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  • 1
    Publication Date: 2015-11-18
    Description: The early Paleozoic Wuyi-Yunkai orogen in South China is a major orogenic belt in East Asia that formed at a similar time as the classic Caledonian orogeny in Europe. Despite the possibility of its being one of the few examples of intraplate orogenesis in the world, details about the orogen remain poorly defined. In this study, we provide age constraints on metamorphic and magmatic events in the eastern segment of the orogen, and the protoliths of the amphibolite-facies metamorphic rocks found there. By combining previous work with our new metamorphic and petrogenetic analyses, we present the following findings: (1) the Wuyi-Yunkai orogeny occurred between mid-Ordovician (〉460 Ma) and earliest Devonian (ca. 415 Ma) time; (2) amphibolite-facies metamorphism in the eastern Wuyi-Yunkai orogen occurred between ca. 460 and 445 Ma, whereas cooling below 500–300 °C occurred by ca. 420 Ma; (3) the orogen exhibits a clockwise pressure-temperature (P-T) path and a maximum pressure of 〉8 kbar, indicating crustal thickening during the orogeny; (4) protoliths of the high-grade metamorphic rocks in the eastern segment of the orogen were dominantly Neoproterozoic (840–720 Ma) volcanic and volcaniclastic rift successions and younger deposits formed in a failed rift, and Paleoproterozoic rocks account for only a small proportion of the outcrops; and (5) the analyzed granites indicate a mixed source of Paleoproterozoic basement and Neoproterozoic continental rift rocks, with elevated melt temperatures of 〉800 °C, which are interpreted as reflecting dehydration melting of basin sediments taken to below midcrustal levels.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2014-12-14
    Description: Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69–75), clinopyroxene (Mg# = 75–84), intercumulus plagioclase (An53–86) and Fe–Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than plagioclase and Fe–Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35–39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive Nd i values (4·3–4·8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr–Nd isotopic disequilibrium between clinopyroxene and plagioclase separates: 87 Sr/ 86 Sr i (0·7038–0·7041) and Nd i (1·0–1·9) of clinopyroxene are lower and higher than the respective ratios of intercumulus plagioclase ( 87 Sr/ 86 Sr i = 0·7042–0·7043, Nd i = 0·4–1·0). The 87 Sr/ 86 Sr i and Nd i of clinopyroxene separates correlate positively and negatively with Zr/Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. 87 Sr/ 86 Sr i increases and Nd i decreases with increasing Ca content of plagioclase, indicating that higher An plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and Nd i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean–Neoproterozoic basement and carbonates as contaminants.
    Print ISSN: 0022-3530
    Electronic ISSN: 1460-2415
    Topics: Geosciences
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  • 3
    Publication Date: 2014-11-16
    Description: The excavation damaged zone (EDZ) around a radioactive waste repository will act as a potential escape route for gases produced from anoxic corrosion of waste containers and other metallic components within the underground facility. For assessment of the impact of the gases on the repository safety, the gas-flow behaviour of the EDZ has to be characterized, understood and predicted. This issue has been recently investigated for the Callovo-Oxfordian and Opalinus claystones at the GRS laboratory. Various kinds of gas-flow experiments were carried out by flushing nitrogen gas through cracked and resealed claystone samples under different hydromechanical conditions. Extensive results obtained include: (a) gas permeability of fractured claystones in relation to fracture closure under loads; (b) effects of gas humidity on the sealing and gas permeability of fractures; (c) gas-flow behaviour in water-saturated and resealed fractures characterized by three key parameters, namely gas-breakthrough pressure, permeability and shut-in pressure; (d) relationships of the gas parameters to the intrinsic permeability of the resealed claystone and the applied confining stress, as well as relationships between the gas parameters; and (e) the impact of gas-pressure rise on the reopening of the closed pathways and/or creation of new ones in resealed claystone.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 4
    Publication Date: 2014-08-06
    Description: Members of the calmodulin-binding transcription activator (CAMTA) family of proteins function as calcium-sensitive regulators of gene expression in multicellular organisms ranging from plants to humans. Here, we show that global or nervous system deletion of CAMTA1 in mice causes severe ataxia with Purkinje cell degeneration and cerebellar atrophy, partially resembling...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 5
    Publication Date: 2014-05-02
    Description: Crushed claystone produced by excavation of repository openings has been investigated as backfill/seal material. The raw coarse-grained claystone can be used for backfilling repository openings and, in mixture with bentonite, for sealing boreholes, drifts and shafts. The investigation programme focused on characterizing the thermo-hydro-mechanical properties of the excavated Callovo-Oxfordian claystone and the compacted claystone–bentonite mixtures, including (1) mechanical compaction, (2) gas and water permeability as a function of porosity, (3) water retention and saturation, (4) swelling capacity and (5) thermal properties of the materials. The major results are presented in this paper.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 6
    Publication Date: 2013-02-13
    Description: [1]  We use a chemical transport model and its adjoint to examine the sensitivity of secondary inorganic aerosol formation to emissions of precursor trace gases from Asia. Sensitivity simulations indicate that secondary inorganic aerosol mass concentrations are most sensitive to ammonia (NH 3 ) emissions in winter and to sulfur dioxide (SO 2 ) emissions during the rest of the year. However, in the annual mean, the perturbations on Asian population-weighted ground-level secondary inorganic aerosol concentrationsof 34% due to changing nitrogen oxide (NO x ) emissions are comparable to those from changing either SO 2 (41%) or NH 3 (25%) emissions. The persistent sensitivity to NO x arises from the regional abundance of NH 3 over Asia that promotes ammonium nitrate formation. IASI satellite observations corroborate the NH 3 abundance. Projected emissions for 2020 indicate continued sensitivity to NO x emissions. We encourage more attention to NO x controls in addition to SO 2 and NH 3 controls to reduce ground-level East Asian aerosol.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
    Publication Date: 2013-10-11
    Description: Gpr97 is essential for the follicular versus marginal zone B-lymphocyte fate decision Cell Death and Disease 4, e853 (October 2013). doi:10.1038/cddis.2013.346 Authors: J-j Wang, L-l Zhang, Hong-x Zhang, C-l Shen, S-y Lu, Y Kuang, Y-h Wan, W-g Wang, H-m Yan, S-y Dang, J Fei, X-l Jin & Z-g Wang
    Keywords: Gpr97knockout miceB lymphopoiesisfollicular B cellslambda 5 gene
    Electronic ISSN: 2041-4889
    Topics: Biology , Medicine
    Published by Springer Nature
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  • 8
    Publication Date: 2013-08-03
    Description: Author(s): Fan Zhang, C. L. Kane, and E. J. Mele We propose a feasible route to engineer one- and two-dimensional time-reversal-invariant topological superconductors (SCs) via proximity effects between nodeless s ± wave iron-based SCs and semiconductors with large Rashba spin-orbit interactions. At the boundary of a time-reversal-invariant topologi... [Phys. Rev. Lett. 111, 056402] Published Fri Aug 02, 2013
    Keywords: Condensed Matter: Electronic Properties, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 9
    Publication Date: 2011-12-28
    Description: Kruppel-like factor 4 (KLF4) is involved in self-renewal of embryonic stem cells and reprogramming of somatic cells to pluripotency. However, its role in lineage-committed stem cells remains largely unknown. Here, we show that KLF4 is expressed in neural stem cells (NSCs) and is down-regulated during neuronal differentiation. Unexpectedly, enhanced expression of KLF4 reduces self-renewal of cultured NSCs and inhibits proliferation of subventricular neural precursors in transgenic mice. Mice with increased KLF4 in NSCs and NSCs-derived ependymal cells developed hydrocephalus-like characteristics, including enlarged ventricles, thinned cortex, agenesis of the corpus callosum, and significantly reduced subcommissural organ. These characteristics were accompanied by elevation of GFAP expression and astrocyte hypertrophy. The ventricular cilia, vital for cerebrospinal fluid flow, are also disrupted in the mutant mice. These results indicate that down-regulation of KLF4 is critical for neural development and its dysregulation may lead to hydrocephalus.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
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    American Physical Society (APS)
    Publication Date: 2012-08-11
    Description: Author(s): Fan Zhang, C. L. Kane, and E. J. Mele We introduce a topological boundary condition to study the surface states of topological insulators within a long-wavelength four-band model. We find that the Dirac point energy, the band curvature, and the spin texture of surface states are crystal-face dependent. For an arbitrary termination of a ... [Phys. Rev. B 86, 081303] Published Fri Aug 10, 2012
    Keywords: Semiconductors II: surfaces, interfaces, microstructures, and related topics
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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