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Physics

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Displaying 1801 - 1825 of 2588

Synchronization between remote sites for the MINOS experiment

November 26, 2012
Author(s)
Stefania Romisch, Steven R. Jefferts, Victor S. Zhang, Thomas E. Parker, Neil Ashby, P Adamson, G. Barr, A. Habig, J Meier, C. James, R. Nicol, R. Plunkett, C. Rosenfeld, Russell Bumgarner, M. Christensen, Jonathan Hirschauer, Blair Fonville, Demetrios Matsakis, Ed Powers, J. Wright, Angela Mckinley
In the context of time-of-flight measurements, the timing at the departure and arrival locations is obviously critical to the outcome of the experiment. In the case of neutrino time-of-flight experiments, the locations are many hundreds of kilometers apart

Ultra-low noise regenerative frequency divider

November 11, 2012
Author(s)
Archita Hati, Craig W. Nelson, Corey A. Barnes, Danielle G. Lirette, Jason A. DeSalvo, David A. Howe
We designed ultra-low noise regenerative divider-by-2 circuits that operate at input frequencies of 20 MHz and 10 MHz. We achieved residual output-referred single-sideband phase noise below -162 dBc/Hz at 10 Hz offset for a single divider at these

The Need for a Robust, Precise Time and Frequency Alternative to GNSS

November 1, 2012
Author(s)
Michael A. Lombardi, Mitch Narins, Per Enge, Ben Peterson, Sherman Lo, Yu-Hsuan Chen, Dennis Akos
Positioning, Navigation, and Timing (PNT) services are key enablers of both essential safety and security applications and economically beneficial capacity and efficiency applications worldwide. Whether users are ground-based, sea-based or in the air

Quasianalytical modal approach for computing Casimir interactions in periodic nanostructures

October 3, 2012
Author(s)
Francesco Intravaia, Paul S. Davids, Ricardo Decca, Vladimir Aksyuk, Daniel Lopez, Diego A. Dalvit
We present an almost fully analytical technique for computing Casimir interactions between 1D periodic lamellar gratings based on a modal approach. Our method improves on previous work on Casimir modal approaches for nanostructures by using the exact form

Interstellar Carbodiimide (HNCNH) - A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features

October 1, 2012
Author(s)
Brett A. McGuire, Ryan A. Loomis, Cameron M. Charness, Geoffery A. Blake, Jan M. Hollis, Francis J. Lovas, Philip R. Jewell, Anthony J. Remijan
Historically, searches for new astronomical molecules resulted in the detection of favorable, high line strength transitions based on a thermal approximation to the excitation of these species in interstellar environments. Given the temperatures of hot

Microsecond Accuracy at Multiple Locations: Is it possible without GPS?

October 1, 2012
Author(s)
Michael A. Lombardi
The microsecond is the most discussed unit in industrial timing systems, because microsecond accuracy is required to support critical infrastructure. Most critical infrastructure timing systems depend upon GPS, simply because microsecond accuracy is easy

Multiexciton dynamics in infrared-emitting colloidal nanostructures probed by a superconducting nanowire single-photon detector

September 30, 2012
Author(s)
Richard L. Sandberg, Lazaro A. Padilha, Mumtaz Qazilbash, Wan Ki Bae, Richard D. Schaller, Jeffrey M. Pietryga, Martin Stevens, Burm Baek, Sae Woo Nam, Victor I. Klimov
Carrier multiplication (CM) is the process in which absorption of a single photon produces multiple electron-hole pairs. Here, we evaluate the effect of particle shape on CM efficiency by conducting a comparative study of spherical nanocrystal quantum dots

The Habitable-Zone Planet Finder: A Stabilized Fiber-Fed NIR Spectrograph for the Hobby-Eberly Telescope

September 24, 2012
Author(s)
Scott A. Diddams, Suvrath Mahadevan, Lawrence W. Ramsey, Chad F. Bender, Ryan Terrien, Jason T. Wright, Samuel Halverson, Fred Hearty, Matthew Nelson, Adam Burton, Stephen L. Redman, Steve Osterman, James Kasting, Michael Endl
We present the scientific motivation and conceptual design for the recently funded Habitable-zone Planet Finder (HPF), a stabilized fiber-fed near-infrared (NIR) spectrograph for the 10 meter class Hobby-Eberly Telescope(HET) that will be capable of

Spin Dynamics in the Time and Frequency Domain

September 15, 2012
Author(s)
Thomas J. Silva
The current status of experimental approaches to analyze the spin wave dynamics in ferromagnetic nanoscale structures is reviewed. Recent developments in frequency- and field swept spectroscopy to determine the resonant response of nanoscale ferromagnets

Zero-energy modes and gate-tunable gap in graphene on hexagonal boron nitride

September 13, 2012
Author(s)
Markus Kindermann, Bruno Uchoa, David L. Miller
In this article, we derive an effective theory of graphene on a hexagonal boron nitride (h-BN) substrate. We show that the h-BN substrate generically opens a spectral gap in graphene despite the lattice mismatch. The origin of that gap is particularly

100-Fold Reduction of Electric-Field Noise in an Ion Trap Cleanded with In Situ Argon-Ion-Beam Bombardment

September 7, 2012
Author(s)
Dustin Hite, Yves Colombe, Andrew C. Wilson, Kenton R. Brown, Ulrich J. Warring, Robert Jordens, John D. Jost, David P. Pappas, Dietrich Leibfried, David J. Wineland, Kyle McKay
Anomalous heating of trapped atomic ions is a major obstacle to their use as quantum bits in scalable quantum computers. The physical origin of this electric field noise is not fully understood, but experimental evidence suggests that it emanates from the

Ultrafast manetization enhancement in metallic multilayers driven by superdiffusive spin current

September 4, 2012
Author(s)
Thomas J. Silva, Justin M. Shaw, Hans T. Nembach, Dennis Rudolf, Chan La-O-Vorakiat, Marco Battiato, Roman Adam, Emrah Turgut, Stefan Mathias, Margaret M. Murnane, Henry C. Kapteyn, Claus M. Schneider
Uncovering the physical mechanisms that govern ultrafast charge and spin dynamics is crucial for understanding correlated matter as well as the fundamental limits of ultrafast spin-based electronics. Spin dynamics in magnetic materials can be driven by

A Sub-Sampling Digital PM/AM Noise Measurement System

September 1, 2012
Author(s)
Craig W. Nelson, David A. Howe
A digital phase/amplitude modulation (PM/AM) noise measurement systems (DNMS) implementing field progammable gate array (FPGA) based digital down converters (DDCs), and 250 MHz analog to digital converters (ADCs) is reported. Measurements in the first

Simulating Quantum Magnetism with Correlated Non-Neutral Ion Plasmas

August 27, 2012
Author(s)
John J. Bollinger, Joseph W. Britton, Brian C. Sawyer
By employing forces which depend on the internal atomic state (or spin) of an atomic ion, the Coulomb potential energy of a strongly coupled array of ions can be modified in a spin-dependent way to mimic effective quantum spin Hamiltonians. Both
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