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  • 1
    Monograph available for loan
    Monograph available for loan
    New York [u.a.] : Springer
    Associated volumes
    Call number: 13028 ; M 93.0038/1 ; G 8103
    In: Advances in physical geochemistry
    Type of Medium: Monograph available for loan
    Pages: xii, 304 S.
    ISBN: 0387905308
    Series Statement: Advances in physical geochemistry 1
    Language: English
    Location: Upper compact magazine
    Location: Upper compact magazine
    Location: Upper compact magazine
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
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  • 2
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Activity-composition relationships of Ca3Al2Si3O12 (grs) in ternary Ca-Mg-Fe garnets of various compositions have been determined by reversed displaced equilibrium experiments at 1000° C and 900° C and pressures of 8 to 17 kbar. The mixing of grs in garnet is nearly ideal at 30 mol% grs, with positive deviations from ideality at lower grs contents. Models of garnet mixing currently in the literature do not predict this trend. Analysis of the present reversals, in conjunction with a garnet mixing model based solely on calorimetry measurements on the binary joins, indicates that a ternary interaction constant for a ternary asymmetric Margules model (Wohl 1953) cannot be constrained. Apparently, some aspects of the garnet binary joins are still not well-known. An alternative asymmetric empirical model, based on analysis of pseudobinary joins of constant Mg/Mg + Fe(Mg #), reproduces the data well and is able to predict grs activity coefficients for garnets with grs contents between 3 and 40 mol% and Mg numbers between 0 and 0.60. The grossular activity coefficient,γ grs, is given by: $$RT\ln \gamma _{grs} = (1 - X_{grs} )^2 [W_{Ca} + 2X_{grs} (W_{FM} - W_{Ca} )]$$ where: $$\begin{gathered} W_{Ca} (J) = - 2060 + 3.57 \times 10^4 (Mg\# ) - 4.95 \times 10^4 (Mg\# )^2 \hfill \\ W_{FM} (J) = 3390 - 3.71 \times 10^4 (Mg\# ) + 6.49 \times 10^4 (Mg\# )^2 \hfill \\ \end{gathered} $$ These expressions are valid only over the composition range investigated. The formulation cannot be used to extract Fe and Mg activity coefficients. There appears to be no temperature or pressure dependence of theW-parameters over theP-T range investigated. The improved definition of the grossular activity coefficient which results from the present work contributes to an improved formulation of the garnet-Al2SiO5-quartz-plagioclase (GASP) geobarometer and other phase equilibria relevant to metamorphic petrology.
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  • 3
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The stability field of the end-member scapolite meionite was determined in piston-cylinder apparatus. Meionite has very high thermal stability at high pressures, exceeding 1500° C at 20 kbar. Below 6 kbar and 1270 ° C scapolite breakdown is subsolidus, to an-orthite + gehlenite + wollastonite + CO2, with a slope of 20 bars/degree. An extrapolation of existing thermodynamic data for CO2 permits calculation of ΔG F o =-2384.5 kcal/mol for meionite at 1270 ° C, very close to the value for 3 anorthite + calcite. Above 1270 ° C, scapolite begins to melt to An+Geh+Liq+CO2, and as pressure increases the melting curve steepens, the Geh and An being progressively replaced by Liq+corundum with Al in 6-coordination. At pressures 〉25kbar dp/dt becomes negative, corundum is the only crystalline product, and CO2 bubbles disappear from the quenched glass, indicating a solubility of CO2 under these conditions of about 5 wt. percent in the liquid. The subsolidus breakdown of meionite at high pressures to grossularite + kyanite + quartz + calcite nearly coincides with the upper pressure limits of anorthite. Thus scapolite is essentially limited to crustal rocks. In view of its great thermal stability, meionite can play a role as a primary mineral in deep-seated basic or intermediate magmatic processes. It is also likely that CO2 coming from the earth's interior will be captured by reaction with plagioclase and clinopyroxene. Scapolite has been noted in basic granulite inclusions from basaltic pipes in three continents. It seems probable that scapolite acts as a major storage site for CO2 in the deep crust.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Immunogenetics 4 (1977), S. 449-462 
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The immune response of six inbred mouse strains (SJL, A, C57BL/6, CBA, BALB/c, and DBA/1) to DNP56BGG was tested under three separate immunization schedules: 1 Μg DNP-BGG in 1 mg Al(OH)3 adjuvant, 50 Μg DNP-BGG in 1 mg A1(OH)3 adjuvant, and 1 Μg DNP-BGG in complete Freund's adjuvant. Individual serum samples were titered using a modified Farr assay. It was found that the first schedule allowed classification of the mice into responder (SJL, A) and nonresponder (C57BL/6, CBA, BALB/ c, DBA/1) strains. The second schedule produced quantitative as well as qualitative differences among the strains and allowed classification of the mice into higher-responder (SJL, A), intermediate-responder (C57BL/6, CBA, BALB/c), and low-responder (DBA/1) categories. When complete Freund's adjuvant was used in the third schedule, the differences among strains became insignificant. The sera from each strain were pooled and assayed for relative antibody affinity and IgM content. Both of these parameters were dependent largely on the dose of antigen and type of adjuvant used, rather than on the particular mouse strain being studied. The mechanism of adjuvant action, and possible cell interactions in the genetic control of the immune response, are discussed.
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  • 5
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The compositions of coexisting orthopyroxene, clinopyroxene and garnet in the CaO-MgO-Al2O3-SiO2 system are fixed at any givenP andT. Reversed hydrothermal experiments over theP/T range 15–40 kb/900°–l,100° C indicate that the garnet composition is nearly constant at Py86Gr14; the Alcontent and Ca/Ca+Mg values of the pyroxenes vary significantly, however: T P Wt. %Al2O3 $$\frac{{Ca}}{{Ca + Mg}} \times 100$$ °C kbar in opx in cpx in opx in cpx 900 15 3.55 2.92 0.72 47.05 900 30 1.62 0.92 0.81 47.30 1,100 20 1.11 0.92 1.22 45.20 1,100 40 1.26 0.88 0.81 45.64 The significant variation of A12O3 content with pressure supports its use as a geobarometer. The Ca/Ca +Mg values of coexisting orthoand clino-pyroxene have been used as a geothermometer. However, the present results show that the presence of A12O3 in the pyroxenes decreases significantly the mutual solubility of the pyroxenes, which may cause errors of up to 200° C if the A12O3 effect is ignored. Thermodynamic analyses of the experimental results for the reaction Mg3Al2Si3O12(gar) =Mg3Al2Si3O12(opx) yield average values ofΔH 0 andΔS 0 of 7.4 Kcal and 5.7 eu, respectively, which are in marginal agreement with calorimetric results. Similar analysis of our results for the reaction MgSiO3(cpx)=MgSiO3(opx) support earlier conclusions that MgSiO3 substitution in clinopyroxene behaves as a regular solution (Holland et al. 1979) and that Al substitution is quasi-ideal (Wood 1979). Application of the present results to garnet lherzolites from southern Africa yields a geotherm which is parallel to those previously proposed, although the indicated heat flow is greater. Similar rocks, from the Solomon Islands, show a much steeper geothermal gradient, as expected for an oceanic plate.
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  • 6
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Aragonite, the dense form of CaCO3, grew hydrothermally at 100–300° C and dry at 300–400° C at very low pressures from calcite strained by grinding. Nearly complete inversion to aragonite occurred in some runs with Ca-Mg chloride solutions at 0–2.4 kb and 100–200° C on strained calcite having a (10¯14) reflection with a half-width of 0.48° 2 Θ Cu Kα. A little aragonite grew dry at one atm. from the ground calcite at 300–400° C in a few hrs. Simultaneous shear during recrystallization of calcite in a rotating squeezer resulted in significant aragonite at 300–400° C several kb. below the stability field. No inversion occurred in any ground calcite when previously annealed in CO2 at 500° C for a few hrs. Thermochemical data show that at least 200 cal/mole of strain energy can be produced in calcite by mild deformation. This much stored energy would lower the pressure requirements of aragonite, relative to the strained calcite by more than 3 kb, and our observation that aragonite growth was faster than strain recovery of calcite indicates that aragonite can grow in nature at reduced pressures from strained calcite. Some experiments were also carried out on highly magnesian calcites with the thought that aragonite might also form at the expense of this metastable material. No aragonite was produced, but the possibility that this mechanism could be operative in nature cannot be discounted. The microtexture of aragonitic deformed marbles from NW Washington (prehnite-pumpellyite facies rocks, courtesy of J. A. Vance) as well as electron probe microanalysis of these rocks indicates that aragonite selectively replaced highly strained calcite. The calcite-aragonite transition is thus a questionable indicator of high-pressure in certain metamorphic rocks.
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 340 (1989), S. 378-380 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Starting materials for the present investigation included phlogopite (KMg3AlSi3O10(OH)2) and sanidine (KAlSi3O8), both synthesized hydrothermally from the constituent oxides. Mixtures of phlogopite + quartz (natural) in 2:3 weight ratio and phlogopite + sanidine + quartz (2:2:3) were encapsulated ...
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  • 8
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 224 (1969), S. 314-317 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] High pressure and high temperature laboratory work with rocks and minerals is beginning to explain some fundamental geophysical observations, and to provide solutions to important problems of the Earth's ...
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  • 10
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We exploited the large difference in the solubility of SiO2 and ZrO2 in H2O to constrain precisely the Gibbs energy of formation of zircon (ZrSiO4). Solubility in H2O was determined at 800°C, 1.2 GPa, by weight loss of synthetic zircon crystals. The experiments yielded fine-grained monoclinic ZrO2 as an incongruent solution product uniformly coating zircon crystals. Experiments on the ZrO2-coated zircon crystals were also carried out with an initially slightly SiO2-oversaturated fluid, causing weight gain by zircon regrowth. The mean SiO2 concentration for forward and reverse experiments was 0.069±0.010 mol/kg H2O (2σ). When combined with precise activity–composition measurements for aqueous SiO2, the data constrain the Gibbs free energy of zircon from its oxides at 298 K, 105 Pa, to be −19.30±1.16 kJ/mol (2σ). This determination is comparable in precision to the best measurements obtainable by more conventional methods, which suggests that determination of the thermochemical properties of other important ceramic materials may also be amenable to this method.
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