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  • III–V semiconductors  (2)
  • Male germ unit  (2)
  • 2,2,4-trimethyl pentane  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1625-1628 
    ISSN: 0392-6737
    Keywords: Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; III–V compounds and systems ; III–V semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Low-temperature PL decay times, τPL, measured for a series of In x Ga1−x As/GaAs quantum wells (QWs) show an almost linear increase with increasing thickness (4≤L z ≤10 nm,x=0.15) and with increasing In composition (0.05≤x≤0.25,L z =8 nm). τPL also increases linearly with temperature up to 50K, as expected for free excitons and does not exhibit the interface effects seen for GaAs/AlGaAs QWs. Wells with different In compositions exhibit a similar temperature behaviour and there is a weak influence of strain on the decay time.
    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. 1791-1795 
    ISSN: 0392-6737
    Keywords: Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; III–V semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Exciton dynamics including thermalisation, radiative recombination and migration in growth-interrupted and hydrogen-passivated GaAs/AlAs single quantum wells have been investigated under non-resonant and resonant excitation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2145
    Keywords: Cymbidium goeringii ; Cytoplasmic diminution ; Generative cell ; Male germ unit ; Vegetative nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pollinia of Cymbidium goeringii (Orchidaceae) were examined at a young stage (approx. 2 weeks before anthesis) and at anthesis using transmission electron microscopy, computer-assisted serial reconstruction and quantitative cytology. At the young stage, the generative cell (GC) has a spherically shaped main body with a large nucleus and 1 to 4 cytoplasmic extensions (up to 10 μm long) physically associated with a groove on one side of the vegetative nucleus (VN). By anthesis, some GCs lose their cytoplasmic extensions, becoming spherical. The GC surface becomes highly wrinkled, the distance between the GC and the VN increases and the two may separate completely. Enucleated cytoplasmic bodies (ECBs) are apparently generated by the GC, as evidenced by their similar ultrastructural appearance and distribution near the GC. ECBs are likely produced from two sites: the GC surface and the tips of cytoplasmic extensions of the GC. Vesicle-containing bodies (VCBs) may be generated from the lateral surface of the GC and may also represent a degeneration stage of ECBs, finally fusing with lipid bodies. Heritable organelles are rare and usually absent in the GC of Cymbidium: 0.176 mitochondria and 0.0042 plastids per GC were observed at the young stage and no mitochondria and 0.019 plastids at anthesis. Of 16 cellular parameters examined during GC development, all decreased with the exception of the surface area and volume of ECBs/ VCBs (which remained stable) and GC vacuoles (which increased). Significant decreases in 11 parameters presumably relate to dehydration of the pollen and male cytoplasmic diminution.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 11 (1990), S. 987-1000 
    ISSN: 1572-9567
    Keywords: mixtures ; normal heptane ; thermal conductivity ; 2,2,4-trimethyl pentane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The paper presents the results of measurements of the thermal conductivity of three binary mixtures of normal heptane and 2,2,4-trimethyl pentane. The measurements were carried out within the temperature range 308–359 K and over the pressure range 0.1–410 MPa with a transient hot-wire instrument. The experimental data have an estimated uncertainty of ±0.3%. The experimental data have been represented by simple polynomials along isotherms as a function of pressure for each composition for the purpose of interpolation. However, an alternative scheme of representation, based upon an heuristic extention of the hard-sphere theory, is shown to give a much more concise representation capable of extrapolation. Indeed, a procedure for the prediction of the thermal conductivity of the mixtures, based on the same theory, which uses no information derived from the present measurements, is shown to yield results of an accuracy sufficient for many purposes.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1615-6102
    Keywords: Cytoplasmic inheritance ; Male cytoplasmic diminution ; Male gamete (angiosperm) ; Male germ unit ; Nicotiana ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The organization of the sperm cells and vegetative nucleus (male germ unit) ofNicotiana tabacum was examined 18 h after semivivo pollination using transmission electron microscopy, computerassisted serial section reconstruction and quantitative cytology. Based on a measurement of 11 cellular parameters in nine reconstructed sperm cell pairs, there are no statistically significant differences between the two cells. The Svn is characterized by a strapshaped cytoplasmic extension that is physically associated with the surface of the vegetative nucleus. The nucleus is located adjacent to the sperm crosswall, with sperm organelles being distributed between the nucleus and the extension. The Sua is a tapered cell with cytoplasmic areas at both poles and deep axial invaginations near the crosswall. This cell has a centrally-located nucleus and a largely polar distribution of organelles. Three mechanisms for cytoplasmic diminution were observed that appear to contribute actively to the loss of cytoplasmic volume and organelles: (1) enucleated cytoplasmic body production in the Sua; (2) vesiculation at the tip of the cytoplasmic projection of the Svn; and (3) vesicle-containing body accumulation in the periplasm of both the Svn and Sua.
    Type of Medium: Electronic Resource
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