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Water calorimetry: A correction to the heat defect calculations
No full textIn a recent publication, we used a reaction model (model III) to calculate the heat defect for the irradiation of aqueous solutions with ionizing radiation at 21 degreesC. Subsequent work has revealed that the literature value used for one of the rate constants in the model was incorrect. A revised model (model IIIR) incorporates the correct rate constant for 21 degreesC. Versions of models III and IIIR were created for irradiations at 4 degreesC. For our current water calorimetry protocol, the values of the heat defect for H-2/O-2-water (water saturated with a flow of 43% H-2 and 57% O-2, by volume) at 21 degreesC predicted by model III and model IIIR are similar but the value for 4 degreesC predicted by III is 30% smaller than the value predicted by IIIR. Model IIIR predicts that the values of the heat defect at 21 degreesC and 4 degreesC lie within the range -0.023+/-0.002, in agreement with the values obtained from our water calorimetry measurements done using pure water and H-2-saturated water at 21 degreesC and 4 degreesC. The yields of hydrogen peroxide in H-2/O-2-water at 21 degreesC and 4 degreesC were measured and agree with the predictions of model IIIR. Our water calorimetry measurements made with pure water and H-2-saturated water are now of sufficient quality that they can be used to determine the heat defect for H-2/O-2-water better than can be done by simulations. However, consistency between the three systems continues to be an excellent check on water purity which is crucial, especially for the pure water system
Diffractive optics from self-assembled DNA
No full textAn algorithm is presented for assembling tiles into a variable spaced grating, the one-dimensional analog of a Fresnel zone plate. The algorithm supports multi-level gratings. The x-ray properties of such a grating, assumed to be constructed from DNA are estimated, leading to the conclusion that thick structures may be useful for intermediate energy x rays, but that thin structures for soft x rays are best used as disposable masks. The diffraction of cold, coherent atoms is a plausible application for single layer stencils
Development of a tunable LED-based colorimetric source
No full textA novel, spectrally tunable light-source utilizing light emitting diodes (LEDs) for radiometric, photometric, and colorimetric applications is described. The tunable source can simulate standard sources and can be used as a transfer source to propagate photometric and colorimetric scales from calibrated reference instruments to test artifacts with minimal increase in uncertainty. In this prototype source, 40 LEDs with 10 different spectral distributions were mounted onto an integrating sphere. A voltage-to-current control circuit was designed and implemented, enabling independent control of the current sent to each set of four LEDs. The LEDs have been characterized for stability and dependence on drive current. The prototype source demonstrates the feasibility of development of a spectrally tunable LED source using LEDs with up to 40 different spectral distributions. Simulations demonstrate that such a source would be able to approximate standard light-source distributions over the visible spectral range-from 380 nm to 780 nm-with deviations on the order of 2%. The tunable LED source can also simulate spectral distributions of special sources such as discharge lamps and display monitors. With this tunable source, a test instrument can be rapidly calibrated against a variety of different source distributions tailored to the anticipated uses of the artifact. Target uncertainties for the calibration of test artifacts are less than 2% in luminance and 0.002 in chromaticity for any source distribution
Self-similarity simplification approaches for the modeling and analysis of Rockwell hardness indentation
No full textThe indentation process of pressing a Rockwell diamond indenter into inelastic material has been studied to provide a means for the analysis, simulation and prediction of Rockwell hardness tests. The geometrical characteristics of the spheroconical-shaped Rockwell indenter are discussed and fit to a general function in a self-similar way. The complicated moving boundary problem in Rockwell hardness tests is simplified to an intermediate stationary one for a flat die indenter using principle of similarity and cumulative superposition approach. This method is applied to both strain hardening and strain rate dependent materials. The effects of different material properties and indenter geometries on the indentation depth are discussed
Richard Deslattes
No full textRICHARD D. DESLATTES
Inducted: 2002
Citation: For his creative work in high-precision metrology and x-ray spectroscopy, including detailed measurements of crystal lattice spacing and the development of x-ray/optical interferometry.
Tenure: 1962 - 2001
Birth: 1931, New Orleans, Louisiana
Death: 2001, Rockville, Maryland
Education:
Loyola University (New Orleans), BS, 1952
Johns Hopkins University, PhD, 1958
Positions held:
NBS Senior Research Fellow
Chief, Quantum Metrology Division, Physics Laboratory
Senior NIST Fellow
Emeritus Senior NIST Fellow
Honors:
U.S. Office of Personnel Management: Arthur S. Flemming Award, 1969
U.S. Department of Commerce: Silver Medal, 1967; Gold Medal, 1979
NBS: Samuel W. Stratton Award, 1974
International Union of Pure and Applied Physics: The Symbols, Units, Nomenclature - Atomic Masses and Fundamental Constants Medal, 1990
Alexander von Humboldt Foundation: Senior U.S. Scientist Awar
Joseph M. Cameron
No full textJOSEPH M. CAMERON
NBS: 1947 - 1977
B: April 6, 1922, Edinboro, Pennsylvania
D: January 23, 2000, Wheaton, Maryland
EDUCATION:
University of Akron, BS (Mathematics), 1942
New York University (Meteorology)
North Carolina State University, MS (Statistics), 1947
American University
PRINCIPAL FIELDS:
Research and Development of Mathematical Methods in Statistics and Measurement Sciences
POSITIONS HELD AT NBS:
Chief, Statistical Engineering Section, Applied Mathematics Division
Chief, Office of Measurement Services, Institute for Basic Standards
HONORS:
U.S. Department of Commerce Gold Medal, 1963
MEMBERSHIPS:
American Statistical Association (Fellow)
American Association for the Advancement of Science (Fellow)
Institute of Mathematical Statistics
Mathematical Association of America
Royal Statistical Society (London)
Biometrics Society
Association for Computing Machinery
American Society for Quality Control
Instrument Society of America
PUBLICATIONS:
Numerous papers on experiment design and applications of statistical and computational
methods in the physical and engineering sciences and in metrology; landmark examples of which include:
Realistic Uncertainties and the Mass Measurement Process, Pontius, T.E. and Cameron, J.M., NBS Monograph 103, 1967.
Use of General Purpose Coding Systems for Statistical Calculations, Cameron, J.M. and
Hilsenrath, J., Proc. IBM Scientific Computing Symposium on Statistics, 1963.
Designs for the Surveillance of the Volt Maintained by a Small Group of Saturated
Standard Cells, Eicke, W.G. and Cameron, J.M., NBS Technical Note 430, 196
NIST standards for microanalysis and the certification process
No full textThe National Institute of Standards and Technology (NIST) has been involved in the development of standards for microanalysis since the middle of the 1960s. Certification of "traceable" standards that can be sold to other laboratories is time-consuming and costly, especially when the extent of microheterogeneity within each specimen becomes part of the uncertainty assigned to the certified values. The process of certification of microanalysis standards and the improvements that have facilitated the process with the development of automation and computerization are reviewed
Treasure of the past X - A spectroscopic determination of scattering lengths for sodium atom collisions (Reprinted from the Journal of Research of the National Bureau of Standards, vol 101, pg 505-520, 1996)
No full textWe report a preliminary value for the zero magnetic field Na S-2(f-1, m = -1)+ Na S-2(f-1, m = -1) scattering length, a(1,-1). This parameter describes the low-energy elastic two-body processes in a dilute gas of composite bosons and determines, to a large extent, the macroscopic wavefunction of a Bose condensate in a trap. Our scattering length is obtained from photoassocative spectroscopy with samples of uncondensed atoms. The temperature of the atoms is sufficiently low that contributions from the three lowest partial waves dominate the spectrum. The observed lineshapes for the purely long-range O-g(-) molecular state enable us to establish key features of the ground state scattering wavefunction. The fortuitous occurrence of a p-wave node near the deepest point (R-e = 72 a(o)) of the O-g(-) potential curve is instrumental in determining a(1,-1) = (52+/-5) a(0) and a(2.2) = (85+/-3) a(0), where the latter is for a collision of two Na S-2(f-2, m-2) atoms
