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  • 1
    Electronic Resource
    Electronic Resource
    Two-liquid partition coefficients: Experimental data and geochemical implications (1976)
    Springer
    Contributions to mineralogy and petrology 56 (1976), S. 119-134 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Partition coefficients for Cs, Ba, Sr, Ca, Mg, La, Sm, Lu, Mn, Ti, Cr, Ta, Zr, and P between immiscible basic and acidic liquids in the system K2O-Al2O3-FeO-SiO2 were experimentally determined at 1,180 °C and 1 atm. Phosphorus is most strongly enriched in the basic melt (by a factor of 10), followed by rare earth elements, Ta, Ca, Cr, Ti, Mn, Zr, Mg, Sr, and Ba (enriched by a factor of 1.5). Of the elements studied, only Cs is enriched in the acidic melt. The two-liquid partition coefficients of Zr, Ta, Sm, and Mn are constant for concentrations ranging from 〈0.1% to as high as 1 wt.-%, suggesting that Henry's law is applicable in silicate melts (at least for these elements) to concentrations well above typical trace element levels in rocks. The strong relative preference of many elements for the basic melt implies that the structural characteristics of basic melts more readily permit stable coordination of cations by oxygen. Partitioning of elements between crystal and liquid in a magma must therefore be influenced by the composition (and consequent structure) of the liquid. Application of the two-liquid partition coefficients to possible occurrences of liquid immiscibility in magmas reveals that typical basalt-rhyolite associations are probably not generated by two-liquid phase separation. However, liquid immiscibility cannot be discounted as a possible origin for lamprophyric rocks containing felsic segregations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375424
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  • 2
    Electronic Resource
    Electronic Resource
    Zircon saturation in felsic liquids: Experimental results and applications to trace element geochemistry (1979)
    Springer
    Contributions to mineralogy and petrology 70 (1979), S. 407-419 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Hydrothermal experiments were carried out at 2 kbar water pressure, 700 °–800 ° C, with the objective of determining the level of dissolved Zr required for precipitation of zircon from melts in the system SiO2-Al2O3-Na2O-K2O. The saturation level depends strongly upon molar (Na2O + K2O)/Al2O3 of the melts, with remarkably little sensitivity to temperature, SiO2 concentration, or melt Na2O/ K2O. For peraluminous melts and melts lying in the quartz-orthoclase-albite composition plane, less than 100 ppm Zr is required for zircon saturation. In peralkaline melts, however, zircon solubility shows pronounced, apparently linear, dependence upon (Na2O + K2O)/Al2O3, with the amount of dissolvable Zr ranging up to 3.9 wt.% at (Na2O + K2O)/Al2O3 = 2.0. Small amounts (1 wt.% each) of dissolved CaO and Fe2O3 cause a 25% relative reduction of zircon solubility in peralkaline melts. The main conclusion regarding zirconium/zircon behavior in nature is that any felsic, non-peralkaline magma is likely to contain zircon crystals, because the saturation level is so low for these compositions. Zircon fractionation, and its consequences to REE, Th, and Ta abundances must, therefore, be considered in modelling the evolution of these magmas. Partial melting in any region of the Earth's crust that contains more than ∼ 100 ppm Zr will produce granitic magmas whose Zr contents are buffered at constant low (〈 100 ppm) values; unmelted zircon in the residual rock of such a melting event will impart to the residue a characteristic U- or V-shaped REE abundance pattern. In peralkaline, felsic magmas such as those that form pantellerites and comendites, extreme Zr (and REE, Ta) enrichment is possible because the feldspar fractionation that produces these magmas from non-peralkaline predecessors does not drive the melt toward saturation in zircon. Zircon solubility in felsic melts appears to be controlled by the formation of alkali-zirconosilicate complexes of simple (2:1) alkali oxide: ZrO2 stoichiometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371047
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrate reductase activity in Paul's scarlet rose suspension cultures and the differential role of nitrate and molybdenum in induction (1978)
    Springer
    Planta 141 (1978), S. 183-189 
    Details
    ISSN: 1432-2048
    Keywords: Antimetabolites ; Cell culture ; Enzyme induction ; Molybdenum ; Nitrate reductase ; Rosa, Paul's Scarlet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Induction of nitrate reductase (EC 1.6.6.1) activity was measured in Paul's Scarlet rose cell suspensions cultured in media containing nitrate (NO 3 - ) or urea (U) as nitrogen source, and with (+Mo) or without molybdenum (-Mo). There was a lag of 30 min during induction by NO 3 - in +Mo cultures but no lag occurred during induction after adding Mo to NO 3 - -Mo or to U-Mo cultures preincubated with NO 3 - . Actinomycin D, cycloheximide, and puromycin completely blocked induction by NO 3 - , but had no effect on the initial rate of induction by Mo. Cycloheximide and puromycin blocked induction by NO 3 - more quickly than actinomycin D. Induction by NO 3 - appeared to involve mRNA-dependent synthesis of apoprotein followed by rapid activation with molybdenum in intact cells independently of protein synthesis. Nitrate-induced apoprotein appeared less stable than the holoenzyme. When induced by NO 3 - in the absence of Mo, apoprotein concentration was about half the amount of maximally induced nitrate reductase. Cycloheximide stabilised preformed nitrate reductase which disappeared steadily in the presence of puromycin. Apoprotein was not stabilised by either antimetabolite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387887
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of N-serve (2-chloro-6-(trichloromethyl)pyridine) formulations on nitrification and on loss of nitrate in sand culture experiments (1979)
    Springer
    Plant and soil 51 (1979), S. 1-12 
    Details
    ISSN: 1573-5036
    Keywords: Acetone ; Ammonium ; Cauliflower ; Denitrification ; Nitrate ; Nitrate reductase ; Nitrification ; N loss ; N recovery ; N-Serve ; Radish ; Turnip ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary N-serve (2-chloro-6-(trichloromethyl)pyridine) was tested as an inhibitor of nitrification of ammonium or urea in sand cultures. Nitrification was reduced but not prevented by N-Serve present at between 5 and 20 ppm in solution or by weight of sand. In the presence of root debris and acetone, used in some experiments at 2–4 ml/l of nutrient to convey N-Serve, denitrification was stimulated under the same conditions and resulted in loss of a large proportion of nitrate, probably mainly as gaseous products and some nitrite. These losses were greater when N-serve was also present. There was also conversion of nitrate to an insoluble form in the sand. A smaller proportional loss of nitrate occurred in other treatments in the presence of root debris when N-Serve was added without acetone, either as the commercial formulation 24E or as a solid. Thus, using N-Serve to inhibit nitrification may encourage denitrifying organisms especially in the presence of carbon sources including root debris or acetone. Large decreases of nitrate reductase activity in plants produced by using N-Serve in the presence of ammonium or urea were caused as much by losses of nitrate in the presence of acetone as by prevention of nitrate formation. Other N-Serve treatments (solid or 24E) decreased enzyme induction by between 50 and 90 per cent as a result mainly of reduced nitrification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02205921
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