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1. Variational quasi-harmonic maps for computing diffeomorphisms

   https://doi.org/10.1145/3592105  

   Wang, Yu; Guo, Minghao; Solomon, Justin (August 2023, ACM Transactions on Graphics)

   Computation of injective (or inversion-free) maps is a key task in geometry processing, physical simulation, and shape optimization. Despite being a longstanding problem, it remains challenging due to its highly nonconvex and combinatoric nature. We propose computation ofvariational quasi-harmonic mapsto obtain smooth inversion-free maps. Our work is built on a key observation about inversion-free maps: A planar map is a diffeomorphism if and only if it is quasi-harmonic and satisfies a special Cauchy boundary condition. We hence equate the inversion-free mapping problem to an optimal control problem derived from our theoretical result, in which we search in the space of parameters that define an elliptic PDE. We show that this problem can be solved by minimizing within a family of functionals. Similarly, our discretized functionals admit exactly injective maps as the minimizers, empirically producing inversion-free discrete maps of triangle meshes. We design efficient numerical procedures for our problem that prioritize robust convergence paths. Experiments show that on challenging examples our methods can achieve up to orders of magnitude improvement over state-of-the-art, in terms of speed or quality. Moreover, we demonstrate how to optimize a generic energy in our framework while restricting to quasi-harmonic maps. 

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2. Reliability of Matching AMPERE Field‐Aligned Current Boundaries With SuperDARN Lower Latitude Ionospheric Convection Boundaries During Geomagnetic Storms

   https://doi.org/10.1029/2024JA033253  

   Walach, M‐T; Fogg, A R; Coxon, J C; Grocott, A; Milan, S E; Sangha, H K; McWilliams, K A; Vines, S K; Lester, M; Anderson, B J (January 2025, Journal of Geophysical Research: Space Physics)

   Abstract High‐latitude ionospheric convection is a useful diagnostic of solar wind‐magnetosphere interactions and nightside activity in the magnetotail. For decades, the high‐latitude convection pattern has been mapped using the Super Dual Auroral Radar Network (SuperDARN), a distribution of ground‐based radars which are capable of measuring line‐of‐sight (l‐o‐s) ionospheric flows. From the l‐o‐s measurements an estimate of the global convection can be obtained. As the SuperDARN coverage is not truly global, it is necessary to constrain the maps when the map fitting is performed. The lower latitude boundary of the convection, known as the Heppner‐Maynard boundary (HMB), provides one such constraint. In the standard SuperDARN fitting, the HMB location is determined directly from the data, but data gaps can make this challenging. In this study we evaluate if the HMB placement can be improved using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), in particular for active time periods when the HMB moves to latitudes below . We find that the boundary as defined by SuperDARN and AMPERE are not always co‐located. SuperDARN performs better when the AMPERE currents are very weak (e.g., during non‐active times) and AMPERE can provide a boundary when there is no SuperDARN scatter. Using three geomagnetic storm events, we show that there is agreement between the SuperDARN and AMPERE boundaries but the SuperDARN‐derived convection boundary mostly lies equatorward of the AMPERE‐derived boundary. We find that disagreements primarily arise due to geometrical factors and a time lag in expansions and contractions of the patterns. 

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3. Dusk‐Dawn Asymmetries in SuperDARN Convection Maps

   https://doi.org/10.1029/2022JA030906  

   Walach, M.‐T.; Grocott, A.; Thomas, E. G.; Staples, F. (December 2022, Journal of Geophysical Research: Space Physics)

   Key Points We study dusk‐dawn asymmetries in 7 years of Super Dual Auroral Radar Network convection maps which are introduced by solar wind orientations, or data processing Asymmetries due to interplanetary magnetic field B y can occur in the strength and location of the convection cells, and the return flow width Asymmetries due to the background model are likely to occur in the locations of the convection cells 

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4. Mapping of specialized metabolite terms onto a plant phylogeny using text mining and large language models

   https://doi.org/10.1111/tpj.16906  

   Busta, Lucas; Hall, Drew; Johnson, Braidon; Schaut, Madelyn; Hanson, Caroline M; Gupta, Anika; Gundrum, Megan; Wang, Yuer; A_Maeda, Hiroshi (October 2024, The Plant Journal)

   SUMMARY Plants produce a staggering array of chemicals that are the basis for organismal function and important human nutrients and medicines. However, it is poorly defined how these compounds evolved and are distributed across the plant kingdom, hindering a systematic view and understanding of plant chemical diversity. Recent advances in plant genome/transcriptome sequencing have provided a well‐defined molecular phylogeny of plants, on which the presence of diverse natural products can be mapped to systematically determine their phylogenetic distribution. Here, we built a proof‐of‐concept workflow where previously reported diverse tyrosine‐derived plant natural products were mapped onto the plant tree of life. Plant chemical‐species associations were mined from literature, filtered, evaluated through manual inspection of over 2500 scientific articles, and mapped onto the plant phylogeny. The resulting “phylochemical” map confirmed several highly lineage‐specific compound class distributions, such as betalain pigments and Amaryllidaceae alkaloids. The map also highlighted several lineages enriched in dopamine‐derived compounds, including the orders Caryophyllales, Liliales, and Fabales. Additionally, the application of large language models, using our manually curated data as a ground truth set, showed that post‐mining processing can largely be automated with a low false‐positive rate, critical for generating a reliable phylochemical map. Although a high false‐negative rate remains a challenge, our study demonstrates that combining text mining with language model‐based processing can generate broader phylochemical maps, which will serve as a valuable community resource to uncover key evolutionary events that underlie plant chemical diversity and enable system‐level views of nature's millions of years of chemical experimentation. 

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5. Discovering Underground Maps from Fashion

   https://doi.org/10.1109/WACV51458.2022.00057  

   Mall, Utkarsh; Bala, Kavita; Berg, Tamara; Grauman, Kristen (January 2022, 2022 IEEE/CVF Winter Conference on Applications of Computer Vision (WACV))

   The fashion sense -- meaning the clothing styles people wear -- in a geographical region can reveal information about that region. For example, it can reflect the kind of activities people do there, or the type of crowds that frequently visit the region (e.g., tourist hot spot, student neighborhood, business center). We propose a method to automatically create underground neighborhood maps of cities by analyzing how people dress. Using publicly available images from across a city, our method finds neighborhoods with a similar fashion sense and segments the map without supervision. For 37 cities worldwide, we show promising results in creating good underground maps, as evaluated using experiments with human judges and underground map benchmarks derived from non-image data. Our approach further allows detecting distinct neighborhoods (what is the most unique region of LA?) and answering analogy questions between cities (what is the "Downtown LA" of Bogota?). 

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