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  • 2000-2004  (2)
  • 1975-1979  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 1902-1908 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: X-ray photoelectron spectroscopy (XPS) was used to study the initial stages of surface oxidation of pseudomorphic Ni monolayers on Cu(111). Oxygen was adsorbed at 150 K followed by annealing the sample to 300 K and 600 K, respectively. For oxygen coverages between 0.4 ML and 2.0 ML we find little change in the peak shapes of the O 1s XPS signal. The Ni 2p3/2 spectra change, however, drastically: the onset of the oxidation is marked by the appearance of a peak doublet shifted with respect to the peak of metallic Ni. Based on these spectra we find a minimum oxygen coverage of 0.7 ML necessary for the onset of oxidation. The oxidation is nearly complete after the adsorption of about 2.0 ML oxygen. The exposure of different Ni coverages (0.5–2.0 ML) to oxygen shows that oxidation takes place only in the top-most Ni layer. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 26 (1977), S. 361-379 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Ursprung und Lebenslauf einer Gewitterlinie, die auf dem südafrikanischen Plateau beobachtet wurde, werden besprochen. Diese Gewitterlinie war mit einer Kaltfront assoziiert, was im allgemeinen in diesem Teil Südafrikas nicht der Fall ist. Die Gewitterlinie bewegte sich mit 35 km/h nach Nordosten, wesentlich schneller als die Front und mit einer mehr nördlichen Komponente als die Höhenwinde. Sie war mindestens 400 km lang, mit einem ununterbrochenen Mittelstück von 110 bis 130 km und nicht miteinander verbundenen Gewittern zu beiden Seiten. Im Raum von Johannesburg und Pretoria fiel Hagel von verschiedenen Gewitterzellen auf kleine Flächen. Radar Echos waren selten höher als 8 km über der Stationshöhe (1490 m über d. M.). Eine Gewitterzelle des Mittelstückes verstärkte sich in Intensität, Höhe und horizontaler Ausbreitung, während sie über Pretoria zog (die Echoobergrenze war zwischen 10 und 11 km); dabei fielen Hagelschlossen bis zu 3 cm Durchmesser. So wie die Nachbarzellen bewegte auch sie sich außergewöhnlich schnell und beinahe parallel zur Längsachse der Gewitterlinie (ostwärts mit 65 km/h) gemäß den Höhenwinden zwischen 600 und 500 mb. Der Echokern war auffällig nach Ostsüdosten geneigt was von der starken Windscherung verursacht wurde. Im Bereich dieses Überhanges fiel der Hagel bevor es am Boden anfing zu regnen.
    Notes: Summary The origin and life cycle of a squall line observed on the South African plateau are reviewed. The squall line was associated with a cold front whereas most squall lines in the subtropical part of the continent are not. It moved to the north-east and to the left of the upper winds at a speed of 35 km/h, which was considerably faster than that of the front. The squall line was at least 400 km long, with an unbroken central region of 110 to 130 km, on both sides of which were well-separated storms. In the area of Johannesburg and Pretoria, small patches of hail were produced by various cells. Radar echoes above 8 km AGL1 were rare. One cell of the unbroken portion while passing over Pretoria intensified rapidly, extended in all three dimensions (echo top up to 11 km AGL) and produced hailstones of up to 3 cm in diameter. Like its neighbouring cells, it moved exceptionally fast and almost parallel to the long axis of the squall line (eastewards at 65 km/h), following the winds between 600 and 500 mb. The echo core was tilted significantly towards east-south-east as a result of the strong wind shear. In the region of this overhang hailstones reached the ground before the onset of rain.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1501-1503 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Macroscopic quantum tunneling imposes an upper limit on the areal density of magnetic disk drives. We derive a general expression for this limit, and apply it to Co-alloy-based longitudinally recorded media, as well as to potential future media based on the high anisotropy material FePt. We estimate the temperature at which the switching rate due to quantum tunneling becomes comparable to the thermally activated switching rate. This is the lowest temperature to which a magnetic storage device can be cooled with the expectation of increasing the areal density by enhancing stability against spontaneous switching. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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