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Title: Essays in the economics of education
Creator: Lee, Hwanoong
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "This dissertation comprises three essays on the Economics of Education. Its ultimate focus is to understand how different agents in the education market respond to releasing information about teacher and school performance and how public interventions influence human capital accumulation. The first essay "The Effect of Releasing Teacher Performance Information to Schools: Teachers' Response and Student Achievement" examines the effects of releasing teacher value-added (VA) information on...
Show more"This dissertation comprises three essays on the Economics of Education. Its ultimate focus is to understand how different agents in the education market respond to releasing information about teacher and school performance and how public interventions influence human capital accumulation. The first essay "The Effect of Releasing Teacher Performance Information to Schools: Teachers' Response and Student Achievement" examines the effects of releasing teacher value-added (VA) information on student performance in two settings; in the first, VA data was released to all potential employers within the district, while in the second, only the current employer received the data. I find that student achievement increased only in the district where the VA scores were provided to all potential employers. These effects were driven solely by improved performance among ex-ante less-effective teachers; the null effects in the other setting, however, were driven by moderate declines in performance among ex-ante highly-effective teachers and small improvements among less-effective teachers. These results highlight the importance of understanding how the design features of VA disclosure translate into the productivity of teachers. The second essay "The Role of Credible Threats and School Competition within School Accountability Systems: Evidence from Focus Schools in Michigan" studies the impact of receiving accountability labels on the student achievement distribution under No Child Left Behind (NCLB) waivers. Using a sharp regression discontinuity (RD) design, I examine the achievement effects of Focus (schools with the largest achievement gaps) labels and find that schools receiving the Focus label improved the performance of low-achieving students relative to their barely non-Focus counterparts, and they did so without hurting high-achieving students. The positive achievement effects for Focus schools were entirely driven by Title 1 Focus schools that faced financial sanctions associated with being labeled the following year. There is no evidence of an achievement effect associated with the Priority label. Next, I examine heterogeneous effects by looking at the number of alternative nearby schooling options. I find that when schools are exposed to a competitive choice environment, receiving the Focus label increased math test scores across the scoring distribution, while schools located in an uncompetitive choice environment improved the test scores of low achievers only. This evidence may suggest the importance of incorporating credible sanctions and school choice options into the school accountability system to maximize the effectiveness of the system on student achievement. Finally, the third essay "The Effects of School Accountability Systems Under NCLB Waiver: Evidence from Priority Schools in Michigan" investigates the impact of receiving Priority labels on the student achievement distribution under No Child Left Behind (NCLB) waivers. Using a sharp regression discontinuity (RD) design, I examine the achievement effects of the Priority (schools with the lowest performance) label and find no evidence of an achievement effect associated with the Priority label. Next, I examine whether assigning the Priority label induced the changes in the composition of students. I define several key measures of student composition and find no evidence that the Priority designation influenced the student composition of schools."--Pages ii-iii.
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Title: Reaction-based modeling and control of an electrically boosted diesel engine
Creator: Men, Yifan
Date: 2019
Collection: Electronic Theses & Dissertations
Description: This dissertation presents the reaction-based modeling of diesel combustion and model-based control of diesel engine air path.The dissertation first presents a control-oriented reaction-based diesel combustion model that predicts the time-based rate of combustion, in-cylinder gas temperature and pressure over one engine cycle. The model, based on the assumption of a homogeneous thermodynamic combustion process, utilizes a two-step chemical reaction mechanism that consists of six species:...
Show moreThis dissertation presents the reaction-based modeling of diesel combustion and model-based control of diesel engine air path.The dissertation first presents a control-oriented reaction-based diesel combustion model that predicts the time-based rate of combustion, in-cylinder gas temperature and pressure over one engine cycle. The model, based on the assumption of a homogeneous thermodynamic combustion process, utilizes a two-step chemical reaction mechanism that consists of six species: diesel fuel (C10.8H18.7), oxygen (O2), carbon dioxide (CO2), water (H2O), nitrogen (N2), and carbon monoxide (CO). The temperature variation rate is calculated based on the rate of change of species concentrations, and the heat loss correlation is also used to study the model performance. The accuracy of the model is evaluated using the test data from a production GM 6.6 L, 8-cylinder, turbocharged engine. The model is calibrated over large engine speed and load range as well as different injection timings and exhaust gas recirculation (EGR) rates by solving the optimization problem. The calibrated reaction-based model accurately predicts the indicated mean effective pressure, while keeping the errors of in-cylinder pressure and temperature small, and at the same time, significantly reduces the calibration effort, especially when the engine is operated under multiple fuel injection operations, comparing to Wiebe-based combustion models. The calibrated model parameters have a strong correlation to engine speed, load and injection timings, and as a result, a universal parameter calibration structure is proposed for entire operational conditions.The second part of the dissertation is to obtain a parametric understanding of diesel combustion by developing a physics-based model that is able to predict the combustion metrics, such as in-cylinder pressure, burn rate, and indicated mean effective pressure (IMEP) accurately, over a wide range of operating conditions, especially with multiple injections. In the proposed model, it is assumed that the engine cylinder is divided into three zones: a fuel zone, a reaction zone, and an unmixed zone. The formulation of reaction and unmixed zones is based on the reaction-based modeling methodology, where the interaction between them is governed by Fick's law of diffusion. The fuel zone is formulated as a virtual zone, which only accounts for mass and heat transfer associated with fuel injection and evaporation. The model is validated using test data under different speed and load conditions, with multiple fuel injections and EGR. It is shown that the three-zone model outperformed the single-zone model in in-cylinder pressure prediction and calibration effort with a mild penalty in computational time. One set of calibration parameters are used for all engine operating conditions.The third part of the dissertation is modeling and control of engine air path with an electrically assisted boosting system. A physics-based control-oriented engine air path model with electrical assistance has been developed. The model is validated with steady-state engine test data and standard driving cycle data. Through one-dimensional simulation, it is found that the electrically assisted boosting system is able to improve engine performance under both steady-state and transient conditions. A model-based controller has been developed for the electric booster (eBoost) and bypass valve to improve the transient performance of engine load response. Experiments have been performed on a Ford 6.7 L, 8-cylinder, turbocharged diesel engine equipped with a prototype eBoost and a standard EGR valve as the bypass valve. Steady-state test results have shown that eBoost is capable of improving engine efficiency by reducing pumping loss, due to reduced turbine speed when eBoost is providing additional boost energy. In the transient process, eBoost is able to significantly reduce the response time of boost pressure tracking, as validated by load step tests.
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Title: Supports for student veterans in higher education : chat and understanding student veterans' sense of community in communities of practice
Creator: Christman, John (Graduate of Michigan State University)
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "In this study, I examined and described the experiences of student veterans across three institutions of higher education. This dissertation has three overlapping purposes. First, this dissertation expands the existing scholarship and research on supports for student veterans in the form of student veteran resource centers, as well as how these supports illustrate others' understanding of the needs of student veterans. Second, this dissertation helps to better understand the degree to which...
Show more"In this study, I examined and described the experiences of student veterans across three institutions of higher education. This dissertation has three overlapping purposes. First, this dissertation expands the existing scholarship and research on supports for student veterans in the form of student veteran resource centers, as well as how these supports illustrate others' understanding of the needs of student veterans. Second, this dissertation helps to better understand the degree to which student veterans feel like they are part of a community and how student veterans are provided with varying levels of support. Third, I conclude by providing stakeholders in higher education with suggestions based on the findings and feedback from my two studies to take into consideration with regard to the creation and implementation of student veteran resource centers. By analyzing the experiences of student veterans, the resource centers, and the administrators who operate them, this study fills important gaps in our understanding of the purposes of these resource centers, as well as how and why student veterans choose to use them. This study pursues answers to two groups of guiding questions: 1. What are the commonalities or differences with regard to the goals of student veteran resource centers at different universities, such as how they are used and what their purposes are? Additionally, how do these commonalities and differences illustrate higher education administrators' understanding of the needs of student veterans? 2. What are the predictors that have the strongest influence on student veterans' sense of community in communities of practice, and given that each university in this study is the recipient of the same award for supporting student veterans, how does each university demonstrate this support and what are the possible differences?"--Pages ii-iii.
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Title: An exploration of gardener support programs, community gardeners' experiences, and associations with perceived dietary choices, food security, and food values
Creator: Beavers, Alyssa
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Gardening is associated with health behaviors, including fruit and vegetable consumption and physical activity. Maintaining these benefits is dependent on sustaining gardens and interest of gardeners, which can be challenged by lack of gardening skills and knowledge and financial cost. Gardener support programs reduce these barriers by providing gardening resources and education, especially important for new gardeners who may lack gardening skills and knowledge. The overall objectives of...
Show more"Gardening is associated with health behaviors, including fruit and vegetable consumption and physical activity. Maintaining these benefits is dependent on sustaining gardens and interest of gardeners, which can be challenged by lack of gardening skills and knowledge and financial cost. Gardener support programs reduce these barriers by providing gardening resources and education, especially important for new gardeners who may lack gardening skills and knowledge. The overall objectives of this dissertation were to understand how and why gardening influences diet, the challenges faced by new gardeners, and aspects of gardener support programs that may be most beneficial to sustaining gardens. The aims of this dissertation were to: 1. Investigate how and why gardening is perceived to influence dietary choices and food security, 2. Explore the experiences of new community gardeners, and 3. Examine the associations between garden characteristics, participation in components of a gardener support program, and continued program participation. For the first aim, in-depth semi-structured qualitative interviews were conducted with 28 experienced members of the Garden Resource Program operated by Keep Growing Detroit, a non-profit organization in Detroit, Michigan. Data were analyzed by thematic coding. Many gardeners perceived that gardening led to increased vegetable intake and decreased intake of less healthy foods, including fast food and processed foods. They perceived knowing how their food was produced, an emotional attachment to food they grew, and that home-grown produce tasted better caused these dietary changes. Gardening was perceived to influence aspects of food security by contributing to financial savings on food and providing ample access to fresh vegetables, which gardeners preserved for year-round use. In the second aim, in-depth semi-structured qualitative interviews were conducted with 15 new community gardeners participating in a randomized controlled trial of community gardening in Denver, Colorado to examine their perceptions of leadership, social interaction in the garden, and challenges. Thematic coding was used to analyze data. Key challenges described by new gardeners included limited time and lack of gardening knowledge. There was variation in new gardeners' perceptions of social interaction in the garden and support from their garden leaders. Engaged garden leaders and other experienced gardeners helped alleviate challenges by sharing their gardening knowledge and assisting new gardeners. In the third aim, data from Keep Growing Detroit's records on 2,318 gardens participating in their program from 2012-2015 was used to examine the association between components of their programming and continued garden participation using multilevel logistic regression and mediation analysis. Program components associated with continued garden participation in the Garden Resource Program included attending educational classes, volunteering, previous years of garden membership in the Garden Resource Program, and receiving seeds and plants. Comprehensive education indirectly increased the likelihood of continued garden membership through participation in other aspects of the program. Overall, these three studies advance the understanding of sustaining and expanding gardening's health impacts by demonstrating how gardening is perceived to influence dietary choices and food security and highlighting the importance of leadership and social interaction, and education and resources to sustain gardeners' participation and improve garden longevity."--Pages ii-iii.
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Title: The informativeness of consumer opinions on firm fundamentals : evidence from Amazon.com
Creator: Jin, Shunyao
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "This study examines whether online consumer product reviews contain information that is associated with firms' earnings and stock returns around earnings announcements. Ex ante, it is unclear whether consumer reviews are useful to investors because consumer reviews have not been easily accessible or widely disseminated. Based on 18,794,143 consumer reviews posted on Amazon.com during 1996-2014, I construct quarterly measures of abnormal tone and abnormal rating of consumer reviews and link...
Show more"This study examines whether online consumer product reviews contain information that is associated with firms' earnings and stock returns around earnings announcements. Ex ante, it is unclear whether consumer reviews are useful to investors because consumer reviews have not been easily accessible or widely disseminated. Based on 18,794,143 consumer reviews posted on Amazon.com during 1996-2014, I construct quarterly measures of abnormal tone and abnormal rating of consumer reviews and link them to earnings surprises and earnings announcement returns. Focusing on concurrent earnings surprises, I find that negative abnormal tone is significantly associated with more negative earnings surprises while positive abnormal tone is not associated with positive earnings surprises. My analyses of abnormal returns around concurrent earnings announcements show that negative abnormal tone is positively associated with earnings announcement returns, but positive abnormal tone is not. Finally, I find that disagreements in review ratings (measured as the standard deviation of consumer review ratings) are positively associated with unexplained trading volume around earnings announcements, while disagreements in review tone (measured as the standard deviation of consumer review tone) are not. Taken together, these findings suggest that abnormal review tone is more useful than abnormal review rating in explaining concurrent earnings surprises and earnings announcement returns, but the disagreements reflected through the distribution of consumer ratings is more informative about the unexplained trading volume around earnings announcements. My results suggest that both the rating and the tone of consumer reviews are informative, but along different dimensions."--Page ii.
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Title: Cluster structure and three-body decay in 14C
Creator: Carpenter, Lisa Marie
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Recent model calculations with most advanced methods for cluster states have shown the need of experimental data to probe the structure of light exotic nuclei, including those with alpha-clustering, such as 14C. The prototype Active Target Time Projection Chamber (pAT-TPC) was used in the present study. The pAT-TPC is a gas-filled thick-target detector with high luminosity and full kinematic acceptance. This type of detector gives access to a full excitation function with a single beam...
Show more"Recent model calculations with most advanced methods for cluster states have shown the need of experimental data to probe the structure of light exotic nuclei, including those with alpha-clustering, such as 14C. The prototype Active Target Time Projection Chamber (pAT-TPC) was used in the present study. The pAT-TPC is a gas-filled thick-target detector with high luminosity and full kinematic acceptance. This type of detector gives access to a full excitation function with a single beam energy. The measurements in this work were carried out by resonant alpha-scattering of a 10Be beam at 38 and 20 MeV delivered by the TwinSol facility at the University of Notre Dame. These experiments measured resonances in 14C that can be compared to models by using R-Matrix reaction theory. Two new negative parity resonances were identified at high excitation energies. Additionally, using a Dalitz-type analysis, three-body decays were analyzed to determine probabilities of 'democratic' and 'sequential' decay. Increasing probability of democratic decay was found at high energy. Results were interpreted using Gamow Shell Model and Anti-Symmetrized Molecular Dynamics calculations which are described in detail."--Page ii.
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Title: Dissecting the driving forces of membrane protein folding under native conditions
Creator: Gaffney, Kristen Ann
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Membrane proteins are a unique class of proteins which reside within cellular membranes. They comprise 20223C30% of all proteins in most organisms. Membrane proteins are involved in a variety of important cellular processes including ATP synthesis, photosynthesis, catalysis, molecular transport and cell signaling. Missense mutations in the genes encoding membrane proteins cause several life-threatening diseases including cystic fibrosis, Alzheimer's disease, and Charcot-Marie Tooth's disease....
Show moreMembrane proteins are a unique class of proteins which reside within cellular membranes. They comprise 20223C30% of all proteins in most organisms. Membrane proteins are involved in a variety of important cellular processes including ATP synthesis, photosynthesis, catalysis, molecular transport and cell signaling. Missense mutations in the genes encoding membrane proteins cause several life-threatening diseases including cystic fibrosis, Alzheimer's disease, and Charcot-Marie Tooth's disease. These mutations are known to cause disease majorly by impacting protein stability, rather than function, via two mechanisms: 1) protein destabilization which leads to excessive degradation and low accumulation of functional protein, 2) stabilization of non-functional misfolded forms of a protein which overwhelm cellular degradation machinery. To fundamentally understand disease mechanisms, it is necessary to understand the molecular forces and mechanisms in the folding of membrane proteins. Although the study of protein folding has been one of the major quests in molecular biology over the last 223C60 years, the understanding of membrane protein folding lags far behind that of soluble proteins. This is primarily due to the lack of available methods to control the reversible folding of membrane proteins under native conditions. Recently, steric trapping, which couples the unfolding of a doubly-biotinylated protein to monovalent streptavidin binding, has emerged as a promising technique to study membrane protein folding directly under native conditions without the use of chemical denaturants, heat, or pulling force. This work presents generalized steric trapping techniques utilizing novel tripartite chemical probes to dissect the folding energy landscape of the intramembrane protease GlpG from Escherichia coli. The new steric trap tools were employed to examine the thermodynamic stability of GlpG and the physical dimension of its unfolded state. Upon the discovery of subglobal unfolding events of GlpG in the region encompassing the active site, an intricate cooperativity network important for maintaining the stability of GlpG was identified using cooperativity profiling at side chain resolution. Finally, double-mutant cycle analysis coupled with stability measurement by steric trapping revealed the weakly coupled hydrogen bond network in the catalytic active site of GlpG.
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Title: Controllability of hyperbolic and degenerate parabolic equations in one dimension
Creator: Bohn, Jonathan Matthew
Date: 2018
Collection: Electronic Theses & Dissertations
Description: In this thesis, we study the controllability problem for two systems of partial differential equations. We will first consider the wave equation with variable coefficients and potential in one dimension, $u_{tt} - (a(x)u_x)_x + pu = 0$, with control function $v(t)$ acting on the boundary. We consider a class of functions corresponding to a special weight function that contains the variable coefficient $a(x)$. From here, we derive a global Carleman estimate for this system, and establish the...
Show moreIn this thesis, we study the controllability problem for two systems of partial differential equations. We will first consider the wave equation with variable coefficients and potential in one dimension, $u_{tt} - (a(x)u_x)_x + pu = 0$, with control function $v(t)$ acting on the boundary. We consider a class of functions corresponding to a special weight function that contains the variable coefficient $a(x)$. From here, we derive a global Carleman estimate for this system, and establish the controllability property. We then later extend the class of admissible functions $a(x)$ for which the controllability property holds true. We then study the controllability problem for the degenerate heat equation in one dimension. For $0\leq \alpha <1$, on $(0,1) \times (0,T)$, we consider $w_t - (x^{\alpha}w_x)_x = f$. This equation is degenerate because the diffusion coefficient $x^{\alpha}$ is positive in the interior of the domain and vanishes at the boundary. We consider this problem under the Robin boundary conditions. Again, we derive a Carleman estimate for this system, taking into account the new boundary terms that arise from the Robin conditions.
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Title: An experimental-computational study on the plastic deformation behavior of body-centered cubic titanium alloys
Creator: Khademi, Vahid
Date: 2018
Collection: Electronic Theses & Dissertations
Description: A combined experimental-computational investigation was performed in the first part of this work to quantify the relationship between plastic strain and crystallographic misorientation. Several material characterization techniques including tensile testing, Scanning Electron Microscopy (SEM), Digital Image Correlation (DIC), and Electron Backscatter Diffraction (EBSD) were combined to study the correlation between plastic strain and crystallographic misorientation at the microscale for two...
Show moreA combined experimental-computational investigation was performed in the first part of this work to quantify the relationship between plastic strain and crystallographic misorientation. Several material characterization techniques including tensile testing, Scanning Electron Microscopy (SEM), Digital Image Correlation (DIC), and Electron Backscatter Diffraction (EBSD) were combined to study the correlation between plastic strain and crystallographic misorientation at the microscale for two body-centered cubic (bcc) titanium (Ti) alloys, namely Ti-13Cr-1Fe-3Al (wt.%) and TIMETAL-21S [Ti 15Mo-3Nb-3Al-0.2Si (wt.%)]. The results revealed that larger grains experienced more misorientation dispersion compared to smaller grains. An empirical equation was proposed to estimate the crystallographic misorientation at the grain scale as a function of plastic strain and grain size. Furthermore, the effects of crystallographic orientation and loading history on the misorientation were investigated. It was observed that {100} oriented grains (with respect to the tensile axis) exhibited more of a tendency for orientation change than {110} and {111} oriented grains. Interrupted loading resulted in higher crystallographic misorientation than monotonic (uninterrupted) loading. A qualitative comparison between the DIC-SEM strain field map and the misorientation maps revealed that there is a better correlation between the hot spots in the KAM map and the DIC-SEM strain field map compares with the correlation between the hot spots in the MD maps and the DIC-SEM stain field map. Some of the metrics, developed in the misorientation analysis, were implemented by EDAX-TSL, Inc. (Mahwah, NJ) in their latest orientation imaging microscopy (OIM) commercial software. Slip trace analysis was performed to characterize the distribution of the plastic deformation modes at RT, 200 ̊C, and 300 ̊C on three bcc Ti alloys: Ti-13Cr-1Fe-3Al (wt.%), TIMETAL-21S, and Ti-29Nb-13Ta-4.6Zr-xO (wt.%), where x is 0.1, 0.3, and 0.7 (wt.%). The results revealed that dislocation slip was the dominant plastic deformation mechanism for Ti-13Cr-1Fe-3Al (wt.%), TIMETAL-21S, Ti-29Nb-13Ta-4.6Zr-0.3O (wt.%), and Ti-29Nb-13Ta-4.6Zr-0.7O (wt.%). The {123}<111> slip systems exhibited the highest contribution, while the {110}<111> showed the least contribution of the observed traces. However, the normalized slip activity (according to the possible slip planes of each system) suggested that the activity of all the systems were relatively equal for the TCFA, while the activity of the {110}<111> was slightly greater than other two slip systems for the TIMETAL-21S. Three deformation mechanisms, i.e., stress-induced martensitic (SIM) transformation (β phase to α” phase), the {332}<113> mechanical twinning, and the slip activity activated and cooperated for the Ti-29Nb-13Ta-4.6Zr-0.1O (wt.%). In the second part of this work, the room temperature (RT) and elevated temperature strength of a low-cost Ti alloy were enhanced through thermomechanical processing (TMP). In-situ and ex-situ TMP treatments were systematically designed and conducted to increase the strength of a low-cost bcc Ti alloy. By performing heat treatments in the range of 300 ̊C to 600 ̊C, it was found that nanoscale and microscale precipitates formed in the bcc matrix, which led to enhance the strength. With an applied mechanical load, the phase transformation process was accelerated. The resulting mechanical properties depended on the type and duration of the TMP treatments. The maximum tensile strength of Ti-13Cr-1Fe-3Al (wt.%) reached approximately 1500 MPa at 410 ̊C. The TMP and alloy composition range was patented internationally.
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Title: Multicolor fluorescence optical tweezers methods and applications to nucleic acid folding
Creator: Chuang, Cho-Ying
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Nucleic acids and proteins are fundamental molecular units of life. To understand their properties, we need powerful tools that allow investigation at the single-molecule level. Over the past three decades, the development of single-molecule force and fluorescence techniques has provided us new knowledge that was previously unattainable through ensemble measurements. However, we lack methods that allow us to precisely measure the mechanical properties of these molecules while visually...
Show moreNucleic acids and proteins are fundamental molecular units of life. To understand their properties, we need powerful tools that allow investigation at the single-molecule level. Over the past three decades, the development of single-molecule force and fluorescence techniques has provided us new knowledge that was previously unattainable through ensemble measurements. However, we lack methods that allow us to precisely measure the mechanical properties of these molecules while visually detecting multiple molecules at the same time. In this dissertation, we maximize the information obtained in single-molecule measurements by pushing the techniques to be more precise and more complex. We then utilize our instrument to directly observe the folding and unfolding of the nucleic acid G-quadruplex structure. Among the single-molecule force techniques, angstrom-resolution has been achieved by optical tweezers using the dual-trap instrument design. Dual-traps can be produced by acousto-optic (AO) devices, which have many advantages, but trap positioning inaccuracies have limited their usage at high-resolution. We have designed a method to remove the inaccuracies by randomizing the phase of the radio frequency that drives the AO device. We demonstrated that the trap inaccuracies are completely eliminated and high-resolution trapping quality is achieved. This advance allows us to perform long duration measurements with reduced drift in trap measurement over time. Next, we present instrumentation advances that combine high-resolution optical tweezers and multicolor confocal fluorescence spectroscopy along with automated single molecule assembly. Multicolor not only allows the detection of multiple observables but also increases the flexibility in the choice of fluorophores. We demonstrated the ability to simultaneously measure angstrom-scale changes in tether extension and single fluorophore signals. The biggest challenge in integrating optical tweezers and fluorescence is the potential for greatly enhanced photobleaching which can make experiments impossible. We showed that the mean number of photons emitted before bleaching is unaffected by the trap laser when interlacing the fluorescence and optical trap lasers. We investigated the photostability of quantum dots and fluorophores. Finally, we devised computer-controlled automation to conserve the fluorophore lifetime. This advance enables us to observe multiple molecules or multiple degrees of freedom within a molecular complex while mechanically manipulate and detect them. Taking advantage of these method and instrumentation advances, we investigate the folding and unfolding of a DNA secondary structure: thrombin-binding aptamer G-quadruplex (TBA-GQ). Studying the kinetics of G-quadruplex formation is essential for understanding telomere regulation (the ends of chromosomes) and therapeutic approaches for disease. TBA-GQ is the smallest G-quadruplex. Although many experiments and simulations have been done on G-quadruplex, the small size and low stability make it very difficult to observe folding and unfolding of TBA-GQ directly. Our high-resolution optical tweezers have the sensitivity and stability to directly observe TBA-GQ at very low forces. We found that with increasing force, the folding rate decreased and the unfolding rate increased. Our work demonstrates that at a given force, the TBA-GQ formation is facilitated by metal ions and is stabilized by thrombin. It also indicates that the equilibrium force increased as KCl concentration increased. From a detailed analysis of the folding and unfolding rate constants vs applied force, we were able to detect a single transition state conserved across all conditions and identify the structure of the transition state as the G-triplex structure.
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Title: Theoretical analysis of electronic, thermal, and mechanical properties in gallium oxide
Creator: Domenico Santia, Marco
Date: 2019
Collection: Electronic Theses & Dissertations
Description: In recent years, Ga2O3 has proven to be a promising semiconductor candidate for a widearray of power electronics and optoelectronics devices due to its wide bandgap, high breakdownvoltage, and growth potential. However, the material suffers from a very low thermalconductivity and subsequent self-heating issues. Additionally, the complexity of the crystalstructure coupled with the lack of empirical data, has restricted the predictive power of modellingmaterial properties using traditional...
Show moreIn recent years, Ga2O3 has proven to be a promising semiconductor candidate for a widearray of power electronics and optoelectronics devices due to its wide bandgap, high breakdownvoltage, and growth potential. However, the material suffers from a very low thermalconductivity and subsequent self-heating issues. Additionally, the complexity of the crystalstructure coupled with the lack of empirical data, has restricted the predictive power of modellingmaterial properties using traditional methods. The objective of this dissertation is toprovide a detailed theoretical characterization of material properties in the wide bandgapsemiconductor Ga2O3 using first-principles methods requiring no empirical inputs. Latticethermal conductivity of bulk β − Ga2O3 is predicted using a combination of first-principlesdetermined harmonic and anharmonic force constants within a Boltzmann transport formalismthat reveal a distinct anisotropy and strong contribution to thermal conduction fromoptical phonon modes. Additionally, the quasiharmonic approximation is utilized to estimatevolumetric effects such as the anisotropic thermal expansion.To evaluate the efficacy of heat removal from β − Ga2O3 material, the thermal boundaryconductance is computed within a variance-reduced Monte-Carlo framework utilizingfirst-principles determined phonon-phonon scattering rates for layered structures containingchromium or titanium as an adhesive layer between a β − Ga2O3 substrate and Au contact.The effect of the adhesive layer improves the overall thermal boundary conductancesignificantly with the maximum value found using a 5 nm layer of chromium, exceeding themore traditional titanium adhesive layers by a factor of 2. This indicates the potential ofheatsink-based thermal management as an effective solution to the self-heating issue.Additionally, this dissertation provides a detailed characterization of the effect of strainon fundamental material properties of β−Ga2O3 . Due to the highly anisotropic nature of thecrystal, the effect strain can have on electronic, mechanical, and optical properties is largelyunknown. Using the quasi-static formalism within a DFT framework and the stress-strainapproach, the effect of strain can be evaluated and combined with the anisotropic thermalexpansion to incorporate an accurate temperature dependence. It is found that the elasticstiffness constants do not vary significantly with temperature. The computed anisotropyis unique and differs significantly from similar monoclinic crystal structures, indicating theimportant role of the polyhedral linkage to the reported anisotropy in material properties.Lastly, the dependence of the dielectric function with respect to strain is evaluated using amodified stress-strain approach. This elasto-optic, or photoelastic, effect is found to be significantfor sheared crystal configurations. This opens up a potential unexplored applicationspace for Ga2O3 as an acousto-optic modulation device
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Title: I. Delivery of carbohydrate antigens by glycopolymers as potential anti-cancer vaccines : II. A study of the impacts of valency and density on immune response against a tumor associated carbohydrate antigen
Creator: Qin, Qian, 1981-
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Tumor associated carbohydrate antigens (TACAs) are overexpressed on tumor cells, which renders them attractive targets for anti-cancer vaccines. To overcome the poor immunogenecity of TACAs, a polymer platform was designed for antigen presentation by taking advantage of the polymeric backbone to deliver TACA and helper T (Th) cell epitope on the same chain. The block copolymer was synthesized by cyanoxyl-mediated free radical polymerization followed by conjugation with a TACA Tn antigen and a...
Show moreTumor associated carbohydrate antigens (TACAs) are overexpressed on tumor cells, which renders them attractive targets for anti-cancer vaccines. To overcome the poor immunogenecity of TACAs, a polymer platform was designed for antigen presentation by taking advantage of the polymeric backbone to deliver TACA and helper T (Th) cell epitope on the same chain. The block copolymer was synthesized by cyanoxyl-mediated free radical polymerization followed by conjugation with a TACA Tn antigen and a mouse Th-cell peptide epitope derived from poliovirus (PV) to afford the vaccine construct. The glycopolymer vaccine elicited a robust immune response with significant titers of IgG antibodies and the antibodies generated recognized Tn antigens on tumor cell surface. For successful carbohydrate based anti-cancer vaccines, it is critical that B cells are activated to secret antibodies targeting TACAs. Despite the availability of many TACA based constructs, systematic understanding of the effects of structural features on anti-glycan antibody responses is lacking. In this study, a series of defined synthetic glycopolymers bearing a representative TACA, i.e., the Thomsen-nouveau (Tn) antigen, have been prepared to probe the induction of early B cell activation and antibody production via a T cell independent mechanism. Valency and density of the antigen in the polymers turned out to be critical. An average of greater than 6 Tn per chain was needed to induce antibody production. Glycopolymers with 40 antigens per chain and backbone molecular weight of 450 kDa gave the strongest stimulation to B cells in vitro, which correlated well with its in vivo activity. Deviations from the desired valency and density led to decreased antibody production or even antigen specific B cell non-responsiveness. These findings provide important insights on how to modulate anti-TACA immune responses facilitating the development of TACA based anti-cancer vaccines using glycopolymers.
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Title: The cost of wildfires in heavily urbanized areas : measuring property value and recreational impacts in Southern California
Creator: Tanner, Sophia
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Wildfire frequency and severity are increasingly important issues in the western United States, as fires threaten lives, properties and outdoor amenities. This dissertation seeks to measure the impact of wildfires in Southern California using nonmarket valuation techniques. In the first essay we employ the hedonic property method to estimate how wildfires affect nearby property values. Using data from 15 years of property sales prices and 20 years of wildfire data, we find that the average...
Show moreWildfire frequency and severity are increasingly important issues in the western United States, as fires threaten lives, properties and outdoor amenities. This dissertation seeks to measure the impact of wildfires in Southern California using nonmarket valuation techniques. In the first essay we employ the hedonic property method to estimate how wildfires affect nearby property values. Using data from 15 years of property sales prices and 20 years of wildfire data, we find that the average impact of a wildfire on housing sales price depends on the market context and whether the event increases, decreases, or does not change prior risk perceptions. This suggests that public policy and availability of risk information can be effective tools in capitalizing wildfire risk in housing markets prior to events. The second essay uses evidence from a choice experiment given to respondents who were intercepted at national forest sites to estimate preferences for environmental attributes of recreation sites. Specifically, the main attribute of interest is fire history, where fire history is given by distinct categories in relation to the dominant vegetation at the site. Using conditional logit, random parameters logit, and latent class models, we find that tree cover, compared to shrubs or barren areas, and water are highly desirable attributes, while evidence of past fires decreases the value of a site. Forest fires that reach the crowns of trees are least desirable, while older forest fires and shrub fires have less of a negative effect. We find evidence of significant preference heterogeneity over the vegetation and fire attributes. The third essay combines revealed preference data from site intercepts and stated preference data from online surveys to estimate the welfare impacts of different fire scenarios at recreation sites. We estimate a multi-site zonal travel cost model of trips to hiking and day use sites in the Angeles National Forest. Stated preference data on reduction in trips to recreation sites under different fire history scenarios are used to calibrate the zonal travel cost model and estimate the welfare impacts of fire. The greatest estimated welfare losses are from recent fires that burn all vegetation as opposed to less intense fires or older fires that have had time to recover. For popular recreation sites, these losses from intense fires can total over $1 million in one summer. Applying this method to a large fire that affected many sites in our study area, we illustrate how losses decrease over time, but can continue well after sites are re-opened due to lasting effects on the landscape.
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Title: THE THEORY AND PRACTICE OF CONTEMPORARY PLACE RELATED CONCEPTS IN URBAN PLANNING
Creator: Salmistu, Sirle
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Since the 1990s, planning theory has focused on the planning process and the engagement of stakeholders. With increasing technologies, attitudinal changes and transformations in lifestyles, new concepts and themes in planning profession seem to emerge at increasing frequencies. Most appear to evolve over a set of good planning principles that have withstood the test of time. Contemporary concepts usually have trendy labels such as New Urbanism, Livable Communities, Sustainable Cities, Smart...
Show moreSince the 1990s, planning theory has focused on the planning process and the engagement of stakeholders. With increasing technologies, attitudinal changes and transformations in lifestyles, new concepts and themes in planning profession seem to emerge at increasing frequencies. Most appear to evolve over a set of good planning principles that have withstood the test of time. Contemporary concepts usually have trendy labels such as New Urbanism, Livable Communities, Sustainable Cities, Smart Cities, Cool Cities and the latest trend of Placemaking. The overarching question that guides this research is what draws planners to continually redefine and market an age-old, fundamentally basic, concept of creating safe, comfortable and attractive places for people?The purpose of this research is to explore and understand the key characteristics of contemporary concepts in urban planning, through the lens of scholarship and theoretical literature and assess whether these concepts are impacting professional planning practice in Michigan. Hence, this dissertation explored answers to the following research questions: 1) How has professional language related to creating places for people evolved since 1990? 2) To what extent do emerging concepts in Urban Planning differ from one another? 3) What planning principles are targeted through contemporary planning concepts? 4) How often do practicing urban planners in Michigan use planning principles and contemporary concepts in their day to day work? and 5) Is there a gap between theory, as evidenced by the knowledge in scholarly literature, and practice within a Michigan context, as it relates to contemporary planning concepts? Methodology of grounded theory guided this research and qualitative research methods were employed. Content analysis of selected scholarly literature and a survey of practicing urban planners were conducted.Ten significant contemporary planning concepts were identified and explored within this study: Creative Cities, Healthy Cities, Livable Cities, New Urbanism, Placemaking, Resilient Cities, Safe Cities, Smart Cities, Smart Growth and Sustainable Cities. The findings from literature analysis demonstrate that each concept has different focus areas and nuances, however, there are also considerable similarities between concepts. A set of 20 planning principles were derived from the scholarly literature on the 10 contemporary concepts. The most pertinent planning principles are related to accessibility, transportation and mobility; citizen participation and collaboration; and green infrastructure. The survey of professional planners, on the other hand, revealed that the principles most often used in practice were considerably different. Only the principle of citizen participation and collaboration overlapped between theory and practice. The other most frequently used planning principles in practice are facilitation of public education and awareness, interdisciplinary collaboration and public-private partnerships and data driven planning. The survey of professionals also showed that the most frequently used contemporary concept is Placemaking, while some of the other popular concepts were Livable Cities, Sustainable Cities and Smart Growth. The gap between theory and practice is best illustrated by the fact that the planning principles most often used by practitioners were related to the least used concepts in practice, or the principles embodied in the most often used concepts were not cited as the most frequently used principles in practice. This suggests that practitioners may use the trendy concept label with little understanding of the premise or principles related to that particular concept. Interestingly, practitioners use planning principles far more frequently in describing their work than popular contemporary concepts. Furthermore, this research proves that the continuous occurrence and evolution of concepts appears to be more of a theoretical exercise and it is not planning practice that is driving the creation of trendy concepts. This two-stage research of examining the theory behind contemporary planning concepts and the survey aimed to reflect on professional planning practice clearly demonstrates the disconnect between planning scholarship and practice.
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Title: EXPLORING SOIL ARTHROPOD ECOLOGY AND MANAGEMENT TACTICS IN PERENNIAL FRUIT CROP SYSTEMS DURING THE WINTER
Creator: Matlock, Jason
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Paralobesia viteana (the grape berry moth) and Venturia inaequalis (causal agent of apple scab) are two key pests of perennial fruit crops in Michigan and the Northeastern US. Both of these pests provide examples of the feedback potential of management decisions: they both overwinter within the cropping system and have multiple reproductive generations per growing season. This allows their populations to carry over from season to season, exacerbating any failures in management from previous...
Show moreParalobesia viteana (the grape berry moth) and Venturia inaequalis (causal agent of apple scab) are two key pests of perennial fruit crops in Michigan and the Northeastern US. Both of these pests provide examples of the feedback potential of management decisions: they both overwinter within the cropping system and have multiple reproductive generations per growing season. This allows their populations to carry over from season to season, exacerbating any failures in management from previous years. Both pests overwinter on the ground in leaf litter. During that time, these organisms are affected by physical changes of the ground habitat and interactions with other ground-dwelling organisms. Manipulation of that habitat to alter the physical properties and community dynamics to decrease overwintering survivorship of these pests may provide growers with additional management tactics. Indeed, there is historical precedent for such tactics originating in the early 1900s. Publications from that time mention grape growers in Northeastern, PA throwing furrows over the leaf litter beneath vine canopies in late fall or early spring and observing reduced grape berry moth emergence. During this same time period, it was discovered that spraying a urea solution onto fallen leaves in apple orchards decreased the spore density released by V. inaequalis in the following season. Unfortunately, our understanding of the mechanisms underlying these techniques are incomplete and their adoption by growers remains low. Furthermore, our general understanding of the activities of floor dwelling organisms during the overwintering period is also limited. Increasing knowledge both of how these specific tactics affect their associated target pests, and of how overwintering populations are structured are essential steps in the development and improvement of winter management tactics. With regard to P. viteana and grape vineyards, I explored the effects of physical damage and burial resulting from a rotary cultivator used at the end of the season. Survivorship of pupae recovered from the vineyard immediately after tillage and held until emergence was not significantly different from those recovered from an untilled control area, indicating little effect of mechanical damage on this pest. However, a single pass of the tillage implement buried three quarters of pupae under at least 1 cm of soil. A laboratory experiment to recreate these conditions resulted in significant increase in mortality when pupae were buried in more than 1 cm of sand. I conclude that interference with adult emergence of diapausing pupae via burial is the primary mechanism by which tillage controls grape berry moth.With regards to apple V. inaequalis and apple orchards, I observed the response of overwintering, ground-dwelling arthropods to 1) the application of urea to fallen leaves; and 2) organic versus conventional management strategies. In addition, I screened the gut contents of collected arthropods for the presence of V. inaequalis to identify potential natural enemy taxa. My primary finding was that orchards host a diverse, winter active arthropod community. Management strategy did not affect family richness or intra-community complexity (alpha diversity). There was also considerable overlap in the dominant families detected under both management strategies. However, the relative abundances of those families did respond to management strategy. These changes were associated with differences in the secondary and tertiary decomposer sub guilds. There was also evidence that organic management supported a greater arthropod population. Urea application caused an up-regulation of tertiary decomposers and a down-regulation of primary decomposers during the first month following application. I also found evidence that the absolute decomposer populations were greater in the urea treatments. I propose that urea application caused a trophic cascade in which increased microbial growth leads to a recruitment of fungal feeding arthropods into leaf litter from surrounding areas of the orchard.
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Title: Examining teacher support for meaningful engagement in scientific modeling
Creator: Ke, Li
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Recent science reform efforts in science education have called for students appropriating authentic scientific practices that resemble the intellectual work of scientists. Among scientific practices, scientific modeling has been considered particularly important as a cornerstone of science as developing, testing, and revising models as embodiment of theory lies at the heart of scientific endeavor. Despite the increasing emphasis on scientific practices in general, and scientific modeling in...
Show moreRecent science reform efforts in science education have called for students appropriating authentic scientific practices that resemble the intellectual work of scientists. Among scientific practices, scientific modeling has been considered particularly important as a cornerstone of science as developing, testing, and revising models as embodiment of theory lies at the heart of scientific endeavor. Despite the increasing emphasis on scientific practices in general, and scientific modeling in specific in the field of science education, engaging classrooms in the practice can be especially challenging for teachers, even for those well-intended ones who are student-centered and inquiry-oriented in their pedagogy. While there is emerging research starting to focus on the interaction of teacher and students regarding the respective goals or expectations of certain scientific practices, there is little research about what aspects of teachers’ instructional practices can support students’ development in the practice of scientific modeling in a meaningful way.In this dissertation study, I seek to address this research gap. I draw on situated cognition as my theoretical lens and use Epistemologies-in-Practices as my analytical framework to investigate how teachers might support students’ meaningful engagement in modeling practices and what effects that support might have on students. In particular, I present a multi-case study of two upper-elementary teachers and one middle school teacher to examine what teaching practices teachers use to support modeling. I also investigate how that interaction might have impacted the nature of students’ engagement in modeling.As such, my overall research questions are:1. How do teachers engage students in modeling practice in a meaningful way?2. How do teachers’ instructional practices seem to influence students’ modeling practices?In all three research studies, I found that teachers’ instructional practices seemed to have influenced how students engaged in the practice of modeling accordingly. Further, it is the ways in which teachers emphasize the epistemic aspects of the practice that matter. The findings suggest that how teachers prioritize, unpack, contextualize, and scaffold the epistemic goals of modeling seem to contribute to students’ meaningful engagement in the modeling practices. Also, the findings also indicate that it is important for teachers to connect the epistemic aspect of the practice with other dimensions for the purpose of meaningful engagement in the practice. I conclude the dissertation with implications for teacher professional learning and the direction for future research.
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Title: The role of rapid adaptation in plant population establishment
Creator: Magnoli, Susan Marie
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Rapid adaptation, or adaptation that occurs on an ecological timescale, has been documented across a wide range of taxa and in many biological contexts, and can potentially alter the outcomes of ecological interactions and ecosystem-level processes. Rapid adaptation is also hypothesized to influence the establishment of species in new habitats, as rapid adaptation can have important demographic consequences for a colonizing population that is not optimally suited to a novel habitat. Examining...
Show moreRapid adaptation, or adaptation that occurs on an ecological timescale, has been documented across a wide range of taxa and in many biological contexts, and can potentially alter the outcomes of ecological interactions and ecosystem-level processes. Rapid adaptation is also hypothesized to influence the establishment of species in new habitats, as rapid adaptation can have important demographic consequences for a colonizing population that is not optimally suited to a novel habitat. Examining the relationship between rapid adaptation and establishment can lead to a better understanding of successful colonization events, such as biological invasions, range expansions, and successful establishment in ecological restorations. In this dissertation, I used manipulative field and greenhouse experiments to examine rapid adaptation, its potential drivers and trait changes that lead to adaptation, and its demographic consequences in two plant populations in recently restored prairies. I found evidence that one population rapidly adapted only six years after establishment, which could potentially influence population persistence. In addition, I found that the plant populations rapidly evolved different strategies of interacting with microbial mutualists, suggesting that these mutualists may act as agents of selection in this system. By providing evidence that rapid adaptation occurs in field populations and examining its potential drivers, my research expands our understanding of the potential causes and consequences of rapid adaptation in recently established plant populations.
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Title: Market discipline, integrity, information disclosure and financial misconduct
Creator: Li, Qingqiu (Graduate of Michigan State University)
Date: 2018
Collection: Electronic Theses & Dissertations
Description: In my dissertation, I explore the factors which impact the outcome of financial misconduct. Financial misconduct imposes negative externalities on firm value, influences investment decisions, and results in both wealth transfer and destruction. The unique governance structure in the asset management industry amplifies the role of investors on firm behavior. I provide novel evidence on the variation in response towards enforcement actions by investor types; I find evidence consistent with two...
Show moreIn my dissertation, I explore the factors which impact the outcome of financial misconduct. Financial misconduct imposes negative externalities on firm value, influences investment decisions, and results in both wealth transfer and destruction. The unique governance structure in the asset management industry amplifies the role of investors on firm behavior. I provide novel evidence on the variation in response towards enforcement actions by investor types; I find evidence consistent with two non-mutually exclusive explanations for this heterogeneity. First, investor sophistication affects the effective cost of information acquisition and processing, making the fund flow discipline less prevalent for retail investors. Second, investors are less likely to punish funds when the costs of moving capital become substantial. Besides investors, other market participants also significantly affect firm behavior. Internal factors, such as corporate culture, along with external factors, such as product market competition, have significant impact on corporate fraud. For example, a lack of focus on integrity in corporate culture is associated with unethical corporate behavior, cultures that neglect integrity are associated with a greater probability of SEC enforcement actions for accounting misstatements. In addition, firms with lower product market differentiation exhibit significantly lower rates of fraud; the relationship is more pronounced for complex firms and is robust to controlling for various measures of competition, predictors of fraud, and industry heterogeneity. Overall, the findings suggest that lower differentiation disciplines firms by facilitating fraud detection through a benchmarking channel.
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Title: Statistical inference with high-dimensional dependent data
Creator: Santo, Shawn M.
Date: 2018
Collection: Electronic Theses & Dissertations
Description: High-dimensional time dependent data appear in practice when a large number of variables are repeatedly measured for a relatively small number of experimental units. The number of repeated measurements can range from two to hundreds depending on the application. Advances in technology have made the process of gathering and storing data such as these relatively low-cost and efficient. Demand to analyze such complex data arises in genetics, microbiology, neuroscience, finance, and meteorology....
Show moreHigh-dimensional time dependent data appear in practice when a large number of variables are repeatedly measured for a relatively small number of experimental units. The number of repeated measurements can range from two to hundreds depending on the application. Advances in technology have made the process of gathering and storing data such as these relatively low-cost and efficient. Demand to analyze such complex data arises in genetics, microbiology, neuroscience, finance, and meteorology. In this dissertation, we first introduce and investigate a novel solution to a classical problem that involves high-dimensional time dependent data. In addition, we propose a new approach to analyze high-dimensional dependent genomics data.First, we consider detecting and identifying change points among covariance matrices of high-dimensional longitudinal data and high-dimensional functional data. The proposed methods are applicable under general temporospatial dependence. A new test statistic is introduced for change point detection, and its asymptotic distribution is established under two different asymptotic settings. If a change point is detected, an estimate for the location is provided. We investigate the rate of convergence for the change point estimator and study how it is impacted by dimensionality and temporospatial dependence in each asymptotic framework. Binary segmentation is applied to estimate the locations of possibly multiple change points, and the corresponding estimator is shown to be consistent under mild conditions for each asymptotic setting. Simulation studies demonstrate the empirical size and power of the proposed test and accuracy of the change point estimator. We apply our procedures on a time-course microarray data set and a task-based fMRI data set. In the second part of this dissertation we consider a hierarchical high-dimensional dependent model in the context of genomics. Our model analyzes RNA sequencing data to identify polymorphisms with allele-specific expression that are correlated with phenotypic variation. Through simulation, we demonstrate that our model can consistently select significant predictors among a large number of possible predictors. We apply our model to an RNA sequencing and phenotypic data set derived from a sounder of swine.
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Title: Quantifying groundwater recharge dynamics using a process-based distributed hydrologic model
Creator: Kang, Guoting
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Groundwater--the lifeblood of groundwater-dependent ecosystems and societies--is facing unprecedented threats from over-extraction, contamination, and changing climate. Groundwater recharge provides a sustainable source of water for aquifers and plays an important role in both surface and sub-surface domains. Understanding and accurately estimating the rate, location, and timing of major recharge events and their seasonal and inter-annual variability is key to safely matching societal needs...
Show moreGroundwater--the lifeblood of groundwater-dependent ecosystems and societies--is facing unprecedented threats from over-extraction, contamination, and changing climate. Groundwater recharge provides a sustainable source of water for aquifers and plays an important role in both surface and sub-surface domains. Understanding and accurately estimating the rate, location, and timing of major recharge events and their seasonal and inter-annual variability is key to safely matching societal needs of water and to maintaining healthy groundwater-dependent ecosystems. This work attempts to understand and quantify recharge dynamics in an agricultural watershed in the Ottawa County, Michigan using field observations of baseflows, groundwater heads, satellite-based evapotranspiration (ET) products and an integrated, process-based hydrologic model. Specific objectives of the work are to: (1) understand the spatial and temporal distribution of high- and low-recharge events and (2) assess the relative impacts of climate, land use, soils, and topography on the spatiotemporal distribution of recharge within the region. County-wide synoptic and time-series baseflow data collected from over 40 small streams between July and November of 2015 were used to quantify the uncertainties in recharge estimation. Precipitation data represent important inputs to hydrologic models and have a major influence on model performance and the estimated recharge. Compared to data from a typical network of rain gauges, the Next-Generation Weather Radar (NEXRAD) provides precipitation data at a much higher spatial resolution. NEXRAD data were blended with traditional rain gauge data to estimate recharge and to evaluate differences relative to recharge estimated using rain gauge data alone. Results indicate that caution should be exercised in using NEXRAD precipitation data for recharge estimation. The representation of recharge and its variability within a numerical model are closely related to the representation of meteorological forcing fields and their spatial structure, land use and land cover, the hydraulic properties of underlying soils and aquifers as well as topography--all of which are represented to varying degrees of accuracy depending on the mesh resolution employed and the algorithms used to represent sub grid-scale processes. To understand the effects of grid resolution on recharge and to identify optimal resolution relative to the size of the watershed, models were setup with different grid resolutions. Recharge patterns follow precipitation patterns more closely at coarse grid sizes since the characteristics of LULC, terrain and hydraulic properties are smoothed at this resolution. Insights gained from the study are expected to aid in the sustainable management of natural resources, particularly groundwater-dependent ecosystems.
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