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  • 1
    Electronic Resource
    Electronic Resource
    Capping of concanavalin A- or ricin-binding sites does not influence phagocytosis in polymorphonuclear leukocytes (1976)
    Springer
    Cellular and molecular life sciences 32 (1976), S. 1264-1266 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rabbit polymorphonuclear leukocytes (PMNs) were capped with territin-conjugated concanavalin A or ricin, and then allowed to phagocytose yeast cells. Phagocytic activity and lectin distribution were determined by ultrastructural morphometry. Capped PMNs were found to phagocytose as efficiently as control PMNs, and always to ingest the particles with a lectin-free portion of their plasma membrane. This clearly indicates that concanavalin A- and ricin-binding sites of the PMN membrane are not involved in the recognition and phagocytosis of yeast particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01953084
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  • 2
    Electronic Resource
    Electronic Resource
    Lead isotopes reveal bilateral asymmetry and vertical continuity in the Hawaiian mantle plume (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 434 (2005), S. 851-856 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The two parallel chains of Hawaiian volcanoes (‘Loa’ and ‘Kea’) are known to have statistically different but overlapping radiogenic isotope characteristics. This has been explained by a model of a concentrically zoned mantle plume, where the Kea chain preferentially samples ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03402
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  • 3
    Electronic Resource
    Electronic Resource
    Abrupt change in magma generation processes across the Central American arc in southeastern Guatemala: flux-dominated melting near the base of the wedge to decompression melting near the top of the wedge (1995)
    Springer
    Contributions to mineralogy and petrology 120 (1995), S. 378-390 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract.  Lavas erupted behind the volcanic front in southeastern Guatemala have many important distinctions from lavas erupted on the volcanic front. These include: generally higher MgO, Nb, Sr, TiO2, and rare earth element concentrations; higher La/Yb and Nb/Y ratios; and lower Ba/La, La/Nb, Ba/Zr and Zr/Nb ratios. These major and trace element distinctions are caused by reduced fractionation during ascent and storage in the crust, lower degrees of melting in the source, and greatly reduced contributions from the subducted Cocos plate in the source. In addition, because all of these important distinctions are even borne in lavas erupted within 20 km of the front, there is little apparent petrogenetic continuity between front and behind-the-front magmas. What little geochemical continuity exists is in radiogenic isotopes: 143Nd/144Nd falls across the arc, Pb isotopic ratios (except 206Pb/204Pb) rise across the arc, and 87Sr/86Sr rise across the arc after an initial discontinuity within 20 km of the front. These continuous across-arc changes in radiogenic isotopes are caused by increased contamination with older, more isotopically disparate rocks, away from the front. Once the effects of crustal contamination are removed, the remaining isotopic variability behind the front is non-systematic and reflects the inherent isotopic heterogeneity of the source, the mantle wedge. Geochemical disconnection in southeastern Guatemala suggests that behind-the-front magmas are produced by decompression melting near the top of the wedge, not by flux-dominated melting near the base of the wedge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050082
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  • 4
    Electronic Resource
    Electronic Resource
    Case studies on the origin of basalt (1983)
    Springer
    Contributions to mineralogy and petrology 84 (1983), S. 382-389 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract This paper presents a method for the systematic trace element modelling of a cogenetic suite of lavas. It is based on the geochemical inversion technique of Allègre and coworkers and utilizes the variations in the trace element concentrations of the lavas to calculate initial concentrations and source mineralogy. We reduce this inversion to a simple, step-by-step procedure: (1) correcting for fractional crystallization; (2) testing the inferred primary melt compositions for consistency with a model of equilibrium partial melts (with constant partition coefficients) formed from identical sources; (3) estimating the proportions of mineral phases entering the melt; (4) computing concentrations and bulk partition coefficients in the initial source relative to the concentration of a common reference element; (5) estimating relative mineral abundances in the source. Except for the fractionation correction, the calculations are done element by element using a direct analytic solution. For the purpose of comparison we apply this method to the same set of data used by Minster and Allègre (1978), a suite of lavas from Grenada (lesser Antilles) originally analyzed by Shimizu and Arculus (1975). The results of both methods agree well for the source abundances of the light REE, whereas the heavy REE abundances are shown to be poorly constrained by the data. Both methods require residual clinopyroxene and garnet in the source, but the ratio of these minerals is not well constrained. We are unable to reproduce the shape of D0 pattern (=bulk partition coefficients of the initial source) given by Minster and Allègre. The reason for this cannot be evaluated without repeating their calculations in detail. The set of data from Grenada is useful for comparison of the methods only, because it is now known from isotopic data that the samples are not truly cogenetic. Possibly better suited sets of samples for petrogenetic modelling are presented in parts II and III of this series.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160289
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  • 5
    Electronic Resource
    Electronic Resource
    Abrupt change in magma generation processes across the Central American arc in southeastern Guatemala: flux-dominated melting near the base of the wedge to decompression melting near the top of the wedge (1995)
    Springer
    Contributions to mineralogy and petrology 120 (1995), S. 378-390 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Lavas erupted behind the volcanic front in southeastern Guatemala have many important distinctions from lavas erupted on the volcanic front. These include: generally higher MgO, Nb, Sr, TiO2, and rare earth element concentrations; higher La/Yb and Nb/Y ratios; and lower Ba/La, La/Nb, Ba/Zr and Zr/Nb ratios. These major and trace element distinctions are caused by reduced fractionation during ascent and storage in the crust, lower degrees of melting in the source, and greatly reduced contributions from the subducted Cocos plate in the source. In addition, because all of these important distinctions are even borne in lavas erupted within 20 km of the front, there is little apparent petrogenetic continuity between front and behind-the-front magmas. What little geochemical continuity exists is in radiogenic isotopes: 143Nd/144Nd falls across the arc, Pb isotopic ratios (except 206Pb/204Pb) rise across the arc, and 87Sr/86Sr rise across the arc after an initial discontinuity within 20 km of the front. These continuous across-arc changes in radiogenic isotopes are caused by increased contamination with older, more isotopically disparate rocks, away from the front. Once the effects of crustal contamination are removed, the remaining isotopic variability behind the front is non-systematic and reflects the inherent isotopic heterogeneity of the source, the mantle wedge. Geochemical disconnection in southeastern Guatemala suggests that behind-the-front magmas are produced by decompression melting near the top of the wedge, not by flux-dominated melting near the base of the wedge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306515
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  • 6
    Electronic Resource
    Electronic Resource
    Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc (1990)
    Springer
    Contributions to mineralogy and petrology 105 (1990), S. 369-380 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Sr and Nd isotopic ratios of Central American volcanics can be described by the mixing of four components, marine sediment from DSDP Site 495, MORB-source mantle (DM), EMORB-source mantle (EM), and continental crust. Most of the isotopic data define a trend between EM and a modified mantle (MM) formed as a mixture of DM and less than 0.5% marine sediment, or fluid derived there from. The MM to EM trend is equally apparent in the incompatible-element data and is most clearly seen in a Ba/La versus La/Yb plot. A hyperbolic trend connects high Ba/La and low La/Yb at the MM end of the trend to low Ba/La and high La/Yb at the EM end. Smooth regional variations in incompatible-element and isotopic ratios correlate with the dip of the subducted slab beneath the volcanic front and the volume of lava erupted during the last 100,000 years (volcanic flux). Steep dip and low flux characterize the MM end-member and shallow dip and high flux characterize the EM end-member. The simplest model to explain the linked tectonic and geochemical data involves melting in the wedge by two distinct mechanisms, followed by mixing between the two magmas. In one case, EM magma is generated by decompression of EM plus DM asthenosphere, which is drawn in and up toward the wedge corner. EM mantle is preferentially melted to small degrees because of the presence of low melting components. The second melt is formed by release of fluid from the subducted slab beneath the volcanic front to form MM magma. Mixing between EM and MM magmas is controlled by subduction angle, which facilitates delivery of EM magma to the volcanic front at low-dip angles and impedes it at steep-dip angles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286825
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