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  • 1
    Publication Date: 1996-09-01
    Print ISSN: 0016-7835
    Electronic ISSN: 1432-1149
    Topics: Geosciences
    Published by Springer
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  • 2
    Publication Date: 1996-09-16
    Print ISSN: 0016-7835
    Electronic ISSN: 1432-1149
    Topics: Geosciences
    Published by Springer
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  • 3
    Publication Date: 2016-11-14
    Description: The reconstruction of geomagnetic field intensity variations during the last 200 kyr from paleomagnetic data is at present the subject of numerous studies and major debate. There is currently no generally accepted record. Here we present a global stacked record of (230Thex-normalized)10Be deposition in marine sediments representing relative variations in 10Be production rate which are translated into field intensity variations. The record shows major periods during which the field intensity was between 10% and 40% of the present day value; namely 30–42, 60–75, 85–110 and 180–192 kyr B.P. Our results are compared to independently derived paleomagnetic studies and Th/U calibrations of 14C dates on corals. During most of the observed period the geomagnetic field intensity was weaker than today, resulting in an overall 30% reduced value for the last 200 kyr.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    ISSN: 1437-3262
    Keywords: Ontong Java Plateau ; Thorium-230 ; Barium ; Productivity ; Lysocline ; Sediment focusing ; Vertical mass accumulation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract We discuss geochemical proxies, reflecting processes of primary productivity, CaCO3 dissolution, and sediment redistribution in a piston core (RNDB 74P) from the Ontong Java Plateau. Due to the shallow water depth, biogenic carbonate is well preserved and a very goodδ 18O stratigraphy is available down to isotopic stage 11.230Thex gives evidence that the sediment accumulation pattern is driven mainly by processes of sediment focusing or winnowing. Due to the constant production of230Th in the water column, the bulk sediment accumulation rates could be corrected for the particle rain deriving from the water column above. The230Thex 0/CaCO3 ratio reflects the well-known Pacific CaCO3 preservation pattern with ice growth dissolution spikes and deglacial preservation spikes. The record of the grain size fraction 〉63 µm supports these results. The downcore concentrations and accumulation rates of barium (Ba) are on a higher level during interglacials and show several peaks. Normalization of Ba with230Thex 0 delivers a more uniform level of the Ba accumulation rates throughout the core. This pattern suggests a constantly higher biological productivity (nearly tenfold) in this area throughout the past 200 kyr compared with an open ocean environment. Barium peaks observed at the climatic transitions 2/1 and 6/5 and in stage 5 are in contrast to a predicted reduction of interglacial productivity at this location. A possible explanation might be the onset of the modern circulation pattern. The transition from Ba-enriched deep water to lower contents in the Atlantic might have resulted in an enhanced deposition of Ba in the Pacific.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0016-7835
    Keywords: Key words Ontong Java Plateau ; Thorium-230 ; Barium ; Productivity ; Lysocline ; Sediment focusing ; Vertical mass accumulation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We discuss geochemical proxies, reflecting processes of primary productivity, CaCO3 dissolution, and sediment redistribution in a piston core (RNDB 74P) from the Ontong Java Plateau. Due to the shallow water depth, biogenic carbonate is well preserved and a very good δ18O stratigraphy is available down to isotopic stage 11. 230Thex gives evidence that the sediment accumulation pattern is driven mainly by processes of sediment focusing or winnowing. Due to the constant production of 230Th in the water column, the bulk sediment accumulation rates could be corrected for the particle rain deriving from the water column above. The 230Thex 0/CaCO3 ratio reflects the well-known Pacific CaCO3 preservation pattern with ice growth dissolution spikes and deglacial preservation spikes. The record of the grain size fraction 〉63 μm supports these results. The downcore concentrations and accumulation rates of barium (Ba) are on a higher level during interglacials and show several peaks. Normalization of Ba with 230Thex 0 delivers a more uniform level of the Ba accumulation rates throughout the core. This pattern suggests a constantly higher biological productivity (nearly tenfold) in this area throughout the past 200 kyr compared with an open ocean environment. Barium peaks observed at the climatic transitions 2/1 and 6/5 and in stage 5 are in contrast to a predicted reduction of interglacial productivity at this location. A possible explanation might be the onset of the modern circulation pattern. The transition from Ba-enriched deep water to lower contents in the Atlantic might have resulted in an enhanced deposition of Ba in the Pacific.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2183-2192 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydrolytic degradation of technical poly(ethylene terephthalate) (PET) was investigated by means of different methods such as size-exclusion chromatography (SEC), viscometry, light-scattering, thin-layer chromatography, end-group titration, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The long-term degradation was simulated by exposing PET filament yarns to aqueous neutral conditions at 90°C for up to 18 weeks. By means of MALDI-MS and thin-layer chromatography, the formation of different oligomers was obtained during polymer degradation. As expected, an ester scission process was found generating acid terminated oligomers (H-[GT]m-OH) and T-[GT]m-OH and ethylene glycol terminated oligomers (H-[GT]m-G), where G is an ethylene glycol unit and T is a terephthalic acid unit. Additionally, the scission of the ester bonds during the chemical treatment led to a strong decrease in the number of cyclic oligomers ([GT]m). The occurrence of di-acid terminated species demonstrated a high degree of degradation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2183-2192, 1997
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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