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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6740-6748 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Deep electron traps in ZnSe crystals grown by the vertical gradient freezing method using a sealed molybdenum capsule were studied by isothermal capacitance transient spectroscopy. These crystals have electron concentrations of 1015–1017 cm−3 in the as-grown state. Besides the deep traps caused by isolated impurities, two characteristic traps were found. One is the most dominant trap in almost all samples studied, with an apparent activation enthalpy of ∼0.3 eV accompanied by an electron capture barrier of 0.05–0.29 eV. The concentration of this trap is less than 3×1015 cm−3. By a deconvolution of its highly broadened spectrum, the nontheoretical emission behavior was recognized as an overlapped emission of a number of different traps with similar emission time constants. That probably corresponds to the difference of the impurity species combined with the native defect in this trap. The other trap has an activation enthalpy of 1.03–1.1 eV and the concentrations of electrons captured by the trap are found to depend logarithmically on the duration of the filling pulse. The origin of this trap is assumed to be an impurity atom associated with extended defects such as dislocations. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3015-3019 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The defect corresponding to shallow etch pits (S-pits) on GaP wafer has been revealed. It is a vacancy-type Frank dislocation loop which surrounds a stacking fault. It is proposed that this loop is formed by the condensation of excess gallium vacancies during cooling of the GaP crystal. The phosphorus precipitates on the dislocation loop result from the condensation of the emitted phosphorous interstitials accompanied by the growth of the loop. Stoichiometry control is necessary to suppress the formation of S-pit defects in low dislocation density compound semiconductor crystals. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5413-5416 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A new technique for measuring the twist elastic constant (K22) using an in-plane electrode structure was investigated. The variation in the temperature dependence of K22 with respect to the molecular structure of fluorinated phenylbicyclohexane (PBC) compounds was investigated. The experimental cell has in-plane electrodes between which the liquid crystal molecules are aligned to an offset angle of azimuthal direction. Using K22 as a fitting parameter, the transmittance–voltage curves for the calculated results are fitted to those for the experimental results. In addition, the investigation of the temperature dependence of K22 revealed that the PBC compound having a para-cyano substituent at the benzene ring exhibits larger splay elastic constant and larger temperature dependence. Finally, molecular association is discussed based on the experimental results. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 8429-8429 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2717-2718 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The (NH4)2Sx surface treatment was applied to the AlGaAs/GaAs heterojunction bipolar transistor. The suppression of the emitter size effect on the current gain was observed for up to 4×4 μm2 emitter size devices, and 2.5 times high current gain was obtained with the improvement of the ideality factor. These results indicate that the surface recombination at emitter-base junction area are largely reduced by this treatment. The (NH4)2Sx treatment also proved to be applicable to the conventional device fabrication processes and highly reliable for the heat treatment.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ion cyclotron range of frequency (ICRF) heating experiments on the Large Helical Device (LHD) [O. Motojima et al. Fus. Eng. Des. 20, 3 (1993)] achieved significant advances during the third experimental campaign carried out in 1999. They showed significant results in two heating modes; these are modes of the ICH-sustained plasma with large plasma stored energy and the neutral beam injection (NBI) plasma under additional heating. A long-pulse operation of more than 1 minute was achieved at a level of 1 MW. The characteristics of the ICRF heated plasma are the same as those of the NBI heated plasma. The energy confinement time is longer than that of International Stellarator Scaling 95. Three keys to successful ICRF heating are as follows: (1) an increase in the magnetic field strength, (2) the employment of an inward shift of the magnetic axis, (3) the installation of actively cooled graphite plates along the divertor legs. Highly energetic protons accelerated by the ICRF electric field were experimentally observed in the energy range from 30 to 250 keV and the tail temperature depended on the energy balance between the wave heating and the electron drag. The transfer efficiency from the high energy ions to the bulk plasma was deduced from the increase in the energy confinement time due to the high energy ions in the lower density discharge, which agrees fairly well with the result obtained by the Monte Carlo simulation. The transfer efficiency is expected to be 95% at an electron density of more than ne=5.0×1019 m−3 even in the high power heating of 10 MW. The accumulation of impurities, e.g., FeXVI and OV was not observed in high rf power and long pulse operation. The well-defined divertor intrinsic to LHD is believed to be useful in reducing the impurity influx. © 2001 American Institute of Physics.
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  • 7
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The poloidal magnetic field was measured to detect the plasma boundary position. It was found that the pressure-induced plasma shift, an observable characteristic of the Pfirsch–Schlüter current, depends strongly on the initial position of the magnetic axis. When the axis was moved by the vertical field inside the torus, the finite-β shift became smaller. Complete suppression of the finite-β plasma shift was achieved in a deeply inward shifted configuration: 7 cm from the standard position Raxis=2.20 m. This effect is explained by magnetohydrodynamic (MHD) equilibrium theory for stellarator toroidal plasmas with a large magnetic hill and deep inward shift. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 489-500 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: External excitation, propagation, and ion heating for the ion-Bernstein wave (IBW) are studied for the single-ion and two-ion species plasmas, using particle simulation. It is found that the value of ω/Ωi near the antenna position influences the excitation characteristics of the IBW. The wavelength and group velocity of the propagating IBW agree well with those calculated from the linear dispersion relation. Corresponding to the experiment done with the JIPP T-II-U device [Phys. Rev. Lett. 54, 2339, (1985)], the 3ΩD heating process in the plasma composed of deuterium-like and hydrogen-like ions is investigated. The wave energy is deposited into the bulk and tail of the deuterium-like ions because of third harmonic cyclotron resonance and the bulk of the hydrogen-like ions because of 3/2 ΩH cyclotron subharmonic resonance.The possibility is also discussed that the heating efficiency may not depend on the concentration of the deuterium-like ion in the 3ΩD heating in the actual tokamak experiment.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1587-1589 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The thermally ionized process of the Ti2+/Ti3+ donor level in Ti-doped ZnSe crystals grown by the vertical gradient freezing method was first analyzed with detailed isothermal capacitance transient spectroscopy. The ionization enthalpy and an apparent electron capture cross section of the trap observed from the Arrhenius plot of the emission time constant were 1.058±0.005 eV and (1.03±0.15)×10−12 cm2, respectively. The temperature dependence of the capture cross section of the ionized Ti3+ state revealed a lattice relaxation energy of 0.29±0.03 eV. The real depth of the donor level was determined to be 0.77 eV below the conduction band. © 1997 American Institute of Physics.
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  • 10
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: A mitogenic component, designated fraction C (Fr C), has been purified from a mutanolysin enzyme digest of Actinomyces cell walls by CM Sephadex C-25 ion-exchange and G-100 gel filtration chromatography. Good mitogenic responses were obtained with Fr C over a broad dose range with peak mitogcnesis seen with 500 μg/culture. Fraction C (mol. wt. = 35,000–40,000) consists of 755 carbohydrate and 23% protein, is non-dialy-sable, resistant to heat, lysozyme or protease treatment, and partially sensitive to base, and all milogenic activity is destroyed by cither periodate or acid treatment. Fraction C is a B-cell mitogcn since it induced responses in nude (nu/nu) and nu/+ BALB/c spleen cell cultures and purified splenic B-cell cultures, but did not stimulate purified splenic T-cell cultures. Similar milogenic fractions for B cells have been obtained from cell walls of A naeslundii and from a human isolate of A. viscosus. Good polyclonal IgM synthesis and plaque-forming cell responses to hapten or erythrocytes were obtained in vitro with the purified cell wall fractions derived from all three Actinomyces strains studied. These results indicate that the Actinomyces cell wall possesses a carbohydrate-rich component which activates B cells und may represent a common determinant of this genus.
    Materialart: Digitale Medien
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