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  • 1995-1999  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Concurrent variation of giant magnetoresistance and saturation Kerr rotation in NiCo/Cu multilayers (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 3371-3373 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dependences of magneto-optical effect, effective optical constants, and giant magnetoresistance (GMR) on the thickness of Cu layers were investigated in NiCo/Cu multilayers prepared by rf magnetron sputtering. A peak of saturation polar Kerr rotation θK, occurred simultaneously with that of GMR ratio when the Cu thickness is around 1.0 nm, where a clear drop of the effective optical constants n and k appeared. The peak of θK is mainly caused by the reduction of the effective optical constants, which dominate over the small drop of the effective off-diagonal elements of the dielectric tensor. The concurrent variation of GMR and θK is related to antiferromagnetic interlayer coupling, which may change the electron band structure and thus the optical and magneto-optical transitions of electrons. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121607
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  • 2
    Electronic Resource
    Electronic Resource
    Modification of band offsets by a ZnSe intralayer at the Si/Ge(111) interface (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2707-2709 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, the use of an ordered ultrathin ZnSe dipole layer to significantly modify the band discontinuity at the Si/Ge(111)-c(2×8) heterojunction is reported. Soft x-ray photoemission spectroscopy (SXPS) was utilized to monitor the evolution of the interface. The ZnSe intralayer increased the valence band offset by ∼0.57 eV, as compared to a negligible valence band offset for the Si/Ge(111) junction. This dramatic modification is interpreted in terms of the charge transfer at the interface. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121106
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  • 3
    Electronic Resource
    Electronic Resource
    Elastic constants and their pressure dependence of Zr41Ti14Cu12.5Ni9Be22.5C1 bulk metallic glass (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1803-1805 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The acoustic velocities and their pressure dependence of bulk Zr41Ti14Cu12.5Ni9Be22.5C1 metallic glass (MG) have been measured up to 0.5 GPa by using a pulse echo overlap method. The elastic constants and thermodynamic parameters as well as their pressure dependence of the MG have been determined. The obtained elastic constants were compared to that of other kinds of glasses. More information about the microstructure, elastic properties, and glass forming ability of the MG was obtained. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123091
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  • 4
    Electronic Resource
    Electronic Resource
    A novel regulatory system required for pathogenicity of Xanthomonas campestris is mediated by a small diffusible signal molecule (1997)
    Oxford BSL : Blackwell Publishing Ltd
    Molecular microbiology 24 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Mutations in the seven clustered rpf genes cause downregulated synthesis of extracellular enzymes and reduced virulence of Xanthomonas campestris pathovar campestris (Xcc). The phenotype of mutants in one of the genes, rpfF, can be restored by a diffusible extracellular factor (DSF) produced by all Xcc strains tested, apart from rpfF and rpfB mutants. DSF accumulates in early stationary phase (when synthesis of enzymes is maximal), but levels decline subsequently. Addition of DSF to exponentially-growing wild-type bacteria does not cause precocious enzyme synthesis. rpfB and rpfF are expressed throughout growth, but the rate increases in early stationary phase. RpfB is predicted to be a long-chain fatty acyl CoA ligase, and RpfF shows some relatedness to enoyl CoA hydratases. The properties of DSF suggest that it may be a fatty-acid derivative, and certain lipid preparations possess DSF activity at higher concentrations. These include lipid extracts and acid-hydrolysed lipopolysaccharide and lipid A from Xcc, and purified dodecanoic and hydroxydodecanoic acid. DSF production is confined to certain xanthomonads. We propose a model for the DSF system, which represents a novel mechanism for regulating virulence factor synthesis in response to physiological or environmental changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.3721736.x
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  • 5
    Electronic Resource
    Electronic Resource
    The rpfA gene of Xanthomonas campestris pathovar campestris, which is involved in the regulation of pathogenicity factor production, encodes an aconitase (1998)
    Oxford BSL : Blackwell Publishing Ltd
    Molecular microbiology 28 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Xanthomonas campestris pv campestris (Xcc) is a plant pathogenic bacterium that controls the production of pathogenicity factors in part by a cluster of genes designated rpf (regulation of pathogenicity factors). Sequence analysis of one of these genes (rpfA) revealed an open reading frame with amino acid sequence similarity to aconitases from other bacteria. Aconitase activity was lower in cellular extracts of an rpfA::Tn5 mutant than in those from the wild type. A zymogram of aconitase activity after native gel electrophoresis showed the presence of two distinct aconitases in Xcc; the major aconitase was absent in the rpfA::Tn5 mutant. This mutant also had reduced levels of extracellular enzymes and extracellular polysaccharide (EPS). Supplying rpfA in trans to the rpfA::Tn5 mutant restored both the major aconitase activity and the synthesis of these pathogenicity factors. The transcription of the genes for two extracellular enzymes (prtA, encoding a serine protease, and engXCA, encoding endoglucanase) was reduced in the rpfA mutant background. Because some eukaryotic aconitases are also involved in iron regulation, we explored a possible connection between rpfA and iron metabolism. Intracellular iron levels in the mutants were lower than in the wild type as assessed by sensitivity to the iron-activated antibiotic, streptonigrin. Wild-type bacteria grown in iron-deficient conditions had a similar sensitivity to streptonigrin as the aconitase mutant. Overall, these results suggest that a prokaryotic aconitase can also act as a regulator of gene expression and that the regulation is possibly related to changes in intracellular iron levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00852.x
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  • 6
    Electronic Resource
    Electronic Resource
    Unification of vertical datums by GPS and gravimetric geoid models with application to Fennoscandia (1998)
    Springer
    Journal of geodesy 72 (1998), S. 64-70 
    Details
    ISSN: 1432-1394
    Keywords: Key words. Vertical datums ; Unification ; GPS ; Geoid ; Fennoscandia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract. The second Baltic Sea Level (BSL) GPS campaign was run for one week in June 1993. Data from 35 tide gauge sites and five fiducial stations were analysed, for three fiducial stations (Onsala, Metsähovi and Wettzell) fixed at the ITRF93 system. On a time-scale of 5 days, precision was several parts in 109 for the horizontal and vertical components. Accuracies were about 1 cm in comparison with the International GPS Geodynamical Service (IGS) coordinates in three directions. To connect the Swedish and the Finnish height systems, our numerical application utilises three approaches: a rigorous approach, a bias fit and a three-parameter fit. The results between the Swedish RH70 and the Finnish N 60 systems are estimated to −19.3 ± 6.5, −17 ± 6 and −15 ± 6 cm, respectively, by the three approaches. The results of the three indirect methods are in an agreement with those of a direct approach from levelling and gravity measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900050149
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrogen energy and solid state fuel cells (1998)
    Springer
    Ionics 4 (1998), S. 444-450 
    Details
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper discusses hydrogen energy and the methods for production of hydrogen. It also provides a review of various materials which are hydrogen permeable. Previous studies on the proton-conducting ceramics and their properties are summarized. The principle of proton-conducting solid state fuel cell for conversing the energy of hydrogen containing fuel is described with a discussion of the advantages of proton-conducting ceramic fuel cells as compared to oxygen-ionic conducting fuel cells. The paper is concluded with a discussion of the major materials related technical challenges in the development of the proton-conducting ceramic fuel cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02375889
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