Related Experiment Video
Updated: Aug 1, 2026

High-throughput Quantitative Real-time RT-PCR Assay for Determining Expression Profiles of Types I and III Interferon Subtypes
Published on: March 24, 2015
Primary Atomic Frequency Standards at NIST
D B Sullivan1, J C Bergquist1, J J Bollinger1
1National Institute of Standards and Technology, Boulder, CO 80305-3328.
Abstract:
The development of atomic frequency standards at NIST is discussed and three of the key frequency-standard technologies of the current era are described. For each of these technologies, the most recent NIST implementation of the particular type of standard is described in greater detail. The best relative standard uncertainty achieved to date for a NIST frequency standard is 1.5×10(-15). The uncertainties of the most recent NIST standards are displayed relative to the uncertainties of atomic frequency standards of several other countries.
Related Concept Videos
Atomic Nuclei: Nuclear Spin State Population Distribution
Atomic Nuclei: Larmor Precession Frequency
Atomic Weight
Other Nuclides: 31P, 19F, 15N NMR
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
Atomic Spectroscopy: Absorption, Emission, and Fluorescence
Atomic Fluorescence Spectroscopy

