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  • 1990-1994  (4)
  • 1900-1904
  • Chemical Engineering  (2)
  • pyroclastic deposits  (2)
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Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Radiocarbon redating of contaminated samples from a tropical volcano: the Mansion ‘Series’ of St Kitts, West Indies (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 326-334 
    Details
    ISSN: 1432-0819
    Keywords: Lesser Antilles ; St Kitts ; Mt Liamuiga radiocarbon dating ; charcoal contamination stratigraphy ; pyroclastic deposits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Heavy rainfall and dense vegetation on tropical volcanoes produce abundant carbonized wood in pyroclastic deposits, in addition to easy contamination of this wood by root systems and soluble humic material. Because the physical nature of the charcoal varies, some samples are more prone to contamination. Two independent studies of the same volcano, Mt Liamuiga on St Kitts in the Lesser Antilles, sometimes using samples from the same carbonized tree, yielded a systematic difference in radiocarbon ages. An exchange of samples and a re-investigation of three physically distinct types of charcoal yielded the following results. Rare, hard, dense charcoal, lacking contamination, which had yielded a spurious age of 2860 years bp, was redated at 1845±58 years bp. Common soft, friable charcoal with good cellular structure proved to be susceptible to contamination. A field decontamination technique utilized by one group seems significant as it yields older ages than when only routine laboratory pre-treatment was used, indicating that the latter technique only partly removes the dried and hard residue produced by the decomposition of modern plant rootlets. A previous date of 24870 years bp obtained from powdery charcoal in a horizon beneath the Mansion ‘Series’ contradicted ages older than 41000 years bp from common friable charcoal in the lower Mansion ‘Series’. The soft powdery charcoal was re-investigated using a sample collected a few centimeters from the original, although field decontamination of this sample was not possible, more extensive laboratory treatment yielded an age of ca. 43000 years bp, again proving that routine laboratory pretreatments are inadequate. A revised geochronology for the Mansion ‘Series’ is described and a cautionary discussion is presented for the benefit of investigators using radiocarbon ages to date volcanic deposits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326459
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Radiocarbon redating of contaminated samples from a tropical volcano: the Mansion 'Series' of St Kitts, West Indies (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 326-334 
    Details
    ISSN: 1432-0819
    Keywords: Key wordsLesser Antilles ; St Kitts ; Mt Liamuiga ; radiocarbon dating ; charcoal contamination ; stratigraphy ; pyroclastic deposits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Heavy rainfall and dense vegetation on tropical volcanoes produce abundant carbonized wood in pyroclastic deposits, in addition to easy contamination of this wood by root systems and soluble humic material. Because the physical nature of the charcoal varies, some samples are more prone to contamination. Two independent studies of the same volcano, Mt Liamuiga on St Kitts in the Lesser Antilles, sometimes using samples from the same carbonized tree, yielded a systematic difference in radiocarbon ages. An exchange of samples and a re-investigation of three physically distinct types of charcoal yielded the following results. Rare, hard, dense charcoal, lacking contamination, which had yielded a spurious age of 2860 years bp, was redated at 1845±58 years bp. Common soft, friable charcoal with good cellular structure proved to be susceptible to contamination. A field decontamination technique utilized by one group seems significant as it yields older ages than when only routine laboratory pre-treatment was used, indicating that the latter technique only partly removes the dried and hard residue produced by the decomposition of modern plant rootlets. A previous date of 24 870 years bp obtained from powdery charcoal in a horizon beneath the Mansion 'Series' contradicted ages older than 41 000 years bp from common friable charcoal in the lower Mansion 'Series'. The soft powdery charcoal was re-investigated using a sample collected a few centimeters from the original, although field decontamination of this sample was not possible, more extensive laboratory treatment yielded an age of ca. 43 000 years bp, again proving that routine laboratory pre-treatments are inadequate. A revised geochronology for the Mansion 'Series' is described and a cautionary discussion is presented for the benefit of investigators using radiocarbon ages to date volcanic deposits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326459
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Family plots for evaluating physical properties of organosilicon compounds (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 373-377 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400217
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    A 2-d numerical study of intermeshing self-wiping screws in biopolymer extrusion (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1157-1163 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 knowledge of flow behavior is important in the study of laminar flow in twin-screw extrusion processes to predict the velocity distribution and to understand the mixing process. The flow of a power law fluid in self-wiping twin-screw extruders is examined using a two-dimensional finite element analysis of a mid-channel section of intermeshing screws. Theory is compared with experiment using food biopolymer and plastic materials. Comparisons showing overprediction of throughputs, but similarities in behavior, suggest that this model could provide an upper limit for melt conveying. For most of the throughput range examined, pumping of intermeshing self-wiping screws appears to be almost independent of the power law flow index of the melt extruded, but the value of the flow index determines the degree of influence intermeshing has on the overall pressure gradient generated in the extruder.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311513
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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