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  • 1
    Digitale Medien
    Digitale Medien
    A hidden pseudogap under the ‘dome’ of superconductivity in electron-doped high-temperature superconductors (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 422 (2003), S. 698-701 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The ground state of superconductors is characterized by the long-range order of condensed Cooper pairs: this is the only order present in conventional superconductors. The high-transition-temperature (high-Tc) superconductors, in contrast, exhibit more complex phase behaviour, which ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/nature01488
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  • 2
    Digitale Medien
    Digitale Medien
    Modulation of Aβ peptides by estrogen in mouse models (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neurochemistry 80 (2002), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Clinical studies have shown that estrogen deprivation through menopause is a risk factor in both the initiation and progression of Alzheimer's disease (AD) and that estrogen replacement therapy may be protective. One of the major pathological features in the human AD brain is the senile plaque, a proteinaceous structure composed mainly of heterogeneous peptides collectively known as A-beta (Aβ). In vitro studies have linked estrogen with Aβ modulation, suggesting that one-way that estrogen depletion at menopause may exacerbate the features of AD is through Aβ accumulation. To test this, two studies were performed on transgenic models of amyloidosis. Firstly, transgenic mice without detectable amyloid aggregates were subjected to ovariectomy and estradiol supplementation, and Aβ levels were assessed. Secondly, the effects of estrogen modulation were assessed in mice at an age when plaques would be forming initially. Overall, Aβ levels were higher in estrogen-deprived mice than intact mice, and this effect could be reversed through the administration of estradiol. These data suggest that, in vivo, estrogen depletion leads to the accumulation of Aβ in the CNS, which can be reversed through replacement of estradiol. These results provide evidence that post-menopausal estrogen depletion may be linked to an increased risk of AD through Aβ modulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0022-3042.2001.00690.x
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  • 3
    Digitale Medien
    Digitale Medien
    Ultraviolet light assisted oxygenation process for submicron YBa2Cu3O7−δ thin film devices (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5411-5418 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have successfully fabricated superconducting nanobridges and grain-boundary junctions from epitaxial YBa2Cu3O7−δ thin films with thickness between 20 and 30 nm and width down to ∼100 nm. The patterning process turned out to severely deteriorate the transport properties resulting in structural damage, corrosion, and oxygen loss. The most crucial steps are the baking procedure used to cure the electron beam resist, the resist development, and the ion beam etching process. By optimizing these steps and applying a suitable post-treatment procedure a significant enhancement of the sample quality could be achieved. An ultraviolet light assisted oxygenation procedure after the patterning process enabled us to achieve superconducting transition temperatures between 80 and 87 K and critical current densities at 4.2 K up to 4×107 A cm−2 for the nanobridges and 5×103–2×105 A cm−2 for the grain boundary junctions. At 4.2 K junctions with width down to 100 nm corresponding to a junction area down to 2.3×10−3 μm2 showed superconductivity. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1459599
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  • 4
    Digitale Medien
    Digitale Medien
    Spin-dependent transport in the double-perovskite Sr2CrWO6 (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3654-3656 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on the preparation and characterization of the double-perovskite compound Sr2CrWO6 with a Curie temperature of 390 K. We have fabricated both Sr2CrWO6 bulk sintered polycrystalline bars and high-quality epitaxial thin films on SrTiO3 substrates by pulsed-laser deposition. The samples were characterized by thermogravimetric analysis, x-ray diffraction, electrical transport, and magnetization measurements. Polycrystalline samples containing a large number of grain boundaries show a large low-field magnetoresistance of up to 100% at 5 K. At room temperature, this effect is reduced to a few percent. Our results show that Sr2CrWO6 is an interesting candidate for room-temperature magnetoelectronic materials. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1421227
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  • 5
    Digitale Medien
    Digitale Medien
    Comparison of Josephson vortex flow transistors with different gate line configurations (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1095-1097 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We performed numerical simulations and experiments on Josephson vortex flow transistors based on parallel arrays of YBa2Cu3O7–δ grain boundary junctions with a cross gate line allowing us to operate the same devices in two different modes named the Josephson fluxon transistor (JFT) and Josephson fluxon–antifluxon transistor (JFAT). The simulations yield a general expression for the current gain versus number of junctions and normalized loop inductance and predict higher current gain for the JFAT. The experiments are in good agreement with simulations and show improved coupling between gate line and junctions for the JFAT as compared to the JFT. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1346625
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  • 6
    Digitale Medien
    Digitale Medien
    Genetic differentiation of European grayling populations across the Main, Danube and Elbe drainages in Bavaria (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 58 (2001), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Analysis of mitochondrial (ND-1/3/4 genes) and nuclear (GH-1 gene, four microsatellite loci) DNA markers of European grayling Thymallus thymallus populations identified strong genetic differentiation between the Rhine/Main, Elbe and Danube drainages in Bavaria, as a result of both present processes and past history. The Danube and the Main-Elbe group diverged about five times earlier than the populations of Main and Elbe. These data suggest that exchange and transfer of grayling stocking material between these drainages should be avoided, to maintain the genetic diversity and integrity of populations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.2001.tb00513.x
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  • 7
    Digitale Medien
    Digitale Medien
    Hydrolytic degradation of PCL/PEO copolymers in alkaline media (2000)
    Springer
    Journal of materials science 11 (2000), S. 227-233 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract PCL/PEO copolymers with different compositions were obtained from ring opening polymerization of ε-caprolactone in the presence of ethylene oxide and characterized by various analytical techniques. Data collected from DSC and X-ray diffractometry suggested that the copolymer chains possess a blocky structure, leading to both PCL and PEO-type crystalline structures. Hydrolytic degradation of these copolymers was carried out in a pH=10.6 carbonate buffer solution at 37 °C. Comparison was made with a PCL homopolymer and a PCL/PEG blend which had the same gross composition as one of the copolymers. The results showed that the presence of PEO sequences considerably enhanced the hydrophilicity of the copolymers as compared with PCL homopolymer. Nevertheless, the degradability of PCL chains was not enhanced due to the phase separation between the two components. These materials should be of great interest for biomedical uses such as matrices for sustained drug delivery because of the presence of both hydrophilic and hydrophobic microdomains. ©2000 Kluwer Academic Publishers
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008920326988
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  • 8
    Digitale Medien
    Digitale Medien
    Combinations of Earth-orientation measurements: SPACE97, COMB97, and POLE97 (2000)
    Springer
    Journal of geodesy 73 (2000), S. 627-637 
    Details
    ISSN: 1432-1394
    Schlagwort(e): Key words: Earth rotation – Combination – Kalman filter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Abstract. Independent Earth-orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very-long-baseline interferometry, and the global positioning system have been combined using a Kalman filter. The resulting combined Earth-orientation series, SPACE97, consists of values and uncertainties for universal time, polar motion, and their rates spanning the period 28 September 1976 to 3 January 1998 at daily intervals. The space-geodetic measurements used to generate SPACE97 have then been combined with optical astrometric measurements to form two additional combined Earth-orientation series: (1) COMB97, consisting of values and uncertainties for universal time, polar motion, and their rates spanning the period 20 January 1962 to 1 January 1998 at 5-day intervals, and (2) POLE97, consisting of values and uncertainties for polar motion and its rate spanning the period 20 January 1900 to 21 December 1997 at monthly intervals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001900050001
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  • 9
    Digitale Medien
    Digitale Medien
    Thermal conductivity and thermal Hall effect in Bi- and Y-based high-T c superconductors (2001)
    Springer
    The European physical journal 20 (2001), S. 189-208 
    Details
    ISSN: 1434-6036
    Schlagwort(e): PACS. 74.72.-h High Tc compounds – 74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: Measurements of the thermal conductivity (kxx) and the thermal Hall effect (kxy) in high magnetic fields in Y- and Bi-based high-T c superconductors are presented. We describe the experimental technique and test measurements on a simple metal (niobium). In the high-T c superconductors kxx and kxy increase below T c and show a maximum in their temperature dependence. kxx has contributions from phonons and quasiparticle (QP) excitations, whereas kxy is purely electronic. The strong increase of kxy below T c gives direct evidence for a strong enhancement of the QP contribution to the heat current and thus for a strong increase of the QP mean free path. Using kxy and the magnetic field dependence of kxx we separate the electronic thermal conductivity ( k xx el ) of the CuO 2 -planes from the phononic thermal conductivity ( k xx ph ). In YBa2Cu3O 7 - δ k xx el shows a pronounced maximum in the superconducting state. This maximum is much weaker in Bi2Sr2CaCu2O 8 + δ , due to stronger impurity scattering. The maximum of k xx el is strongly suppressed by a magnetic field, which we attribute to the scattering of QPs on vortices. An additional magnetic field independent contribution to the maximum of kxx occurs in YBa2Cu3O 7 - δ , reminiscent of the contribution of the CuO-chains, as determined from the anisotropy in untwined single crystals. Our data analysis reveals that below T c as in the normal state a transport (τ) and a Hall ( ) relaxation time must be distinguished: The inelastic (i.e. temperature dependent) contribution to τ is strongly enhanced in the superconducting state, whereas displays the same temperature dependence as above T c . We determine also the electronic thermal conductivity in the normal state from kxy and the electrical Hall angle. It shows an unusual linear increase with temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00011098
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  • 10
    Digitale Medien
    Digitale Medien
    Magnetoconductance Fluctuations and Re-entrance Effect in Normal-metal/Superconductor Nanostructures (2000)
    Springer
    Journal of low temperature physics 118 (2000), S. 679-687 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The proximity of a superconductor strongly influences theelectronic properties of a normal metal. We report onmeasurements of the re-entrant behavior of the conductance ofmesoscopic gold/niobium heterostructures. At very lowtemperature a novel peak shows up in the conductance vs.voltage characteristics which can be suppressed by smallmagnetic fields of several mT. Furthermore, the proximityeffect gives rise to unique electronic interferencecontributions resulting in an increase of the rms of theconductance fluctuations by a factor of 2 $$\sqrt 2 $$ in ourheterostructures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004647529550
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