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  • 1990-1994  (7)
  • 1985-1989  (2)
  • 1975-1979  (1)
  • 1970-1974  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5370-5372 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Meissner effect measurements were used to characterize the effect of copper depletion and silver substitution on the bulk superconducting properties of YBa2Cu3Oy. A strong copper composition dependence of superconductivity was observed: A 20% depletion of copper from the samples resulted in an 88% decrease in the strength of superconductivity in YBa2Cu3Oy as measured by the Meissner effect. Because flux trapping and field penetration were likely to be significant in the high-Tc materials, it was difficult to determine the volume fraction of superconducting material in the samples. Variations in the lattice constants were consistent with copper composition-induced disorder on the orthorhombic lattice which became more pseudocubic, i.e., a(approximately-equal-to)b=c/3, with copper depletion. The addition of silver had essentially no effect on superconductivity or the lattice constants of YBa2Cu3Oy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 47 (1992), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Seven varieties of white clover (Trifolium repens L.), of varying leaf size from large to small, were sown with perennial ryegrass (Lolium perenne L.) in 1985, at an upland site, and compared over three harvest years under a cutting management (5-6 cuts), and under continuous grazing by sheep. Fertilizer N input totalled 80 kg ha−1 in both the cutting and the grazing trial. The same varieties were included in two official National List (NL) trials sown the same year at a nearby site; these comprised a yield trial with 6-7 cuts and a persistency trial mown very frequently (17 cuts) to simulate intensive grazing.At the upland site the large-leaved varieties, Milkanova and Blanca, were the highest yielding under cutting (mean 3·3 t DM ha−1), and the small-leaved S184 and Kent the lowest yielding (mean 2·3 t DM ha−1). The rankings were reversed under grazing (corresponding yields 1·1 and 2·1 t DM ha−1). The medium-leaved varieties Donna, Menna and Grasslands Huia behaved similarly to the large-leaved varieties. Ranking order in the cutting trial was similar to that in the NL trial.Ground covers after three harvest years differed significantly only under grazing, when the small-leaved varieties had a 2-3 times greater cover than the larger-leaved varieties. A poor separation of the varieties in the NL persistency trial suggests that defoliation was not sufficiently severe to simulate intensive grazing.These comparisons indicate that the performance of clover varieties under the cutting regimes used should not be extrapolated to continuous sheep grazing.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1859-1861 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth of cubic boron nitride (cBN) films by magnetron sputtering on Si (100) substrates. The films are grown in the presence of negative substrate bias voltages and a nitrogen plasma produced by an electron cyclotron resonance source. We find evidence for a sharp low-voltage threshold in the substrate bias (−105 V) beyond which the samples are predominantly cBN. The structural quality of the cBN films is optimized in a narrow range of voltages near this threshold. We discuss the important role of energetic ions in the formation of cBN in light of recent theoretical findings.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1251-1253 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report results from cathodoluminescence spectroscopy of boron nitride films grown on Si(100) substrates by ion-source-assisted magnetron sputtering of a hexagonal BN target. Three main peaks are observed in the near-band-gap region for hexagonal boron nitride films at energies of 4.90, 5.31, and 5.50 eV. We also report deep-level emission spectra of predominantly cubic boron nitride films which are correlated with sample growth conditions. In particular we show that the emission intensity, position, and linewidth are strongly dependent on the substrate bias voltage used during sample growth.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2112-2114 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft x-ray core-level photoabsorption has been measured from three forms of boron nitride, namely the hexagonal (hBN), cubic (cBN), and incoherent (iBN) phases. The B 1s and N 1s photoabsorption spectra of the hBN sample show evidence of both σ*- and π*-empty states, indicative of sp2 bonding, while the cBN absorption spectra exhibits only sp3 bonding in absorption features characteristic of the zincblende structure. The incoherent phase of BN in the form of a thin film on a Si substrate possesses σ* and π* states similar to hBN. The B 1s π* absorption features of the iBN film show an angular dependence which suggests that the microstructure consists of hexagonal-phase layer planes oriented normal to the BN/Si interface.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 108 (1986), S. 7104-7105 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5518-5522 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report transport critical-current measurements of the YBa2Cu3Oy high-Tc superconductors using a contactless transformer technique. A critical-current density of 15.9±1.0 A/cm was observed at 77 K for samples fabricated by a standard preparation method for the high-Tc superconductors. The addition of a small amount of silver to samples of YBa2Cu3Oy has a dramatic degrading effect on the critical current. This is in sharp contrast to the Meissner-effect results, where silver addition has a minimal effect. No significant systematic frequency dependence of the critical-current determination was found between 10 and 5000 Hz. Visual observations of "blips'' in oscilloscope traces and an extrapolation of signals to zero blip height gave consistent results and established an uncertainty of ∼3% for critical-current determination. The range of dimensions of the ring-shaped samples yielded an uncertainty of ∼3% for the cross-sectional area. The overall uncertainty for an absolute measurement of the critical-current density is consequently ∼6%. The uncertainty in relative measurements of the critical-current density is very much less.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 253-254 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 5 (1972), S. 133-134 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The paper describes the use of computer-generated patterns and a photo-etching technique to produce high quality optical diffraction masks containing several thousand holes for the study of short-range order in crystals.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 4 (1971), S. 20-30 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A brief outline of the essential features of the geometry of X-ray fibre diffraction patterns is given and leads to a discussion of the beginnings of a systematic study, using optical diffraction patterns, of the correspondence between various features of the structure and effects in the X-ray scattering pattern.
    Type of Medium: Electronic Resource
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