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  • 1995-1999  (7)
  • Chemistry  (6)
  • Analytical Chemistry and Spectroscopy  (1)
  • environmental indices  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Environmental monitoring and assessment 58 (1999), S. 283-303 
    ISSN: 1573-2959
    Schlagwort(e): environmental indices ; indicator selection ; indirect inference ; landscape indicators ; measurement theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Indicators are used to draw conclusions about ecological endpoints when these endpoints cannot be measured directly. In many cases, inferences about an endpoint are only possible because assumptions have been made about the relationship between indicator and endpoint; we refer to such indicators as judgement indicators. The validity of inferences made using a judgement indicator can be gauged by examining the known or assumed form of the general relationship between indicator and endpoint. The rules for this kind of inference are a consequence of scale invariance, which originates from measurement theory. For simple indicators comprised of a single indicator measurement, the inferences allowed – equivalence, rank, equality of intervals, and equality of ratios – depend on whether the data are nominal, ordinal, interval, or ratio scaled. For composite indicators containing two or more simple indicators, inferences are also affected by the mathematical form of combination; e.g., whether the terms are summed or multiplied. Standardizing simple or composite indicators can allow inferences about the relative importance of observations, based on the natural range of occurrence. Scale invariance is a particularly important consideration in landscape assessments, since these often make use of judgement indicators.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 823-830 
    ISSN: 0887-624X
    Schlagwort(e): atom transfer radical polymerization ; poly(N-vinylpyrrolidinone-g-styrene) ; macromonomer method ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Atom transfer radical polymerization has been used to prepare well-defined vinyl macromonomers of polystyrene using vinyl chloroacetate as an initiator. Because styrene and vinyl chloroacetate do not copolymerize, no branching or incorporation of the initiator into the backbone was observed. Macromonomers of several molecular weights were prepared and copolymerized free radically with N-vinylpyrrolidinone in varying feed ratios in order to produce poly(NVP-g-Sty) graft copolymers. The macromonomers used were of sufficiently high molecular weight to form physical crosslinks in solvents which favor the hydrophilic NVP, such as water, which prevent the copolymer from dissolving and cause it to swell. These materials, therefore, formed hydrogels of swellabilities in water exceeding 95%, depending on the amount of styrene that was incorporated into the copolymer. Limitations of and alternatives to this method are also discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 823-830, 1998
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 1057-1066 
    ISSN: 1022-1336
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Mono and difunctional polystyrenes containing active halogenated end groups were prepared by atom transfer radical polymerization (ATRP). Substitution reactions were explored to convert the halogen termini to azido groups, followed by readuction to form the amino functional polymer. Quantitative conversion of the end groups was observed in each transformation reaction. 1H NMR demonstrated the formation of the azide from the bromide functionality without elimination. The difunctional α,ω-diaminopolystyrene was reacted with terephthaloyl chloride in a condensation process to produce chain-extended polystyrene containing amide bonds along the polymer backbone.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 19 (1998), S. 665-670 
    ISSN: 1022-1336
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The addition of zero-valent copper to the self-condensing vinyl polymerization (SCVP) of novel AB* (meth)acrylic monomers using atom transfer radical polymerization (ATRP) catalyst systems has allowed for their successful polymerization. Polymerization under homogeneous and heterogeneous catalyst conditions without additional Cu(0) were unsuccessful. The catalyst system that was designed comprised of Cu(I) bromide, 4,4′-bis(5-nonyl)-2,2′-bipyridine, and Cu(0) metal (powder or turning). From 1H NMR spectroscopy, the degree of branching was estimated for the acrylic polymers, DB = 0.48. The degree of branching could not be determined for methacrylates by this method due to overlapping signals in the 1H NMR spectra.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 19 (1998), S. 47-52 
    ISSN: 1022-1336
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates were prepared by atom transfer radical polymerization. Poly(vinyl chloride) containing small amount of pendent chloroacetate units was used as a macroinitiator. The formation of the graft copolymer was confirmed with size exclusion chromatography (SEC), 1H NMR and IR spectroscopy. The graft copolymers with increasing incorporation of butyl acrylate result in an increase of molecular weight. One glass transition temperature (Tg) was observed for all copolymers. Tg of the copolymer with butyl acrylate decreases with increasing content of butyl acrylate.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The atom transfer radical polymerization (ATRP) of styrene has been studied using complexes of copper carboxylates. Compared with systems employing copper halides as the catalyst, the use of the copper carboxylates resulted in faster polymerization rates and higher polydispersities. A ligand (dNbpy) to Cu(I) carboxylate ratio of 1 was sufficient to achieve the maximum rate of polymerization. The addition of a small amount of either Cu(II) or Cu(I) halide to the copper carboxylate system yielded polymers with better controlled molecular weights and lower polydispersities yet the polymerization still remained relatively fast.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1227-1233 
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A combined magnetic sector-time-of-flight instrument has been constructed and used with both continuous (liquid secondary ion mass spectrometry and electrospray ionization) and pulsed (matrix-assisted laser desorption/ionization) ion sources. The design includes provision for both low- and high-energy gas collision induced decompositions and orthogonal acceleration of the product ions into the time-of-flight mass analyser. Tandem mass spectra may be acquired for singly and multiply charged precursor ions and reliable mass measurements are easily obtained. Product-ion mass spectra are quite reproducible regardless of any instability in the precursor ion beam intensity.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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