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arXiv 2019年

作者： Kolopanis, Matthew Jacobs, Daniel C. Cheng, Carina Parsons, Aaron R. Kohn, Saul A. Pober, Jonathan C. Aguirre, James E. Ali, Zaki S. Bernardi, Gianni Bradley, Richard F. Carilli, Chris L. DeBoer, David R. Dexter, Matthew R. Dillon, Joshua S. Kerrigan, Joshua Klima, Pat Liu, Adrian MacMahon, David H.E. Moore, David F. Thyagarajan, Nithyanandan Nunhokee, Chuneeta D. Walbrugh, William P. Walker, Andre School of Earth and Space Exploration Arizona State U. TempeAZ United States Astronomy Dept. U. California BerkeleyCA United States Radio Astronomy Lab. U. California BerkeleyCA United States Dept. of Physics and Astronomy U. Penn. PhiladelphiaPA United States Dept. of Physics Brown University Providence RI United States INAF-Istituto di Radioastronomia via Gobetti 101 Bologna40129 Italy Department of Physics and Electronics Rhodes University PO Box 94 Grahamstown6140 South Africa South African Radio Astronomy Observatory Black River Park 2 Fir Street Observatory Cape Town7925 South Africa Dept. of Electrical and Computer Engineering U. Virginia CharlottesvilleVA United States National Radio Astronomy Obs. CharlottesvilleVA United States Dept. of Astronomy U. Virginia CharlottesvilleVA United States National Radio Astronomy Observatory SocorroNM United States Cavendish Lab. Cambridge United Kingdom Department of Physics and McGill Space Institute McGill University MontrealQC Canada CIFAR Azrieli Global Scholar Gravity & the Extreme Universe Program Canadian Institute for Advanced Research 661 University Ave. Suite 505 TorontoONM5G 1M1 Canada

We present limits on the 21cm power spectrum from the Epoch of Reionization (EoR) using data from the 64 antenna configuration of the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) analyzed through a power spectrum pipeline independent from previous PAPER analyses. Previously reported results from PAPER have been found to contain significant signal loss (Cheng et al. 2018). Several lossy steps from previous PAPER pipelines have not been included in this analysis, namely: delay-based foreground filtering, optimal fringe-rate filtering, and empirical covariance-based estimators. Steps which remain in common with previous analyses include redundant calibration and local sidereal time (LST) binning. The power spectra reported here are effectively the result of applying a linear Fourier transform analysis to the calibrated, LST binned data. This analysis also uses more data than previous publications, including the complete available redshift range of z ∼ 7.5 to 11. In previous PAPER analyses, many power spectrum measurements were found to be detections of noncosmological power at levels of significance ranging from two to hundreds of times the theoretical noise. Here, excess power is examined using redundancy between baselines and power spectrum jackknives. The upper limits we find on the 21cm power spectrum from reionization are (1500 mK)2, (1900 mK)2, (280 mK)2, (200 mK)2, (380 mK)2, (300 mK)2 at redshifts z = 10.87, 9.93, 8.68, 8.37, 8.13, and 7.48, respectively. For reasons described in (Cheng et al. 2018), these limits supersede all previous PAPER results (Ali et al. 2018). Copyright © 2019, The Authors. All rights reserved.

关键词： Power spectrum

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High-depth African genomes inform human migration and health (vol 586, pg 741, 2020)

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NATURE 2021年第7856期592卷 E26-E26页

作者： Choudhury, Ananyo Aron, Shaun Botigue, Laura R. Sengupta, Dhriti Botha, Gerrit Bensellak, Taoufik Wells, Gordon Kumuthini, Judit Shriner, Daniel Fakim, Yasmina J. Ghoorah, Anisah W. Dareng, Eileen Odia, Trust Falola, Oluwadamilare Adebiyi, Ezekiel Hazelhurst, Scott Mazandu, Gaston Nyangiri, Oscar A. Mbiyavanga, Mamana Benkahla, Alia Kassim, Samar K. Mulder, Nicola Adebamowo, Sally N. Chimusa, Emile R. Muzny, Donna Metcalf, Ginger Gibbs, Richard A. Matovu, Enock Bucheton, Bruno Hertz-Fowler, Christiane Koffi, Mathurin Macleod, Annette Mumba-Ngoyi, Dieudonne Noyes, Harry Nyangiri, Oscar A. Simo, Gustave Simuunza, Martin Rotimi, Charles Ramsay, Michele Choudhury, Ananyo Choudhury, Ananyo Aron, Shaun Botigue, Laura Sengupta, Dhriti Botha, Gerrit Bensellak, Taoufik Wells, Gordon Kumuthini, Judit Shriner, Daniel Fakim, Yasmina J. Ghoorah, Anisah W. Dareng, Eileen Odia, Trust Falola, Oluwadamilare Adebiyi, Ezekiel Hazelhurst, Scott Mazandu, Gaston Nyangiri, Oscar A. Mbiyavanga, Mamana Benkahla, Alia Kassim, Samar K. Mulder, Nicola Adebamowo, Sally N. Chimusa, Emile R. Rotimi, Charles Ramsay, Michele Adeyemo, Adebowale A. Lombard, Zane Hanchard, Neil A. Adebamowo, Clement Agongo, Godfred Boua, Romuald P. Oduro, Abraham Sorgho, Hermann Landoure, Guida Cisse, Lassana Diarra, Salimata Samassekou, Oumar Anabwani, Gabriel Matshaba, Mogomotsi Joloba, Moses Kekitiinwa, Adeodata Mardon, Graeme Mpoloka, Sununguko W. Kyobe, Samuel Mlotshwa, Busisiwe Mwesigwa, Savannah Retshabile, Gaone Williams, Lesedi Wonkam, Ambroise Moussa, Ahmed Adu, Dwomoa Ojo, Akinlolu Burke, David Salako, Babatunde O. Matovu, Enock Bucheton, Bruno Hertz-Fowler, Christiane Koffi, Mathurin Macleod, Annette Mumba-Ngoyi, Dieudonne Noyes, Harry Nyangiri, Oscar A. Simo, Gustave Simuunza, Martin Awadalla, Philip Bruat, Vanessa Gbeha, Elias Adeyemo, Adebowale A. Lombard, Zane Hanchard, Neil A. Sydney Brenner Institute for Molecular Bioscience Faculty of Health Sciences University of the Witwatersrand Johannesburg South Africa School of Electrical and Information Engineering University of the Witwatersrand Johannesburg South Africa Division of Human Genetics National Health Laboratory Service and School of Pathology Faculty of Health Sciences University of the Witwatersrand Johannesburg South Africa Navrongo Health Research Centre Navrongo Ghana Clinical Research Unit of Nanoro Institut de Recherche en Sciences de la Sante Bobo-Dioulasso Burkina Faso Center for Research in Agricultural Genomics (CRAG) Plant and Animal Genomics Program CSIC-IRTA-UAB-UB Barcelona Spain Computational Biology Division and H3ABioNet Department of Integrative Biomedical Sciences IDM University of Cape Town Cape Town South Africa System and Data Engineering Team Abdelmalek Essaadi University ENSA Tangier Morocco Centre for Proteomic and Genomic Research (CPGR) Cape Town South Africa South African National Bioinformatics Institute University of the Western Cape Bellville South Africa Africa Health Research Institute Durban South Africa Center for Research on Genomics and Global Health National Human Genome Research Institute National Institutes of Health Bethesda MD USA Department of Agriculture and Food Science Faculty of Agriculture University of Mauritius Reduit Mauritius Department of Digital Technologies Faculty of Information Communication & Digital Technologies University of Mauritius Reduit Mauritius Department of Public Health and Primary Care University of Cambridge Cambridge UK Institute of Human Virology Nigeria Abuja Nigeria Department of Epidemiology and Public Health University of Maryland School of Medicine University of Maryland Baltimore Baltimore MD USA University of Maryland Greenebaum Comprehensive Cancer Center University of Maryland School of Medicine University of Maryland Baltimore Baltimore MD USA Institute of Human Virology and Greeneba

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Role of electron and phonon temperatures in the helicity-independent all-optical switching of GdFeCo

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Physical Review B 2016年第18期94卷 184406-184406页

作者： J. Gorchon R. B. Wilson Y. Yang A. Pattabi J. Y. Chen L. He J. P. Wang M. Li J. Bokor Lawrence Berkeley National Laboratory 1 Cyclotron Road Berkeley California 94720 USA Department of Electrical Engineering and Computer Sciences University of California Berkeley California 94720 USA Department of Mechanical Engineering and Materials Science & Engineering Program University of California Riverside California 92521 USA Department of Materials Science and Engineering University of California Berkeley California 94720 USA Department of Electrical and Computer Engineering University of Minnesota Minneapolis Minnesota 55455 USA

Ultrafast optical heating of the electrons in ferrimagnetic metals can result in all-optical switching (AOS) of the magnetization. Here we report quantitative measurements of the temperature rise of GdFeCo thin films during helicity-independent AOS. Critical switching fluences are obtained as a function of the initial temperature of the sample and for laser pulse durations from 55 fs to 15 ps. We conclude that nonequilibrium phenomena are necessary for helicity-independent AOS, although the peak electron temperature does not play a critical role. Pump-probe time-resolved experiments show that the switching time increases as the pulse duration increases, with 10 ps pulses resulting in switching times of ∼13 ps. These results raise new questions about the fundamental mechanism of helicity-independent AOS.

关键词： Magnetism Magnetization switching

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A feasibility study of using event-related potential as a biometrics

A feasibility study of using event-related potential as a bi...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： Yih-Choung Yu Sicheng Wang Lisa A. Gabel Department of Electrical and Computer Engineering Lafayette College Easton PA USA School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA USA Department of Psychology and the Neuroscience Program Lafayette College Easton PA USA

The use of an individual's neural response to stimuli (the event-related potential or ERP) has potential as a biometric because it is highly resistant to fraud relative to other conventional authentication systems. P300 is an ERP in human electroencephalography (EEG) that occurs in response to an oddball stimulus when an individual is actively engaged in a target detection task. Because P300 is consistently detectable from almost every subject, it is considered a potential signal for biometric applications. This paper presents a feasibility study of using topological plots of P300 as a biometric in subject authentication. The variation in latency and location of P300 response of 24 participants performing the P300Speller task were studied. Data sets from four participants were used for algorithm training; data from the other 20 participants were used as imposters for algorithm validation. The result showed that the algorithm was able to correctly identify three out of these four participants. Validation test also proved that the algorithm was able to reject 95% of the imposters for those three authenticated participants.

关键词： Biometrics (access control) Electroencephalography Training Authentication Feature extraction Correlation coefficient Correlation

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Erratum: “Growth and characterization of β-Ga2O3 thin films by molecular beam epitaxy for deep-UV photodetectors” [J. Appl. Phys. 122, 095302 (2017)]

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Journal of Applied Physics 2018年第13期124卷

作者： Susmita Ghose Shafiqur Rahman Liang Hong Juan Salvador Rojas-Ramirez Hanbyul Jin Kibog Park Robert Klie Ravi Droopad 1Material Science Engineering and Commercialization Program Texas State University San Marcos Texas 78666 USA 2Department of Physics University of Illinois at Chicago Chicago Illinois 60607 USA 3Ingram School of Engineering Texas State University San Marcos Texas 78666 USA 4School of Electrical and Computer Engineering Ulsan National Institute of Science and Technology (UNIST) Ulsan 44919 South Korea 5Department of Physics Ulsan National Institute of Science and Technology (UNIST) Ulsan 44919 South Korea

We noticed an omission of the acknowledgment and provide it here with apologies:1

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Repulsion-attraction switching of nematic colloids formed by liquid crystal dispersions of polygonal prisms

arXiv

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arXiv 2017年

作者： Senyuk, B. Liu, Q. Nystrom, P.D. Smalyukh, I.I. Dept. of Physics and Soft Materials Research Center Univ. of Colorado at Boulder BoulderCO80309 United States Materials Science and Engineering Program Univ. of Colorado at Boulder BoulderCO80309 United States Dept. of Electrical Computer and Energy Engineering Univ. of Colorado at Boulder BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory Univ. of Colorado at Boulder BoulderCO80309 United States

Self-assembly of colloidal particles due to elastic interactions in nematic liquid crystals promises tunable composite materials and can be guided by exploiting surface functionalization, geometric shape and topology, though these means of controlling self-assembly remain limited. Here, we realize low-symmetry achiral and chiral elastic colloids in the nematic liquid crystals using colloidal polygonal concave and convex prisms. We show that the controlled pinning of disclinations at the prisms edges alters the symmetry of director distortions around the prisms and their orientation with respect to the far-field director. The controlled localization of the disclinations at the prism's edges significantly influences anisotropy of the diffusion properties of prisms dispersed in liquid crystals and allows one to modify their self-assembly. We show that elastic interactions between polygonal prisms can be switched between repulsive and attractive just by controlled re-pinning the disclinations at different edges using laser tweezers. Our findings demonstrate that elastic interactions between colloidal particles dispersed in nematic liquid crystals are sensitive to the topologically equivalent but geometrically rich controlled configurations of the particle-induced defects. Copyright © 2017, The Authors. All rights reserved.

关键词： Topology

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Tuning and switching a plasmonic quantum dot 'sandwich' in a nematic line defect

arXiv

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arXiv 2017年

作者： Mundoor, Haridas Sheetah, Ghadah Park, Sungoh Ackerman, Paul J. Smalyukh, Ivan I. Van De Lagemaat, Jao Department of Physics University of Colorado BoulderCO80309 United States Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Soft Materials Research Center Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States National Renewable Energy Laboratory GoldenCO80401 United States

We study the quantum-mechanical effects arising in a single semiconductor core/shell quantum dot controllably sandwiched between two plasmonic nanorods. Control over the position and the "sandwich" confinement structure is achieved by the use of a linear-trap, liquid-crystal line defect and laser tweezers that 'push' the sandwich together. This arrangement allows for the study of exciton-plasmon interactions in a single structure, unaltered by ensemble effects or the complexity of dielectric interfaces. We demonstrate the effect of plasmonic confinement on the photonantibunching behavior of the quantum dot and its luminescence lifetime. The quantum dot behaves as a single emitter when nanorods are far away from the quantum dot but shows possible multiexciton emission and a significantly decreased lifetime when tightly confined in a plasmonic 'sandwich'. These findings demonstrate that liquid crystal defects, combined with laser tweezers, enable a versatile platform to study plasmonic coupling phenomena in a nanoscale laboratory, where all elements can be arranged almost at will. Copyright © 2017, The Authors. All rights reserved.

关键词： Semiconductor quantum dots

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Impact of carrier localization on recombination in InGaN quantum wells and the efficiency of nitride light-emitting diodes: Insights from theory and numerical simulations

arXiv

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arXiv 2017年

作者： Jones, Christina M. Teng, Chu-Hsiang Yan, Qimin Ku, Pei-Cheng Kioupakis, Emmanouil Applied Physics Program University of Michigan 450 Church St Ann ArborMI48109 United States Electrical Engineering and Computer Science Department University of Michigan 1301 Beal Ave Ann ArborMI48109 United States Department of Physics Temple University 1925 N. 12th St PhiladelphiaPA19122 United States Materials Science and Engineering Department University of Michigan 2300 Hayward St Ann ArborMI48109 United States

We examine the effect of carrier localization due to random alloy fluctuations on the radiative and Auger recombination rates in InGaN quantum wells as a function of alloy composition, crystal orientation, carrier density, and temperature. Our results show that alloy fluctuations reduce individual transition matrix elements by the separate localization of electrons and holes, but this effect is overcompensated by the additional transitions enabled by translational symmetry breaking and the resulting lack of momentum conservation. Hence, we find that localization increases both radiative and Auger recombination rates, but that Auger recombination rates increase by one order of magnitude more than radiative rates. Furthermore, we demonstrate that localization has an overall detrimental effect on the efficiency-droop and green-gap problems of InGaN LEDs. Copyright © 2017, The Authors. All rights reserved.

关键词： Crystal orientation

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Choreographic and somatic approaches for the development of expressive robotic systems

arXiv

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arXiv 2017年

作者： LaViers, Amy Cuan, Catie Heimerdinger, Madison Huzaifa, Umer Maguire, Catherine McNish, Reika Nilles, Alexandra Pakrasi, Ishaan Bradley, Karen Mata, Kim Brooks Chakraborty, Novoneel Vidrin, Ilya Zurawski, Alexander Mechanical Science and Engineering Department University of Illinois Urbana-Champaign United States Aerospace Engineering Department University of Illinois Urbana-Champaign United States Laban/Bartenieff Institute of Movement Studies Kinesiology and Community Health Department University of Illinois Urbana-Champaign United States Computer Science Department University of Illinois Urbana-Champaign United States Dance Program University of Virginia Integrated Movement Studies Centre for Dance Research Coventry University Department of Theatre Dance and Media Harvard University

As robotic systems are moved out of factory work cells into human-facing environments questions of choreography become central to their design, placement, and application. With a human viewer or counterpart present, a system will automatically be interpreted within context, style of movement, and form factor by human beings as animate elements of their environment. The interpretation by this human counterpart is critical to the success of the system’s integration: "knobs" on the system need to make sense to a human counterpart;an artificial agent should have a way of notifying a human counterpart of a change in system state, possibly through motion profiles;and the motion of a human counterpart may have important contextual clues for task completion. Thus, professional choreographers, dance practitioners, and movement analysts are critical to research in robotics. They have design methods for movement that align with human audience perception;they can help identify simplified features of movement that will effectively accomplish human-robot interaction goals;and they have detailed knowledge of the capacity of human movement. This article provides approaches employed by one research lab, specific impacts on technical and artistic projects within, and principles that may guide future such work. The background section reports on choreography, somatic perspectives, improvisation, the Laban/Bartenieff Movement System, and robotics. From this context methods including embodied exercises, writing prompts, and community building activities have been developed to facilitate interdisciplinary research. The results of this work is presented as an overview of a smattering of projects in areas like high-level motion planning, software development for rapid prototyping of movement, artistic output, and user studies that help understand how people interpret movement. Finally, guiding principles for other groups to adopt are posited. Copyright © 2017, The Authors. All rights reserv

关键词： Robotics

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Plasmon-Exciton interactions probed using spatial coentrapment of nanoparticles by topological singularities

arXiv

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arXiv 2017年

作者： Ackerman, P.J. Mundoor, Haridas Smalyukh, I.I. Lagemaat, Jao Vande Department of Physics University of Colorado BoulderCO80309 United States Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Liquid Crystal Materials Research Center and Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States National Renewable Energy Laboratory GoldenCO80401 United States

We study *** interaction by using topological singularities to spatially confine, selectively deliver, cotrap and optically probe colloidal semiconductor and plasmonic nanoparticles. The interaction is monitored in a single quantum system in the bulk of a liquid crystal medium where nanoparticles are manipulated and nanoconfined far from dielectric interfaces using laser tweezers and topological configurations containing singularities. When quantum dot-in-a-rod particles are spatially colocated with a plasmonic gold nanoburst par-ticle in a topological singularity core, its uorescence in-creases because blinking is significantly suppressed and the radiative decay rate increases by nearly an order of magni-tude owing to the Purcell effect. We argue that the blinking suppression is the result of the radiative rate change that mitigates Auger recombination and quantum dot ionization, consequently reducing nonradiative recombination. Our work demonstrates that topological singularities are an effec-tive platform for studying and controlling *** interactions. Copyright © 2017, The Authors. All rights reserved.

关键词： Semiconductor quantum dots

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