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  • PROPULSION SYSTEMS  (52)
  • Analytical Chemistry and Spectroscopy  (46)
  • ASTROPHYSICS
  • 1970-1974  (98)
  • 1955-1959
  • 1972  (98)
Collection
Keywords
Publisher
Years
  • 1970-1974  (98)
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    13C, 14N, 15N and 17O NMR spectra of nitropyrroles and nitroimidazoles (1972)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 4 (1972), S. 153-160 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon, nitrogen and oxygen NMR spectra of some nitro derivatives of pyrrole and imidazole have been investigated. The 13C chemical shifts of para-carbons and the 17O chemical shifts of the nitro group correlate qualitatively with the electron densities on these carbon and oxygen atoms, which in turn depend upon the degree of conjugation of the nitro groups with the heterocyclic ring. Conjugation of several nitro groups with the benzene ring is in most cases not impaired by mutual interactions and the 13C shifts show good additivity. Such additivity is much worse in pyrrole and imidazole derivatives. Taken together with the diamagnetic nature of these deviations from additivity, this leads to a possible conclusion about the less pronounced conjugation of the nitro groups with the heterocyclic ring in heterocyclic dinitro derivatives.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270040118
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  • 2
    Electronic Resource
    Electronic Resource
    13C, 14N, 15N and 17O NMR spectra of the charged species of nitropyrroles and nitroimidazoles (1972)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 4 (1972), S. 197-202 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Changes in 13C and 14N chemical shifts of the nitro derivatives of nitrogen heterocycles upon ionization (anion or cation formation) are twofold - first a uniform paramagnetic or in the case of protonation, a uniform diamagnetic shift of all the ring resonances that parallels the changes in the respective ultraviolet spectra and must be caused by changes in the molecular excited states, and second - the influence of the conjugated nitro group. About one third of the total negative anion charge may be localized on the nitro group, which causes unusually large shifts of the ring 13C resonances in this case.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270040202
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  • 3
    Electronic Resource
    Electronic Resource
    An NMR study of phenol self-association (1972)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 4 (1972), S. 453-462 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents a study of the chemical shift of the phenol hydroxyl group as a function of concentration and temperature in cyclohexane, methylcyclohexane and carbon tetrachloride solutions. The chemical shift of monomeric phenol has been found. For these solutions monomertrimer equilibrium is observed within the entire temperature range and within a wide concentration range. At low phenol concentrations, from 1 to 3 mole-%, the monomer-dimer equilibrium is observed in cyclohexane, methylcyclohexane and carbon tetrachloride solutions. Chemical shift of the hydroxyl group of trimeric phenol is temperature-dependent.From the experimental data the association constants and thermodynamic functions of the systems under study have been determined. The association constants differ for the above systems at the same temperatures. Association entropy ΔS changes from one system to another, while ΔH is the same for all systems.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270040404
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  • 4
    Electronic Resource
    Electronic Resource
    Mass spectra of methylsubstituted monosila- and monogermacyclobutanes, 1,2- disila- and 1,2-digermacyclopentanes. Some correlations with thermal decomposition (1972)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1972), S. 309-316 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of 1,1-dimethyl-1-silacyclobutane (I - as reported by Cherniak et al.),6, 1,1-dimethyl-1-germacyclobutane (II), 1,1,2,2-tetramethyl-1,2-disilacyclopentane (III) and 1,1,2,2-tetramethyl-1,2-digermacyclopentane (IV) are compared and some correlations between electron-impact fragmentation and thermal decomposition are derived. The mass spectra of the germanium compounds with respect to the silicone compounds are enriched by light fragment ions and exhibit lower intensities of odd-electron ions. The composition of some ions and apparently of neutral fragments coincides with that of the unstable intermediates which are suggested in the thermal decomposition mechanism of some related compounds. The loss of C2H4 is more characteristic under electron-impact as well as in thermal decomposition of Si-compounds, while C3H6 is preferable eliminated by the Ge-compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210060309
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  • 5
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    Upper-stage space shuttle propulsion by means of separate scramjet and rocket engines (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A preliminary mission study of a reusable vehicle from staging to orbit indicates payload advantages for a dual-propulsion system consisting of separate scramjet and rocket engines. In the analysis the scramjet operated continuously and the initiation of rocket operation was varied. For a stage weight of 500,000 lb the payload was 10.4 percent of stage weight or 70 percent greater than that of a comparable all-rocket-powered stage. When compared with a reusable two-state rocket vehicle having 50,000 lb payload, the use of the dual propulsion system for the second stage resulted in significant decreases in lift-off weight and empty weight, indicating possible lower hardware costs.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TN-D-6762 , E-6555
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Evaluation of acoustic cavities for combustion stabilization. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The stabilizing influence of acoustic cavities (quarterwave acoustic resonators) on acoustic modes of combustion instability has been studied. The ability to analytically predict cavity damping was improved. Relatively good agreement between predicted damping and measured stability was demonstrated. Full-scale motor firings were made to evaluate the influence of several parameters on stability. Results from these firings showed that stability was changed, but not dramatically, by changes in the engine operating conditions. Variations in the film-coolant flowrate do not significantly affect cavity stabilization. The ability to stabilize an engine with unconventional cavity configurations was demonstrated.
    Keywords: PROPULSION SYSTEMS
    Type: AIAA PAPER 72-1147 , Joint Propulsion Specialist Conference; Nov 29, 1972 - Dec 01, 1972; New Orleans, LA; US
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
    Electronic Resource
    Electronic Resource
    Mass spectrometry in the investigation of β-lysine-containing peptides (1972)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1972), S. 1-8 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectrometry can be used for amino acid sequence determination in β-lysine-containing peptides and for the identification of α- and β-lysine residues in peptides, as well as for amide bond type determination in β-lysine peptides. The peptide bond in streptothricin D is shown to be formed through the participation of an ε-amino group of the L-β-lysine residue.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210060102
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  • 8
    Electronic Resource
    Electronic Resource
    Ionization and dissociation of some perfluoroalkylene-linked silanes and cyclic siloxanes under electron-impact (1972)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1972), S. 425-427 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of two silanes and two cyclic siloxanes of the general formulae HSi(CH3)2-C6H4—(CF2)n—C6H4(CH3)2SiH and (n = 2 and 3) are reported and discussed. Although some major differences are apparent between the spectra of the two silanes, the fragmentation patterns of the cyclic siloxanes are largely identical.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210060408
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  • 9
    Electronic Resource
    Electronic Resource
    The mass spectra of carboxylic acids - V: Carboxyl-carboxyl interaction in the fragmentation of some cycloalkene-1,2-dicarboxylic acids (1972)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1972), S. 549-557 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fragmentation mechanisms of the six isomeric cyclohexene-1,2-dicarboxylic acids are discussed. Only the 1-cyclohexene acid, by virtue of the major sequential losses of H2O and CO2 from the molecular ion, is readily distinguishable from its isomers, all of whose mass spectra are closely similar. In contrast to cis and trans cyclohexane-1,2-dicarboxylic acids, whose mass spectra were markedly different, the cis and trans cyclohexene-1,2-dicarboxylic acids fragment in a similar fashion. The mass spectra of 1-cyclopentene-1,2-dicarboxylic acid and 1-cyclobutene-1,2-dicarboxylic acid also exhibit a strong carboxyl-carboxyl interaction; the fragmentation behaviour of the 1-cyclopenteneacid is, however, more complex than that of the 1-cyclohexene and 1-cyclobutene acids.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210060511
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  • 10
    Electronic Resource
    Electronic Resource
    Dimethyl ketals of methylcyclohexanones as fragmentation-directing derivatives (1972)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1972), S. 949-952 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of dimethyl ketal derivatives of cyclohexanone and the 2-, 3- and 4-methylcyclohexanones are discussed relative to their usefulness in indicating the point of alkyl substitution. Major fragments in the spectra (m/e 101 and m/e 115) arise by α-cleavage, hydrogen rearrangement and further cleavage to give even-electron species. The spectra yield structural information equivalent to that obtained from the corresponding ethylene ketals. The ease of preparation of dimethyl ketals and the mildness of reaction conditions relative to ethylene ketals warrant further exploitation of dimethyl ketals as fragmentation-directing derivatives in mass spectrometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210060903
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