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  • 1
    ISSN: 1432-1432
    Keywords: Transfer RNA ; Acceptor helix stem ; Primordial code ; Statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The specificity of interaction of amino acids with triplets in the acceptor helix stem of tRNA was investigated by means of a statistical analysis of 1400 tRNA sequences. The imprint of a prototypic genetic code at position 3–5 of the acceptor helix was detected, but only for those major amino acids, glycine, alanine, aspartic acid, and valine, that are formed by spark discharges of simple gases in the laboratory. Although remnants of the code at position 3–5 are typical for tRNAs of archaebacteria, eubacteria, and chloroplasts, eukaryotes do not seem to contain this code, and mitochondria take up an intermediary position. A duplication mechanism for the transposition of the original 3–5 code toward its present position in the anticodon stern of tRNA is proposed. From this viewpoint, the mode of evolution of mRNA and functional ribosomes becomes more understandable.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Corrosion-resistant, hermetic microelectronic packages for aerospace applicationsCorrosion-resistant, high reliable aerospace electronics need expensive ceramic substrates, noble metal conductors and very clean stainless steel or ceramic packages. The requirements, material technologies, problems and more economical packages are described.
    Notes: Zur Vermeidung von Korrosionsschäden an Sicherheitselektroniken der Luft- und Raumfahrt sowie der Wehrtechnik werden vorzugsweise Keramik-Substrate und Edelmetall-Leiter sowie völlig feuchte- und salzfreie, hermetisch verschlossene Metall oder Keramikgehäuse verwendet. Die Anforderungen, Materialien, Technologien und Probleme der hermetischen Mikroelektronik-Verpackung wird im folgenden Aufsatz näher beschrieben werden.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0630
    Keywords: 52.25.Dg ; 79.20.Nc ; 82.65.Yh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The elementary mechanisms are described which determine the plasma and surface processes during the plasma-enhanced chemical vapour deposition of hydrogenated carbon films from methane. Corresponding model calculations are reviewed and critically discussed in comparison to experimental results. A realistic modeling requires the simultaneous and self-consistent treatment of plasma and surface effects. Several experimental data sets on plasma parameters and the growth and the composition of the films have been reproduced successfully. However, a broader experimental data base is needed for more critical tests of the models. The reliability of the modeling, in particular of the surface effects, is still limited due to the poor availability of elementary data.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0630
    Keywords: PACS: 68.55.-a; 61.82.Bg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The amorphous non-equilibrium state of the system Fe/Al is studied in bulk and thin-film systems. For bulk samples prepared by ion-beam mixing of laser-deposited multilayers, a bcc solid solution is found for alloys with up to 70 at. % Al. Around 75 at. % Al a Fe2Al5-like crystalline phase is found. An amorphous state with Fe2Al5-like short-range order is found for 80 at. % Al. In thin films, for example the amorphous Al-rich transition layer of a laser-deposited Fe/Al multilayer, the amorphous state can exist for up to 30 at. % Fe due to the high interfacial energy. By ion-beam mixing at low temperatures (about 140 K) an oversaturation with 40 at. % Fe can be achieved.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0630
    Keywords: PACS: 68.55.-a; 61.82.Bg; 81.40.Rs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Co/Cu multilayers were prepared by crossed-beam pulsed laser deposition and characterized by high-angle X-ray diffraction, as well as specular and non-specular reflection. Ion-beam mixing of the multilayers with 150 keV Cu+ ions and a fluence of up to 5×1015 cm-2 leads to the formation of a granular system of superparamagnetic Co clusters in Cu, as shown by magnetic measurements.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 55-57 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is demonstrated that the intrinsic stress in cubic boron nitride films can be significantly relaxed during growth by simultaneous medium-energy ion implantation. The stress in the growing film has been studied in situ using cantilever curvature measurements and has been reduced to below 2 GPa by simultaneous Ar+ or N+ ion implantation with an energy of 70 and 35 keV, respectively. The resulting cubic boron nitride films show an increased long-term stability. The results reveal that the stress in cBN is not reduced due to segregation of boron at grain boundaries. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1404-1406 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism of diffusional transport during low-energy ion nitriding of aluminum has been investigated using marker and isotope sequence techniques in connection with ion-beam analysis. For an ion energy of 1 keV and a temperature of 400 °C, it is shown that the nitride grows at the surface with aluminum being supplied by diffusion from the underlying bulk. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3401-3403 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A plasma-enhanced chemical vapor deposition process by means of the so-called running discharge has been developed. Amorphous hydrogenated carbon (C:H) films were deposited over a length of 2.5 m on the inner wall of an assembled waveguide system. The average deposition rate from a running discharge in methane was 0.27 A(ring)/s. An increase of the average deposition rate to 2.6 A(ring)/s was achieved using acetylene as process gas, while the H/C ratio in the C:H films remains nearly constant at one. The breakdown of a discharge in the metallic waveguide has been studied in argon plasmas depending on magnetic field, microwave power, and gas pressure. A sharp transition between a magnetically enhanced localized discharge and a running discharge was observed at increasing pressure in the range of some Pascal at a microwave power of 100 W. The running velocity (∼104 m/s) of the plasma package increases with increasing microwave power and increasing gas pressure. This plasma behavior has been further investigated by means of the power balance and plasma modeling in methane.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1771-1773 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We compare reported compositions of a-C:H films in a ternary phase diagram. It is assumed that the films comprised three phases: sp3 hybridized carbon, sp2 hybridized carbon and hydrogen. The data are found to split into two well-separated groups. This separation depends on the method used to measure the sp3/sp2 ratio. We conclude from the comparison of NMR and infrared data that infrared analysis does not provide a quantitative measure of the sp3/sp2 ratio.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 937-939 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An electron cyclotron resonance plasma was used to prepare C:H layers from methane. The temperature dependence of the deposition rate was investigated at substrate temperatures ranging from room temperature to 700 K, at a gas pressure of 1.6 Pa. Despite low ion energies corresponding to the plasma potential, transparent hard coatings were obtained at elevated temperature with a density up to 2 g cm−3. A deposition model is proposed which describes the growth from an adsorbed layer, including surface reactions with radicals and atomic hydrogen as well as the direct incorporation of ions. Two different deposition processes can be identified, yielding polymerlike films in the temperature range up to 450 K and dense hydrocarbons above this temperature. The observed temperature dependence of the film properties such as H/C ratio, index of refraction, and density is consistent with the predictions of the model.
    Type of Medium: Electronic Resource
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