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  • INSTRUMENTATION AND PHOTOGRAPHY  (270)
  • Inorganic Chemistry  (218)
  • 2020-2023
  • 1975-1979  (430)
  • 1950-1954  (8)
  • 1940-1944  (7)
  • 1920-1924  (43)
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  • 1
    Publication Date: 2011-08-17
    Description: Described in detail is a laser induced fluorescence system which has been successfully interfaced with two aircraft sampling platforms (i.e., Sabreliner jet and an L-188C Electra). This system, which has been under development for four years, presently consists of the following major components: (1) a Nd-Yag laser driven oscillator-amplifier dye laser; (2) a sampling manifold with associated fluorescence detection optics; (3) an OH calibration chamber; (4) a laser beam steering assembly; and (5) sampling electronics and data processing hardware. During the last three years, this system has been flown some 50,000 air miles making tropospheric OH radical measurements over the latitude range of 70 N to 57 S. OH concentrations measured during these flights have ranged from 30 parts-per-quadrillion (3.7 x 10 to the 5th molecules/sq cm) at altitudes of 6 km to 0.8 parts-per-trillion (2.0 x 10 to the 7th molecules/sq cm) at 0.5 km. Computations have been completed which indicate that the existing aircraft system with modest modifications should also be capable of detecting natural tropospheric levels of NO, SO2, CH2O, NO2, HNO2, NO3, H2O2 and CS2 by using both conventional laser-induced fluorescence methodology and multiphoton techniques.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 50; Dec. 197
    Format: text
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  • 2
    Publication Date: 2019-06-27
    Description: Measurements obtained with laser velocimetry in a Mach 2.9 separated turbulent boundary layer and in the transonic flow past a two-dimensional airfoil section are presented and compared to data realized by conventional techniques. Agreement in mean velocities was realized where the pressure measurements could be considered reliable; however, in regions of instantaneous reverse velocities, the laser results were found to be consistent with the physics of the flow whereas the pressure data were not. Streamwise turbulence intensities are also presented. In the transonic airfoil study, velocity measurements obtained immediately outside the upper surface boundary layer of a 6-inch chord NACA 64A010 airfoil are compared to edge velocities inferred from surface pressure measurements. For free-stream Mach numbers of 0.6 and 0.8, the agreement in results was very good. "Dual scatter" optical arrangements in conjunction with a single particle, counter-type signal processor were employed in these investigations.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-X-73117 , A-6510
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-27
    Description: The response of a tungsten-scintillator ionization spectrometer to accelerated particle beams has been investigated. Results obtained from exposure of the approx. 1000 g/sq cm apparatus to 5, 10, and 15 GeV/c electrons and pions as well as to 2.1 GeV/nucleon C-12 and O-16 ions are presented. These results include cascade-development curves, fractions of the primary energy measured by the spectrometer, and resolutions of the apparatus for measuring the primary energies. For 15 GeV/c electrons, an average of about 82% of the incident energy is measured by the apparatus with resolution (normal standard deviation) of about 6%. For 15 GeV/c pions, an average of about 65% of the incident energy is measured with resolution of about 18%. The energy resolution improves with increasing energy and with increasing depth of the spectrometer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Nuclear Instruments and Methods; 126; 1975
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  • 4
    Publication Date: 2019-06-27
    Description: A simple technique for single-scan T1 measurements in solids is proposed and analyzed for single exponential spin-lattice relaxation. In this technique, the direct spin heating caused by the sampling process is significantly reduced in comparison with conventional techniques by utilizing the 'solid echo' to refocus the magnetization. The applicability of this technique to both the solid and liquid phases is demonstrated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 49; Aug. 197
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  • 5
    Publication Date: 2019-06-27
    Description: The problems of developing large-area, gas-scintillation proportional counters with high resolution are considered. It is found that simple large-area, parallel-grid proportional counters suffer from a variation in gain over the counter window. Some success has been achieved in overcoming this problem by focusing the charge cloud as it drifts into the multiplication region. Measurements are reported for various mixtures of argon and xenon as well as pure xenon.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 6
    Publication Date: 2019-07-13
    Description: Wind tunnel investigations of a shock-induced separated flow and the flow about a two-dimensional airfoil section at transonic speeds using laser velocimetry techniques are described. Laser velocimeter data are presented and compared with conventional pressure type measurements (pitot and static pressure probe measurements for the shock-induced separation, and surface pressure measurements for the two-dimensional airfoil section). In addition to these data comparisons, a simple optical arrangement for the incorporation of a Bragg cell in a laser velocimeter system is described. The effects of particle concentration gradients within a turbulent boundary layer on laser velocimeter measurements are also demonstrated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Minnesota Symposium on Laser Anemometry; Oct 22, 1975 - Oct 24, 1975; Bloomington, MN
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  • 7
    Publication Date: 2019-07-13
    Description: The laser-induced fluorescence technique for obtaining direct measurements of atmospheric OH and other gases is described. A narrow-band UV laser is tuned to one or more of the electronic absorption bands of a specified molecule so as to cause fluorescence from a bonding excited electronic state. The monitored wavelength is longer than the laser wavelength. Equipment, specifics for OH detection, data processing, and interference are discussed, and application of the technique to the detection of NO, SO2, and CH2O is considered.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Symposium on Meteorological Observations and Instrumentation; Apr 10, 1978 - Apr 14, 1978; Denver, CO
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  • 8
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal Structure of Thallium(I) Hexaiodomercurate(II), Tl4HgI6In the structure of the tetragonal Tl4HgI6 (a = 944.6 pm, c = 926.0 pm, Z = 2, space group P 4/mnc) isolated, in c-direction compressed HgI6 octahedra are situated. The mercury atoms are disordered; they occupy statistically 4 positions in the equatorial plane of the octahedra in such a manner that strongly deformed HgI4 tetrahedra are produced. The thallium atoms are eightfold coordinated like a bicapped trigonal prism. The relationship between the Tl4HgI6 structure and the cubical K2PtCl6 type will be discussed.
    Notes: In der Struktur des tetragonalen Tl4HgI6 (a = 944,6 pm, c = 926,0 pm, Z = 2, Raumgruppe P 4/mnc) liegen isolierte, in Richtung der c-Achse gestauchte HgI6-Oktaeder vor. Die Quecksilberatome sind fehlgeordnet; sie besetzen statistisch 4 Positionen in der Äquatorebene der Oktaeder derart, daß stark verzerrte HgI4-Tetraeder entstehen. Die Thallium-Atome sind achtfach in Form eines bicapped trigonalen Prismas koordiniert. Die Beziehungen der Tl4HgI6-Struktur zum kubischen K2PtCl6-Typ werden diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organocobalt-Clusterverbindungen. 26. Die Darstellung von Mercaptosubstituenten enthaltenden Methylidyntricobaltnonacarbonyl-KomplexenDie Umsetzung von Bromo- und Chloromethylidyntricobaltnonacarbonyl, XCCo3(CO)9 (X = Br, Cl) mit Zinndimethylbis(alkylmercaptiden), (CH3)2Sn(SR)2 in Toluol unter Rückfluß in 20-30 min stellt eine gute Methode zur Herstellung von schwefelsubstituierten Methylidyntricobaltnonacarbonylkomplexen des Typs RSCCo3(CO)9 (R = Alkyl, Aryl, Acetyl, Benzoyl) dar. Ebenfalls effektiv, aber weniger praktisch waren Trimethylzinnalkylmercaptide und Quecksilber-bis(ethylmercaptid).
    Notes: The reaction of bromo- and chloromethylidynetricobalt nonacarbonyl, XCCo3(CO)9 (X = Br, Cl) with dimethyltin bis (alkyl mercaptides), (CH3)2Sn(SR)2, in toluene solution at reflux for 20-30 min provides a useful procedure for the preparation of sulfur-substituted methylidynetricobalt nonacarbonyl complexes of type RSCCo3(CO)9 (R = alkyl, aryl, acetyl, benzoyl). Also effective, but less practical, in such applications were trimethyltin alkylmercaptides and mercury bis (ethyl mercaptide).
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 29Si-NMR Spectroscopy of Silicate Solutions. II. On the Dependence of the Structure of Silicate Anions in Water Solutions from the Na : Si RatioThe 29Si-FT-NMR spectra of 13 sodiumsilicate solutions with different Na:Si ratios are investigated with regard to the structure of the silicate anions in the solutions. The 5 typical building units (Monosilicate, end-, middle-, branching and crosslinking groups) show characteristic and non overlapping ranges of the 29Si chemical shift with many signals splittings caused by different neighbouring group effects. The relative intensities of the signals give informations on the concentrations and the equilibrium of condensation of the silicate anions in dependence of the Na:Si ratio. It is shown, that many types of anions with different degree of condensation coexist in an equilibrium, which is shiftet to the polymer silicate anions with high content of branching and crosslinking groups on the decrease of the Na:Si ratio.
    Notes: Die 29Si-FT-NMR-Spektren von 13 Natriumsilicatlösungen mit unterschiedlichem Na:Si-Verhältnis werden in Hinblick auf die Struktur der in den Lösungen auftretenden Silicatanionen untersucht. Für die 5 möglichen Baugruppen (Monosilicat, Endgruppen. Mittelgruppen, Verzweigungs- und Vernetzungsgruppen) lassen sich definierte Bereiche der 29Si-chemischen Verschiebung angeben, in denen durch Einfluß der weiteren strukturellen Umgebung i. a. zahlreiche Signalaufspaltungen beobachtet werden. Aus den relativen Intensitäten der Signale können Aussagen über die Konzentrationsverteilung und damit über das Kondensationsgleichgewicht der Silicatanionen in Abhängigkeit vom Na:Si-Verhältnis abgeleitet werden. Es zeigt sich, daß zahlreiche Anionentypen mit unterschiedlichem Kondensationsgrad nebeneinander in einem Gleichgewicht vorliegen, das sich mit fallendem Na:Si-Verhältnis stark auf die Seite höhermolekularer Silicatanionen mit hohem Gehalt an Verzweigungs- und Vernetzungsgruppen verschiebt.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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