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Displaying 676 - 700 of 925

Are Bragg Peaks Gaussian?

March 12, 2014
Author(s)
Boualem Hammouda
It is common practice to assume that Bragg scattering peaks have Gaussian shape. The Gaussian shape function is used to perform instrumental smearing corrections. Using Monte Carlo ray tracing simulation, the resolution of a realistic small-angle neutron

Certification of Total Arsenic in Blood and Urine Standard Reference Materials by Radiochemical Neutron Activation Analysis and Inductively Coupled Plasma Mass Spectrometry

March 1, 2014
Author(s)
Rick L. Paul, William C. Davis, Karen E. Murphy, Colleen E. Bryan Sallee, Lee L. Yu, William F. Guthrie, Dennis D. Leber, Thomas W. Vetter
A newly developed procedure for determination of arsenic by radiochemical neutron activation analysis was used to measure arsenic in SRM 955c Toxic Elements in Caprine Blood and SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing

Polarized 3HE Spin Filters for Neutron Science

February 12, 2014
Author(s)
Thomas R. Gentile, Wei-Chen N. Chen
The large spin dependence of the absorption cross section for neutrons by 3He gas provides a method to polarize neutron beams. For certain applications, such polarized 3He-based neutron "spin filters" have advantages over conventional neutron optical

High-Accuracy Measurements of the Vapor Pressure of Ice Referenced to the Triple Point

December 6, 2013
Author(s)
Katarzyna E. Bielska, Daniel K. Havey, Gregory E. Scace, D Lisak, Allan H. Harvey, Joseph T. Hodges
The vapor pressure of hexagonal (Ih) ice was measured over the temperature range 175 K to 253.4 K and referenced to the value at the triple point of water. This experiment combined a highly accurate humidity generation system containing an ice-coated

Improved Determination of the Neutron Lifetime

December 2, 2013
Author(s)
Jeffrey S. Nico, A. T. Yue, Maynard S. Dewey, David M. Gilliam, G L. Greene, A. Laptev, William M. Snow, F. E. Wiefeldt
The most precise determination of the neutron lifetime using the beam method was completed in 2005 and reported a result of tau_n = (886.3 ± 1.2 [stat] ± 3.2 [sys]) s. The dominant uncertainties were attributed to the absolute determination of the fluence

On the Determination of Carbon by PGAA

November 10, 2013
Author(s)
Rolf L. Zeisler, Rick L. Paul, Jeffrey A. Fagan, Zsolt R?vay, Stefan S?llradl
Determination of carbon was achieved with reduction of background in prompt gamma activation analysis.

Polychromatic energy-dispersive neutron diffraction at a continuous source

August 3, 2013
Author(s)
Jason M. Simmons, Jeremy Cook, Richard M. Ibberson, Charles Majkrzak, Dan Neumann
A design for a continuous source, polychromatic beam powder neutron diffractometer based on an energy-dispersive detection methodology is proposed. Such an instrument would offer significantly higher incident neutron flux, with an attendant increase in

Effect of Supercritical Carbon Dioxide on the Thermodynamics of Model Styrene-Acrylonitrile Copolymer-Poly(methyl methacrylate) Blends Studied by Small-Angle Neutron Scattering

July 25, 2013
Author(s)
Sebnem Inceoglu, Nicholas P. Young, Andrew J. Jackson, Steven Kline, Stephane Costeux, Nitash P. Balsara
Small-angle neutron scattering was used to study a binary blend of styrene-acrylonitrile copolymer (SAN) and deuterated poly(methyl methacrylate) (dPMMA), as wellas a multicomponent mixture of SAN, dPMMA, and supercritical carbon dioxide (scSO 2). The

Improving quantitative neutron radiography through image restoration

July 20, 2013
Author(s)
Daniel S. Hussey, Elias M. Baltic, Kevin J. Coakley, David L. Jacobson
This in-situ study examines the water content in polymer electrolyte fuel cells (PEFCs) using neutron radiography. Various conditions such as different polytetraflouroethylene (PTFE) loadings in the gas diffusion media including the micro-porous layer (MPL

Formation of Disk- and Stacked Disk-Like Self-Assembled Morphologies from Cholesterol Functionalized Aliphatic Polycarbonate Containing Amphiphilic Diblock Copolymers

June 10, 2013
Author(s)
Vivek M. Prabhu, Shrinivas Venkataraman, Ashlynn Lee, Yi Yan Yang, James Hedrick, Hareem Maune
In this study, a cholesterol functionalized aliphatic cyclic carbonate monomer, 2-(5-methyl-2-oxo-1,3-dioxane-5-carboxyloyloxy)ethyl carbamate (MTC-Chol) was synthesized. The organo-catalytic ring opening polymerization of MTC-Chol was accomplished by

Light-Wave Mixing and Scattering with Quantum Gases

May 21, 2013
Author(s)
Lu Deng, Chengjie Zhu, Edward W. Hagley
We present a general theoretical framework on light-wave mixing and scattering in quantum gases. We show that all such processes that originate from elementary excitations are stimulated Raman or hyper-Raman in nature. In the forward direction, the third

Structure and Stability of SnO2 Nanocrystals and Surface-Bound Water Species

May 8, 2013
Author(s)
Rick L. Paul, Hsiu-Wen Wang, David J. Wesolowski, Thomas E. Proffen, Lucus Vicek, Wei Wang, Lawrence F. Allard, Alexander I. Kolesnikov, Mikhail Feygenson, Lawrence M. Anovitz
The structure of SnO2 nanoparticles (avg. 5 nm diameter) with a few layers of water on the surface has been elucidated by atomic pair distribution function (PDF) methods using in situ neutron total scattering data and molecular dynamics (MD) simulations

Wide Angle Polarization Analysis with Neutron Spin Filters

April 29, 2013
Author(s)
Qiang NMN Ye, Thomas R. Gentile, Jeffrey R. Anderson, Collin L. Broholm, WangChun Chen, Z DeLand, Ross W. Erwin, C. B. Fu, John E. Fuller III, Aaron V. Kirchhoff, J. A. Rodriguez-Rivera, V. Thampy, T G. Walker, Shannon Watson
We report substantial improvements in a compact wide angle neutron spin filter system that was recently employed on the Multi-Axis Crystal Spectrometer at the Center for Neutron Research at the U.S. National Institute of Standards and Technology. The
Displaying 676 - 700 of 925
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