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  • 1
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    ESA
    In:  EPIC3Proceedings of OceanObs09: Sustained Ocean Observations and Information for Society (Vol. 2), Venice, Italy, 21-25 September 2009, Hall, J., Harrison D.E. & Stammer, D., Eds., ESA Publication WPP-306., Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society (Vol. 2), ESA, Public
    Publication Date: 2017-07-04
    Description: The tools of geodesy have the potential to transform the Ocean Observing System. Geodetic observations are unique in the way that these methods produce accurate, quantitative, and integrated observations of gravity, ocean circulation, sea surface height, ocean bottom pressure, and mass exchanges among the ocean, cryosphere, and land. These observations have made fundamental contributions to the monitoring and understanding of physical ocean processes. In particular, geodesy is the fundamental science to enable determination of an accurate geoid model, allowing estimate of absolute surface geostrophic currents, which are necessary to quantify ocean’s heat transport. The present geodetic satellites can measure sea level, its mass component and their changes, both of which are vital for understanding global climate change. Continuation of current satellite missions and the development of new geodetic technologies can be expected to further support accurate monitoring of the ocean. The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) provides the means for integrating the geodetic techniques that monitor the Earth's time-variable surface geometry (including ocean, hydrologic, land, and ice surfaces), gravity field, and Earth rotation/orientation into a consistent system for measuring ocean surface topography, ocean currents, ocean mass and volume changes. This system depends on both globally coordinated ground-based networks of tracking stations as well as an uninterrupted series of satellite missions. GGOS works with the Group on Earth Observations (GEO), the Committee on Earth Observation Satellites (CEOS) and space agencies to ensure the availability of the necessary expertise and infrastructure. In this white paper, we summarize the community consensus of critical oceanographic observables currently enabled by geodetic systems, and the requirements to continue such measurements. Achieving this potential will depend on merging the remote sensing techniques with in situ measurements of key variables as an integral part of the Ocean Observing System.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Book , peerRev
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2659-2666 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting Nb/AlOx/Nb tunnel junctions have been fabricated on Si membrane windows of only 1.2 μm thickness acting as substrates. The membrane windows with areas between (600 μm)2 and (1200 μm)2 remained undamaged after the different fabrications steps. The tunnel junctions positioned on the membranes and the bulk silicon substrate have very similar current-voltage characteristics. Using low-temperature scanning electron microscopy the two-dimensional heat diffusion process has been imaged in the detector geometry. This two-dimensional heat diffusion leads to a new cryoelectronic radiation detector concept combining high energy and spatial resolution with a large effective detector area. Applications of this detector concept include soft-x-ray spectroscopy and the nuclear β decay.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 584-591 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The chemical composition of the surfaces and interfaces of NbN-MgO-NbN trilayers has been studied by x-ray photoelectron spectroscopy during the fabrication of the trilayer without breaking the vacuum. The NbN and MgO layers were prepared by rf magnetron sputtering. The results of the chemical analysis have been correlated to the electrical characteristics of the completed NbN-MgO-NbN tunnel junctions. During the deposition of the MgO barrier layer the presence of a high amount of energetic oxygen ions and atoms in the sputtering plasma results in a strong plasma oxidation of the NbN base electrode and, hence, in mixed Nb2O5-MgO barriers. The oxygen ions and atoms are generated by the dissociation of the target material and the water of the background pressure. Their amount was found to increase with increasing argon pressure during the MgO sputtering process. Also, adsorption layers of hydroxides on the MgO-target result in the formation of an uncontrollable amount of niobium oxide components at the interface between the NbN base electrode and the MgO barrier. The current-voltage characteristics of tunnel junctions with such barriers show large subgap leakage currents. Pure MgO barriers can be prepared by reducing the oxygen bombardment of the NbN films during the MgO deposition. Pure MgO barriers are oxygen deficient and easily adsorb hydroxides. These hydroxides react with the first layers of the NbN top electrode to NbO2 and NbO thereby reducing and broadening the sumgap value of the tunnel junctions. Tunnel junctions with pure MgO barriers of a nominal thickness of less than 2 nm usually have current-voltage characteristics indicative for microshorts. A special annealing procedure of the NbN-MgO bilayers prior to the deposition of the top electrode desorbs the hydroxides, transforms Mg(OH)2 to MgO without forming metallic magnesium and prevents the formation of intermediate layers of niobium suboxides and metallic shorts.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5411-5418 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have successfully fabricated superconducting nanobridges and grain-boundary junctions from epitaxial YBa2Cu3O7−δ thin films with thickness between 20 and 30 nm and width down to ∼100 nm. The patterning process turned out to severely deteriorate the transport properties resulting in structural damage, corrosion, and oxygen loss. The most crucial steps are the baking procedure used to cure the electron beam resist, the resist development, and the ion beam etching process. By optimizing these steps and applying a suitable post-treatment procedure a significant enhancement of the sample quality could be achieved. An ultraviolet light assisted oxygenation procedure after the patterning process enabled us to achieve superconducting transition temperatures between 80 and 87 K and critical current densities at 4.2 K up to 4×107 A cm−2 for the nanobridges and 5×103–2×105 A cm−2 for the grain boundary junctions. At 4.2 K junctions with width down to 100 nm corresponding to a junction area down to 2.3×10−3 μm2 showed superconductivity. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 86 (1964), S. 2595-2600 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 8005-8015 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using Low Temperature Scanning Electron Microscopy (LTSEM) we have studied the spread of the critical current values in one- and two-dimensional arrays of high-Tc grain boundary Josephson junctions (GBJs). For series arrays the critical current values and the magnetic field dependences of all GBJs within the array could be imaged by LTSEM. Our measurements showed that part of the spread of the critical current values derived from measurements of the current-voltage characteristics is caused by variations of the local magnetic field at the junction position. For bicrystal GBJs a Gaussian distribution of the critical current values with a spread as small as ±20% was found. For the investigated step-edge and biepitaxial GBJs the spread of the critical current values was considerably larger. The LTSEM technique also was used to study the spatial homogeneity of the critical current density of the different types of YBa2Cu3O7−δ grain boundary Josephson junctions with a spatial resolution of 1μm. Whereas the critical current density of bicrystal GBJs showed only small variations on this length scale, strong inhomogeneities were found for step-edge and biepitaxial GBJs. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4581-4587 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature and the dc magnetic field dependence of the effective surface impedance Zs of epitaxial YBa2Cu3O7−x thin films on [001] tilt SrTiO3 bicrystals with tilt angles of 36.8° and 24° have been investigated at 87 GHz. The effects of the grain boundaries become increasingly important with decreasing characteristic voltage IcRn and increasing unit areal normal resistance RnA. The boundaries can consistently be described with a resistively shunted Josephson transmission line model taking into account the effect of finite film thickness. Thermal or magnetic loading of the junction leads to additional losses, whereas the effective microwave penetration depth exhibits a specific extremal behavior. From the magnetic response of Zs at 4.2 K, the junction lower critical fields as well as the values of IcRn and RnA can be deduced. The data agree well with dc transport measurements.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1843-1845 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three-terminal YBa2Cu3O7−δ thin film devices based on a parallel array of grain boundary Josephson junctions were fabricated. The multiloop superconducting device is controlled by the magnetic field generated by a current Ictrl, which modulates the critical current Ic through the Josephson junction array. For these devices a current gain ranging between 2 at 77 K and 5 at 30 K was obtained. The spatial homogeneity of the device properties was studied by low-temperature scanning electron microscopy and by the determination of the supercurrent correlation function. Comparing the measured and the theoretically expected supercurrent correlation function shows that the device characteristics agree well with those expected from the device geometry.
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