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The Alien Language: Game The Developmental Trajectory of Auditory and Visual Statistical Learning
No full textStatistical learning (SL) extends across multiple stimulus domains and modalities, including vision, audition, and touch. However, it remains to be seen whether SL is supported by a modality-general or modality-specific mechanism(s). Prior work examined this by varying the rate of presentation across modalities, finding evidence of modality-specific constraints on learning (Emberson, Conway & Christiansen, 2011). In a prior experiment, I extended this work by testing the effect of presentation rate in standardized audio and visual SL tasks. The results of this project provided evidence against modality constraints to SL, suggesting instead that the mechanism is modality-general in nature. However, SL’s developmental trajectories in school age children are highly debated and minimally researched, begging the question of whether modality constraints on statistical learning exist at any point during development. Utilizing a gamified version, The Alien Language Game, of the task used in my prior experiment, I was able to examine the mechanism’s performance in the visual and auditory domains at two rates of presentation in children 7- to 12- years-old. Performance in the auditory domain was significantly better than that of the visual domain, with performance in visual task at both rates of presentation at or below chance, suggesting the SL mechanism is better equipped to track temporal dependencies of auditory stimuli. However, performance at the slower rate of presentation in both the auditory and visual domains improved with age. Thus, my results provide evidence that differ from previous predictions of modality constraints on SL (see Emberson et al., 2011), suggesting the developmental trajectory of visual and auditory SL is different than previously predicted
Comparison of Thalamic Atlases and Segmentation Techniques in Defining Motor and Sensory Nuclei for Deep Brain Stimulation Targeting In Essential Tremor
No full textIntroduction
Deep brain stimulation (DBS) of the ventral intermediate (VIM) nucleus of the thalamus is a proven treatment for essential tremor (ET). Neurosurgeons rely on thalamic atlases to locate relevant nuclei for stimulation; however, many atlases are available, with different divisions of motor and sensory subnuclei. Segmenting anatomical targets using diffusion tensor imaging (DTI) offers a patient-specific alternative to traditional atlas-based approaches. This work compares the effectiveness of multiple atlases and segmentation techniques in defining motor and sensory subnuclei, evaluated based on the correspondence of clinical outcomes with tissue activation models of an ET patient dataset.
Objective
This research investigates the differences between thalamic atlases, how segmentation techniques are used to parcellate patient thalami, and the clinical correspondence of various atlases and segmentation techniques to determine the relative effectiveness of atlases in defining the motor and sensory subnuclei. Materials and Methods 22 ET patients who underwent unilateral VIM DBS were analyzed retrospectively. Six prominent thalamic atlases were obtained from LEAD-DBS. The atlases segmented the patient thalami in two ways: atlas-based segmentation (ABS) used the atlas to determine subnuclei divisions, and DTI-based segmentation (DTIBS) incorporated tissue properties to create clusters of subnuclei.
Results
High motor and low sensory activation are expected for tremor reduction stimulation, and ABS produced this trend across all atlases, whereas DTIBS produced this trend in only half of the atlases. Greater sensory stimulation is expected for paresthesia outcomes compared to tremor reduction outcomes, and ABS yielded this trend in almost all atlases, whereas DTIBS yielded this trend in only half of the atlases. ABS was more generalizable than DTIBS across atlases. The Jakab atlas was the only atlas to show the expected motor and sensory stimulation trend associated with each clinical outcome when using either ABS or DTIBS, making it the most clinically accurate atlas investigated.
Significance
This work presents an analysis of six prominent atlases that are used for indirect targeting of the VIM thalamus for DBS. The findings of this study may be used to inform the choice of atlas and segmentation approach used in surgical planning for DBS lead localization
Same Dynamics, Different Graph: Exploring Correlations, Similarities, and Renormalization of Dynamics on Networks Using Temporal Distance Theory
Full text linkAnalyzing dynamics that take place on graphs (networks) is fundamental to modern network theory, with applications spanning biology, social networks, and engineering systems. A significant body of research exists that considers the similarity and scaling of network topologies. However, understanding how dynamic behavior varies across different graph topologies - particularly how signals propagate and dynamic behaviors scale between small and large networks - remains a significant challenge.
To address this challenge, this thesis presents a comprehensive framework to analyze how dynamic signals propagate and scale on network topologies using temporal distance theory. Three research goals were accomplished. First, a statistical analysis of dynamic signal propagation patterns on the complete set of non-isomorphic graphs with 9 or less vertices (nodes) was performed. Using temporal distance theory to generate the data eliminated the need for over a hundred million simulations across 273,191 network topologies and three distinct dynamic models. Second, a novel algorithm was developed to quantitatively measure the similarity between dynamics taking place on different networks called TD-Match. TD-Match is robust to graph isomorphs and can be used as a look-up function for dynamically similar networks in complete sets of network topologies. By comparing the similarity of the dynamics on graphs, this methodology can reveal graph sets that contain same dynamics, different graphs. Finally, this work developed a novel methodology for dimensionally scaling, or renormalizing, a network that focuses on the characteristics of the dynamics propagating on that network, independent of topology. As far as the author is aware, this is the first renormalization method that prioritizes dynamic signals on the network instead of network topology. A new tool called TD-MORPH was developed to explore TD-Match and dynamic renormalization.
The statistical analyses, TD-Match algorithm, and dynamic renormalization method offer a new framework for network analysis. This work provides a computationally efficient foundation for future studies seeking insight into the interplay between graph structures and network dynamics
Ian Milligan - Ethics, Emails, and Archives: Using (and Misusing) the September 11 Digital Archive
No full textIan Milligan spoke with us on the topic of “Ethics, Emails, and Archives: Using (and Misusing) the September 11 Digital Archive.” Minutes after American Airlines Flight 11 crashed into the North tower of the World Trade Center complex on September 11th, 2001, emails and online discussions surged, capturing real-time reactions from shock to speculation about global repercussions. Many of these digital interactions were preserved in the September 11 Digital Archive, an early example of an event-based archive. Despite the invaluable insights offered into collective responses, ethical complexities and practical challenges, including fragmented metadata, inconsistent file formats, and privacy concerns, have significantly limited the use of this collection (scholarly and popular alike
Drag Reduction in Ground Vehicles using a Model Porous Medium
Full text linkThis research investigates aerodynamic drag reduction on a 25° Slanted Ahmed Body (SAB) by integrating porous media model rods through combined experimental and computational methods at a Reynolds number of 1.16×10⁴. Two porous media configurations: short rods (6.75% of the model height) and long rods (20.0% of the model height), both featuring cylindrical rods with 80% porosity, were systematically compared against a baseline SAB. In-depth analyses were performed to investigate the wake flow topology, recirculation region characteristics, pressure coefficient distribution, Reynolds stress distributions and drag coefficient. Experimental investigations employed particle image velocimetry for precise flow visualization, while Reynold Averaged Navier-Stokes numerical simulations through a COMSOL Multiphysics software were used to complement and extend the experimental insights. Key findings revealed that incorporating porous rods significantly enhanced wake filling, marked by accelerated recovery of streamwise momentum and reduced wake momentum deficits. This wake filling effect contributed directly to an increased base pressure and notable reduction in pressure drag. Moreover, the porous model rods effectively modified Reynolds stress distributions, resulting in more stabilized, coherent wake structures with increased recirculation length and stability. Quantitatively, the long rod configuration yielded the most substantial aerodynamic improvement, achieving an 8.27% drag reduction compared to the baseline SAB, while the short rod configuration demonstrated a modest but meaningful reduction of approximately 3%. These comprehensive analyses confirm the efficacy of a porous medium as an innovative passive drag-reduction strategy in automotive applications, emphasizing their potential to optimize vehicle aerodynamic performance through targeted wake stabilization and pressure recovery enhancements
The Effect of Sequence on Structure and Microbial Properties of Insect Antimicrobial Peptides
No full textAntibiotic resistance is a growing crisis worldwide, and antimicrobial peptides (AMPs) are emerging as a promising alternative to traditional antibiotics. AMPs, short chains of 10-60 amino acids, are produced by a wide variety of organisms, including insects. This work is focused on the cecropin family, a group of insect AMPs known for their α-helical structure and low toxicity to mammalian cells. Cecropin sequences were sourced from protein databases, with mature peptide forms isolated by removing signal sequences and duplicates. We examine how small variations in amino acid sequences, particularly in regions predicted to serve as hinges between two α-helices, impact both the biophysical properties and antimicrobial behavior of these peptides. The peptides were first categorized by biochemical properties, including hydrophobicity, amphiphilicity, and net charge, to predict their antimicrobial activity. Structural modeling for one category of peptides predicted three primary α-helical conformations, linear, bent, and hinged, suggesting that similarly sequenced peptides can have differing abilities to form multiple conformations and potential membrane insertion mechanisms or capabilities. However, differences in amino acid properties at positions 22 and 23 were suggestive of their predicted structure. Selected peptides were synthesized and their structure was analyzed, which confirmed that they adopt α-helical structures in membrane-mimetic environments, though observed differences in α-helicity between peptides were not correlated with predicted structures. Then, the antimicrobial activity of each peptide was determined against bacterial species including Escherichia coli, Pseudomonas aeruginosa, and two strains of Providencia burhodogranariea. Differences in antibacterial activity were observed, revealing that even small sequence and structural differences can significantly impact peptide efficacy. While increased predicted linearity generally corresponded with greater activity, supporting expectations based on hinge flexibility, this trend was not consistent across all bacterial species. This work aims to improve the rational design of AMPs with improved specificity and potency, addressing the urgent need for new antimicrobial agents in the face of rising antibiotic resistance
Assessing Genetic Diversity and Population Structure in the Imperiled Aconitum reclinatum (white monkshood), an Endemic Wildflower of Central Appalachia
No full textAconitum reclinatum, white monkshood (Ranunculaceae), is a Pennsylvania critically imperiled plant species found in five states of the Appalachian region of the United States: Pennsylvania, West Virginia, Virginia, North Carolina, and Tennessee. This plant is adapted to cool, moist environments but faces threats from increasing habitat loss, deer browse, logging, and changes in rainfall and temperature associated with climate change. Comprehensive knowledge of A. reclinatum genetic population structure remains limited. To address this, we collaborated with Natural Heritage programs within the range of A. reclinatum to sample populations across the species distribution and generate a genotyping-by-sequencing data set of single-nucleotide polymorphisms (SNPs). This dataset was used to calculate population statistics (heterozygosity, inbreeding coefficient, fixation index) and infer population health and structure by conducting a Principal Component Analysis (PCA), spare non-negative matrix factorization (sNMF) analysis, and testing for a correlation between geographic and genetic distance. Our findings suggest strong genetic structure among populations of A. reclinatum and genetic isolation between populations. Natural Heritage programs should continue efforts to maintain populations and initiate further efforts for some populations that are experiencing lower genetic health. Additionally, genetic rescue may be required for some populations, although compatibility should be tested before it is implemented
How does Neurocognitive Dysfunction and Personality Pathology Impact Older Adults\u27 Use of the Healthcare System?
No full textPerformance as Political Resistance: Looking at Theatrical Approaches to Advocacy/Public Policy Through the Lens of the AIDS Crisis
No full textStable polynomials and admissible numerators in product domains
No full textGiven a polynomial p with no zeros in the polydisk, or equivalently the poly-upper half-plane, we study the problem of determining the ideal of polynomials q with the property that the rational function q/p is bounded near a boundary zero of p. We give a complete description of this ideal of numerators in the case where the zero set of p is smooth and satisfies a nondegeneracy condition. We also give a description of the ideal in terms of an integral closure when p has an isolated zero on the distinguished boundary. Constructions of multivariate stable polynomials are presented to illustrate sharpness of our results and necessity of our assumptions