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  • 1995-1999  (2)
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  • 2000-2004  (1)
  • 1995-1999  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2725-2727 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High density nanocrystalline MgB2 bulk superconductors with distinctly improved pinning were prepared by mechanical alloying of Mg and B powders at ambient temperatures followed by hot pressing. The nanocrystalline samples reveal high jc=105 A/cm2 at 20 K and 1 T together with an irreversibility line strongly shifted towards higher fields resulting in Hirr(T)∼0.8 Hc2(T), whereas typically Hirr(T)∼0.5 Hc2(T) is observed for untextured bulk samples. These values exceed those of all other reported bulk samples and are in the range of values for thin films. The improved pinning of this material, which mainly consists of spherical grains about 40–100 nm in size, is attributed to the large number of grain boundaries in the nanocrystalline state. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1463
    Keywords: Parkinson's disease ; depression ; biogenic amines ; cerebrospinal fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Introduction. Etiology of depression in Parkinsons disease (PD) is associated with serotonergic dysfunction. Previous studies, supporting this hypothesis, were performed on patients treated with antiparkinsonian drugs. To eliminate the influence of parkinsonian drug therapy and to elucidate significance of different biochemical pathways in PD associated with depression we determined levels of biogenic amines in cerebrospinal fluid (CSF) of 26 untreated “de novo” Parkinsonian patients.Material and methods. Patients were scored with the Hamilton depression scale (HD) and subdivided into groups with HD score ≥ 18 and HD score 〈18. Diagnosis of depression was made according to DSM III R. Both groups were matched for age and motor disability.Results. In both groups no significant differences appeared between CSF levels of dopamine, noradrenaline, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 3-methoxy-4-hydroxyphenylglycol and 5-hydroxyindole acetic acid, determined by high-performance liquid chromatography.Discussion. In contrast to previous studies on treated Parkinsonian patients no sign of altered serotonin metabolism especially in context with severity of depression in early stages of PD was found. Due to our results, we suggest, that biochemical markers of depression in CSF of PD may be influenced by antiparkinsonian therapy and that depression in PD may respond to serotonin reuptake inhibitors mainly in later stages of PD.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Bulk melt textured YBCO samples in the shape of discs were prepared by a top seeding method using Sm-123 crystals. The field distribution of the trapped field on the surface of the samples was measured at 77 K by means of a Hall probe. In single grains with diameter of 20 mm the trapped field reached maximum values up to 0.56 T at 77 K. Investigating the temperature dependence of the maximum trapped field, a value of 5.5 T at 30 K was found for the best sample. At the same temperature, degradation of the trapped field by a factor of about 10 was observed for a second sample after field cooling in a field of 7 T. This degradation is explained by damage to the sample due to magnetic stresses. At the centre of the sample a magnetic stress of 11 MPa is estimated to be responsible for this damage. Additionally YBCO material has been tested in a high speed motor with superconducting magnetic bearings (SMB) in order to demonstrate the passive stabilization properties of SMB. In first tests the shaft rotated with a speed of 12 000 rpm limited by air drag.
    Type of Medium: Electronic Resource
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