检索结果-内蒙古大学图书馆

arXiv 2020年

作者： Nikam, rohit Xu, Xiao Kanduč, Matej dzubiella, Joachim Research Group for Simulations of Energy Materials Helmholtz-Zentrum Berlin für Materialien und Energie Hahn-Meitner-Platz 1 BerlinD-14109 Germany Institut für Physik Humboldt-Universität zu Berlin Newtonstr. 15 BerlinD-12489 Germany School of Chemical Engineering Nanjing University of Science and Technology 200 Xiao Ling Wei Nanjing210094 China Department of Theoretical Physics Jožef Stefan Institute Jamova 39 LjubljanaSI-1000 Slovenia Applied Theoretical Physics – Computational Physics Physikalisches Institut Albert-Ludwigs-Universität Freiburg Hermann-Herder-Str. 3 FreiburgD-79104 Germany

When a highly charged globular macromolecule, such as a dendritic polyelectrolyte or charged nanogel, is immersed into a physiological electrolyte solution, monovalent and divalent counterions from the solution bind to the macromolecule in a certain ratio and thereby almost completely electroneutralize it. For charged macromolecules in biological media, the number ratio of bound mono- versus divalent ions is decisive for the desired function. A theoretical prediction of such a sorption ratio is challenging because of the competition of electrostatic (valency), ion-specific, and binding saturation effects. Here, we devise and discuss a few approximate models to predict such an equilibrium sorption ratio by extending and combining established electrostatic binding theories such as donnan, Langmuir, Manning as well as Poisson–Boltzmann approaches, to systematically study the competitive uptake of mono- and divalent counterions by the macromolecule. We compare and fit our models to coarse-grained (implicit-solvent) computer simulation data of the globular polyelectrolyte dendritic polyglycerol sulfate (dPGS) in salt solutions of mixed valencies. The dPGS has high potential to serve in macromolecular carrier applications in biological systems and at the same time constitutes a good model system for a highly charged macromolecule. We finally use the simulation-informed models to extrapolate and predict electrostatic features such as the effective charge as a function of the divalent ion concentration for a wide range of dPGS generations (sizes). Copyright © 2020, The Authors. All rights reserved.

关键词： Polyelectrolytes

来源：评论

学校读者我要写书评

暂无评论

New Assembly Method for Cellulose derived Graphene Quantum dots-Sensitized Solar Cells

Research Square

引用

research Square 2021年

作者： Mahalingam, Savisha Lau, Kam Sheng Omar, Azimah Manap, Abreeza Chelvanathan, Puvaneswaran Chia, Chin Hua Amin, Nowshad Mathews, Illona Juliana Afandi, Nurfanizan Abd rahim, Nasrudin Institute of Sustainable Energy Universiti Tenaga Nasional Jalan IKRAM-UNITENSelangor Kajang43000 Malaysia Materials Science Program Department of Applied Physics Faculty of Science and Technology Universiti Kebangsaan Malaysia Selangor Bangi43600 Malaysia Level 4 Wisma R&D University of Malaya Jalan Pantai Baharu Kuala Lumpur59990 Malaysia Department of Mechanical Engineering College of Engineering Universiti Tenaga Nasional Jalan IKRAM-UNITEN Selangor Kajang43000 Malaysia Solar Energy Research Institute Universiti Kebangsaan Malaysia Jalan IKRAM-UNITEN Selangor Bangi43600 Malaysia Sunway University No. 5 Jalan Universiti Selangor Bandar Sunway47500 Malaysia Renewable Energy Research Group King Abdulaziz University Jeddah21589 Saudi Arabia

Unambiguously layer by layer (LBL) assembly of graphene quantum dots (GQds) and dye (GQds/dye) on TiO2 photoanode is the traditional and straightforward approach in the fabrication of graphene quantum dot-sensitized solar cells (QdSSCs). Unfortunately, limited light absorption and low affinity of GQds to TiO2 surface shadow the advantages of LBL and constrains its practical application. Herein, a new strategy of mixture configuration (GQds+dye) was investigated. A distinctive nanoporous honeycomb hexagonal carbon network of GQds was found with fewer defects single crystalline structure, and an average size of 9.87 nm was produced from cellulose. Experimental results demonstrated that LBL exhibited the highest efficiency of 16.76 % under low illumination but a lower efficiency (1.43%) than the mixture method (2.91%) under standard light. The increased Jsc (5.075 mA/cm2) and high charge collection efficiency (0.96) in the mixture sample indicated enhanced electron collection at TiO2. The less -OH groups on TiO2 provides a good surface intact of GQds and N719. In addition to that, the high surface potential (33.47 mV) of the premixed sample restricted the photogenerated electrons to go into a deep state, reducing back electron transfer. Therefore, mixture assembly of co-sensitization is an effective approach for light-harvesting in QdSSC. © 2021, CC BY.

关键词： dye-sensitized solar cells

来源：评论

学校读者我要写书评

暂无评论

XCloud-VIP: Virtual Peak Enables Highly Accelerated NMr Spectroscopy and Faithful Quantitative Measures

arXiv

引用

arXiv 2021年

作者： Guo, di Tu, Zhangren Guo, Yi Zhou, Yirong Wang, Jian Wang, Zi Qiu, Tianyu Xiao, Min Chen, Yinran Feng, Liubin Huang, Yuqing Lin, donghai Hong, Qing Goldbourt, Amir Lin, Meijin Qu, Xiaobo The School of Computer and Information Engineering Fujian Engineering Research Center for Medical Data Mining and Application Xiamen University of Technology Xiamen361024 China Department of Electronic Science Biomedical Intelligent Cloud R&D Center Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance Xiamen University Xiamen361102 China School of Opto-Electronic and Communication Engineering Xiamen University of Technology Xiamen361024 China Department of Computer Science School of Information Xiamen University Xiamen361102 China College of Chemistry and Chemical Engineering Key Laboratory for Chemical Biology of Fujian Province High-field NMR Center Xiamen University Xiamen361005 China China Mobile Group Xiamen361005 China School of Chemistry Tel Aviv University Tel Aviv6997801 Israel Department of Applied Marine Physics and Engineering College of Ocean and Earth Sciences Xiamen University Xiamen361102 China

—Nuclear Magnetic resonance (NMr) spectroscopy is an important bio-engineering tool to determine the metabolic concentrations, molecule structures and so on. The data acquisition time, however, is very long in multi-dimensional NMr. To accelerate data acquisition, non-uniformly sampling is an effective way but may encounter severe spectral distortions and unfaithful quantitative measures when the acceleration factor is high. By modelling the acquired signal as the superimposed exponentials, we proposed a virtual peak (VIP) approach to self-adapt the prior spectral information, such as the resonance frequency and peak lineshape, and then feed these information into the reconstruction. The proposed method is further implemented with cloud computing to facilitate online, open, and easy access. results on simulated and experimental data demonstrate that, compared with the low-rank Hankel matrix method, the new approach reconstructs high-fidelity NMr spectra from highly undersampled data and achieves more accurate quantification. The maximum quantitative errors of distances between nuclear pairs and concentrations of metabolites in mixtures have been reduced by 61.1% and 57.7%, respectively. Copyright © 2021, The Authors. All rights reserved.

关键词： Nuclear magnetic resonance spectroscopy

来源：评论

学校读者我要写书评

暂无评论

Graphene oxide MgFe2O4 nanocomposites for Cr(VI) remediation: a comparative modeling study

引用

Nanotechnology for Environmental Engineering 2018年第1期3卷 1-11页

作者： Hosseini, Seyed Ali Talebipour, Sahar Neyestani, Mahmoud reza ranjan, Shivendu dasgupta, Nandita Department of Applied Chemistry Faculty of Chemistry Urmia University Urmia Iran Department of Chemistry Faculty of Science Zanjan University Zanjan Iran R&D and Technology Development E-Spin Nanotech Pvt Ltd SIDBI Incubation Center IIT Kanpur KanpurUttar Pradesh208016 India Nano-food Research Group School of Bio Sciences and Technology VIT University VelloreTamil Nadu India

The article describes the synthesis and application of magnesium ferrite nanoparticles (MgFe2O4 NPs) and engineered MgFe2O4 nanocomposites (NCs) by graphene oxide as green and easy separable magnetic adsorbents in removal of Cr(VI) from environmental pollutant. The statistical study of the adsorption process and optimization was accomplished with central composite design method of response surface methodology (rSM) approach. The optimum conditions, predicted by rSM, were achieved at pH, contact time, initial Cr(VI) concentration and adsorbent dosage of 2, 60 min, 40 mg L−1 and 0.15 g, respectively. The removal of Cr(VI) under optimum situations was 97%, and the achieved result in practice was found to be 99%. Pareto analysis suggests the importance relative order of the factors as: pH > concentration of Cr(VI) > time > adsorbent dosage under optimized situations. The engineered nanocomposite was further analyzed for real groundwater samples, and 92% Cr(VI) remediation was resulted. The study is the first study for efficient Cr(VI) remediation from real groundwater sample using novel engineered nanocomposites and has potential to have societal as well as industrial impact in the form of process or product development. © 2018, Springer International Publishing AG, part of Springer Nature.

关键词： Nanocomposites

来源：评论

学校读者我要写书评

暂无评论

Experimental realization of Atomic-Scale Magnonic Crystals

引用

Physical review Letters 2019年第25期123卷 257202-257202页

作者： H. J. Qin S. Tsurkan A. Ernst Kh. Zakeri Heisenberg Spin-dynamics Group Physikalisches Institut Karlsruhe Institute of Technology Wolfgang-Gaede-Straße 1 D-76131 Karlsruhe Germany NanoSpin Department of Applied Physics Aalto University School of Science FI-00076 Aalto Finland Institute for Theoretical Physics Johannes Kepler University Altenberger Straße 69 4040 Linz Austria Max-Planck-Institut für Mikrostrukturphysik Weinberg 2 D-06120 Halle Germany

We introduce a new approach of materials design for terahertz magnonics making use of quantum confinement of terahertz magnons in layered ferromagnets. We show that in atomically designed multilayers composed of alternating atomic layers of ferromagnetic metals one can efficiently excite different magnon modes associated with the quantum confinement in the third dimension, i.e., the direction perpendicular to the layers. We demonstrate experimentally that the magnonic band structure of these systems can be tuned by changing the material combination and the number of atomic layers. We realize the idea of opening band gaps, with a size of up to several tens of millielectronvolts, between different terahertz magnon bands and thereby report on the first step toward the realization of atomic-scale magnonic crystals.

关键词： First-principles calculations Magnetic coupling Magnetic interactions Magnons Ultrafast magnetic effects

来源：评论

学校读者我要写书评

暂无评论

The MeerKAT Pulsar Timing Array: The first search for gravitational waves with the MeerKAT radio telescope

arXiv

引用

arXiv 2024年

作者： Miles, Matthew T. Shannon, ryan M. reardon, daniel J. Bailes, Matthew Champion, david J. Geyer, Marisa Gitika, Pratyasha Grunthal, Kathrin Keith, Michael J. Kramer, Michael Kulkarni, Atharva d. Nathan, rowina S. Parthasarathy, Aditya Singha, Jaikhomba Theureau, Gilles Thrane, Eric Abbate, Federico Buchner, Sarah Cameron, Andrew d. Camilo, Fernando Moreschi, Beatrice E. Shaifullah, Golam Shamohammadi, Mohsen Possenti, Andrea Krishnan, Vivek Venkatraman Centre for Astrophysics and Supercomputing Swinburne University of Technology PO Box 218 HawthornVIC3122 Australia The ARC Centre of Excellence for Gravitational Wave Discovery MPI für Radioastronomie Auf dem Hügel 69 Bonn53121 Germany Group Department of Mathematics and Applied Mathematics University of Cape Town Cape Town7700 South Africa Jodrell Bank Centre for Astrophysics University of Manchester Alan-Turing Building Oxford Street ManchesterM13 9PL United Kingdom School of Physics and Astronomy Monash University ClaytonVIC3800 Australia ASTRON Netherlands Institute for Radio Astronomy Oude Hoogeveensedijk 4 Dwingeloo7991 PD Netherlands Anton Pannekoek Institute for Astronomy University of Amsterdam Science Park 904 Amsterdam1098 XH Netherlands Laboratoire de Physique et Chimie de l’Environnement et de l’Espace LPC2E UMR7328 Université d’Orléans CNRS CNES OSUC Observatoire de Paris OrléansF-45071 France Laboratoire Univers et Théories Observatoire de Paris Université PSL Université de Paris Cité CNRS MeudonF-92190 France I-09047 Italy South African Radio Astronomy Observatory 2 Fir Street Black River Park Observatory7925 South Africa Dipartimento di Fisica "G. Occhialini" Universitá degli Studi di Milano-Bicocca Piazza della Scienza 3 MilanoI-20126 Italy

Pulsar Timing Arrays search for nanohertz-frequency gravitational waves by regularly observing ensembles of millisecond pulsars over many years to look for correlated timing residuals. recently the first evidence for a stochastic gravitational wave background has been presented by the major Arrays, with varying levels of significance (∼2-4σ). In this paper we present the results of background searches with the MeerKAT Pulsar Timing Array. Although of limited duration (4.5 yr), the ∼ 250,000 arrival times with a median error of just 3πs on 83 pulsars make it very sensitive to spatial correlations. detection of a gravitational wave background requires careful modelling of noise processes to ensure that any correlations represent a fit to the underlying background and not other misspecified processes. Under different assumptions about noise processes we can produce either what appear to be compelling Hellings-downs correlations of high significance (3-3.4σ) with a spectrum close to that which is predicted, or surprisingly, under slightly different assumptions, ones that are insignificant. This appears to be related to the fact that many of the highest precision MeerKAT Pulsar Timing Array pulsars are in close proximity and dominate the detection statistics. The sky-averaged characteristic strain amplitude of the correlated signal in our most significant model is ℎcyr = 7.5+−0.90.8 × 10−15 measured at a spectral index of α = −0.26, decreasing to ℎcyr = 4.8+0.8−0.9 × 10−15 when assessed at the predicted α = −2/3. These data will be valuable as the International Pulsar Timing Array project explores the significance of gravitational wave detections and their dependence on the assumed noise models. Copyright © 2024, The Authors. All rights reserved.

关键词： Pulsars

来源：评论

学校读者我要写书评

暂无评论

Proton acceleration in thermonuclear nova explosions revealed by gamma rays (Apr, 10.1038/s41550-022-01640-z, 2022)

引用

NATUrE ASTrONOMY 2022年第6期6卷 760-760页

作者： Acciari, V. A. Ansoldi, S. Antonelli, L. A. Engels, A. Arbet Artero, M. Asano, K. Baack, d. Babic, A. Baquero, A. de Almeida, U. Barres Barrio, J. A. Batkovic, I. Gonzalez, J. Becerra Bednarek, W. Bellizzi, L. Bernardini, E. Bernardos, M. Berti, A. Besenrieder, J. Bhattacharyya, W. Bigongiari, C. Biland, A. Blanch, O. Bokenkamp, H. Bonnoli, G. Bosnjak, Z. Busetto, G. Carosi, r. Ceribella, G. Cerruti, M. Chai, Y. Chilingarian, A. Cikota, S. Colak, S. M. Colombo, E. Contreras, J. L. Cortina, J. Covino, S. d'Amico, G. d'Elia, V. da Vela, P. dazzi, F. de Angelis, A. de Lotto, B. del Popolo, A. delfino, M. delgado, J. Mendez, C. delgado depaoli, d. di Pierro, F. di Venere, L. Espineira, E. do Souto Prester, d. dominis donini, A. dorner, d. doro, M. Elsaesser, d. ramazani, V. Fallah Alonso, L. Farina Fattorini, A. Fonseca, M. V. Font, L. Fruck, C. Fukami, S. Fukazawa, Y. Lopez, r. J. Garcia Garczarczyk, M. Gasparyan, S. Gaug, M. Giglietto, N. Giordano, F. Gliwny, P. Godinovic, N. Green, J. G. Green, d. Hadasch, d. Hahn, A. Hassan, T. Heckmann, L. Herrera, J. Hoang, J. Hrupec, d. Hutten, M. Inada, T. Ishio, K. Iwamura, Y. Martinez, I. Jimenez Jormanainen, J. Jouvin, L. Kerszberg, d. Kobayashi, Y. Kubo, H. Kushida, J. Lamastra, A. Lelas, d. Leone, F. Lindfors, E. Linhoff, L. Lombardi, S. Longo, F. Lopez-Coto, r. Lopez-Moya, M. Lopez-Oramas, A. Loporchio, S. de Oliveira Fraga, B. Machado Maggio, C. Majumdar, P. Makariev, M. Mallamaci, M. Maneva, G. Manganaro, M. Mannheim, K. Maraschi, L. Mariotti, M. Martinez, M. Aguilar, A. Mas Mazin, d. Menchiari, S. Mender, S. Micanovic, S. Miceli, d. Miener, T. Miranda, J. M. Mirzoyan, r. Molina, E. Moralejo, A. Morcuende, d. Moreno, V. Moretti, E. Nakamori, T. Nava, L. Neustroev, V. rosillo, M. Nievas Nigro, C. Nilsson, K. Nishijima, K. Noda, K. Nozaki, S. Ohtani, Y. Oka, T. Otero-Santos, J. Paiano, S. Palatiello, M. Paneque, d. Paoletti, r. Paredes, J. M. Pavletic, L. Penil, P. Persic, M. Pihet, M. Moroni, P. G. Prada Prandini, E. Priyadarshi, C. Puljak, I. rhode, W. ribo, M. rico, Universidad de La Laguna Instituto de Astrofísica de Canarias and Departamento de Astrofísica La Laguna Spain (GRID:grid.10041.34) (ISNI:***) Università di Udine and INFN Trieste Udine Italy (GRID:grid.5390.f) (ISNI:0000 0001 2113 062X) International Center for Relativistic Astrophysics (ICRA) Rome Italy (GRID:grid.5390.f) National Institute for Astrophysics (INAF) Rome Italy (GRID:grid.4293.c) (ISNI:0000 0004 1792 8585) Max-Planck-Institut für Physik Munich Germany (GRID:grid.435824.c) (ISNI:0000 0001 2375 0603) The Barcelona Institute of Science and Technology (BIST) Institut de Física d’Altes Energies (IFAE) Barcelona Spain (GRID:grid.473715.3) (ISNI:0000 0004 6475 7299) Japanese MAGIC Group: Institute for Cosmic Ray Research (ICRR) The University of Tokyo Kashiwa Japan (GRID:grid.26999.3d) (ISNI:0000 0001 2151 536X) Technische Universität Dortmund Dortmund Germany (GRID:grid.5675.1) (ISNI:0000 0001 0416 9637) Croatian MAGIC Group: University of Zagreb Faculty of Electrical Engineering and Computing (FER) Zagreb Croatia (GRID:grid.4808.4) (ISNI:0000 0001 0657 4636) Universidad Complutense de Madrid IPARCOS Institute and EMFTEL Department Madrid Spain (GRID:grid.4795.f) (ISNI:0000 0001 2157 7667) Centro Brasileiro de Pesquisas Físicas (CBPF) Rio de Janeiro Brazil (GRID:grid.418228.5) (ISNI:0000 0004 0643 8134) Università di Padova and INFN Padua Italy (GRID:grid.5608.b) (ISNI:0000 0004 1757 3470) University of Lodz Department of Astrophysics Faculty of Physics and Applied Informatics Lodz Poland (GRID:grid.10789.37) (ISNI:0000 0000 9730 2769) Università di Siena and INFN Pisa Siena Italy (GRID:grid.9024.f) (ISNI:0000 0004 1757 4641) Deutsches Elektronen-Synchrotron (DESY) Zeuthen Germany (GRID:grid.7683.a) (ISNI:0000 0004 0492 0453) ETH Zürich Zurich Switzerland (GRID:grid.5801.c) (ISNI:0000 0001 2156 2780) Instituto de Astrofísica de Andalucía-CSIC Granada Spain (GRID:grid.450285.e) (ISNI:0000 0004 1793 7043) Università di Pisa and INFN Pisa Pisa Italy (GRID:grid.5395.

Classical novae are cataclysmic binary star systems in which the matter of a companion star is accreted on a white dwarf1,2. Accumulation of hydrogen in a layer eventually causes a thermonuclear explosion on the surface of the white dwarf3, brightening the white dwarf to ~105 solar luminosities and triggering ejection of the accumulated matter. Novae provide the extreme conditions required to accelerate particles, electrons or protons, to high energies. Here we present the detection of gamma rays by the MAGIC telescopes from the 2021 outburst of rS Ophiuchi, a recurrent nova with a red giant companion, which allowed us to accurately characterize the emission from a nova in the 60 GeV to 250 GeV energy range. The theoretical interpretation of the combined Fermi LAT and MAGIC data suggests that protons are accelerated to hundreds of gigaelectronvolts in the nova shock. Such protons should create bubbles of enhanced cosmic ray density, of the order of 10 pc, from the recurrent *** of the 2021 outburst of the nova rS Oph in very-high-energy gamma rays by the MAGIC telescopes is reported. Investigation of the gamma-ray emission provides evidence for acceleration of protons within the nova shock, which then propagate outwards to create bubbles of enhanced cosmic ray density.

关键词：

来源：评论

学校读者我要写书评

暂无评论

The long period of 3He-rich solar energetic particles measured by Solar Orbiter on 2020 November 17-23

arXiv

引用

arXiv 2021年

作者： Bučík, radoslav Mason, G.M. Gómez-Herrero, r. Lario, d. Balmaceda, L. Nitta, N.V. Krupař, V. dresing, N. Ho, G.C. Allen, r.C. Carcaboso, F. rodríguez-Pacheco, J. Schuller, F. Warmuth, A. Wimmer-Schweingruber, r.F. von Forstner, J.L. Freiherr Andrews, G.B. Berger, L. Cernuda, I. Espinosa Lara, F. Lees, W.J. Martín, C. Pacheco, d. Prieto, M. Sánchez-Prieto, S. Schlemm, C.E. Seifert, H. Tyagi, K. Maksimovic, M. Vecchio, A. Kollhoff, A. Kühl, P. Xu, Z.G. Eldrum, S. Southwest Research Institute San AntonioTX78238 United States Applied Physics Laboratory Johns Hopkins University LaurelMD20723 United States Universidad de Alcalá Space Research Group Alcalá de Henares28805 Spain Heliophysics Science Division NASA Goddard Space Flight Center GreenbeltMD United States George Mason University FairfaxVA United States Lockheed Martin Advanced Technology Center Palo AltoCA94304 United States Goddard Planetary Heliophysics Institute University of Maryland Baltimore County BaltimoreMD21250 United States Institut für Experimentelle und Angewandte Physik Christian-Albrechts-Universität zu Kiel Kiel Germany Leibniz-Institut für Astrophysik Potsdam PotsdamD-14482 Germany LESIA Observatoire de Paris Université PSL CNRS Sorbonne Université Université de Paris France Radboud Radio Lab Department of Astrophysics Radboud University Nijmegen Netherlands

We report observations of a relatively long period of 3He-rich solar energetic particles (SEPs) measured by Solar Orbiter. The period consists of several well-resolved ion injections. The high-resolution STErEO-A imaging observations reveal that the injections coincide with EUV jets/brightenings near the east limb, not far from the nominal magnetic connection of Solar Orbiter. The jets originated in two adjacent, large, and complex active regions as observed by the Solar dynamics Observatory when the regions rotated to the Earth's view. It appears that the sustained ion injections were related to the complex configuration of the sunspot group and the long period of 3He-rich SEPs to the longitudinal extent covered by the group during the analyzed time period. Copyright © 2021, The Authors. All rights reserved.

关键词： Orbits

来源：评论

学校读者我要写书评

暂无评论

The MeerKAT Pulsar Timing Array: The 4.5-year data release and the noise and stochastic signals of the millisecond pulsar population

arXiv

引用

arXiv 2024年

作者： Miles, Matthew T. Shannon, ryan M. reardon, daniel J. Bailes, Matthew Champion, david J. Geyer, Marisa Gitika, Pratyasha Grunthal, Kathrin Keith, Michael J. Kramer, Michael Kulkarni, Atharva d. Nathan, rowina S. Parthasarathy, Aditya Porayko, Nataliya K. Singha, Jaikhomba Theureau, Gilles Abbate, Federico Buchner, Sarah Cameron, Andrew d. Camilo, Fernando Moreschi, Beatrice E. Shaifullah, Golam Shamohammadi, Mohsen Krishnan, Vivek Venkatraman Centre for Astrophysics and Supercomputing Swinburne University of Technology PO Box 218 HawthornVIC3122 Australia OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery Australia MPI für Radioastronomie Auf dem Hügel 69 Bonn53121 Germany Group Department of Mathematics and Applied Mathematics University of Cape Town Cape Town7700 South Africa Jodrell Bank Centre for Astrophysics University of Manchester Alan-Turing Building Oxford Street ManchesterM13 9PL United Kingdom School of Physics and Astronomy Monash University ClaytonVIC3800 Australia ASTRON Netherlands Institute for Radio Astronomy Oude Hoogeveensedijk 4 Dwingeloo7991 PD Netherlands Anton Pannekoek Institute for Astronomy University of Amsterdam Science Park 904 Amsterdam1098 XH Netherlands Dipartimento di Fisica "G. Occhialini" Universitá degli Studi di Milano-Bicocca Piazza della Scienza 3 MilanoI-20126 Italy Laboratoire de Physique et Chimie de l’Environnement et de l’Espace LPC2E UMR7328 Université d’Orléans CNRS CNES OSUC Observatoire de Paris OrléansF-45071 France Laboratoire Univers et Théories Observatoire de Paris Université PSL Université de Paris Cité CNRS MeudonF-92190 France INAF – Osservatorio Astronomico di Cagliari Via della Scienza 5 CA SelargiusI-09047 Italy South African Radio Astronomy Observatory 2 Fir Street Black River Park Observatory7925 South Africa

Pulsar timing arrays are ensembles of regularly observed millisecond pulsars timed to high precision. Each pulsar in an array could be affected by a suite of noise processes, most of which are astrophysically motivated. Analysing them carefully can be used to understand these physical processes. However, the primary purpose of these experiments is to detect signals that are common to all pulsars, in particular signals associated with a stochastic gravitational wave background. To detect this, it is paramount to appropriately characterise other signals that may otherwise impact array sensitivity or cause a spurious detection. Here we describe the second data release and first detailed noise analysis of the pulsars in the MeerKAT Pulsar Timing Array, comprising high-cadence and high-precision observations of 83 millisecond pulsars over 4.5 years. We use this analysis to search for a common signal in the data, finding a process with an amplitude of log10 ACUrN = (Formula Presented) and spectral index γCUrN = (Formula Presented). Fixing the spectral index at the value predicted for a background produced by the inspiral of binary supermassive black holes, we measure the amplitude to be log10 ACUrN = (Formula Presented) at a significance expressed as a Bayes factor of ln(B) = 4.46. Under both assumptions, the amplitude that we recover is larger than those reported by other PTA experiments. We use the results of this analysis to forecast our sensitivity to a gravitational wave background possessing the spectral properties of the common signal we have measured. Copyright © 2024, The Authors. All rights reserved.

关键词： Pulsars

来源：评论

学校读者我要写书评

暂无评论

Combined searches for dark matter in dwarf spheroidal galaxies observed with the MAGIC telescopes, including new data from Coma Berenices and draco

arXiv

引用

arXiv 2021年

作者： Acciari, V.A. Ansoldi, S. Antonelli, L.A. Engels, A. Arbet Artero, M. Asano, K. Baack, d. Babić, A. Baquero, A. de Almeida, U. Barres Barrio, J.A. Batković, I. González, J. Becerra Bednarek, W. Bellizzi, L. Bernardini, E. Bernardos, M. Berti, A. Besenrieder, J. Bhattacharyya, W. Bigongiari, C. Biland, A. Blanch, O. Bökenkamp, H. Bonnoli, G. Bošnjak, Ž. Busetto, G. Carosi, r. Ceribella, G. Cerruti, M. Chai, Y. Chilingarian, A. Cikota, S. Colak, S.M. Colombo, E. Contreras, J.L. Cortina, J. Covino, S. d’Amico, G. d’Elia, V. da Vela, P. dazzi, F. de Angelis, A. de Lotto, B. delfino, M. delgado, J. Mendez, C. delgado depaoli, d. di Pierro, F. di Venere, L. Espiñeira, E. do Souto Prester, d. dominis donini, A. dorner, d. doro, M. Elsaesser, d. ramazani, V. Fallah Fattorini, A. Fonseca, M.V. Font, L. Fruck, C. Fukami, S. López, r.J. García Garczarczyk, M. Gasparyan, S. Gaug, M. Giglietto, N. Giordano, F. Gliwny, P. Godinović, N. Green, J.G. Green, d. Hadasch, d. Hahn, A. Heckmann, L. Herrera, J. Hoang, J. Hrupec, d. Hütten, M. Inada, T. Ishio, K. Iwamura, Y. Jiménez, I. Jormanainen, J. Jouvin, L. Karjalainen, M. Kerszberg, d. Kobayashi, Y. Kubo, H. Kushida, J. Lamastra, A. Lelas, d. Leone, F. Lindfors, E. Linhoff, L. Lombardi, S. Longo, F. López-Coto, r. López-Moya, M. López-Oramas, A. Loporchio, S. de Oliveira Fraga, B. Machado Maggio, Camilla Majumdar, P. Makariev, M. Mallamaci, M. Maneva, G. Manganaro, M. Mannheim, K. Maraschi, L. Mariotti, M. Martínez, M. Mazin, d. Menchiari, S. Mender, S. Mićanović, S. Miceli, d. Miener, T. Miranda, J.M. Mirzoyan, r. Molina, E. Moralejo, A. Morcuende, d. Moreno, V. Moretti, E. Neustroev, V. Nigro, C. Nilsson, K. Ninci, d. Nishijima, K. Noda, K. Nozaki, S. Ohtani, Y. Oka, T. Otero-Santos, J. Paiano, S. Palatiello, M. Paneque, d. Paoletti, r. Paredes, J.M. Pavletić, L. Peñil, P. Persic, M. Pihet, M. Moroni, P.G. Prada Prandini, E. Priyadarshi, C. Puljak, I. rhode, W. ribó, M. rico, J. righi, C. Instituto de Astrofísica de Canarias and Dpto. de Astrofísica Universidad de La Laguna Tenerife La LagunaE-38200 Spain Università di Udine and INFN Trieste UdineI-33100 Italy RomeI-00136 Italy ETH Zürich ZürichCH-8093 Switzerland E-08193 Spain University of Tokyo Chiba Kashiwa277-8582 Japan Technische Universität Dortmund D-44221 Dortmund Germany Zagreb10000 Croatia IPARCOS Institute EMFTEL Department Universidad Complutense de Madrid MadridE-28040 Spain URCA RJ Rio de Janeiro22290-180 Brazil Università di Padova and INFN PadovaI-35131 Italy University of Lodz Faculty of Physics and Applied Informatics Department of Astrophysics Lodz90-236 Poland Università di Siena and INFN Pisa SienaI-53100 Italy ZeuthenD-15738 Germany Max-Planck-Institut für Physik MünchenD-80805 Germany Università di Pisa INFN Pisa PisaI-56126 Italy Universitat de Barcelona ICCUB IEEC-UB BarcelonaE-08028 Spain Armenian MAGIC Group A. Alikhanyan National Science Laboratory Yerevan0036 Armenia Centro de Investigaciones Energéticas Medioambientales y Tecnológicas MadridE-28040 Spain INFN MAGIC Group INFN Sezione di Torino Università degli Studi di Torino TorinoI-10125 Italy INFN MAGIC Group INFN Sezione di Bari Dipartimento Interateneo di Fisica dell’Università e del Politecnico di Bari BariI-70125 Italy Croatian MAGIC Group University of Rijeka Department of Physics Rijeka51000 Croatia Universität Würzburg WürzburgD-97074 Germany Finnish MAGIC Group Finnish Centre for Astronomy with ESO University of Turku TurkuFI-20014 Finland Departament de Física CERES-IEEC Universitat Autònoma de Barcelona BellaterraE-08193 Spain Armenian MAGIC Group ICRANet- Armenia at NAS RA Yerevan0019 Armenia Split21000 Croatia Croatian MAGIC Group Josip Juraj Strossmayer University of Osijek Department of Physics Osijek31000 Croatia Japanese MAGIC Group Department of Physics Kyoto University Kyoto606-8502 Japan Japanese MAGIC Group Department of P

Milky Way dwarf spheroidal galaxies (dSphs) are among the best candidates to search for signals of dark matter annihilation with Imaging Atmospheric Cherenkov Telescopes, given their high mass-to-light ratios and the fact that they are free of astrophysical gamma-ray emitting sources. Since 2011, MAGIC has performed a multi-year observation program in search for Weakly Interacting Massive Particles (WIMPs) in dSphs. results on the observations of Segue 1 and Ursa Major II dSphs have already been published and include some of the most stringent upper limits (ULs) on the velocity-averaged cross-section hσannvi of WIMP annihilation from observations of dSphs. In this work, we report on the analyses of 52.1 h of data of draco dSph and 49.5 h of Coma Berenices dSph observed with the MAGIC telescopes in 2018 and in 2019 respectively. No hint of a signal has been detected from either of these targets and new constraints on the hσannvi of WIMP candidates have been derived. In order to improve the sensitivity of the search and reduce the effect of the systematic uncertainties due to the J-factor estimates, we have combined the data of all dSphs observed with the MAGIC telescopes. Using 354.3 h of dSphs good quality data, 95 % CL ULs on hσannvi have been obtained for 9 annihilation channels. For most of the channels, these results reach values of the order of 10−24 cm3/s at ∼1 TeV and are the most stringent limits obtained with the MAGIC telescopes so far. Copyright © 2021, The Authors. All rights reserved.

关键词： Galaxies

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：