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Demographics of black holes at g scales: accretion flows, jets, and shadows

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arXiv 2024年

作者： Nair, Dhanya G. Nagar, Neil M. Ramakrishnan, Venkatessh Wielgus, Maciek Arratia, Vicente Krichbaum, Thomas P. Zhang, Xinyue A. Ricarte, Angelo Silpa, S. Hernández-Yévenes, Joaquín Ford, Nicole M. Bandyopadhyay, Bidisha Gurwell, Mark Burridge, Roman Pesce, Dominic W. Doeleman, Sheperd S. Kim, Jae-Young Kim, Daewon Janssen, Michael von Fellenberg, Sebastiano D. Fromm, Christian M. Lee, Deokhyeong Falcke, Heino Wagner, Jan Bower, Geoffrey C. Baczko, Anne-Kathrin Kim, Dong-Jin Akiyama, Kazunori Asada, Keiichi Arevalo, Patricia Bignall, Hayley Blackburn, Lindy Broderick, Avery E. Brunthaler, Andreas Chan, Chi-Kwan Doi, Akihiro Fish, Vincent L. Fomalont, Edward Gómez, José L. Haggard, Daryl Hada, Kazuhiro Herrera-Camus, Rodrigo Hoak, Daniel Hughes, David Hlavacek-Larrondo, Julie Jorstad, Svetlana Johnson, Michael D. Kawashima, Tomohisa Keating, Garrett K. Kharb, Preeti Koay, Jun Yi Koyama, Shoko Kuo, Cheng-Yu Leigh, Nathan W.C. Lira, Paulina Lindqvist, Michael Lobanov, Andrei P. Lo, Wen-Ping Lu, Ru-Sen Markoff, Sera MacDonald, Nicholas R. Martínez-Aldama, Mary Loli Matthews, Lynn D. Matsushita, Satoki Mezcua, Mar Moscibrodzka, Monika Müller, Hendrik Nagai, Hiroshi Nakamura, Masanori Natarajan, Priyamvada Narayanan, Gopal Nowak, Michael A. Olivares Sánchez, Héctor Raúl Park, Jongho Psaltis, Dimitrios Pu, Hung-Yi Porth, Oliver Rao, Ramprasad Reynolds, Cormac Reeves, Rodrigo Romero-Cañizales, Cristina Ros, Eduardo Rottmann, Helge Roy, Alan L. Schleicher, Dominik Savolainen, Tuomas Impellizzeri, C.M. Violette Treister, Ezequiel Wiik, Kaj Zensus, J. Anton Astronomy Department Universidad de Concepción Casilla 160-C Concepción Chile Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Finnish Centre for Astronomy with ESO University of Turku FI-20014 Finland Instituto de Astrofisica de Andalucia-CSIC Glorieta de la Astronomia s/n GranadaE-18008 Spain Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138 United States Department of Physics McGill University 3600 rue University MontréalQCH3A 2T8 Canada Massachusetts Institute of Technology Haystack Observatory 99 Millstone Road WestfordMA01886 United States Black Hole Initiative Harvard University 20 Garden Street CambridgeMA02138 United States National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory OnsalaSE-43992 Sweden Institute of Astronomy and Astrophysics Academia Sinica 645 N. A’ohoku Place HiloHI96720 United States Department of Physics and Astronomy University of Hawaii at Manoa 2505 Correa Road HonoluluHI96822 United States Perimeter Institute for Theoretical Physics 31 Caroline Street North WaterlooONN2L 2Y5 Canada Department of Physics and Astronomy University of Waterloo 200 University Avenue West WaterlooONN2L 3G1 Canada Waterloo Centre for Astrophysics University of Waterloo Waterloo Canada Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Ave. TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Ave. TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 N. Santa Rita TucsonAZ85721 United States Radboud University P.O. Box 9010 Nijmegen6500 GL Netherlands Institut für Theoretische Physik Goethe-Universität Frankfurt Max-von-Laue-Straße 1 Frankfurt am MainD-60438 Germany Institut für Theoretische Physik und Astrophysik Universität

Using the Event Horizon Telescope (EHT), the gravitationally lensed rings around the supermassive black holes (SMBHs) in Messier 87 (M87), which has billions of solar masses and a strong jet, and Sagittarius A* (Sgr A*), which has millions of solar masses and a weak or no jet, have now been successfully imaged at a resolution under 10 gravitational radii (Rg = GM/c2, where M is the SMBH mass). To expand studies beyond M87 and Sgr A*, we have constructed the ‘Event Horizon and Environs (ETHER)’ sample, a comprehensive database currently encompassing approximately 3.15 million SMBH mass estimates, ∼ 20,000 Very-Long Baseline Interferometry (VLBI) radio flux densities, and ∼ 36,000 hard X-ray flux densities. This database is designed to identify and optimize target selection for the EHT and its upgrades on the ground and in space. Within the ETHER database, we have identified a ‘Gold Sample’ (GS) of nearby low-luminosity Active Galactic Nuclei (AGNs) that are optimal for studying jet bases, and potentially imaging black hole shadows, with the EHT and its upgrades. We observed 27 of these AGNs using the EHT from 2022 to 2024, providing a unique opportunity to resolve and image accretion flows and jets at resolutions of ≤ 100 Rg. Only a few SMBHs have sufficiently high enough flux density to be imaged at scales of ≤ 50 Rgwith the present EHT. Among these are M87, Sgr A*, NGC 4594 (Sombrero/M104), NGC 4261, and NGC 4374 (Messier 84/M84). Of these, NGC 4261, Sombrero, and M84 have been observed and/or are scheduled for deep imaging with EHT+ALMA from 2023 to 2025. Sombrero, NGC 4261, M84, NGC 4278, and NGC 5232 are clearly detected in our EHT+ALMA observations in 2022, indicating that the 230 GHz flux density from the accretion flows is significantly high. Ongoing imaging of the ETHER GS will enable measurements of black hole mass and spin, help constrain General Relativity (GR), and enrich our understanding of jet launching and accretion inflows across a broad multi-param

关键词： Radiation flux density

Multi-frequency effect towards High Conductivity Overburden Responses using Horizontal Coplanar (HCP) coil configuration for Landslide Hazard Instrumentation

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IOP Conference Series: Earth and Environmental Science 2019年第1期273卷

作者： Bukhari Bukhari Muhammad Syukri Surbakti Nazli Ismail Nasrullah Idris Elin Yusibani Muhammad Isa Saumi Syahreza Department of Physics Faculty of Mathematics and Natural Sciences Universitas Syiah Kuala Banda Aceh 23111 Indonesia. Doctorate Program of Mathematics and Applied Science (DMAS) Postgraduate Program Universitas Syiah Kuala Banda Aceh 23111 Indonesia. Tsunami and Disaster Mitigation Research Center (TDMRC) Universitas Syiah Kuala Banda Aceh 23111 Indonesia.

The instrumentation for the sensing of natural disaster phenomena as like as landslide instrumentation has acquired great importance for the instrumentation community. The novel instrumentation for landslide application has been made and calibrated using Horizontal Coplanar (HCP) coil orientation. The early instrumentation for landslide slopes was gradually equipped with standard and automatic instrumentation consisting of three the piezometric cells, two deep-seated steel wire extensometers, four in clinometric tubes, a rainfall gauge, a snow gauge and an air thermometer. This novel instrumentation works in electromagnetic methods similar with electromagnetic methods in geophysics. HCP coil orientation is a coplanar array where both coils are horizontal. In HCP, the depth of sounding is about 1.5 times of the coils separation which have maximum coupled configuration (HCP, VCP, and Vertical Coaxial configuration). The overburden response had inverted the percent value of maximum negative response then there were three maximum response amplitude peaks. Measurement and data processing were performed using a computer through Delphi program. The diagonal cross sections of the overburden as the centre were the maximum value of inverted response of anomaly positions. In aluminium thin plate overburden, the diagonal cross section point as the overburden centre was the maximum value of inverting value of the highest minimum response amplitude. The measurement graphic in the computer screen with several types of overburdens would be displayed. As the result, that the overburden widths for overburden were determined by subtracted of two turning points positions. The overburden positions were accurate for Type P overburden. The master curve had a high anomaly contrasts with two of positive anomaly peaks. Otherwise, the anomaly positions were between two of the negative anomaly peaks.

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Model reduction with memory and the machine learning of dynamical systems

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arXiv 2018年

作者： Ma, Chao Wang, Jianchun Weinan, E. Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Department of Mechanics and Aerospace Engineering Southern University of Science and Technology Shenzhen518055 China Beijing Institute of Big Data Research Beijing100871 China

The well-known Mori-Zwanzig theory tells us that model reduction leads to memory effect. For a long time, modeling the memory effect accurately and efficiently has been an important but nearly impossible task in developing a good reduced model. In this work, we explore a natural analogy between recurrent neural networks and the Mori-Zwanzig formalism to establish a systematic approach for developing reduced models with memory. Two training models-a direct training model and a dynamically coupled training model-are proposed and compared. We apply these methods to the Kuramoto-Sivashinsky equation and the Navier-Stokes equation. Numerical experiments show that the proposed method can produce reduced model with good performance on both short-term prediction and long-term statistical properties. Copyright © 2018, The Authors. All rights reserved.

关键词： Recurrent neural networks

The putative center in NGC 1052

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arXiv 2025年

作者： Baczko, Anne-Kathrin Kadler, Matthias Ros, Eduardo Fromm, Christian M. Wielgus, Maciek Perucho, Manel Krichbaum, Thomas P. Baloković, Mislav Blackburn, Lindy Chan, Chi-Kwan Issaoun, Sara Janssen, Michael Ricci, Luca Akiyama, Kazunori Albentosa-Ruíz, Ezequiel Alberdi, Antxon Alef, Walter Algaba, Juan Carlos Anantua, Richard Asada, Keiichi Azulay, Rebecca Bach, Uwe Ball, David Bandyopadhyay, Bidisha Barrett, John Bauböck, Michi Benson, Bradford A. Bintley, Dan Blundell, Raymond Bouman, Katherine L. Bower, Geoffrey C. Boyce, Hope Bremer, Michael Brinkerink, Christiaan D. Brissenden, Roger Britzen, Silke Broderick, Avery E. Broguiere, Dominique Bronzwaer, Thomas Bustamante, Sandra Byun, Do-Young Carlstrom, John E. Ceccobello, Chiara Chael, Andrew Chang, Dominic O. Chatterjee, Koushik Chatterjee, Shami Chen, Ming-Tang Chen, Yongjun Cheng, Xiaopeng Cho, Ilje Christian, Pierre Conroy, Nicholas S. Conway, John E. Cordes, James M. Crawford, Thomas M. Crew, Geoffrey B. Cruz-Osorio, Alejandro Cui, Yuzhu Dahale, Rohan Davelaar, Jordy De Laurentis, Mariafelicia Deane, Roger Dempsey, Jessica Desvignes, Gregory Dexter, Jason Dhruv, Vedant Dihingia, Indu K. Doeleman, Sheperd S. Dougall, Sean Taylor Dzib, Sergio A. Eatough, Ralph P. Emami, Razieh Falcke, Heino Farah, Joseph Fish, Vincent L. Fomalont, Edward Ford, H. Alyson Foschi, Marianna Fraga-Encinas, Raquel Freeman, William T. Friberg, Per Fuentes, Antonio Galison, Peter Gammie, Charles F. García, Roberto Gentaz, Olivier Georgiev, Boris Goddi, Ciriaco Gold, Roman Gómez-Ruiz, Arturo I. Gómez, José L. Gu, Minfeng Gurwell, Mark Hada, Kazuhiro Haggard, Daryl Haworth, Kari Hecht, Michael H. Hesper, Ronald Heumann, Dirk Ho, Luis C. Ho, Paul Honma, Mareki Huang, Chih-Wei L. Huang, Lei Hughes, David H. Impellizzeri, C.M. Violette Inoue, Makoto James, David J. Jannuzi, Buell T. Jeter, Britton Jiang, Wu Jiménez-Rosales, Alejandra Johnson, Michael D. Jorstad, Svetlana Joshi, Abhishek V. Jung, Taehyun Karami, Mansour Karuppusamy, Ramesh Kawashima, Tomohisa Keating, Garrett K. Kettenis, M Department of Space Earth and Environment Chalmers University of Technology GothenburgSE-41296 Sweden Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Institut für Theoretische Physik und Astrophysik Universität Würzburg Emil-Fischer-Str. 31 WürzburgD-97074 Germany Institut für Theoretische Physik Goethe-Universität Frankfurt Max-von-Laue-Straße 1 Frankfurt am MainD-60438 Germany Departament d'Astronomia i Astrofísica Universitat de València C. Dr. Moliner 50 Burjassot ValènciaE-46100 Spain Observatori Astronòmic Universitat de València C. Catedrático José Beltrán 2 Paterna ValènciaE-46980 Spain Yale Center for Astronomy & Astrophysics Yale University 52 Hillhouse Avenue New HavenCT06511 United States Black Hole Initiative Harvard University 20 Garden Street CambridgeMA02138 United States Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138 United States Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Ave. TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Ave. TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 N. Santa Rita TucsonAZ85721 United States Radboud University PO Box 9010 Nijmegen6500 GL Netherlands Massachusetts Institute of Technology Haystack Observatory 99 Millstone Road WestfordMA01886 United States National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n GranadaE-18008 Spain Department of Physics Faculty of Science Universiti Malaya Kuala Lumpur50603 Malaysia Department of Physics & Astronomy The University of Texas at San Antonio One UTSA Circle San AntonioTX78249 United States Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Sec. 4 Roosevelt Rd. Taipei10617 Taiwan Astronomy Depart

Context. Many active galaxies harbor powerful relativistic jets, however, the detailed mechanisms of their formation and acceleration remain poorly understood. Aims. To investigate the area of jet acceleration and collimation with the highest available angular resolution, we study the innermost region of the bipolar jet in the nearby low-ionization nuclear emission-line region (LINER) galaxy NGC 1052. Methods. We combined observations of NGC 1052 taken with VLBA, GMVA, and EHT over one week in the spring of 2017. Our study is focused on the size and continuum spectrum of the innermost region containing the central engine and the footpoints of both jets. We employed a synchrotron-self absorption model to fit the continuum radio spectrum and we combined the size measurements from close to the central engine out to ∼1 pc to study the jet collimation. Results. For the first time, NGC 1052 was detected with the EHT, providing a size of the central region in-between both jet bases of 43 µas perpendicular to the jet axes, corresponding to just around 250 RS (Schwarzschild radii). This size estimate supports previous studies of the jets expansion profile which suggest two breaks of the profile at around 3 × 103 RS and 1 × 104 RS distances to the core. Furthermore, we estimated the magnetic field to be 1.25 Gauss at a distance of 22 µas from the central engine by fitting a synchrotron-self absorption spectrum to the innermost emission feature, which shows a spectral turn-over at ∼130 GHz. Assuming a purely poloidal magnetic field, this implies an upper limit on the magnetic field strength at the event horizon of 2.6 × 104 Gauss, which is consistent with previous measurements. Conclusions. The complex, low-brightness, double-sided jet structure in NGC 1052 makes it a challenge to detect the source at millimeter (mm) wavelengths. However, our first EHT observations have demonstrated that detection is possible up to at least 230 GHz. This study offers a glimpse through the dens

关键词： Synchrotrons

Homogenization for a class of generalized langevin equations with an application to thermophoresis

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arXiv 2017年

作者： Lim, Soon Hoe Wehr, Jan Program in Applied Mathematics University of Arizona KTH Royal Institute of Technology Stockholm University Roslagstullsbacken 23 StockholmSE-10691 Sweden Department of Mathematics Program in Applied Mathematics University of Arizona Department of Mathematics University of Arizona TucsonAZ85721 United States

We study a class of systems whose dynamics are described by generalized Langevin equations with state-dependent coefficients. We find that in the limit, in which all the characteristic time scales vanish at the same rate, the position variable of the system converges to a homogenized process, described by an equation containing additional drift terms induced by the noise. The convergence results are obtained using the main result in [1], whose version is proven here under a weaker spectral assumption on the damping matrix. We apply our results to study thermophoresis of a Brownian particle in a non-equilibrium heat bath. Copyright © 2017, The Authors. All rights reserved.

关键词： Differential equations

Geometry-based data generation

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arXiv 2018年

作者： Lindenbaum, Ofir Stanley, Jay S. Wolf, Guy Krishnaswamy, Smita Department of Genetics Yale University New HavenCT United States Applied Mathematics Program Yale University New HavenCT United States Computational Biology & Bioinformatics Program Yale University New HavenCT United States Department of Computer Science Yale University New HavenCT United States

We propose a new type of generative model of high-dimensional data that learns a manifold geometry of the data, rather than density, and can generate points evenly along this manifold. This is in contrast to existing generative models that represent data density, and are strongly affected by noise and other artifacts of data collection. We demonstrate how this approach corrects sampling biases and artifacts, and improves several downstream data analysis tasks such as clustering and classification. Finally, we demonstrate that this approach is especially useful in biology where, despite the advent of single-cell technologies, rare subpopulations and gene-interaction relationships are affected by biased sampling. We show that SUGAR can generate hypothetical populations and reveal intrinsic patterns and mutual-information relationships between genes on a single cell dataset of hematopoiesis. Copyright © 2018, The Authors. All rights reserved.

关键词： Clustering algorithms

Semidefinite programming approach for the quadratic assignment problem with a sparse graph

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arXiv 2017年

作者： Bravo Ferreira, José F.S. Khoo, Yuehaw Singer, Amit Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Department of Mathematics Stanford University StanfordCA94305 United States Department of Mathematics and Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

The matching problem between two adjacency matrices can be formulated as the NP-hard quadratic assignment problem (QAP). Previous work on semidefinite programming (SDP) relaxations to the QAP have produced solutions that are often tight in practice, but such SDPs typically scale badly, involving matrix variables of dimension n2 where n is the number of nodes. To achieve a speed up, we propose a further relaxation of the SDP involving a number of positive semidefinite matrices of dimension O(n) no greater than the number of edges in one of the graphs. The relaxation can be further strengthened by considering cliques in the graph, instead of edges. The dual problem of this novel relaxation has a natural three-block structure that can be solved via a convergent Augmented Direction Method of Multipliers (ADMM) in a distributed manner, where the most expensive step per iteration is computing the eigendecomposition of matrices of dimension O(n). The new SDP relaxation produces strong bounds on quadratic assignment problems where one of the graphs is sparse with reduced computational complexity and running times, and can be used in the context of nuclear magnetic resonance spectroscopy (NMR) to tackle the assignment problem. Copyright © 2017, The Authors. All rights reserved.

关键词： Combinatorial optimization

Trophic Interactions Are Key to Understanding the Effects of Global Change on the Distribution and Functional Role of the Brown Bear

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Global Change Biology 2025年第6期31卷 e70252页

作者： Lucas, Pablo M. Thuiller, Wilfried Talluto, Lauren Polaina, Ester Albrecht, Jörg Selva, Nuria De Barba, Marta Penteriani, Vincenzo Guéguen, Maya Balkenhol, Niko Dutta, Trishna Fedorca, Ancuta Frank, Shane C. Zedrosser, Andreas Afonso-Jordana, Ivan Ambarlı, Hüseyin Ballesteros, Fernando Bashta, Andriy-Taras Bilgin, Cemal Can Bogdanović, Neda Bojārs, Edgars Bojarska, Katarzyna Bragalanti, Natalia Brøseth, Henrik Chynoweth, Mark W. Ćirović, Duško Ciucci, Paolo Corradini, Andrea De Angelis, Daniele de Gabriel Hernando, Miguel Domokos, Csaba Dutsov, Aleksander Ertürk, Alper Filacorda, Stefano Frangini, Lorenzo Groff, Claudio Heikkinen, Samuli Hoxha, Bledi Huber, Djuro Huitu, Otso Ionescu, Georgeta Ionescu, Ovidiu Jerina, Klemen Jurj, Ramon Karamanlidis, Alexandros A. Kindberg, Jonas Kojola, Ilpo López-Bao, José Vicente Männil, Peep Melovski, Dime Mertzanis, Yorgos Molinari, Paolo Molinari-Jobin, Anja Mustoni, Andrea Naves, Javier Ogurtsov, Sergey Özüt, Deniz Palazón, Santiago Pedrotti, Luca Perović, Aleksandar Piminov, Vladimir N. Pop, Ioan-Mihai Popa, Marius Psaralexi, Maria Quenette, Pierre-Yves Rauer, Georg Reljic, Slaven Revilla, Eloy Saarma, Urmas Saveljev, Alexander P. Sayar, Ali Onur Şekercioğlu, Çagan H. Sergiel, Agnieszka Sîrbu, George Skrbinšek, Tomaž Skuban, Michaela Soyumert, Anil Stojanov, Aleksandar Tammeleht, Egle Tirronen, Konstantin Trajçe, Aleksandër Trbojević, Igor Trbojević, Tijana Zięba, Filip Zlatanova, Diana Zwijacz-Kozica, Tomasz Pollock, Laura J. Institute of Nature Conservation Polish Academy of Sciences Kraków Poland Department of Biology and Biotechnologies “Charles Darwin” Sapienza Università di Roma Rome Italy Departamento de Biología Vegetal y Ecología Universidad de Sevilla Sevilla Spain Univ. Grenoble Alpes Univ. Savoie Mont Blanc CNRS LECA Grenoble France Department of Ecology University of Innsbruck Innsbruck Austria Department of Ecology Swedish University of Agricultural Sciences Uppsala Sweden Senckenberg Biodiversity and Climate Research Centre (SBiK-F) Frankfurt am Main Germany Estación Biológica de Doñana CSIC Sevilla Spain Departamento de Ciencias Integradas Facultad de Ciencias Experimentales Centro de Estudios Avanzados en Física Matemáticas y Computación Universidad de Huelva Huelva Spain Biotechnical Faculty Department of Biology University of Ljubljana Ljubljana Slovenia DivjaLabs Ltd. Ljubljana Slovenia Department of Evolutionary Ecology National Museum of Natural Sciences (MNCN-CSIC) Madrid Spain Wildlife Sciences University of Goettingen Goettingen Germany European Forest Institute Bonn Germany Department of Wildlife National Institute for Research and Development in Forestry “Marin Drăcea” Brasov Romania Department of Silviculture Transilvania University of Brasov Brasov Romania Faculty of Technology Natural Sciences and Maritime Sciences Department of Natural Sciences and Environmental Health University of South-Eastern Norway Bø i Telemark Norway Departament de Territòri Paisatge e Gestion Ambientau Conselh Generau d'Aran Vielha Spain Department of Wildlife Ecology and Management Faculty of Forestry No: 130 Düzce University Düzce Turkey Brown Bear Foundation Santander Spain Institute of Ecology of the Carpathians NAS Ukraine Lviv Ukraine National Park “Skolivski Beskydy” Lviv Region Skole Ukraine Department of Biology Middle East Technical University Ankara Turkey Faculty of Biology University of Belgrade Belgrade Serbia Estonian University of Life Scie

Biotic interactions are expected to influence species' responses to global changes, but they are rarely considered across broad spatial extents. Abiotic factors are thought to operate at larger spatial scales, while biotic factors, such as species interactions, are considered more important at local scales within communities, in part because of the knowledge gap on species interactions at large spatial scales (i.e., the Eltonian shortfall). We assessed, at a continental scale, (i) the importance of biotic interactions, through food webs, on species distributions, and (ii) how biotic interactions under scenarios of climate and land-use change may affect the distribution of the brown bear (Ursus arctos). We built a highly detailed, spatially dynamic, and empirically sampled food web based on the energy contribution of 276 brown bear food species from different taxa (plants, vertebrates, and invertebrates) and their ensemble habitat models at high resolution across Europe. Then, combining energy contribution and predicted habitat of food species, we modelled energy contribution across space and included these layers within Bayesian-based models of the brown bear distribution in Europe. The inclusion of biotic interactions considerably improved our understanding of brown bear distribution at large (continental) scales compared with Bayesian models including only abiotic factors (climate and land use). Predicted future range shifts, which included changes in the distribution of food species, varied greatly when considering various scenarios of change in biotic factors, providing a warning that future indirect climate and land-use change are likely to have strong but highly uncertain impacts on species biogeography. Our study confirmed that advancing our understanding of ecological networks of species interactions will improve future projections of biodiversity change, especially for modelling species distributions and their functional role under climate and land-use chan

关键词： climate change community ecosystem food web habitat human impact land use predator–prey species distribution model Ursus arctos

Computing Optimal Interfacial Structure of Modulated Phases

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Communications in Computational Physics 2017年第1期21卷 1-15页

作者： Jie Xu Chu Wang An-Chang Shi Pingwen Zhang LMAM and School of Mathematical Sciences Peking UniversityBeijing 100871China Program in Applied and Computational Mathematics Princeton UniversityPrincetonNew Jersey 08544USA Department of Physics and Astronomy McMaster UniversityHamiltonOntario L8S4M1Canada

We propose a general framework of computing interfacial structures between two modulated *** we propose to use a computational box consisting of two half spaces,each occupied by a modulated phase with given position and *** boundary conditions and basis functions are chosen to be commensurate with the bulk *** observe that the ordered nature of modulated structures stabilizes the interface,which enables us to obtain optimal interfacial structures by searching local minima of the free energy *** framework is applied to the Landau-Brazovskii model to investigate interfaces between modulated phases with different relative positions and *** types of novel complex interfacial structures emerge from the calculations.

关键词： Interface modulated phase metastable state compatibility Landau-Brazovskiimodel