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  • Polymer and Materials Science  (10)
  • Electrical impedance tomography (EIT)  (2)
  • Experimental denervation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 251 (1994), S. 36-40 
    ISSN: 1434-4726
    Keywords: Facial muscle ; Enzyme histochemistry ; Facial palsy ; Experimental denervation ; Reinnervation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The morphological changes in rat facial muscles were evaluated after permanent denervation and were compared with findings after immediate reinnervation. Thirty rats underwent transection of the left and right facial nerves immediately followed by hypoglossal-facial nerve anastomosis on the right side (muscular reinnervation) and removal of 8–10 mm of the facial plexus on the left side (permanent muscular denervation). Levator labii muscle samples of both sides were collected sequentially at 2, 6, 7, 10, 20, and 24 weeks after surgery and submitted to routine histological and enzyme histochemical staining procedures. In normal levator labii muscles a typical “chessboard” pattern was found, with type I fibers being smaller than type II fibers. These latter fibers also were more prevalent than the type I fibers. Among the type II fiber subtypes, the type IIB fibers were larger and more frequent. Two weeks after surgery, there were no differences between denervated facial muscles and those undergoing reinnervation. Both showed atrophic myofibers among normal-sized fibers and slight fibrosis. Those muscles denervated for more than 2 weeks displayed increasing fiber atrophy with frequent loss of typability, as well as proliferation of connective tissue and fat cells in perimysial and endomysial sites. After denervation for 20 weeks only a few atrophic fibers were found in wide areas of fibrosis and fat cells. Following nerve anastomosis the reinnervated levator labii muscle showed much less fiber atrophy. Regrowth to normal fiber diameters was found with only a few atrophic myofibers 10 weeks after anastomosis although a moderate fibrosis predominated at perimysial sites. Reinnervated facial muscle fibers displayed a typical type-grouping pattern and also frequent lack of typability.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 390-394 
    ISSN: 1741-0444
    Keywords: Electrical impedance tomography (EIT) ; Electrical phantom ; Impedance spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The architecture of a novel phantom for electrical impedance tomography (EIT) is proposed. The design employs active elements, which include multiplying digital to analogue converters (MDAC), so that the impedance distribution in the phantom may be varied dynamically using computer control. The phantom is designed to assist in the validation of an EIT system under test. A number of published layouts for passive phantoms are analysed, and the requirements for an active element are specified for the most applicable of these. The use of active elements throughout a phantom imposes significant costs because of the need for each active element to operate independently. This proposal limits the cost and complexity by employing active elements in a restricted region of the phantom. Currently available technology, principally due to the limited analogue bandwidth of the MDAC, precludes the construction of a fully capable phantom from active elements. However, a design is specified that would enable its future development to cover the frequency range from 10kHz to 1 MHz.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 395-400 
    ISSN: 1741-0444
    Keywords: Electrical impedance tomography (EIT) ; Synthesised impedance ; Multiplying DAC ; Impedance spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A practical design for the synthesis of a digitally controlled electrical impedance element is presented. The impedance element comprises a real impedance element in series with a voltage source whose magnitude is determined by the applied voltage multiplied by a factor k. The value of k is shown strongly to affect the circuit's performance. Results are presented which demonstrate the correspondence between circuit models and practical measurements. When negative values for k were employed the circuit element offered a controlled impedance range of 1:1000 and was stable to at least 1.5MHz, providing that low source impedance values were used. With a positive k, a restricted range of impedance values could be obtained and the value of source impedance was less critical, though the circuit's performance was acceptable only to about 100 kHz. Consideration is given to the specification of a multiplier that would permit the circuit's range of application to be extended to low megahertz frequencies.
    Type of Medium: Electronic Resource
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  • 4
    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: The present paper deals with investigations on the thermal stability and the structure of some polychalcones by means of pyrolysis-gaschromatography. The decrease of electronic interaction due to the interruption of conjugation of the π-electronic system in the main chain of macromolecules is also reflected in the resulting chromatograms.
    Notes: In der vorliegenden Arbeit werden aus gaschromatographisch-pyrolytischen Untersuchungsergebnissen einige Aussagen über die Wärmebeständigkeit und Struktur von Polychalkonen abgeleitet. Es zeigt sich, daß die Abschwächung der Elektronenwechselwirkung durch Unterbrechung der Konjugation des π-Elektronensystems in der Hauptkette der Makromoleküle sich in den erhaltenen Chromatogrammen widerspiegelt.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 6 (1969), S. 24-38 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In this work various methods concerning the determination of compatibility of polymers are discussed. The conclusion is, that the earlier proposed “kinetical” method, besides the method of phase separation in common solution, is one of the surest methods of compatibility determination for polymers. However, over the latter, the kinetical method offers the advantage of rapidity and the possibility to predict the thermostability, the interactions of functional groups and the formation of solution in the solide state. While the interaction of functional groups may be established also by IR-spectroscopy, the other methods permit no conclusions of this kind. Generally it is very difficult to make statements on the formation of solution in the solid state on the basis of other methods of compatibility investigation. Quite useless, at least for our polymer mixtures, are the measurements of viscosity in concentrated as well as in dilute polymer solutions.
    Notes: In vorliegender Arbeit werden verschiedene Methoden für Verträglichkeitsbestimmungen von Polymeren vergleichend besprochen, wobei sich die früher vorgeschlagene kinetische Methode, neben der Phasentrennung in gemeinsamer Lösung, als eine der sichersten erweist. Gegen letztgenannte Methode bietet sie aber den Vorteil, daß sie viel schneller ist und auch Aussagen über Thermostabilität, Wechselwirkung von funktionellen Gruppen und Lösungsbildung im festen Zustand ermöglicht. Wenn die Wechselwirkung von funktionellen Gruppen auch IR-spektroskopisch eindeutig festgelegt werden kann, so erlauben andere Methoden diesbezüglich keine Schlüsse, und am schwersten ist es im allgemeinen, Aussagen über Lösungsbildung im festen Zustand auf Grund der Ergebnisse anderer Untersuchungsmethoden zu machen. Ganz unbrauchbar, zumindest in den von uns untersuchten Fällen, erweisen sich Viskositätsmessungen sowohl in konzentrierten als auch in verdünnten Polymerlösungen.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 13 (1975), S. 2259-2268 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrolysis, in combination with gas-chromatography technique, was used in the determination of the structure and study of the thermal degradation mechanism of the condensation polymers obtained by Friedel-Crafts reactions of poly(vinyl chloride) with benzene, toluene, and naphthalene. The separation of the pyrolysis products was made using a column packed with chromosorb W (80-100 mesh) coated with 15% silicone SE-52. The identification of the pyrolysis products resulted as a consequence of the thermal decomposition of condensation polymers and their semiquantitative estimation led to the final conclusion that the initial normal chlorine substitution in the macromolecular chain of poly(vinyl chloride) is followed by an important intramolecular cyclization reaction yielding 1,3-methyleneindan units.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 108 (1967), S. 182-192 
    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: The kinetics of the dehydrochlorination of PVC are discussed. Thermogravimetric results show that the activation energy is influenced by both the degree of conversion and the rate of heating up the sample. The activation energy for initiation was found to have a far greater value (72.5 kcal/mole) than has generally been assumed. Other unexpected results related to this are also discussed.
    Notes: Die Kinetik der Dehydrochlorierung von PVC wird diskutiert. Thermogravimetrisch gewonnene Ergebnisse zeigen, daß die Aktivierungsenergie vom Umsatz und von der Geschwindigkeit, mit der die Probe aufgeheizt wird, abhängt. Die Aktivierungsenergie fü den Start hat einen viel größeren Wert (72,5 kcal/Mol) als allgemein angenommen wird. Abschließend werden auch einige unerwartete Ergebnisse zu klären versucht.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 132 (1970), S. 259-268 
    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: The influences of the initiator- and the PVA-concentration as well as of the rate of stirring upon the reaction rate of the suspension polymerization of vinyl acetate were studied. This polymerization is determined by the rate of stirring and obeys own laws, so that it is not possible to identify the suspension polymerization with a “finely divided bulkpolymerization cooled with water”.
    Notes: Es wird der Einfluß der Initiator- und Polyvinylalkoholkonzentration sowie der Rührgeschwindigkeit auf die Reaktionsgeschwindigkeit der Perlpolymerisation des Vinylacetats untersucht und gefunden, daß die Perlpolymerisation von der Rührgeschwindigkeit abhängig ist. Aus diesem Ergebnis wird geschlossen, daß die Perlpolymerisation in diesem Fall nicht uneingeschränkt als eine „wassergekühlte Massenpolymerisation in fein verteiltem Zustand“ angesechen werden kann, sondern eigene Gesetzmäßigkeiten befolgt.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 9
    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: The results of the kinetic isothermal, thermal-dynamic (i.e. with constant heating rate) and of the gaschromatographic-pyrolytic study of the thermal degradation of different polystyrenes show the mechanism of the degradation reaction to be complex and not simple depolymerisation. The kinetic parameters of the thermal degradation depend as well on the molecular weight as on the nature of the polystyrene and the degree of conversion. On these reasons, one observes under thermal-dynamic conditions an influence of the heating rate on the total activation energy.
    Notes: Die Ergebnisse der kinetisch-isothermen, thermisch-dynamischen (d. h. mit konstanter Aufheizgeschwindigkeit) und gaschromatographisch-pyrolytischen Untersuchungen des thermischen Abbaues von verschiedenen Polystyrolen lassen darauf schließen, daß der Abbaumechanismus komplexer Natur ist und nicht nur nach einem einfachen Depolymerisationsmechanismus verläuft. Die kinetischen Parameter des thermischen Abbaus sind sowohl vom Molekulargewicht als auch von der Art des Polystyrols und dem Umsatzgrad abhängig. Aus diesem Grunde wird unter thermisch-dynamischen Bedingungen auch ein Einfluß der Aufheizgeschwindigkeit auf die Bruttoaktivierungsenergie festgestellt.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 141 (1971), S. 127-144 
    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: A critical discussion of the recommended methods for compatibility determinations in polymer mixtures by viscosimetry measurements shows, that in the case of the systems PVC/PVAc/cyclohexanone the best results are obtained by comparison of the parameters of interaction. In this case it is possible to estimate the optimal rapport of mixture. Extending the thermodynamic methods to polymer/polymer/solvent systems, it can be shown, that the systems studied here are characterized by far-reaching interactions, indicating an interaction of the functional groups of the polymer chains. This confirms our previous conclusion, that the polymers show two kinds of compatibility, that is, true compatibility of the macromoleculare chains and pseudo-compatibility due to the interactions of the functional groups.
    Notes: Es werden die in der Literatur empfohlenen Methoden für Verträglichkeitsbestimmungen in Polymergemischen aus Viskositätsmessungen an Hand des Systems PVC/PVAc/Cyclohexanon kritisch besprochen, wobei festgestellt wird, daß die besten Ergebnisse durch Vergleich der abgeleiteten Wechselwirkungsparameter erzielt werden, da optimale Mischungsverhältnisse ablesbar sind. Unter Ausdehnung der thermodynamischen Methoden auf Polymer/Polymer/Lösungsmittel-Systeme wird gezeigt, daß die untersuchten Systeme durch weitreichende Wechselwirkungen gekennzeichnet sind, was vor allem auf Wechselwirkungen zwischen den funktionellen Gruppen der Polymeren hindeutet. Diese Schlußfolgerung bestätigt unsere frühere Annahme, daß bei Polymeren zwischen einer Verträglichkeit der Makromolekülketten und einer Pseudoverträglichkeit infolge von Wechselwirkungen der funktionellen Gruppen zu unterscheiden ist.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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