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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 509-519 
    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: A postirradiation process was evaluated in polymerizing vinyl monomers on poly(ethylene terephthalate) (PET) film, fiber, and fabric. The use of DMF, pyridine, and DMSO as swelling agents to facilitate monomer incorporation and effective polymerization were also investigated. The solvents were effective in promoting the incorporation of acrylic acid (AA) in PET film and that of n-vinyl-2-pyrrolidinone (VP) in Dacron 54. AA, a good swelling agent for PET, produced equivalent polymerization yield and moisture regain results with or without any solvent on Dacron 54 and 64. Polymerization yields on films increased with increasing total doses, but those on yarns and fabrics were independent of total dose. The different results obtained on film versus yarn and fabric from solvent treatment and total dose is thought to be due to the different surface-volume ratio of these substrates. The moisture properties of the substrates were dependent mainly upon the monomer type. Among the monomers studied, VP gave highest moisture regain values, followed by AA. The tensile properties of the modified Dacron 54 were not affected. However the breaking elongation of the modified Dacron 64 was slightly lowered by postirradiation polymerization without solvent treatment and was increased when solvent treatment was included.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-06-28
    Description: Sea-level rise (SLR) is one of the most conspicuous examples of the environmental impact of recent climate change. Since SLR rates are not uniform around the planet, local and regional data are needed for proper adaptation plans. 210 Pb-dated sediment cores were analyzed to determine the trends of sediment accretion rates (SARs) at three tropical saltmarshes in the Estero de Urias lagoon (Gulf of California, Mexico), in order to estimate the SLR trends during the past ~100 years, under the assumption that these ecosystems accrete at a similar rate to SLR. A chemometric approach, including multivariate statistical analysis (factor analysis) of geochemical data (including 13 C; 15 N; C/N ratios; and Br, Na, and Cl as proxies for marine transgression) was used to identify the marine transgression in the sediment records. Based on core geochemistry, only one of the three cores provided a long-term record attributable to marine transgression. SLR trends, estimated from SARs, showed increasing values, from a minimum of 0.73 ± 0.03 mm yr –1 at the beginning of the 20th century and up to 3.87 ± 0.12 mm yr –1 during the period 1990–2012. The estimated SLR trend between 1950 and 1970 was comparable to the tide gauge records in Mazatlan City for the same period. Results showed the caveats and strengths of this methodology to reconstruct decadal SLR trends from the sedimentary record, which can be used to estimate long-term SLR trends worldwide in regions where monitoring data are scarce or absent.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 3
    Publication Date: 2012-04-01
    Description: The Virulundo carbonatite in Angola is one of the largest in the world and contains pyrochlore as an accessory mineral in all of the carbonatite units (calciocarbonatites, ferrocarbonatites, carbonatite breccias and trachytoids). The primary magmatic pyrochlore is fluorine dominant and typically contains about equal molar quantities of Ca and Na at the A site. High-temperature hydrothermal processes have resulted in the pseudomorphic replacement of the primary pyrochlore by a second generation of pyrochlore with less F and Na. Low-temperature hydrothermal replacement of the first and second generation pyrochlore, associated with quartz-carbonate-fluorite vein formation in the carbonatite, has produced a third generation of pyrochlore, with a high Sr content. The Sr appears to have been released by low-temperature hydrothermal replacement of the primary magmatic carbonates. Finally, supergene alteration processes have produced late-stage carbonates, goethite, hollandite and rare earth element (REE) minerals (mainly synchysite-(Ce), britholite-(Ce), britholite-(La), cerite-(Ce)). Cerium separated from the other REEs in oxidizing conditions and Ce4+ was incorporated into a late generation of supergene pyrochlore, which is strongly enriched in Ba and strongly depleted in Ca and Na.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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  • 4
    Publication Date: 2012-04-01
    Description: The Virulundo carbonatite in Angola is one of the largest in the world and contains pyrochlore as an accessory mineral in all of the carbonatite units (calciocarbonatites, ferrocarbonatites, carbonatite breccias and trachytoids). The primary magmatic pyrochlore is fluorine dominant and typically contains about equal molar quantities of Ca and Na at the A site. High-temperature hydrothermal processes have resulted in the pseudomorphic replacement of the primary pyrochlore by a second generation of pyrochlore with less F and Na. Low-temperature hydrothermal replacement of the first and second generation pyrochlore, associated with quartz-carbonate-fluorite vein formation in the carbonatite, has produced a third generation of pyrochlore, with a high Sr content. The Sr appears to have been released by low-temperature hydrothermal replacement of the primary magmatic carbonates. Finally, supergene alteration processes have produced late-stage carbonates, goethite, hollandite and rare earth element (REE) minerals (mainly synchysite-(Ce), britholite-(Ce), britholite-(La), cerite-(Ce)). Cerium separated from the other REE s in oxidizing conditions and Ce4+ was incorporated into a late generation of supergene pyrochlore, which is strongly enriched in Ba and strongly depleted in Ca and Na.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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