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  • 1990-1994  (37)
  • 1994  (37)
Materialart
Erscheinungszeitraum
  • 1990-1994  (37)
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2286-2288 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using a high Tc superconducting grain boundary Josephson junction, harmonic mixing experiments in the mm waveband were carried out, aiming at as large a harmonic number and as high a signal frequency as possible. The dependencies of intermediate frequency output on dc bias, harmonic number, frequency of local oscillator (LO), and other parameters were carefully studied. Until now, our best result was the mixing between the signal at 95 GHz and the 105th harmonic of LO at about 900 MHz. Preliminary experiments using a high Tc harmonic mixer and phase-locking loop were tried to stabilize the frequency of a mm wave source.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The band structure and magnetic properties are studied for RFe11TiNx (R=Y, Nd, Sm; x=0,1) rare-earth iron intermetallic compounds using the linear muffin tin orbital with the atomic sphere approximation (LMTO-ASA) method. In order to elucidate the role played by the rare-earth atoms in these compounds, a full electron calculation is performed using a semirelativistic spin-polarized LMTO-ASA method in the local spin density approximation (LSDA) regime. The 4f electrons of the rare-earth atoms are considered to be valence electrons in the self-consistent calculations. For NdFe11TiN, a calculation in which the 4f electrons are treated as core-frozen states is also performed, and is compared with the full electron calculation. The effects of N atoms in these compounds are also discussed.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1279-1286 
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A high brightness krypton fluoride Raman laser (wavelength 0.268 μm) generating 0.3 TW, 12 ps pulses with 20 μrad beam divergence and a prepulse of less than 10−10 has been focused to produce a 10 μm wide line focus (irradiances ∼0.8–4×1015 W cm−2) on plastic targets with a diagnostic sodium fluoride (NaF) layer buried within the target. Axial and lateral transport of energy has been measured by analysis of x-ray images of the line focus and from x-ray spectra emitted by the layer of NaF with varying overlay thicknesses. It is shown that the ratio of the distance between the critical density surface and the ablation surface to the laser focal width controls lateral transport in a similar manner as for previous spot focus experiments. The measured axial energy transport is compared to medusa [J. P. Christiansen, D. E. T. F. Ashby, and K. V. Roberts, Comput. Phys. Commun. 7, 271 (1974)] one-dimensional hydrodynamic code simulations with an average atom post-processor for predicting spectral line intensities. An energy absorption of ∼10% in the code gives agreement with the experimental axial penetration. Various measured line ratios of hydrogen- and helium-like Na and F are investigated as temperature diagnostics in the NaF layer using the ration [R. W. Lee, B. L. Whitten, and R. E. Strout, J. Quant. Spectrosc. Radiat. Transfer 32, 91 (1984)] code.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3066-3068 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Reflection high-energy electron diffraction intensity oscillations during Ge heteroepitaxy on Si(100) have been observed using a gas source molecular beam epitaxy system. Intensity oscillations can be observed over 6 ML (monolayers) of growth in the temperature range 400–650 °C. The oscillation frequency, however, varies from the first to subsequent layers and this variation is interpreted primarily as a change in the limiting growth kinetics as the surface composition changes from Si to Ge. Growth temperature and GeH4 flux dependence data indicate that the surface Ge concentration increases gradually, not abruptly, over the first several layers of deposition. Surface roughening effects which are attributed to Stranski–Krastanov type growth, are also found to contribute to the nonuniform oscillation frequency. © 1994 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1989-1991 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the measurements of the electron-hole recombination rate in aqueous CdS colloids on the femtosecond time scale. A fast 2-ps decay and a slower 45-ps decay have been observed, and the decay dynamics are found to be very sensitive to the excitation laser intensity. Geminate electron-hole recombination, responsible for the 45-ps decay, dominates the decay process at low excitation intensities, while nongeminate recombination, accounting for the 2-ps decay, becomes more important at high excitation intensities.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: High quality YBa2Cu3O7−δ (YBCO) films have been epitaxially grown on low dielectric constant, low loss tangent (001)MgF2 substrates using a double buffer layer scheme. The YBCO films are (001) oriented, exhibit Tc's of 88–89 K with transition widths ≤0.5 K and Jc's of 4×106 A/cm2 at 77 K in zero field. Dielectric resonator experiments indicate unloaded Q values in excess of 30 000 at 77 K and 24 GHz in the unpatterned films. Films patterned into meanderline resonators and operating at 10 GHz, 79 K, exhibit surface resistance (Rs)〈1 m Ω suggesting near-future realization of low loss superconducting components in the millimeter-wave region.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6222-6225 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report the direct femtosecond measurements of the electron transfer process from CdS to TiO2 particles in a coupled colloidal system. The electrons initially created in the conduction band and quickly trapped at the liquid–solid interface in aqueous CdS colloids are found to be transferred to the colloidal TiO2 particles with a time constant of 2 ps, resulting in significantly slower electron–hole recombination. These coupled semiconductor colloids provide a potentially useful system for achieving efficient charge separation, which is important for many chemical reactions involving heterogeneous electron transfer.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 1668-1673 
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 3859-3864 
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 34 (1994), S. 0 
    ISSN: 1365-3180
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Responses of 10 natural or agricultural populations of Xanthium strumarium to sublethal rates of bentazone applied post-emergence were examined under field conditions. Both vegetative growth and reproduction of sprayed plants were affected by the herbicide. Some populations were more tolerant of bentazone than the others, but the degree of herbicide tolerance did not depend on the previous herbicide experience of a population. Bentazone treatment significantly reduced the weight per fruit in some populations, which in turn could affect the survival and growth of the subsequent seedlings. La réponse depopulations de Xanthium strumarium à des doses sublétales de bentazoneNous avons étudié au champ la réponse de dix populations naturelles ou agricoles de Xanthium strumariumà des doses sublétales de bentazone appliquée en post-levée. L'herbicide affectait la croissance et la reproduction des plantes traitées. Quelques populations étaient plus tolérantes à la bentazone que d'autres, mais le degré de tolérance ne dépendait pas de l'exposition préalable des populations à l'herbicide. La bentazone réduisait significativement le poids des fruits dans quelques populations, ce qui pouvait affecter ensuite la survie et la croissance des jeunes plantes qui en étaient issues. Wirkung subletaler Dosen von Bentazon auf Xanthium strumariumZehn Herkünfte von Xanthium strumarium wurden im Nachauflauf mit subletalen Dosen von Bentazon unter Feldbedingungen behandelt. Sowohl das vegetative Wachstum als auch die Samenbildung der behandelten Pflanzen wurden durch das Herbizid beeinträchtigt. Einige Herkünfte waren weniger empfindlich, doch der Grad der Herbizidempfindlichkeit stand nicht im Einklang mit früheren Erfahrungen über die Wirkung des Herbizids. Durch die Bentazon-Be-handlungen nahm das Gewicht der Samen bei einigen Herkünften signifikant ab, so daß ihre Lebensfähigkeit und das Wachstum der Keimpflanzen beeinträchtigt sein könnten.
    Materialart: Digitale Medien
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