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  • Positron tomography  (2)
  • 43.25  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Dynamical Hopf bifurcation in piezoelectric semiconductor resonators (1989)
    Springer
    Applied physics 48 (1989), S. 177-180 
    Details
    ISSN: 1432-0630
    Keywords: 72.20H ; 43.25 ; 72.80E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Time-dependent Hopf bifurcations in the current-voltage characteristics of piezoelectric semiconductor resonators were investigated experimentally. The switching transition between acoustic bistable states was observed under a quasi-static variation of applied voltage. The peculiar pulse responses of the resonant currents were observed when the rise-time of the pulses exceeded the eigen-period of the system. The existence of a metastable state in the dynamical Hopf bifurcation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01141281
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Haemodynamics and oxygen metabolism in patients after reversible ischaemic attack or minor ischaemic stroke assessed with positron emission tomography (1987)
    Springer
    Neuroradiology 29 (1987), S. 416-421 
    Details
    ISSN: 1432-1920
    Keywords: Reversible ischaemic attacks ; Positron tomography ; Cerebral blood flow ; Cerebral blood volume ; Cerebral oxygen metabolism ; Carotid stenosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Regional cerebral blood flow (CBF), blood volume (CBV) and oxygen metabolic rate (CMRO2) were evaluated and compared among normals, patients with recent reversible ischaemic attacks (RIAs) and patients with chronic minor infarction using positron emission tomography. Average CBF together with CMRO2 significantly decreased in the infarction group in the middle cerebral artery territory of the affected hemisphere while the mean values for RIAs were intermediate between the other two groups. CBV also reduced, however it was more preserved compared to flow as seen in decreased CBF/CBV values. Significant interhemispheric difference was found in CBF/CBV ratio, but it did not clearly correlate with OEF changes. Higher OEF was noted only in the restricted brain regions of RIAs where CBF showed large hemispheric asymmetry. However, in other regions, the coupled decline of blood flow and metabolism was found which suggests tissue damage or neuronal cell loss in the brain with previous RIA symptoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341736
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Positron CT imaging of an impending stroke (1988)
    Springer
    Neuroradiology 30 (1988), S. 276-279 
    Details
    ISSN: 1432-1920
    Keywords: Transient ischemic attack ; Cerebral infarction ; Cerebral blood flow ; Positron tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We present PET findings of a case of a transient ischemic attack which later progressed to cerebral infarction. Cerebral blood flow at the stroke focus in the right parietal cortex measured after a TIA attack and before stroke was as low as 24 ml/100 g/min with some increase in oxygen extraction fraction and blood volume. The condition was compatible with “misery perfusion”. This case may be an example suggestive that the “misery perfusion sign” is a warning of impending stroke and its poor prognosis if left without appropriate treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341844
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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