检索结果-内蒙古大学图书馆

arXiv 2024年

作者： Carlin, Jeffrey L. Sand, David J. Mutlu-Pakdil, Burçin Crnojević, Denija Doliva-Dolinsky, Amandine Garling, Christopher T. Peter, Annika H.G. Brodie, Jean P. Forbes, Duncan A. Hargis, Jonathan R. Romanowsky, Aaron J. Spekkens, Kristine Strader, Jay Willman, Beth AURA/Rubin Observatory 950 North Cherry Avenue TucsonAZ85719 United States Department of Astronomy/Steward Observatory 933 North Cherry Avenue TucsonAZ85721-0065 United States Department of Physics and Astronomy Dartmouth College HanoverNH03755 United States Department of Physics & Astronomy University of Tampa 401 West Kennedy Boulevard TampaFL33606 United States Department of Physics & Astronomy Dartmouth College HanoverNH03755 United States Department of Astronomy University of Virginia 530 McCormick Road CharlottesvilleVA22904 United States CCAPP Department of Physics Department of Astronomy The Ohio State University ColumbusOH43210 United States Centre for Astrophysics and Supercomputing Swinburne University John Street HawthornVIC3122 Australia Department of Astronomy & Astrophysics University of California Santa Cruz 1156 High Street Santa CruzCA95064 United States Centre for Astrophysics and Supercomputing Swinburne University HawthornVIC3122 Australia Space Telescope Science Institute 3700 San Martin Drive BaltimoreMD21218 United States University of California Observatories 1156 High Street Santa CruzCA95064 United States Department of Physics & Astronomy San José State University One Washington Square San JoseCA95192 United States Department of Physics Engineering Physics and Astronomy Queen's University KingstonONK7L 3N6 Canada Center for Data Intensive and Time Domain Astronomy Department of Physics and Astronomy Michigan State University East LansingMI48824 United States LSST Discovery Alliance 933 North Cherry Avenue TucsonAZ85719 United States

We present the first comprehensive census of the satellite population around a Large Magellanic Cloud (LMC) stellar-mass galaxy, as part of the Magellanic Analog Dwarf Companions and Stellar Halos (MADCASH) survey. We have surveyed NGC 2403 (D = 3.0 Mpc) with the Subaru/Hyper Suprime-Cam imager out to a projected radius of 90 kpc (with partial coverage extending out to ∼ 110 kpc, or ∼ 80% of the virial radius of NGC 2403), resolving stars in the uppermost ∼2.5 mags of its red giant branch. By looking for stellar overdensities in the red giant branch spatial density map, we identify 149 satellite candidates, of which only the previously discovered MADCASH J074238+65201- dw is a bona fide dwarf, together with the more massive and disrupting satellite DDO 44. We carefully assess the completeness of our search via injection of artificial dwarf galaxies into the images, finding that we are reliably sensitive to candidates down to MV ∼ -7.5 mag (and somewhat sensitive to even fainter satellites). A comparison of the satellite luminosity function of NGC 2403 down to this magnitude limit to theoretical expectations shows overall good agreement. This is the first of a full sample of 11 Magellanic Cloud-mass host galaxies we will analyze, creating a statistical sample that will provide the first quantitative constraints on hierarchical models of galaxy formation around low-mass hosts. © 2024, CC BY.

关键词： Population statistics

来源：评论

学校读者我要写书评

暂无评论

A systematic theoretical study on FeOx-supported single-atom catalysts： M1/FeOx for CO oxidation

引用

Nano Research 2018年第3期11卷 1599-1611页

作者： Jinxia Liang Qi Yu Xiaofeng Yang Tao Zhang Jun Li Guizhou Provincial Key Laboratory of Computational Nano-Material Science Guizhou Synergetic Innovation Center of Scientific Big Data for Advanced Manufacturing Technology Guizhou Education University Guiyang 550018 China Shaanxi Key Laboratory of Catalysis Shaanxi University of Technology Hanzhong 723000 China Department of Chemistry and Key Laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education Tsinghua University Beijing 100084 China State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 China

A single-atom catalyst （SAC） that was first proposed by us in 2011 has aroused significant recent interest. Among the various SACs, FeOx-based ones including Pt1/FeOx, Ir1/FeOx, Au1/FeOx, Ni1/FeOx, and Fe1/FeOx have been investigated either experimentally or theoretically for CO oxidation. However, a systematic study of FeO,-based SACs has not been conducted. For a comprehensive understanding of FeOx-supported single-metal-atom catalysts, extensive density functional theory calculations were carried out on the activities and catalytic mechanisms of SACs with the 3d, 4d, and 5d metals of group VIII to IB, i.e., M1/FeOx （M = Fe, Co, Ni, Cu; Ru, Rh, Pd, Ag; Os, Ir, Pt, Au） for CO oxidation. Remarkably, a new noble metal SAC, Pd1/FeOx, with high activity in CO oxidation was found and is predicted to be even better than the previously reported Pt1/FeOx and Ni1/FeOx. In comparison, other M1/FeOx SACs （M = Fe, Co, Cu; Ru, Rh, Ag; Os, Ir, Au） showed only low activities in CO oxidation. Moreover, the adsorption strength of CO on the single-atom active sites was found to be the key in determining the catalytic activity of these SACs for CO oxidation, because it governs the recoverability of oxygen vacancies on their surfaces in the formation of a second CO2 during CO oxidation. Our systematic studies of FeOx-supported SACs will help in understanding the fundamental mechanisms of the interactions between singly dispersed surface metal atoms and FeOx substrate and in designing highly active FeOx-supported SACs.

关键词： single-atom catalyst M1/FeOx density functional theory heterogeneous catalysis

来源：评论

学校读者我要写书评

暂无评论

Distributed Deep Learning Model for Intelligent Video Surveillance Systems with Edge Computing

arXiv

引用

arXiv 2019年

作者： Chen, Jianguo Li, Kenli Deng, Qingying Li, Keqin Yu, Philip S. College of Computer Science and Electronic Engineering Hunan University National Supercomputing Center in Changsha Hunan Changsha410082 China School of Mathematics and Computational Science Xiangtan University Xiangtan411105 China Department of Computer Science State University of New York New PaltzNY12561 United States Department of Computer Science University of Illinois at Chicago ChicagoIL60607 United States Institute for Data Science Tsinghua University Beijing100084 China

In this paper, we propose a Distributed Intelligent Video Surveillance (DIVS) system using Deep Learning (DL) algorithms and deploy it in an edge computing environment. We establish a multi-layer edge computing architecture and a distributed DL training model for the DIVS system. The DIVS system can migrate computing workloads from the network center to network edges to reduce huge network communication overhead and provide low-latency and accurate video analysis solutions. We implement the proposed DIVS system and address the problems of parallel training, model synchronization, and workload balancing. Task-level parallel and model-level parallel training methods are proposed to further accelerate the video analysis process. In addition, we propose a model parameter updating method to achieve model synchronization of the global DL model in a distributed EC environment. Moreover, a dynamic data migration approach is proposed to address the imbalance of workload and computational power of edge nodes. Experimental results showed that the EC architecture can provide elastic and scalable computing power, and the proposed DIVS system can efficiently handle video surveillance and analysis tasks. Copyright © 2019, The Authors. All rights reserved.

关键词： Edge computing

来源：评论

学校读者我要写书评

暂无评论

Apercal - The Apertif calibration pipeline

arXiv

引用

arXiv 2021年

作者： Adebahr, Björn Schulz, R. Dijkema, T.J. Moss, V.A. Offringa, A.R. Kutkin, A. van der Hulst, J.M. Frank, B.S. Vilchez, N.P.E. Verstappen, J. Adams, E.K. de Blok, W.J.G. Denes, H. Hess, K.M. Lucero, D. Morganti, R. Oosterloo, T. Pisano, D.-J. Ivashina, M.V. van Cappellen, W.A. Connor, L.D. Coolen, A.H.W.M. Damstra, S. Loose, G.M. Maan, Y. Maccagni, F.M. Mika, A. Mulder, H. Oostrum, L.C. Orrú, E. Smits, R. van der Schuur, D. van Leeuwen, J. Vohl, D. Wijnholds, S.J. Ziemke, J. Bochum Germany ASTRON Dwingeloo Netherlands CSIRO Astronomy and Space Science Sydney Australia University of Sydney Sydney Australia Cavendish Laboratory Cambridge United Kingdom Kapteyn Astronomical Institute University of Groningen Groningen Netherlands Department of Physics Virginia Tech BlacksburgVA United States Astro Space Center of Lebedev Physical Institute Profsoyuznaya Str. 84/32 Moscow117997 Russia 2 Fir Street Observatory 7925 South Africa Inter-University Institute for Data Intensive Astronomy Department of Astronomy University of Cape Town Private Bag X3 Rondebosch 7701 South Africa University of Cape Town University Private Bag Rondebosch Cape Town7701 South Africa Department of Physics and Astronomy West Virginia University White Hall Box 6315 MorgantownWV26506 United States Dept. of Electrical Engineering Chalmers University of Technology Gothenburg Sweden Anton Pannekoek Institute University of Amsterdam Postbus 94249 Amsterdam1090 GE Netherlands Rijksuniversiteit Groningen Center for Information Technology P.O. Box 11044 Groningen9700 CA Netherlands Netherlands eScience Center Science Park 140 Amsterdam1098 XG Netherlands INAF Osservatorio Astronomico di Cagliari Via della Scienza 5 CA Selargius09047 Italy

Apertif (APERture Tile In Focus) is one of the Square Kilometre Array (SKA) pathfinder facilities. The Apertif project is an upgrade to the 50-year-old Westerbork Synthesis Radio Telescope (WSRT) using phased-array feed technology. The new receivers create 40 individual beams on the sky, achieving an instantaneous sky coverage of 6.5 square degrees. The primary goal of the Apertif Imaging Survey is to perform a wide survey of 3500 square degrees (AWES) and a medium deep survey of 350 square degrees (AMES) of neutral atomic hydrogen (up to a redshift of 0.26), radio continuum emission and polarisation. Each survey pointing yields 4.6 TB of correlated data. The goal of Apercal is to process this data and fully automatically generate science ready data products for the astronomical community while keeping up with the survey observations. We make use of common astronomical software packages in combination with Python based routines and parallelisation. We use an object oriented module-based approach to ensure easy adaptation of the pipeline. A Jupyter notebook based framework allows user interaction and execution of individual modules as well as a full automatic processing of a complete survey observation. If nothing interrupts processing, we are able to reduce a single pointing survey observation on our five node cluster with 24 physical cores and 256 GB of memory each within 24h keeping up with the speed of the surveys. The quality of the generated images is sufficient for scientific usage for 44 % of the recorded data products with single images reaching dynamic ranges of several thousands. Future improvements will increase this percentage to over 80 %. Our design allowed development of the pipeline in parallel to the commissioning of the Apertif system. © 2021, CC BY.

关键词： Surveys

来源：评论

学校读者我要写书评

暂无评论

Measurement of the U236(n,f) cross section for neutron energies from 0.4 MeV to 40 MeV from the back-streaming white neutron beam at the China Spallation Neutron Source

引用

Physical Review C 2020年第3期102卷 034604-034604页

作者： Zhizhou Ren Yiwei Yang Jie Wen Hairui Guo Zhongwei Wen Rong Liu Zijie Han Weili Sun Xingyan Liu Qiping Chen Tao Ye Qi An Huaiyong Bai Jie Bao Ping Cao Yonghao Chen Pinjing Cheng Zengqi Cui Ruirui Fan Changqing Feng Minhao Gu Fengqin Guo Changcai Han Guozhu He Yongcheng He Yuefeng He Hanxiong Huang Weiling Huang Xiru Huang Xiaolu Ji Xuyang Ji Haoyu Jiang Wei Jiang Hantao Jing Ling Kang Mingtao Kang Bo Li Lun Li Qiang Li Xiao Li Yang Li(a) Yang Li(b) Shubin Liu Guangyuan Luan Yinglin Ma Changjun Ning Binbin Qi Jie Ren Xichao Ruan Zhaohui Song Hong Sun Xiaoyang Sun Zhijia Sun Zhixin Tan Hongqing Tang Jingyu Tang Pengcheng Wang Qi Wang Taofeng Wang Yanfeng Wang Zhaohui Wang Zheng Wang Qingbiao Wu Xiaoguang Wu Xuan Wu Likun Xie Han Yi Li Yu Tao Yu Yongji Yu Guohui Zhang Jing Zhang Linhao Zhang Liying Zhang Qingmin Zhang Qiwei Zhang Xianpeng Zhang Yuliang Zhang Zhiyong Zhang Yingtan Zhao Liang Zhou Zuying Zhou Danyang Zhu Kejun Zhu Peng Zhu Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics Mianyang 621900 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China State Key Laboratory of Particle Detection and Electronics China Department of Modern Physics University of Science and Technology of China Hefei 230026 China State Key Laboratory of Nuclear Physics and Technology School of Physics Peking University Beijing 100871 China Key Laboratory of Nuclear Data China Institute of Atomic Energy Beijing 102413 China Institute of High Energy Physics Chinese Academy of Sciences (CAS) Beijing 100049 China Spallation Neutron Source Science Center Dongguan 523803 China University of South China Hengyang 421001 China Northwest Institute of Nuclear Technology Xi'an 710024 China Department of Engineering and Applied Physics University of Science and Technology of China Hefei 230026 China School of Physics Beihang University Beijing 100083 China Xi'an Jiaotong University Xi'an 710049 China

A new measurement of the neutron-induced fission cross section of U236 relative to the standard U235(n,f) cross section from 0.4–40 MeV was carried out by the time-of-flight method and a multicell fast fission ionization chamber at the China Spallation Neutron Source-Back-n white neutron source. The measured resonance peaks and the distribution of fission event-energy spectrum from the U235(n,f) reaction are in good agreement with that of the ENDF/B-VIII.0 evaluation, which confirms the reliability of the experimental setup. The measured U236/235U fission cross section ratios in 0.4–40 MeV neutron energy region are compared to previous measurements. The U236 fission cross section with the relative experimental uncertainty of 11.2%–2.9% in 0.4–1 MeV and 2.9%–2.8% in 1–40 MeV is determined and compared to calculation, previous measurements, and main evaluations. The present theoretical result with calculation program UNF reproduces the experimental data and the LANSCE data better than ENDF/B-VIII.0 evaluation does in the secondary fission region. The result confirms current evaluations from 0.4–40 MeV in most energy points and provides the experimental data for evaluating the discrepancies in the relevant energy region.

关键词： Fission Neutron physics A ≥ 220 Spectrometers & spectroscopic techniques

来源：评论

学校读者我要写书评

暂无评论

Highly Stereoselective Diels–Alder Reactions Catalyzed by Diboronate Complexes**

引用

Angewandte Chemie 2023年第33期135卷

作者： Dr. Yuan-He Li Dr. Su-Lei Zhang Dr. Yong Lu Bo Xiao Dr. Tian-Yu Sun Qian-Qian Xu Prof. Dr. Jia-Hua Chen Prof. Dr. Zhen Yang Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS) Peking-Tsinghua Center for Life Sciences Peking University Beijing 100871 China Contribution: Data curation (lead) Investigation (lead) Methodology (lead) Validation (lead) Writing - original draft (lead) Writing - review & editing (lead) Contribution: Methodology (supporting) Writing - review & editing (supporting) Contribution: Data curation (supporting) Writing - review & editing (supporting) Lab of Computational Chemistry and Drug Design State Key Laboratory of Chemical Oncogenomics Peking University Shenzhen Graduate School Shenzhen 518055 China Contribution: Supervision (supporting) Writing - review & editing (supporting) Shenzhen Bay Laboratory Shenzhen 518055 China State Key Laboratory of Chemical Oncogenomics Key Laboratory of Chemical Genomics Peking University Shenzhen Graduate School Shenzhen 518055 China Contribution: Conceptualization (lead) Funding acquisition (lead) Supervision (lead) Writing - review & editing (supporting)

A highly enantioselective catalytic system for exo -Diels–Alder reactions was developed based on the newly discovered bispyrrolidine diboronates (BPDB). Activated by various Lewis or Brønsted acids, BPDB can catalyze highly stereoselective asymmetric exo -Diels–Alder reactions of monocarbonyl-based dienophiles. When 1,2-dicarbonyl-based dienophiles are used, the catalyst can sterically distinguish between the two binding sites, which leads to highly regioselective asymmetric Diels–Alder reactions. BPDB can be prepared as crystalline solids on a large scale and are stable under ambient condition. Single-crystal X-ray analysis of the structure for acid-activated BPDB indicated that its activation involves cleavage of a labile B←N bond.

关键词： Asymmetric Catalysis Bispyrrolidine Diboronates Diels–Alder Reaction Exo-Selectivity Pericyclic Reaction

来源：评论

学校读者我要写书评

暂无评论

Real-time prediction of COVID-19 related mortality using electronic health records

arXiv

引用

arXiv 2020年

作者： Schwab, Patrick Mehrjou, Arash Parbhoo, Sonali Celi, Leo Anthony Hetzel, Jürgen Hofer, Markus Schölkopf, Bernhard Bauer, Stefan F. Hoffmann-La Roche Ltd Basel Switzerland Max Planck Institute for Intelligent Systems Tübingen Germany ETH Zurich Switzerland John A. Paulson School of Engineering and Applied Sciences Harvard University Cambridge United States Department of Medicine Beth Israel Deaconess Medical Center Harvard Medical School Boston United States MIT Critical Data Laboratory for Computational Physiology Institute for Medical Engineering and Science Harvard-MIT Health Sciences & Technology Cambridge United States Department of Medical Oncology and Pneumology University Hospital of Tübingen Germany Department of Pneumology Kantonsspital Winterthur Switzerland CIFAR Azrieli Global Scholar

Coronavirus Disease 2019 (COVID-19) is an emerging respiratory disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with rapid human-to-human transmission and a high case fatality rate particularly in older patients. Due to the exponential growth of infections, many healthcare systems across the world are under pressure to care for increasing amounts of at-risk patients. Given the high number of infected patients, identifying patients with the highest mortality risk early is critical to enable effective intervention and optimal prioritisation of care. Here, we present the COVID-19 Early Warning System (CovEWS), a clinical risk scoring system for assessing COVID-19 related mortality risk. CovEWS provides continuous real-time risk scores for individual patients with clinically meaningful predictive performance up to 192 hours (8 days) in advance, and is automatically derived from patients' electronic health records (EHRs) using machine learning. We trained and evaluated CovEWS using de-identified data from a cohort of 66 430 COVID-19 positive patients seen at over 69 healthcare institutions in the United States (US), Australia, Malaysia and India amounting to an aggregated total of over 2 863 years of patient observation time. On an external test cohort of 5 005 patients, CovEWS predicts COVID-19 related mortality from 78.8% (95% confidence interval [CI]: 76.0, 84.7%) to 69.4% (95% CI: 57.6, 75.2%) specificity at a sensitivity greater than 95% between respectively 1 and 192 hours prior to observed mortality events - significantly outperforming existing generic and COVID-19 specific clinical risk scores. CovEWS could enable clinicians to intervene at an earlier stage, and may therefore help in preventing or mitigating COVID-19 related mortality. Copyright © 2020, The Authors. All rights reserved.

关键词： Coronavirus

来源：评论

学校读者我要写书评

暂无评论

Association of structural MRI with Braak staging using neural network-based risk scoring

引用

Alzheimer's & Dementia 2023年第S3期19卷

作者： Matthew I. Miller Shangran Qiu Prajakta S. Joshi Joyce Lee Rhoda Au Vijaya B. Kolachalama Boston University School of Medicine Boston MA USA College of Arts & Sciences Boston University Boston MA USA Framingham Heart Study Boston University Chobanian & Avedisian School of Medicine Boston MA USA Boston University Alzheimer’s Disease Center Boston University Boston MA USA Boston University School of Public Health Boston MA USA Department of Anatomy and Neurobiology Boston University Chobanian & Avedisian School of Medicine Boston MA USA Hariri Institute for Computing and Computational Science & Engineering Boston University Boston MA USA Faculty of Computing & Data Sciences Boston University Boston MA USA Boston University Alzheimer’s Disease Center Boston University Chobanian & Avedisian School of Medicine Boston MA USA Whitaker Cardiovascular Institute Boston University Chobanian & Avedisian School of Medicine Boston MA USA

Background The gold standard of Alzheimer’s disease (AD) diagnosis remains histopathologic examination of neuropathologic changes. However, the dependence on post-mortem microscopic analysis limits the role of pathology in clinical care. Magnetic resonance imaging (MRI) is routinely used to diagnose suspected dementia (DE) due to AD, but correlating neuroimaging to underlying pathologic changes remains challenging. Herein, we report the development of two risk scores derived from convolutional neural network (CNN) processing of MRI scans, which we then validate against Braak staging of neurofibrillary tangles from autopsy reports. Method Using T1-weighted MRIs from the National Alzheimer’s Coordinating center (NACC), we trained two CNNs (Figure 1) to predict continuous scores for overall cognitive status (“COG” score) and AD probability (“ALZ” score). The COG score, ranging from 0-2, graded a subject’s cognitive status on a spectrum from normal cognition (NC, 0), to mild cognitive impairment (MCI, 1), and DE due to any cause (2). The ALZ score then graded each DE individual’s probability of AD from 0 to 1. These CNNs were then applied to a subset of participants with autopsy reports available within 6 months of MRI. CNN performance was evaluated by area under receiver operating characteristic curve (AUC). Differences in risk scores were assessed by Kruskal-Wallis H testing with post hoc Dunn testing. Result The CNN models for COG and ALZ score estimation were trained on 4,822 NACC participants. Thresholding of COG scores distinguished individuals with DE from those with NC and MCI (AUC = 0.87). ALZ scores distinguished individuals with AD from those with non-AD causes of DE (AUC = 0.77). Among 74 persons with available neuropathology data, COG scores differed significantly among Braak staging groups (p<0.001), increasing from a mean of 0.99±0.36 in Stage 1 to 1.47±0.41 in Stage 6 (p = 0.010). Significant differences in ALZ scores were also observed (p = 0.039) betwe

关键词：

来源：评论

学校读者我要写书评

暂无评论

Streams, Shells, and Substructures in the Accretion-Built Stellar Halo of NGC 300

arXiv

引用

arXiv 2025年

作者： Fielder, Catherine E. Sand, David J. Jones, Michael G. Crnojević, Denija Drlica-Wagner, Alex Bennet, Paul Carlin, Jeffrey L. Cerny, William Doliva-Dolinsky, Amandine Hunter, Laura C. Karunakaran, Ananthan Limberg, Guilherme Mutlu-Pakdil, Burçin Pace, Andrew B. Pearson, Sarah Smercina, Adam Spekkens, Kristine Starkenburg, Tjitske Strader, Jay Stringfellow, Guy S. Tollerud, Erik Bom, Clecio R. Carballo-Bello, Julio A. Chaturvedi, Astha Choi, Yumi James, David J. Martínez-Vázquez, Clara E. Riley, Alex Sakowska, Joanna Vivas, Kathy Steward Observatory University of Arizona 933 North Cherry Avenue TucsonAZ85721-0065 United States Department of Physics and Astronomy University of Tampa 401 West Kennedy Boulevard TampaFL33606 United States Astronomy & Astrophysics University of Chicago ChicagoIL60637 United States Fermi National Accelerator Laboratory BataviaIL United States Space Telescope Science Institute 3700 San Martin Drive BaltimoreMD21218 United States AURA/Rubin Observatory 950 North Cherry Avenue TucsonAZ85719 United States Department of Astronomy Yale University New HavenCT06520 United States Department of Physics and Astronomy Dartmouth College HanoverNH03755 United States Department of Astronomy & Astrophysics University of Toronto TorontoONM5S 3H4 Canada Dunlap Institute for Astronomy and Astrophysics University of Toronto TorontoONM5S 3H4 Canada Kavli Institute for Cosmological Physics University of Chicago ChicagoIL60637 United States Department of Astronomy University of Virginia 530 McCormick Rd CharlottesvilleVA22904 United States Niels Bohr Institute University of Copenhagen Copenhagen Denmark Department of Physics and Space Science Royal Military College of Canada P.O. Box 17000 Station Forces KingstonONK7K 7B4 Canada Department of Physics Engineering Physics and Astronomy Queen's University KingstonONK7L 3N6 Canada Department of Physics & Astronomy CIERA Northwestern University EvanstonIL United States Center for Data Intensive and Time Domain Astronomy Department of Physics and Astronomy Michigan State University East LansingMI48824 United States Center for Astrophysics and Space Astronomy University of Colorado 389 UCB BoulderCO80309-0389 United States Centro Brasileiro de Pesquisas Fisicas Rua Dr. Xavier Sigaud 150 RJ Rio de Janeiro22290-180 Brazil Instituto de Alta Investigación Universidad de Tarapacá Casilla 7D Arica Chile Department of Physics University of Surrey GuildfordGU2 7XH United Kingdom NSF NOIRLab 95

We present deep optical observations of the stellar halo of NGC 300, an LMC-mass galaxy, acquired with the DEEP sub-component of the DECam Local Volume Exploration survey (DELVE) using the 4 m Blanco Telescope. Our resolved star analysis reveals a large, low surface brightness stellar stream (MV ∼ -8.5;[Fe/H] = -1.4± 0.15) extending more than 40 kpc north from the galaxy's center. We also find other halo structures, including potentially an additional stream wrap to the south, which may be associated with the main stream. The morphology and derived low metallicities of the streams and shells discovered surrounding NGC 300 are highly suggestive of a past accretion event. Assuming a single progenitor, the accreted system is approximately Fornax-like in luminosity, with an inferred mass ratio to NGC 300 of approximately 1 : 15. We also present the discovery of a metal-poor globular cluster (Rproj = 23.3 kpc;MV = -8.99± 0.16;[Fe/H] ≈ -1.6± 0.6) in the halo of NGC 300, the furthest identified globular cluster associated with NGC 300. The stellar structures around NGC 300 represent the richest features observed in a Magellanic Cloud analog to date, strongly supporting the idea that accretion and subsequent disruption is an important mechanism in the assembly of dwarf galaxy stellar halos. © 2025, CC BY-SA.

关键词： Stars

来源：评论

学校读者我要写书评

暂无评论

On the generalization of DIRECTFN for singular integrals over quadrilateral patches

arXiv

引用

arXiv 2017年

作者： Tambova, Alexandra Litsarev, Mikhail Guryev, Georgy Polimeridis, Athanasios G. Center for Computational Data-Intensive Science and Engineering Skoltech Moscow Russia

A set of fully numerical algorithms for evaluating the four-dimensional singular integrals arising from Galerkin surface integral equation methods over conforming quadrilateral meshes is presented. This work is an extension of DIRECTFN, which was recently developed for the case of triangular patches, utilizing in a same fashion a series of coordinate transformations together with appropriate integration re-orderings. The resulting formulas consist of sufficiently smooth kernels and exhibit several favorable characteristics when compared with the vast majority of the methods currently available. More specifically, they can be applied-without modifications-to the following challenging cases: 1) weakly and strongly singular kernels, 2) basis and testing functions of arbitrary order, 3) planar and curvilinear patches, 4) problem-specific Green functions (e.g. expressed in spectral integral form), 5) spectral convergence to machine precision. Finally, we show that the overall performance of the fully numerical schemes can be further improved by a judicious choice of the integration order for each dimension. Copyright © 2017, The Authors. All rights reserved.

关键词： Galerkin methods

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：