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  • 1
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Multidetektor ; CT ; MSCT ; Larynx ; Tumoren ; Multiplanare Rekonstruktion ; Key words Computer tomography ; Larynx Head and neck tumors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The purpose of the study was to preoperatively investigate small laryngeal carcinomas using multi-slice spiral CT (MSCT) and subsequent multiplanar reconstructions (MPR) and to compare the results to the detailed spread found at surgery and histology. Nine patients with small (T1, T2) laryngeal cancer were investigated on a MSCT scanner (Siemens plus 4 Volume Zoom, Siemens). A 4×1 mm collimation, 120 kV, 200 mAs and a 0.5 seconds rotation time were used, allowing a coverage of the entire larynx in approximately 10 seconds within a single breathhold. Multiplanar reconstruction’s (MPR) in sagittal and coronal plane were reconstructed in all patients and rated in consensus reading. In 8 of nine patients, the glottic spread was detected by MSCT, in one cause of a supraglottic tumor a glottic invasion was excluded. The infiltration of the anterior commissure, the infiltration into the subglottic space and the extension into the hypopharynx was correctly assessed in all patients. MSCT was not able to predict infiltration of the arythnoids in two patients. The use of multi-slice spiral CT for the preoperative assessment of small laryngeal tumors shows great promise. The detection or exclusion of subtle spread of these tumors into the supra- or subglottic space and along the glottic level was possible with high accuracy. As the examination time is short, artifacts are rare and multiplanar reconstructions gain in clinical importance.
    Notes: Zusammenfassung Zielsetzung war, kleine Larynxkarzinome mit der Mehrschicht-Spiral-CT (MSCT) und nachfolgenden multiplanaren Rekonstruktionen (MPR) präoperativ zu untersuchen. 9 Patienten mit histologisch gesichertem Larynxkarzinom der Stadien T1 und T2 wurden untersucht. Alle Untersuchungen wurden an einem Mehrschicht-Spiral-CT (Somatom Plus 4 Volume Zoom, Siemens, Forchheim) durchgeführt. Die Abtastung erfolgte mit 4×1 mm Kollimation, 120 kV, 200 mAs bei einer Rotationszeit der Röhre von 0,5 s. Die Beurteilung einer Infiltration erfolgte durch die Bewertung aller drei Ebenen. Das glottische Wachstum entlang der Stimmlippen konnte in 8 von 9 Patienten richtig-positiv nachgewiesen werden. In einem Fall eines supraglottischen Tumors konnte eine glottische Infiltration ausgeschlossen werden. Die Infiltration der vorderen Kommissur, die Infiltration in den subglottischen Raum und die Ausdehnung in den Hypopharynx konnte ebenfalls sicher nachgewiesen bzw. ausgeschlossen werden. Die Infiltration der Aryknorpel konnte in 7 von 9 Fällen korrekt durch die MSCT vorhergesagt werden. Der Einsatz der Mehrschicht-Spiral-CT bei kleinen Larynxkarzinomen zeigt eine hohe Genauigkeit zum Nachweis bzw. zum Ausschluß von Infiltrationen sowohl in der glottischen Ebene, wie auch in den supra- oder subglottischen Raum. Bedingt durch die kurze Untersuchungszeit sind Bewegungsartefakte selten. Multiplanare Rekonstruktionen (MPR) sind klinisch sehr wertvoll.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 33 (1958), S. 503-504 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 1651-1653 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Theoretical treatment had shown that syndiotactic propagation should be slightly favored energetically over isotactic propagation in free radical vinyl chloride polymerization. This prediction has been confirmed experimentally by x-ray and infrared investigations of vinyl chloride polymers prepared at various temperatures. The initiator was a peroxide, azodiisobutyronitrile, or tri-n-butylboron, and had no detectable influence on the x-ray and infrared results. As the polymerization temperature is lowered, the number of lines or arcs in the x-ray diffraction pattern and their sharpness gradually increase as a result of the increased crystallinity arising from improved regularity. The regular sequences are indicated to have the syndiotactic configuration from the chain repeat distance. The change in the infrared absorbance ratio of two carbon-chlorine stretching bands with polymerization temperature can be interpreted in agreement with increasing syndiotacticity at decreasing temperature. With the use of simplifying assumptions, the activation energy difference between isotactic and syndiotactic propagation is estimated to be of the order of one-half kcal/mole. The stereoregulated free radical polymerization of vinyl chloride is thus qualitatively similar to that disclosed for other monomers.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 1 (1963), S. 951-964 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study was made of the effect of polymerization temperature on the syndiotacticity of polyvinyl formate. Vinyl formate was polymerized with ultraviolet light initiation in the temperature range from -20 to +30°C. The value of (Ep  -  Et)/2 obtained, 4.5 kcal./mole, is characteristic of those values obtained by other workers for the free radical-initiated polymerization of vinyl acetate. A linear relationship was found to exist between the viscosities of the polyvinyl formates and those of the derived polyvinyl alcohols. The degree of polymerization of polyvinyl formate may be calculated from the equation: [η] = 4.42 × 10-3 DP0.63. The low temperature polymerization of vinyl for- mate results in more syndiotactic polymer, as shown by x-ray diffraction. Polyvinyl for-mate obtained at more elevated polymerization temperatures did not demonstrate the same degree of order. No difference was found between the infrared spectra of the polyvinyl formates. The polyvinyl alcohol derived from polyvinyl formate polymerized at low temperatures (0 to -35°C.) exhibits water resistance and forms a colored iodine complex similar to that obtained with the syndioactic polyvinyl alcohol derived from polyvinyl trifluoroacetate. Conventional polyvinyl alcohol and that derived from polyvinyl acetate polymerized at -30°C. do not exhibit the same properties. Minor differences in the 1,2-glycol content in the various polyvinyl alcohols do not account for the differences in the observations. The amount of head-to-head addition in various vinyl aliphatic esters seems to be related to the inductive strength of the acid portion of the ester. No difference was found between the crystallinities of the various polyvinyl alcohols, as measured by film density. Heat treatment increases the crystallinities about the same amount, but the water resistance of the stereoregular materials remains higher. From the good correlation between the observations made on polyvinyl formate and the derived polyvinyl alcohol, it is concluded that syndiotactic polyvinyl formate, and hence syndiotactic polyvinyl alcohol, is obtained by the low temperature free radical-initiated polymerization of vinyl formate. Increased syndiotacticity is more readily obtained in polyvinyl formate than in polyvinyl acetate, indicating the greater influence of inductive effect compared with the steric effect in controlling stereoregularity during free-radical propagation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chloral was polymerized by means of cationic and anionic initiators and the products compared. Anionic catalysts readily produce high molecular weight polymer (DP ∼ 300-600), but a DP of only 200 could be produced with cationic catalysts. The anionic system apparently initiates and propagates polymerization much more readily than the cationic system. This effect is attributed to the inductive effects of the chlorine atoms on the chloral. Little difference was found when products of similar DP were compared as to x-ray diffraction pattern, infrared spectrum and tractability. This is believed due to the single type of structure which is sterically favored. Various cyclic compounds of chloral could not be made to undergo polymerization under cationic initiation. The conditions required to effect ring opening were too rigorous to enable polymerization to take place.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 3 (1965), S. 3741-3751 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Although dichloroacetaldehyde has only one chlorine less than chloral, the polymerization and polymer characteristics are quite different. Dichloroacetaldehyde is readily polymerized by Lewis acid catalysts to polymer with terminal hydroxyl groups. The catalyst BF3·Et2O, at 0°C., produces very high molecular weight polymer, in bulk polymerization. A DPn of about 400 is readily attainable. The characteristics of the polymerization indicate a cationic type, with greater dependence of DP upon chain termination rather than chain transfer. The polymer is readily end-capped by acetic anhydride, with a pyridine catalyst, to increase its thermal stability. Melting point, infrared spectra, and x-ray diffraction measurements confirm that the polymer produced under these conditions is amorphous. Cast films of the polymer could be only partially oriented The polymer is soluble in many common organic solvents.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polychloral diol, unlike polyoxymethylene diol, is not readily capped in the presence of alkali catalysts. Polychloral is capped under acid conditions by acid anhydrides and chlorides and does not appear to undergo degradation during the process. Evidence for end-capping is provided by infrared analysis in the case of the low DP polychloral, metachloral. End-capped polychlorals possess good stability towards hot dimethylformamide and good stability at elevated temperatures (255°C.). From the melting points of copolymers, polychloral itself is estimated to have a melting point of about 460°C. The high melting point is consistent with the rigidity of the polymer chain. A means of estimating the DP of the polymer is proposed, based on a form of endgroup analysis. By this technique, metachloral is estimated to have a DP of about 50.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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