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  • Articles  (34)
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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Four ecotypes of Phragmites australis from different habitats in northwest China were examined to compare their photosynthetic characteristics. In a swamp ecotype, the Δ13C value of leaf materials was −34.0‰, and bundle sheath cells contained a small amount of organelles and round-shaped chloroplasts, as being similar to typical C3 plants. In a dune ecotype, the Δ13C value was −20.9‰ and bundle sheath cells contained oval-shaped chloroplasts with poorly-developed grana. In light and heavy salt meadow ecotypes, Δ13C values were −30.6‰ and −35.6‰, respectively. The shape of bundle sheath chloroplasts in the light salt meadow ecotype was intermediate between those of the swamp and dune ecotypes. Abundance of bundle sheath organelles in the heavy salt meadow ecotype was intermediate. The swamp ecotype had photosynthetic enzyme activities typical of C3 type plants, whereas the dune ecotype had an increased activity of phosphoenolpyruvate carboxylase (PEPC), a key C4 enzyme, and a decreased ribulose 1,5-bisphosphate carboxylase (Rubisco) activity. The light salt meadow and heavy salt meadow ecotypes had substantial activities of PEPC, which indicates potential for C4 photosynthesis. These data suggest that this species evolved the C3-like ecotype in swamp environments and the C4-like C3-C4 intermediate in dune desert environments, and C3-like C3-C4 intermediates in salt environments.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Until now, the origin of hard magnetic properties of rapidly quenched Nd-Fe-B alloys with lower Nd concentration is not clear. In this paper, the phase compositions of rapidly quenched Nd4Fe77.5B18.5 alloys annealed under different conditions have been studied by using zero-field spin-echo nuclear magnetic resonance (NMR) and Mössbauer effect (ME) techniques. It is found that there exists a certain amount of Nd2Fe14B phase in the samples annealed at 960 °C and ingot alloy, which have poor hard magnetic properties; while, the sample annealed under optimal condition consists only of bct-Fe3B as the main phase and a small amount of a-Fe. However, the ME result indicates that about 5 at. % Fe atoms in FeIII (8 g) site of bct-Fe3B have been replaced by Nd atoms; the NMR result demonstrates that 11B NMR spectrum is the characteristic peak of bct-Fe3B, but it broadens asymmetrically to the high frequency side, which is due to the bct-Fe3B influenced by Nd atoms. The amplitude of radio frequency (rf) excitation field required to get the maximum 11B spin-echo signal from bct-Fe3B in the sample annealed at 839 °C is only about one third as much as that required to excite the 11B in the bct-Fe3B influenced by Nd atoms in the sample annealed at 670 °C for a short time, which implies the latter has a larger coercivity field than the former. It is concluded that the origin of hard magnetic properties of Nd4Fe77.5B18.5 alloy is not related to the 2:14:1 phase, but to the change of bct-Fe3B itself.
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Fe–B amorphous alloys powders with high boron concentration can be prepared by borohydride reduction (BHR). By adjusting technological factors, the Fe100−xBx amorphous powders with compositions ranging from x=17 to 40 can be easily obtained, but it is difficult to make the amorphous ribbons with such a high B concentration by using rapidly quenched technique, which can usually obtain the amorphous ribbons with the compositions ranging from x=12 to 25. Up to now, there are different points of view about if the short range order (SRO) in the Fe–B amorphous powders prepared by the BHR around room temperature is the same with that in the amorphous ribbons made by rapidly quenched and vapor depositing techniques. In this paper, the SRO in Fe100−xBx amorphous powders with various boron concentration prepared by the BHR have been studied by the zero field spin echo nuclear magnetic resonance (NMR) technique. It was shown that the types of SRO in these samples vary with the B concentration. There exist Fe3B- and Fe2B-like SRO and a small amount of α-Fe in the samples with lower B concentration, while there are Fe3B- and FeB-like SRO in the alloys with higher B concentration. Fe3B-like SRO, however, only exists in the amorphous ribbons obtained by rapidly quenched method. It can be concluded that there are different types of SRO in the amorphous alloys prepared by different methods. This conclusion can explain the reason why the average hyperfine field at Fe sites deceases with the B concentration increasing.
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    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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