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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8844-8846 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation by photoluminescence (PL) spectroscopy of cross-barrier recombination between spatially separated two-dimensional electron and hole gases confined respectively in the quantum well (QW) and collector accumulation layer of a GaAs/AlGaAs double-barrier resonant tunneling structure. At the onset of the n=3(E3) resonance in the current–voltage characteristic, the energy of the cross-barrier transition Ecr is found to coincide with that of the PL peak arising from recombination of electrons from the E3 confined level in the QW with n=1 confined hole states (E3lh recombination). Similarly, at the onset of the E4 resonance, Ecr≈E4lh. We show that this behavior arises as a consequence of the symmetrical potential distribution within the structure at the onsets of the resonances. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2141-2143 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This letter reports the observation of intersubband electroluminescence from a single-period resonant tunneling structure. Intersubband emission (λ(approximate)8.4 μm), with a full width at half maximum of 7 meV, was observed from a GaAs/AlGaAs triple barrier structure with quantum well widths of 66 and 33 Å. The emission was coupled out of the sample by a metallic grating with a period of 5 μm deposited on the surface. The intensity of emission follows the resonance behavior in the I–V characteristics. As the temperature increases from 10 to 200 K, the emission intensity decreases monotonically by a factor of ∼2 and the emission energy shifts down slightly (ΔE(approximate)2.7 meV). The temperature dependence of the emission energy is explained by a combination of thermal broadening of the electron distribution and the nonparabolicity of the conduction bands. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 54 (1998), S. 876-879 
    ISSN: 1420-9071
    Keywords: Key words. Ladybird beetle; Coccinella; Coccinellidae; pheromone; attractant; pyrazine; predator.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The distinctive odour of the seven-spot ladybird beetle, Coccinella septempunctata, had not previously been identified unequivocally, although it was considered likely to arise from olfactorily potent pyrazines. The component responsible was located by human organoleptic evaluation of the gas chromatography effluent from ladybird volatiles and was fully characterized as 2-isopropyl-3-methoxypyrazine. Although insects may not be expected to have similar olfactory sensitivities to human beings, this compound was found to fulfil a pheromonal role in the attraction between adult C. septempunctata, typical of many ladybird species. Thus, in a behavioural assay, both males and females were attracted by amounts of this pyrazine equivalent to the ladybird volatiles.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 9 (1979), S. 777-782 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The various reasons for current efficiency losses in indirect electrochemical processing are considered. Using the Cr(VI) oxidation ofo-toluene sulphonamide as a model, it is shown that accretion of organic residues is an important factor contributing to current efficiency losses. Other evidence is provided to suggest that film formation on the electrode surface acts selectively to promote oxygen evolution rather than Cr(III) re-oxidation.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-1561
    Keywords: Seven-spot ladybird ; Coccinella septempunctata ; Coleoptera ; Coccinellidae ; electrophysiology ; single neuron recording ; dose-response ; behavior ; olfactometer ; aphid alarm pheromone ; (E)-β-farnesene ; (−)-β-caryophyllene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Electrophysiological responses of adult seven-spot ladybirds, Coccinella septempunctata, to (E)-β-farnesene, an aphid alarm pheromone, and (−)-β-caryophyllene, a plant-derived alarm pheromone inhibitor, were investigated by recording from single olfactory cells (neurons) on the antenna. Cells having high specificity for each of the two compounds were identified. Furthermore, these two cell types were frequently found in close proximity, with a larger amplitude consistently recorded for the cell responding specifically to (E)-β-farnesene. Preliminary behavioral studies in a two-way olfactometer showed that walking adults were significantly attracted to (E)-β-farnesene; this activity was inhibited with increasing proportions of (−)-β-caryophyllene. The possible ecological significance of colocation or pairing of olfactory cells for semiochemicals with different behavioral roles is discussed.
    Type of Medium: Electronic Resource
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