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  • Springer  (35)
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  • 1
    Electronic Resource
    Electronic Resource
    Recombination processes in strain-induced InGaAs quantum dots (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1699-1703 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02457266
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  • 2
    Electronic Resource
    Electronic Resource
    Electric-field-induced exciton ionization in a GaAs/AlGaAs superlattice (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1759-1762 
    Details
    ISSN: 0392-6737
    Keywords: Optical transient phenomena (including quantum beats, dephasings and revivals, photon echoes, free induction decay, and optical mutation) ; Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Optical properties of thin films, surfaces and thin layer structures (including superlattices, heterostructures, and intercalation compounds) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We study exciton ionization induced by an axial electric field in a strongly coupled GaAs/Al0.3 Ga0.7 As superlattice at low temperatures. The field-induced ionization times of the heavy-hole 1s exciton in the miniband field regime are determined from transient four-wave-mixing experiments and theoretical model calculations. They are found to lie between the field ionization times of excitons in bulk semiconductors, and in strongly confined quantum well systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457276
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  • 3
    Electronic Resource
    Electronic Resource
    Coherent exciton-photon dynamics in single, double, and quintuple quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1769-1774 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02457278
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  • 4
    Electronic Resource
    Electronic Resource
    Weitere Beiträge zur Kenntnis von Solen mit Strukturviskosität, II (1927)
    Springer
    Colloid & polymer science 43 (1927), S. 181-187 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung 1. Die „Struktur-Turbulenz“ genannte Viskositätsanomalie beim Ammoniumoleat-Sol findet sich in ganz gleichartiger Weise (auch in Einzelheiten) wieder bei Baumwollgelb-Solen (salzhaltig und gereinigt) und bei Hg-Sulfosalizylsäure-Gelen. Die Anomalie wurde gefunden sowohl im Couette (E. Hatschek und R. S. Jane) als auch bei Kapillarviskosimetern verschiedener Konstruktion (Wo. Ostwald und R. Auerbach). 2. Bei Na2SO4-haltigen Baumwollgelb-Solen verschiedener Konzentration entwickelt sich die Struktur-Turbulenz und verschwindet wieder bei zunehmender Konzentration, entsprechend der früher beschriebenen anomalen Konzentrationsfunktion der Viskosität dieser Sole mit einem Viskositätsmaximum bei etwa 1,3 Proz. Sole von letzterer Konzentration zeigen die Anomalie nicht, sondern geben glatte Strukturäste, die ausgezeichnet der Gleichung von A. de Waele-Wo. Ostwald gehorchen. 3. Die bisher gefundenen Sole mit ausgesprochener Struktur-Turbulenz zeigen gleichzeitig auch ausgesprochene Scherelastizität.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01428710
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  • 5
    Electronic Resource
    Electronic Resource
    Weitere Beiträge zur Kenntnis von Solen mit Struktur- Viskosität; I (1927)
    Springer
    Colloid & polymer science 43 (1927), S. 155-181 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01428709
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of antimony species with high-performance liquid chromatography using element specific detection (1997)
    Springer
    Fresenius' journal of analytical chemistry 359 (1997), S. 484-491 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method for the fast and simultaneous determination of Sb(III) and Sb(V) is presented involving the use of anion exchange high-performance liquid chromatography (HPLC), a complexing reagent in the mobile phase, and element specific detection with flame atomic absorption spectrometry (FAAS) or inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic parameters such as nature and concentration of the complexing and eluting compounds and pH of the mobile phase were investigated in detail. Additionally, the separation of inorganic Sb(III) and Sb(V) from organically bounded antimony (as (CH3)3SbCl2 and (CH3)3Sb(OH)2) was investigated by using anion, and cation exchange, and reversed phase HPLC. Best separation was obtained with anion exchange HPLC under alkaline conditions. Cation exchange and reversed-phase HPLC were not useful for the separation of the above compounds. With FAAS concentrations in the upper mg L–1 range are detectable, which is not sensitive enough for the analyses of environmental samples. When the chromatographic system was coupled to ICP-MS, the detection limits are in the lower μg L–1 range. The method was applied to various environmental samples with anthropogenic and naturally elevated Sb concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050618
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  • 7
    Electronic Resource
    Electronic Resource
    Arsenic metabolism in seaweed-eating sheep from Northern Scotland (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 116-121 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cation exchange and anion exchange liquid chromatography were coupled to an ICP-MS and optimised for the separation of 13 different arsenic species in body fluids (arsenite, arsenate, dimethylarsinic acid (DMAA), monomethylarsonic acid (MMAA), trimethylarsine oxide (TMAO), tetramethylarsonium ion (TMA), arsenobetaine (AsB), arsenocholine (AsC), dimethylarsinoyl ethanol (DMAE) and four common dimethylarsinoylribosides (arsenosugars). The arsenic species were determined in seaweed extracts and in the urine and blood serum of seaweed-eating sheep from Northern Scotland. The sheep eat 2–4 kg of seaweed daily which is washed ashore on the most northern Island of Orkney. The urine, blood and wool of 20 North Ronaldsay sheep and kidney, liver and muscle from 11 sheep were sampled and analysed for their arsenic species. In addition five Dorset Finn sheep, which lived entirely on grass, were used as a control group. The sheep have a body burden of approximately 45–90 mg arsenic daily. Since the metabolism of arsenic species varies with the arsenite and arsenate being the most toxic, and organoarsenic compounds such as arsenobetaine the least toxic compounds, the determination of the arsenic species in the diet and their body fluids are important. The major arsenic species in their diet are arsenoribosides. The major metabolite excreted into urine and blood is DMAA (95 ± 4.1%) with minor amounts of MMAA, riboside X, TMA and an unidentified species. The occurrence of MMAA is assumed to be a precursor of the exposure to inorganic arsenic, since demethylation of dimethylated or trimethylated organoarsenic compounds is not known (max. MMAA concentration 259 μg/L). The concentrations in the urine (3179 ± 2667 μg/L) and blood (44 ± 19 μg/kg) are at least two orders of magnitude higher than the level of arsenic in the urine of the control sheep or literature levels of blood for the unexposed sheep. The tissue samples (liver: 292 ± 99 μg/kg, kidney: 565 ± 193 μg/kg, muscle: 680 ± 224 μg/kg) and wool samples (10 470 ± 5690 μg/kg) show elevated levels which are also 100 times higher than the levels for the unexposed sheep.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000482
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  • 8
    Electronic Resource
    Electronic Resource
    THz-imaging: a new method for density mapping of wood (1998)
    Springer
    Wood science and technology 32 (1998), S. 421-427 
    Details
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary This paper presents a new technique for fast and non-intrusive density mapping of wood based on far-infrared spectroscopy. The transmission of a piece of beech 1.7 mm thick is investigated between 0.1 and 2.5 THz. In this spectral range we find wood to be fairly transparent, but density inhomogeneities and structural details such as annual rings become visible in the transmission profile. The measured absorption correlates well with the wood density independently obtained by the gravitometric-volumetric method. Thus it finally becomes possible to transform the THz images into 2-dimensional density maps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702799
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  • 9
    Electronic Resource
    Electronic Resource
    Model calculations of diffusion limited trapping dynamics in quantum well laser structures (1989)
    Springer
    Applied physics 48 (1989), S. 509-515 
    Details
    ISSN: 1432-0630
    Keywords: 73.20.Dx ; 78.55.Cr ; 78.47.+p
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We present a phenomenological theoretical model to treat the trapping of carriers into quantum wells of semiconductor laser structures. We consider explicitely the transport within the barrier layers by solving the continuity equation with the appropriate boundary conditions taking into account surface recombination, radiative and nonradiative recombination in the barrier layers and trapping of carriers into the quantum wells. The experimental findings for the trapping dynamics in GaAs/AlGaAs quantum well structures can be consistently interpreted by the model calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617851
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  • 10
    Electronic Resource
    Electronic Resource
    Design and application of a femtosecond optical parametric oscillator for time-resolved spectroscopy of semiconductor heterostructures (1995)
    Springer
    Applied physics 60 (1995), S. 459-467 
    Details
    ISSN: 1432-0649
    Keywords: 42.65.Ky ; 42.50.Md ; 71.35. + z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Femtosecond pulses of a collinearly pumped Optical Parametric Oscillator (OPO) are applied for investigations of the carrier dynamics in ternary and quaternary semiconductor quantum wells. The design and the specifications of the OPO are given in detail. We show that no measurable jitter exists between the pump pulses and the output pulses of the OPO. Therefore, it is possible to use the OPO and its pump laser for two-color experiments with a time resolution limited by the pulse lengths. We present and discuss results of transient four-wave mixing experiments on (InGa) As/InP quantum wells, and find a new kind of polarization-dependent quantum beat phenomenon. In addition, non-degenerate experiments on quantum wells from the quaternary (InGaAl) As material system, using two pulses at different wavelengths (one from the OPO and one from the pump laser), are discussed as a novel experimental technique to study carrier trapping into quantum wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081327
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