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  • 1
    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: Bei der Bestrahlung von Polymethylmethacrylat (PMMA) mit Röntgensynchrotronstrahlung ändert sich die chemische Struktur des Polymeren. Die Ergebnisse der analytischen Untersuchungen dieser Arbeit weisen darauf hin, daß neben einem Abbau der Polymerketten auch einzelne Esterseitengruppen abgespalten werden. Durch die Bestrahlung entstehende Langkettenverzweigungen wurden bei PMMA nicht gefunden. Dadurch unterscheiden sich die physikalischen und chemischen Eigenschaften des bestrahlten Polymeren von denen des unbestrahlten.
    Notes: The irradiation of poly(methyl methacrylate) changes the chemical constitution of the polymer. In addition to a decrease in molar mass further radiation-induced radical reactions cause changes in the chemical constitution of the polymer. Analysis of the reaction products shows that formation of long-chain branching can be excluded. Along with degradation of the chain lengths, ester groups in the side chains are attacked. The result is a modified polymer with a physical and chemical behaviour different from that of the starting polymer.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel synthetic foot-and-mouth disease virus (FMDV) peptide vaccine consisting of a synthetic B-cell and macrophage activator covalently linked to an amphiphilic α-helical T-cell epitope was developed. The low molecular weight vaccine of 3400 daltons is composed of virus VP1 antigenic determinant and the immunologically active lipotripeptide tripalmitoyl-S-glyceryl-cysteinyl-seryl-serine (P3CSS) as built-in adjuvant. The vaccine, tripalmitoyl-S-glyceryl-cysteinyl-seryl-seryl-FMDV-VP1 (VP1 = serotype O1K 135-154) induces protection against homologous challenge and serotype-specific virus neutralizing antibodies in guinea pigs after single administration without further adjuvants or carriers. A P3CSS conjugate with the FMDV-VP1 segment 135-154 of strain O Wuppertal produced only poor cross-protection against challenge with O1K virus.The antigenic determinant VP1(135-154) is an amphiphilic α-helix, as shown by CD. Molecular dynamics simulations (MDS) carried out using the highly homologous α-helical alcohol dehydrogenase (ADH) segment H3 as starting conformation for VP1(138-149) suggest that the FMDV segment 138-149 may adopt α-helical conformation during binding to its T-cell receptor, and that the development of the system during MDS may be considered as the dissociation step of the complex.
    Additional Material: 5 Ill.
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  • 3
    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 der Röntgentiefenlithographie wird Polymethylmethacrylat (PMMA) gezielt mit Röntgensynchrotronstrahlung bestrahlt. Dadurch ändert sich die chemische Struktur des Polymeren, so daß es mit Hilfe eines selektiven Lösemittelgemisches vom restlichen unbestrahlten Polymeren abgetrennt werden kann. Ein wesentlicher Punkt der strahleninduzierten Strukturänderungen von PMMA ist die Molmassenabnahme, welche durch den Einsatz einer SEC-MALLS Kopplung zur Absolutbestimmung der Molmasse erstmals quantitativ bestimmt werden konnte. Zur Darstellung des experimentell ermittelten Verlaufs wurde eine kinetische Funktion abgeleitet, welche den Zusammenhang zwischen Dosis und Molmasse mit sehr guter Genauigkeit wiedergibt.
    Notes: Poly(methyl methacrylate) is a preferred material used in X-ray lithography. One effect observed after irradiation is a change of its chemical structure, combined with a decrease of the molar mass. This was analysed quantitatively using size exclusion chromatography combined with multi-angle laser-light scattering. Based on a kinetic model, an equation was derived which gives a satisfactory description of the dependence of the molar mass on the radiation dose.
    Additional Material: 4 Ill.
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  • 4
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Explosion hazard analysis of inflammable gas released spontaneously into the atmosphere. The processes of flash evaporation, atmospheric vapour cloud formation ignition and explosion after the bursting of vessels containing liquefied gas have been studied by model experiments with propylene heated up to 70°C and pressurized to 60 bar. The experiments have shown that a blast wave with considerable peak pressure in the vicinity of the vessel is produced already by flash expansion of the propylene. The experimentally determined decrease of peak pressure with growing distance could be scaled up to vessels of arbitrary size and different propylene temperatures. Scaling laws could be established as well for the calculation of peak pressure and positive pressure duration of the deflagration wave as functions of released mass and distance. The experiments have not revealed any evidence of a detonation process even when the cloud was ignited by an explosive charge.
    Additional Material: 15 Ill.
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1775-1785 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermotropic liquid-crystalline polyesters with either 4,4″-p-terphenylylene or p-phenylene-oxyterephthaloyloxy-p-phenylene as mesogenic units and dimethylsiloxane spacers in the main chain were synthesized. The thermal behaviour was studied by means of differential scanning calorimetry, polarizing microscopy, and X-ray diffractometry. The polymers show mainly smectic mesomorphism. The transition temperatures were found to be much lower than in the corresponding polyesters containing polymethylene or poly(oxyethylene) spacers.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 4 (1966), S. 731-743 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Gel permeation chromatography is an elution chromatographic process depending on the permeation of the solute through a bed of gel particles. This process is used in the estimation of molecular weight distributions of polymers, since elution occurs in decreasing order of molecular size. The eluting species, however, are not perfectly fractionated, and apparent broadening of the distribution occurs. This broadening results from an axial (longitudinal) mixing of the eluting species. Consideration of the accessible bed volume for each species permits a correction to be made for this axial dispersion. The concept was applied to heterodisperse distributions by solving the resulting simultaneous equations. A least-squares regression may be employed to utilize the experimental data most effectively. The experimental chromatogram can be described in terms of accessible bed volume and dispersion coefficient of each species together with flow rate, sample concentration, and chromatograph column geometry. The chromatogram corrected for the axial dispersion describes the molecular weight distribution more accurately than does the experimentally determined curve. The correction procedure was applied to a well-characterized polystyrene; the results of the gel permeation chromatography show excellent confirmation of the results of fractionation and of other instrumental analyses.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 24 (1986), S. 269-272 
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1325-1330 
    ISSN: 0887-624X
    Keywords: polymer liquid crystals ; branched spaces ; thermal properties ; X-ray scattering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new promising concept of spacer modification in main chain liquid crystalline polymers is the use of branched alkylene spacers. In this article we give as a first example the polyesters of p, p′-terphenyl-4,4′-dicarboxylic acid as mesogenic unit and disubstituted propylene spacers. The steric restrictions of the spacers lower the melting points compared with the polyesters with linear spacer but they do not flexibilize the main chains as linear alkylspacers do. This leads to a residual stability range of the liquid crystalline state in the homologues of polyesters with disubstituted spacer. The melting and clearing points are lowered to the same extent. Because of the solubility of the higher homologues in common solvents it is possible for the first time to determine molecular masses of this polymer class based on p, p′-terphenyl-4,4′-dicarboxylic acid and aliphatic diols more exactly. X-ray scattering indicates that long side chains are arranged parallel to the main chain and have no longer influence on transition temperatures and intermolecular distances. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 4 (1973), S. 374-378 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Observations on the incorporation of Siliconcarbide-Particles in Electrodeposited Nickel. Electrodeposited composite coatings with incorporated SiC-particles are produced by codeposition of nickel and SiC suspended in the plating bath. Until now the mechanisms of the deposition and incorporation of the particles in the matrix material are not fully known. In this paper some observations on the incorporation are described using scanning electron microscope techniques.
    Notes: Galvanisch hergestellte Nickeldispersionsschichten mit Einlagerungen von Siliziumkarbid (SiC) entstehen durch gleichzeitige Abscheidung von Nickel und im Elektrolyten in Suspension gehaltenen SiC-Partikeln. Ungeklärt ist bislang, nach welchen Mechanismen die Abscheidung (Annäherung an die Metalloberfläche und Haften) und der Einbau der Teilchen in der Nickelmatrix abläuft. Zur Klärung der Einbauvorgänge wurden einige Untersuchungen mit dem Rasterelektronenmikroskop durchgeführt.
    Additional Material: 13 Ill.
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