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  • 1
    Digitale Medien
    Digitale Medien
    Optimization of monochromator crystal bending designs using computer simulations : The 9th National conference on synchrotron radiation instrumentation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3355-3355 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Sagittal focusing of a synchrotron radiation beam by cylindrically bending the second crystal in a double-crystal monochromator is an important way of increasing beam density at the sample posiion. In this paper we describe results obtained by finite element analysis of various optimized Si (111) crystal shapes. For the bending magnet and wiggler sources, we analyzed ribbed crystals and found conditions at which the sagittal curvature is cylindrical and the anticlastic effect is minimized. For the undulator A source, we found that a single slot in the center of a thick plate would be sufficient to eliminate the anticlastic effect and ensure cylindrical sagittal bending. Autofocusing of the beam by means of a trapezoidal slot was investigated, and simulation results are discussed. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147485
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  • 2
    Digitale Medien
    Digitale Medien
    Growth of zinc blende-GaN on β-SiC coated (001) Si by molecular beam epitaxy using a radio frequency plasma discharge, nitrogen free-radical source (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6124-6127 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the growth of zinc blende-GaN epitaxial films on β-SiC coated (001) Si substrates using a molecular beam epitaxy approach in which the reactive nitrogen species are generated in a remote 13.56 MHz rf plasma discharge, nitrogen free-radical source. We postulate, based on optical emission spectroscopy studies of the remote plasma, that, in our study, nitrogen atoms are the species primarily responsible for efficient nitridation. The zinc blende nature of the GaN films was confirmed by in situ reflection high-energy electron diffraction, ex situ x-ray diffraction, and ex situ low-temperature photoluminescence analyses. Our zinc blende-GaN film growth rates (∼0.3 μm/h) are higher than those reported to date that involve the use of electron cyclotron resonance type reactive nitrogen sources.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.355176
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  • 3
    Digitale Medien
    Digitale Medien
    Dynamic electrical response of Y1Ba2Cu3O7−x (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3767-3775 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We studied the dynamic electrical properties of epitaxial Y1Ba2Cu3O7−x superconducting thin films on strontium titanate and MgO substrates. A fast nonlinear switching of a high-Tc film between the dissipative and superconducting states has been demonstrated. These measurements show that the rise and the fall times of these transitions are faster than 250 ps (which are presumably limited by the speed of the measurement electronics). This fast nonlinear switching may lead to opportunities for new high-frequency electronic devices including, for example, fast logic gates or threshold devices. We have proposed and demonstrated the application of such a nonlinear switching in a novel noise discrimination scheme for speeds of several hundred MHz. The proposed method is simple and effective in the enhancement of signal-to-noise ratio in digital electronic circuits.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345021
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  • 4
    Digitale Medien
    Digitale Medien
    Optical response of nongranular high-Tc Y1Ba2Cu3O7−x superconducting thin films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3054-3068 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the optical response of c-axis oriented crystalline Y1Ba2Cu3O7−x thin films (bridge and meander devices) on strontium titanate and MgO substrates. cw optical response to a He-Ne laser radiation (wavelength of 0.63 μm) was primarily bolometric. The pulsed optical response was studied with Q-switched and mode-locked Q-switched short pulses from a Nd:YAG laser at the wavelength of 1.06 μm. We identify two distinct components contributing to the pulsed optical response: a nonbolometric (as fast as 1 ns) and a bolometric component (several ns). The bolometric component is strong at temperatures in the vicinity of the transition region to the normal state. The nonbolometric component is dominant at temperatures below the transition region showing weak temperature dependence and a linear dependence on the bias current. These results are discussed using the flux motion model and also electron-phonon scattering relaxation dynamics of nonequilibrium superconductors based on the theory of Bardeen-Cooper-Schrieffer. The results suggest that with proper optimization of device parameters (geometry, critical current density, etc.) sensitive bolometers and high-speed detectors covering a broad electromagnetic spectrum (visible and infrared) may be developed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345435
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  • 5
    Digitale Medien
    Digitale Medien
    Imaging of current-induced superconducting-resistive transitions by scanning electron microscopy in laser-deposited superconducting thin films of Y1Ba2Cu3O7−x (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 911-913 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the transport current-induced resistive transitions in predominantly c-axis oriented crystalline Y1Ba2Cu3O7−x superconducting thin films with scanning electron microscopic (SEM) imaging and its correlation with dc current-voltage (I-V) measurements. We find that there is a nonlinear gradual transition region in the I-V curves that is caused by macroscopic effects (current "crowding'', substrate defects, film thickness variation, etc.) and by microscopic dissipation effects. At a high current there is an abrupt transition to the normal state in the I-V curve due to Joule heating. The SEM mapping provides a direct image of the above effects and is useful for characterization and study of fundamental transport properties of high Tc thin films.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101620
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  • 6
    Digitale Medien
    Digitale Medien
    Observation of fast nonbolometric optical response of nongranular high Tc Y1Ba2Cu3O7−x superconducting thin films (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1594-1596 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report fast optical response measurements in predominantly c-axis oriented crystalline Y1Ba2Cu3O7−x superconducting thin films at the wavelength of 1.06 μm. We identify two distinct components contributing to the optical response: a nonbolometric (as fast as 1 ns) and a bolometric component (several ns). The bolometric component is stronger at temperatures in the vicinity of the transition region to the normal state. The nonbolometric component is dominant at temperatures below the transition region showing weak temperature dependence and a linear dependence on the bias current. This nonbolometric component may be evidence for nonequilibrium effects (e.g., breaking of Cooper pairs and generation of quasiparticles or other mechanisms). These results suggest that with proper optimization of device parameters (its geometry, critical current density, etc.) high-speed detectors with reasonable sensitivity covering a broad electromagnetic spectrum (visible and infrared) may be developed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101390
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  • 7
    Digitale Medien
    Digitale Medien
    High Tc superconducting film as a fast nonlinear switch for noise discrimination in digital circuits (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2704-2706 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Measurements of fast nonlinear switching of a high Tc superconducting thin film at 70 K between the dissipative state (induced by an electrical current) and superconducting state are reported. System rise and fall times are measured to be about 1 ns and are limited by the parasitic components of the electrical circuitry. A novel scheme for noise discrimination in digital circuits using this switching has been proposed and experimentally demonstrated for speeds exceeding 200 Mb/s. This method allows significant reduction of amplitude noise and improvement of signal-to-noise ratio in digital circuits.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.100551
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  • 8
    Digitale Medien
    Digitale Medien
    Growth by molecular beam epitaxy and electrical characterization of Si-doped zinc blende GaN films deposited on β-SiC coated (001) Si substrates (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 91-93 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the electrical characteristics of heavily Si-doped zinc blende GaN epilayers deposited on β-SiC coated (001) Si substrates. The β-GaN films were grown by molecular beam epitaxy using a rf plasma discharge, nitrogen free-radical source, and the doping concentration in the films was controlled over the range 1.5×1018–3.0×1020 cm−3 by suitably adjusting the temperature of a Si effusion cell. We have found that Si incorporation in β-GaN results in a relatively deep donor level (∼62 meV below the conduction band edge at a carrier concentration at room temperature of 1018 cm−3). Also, we present evidence of simultaneous high mobility conduction band conduction (dominant at high temperatures) and low mobility impurity band conduction (dominant at temperatures 〈70 K) in heavily doped (nRT(approximately-greater-than)1019 cm−3) material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.113085
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  • 9
    Digitale Medien
    Digitale Medien
    MALIGNANT CHANGE IN A VERRUCOUS NEVUS (1978)
    Oxford, UK : Blackwell Publishing Ltd
    International journal of dermatology 17 (1978), S. 0 
    Details
    ISSN: 1365-4632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: : A 41-year-old man developed squamous-cell carcinoma within a verrucous nevus of linear distribution of a long duration. Controversial cases have been reported in the literature. Such malignant change in verrucous nevus is extremely rare.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-4362.1978.tb06067.x
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  • 10
    Digitale Medien
    Digitale Medien
    Photosynthesis (1953)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biochemistry 22 (1953), S. 423-458 
    Details
    ISSN: 0066-4154
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Chemie und Pharmazie , Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.bi.22.070153.002231
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