1,469 research outputs found
MICROWAVE SPECTRUM AND STRUCTURE OF
No full text1. (a) M.A. Dvorak, R.S. Ford, R.D. Suenram, F.J. Lovas and K.R. Leopold, J. Am. Chem. Soc., 114, 108 (1992); (b) M.A. Dvorak, R.S. Ford., R.D. Suenram, F.J. Lovas and K.R. Leopold, 46th International Symposium on Molecular Spectroscopy, June 1991, paper FA9Author Institution: Department of Chemistry, University of Minnesota; Molecular Physics Division, National Institute of Standards and Technology; Department of Chemistry, University of MinnesotaRotational spectra of the complex have been observed using pulsed nozzle Fourier transform microwave spectroscopy. Spectra have been observed for the and species with both and , and the hyperfine structure analyzed. The complex has the expected structure, with the nitrogen end of the HCN toward the boron, but the observed BN bond length of 2.54(6) \AA is notably shorter than that in the related weakly bound systems and . We compare the structure, energetics, force constants, and quadrupole coupling constants of the complex with those of other species formed from and nitrogen donors and extend our previous of gas phase structure correlations as a means of mapping reaction paths for simple chemical transformations
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
MICROWAVE STUDY OF THE TRIOSE SUGAR SYSTEM: GLYCERALDEHYDE AND 1,2-DIHYDROXY-2-PROPANONE
No full textJ.M. Hollis, F.J. Lovas, and P.R. Jewell, Astrophys. J. (Letters) 540, L107 (2000).Author Institution: Institut f\""ur Physikalische Chemie, University of Ilinois; Astronomy Department, National Institute of Standards and Technology; Optical Technology Division, National Institute of Standards and Technology; Optical Technology Division, University of OsloRecently, the simplest sugar, glycolaldehyde was identified in the Sgr B2 molecular cloud by . As a result of this discovery, we became interested in studying the next larger sugars characterized as trioses. The triose sugars consist of the aldehyde form, glyceraldehyde, and the ketone form, 1,3-dihydroxy-2-propanone. The microwave spectra were obtained with the NIST Fourier-transform pulsed-nozzle microwave spectrometer that was equipped with a heated nozzle located in one mirror. A few tenths of a gram of solid sample was placed in the nozzle base, which was heated to between and and pressurized with Ne. Broad survey scans were run from 10 GHz to 26 GHz in both samples. In the glyceraldehyde study, three conformers of the parent species were identified as well as 1,3-dihydroxy-2-propanone. In addition three decomposition products were also identified: formic acid, trans-methyl glyoxal, and a previously unknown product 2-hydroxy-2-propen-1-al. Ab initio calculations were carried out with the Gaussian 98 program at the level to aid in the identification of each of the new species. The survey scan from 1,3-dihydroxy-2-propanone confirmed the identification of this species initially assigned in the glyceraldehyde study, and also exhibited spectra from the three decomposition products. However, the three conformers of glyceraldehyde were not present. Details of the measurements, assignments and ab initio results will be presented
STRUCTURE OF ACETALDEHYDE IN EXCITED TORSIONAL STATES FROM THE MILLIMETER WAVE SPECTRUM.
No full text1)Nadgaran H., Baker J.G., ``Twelfth Colloquium on High Resolution Spectroscopy'', Dijon, France, J38 (1991). 2)Maes H., Wlodarczak G., Boucher D. and Demaison J.Z., Naturforsch, 42a, 97-102 (1987). 3)Kleiner I., Hougen J.T., Suenram R.D., Lovas F.J. and Godefroid M., J.Mol.Spect., 148, 38-49 (1991). 4)Kleiner I., Hougen J.T., Suenram R.D. and Lovas F.J., J.Mol.Spect., 153, 578-586 (1992). 5)Nadgaran H., Baker J.G., ``47th International Symposium on Molecular Spectroscopy'', Columbus, Ohio, USA, FD14 (1992).Author Institution: c/o N.Riazi, Department of Physics., University of Shiraz; Schuster Laboratory, University of ManchesterWe have carried out comparative single-state and global fits to the millimeter wave spectra of the ground and excited torsional states of acctaldehyde measured by ourselves and other , using an IAM technique not calling for large matrix . The Hamiltonian used also utilises a planar rotation which transforms the quartic and sextic centrifugal distortion terms to an internal axes . The structure of the molecule derived from the single-state fits shows changes in both methyl and aldehyde group structures corresponding to increasing proton repulsions as the barrier is surmounted, but the use of global fit parameters leads to quite unreasonable molecular geometries
Roughness Induced Boundary Layer Transition in Incompressible Flow
No full textThe fluid dynamics process leading to laminar-turbulent transition behind an isolated roughness element is investigated in the incompressible regime using particle image velocimetry. The study covers the effect of roughness size and geometry on the promotion of transition. The measurement domain covers a large streamwise range from the near wake to the onset of the turbulent regime. Planar PIV measurements reveal the basic flow pattern and the turbulent structure of the flow characterizing by the velocity fluctuation statistics (RMS of the streamwise and wall-normal velocity component and Reynolds shear stress). The high Reynolds shear stress level reaching the region near the wall in the downstream area indicates the onset of turbulent boundary layer
Donald R. Johnson
No full textDONALD R. JOHNSON
Inducted: 2008
Citation:
For outstanding research contributions in spectroscopy and astronomy as well as for distinguished managerial leadership exemplified in the creation of the Center for Advanced Research in Biotechnology (CARB) and the establishment of new NIST extramural programs under the Technology Competitiveness Act of 1988.
Tenure: 1967-1993
Birth: 1938, Tacoma, Washington
Education:
University of Puget Sound, BS (Physics), 1960
University of Idaho, MS (Physics), 1962
University of Oklahoma, PhD (Physics), 1967
Positions held:
Physicist, Molecular Spectroscopy Section, Atomic Physics Division, 1967-76
Analyst, Program Office, 1976-78
Deputy Director, National Measurement Laboratory, 1978-83
Director, National Measurement Laboratory, 1983-88
Director, Task Force on Industrial Technology Services, 1987-88
Special Assistant to Undersecretary of Commerce for Technology Policy, 1989-90
Director, Technology Services, 1988-93
Honors:
Fellow, American Physical Society
Arthur S. Fleming Award for Outstanding Service in the Federal Government (1976)
Department of Commerce Silver Medal (1973) and Gold Medal (1977)
Senior Executive Service, Meritorious Executive (1981) and Distinguished Executive (1988)
Department of Commerce Outstanding Volunteer (1990)
Memberships:
American Physical Society Council 8 years; Chair, Langmuir Prize Committee
ASTM Board of Directors 6 years; Committee on Research and Technical Planning
American Society of Mechanical Engineers; Board on Research and Technology Development
Commission of the European Communities; Bureau of Reference Materials Evaluation Group
National Conference of Standards Laboratories
Advisory Board to House Space & Technology Task Force on Technology Policy
Maryland Governor’s Commission on Excellence in Higher Education
Publications:
40 archival scientific papers plus numerous articles on NBS/NIST including:
Johnson, D.R., and Powell, F.X., “Microwave Detection of Thioformaldehyde,” Science, 679-80 (1970)
Johnson, D.R., and Pearson, R., “Molecular Spectroscopy Microwave Region,” Methods of Experimental Physics, 13B, 102-33 (1976)
Johnson, D.R., and Lovas, F.J., “Microwave Detection of the Molecular Transient Methyleneimine,” Chem. Phys. Lett, 15(1), 65-8 (1972)
Clark, F.O., Lovas, F.J., and Johnson, D.R., “Dimethyl Ether in Orion,” Astrophys. J., 229(2, Pt. 1), 553-9 (1979)
Snyder, L.E., Hollis, J.M., Ulich, B.L., Lovas, F.J., Johnson, D.R., and Buhl, “Radio Detection of Interstellar Sulfur Dioxide,” Astrophys. J., 198(2, Pt. 2), L81-L84 (1975)
Snyder, L.E., Lovas, F.J., and Johnson, D.R., “Silicon Monoxide - Detection of Maser Emission from the Second Vibrationally Excited State,” Astrophys. J., 192(2, Pt. 2), L97-L100 (1974
Keterampilan Hukum, Panduan untuk Mahasiswa, Akademisi dan Praktisi
No full textSkills book for Indonesian students and lawyers in Indonesian, based on the skills method of the Faculty of Law of Maastricht University. Each chapter has been written by a different author, but the overall structure is based on the structure of Vaardigheden voor juristen
Evolution of Microwave Spectroscopy at the National Bureau of Standards (NBS) and the National Institute of Standards and Technology (NIST)
No full textThis paper describes the beginning and evolution of microwave rotational spectroscopic research starting in 1954 at the National Bureau of Standards (NBS), located at that time in Washington, DC, through the present at NIST in Gaithersburg, MD. David Lide was hired in 1954 to start this research employing Stark modulated waveguide septum cells. When Donald R. Johnson joined the lab in 1968, he developed parallel plate cells coupled with rf and DC discharge methods to study free radicals and transient species. In the mid 1980s Lovas and Suenram constructed a pulsed molecular beam Fourier Transform microwave (FTMW) spectrometer to study hydrogen bonded and van der Waals dimers and trimers. This article describes the types of molecules studied and the type molecular properties derived from these measurements as well as some of the instruments developed for these studies. The two major areas of application described are atmospheric chemistry and molecular radio astronomy
RAD-3 SUBMILLIMETER-WAVE SEPECTRUM OF ACETALDEHYDE
No full text S.P. Below V.M. Demkin A.F. Krupnov and M. Yu. Tretyakov Xth International Conference on High Resolution Infrared Spectroscopy, Liblice, Czechoslvakia, 1988. I. Kleiner, M. Godefroid. M. Herman and A.R. W. McKellar, J. Mol. Spectrosc. 142, 238 (1990). I. Kleiner, J.T. Hougen, R.D. Suenram, F.J. Lovas and M. Godefroid, J. Mol. Spectrosc. 148, 38 (1991) Kleiner, J.T. Hougen, R.D. Suenram, F.J. Lovas and M. Godefrold, J. Mol. Spectrosc. 153, 000 (1992).Author Institution: Molecular Spectroscopy laboratory, Applied Physics Institute; Molecular Physics Division, National Institute of standards and Technology; Laboratoire de Physique Mol\'{e}culaire at Applications, Universit\'{e} Pierre et Marle curie et C.N. R.S.A broad-band room-temperature submillimeter wave spectrum containing approximately 5000 lines of in the region from 165 to 417 GHz has been recorded with the RAD-3 in Nizhni Novgorod (formerly Gorky). The sample pressure of approximately 0.1. Torr leads to typical linewidths of 8 MHz, which when combined with some uncertainties in the frequencies used for calibration. Leads to measurement uncertainties of less than 1 MHz for unblended lines. We shall describe the instrument in some detail. Pure rotational transitions with J values from 10 to 20, originating in the torsional ground () and first excited () states, can be relatively easily identified using computer programs and molecular parameters determined in earlier . Because of the broad-band spectral coverage of the RAD-3 spectrometer, these assigments can be confirmed in most cases by ``combination-difference loops” of 4 lines, whose frequencies sum to values less than Times the 1 MHz measurement precision. The goal of the present work is not a study of and 1 transition, however, but involves instead a search for lines originating in higher ( or 3) torsional states. We shall report on our attempts to find such lines in this RAD-3 spectrum
THE SUBMILLIMETER-WAVE SPECTRUM OF PROPIONITRILE
No full textF.J. Lovas, {J. Phys. Chem. Ref. Data.} \textbf{11}, 251 (1982).Author Institution: Department of Physics, The Ohio State University; Department of Physics, University of New Brunswick, FrederictonThe ground state rotational spectrum of propionitrile was observed in the 259 - 610 GHz frequency range. A total of 952 transitions including 732 newly measured ones through J = 70 and were fit to a Watson A-reduced Hamiltonian with a root-mean-square deviation of 61 kHz. The fit determined the rotational constants A, B and C along with a complete set of quartic and sextic distortion constants and six octic distortion constants. No splittings due to internal rotation or quadrupole were observed. The refinement of the constants should have improved predictive power over the previous , especially at high J values
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