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  • 1
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The effect of CO2 on mantle peridotites is modeled by experimental data for the system CaO-MgO-SiO2-CO2 at 2.7 GPa. The experiments provide isotherms for the vapor-saturated liquidus surface, bracket piercing points for field boundaries on the surface, and define the positions and compositions of isobaric invariant liquids on the boundaries (eutectics and peritectics). CO2-saturated carbonatitic liquids (〉80% carbonate) exist through approximately 200 °C above the solidus, with a transition to silicate liquids (〉80% silicate) within ∼75 °C across a plateau on the liquidus. Carbonate-rich magmas cannot cross the silicate-carbonate liquidus field boundary, so the carbonate liquidus field is therefore a forbidden volume for liquid magmas. This confirms the fact that rounded, pure carbonates in mantle xenoliths cannot represent original liquids. A P-T diagram is constructed for the carbonation and melting reactions for mineral assemblages corresponding to lherzolite, harzburgite, websterite and wehrlite, with carbonate, CO2 vapor (V), or both. The changing compositions of liquids in solidus reactions on the P-T diagram are illustrated by the changing compositions of eutectic and peritectic liquids on the liquidus surface. At an invariant point Q (∼2.8 GPa/1230 °C), all peridotite assemblages coexist with a calcite-dolomite solid solution (75 ± 5% CaCO3) and a dolomitic carbonatite melt [57% CaCO3 (CC), 33% MgCO3 (MC), 10% CaMgSi2O6 (Di)], with 63% CC in the carbonate component. At higher pressures, dolomite-lherzolite, dolomite-harzburgite-V, and dolomite-websterite-V melt to yield similar liquids. Magnesian calcite-wehrlite is the only peridotite melting to carbonatitic liquids (more calcic) at pressures below Q (∼70 km). Dolomitic carbonatite magma rising through mantle to the near-isobaric solidus ledge near Q will begin to crystallize, releasing CO2 (enhancing crack propagation), and metasomatizing lherzolite toward wehrlite.
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  • 2
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract New experimental data in CaO-MgO-SiO2-CO2 at 1 GPa define the vapor-saturated silicate-carbonate liquidus field boundary involving primary minerals calcite, forsterite and diopside. The eutectic reaction for melting of model calcite (1% MC)-wehrlite at 1 GPa is at 1100 °C, with liquid composition (by weight) 72% CaCO3 (CC), 9% MgCO3 (MC), and 18% CaMgSi2O6 (Di). These data combined with previous results permit construction of the isotherm-contoured vapor-saturated liquidus surface for the calcite/dolomite field, and part of the adjacent forsterite and diopside fields. Nearly pure calcite crystals in mantle xenoliths cannot represent equilibrium liquids. We recently determined the complete vapor-saturated liquidus surface between carbonates and model peridotites at 2.7 GPa; the peritectic reaction for dolomite (25% MC)-wehrlite at 2.7 GPa occurs at 1300 °C, with liquid composition 60% CC, 29% MC, and 11% Di. The liquidus field boundaries on these two surfaces provide the road-map for interpretation of magmatic processes in various peridotite-CO2 systems at depths between the Moho and about 100 km. Relationships among kimberlites, melilitites, carbonatites and the liquidus phase boundaries are discussed. Experimental data for carbonatite liquid protected by metasomatic wehrlite have been reported. The liquid trends directly from dolomitic towards CaCO3 with decreasing pressure. The 1.5 GPa liquid contains 87% CC and 4% Di, much lower in silicate components than our phase boundary. However, the liquids contain approximately the same CaCO3 (90 ± 1 wt%) in terms of only carbonate components. For CO2-bearing mantle, all magmas at depth must pass through initial dolomitic compositions. Rising dolomitic carbonatite melt will vesiculate and may erupt as primary magmas through cracks from about ˜70 km. If it percolates through metasomatic wehrlite from 70 km toward the Moho at 35–40 km, primary calcic siliceous carbonatite magma can be generated with silicate content at least 11–18% (70–40 km) on the silicate-carbonate boundary.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 49 (1996), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The isolation of seven tri-, and 133 di-nucleotide microsatellite markers from a tilapia, Oreochromis niloticus, is described. An efficient methodology for isolating large numbers of such markers and their potential applications in applied aquaculture and evolutionary genetics are discussed.
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  • 4
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 6
    ISSN: 0040-6090
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 5043-5054 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Damage accumulation in polycrystalline alumina subjected to cyclic thermal loading was studied via non-destructive elastic modulus and internal friction measurements. These nondestructive techniques were sensitive to cracks formed by thermal loading. Thermal shock damage was observed to saturate as a function of an increasing cumulative number of thermal shock cycles. The observed power law relationship between the damage saturation and thermal shock difference implies a fatigue-like power law relation in stress. The exponent has a value of approximately 12 for the range of ΔT included in this study. Thermal shock damage induced changes in internal friction were found to be a function of a crack damage parameter. These thermal fatigue results of polycrystalline (unreinforced) alumina are also compared to thermal fatigue results for SiC whisker-alumina composites.
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  • 8
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Effects of the thermally grown wustite on the fatigue crack initiation and growth in HSLA steel are evaluated as a function of oxide thickness, strain amplitude, and gaseous environment in the push-pull plastic strain control mode, with special attention being given to the early stage of microcrack initiation. Specimens with a wustite surface layer thermally grown to 0.2 and 0.6 μm thicknesses show predominantly intergranular cracking at plastic strain amplitudes of 5×10−4 and 1×10−3 both in air and in ultrahigh vacuum (UHV), in contrast to the as-polished specimens where slip band cracking is the favoured mode. The cracking mode in the oxide layer is discussed in terms of the strain amplitude and the dislocation behaviour near the oxide/metal interface. The features of microcrack initiation in the oxide layer is not affected by the gaseous environment. Once, however, the surface oxide fractures, the rate of crack growth through the base metal is greatly reduced in UHV.
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  • 9
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effects of La content and rapid thermal annealing (RTA) on the capacitance (C–V) and leakage current (J–E) properties of the PLT films were investigated. The films were deposited on Pt/Ti/SiO2/Si substrates at 480 °C by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD). The La doped films showed slim P–E hysteresis curves and almost no frequency dependency of permittivity. As the La content increased beyond 11%, Pb was excessively incorporated into the PLT film, resulting in non-stoichiometric compositions with (Pb+La)/Ti〉1, degraded crystallinity and decreased capacitance. After RTA at 700 °C, C–V curves became symmetric and leakage current characteristics were improved, but the crystallinity and the ferroelectricity of the films were not so much improved although the film became stoichiometric. The leakage current of the films was controlled by Schottky conduction except for the low electric field region where the trap current of mobile charges or hopping conduction appeared to be dominant. In order to explain the RTA dependence of the C–V shift and the polarity dependence of the J–E characteristics of the PLT films, a physical model was suggested, based on the surface states and Pb vacancies, which affects the width of the space charge region and the height of the Schottky barrier. © 1998 Kluwer Academic Publishers
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  • 10
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract When a 1∶1 weight mixture of (2,-4-dinitrophenyl)-L-alanine (DPA) and 2-methyl-4-nitroaniline (MNA) is dissolved in a 50∶50 volume mixture of ethyl acetate and hexane, two types of crystals were observed on slow evaporation. In the first stage of crystallization, light-yellow plates of MNA measuring up to 25 mm×5 mm×1 mm were formed, which belong to the triclinic space group P1 with lattice parameters a=0.7621 (3) nm, b=0.795 2(5) nm, c=0.8200 (2) nm, α=111.84(2)°, β= 93.76(2)°, γ=116.84(3)°, Z=2. The volume of the unit cell containing two molecules is 361.9(1)×10−3 nm3. The powder SHG efficiency of the triclinic polymorph (MNA(T)) is about the same as that of the monoclinic MNA(M). The Raman spectrum of the new crystal is similar to that of MNA(M) crystallized from the vapour phase or solution, except for the change in the intensity of a few bands. The DSC data show minor differences in the melting points and specific heats for the two phases. The second stage of crystallization resulted in the formation of orange-yellow coloured crystals of the DPA:MNA complex, in the monoclinic space group P21 with lattice parameters a =0.6876(1) nm, b=0.7621(3) nm, c=1.7626(4) nm, β=96.62(2)°, V=917.5 ×10−3 nm3, Z=2 for C16H17N5O8. The Raman spectrum of DPA:MNA consists of bands from both DPA and MNA. The complex melts at 138(1)°C with a specific heat of 25.3(4) cal g−1 according to the DSC measurements. The powder SHG efficiency is nearly the same as that of methyl-(2,4-dinitriphenyl)-aminoproanoate (MAP).
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