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  • Polymer and Materials Science  (8)
  • Cerebral blood flow  (2)
  • precursor  (2)
  • 72.20H  (1)
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Material
Years
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and properties of oligo- and polymethylsilazanes as a precursor for silicon nitride (1992)
    Springer
    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 143-149 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00696541
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  • 2
    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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  • 3
    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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  • 4
    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
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation of Silicon Oxycarbide Ceramic Films by Pyrolysis of Polymethyl- and Polyvinylsilsesquioxanes (1999)
    Springer
    Journal of sol gel science and technology 16 (1999), S. 227-234 
    Details
    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
    URL: http://dx.doi.org/10.1023/A:1008765103113
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  • 6
    Electronic Resource
    Electronic Resource
    Skeletal deformation vibrations and rotational isomerism of methylbutenes and methylpentenes as model compounds of 1,4-polyisoprene (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 1419-1434 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of methylbutenes and methylpentenes in the skeletal deformation region have been measured. The force constants for the skeletal deformation vibrations are determined from the frequencies of isobutylene, isobutylene-d6, and methylbutenes. The frequencies of methylpentenes are calculated for the various conformations, and the stable rotational isomers determined. The energy differences between the isomers are determined from the temperature dependence of the spectra. These results are correlated with the conformations of cis-and trans-1,4-polyisoprene chains, and possible conformations are suggested.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1968.160060802
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation and properties of polyborosiloxanes as precursors for borosilicate formation of SiO2-B2O3 gel fibers and oxides by the sol-gel method using tetraacetoxysilane and boron tri-n-butoxide (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1049-1056 
    Details
    ISSN: 0887-624X
    Keywords: tetraacetoxysilane ; boron tri-n-butoxide ; sol-gel method ; condensation ; SiO2 - B2O3 gel fibers ; borosilicates ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formation of SiO2-B2O3 gel fibers and oxides was investigated by the sol-gel method using tetraacetoxysilane (TAS) and boron tri-n-butoxide (BTB). Low molecular weight borosiloxanes (BS) were formed by the reaction of TAS with BTB in THF. Partial alkoxylation and hydrolysis of BS followed by further condensation of the resulting polymer (PBS) solutions led to the formation of highly polymerized polyborosiloxanes (HPBS) with good spinnability. Gel fibers were obtained by dry spinning of HPBS. The compositions of PBS and gels were not consistent with that in feed. Heat treatment of the gels, however, provided SiO2-B2O3 oxides with compositions almost compatible with those of the gels. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320606
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  • 8
    Electronic Resource
    Electronic Resource
    Preparation and properties of flexible thin films by acid-catalyzed hydrolytic polycondensation of methyltrimethoxysilane (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 751-754 
    Details
    ISSN: 0887-624X
    Keywords: methyltrimethoxysilane ; hydrolytic polycondensation ; polysiloxane ; thin films ; structure ; tensile strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330416
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  • 9
    Electronic Resource
    Electronic Resource
    Oxidation study of 3d transition metals (Cr, Fe, Co and Ni) and rare earth (Tb): Application to auger depth profiling of magneto-optical disk (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 22 (1994), S. 14-17 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Through the oxygen exposure experiments on 3d transition metals (Cr, Fe, Co and Ni) and rare earth (Tb), we studied the initial oxidation by means of Auger peak-to-peak height (APPH) method. Based on the results obtained, a simple technique using the ratio of APPH was applied to the Auger depth profile analysis of magneto-optical disk (MOD). It was clearly indicated that the preferential oxidation of Tb occurred only at the lower interface between the TbFeCo and metal-oxide layers, and this technique can be used to obtain the chemical information about the interface oxidation in Auger depth profiling.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740220106
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular structure of stereoisomers of 2,4,6-trichloroheptane as model compounds of polyvinyl chloride (1965)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 86 (1965), S. 43-63 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Wechselbeziehung zwischen der Kettenkonformation und der Konfiguration der Trimeren-Modelle des Polyvinylchlorids, nämlich der Isomeren von 2,4,6-Trichlorheptan, wird mittels der Ultrarot- und Kernresonanz-Spektren und des Dipolmoments diskutiert. Nach den so erhaltenen Ergebnissen werden auch die Kettenkonformation und die Taktizität des Polyvinylchlorids diskutiert.
    Notes: The correlation between the configuration and conformation of the three-unit models of polyvinyl chloride, isomers of 2,4,6-trichloroheptane, is discussed by means of IR, NMR spectra, and dipole moment measurements. On the basis of the information obtained the chain conformation and the tacticity of polyvinyl chloride are also discussed.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1965.020860105
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