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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1699-1703 
    ISSN: 0392-6737
    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Localized single-particle electronic states (including impurities) ; III–V compounds and systems ; Photoluminescence ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have performed time-integrated and time-resolved photoluminescence experiments on high-quality stressor-induced InGaAs/GaAs quantum dots. The optical spectra of these dot structures exhibit large quantization effects together with remarkably low inhomogeneous broadenings of the respective excitonic transitions. Thus a detailed investigation of the relaxation and recombination dynamics within the distinct electronic dot states becomes feasible. We find that the initial relaxation of optically generated carriers down to the lowest dot states is very efficient. This fast thermalization is ascribed to Coulomb scattering between carriers confined in dot states and carriers located in the higher-energetic quantum well states.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1769-1774 
    ISSN: 0392-6737
    Keywords: Optical transient phenomena (including quantum beats, dephasings and revivals, photon echoes, free induction decay, and optical nutation) ; Excitons and related phenomena (including electron-hole drops) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have studied experimentally the coherent exciton-photon dynamics in a single, a double, and a quintuple quantum well structure under resonant excitation. In pump and probe experiments we observe an initial fast decay of the exciton population. This initial decay depends on the number of quantum wells. The population decay is accompanied by a coherent light emission induced by the first-order polarization, the intensity of which increases quadratically with the quantum well number. Interference effects and electromagnetic coupling effects between polarizations located in distinct quantum wells probably play a crucial role in the superlinear coherent emission process.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 14 (1931), S. 751-778 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 6 (1975), S. 399-407 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Problems regarding the raw material supply of steel improving heavy and minor alloy metals.The supply situation of steel improving heavy and minor alloy metals reveals that the absolute and relative concentration of the raw material output as well as the regional supply agglomeration in developing countries is much more marked as is the case with crude oil. Future development is expected to increase even the import dependence of few large producing countries in the Third World, thus increasing the risk of short-term availability bottlenecks, shortcomings in deliveries and cartelizations in view of a sharply rising demand of alloy metals and a shortage of Europe's own production. Besides the promotion of industrial potentialities to ensure a better adaptability to given supply situations - particularly recycling, substitution and stockpiling - there is a need for a government flanking raw material policy with national and international objectives.
    Notes: Die Versorgungslage bei stahlveredelnden Schwer- und Sondermetallen zeigt, daß die absolute und relative Konzentration der Rohstofförderung sowie die regionale Angebotsballung in Entwicklungsländern sehr viel ausgeprägter ist als beim Rohöl. Die zukünftige Entwicklung läßt erwarten, daß die Importabhängigkeit von wenigen großen Förderländern in der 3. Welt noch zunehmen wird, so daß sich die Gefahr von kurzfristigen Verfügbarkeitsengpässen, Belieferungsausfällen und Kartellbildungen, angesichts des stark steigenden Bedarfs an Legierungsrohstoffen und fehlender Eigenproduktion in Europa, verstärken wird. Neben der Förderung industrieller Möglichkeiten zur Erhöhung der Anpassungsfähigkeit an jeweilige Versorgungslagen - insbesondere Recycling, Substitution und Lagerbildung - besteht die Notwendigkeit einer staatlichen flankierenden Rohstoffpolitik mit nationaler und internationaler Zielstellung.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0268-2605
    Keywords: trimethylantimony ; molecular rearrangement ; demethylation ; speciation ; hydride generation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of hydride generation for the speciation of antimony compounds was examined with respect to the problem of molecular "rearrangement'. Specifically, demethylation of trimethylstilbine during the analysis of trimethylantimony dichloride (Me3SbCl2) was studied. Previously published observations that enhanced demethylation takes place as a result of inadequate preconditioning of the analytical apparatus were found to be not reproducible. However, demethylation was enhanced as the pH decreased when using two different analytical methods: semi-continuous flow hydride generation-gas chromatography-atomic absorption spectrometry (HG- GC-AAS), and batch-type hydride generation- gas chromatography-inductively coupled plasma mass spectrometry (HG-GC-ICP MS). Applications of the hydride generation method to environmental samples revealed differences in analytical results at high and low pH, and enhanced demethylation taking place because of the matrix in a fungal extract sample. The authors recommend that researchers using the method of hydride generation for antimony compounds carefully test the reaction conditions with standard compounds and use the method of standard addition only. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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