Now showing items 783-802 of 841

    • Ultrafast Carrier Dynamics of Monolayer WS2 via Broad-Band Time-Resolved Terahertz Spectroscopy 

      Gustafson, Jon K.; Cunningham, Paul D.; McCreary, Kathleen M.; Jonker, Berend T.; Hayden, L. Michael (American Chemical Society, 2019-11-19)
      We report on the ultrafast carrier dynamics of monolayer WS2 using broad-band time-resolved terahertz spectroscopy (TRTS). We find that upon photoexcitation, there is an increase in the conductivity. We attribute this ...
    • Ultralow-power nonlinear optics using tapered optical fibers in metastable xenon 

      Pittman, T.B.; Jones, D.E; Franson, J.D. (American Physical Society (APS), 2013-11-06)
      We demonstrate nanowatt-level saturated absorption using a subwavelength diameter tapered optical fiber (TOF) suspended in a gas of metastable xenon atoms. This ultralow-power nonlinearity is enabled by a small optical ...
    • Ultralow-power nonlinear optics using tapered optical fibers in noble gases 

      Pittman, T.B.; Jones, D.E; Franson, J.D. (OSA Publishing, 2014)
      We demonstrate ultralow-power optical nonlinearities using a sub-wavelength diameter tapered optical fiber in a gas of metastable xenon atoms. The use of inert noble gases offers advantages over reactive alkali vapors such ...
    • Ultrastrong coupling of polar phonons and effective epsilon-near-zero modes in coaxial nanocavities 

      Yoo, Daehan; Leon-Perez, Fernando de; Lee, In-Ho; Mohr, Daniel A.; Pelton, Matthew; Raschke, Markus B.; Caldwell, Joshua D.; Martın-Moreno, Luis; Oh, Sang-Hyun (2020-02-29)
      Ultrastrong coupling (USC), where the light-matter coupling strength is comparable to the resonance frequency of the uncoupled bare system, presents new frontiers in nanophotonics. However, it has remained notoriously ...
    • Unidentified Gamma-ray Sources as Targets for Indirect Dark Matter Detection with the Fermi-Large Area Telescope 

      Coronado-Blázquez, Javier; Sánchez-Conde, Miguel A.; Domínguez, Alberto; Aguirre-Santaella, Alejandra; Di Mauro, Mattia; Mirabald, Néstor; Nieto, Daniel; Charles, Eric (2019-06)
      One of the predictions of the ΛCDM cosmological framework is the hierarchical formation of structure, giving rise to dark matter (DM) halos and subhalos. When the latter are massive enough they retain gas (i.e., baryons) ...
    • The Unique, Optically-Dominated Quasar Jet of PKS 1421-490 

      Gelbord, J.M.; Marshall, H.L.; Worrall, D.M.; Birkinshaw, M.; Lovell, J.E.J.; Ojha, R.; Godfrey, L.; Jauncey, D.L.; Schwartz, D.A.; Perlman, E.S.; Georganopoulos, M.; Murphy, D.W. (MIT School of Science, 2005-01-10)
    • A Universal Scaling for the Energetics of Relativistic Jets from Black Hole Systems 

      Nemmen, R. S.; Georganopoulos, M.; Guiriec, S.; Meyer, E. T.; Gehrels, N.; Sambruna, R. M. (American Association for the Advancement of Science (AAAS), 2012-12-14)
      Black holes generate collimated, relativistic jets, which have been observed in gamma-ray bursts (GRBs), microquasars, and at the center of some galaxies [active galactic nuclei (AGN)]. How jet physics scales from stellar ...
    • Unusual flaring activity in the blazar PKS 1424−418 during 2008−2011 

      Buson, S.; Longo, F.; Larsson, S.; Cutini, S.; Finke, J.; Ciprini, S.; Ojha, R.; D'Ammando, F.; Donato, D.; Thompson, D. J.; Desiante, R.; Bastieri, D.; Wagner, S.; Hauser, M.; Fuhrmann, L.; Dutka, M.; Müller, C.; Kadler, M.; Angelakis, E.; Zensus, J. A.; Stevens, J.; Blanchard, J. M.; Edwards, P. G.; Lovell, J. E. J.; Gurwell, M. A.; Wehrle, A. E.; Zook, A. (EDP sciences, 2014-09-16)
      Context. Blazars are a subset of active galactic nuclei (AGN) with jets that are oriented along our line of sight. Variability and spectral energy distribution (SED) studies are crucial tools for understanding the physical ...
    • The unusual multiwavelength properties of the gamma-ray source PMN J1603−4904 

      Müller, Cornelia; Kadler, M.; Ojha, R.; Böck, M.; Krauß, F.; Taylor, G. B.; Wilms, J.; Blanchard, J.; Carpenter, B.; Dauser, T.; Dutka, M.; Edwards, P. G.; Gehrels, N.; Grossberger, C.; Hase, H.; Horiuchi, S.; Kreikenbohm, A.; Lovell, J. E. J.; McConville, W.; Phillips, C.; Plötz, C.; Pursimo, T.; Quick, J.; Ros, E.; Schulz, R.; Stevens, J.; Tingay, S. J.; Trüstedt, J.; Tzioumis, A. K.; Zensus, J. A. (EDP sciences, 2014-01-30)
      Context. We investigate the nature and classification of PMN J1603−4904, a bright radio source close to the Galactic plane, which is associated with one of the brightest hard-spectrum γ-ray sources detected by Fermi/LAT. ...
    • An update on MASIV: How intrinsic properties influence interstellar scintillation of AGN 

      Bignall, Hayley; Koay, Jun Yi; Lovell, Jim; Jauncey, Dave; Macquart, Jean-Pierre; Pursimo, Tapio; Ojha, Roopesh; Rickett, Barney; Kedziora-Chudczer, Lucyna; Reynolds, Cormac; Khoo, Sue (Proceedings of Science, 2012-04-17)
      Many flat-spectrum AGN exhibit short timescale variations when observed at radio wavelengths, due to interstellar scintillation (ISS). The observed variations depend on source angular size and "core dominance", as well as ...
    • Update on the Activities of the GGOS Bureau of Networks and Observations 

      Pearlman, Michael R.; Pavlis, Erricos C.; Ma, Chopo; Noll, Carey; Thaller, Daniela; Richter, Bernd; Gross, Richard; Neilan, Ruth; Mueller, Juergen; Barzaghi, Ricardo; Bergstrand, Sten; Saunier, Jerome; Tamisiea, Mark (National Aeronautics and Space Administration, 2016)
      The recently reorganized GGOS Bureau of Networks and Observations has many elements that are associated with building and sustaining the infrastructure that supports the Global Geodetic Observing System (GGOS) through the ...
    • Upstream Ultra‐Low Frequency Waves Observed by MESSENGER's Magnetometer: Implications for Particle Acceleration at Mercury's Bow Shock 

      Romanelli, N.; DiBraccio, G.; Gershman, D.; Le, G.; Mazelle, C.; Meziane, K.; Boardsen, S.; Slavin, J.; Raines, J.; Glass, A.; Espley, J. (American Geophysical Union, 2020-04-09)
      We perform the first statistical analysis of the main properties of waves observed in the 0.05–0.41 Hz frequency range in the Hermean foreshock by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) ...
    • Using Clickers for Deliberate Practice in Five Large Science Courses 

      Hodges, Linda C.; Anderson, Eric C.; Carpenter, Tara S.; Cui, Lili; Feeser, Elizabeth A.; Gierasch, Tiffany Malinky (NSTA, 2017-11-01)
      Clickers are often used as an active learning tool in face-to-face classes to enhance student engagement and assess student learning. In this article we share the variety of ways that we use clicker questions ...
    • Using Gamma Ray Monitoring to Avoid Missing the Next Milky Way Type Ia Supernova 

      Wang, Xilu; Fields, Brian D.; Lien, Amy Yarleen (2019-04-10)
      A Milky-Way Type Ia Supernova (SNIa) could be unidentified or even initially unnoticed, being dim in radio, X-rays, and neutrinos, and suffering large optical/IR extinction in the Galactic plane. But SNIa emit nuclear ...
    • Using Reading Quizzes in STEM Classes—The What, Why, and How 

      Hodges, Linda C.; Anderson, Eric C.; Carpenter, Tara S.; Cui, Lili; Gierasch, Tiffany Malinky; Leupen, Sarah; Nanes, Kalman M.; Wagner, Cynthia R. (National Science Teachers Association, 2015)
      Many active learning pedagogies depend on students' preparing for class in advance. One common method for holding students accountable for this preparation is the use of reading quizzes. When used thoughtfully, reading ...
    • Using the SED to locate the Gamma-ray emission site of powerful blazars 

      Georganopoulos, Markos; Meyer, E. T.; Fossati, G. (2012-02-28)
      The location of the Gamma-ray emission of powerful blazars is a matter of active debate. Is the location within the UV emitting sub-pc scale broad line region, or farther out at pc scales where the molecular torus IR ...
    • Variability and Proper Motion of X-ray Knots in the Jet of Centaurus A 

      Snios, Bradford; Wykes, Sarka; Nulsen, Paul E. J.; Kraft, Ralph P.; Meyer, Eileen T.; Birkinshaw, Mark; Worrall, Diana M.; Hardcastle, Martin J.; Roediger, Elke; Forman, William R.; Jones, Christine (2019-01-22)
      We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 years, collective proper motion of 11.3±3.3 mas yr We report results ...
    • The variable and non-variable X-ray absorbers in Compton-thin type-II Active Galactic Nuclei 

      Laha, Sibasish; Markowitz, Alex G.; Krumpe, Mirko; Nikutta, Robert; Rothschild, Richard; Saha, Tathagata (2020-05-12)
      We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broad band spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the ...
    • Velocity-dependent optical forces and Maxwell’s demon 

      Franson, J. D. (Nature, 2019-09-24)
      An atom placed in a focused laser beam will experience a dipole force due to the gradient in the interaction energy, which is analogous to the well-known optical tweezers effect. This force will be dependent on the velocity ...