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Karen Brown (Acting NIST Director, 2000-2001) at NIST 2001 Centennial History and Reunion Day
No full textNIST held a number of events to mark its centennial celebration in March 2001. The NIST History and Centennial Symposium-Reunion Day for NIST staff and alumni was held on March 5 AT NIST Boulder and NIST Gaithersburg, pictured here. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection consists of images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Dierdre McMahon (R) at NIST 2001 Centennial History and Reunion Day
No full textNIST held a number of events to mark its centennial celebration in March 2001. The NIST History and Centennial Symposium-Reunion Day for NIST staff and alumni was held on March 5 AT NIST Boulder and NIST Gaithersburg, pictured here. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection consists of images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Concrete mixing methods and concrete mixers: State of the art
No full textAs for all materials, the performance of concrete is determined by its microstructure. Its microstructure is determined by its composition, its curing conditions, and also by the mixing method and mixer conditions used to process the concrete. This paper gives an overview of the various types of mixing methods and concrete mixers commercially available used by the concrete industry. There are two main types of mixers used: batch mixers and continuous mixers. Batch mixers are the most common. To determine the mixing method best suited for a specific application, factors to be considered include: location of the construction site (distance from the batching plant), the amount of concrete needed, the construction schedule (volume of concrete needed per hour), and the cost. Ultimately, the quality of the concrete produced determines its performance after placement. An important measure of the quality is the homogeneity of the material after mixing. This paper will review mixing methods in regards to the quality of the concrete produced. Some procedures used to determine the effectiveness of the mixing will be examined
Treasure of the Past VI: Standard potential of the silver-silver-chloride electrode from 0 degrees to 95 degrees C and the thermodynamic properties of dilute hydrochloric acid solutions
No full textStatistics and measurements
No full textFor more than 50 years, the Statistical Engineering Division (SED) has been instrumental in the success of a broad spectrum of metrology projects at NBS/NIST. This paper highlights fundamental contributions of NBS/NIST statisticians to statistics and to measurement science and technology. Published methods developed by SED staff, especially during the early years, endure as cornerstones of statistics not only in metrology and standards applications, but as data-analytic resources used across all disciplines. The history of statistics at NBS/NIST began with the formation of what is now the SED. Examples from the first five decades of the SED illustrate the critical role of the division in the successful resolution of a few of the highly visible, and sometimes controversial, statistical studies of national importance. A review of the history of major early publications of the division on statistical methods, design of experiments, and error analysis and uncertainty is followed by a survey of several thematic areas. The accompanying examples illustrate the importance of SED in the history of statistics, measurements and standards: calibration and measurement assurance, interlaboratory tests, development of measurement methods, Standard Reference Materials, statistical computing, and dissemination of measurement technology. A brief look forward sketches the expanding opportunity and demand for SED statisticians created by current trends in research and development at NIST
The kilogram and measurements of mass and force
No full textThis paper describes the facilities, measurement capabilities, and ongoing research activities in the areas of mass and force at the National Institute of Standards and Technology (NIST). The first section of the paper is devoted to mass metrology and starts with a brief historical perspective on the developments that led to the current definition of the kilogram. An overview of mass measurement procedures is given with a brief discussion of current research on alternative materials for mass standards and surface profiles of the U.S. national prototype kilograms. A brief outlook into the future possible redefinition of the unit of mass based on fundamental principles is included. The second part of this paper focuses on the unit of force and describes the realization of the unit, measurement procedures, uncertainty in the realized force, facilities, and current efforts aimed at the realization of small forces
Materials research with neutrons at NIST
No full textThe NIST Materials Science and Engineering Laboratory works with industry, standards bodies, universities, and other government laboratories to improve the nation's measurements and standards infrastructure for materials. An increasingly important component of this effort is carried out at the NIST Center for Neutron Research (NCNR), at present the most productive center of its kind in the United States. This article gives a brief historical account of the growth and activities of the Center with examples of its work in major materials research areas and describes the key role the Center can expect to play in future developments
Treasure of the Past IX: Exposure Standardization of Iodine-125 Seeds Used for Brachytherapy
No full textA method for calibrating iodine-125 seeds in terms of exposure has been established. The standard free-air ionization chamber, used for measuring soft x rays, was chosen for the measurements. Arrays of four to six seeds were used to enhance the ionization-current-to-background-current ratio. Seedfs from an array were measured individually in a re-entrant chamber. The quotient of the exposure rate for the array by the sum of the ionization currents in the re-entrant chamber is the calibration factor for the re-entrant chamber. Calibration factors were established for three types of iodine-125 seeds. The overall uncertainty for the seed exposure calibrations is less than 6 %
Macromolecular crystallography and structural biology databases a NIST
No full textIn the late 1970s, macromolecular crystallography at NIST began with collaboration between NIST and NIH to establish a single-crystal neutron diffractometer. This instrument was constructed and employed to solve a number of crystal structures: bovine ribonuclease A, bovine-ribonuclease-uridine vanadate complex, and porcine insulin. In the mid 1980s a Biomolecular Structure Group was created establishing NIST capabilities in biomolecular singe-crystal x-ray diffraction. The group worked on a variety of structural problems until joining the NIST/UMBI Center for Advanced Research in Biotechnology ( CARB) in 1987. Crystallographic studies at CARB were then focused on protein engineering efforts that included among others chymosin, subtilisin BPN', interleukin 1beta and glutathione S-transferase. Recently, the structural biology efforts have centered on enzymes in the chorismate metabolic pathways involved in amino acid biosynthesis and in structural genomics that involves determining the structures of hypothetical proteins to aid in assigning function. In addition to crystallographic studies, structural biology database activities began with the formal establishment of the Biological Macromolecule Crystallization Database in 1989. Later, in 1997, NIST in partnership with Rutgers and UCSD formed the Research Collaboratory for Structural Bioinformatics that successfully acquired the Protein Data Bank. The NIST efforts in these activities have focused on data uniformity, establishing and maintaining the physical archive, and working with the NMR community
Standard Reference Material (SRM 1990) for single crystal diffractometer alignment
No full textAn international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and ( 2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material(R) for single crystal diffractometer alignment. This SRM is a set of approximate to 3500 units of Cr-doped Al2O3, or ruby spheres [ (0.420.011 mole fraction % C ( expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals: the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a = 4.7608 Angstrom +/- 0.0062 Angstrom, and c = 12.9979 Angstrom +/- 0.020 Angstrom ( 95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at ( Bell Laboratories) Lucent Technologies and at NRC of Canada ( 39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Hagg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies are rhombohedral, with space group R 3 c. The certified mean unit cell parameters are a = 4.76080 +/- 0.00029 Angstrom, and c = 12.99568 Angstrom +/- 0.00087 Angstrom ( expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Hagg transmission measurements on five samples of powdered rubies ( a = 4.7610 Angstrom +/- 0.0013 Angstrom, and c = 12.9954 Angstrom +/- 0.0034 Angstrom) agreed well with the values obtained from the single crystal spheres