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  • 1
    Electronic Resource
    Electronic Resource
    The mechanism of kinetic oscillations in catalytic oxidation of CO on Pt(210) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6162-6170 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Under isothermal conditions at low pressure (10−4 Torr), the catalytic oxidation of CO on a Pt(210) surface exhibits kinetic oscillations which have been investigated using Video-LEED, measurement of the CO2 production rate and the variation of work function. An induction period of ∼30 to 60 min, which has been shown to be due to a facetting of the surface exists before the appearance of kinetic oscillations. If reaction conditions are chosen which correspond to the high rate branch of Langmuir Hinshelwood kinetics, the Pt(210) surface facets into (310) and (110) orientations. The facetting process is associated with a decrease in catalytic activity caused by a lowering of the oxygen sticking coefficient. In situ LEED experiments demonstrated that the oscillations in the reaction rate are associated with periodic intensity variations of the half-order LEED beams belonging to (110) facets. Thus, the oscillations appear to be driven by the CO-induced 1×1(arrow-right-and-left)1×2 phase transition on (110) facets in the same way as has been verified for the system Pt(110)/CO+O2. The involvement of a facetting process explains the characteristic properties of kinetic oscillations on Pt(210) such as the relatively low high-temperature limit of ≈500 K, the existence of an induction period and the period length which is on the order of minutes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461584
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetic oscillations in catalytic CO oxidation on a cylindrical Pt single crystal surface (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 5193-5204 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A Pt single crystal of cylindrical shape (axis II [001]) whose surface exhibits all orientations of the [001] zone has been used to study coupling effects between orientations which exhibit kinetic oscillations in catalytic CO oxidation. On the clean surface, one can distinguish between an orientational range in between (110) and (320) which exhibits a 1×2 reconstruction, a nonreconstructed surface range around (210) and a hex reconstructed surface range around (100). Structural transitions proceed continuously via atomic steps between (110) and (210), while the orientational range extending from (210) to (100) is faceted. With a rotatable Kelvin probe, the orientational dependence of the work function could be followed. The results revealed that the variation of the oxygen sticking coefficient sO2 displays a mirror-like behavior with respect to the work function variation of the clean surface such that the orientation with the lowest work function (210) exhibits the highest sO2. Kinetic oscillations were studied in the 10−5 and 10−4 Torr range. By means of two Kelvin probes, the Δφ oscillations could be followed simultaneously at two different orientations, while the integral behavior of the cylinder surface was monitored via the CO2 production rate. A strong broadening of the oscillatory region in parameter space, as compared to a flat surface, was detected for the oscillatory range around (100). In the vicinity of this orientation, spatial coupling is provided via reaction fronts which propagate from (210) toward (110). Gas-phase coupling is only observed with the (110) orientations. Prolonged oscillation experiments cause faceting resulting in an increase of catalytic activity around (100), while the orientations around (210) lose catalytic activity by faceting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463818
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  • 3
    Electronic Resource
    Electronic Resource
    Plasmon excitation modes in nanowire arrays (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2733-2736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron energy loss spectrometry and energy-filtered transmission electron microscopy reveal characteristic plasmon excitations in both isolated Bi nanowires and an array of Bi nanowires within an Al2O3 matrix. As the average nanowire diameter decreases from 90 to 35 nm, both the volume plasmon energy and peak width increase. In addition, a lower-energy excitation is present in a very localized region at the Bi–Al2O3 interface. These results are discussed in the context of quantum confinement and the influence of interfaces on the electronic properties of nanocomposite materials. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337940
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  • 4
    Electronic Resource
    Electronic Resource
    A multipurpose scanning probe microscope (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2591-2594 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile scanning probe microscope is described that offers the combination of use for imaging in ambient atmosphere, under a liquid, and in ultrahigh vacuum. In contrast to any home-built or commercial instruments available at present, these features are realized here in a single instrument. A compact size instrument is achieved by a piezoelectrically driven sample approach mechanism. The sample or the tip can be scanned providing two separate scanning modes which cover a total scan range from 20 A(ring) to 10 μm. An area of 30 mm2 can be scanned without breaking the tip/sample contact. Exchangeable tip mounts facilitate an easy change between prealigned tips. The design of the scanning force microscope is based on the optical deflection method for imaging in the contact mode. The microscope can be used as a scanning tunneling microscope as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143872
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  • 5
    Electronic Resource
    Electronic Resource
    Seed Availability as a Limiting Factor in Forest Recovery Processes in Costa Rica (2000)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 8 (2000), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abandoned pastures and secondary forests are increasingly prominent features of tropical landscapes. Forest regrowth on abandoned pastures is generally slow and virtually limited to regeneration from seeds from external sources, since agricultural activities alter site conditions. We hypothesize that seed availability is a major limiting factor in forest recovery on abandoned pastures. This hypothesis was tested by studying the seed bank, seed rain, and seed predation in a small pasture (1 ha) situated in a forest-pasture mosaic in northwestern Costa Rica. The tree seed density in the pasture seed bank was much lower (21/m2) than the density in the seed bank of a neighboring secondary forest (402/m2). Within a period of five weeks, 23 tree seeds entered the pasture by seed rain. This number is low compared to densities found in closed forests but higher than densities reported in other studies where virtually no seeds were found beyond 20 m from the forest edge. Possibly the small size of the pasture with seed sources nearby and the small-scale landscape mosaic enhance seed dispersal. Predation limits the seed density in pastures, with 42% of the woody species consumed by predators. The low seed density in the seed bank, and hampered recruitment combined with significant losses, pose severe restrictions to forest recovery on abandoned pastures. Moderate land use, and small sized clearings with seed sources nearby may increase the pace of recovery. Nevertheless, forest establishment may still take a considerable time. Thus, enlarging the available pool of species may be a worthwhile management strategy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100x.2000.80056.x
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  • 6
    Electronic Resource
    Electronic Resource
    Site-specific surface interaction of adsorbed water and halogens on copper indium selenide (CuInSe2) surfaces (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 782-790 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100181a048
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  • 7
    Electronic Resource
    Electronic Resource
    High resolution zero kinetic energy photoelectron spectroscopy of benzene and determination of the ionization potential (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4737-4744 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the direct high-resolution determination of the ionization potential of benzene and the observation of rotational structure in the vibronic ground state of the benzene ion. We employ a new technique of two-color high-resolution zero kinetic energy photoelectron spectroscopy (ZEKE-PES) via selection of an intermediate resonant (neutral) state. The ZEKE-PES method allows for the investigation of rotationally resolved photoionization dynamics and the direct high-precision determination of ionization potentials, the precision being derived directly from the laser wavelength calibration. For benzene we determine an IP of 74 555.0±0.4 cm−1. We compare this method to ionization potential measurements from ion yield measurements under various conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452694
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  • 8
    Electronic Resource
    Electronic Resource
    Theoretical crack path prediction (2005)
    PO Box 1354, 9600 Garsington Road, Oxford OX4 2XG, UK. : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 28 (2005), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In many practical cases, the crack growth leads to abrupt failure of components and structures. For reasons of a reliable quantification of the endangerment due to sudden fracture of a component, therefore, it is of enormous importance to know the threshold values, the crack paths and the growth rates for the fatigue crack growth as well as the limiting values for the beginning of unstable crack growth (fracture toughness). This contribution deals with the complex problem of a—however initiated—crack, that is subjected to a mixed-mode loading. It will present the hypotheses and concepts, which describe the superposition of Mode I and Mode II (plane mixed mode) as well as the superposition of all three modes (Mode I, II and III) for spatial loading conditions. Those concepts admit a quantitative appraisal of such crack situations and a characterization of possible crack paths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.2004.00855.x
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  • 9
    Electronic Resource
    Electronic Resource
    Mutations in MVK , encoding mevalonate kinase, cause hyperimmunoglobulinaemia D and periodic fever syndrome (1999)
    [s.l.] : Nature America Inc.
    Nature genetics 22 (1999), S. 175-177 
    Details
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Hyperimmunoglobulinaemia D and periodic fever syndrome (HIDS; MIM 260920) is an autosomal recessive disorder characterized by recurrent episodes of fever associated with lymphadenopathy, arthralgia, gastrointestinal dismay and skin rash. Diagnostic hallmark of HIDS is a constitutively elevated ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/9691
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  • 10
    Electronic Resource
    Electronic Resource
    Neuraminic acid-specific modification and tritium labelling of gangliosides
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism 486 (1977), S. 145-160 
    Details
    ISSN: 0005-2760
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2760(77)90079-0
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