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Direct space structure solution applications
No full textThe crystal structures of 2,4,6-triisopropyl-benzenesulfonamide, 1,2,3-trihydroxybenzenehexamethylenetetramine (1/1), 5-bromonicotinic acid and chlorothalonil form II have been solved from x-ray powder diffraction data, by application of a direct space structure solution approach using the Monte Carlo method and confirmed by Rietveld refinement. In the sulfonamide, the molecules are linked by N - H...O hydrogen bonds into two-dimensional sheets built from alternating eight and twenty-membered rings. In the cocrystal, the molecules are linked by O-H...N hydrogen bonds to form puckered molecular ribbons that are in turn linked into a continuous 3D framework by C-H...pi ( arene) interactions. 5-bromonicotinic acid also displays atypical hydrogen-bonding behaviour by formation of dimers through a self-complementary acid-acid hydrogen-bond motif that are connected into antiparallel ribbons by C - H...O and C - H...N hydrogen bonds. Structure determination of the cocrystal and the bromonicotinic acid was successful despite the presence of preferred orientation in the data, whereas the distortion of the chlorothalonil data was so severe that structure solution was only possible when the effects of preferred orientation were minimized. Both the disordered structure, and an ordered structural approximation of chlorothalonil form II have been determined and rationalized
Evaluation of handheld radionuclide identifiers
No full textCharacterization of commercially available instruments for measurement and identification of unknown radionuclides was carried out in support of the development and testing of the American National Standards Institute (ANSI) standard, N42.34, "Performance Criteria for Hand-held Instruments for the Detection and Identification of Radionuclides." Measurements were based on the performance of the devices, i.e., the capability of the detectors to ensure a correct radionuclide identification in a given time interval for various radioactive sources
Frequency-domain models for nonlinear microwave devices based on large-signal measurements
No full textIn this paper, we introduce nonlinear large-signal scattering ( S) parameters, a new type of frequency-domain mapping that relates incident and reflected signals. We present a general form of nonlinear large-signal S-parameters and show that they reduce to classic S-parameters in the absence of nonlinearities. Nonlinear large-signal impedance (Z) and admittance (Y) parameters are also introduced, and equations relating the different representations are derived. We illustrate how nonlinear large-signal S-parameters can be used as a tool in the design process of a nonlinear circuit, specifically a single-diode 1 GHz frequency-doubler. For the case where a nonlinear model is not readily available, we developed a method of extracting nonlinear large-signal S-parameters obtained with artificial neural network models trained with multiple measurements made by a nonlinear vector network analyzer equipped with two sources. Finally, nonlinear large-signal S-parameters are compared to another form of nonlinear mapping, known as nonlinear scattering functions. The nonlinear large-signal S-parameters are shown to be more general
Edmund A. DiMarzio
No full textEDMUND A. DIMARZIO
NBS/NIST: 1963 - 1998
B: March 23, 1932, Philadelphia, Pennsylvania
EDUCATION:
St. Joseph’s University, BS (Physics: co-op student), 1954
University of Pennsylvania, MS (Physics), 1960
Catholic University of America, PhD (Physics), 1967
PRINCIPAL FIELD:
Polymer Physics
POSITIONS HELD AT NBS/NIST:
Physicist, Polymers Division
HONORS:
National Science Foundation Fellow, 1955
High Polymer Physics Prize of the American Physical Society (with J. H. Gibbs), 1967
Stratton Award (with E. Passaglia and J. I. Lauritzen), 1971
Maurice Huggins Award of the Gordon Research Conferences, 1988
Listed in Who’s Who in America, 2004
MEMBERSHIPS:
American Physical Society (Fellow)
Sigma Xi
PUBLICATIONS:
120 publications including:
E.A. Di Marzio, “A Unified Theory of Matter; the Fundamental Physical Law”, Foundation of Physics, 7 885 (1977).
E.A. Di Marzio, “The Ten Classes of Polymer Phase Transitions; Their Use as Models for Self-Assembly”, Progress in Polymer Science, 24 4063 (2002).
J.H. Gibbs and E.A. Di Marzio, “Nature of the Glass Transition and the Glassy State”, Journal of Chemical Physics, 28 373 (1958).
E.A. Di Marzio, “Proper Accounting of a Polymer Near a Surface”, Journal of Chemical Physics, 42 2101 (1965)
Clark A. Hamilton
No full textCLARK A. HAMILTON
NBS/NIST: 1971 - 1999
B: April 22, 1944, Rochester, New York
EDUCATION:
Union College, BS (Electrical Engineering), 1966
University of Rochester, MS (Electrical Engineering), 1968
University of Rochester, PhD (Electrical Engineering), 1971
PRINCIPAL FIELDS:
Josephson effect and superconductivity; optical power sensors; superconductive digital logic, sampling devices and analog to digital converters; Josephson voltage standards
POSITIONS HELD AT NBS/NIST:
Post Doctoral Research Fellow
Electronics Engineer, Electromagnetic Technology Division
Project Leader, Josephson voltage standard development, Electromagnetic Technology Division
HONORS:
Hertz Fellow 1969-1971
US DOC Gold Medal for Advances in Superconductive Electronics 1983
US DOC Gold Medal for Josephson Voltage Standard 1989
National Institute of Standards and Technology Fellow 1989
Institute of Electrical and Electronic Engineers Electrotechnology Transfer Award 1995
NCSL International Wildhack Award 2001
International Union of Pure and Applied Physics SUNAMCO (Symbols, Units, Nomenclature, Atomic Masses and Fundamental Physical Constants) Award 2001
MEMBERSHIPS:
Institute of Electrical and Electronics Engineers (Fellow)
NCSL Intrinsic/Derived Standards Committee
PUBLICATIONS:
More than 80 publications including:
C.A. Hamilton, "Josephson Voltage Standards," Review of Scientific Instruments invited review, (2000), also presented as a plenary talk at CPEM 2000 in Sydney Australia.
C. A. Hamilton and Y. H. Tang, "Evaluating the Uncertainty of Josephson Voltage Standards," Metrologia, (1999).
C. A. Hamilton, R. L. Kautz, R. L. Steiner, and F. L. Lloyd, "A practical Josephson voltage standard at 1 volt, " IEEE Electron Device Letters, the seminal paper of the Josephson array voltage standard (1985).
C. A. Hamilton, Y. H. Tang, M. Kelley, S. Kupferman, D. Deaver, J. Ball, and B. Wood, Josephson Voltage Standard – Recommended Intrinsic Derived Standards Practice, NCSL International, 2002
Direct methods optimised for solving crystal structure by powder diffraction data: Limits, strategies, and prospects
No full textThe ab-initio crystal structure solution by powder diffraction data requires great efforts because of the collapse of the experimental information onto the one dimensional 2theta axis of the pattern. Different strategies will be described aiming at improving the process of extraction of the integrated intensities from the experimental pattern in order to make more straightforward the structure solution process by direct methods. Particular attention will be devoted to the EXPO program. Some of its performance will be analysed and results will be shown
Simulation of sheared suspensions with a parallel implementation of QDPD
No full textA parallel quaternion-based dissipative particle dynamics (QDPD) program has been developed in Fortran to study the flow properties of complex fluids subject to shear. The parallelization allows for simulations of greater size and complexity and is accomplished with a parallel link-cell spatial (domain) decomposition using MPI. The technique has novel features arising from the DPD formalism, the use of rigid body inclusions spread across processors, and a sheared boundary condition. A detailed discussion of our implementation is presented, along with results on two distributed memory architectures. A parallel speedup of 24.19 was obtained for a benchmark calculation on 27 processors of a distributed memory cluster
The remarkable metrological history of radiocarbon dating [II]
No full textThis article traces the metrological history of radiocarbon, from the initial breakthrough devised by Libby, to minor (evolutionary) and major (revolutionary) advances that have brought C-14 measurement from a crude, bulk [8 g carbon] dating tool, to a refined probe for dating tiny amounts of precious artifacts, and for "molecular dating" at the 10 micro g g to 100 micro g level. The metrological advances led to opportunities and surprises, such as the non-monotonic dendrochronological calibration curve and the "bomb effect," that gave rise to new multidisciplinary areas of application, ranging from archaeology and anthropology to cosmic ray physics to oceanography to apportionment of anthropogenic pollutants to the reconstruction of environmental history. Beyond the specific topic of natural C-14, it is hoped that this account may serve as a metaphor for young scientists, illustrating that just when a scientific discipline may appear to be approaching maturity, unanticipated metrological advances in their own chosen fields, and unanticipated anthropogenic or natural chemical events in the environment, can spawn new areas of research having exciting theoretical and practical implications
X-ray spectrometry of copper: New results on an old subject
No full textWe review recent, and some less recent, measurements of several emission spectra of copper. The results are discussed with special emphasis on elucidating the structure of the Kalpha(1,2) and Kbeta(1,3) diagram lines and their underlying transitions. These lines are found to contain approximate to 30 % contribution from 3d spectator hole transitions. Other multielectronic transitions, the 2p spectator hole ( satellites) and 1s spectator hole (hypersatellites) transitions were also measured. They are discussed paying special attention to the evolution of the lineshapes and intensities from the excitation threshold to saturation. Trends in the measured quantities depending on the spectator hole's shell and subshell are also discussed