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  • Chemistry  (8)
  • NUMERICAL ANALYSIS  (3)
  • 61.10  (1)
  • 1990-1994  (4)
  • 1985-1989  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Direct determination of X-Ray reflection phases for noncentrosymmetric crystals (1985)
    Springer
    Applied physics 37 (1985), S. 57-64 
    Details
    ISSN: 1432-0630
    Keywords: 61.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An experimental method is described for the phase determination of x-ray reflections from noncentrosymmetric crystals. This method results from considerations on the phase dependence of line profiles in three-beam reflection-type diffractions for wavelength λ above and below a critical absorption edgeλ E of the heaviest constituent atom in the crystals. A relationS p =S L ·S R for phase determination is derived theoretically and verified experimentally forλ〈λ E ,S p being the sign of the sine of invariant phase,S L the sign defined from the line profile, andS R determined by the rotation of the crystal lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617869
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Polymerization of isobutylene by the adamantane bromide-diethylaluminum chloride catalyst system (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 3127-3141 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isobutylene has been polymerized in a continuous stirred tank reactor using a catalyst system comprised of 1-bromoadamantane and diethylaluminum chloride. The polymerization was carried out in hexane solvent at -15 to -27°C and gave 100% conversion to polyisobutylene (PIB) of 1000-3000 Mw. The results of pyrolysis-gas chromatography-mass spectrometry analyses are consistent with a mechanism involving the formation of the adamantyl cabocation and its addition to an isobutylene molecule to initiate polymerization. 13C-NMR analyses show that the PIB products contain R2C—CR2 and R2C—CHR olefin types. Information on the nature of these olefins and the route to their formation has been developed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080251116
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Letters to the editor (1986)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 1405-1406 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690320830
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  • 4
    Electronic Resource
    Electronic Resource
    Copolyesters. I. Sequence distribution of poly(butylene terephthalate-co-adipate) copolyesters determined by 400 MHz NMR (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 1053-1057 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400537
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  • 5
    Electronic Resource
    Electronic Resource
    Competitive adsorption of water-soluble polymers on attapulgite clay (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1293-1299 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The individual, competitive, and displacement adsorption of polyvinyl alcohol (PVOH), hydroxyethyl cellulose (HEC), and hydroxypropylmethyl cellulose (HPMC) in aqueous solution onto an attapulgite clay has been systematically studied. For the individual adsorption experiments, the amount of polymer adsorbed at equilibrium decreased in the order PVOH, HEC, HPMC. In the competitive adsorption experiments, the adsorption level of each polymer is diminished by the presence of a competing polymeric species. Binary mixtures of a cellulosic polymer (HEC or HPMC) with PVOH result in a substantial reduction in the amount of cellulosic polymer adsorbed. In the displacement adsorption studies, the sequential addition of HEC or HPMC is not able to displace previously adsorbed PVOH molecules to any appreciable extent. However, the addition of PVOH to previously equilibrated HEC/clay or HPMC/clay suspensions results in a large amount of the adsorbed cellulosic polymer being displaced by PVOH, especially under conditions of high surface coverage. These results indicate that PVOH is preferentially adsorbed on the clay surface and the strength of attachment to the surface is greater for PVOH than for either cellulosic polymer.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430710
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  • 6
    Electronic Resource
    Electronic Resource
    Fragment-molecule adduct ion formation in positive methane chemical ionization mass spectrometry1 (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1988), S. 129-134 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fragment-molecule (F+M) adduct ions of a variety of heterocyclic systems have been observed in positive methane chemical ionization spectra at relatively low sample concentrations, i.e. in the microgram range. The relative abundance of these adduct ions increases with sample concentration. Possible mechanisms of formation of F+M are discussed. Formation of such ions should be recognized as an artifact, otherwise such F+M adduct ions in chemical and electron ionization may be mistaken for impurities present in a sample.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210230211
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  • 7
    Electronic Resource
    Electronic Resource
    Single and double hydrogen migration in the fragmentation of 3-methyl-2-butyl trifluoroacetate (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 25 (1990), S. 409-414 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three of the main oxygen-containing fragments resulting from 3-methyl-2-butyl trifluoroacetate (11) had been identified previously as the 1-triflnoroacetoxyethyl cation (m/z 141, 12, product of simple cleavage), and the products of single (m/z 142) and double hydrogen transfer (m/z 143, protonated ethyl trifluoroacetate). Collisionally activated dissociation of m/z 142 and the isotopomers resulting from 11-2-d, 11-1-d3, 11-5,6-d6, and 11-18O2 has established that m/z 142 is the oxygen protonated 1-trifluoroacetoxyethyl free radical (17) formed by hydrogen shift irom a γ-methyl group to oxygen in the molecular ion, rather than in a complex (18) between 12 and the 2-propyl free radical, as expected based on a mechanistic model existing in the literature. The second hydrogen transferred originates in the other γ-methyl group; its migration may occur, but does not have to, in the complex between 17 and a molecule of propene, prior to dissociation of the two fragments. Collision-activated dissociation has now shown that the m/z 140 ion observed in the spectrum is the molecular ion of vinyl trifluoroacetate, possibly formed by a hydrogen transfer from 12 to the 2-propyl radical in the complex 18. The hydrogen migration to oxygen exhibits no isotope effect, whereas the transfers to carbon atoms exhibit small primary and α secondary kinetic isotope effects. Exclusive migration of the tertiary hydrogen from C(3) occurs in the formation of 2-methylbutene cation radical (m/z 70) from the molecular ion. The hydrocarbon ion fragments and the heteroatom-containing fragments are formed from 11 by disjoint pathways.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210250804
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  • 8
    Electronic Resource
    Electronic Resource
    Fragmentation processes of methylbutyl trifluoroacetates studied by tandem quadrupole mass spectrometry and isotope labelingA report of preliminary work was presented at the 34th Annual Conference on Mass Spectrometry and Related Topics, Cincinnati, Ohio, 8-13 June 1986. (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 737-747 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fragmentation patterns of 3-methyl-2-butyl trifluoroacetate and 2-methyl-2-butyl trifluoroacetate were investigated by GC/MS/MS, with electron impact and collision-induced dissociation, on regular and isotope-labeled (deuterium and 18O) esters. The atoms found in various fragments could be traced back to specific positions in the parent molecules. In this way, molecular rearrangements potentially occurring during the formation of esters by trifluoroacetolysis of 3-methyl-2-butyl p-toluenesulfonate or trifluoroacetic acid addition to various 2-methylbutenes could be shown. Rearrangements also occurred during the fragmentation, particularly during the expulsion of the small fragments CO, C2H4 and F2CO. For the decompositions of oxygen-containing ions these rearrangements were highly specific. By contrast, alkyl cations lead to fragments that are fully scrambled (statistical label distribution). Alkene radical cations ([CnH2n]+ ·) fragment to daughter ions that are extensively, but less than statistically scrambled. Hydrogen scrambling may also occur in fluoroalkyl cation fragments.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210240906
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrolysis of 2-aminoethanethiolsulfate ions (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 26 (1994), S. 545-549 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the acid catalyzed hydrolysis of 2-aminoethanethiolsulfate (AETS) ions were investigated. The dependence of the hydrolysis rate constant on acidity and temperature was determined. The hydrolysis rate equation can be expressed as \documentclass{article}\pagestyle{empty}\begin{document}$$ d{{\left[{{\rm AETS}} \right]} \mathord{\left/ {\vphantom {{\left[{{\rm AETS}} \right]} {dt}}} \right. \kern-\nulldelimiterspace} {dt}} = - k{\rm H}_{\rm o} \left[{{\rm AETS}} \right] $$\end{document} where Ho is the Hammett acidity function. The rate constant, k, can be expressed as The pKa's for the compound were measured and literature value of pKa was found to be in error. The values determined in this study are pKa1 〈 -0.5 and pKa2 = 9.1 ± 0.1. General acid catalysis of the hydrolysis reaction was found not to proceed to a significant degree. © 1994 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550260507
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  • 10
    facet.materialart.
    Unknown
    Solution of elliptic partial differential equations by fast Poisson solvers using a local relaxation factor. 2: Two-step method (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A two-step semidirect procedure is developed to accelerate the one-step procedure described in NASA TP-2529. For a set of constant coefficient model problems, the acceleration factor increases from 1 to 2 as the one-step procedure convergence rate decreases from + infinity to 0. It is also shown numerically that the two-step procedure can substantially accelerate the convergence of the numerical solution of many partial differential equations (PDE's) with variable coefficients.
    Keywords: NUMERICAL ANALYSIS
    Type: NASA-TP-2530 , E-2528-1 , NAS 1.60:2530
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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