ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Thermal degradation of poly((E,E)-[6.2]paracyclophane-1,5-diene) (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2781-2790 
    Details
    ISSN: 0887-624X
    Keywords: poly((E,E)-[6.2]paracyclophane-1,5-diene ; thermal analysis ; thermal degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal degradation of poly((E,E)-[6.2]paracyclophane-1,5-diene) is studied in inert and oxidative environments by using thermogravimetric analysis, pyrolysis GC/MS, pyrolysis GC/FT-IR, and variable temperature-diffuse reflectance infrared spectroscopy (VT-DRIFTS). Thermal degradation in helium begins by depolymerization yielding a volatile product capable of abstracting hydrogens from the polymer residue. Multiple hydrogen abstractions result in a variety of volatile species containing benzyl-benzyl bonds. In the presence of oxygen, polymer decomposition is dictated by reactions of peroxy and hydroperoxy radicals. At low temperatures, oxygenated species are the primary products. At higher temperatures, increased unsaturation is detected in the polymer residue. In both inert and oxidative environments, the strain associated with alignment of paracyclophane aromatic rings is lost during the initial stages of thermal degradation. © 1992 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301314
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Effects of inorganic oxides on polymer binder burnout. II. Poly(butyl methacrylate) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1911-1920 
    Details
    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
    Notes: The effects of silica, mullite, α-alumina, and γ-alumina on the nonoxidative thermal degradation of poly(butyl methacrylate) are described. Under conditions similar to those employed for nonoxidative ceramic sintering, more volatile alkyl aromatic species were detected when polymer/oxide samples were heated than when the neat polymer was heated. Relative to the neat polymer, all of the inorganic oxides inhibited monomer evolution and promoted an ester decomposition reaction that yielded butene. Infrared analysis indicated that poly(methacrylic acid) segments resulting from ester decomposition reacted to form anhydride. The presence of water vapor during the thermal degradation of the neat polymer and polymer/oxide samples lowered the temperatures at which monomer evolution maximized but had little effect on butene evolution. When the polymer was coated on γ-alumina, significant amounts of carboxylate were formed above 400°C as a result of deprotonating poly(methacrylic acid) functionalities on the γ-alumina surface. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Effects of alkali halides on the thermal decompositions of poly(methyl methacrylate) and poly(2-hydroxy ethyl methacrylate) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1209-1219 
    Details
    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
    Notes: The effects of alkali halides on the nonoxidative thermal degradations of poly(methyl methacrylate) and poly(2-hydroxy ethyl methacrylate) are described. The magnitudes of the effects of various alkali halides on polymer thermal degradation were found to depend on the salt and the polymer. Mass spectrometric analysis of volatiles evolved during polymer degradation detected alkyl halides formed by reactions between the salts and polymers. Compared to poly(methyl methacrylate), more alkyl halide was evolved from samples containing alkali halides and poly(2-hydroxy ethyl methacrylate). To varying degrees, salts also catalyzed ester decomposition reactions for this polymer. Infrared spectroscopic analysis results showed that carboxylate salts, carbonate, and carbon monoxide were formed by heating polymer/salt mixtures. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Effects of inorganic oxides on polymer binder burnout. I. Poly(vinyl butyral) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1901-1909 
    Details
    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
    Notes: The effects of silica, mullite, α-alumina and γ on the nonoxidative thermal degradation of poly(vinyl butyral) are described. To varying degrees, all of the inorganic oxides catalyzed reactions that produced butanal. Other significant products included: water, butenal, acetic acid, and alkyl aromatics. Two distinct evolution steps were detected for samples containing mullite and α-alumina, suggesting that multiple interactions existed between these oxides and the polymer. The relative amounts of volatile aromatic products evolved by heating polymer/oxide samples were greater than the amounts generated from the neat polymer. For the polymer/γ-alumina sample, carboxylate species were detected on oxide surfaces above 250°C, indicating that a reaction between the polymer and γ-alumina occurred. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Effects of catalyst acidity and HZSM-5 channel volume on the catalytic cracking of poly(ethylene) (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1151-1159 
    Details
    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
    Notes: The effects of catalyst acidity and the restricted reaction volume afforded by the HZSM-5 zeolite structure on the volatile cracking products derived from poly(ethylene) are investigated. The effectiveness of silica-alumina, HZSM-5, and sulfated zirconia acid catalysts for poly(ethylene) cracking are compared. When high catalyst to polymer ratios are employed and volatile products are rapidly removed during cracking, the most abundant volatile products generated by poly(ethylene) cracking are propene and isoalkenes. The relative amount of propene produced and the temperatures corresponding to the maximum rate of volatile hydrocarbon production are found to be related to catalyst acidity. The restricted volume inside HZSM-5 channels facilitates oligomerization and the production of small alkyl aromatics. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580709
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Die Biosynthese von Vitamin B1 (Thiamin): ein Beispiel für biochemische Vielfalt (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 109 (1997), S. 1096-1111 
    Details
    ISSN: 0044-8249
    Keywords: Biosynthesen ; Enzyme ; NMR-Spektroskopie ; Vitamine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Aufklärung der Biosynthesewege zu Thiamin (Vitamin B1) und dessen Pyrophosphatester, dem wichtigen Coenzym Cocarboxylase, ist und bleibt für Forscher eine Herausforderung. Die Thiamin-Biosynthese gliedert sich in die voneinander unabhängigen Synthesewege zur Pyrimidin-Einheit 4-Amino-5-hydroxymethyl-2-methylpyrimidin und zur Thiazol-Einheit 5-(2-Hydroxyethyl)-4-methylthiazol sowie den Weg dieser Untereinheiten zum Vitamin. Die Schritte des letztgenannten Prozesses wurden vor ungefähr zwanzig Jahren vollständig aufgeklärt. Dabei stellte sich heraus, daß sich der Syntheseweg in aeroben Bakterien und Hefen zu einem gewissen Grad vom Syntheseweg in Enterobakterien unterscheidet. Dagegen sind die Synthesewege zu den Untereinheiten noch nicht zufriedenstellend erforscht. Die Pyrimidin- und die Thiazol-Einheit entstehen in Bakterien und in Hefen auf unterschiedlichen Synthesewegen. Eine Schwierigkeit war, daß das Einbaumuster markierter Vorläufer, das von verschiedenen Arbeitsgruppen bei unterschiedlichen Mikroorganismen festgestellt wurde, nicht mit einem einzigen Biosyntheseweg für jede der beiden Untereinheiten in Einklang war. Man ist heute davon überzeugt, daß in Enterobakterien und Hefen unterschiedliche Wege vorliegen, so daß die Biosynthese von Vitamin B1 ein Beispiel für biochemische Vielfalt ist. Darüber hinaus war die geringe Menge an Thiamin, die in mikrobiologischen Kulturen synthetisiert wird (ca. 15 μg pro Liter Kultur), eine weitere Schwierigkeit. Daher waren die Untersuchungen bis in die jüngste Zeit entweder auf die Verwendung radioaktiver Tracer oder den Einsatz stabiler Isotope mit anschließender massenspektrometrischer Analyse beschränkt. Wie bekannt, führen beide Methoden zu Problemen bei der Interpretation der Resultate. Die Hochfeld-13C-NMR-Spektroskopie, die aussagekräftigste moderne Methode zur Ermittlung von Einbaumustern, wurde erst kürzlich erfolgreich zur Untersuchung der Thiamin-Biosynthese eingesetzt. Wegen dieser prinzipiellen und experimentellen Schwierigkeiten sind selbst die ersten Vorläufer der beiden relativ einfachen heterocyclischen Untereinheiten von Thiamin nicht eindeutig erkannt. Die Suche nach den Zwischenstufen, die Untersuchung der Enzyme und die Identifizierung der beteiligten Gene sind Gegenstand der aktuellen Forschung.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19971091005
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Applications of Fourier transform mass spectrometry (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Mass Spectrometry Reviews 2 (1983), S. 389-415 
    Details
    ISSN: 0277-7037
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mas.1280020303
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Biosynthesis of Vitamin B1 (Thiamin): An Instance of Biochemical Diversity (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 36 (1997), S. 1032-1046 
    Details
    ISSN: 0570-0833
    Keywords: biosynthesis ; enzymes ; NMR spectroscopy ; vitamins ; Biosynthesis ; NMR spectroscopy ; Vitamins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The elucidation of the biosynthetic pathway to thiamin (Vitamin B1) and its pyrophosphate ester, the important coenzyme “cocarboxylase”, has challenged researchers for many years and continues to do so. The problem of the origin of thiamin can be separated into three parts: the independent pathways to the pyrimidine moiety 4-amino-5-hy-droxymethyl-2-methylpyrimidine and to the thiazole moiety 5-(2-hydroxyethyl)-4-methylthiazole, and the route from these subunits to the vitamin. The steps in the latter process were fully established some twenty years ago, and it was shown that the route in aerobic bacteria and yeast differs to some extent from that in enteric bacteria. The pathways to the subunits, on the other hand, are still not clarified. Significant differences exist in the routes whereby each of the two subunits, the pyrimidine moiety and the thiazole moiety, originate in bacteria and yeast. One difficulty that delayed progress was that the incorporation patterns of labeled precursors, which were observed by different research groups in different microorganisms, could not be reconciled on the basis of a single pathway to each of the two subunits. It is now accepted that in each case different pathways exist in enteric bacteria and yeast, and that the biosynthesis of Vitamin B1 represents an instance of biochemical diversity. A second factor that added to the difficulties is the minute amount of thiamin synthesized in microbiological cultures (about 15 μg per L culture). This limited the investigations until very recently either to the use of radioactive tracers or to the use of stable isotopes in conjunction with mass spectrometric analysis. It is widely recognized that both methods are associated with pitfalls in the interpretation of results. High-field 13C NMR, the most powerful modern method available for the determination of incorporation patterns, has only very recently been successfully employed in investigations of thiamin biosynthesis. As a result of the conceptual and experimental problems, even the primary precursors of each of the two relatively simple heterocyclic subunits of thiamin are still not completely established. A search for committed intermediates, the study of the enzymes, and identification of the genes that are involved are the matter of current research.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199710321
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...