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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3188-3190 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a combined experimental and theoretical investigation of intra- and intersubband carrier relaxation in GaAs/AlAs quantum wells following femtosecond laser excitation at low density. Time-resolved optical absorption has been measured using 125 fs pulses from a tunable Ti:sapphire laser which allows carriers to be excited preferentially into different subbands. The experiments have been analyzed using a multi-subband Monte Carlo simulation which contains all the important scattering mechanisms. Electron-phonon scattering rates obtained from dielectric continuum theory have been used, and we find excellent agreement with the experiment. The dominance of interface phonons in intrasubband relaxation is confirmed. © 1995 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 73 (1998), S. 199-201 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present optical gain and loss spectra measured over a range of carrier densities at low temperature in hexagonal GaN epilayers. We have determined the optical loss directly to be ∼80 cm−1. Photoluminescence spectra show that stimulated emission in our samples arises from electron–hole plasma recombination. © 1998 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3434-3436 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A way of analyzing the data in a variable stripe length method gain experiment is presented. We confirm that the stripe length dependence of the gain in In0.02Ga0.98N/In0.16Ga0.84N multiple quantum wells is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity as a function of the stripe length. This is found to fit very well with our data, even beyond the saturation region. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1097-1099 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present spectrally resolved and time-integrated four-wave mixing measurements at coherent dynamics of bound excitons in a high-quality GaN epilayer. Coherent excitation, with co-circular polarized light, of the neutral donor-bound excitons (D 0X) and A excitons (XA) results in quantum beats, corresponding to the energy splitting between D 0X and XA. The temperature-dependent dephasing rate is used to deduce the strength of the D 0X-acoustic–phonon interaction via the homogeneous linewidth. © 2001 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 265 (1977), S. 415-421 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A concept is developed for the regulation of populations by density-dependent movement, rather than by overt competition alone. Fitness is seen as maximising the reproductive advantage of a balance between migratory and congregatory behaviours. Population density is shown to be spatially, as well ...
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 80 (1996), S. 511-519 
    ISSN: 1570-7458
    Keywords: sweet potato whitefly ; temperature ; relative humidity ; migration and dispersal ; virus transmission ; Homoptera ; Aleyrodidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ability of the sweet potato whitefly, Bemisia tabaci Gennad., to survive a range of environmental conditions was investigated in the laboratory. The range of temperature and humidity investigated corresponds to the normal climatic range during B. tabaci's summer migration in Israel. Adult whiteflies confined to small test cages were exposed to combinations of temperature (25, 30, 35, and 41 °C) and relative humidity (20, 50, 80, and 100%) for periods of 2, 4, or 6 h. A logistic regression model describing the four-dimensional surface defining percent survival as a function of time, temperature, and humidity was developed. Using stepwise regression to exclude non-significant terms, the linear predictor included temperature, and the products of temperature and time, and humidity and time. The model accounted for 75% of the variance. A reparameterization of the fitted regression model suggests that survival potential is conditioned by temperature conditions prevailing during the previous 10 h. Whitefly survival after 2 h exposure ranged from ≈ 90% survival at 20°C and 100% RH, to 〈2% survival at 41°C and 20% r.h.. No whiteflies survived more than 2 h exposure at these latter extremes of temperature and humidity. Survival rates decreased slightly after experimental whiteflies were kept in a cage with food a further 20 h at 25±2°C, 55±5% r.h. Investigations of the effects of hunger and virus infection, showed that both increased mortality.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 57 (1996), S. 938 -945 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1429-1433 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Localised single-particle electronic states (excluding impurities) ; Photoluminescence ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Time-resolved photoluminescence experiments in a wide carrier density range up to and beyond the threshold for stimulated emission in ZnSe/ZnS x Se1−x superlattices are presented. Different localisation mechanisms of free excitons are identified giving rise to different radiative recombination channels. At high carrier density localised energy states merge into miniband that allows for exciton-exciton interaction, such as screening of the free-exciton absorption and inelastic exciton-exciton scattering.
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 332 (1988), S. 721-722 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Our original collection4 of 156 data sets from the literature, later supplemented to 221 sets by Downing3, was not ideal5 for inter-specific comparison of b values, comprising samples of selected species collected by diverse methods at varying scales. Such data lack precision when units per sample ...
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 303 (1983), S. 801-804 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Anderson et a/.1 use markovian population models to restate the proposition10'11 that environmental and demographic stochasticity determine the relationship between the mean and variance. In such models spatial behaviour, including migration, may affect demographic rates, but its effect is ...
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