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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
    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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  • 3
    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.
    Type of Medium: Electronic Resource
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  • 4
    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.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2019-07-13
    Description: eXTP is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. Primary goals are the determination of the equation of state of matter at supra-nuclear density, the measurement of QED effects in highly magnetized star, and the study of accretion in the strong-field regime of gravity. Primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes. The mission carries a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time ever the simultaneous spectral-timing-polarimetry studies of cosmic sources in the energy range from 0.5-30 keV (and beyond). Key elements of the payload are: the Spectroscopic Focusing Array (SFA) - a set of 11 X-ray optics for a total effective area of approx. 0.9 m(exp. 2) and 0.6 m(exp. 2) at 2 keV and 6 keV respectively, equipped with Silicon Drift Detectors offering less than 180 eV spectral resolution; the Large Area Detector (LAD) - a deployable set of 640 Silicon Drift Detectors, for a total effective area of approx. 3.4 m(exp. 2), between 6 and 10 keV, and spectral resolution better than 250 eV; the Polarimetry Focusing Array (PFA) - a set of 2 X-ray telescope, for a total effective area of 250 cm(exp. 2) at 2 keV, equipped with imaging gas pixel photoelectric polarimeters; the Wide Field Monitor (WFM) - a set of 3 coded mask wide field units, equipped with position-sensitive Silicon Drift Detectors, each covering a 90 degrees x 90 degrees field of view. The eXTP international consortium includes major institutions of the Chinese Academy of Sciences and Universities in China, as well as major institutions in several European countries and the United States. The predecessor of eXTP, the XTP mission concept, has been selected and funded as one of the so-called background missions in the Strategic Priority Space Science Program of the Chinese Academy of Sciences since 2011. The strong European participation has significantly enhanced the scientific capabilities of eXTP. The planned launch date of the mission is earlier than 2025.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN43898 , SPIE Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray Conference 2016; 26 Jun. 2016; Edinburgh; United Kingdom|Proceedings of SPIE (ISSN 0277-786X) (e-ISSN 1996-756X); 9905; 99051Q
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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: 2018-04-25
    Description: Author(s): Da-Jian Zhang, C. L. Liu, Xiao-Dong Yu, and D. M. Tong Quantifying coherence has received increasing attention, and considerable work has been directed towards finding coherence measures. While various coherence measures have been proposed in theory, an important issue following is how to estimate these coherence measures in experiments. This is a chall... [Phys. Rev. Lett. 120, 170501] Published Tue Apr 24, 2018
    Keywords: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 8
    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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  • 9
    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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  • 10
    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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