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  • 1
    Electronic Resource
    Electronic Resource
    Metal Schottky barrier contacts to alpha 6H-SiC (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4757-4760 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of Schottky barrier contacts to n-type 6H-SiC for a number of metals chosen to include a variety of physical and chemical properties has been investigated. The metals (Pd, Au, Ag, Tb, Er, Mn, Al, and Mg) were deposited onto room temperature surfaces terminated with a submonolayer coverage of oxygen. The metal/6H-SiC interface chemistry and Schottky barrier height φB during contact formation were obtained with x-ray photoemission spectroscopy; the electrical properties of subsequently formed thick contacts were characterized by current-voltage and capacitance-voltage techniques. The øB values for these metals extend over a wide 1.3 eV range. To a varying degree φB depends on the 6H-SiC crystal face (Si vs C). Mg and Al (Si face of latter) have φB=0.3 eV, a value which is suitable for nonalloyed ohmic contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352086
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  • 2
    Electronic Resource
    Electronic Resource
    Hall measurements as a function of temperature on monocrystalline SiC thin films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6375-6381 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hall measurements were conducted at temperatures up to 1000 K on unintentionally doped n-type β(3C)- and α(6H)-SiC thin films epitaxially grown on both on-axis and vicinal Si (100) and α(6H)-SiC (0001) by chemical vapor deposition. The carrier concentration versus temperature data were analyzed using a compensation model. The β-SiC films grown on Si were highly compensated (NA/ND=0.73–0.98). The compensation ratio was not as large in the SiC films grown on α-SiC (NA/ND=0.36, for β-SiC on α-SiC, and 0.02, for α-SiC on α-SiC). The donor ionization energy for β-SiC on Si was calculated to be 14–21 meV. Analogous values for β- and α-SiC films on α-SiC were 33 and 84 meV, respectively. These values are smaller than those for N determined from photoluminescence studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345159
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Visual response characteristics of neurons in the nucleus isthmi magnocellularis and nucleus isthmi parvocellularis of pigeons (1991)
    Springer
    Experimental brain research 87 (1991), S. 624-633 
    Details
    ISSN: 1432-1106
    Keywords: Pigeons ; Nucleus isthmi (Ipc and Imc) ; Extracellular recording ; Direction and orientation selectivity ; Retinotopography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The visual response characteristics of single cells in the nucleus isthmi (NI) of pigeons were investigated using standard extracellular recording techniques. The results show that both major components of NI, the parvocellular NI (Ipc) and the magnocellular NI (Imc), have a tight retinotopic organization where nasal regions of the visual field are mapped onto the rostral poles of Ipc and Imc, and temporal regions of the visual field are mapped onto the caudal poles. The more ventral regions of these nuclei receive input from more inferior regions of visual space. The receptive fields (RFs) of both Ipc and Imc are large and oval-shaped, and their long axis is oriented vertically in the visual field. Most RFs are distributed on the contralateral visual horizon, and no binocular responses were found in either Ipc or Imc. All of the excitatory RFs of NI cells were surrounded by large inhibitory regions which participated in the dramatic modulation of the driven visual response when a large background pattern was moved across this zone. Although both Ipc and Imc neurons are driven best by small dark spots, some of them also show orientation selectivity to bars which may result from their ovalshaped RF (74% of Imc cells, 20/38, were orientation selective as compared to 10% of the Ipc cells, 3/30). It is suggested that some tectal cells with small RFs, and which originate from a vertically oriented zone may converge onto a single NI neuron to produce the elliptical shaped receptive fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227087
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanisms of iron acquisition from siderophores by microorganisms and plants (1991)
    Springer
    Plant and soil 130 (1991), S. 179-198 
    Details
    ISSN: 1573-5036
    Keywords: chelate ; ecology ; membrane transport ; plant iron nutrition ; plant-microbial interactions ; rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Most bacteria, fungi, and some plants respond to Fe stress by the induction of high-affinity Fe transport systems that utilize biosyrthetic chelates called siderophores. To competitively acquire Fe, some microbes have transport systems that enable them to use other siderophore types in addition to their own. Bacteria such as Escherichia coli achieve this ability by using a combination of separate siderophore receptors and transporters, whereas other microbial species, such as Streptomyces pilosus, use a low specificity, high-affinity transport system that recognizes more than one siderophore type. By either strategy, such versatility may provide an advantage under Fe-limiting conditions; allowing use of siderophores produced at another organism's expense, or Fe acquisition from siderophores that could otherwise sequester Fe in an unavailable form. Plants that use microbial siderophores may also be more Fe efficient by virtue of their ability to use a variety of Fe sources under different soil conditions. Results of our research examining Fe transport by oat indicate parity in plant and microbial requirements for Fe and suggest that siderophores produced by root-colonizing microbes may provide Fe to plants that can use the predominant siderophore types. In conjunction with transport mechanisms, ecological and soil chemical factors can influence the efficacy of siderophores and phytosiderophores. A model presented here attempts to incorporate these factors to predict conditions that may govern competition for Fe in the plant rhizosphere. Possibly such competition has been a factor in the evolution of broad transport capabilities for different siderophores by microorganisms and plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011873
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  • 5
    Electronic Resource
    Electronic Resource
    Small-scale crack blunting at a bimaterial interface with Coulomb friction (1991)
    Springer
    International journal of fracture 52 (1991), S. 293-306 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The deformation field near the tip of a tensional crack impinging upon a normally loaded bimaterial frictional interface is studied. By allowing the two materials to slide with respect to each other along the interface the high stresses around the crack tip are relaxed. The region of slip as well as the stress distribution inside the slip zone is obtained as a function of the far field loading parameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034085
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  • 6
    Electronic Resource
    Electronic Resource
    Vertical stress distribution due to an arbitrarily shaped foundation using triangulation and an analytical expression for a triangular loaded region (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 15 (1991), S. 51-60 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Using the basic Boussinesq's equation, the expression for the vertical stress distribution (σz) underneath any point on the ground surface due to a general triangular loaded region in a preferred orientation with a linearly varied loading has been successfully derived. When the triangle is not in a preferred orientation, a simple axis transformation is required and the expression will be equally applicable. Based on this expression, σz due to an arbitrarily shaped loaded foundation can simply be determined by first triangulating the loaded area and summing up the contributions from each generated triangular region. The procedures for triangulating and calculating the stress distribution can be simply automated through computer programs.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610150105
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  • 7
    Electronic Resource
    Electronic Resource
    A numerical model for wave scattering problems in infinite media due to p- and sv-wave incidences (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1661-1682 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Based on elastic wave motion theory and the superposition concept, a numerical model for wave scattering problems in infinite media due to P-wave and SV-wave incidences is presented in this paper. Since this model is based on a coupled system of finite and infinite elements for simulating wave propagation in infinite media, the complexity of geometry and the variability of material properties in the foundation can be realistically simulated. Through a systematic study of the characteristics of a plane harmonic P-wave and SV-wave incidences on a fixed boundary, the concept of stress increase factors and stress factors which can be used to calculate the generalized stresses on the wave input boundary due to the SV-wave and P-wave incidences is also proposed. The effects of incident wave mode, incident angle and Poisson's ratio in the foundation on the stress increase factors and the stress factors have been studied in detail. Finally, the proposed model has been applied to a half-plane foundation and a semi-circular canyon to calculate SV-wave and P-wave scattering problems. The numerical results obtained show good agreement with the theoretical results and Wong's analytical results.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330808
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  • 8
    Electronic Resource
    Electronic Resource
    Discussion on: Vertical stress distribution due to an arbitrarily shaped foundation using triangulation and an analytical expression for a triangular loaded region (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 16 (1992), S. 377-381 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610160506
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