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  • 1
    ISSN: 1432-1920
    Keywords: MRI ; CSF flow ; CSF production ; Blood flow, superior sagittal sinus ; Pseudotumour cerebri ; Benign intracranial hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A velocity-sensitive magnetic resonance imaging (MRI) phase-mapping method was used for noninvasive study of cerebrospinal fluid (CSF) flow in the cerebral aqueduct, for indirect calculation of supra-tentorial CSF production, and for measurement of blood flow in the superoor sagittal sinus (SSS). We examined 12 patients with idiopathic intracranial hypertension (HH; pseudotumour cerebri), and 10 healthy volunteers. The peak caudal and rostal CSF flow in the aqueduct during the cardiac cycle did not differ significantly between the patients and the volunteers. A significant correlation was found between the CSF volume flow amplitude and the resistance to cerebrospinal fluid out-flow in the patients (p〈0.05). The calculated mean supratentorial CSF production rate was 0.79 ml/min in the patients and 0.70 ml/min in the controls, but this difference was not statistically significant. However, the MRI measurements suggested CSF hypersecretion in three patients, whereas increased transependymal passage of CSF could have been the cause of negative calculated CSF production rates in two others. A tendency towards lower mean blood flow in the SSS (mean 345 ml/min) in the patients than in the controls (mean 457 ml/min) was found, and in two patients showed very low values. We showed that MRI phase-mapping may be used to study the relative importance of the pathophysiological factors thought to play a role in the development of IIH.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6036
    Keywords: 74.25.Gz ; 74.25.Kc ; 78.30.Er
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report a far-infrared reflectivity study of DyBa2Cu4O8, HoBa2Cu4O8 and Y2Ba4Cu7O15−δ superconductors in the temperature range 10–300 K. The assignment of thez-polarized infrared-acitve vibrations of the rare-earth-ion (R) was verified by the substitution ofR. Since the structure of the Y2Ba4Cu7O15−δ compound inz-direction is an ordered sequence of YBa2Cu3O7−δ and YBa2Cu4O8 blocks, the phonon spectrum of Y2Ba4Cu7O15−δ is a superposition of their respective phonon modes. The temperature dependence of the infrared-active phonons in RBa2Cu4O8 and Y2Ba4Cu7O15−δ was analyzed. A narrowing of the plane-oxygen phonon upon sample cooling was found to occur atT c , as it was reported for single-chain YBa2Cu3O7 materials; however a pronounced frequency softening of this mode for both RBa2Cu4O8 and Y2Ba4Cu7O15−δ was found to start well aboveT c , suggesting the interaction of infrared-active phonons with an excitation gap similar to that observed in spin-dependent measurements.
    Type of Medium: Electronic Resource
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