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Creators/Authors contains: "Mitchell, A."

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  1. The research on coastal hazards predicts substantial adverse impacts of chronic and episodic flooding on populated coastal areas. Despite the growing evidence about anticipated flood risks, many coastal communities are still not adapting. The observed disconnect between science on physical impacts and adaptation decisionmaking in part reflects stakeholders’ inability to envision the implications of these impacts on socioeconomic systems and the built environment in their jurisdictions. This inertia is particularly apparent in the discourse on flood-driven displacement and relocation. There is a lack of knowledge about direct and indirect flood impacts on community attributes and services that contribute to relocation decision-making. This study holistically evaluates the flood exposure on municipal features vital for socioeconomic stability, livelihoods, and quality of life across spatiotemporal scales. As such, it uses a more nuanced approach to relocation risk assessment than those solely focused on direct inundation impacts. It measures flood exposure of land use, land cover, and sociocultural and economic dimensions that are important drivers of relocation in selected rural and urban areas. The approach uses a 50-year floodplain to delineate populated coastal locations exposed to 2% Annual Exceedance Probability (AEP) storm surge projections adjusted for 2030, 2060, and 2090 sea level rise (SLR) scenarios. It then evaluates the potential impacts of this flood exposure on different types of land uses and critical socioeconomic assets in rural (Dorchester and Talbot Counties, Maryland, USA) and urban (Cities of Hampton, Norfolk, Portsmouth, and Virginia Beach, Virginia, USA) settings. The results show that some urban land uses, such as open space, military and mixed-use, and rural residential and commercial areas, might experience significantly more flooding. There are also notable differences in the baseline flood exposure and the anticipated rate and acceleration in the future among selected communities with significant implications for relocation planning. 
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    Free, publicly-accessible full text available September 1, 2024
  2. Abstract

    We investigated how the human brain integrates experiences of specific events to build general knowledge about typical event structure. We examined an episodic memory area important for temporal relations, anterior-lateral entorhinal cortex, and a semantic memory area important for action concepts, middle temporal gyrus, to understand how and when these areas contribute to these processes. Participants underwent functional magnetic resonance imaging while learning and recalling temporal relations among novel events over two sessions 1 week apart. Across distinct contexts, individual temporal relations among events could either be consistent or inconsistent with each other. Within each context, during the recall phase, we measured associative coding as the difference of multivoxel correlations among related vs unrelated pairs of events. Neural regions that form integrative representations should exhibit stronger associative coding in the consistent than the inconsistent contexts. We found evidence of integrative representations that emerged quickly in anterior-lateral entorhinal cortex (at session 1), and only subsequently in middle temporal gyrus, which showed a significant change across sessions. A complementary pattern of findings was seen with signatures during learning. This suggests that integrative representations are established early in anterior-lateral entorhinal cortex and may be a pathway to the later emergence of semantic knowledge in middle temporal gyrus.

     
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  3. Abstract

    The20Ne(α,p)23Na reaction rate is important in determining the final abundances of various nuclei produced in type Ia supernovae. Previously, the ground state cross section was calculated from time reversal reaction experiments using detailed balance. The reaction rates extracted from these studies do not consider contributions from the population of excited states, and therefore, are only estimates. A resonance scan, populating both the ground and first excited states, was performed for the20Ne(α,p)23Na reaction, measuring between 2.9 and 5 MeV center of mass energies at the Nuclear Science Lab at the University of Notre Dame. Data analysis is underway and preliminary results show substantial contribution from the excited state reaction.

     
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    Free, publicly-accessible full text available September 1, 2024
  4. Abstract We report the thermoresponsive assembly and rheology of an amphiphilic thermosensitive graft copolymer, poly(ethylene glycol)-graft-(poly(vinyl caprolactam)- co -poly(vinyl acetate)) (commercial name Soluplus ® ), which has been investigated for potential biomedical applications. It has received attention due to is ability to solubilize hydrophobic drugs and for its thickening behavior close to body temperature. Through use of the synchrotron at Brookhaven National Lab, and collaboration with the department of energy, the nanoscale structure and properties can be probed in greater detail. Soluplus ® undergoes two structural changes as temperature is increased; the first, a concentration independent change where samples become turbid at 32 °C. Increasing the temperature further causes the formation of physically associated hydrogels. This sol-gel transition is concentration dependent and occurs at 32 °C for 40 wt% samples, and increases to 42 °C for 10 wt% samples. From variable temperature SAXS characterization micelles of 20–25 nm in radius can be seen and maintain their size and packing below 32 °C. A gradual increase in the aggregation of micelles corresponding to a thickening of the material is also observed. Close to and above the gelation temperature, micelles collapse and form a physically associated 3D network. A model is proposed to explain these physical effects, where the poly(vinyl caprolactam) group transitions from the hydrophilic corona at room temperature to the hydrophobic core as temperature is increased. 
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  5. Control noise is a limiting factor in the low-frequency performance of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO). In this paper, we model the effects of using new sensors called Homodyne Quadrature Interferometers (HoQIs) to control the suspension resonances. We show that if we were to use HoQIs, instead of the standard shadow sensors, we could suppress resonance peaks up to tenfold more while simultaneously reducing the noise injected by the damping system. Through a cascade of effects, this will reduce the resonant cross-coupling of the suspensions, allow for improved stability for feed-forward control, and result in improved sensitivity of the detectors in the 10–20 Hz band. This analysis shows that improved local sensors, such as HoQIs, should be used in current and future detectors to improve low-frequency performance. 
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  6. What happens when a diverse group of youth ages 11 through 14 are introduced to data science using authentic, public, multivariate data in an out-of-school context assuming no special prerequisite knowledge? We designed three 10-hour Data Club modules in which real-world data and the questions students asked of such data drove the learning process. Each module was grounded in a topic that youth connected with at a personal level. Youth learned how to use a free online data platform that made it easy to rearrange, group, filter, and graph data. Within the progression of the module, we used youths’ own questions, data moves, and data visualizations to engage them in critical inquiry and foster productive habits of mind for working with data. Our goal was for youth to emerge from the Data Clubs experience feeling empowered to interact with, ask questions of, and reason about and from data.

     
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  7. Abstract

    Collagen organization plays an important role in maintaining structural integrity and determining tissue function. Polarization-sensitive optical coherence tomography (PSOCT) is a promising noninvasive three-dimensional imaging tool for mapping collagen organization in vivo. While PSOCT systems with multiple polarization inputs have demonstrated the ability to visualize depth-resolved collagen organization, systems, which use a single input polarization state have not yet demonstrated sufficient reconstruction quality. Herein we describe a PSOCT based polarization state transmission model that reveals the depth-dependent polarization state evolution of light backscattered within a birefringent sample. Based on this model, we propose a polarization state tracing method that relies on a discrete differential geometric analysis of the evolution of the polarization state in depth along the Poincare sphere for depth-resolved birefringent imaging using only one single input polarization state. We demonstrate the ability of this method to visualize depth-resolved myocardial architecture in both healthy and infarcted rodent hearts (ex vivo) and collagen structures responsible for skin tension lines at various anatomical locations on the face of a healthy human volunteer (in vivo).

     
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