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  • Organic Chemistry  (3)
  • Productivity  (2)
  • Vertical mass accumulation rate  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Geochemistry of a piston core from Ontong Java Plateau (western equatorial Pacific): evidence for sediment redistribution and changes in paleoproductivity (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 536-545 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02369008
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Geochemistry of a piston core from Ontong Java Plateau (western equatorial Pacific): evidence for sediment redistribution and changes in paleoproductivity (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 536-545 
    Details
    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
    URL: http://dx.doi.org/10.1007/s005310050094
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthese von 1-(β-D-Arabinofuranosyl)-pyrimidinen (1983)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 325 (1983), S. 387-392 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of 1-(β-D-Arbinofuranosyl)-pyrimidinesNew synthetic methods of 1-(β-D-arabinofuranosyl)-pyrimidines are described. 1-(β-D-arabinofuranosyl)-uracil, 1-(β-D-arabinofuranosyl)-5-fluorouracil, 1-(β-D-arabinofuranosyl)-thymine, and 1-(β-D-arabinofuranosyl)-cytosine can be obtained in a high yield by the splitting of the anhydrobond in 2,2′-anhydropyrimidines in dipolar aprotic solvents, such as HMPT, DMF, and DMSO, respectively, in the presence of activated elemental copper.Unlike the formation of cyclopyrimidiens ribonucleosides are directly transformed to the corresponding arabinofuranosyl derivatives by the reaction with diphenylcarbonate and NaHCO3 in the presence of copper. The reaction proceeds probably via an intermediate formation of the cycloproduct. Further aspects on the mechanism are described.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19833250307
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  • 4
    Electronic Resource
    Electronic Resource
    Eine neue Methods zur Einführung von CF3- und C2F5-Gruppen in Pyrimidinderivate und die Anti-Herpes-Aktivität der Verbindungen (1984)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 326 (1984), S. 985-993 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Method of the Introduction of CF3- and C2F5-Groups into Pyrimidine Derivatives and their Antiherpes ActivityA new method of the perfluoroalkylation of uracil derivatives is described. The irradiation of aqueous solutions of uracil and uracilnucleosides with bis-(perfluoroalkyl) mercury (CnF2n+1)2Hg n = 1, 2 under the exclusion of oxygen in the presence of catalytic amounts of azo-bis-isobutyronitril at 254 nm for several hours gave new 5-perfluoroalkylated compounds. In this way we obtained 5-trifluoromethyluracil (5a), 5-pentafluoroethyluracil (5b), 5-trifluoromethyl-2′-deoxyuridine (6a), 5-pentafluoroethyl-2′-deoxyuridine (6b) and 1-(ß-D-arabinofuranosyl)-5-trifluoromethyluracil (7a) in different yields. The perfluoroalkylated compounds were tested against HSV-1 and HSV-2 viruses on human lungefibroblasts. The compounds are markedly less potent than other known nonfluorinated compounds.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19843260618
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Ueber einige Azoderivate des m-Nitro-p-toluidins, (1901)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 63 (1901), S. 562-568 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19010630132
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    Paper (German National Licenses)
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