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  • Cerebral blood flow  (2)
  • precursor  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 16 (1999), S. 227-234 
    ISSN: 1573-4846
    Keywords: polysilsesquioxane ; precursor ; pyrolysis ; silicon oxycarbide ; ceramics ; films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The sol-gel reactions of methyl- and vinyltrimethoxysilane under controlled conditions provided the corresponding polysilsesquioxanes and flexible thin films on further condensation of the precursors. Silicon oxycarbides containing a large amount of free carbon 58 mol% and 90 mol% were obtained in high yields 90 wt% on pyrolyzing the precursors of polymethyl-and polyvinylsilsesquioxane at 1400°C under N2 atmosphere, respectively. Moreover, pyrolytic polycondensation of polyvinylsilsesquioxane was found to give the silicon oxycarbide ceramic films without deformations and cracks. The composition and properties of films were investigated.
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 143-149 
    ISSN: 1572-8870
    Keywords: Methyl(triisocyanato)silane ; ammonolysis ; polysilazane ; precursor ; silicon nitride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis and properties of polymethylsilazanes were investigated. Controlled ammonolysis of methyl(triisocyanato)silane (MTIS) at the molar ratios NH3/MTIS=4 and 6 gave polymethylsilazanes3 and4, which were soluble in tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO) but insoluble when isolated as powders. The concentrated polymer solution showed spinnability and film formation. Thermogravimetric analysis of3 and4 showed weight losses of 67 and 16%, respectively. Species4 may be a precursor for silicon/carbon/nitrogen ceramics.
    Type of Medium: Electronic Resource
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