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WWVB: A Half Century of Delivering Accurate Frequency and Time by Radio
No full textIn commemoration of its 50th anniversary of broadcasting from Fort Collins, Colorado, this paper provides a history of the National Institute of Standards and Technology (NIST) radio station WWVB. The narrative describes the evolution of the station, from its origins as a source of standard frequency, to its current role as the source of time-of-day synchronization for many millions of radio controlled clocks
Post-Irradiation Study of the Alanine Dosimeter
No full textPost-irradiation stability of high-dose dosimeters has traditionally been an important measurement influence quantity. Though the exceptional stability of the alanine dosimeter response with time has rendered this factor a non-issue for routine work, the archival quality of the alanine dosimeter has not been characterized. Here the alanine pellet dosimeter response is measured up to seven years post-irradiation for a range of absorbed doses. This long-term study is accompanied by an examination of the environmental influence quantities (e.g., ambient light) on the relatively short-term (3-4 month) stability of both pellet and film commercial dosimeters. Both dosimeter types demonstrated exceptional stability in the short term and proved to be relatively insensitive to common influence quantities. The long-term data revealed a complex dose-dependent response trend
A Framework for Reproducible Latent Fingerprint Enhancements
No full textPhotoshop processing of latent fingerprints is the preferred methodology among law enforcement forensic experts, but that appproach is not fully reproducible and may lead to questionable enhancements. Alternative, independent, fully reproducible enhancements, using IDL Histogram Equalization and IDL Adaptive Histogram Equalization, can produce better-defined ridge structures, along with considerable background information. Applying a systematic slow motion smoothing procedure to such IDL enhancements, based on the rapid FFT solution of a Lévy stable fractional diffusion equation, can attenuate background detail while preserving ridge information. The resulting smoothed latent print enhancements are comparable to, but distinct from, forensic Photoshop images suitable for input into automated fingerprint identification systems, (AFIS). In addition, this progressive smoothing procedure can be reexamined by displaying the suite of progressively smoother IDL images. That suite can be store
Fired Cartridge Case Identification Using Optical Images and the Congruent Matching Cells (CMC) Method
No full textThe Congruent Matching Cells (CMC) method for ballistics identification was invented at the National Institute of Standards and Technology (NIST). The CMC method is based on the correlation of pairs of small correlation cells instead of the correlation of entire images. Four identification parameters – TCCF, Tθ, Tx and Ty are proposed for identifying correlated cell pairs originating from the same firearm. The correlation conclusion (matching or non-matching) is determined by whether the number of CMC is ≥6. This method has been previously validated using a set of 780 pair-wise 3D topography images. However, most ballistic images stored in current local and national databases are in an optical intensity (grayscale) format. As a result, the reliability of applying the CMC method on optical intensity images is an important issue. In this paper, optical intensity images of breech face impressions captured on the same set of 40 cartridge cases are correlated and analyzed for the validatio
Measurement of Microsphere Concentration Using a Flow Cytometer with Volumetric Sample Delivery
No full textMicrosphere concentrations are needed to assign equivalent reference fluorophores (ERF) units to microspheres used in quantitative flow cytometry. A flow cytometer with a syringe based sample delivery system was evaluated for the measurement of the concentration of microspheres contained in a vial of lyophilized microspheres certified by BD Biosciences to contain 50,600 microspheres. The concentration was measured by counting the number of microspheres contained in the volume delivered by the flow cytometer and dividing the number by the volume. The syringe volume was calibrated both in the delivery and draw modes, and the results of the volume calibration were summarized by two calibration lines. The delivered volume was obtained by dividing the number of recorded events by the concentration of microsphere count standard in the sample tube. The draw volume was obtained by weighting the sample tube before and after the draw. The slope of the draw volume calibration line was equal to 1
Analysis of 1-Minute Potentially Available Fluoride from Dentifrice
No full textPrevious reports found that some fluoride-containing dentifrices do not release effective concentrations of fluoride during brushing. Failure to release fluoride can be due to dentifrice matrix components that interfere with the solubilization of the fluoride salts during brushing. A new generation of dentifrices has the capability to precipitate beneficial fluoride salts during tooth brushing. Therefore, a method that assesses the potentially available fluoride during the 1-minute brushing is needed. A new filter-paper absorption method to assess the 1-min bioavailable fluoride concentration was developed to meet this need. This method utilizes coiled filter paper that rapidly absorbs the aqueous phase of the dentifrice slurry followed by centrifugation to recover that fluid for fluoride measurement via fluoride ion-selective electrode. The analytical method was used to successfully determine the total fluoride and 1-min bioavailable fluoride in eight dentifrice products containing sodium fluoride (NaF), disodium monofluorophosphate (Na2FPO3, MFP), stannous fluoride (SnF2), or NaF with amorphous calcium phosphate (NaF + ACP). The results showed that some of the dentifrices tested had significantly lower potentially available fluoride than the total fluoride. For a MFP-containing sample, aged seven years past its expiry date, there was significant reduction in the bioavailable fluoride compared to MFP products that were not aged. Other than the aged MFP and the SnF2-containing samples the bioavailable fluoride for all products tested had at least 80 % of the label fluoride concentration. The filter paper absorption method yielded reproducible results for the products tested with MFP samples showing the largest variations
The Metrology of a Rastered Spot of X Rays used in Security Screening
No full textIn recent times, ionizing radiation has been used around the world to screen persons for non-medical purposes, namely to detect bulk explosives or other contraband hidden on the body including materials not registered by metal detectors. In contrast to conventional transmission or projection imaging, backscatter and forward-scatter systems employ a "flying spot" of x rays and large-area detectors. A small spot is rastered across an individual and the Compton scatter signal collected by these detectors is quickly integrated and assigned to a pixel value in an image corresponding to the transient location of the small flying spot. These systems have been controversial due in part to possible radiation health risks, and lack of independent and accurate measurements of radiation exposures to the subjects, bystanders, and operators of such systems. In this paper we will outline the techniques and instrumentation used at the National Institute of Standards and Technology (NIST) to accuratel
An Additive Manufacturing Test Artifact
No full textA test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system
Walter J. Lafferty
No full textWALTER J. LAFFERTY
NBS/NIST: 1961-1995
INDUCTED: 2014
B: 1934, Wilmington, Delaware
EDUCATION:
University of Delaware, BS (Chemistry), 1956
Massachusetts Institute of Technology, PhD (Physical Chemistry), 1962
Johns Hopkins University, Postdoctoral Research Associate, 1961
CITATION:
For seminal contributions to measurement and compilation of spectral, structural, and force-field molecular properties important in predictive chemical and physical modeling.
POSITIONS HELD AT NBS/NIST:
Research Chemist, Radiometry Section, Physics Division, 1961-1995
Scientist Emeritus, Sensor Science Division, PML, 1995-Present
HONORS:
U.S. Department of Commerce Silver Medal (1973)
Visiting Leverhulm Fellow, University of Reading, England (1971-1972)
Visiting Professor, Univ. de Pierre et Marie Curie, Paris (July 1988 & March 1989, 1990, 1991)
Visiting Professor, Univ. de Paris Sud (Feb. 1990, Feb. 1994, Feb. 1995, March 1996, March 1997, March 1998, Feb. 1999, Feb. 2000, Feb. 2001, March 2002, March 2003)
IBERDROLA Visiting Professor, CSIC, Madrid (1995)
MEMBERSHIPS:
Coblentz Society
American Physical Society
American Chemical Society
PUBLICATIONS:
More than 130 publications including:
Lafferty, W.J., Maki, A.G., and Plyler, E.K., “High Resolution Infrared Determination of the Structure of Carbon Suboxide,” J. Chem. Phys. 40, 244 (1964)
Lafferty, W.J., Maki, A.G., and Coyle, T.D., “High Resolution Infrared Spectrum of Diborane,” J. Mol. Spectrosc. 33, 345 (1970)
Harmony, M.D., Laurie, V.W., Kuczkowski, R.L., Schwendeman, R.H., Ramsay, D.A., Lovas, F.J., Lafferty, W.J., and Maki, A.G., “Molecular Structure of Gas-Phase Polyatomic Molecules Determined by Spectroscopic Methods,” J. Phys. Chem. Ref. Data 8, 619 (1979)
Pine, A.S. and Lafferty, W.J., “Rotational Structure and Vibrational Predissociation in the H-F Stretching Bands of the HF Dimer,” J. Chem. Phys. 78, 2154 (1983)
Pine, A.S., Lafferty, W.J., and Howard, B.J., “Vibrational Predissociation, Tunneling and Rotational Saturation in the HF and DF Dimers,” J. Chem. Phys. 81, 2939 (1984)
Fraser, G.T., Pine, A.S., Lafferty, W.J., and Miller, R.E, “Sub-Doppler Infrared Spectrum of the Carbon Dioxide Trimer,” J. Chem. Phys. 87, 1502 (1987
List of Names Mentioned in Oral history interview of John W. Cahn, Thursday, May 30, 2013, / with J. William Gadzuk, William Boettinger, Frank Gayle, Jonathan Guyer, Mike Moldover, and Jack Rush.
No full textOral History interview of John W. Cahn conducted on Thursday, May 30, 2013 at the National Institute of Standards and Technology in Gaithersburg, Maryland