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  • 1
    Electronic Resource
    Electronic Resource
    Correlation of critical current and resistance fluctuations in bicrystal grain boundary Josephson junctions (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1929-1931 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed a detailed analysis of the low frequency 1/f noise in YBa2Cu3O7−δ and Bi2Sr2CaCu2O8+x grain boundary Josephson junctions (GBJs) fabricated on SrTiO3 bicrystal substrates. The normalized fluctuation of the critical current, δIc/Ic, and the normal resistance, δRn/Rn were found to be almost independent of temperature and the misorientation angle. Furthermore, the magnitude of the fluctuations is very similar for both high-Tc cuprates. Correlation experiments showed that the fluctuations of Ic and Rn are anti-correlated. Our analysis strongly suggests that the source of 1/f noise in high-Tc bicrystal GBJs are localized defect states in an insulating grain boundary barrier with fluctuating electron occupation. The effective charge trapping time within single traps was found to decay exponentially with increasing bias voltage. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114571
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  • 2
    Electronic Resource
    Electronic Resource
    Superconducting Nd1.85Ce0.15CuO4−y bicrystal grain boundary Josephson junctions (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2888-2890 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the electric transport properties of symmetrical [001] tilt Nd1.85Ce0.15CuO4−y (NCCO) bicrystal grain boundary Josephson junctions (GBJs) fabricated on SrTiO3 bicrystal substrates with misorientation angles of 24° and 36.8°. The superconducting properties of the NCCO GBJs are similar to those of GBJs fabricated from the hole doped high temperature superconductors (HTS). The critical current density Jc decreases strongly with increasing misorientation angle. The products of the critical current Ic and the normal resistance Rn (∼100 μV at 4.2 K) are small compared to the gap voltage and fit well to the universal scaling law IcRn∝Jc found for GBJs fabricated from the hole doped HTS. This suggests that the symmetry of the order parameter, which most likely is different for the electron and the hole doped HTS, has little influence on the characteristic properties of symmetrical [001] tilt GBJs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121449
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  • 3
    Electronic Resource
    Electronic Resource
    Scaling behavior of 1/f noise in high-temperature superconductor Josephson junctions (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 120-122 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extensive studies of the low frequency 1/f noise in high-temperature superconducting (HTS) Josephson junctions of various types and materials have been performed for a wide range of operating parameters. The origin of the measured voltage fluctuations can be traced back to the trapping and release of charge carriers in trapping centers in an insulating barrier, giving rise to correlated fluctuations of the junction critical current Ic and normal-state resistance Rn. We observed a linear dependence of the normalized critical current and resistance fluctuations on Rn, which suggests a constant density of trapping centers for the HTS Josephson junctions. The scaling of the normalized fluctuations is in good agreement with the previously found scaling relation IcRn∝1/Rn and supports a junction model assuming a leaky tunnel barrier. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119281
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  • 4
    Electronic Resource
    Electronic Resource
    13C NMR studies of the fluxes in the central metabolism of Corynebacterium glutamicum during growth and overproduction of amino acids in batch cultures (1995)
    Springer
    Applied microbiology and biotechnology 44 (1995), S. 489-495 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The carbon flux distribution in the central metabolism of Corynebacterium glutamicum was studied in batch cultures using [1-13C]- and [6-13C]glucose as substrate during exponential growth as well as during overproduction of L-lysine and L-glutamate. Using the 13C NMR data in conjunction with stoichiometric metabolite balances, molar fluxes were quantified and normalised to the glucose uptake rate, which was set to 100. The normalised molar flux via the hexose monophosphate pathway was 40 during exponential growth, whereas it was only 17 during L-glutamate production. During L-lysine production, the normalised hexose monophosphate pathway flux was elevated to 47. Thus, the carbon flux via this pathway correlated with the NADPH demand for bacterial growth and L-lysine overproduction. The normalised molar flux in the tricarboxylic acid cycle at the level of 2-oxoglutarate dehydrogenase was 100 during exponential growth and 103 during L-lysine secretion. During L-glutamate formation, the normalised flux through the tricarboxylic acid cycle was reduced to 60. In contrast to earlier NMR studies with C. glutamicum, no significant activity of the glyoxylate pathway could be detected. All experiments indicated a strong in vivo flux from oxaloacetate back to phosphoenolpyruvate and/or pyruvate, which might be due to phosphoenolpyruvate carboxykinase activity in C. glutamicum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050587
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  • 5
    Electronic Resource
    Electronic Resource
    13C NMR studies of the fluxes in the central metabolism of Corynebacterium glutamicum during growth and overproduction of amino acids in batch cultures (1995)
    Springer
    Applied microbiology and biotechnology 44 (1995), S. 489-495 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The carbon flux distribution in the central metabolism of Corynebacterium glutamicum was studied in batch cultures using [1-13C]- and [6-13C]glucose as substrate during exponential growth as well as during overproduction of l-lysine and l-glutamate. Using the 13C NMR data in conjunction with stoichiometric metabolite balances, molar fluxes were quantified and normalised to the glucose uptake rate, which was set to 100. The normalised molar flux via the hexose monophosphate pathway was 40 during exponential growth, whereas it was only 17 during l-glutamate production. During l-lysine production, the normalised hexose monophosphate pathway flux was elevated to 47. Thus, the carbon flux via this pathway correlated with the NADPH demand for bacterial growth and l-lysine overproduction. The normalised molar flux in the tricarboxylic acid cycle at the level of 2-oxoglutarate dehydrogenase was 100 during exponential growth and 103 during l-lysine secretion. During l-glutamate formation, the normalised flux through the tricarboxylic acid cycle was reduced to 60. In contrast to earlier NMR studies with C. glutamicum, no significant activity of the glyoxylate pathway could be detected. All experiments indicated a strong in vivo flux from oxaloacetate back to phosphoenolpyruvate and/or pyruvate, which might be due to phosphoenolpyruvate carboxykinase activity in C. glutamicum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169949
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  • 6
    Electronic Resource
    Electronic Resource
    Conformations of kinesin: solution vs. crystal structures and interactions with microtubules (1998)
    Springer
    European biophysics journal 27 (1998), S. 455-465 
    Details
    ISSN: 1432-1017
    Keywords: Key words Microtubules ; Motor proteins ; Kinesin ; X-ray crystallography ; Small angle X-ray scattering ; Cell motility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Recently, the molecular structures of monomeric and dimeric kinesin constructs in complex with ADP have been determined by X-ray crystallography (Kull et al. 1996; Kozielski et al. 1997 a; Sack et al. 1997). The “motor” or “head” domains have almost identical conformations in the known crystal structures, yet the kinesin dimer is asymmetric: the orientation of the two heads relative to the coiled-coil formed by their neck regions is different. We used small angle solution scattering of kinesin constructs and microtubules decorated with kinesin in order to find out whether these crystal structures are of relevance for kinesin's structure under natural conditions and for its interaction with microtubules. Our preliminary results indicate that the crystal structures of monomeric and dimeric kinesin are similar to their structures in solution, though in solution the center-of-mass distance between the motor domains of the dimer could be slightly greater. The crystal structure of dimeric kinesin can be interpreted as representing two equivalent conformations. Transitions between these or very similar conformational states may occur in solution. Binding of kinesin to microtubules has conformational effects on both, the kinesin and the microtubule. Solution scattering of kinesin decorated microtubules reveals a peak in intensity that is characteristic for the B-surface lattice and that can be used to monitor the axial repeat of the microtubules under various conditions. In decoration experiments, dimeric kinesin dissociates, at least partly, leading to a stoichiometry of 1:1 (one kinesin head per tubulin dimer; Thormählen et al. 1998 a) in contrast to the stoichiometry of 2:1 reported for dimeric ncd. This discrepancy is possibly due to the effect of steric hindrance between kinesin dimers on adjacent binding sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050156
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  • 7
    Electronic Resource
    Electronic Resource
    Catalytic deamination of asparagine (1970)
    Springer
    Cellular and molecular life sciences 26 (1970), S. 35-36 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Es wird die katalytische Deaminierung des Asparagins mittels Cu++ bei 80°–100°C beschrieben. In diesem Temperaturbereich findet die Reaktion auch in Lösungen statt, während die Katalyse im Trockenrückstand bedeutend stärker ist. Die optimale Konzentration des Cu++ (bezogen auf das Asparagin) ist 1∶4M. Unter den günstigsten Bedingungen werden 20% des Asparagins zu Asparaginsäure deaminiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01900375
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  • 8
    Electronic Resource
    Electronic Resource
    Andreev bound states in high temperature superconductors (1998)
    Springer
    The European physical journal 5 (1998), S. 423-438 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.25.Fy Transport properties [:AND:] 74.50.+r Proximity effects, weak links, tunneling phenomena, and Josephson effects - 74.72.-h High-Tc compounds - 74.76.Bz High-Tc films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Andreev bound states at the surface of superconductors are expected for any pair potential showing a sign change in different k-directions with their spectral weight depending on the relative orientation of the surface and the pair potential. We report on the observation of Andreev bound states in high temperature superconductors (HTS) employing tunneling spectroscopy on bicrystal grain boundary Josephson junctions (GBJs). The tunneling spectra were studied as a function of temperature and applied magnetic field. The tunneling spectra of GBJ formed by YBa2Cu3O (YBCO), Bi2Sr2CaCu2O (BSCCO), and La1.85Sr0.15CuO4 (LSCO) show a pronounced zero bias conductance peak that can be interpreted in terms of Andreev bound states at zero energy that are expected at the surface of HTS having a d-wave symmetry of the order parameter. In contrast, for the most likely s-wave HTS Nd1.85Ce0.15CuO4-y (NCCO) no zero bias conductance peak was observed. Applying a magnetic field results in a shift of spectral weight from zero to finite energy. This shift is found to depend nonlinearly on the applied magnetic field. Further consequences of the Andreev bound states are discussed and experimental evidence for anomalous Meissner currents is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050463
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  • 9
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    Superconducting Nd1.85Ce0.15CuO4−y bicrystal grain boundary Josephson junctions (1998)
    American Institute of Physics
    Details
    Publication Date: 1998-06-01
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Transfer function and thermal noise of YBa2Cu3O7−δ direct current superconducting quantum interference devices operated under large thermal fluctuations (1999)
    American Institute of Physics
    Details
    Publication Date: 1999-04-12
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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