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  • Polymer and Materials Science  (1,557)
  • 1985-1989  (836)
  • 1975-1979  (721)
  • 1920-1924
  • 1
    Electronic Resource
    Electronic Resource
    Influence of hydrogen bonding, main chain-side chain interactions, and protecting groups on the excimer formation of bis(pyrenylalanine) peptides (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1833-1857 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dipeptides of the aromatic fluorescent amino acid, pyrenylalanine, are studied using both stationary and transient fluorescence techniques. Since the conformational transitions of the peptide chain are slow compared to the decay of the pyrene excited state, both ground state conformations, adopted by the peptide, i.e., C5 and C7, can be monitored separately. Kinetic models are proposed to describe the molecular dynamics of the peptide chain as probed by the intramolecular excimer formation between both pyrene chromophores. These kinetic schemes explain the influence of solvent, chain chirality, main chain-side chain interactions, and nature of the protecting groups on the emission spectrum and the fluorescence decay profile of these model peptides. These schemes also provide a tool to calculate rate constants of conformational transitions and excimer formation. By comparing the kinetic and thermodynamic parameters of the various compounds, the influence of a structural modification on the molecular dynamics of the peptide chain is determined.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360261103
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of crystallization in stretched rubber by rapid-passage NMR (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 1489-1497 
    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: Continuous-wave rapid-passage proton NMR (30 MHz) was performed on lightly crosslinked natural cis-polyisoprene at elongations up to 720%, at temperatures between -100° and 100°C, and after delays of up to several weeks after stretch. A method of separating the spectra into a narrow and a wide component was developed and applied. The results are interpreted in terms of the effects of a glass transition and strain-induced crystallinity and are in general agreement with results by other methods. The degree of crystallinity is found to increase strongly with strain (from zero for unstretched samples to 31% at elongations of 720% at room temperature), to increase with time, reaching equilibirium most rapidly in the most highly strained samples, and to decrease approximately linearly with temperature above about 20°C.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070210605
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  • 3
    Electronic Resource
    Electronic Resource
    Dielectric and mechanical properties of poly(vinyl chloride)-dioctylphthalate systems (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 2009-2020 
    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 mechanical properties, tensile strength, and elongation were investigated for poly(vinyl chloride) (PVC) samples mixed with dioctylphthalate (DOP) at concentrations from 0 to 100 parts per hundred parts PVC at 23°C. It was found that the tensile strength decreased with the increase of concentration, and the elongation was increased until a concentration of 30 DOP content, and then decreased. This leads to the suggestion that intermolecular plasticization is dominant until 30 DOP content, while interstructural plasticization is prevailing for higher concentrations. The permittivity ε′ and the dielectric loss factor ε″ of the same samples have been measured in the frequency range 102-105 Hz at temperatures from 3 to 96°C. Results show that as the DOP content increases in PVC, the dielectric absorption becomes broader, and the glass transition temperature Tg is lowered. The magnitude of the loss peak decreases with an increase of DOP content to a minimum at concentrations from 40 to 60 DOP content. At higher concentrations the loss peak is increased and Tg is unaltered. Another absorption was observed at 100 Hz and at high temperatures, which was attributed to Maxwell-Wagner effect or direct current conductivity or both of them. It was found that the sample containing 40 parts DOP in 100 parts PVC possesses the best mechanical and electrical properties.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300518
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of reactant ratio and reflux time on the properties of resole (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 291-293 
    Details
    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 Einfluß des Molverhältnisses Phenol: Formaldehyd auf die Viskosität und den Feststoffanteil des Harzes wurde untersucht. Die Bedingungen zur Herstellung eines Resols mit hohem Feststoffanteil und niedriger ViskositäUt werden aufgezeigt.
    Notes: The effect of the molar ratio phenol: formaldehyde on the viscosity and the solid content of the resin has been investigated. The conditions for preparation of a resole with high solid content and low viscosity are studied
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1987.010380508
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  • 5
    Electronic Resource
    Electronic Resource
    The interactions between wood components and formaldehyde-based resins. I. Monofunctional resin model compoundsPresented in part at the Fourth International Symposium on Wood and Pulping Chemistry, Paris, April 27-30, 1987. (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 173 (1989), S. 137-152 
    Details
    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: Die Resultate von Untersuchungen über die chemische Wechselwirkung zwischen einigen monofunktionellen Modellverbindungen, die die Struktur und Reaktivität von wärmehärtbaren Phenol- und Harnstoff-Formaldehyd-Harzen simulieren, mit Holzkomponenten (Hemicellulosen, Cellulose und Lignin) werden dargelegt. Während Hemicellulosen deutlich dazu neigen, Kondensationsprodukte mit diesen Modellverbindungen zu ergeben, reagieren Lignine in manchen Fällen weniger leicht und abhängig davon, durch welchen Prozeß sie gewonnen worden sind, und abhängig von der Art der Modellverbindung. Cellulose reagierte wegen ihrer Kristallinität nicht unter den gegebenen Bedingungen.
    Notes: Results are presented on the chemical interactions occurring when some monofunctional model compounds simulating the structure and reactivity of thermosetting phenol- and urea-formaldehyde resins are mixed with wood components (hemicelluloses, cellulose, and lignins). Whereas hemicelluloses clearly show a propensity to give condensation products with these model compounds, lignins can react less readily in some instances depending on the delignification procedure used to isolate them and on the type of model compound. Cellulose did not react under the conditions chosen, mostly because of its crystalline character.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051730111
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  • 6
    Electronic Resource
    Electronic Resource
    New structures of LD-alternating polypeptides in solution and in the solid state (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1109-1114 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140518
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  • 7
    Electronic Resource
    Electronic Resource
    Hydration of B-DNA: Comparison between the water network around poly(dG) · poly(dC) and poly(dG-dC) · poly(dG-dC) on the basis of Monte Carlo computations (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 741-761 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computational method is elaborated for studying the water environment around regular polynucleotide duplexes; it allows rigorous structural information on the hydration shell of DNA to be obtained. The crucial aspect of this Monte Carlo simulation is the use of periodical boundary conditions. The output data consists of local maxima of water density in the space near the DNA molecule and the properties of one- and two-membered water bridges as function of pairs of polar groups of DNA.In the present paper the results for poly(dG) · poly(dC) and poly(dG-dC) · poly(dG-dC) are presented. The differences in their hydration shells are of a purely structural nature and are caused by the symmetry of the polar groups of the polymers under study, the symmetry being reflected by the hydration shell.The homopolymer duplex hydration shell mirrors the mononucleotide repeat. The water molecules contacting the polynucleotide in the minor groove are located nearly in the plane midway between the planes of successive base pairs. One water molecule per base pair forms a water bridge facing two polar groups of bases from adjacent base pairs and on different strands making a “spine”-like structure. In contrast, the major groove hydration is stabilized exclusively by two-membered water bridges; the water molecules deepest in the groove are concentrated near the plane of the corresponding base pair.The alternating polymer is characterized by a marked dyad symmetry of the hydration shell corresponding to the axis between two successive base pairs. The minor groove hydration of the dCpdG step resembles the characteristic features of the homopolymer, but the bridge between the O2 oxygens of the other base-stacking type is formed by two water molecules. The major groove hydration is characterized by high probability of one-membered water bridges and by localization of a water molecule on the dyad axis of the dGpdC step.The found structural elements are discussed as reasonable invariants of a dynamic hydration shell.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280305
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  • 8
    Electronic Resource
    Electronic Resource
    Conformational properties of 2,3-methanopyroglutamic acid in peptides: Nmr and X-ray diffraction studies (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 123-128 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of replacing L-pyroglutamic acid with the cyclopropane analogue 2,3-methanopyroglutamic acid (2,3-MeGlp) on conformation and enzymatic stability have been investigated in 2,3-MeGlp-NHMe and the novel thyrotropin releasing hormone (TRH) analogue [2,3-MeGlp1]-TRH by x-ray diffraction and nmr. While 2,3-MeGlp-NHMe adopts a folded conformation (small ψ angle) in the solid state, several conformations are available to the molecule in solution. 1H-nmr of the diastereomeric mixture [(±)-2,3-MeGlp1]-TRH indicates a close orientation of the pyrrolidone and imidazole rings. The 2,3-MeGlp-His amide bond is considerably more stable to pyroglutamate aminopeptidase than the Glp-His bond in TRH.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280114
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  • 9
    Electronic Resource
    Electronic Resource
    Infrared spectroscopic studies on polyethylene, 7Part 6: cf.: W. F. Maddams, J. Woolmington, Makromol. Chem. 186, 1665 (1985).. The use of the methyl deformation band for branch characterisation (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 333-339 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The factors relating to measuring the position of the methyl deformation mode at about 1378 cm-1 with sufficient precision to permit its use for the identification of the different branches present in the various types of “linear” low density polyethylene(as manufactured by the copolymerization of ethylene and a 1-alkene) have been examined systematically. With a data density of eight points per wavenumber, and the well established subtraction procedure with polymethylene or with a near-linear polyethylene to remove the overlapping methylene deformation band, it is possible to achieve a precision of ±0,15 cm-1. This is ample to distinguish between methyl, ethyl, and butyl or hexyl branches, but not to characterise uniquely these last two. The use of Fourier self-deconvolution to separate the methyl band has also proved very effective. The precision obtainable when these methods are applied to spectra measured with one data point per wavenumber is somewhat lower, but is still adequate for characterisational purposes. The results for a series of polymers containing ethyl branches at various concentrations suggest a small difference for the peak position for branches present in crystalline and amorphous regions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890208
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  • 10
    Electronic Resource
    Electronic Resource
    Chymotrypsin catalysed hydrolysis of a drug model, p-nitroanalide bound onto polyanionic carriers (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 9 (1985), S. 159-162 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Enzymatic hydrolysis of polymeric substrates bearing identical side chains (containing N- (6-aminohexanoyl)-L-phenylalanine-p-nitroanilide moieties) was studied as a function of chemical structure of the main chain. Kinetic parameters of synthesized derivatives, i.c. poly(N-vinylpyrrolidone-co-maleic acid) (A), poly(trimethylene hydrogen phosphate) (B), and poly(2-hydroxypropylmethacrylamide) (C) were evaluated and referred to the corresponding literature data. The Michaelis constants were found to decrease in the following sequence: B 〉 C 〉 A.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.020091985122
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