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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 199 (1963), S. 1273-1275 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In contrast to the test of July 9, 1962, the four OctoberNovember tests displayed generally weak and variable signatures at our station. The magnetotelluric records consisted of the usual continuum background plus a series of short oscillatory transients 0.51 sec long. The broadband VLF noise ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0887-624X
    Keywords: PEEK ; reactive oligomer ; crosslinking ; differential scanning calorimetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino-terminated polyetheretherketone (PEEK) oligomers were prepared by the condensation of 4,4′-difluorobenzophenone and hydroquinone in the presence of a calculated excess of m-aminophenol endblocker. The molecular weight of the oligomer was controlled by the manipulation of the ratio of difluoride to hydroquinone with the appropriate stoichiometric amount of m-aminophenol ensuring amino termination. The thermally induced self-crosslinking of these oligomers was studied by differential scanning calorimetry (DSC). Curing was found to be quite slow, taking up to 1 h to reach completion at 668 K. Cured materials were all completely amorphous in contrast to the semi-crystalline starting material. The limiting Tg reached on curing was found to be proportional to the percentage of reactive terminal groups, as would be expected.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyetheretherketone-polydimethylsiloxane (PEEK-PDMS) block copolymers were synthesized from the condensation of dimethylamino terminated PDMS and hydroxy terminated PEEK oligomers in 1-chloronapthalene. Yields for block copolymers synthesised from low molecular weight PDMS oligomers were good but yields were significantly reduced when higher molecular weight PDMS oligomers were used. This was related to the limited solubility of higher molecular weight PDMS in the reaction solvent. Differential scanning calorimetry (DSC) studies indicated that phase separation of the block copolymers occurred at very short segment length (M̄n 〈 4000). A depression in the crystallinity of both the PEEK and PDMS phases in the block copolymer was observed. Thermogravimetric analysis (TGA) studies indicated that the PEEK-PDMS block copolymers displayed insufficient thermo-oxidative stability to be melt-processed successfully in PEEK based blends.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 177 (1998), S. 229-241 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Understanding the magnitude and temporal structure of variations in solar ultraviolet and extreme ultraviolet irradiance is critical to understanding solar forcing of the Earth's upper and middle atmosphere and hence to assessing the relative impact of natural and anthropogenic influences on Earth's atmospheric environment. Satellite based measurements of such variations are limited to recent times, are short in duration and subject to gaps making necessary ground-based surrogates with longer and more continuous coverage. Using indices derived from synoptic solar magnetograms taken at the Mount Wilson 150-foot solar tower, we have constructed models of several UV and near EUV lines and fluxes which correlate strongly (r 〉 0.90) with satellite data. These lines and fluxes include the Mgii h and k core-to-wing ratio, the Lα line and the 200–205 nm flux.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 33 (1994), S. 321-327 
    ISSN: 0959-8103
    Keywords: polyethersulphone ; reactive oligomer ; thermosetting resin ; 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: Routes to thermosetting polyethersulphones (PES) by endcapping an hydroxy terminated oligomer with thermally reactive propargyl, vinylbenzyl and cyanate groups were investigated. Model compounds were prepared to establish suitable routes to the reactive oligomers. DSC was used to study curing behaviour of oligomers and model compounds.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High molecular weight alternating block copolymers of polyethesulphone (PES) and polydimethylsiloxane (PDMS) were prepared by the condensation of dimethylamino-terminated PDMS oligomers and hydroxy-terminated PES oligomers in 1,2-dichlorobenzene. Microphase separation of the block copolymers at exceptionally short block lengths was observed by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The Si—O—C intersegment linkage in these materials appeared to display poor hydrolytic stability which is contrary to results obtained for other block copolymers.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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