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NIST Authors in Bold

Displaying 11551 - 11575 of 73927

Complementary Use of Optical Metrology and X-Ray Computed Tomography for Surface Finish and Defect Detection in Laser Powder Bed Fusion Additive Manufacturing

July 25, 2018
Author(s)
Jason C. Fox, Felix H. Kim, Zachary C. Reese, Christopher Evans
The development of additive manufacturing (AM) has allowed for production of high-value and complex parts that reduce time-to-market and cost to manufacture. A key benefit to the AM process is the capability to create lattice structures and highly complex

ASTM E3125 Laser Scanner Standard: Challenges and Role of NIST

July 24, 2018
Author(s)
Prem K. Rachakonda
The Dimensional Metrology Group (DMG) at National Institute of Standards & Technology (NIST), along with various other organizations were involved in the development of the ASTM E3125-17 documentary standard for 3D imaging systems. The ASTM E57 committee

Determination of polypeptide conformation in water with nanoscale resolution in water

July 24, 2018
Author(s)
Georg Ramer, Francesco Ruggeri, Aviad Levin, Toumas Knowles, Andrea Centrone
The conformational structure and folding of proteins are central to many biological processes. However, misfolding of proteins and peptides can lead to toxic aggregates that are involved in Alzheimer’s and other neurodegenerative disorders. Methods to

Dual-comb interferometry via repetition-rate switching of a single frequency comb

July 24, 2018
Author(s)
David R. Carlson, Daniel D. Hickstein, Daniel C. Cole, Scott A. Diddams, Scott B. Papp
We experimentally demonstrate a versatile technique for performing dual-comb interferometry using a single frequency comb. By rapid switching of the repetition rate, the output pulse train can be delayed and heterodyned with itself to produce

Measurement of Thermal Processing Variability in Powder Bed Fusion

July 24, 2018
Author(s)
Jarred C. Heigel, Eric P. Whitenton
Laser powder bed fusion (LPBF) is an additive manufacturing (AM) technology used to manufacture high-value metal parts. The layer-by-layer nature of the process allows complex geometries and internal features, such as conformal cooling channels, to be

Imaging Through Fire Using Narrow-Spectrum Illumination

July 23, 2018
Author(s)
Christopher M. Smith, Matthew Hoehler
This paper demonstrates a simple method to enhance visibility through clean-burning flames that allows new opportunities to perform optical metrology in fire research. The method combines narrow-spectrum, blue illumination and matched optical filters to

New determination of the 229Th half-life

July 23, 2018
Author(s)
Richard Essex, Jacqueline L. Mann, Ronald Colle, Lizbeth Laureano-Perez, Megan E. Bennett, Heather Dion, Ryan P. Fitzgerald, Amy M. Gaffney, Amelie Hubert, Robert E. Steiner, Ross W. Williams, Alkiviadis Gourgiotis, William S. Kinman
A new determination of the 229Th half-life was made based on measurements of the 229Th massic activity of a high-purity solution for which the 229Th molality had previously been measured. The 229Th massic activity was measured by direct comparison with SRM

Evaluation of Formaldehyde Reference Material for Chamber Emission Testing

July 22, 2018
Author(s)
Dustin G. Poppendieck, Na Li, Wenhao Chen
Formaldehyde reference materials are being developed by the National Institute of Standards and Technology (NIST) for use in regulatory emission testing certification programs. Emission rates for a prototype formaldehyde reference material were determined

Simmering Sauces! Elevated Formaldehyde Concentrations from Gas Stove Burners

July 22, 2018
Author(s)
Dustin G. Poppendieck, Mengyan Gong
Formaldehyde is listed as a human carcinogen, and can be formed as a primary by-product during combustion processes. Past studies have not detected elevated formaldehyde concentrations from gas stoves, perhaps due to the time averaging nature of previous

Do Very Small POSS Nanoparticles Perturb s-PMMA Chain Conformations?

July 21, 2018
Author(s)
Nicolas Jouault, Sanat K. Kumar, Robert J. Smalley, Changzai Chi, Robert Moneta, Barbara Wood, Holly Salerno, Yuri B. Melnichenko, Lilin He, William E. Guise, Boualem Hammouda, Michael K. Crawford
Small-Angle Neutron Scattering (SANS) measurements of polymers mixed with weakly attractive 1.0 nm diameter polyhedral oligomeric silsesquioxane (POSS) nanoparticles (NPs) show no observable changes in the chain radius of gyration R g, regardless of the

A radial calibration window for analytical ultracentrifugation

July 20, 2018
Author(s)
Thomas W. LeBrun, Peter Schuck, Wei Ren, Justine Yoon, Xianghui Dong, Nicole Y. Morgan, Jeffrey Fagan, Huaying Zhao
Analytical ultracentrifugation (AUC) is a first-principles based method for studying particles in solution by monitoring the evolution of their radial concentration distribution as a function of time in the presence of a high centrifugal field. In

A Spin-1 Representation for Dual-Funnel Energy Landscapes

July 20, 2018
Author(s)
Justin E. Elenewski, Kirill Velizhanin, Michael P. Zwolak
The interconversion between left- and right-handed helical folds of a polypeptide defines a dual-funneled free energy landscape. In this context, the funnel minima are connected through a continuum of unfolded conformations, evocative of the classical

Epitaxial graphene for quantum resistance metrology

July 20, 2018
Author(s)
Mattias Kruskopf, Randolph Elmquist
A new generation of graphene-based quantum Hall resistance standards promises high precision for the unit ohm under relaxed measurement conditions, enabling the use of compact measurement systems. To meet the requirements of metrological applications

Photon thermalization via laser cooling of atoms

July 19, 2018
Author(s)
Chiao-Hsuan Wang, Michael Gullans, James V. Porto, William D. Phillips, Jacob Taylor
The cooling of atomic motion by scattered light enables a wide variety of technological and scientific explorations. Here we focus on laser cooling from the perspective of the light — specifi- cally, the scattering of light between different optical modes
Displaying 11551 - 11575 of 73927
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