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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we have prepared Fe/Cu, Ag, Au/Fe sandwiches by ion beam sputtering and studied the interlayer coupling behavior by ferromagnetic resonance technique. In these sandwiches the Fe and noble metal layers are polycrystalline in the textures of (110) and (111), respectively. It is found that the in-plane resonance field and the linewidth oscillate as a function of nonmagnetic layer thickness in a period of about 1.0 nm for Fe/Cu, Au/Fe structures, and 1.4 nm for Fe/Ag/Fe system. It is suggested that the interlayer coupling strength between the ferromagnetic layers oscillates in the same period with the resonance field. An in-plane anisotropy was found in Fe/Ag/Fe system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 23 (1999), S. 178-187 
    ISSN: 1476-5535
    Keywords: Keywords: actinomycete diversity; phylogeny; rRNA; tropical rainforest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Five thousand actinomycetes were isolated from soil samples collected from rainforests in Singapore and the generic identities of these isolates were determined by using a procedure that combined morphological, chemotaxonomic and 16S rDNA sequence-based phylogenetic analyses. Actinomycetes belonging to a total of 36 genera were identified. The most abundant isolates are members of Streptomyces, Micromonospora, Actinoplanes, Actinomadura, Nonomuria, Nocardia and Streptosporangium. By phylogenetic analysis of 16S rDNA sequences of our isolates together with those of known actinomycete species, we also evaluated the species diversity of several genera including Streptomyces, Micromonospora, Nonomuria, and Actinomadura. We found that: first, the tropical isolates are present in most clades represented by known species; and second, many tropical isolates form new clades distant from the known species, indicating the presence of unidentified taxa at both species and genus levels. Based on these results, we conclude that actinomycete diversity in the tropical rainforest is very great and should represent an excellent source for discovery of novel bioactive compounds.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1765-1767 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room temperature photoreflectance (PR) was used to investigate the surface state densities of GaAs and In0.52Al0.48As surface intrinsic-n+ structures. The built-in electric field and thus the surface barrier height are evaluated using the observed Franz–Keldysh oscillations in the PR spectra. Based on the thermionic emission theory and current-transport theory, the surface state density as well as the pinning position of the Fermi level can be determined from the dependence of the surface barrier height on the pump beam intensity. Even though this method is significantly simpler, easier to perform, and time efficient compared with other approaches, the results obtained agree with the literature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5407-5412 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The self-encapsulation kinetics of Ag/Al bilayers were studied both experimentally and theoretically as part of the effort to introduce Ag as an alternative metallization scheme for future ultra-large-scale-integrated technologies. Theoretical modeling was based on an analytical solution of a modified diffusion equation, which incorporated the diffusion of Al atoms through the Ag layers during the Ag/Al bilayer encapsulation progress. The amount of segregated Al atoms was monitored by both Rutherford backscattering spectrometry and film resistivity measurements, and correlated well with the theoretical predictions. These findings showed that the kinetics of the self-encapsulation could be significantly affected by both (i) the chemical affinity between Al and Ag atoms, and (ii) the interfacial energy between the metal layer (Ag) and the newly formed AlxOyNz diffusion barriers. Higher anneal temperatures were shown to accelerate the encapsulation process, and hence, achieved a lower resistivity in the underneath Ag layer. This model, in addition, confirmed the self-passivating characteristics of AlxOyNz diffusion barriers formed by Ag/Al bilayers annealed between 500 and 725 °C. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Trace non-recycling impurities have been injected into Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] plasmas in order to determine impurity transport coefficients. Subsequent impurity emission has been observed with spatially scanning x-ray and Vacuum Ultra-Violet (VUV) spectrometer systems. Measured time-resolved brightness profiles of helium- and lithium-like transitions have been compared with those calculated from a transport code which includes impurity diffusion and convection in conjunction with an atomic physics package for individual line emission. During Low-Confinement-Mode (L-mode) plasmas, the transport can be characterized by pure diffusion, with coefficients ∼5000 cm2/s, reflecting the ∼20 ms decay in the x-ray and VUV line brightnesses. During High-Confinement-Modes (H-modes), the impurity confinement times are much longer, and the modelling requires that there be a strong inward convection (of order 1000 cm/s) near the plasma edge, with greatly reduced diffusion (of order 100 cm2/s), also in the region of the edge transport barrier. These edge values of the transport coefficients during H-mode are qualitatively similar to the neo-classical values. Nitrogen has also been injected, and after the H- to L-mode transition, the inner shell satellite lines of lithium-like nitrogen dominate in intensity the resonance line of helium-like N5+ in a thin shell near the plasma edge. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5302-5304 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of samples consisting of a strained layer of GaNxAs1−x of different thickness, covered by a GaAs cap layer of 100 nm were grown by molecular-beam epitaxy. The samples have been characterized by high-resolution x-ray diffraction and simulations based on the dynamical theory in order to determine the strain relaxation in GaNxAs1−x layers. It is found that there is a huge difference between the critical thickness determined by x-ray diffraction and the theoretical calculations according to the Matthews and Blakeslee model. The critical thickness of GaNxAs1−x on GaAs is ten times smaller than the theoretical value. The strain relaxation is a crucial point that affects the quality of GaNAs. Photoluminescence measurements are in good agreement with the x-ray diffraction results. The optical properties degraded rapidly when the GaNxAs1−x thickness exceeded the critical thickness determined above. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: X-ray spectra from Alcator C-Mod plasmas have been collected using a high wavelength resolution, five spectrometer array during a wide range of operating conditions, providing a large variety of diagnostic information. Each independently scannable von Hamos type spectrometer has a wavelength range of 2.8–4.0 A(ring), and the complete Rydberg series of helium- and hydrogenlike argon have been observed. Spectra of Δn=1 ground state transitions and satellites taken along different chords have been simulated using the results from a collisional-radiative model and the mist transport code. Line ratios are very sensitive to the electron temperature and deduced profiles are in good agreement with ECE profiles. Line intensities have been utilized to obtain absolute argon densities. The widths of the strongest lines have been used to deduce ion temperature profiles. Transitions from around n=9 to the ground state are populated by charge exchange in the outer regions of the plasma and these line intensities have been used to determine the neutral hydrogen density profile. Spectra from heliumlike scandium have been obtained during injection experiments and time histories and line intensities have been utilized to determine impurity transport coefficients. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Risk analysis 18 (1998), S. 0 
    ISSN: 1539-6924
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Estimates were made of the numbers of liver carcinogens in 390 long-term bioassays conducted by the National Toxicology Program (NTP). These estimates were obtained from examination of the global pattern of p-values obtained from statistical tests applied to individual bioassays. Representative estimates of the number of liver carcinogens (90% confidence interval in parentheses) obtained in our analysis compared to NTP's determination are as follows: female rats—49 (23, 76), NTP = 30; male rats—88 (59, 116), NTP = 35; female mice—131 (105, 157), NTP = 81; male mice—100 (73, 126), NTP = 61; overall—166 (135, 197), NTP = 108. The estimator from which these estimates were obtained is biased low by an unknown amount. Consequently, this study provides persuasive evidence of the existence of more rodent liver carcinogens than were identified by the NTP.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The novel compounds Nd3Fe29−xTx (T=V and Cr) have been successfully synthesized. Their x-ray patterns can be indexed with a monoclinic symmetry and the A2/m space group. The Curie temperatures of Nd3Fe29−xTx are 455 and 413 K for T=V and Cr, the saturation magnetization at 4.2 K and room temperature are 54.7 and 46.8 μB/f.u. for T=V and 49.9 and 32.2 μB/f.u. for T=Cr, and the anisotropy fields at 4.2 K and room temperature are 12.8 and 2.4 T for T=V and 9.1 and 1.2 T for T=Cr, respectively. The spin reorientations of the easy magnetization direction of Nd3Fe29−xTx are observed at around 230 K for T=V and 135 K for T=Cr, respectively. After nitrogenation the relative volume expansion was about 6%, Curie temperature of each nitride increased about 50%, and the transition temperature Tsr of the spin reorientations of the nitride also increased 145 K for T=V and 250 K for T=Cr, respectively, compared with its parent compound. Nitrogenation resulted in remarkable improvements in the saturation magnetization and anisotropy fields at 4.2 K and room temperature. Magnetohistory effects for Nd3Fe29−xTx and Nd3Fe29−xTxN4 (T=V and Cr) in a low field have been observed. © 1997 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5256-5258 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the electronic structure and optical properties, in the photon energy range of 3.0–4.5 eV, of sputtered Co/Ag multilayers with a scanning ellipsometer and Kerr spectrometer. It is found for the multilayer series Co(1.2 nm)/Ag and Co/Ag with dCo/dAg=2/3 that the screened plasma frequency ωp* of the multilayers and the interband transition frequency ω0 for L3→L2′ (d band to Fermi surface near the L point) in the Ag layers shift towards lower energy with increasing Ag layer thickness or modulation wavelength. For the second series of samples, the Kerr rotation peak also shifts towards lower energy with increasing modulation wavelength. For a third series of Co/Ag(1.3 nm) multilayers, only ω0 moves towards lower energy with an increasing Co layer thickness. The variation of ω0 is not easily explained in terms of internal strains and changes of the lattice constants in the Ag layers. Further theoretical analysis is needed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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