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  • 1
    Electronic Resource
    Electronic Resource
    Deactivation of a Palladium-Supported Alumina Catalyst by Hydrogen Sulfide during the Oxidation of Methane (1994)
    s.l. : American Chemical Society
    Langmuir 10 (1994), S. 3567-3570 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00022a032
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  • 2
    Electronic Resource
    Electronic Resource
    Ultimate resolution electron energy loss spectroscopy at H/Si(100) surfaces (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 6636-6643 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have re-investigated the well-studied hydrogen covered Si(100) surface using high resolution electron energy loss spectroscopy (HREELS) with a spectral resolution down to 13 cm1, representing an improvement by a factor of 3–4 compared to earlier work. For the first time in HREELS, it has been possible to clearly distinguish between the stretching vibrations of H-Si-Si-H units on monohydride surfaces with a 2×1 low energy electron diffraction pattern, on the one hand, and SiH2 units on dihydride surfaces with 1×1 symmetry on the other hand, the two being shifted by 5 cm-1 with respect to each other, in good agreement with results from infrared spectroscopy. Furthermore, we find trihydride units even for relatively low exposures beyond monohydride saturation coverage from their distinct stretching frequencies, and this points towards early etching stages. The question of the scattering mechanism applicable in our experiments is discussed. Since there are no spectral limitations in HREELS, we can analyze the bending and scissor vibrations with similar accuracy as the stretching vibration. Again, we observe fine structure in our loss peaks, the umbrella mode, for example, giving once more evidence for trihydride species at the surface. The complicated line shape of all vibrational modes can thus be used to deduce detailed structural information about the surface atomic structure, opening up entirely new possibilities by employing HREELS for the structural characterization of (silicon) surfaces with atomic hydrogen as a local probe. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369038
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  • 3
    Electronic Resource
    Electronic Resource
    Boric Acid in the Aqueous Carboxylation of m-Aminophenol to p-Aminosalicylic Acid1 (1958)
    s.l. : American Chemical Society
    The @journal of organic chemistry 23 (1958), S. 1422-1424 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo01104a005
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  • 4
    Electronic Resource
    Electronic Resource
    Repeated latex aeroallergen challenges employing a hooded exposure chamber: safety and reproducibility (2001)
    Copenhagen : Munksgaard International Publishers
    Allergy 56 (2001), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Bronchial, nasal, and conjunctival challenges are useful for clarifying discordant clinical history (Hx) and skin and/or serologic tests and in assessing semiquantitative changes in biologic sensitivity over time. The objective of this study was to determine the safety and reproducibility of repeated latex-allergen challenges with a hooded exposure chamber (HEC). Methods: The HEC system comprises a powered forced-air respirator with a fitted face shield and hood that uses glove-derived latex-allergen associated cornstarch particles (LAC) to expose simultaneously the conjunctiva, nose, and lungs. Serial control and incremental LAC challenges are conducted until an endpoint based on upper and/or lower respiratory tract symptoms and peak expiratory flow rates is reached. Six latex-allergic (Hx and puncture skin test [PST]- and 5/6 radioallergosorbent test [RAST]-positive) subjects were challenged on three separate occasions at least 2 weeks apart. Serial latex PST midpoints and serum anti-latex IgE by RAST were monitored at each visit and at a fourth follow-up visit. Results: All subjects responded to LAC, but not to air or control cornstarch administered as controls. All responses were confined to mild symptoms of allergic rhinoconjunctivitis and/or asthma that either resolved spontaneously or were reversed with inhaled albuterol. No subject experienced a systemic or delayed reaction. There were no significant changes in the endpoint LAC doses over the three challenge visits (P〉0.2). The mean coefficient of variation for log2 endpoints within-subjects was 17.3±17.2% (SD). The serum latex-specific IgE was not significantly boosted by the three challenges (P〉0.2). The concentration of latex extract necessary to produce an 8-mm wheal by PST was not significantly changed during the study (P〉0.1), indicating that latex sensitivity was not affected by the repeated LAC exposures. Conclusions: The results of this study indicate that repeated HEC latex-allergen challenges are both reproducible and safe, and do not increase latex sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1398-9995.2001.00075.x
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  • 5
    Electronic Resource
    Electronic Resource
    Caribou movement as a correlated random walk (2000)
    Springer
    Oecologia 123 (2000), S. 364-374 
    Details
    ISSN: 1432-1939
    Keywords: Key words Caribou ; Correlated random walk ; Movement ; Rangifer tarandus ; Ungulate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Movement is a primary mechanism coupling animals to their environment, yet there exists little empirical analysis to test our theoretical knowledge of this basic process. We used correlated random walk (CRW) models and satellite telemetry to investigate long-distance movements of caribou, the most vagile, non-volant terrestrial vertebrate in the world. Individual paths of migratory and sedentary female caribou were quantified using measures of mean move length and angle, and net squared displacements at each successive move were compared to predictions from the models. Movements were modelled at two temporal scales. For paths recorded through one annual cycle, the CRW model overpredicted net displacement of caribou through time. For paths recorded over shorter intervals delineated by seasonal behavioural changes of caribou, there was excellent correspondence between model predictions and observations for most periods for both migratory and sedentary caribou. On the smallest temporal scale, a CRW model significantly overpredicted displacements of migratory caribou during 3 months following calving; this was also the case for sedentary caribou in late summer, and in late winter. In all cases of overprediction there was significant positive autocorrelation in turn direction, indicating that movements were more tortuous than expected. In one case of underprediction, significant negative autocorrelation of sequential turn direction was evident, indicating that migratory caribou moved in straightened paths during spring migration to calving grounds. Results are discussed in light of known migration patterns and possible limiting factors for caribou, and indicate the applicability of CRW models to animal movement at vast spatial and temporal scales, thus assisting in future development of more sophisticated models of population spread and redistribution for vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420051023
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  • 6
    Electronic Resource
    Electronic Resource
    Winter foraging by muskoxen: a hierarchical approach to patch residence time and cratering behaviour (1995)
    Springer
    Oecologia 104 (1995), S. 39-44 
    Details
    ISSN: 1432-1939
    Keywords: Foraging ; Muskoxen ; Scale ; Snow ; Patch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the temporal and spatial patterns of feeding behaviours of muskoxen during winter in the High Arctic. Pawing motions (to uncover forages beneath snow cover) were strongly aggregated into temporal bouts. Similarly, feeding stations (areas exploitable without motion of the forelegs) were aggregated into spatial patches. Muskoxen responded to greater snow accumulation at feeding sites by increasing the rates of pawing, rates of pawing bouts, number of pawing strokes per bout, and station residence times. Patch residence times showed little relationship to snow or forage abundance because, as muskoxen increased station residence times, they decreased the number of stations per patch. Muskoxen displaced one another from feeding stations more frequently as snow thickness and group size increased. Time spent at feeding stations was positively correlated to travel costs, in accordance with the marginal value model of patch residence. The model was not supported, however, at the scale of the feeding patch. The results indicate that behavioural responses of muskoxen to foraging conditions differ across scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365560
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  • 7
    Electronic Resource
    Electronic Resource
    Understanding and tuning the epitaxy of large aromatic adsorbates by molecular design (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 425 (2003), S. 602-605 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] If the rich functionality of organic molecules is to be exploited in devices such as light-emitting diodes or field-effect transistors, interface properties of organic materials with various (metallic and insulating) substrates must be tailored carefully. In many cases, this calls for ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01901
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  • 8
    Electronic Resource
    Electronic Resource
    Microscopic structure of semiconductor surfaces (1990)
    Springer
    Applied physics 51 (1990), S. 305-316 
    Details
    ISSN: 1432-0630
    Keywords: 81.40 ; 82.30 ; 82.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract To study the initial reaction steps of hydrogen, oxygen, and water, on differently prepared single crystal surfaces of silicon, germanium/silicon alloys, indium phosphide and gallium arsenide, we used high-resolution electron energy-loss spectroscopy (HREELS) in combination with low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Very recently, we started a program on the hydrogenation of III–V compound semiconductors, and on the oxidation of Si and III–V compound semiconductors, using alkali metals as a catalyst. This paper summarizes the present stage of our investigations, describing in particular aspects of the microscopic structure of differently prepared semiconductor surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324310
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  • 9
    Electronic Resource
    Electronic Resource
    High-resolution electron energy-loss spectroscopy at epitaxially grown GaAs (1 0 0 ) A comparison between theory and experiment (1995)
    Springer
    Applied physics 60 (1995), S. 567-572 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 68.55; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  High-Resolution Electron Energy-Loss Spectroscopy (HREELS) is shown to be a very sensitive tool to investigate the space-charge regime of n- respectively p-type semiconductors. The most simple model we applied to fit experimental spectra is based on a step-like distribution of free carriers with the Drude dielectric response function. In this case, the dispersion of surface plasmon excitations is neglected, but it is considered in the Thomas-Fermi and the Debye-Hückel models. We use these models to fit HREELS-spectra, obtained from heavily Si-doped GaAs(1 0 0), which was grown by Molecular Beam Epitaxy (MBE). A comparison shows that the Drude model overestimates both the free-carrier concentration and the plasmon damping factor. The use of a more realistic smooth free-carrier profile, obtained by the self-consistent solution of the Schrödinger and Poisson equations, leads to plasmon excitations with lower frequencies. Besides Ohmic damping, the calculations show that Landau damping should be incorporated in order to obtain a better fit, particularly at intermediate frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538530
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  • 10
    Electronic Resource
    Electronic Resource
    High-resolution electron energy-loss spectroscopy at epitaxially grown GaAs(100) (1995)
    Springer
    Applied physics 60 (1995), S. 567-572 
    Details
    ISSN: 1432-0630
    Keywords: 68.55 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract High-Resolution Electron Energy-Loss Spectroscopy (HREELS) is shown to be a very sensitive tool to investigate the space-charge regime of n-respectively p-type semiconductors. The most simple model we applied to fit experimental spectra is based on a step-like distribution of free carriers with the Drude dielectric response function. In this case, the dispersion of surface plasmon excitations is neglected, but it is considered in the Thomas-Fermi and the Debye-Hückel models. We use these models to fit HREELS-spectra, obtained from heavily Si-doped GaAs(100), which was grown by Molecular Beam Epitaxy (MBE). A comparison shown that the Drude model overestimates both the free-carrier concentration and the plasmon damping factor. The use of a more realistic smooth free-carrier profile, obtained by the self-consistent solution of the Schrödinger and Poisson equations, leads to plasmon excitations with lower frequencies. Besides Ohmic damping, the calculations show that Landau damping should be incorporated in order to obtain a better fit, particularly at intermediate frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538530
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    Paper (German National Licenses)
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