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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3581-3588 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present calculations and measurements of current as a function of voltage I(V), and conductivity at low voltage as a function of temperature, G(T), for n+ -GaAs/i- Alx Ga1−x As/n+ -GaAs single-barrier tunneling structures. The current is modeled by its tunneling and thermionic emission components. The shape of the conduction-band edge is obtained by solving Poisson's equation self-consistently, together with two different models for the charge density. In the first model, the electron density is evaluated semiclassically, and in the second, the electron density is calculated from the electronic wave functions. Good agreement is obtained with both models between the experimental and the calculated I(V) and G(T) characteristics over the 4.2–200 K temperature range. The fits obtained are very sensitive to small variations (1%) in barrier width and effective barrier height, which allows one to determine these parameters within a narrower uncertainty range.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 34 (1956), S. 469-472 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Zusammenfassung Es wird über Erfahrungen mit der Corticoidbestimmungsmethode nachStaudinger undBauer berichtet. Mit diesem Verfahren werden die freien und conjugierten Corticoide gleichzeitig erfaßt. Ihr Ausscheidungsverhältnis beträgt etwa 1:9. Die Steroidwerte steigen mit dem Alter der Kinder kontinuierlich an. Nach den ersten Lebensjahren zeigen sie etwa gleichbleibende Relationen zu Körperoberfläche und -gewicht. Ein Vergleich der Corticoidwerte mit den ausgeschiedenen Harnmengen ergibt für die ersten Lebensjahre ein proportionales Verhalten der beiden Größen. Mit zunehmendem Alter vermindert sich diese Korrelation; die Steroidausscheidung wird unabhängiger vom Harnvolumen. Ursächlich kommen für diese Beziehungen sowohl eine gesteigerte adrenale Produktion wie eine verstärkte Clearance der Steroide unter dem Einfluß vermehrter Wasserzufuhr in Betracht. Wir möchten die zweite Erklärung für die wahrscheinlichere halten.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 277 (1985), S. 98-104 
    ISSN: 1432-069X
    Keywords: Chondrogenesis ; Retinoids ; Differentiation ; Limb-bud mesenchyme ; In vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of all-trans retinoic acid, 13-cis retinoid acic and two aromatic retinoids (Ro 10-1670, Ro 11-1430) on the chondrogenic differentiation of mesenchymal cells in vitro was studied electronmicroscopically. Organ cultures of limb buds from mouse embryos (Day 11) and high-density cultures of embryonic-mouse mesenchymal cells (Day 12) were used as experimental models. After a 6-day culture in the control medium, the development of hyaline cartilage was observed in both systems. In cultures which were treated with retinoids from Day 1 through Day 3 and then incubated in the control medium for 3 more days, the mesenchymal cells still maintained the morphological features of the blastema stage; cartilage synthesis was reduced (low retinoid concentrations) or completely absent (high retinoid concentrations). These findings indicate that the treatment of embryonic-mouse mesenchymal cells with retinoids induces a persistent and dose-dependent inhibition of chondrogenic differentiation, which in quantitative terms, is variably expressed during treatment with different retinoids. These inhibitory effects of retinoids on chondrogenesis are probably implicated in the pathogenetic mechanisms of their teratogenic action in vivo.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Thermoreceptors ; Hygroreceptors ; Sensillum styloconicum ; Sensillum-lymph space ; Morphometry ; Bombyx mori, Antheraea pernyi, A. polyphemus (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The thermo/hygroreceptive sensilla styloconica of the silkmoths Bombyx mori, Antheraea pernyi, and A. polyphemus were reconstructed from serial sections of cryofixed and chemically fixed specimens. The volume and surface area of the different sensillar cells were calculated from the area and circumference of consecutive section profiles. In addition, data are provided on the length and diameter of the outer and inner dendritic segments of the receptor cells. The morphometric data obtained from the three species are highly consistent and significantly different from those of olfactory sensilla trichodea of the same species. In each sensillum two type-1 receptor cells (hygroreceptors) are associated with one type-2 cell with a lamellated outer dendritic segment, a comparatively thick inner dendritic segment, and a particularly large soma (thermoreceptor). In contrast to olfactory sensilla, the thecogen cell is the largest auxiliary cell forming an extensive apical labyrinth bordering the inner sensillum-lymph space, whereas an inconspicuous trichogen cell and a medium-sized tormogen cell border a comparatively small outer sensillum-lymph cavity. Moreover, both sensillum-lymph spaces are separated from each other not only by the dendrite sheath, but also by the trichogen cell. The results are discussed with regard to recent electrophysiological observations and current hypotheses on the function of sensilla.
    Type of Medium: Electronic Resource
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