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arXiv 2019年

作者： Topaz, Chad M. Cart, James Eaton, Carrie Diaz Shrout, Anelise Hanson Higdon, Jude A. İnce, Kenan Katz, Brian Lewis, Drew Libertini, Jessica Smith, Christian Michael Department of Mathematics and Statistics Williams College WilliamstownMA United States Institute for the Quantitative Study of Inclusion Diversity and Equity WilliamstownMA United States Office of Institutional Research Williams College WilliamstownMA United States Digital and Computational Studies Program Bates College LewistonME United States Department of Mathematics Westminster College Salt Lake CityUT United States Department of Mathematics and Statistics Smith College NorthamptonMA United States Department of Mathematics and Statistics University of South Alabama MobileAL United States Department of Applied Mathematics Virginia Military Institute LexingtonVA United States Department of Sociology University of Wisconsin-Madison MadisonWI United States

In its December 2019 edition, the Notices of the American Mathematical Society published an essay critical of the use of diversity statements in academic hiring. The publication of this essay prompted many responses, including three public letters circulated within the mathematical sciences community. Each letter was signed by hundreds of people and was published online, also by the American Mathematical Society. We report on a study of the signatories’ demographics, which we infer using a crowdsourcing approach. Letter A highlights diversity and social justice. The pool of signatories contains relatively more individuals inferred to be women and/or members of underrepresented ethnic groups. Moreover, this pool is diverse with respect to the levels of professional security and types of academic institutions represented. Letter B does not comment on diversity, but rather, asks for discussion and debate. This letter was signed by a strong majority of individuals inferred to be white men in professionally secure positions at highly research intensive universities. Letter C speaks out specifically against diversity statements, calling them "a mistake," and claiming that their usage during early stages of faculty hiring "diminishes mathematical achievement." Individuals who signed both Letters B and C, that is, signatories who both privilege debate and oppose diversity statements, are overwhelmingly inferred to be tenured white men at highly research intensive universities. Our empirical results are consistent with theories of power drawn from the social sciences. Copyright © 2019, The Authors. All rights reserved.

关键词： Population statistics

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Synergies between low- And intermediate-redshift galaxy populations revealed with unsupervised machine learning

arXiv

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arXiv 2021年

作者： Turner, Sebastian Siudek, Malgorzata Salim, Samir Baldry, Ivan K. Pollo, Agnieszka Longmore, Steven N. Malek, Katarzyna Collins, Chris A. Lisboa, Paulo J. Krywult, Janusz Moutard, Thibaud Vergani, Daniela Fritz, Alexander Astrophysics Research Institute Liverpool John Moores University 146 Brownlow Hill LiverpoolL3 5RF United Kingdom Institut de F'isica d'Altes Energies The Barcelona Institute of Science and Technology Bellaterra08193 Spain National Centre for Nuclear Research ul. Hoza 69 Warsaw00-681 Poland Department of Astronomy Indiana University BloomingtonIN47405 United States Astronomical Observatory of the Jagiellonian University ul. Orla 171 Kraków30-244 Poland Aix Marseille Univ. CNRS CNES LAM Marseille France Department of Applied Mathematics Liverpool John Moores University Byrom Street LiverpoolL3 3AF United Kingdom Institute of Physics Jan Kochanowski University ul. Swietokrzyska 15 Kielce25-406 Poland Department of Astronomy & Physics The Institute for Computational Astrophysics Saint Mary's University 923 Robie Street HalifaxNSB3H 3C3 Canada INAF OAS Bologna Via P. Gobetti 93 BolognaI-40129 Italy Lichtenbergstraße 8 GarchingD-85748 Germany

The colour bimodality of galaxies provides an empirical basis for theories of galaxy evolution. However, the balance of processes that begets this bimodality has not yet been constrained. A more detailed view of the galaxy population is needed, which we achieve in this paper by using unsupervised machine learning to combine multi-dimensional data at two different epochs. We aim to understand the cosmic evolution of galaxy subpopulations by uncovering substructures within the colour bimodality. We choose a clustering algorithm that models clusters using only the most discriminative data available, and apply it to two galaxy samples: one from the second edition of the GALEX-SDSS-WISE Legacy Catalogue (GSWLC-2;z ∼ 0.06), and the other from the VIMOS Public Extragalactic Redshift Survey (VIPERS;z ∼ 0.65). We cluster within a nine-dimensional feature space defined purely by rest-frame ultraviolet-through-near-infrared colours. Both samples are similarly partitioned into seven clusters, breaking down into four of mostly star-forming galaxies (including the vast majority of green valley galaxies) and three of mostly passive galaxies. The separation between these two families of clusters suggests differences in the evolution of their galaxies, and that these differences are strongly expressed in their colours alone. The samples are closely related, with star-forming/green-valley clusters at both epochs forming morphological sequences, capturing the gradual internally-driven growth of galaxy bulges. At high stellar masses, this growth is linked with quenching. However, it is only in our low-redshift sample that additional, environmental processes appear to be involved in the evolution of low-mass passive galaxies. © 2021, CC BY.

关键词： Galaxies

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Model-mapped random phase approximation to evaluate superconductivity in the fluctuation exchange approximation from first principles

arXiv

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arXiv 2018年

作者： Sakakibara, Hirofumi Kotani, Takao Department of applied mathematics and physics Tottori university Tottori680-8552 Japan Computational Condensed Matter Physics Laboratory RIKEN WakoSaitama351-0198 Japan

We have applied the model-mapped RPA [H. Sakakibara et al., J. Phys. Soc. Jpn. 86, 044714 (2017)] to the cuprate superconductors La2CuO4 and HgBa2CuO4, resulting two-orbital Hubbard models. All the model parameters are determined based on first-principles calculations. For the model Hamiltonians, we perform fluctuation exchange calculation. Results explain relative height of Tc observed in experiment for La2CuO4 and HgBa2CuO4. In addition, we give some analyses for the interaction terms in the model, especially comparisons with those of the constrained RPA. Copyright © 2018, The Authors. All rights reserved.

关键词： Copper compounds

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Optimal undirectional amplification induced by optical gain in optomechanical systems

arXiv

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arXiv 2019年

作者： Song, L.N. Zheng, Qiang Xu, Xun-Wei Jiang, Cheng Li, Yong Beijing Computational Science Research Center Beijing100193 China School of Mathematics Guizhou Normal University Guiyang550001 China Department of Applied Physics East China Jiaotong University Nanchang330013 China School of Physics and Electronic Electrical Engineering Huaiyin Normal University Huai’an223300 China Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China

We propose a three-mode optomechanical system to realize optical nonreciprocal transmission with unidirectional amplification, where the system consists of two coupled cavities and one mechanical resonator which interacts with only one of the cavities. Additionally, the optical gain is introduced into the optomechanical cavity. It is found that for a strong optical input, the optical transmission coefficient can be greatly amplified in a particular direction and suppressed in the opposite direction. The expressions of the optimal transmission coefficient and the corresponding isolation ratio are given analytically. Our results pave a way to design high-quality nonreciprocal devices based on optomechanical *** Codes 81V80 Copyright © 2019, The Authors. All rights reserved.

关键词： Light transmission

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APPLE picker: Automatic particle picking, a low-effort cryo-EM framework

arXiv

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arXiv 2018年

作者： Heimowitz, Ayelet Andén, Joakim Singer, Amit Program in Applied and Computational Mathematics Princeton University PrincetonNJ United States Center for Computational Biology Flatiron Institute New YorkNY United States Department of Mathematics Princeton University PrincetonNJ United States

Particle picking is a crucial first step in the computational pipeline of single-particle cryo-electron microscopy (cryo-EM). Selecting particles from the micrographs is difficult especially for small particles with low contrast. As high-resolution reconstruction typically requires hundreds of thousands of particles, manually picking that many particles is often too time-consuming. While semi-automated particle picking is currently a popular approach, it may suffer from introducing manual bias into the selection process. In addition, semi-automated particle picking is still somewhat time-consuming. This paper presents the APPLE (Automatic Particle Picking with Low user Effort) picker, a simple and novel approach for fast, accurate, and fully automatic particle picking. While our approach was inspired by template matching, it is completely template-free. This approach is evaluated on publicly available datasets containing micrographs of β-Galactosidase, T20S proteasome, 70S ribosome and keyhole limpet hemocyanin projections. Copyright © 2018, The Authors. All rights reserved.

关键词： Support vector machines

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Anisotropic and mutable magnetization in Kondo lattice CeSb2

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Chinese physics B 2017年第6期26卷 319-323页

作者：张云朱燮刚胡丙锋谭世勇谢东华冯卫刘琴张文刘瑜宋海峰罗丽珠张政军赖新春 Science and Technology on Surface Physics and Chemistry Laboratory Department of Engineering Physics Tsinghua University Key Laboratory of Neutron Physics Institute of Nuclear Physics and ChemistryChina Academy of Engineering Physics Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Software Center for High Performance Numerical Simulation China Academy of Engineering Physics Key Laboratory of Advanced Materials (MOE) School of Materials Science and EngineeringTsinghua University

We have systematically studied the behaviors of the resistivity and magnetization of CeSb2 single crystals as a function of temperature and external field. Four anomalies in the resistivity/magnetization-versus-temperature curves are observed at low magnetic field. They are located at 15.5 K, 11.5 K, 9.5 K, and 6.5 K, corresponding to the paramagnetic–magnetically ordered state（MO）, MO-antiferromagnetic（AFM）, AFM–AFM, and AFM–ferromagnetic（FM） transitions, *** anomaly at 9.5 K is only visible with H‖[010] by magnetic susceptibility measurements, indicating that the AFM–AFM transition only happens along [010] direction in ab-plane. The four magnetic transitions are strongly suppressed by high external field. Finally, the field-temperature phase diagrams of CeSb2 with different orientations of the applied field in ab-plane are constructed and indicate the highly anisotropic nature of the magnetization of CeSb2.

关键词： CeSb2 electronic properties magnetic properties

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Current md forcefields fail to capture key features of protein structure and fluctuations: a case study of cyclophilin a and t4 lysozyme

arXiv

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arXiv 2020年

作者： Mei, Zhe Grigas, Alex T. Treado, John D. Corres, Gabriel Melendez Vuorte, Maisa Sammalkorpi, Maria Regan, Lynne Levine, Zachary A. O’Hern, Corey S. Department of Chemistry Yale University New HavenCT06520 United States Integrated Graduate Program in Physical and Engineering Biology Yale University New HavenCT06520 United States Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States Department of Mechanical Engineering and Materials Science Yale University New HavenCT06520 United States Department of Biology UPR Humacao Puerto RicoHumacao00792 Puerto Rico Department of Chemistry and Materials Science School of Chemical Engineering Aalto University Aalto Finland Department of Bioproducts and Biosystems School of Chemical Engineering Aalto University Aalto Finland Institute of Quantitative Biology Biochemistry and Biotechnology Center for Synthetic and Systems Biology School of Biological Sciences University of Edinburgh Edinburgh United Kingdom Department of Pathology Yale School of Medicine New HavenCT06520 United States Department of Molecular Biophysics and Biochemistry Yale University New HavenCT06520 United States Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States

Globular proteins undergo thermal fluctuations in solution, while maintaining an overall well-defined folded structure. In particular, studies have shown that the core structure of globular proteins differs in small, but significant ways when they are solved by x-ray crystallography versus solution-based NMR spectroscopy. Given these discrepancies, it is unclear whether molecular dynamics (MD) simulations can accurately recapitulate protein conformations. We therefore perform extensive MD simulations across multiple force fields and sampling techniques to investigate the degree to which computer simulations can capture the ensemble of conformations observed in experiments. By analyzing fluctuations in the atomic coordinates and core packing, we show that conformations sampled in MD simulations both move away from and sample a larger conformational space than the ensemble of structures observed in NMR experiments. However, we find that adding inter-residue distance restraints that match those obtained via Nuclear Overhauser Effect measurements enables the MD simulations to sample more NMR-like conformations, though significant differences between the core packing features in restrained MD and the NMR ensemble remain. Given that the protein structures obtained from the MD simulations possess smaller and less dense protein cores compared to those solved by NMR, we suggest that future improvements to MD forcefields should aim to increase the packing of hydrophobic residues in protein cores. © 2020, CC BY.

关键词： Molecular dynamics

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EMPRESS. XII. Statistics on the Dynamics and Gas Mass Fraction of Extremely-Metal Poor Galaxies

arXiv

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arXiv 2023年

作者： Xu, Yi Ouchi, Masami Isobe, Yuki Nakajima, Kimihiko Ozaki, Shinobu Bouché, Nicolas F. Wise, John H. Emsellem, Eric Kusakabe, Haruka Hattori, Takashi Nagao, Tohru Chiaki, Gen Fukushima, Hajime Harikane, Yuichi Hayashi, Kohei Hirai, Yutaka Kim, Ji Hoon Maseda, Michael V. Nagamine, Kentaro Shibuya, Takatoshi Sugahara, Yuma Yajima, Hidenobu Aoyama, Shohei Fujimoto, Seiji Fukushima, Keita Hatano, Shun Inoue, Akio K. Ishigaki, Tsuyoshi Kawasaki, Masahiro Kojima, Takashi Komiyama, Yutaka Koyama, Shuhei Koyama, Yusei Lee, Chien-Hsiu Matsumoto, Akinori Mawatari, Ken Moriya, Takashi J. Motohara, Kentaro Murai, Kai Nishigaki, Moka Onodera, Masato Ono, Yoshiaki Rauch, Michael Saito, Tomoki Sasaki, Rin Suzuki, Akihiro Takeuchi, Tsutomu T. Umeda, Hiroya Umemura, Masayuki Watanabe, Kuria Yabe, Kiyoto Zhang, Yechi Institute for Cosmic Ray Research The University of Tokyo 5-1-5 Kashiwanoha Chiba Kashiwa277-8582 Japan Department of Astronomy Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-0033 Japan National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan University of Tokyo Chiba Kashiwa277-8583 Japan Department of Physics Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-0033 Japan Univ Lyon Univ Lyon1 ENS de Lyon CNRS Centre de Recherche Astrophysique de Lyon UMR5574 Saint-Genis-LavalF-69230 France Center for Relativistic Astrophysics School of Physics Georgia Institute of Technology AtlantaGA30332 United States European Southern Observatory Karl-Schwarzschild-Straße 2 Garching85748 Germany Observatoire de Genéve Université de Genéve 51 Ch. des Maillettes Versoix1290 Switzerland 650 North A’ohoku Place HiloHI96720 United States Research Center for Space and Cosmic Evolution Ehime University Bunkyo-cho 2-5 Ehime Matsuyama790-8577 Japan Center for Computational Sciences University of Tsukuba Ten-nodai 1-1-1 Tsukuba Ibaraki305-8577 Japan Department of Physics and Astronomy University College London Gower Street LondonWC1E 6BT United Kingdom National Institute of Technology Ichinoseki College Hagisho Ichinoseki021-8511 Japan Astronomical Institute Tohoku University 6-3 Aoba Aramaki Aoba-ku Miyagi Sendai980-8578 Japan Department of Physics and Astronomy University of Notre Dame 225 Nieuwland Science Hall Notre DameIN46556 United States Astronomy Program Department of Physics and Astronomy Seoul National University 1 Gwanak-ro Gwanak-gu Seoul08826 Korea Republic of SNU Astronomy Research Center Seoul National University 1 Gwanak-ro Gwanak-gu Seoul08826 Korea Republic of Department of Astronomy University of Wisconsin-Madison 475 N. Charter Street MadisonWI53706 United States Theoretical Astrophysics Department of Earth & Space S

We present demography of the dynamics and gas-mass fraction of 33 extremely metal-poor galaxies (EMPGs) with metallicities of 0.015 − 0.195 Zo and low stellar masses of 104 − 108 Mo in the local universe. We conduct deep optical integral-field spectroscopy (IFS) for the low-mass EMPGs with the medium high resolution (R = 7500) grism of the 8m-Subaru FOCAS IFU instrument by the EMPRESS 3D survey, and investigate Hα emission of the EMPGs. Exploiting the resolution high enough for the low-mass galaxies, we derive gas dynamics with the Hα lines by the fitting of 3-dimensional disk models. We obtain an average maximum rotation velocity (vrot) of 15 ± 3 km s−1 and an average intrinsic velocity dispersion (σ0) of 27 ± 10 km s−1 for 15 spatially resolved EMPGs out of the 33 EMPGs, and find that all of the 15 EMPGs have vrot/σ0 rot/σ0 with the decreasing stellar mass and metallicity. We derive the gas mass fraction (fgas) for all of the 33 EMPGs, and find no clear dependence on stellar mass and metallicity. These vrot/σ0 and fgas trends should be compared with young high-z galaxies observed by the forthcoming JWST IFS programs to understand the physical origins of the EMPGs in the local universe. © 2023, CC BY.

关键词： Galaxies

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Thermal conductivity of CaSiO3 perovskite at lower mantle conditions

arXiv

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arXiv 2020年

作者： Zhang, Zhen Zhang, Dong-Bo Onga, Kotaro Hasegawa, Akira Ohta, Kenji Hirose, Kei Wentzcovitch, Renata M. Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States College of Nuclear Science and Technology Beijing Normal University Beijing100875 China Beijing Computational Science Research Center Beijing100193 China Department of Earth and Planetary Sciences Tokyo Institute of Technology Meguro Tokyo152-8551 Japan National Metrology Institute of Japan National Institute of Advanced Industrial Science and Technology Tsukuba Ibaraki305-8563 Japan Department of Earth and Planetary Science University of Tokyo Bunkyo Tokyo113-0033 Japan Earth-Life Science Institute Tokyo Institute of Technology Meguro Tokyo152-8550 Japan Department of Earth and Environmental Sciences Columbia University New YorkNY10027 United States Lamont-Doherty Earth Observatory Columbia University PalisadesNY10964 United States

Thermal conductivity (!) of mantle minerals is a fundamental property in geodynamic modeling. It controls the style of mantle convection and the time scale of the mantle and core cooling. Cubic CaSiO3 perovskite (CaPv) is the third most abundant mineral in the lower mantle (LM) (7 vol%). However, despite its importance, no theoretical or experimental estimate of CaPv's ! exists. Theoretical investigations of its properties are challenging because of its strong anharmonicity. Experimental measurements at relevant high pressures and temperatures are equally challenging. Here we present ab initio results for CaPv's ! obtained using an established phonon quasiparticle approach that can address its strong anharmonicity. We also offer experimental measurements of !. Predictions and measurements are in good agreement and reveal a surprisingly large ! for cubic CaPv. Despite its relatively low abundance, CaPv's ! might increase the lower mantle ! by approximately 10%, if accounted for. ! of mantle regions enriched in crust material will be more strongly impacted. Copyright © 2020, The Authors. All rights reserved.

关键词： Perovskite

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The Simons Observatory: Modeling optical systematics in the large aperture telescope

arXiv

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arXiv 2020年

作者： Gudmundsson, Jon E. Gallardo, Patricio A. Puddu, Roberto Dicker, Simon R. Adler, Alexandre E. Ali, Aamir M. Bazarko, Andrew Chesmore, Grace E. Coppi, Gabriele Cothard, Nicholas F. Dachlythra, Nadia Devlin, Mark Dünner, Rolando Fabbian, Giulio Galitzki, Nicholas Golec, Joseph E. Patty Ho, Shuay-Pwu Hargrave, Peter C. Kofman, Anna M. Lee, Adrian T. Limon, Michele Matsuda, Frederick T. Mauskopf, Philip D. Moodley, Kavilan Nati, Federico Niemack, Michael D. Orlowski-Scherer, John Page, Lyman A. Partridge, Bruce Puglisi, Giuseppe Reichardt, Christian L. Sierra, Carlos E. Simon, Sara M. Teply, Grant P. Tucker, Carole Wollack, Edward J. Xu, Zhilei Zhu, Ningfeng The Oskar Klein Centre Department of Physics Stockholm University StockholmSE-106 91 Sweden Department of Physics Cornell University IthacaNY14853 United States Instituto de Astrofísica Centro de Astro-Ingeniería Facultad de Física Pontificia Universidad Católica de Chile Macul Santiago Chile Department of Physics and Astronomy University of Pennsylvania PhiladelphiaPA19104 United States Department of Physics University of California BerkeleyCA94720 United States Joseph Henry Laboratories of Physics Jadwin Hall Princeton University PrincetonNJ08544 United States Department of Astronomy and Astrophysics The University of Chicago ChicagoIL60637 United States Department of Applied and Engineering Physics Cornell University IthacaNY14853 United States Department of Physics & Astronomy University of Sussex BrightonBN1 9QH United Kingdom Department of Physics University of California San Diego San diegoCA92093 United States Department of Physics University of Chicago ChicagoIL60637 United States School of Physics and Astronomy Cardiff University CardiffCF24 3AA United Kingdom The University of Tokyo Institutes for Advanced Study The University of Tokyo KashiwaChiba277-8583 Japan School of Earth and Space Exploration Department of Physics Arizona State University TempeAZ85281 United States Astrophysics Research Centre University of KwaZulu-Natal Westville Campus Durban4041 South Africa School of Mathematics Statistics & Computer Science University of KwaZulu-Natal Westville Campus Durban4041 South Africa Department of Physics University of Milano-Bicocca Milano Italy Department of Astronomy Cornell University IthacaNY14853 United States Department of Astronomy Haverford College HaverfordPA19041 United States Computational Cosmology Center Lawrence Berkeley National Laboratory BerkeleyCA94720 United States School of Physics University of Melbourne ParkvilleVIC3010 Australia Fermi National Accelerator Laboratory MS2

We present geometrical and physical optics simulation results for the Simons Observatory Large Aperture Telescope. This work was developed as part of the general design process for the telescope;allowing us to evaluate the impact of various design choices on performance metrics and potential systematic effects. The primary goal of the simulations was to evaluate the final design of the reflectors and the cold optics which are now being built. We describe non-sequential ray tracing used to inform the design of the cold optics, including absorbers internal to each optics tube. We discuss ray tracing simulations of the telescope structure that allow us to determine geometries that minimize detector loading and mitigate spurious near-field effects that have not been resolved by the internal baffling. We also describe physical optics simulations, performed over a range of frequencies and field locations, that produce estimates of monochromatic far field beam patterns which in turn are used to gauge general optical performance. Finally, we describe simulations that shed light on beam sidelobes from panel gap diffraction. Copyright © 2020, The Authors. All rights reserved.

关键词： Physical optics

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