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Displaying 1 - 25 of 422

Traceable Comparisons of Water-Triple-Point Cells

November 8, 2024
Author(s)
Weston L. Tew
A specific sub-set of comparison data is presented for two NIST water-triple-point cells that provide traceability to the results of the 2023 Consultative Committee for Thermometry CCT-K7.2021 CIPM Key Comparison of Water-Triple-Point Cells. NIST had

Comparison of Three Methods for Oscillating Flow Measurements in Cryocoolers

October 16, 2024
Author(s)
Ryan Snodgrass, Vincent Kotsubo, Joel Ullom
Measurement of oscillating mass flows is typically required for the study of cryocoolers and cryocooler compressors. Although many measurement techniques are used in the cryocooler literature, detailed comparisons are lacking, so it can be challenging for

Speed of Sound for Understanding Metals in Extreme Environments

October 7, 2024
Author(s)
Elizabeth Rasmussen, Boris Wilthan
Knowing material behavior is crucial to successful design, especially given the growing number of next-generation energy, defense, and manufacturing systems operating in extreme environments. Specific applications for materials in extreme environments

Linking excess entropy and acentric factor in spherical fluids

September 9, 2024
Author(s)
Tae Jun Yoon, Ian Bell
Introduced by Kenneth Pitzer in 1955, the acentric factor (ω) became a standard quantity in chemical thermodynamics, representing a molecule's "shape" effect on the deviation from the corresponding state behavior. Nevertheless, its interpretation remains

Anisotropic coarse-grain Monte Carlo simulations of lysozyme, lactoferrin, and NISTmAb by precomputing atomistic models

September 5, 2024
Author(s)
Harold Hatch, Christina Bergonzo, Marco Blanco, Guangcui Yuan, Sergei Grudinin, Mikael Lund, Joseph E. Curtis, Alexander Grishaev, Yun Liu, Vincent K. Shen
We develop a multiscale coarse-grain model of the NIST Monoclonal Antibody Reference Material 8671 (NISTmAb) to enable systematic computational investigations of high-concentration physical instabilities such as phase separation, clustering, and

Monte Carlo molecular simulations with FEASST version 0.25.1

September 5, 2024
Author(s)
Harold Hatch, Daniel Siderius, Vincent K. Shen
FEASST is an open-source Monte Carlo software for particle-based simulations. This software, which was released in 2017, has been used to study phase equilibrium, self-assembly, aggregation or gelation in biological materials, colloids, polymers, ionic

Optical n(p, T_90) measurement suite 2: H_2O and D_2O

May 28, 2024
Author(s)
Patrick Egan, Yuanchao Yang
A suite of measurements of refractive index n(p, T_90) is reported for gas phase ordinary water H_2O and heavy water D_2O. The methodology is optical refractive index gas metrology, operating at laser wavelength 633 nm and covering the range (293 T_90 43

Dynamic acoustic optimization of pulse tube refrigerators for rapid cooldown

April 23, 2024
Author(s)
Ryan Snodgrass, Vincent Kotsubo, Scott Backhaus, Joel Ullom
Pulse tube refrigerators are a critical enabling technology for many disciplines that require low temperatures. These refrigerators dominate the total power consumption of most modern cryostats, including those that reach millikelvin temperatures using

The Four-sinker Densimeter: A New Instrument for the Combined Investigation of Accurate Densities and Sorption Phenomena of Gases and Gas Mixtures

February 29, 2024
Author(s)
Luca Bernadini, Reiner Kleinrahm, Katharina Moritz, Mark O. McLinden, Markus Richter
An apparatus for high-accuracy gas density and adsorption measurements over the range of temperature from (193 to 423) K and pressure from (0 to 15) MPa is described. This instrument is based on the two-sinker densimetry principle and incorporates a

Optical n(p, T_90) measurement suite 1: He, Ar, and N_2

November 23, 2023
Author(s)
Patrick Egan, Yuanchao Yang
An n(p, T90) measurement suite is reported for the gases helium, argon, and nitrogen. The methodology is optical refractive-index gas metrology, operating at laser wavelength 633 nm and covering the temperature range (293 T 433) K and pressures p 0.5

Small Corrections to 1989 NIST Constant-Volume Gas Thermometry Data

November 17, 2023
Author(s)
Allan H. Harvey
Constant-volume gas thermometry data published in 1989 for the difference between the thermodynamic temperature and the International Practical Temperature Scale of 1968 are corrected in two ways. A refined estimate of the thermal expansivity of the

Ab initio Calculation of Fluid Properties for Precision Metrology

September 12, 2023
Author(s)
Giovanni Garberoglio, Christof Gaiser, Roberto Maria Gavioso, Allan H. Harvey, Robert Hellmann, Bogumil Jeziorski, Karsten Meier, Michael R. Moldover, Laurent Pitre, Krzysztof Szalewicz, Robin Underwood
Recent advances regarding the interplay between ab initio calculations and metrology are reviewed, with particular emphasis on gas-based techniques used for temperature and pressure measurements. Since roughly 2010, several thermophysical quantities – in

An Equation of State for the Thermodynamic Properties of Helium

August 10, 2023
Author(s)
Diego Ortiz Vega, Kenneth Hall, James Holste, Allan H. Harvey, Eric W. Lemmon
This report documents the equation of state for fluid helium implemented in Version 10 of NIST's REFPROP Standard Reference Database. The equation of state is expressed as the molar Helmholtz energy as a function of temperature and density, and is valid

Quantum Entropic Effects in the Liquid Viscosities of Hydrogen, Deuterium, and Neon

July 26, 2023
Author(s)
Ian Bell, Jacob Leachman, Albert Rigosi, Heather Hill
The extreme conditions have limited the availability and accuracy of experimental thermophys- ical property measurements for cryogens, particularly transport properties. Traditional scaling techniques such as corresponding states theory have long been

pH response of sequence-controlled polyampholyte brushes

May 31, 2023
Author(s)
Xin Yuan, Harold Hatch, Jacinta Conrad, Amanda Marciel, Jeremy Palmer
We use molecular simulation to investigate the pH response of sequence-controlled polyampholyte brushes (PABs) with polymer chains consisting of alternating blocks of weakly acidic and basic monomers. Changes in the ionization state, height, lateral
Displaying 1 - 25 of 422