<p>Aquatic macroinvertebrates of channelized headwater streams in agricultural landscapes are exposed to alterations in chemistry and physical characteristics of benthic sediments. These habitat alterations are known to influence communities of aquatic macroinvertebrates. Benthic sediments can have a wide range of impacts and influences on aquatic macroinvertebrates. I hypothesized that sediments would play a significant role in determining macroinvertebrate community structure within agriculturally dominated headwater streams. I evaluated the influences of sediment chemistry characteristics and physical characteristics on aquatic macroinvertebrate communities in Cedar Creek, Indiana and Michigan, and the Upper Big Walnut Creek, Ohio, during 2017 and 2018. Macroinvertebrates were collected twice per year using artificial substrate and leaf pack samplers and identified to the family level. Sediments were sampled two times per year and analyzed for seven physical characteristics and twenty sediment chemistry characteristics. Principle component analyses were used to create axes that are indicators of gradients of sediment chemistry and physical characteristics that occur among the samples. Macroinvertebrate community metrics used in the analyses included abundance, Shannon Diversity Index, Hilsenhoff Biotic Index scores, Invertebrate Community Index scores, percentage of collector-filters, percentage of scrapers, percentage of Chironomidae and a Berger-Parker Reciprocal Index of dominance. Linear Mixed Effect Model analyses revealed that both sediment chemistry and physical characteristics influence macroinvertebrate community metrics. Aquatic macroinvertebrate abundance was negatively correlated with increasing concentrations of simazine and decreasing concentrations of calcium. Percentages of Chironomidae were positively correlated with increasing percentages of sand and decreasing percentages of clay and decreasing diversity of sediment particle sizes. My data supported the hypothesis that benthic sediments play an important role in determining aquatic macroinvertebrate community structure in headwater streams of agriculturally dominated landscapes. Gradients of chemical characteristics containing simazine and calcium were observed to be negatively correlated with macroinvertebrate abundance. Gradients of physical characteristics including percentages of sand and clay along with the diversity of particle sizes were observed to be positively correlated with percentage of chironomids. My research increases the knowledge that benthic sediments, chemically and physically, can lead to alterations in aquatic macroinvertebrate communities within Midwestern headwater streams. </p>

The objective of this research is to investigate the effects of tip clearance on the stage and component performance in a high-speed centrifugal compressor. The experimental data were compared against results from a numerical model to assess the ability of the numerical simulation to predict the effects of tip clearance. Experimental data were collected at Purdue University on the Single Stage Centrifugal Compressor (SSCC), a high-speed, high-pressure ratio test compressor sponsored by Honeywell Aerospace. Numerical simulations were completed using the ANSYS CFX software suite and part of the research computing clusters located at Purdue University.<div><br></div><div>Two tip clearances were tested, the nominal tip clearance and a tip clearance that is 66% larger than the nominal clearance, at speeds from 60% to 100% corrected speed. To compare data points with different tip clearances, various parameters were evaluated, and one was chosen. The value of TPR/inlet corrected mass flow rate best represented similar loading conditions, and thus similar incidences, for each tip clearance and was chosen as the best method for comparing similar data points taken with different clearances. Stage and component performance were focused on the sensitivity of each performance parameter to the changing of the tip clearance. The stage total pressure ratio and stage efficiency showed moderate sensitivity while the stage work factor showed much lower sensitivity. The impeller is more sensitive to changing tip clearances than the stage is, showing greater changes when comparing data from each tip clearance. The diffuser was on the same order of sensitivity as the impeller, with marginally higher sensitivities for some parameters. It was found that by the typical performance metrics, the diffuser performs worse at the nominal clearance than at the larger clearance. Upon further investigation though, the impeller is providing a higher static pressure and therefore, more diffusion, at the nominal clearance so the diffuser must perform less diffusion during nominal clearance operation.<br></div><div><br></div><div>To assess the validity of a prediction of the performance and sensitivity of the stage and components to the tip clearance, a numerical model was developed and validated. The numerical model was able to reasonably predict the stage performance with better comparisons of performance in the impeller and worse in the diffuser. The instrumentation in the experiment was replicated in the software to calculate performance the same way it is calculated experimentally so that the results would be comparable. While the performance of the stage and components was lacking in some areas, the trends predicted were similar to those calculated from the experimental data. As with the performance, the trends in the impeller matched very well between the experiment and the numerical simulation. The trends in stage and diffuser performance were predicted more accurately than the stage and diffuser performance maps and were able to capture the magnitude of the change in performance caused by changing the tip clearance. <br></div>

<p><i>Purpose</i>. Sentence production is impaired in many persons with aphasia (PWA). Structural priming, a speaker’s tendency to re-use a previously heard sentence structure, has been shown to facilitate sentence production in PWA. Man et al. (2019), however, found that PWA showed significant priming only in transitive sentences but not in dative sentences when these two different types of sentences were presented in an alternating manner within a session [Man, G., Meehan, S., Martin, N., Branigan, H., Lee, J. (2019). Effects of Verb Overlap on Structural Priming in Dialogue: Implications for Syntactic Learning in Aphasia. <i>Journal of Speech, Language, and Hearing Research, 62</i>, 1933-1950]. This study sought to examine whether presenting transitive vs. dative stimuli in a blocked format would yield more consistent priming effects in PWA.</p><p><i>Methods. </i>Twelve PWA and twelve healthy older adults (HOA) completed a dialogue-like priming task, where participants took turns describing pictures with the experimenter. Importantly, each participant received two blocks of transitive and dative priming. In addition, we repeated verbs between prime and target items for half of each block to test if lexical overlap boosts priming, i.e., lexical boost. We measured how often the participant re-used the same syntactic structure they heard the experimenter produce previously when they described their own picture. </p><p><i>Results. </i>HOA showed significant priming and lexical boost in the transitive block and significant priming in the dative block, replicating Man et al. (2019). PWA, showed near significant priming in the transitive block. Importantly, the priming effect became significant when the verb was repeated between prime and target, indicating lexical boost. However, PWA failed to show priming in the dative block. </p><p><i>Discussion.</i> Using a blocked stimulus design only modulated lexically-mediated priming in transitives for PWA, different from Man et al. (2019). Findings suggest that while it is feasible to use structural priming to ameliorate sentence production deficits in PWA, the presentation of target stimuli would likely not influence outcomes.</p><p></p><p></p>

<p> Hypersonic boundary-layer transition greatly affects aerodynamic heating, skin friction, aircraft stability and other characteristics on flight vehicles. Understanding the factors leading to laminar-turbulent transition is pivotal in hypersonic aircraft design. Various instabilities and modes may facilitate transition at hypersonic speeds including first and second-mode waves, Görtler vortices, and cross-flow which may be stationary or traveling. The research presented here will focus on investigating traveling cross-flow instabilities on a 7° half-angle cone at 6° angle of attack. The experiments were conducted in the Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) at Purdue University. The low freestream noise of the quiet tunnel facility made it ideal for studying boundary layer transition due to its more, ”flight like” environment when compared to traditional tunnel environments. Previous experiments by Ryan Henderson, Chris Ward, and Joshua Edelman focused on studying the cross-flow instability on right circular cones at angle of attack (AoA) in the BAM6QT. From these experiments it was decided that a means for taking off-surface pressure measurements on a cone was needed. This work sets out to create a micro-pitot traverse system capable of doing such. The system is able to measure pressure fluctuations within the boundary layer of cone models at precise axial, azimuthal and wall-normal locations. The design for the traverse was based off a traverse used at Notre Dame which was designed by David Cavalieri in his PhD dissertation for Illinois Institute of Technology. Micro-pitot probes created using hypodermic tubing and Kulite sensors were created to attach to the end of the traverse and take pressure measurements. The micro-pitot probes were placed such that they formed two distinct spatial pairs capable of measuring both the phase speed and propagation angle of traveling cross-flow instabilities using the difference in time of arrival of the traveling instability between the sensor pairs. The micro-pitot probes developed were made from telescoped hypodermic tubes housing Kulite XCE-061-15A sensors. The telescoped tubing assembly caused attenuation at higher frequencies affecting the micro-pitot probes ability to measure pressure fluctuations at higher frequencies. It was necessary to increase the dynamic performance of the micro-pitot probes in order to capture the cross-flow instability. To accomplish this a custom built frequency 17 compensator was designed to correct for this attenuation. The process for designing the compensator utilized a Mach 4 supersonic jet system (SSJ) to estimate a transfer function model for the tubing assembly. This was done by comparing the spectral content of an untubed Kulite sensor and a micro-pitot sensor in the SSJ. The transfer function model was then used to develop the compensator improving measurements made with the micro-pitot up to 50 kHz. The micro-pitot traverse system was then used in a series of tests in the BAM6QT to validate its ability to function as designed. The traverse needed to provide a rigid platform for the micro-pitot probes during tunnel operation. The deflection of the pitot head was recorded using a shadowgraph system. This allowed real time measurements for the deflection of the pitot head during tunnel operation to be taken. These measurements were compared to theoretical calculations to ensure deflections were within acceptable limits. Also, of key importance was the survivability of the traverse system after repeated runs in the BAM6QT. This focused on the ability of the traverse to continue providing movement in all three-directions and its ability to resist wear in the tunnel environment. The only cause for concern noted over the course of three tunnel entries centered around the motor used for wall-normal movement. This motor suffered repeated damage impairing the traverses ability to function as intended. Observations regarding this issue and solutions implemented to mitigate the impact of this damage are discussed. Finally, the micro-pitot was combined with the traverse system and used in conjunction with surface mounted sensors on a axisymmetric cone to measure traveling cross-flow instabilities. Damage to Kulites needed for the micro-pitot prohibited three sensors from being used in the tunnel. For this reason only propagation angles and phase speed calculations for traveling cross-flow waves were calculated using the surface mounted sensors. However, one micro-pitot sensor was used to measure spectral content near the surface mounted sensors. The spectral content of the micro-pitot was compared to the surface mounted sensors in order to validate that the micro-pitot could measure the desired instability once more are acquired </p>

Studies of mechanics and deformation in metal cutting operations have been largely limited to steady-state processes assuming constant forces and shear strain of cutting. However, ‘transient’ or varying deformation conditions are frequently encountered in manufacturing processes, when one or more processing parameters vary during the progress of the cut. Such conditions impose a lower overall strain on the resulting chip and affect the cutting forces and energies. In this study, the transient deformation characteristics are studied through the analysis of chip attributes (hardness and shape change) in a periodic cutting technique, Modulation Assisted Machining (MAM). In MAM, a sinusoidal modulation is superimposed on the tool feed, resulting in periodic engagement between the tool and workpiece. Deformation is confined to a specific volume of material and is also transient due to varying local conditions, manifesting an inhomogeneous and lower shear strain compared to steady-state cutting. A wide variety of deformation conditions from near steady-state to completely transient was achieved through the control of modulation frequency, which determines the contact length in each cutting cycle. Particles produced at lower frequencies exhibit increased hardness, consistent with the deformation more approaching steady state. Micro-indentation tests performed on each particle tracked the local variations in hardness along the length of cut, which agreed well with the non-uniform shape change observed on the cross-section of the particles. Microstructural examination of the chips made with and without modulation helped further describe the different deformation modes acting under periodic and continuous cutting conditions. MAM is also a valuable technique for metal powder processing. Individual chip particles are produced during each modulation cycle with controllable shape and size, and composition identical to that of the workpiece. Advantages of the process include a significant reduction in the specific energy of production, zero compositional variance and a tight distribution of particle sizes compared to atomization. Implications of scaling up the process for large-scale production and the possible applications of the metal particles made with MAM are highlighted.

<div>The atomization of jets and droplets undergoing breakup in high-speed flows has been experimentally measured and theoretically modeled. Systems for producing individual droplet breakup and full jet breakup were designed, and a wide range of diagnostics were developed and adapted to measure the results with reduced uncertainty.</div><div><br></div><div>A detailed methodology for investigating high-speed sprays in the Purdue Experimental Turbine Aerothermal Lab is presented. Optical diagnostic techniques were carefully selected and optimized for the test section geometries and flow features, such that images could be collected at high frequencies of 20 kHz with high resolutions. Developed image processing routines are outlined to demonstrate how backlit imaging with specialized lenses allowed for more accurate spray depth measurements in supersonic conditions, which were then used in regression modeling routines to derive empirical correlations that factored in test section geometry, flow conditions, and injector design. A Mie scattering imaging technique was used for quantitative analysis of the supersonic spray plume profile and measurement of the spray width. 20 kHz shadowgraphy provided sufficient gradients for analysis of the unsteadiness of the spray and surrounding supersonic flow at the point of injection. Droplet sizes and velocities were measured in subsonic conditions using digital in-line holography, in which recent advancements to the reconstruction algorithm were implemented to reduce out-of-plane measurement uncertainty, and phase Doppler particle analysis.</div><div><br></div><div>The breakup of a single drop undergoing multi-mode breakup was analytically characterized, with the proposal of a new breakup criterion in the Taylor analogy breakup model. Hill vortices within the drop were proposed as a new flow mechanism promoting multi-mode breakup. Product drop sizes from the ring breakup were predicted and compared with experimental results.</div>

<p>The writing centers created to serve predominately white institutions (PWIs) are not designed to meet the needs of Indigenous writers. Despite ostensible moves towards equity and social justice, Indigenous peoples often remained overlooked in writing center studies, partly due to the lack of attention paid to centers in Indigenous-serving institutions. <em>Weaving Centers of Resistance</em> responds to this gap by mapping the writing centers and tutoring centers at Indigenous serving institutions, investigating how tutoring pedagogy for writing is adapted in these contexts, and developing recommendations for culturally relevant writing center pedagogy. The research was conducted in three stages: A survey designed to collect basic demographic information was sent to 33 Tribal Colleges and Universities (TCUs),  35 Native American-serving, Non-Tribal Institutions (NASNTIs), and 13 Native Hawaiian-serving Institutions (NHSIs). From participants in the survey, 10 writing and tutoring center practitioners were recruited for two rounds of virtual interviews. Finally, two interview participants were recruited for virtual case study interviews. This dissertation is divided into seven chapters. The first chapter contextualizes this project in Indigenous movements towards rhetorical sovereignty set against composition’s implication in racist ideologies. The second chapter lays out the history of western colonial education, surveys Indigenous topics in writing center studies, and argues for decolonizing the writing center movement towards just pedagogies. The third chapter troubles empirical methodologies within writing center studies and discusses the methodologies and methods used for this study. The fourth chapter offers findings from the survey sent to Indigenous-serving institutions. The fifth chapter introduces the ten writing and tutoring center practitioners interviewed for this study. The sixth chapter reports on themes developed in qualitative coding of interviews. The final chapter synthesizes the findings, discusses limitations, and offers a path forward for writing center practitioners working with Indigenous peoples. A few of the key findings of this project are the prevalence of learning centers in Indigenous-serving institutions, the deeply intersectional challenges faced by Indigenous writers, and the importance of relationship for tutoring in Indigenous contexts. This work attempts to offer practitioners in Native educational contexts better tools to teach writing from Indigenous perspectives and provides scholars across humanities strategies for rethinking resistance to linguistic colonialism.</p>

<p>The solar system that we live in today bears only a passing resemblance to the solar system that existed 4.5 billion years ago. As our young star shed the gas nebula from which it was born, a disk of dust and rocky bodies emerged in the space between the Sun and Jupiter. Over the next hundred million years, this planetary disk evolved and gave rise to the terrestrial planets of the inner solar system. Clues left behind during this early stage of evolution can be seen in the orbital architecture of the modern planets, the cratering records of rocky bodies, and the signatures of the solar system's secular modes. </p> <p><br></p> <p>Past works in the fields of terrestrial planet accretion and solar system evolution typically do not include collisional fragmentation. While the mechanics of collisional fragmentation are well studied, the incorporation of this processes into simulations of terrestrial planet formation is computationally expensive via traditional methods. For this reason, many works elect to exclude collisional fragmentation entirely, improving computational performance but neglecting a known process that could have played a significant role in the formation of the solar system. In this dissertation, I develop a collisional fragmentation algorithm, called Fraggle, and incorporate it into the n-body symplectic integrator Swiftest SyMBA. Along with performance enhancements and modern programming practices, Swiftest SyMBA with Fraggle is a powerful tool for simulating the formation and evolution of the inner solar system. </p> <p><br></p> <p>In this dissertation, I use Swiftest SyMBA} with Fraggle to study the effect of collisional fragmentation on the accretion and orbital architecture of the terrestrial planets, as well as the cratering record of early Mars. I show that collisional fragmentation is a significant process in the early solar system that creates a spatially heterogeneous and time-dependent population of collisional debris that fluctuates as the solar system evolves. This ever-changing population results in cratering records that are unique across the inner solar system. The work presented in this dissertation highlights the need for independent cratering chronologies to be established for all rocky bodies in the solar system, as well as the need for future models of solar system accretion to include the effects of collisional fragmentation. </p> <p><br></p> <p>While the cratering records and orbits of the terrestrial planets are two means by which to study the solar system's ancient past, analysis of the evolution of the secular modes of the solar system offers a third method. A secular mode arises due to the precession of the orbit of a planet over time. Each body's orbit precesses at a specific fundamental frequency, or mode, that has the power to shape the orbital architecture of the solar system. I show that jumps in the eccentricity of Mars can trigger short-lived power sharing relationships between secular modes, resulting in periods in which the strength and fundamental frequencies of modes fluctuates. While evidence of these past jumps in Mars' eccentricity would likely not be visible today in the secular modes of the inner solar system, the work presented in this dissertation poses additional questions. In particular, questions related to other possible triggers of power sharing relationships, as well as the effects of power sharing relationships on the stability of small bodies during these periods of fluctuation, are particularly compelling.</p> <p><br></p> <p>The work presented in this dissertation contributes to the fields of numerical modeling, solar system evolution, collisional fragmentation, martian cratering, and secular modes and resonances. As a whole, it explores avenues by which we can understand the very earliest period of our solar system's history and develops a model that will allow for continued research in this field. </p>

<p dir="ltr">Protein phosphorylation is a ubiquitous post-translational modification controlled by the opposing activities of protein kinases and phosphatases, which regulate diverse biological processes in all kingdoms of life. One of the key challenges to a complete understanding of phosphoregulatory networks is the unambiguous identification of kinase and phosphatase substrates. Liquid chromatography-coupled mass spectrometry (LC-MS/MS) and associated phosphoproteomic tools enable global surveys of phosphoproteome changes in response to signaling events or perturbation of phosphoregulatory network components. Despite the power of LC-MS/MS, it is still challenging to directly link kinases and phosphatases to specific substrate phosphorylation sites in many experiments. Here we described two methods for the LC-MS/MS-based characterization of protein phosphatases and kinases. The first is an <i>in-vitro</i> method designed to probe the inherent substrate specificity of kinase or phosphatases. This method utilizes an enzyme reaction with synthetic peptides, serving served as substrate proxies, coupled with LC-MS/MS for rapid, accurate high-throughput quantification of the specificity constant (<i>k</i>_<em>cat</em><i>/K</i>_<em>M</em>) for each substrate in the reaction and amino acid preference in the enzyme active site, providing insight into their cellular roles. The second couple’s auxin-inducible degradation system (AID) with phosphoproteomics for protein functional characterization. AID is a surrogate for specific chemical inhibition, which minimizes non-specific effects associated with long-term target perturbation. Using this system, we demonstrate-PP2A in complex with its B-subunit Rox Three Suppressor 1 (PP2A^Rts1) contributes to the phosphoregulation of a conserved fungal-specific membrane protein complex called the eisosome. By maintaining eisosomes in their hypophosphorylated state, PP2A^Rts1 aids fungal cells in preserving metabolic homeostasis. This work demonstrates the power of mass spectrometry as a critical tool for protein functional characterization.</p>

<p>In the pursuit to develop safe and reliable lithium-ion batteries, it is imperative to understand all the variabilities that revolve around electrodes. Current cutting-edge physics-based simulations employ an image-based technique. This technique uses images of electrodes to extract effective properties that are used in these physics-based simulations or employ the simulation on the structure itself. Though the electrode images have spatial variability, various particle morphology, and aberrations that need to be accounted for. This work seeks out to help quantify these variabilities and pinpoint uncertainties that arise in image-based simulations by using machine learning and other data analytic techniques. First, we looked at eighteen graphite electrodes with various particle morphologies to gain a better understanding on how heterogeneity and anisotropy interplay with each other. Moreover, we wanted to see if higher anisotropic particles led to greater heterogeneity, and a higher propensity for changes in effective properties. Multiple image-based algorithms were used to extract tortuosity, conductivity, and elucidate particle shape without the need for segmentation of individual particles. What was found is highly anisotropic particles induces greater heterogeneity in the electrode images, but also tightly packed isotropic particles can do the same. These results arise from porous pathways becoming bottlenecked, resulting in greater likelihood to change values with minimal changes in particle arrangement. Next, a model was deployed to see how these anisotropies and heterogeneities impact electrochemical performance. The thought of whether particle morphology and directional dependencies would have impact on plating energy and heat generation, leading to poor electrochemical performance. By using a pseudo-2D model, we elucidated that the larger the tortuosity the greater the propensity to plate and generate heat. Throughout these studies, it became clear that the segmentation of the greyscale images became the origin for subjectiveness to appear in these studies. We sought to quantify this through machine learning techniques, which employed a Bayesian convolutional neural network. By doing so we aimed to see if image quality impacts uncertainties in our effective properties, and whether we might be able to predict this from image characteristics. Being able to predict effective property uncertainty through image quality did not prove possible, but the ability to predict physics properties based on geometric was able to be done. With the largest uncertain particles occurring at the phase boundaries, morphologies that have a large specific surface area presented with the highest structural uncertainty. Lastly, we wanted to see the impact carbon binder domain morphology uncertainty impacts our effective properties. By using a set of sixteen NMC electrodes, which specify the carbon binder domain weight percentage, we can see how uncertainties in morphology, segmentation, spatial variability, and manufacturing variability impact effective properties. We expected there to be an interplay on which uncertainty impacts various effective properties, and if manufacturing variability plays a large role in determining this. By using surrogate models and statistical methods, we show that there is an eb and flow in uncertainties and effective properties are dependent on which uncertainty is being changed.</p>