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  • 1
    Digitale Medien
    Digitale Medien
    Crystal structure and magnetism of LaCo13−x−yFexSiy compounds (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 336-341 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The crystal structure and magnetic properties of LaCo13−x−yFexSiy compounds were investigated by means of x-ray powder diffraction and magnetization measurements. The substitution of Si for Co induces an order–disorder transition from the cubic NaZn13-type to its tetragonal derivative structure, while the substitution of Fe for Co does not induce such a phase transition. After annealing treatment, the homogeneous range of the cubic phase is narrowed and that of the tetragonal phase is extended. From crystallographic and thermodynamic points of view, the sta- bility of the cubic and the tetragonal phases is discussed. The measured magnetic moment of LaCo13−x−yFexSiy coincides well with the theoretical prediction based on the magnetic valence model. Within the framework of this model, LaCo13−x−yFexSiy compounds can be considered as strong ferromagnets and their magnetic moment can be theoretically predicted. The composition dependence of Curie temperature is discussed within the mean field approximation. At higher iron concentration the decrease of Curie temperature with Fe concentration might be attributed to the increase of the number of antiferromagnetically coupled Fe–Fe pairs and the decrease of the ferromagnetic coupling between transition metal atoms. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.362786
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  • 2
    Digitale Medien
    Digitale Medien
    Growth and photorefractive properties of Mn-doped (KNa)0.1(Sr0.6Ba0.4)0.9Nb2O6 crystals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8835-8837 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: (KNa)0.1(Sr0.6Ba0.4)0.9Nb2O6, or KNSBN, crystals have been grown with two different Mn concentrations: 0.02 wt % and 0.04 wt %. Two-wave mixing and self-pumped phase conjugation experiments were carried out on these crystals at 632.8 nm wavelength. The measured two-wave coupling gains for the 0.02 wt % and 0.04 wt % crystals are larger than 7 cm−1 and 9 cm−1, respectively, and the two-wave coupling time response is faster for the 0.4 wt % crystal. In addition, the self-pumped phase conjugation reflectivity of the 0.04 wt % crystal is measured to be as high as 70%. It is shown that the Mn dopant can increase effectively the absorption coefficient and enhance the photorefractive properties of KNSBN. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.362561
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  • 3
    Digitale Medien
    Digitale Medien
    Production of lithospermic acid B and rosmarinic acid in hairy root cultures of Salvia miltiorrhiza (1999)
    Springer
    Journal of industrial microbiology and biotechnology 22 (1999), S. 133-138 
    Details
    ISSN: 1476-5535
    Schlagwort(e): Keywords: Salvia miltiorrhiza; Lamiaceae; Agrobacterium rhizogenes; hairy roots; lithospermic acid B; rosmarinic acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Hairy root cultures of Salvia miltiorrhiza were established by infecting sterile plantlets with Agrobacterium rhizogenes ATCC 15834, and the transformation was proved by direct detection of the inserted T-DNA by the polymerase chain reaction. As determined by HPLC, these hairy root cultures had the ability to produce lithospermic acid B (LAB), rosmarinic acid (RA) and other related phenolic compounds, the water-soluble active components of the plant. The effect of five different basal media, MS, MS-NH〈INF〉4〈/INF〉 (MS without ammonium nitrate), B5, WPM and 6,7-V on the root growth and phenolic compound production was studied. It was found that MS-NH〈INF〉4〈/INF〉 and 6,7-V media were superior to MS, B5 and WPM media in terms of both root growth and phenolic compound production. The time course of biomass accumulation and phenolic compound formation was also examined in the culture using MS-NH〈INF〉4〈/INF〉medium. During cultivation, the content of RA in the roots was stable being approximately 0.48% of dry weight while the content of LAB fluctuated between 0.73% and 1.61% of dry weight, and decreased gradually at the stationary phase of growth. The highest production of LAB and RA was about 64 mg L−1 and 23 mg L−1, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/sj.jim.2900624
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  • 4
    Digitale Medien
    Digitale Medien
    N2O decomposition over [Fe]-ZSM-5 and Fe-HZSM-5 zeolites (1995)
    Springer
    Catalysis letters 34 (1995), S. 163-177 
    Details
    ISSN: 1572-879X
    Schlagwort(e): N2O (nitrous oxide) catalytic decomposition ; [Fe]-ZSM-5 zeolite catalyst ; Fe-HZSM-5 catalyst ; effect of oxygen on N2O decomposition rate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The N2O decomposition over an [Fe]-ZSM-5 and an Fe-HZSM-5 zeolite was studied. We found that framework incorporated iron species were much more active than Fe(III) introduced as framework charge countercations by ion exchange (TOF at 0.1 vol% N2O:1.47 × 10−4 at 280°C for [Fe]-ZSM-5 vs. 2.58 × 10−4 at 468°C for Fe-HZSM-5). The higher activity of [Fe]-ZSM-5 was attributed to the uniqueness of framework iron species. Both [Fe]-ZSM-5 and Fe-HZSM-5 zeolites showed enhanced activity in the presence of excess oxygen. This is in sharp contrast to ruthenium exchanged zeolites which showed strong oxygen inhibiting effect on the rate of N2O decomposition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00808332
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  • 5
    Digitale Medien
    Digitale Medien
    Crystal structure and superconductivity of TlBa2CaCu2O6.5 (1988)
    Springer
    The European physical journal 73 (1988), S. 9-13 
    Details
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this article, the crystal structure and superconductivity of a new superconducting phase TlBa2CaCu2O6.5 (T c =72.5 K) in Tl−Ba−Ca−Cu−O system are studied. The crystal structure of the compound TlBa2CaCu2O6.5 has been determined by means of X-ray powder diffraction method. It belongs to primary tetragonal lattice with lattice parameters:a=3.847 Å,c=12.73 Å. Its space group isD 4h 1 −P4/mmm. Each unit cell contains one formular unit. The arrangements of ions in a unit cell are following: 1 Ca, and 1 Tl cations occupy 1(a) and 1(d) equivalent point positions respectively. 2 Cu cations occupy 2(h) (z=0.127) equivalent point positions. 2 Ba cations occupy 2(g) (z=0.281) equivalent point positions. 6.5 O anions respectively occupy 1(b), 2(h) (z=0.281) and 4(i) (z=0.127) equivalent point positions. Occupation factor is 0.929. The crystal structure of TlBa2CaCu2O6.5 is quite similar to those of the other superconducting phases in Tl−Ba−Ca−Cu−O system. All cations are distributed at positions of (0, 0,z) and (1/2, 1/2,z) alternately. The oxygen deficient pseudo-perovskite unit Ba−Cu−Ca−Cu−Ba is separated two Tl−O layers in the crystal structure of Tl2Ba2CaCu2O8. However, the oxygen deficient pseudo-perovskite unit Ba−Cu−Ca−Cu−Ba is separated by single Tl−O layer in the crystal structure of TlBa2CaCu2O6.5. The relations among the crystal structures of the superconducting phases as well as the relation between the crystal structure and superconductivity are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01312148
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  • 6
    Digitale Medien
    Digitale Medien
    The crystal structure and superconductivity of the new superconducting phase TlSr2Ca0.5Er0.5Cu2O6.75 (1989)
    Springer
    The European physical journal 76 (1989), S. 277-281 
    Details
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The crystal structure of the superconducting phase TlSr2Ca1−xErxCu2O6.5+x/2 (x=0.5) in the Tl−Sr−Ca−Er−Cu−O system was determined using the X-ray powder diffraction method. It belongs to a primary tetragonal cell with lattice constantsa=3.798,c=12.014 Å, with a space group ofD 4h 1 −P4/mmm. Each unit cell contains one formula unit. The positions of ions in the unit cell are as follows: 0.5 Ca and 0.5 Er cations disorderly occupy 1(d) equivalent point position, each with an occupation factor of 0.5; 1. Tl cation occupies the equivalent point position 1 (a); 2. Cu cations occupy 2 (g) withz=0.365; 2 Sr cations occupy 2(h) withz=0.220; 7 O anions respectively occupy 1(c), 2(g), (z=0.165) and 4(i) (z=0.365) equivalent point positions. The zero-resistance superconducting transition temperatureT c (0) decreased slightly with increased Er content in the Tl−Sr−Ca−Er−Cu−O system. The crystal structure of TlSr2Ca0.5Er0.5Cu2O6.75 is very similar to that of TlBa2CaCu2O6.5 in the Tl−Ba−Ca−Cu−O system or RBa2Cu3O7 in the R−Ba−Cu−O system. In the superconducting phase with an oxygen-deficient perovskite-like structure, the similarity of cation-oxygen coordination polyhedra is important for cation substitution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01321903
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  • 7
    Digitale Medien
    Digitale Medien
    Optimum control of bobsled steering (1995)
    Springer
    Journal of optimization theory and applications 85 (1995), S. 1-19 
    Details
    ISSN: 1573-2878
    Schlagwort(e): Minimum-time problem ; optimal control ; bobsled steering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Minimum-time and smooth-steering control algorithms are developed for bobsled optimal control. Numerical solutions are obtained both for one-curve optimal control and whole-course piecewise optimal control with application to realistic three-dimensional track surface shapes. Specific results are calculated for the Lillehammer Olympic Track.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02192297
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