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Distributed branch points and the shape of elastic surfaces with constant negative curvature

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arXiv 2020年

作者： Shearman, Toby L. Venkataramani, Shankar C. Program in Applied Mathematics University of Arizona 617 N. Santa Rita Avenue TucsonAZ85721 United States Department of Mathematics University of Arizona 617 N. Santa Rita Avenue TucsonAZ85721 United States

We develop a theory for distributed branch points and investigate their role in determining the shape and influencing the mechanics of thin hyperbolic objects. We show that branch points are the natural topological defects in hyperbolic sheets, they carry a topological index which gives them a degree of robustness, and they can influence the overall morphology of a hyperbolic surface without concentrating energy. We develop a discrete differential geometric (DDG) approach to study the deformations of hyperbolic objects with distributed branch points. We present evidence that the maximum curvature of surfaces with geodesic radius R containing branch points grow sub-exponentially, O(ec√R) in contrast to the exponential growth O(ec'R) for surfaces without branch points. We argue that, to optimize norms of the curvature, i.e. the bending energy, distributed branch points are energetically preferred in sufficiently large pseudospherical surfaces. Further, they are distributed so that they lead to fractal-like recursive buckling *** Codes 53C42(Primary) 53A70, 53C80, 35Q74, 74K99 (Secondary) Copyright © 2020, The Authors. All rights reserved.

关键词： Morphology

On the Age of Status Updates in Unreliable Multi-Source M/G/1 Queueing Systems

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arXiv 2022年

作者： SenthilKumar, Muthukrishnan Dadlani, Aresh Moradian, Masoumeh Khonsari, Ahmad Tsiftsis, Theodoros A. The Department of Applied Mathematics and Computational Sciences Psg College of Technology Coimbatore641004 India The Faculty of Arts - Interdisciplinary Studies University of Alberta EdmontonABT6G 2E7 Canada The Department of Electrical and Computer Engineering Nazarbayev University Astana010000 Kazakhstan The School of Computer Science Institute for Research in Fundamental Sciences Tehran Iran The Department of Electrical and Computer Engineering University of Tehran Iran The Institute for Research in Fundamental Sciences Tehran Iran The School of Intelligent Systems Science and Engineering Jinan University Zhuhai Campus Zhuhai519070 China

The timeliness of status message delivery in communications networks is subjective to time-varying wireless channel transmissions. In this paper, we investigate the age of information (AoI) of each source in a multi-source M/G/1queueingupdatesystem with active server failures. In particular, we adopt the method of supplementary variables to derive a closed-form expression for the average AoI in terms of system parameters, where the server repair time follows a general distribution and the service time of packets generated by independent sources is a general random variable. Numerical results are provided to validate the effectiveness of the proposed packet serving policy under different parametric settings. © 2022, CC BY.

关键词： Real time systems

Overview of the Head and Neck Tumor Segmentation for Magnetic Resonance Guided Applications (HNTS-MRG) 2024 Challenge

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arXiv 2024年

作者： Wahid, Kareem A. Dede, Cem El-Habashy, Dina M. Kamel, Serageldin Rooney, Michael K. Khamis, Yomna Abdelaal, Moamen R.A. Ahmed, Sara Corrigan, Kelsey L. Chang, Enoch Dudzinski, Stephanie O. Salzillo, Travis C. McDonald, Brigid A. Mulder, Samuel L. McCullum, Lucas Alakayleh, Qusai Sjogreen, Carlos He, Renjie Mohamed, Abdallah S.R. Lai, Stephen Y. Christodouleas, John P. Schaefer, Andrew J. Naser, Mohamed A. Fuller, Clifton D. Department of Radiation Oncology The University of Texas MD Anderson Cancer HoustonTX United States Department of Imaging Physics The University of Texas MD Anderson Cancer HoustonTX United States Transitional Year Program Corewell Health Wiliam Beaumont Royal OakMI United States Department of Radiation Oncology University of Maryland School of Medicine BaltimoreMD United States Department of Clinical Oncology and Nuclear Medicine Faculty of Medicine Alexandria University Alexandria Egypt UT MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences Houston United States Department of Radiation Oncology Baylor College of Medicine HoustonTX United States Department of Head and Neck Surgery The University of Texas MD Anderson Cancer HoustonTX United States Elekta AtlantaGA United States Department of Computational Applied Mathematics and Operations Research Rice University HoustonTX United States

Magnetic resonance (MR)-guided radiation therapy (RT) is enhancing head and neck cancer (HNC) treatment through superior soft tissue contrast and longitudinal imaging capabilities. However, manual tumor segmentation remains a significant challenge, spurring interest in artificial intelligence (AI)-driven automation. To accelerate innovation in this field, we present the Head and Neck Tumor Segmentation for MR-Guided Applications (HNTS-MRG) 2024 Challenge, a satellite event of the 27th International Conference on Medical Image Computing and Computer Assisted Intervention. This challenge addresses the scarcity of large, publicly available AI-ready adaptive RT datasets in HNC and explores the potential of incorporating multi-timepoint data to enhance RT auto-segmentation performance. Participants tackled two HNC segmentation tasks: automatic delineation of primary gross tumor volume (GTVp) and gross metastatic regional lymph nodes (GTVn) on pre-RT (Task 1) and mid-RT (Task 2) T2-weighted scans. The challenge provided 150 HNC cases for training and 50 for testing, hosted on *** using a Docker submission framework. In total, 19 independent teams from across the world qualified by submitting both their algorithms and corresponding papers, resulting in 18 submissions for Task 1 and 15 submissions for Task 2. Evaluation using the mean aggregated Dice Similarity Coefficient showed top-performing AI methods achieved scores of 0.825 in Task 1 and 0.733 in Task 2. These results surpassed clinician interobserver variability benchmarks, marking significant strides in automated tumor segmentation for MR-guided RT applications in HNC. © 2024, CC BY.

关键词： Magnetic resonance imaging

Discovery of the type-II superconductor Ta4Rh2C1−δ with a high upper critical field

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Physical Review Research 2025年第2期7卷 023147-023147页

作者： KeYuan Ma Sara López-Paz Karolina Gornicka Harald O. Jeschke Tomasz Klimczuk Fabian O. von Rohr Max Planck Institute for Chemical Physics of Solids 01187 Dresden Germany Department of Quantum Matter Physics University of Geneva CH-1211 Geneva Switzerland Faculty of Applied Physics and Mathematics and Advanced Materials Centre Gdansk University of Technology Gdansk 80-233 Poland Research Institute for Interdisciplinary Science Okayama University Okayama 700-8530 Japan

We report on the discovery of superconductivity in the previously unknown compound Ta4Rh2C1−δ. Ta4Rh2C1−δ crystallizes in the η-carbide structure type, in the cubic space group Fd3¯m (No. 227) with a unit cell parameter of a=11.7947 Å. Temperature-dependent magnetic susceptibility, resistivity, and specific-heat capacity measurements reveal that Ta4Rh2C1−δ is a type-II bulk superconductor with a critical temperature of Tc=6.4K and a normalized specific-heat jump ΔC/γTc=1.56. Notably, we find that Ta4Rh2C1−δ has a high upper critical field of μ0Hc2(0)=17.4T, which exceeds the BCS weak-coupling Pauli limit of μ0HPauli=11.9T.

关键词： Magnetic susceptibility

Modeling of anisotropy effects in phosphorene devices

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Physical Review applied 2025年第6期23卷 064031-064031页

作者： Amirali Chalechale Roderick Melnik Zoran L. Miškovic Department of Applied Mathematics University of Waterloo Waterloo Ontario N2L 3G1 Canada MS2Discovery Interdisciplinary Research Institute M2Net Lab Wilfrid Laurier University Waterloo Ontario N3L 3V6 Canada

In this paper, we present a model for the drift mobility tensor of a monolayer black phosphorus (phosphorene), encapsulated between two dielectrics. The model employs the energy-loss method to derive analytical expressions, accounting for pointlike charge-impurity distribution at various depths within the structure. Anisotropy, a critical factor in phosphorene-based devices, profoundly influences charge-transport properties by shaping the underlying device physics and behavior. Through the detailed analysis of various internal and external parameters, we reveal how anisotropy leads to significant differences in mobility between the armchair and zigzag directions. Both correlated and uncorrelated impurities are studied extensively and the current-voltage characteristics are derived, along with their sensitivity to the rotation angle of the phosphorene conducting channel. The longitudinal current density induced by the external electric field (along the x direction) is derived under two types of boundary conditions applied in the transverse direction in the channel corresponding to a zero electric field or a zero current in the y direction. This approach enables a thorough analysis of the effect of the misalignment angle of phosphorene. This work lays the foundation for the design and optimization of high-performance phosphorene-based nano- and optoelectronic devices by deepening the understanding of anisotropic charge transport.

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A comparative analysis of lead (Pb) and cadmium heavy metals contents in bottled and refilled drinking water in Sukarame District, Bandar Lampung

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AIP Conference Proceedings 2024年第1期3058卷

作者： Welly Anggraini Iqlima Amelia Anisa Oktina Sari Pratama Mala Pratama Devi Cendekia Rizkia Dita Farenda Biology Education Department Tarbiyah and Teacher Training Faculty Raden Intan State Islamic University of Lampung Lampung Indonesia Mathematics and Natural Science Education Faculty Universitas Pendidikan Indonesia Bandung Indonesia Department of Agricultural Technology Applied Chemistry Study Program D4 Politeknik Negeri Lampung Lampung Indonesia

The primary need of humans is access to safe drinking water. These requirements expand the availability of water supply facilities, refilled drinking water, and bottled drinking water. Heavy metals are transition elements with large atomic masses. This study aims to assess the heavy metals lead (Pb) and cadmium (Cd) in bottled and refilled drinking water using Ministry of Health Regulation No. 492/Menkes/Per/IV/2010. An atomic absorption spectrophotometer was used to test samples of five local bottled drinking water brands and twelve refilled drinking water Sukarame sub-district. The tests found that certain heavy metals exceeded the government’s maximum level. The AMDK5, with a Pb content of-0.007 mg/L and a Cd concentration of 0.001 mg/L, was one of five bottled water samples with acceptable quality. The Pb and Cd content in the other four samples, on the other hand, surpassed the maximum standard. Pb and Cd levels in refilled drinking water were measured, and the results were mixed. Pb values in five of the twelve refilled drinking water samples exceeded the maximum standard of 0.01 mg/L. Furthermore, the Cd content in twelve samples of refilled drinking water exceeded 0.003 mg/L, which violated the requirement.

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THE SPECTRAL UNDERPINNING OF WORD2VEC

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arXiv 2020年

作者： Jaffe, Ariel Kluger, Yuval Lindenbaum, Ofir Patsenker, Jonathan Peterfreund, Erez Steinerberger, Stefan Program in Applied Mathematics Yale University New Haven United States Department of Pathology Yale School of Medicine New Haven United States School of Computer Science and Engineering Hebrew University Jerusalem Israel Department of Mathematics Yale University New Haven United States

Word2vec due to Mikolov et al. (2013) is a word embedding method that is widely used in natural language processing. Despite its great success and frequent use, theoretical justification is still lacking. The main contribution of our paper is to propose a rigorous analysis of the highly nonlinear functional of word2vec. Our results suggest that word2vec may be primarily driven by an underlying spectral method. This insight may open the door to obtaining provable guarantees for word2vec. We support these findings by numerical simulations. One fascinating open question is whether the nonlinear properties of word2vec that are not captured by the spectral method are beneficial and, if so, by what mechanism. Copyright © 2020, The Authors. All rights reserved.

关键词： Spectroscopy

Spectral Top-Down Recovery of Latent Tree Models

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arXiv 2021年

作者： Aizenbud, Yariv Jaffe, Ariel Wang, Meng Hu, Amber Amsel, Noah Nadler, Boaz Chang, Joseph T. Kluger, Yuval Program in Applied Mathematics Yale University New HavenCT06511 United States Department of Computer Science Weizmann Institute of Science Rehovot76100 Israel Department of Statistics Yale University New HavenCT06520 United States Interdepartmental Program in Computational Biology and Bioinformatics Yale University New HavenCT06511 United States Department of Pathology Yale University New HavenCT06511 United States

Modeling the distribution of high dimensional data by a latent tree graphical model is a prevalent approach in multiple scientific domains. A common task is to infer the underlying tree structure, given only observations of its terminal nodes. Many algorithms for tree recovery are computationally intensive, which limits their applicability to trees of moderate size. For large trees, a common approach, termed divide-and-conquer, is to recover the tree structure in two steps. First, recover the structure separately of multiple, possibly random subsets of the terminal nodes. Second, merge the resulting subtrees to form a full tree. Here, we develop Spectral Top-Down Recovery (STDR), a deterministic divide-and-conquer approach to infer large latent tree models. Unlike previous methods, STDR partitions the terminal nodes in a non random way, based on the Fiedler vector of a suitable Laplacian matrix related to the observed nodes. We prove that under certain conditions, this partitioning is consistent with the tree structure. This, in turn, leads to a significantly simpler merging procedure of the small subtrees. We prove that STDR is statistically consistent and bound the number of samples required to accurately recover the tree with high probability. Using simulated data from several common tree models in phylogenetics, we demonstrate that STDR has a significant advantage in terms of runtime, with improved or similar accuracy. Copyright © 2021, The Authors. All rights reserved.

关键词： Recovery

Acute Respiratory Failure From Early Pandemic COVID-19: Noninvasive Respiratory Support vs Mechanical Ventilation

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CHEST Critical Care

CHEST Critical Care 2024年第1期2卷 100030-100030页

作者： Fisher, Julia M. Subbian, Vignesh Essay, Patrick Pungitore, Sarah Bedrick, Edward J. Mosier, Jarrod M. Statistics Consulting Laboratory The University of Arizona College of Medicine Tucson AZ United States Department of Systems and Industrial Engineering The University of Arizona College of Medicine Tucson AZ United States Department of Biomedical Engineering College of Engineering The University of Arizona College of Medicine Tucson AZ United States BI05 Institute The University of Arizona College of Medicine Tucson AZ United States Program in Applied Mathematics The University of Arizona College of Medicine Tucson AZ United States The University of Arizona the Department of Emergency Medicine The University of Arizona College of Medicine Tucson AZ United States Division of Pulmonary Allergy Critical Care and Sleep Department of Medicine The University of Arizona College of Medicine Tucson AZ United States

Background: The optimal strategy for initial respiratory support in patients with respiratory failure associated with COVID-19 is unclear, and the initial strategy may affect outcomes. Research Question: Which initial respiratory support strategy is associated with improved outcomes in patients with COVID-19 with acute respiratory failure? Study Design and Methods: All patients with COVID-19 requiring respiratory support and admitted to a large health care network were eligible for inclusion. We compared patients treated initially with noninvasive respiratory support (NIRS;noninvasive positive pressure ventilation by facemask or high-flow nasal oxygen) with patients treated initially with invasive mechanical ventilation (IMV). The primary outcome was time to in-hospital death analyzed using an inverse probability of treatment weighted Cox model adjusted for potential confounders. Secondary outcomes included unweighted and weighted assessments of mortality, lengths of stay (ICU and hospital), and time to intubation. Results: Nearly one-half of the 2,354 patients (47%) who met inclusion criteria received IMV first, and 53% received initial NIRS. Overall, in-hospital mortality was 38% (37% for IMV and 39% for NIRS). Initial NIRS was associated with an increased hazard of death compared with initial IMV (hazard ratio, 1.42;95% CI, 1.03-1.94), but also an increased hazard of leaving the hospital sooner that waned with time (noninvasive support by time interaction: hazard ratio, 0.97;95% CI, 0.95-0.98). Interpretation: Patients with COVID-19 with acute hypoxemic respiratory failure initially treated with NIRS showed an increased hazard of in-hospital death. © 2023 The Authors

关键词： COVID-19 high-flow nasal oxygen mechanical ventilation noninvasive respiratory support respiratory failure