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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geostandards and geoanalytical research 28 (2004), S. 0 
    ISSN: 1751-908X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Various zircons of Proterozoic to Oligocene ages (1060-31 Ma) were analysed by laser ablation-inductively coupled plasma-mass spectrometry. Calibration was performed using Harvard reference zircon 91500 or Australian National University reference zircon TEMORA 1 as external calibrant. The results agree with those obtained by SIMS within 2s error. Twenty-four trace and rare earth elements (P, Ti, Cr, Y, Nb, fourteen REE, Hf, Ta, Pb, Th and U) were analysed on four fragments of zircon 91500. NIST SRM 610 was used as the reference material and 29Si was used as internal calibrant. Based on determinations of four fragments, this zircon shows significant intra-and inter-fragment variations in the range from 10% to 85% on a scale of 120 μm, with the variation of REE concentrations up to 38.7%, although the chondrite-normalised REE distributions are very similar. In contrast, the determined age values for zircon 91500 agree with TIMS data and are homogeneous within 8.7 Ma (2s). A two-stage ablation strategy was developed for optimising U-Pb age determinations with satisfactory trace element and REE results. The first cycle of ablation was used to collect data for age determination only, which was followed by continuous ablation on the same spot to determine REE and trace element concentrations. Based on this procedure, it was possible to measure zircon ages as low as 30.37 0.39 Ma (MSWD = 1.4; 2s). Other examples for older zircons are also given.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1014-1016 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report successful fabrication of GaAs/Al0.26Ga0.74As double-heterostructure laser diodes grown on patterned Si substrates by molecular beam epitaxy. The patterned substrates consist of exposed Si stripes with widths ranging from 9 to 70 μm and surrounded by 900 A(ring) of SiN films on both sides. Oxide-defined contact stripe lasers with stripe widths ranging from 3 to 50 μm (corresponding to each of the SiN-defined stripe windows) were fabricated. Reduction of laser threshold current densities compared to similar lasers grown on nonpatterned Si substrates is observed, and is attributed to current confinement effect by the high-resistivity polycrystalline GaAs/AlGaAs films surrounding the active devices. From the measurements on the longitudinal mode spectrum and far-field patterns, lateral index guiding is also observed for the 10-μm-wide selective-area grown laser.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2695-2697 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs films were grown on Si substrates by a two-step method in which a thin buffer layer was first deposited using a modulated molecular beam epitaxy (MBE) technique followed by a thick layer grown by conventional molecular beam epitaxy. The film quality was evaluated using 77 K photoluminescence (PL) and double-crystal x-ray rocking curves. It was found that GaAs films grown in this way have a superior crystalline quality compared to the films prepared by normal two-step MBE. To investigate the nucleation of this buffer layer, thin GaAs layers (150 A(ring)) were grown on Si substrates and examined by plan-view and cross-sectional transmission electron microscope. A thin, two-dimensional nucleation pattern was found in this sample, in clear contrast to the three-dimensional nucleation islands found in samples grown by conventional MBE. This showed conclusively that modulated beam molecular beam epitaxy resulted in a more uniform and two-dimensional nucleation during the initial stage of the growth as speculated earlier and is believed to be the reason for the improvement of the crystalline quality of the overgrown layer.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The metal-sulphur active sites of hydrogenases catalyse hydrogen evolution or uptake at rapid rates. Understanding the structure and function of these active sites—through mechanistic studies of hydrogenases, synthetic assemblies and in silico models—will help guide the design of ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2394-2396 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) at 77 K is used to study tensile stress variations in chemically etched stripes of a 3-μm-thick GaAs film grown on Si substrate. The etched patterns consist of 1-mm-long stripes with widths ranging from 100 to 4 μm and 4 μm by 4 μm squares. We observed monotonic shift of PL peaks towards shorter wavelength for decreasing stripe width. In particular, when the width of the stripe is less than 7 μm, tensile stress is essentially uniaxial as evident from the magnitude of shift in PL peaks. The polarization characteristics of the PL spectra of these uniaxially stressed stripes are investigated and found to agree well with theoretical predictions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1955-1957 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The polarization of laser radiations from AlGaAs/GaAs double-heterostructure lasers grown on planar, trenched, and SiN-patterned Si substrates are examined. It was found that TM modes lase first in most of these lasers. Competition between TE and TM modes also occurs in some devices. A qualitative explanation is given on the basis of stress-induced changes in the optical gains between TE and TM modes. The difference in the polarization behavior among these lasers indicates that the residual tensile stress is influenced by substrate patterning.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 70 (2005), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : The effects of high hydrostatic pressure (HHP) on flavor-binding properties of whey protein concentrate (WPC) were determined with benzaldehyde, heptanone, octanone, and nonanone. After HHP treatment (600 MPa, 50 °C, for 0-, 10-, or 30-min holding time), flavor-binding properties of WPC were studied by intrinsic fluorescence titration and static headspace analysis. The HHP treatments increased the number of binding sites and the apparent dissociation constants of WPC for benzaldehyde. HHP treatment of WPC for 0 min increased the number of binding sites of WPC for heptanone and octanone. As observed by headspace analysis, HHP treatments did not result in significant changes in the flavor retention for benzaldehyde in WPC solutions. Flavor retention of 100 ppm and 200 ppm heptanone and octanone in HHP-treated (10 min) WPC was significantly lower than for untreated WPC and HHP-treated WPC for 0 min or 30 min. For flavor retention of nonanone, significant decreases were only observed at 100 ppm when WPC solutions were HHP-treated for 10 min. While use of HHP treatment of WPC has potential in real food systems, these findings demonstrate the importance of careful selection of HHP treatment times and flavor concentrations for desired outcomes in food applications.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 1142-1143 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The title compound, C17H13N3, is a versatile precursor for polymeric terpyridine derivatives and their metal complexes. The molecule has transoid and near-coplanar pyridine rings. However, the vinyl group is forced out of the plane of the terpyridyl moiety by a close H...H contact.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 317-318 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The title compound, C9H10Br2O, is a major product of the radical bromination of 4-methoxy-1,2-dimethylbenzene. Each Br atom is involved in a close contact with the O atom of a neighbouring molecule, forming a geometry that is suggestive of weak intermolecular O\rightarrowBr charge-transfer interactions.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 1253-1255 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: trans-Dibromobis(5-tert-butylpyrazole-N2)copper(II), trans-[CuBr2(HpztBu)2] (HpztBu is 5-tert-butylpyrazole, C7H12N2), exhibits a distorted square-planar geometry with a significant tetrahedral twist, while trans-dibromotetrakis(5-tert-butylpyrazole-N2)copper(II), trans-[CuBr2(HpztBu)4], adopts a distorted octahedral geometry across a crystallographic inversion centre. Both compounds exhibit intramolecular N—H...Br hydrogen-bonding interactions.
    Type of Medium: Electronic Resource
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