationship between electronic and nuclear degrees of freedom suggests significant mixing of their wavefunctions and an interdependence of these molecular properties that can map onto the...
Show moreControlling the processes which occur following absorption of photon is beneficial for any conceivable application which seeks to convert light into chemical potential. Transition metal chromophores often undergo ultrafast photoinduced transformations which involve significant nuclear motion. This intricate relationship between electronic and nuclear degrees of freedom suggests significant mixing of their wavefunctions and an interdependence of these molecular properties that can map onto the photophysical dynamics. In systems such as these, the rich dynamical information encoded in vibrational coherences can in principle provide unique insight into the nature of this coupling. Furthermore, this has the potential to provide subtle clues for how one could exert some degree of kinetic control through informed structural, compositional, and environmental modifications. This dissertation describes efforts to use excited state vibrational coherences to glean mechanistic information about ultrafast excited state decay in several first-row transition metal chromophore systems and, further, to exploit that information to reengineer the chromophore to alter the photophysical properties.This dissertation begins by using ultrafast transient absorption measurements to provide an updated kinetic model for a series of chromium(III) tris-betadiketonate compounds. Following prompt 4T2 → 2E ISC to the lowest energy excited state, thermally activated back-intersystem crossing repopulates the 4T2 state which internally converts to the ground state on the 10303 ps timescale. Steric bulk in the periphery of the molecule reduces the rate of internal conversion resulting in significantly different spectral evolution. Identical low frequency symmetric breathing modes with dephasing times ranging from 2003030-2500 fs were identified in the 2E excited state of each molecule. The more rapid dephasing times are likely due to IVR. Similar methodology was then used to characterize the excited state dynamics in a structurally related series of cobalt(III) tris-betadiketonate compounds. Following ligand field excitation into the 1T1g state, each compound had essentially identical biphasic kinetics with ground state recovery occurring with a 2 0303ps time constant from an excited state of (t2g)5(eg*) electron configuration. Low frequency metal-ligand breathing modes similar to those observed in the chromium systems were observed with dephasing times consistently on the order of 2003030 fs.Finally, two methods to elongate MLCT lifetimes of iron(II) polypyridyl compounds were demonstrated. In the first, the vibrational modes which drive the ultrafast, sub-200 fs MLCT deactivation to the lower energy metal-centered excited states in a [Fe(cage)]2+ control molecule were identified by their coherent oscillations in a transient absorption experiment. These modes were subsequently hindered by incorporation of electronically benign copper(I) atoms to the N4 coordination environments in the periphery of the ligand scaffold resulting in a > 20-fold increase in the MLCT lifetime. In the final study, it was shown that the excited state properties of iron(II) polypyridyl type systems can be systematically and dramatically tuned by swapping out a single bidentate phenanthroline ligand of a [Fe(phen)3]2+ control molecule with stronger-field cyanide or acyclic dicarbene ligands. This modular approach to tuning the kinetics resulted in a > 25-fold increase in the MLCT lifetime and a fundamentally different decay pathway.
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