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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Quantifiable frozen-stress photoelastic techniques were used to analyze stresses induced in mandibular models by a conventional free-end saddle removable partial denture. Four quasi-anatomical mandibular models were constructed for processing, together with their respective calibration specimens, through identical time/temperature stress-freezing cycles. After processing and slicing, an unloaded control model demonstrated some low-order fringes adjacent to the coronal third of the abutment tooth roots, but was otherwise stress free. A lower bilateral free-end saddle partial denture was constructed and fitted in turn to each of the remaining three models. Each denture/model combination was then loaded and processed through a stress-freezing cycle. After processing, 6-mm slices were cut from selected regions for analysis for the presence of stresses. Using a polariscope with circular polarized, monochromatic light, values for maximum shear stress were calculated at selected points in the slices taken from the three loaded models. Variations up to 28% of the mean were obtained for the three experimental models as compared with the consistent results for the material fringe values obtained from the calibration specimens. The study pointed out the problems involved in using photoelastic stress analysis on complicated anatomical models. The interpretation of the results from such studies should be approached with caution.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kathodische Reduktion einiger Arsoniumsalze in Gegenwart von Carbonylverbindungen
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 205-208 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Um Informationen über den Polarisationsmechanismus von Poly(pyromellitimid) zu erhalten, wurden die thermisch stimulierten Entladungsströme von Filmen gemessen, die bei unterschiedlichen Temperaturen und Feldstärken polarisiert worden waren. Die TSDC-Spektren weisen drei Peaks mit Maxima bei den Temperaturen (100 ± 1)°C, (196 ± 1)°C und (249 ± 1)°C auf, die mit ß, α bzw. η bezeichnet werden. Der ß-Peak wird dem am Poly(pyromellitimid) absorbierten Wasser und der Dipolorientierungspolarisation von restlichen reaktiven Gruppen zugeordnet. Die α- und η-Peaks wurden der Raumladungspolarisation bzw. den an den Elektroden injizierten Oberflächenladungen zugeschrieben. Weiter wurden die Aktivierungsenergie und die Relaxationszeiten für diese Peaks berechnet. Die Aktivierungsenergie hängt von der Feldstärke ab, bei der die Probe polarisiert wurde.
    Notes: In order to elucidate the mechanisms responsible for the polarization of poly(pyromellitimide) thermally stimulated discharge currents were investigated with films, polarized at various temperatures and electric fields. TSDC spectra consist of three peaks having temperature maxima of (100 ± 1)°C, (196 ± 1)°C and (249 ± 1)°C which are termed as ßα and η peaks, respectively. The ß peak was attributed to the absorbed water in poly(pyromellitimide) and the dipole-orientation polarization associated with the residual reactive groups. The α and η peaks were assigned to the space charge polarization and to the surface charge injected from the electrodes, respectively. The values of activation energy and relaxation times were also calculated for these peaks. The activation energy is found to vary with the polarizing field.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Photoelektretzustand in Polyimidfilmen (Kapton) wurde in Abhängigkeit von der Intensität der Beleuchtung mit sichtbarem und UV-Licht untersucht. Die Photoelektret-Ladung nimmt mit der Beleuchtungsintensität zu und erreicht eine Sättigung in Übereinstimmung mit dem Reziprozititätsgesetz. Die Zerfallskurven deuten auf die Existenz von flachen und tiefen Haftstellen (Traps) im Kapton hin. Ultraviolettstrahlung erwies sich hinsichtlich der Photopolarisation als wirksamer als sichtbares Licht. Wärmebehandlung der Filme führt zu einer Verringerung der Photoelektretladung, was auf einer Abnahme der Anzahl der Haftstellen beruhen kann. Weiter wurde der Autophotoelektretzustand im Kapton untersucht. Die Untersuchungen sind für Anwendungen von Kapton in der Elektrophotographie und bei der Umwandlung von Solarenergie von Interesse.
    Notes: The photoelectret state in Kapton polyimide film as a function of intensity of illumination has been investigated using visible light and ultraviolet radiation. Experiments were carried out both with as-received and heat treated Kapton samples. The photoelectret charge is observed to increase with the intensity of illumination tending towards saturation which is in accordance with the reciprocity law. The nature of decay curves shows the presence of shallow and deep trap levels in Kapton. Ultraviolet radiations were found more efficient for photopolarization than visible light. Heat treatment results in reduction of photoelectret charge which may be due to the decrease in the number of traps owing to high temperature aging. The autophotoelectret state has also been investigated in Kapton. This study is useful for exploring the possibilities of using Kapton in electrophotographic process and solar energy conversion devices.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 91-91 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 34 (1983), S. 667-673 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The parallel action of various active centers in ionic systems is discussed both from the point of view of their specifity and contribution to the overall experimental effects. The ways of formation and concrete types of coexisting active centers in the anionic, cationic and by transition metal derivatives induced polymerization processes are considered. As examples of the multicenters phenomena the aggregation, dissociation, isomerization, inter- and intramolecular complexation are discussed.
    Notes: Die gleichzeitige Wirkung verschiedener aktiver Zentren in ionischen Systemen wird sowohl unter dem Aspekt ihrer Besonderheiten als auch hinsichtlich ihres relativen Anteils an experimentellen Gesamteffekten betrachtet. Bildungsweise und konkrete Typen von koexistierenden aktiven Zentren in anionischen, kationischen und durch Übergangsmetallderivate initiierten Polymerisationsprozessen werden diskutiert. An Beispielen der Aggregierung, Dissoziation, Isomerisation, intermolekularen und intramolekularen Komplexbildung werden die Mehrzentreneffekte besprochen.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The anionic polymerization of acrylonitrile was studied in nonpolar solvents. Active vinylpyridine oligomers and polymers (2-VP, 4-VP) prepared by an independent synthesis were used as initiators. The efficiency of the initiation and the conversion were determined in dependence on the nature of the initiator.
    Notes: Die anionische Acrylnitril-Polymerisation wird in unpolaren Lösungsmitteln untersucht. Als Initiatoren dienen unabhängig synthetisierte aktive Vinylpyridin-Oligomere bzw. -Polymere (2-VP, 4-VP). Die Effektivität der Initiierung und die Höhe des Umsatzes werden in Abhängigkeit von der Natur des Initiators bestimmt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The anionic copolymerization of acrylonitrile with acrylates and methylmethacrylate initiated by lithium-tert-butoxide in dimethylformamide was investigated in the temperature range of -30 to +10°C. Based on the way of incorporation of the esters, the chemical inhomogeneity and the structure of the copolymers, the copolymerization parameters calculated by the model of Mayo and Lewis were examined with respect to their validity for this anionic process.
    Notes: Die anionische copolymerisation von Acrylnitril mit Acrylaten und Methylmethacrylat, initiiert durch Lithium-tertbutoxid in Dimethylformamid, wurde im Temperaturbereich -30°C und +10°C untersucht. Aus dem Einbauverhalten der Ester, der chemischen Uneinheitlichkeit und der Struktur der Copolymerisate werden die nach dem Modell von Mayo und Lewis berechneten Copolymerisationsparameter hinsichtlich ihrer Gültigkeit für diesen anionischen Prozeß überprüft.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Copolymerisation von Acrylnitril und Acrylaten wurde in Dimethylformamid bei hohem Acrylnitril/Acrylat-Verhältnis im Temperaturbereich von -50 bis +10°C durch Lithiumalkoxide initiiert. Die Bedingungen zur direkten Präparation von Spinnlösungen der Copolymere wurden erarbeitet. Das Lösungsspinnen dieser Copolymere durch Orientierungsfällung ergab Fasern mit hohen Festigkeitswerten.
    Notes: The copolymerization of acrylonitrile with acrylates has been initiated by lithium alkoxides in dimethylformamide at a high acrylonitrile/acrylate ratio over the temperature range from -50 to 10°C. The conditions for a direct preparation of spinning solutions of the copolymers were determined. The solution-spinning of these copolymers by orientational precipitation yielded fibres exhibiting high strength properties.
    Additional Material: 3 Tab.
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