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  • 1990-1994  (7)
  • 1985-1989  (4)
  • Chemistry  (9)
  • St Kitts  (2)
  • 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
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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
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    Paper (German National Licenses)
    Fulltext
  • 3
    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
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    Paper (German National Licenses)
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  • 4
    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
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Stable isotope ratio analysis of leucine and ketoisocaproic acid in blood plasma by gas chromatography/mass spectrometry. Use of tertiary butyldimethylsilyl derivatives (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 14-16 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020105
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure losses in the packing stage of injection molding (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1282-1289 
    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: The pressure loss between the mold and the nozzle in the injection molding of bar and box moldings has been monitored. The pressure drop observed during filling of the mold is reduced during the packing stage but remains finite. This has been attributed in the literature to solidification of polymer across the cavity transducer and to melt relaxation phenomena. Experiments have been carried out with hot molds to prolong the packing stage at the expense of the ‘cooling’ stage. Under these circumstances the pressure drop is reduced but not eliminated. The observed pressure drop may be related to the viscosity of the melt and its dependence on pressure and temperature although strain-induced crystallization and the pressure dependence of the melting point can confer effects similar to the cooling stage.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760261808
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  • 7
    Electronic Resource
    Electronic Resource
    Pumping characteristics of self-wiping twin-screw extruders - A theoretical and experimental study on biopolymer extrusion (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 433-440 
    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: The flow of Newtonian and non-Newtonian fluids which obeys a power law relationship between shear stress and shear rate has been modeled in the melt conveying section of a self-wiping co-rotating twin-screw extruder using a finite element analysis of an unwound channel section. Predictions of throughput against pressure gradient are compared with experimentally obtained results for maize grits which is represented as a power law material. Rheological data applicable to extrusion simulation were obtained from capillary rheometry. Comparisons are reasonable with predicted characteristic showing similar behavior.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290702
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  • 8
    Electronic Resource
    Electronic Resource
    Endiin-Verbindungen mit säure-, base- und lichtempfindlichen Triggergruppen; chemische Simulierung der Dynemicin-A-ReaktionskaskadeDiese Arbeit wurde von den National Institutes of Health (USA) und von der National Science Foundation (USA) gefördert. A. L. S. dankt dem britischen Science and Engineering Research Council für ein NATO-Stipendium. (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 103 (1991), S. 1034-1038 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19911030842
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Some features of the injection molding of short fiber reinforced thermoplastics in center sprue-gated cavities (1987)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 8 (1987), S. 16-21 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper describes an investigation into the fiber orientation in a number of center sprue fed cavities in short glass fiber filled polypropylene and nylon. The data have been interpreted in terms of a generalized five-layer structure resulting from the frozen skin formation and the high and low shear levels in the flowing melt. The implications for scaling up the mold size are discussed from the results obtained with different shot volumes. The fiber structure was observed to depend on location in the molding, local injection time, and injection rate. In addition the occurrence of fiber-free layers within the moldings using the filled polypropylene increases with an increase in shot volume, which produces an inherent ‘scale-up’ problem. Notwithstanding the mold geometry subtleties, the fiber orientation in all the moldings follows similar patterns and trends.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750080104
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  • 10
    Electronic Resource
    Electronic Resource
    Ceramic coating chemically vapour deposited on high speed steel substrates: Scratch adhesion test phenomena (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 352-356 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The scratch test is widely used to assess the adhesion of ceramic coatings deposited on cermet and alloy substrates by both physical vapour deposition and chemical vapour deposition (CVD). It has been observed during such tests that, depending on the coating type, complete coating removal from the scratch channels can be preceded by flaking of the coating at the edges of the channels. An attempt has been made to ascertain, for CVD coated powder metallurgy (PM) high speed steel (HSS) cutting tool inserts, whether a relationship exists between the presence/absence and type of pre-critical load coating flaking observed during scratch testing and interfacial compositional variations determined by Auger electron spectroscopy (AES). Scratch test and AES results are presented for the following CVD coated PM HSS inserts: titanium nitride (TiN) coated, where no flaking has been observed; titanium carbide (TiC) coated, where mixed adhesive/cohesive flaking of the TiC coating has been observed and multilayer aluminium oxide (Al2O3) coated, where adhesive flaking of the Al2O3coating has been observed. In the case of the TiN and TiC coated inserts it is not considered that differences in coating/substrate interdiffusion zone thickness alone are responsible for the observed divergence in scratch test behaviour. Differences in coating microhardness are also suggested to be a significant factor. The behaviour of the multilayer Al2O3 coated insert during scratch testing is thought more likely to be singularly associated with interfacial chemistry.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200505
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