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  • Analytical Chemistry and Spectroscopy  (15)
  • Field theory, general methods
  • conductivity parameter
  • 1990-1994  (5)
  • 1980-1984  (11)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Relative performances of central and dipole frequency soundings over a layered earth (1982)
    Springer
    Pure and applied geophysics 120 (1982), S. 527-537 
    Details
    ISSN: 1420-9136
    Keywords: Loop sources ; electromagnetic response ; conductivity parameter ; resolution of curves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Variable frequency soundings in the audio-range replaces shallow conventional direct current methods for determination of layer parameters when surface layer resistivity is high. Central frequency soundings (CFS) is one such method that involves measurement of the existing vertical magnetic field component induced at the centre of a horizontal circular or square loop. Dipole method of frequency sounding using small horizontal coplanar loops (abbreviated DFS) measuring the same field component is also considered. Theoretical studies on CFS and DFS over two- and three-layer horizontally stratified earth are carried out and the response characteristics computed and analysed. Theoretical response curves for CFS and DFS over two- and three-layer earth models are presented in convenient forms. Response curves under similar geological-physical conditions are compared. The study indicates that the relative superiority of a method is controlled largely by the nature of the conductivity contrast and the ratio of the first layer thickness to loop radius or dipole separation. While CFS shows a better resolution of conductivity contrast, DFS works better at high frequencies. For resistive substratum, however, both lack proper resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879834
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  • 2
    Electronic Resource
    Electronic Resource
    Elemental analysis of gel-grown rare earth molybdate crystals using energy-dispersive X-ray fluorescence spectrometry (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 23 (1994), S. 247-250 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Rare earth molybdate crystals such as those based on lanthanum, neodymium and some mixed molybdates, grown by the gel method, were analysed for major and trace impurity elemental concentrations using energy-dispersive X-ray fluorescence spectrometry in order to understand the characteristics of the material in terms of structural perfection and composition. The method used permits the simultaneous determination of rare earth elements such as La and Nd and also Mo and impurities such as Fe and Zn. Based on the observed concentrations of major elements, it is shown that the formulae so far assumed for some of these composites may be incorrect and may need a major refinement. Monoenergetic X-rays of 22.1 and 59.6 keV were employed for fluorescence excitation and optimum detection efficiency was obtained for a large number of elements. Pulverized samples mixed with cellulose powder and specimens prepared in the form of pellets were used. The fundamental parameter method was used for the quantitative estimation of elemental concentration.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300230603
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  • 3
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectra of kauranoid diterpenesSymposium on Recent Developments in Organic Chemistry, Calcutta (1979). Abstracts, p. 38. (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 58-60 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR spectra of a number of (-)-ent-kauranoids have been studied. An unambiguous selfconsistent assignment of resonances has been made by considering the changes in chemical shifts produced by the change of substituent(s).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140114
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  • 4
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectral studies on some labdane diterpenoids (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 16 (1981), S. 75-77 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR signal assignments of the labdane diterpenoids andrographolide and 14-deoxyandrographolide, along with their acetates, and isodeoxyandrographolide have been made. This study indicates that the C-6 and C-11 resonance assignments of isovirescenol-B, made earlier, should be interchanged.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270160122
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  • 5
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR signals of some natural coumarins and their derivatives (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 17 (1981), S. 222-224 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of the natural coumarins ostruthin, osthol, aegelinol (enantiomer of decursinol), luvangetin, seselin, anomalin, oxypeucedanin (and its enantiomer prangolarin) and oxypeucedanin hydrate and some of their derivatives have been studied. Self-consistent resonance assignments have been made following chemical shift theory and using simple models. Carbon-hydrogen coupling constants of some compounds are also reported. The alkoxy group/s at C-5 and/or C-8 in linear furocoumarins, as well as in linear pyranocoumarins, have unusually small shielding effects on the ortho- and para-carbons. This study also indicates that the C-4a and C-8 resonance assignments of osthol, made earlier, should be reversed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270170319
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  • 6
    Electronic Resource
    Electronic Resource
    Carbon-13 spectral studies of some chalcones and flavanones (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 18 (1982), S. 241-242 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 signal assignments of 2′,4′-dihydroxychalcone, flemichapparin, pashanone, isodidymocarpin, pedicellin, pedicinin, methylpedicinin, didymocarpin-A and the corresponding quinoflavanone dehydrodidymocarpin-A are reported.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270180415
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  • 7
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectroscopy of some pentacyclic triterpenoids (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 15 (1981), S. 399-400 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR signal assignment of a number of polyoxygenated triterpenes of the olean-12-ene and urs-12-ene series, carried out by considering the changes in chemical shift produced by the change of oxygenation pattern(s), and using methyl oleanolate as a model, are reported.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270150415
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  • 8
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectra of tembamide, aegeline and related amides (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 16 (1981), S. 65-67 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR spectral studies of tembamide (1) and aegeline (2), constituents of Fagara hyemalis and Aegle marmelos respectively, and a series of their structurally related amides (3-13) have been carried out. The assignment of the resonances of two related dimers are also reported. The assignment of the various resonances were made by considering the changes in chemical shifts produced by the change of substituents and also by using 1, 13 and a related compound as model compounds.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270160118
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  • 9
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectra of some novel migrated hopanes and 21α-H hopanes (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 17 (1981), S. 148-150 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The carbon-13 NMR spectra of the novel rearranged hopanes, spergulagenin-A and related triterpenoids, and 21α-Hopanes, mollugogenol-A, mollugogenol-G diacetate and related compounds, were recorded. Their analyses were aided by the chemical shifts of some model compounds and by the change in chemical shifts produced on change of substituents/s.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270170215
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  • 10
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectra of some labdane diterpenoids (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 17 (1981), S. 301-302 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 signal assignments of the labdane diterpenoids phlogantholide-A, its diacetate and isophlogantholide-A are reported. The assignments of the 13C NMR signals of 14-deoxyandrographolide and its diacetate, made earlier, have now been confirmed by lanthanide shift studies on the former and also by 13C spectral studies on anhydroandrographolide diacetate and 14-deoxy-11,12-didehydroandrographolide diacetate.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270170416
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