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  • 1
    Electronic Resource
    Electronic Resource
    Properties of pulsed laser deposited scandium-doped barium hexaferrite films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4630-4632 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties of thin films of BaScxFe12−xO19 (x=0.4) were determined by structural and magnetic measurements. Films were deposited by pulsed laser ablation deposition onto c-plane sapphire at oxygen pressures between 10 and 100 mTorr. X-ray diffraction measurements showed all films to be single-phase c-axis oriented hexaferrites with expanded c-axis lattice constants compared to x=0 films. Magnetometry measurements showed that all films had the easy axis (c-axis) normal to the film plane, with a mean saturation magnetization value of 3.8 kG. The mean uniaxial anisotropy field value was 10.6 kOe. This ability to adjust the uniaxial anisotropy field in hexaferrite films through selective substitution will be important for future planar microwave devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370430
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic properties of Zn–Mg ferrite fine powders (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5435-5435 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several fine powder samples of ZnxMg1−xFe2O4, 0≤x≤1, were prepared by the supercritical sol-gel (aerogel) process, and were annealed at 500 °C for 2 h. The structure, crystallite size and inversion parameter were determined by x-ray diffraction. The crystallite diameter of the as-prepared powders ranged from 6.5 to 8.5 nm. The minimum size was achieved for the samples with 0.25≤x≤0.50. After annealing the crystallite size increased by an average of 3 nm. The values of the inversion parameters, before and after annealing, reflect roughly the chemical preference of Zn cations to the tetrahedral sites and Mg cations to the octahedral sites of the spinel structure. However, these values indicate that the as-prepared materials were not in the equilibrium state. The magnetic properties were studied by 57Fe Mössbauer spectroscopy over a temperature range of 25 K to room temperature. Taking advantage of their sensitivity to the superparamagnetic behavior induced by the size effects, the Mössbauer spectra were used to determine the blocking temperatures. The calculated values peaked at x=0.50 for both the as-prepared and annealed powders. SQUID magnetometry measurements are currently underway. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362330
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  • 3
    Electronic Resource
    Electronic Resource
    EXAFS and magnetic characterization of inverted ball milled zinc ferrite powders (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5431-5431 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Divalent zinc is commonly used as a replacement cation in ferrites, as it increases the material magnetization when substituted in moderate amounts. However, pure zinc ferrite (ZnFe2O4) is a normal spinel, as zinc has a strong preference for the tetrahedral (A) site in the spinel structure, with Fe occupying the octahedral (B) sites. Then antiferromagnetic B–B coupling dominates the magnetic behavior yielding a material with a Neel temperature near 10 K. It is typically difficult to produce inverted zinc ferrite due to this strong site preference, but recently we produced fine zinc ferrite powders having an inversion parameter of 0.20 using an aerogel process. Ball milling these powders increased the inversion parameter to 0.55, and the median particle size from 14 to 40 nm. To confirm the x-ray diffraction inversion parameters, extended x-ray absorption fine structure (EXAFS) measurements were taken on these powders and ZnFe2O4 standards for both the Fe Kα and Zn Kα absorption edges. Fourier transformed results were fingerprinted against theroretical radial distrubtion functions generated from multiple-scattering FEFF codes for scattering atoms located on the tetrahedral and octahedral sites. Qualitatively, the zinc ferrite standard appears as a normal spinel, while both the iron and zinc radial distributions for the ball milled sample showed large site occupation of both A and B sites. This sample shows superparamagnetic behavior at room temperature, with some ferrimagnetic particles exceeding the critical volume, as indicated by a 15 Oe coercive field. The saturation magnetization of the metastable ball milled powder exceeds 2100 G. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361853
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  • 4
    Electronic Resource
    Electronic Resource
    Ferromagnetic resonance of micrometer-sized samples : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4307-4309 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Submicrometer-sized slotline and coplanar waveguide devices were used for ferromagnetic resonance (FMR) measurement on submicrometer-sized magnetic fine particles. FMR measurements were taken on individual magnetic disks, having diameters ranging from 50 to 1 μm, using either a slotline–coplanar waveguide (CPW) junction device or a coplanar waveguide transmission line junction device. The magnetic samples were etched from a 105 nm thick amorphous Fe80B15Si5 film on a quartz substrate. Absorption modes, which were measured with the submicrometer-sized slotline CPW, followed the Kittel magnetic resonance model for frequencies from 1 to 20 GHz for the 1 μm diam disk. By detecting the second harmonic of the lock-in amplifier's reference signal, we have measured disk samples as small as 1 μm in diameter. We estimated that the sensitivity is of the order of 3×109 spins, almost four orders of magnitude better than the sensitivity of a standard electron paramagnetic resonance system. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364810
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  • 5
    Electronic Resource
    Electronic Resource
    Reduced-temperature crystallization of thin amorphous Fe80B20 films studied via empirical modeling of extended x-ray absorption fine structure (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2073-2075 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of the local atomic environment around Fe atoms in very thin (15 nm), amorphous, partially crystallized and fully crystallized films of Fe80B20 was studied using extended x-ray absorption fine structure (EXAFS) measurements. The relative atomic fraction of each crystalline phase present in the annealed samples was extracted from the Fe EXAFS data by a least-squares fitting procedure, using data collected from t-Fe3B, t-Fe2B, and α-Fe standards. The type and relative fraction of the crystallization products follows the trends previously measured in Fe80B20 melt-spun ribbons, except for the fact that crystallization temperatures are ≈200 K lower than those measured in bulk equivalents. This greatly reduced crystallization temperature may arise from the dominant role of surface nucleation sites in the crystallization of very thin amorphous films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116307
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  • 6
    Electronic Resource
    Electronic Resource
    High-sensitivity ferromagnetic resonance measurements on micrometer-sized samples (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2756-2758 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic resonance measurements were taken on a 4 μm diam disk using a planar microwave transmission line device. The absorption modes of a sample placed on this device can be measured by monitoring the microwave power transmitted across the device while a swept magnetic field varies the sample absorption through resonance. Results for the disk, which was etched from a 105 nm thick amorphous Fe80B15Si5 film, followed the Kittel model over the frequency range from 2 to 20 GHz, in agreement with parameters measured on 5 mm diam disks by a microwave cavity. These results indicate the device has a sensitivity of 3×109⋅ΔH spins, almost two orders of magnitude better than microwave cavity measurements. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118974
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  • 7
    Electronic Resource
    Electronic Resource
    Bacterium genome sequence (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 654-654 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] OLIVER REPLIES - Kumar and colleagues demonstrate that techniques now exist in a wide range of organisms which will permit the systematic analysis of gene function. Such an analysis is most meaningful in organisms such as Saccharomyces cerevisiae, whose genome has been completely sequenced, and it ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381654a0
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  • 8
    Electronic Resource
    Electronic Resource
    A Morphological Classification Scheme for ULIRGs (1999)
    Springer
    Astrophysics and space science 266 (1999), S. 137-142 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002657900368
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  • 9
    Electronic Resource
    Electronic Resource
    Development of yeast strains for the efficient utilisation of starch: evaluation of constructs that express α-amylase and glucoamylase separately or as bifunctional fusion proteins (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 1067-1076 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Eight constructions involving the Bacillus subtilis α-amylase gene (amyE), a mouse pancreatic α-amylase cDNA (AMY2) and an Aspergillus awamori glucoamylase cDNA (glaA) were prepared: three fusion genes, involving one α-amylase and the glucoamylase, two double-cassette plasmids (expressing one or other α-amylase and the glucoamylase) and three single-cassette plasmids, expressing the individual coding sequences. Following transformation of each plasmid into Saccharomyces cerevisiae, a plate test revealed that the largest starch hydrolysis halo was produced by the strain bearing the B. subtilis α-amylase/glucoamylase fusion (BsAAase/GAase), and the smallest halo by the one expressing the mouse pancreatic α-amylase/glucoamylase fusion (MAAase/GAase). When assayed for enzymatic activity in liquid medium, the strains bearing the fusion and the double-cassette plasmids involving B. subtilis α-amylase and the glucoamylase exhibited both enzymic activities. Moreover, the BsAAase/GAase hybrid was able to adsorb and digest raw starch. The MAAse/GAase fusion protein was found to exhibit only α-amylase activity. Finally, the capacity to grow on soluble and corn starch was tested in liquid medium for the strains bearing plasmids coding for the fusion proteins and the separate enzymes. The strain carrying the double-cassette BsAAase + GAase, which produced one of the smallest hydrolysis haloes in the place test, showed the best performance, not only in digesting soluble and corn starch but also in using all of the hydrolysis products for growth. The transformant bearing the BsAAase/GAase fusion was able to grow on soluble starch, but not on corn starch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166927
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  • 10
    Electronic Resource
    Electronic Resource
    Ethanol production using nuclear petite yeast mutants (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 511-516 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two respiratory-deficient nuclear petites, FY23Δpet191 and FY23Δcox5a, of the yeast Saccharomyces cerevisiae were generated using polymerase-chain-reaction-mediated gene disruption, and their respective ethanol tolerance and productivity assessed and compared to those of the parental grande, FY23WT, and a mitochondrial petite, FY23ρ0. Batch culture studies demonstrated that the parental strain was the most tolerant to exogenously added ethanol with an inhibition constant. K i, of 2.3% (w/v) and a specific rate of ethanol production, q p, of 0.90 g ethanol g dry cells−1 h−1. FY23ρ0 was the most sensitive to ethanol, exhibiting a K i of 1.71% (w/v) and q p of 0.87 g ethanol g dry cells−1 h−1. Analyses of the ethanol tolerance of the nuclear petites demonstrate that functional mitochondria are essential for maintaining tolerance to the toxin with the 100% respiratory-deficient nuclear petite, FY23Δpet191, having a K i of 2.14% (w/v) and the 85% respiratory-deficient FY23Δcox5a, having a K i of 1.94% (w/v). The retention of ethanol tolerance in the nuclear petites as compared to that of FY23ρ0 is mirrored by the ethanol productivities of these nuclear mutants, being respectively 43% and 30% higher than that of the respiratory-sufficient parent strain. This demonstrates that, because of their respiratory deficiency, the nuclear petites are not subject to the Pasteur effect and so exhibit higher rates of fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051206
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