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  • 1
    Publication Date: 2019-07-17
    Description: We used remote-sensing and in situ measurements of surface accumulation rate, ice surface velocity, thickness and elevation to evaluate the mass budgets of grounded ice-flow regimes that form the Lambert Glacier-Amery Ice Shelf system. Three distinct drainage regimes are considered: the western and eastern margins of the ice shelf, and the southern grounding line at the major outlet glacier confluence, which can be identified with drainage zones 9, 11 and 10 respectively of Giovinetto and Zwally (2000). Our findings show the entire grounded portion of the basin is approximately in balance, with a mass budget of -4.2_9.8 Gt a-1. Drainages 9, 10 and 11 are within balance to the level of our measurement uncertainty, with mass budgets of -2.5_2.8 Gt a-1, -2.6_7.8 Gt a-1 and 0.9_2.3 Gt a-1, respectively. The region upstream of the Australian Lambert Glacier basin (LGB) traverse has a net mass budget of 4.4_6.3 Gt a-1, while the downstream region has -8.9_9.9 Gt a-1. These results indicate that glacier drainages 9, 10 and 11, upstream and downstream of the Australian LGB traverse, are in balance to within our measurement error.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 2
    Publication Date: 2019-07-17
    Description: We used in situ measurements and remote-sensing data sets to evaluate the mass budgets of the Lambert, Mellor and Fisher Glaciers and the basal melting and freezing rates beneath their flowbands on the Amery Ice Shelf. Our findings show the Lambert and Mellor Glaciers upstream of the ANARE Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a−1 and 2.1±2.4 Gt a−1, respectively, while the Fisher Glacier is approximately in balance. The upstream region as a whole has a positive imbalance of 5.9±4.9 Gt a−1. The three same glaciers downstream of the ANARE LGB traverse line are in negative imbalance, where the whole downstream region has a negative imbalance of −8.5±5.8 Gt a−1. Overall the mass budgets of the Lambert, Mellor, and Fisher Glaciers are close to balance, and the collective three-glacier system is also nearly in balance with a mass budget of −2.6±6.5 Gt a−1. The significant positive imbalances for the interior basin upstream of the ice-movement stations established in the early 1970s (GL line) reported previously are possibly due to an overestimate of the total accumulation and an underestimate of the ice flux through the GL line.The mean melting rate is −23.0±3.5 m ice a−1 near the southern grounding line, which decreases rapidly downstream, and transitions to refreezing at around 300 km from the southern extremity of the Amery Ice Shelf. Freezing rates along the flowbands are around 0.5±0.1 to 1.5±0.2 m ice a−1. The percentage of ice lost from the interior by basal melting beneath the flowbands is about 80%±5%. The total basal melting and refreezing beneath the three flowbands is 50.3±7.5 Gt ice a−1 and 7.0±1.1 Gt ice a−1, respectively. We find a much larger total basal melting and net melting than the results for the whole Amery Ice Shelf derived from previous modeling and oceanographic measurements.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
    Publication Date: 2019-07-17
    Description: The temporal and spatial variability of the annual accumulation rate and the mass budgets of five sub-basins of the Lambert GlacierAmery Ice Shelf system (LAS), East Antarctica, at high elevations are assessed using a variety of datasets derived from field measurements and modeling. The annual temporal variations of the accumulation rate for four cores from the west and east sides of the LAS are around ±34%. Decadal fluctuation of the accumulation from the DT001 firn core drops to ±10%, and the 30 year fluctuation to ±5%, which is assumed to contain the information about the regional and long-term trend in accumulation. The 15-point running mean of the annual accumulation rate derived from stake measurements can remove most of the high-frequency spatial variation so as to better represent the local accumulation. Model simulations show that the spatial variability of erosion/ deposition of snow by the wind has a noticeable impact on the surface mass balance at the higher parts of the LAS. Mass-budget estimates at high-elevation sub-basins of the LAS suggest drainage 9 has a negative imbalance of 0.7±0.4 Gt a1, Lambert and Mellor Glaciers have a positive imbalance of 3.9±2.1 and 2.1±2.4 Gt a1 respectively, and Fisher Glacier and drainage 11 are approximately in balance. The higher-elevation region as a whole has a positive mass imbalance of 4.4±6.3 Gt a1, which is consistent with the most recent radar altimetry assessment that shows an overall thickening over this region.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
    Publication Date: 2019-07-17
    Description: Antarctic snowfall exhibits substantial variability over a range of timescales, with consequent impacts on global sea level and the mass balance of the ice sheets. To assess how snowfall has affected the thickness of the ice sheets in Antarctica and to provide an extended perspective, we derived a 50-year time series of snowfall accumulation over the continent is derived by combining model simulations and observations primilarly from ice cores. There has been no statistically significant change in snowfall since the 1950s indicating that Antarctic precipitation is not mitigating global sea level rise as expected, despite recent winter warming of the overlying atmosphere.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1204-1208 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amorphous Ir–Si layer of several nanometers thick on Si(100)2×1 deposited at room temperature has been characterized by using both low energy electron diffraction (LEED) and synchrotron photoemission techniques. The double domain Si(100)2×1 LEED pattern disappeared when the deposited Ir onto Si(100) was higher than 1 ML. The ultrathin amorphous Ir–Si layer consisted of three different IrxSiy alloys, rather than a single homogeneous IrxSiy alloy as predicted by the conventionally used Gibbs free energy calculation in the solid state amorphization. The growth of the amorphous Ir–Si layer on Si(100) strongly depended on the interaction between Ir and Si(100) at the initial stage of Ir deposition. Three types of Ir–Si bonding formed on Si(100) at 1 ML Ir coverage and gradually evolved to be three different amorphous IrxSiy alloys. The growth mode of the amorphous Ir–Si layer was proposed to be the modified Stranski–Krastanov growth. The transition from layer-by-layer-like to island growth occurred at Ir coverage of ∼3 ML. The major amorphous IrxSiy alloy switched from Si to Ir rich when Ir coverage is over ∼3 ML. © 2002 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3707-3710 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of oxygen pressure on epitaxial quality of La0.3Sr1.7AlTaO6 (LSAT) films deposited by laser ablation on SrTiO3(100), LaAlO3(100), and MgO(100) substrates has been investigated. X-ray diffraction shows only (00l) peaks in the oxygen pressure range from 10−3 to 500 mTorr. However, the crystallinity of LSAT films is found to be sensitive to oxygen pressure and dependent on substrates. LSAT films on SrTiO3 have the narrowest full width at half maximum (FWHM) of 0.05° at 300 mTorr. The films on LaAlO3 exhibit a FWHM of 0.3° at 50–100 mTorr. On MgO substrate, significant improvement of crystallinity is achieved at 200–300 mTorr, but rocking curves give an FWHM of 0.70°–1.00° due to the large lattice mismatch between LSAT and MgO. Atomic force microscopy analyses demonstrate smooth LSAT surfaces without identified grains. Reflection high-energy electron diffraction studies suggest a two-dimensional growth mode for LSAT films on SrTiO3 and LaAlO3 and a three-dimensional growth mode for LSAT films on MgO. Cross-sectional high-resolution electron micrographs indicate that LSAT films on SrTiO3 and LaAlO3 have defect-free epitaxial structure and atomically flat interfaces. An 80 Å thick intermediate layer with partially disordering is observed between LSAT films and MgO substrates. © 2000 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2406-2408 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the superconducting properties of Nd(Ba1−xNdx)2Cu3O7−δ (Nd123, x≈0.1) single crystals grown by the traveling-solvent floating-zone method under 0.1% O2 in Ar atmosphere. An anomalous peak effect in the magnetization hysteresis (M–B) loop is observed in the Nd123 single crystals as well as in the Nd123 bulk crystals prepared by the oxygen-controlled melt growth (OCMG) method. The critical current density (Jc) of the Nd123 single crystals is 70 600 A/cm2 in 1.0 T at 77 K for the applied field perpendicular to the a-b plane. Uniform flux density distribution with the same shape as the sample is observed in the field perpendicular to the a-b plane by the magneto-optical flux-density observation. Finely dispersed white regions in the dark-field image due to Nd substitutions for Ba are observed in the Nd123 matrix by the transmission electron microscopy. The high Jc value of the Nd123 single crystals in the applied field is explained by the field-induced pinning centers caused by the Nd–Ba substitutions in the Nd123 matrix. © 1995 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2775-2777 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bi-based superconducting phases have been studied by transmission electron microscopy. The strong one-dimensional modulations in undoped and Ce-doped monoclinic Bi2 Sr2 CuO6 (2201) samples are different from one another. We have found a new 2201 phase containing Pb and Ca with orthorhombic symmetry in nominal (Bi0.90 Pb0.10 )2 Sr2 CaCu2 O8 crystals. Its structure with space group Bbmb and two-dimensional modulation are analogous to those of the Pb-doped higher members of the structural series Bi2 Sr2 Can−1 Cun O2n+4 . Hence, this new orthorhombic rather than the monoclinic 2201 phase should be the first member of the structural series.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1879-1881 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Carbon nanotube junctions are of great interest in the fundamental research and nanoelectronic applications. Identical carbon nanotube Y junctions have been successfully synthesized by pyrolysis of methane over cobalt supported on magnesium oxide. The Y junctions have very straight arms with uniform diameters, and the angles between the three arms are close to 120°. Based on the analysis on the structure of the Y junctions the growth mechanism has been discussed. The fact that all the Y junctions grow in a similar way may be very important in the development of nanoelectronic devices. © 2001 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1086-1088 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Patterned growth of freestanding carbon nanotube(s) on submicron nickel dot(s) on silicon has been achieved by plasma-enhanced-hot-filament-chemical-vapor deposition (PE-HF-CVD). A thin film nickel grid was fabricated on a silicon wafer by standard microlithographic techniques, and the PE-HF-CVD was done using acetylene (C2H2) gas as the carbon source and ammonia (NH3) as a catalyst and dilution gas. Well separated, single carbon nanotubes were observed to grow on the grid. The structures had rounded base diameters of approximately 150 nm, heights ranging from 0.1 to 5 μm, and sharp pointed tips. Transmission electron microscopy cross-sectional image clearly showed that the structures are indeed hollow nanotubes. The diameter and height depend on the nickel dot size and growth time, respectively. This nanotube growth process is compatible with silicon integrated circuit processing. Using this method, devices requiring freestanding vertical carbon nanotube(s) such as scanning probe microscopy, field emission flat panel displays, etc. can be fabricated without difficulty. © 1999 American Institute of Physics.
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