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Search Publications by: Denis E. Bergeron (Fed)

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Displaying 51 - 75 of 78

Evidence against solar influence on nuclear decay constants

August 24, 2016
Author(s)
Denis E. Bergeron, Ryan P. Fitzgerald, Leticia S. Pibida, Stefaan Pomme
The exponential decay of radionuclides as a function of time is a cornerstone of nuclear physics and radionuclide metrology. Decay constants for spontaneous radioactive decay are considered invariable in time and space. This convenient trait allows

Micellar phase boundaries under the influence of ethyl alcohol

May 16, 2016
Author(s)
Denis E. Bergeron
The Compton spectrum quenching technique is used to monitor the effect of ethyl alcohol (EtOH) additions on phase boundaries in two systems. In toluenic solutions of the nonionic surfactant, Triton X-100, EtOH shifts the boundary separating the first clear

Comparison of C-14 liquid scintillation counting at NIST and NRC Canada

March 1, 2016
Author(s)
Denis E. Bergeron, Raphael Galea, Lizbeth Laureano-Perez, Brian E. Zimmerman
An informal bilateral comparison of 14C liquid scintillation (LS) counting at the National Research Council of Canada (NRC) and the National Institute of Standards and Technology (NIST) has been completed. Two solutions, one containing 14C-labeled sodium

Long-term stability of carrier-added Ge-68 standardized solutions

March 1, 2016
Author(s)
Brian E. Zimmerman, Denis E. Bergeron, Ryan P. Fitzgerald, Jeffrey T. Cessna
Tests for chemical stability were carried out on carrier-added 68Ge solutions prepared and calibrated in 2007 and 2011 to evaluate the suitability of the specific composition as a potential Standard Reference Material. Massic count rates of the stored

Revision of the NIST Standard for 223Ra: New Measurements and Review of 2008 Data

July 1, 2015
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Leticia S. Pibida
After discovering a discrepancy in the transfer standard currently being disseminated by the National Institute of Standards and Technology (NIST), we have performed a new primary standardization of the alpha-emitter 223Ra using Live-timed Anticoincidence

Two determinations of the 223Ra half-life

May 1, 2015
Author(s)
Denis E. Bergeron, Ryan P. Fitzgerald
Ra-223 is an alpha-emitter that is being used as a bone-seeking radiotherapeutic agent. The relatively large uncertainty on its half-life (0.26 %, Bé et al., 2011) is an impediment to precision activity assays. We have performed two series of measurements

Determination of photon emission probabilities for the main gamma-rays of 223Ra in equilibrium with its progeny

March 11, 2015
Author(s)
Leticia S. Pibida, Brian E. Zimmerman, Ryan P. Fitzgerald, Lynne E. King, Jeffrey T. Cessna, Denis E. Bergeron
The currently published 223Ra gamma-ray emission probabilities display a wide variation in the values depending on the source of the data. The National Institute of Standards and Technology performed activity measurements on a 223Ra solution that was used

Secondary standards for 223Ra revised

March 5, 2015
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Brian E. Zimmerman
Dose calibrator dial settings reported by NIST in 2010 (ARI v. 68, p. 1367) are now known to give erroneously low (by 10 %) activity readings. The original determinations were based on a chain of calibrations; a broken link in this chain was recently

A review of NIST primary activity standards for 18F: 1982 to 2013

August 27, 2014
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Bert M. Coursey, Ryan P. Fitzgerald, Brian E. Zimmerman
The new NIST activity standardization for 18F differs from results obtained between 1998 and 2008 by 4 %. The new results are considered to be very reliable; they are based on a battery of robust primary measurement techniques and bring the NIST standard

Dose calibrator manufacturer-dependent bias in assays of 123I

March 26, 2014
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Daniel B. Golas, Rheannan K. Young, Brian E. Zimmerman
Calibration factors for commercial ionization chambers (i.e. dose calibrators) were determined for a solution of 123I; the activity was based on the 1976 NBS standard. A link between the NIST standard and the International Reference System (SIR) was

A New NIST Primary Standardization of 18F

February 1, 2014
Author(s)
Ryan P. Fitzgerald, Brian E. Zimmerman, Denis E. Bergeron, Jeffrey T. Cessna, Leticia S. Pibida, Denise S. Moreira
A new primary standardization of 18F by NIST is reported. The standard is based on live-timed beta- gamma anticoincidence counting with confirmatory measurements by three other methods: (i) liquid scintillation (LS) counting using CIEMAT/NIST 3H efficiency

Micelle size effect on Fe-55 Liquid Scintillation Efficiency

December 1, 2013
Author(s)
Denis E. Bergeron, Lizbeth Laureano-Perez
We used efficiency tracing techniques to study the micelle size effect on liquid scintillation counting of the low-energy Auger electron emitter, 55Fe. We determined micelle hydrodynamic diameters for specific LS cocktails via dynamic light scattering, and

Results of an international comparison for the activity measurement of 177Lu

March 6, 2012
Author(s)
Brian E. Zimmerman, Denis E. Bergeron, Jeffrey T. Cessna
An international Key Comparison of 177Lu has recently been carried out. Twelve laboratories performed assays for radioactivity content on aliquots of a common master solution of 177Lu, leading to eleven results submitted for entry into the Key Comparison

TDCR Measurements on Pu-241 at NIST

December 21, 2010
Author(s)
Denis E. Bergeron, Brian E. Zimmerman
We have performed a series of measurements on a Pu-241 solution using the triple-to-double coincidence ratio (TDCR) liquid scintillation technique. A similar series of measurements in 2007 revealed significant discord between activity values determined via

Development of secondary standards for radium-223

November 5, 2009
Author(s)
Denis E. Bergeron, Brian E. Zimmerman, Jeffrey T. Cessna
223Ra is a bone-seeking alpha emitter, and as such is currently being evaluated as a radiopharmaceutical for the treatment of skeletal metastases. In the clinical setting, dosage measurements are typically achieved with reentrant ionization chambers

Ligand Exchange Reactions in the Formation of Diphosphine-Protected Gold Clusters

August 14, 2008
Author(s)
Denis E. Bergeron, Orkid Coskuner, Jeffrey W. Hudgens, Carlos A. Gonzalez
Electrospray ionization mass spectrometry is employed to study the formation of L3- and L5-protected gold clusters (L3 = 1,3-Bis(diphenylphosphino)propane; L5 = 1,5-Bis(diphenylphosphino)pentane), and it is found that molecular complexes in which Au+ is
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