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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: Systematic analysis of the signal responsive gene regulatory network governing Myxococcus xanthus development
Creator: Saha, Shreya
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Studies of signal-induced gene expression in bacteria have contributed to understanding of how bacteria cope with environmental stress. As an extensively studied model, Myxococcus xanthus provides fascinating insights into how changes at the level of gene expression enable which bacteria to survive environmental insults such as nutrient limitation. Upon starvation M. xanthus cells glide into aggregates and form mounds that mature into fruiting bodies as some cells form spores. Previously, our...
Show moreStudies of signal-induced gene expression in bacteria have contributed to understanding of how bacteria cope with environmental stress. As an extensively studied model, Myxococcus xanthus provides fascinating insights into how changes at the level of gene expression enable which bacteria to survive environmental insults such as nutrient limitation. Upon starvation M. xanthus cells glide into aggregates and form mounds that mature into fruiting bodies as some cells form spores. Previously, our group defined 24-30 h poststarvation as the critical period for commitment to spore formation, when cells commit to form spores despite perturbation of the starvation signal by nutrient addition. The process of multicellular development that culminates in sporulation is governed by a network of signal-responsive transcription factors that integrate signals for starvation and cellular alignment. In this dissertation I present the first systematic approach to elucidate the network dynamics during the commitment period.In the network, MrpC is a starvation-responsive transcription factor, whereas FruA is a transcription factor that responds to cellular alignment conveyed by C-signaling. Transcription of fruA is dependent on MrpC binding, and FruA activity is proposed to be posttranslationally regulated by C-signaling, although the mechanism is unknown. FruA and MrpC cooperatively regulate transcription of the dev operon. My systematic analysis of the network dynamics supported a model in which posttranslational activation of FruA by C-signaling is critical for dev transcription and for commitment to spore formation. Similar to dev, MrpC and C-signal-activated FruA combinatorially controlled transcription of the late-acting fadIJ operon involved in spore metabolism. Regulation of late-acting operons implicated in spore coat biogenesis (exoA-I, nfsA-H, MXAN_3259-MXAN_3263) was discovered to be under complex control by MrpC and FruA. My evidence suggests that transcription of these operons depends at least in part on a C-signal-dependent switch from negative regulation by unactivated FruA to positive regulation by activated FruA during the period leading up to and including commitment to sporulation. MrpC negatively regulated exo and MXAN_3259 during mound formation, but positively regulated nfs. During commitment to sporulation, MrpC continued to positively regulate nfs, switched to positive regulation of MXAN_3259, and continued to negatively regulate exo. A third transcription factor, Nla6, appeared to be a positive regulator of all the late genes. We propose that in combination with regulation by Nla6, differential regulation by FruA in response to C-signaling and by MrpC controls late gene expression to ensure that spore resistance and surface characteristics meet environmental demands.
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Title: Determinants of eating behaviors of us army ROTC cadets in Midwestern universities
Creator: George, Beatriz G.
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Young adults 18-25 years of age, the largest demographic of the military, experience a high burden of obesity and eating disorders (ED) despite an emphasis on physical fitness, body composition, and operational readiness. Etiologic models for obesity and ED suggest body dissatisfaction (BD), dieting, negative affect (NA), and affect regulation represent potentially shared pathways. However, no studies have examined these factors and their shared pathways in military personnel, including ROTC...
Show moreYoung adults 18-25 years of age, the largest demographic of the military, experience a high burden of obesity and eating disorders (ED) despite an emphasis on physical fitness, body composition, and operational readiness. Etiologic models for obesity and ED suggest body dissatisfaction (BD), dieting, negative affect (NA), and affect regulation represent potentially shared pathways. However, no studies have examined these factors and their shared pathways in military personnel, including ROTC cadets. The overarching aim of this dissertation research was to investigate if ED symptoms were associated with body mass index (BMI), an indicator of obesity, and to describe potential correlates of their development. Three specific aims of this research focus on: 1) the prevalence and correlates of ED risk classification and symptoms in ROTC cadets, 2) the association between ED symptoms and BMI, and their potentially shared mechanisms, psychological inflexibility related to BD and dieting, and 3) the gaps in knowledge about eating behaviors and mediators of eating behaviors within the ROTC context and from perspective of ROTC cadets.In 2018, US Army ROTC cadets (n = 205) were recruited from two Midwestern universities and completed questionnaires about demographics, military-specific eating behaviors and mediators of eating behaviors, ED symptoms, and anthropometric measures. Chi-square, multivariable logistic regression, and multiple linear regression were performed in determining the rate of ED risk classification and correlates of ED risk classification and symptoms (Aim 1). Two measures of psychological inflexibility related to BD and dieting, in addition to the data for Aim 1, were used in mediation path analysis to examine the association of ED symptoms to BMI, and the indirect effects as mediated by psychological inflexibility related to BD and dieting (Aim 2). A purposively selected sample of eighteen cadets participated in one-on-one, semi-structured telephone interviews on eating behaviors and their mediators in the context of ROTC (Aim 3). Interviews were analyzed using thematic analysis to identify the most important themes and determinants related to eating behaviors in ROTC cadets.We found that ED symptoms and ED risk classification are prevalent in a sample of US Army ROTC cadets (10.1% of sample). Correlates associated with greater likelihood of ED risk classification and elevated ED symptoms were: sex, dieting, and military contextual factors such as attempting dieting and weight loss to meet body composition standards, and peers' comments on weight. Total ED symptoms scores were positively associated with BMI and partially mediated by psychological inflexibility related to BD and dieting. Cadets discussed perceived determinants of eating behaviors which included traditional determinants (e.g. time, money, nutrition knowledge) and ROTC-context specific determinants (e.g. preparation for body composition assessments and body image perceptions), which contributed to unhealthy weight control behaviors (dieting) and negative body image perceptions (BD) for some cadets. In conclusion, the prevalent correlates for eating disorder symptoms and risk in the sample of US Army ROTC cadets in this study were factors related to the enforcement of body composition standards and body image perceptions in the military context which may contribute to the development of dieting, BD, and NA. Longitudinal and/or intervention studies on this important topic may benefit our understanding of how ED symptoms and obesity develop over time and how targeting dieting, BD, NA, and affect regulation may be leveraged to mitigate ED and obesity to promote physical fitness, operational readiness and health in military personnel.
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Title: Measuring the half-life of O-26
Creator: Redpath, Thomas
Date: 2019
Collection: Electronic Theses & Dissertations
Description: An interesting property of some neutron-unbound systems is true two-neutron emission where the neutrons are emitted simultaneously as opposed to a sequential decay through an intermediate state. Since neutrons are only affected by the angular momentum barrier, the timescale for this process is much shorter than for two proton emission which is dominated by the Coulomb barrier. One such case is ²2076O where a very low decay energy was measured and the two valence neutrons are expected to...
Show moreAn interesting property of some neutron-unbound systems is true two-neutron emission where the neutrons are emitted simultaneously as opposed to a sequential decay through an intermediate state. Since neutrons are only affected by the angular momentum barrier, the timescale for this process is much shorter than for two proton emission which is dominated by the Coulomb barrier. One such case is ²2076O where a very low decay energy was measured and the two valence neutrons are expected to occupy d-wave orbitals. Also, the ground state of ²2075O is located 700 keV higher. Using the data from a previous measurement of the decay energy, the MoNA collaboration extracted a lifetime of 4:5+1:1-1:5(stat) ± 3(syst) ps with a confidence level of 82% (1). Results from a recent measurement give T1/2 = 5:0+2:0-1:6 (stat) ±1:7 (syst) ps and support the previous finding.Measurements of neutron-unbound systems using invariant mass spectroscopy are often performed using low-intensity radioactive ion beams. Low reaction yields can be countered by using a thicker target but at the expense of larger uncertainties in the reconstructed invariant mass. A new segmented target was designed to address this trade-off, and it was first used in this experiment to re-measure the ground state half-life of ²2076O.
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Title: Analysis of drinking water quality and sanitation in a peri-urban area of Dar es Salaam, Tanzania
Creator: Ngasala, Tulakemelwa Mhamilawa
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "While the Sustainable Development Goal 6 called for universal access to water and sanitation by 2030, the challenge of achieving this goal seems daunting in the context of the bourgeoning peri- urban communities of the developing world. These areas are often in a regulatory grey area, receiving municipal water on an irregular basis and lacking sanitation and other basic services. And yet, SDG 6 recognizes that improving global health and wellbeing is critically linked to addressing this...
Show more"While the Sustainable Development Goal 6 called for universal access to water and sanitation by 2030, the challenge of achieving this goal seems daunting in the context of the bourgeoning peri- urban communities of the developing world. These areas are often in a regulatory grey area, receiving municipal water on an irregular basis and lacking sanitation and other basic services. And yet, SDG 6 recognizes that improving global health and wellbeing is critically linked to addressing this problem. A multi-method study of the peri-urban area of Dar es Salaam was conducted to determine the extent of the problem and to make recommendations for system-wide approaches to alleviate the risk of waterborne disease. Existing water sources in the area were identified. Water collection and storage practices were assessed at the household level to determine how water from relatively clean sources becomes contaminated. Escherichia coli (E. coli), nitrate, and total dissolved solid (TDS) were analyzed as indicators for the sewage contamination. Bivariate correlation and univariate regression analyses were used to identify the sources of contamination. The assessment focused on the relationship and association of water contamination with site-specific variables. The variable that had the highest negative impact to the water source was analyzed by using a groundwater flow and contaminant transport model as a tool to make recommendations for proper site-specific sanitation practices. Of the three water sources identified (city water, vendors, and domestic wells), water quality analysis showed that city water at the point of collection (POC) was deemed excellent, whereas it diminished at the point of use (POU) for all three water sources. Reasons for change in water quality at POU and POC were due to mixing of water from different water sources at homes during storage. Using a multinomial regression model, the main reason for mixing water was determined to be the dilution of the salty taste of well water (p < 0.05) and insufficient storage containers (p < 0.05). Of the three water sources identified, domestic wells were found to be the most contaminated. Further analysis on the domestic wells showed a significant contamination, where 80% of wells tested contained E. coli. Also, 58% and 81% of wells tested had concentrations of nitrate and TDS, respectively, that exceeded the WHO guidelines. Univariate regression analysis confirmed the association of contaminants with distance of a well from a sanitation system and well depth (p < 0.05). Groundwater transport modeling showed a strong correlation between the tracer and contaminants and the tracer and distance and helped identify the safe well setback distance that is specific to site conditions, soil type, and aquifer properties. Groundwater modeling was shown to be a good assessment tool for contamination within an aquifer system in urban overpopulated areas of developing countries. Our findings also indicate that the risk of exposure to waterborne disease comes from a combination of factors that involve multiple actors, from improved awareness and sanitation practices to improved regulatory oversight, supply practices, and sanitation technologies."--Pages ii-iii.
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Title: Contemporary liberalism and the nation
Creator: Fram, Daniel
Date: 2019
Collection: Electronic Theses & Dissertations
Description: What is the status and legitimacy of the nation within the horizon of liberalism today? Surveying three representative, contrasting, recent works in contemporary political philosophy, I argue that the nation loses its status and legitimacy from every side. John Rawls's allegedly status-quo preserving theory in The Law of Peoples (Rawls 1999) defends only the shell of sovereignty and in fact points toward cosmopolitan aspirations. Cosmopolitan liberals, and conservative nationalists, therefore...
Show moreWhat is the status and legitimacy of the nation within the horizon of liberalism today? Surveying three representative, contrasting, recent works in contemporary political philosophy, I argue that the nation loses its status and legitimacy from every side. John Rawls's allegedly status-quo preserving theory in The Law of Peoples (Rawls 1999) defends only the shell of sovereignty and in fact points toward cosmopolitan aspirations. Cosmopolitan liberals, and conservative nationalists, therefore, claim with reason that liberalism is not capable of conferring status and legitimacy on the nation's "arbitrary" restrictions of individual autonomy (Nussbaum and Cohen 1996, MacIntyre 2003). But, in doing so, cosmopolitan liberalism creates a grave problem, for liberalism depends upon citizens to uphold freedom and upon limits to freedom to make freedoms meaningful. One would think to turn toward so-called liberal nationalist theories of liberalism, like David Miller's On Nationality (Miller 1995). But these, in turn, defend the nation only by depleting it of any content and rendering the very concept of the nation hollow. Neither of these two possible corrections of liberalism solves its problems with particularity and social unity; each only exacerbates them. My work as a whole therefore shows that contemporary liberalism tends to undermine the nation, on which it nevertheless relies. I demonstrate each part of the argument in separate chapters: two on Rawls's liberalism, one on Nussbaum's cosmopolitanism, and two on David Miller's liberal nationalism. These three perspectives represent a fairly complete spectrum of contemporary liberal thinking about the status of the nation.
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Title: Weighting in multilevel models
Creator: Tong, Bing
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Large-scale survey programs usually use complex sampling designs such as unequal probabilities of selection, stratifications, and/or clustering to collect data to save time and money. This leads to the necessity to incorporate sampling weights into multilevel models in order to obtain accurate estimates and valid inferences. However, the weighted multilevel estimators have been lately developed and minimal guidance is left on how to use sampling weights in multilevel models and which...
Show moreLarge-scale survey programs usually use complex sampling designs such as unequal probabilities of selection, stratifications, and/or clustering to collect data to save time and money. This leads to the necessity to incorporate sampling weights into multilevel models in order to obtain accurate estimates and valid inferences. However, the weighted multilevel estimators have been lately developed and minimal guidance is left on how to use sampling weights in multilevel models and which estimator is most appropriate.The goal of this study is to examine the performance of multilevel pseudo maximum likelihood (MPML) estimation methods using different scaling techniques under the informative and non-informative condition in the context of a two-stage sampling design with unequal probabilities of selection. Monte Carlo simulation methods are used to evaluate the impact of three factors, including informativeness of the sampling design, intraclass correlation coefficient (ICC), and estimation methods. Simulation results indicate that including sampling weights in the model still produce biased estimates for the school-level variance. In general, the weighted methods outperform the unweighted method in estimating intercept and student-level variance while the unweighted method outperforms the weighted methods for school-level variance estimation in the informative condition. In general, the cluster scaling estimation method is recommended in the informative sampling design. Under the non-informative condition, the unweighted method can be considered a better choice than the weighted methods for all the parameter estimates. Besides, the ICC has obvious effects on school-level variance estimates in the informative condition, but in the noninformative condition, it also affects intercept estimates. An empirical study is included to illustrate the model.
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Title: I. amhb : (anti)aromaticity-modulated hydrogen bonding. ii. evaluation of implicit solvation models for predicting hydrogen bond free energies
Creator: Kakeshpour, Tayeb
Date: 2019
Collection: Electronic Theses & Dissertations
Description: My doctoral research under Professor James E. Jackson focused on hydrogen bonding (H-bonding) using physical organic chemistry tools. In the first chapter, I present how I used quantum chemical simulations, synthetic organic chemistry, NMR spectroscopy, and X-ray crystallography to provide robust theoretical and experimental evidence for an interplay between (anti)aromaticity and H-bond strength of heterocycles, a concept that we dubbed (Anti)aromaticity-Modulated Hydrogen Bonding (AMHB). In...
Show moreMy doctoral research under Professor James E. Jackson focused on hydrogen bonding (H-bonding) using physical organic chemistry tools. In the first chapter, I present how I used quantum chemical simulations, synthetic organic chemistry, NMR spectroscopy, and X-ray crystallography to provide robust theoretical and experimental evidence for an interplay between (anti)aromaticity and H-bond strength of heterocycles, a concept that we dubbed (Anti)aromaticity-Modulated Hydrogen Bonding (AMHB). In the second chapter, I used accurately measured hydrogen bond energies for a range of substrates and solvents to evaluate the performance of implicit solvation models in combination with density functional methods for predicting solution phase hydrogen bond energies. This benchmark study provides useful guidelines for a priori modeling of hydrogen bonding-based designs.Coordinates of the optimized geometries and crystal structures are provided as supplementary materials.
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Title: Multi-scale approaches to global challenges in a telecoupled world
Creator: Xu, Zhenci
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Global challenges such as water crisis, energy insecurity, biodiversity loss, land use change and climate change pose threats to the world's sustainability. Globalization enhances the connection of distant areas through various environmental and socioeconomic interactions. To solve the increasing challenges of achieving global sustainability in the context of globalization, the new telecoupling framework (socioeconomic and environmental interactions over distances) is proposed (Liu et al....
Show moreGlobal challenges such as water crisis, energy insecurity, biodiversity loss, land use change and climate change pose threats to the world's sustainability. Globalization enhances the connection of distant areas through various environmental and socioeconomic interactions. To solve the increasing challenges of achieving global sustainability in the context of globalization, the new telecoupling framework (socioeconomic and environmental interactions over distances) is proposed (Liu et al. 2013). A growing body of research has been exploring the dynamics, impacts, mechanisms, and structure of distant interactions involving global challenges. However, based on the telecoupling framework, we find no research that studies the evolution of multiple global environmental and socioeconomic interaction networks together. Also, the interactions between two kinds of distant virtual resource transfers simultaneously and the drivers of virtual resource transfers at the national scale are still unknown. Little research explores the evolution of virtual resource transfers at a national scale. The impacts of distant interactions on sending systems' sustainability at the regional scale has rarely been quantified and systematically analyzed. To address these knowledge gaps, I did the following work: First, I assessed the evolution of global telecouplings such as water, energy, land, CO2 emission, nitrogen emission and financial capital transfer networks and discussed how they have impacts on global water scarcity, energy crisis, land use change, global warming and nitrogen pollution. Second, I evaluated the interactions across two kinds of national telecouplings (interregional water and energy networks), and discussed their implications for the trading region's water scarcity and energy security, and explore the drivers of national telecouplings. Third, I studied the evolution of national virtual energy network. Fourth, I explored the water and food sustainability in a sending system of telecoupling (food transfer aimed at ensuring food security in the receiving system) at the regional scale. These four works have been accomplished in four chapters, respectively.Main findings from this dissertation include: At the global scale, the volumes of all these flows, except for land flow, increased over time. Financial capital flows increased most (188.9%), followed by flows of CO2 (59.3%), energy (58.1%), water (50.7%) and nitrogen (10.5%), while land transfer decreased by 8.8%. At the national scale using China as a demonstration, 40% of provinces gained one kind of resource (either water or energy) through trade at the expense of losing the other kind of internal resource (energy or water), and 20% of provinces suffered a double loss of both water and energy. The remaining provinces gained both water and energy. Over time, the total virtual energy transferred from energy-scarce to energy-abundant provinces increased from 43.2% to 47.5% from 2007 to 2012. At a regional scale, irrigated agriculture's annual water footprint in the North China Plain increased from 53 billion m3 in 1986 to 78 billion m3 in 2010. All counties faced unsustainable water use - local water consumption was greater than local renewable freshwater - even as the average crop water productivity increased from 0.90 kg.m-3 to 1.94 kg.m-3. These findings provide useful information for policy making to address environmental and socioeconomic challenges and build distant cooperation across multiple scales.
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Title: On superconvergent discontinuous Galerkin methods for Schrödinger equations and sparse grid central discontinuous Galerkin method
Creator: Chen, Anqi
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "In this thesis, we design and analyze a discontinuous Galerkin (DG) method for one-dimensional Schrodinger equations under a general class of numerical fluxes, and another efficient DG method for high-dimensional hyperbolic equations.In the first DG method, we develop an ultra-weak discontinuous Galerkin (UWDG) method to solve the one-dimensional nonlinear Schrödinger equation. Stability conditions and error estimates are derived for the scheme with a general class of numerical fluxes. The...
Show more"In this thesis, we design and analyze a discontinuous Galerkin (DG) method for one-dimensional Schrodinger equations under a general class of numerical fluxes, and another efficient DG method for high-dimensional hyperbolic equations.In the first DG method, we develop an ultra-weak discontinuous Galerkin (UWDG) method to solve the one-dimensional nonlinear Schrödinger equation. Stability conditions and error estimates are derived for the scheme with a general class of numerical fluxes. The error estimates are based on detailed analysis of the projection operator associated with each individual flux choice. Depending on the parameters, we find out that in some cases, the projection can be defined element-wise, facilitating analysis. In most cases, the projection is global, and its analysis depends on the resulting 2 x 2 block-circulant matrix structures. For a large class of parameter choices, optimal a priori L2 error estimates can be obtained. Numerical examples are provided verifying theoretical results.In addition to the stability and error analysis, we analyze the superconvergence properties of the UWDG method for one-dimensional linear Schrodinger equation with various choices of flux parameters. Depending on the flux choices and if the polynomial degree k is even or odd, we prove 2k or (2k - 1)-th order superconvergence rate for cell averages and numerical flux of the function, as well as (2k - 1) or (2k - 2)-th order for numerical flux of the derivative. In addition, we prove superconvergence of (k + 2) or (k + 3)-th order of the UWDG solution towards a special projection. At a class of special points, the function values and the first and second order derivatives of the UWDG solution are superconvergent with order k + 2, k + 1, k, respectively. The proof relies on the correction function techniques initiated in Cao, et. al. (2014), and applied to Cao, et. al. (2017) for direct DG (DDG) methods for diffusion problems. By negative norm estimates, we apply the post processing technique and show that the accuracy of our scheme can be enhanced to order 2k. Theoretical results are verified by numerical experiments.In the second DG method, we develop sparse grid central discontinuous Galerkin (CDG) scheme for linear hyperbolic systems with variable coefficients in high dimensions. The scheme combines the CDG framework with the sparse grid approach, with the aim of breaking the curse of dimensionality. A new hierarchical representation of piecewise polynomials on the dual mesh is introduced and analyzed, resulting in a sparse finite element space that can be used for non-periodic problems. Theoretical results, such as L2 stability and error estimates are obtained for scalar problems. CFL conditions are studied numerically comparing discontinuous Galerkin (DG), CDG, sparse grid DG and sparse grid CDG methods. Numerical results including scalar linear equations, acoustic and elastic waves are provided."--Pages ii-iii.
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Title: Solidarity, safety, and online sovereignty : an inquiry into the social media sharing practices of indigenous and chicana women
Creator: Hutchinson, Leslie A.
Date: 2019
Collection: Electronic Theses & Dissertations
Description: This dissertation contains a cultural, digital rhetorics inquiry into the social media sharing practices of Indigenous and Chicana women. Working alongside three women from her local community, I investigated how these women navigate concerns about online safety, intellectual property, and surveillance. To conduct my study, I integrated cultural rhetorics research methods into my research design, which informed how I collected data through hosting a talking circle and conducting follow-up...
Show moreThis dissertation contains a cultural, digital rhetorics inquiry into the social media sharing practices of Indigenous and Chicana women. Working alongside three women from her local community, I investigated how these women navigate concerns about online safety, intellectual property, and surveillance. To conduct my study, I integrated cultural rhetorics research methods into my research design, which informed how I collected data through hosting a talking circle and conducting follow-up interviews. Then, using grounded theory to analyze my data, I found that: 1) though these women experience various social oppressions within social media spaces, they find and create community to collectively act in resistance; and 2) the acts of resistance in which these women engage expand scholarly understandings of how social media platforms are designed to asymmetrically oppress users from marginalized backgrounds. Together, these findings dispel the myth that women-and particularly women of color-have had no stake in the development of online platforms. I argue, rather, that despite how these platforms are designed, women of color critically enact cultural sovereignty in online spaces through asserting their identities, fighting for political rights, and creating community in acts of not only resistance, but survivance.
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Title: Optogenetic analysis of excitatory and inhibitory neurotransmission in the enteric nervous system
Creator: Perez-Medina, Alberto L.
Date: 2019
Collection: Electronic Theses & Dissertations
Description: The enteric nervous system (ENS) is embedded within the gastrointestinal (GI) tract and controls GI function. Impaired ENS function leads to altered patterns of motility and secretion, causing GI disease. For instance, functional gastrointestinal disorders (FGID) are caused by poorly understood alterations in the structure and function of nerves, smooth muscle cells (SMC), and other cell types in the GI tract. It is estimated that these disorders comprise about 41% of the total GI...
Show moreThe enteric nervous system (ENS) is embedded within the gastrointestinal (GI) tract and controls GI function. Impaired ENS function leads to altered patterns of motility and secretion, causing GI disease. For instance, functional gastrointestinal disorders (FGID) are caused by poorly understood alterations in the structure and function of nerves, smooth muscle cells (SMC), and other cell types in the GI tract. It is estimated that these disorders comprise about 41% of the total GI complications in the United States. Also, altered patterns of motility that occur in the GI muscles is a hallmark characteristic of FGIDs. Although the ENS is fairly understood, further elucidation of the enteric circuitry that governs GI motility would help to understand the pathophysiology of FGID. For that reason, identifying the contributions of classes of enteric neurons that control GI motility and secretion could aid in the identification of novel therapeutic targets for the treatment of FGIDs. A widely used method to study neural control of GI motility is sharp-electrode electrophysiological recordings from the smooth muscle or enteric neurons. Conventional, intracellular electrophysiological recordings have relied on electrical stimulation of enteric neurons which will activate all neurons in an ex vivo preparation of the ENS, and does not allow cell-specific activation of individual subpopulations of myenteric neurons. To overcome this problem, we used immunohistochemical methods to identify subpopulations of myenteric neurons and the optogenetically activated protein channelrhodopsin-2 (ChR2) that can be selectively expressed in subsets of enteric neurons. In Chapter 3, immunohistochemical studies of the mouse enteric nervous system are performed using the purinergic neuronal marker, vesicular nucleotide transporter (VNUT) along with markers for specific subsets of myenteric neurons and nerve fibers (e.g., neuronal nitric oxide synthase, choline acetyltransferase, calretinin, calbindin, and tyrosine hydroxylase),. Chapter 4 compares electrical and optogenetic electrophysiology recordings from myenteric neurons of mice that express ChR2 in nNOS neurons. The studies described in Chapter 5 use ChAT-ChR2-YFP-BAC transgenic mice which have eYFP tagged ChR2 expressed in cholinergic neurons. Optogenetics was used to isolate the cholinergic component of the ENS. The findings discussed in this dissertation provides evidence of a more sophisticated enteric circuitry of GI motility. (1) Purinergic neurons are likely a separate subpopulation of enteric neurons. VNUT is only expressed in the form of punctate varicosities at the nerve fibers and is not endogenously expressed in the soma of enteric neurons. VNUT also does not appear to colocalize with other neuronal immunoreactive markers within the myenteric plexus (mp), the tertiary plexus (tp), or circular smooth muscle layer of all tested tissue preps. (2) BLS of ChR2 expressed in nNOS neurons induced a purinergic/nitrergic biphasic IJP, suggesting that nNOS IMNs co-releases a purine as a neurotransmitter. Ectopic expression of ChR2 in non-nNOS neurons, however, could explain the biphasic IJP responses during electrophysiology recordings. Hence, the existence of separate subset populations of IMN populations (e.g., nNOS only and purinergic only IMNs) can't be ruled out. (3) BLS of ChR2 expressed in ChAT positive neurons induced EJPs and IJP responses. Inhibition of the nicotinic ACh receptor (nAChR) with mecamylamine significantly reduced the light-evoked IJP. Bath application of the purinergic P2Y1 antagonist, MRS 2179, was sufficient to abolish the IJP response, while the muscarinic ACh receptor antagonist, Scopolamine, abolished the EJP response. The data suggest that BLS of ChR2 activates cholinergic EMNs and cholinergic interneurons, and that activation of the cholinergic interneurons activates purinergic only IMNs that supply the smooth muscle, resulting in a predominant purinergic only IJP. Taken together, this work provides evidence for a diverse and more complex enteric neural circuit of GI motility. Future experiments should, however, focus on studying these enteric circuits at the level of the neuron, as these studies can provide a more in-depth analysis of the enteric circuitry.
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Title: Integrated pest management strategies for control of potato early die in Michigan potato systems
Creator: Cole, Emilie
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Root lesion nematodes (Pratylenchus penetrans) in conjunction with the fungal pathogen Verticillium dahliae create the disease complex, potato early die, which can drastically reduce potato (Solanum tuberosum L.) yields. In Michigan, this disease complex is often managed using broad-spectrum soil fumigants such as methyl bromide, metam sodium and 1,3- dichloropropene, which can be harmful to applicators as well as soil and environmental health. Since the phase-out of methyl bromide in 2005,...
Show moreRoot lesion nematodes (Pratylenchus penetrans) in conjunction with the fungal pathogen Verticillium dahliae create the disease complex, potato early die, which can drastically reduce potato (Solanum tuberosum L.) yields. In Michigan, this disease complex is often managed using broad-spectrum soil fumigants such as methyl bromide, metam sodium and 1,3- dichloropropene, which can be harmful to applicators as well as soil and environmental health. Since the phase-out of methyl bromide in 2005, alternative control tactics to soil fumigants have become increasingly important to potato growers. In this thesis I investigated the use of (1) manures and manure-based composts and (2) non-fumigant nematicides and fungal-based biocontrols and their efficacy in reducing potato early die incidence. In laboratory trials, poultry manure and a blend of poultry and dairy manure compost (Layer Ash Blend) provided significant control of root lesion nematodes with 0% survivorship at rates of 5% (vol/vol) or higher. In field trials, I did not observe significant (P < 0.05) reductions in nematode populations regardless of treatment but did see a reduction in germinating V. dahliae microsclerotia in plots treated with poultry manure. Of the nematicides tested, Salibro treatments significantly reduced root lesion nematode and V. dahliae populations. From this research, it is clear that non-fumigant alternatives are possible for Michigan potato growers.
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Title: Ecology and diversity of the lichen symbiosis : following established patterns, or an exception to the rule?
Creator: Scharnagl, Klara
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Few phenomena of biodiversity have perplexed researchers as much as the latitudinal diversity gradient. Though many taxa have been shown to follow this pattern of high species richness in the tropics and lower species richness towards the poles, no consensus has yet been reached regarding the drivers of this global pattern. Symbiosis, a long term and physically intimate interaction between two organisms, is a prevalent biotic interaction across the tree of life, yet few studies of the...
Show moreFew phenomena of biodiversity have perplexed researchers as much as the latitudinal diversity gradient. Though many taxa have been shown to follow this pattern of high species richness in the tropics and lower species richness towards the poles, no consensus has yet been reached regarding the drivers of this global pattern. Symbiosis, a long term and physically intimate interaction between two organisms, is a prevalent biotic interaction across the tree of life, yet few studies of the latitudinal diversity gradient have looked at symbiotic organisms. One example of symbiosis is the lichen symbiosis, an association between a filamentous fungal partner and a photosynthetic partner of green algae or cyanobacteria. Little is known about the latitudinal diversity gradient of lichens, yet their terrestrial ubiquity and symbiotic nature could provide insight into the drivers of this global pattern. To assess whether lichenized fungi follow a latitudinal diversity gradient, I compiled a dataset from three repositories for digitized herbarium specimen data: the Consortium for North American Lichen Herbaria, the Global Biodiversity Information Facility, and the Institutos Nacionais de Ciencia e Tecnologia. The fully compiled and quality-controlled dataset contained over 900,000 datapoints representing over 8,000 species. The raw species richness data revealed a peak in richness north of the equator outside of the tropics, however, this pattern mirrored the number of collections per latitudinal band. To correct for sampling effort biases in the digitized herbarium data, I rarefied species richness. I further corrected the rarefied species richness for land area, given the wide range of land area per latitudinal band in the Americas. This rarefied and land-area-corrected species richness data supports a latitudinal diversity gradient of lichenized fungi in the Americas. In a comparison to lichen checklist data at the country or state level, I revealed that tropical regions are underrepresented in the digitized herbarium data.To test the influence of sampling effort bias on the patterns revealed by the digitized herbarium data, I designed a field sampling approach directly targeted at the question of whether epiphytic lichens follow a latitudinal diversity gradient. This approach can help remove bias present in digitized herbarium data because they result from the compilation of many studies, each of which had its own taxonomic, regional, or ecological focus. To do so, I sampled from nine lowland forest sites across a 70-degree span of latitude in the Americas. At each site, I randomly chose ten plots, and sampled from ten trees within each plot for a total of nine hundred trees sampled. At each tree, I randomly chose a cardinal direction and placed a 20x40cm grid on the tree, collecting all lichens that fell within that grid. Thus, each site had the same amount of area surveyed for epiphytic lichen diversity. Lichens were identified to species in the lab. Data from systematic field sampling corroborate the latitudinal diversity gradient of (epiphytic) lichens. In a mixed effects model including tree and climate data, I found that this pattern is largely explained by host tree (substrate) diversity.With increasing land use change and impacts from climate change across the globe, it is increasingly important for us to set a baseline of patterns of diversity at large scales, as I did in my first two chapters, to then assess how these impacts are affecting the diversity of symbiotic organisms at different scales. For my third chapter, I applied my knowledge of lichen diversity to assess the impacts of three tropical forest restoration treatments on epiphytic lichens. The natural regeneration treatment had a small cohort of lichen species likely specialized to the high light and dry environment. The plantation and nucleation treatments had a mix of light and shade tolerant species and experienced higher competition from epiphytic bryophytes. The overall highest diversity of epiphytic lichens was found in the nucleation treatment, supporting this as the combination of the most cost-effective strategy that restores the greatest amount of tropical biodiversity.
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Title: Dynamic network analysis with applications to functional neural connectivity
Creator: Golibagh Mahyari, Arash
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Contemporary neuroimaging techniques provide neural activity recordings with increasing spatial and temporal resolution yielding rich multichannel datasets that can be exploited for detailed description of anatomical and functional connectivity patterns in the brain. Studies indicate that the changes in functional connectivity patterns across spatial and temporal scales play an important role in a wide range of cognitive and executive processes such as memory and attention as well as in the...
Show more"Contemporary neuroimaging techniques provide neural activity recordings with increasing spatial and temporal resolution yielding rich multichannel datasets that can be exploited for detailed description of anatomical and functional connectivity patterns in the brain. Studies indicate that the changes in functional connectivity patterns across spatial and temporal scales play an important role in a wide range of cognitive and executive processes such as memory and attention as well as in the understanding the causes of many neural diseases and psychopathologies such as epilepsy, Alzheimers, Parkinsons and schizophrenia. Early work in the area was limited to the analysis of static brain networks obtained through averaging long-term functional connectivity, thus neglecting possible time-varying connections. There is growing evidence that functional networks dynamically reorganize and coordinate on millisecond scale for the execution of mental processes. Functional networks consist of distinct network states, where each state is defined as a period of time during which the network topology is quasi-stationary. For this reason, there has been an interest in characterizing the dynamics of functional networks using high temporal resolution electroencephalogram recordings. In this thesis, dynamic functional connectivity networks are represented by multiway arrays, tensors, which are able to capture the complete topological structure of the networks. This thesis proposes new methods for both tracking the changes in these dynamic networks and characterizing or summarizing the network states. In order to achieve this goal, a Tucker decomposition based approach is introduced for detecting the change points for task-based electroencephalogram (EEG) functional connectivity networks through calculating the subspace distance between consecutive time steps. This is followed by a tensor-matrix projection based approach for summarizing multiple networks within a time interval. Tensor based summarization approaches do not necessarily result in sparse network and succinct states. Moreover, subspace based summarizations tend to capture the background brain activity more than the low energy sparse activations. For this reason, we propose utilizing the sparse common component and innovations (SCCI) model which simultaneously finds the sparse common component of multiple signals. However, as the number of signals in the model increases, this becomes computationally prohibitive. In this thesis, a hierarchical algorithm to recover the common component in the SCCI model is proposed for large number of signals. The hierarchical recovery of SCCI model solves the time and memory limitations at the expense of a slight decrease in the accuracy. This hierarchical model is used to separate the common and innovation components of functional connectivity networks across time. The innovation components are tracked over time to detect the change points, and the common component of the detected network states are used to obtain the network summarization. SCCI recovery algorithm finds the sparse representation of the common and innovation components of signals with respect to pre-determined dictionaries. However, input signals are not always well-represented by pre-determined dictionaries. In this thesis, a structured dictionary learning algorithm for SCCI model is developed. The proposed method is applied to EEG data collected during a study of error monitoring where two different types of brain responses are elicited in response to the stimulus. The learned dictionaries can discriminate between the response types and extract the error-related potentials (ERP) corresponding to the two responses."--Pages ii-iii.
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Title: MULTI SCALE SIMULATIONS FOR EFFICIENT MULTI-STEP REACTION CASCADES
Creator: Chavan, Kanchan Suklal
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Efficient multi-step reaction cascades are vital for the pharmaceutical industry and electrochemical devices. Conventionally, one-pot synthesis has been used to carry out such multi-step reaction cascades, which have poor selectivity and yield due to lack of control over the transport of chemical species and kinetics in the system. Therefore, it is desirable to engineer an integrated catalytic system with highly selective catalysts and efficient transport mechanisms.Nature has developed...
Show moreEfficient multi-step reaction cascades are vital for the pharmaceutical industry and electrochemical devices. Conventionally, one-pot synthesis has been used to carry out such multi-step reaction cascades, which have poor selectivity and yield due to lack of control over the transport of chemical species and kinetics in the system. Therefore, it is desirable to engineer an integrated catalytic system with highly selective catalysts and efficient transport mechanisms.Nature has developed highly efficient transport mechanisms via strategic architectures that use electrostatic interactions, physical confinement, and swing arm techniques to reduce diffusional losses. Such controlled transport is known as ‘substrate channeling’. These natural mechanisms provide essential clues to design novel catalytic platforms. The physical confinement of an intermediate pathway has the potential for 100% intermediate transport. This provides motivation to study the transport in nanoscale confinement. Maximum intermediate retention with minimum bulk access is a key to obtain maximum channeling efficiency. In this work, we study the effect of nanoscale confinement using continuum modeling and molecular dynamics approaches. Continuum modeling of tunnel structures that have active sites confined within shows that increasing confined distance between active site and bulk improves product yield significantly in a kinetically limited system. Molecular dynamics study of interactions between intermediate and tunnel geometry demonstrates that Knudsen diffusion lowers the effective diffusivity of the intermediate. The orientation of solvent molecules inside the tunnel plays a major role in enhancing Knudsen diffusion inside the tunnel. Finally, to increase the intermediate retention, charged molecules may be introduced at the tunnel ends, and retention is highly sensitive to the polarity of the intermediates. Further, we studied existing integrated catalytic platforms for carbon dioxide reduction reaction (CO2RR) and glycerol oxidation reaction cascades. Microkinetic modeling of CO2RR combined with the density functional theory (DFT) technique demonstrates that CO2RR dominates at lower potential with a high surface coverage of carboxylate, a stable intermediate. Nudged elastic band theory calculations of transition states were used to define the transition state of each step of the reaction. A one-dimensional continuum model study of the glycerol oxidation cascade reveals the sensitivity of convective forces in the system on the intermediate transport. Overall, in this work, various aspects of transport and kinetics of the multi-step reaction cascades were studied computationally. This work acts as a primary guide to design novel integrated catalytic platforms for efficient multi-step reaction cascades
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Title: ANALYSIS OF ERWINIA AMYLOVORA POPULATION DYNAMICS AT FLOWER BLOOM AND FURTHER SYSTEMIC MOVEMENT OF THE PATHOGEN THROUGH HOST TISSUE
Creator: Slack, Suzanne M.
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Population dynamics of Erwinia amylovora have been utilized for many applications over the past 50 years. In this work, populations were tracked over the course of apple bloom under naturally occurring environmental conditions. Flower stigmas inoculated on the 1st day of being open can harbor large (107) populations after 3 or 5 days post inoculation, with 100-fold increases in E. amylovora stigma populations observed in atmospheric conditions with daily average temperatures near 14oC. These...
Show morePopulation dynamics of Erwinia amylovora have been utilized for many applications over the past 50 years. In this work, populations were tracked over the course of apple bloom under naturally occurring environmental conditions. Flower stigmas inoculated on the 1st day of being open can harbor large (107) populations after 3 or 5 days post inoculation, with 100-fold increases in E. amylovora stigma populations observed in atmospheric conditions with daily average temperatures near 14oC. These large 100-fold increases seem to occur at night, indicating that Erwinia amylovora is able to infect flowers in colder field temperatures than previously reported. In tandem, timing of antibiotic application relative to E. amylovora presence on flower stigmas had little impact on population dynamics, with streptomycin and kasugamycin consistently reducing populations while oxytetracycline was more variable. This study also led to the identification that Kasumin is prone to photodegradation. Culturable bacteria, yeast, and fungal populations were assessed over the course of bloom in relation to application of a biological control agent yeast (Aureobasidium pullulans) and a contact sterilant. Though populations fell rapidly directly after application, by 24 hours all populations returned to pre-spray levels. In regards to further systemic spread, a type three secretion system effector was indicted in blocking the abscission of infected flowers. The use of prohexadione calcium (Pro-ca) and acibenzolar-S-methyl (ASM) reduced internal E. amylovora spread in a seemingly synergistic manner on young trees, with rates of 28.3 g Pro-Ca + 28.3 g ASM or 56.6 g Pro-Ca + 28.3 g ASM. The sum of this work gives us a better understanding of E. amylovora population dynamics in field conditions as well as the population response to current treatment options.
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Title: Some observations on the flow of water
Creator: Ellis, George H.
Date: 1912
Collection: Electronic Theses & Dissertations

Title: The ones who need the most : race, ability, and restorative justice in an urban school
Creator: Presberry, Cierra Brittney
Date: 2020
Collection: Electronic Theses & Dissertations
Description: This dissertation examines how the intersection of race and ability impact an urban school's implementation of restorative justice. Because restorative justice can ideally be used in any setting with any group of people, its generalization often overlooks exceptionally vulnerable or traditionally silenced populations. As such, using Critical Race Theory and related frameworks such as Dis/ability Critical Race Studies and Critical Race Parenting, this work specifically highlights how Black...
Show moreThis dissertation examines how the intersection of race and ability impact an urban school's implementation of restorative justice. Because restorative justice can ideally be used in any setting with any group of people, its generalization often overlooks exceptionally vulnerable or traditionally silenced populations. As such, using Critical Race Theory and related frameworks such as Dis/ability Critical Race Studies and Critical Race Parenting, this work specifically highlights how Black students with disabilities, their teachers, and their parents are impacted by, and engaged with restorative justice at school. This dissertation is written in the form of three papers. In paper one, I conduct an interview study in order to examine insights from special education teachers about their role in using restorative justice and how it impacts their students, particularly in terms of how race and ability are pivotal factors. In paper two, I conceptualize restorative justice literacies. This entails an examination of how reading, writing, and speaking play a role in how marginalized populations are able to understand and participate in restorative justice practices. This research took place in the form of case study, with student observation, interviews, and document analysis being primary sources of data. Finally, in paper three, I analyze the perspectives of the parents of students from paper three regarding their engagement with restorative justice. Findings from my research highlight aspects of the experiences and needs of students with disabilities that have yet to be addressed within literature on restorative justice, and has positive implications for the ways that school communities can better understand and accommodate students with disabilities within both general and special education settings.
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Title: Impacts of changing precipitation on nitrogen cycling in different landscape positions and cropping systems
Creator: Glanville, Kathryn
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Soil nitrogen (N) influences crop yields and can interact with climate change. Soil N has many transformations and transfers that are hard to quantify and control. These N transformations and transfers are mediated by many factors, including temperature, water, and carbon. Thus, impending climate change may strongly affect N cycling across cropping systems. To minimize N losses and increase crop production, we must maximize N use efficiency (NUE). Past research shows precipitation and soil...
Show moreSoil nitrogen (N) influences crop yields and can interact with climate change. Soil N has many transformations and transfers that are hard to quantify and control. These N transformations and transfers are mediated by many factors, including temperature, water, and carbon. Thus, impending climate change may strongly affect N cycling across cropping systems. To minimize N losses and increase crop production, we must maximize N use efficiency (NUE). Past research shows precipitation and soil moisture act as the primary physical drivers of terrestrial N cycling and losses. To improve NUE with changing precipitation patterns, controls on N cycling in terrestrial systems must be identified. Thus, experiments to elucidate the linkage between hydrological and biogeochemical controls are valuable (Chapter 1). Many aspects of the N cycle are influenced by a changing climate - two are especially important: nitrous oxide fluxes (N2O) and biological nitrogen fixation (BNF). N2O is a powerful greenhouse gas with over 250 times the radiative forcing of CO2. In Chapter 2, I test the hypothesis that changing rainfall patterns strongly alter N2O fluxes in agricultural soils as modulated by cropping system. I use rainfall manipulation shelters to expose soils to the same amount of rainfall delivered at different intervals (3-days, 14-days, and 28-days). Results from the 2016 and 2017 field seasons show cumulative N2O fluxes were 1.4 to 2 times higher when rainfall occurred in 28-day rather than shorter intervals in corn systems. Fluxes were related to changes in denitrifier enzyme activity for both years. In switchgrass systems N2O emissions were not significantly affected by rainfall intervals.In Chapter 3, I test the hypothesis that changing rainfall patterns that alter N2O fluxes will be modulated by landscape position as landscape position affects soil texture and carbon. Over two field seasons cumulative N2O fluxes were higher in toeslope positions than in summit positions, and longer rainfall intervals had higher fluxes in summits only, consistent with higher soil carbon and finer soil texture in toeslope positions. Knowledge of these landscape patterns deserve inclusion in models of current and future climate change effects in order to better quantify and mitigate agricultural N2O fluxes.In Chapter 4, I test the hypothesis that BNF is particularly vulnerable to changing rainfall patterns in till vs. no-till and in summit vs. toeslope positions due to differences in texture and organic matter. Results reinforce the importance of topographic position for predicting soybean BNF and show that summit positions are more sensitive to additional rainfall. Results also show changes in rainfall intensity affect BNF in tilled differently than in no-till soils. Models that incorporate these interactions will be better able to characterize legume crop performance and N fixation across landscapes and improve global estimates for BNF. Understanding these interactions in the agricultural US Midwest may help us improve sustainability of N use in cropping systems with a changing climate.
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