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    Understanding the Role Mechanical Properties of Lithium Metal and Reacted Interphases Play in Solid-Solid Interfacial Chemo-Mechanics of Batteries
    (Georgia Institute of Technology, 2023-06-02) Marchese, Thomas S. ; McDowell, Matthew T. ; Realff, Mary L. ; Materials Science and Engineering
    Batteries are being incorporated into many technologies around us in the age of the ‘smart home’ and wearable technology. This, along with the electrification of vehicles, is creating exponential growth in the demand for high energy density batteries. Commercialization of lithium metal anode solid-state batteries would increase the energy density and safety by replacing the flammable liquid electrolyte with a solid-state electrolyte. Understanding the mechanical properties of lithium metal foil for battery anodes is imperative to forming and maintaining the solid-solid interfaces in these systems. Alkali metals have low yield strength (~1 MPa or lower) and are sensitive to creep; such deformation behavior needs to be understood under realistic multi-contact conditions prior to commercial implementation. Here, we demonstrate a new constant loading indentation mechanical deformation technique that employs indenter arrays of different sizes and spacings dropped into contact by force of gravity. The indenters probe the average material response to an array of contacting points, which is directly applicable to the conditions realized in bench-scale solid-state battery production. Testing across three different stainless steel indenter array sizes and a stainless-steel single pillar indenter of equivalent cumulative contact surface area at a single loading value demonstrated size effects of lithium metal foil. Examining the average total deformation observed over 12 minutes, the single pillar indenter averaged a total displacement of 99.40 ± 36.67 μm and the large indenter array averaged 99.16 ± 17.98 μm. Less deformation was seen by the medium indenter array which averaged 29.93 ± 9.06 μm, and by the small indenter array which averaged 45.00 ± 6.41 μm in total displacement. The smaller indenters are seen to penetrate to a lower depth due to increased frictional resistance by greater total surface area in contact and earlier horizontal interaction of neighboring indenters deformation volumes. This indentation array technique provides important knowledge for analyzing realistic deformation behavior of lithium and will provide insight into the action of creep in “healing” voids at the alkali anode/SSE interface. The importance of conformal component contact cannot be overstated in the creation of stable and reproducible electrochemical performance for lithium metal solid-state batteries.
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    Exploration of Commuting Patterns in San Francisco Bay Area
    (Georgia Institute of Technology, 2020-07) Liu, Lier ; Georgia Institute of Technology. School of City and Regional Planning
    Transportation has been an important aspect in life, both offering convenience and efficiency and potentially bringing inconvenience and delay to people. San Francisco Bay Area has always been famous for its comprehensive transportation networks and various transportation modes; meanwhile the issue of transportation congestion has caused severe consequences in people’s lives such as wasted time and gasoline, polluted air, and traffic accidents. This project aims to explore the commuting patterns in the San Francisco Bay Area and analyze people’s commuting behaviors and some demographic datasets. Correlations between demographic features and people’s commuting choices and behaviors are explored, along with three representative new commuting methods, Bay Area Rapid Transit, Lyft bike sharing Bay Wheel, and Uber. Such thorough studies can potentially offer policy implications for transportation planners and policy makers, for the sake of establishing faster transportation networks and avoiding traffic delay to a larger extent.
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    Efficient Calculation of Frame Level Complex Predicates in Video Analytics
    (Georgia Institute of Technology, 2023-01-18) Sengupta, Aubhro ; Arulraj, Joy ; Computer Science
    The field of video analytics focuses on extracting useful information from video. Lets consider a scenario in which we have a large amount of video from a traffic camera at a certain busy intersection and we are looking for a black sedan. State of the art object detectors such as FasterRCNN [3] utilize computationally expensive methods like convolutional neural networks that analyze a frame of video and estimate the number of the object of interest and the locations of every instance of that object in the frame. The most basic approach to solving this problem would simply be to execute the object detector on all frames of the video and collect the frames which contain at least one black sedan to return to the user. However, this approach is impractical on longer videos as CNNs are computationally expensive and thus too slow. Instead the number of frames evaluated by the object detector must be limited. This field focuses on developing strategies for doing so, such as sampling, filtering, proxy models, and clustering.
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    Production of ryanodine receptor calcium release channel ATP-binding site mutants
    (Georgia Institute of Technology, 2023-01-18) Cutter, Catarina Santos ; Spencer, Chrissy ; Balog, Edward ; Jang, Young ; Biology
    Ryanodine receptors (RyRs) are a class of mammalian ion channels which are the primary efflux pathways for the release of Ca2+ from the sarcoplasmic reticulum. They play a critical role in muscle excitation-contraction coupling (ECC). Because it is the largest known ion channel, the mechanisms for its activation are not fully understood. ATP is a well characterized channel activator. However, its mechanism of activation has not been determined and the importance of ATP regulation of RyRs in vivo is not clear. In 2016, des George, et al. published a structure of RyR1 with ATP bound. The adenosine group of ATP is contained within a hydrophobic cleft while the triphosphate tail is extended and interacts with positively charged residues. The goal of this study was to identify residues important for ATP binding to the channel. Site-directed mutagenesis of the receptor was used to substitute specific residues in order to change their size and or charge. After transfection with recombinant DNA, HEK293 cells were harvested for isolation of microsomal membranes. Two of the largest hydrophobic residues of the cleft were replaced with alanine with the goal of drastically reducing or abolishing ATP binding to RyR1. The selected mutations F4960A and L4985A were expected to impair channel activation by both ATP and adenosine. After initial verification of wild type channel expression in HEK293 cells, later transfections with wild type and mutant RyR1 DNA failed to produce detectable amounts of protein. Low DNA transfection efficiency combined with the low yield of microsomal membrane likely contributed to the inability to detect channels in these preparations. Optimizing DNA transfections and scaling up the cell culture may increase the likelihood of successful protein production.
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    Provenance Analysis of the Bouse Formation, Lower Colorado River from Detrital Zircon (U-Th)/Pb Geochronology
    (Georgia Institute of Technology, 2023-01-18) Motz, Samantha L. ; Lang, Karl ; Rivera-Hernandez, Frances ; Earth and Atmospheric Sciences
    The timing and mechanism of Colorado River integration from the Grand Canyon to the Gulf of California have long been debated. Early research proposed river integration developed “bottom-up” due to Pliocene marine incursion and regional uplift. However, mapping, stratigraphy, and geochemical analyses of early Colorado River deposits instead support a “top-down” integration by progressive filling of lake basins connected by the Colorado River. Key to this debate are interpretations of the depositional environment of the Pliocene Bouse Formation. Here we present a new dataset of detrital zircon (U-Th)/Pb geochronology (n = 1774 single-grain ages) to explore the sedimentary provenance of sand horizons in the Bouse Formation. Our results span 13 Bouse samples from four sub-basins in the lower Colorado River corridor: Mohave, Chemehuevi, Parker, and Cibola. Additional samples of underlying Pyramid gravel and modern sediment from the Colorado River, Bill Williams River, and Silver Creek are presented for comparison. Except for three samples from the Mohave sub-basin, statistical comparison of grain-age populations illustrates that the Bouse Formation has a non-local provenance consistent with a large drainage area comparable to the modern Colorado River. The excepted samples reflect derivation from local source rocks. Within the Bouse Formation’s stratigraphy, grain-age populations do not vary. Still, inter-sub-basins vary geographically, which we attribute to the progressive admixture of zircons from local source rocks and tributaries. Overall, our provenance analysis is consistent with the deposition of Bouse sand horizons as delta-front turbidities originating from a river with a well-mixed and lithologically diverse sediment load. Exceptional samples from the Mohave sub-basin may be explained by interbedding of transverse fan-deltas from local tributaries. Our analysis does not support the deposition of the Bouse Formation in separated and locally sourced lake systems. Instead, it promotes deposition by a single, high-discharge river rapidly progressing southward, integrating previously separated sub-basins.
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    Oracle Guided Image Synthesis with Relative Queries
    (Georgia Institute of Technology, 2023-01-18) Helbling, Alec Fisher ; Rozell, Christopher ; Riedl, Mark ; Computer Science
    Isolating and controlling specific features in the outputs of generative models in a user-friendly way is a difficult and open-ended problem. We develop techniques that allow a user to generate an image they are envisioning in their head by answering a sequence of relative queries of the form "do you prefer image a or image b?" Our framework consists of a Conditional VAE that uses the collected relative queries to partition the latent space into preference-relevant features and non-preference-relevant features. We then use the user's responses to relative queries to determine the preference-relevant features that correspond to their envisioned output image. Additionally, we develop techniques for modeling the uncertainty in images' predicted preference-relevant features, allowing our framework to generalize to scenarios in which the relative query training set contains noise.
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    Emotional wellbeing in those with chronic illness due to a genetic mutation in valosin-containing protein
    (Georgia Institute of Technology, 2023-01-18) Jones, Mallory ; Holder, Mary ; Dahlman, James ; Neuroscience (Undergrad)
    Valosin-containing protein (VCP) is a ubiquitous protein and a member of the ATPases Associated with a variety of cellular Activities (AAA proteins) superfamily. VCP has many functions in the cell including protein quality control, membrane fusion, and maintenance of the cell cycle and apoptosis. Mutations of the gene encoding VCP lead to a rare but devastating disorder with several pathologies including inclusion body myopathy, Paget’s disease of bone, ALS, and frontotemporal dementia. People who develop VCP Disease often feel disenfranchised with their diagnosis, being unable to access appropriate treatments or support systems. Another complication of its rare nature is that this disease is frequently misdiagnosed, due in large part to lack of awareness. Advocacy programs like Cure VCP Disease, Inc. seek to educate caregivers, patients, and medical professionals about the disease and advocate for increased research and resources devoted to its cure. These groups are an integral facet of the rare disease community, and it is imperative that the scientific community bolster and encourage the work of these groups. This review will examine existing literature concerning VCP Disease and will present what is currently known of this multisystem proteinopathy through the lens of patient advocacy. Unpublished and deidentified testimonials of several patients and caregivers will be presented to emphasize the importance of patient advocacy work. Additionally, grip strength data obtained using a dynamometer is analyzed in an effort to identify factors for prediction of symptom progression.
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    Predicting Metabolic Cost Using Cumulative Muscle Activation Per unit Distance
    (Georgia Institute of Technology, 2023-01-18) Carter, Jacob M. ; Sawicki, Greg ; Fernandez, Todd ; Behravesh, Essy ; Trejo, Lindsey ; Biomedical Engineering (Joint GT/Emory Department)
    Many studies are currently being conducted in order to optimize the functions of exoskeletons in a way that generates the greatest benefit for the user. However, this research is hampered by the traditional methodology of measuring metabolic cost, indirect calorimetry. This study proposes an alternative method, based not on the overall gas exchange of the body, but rather the relative activity of the relevant muscle groups in a method known as Cummulative Muscle Activation Per unit Distance(CMAPD) analysis.
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    Intelligent Buffer Pool Prefetching
    (Georgia Institute of Technology, 2023-01-18) Suresh, Sylesh Kyle ; Arulraj, Joy ; Kim, Hyesoon ; Computer Science
    Buffer pools are essential for disk-based database management system (DBMS) performance as accessing memory on disk is orders of magnitude more expensive than accessing data in-memory. As such, one of the most important techniques for DBMS performance improvement is proper buffer pool management. Although much work has already gone into page replacement policies for buffer pools, relatively little attention has been paid to developing intelligent page prefetching strategies. Commonly used sequential prefetching strategies only handle sequential accesses but fail to predict more complex page reference patterns. More complex prediction techniques exist---particularly those that leverage the predictive power of deep learning. Although such models can achieve a high prediction accuracy, due to their size and complexity, they cannot deliver predictions in time for the corresponding pages to be prefetched. With the tension between timeliness and prediction accuracy in mind, in this work, we introduce a machine learning-based strategy capable of predicting useful pages to prefetch for complex memory access patterns with an inference latency low enough for its predictions to be delivered in time. When evaluated on a subset of the TPC-C benchmark, our strategy is capable of reducing execution time by up to 13% while a commonly-used sequential prefetching yields only a 6% reduction.
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    Identifying the potential effect of zolmitriptan on the 1b pathway of Golgi tendon organs in regulating intermuscular inhibition in the extremities to find a link in the mechanism of spasticity
    (Georgia Institute of Technology, 2023-01-18) Davis, Adam Eugene ; Nichols, T. Richard ; Neuroscience (Undergrad)
    The deep dorsal horn (DDH) of the spinal cord is a major integration center for receiving a variety of neural projections from the brainstem as well as a variety of afferent inputs from muscle spindles and Golgi tendon organs (GTOs) in the muscles. Following spinal cord injury (SCI) to the DDH, an overall loss of serotonergic input from the brainstem is observed, for which there is evidence to suggest that this may play a role in inhibiting the activity of bursting interneurons in the DDH, possibly leading to uncontrolled motoneuron activity, hyperreflexia. GTOs primarily supply the force feedback network (FBB), which also receives supraspinal input through the DDH, likely also affected by its loss in SCI. The purpose of this current study is to investigate if FBB function changes, with or without SCI, after the administration of a specific serotonin reuptake inhibitor (SSRI), zolmitriptan, which inhibits the activity of the bursting interneurons. FBB function was determined primarily as inhibitory signals from the flexor hallucis longus (FHL) onto the gastrocnemius (GAS), the muscle tensions compared after being stretched individually and pairwise, with some data from rectus femoris (RF) onto GAS. The autogenic stretch reflex was analyzed only in GAS. Animals with an intact spinal cord (n=1) and with a lateral hemisection (n=2) were used to compare the changes in reflexes following zolmitriptan administration. Data was variable across the subjects with no clear effect on the autogenic stretch reflex in GAS. The more stable lateral hemisection subject revealed that zolmitriptan largely and consistently increased inhibition from FHL onto GAS from a miniscule baseline, suggesting connectivity between the GTO circuit and the bursting interneurons of the DDH. Notably in the intact spinal cord animal, there was an immediate and complete correction of oscillations in the baseline tension of all muscles after drug administration, treating a symptom of hyperreflexia. These results suggest a connection between the two systems or a more significant role of this particular serotonin receptor on GTO circuit and the DDH. More studies may provide a deeper understanding of this network and these findings.