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  • Articles  (109)
  • 1990-1994  (53)
  • 1985-1989  (54)
  • 1945-1949  (2)
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  • 11
    Electronic Resource
    Electronic Resource
    Ion-induced depletion of hydrogen from a soft carbonized layer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3833-3837 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft carbonized layers prepared in a glow discharge, with a hydrogen concentration of H:C∼4/3, are exposed to helium ion bombardment at energies between 0.3 and 2.6 MeV. A strong ion-induced depletion of up to 3×103 H atoms per incident 4He+ ion is observed by means of high-energy ion beam analysis. The hydrogen release is shown to be a local process, with the electronic energy deposition as the main responsible mechanism. The results are successfully compared to a model which takes into account local bond breaking and retrapping and the local formation of hydrogen molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343399
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  • 12
    Electronic Resource
    Electronic Resource
    Absolute density determination of CH radicals in a methane plasma (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 971-973 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-induced fluorescence was applied at the B–X transition of the CH radical to measure absolute densities of the CH radicals in an electron cyclotron resonance methane plasma. The absolute experimental uncertainty is only about 30% due to a new calibration procedure. The CH density correlates well with optical emission from the CH A–X and B–X transitions over a wide pressure range. Experimental results are in satisfactory agreement with predictions from a model based on rate equations for the electron-induced dissociation and ionization of the parent methane gas. This model also includes the interaction of the plasma species with the surrounding walls and the particle transport due to pumping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110949
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  • 13
    Electronic Resource
    Electronic Resource
    On the structure of thin hydrocarbon films (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1771-1773 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.110683
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  • 14
    Electronic Resource
    Electronic Resource
    Deposition of dense hydrocarbon films from a nonbiased microwave plasma (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 937-939 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.108525
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  • 15
    Electronic Resource
    Electronic Resource
    Modeling of the sp3/sp2 ratio in ion beam and plasma-deposited carbon films (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2391-2393 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Model calculations are described which predict the fraction of tetrahedral (sp3) versus graphitic (sp2) bonding in ion beam or plasma-deposited amorphous carbon films on the basis of the preferential displacement of sp2 atoms. Displacement yields obtained from static trim simulations are used as input data for a simple analytical growing layer model of ion beam deposition. The sp3/sp2 ratio is found to increase with increasing carbon ion energy between 30 eV and 1 keV. Assuming equal probabilities for a free (implanted or displaced) atom to become trapped at either sp2 or sp3 sites results in sp3/sp2 ratios between 1 and 3.5. More refined dynamic simulations with tridyn confirm the trends with slightly lower sp3/sp2 ratios for ion beam or plasma deposition, also involving hydrogen. A decrease of the sp3/sp2 ratio towards high energies cannot be explained by preferential displacement only, in contrast to proposals in recent literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106026
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  • 16
    Electronic Resource
    Electronic Resource
    Running waveguide discharge for inner coating of metal tubes (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3401-3403 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.111291
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  • 17
    Electronic Resource
    Electronic Resource
    Effect of Humidity on Properties of Plasticized Ethylcellulose (1947)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 39 (1947), S. 1149-1152 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie50453a019
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  • 18
    Electronic Resource
    Electronic Resource
    Permeation of implanted deuterium through Ni near room temperature (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 2733-2738 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The permeation of 2–22-keV deuterons implanted into 25-μm-thick cold-rolled Ni foils was studied near room temperature. The results are generally characterized by a time lag τ and a steady-state permeation rate J. The variation of τ with beam intensity and temperature indicates an average relative concentration of ∼4×10−4 of saturable bulk traps of binding energy 0.26±0.01 eV, plus a larger concentration of weaker traps. At the highest energy, J is well described by theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335415
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  • 19
    Electronic Resource
    Electronic Resource
    Isotopic exchange in hard amorphous carbonized layers (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 163-168 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hard amorphous films of a-C:H and a-C:D were deposited by a rf glow discharge in either CH4 or CD4 . By ion bombardment with protons and deuterons, the H/D exchange process was studied as function of the bombardment fluence by means of depth profile measurements. The local hydrogen and deuterium contents are not adding up to a constant "saturation'' value: the local mixing model is not valid. Instead of that an initial depletion appears, which depends on the incident energy of the ions. At higher fluences, the total (H+D):C ratio tends to increase again, due to an increasing influence of the deposition process. This demonstrates a structural difference between a-C:H films and hydrogen-saturated layers of implanted carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345296
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  • 20
    Electronic Resource
    Electronic Resource
    Statistical evidence for remnants of the primordial code in the acceptor stem of prokaryotic transfer RNA (1992)
    Springer
    Journal of molecular evolution 34 (1992), S. 471-477 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00160461
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