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  • 11
    Electronic Resource
    Electronic Resource
    Ein einfaches Verfahren zur Bestimmung gültiger Bruchzähigkeitswerte von Hartmetallen (1978)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 9 (1978), S. 128-132 
    Details
    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: A Simple Method of Determining Valid Fracture Toughness Data of Cemented CarbidesFrom a comparison of published data it follows that a valid determination of the fracture toughness of cemented carbides depends on the use of samples containing sharp cracks. It is shown that using the technique of controlled fracture experiments sharp cracks of a given length can be introduced easily and reproducibly into bend specimens. A new evaluation method permits the fracture toughness to be calculated without knowing the crack length if the compliance of the pre-cracked specimen is measured. The KIc values determined in this way are characterized by a very small scatter and agree well with data from the literature which were obtained from specimens of similar composition. A comparison of the flaw size calculated from KIc and the bend strength to the failure size detected in fractographic studies shows very good agreement.
    Notes: Ein Vergleich von Literaturergebnissen ergibt, daß die Bruchzähigkeit von Hartmetallen nur dann gültig bestimmt wird, wenn Proben mit scharfen Anrissen benutzt werden. Es wird gezeigt, daß mit Hilfe der Technik des kontrollierten Bruchversuchs scharfe Anrisse vorgegebener Länge in Biegeproben leicht und reproduzierbar erzeugt werden können. Eine neuartige Auswertemethode gestattet es, die Bruchzähigkeit ohne Kenntnis der Rißlänge zu ermitteln, wenn statt dessen die Nachgiebigkeit der Nachgiebigkeit der angerissenen Probe gemessen wird. Die so bestimmten KIc -Werte weisen eine sehr geringe Streuung auf und stimmen mit Literaturwerten, die über ebenfalls scharf angerissene Hartmetalle ähnlicher Zusammensetzung bekannt sind, gut überein. Der Vergleich zwischen der aus KIc und der Bruchspannung berechneten Fehlergröße mit der fraktographisch gefundenen zeigt sehr gute Übereinstimmung.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19780090406
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  • 12
    Electronic Resource
    Electronic Resource
    Berechnung des Kriechverhaltens zylindrischer Hohlkörper mit radialem Temperaturgradienten (1979)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 10 (1979), S. 243-248 
    Details
    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: Theoretical Investigation of the Creep Behaviour of a Tube Subjected to Thermal and Mechanical LoadingA tube specimen, in which a constant temperature distribution of axial symmetry is maintained and which is subjected to a constant axial tensile stress is considered. Calculation of the thermal stress and creep strain distribution requires detailed knowledge of the physical properties of the material. A stress analysis, based on successive approximations, is given, which has been extended into the plastic deformation range. As a result, it can be shown that the initial stress pattern is redistributed by time-dependent creep, yielding in a more homogeneous uniaxial stress distribution. From these results a simple formula is derived which gives the steady state stress distribution as well as a characteristic mean or “effective” value of the temperature within the tube wall.
    Notes: Das Kriechverhalten einer zylindersymmetrischen Hohlprobe, die mit einem radialen Temperaturgradienten belegt ist und axial belastet wird, wird theoretisch untersucht. Ausgehend von der genauen Kenntnis der physikalischen Werkstoffeigenschaften wird die elastische Spannungsverteilung berechnet und die Analyse mittels einer numerischen Approximationsmethode auf den nicht-elastischen Bereich erweitert. Es zeigt sich, daß durch zeitabhängige Fließvorgänge Spannungsumverteilungen stattfinden, die schon im Bereich kleiner Dehnungen zu einem einachsigen, stationären Spannungszustand führen. Aus diesen Ergebnissen wird ein einfacher Ansatz für ein charakteristisches Beanspruchungsprofil abgeleitet, dessen Merkmale die stationäre Spannungsverteilung und eine mittlere Temperatur sind, mit denen das Gesamtkriechverhalten dargestellt werden kann. Der Einfluß lokaler Kriechschädigung auf die Restlebensdauer wird abgeschätzt.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19790100707
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  • 13
    Electronic Resource
    Electronic Resource
    C—C-Verknüpfung von Carbonsäuren mit Allylalkoholen unter Verwendung von 2-Phenylglycin als VehikelDer BASF AG, Ludwigshafen, danken wir für Chemikalienspenden.Professor Burckhardt Helferich zum 90. Geburtstag gewidmet (1977)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 89 (1977), S. 408-410 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19770890610
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  • 14
    Electronic Resource
    Electronic Resource
    The triple helix ⇌ coil conversion of collagen-like polytripeptides in aqueous and nonaqueous solvents. Comparison of the thermodynamic parameters and the binding of water to (L-Pro-L-Pro-Gly)n and (L-Pro-L-Hyp-Gly)n (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 601-622 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collagen-like peptides (L-Pro-L-Pro-Gly)n and (L-Pro-L-Hyp-Gly)n with n = 5 and 10, were examined in terms of their triple helix ⇌ coil transitions in aqueous and nonaqueous solvents. The peptides were soluble in 1,2-propanediol containing 3% acetic acid and they were found to form triple-helical structures in this solvent system. The water content of the solvent system and the amount of water bound to the peptides were assayed by equilibrating the solvent with molecular sieves and carrying out Karl Fischer titrations on the solvent phase. After the solvent was dehydrated, much less than one molecule of water per tripeptide unit was bound to the peptides. Since the peptides remained in a triple-helical conformation, the results indicated that water was not an essential component of the triple-helical structure. Comparison of peptides with the same chain length demonstrated that the presence of hydroxyproline increased the thermal stability of the triple helix even under anhydrous conditions. The results, therefore, did not support recent hypotheses that hydroxyproline stabilizes the triple helix of collagen and collagen-like peptides by a specific interaction with water molecules. Analysis of the thermal transition curves in several solvent systems showed that although the peptides containing hydroxyproline had tm values which were 18.6° to 32.7°C higher, the effect of hydroxyproline on ΔG was only 0.1 to 0.3 kcal per tripeptide unit at 25°C. The results suggested, therefore, that the influence of hydroxyproline on helical stability may be explained by intrinsic effects such as dipole-dipole interactions or by changes in the solvation of the peptides by alcohol, acetic acid, and water. A direct calorimetric measurement of the transition enthalpy for (L-Pro-L-Pro-Gly)n in 3% or 10% acetic acid gave a value of -1.84 kcal per tripeptide unit for the coil-to-helix transition. From the value for enthalpy and from data on the effects of different chain lengths on the thermal transition, it was calculated that the apparent free energy for nucleation was +5 kcal/mol at 25°C (apparent nucleation parameter = 2 × 10-4 M-2). The value was dependent on solvent and on chemical modification of end groups.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160310
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  • 15
    Electronic Resource
    Electronic Resource
    A computer implementation of frequency-temperature superposition for dynamic mechanical transformations (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 791-799 
    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 usual procedure for shifting dynamic mechanical data, involving the construction of a master plot, was compared with a simpler, computer-implemented double shift procedure, which obviates the need for such a construction. Data reproducibility indicates that the double shift may successfully be shifted to frequencies greater than one decade to either side of the experimental range.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1975.070190316
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  • 16
    Electronic Resource
    Electronic Resource
    Mechanochemical aspects of repetitive impacts and sliding on polymers (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 24 (1979), S. 1503-1514 
    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: Scattered data exist in the literature on the chemical reactions which occur during mechanical contact. It is our contention that these reactions occur as a direct result of the high temperatures generated at the contact interface, due to the dissipation of mechanical energy. A theoretical analysis is used to identify and rank the various sources of heat generation during repetitive impact or sliding. New data, on both filled and unfilled polymers and elastomers, supported by data from the literature, are used to show that the resultant temperature rise causes reactions at the interface; the extents of these reactions depend on the polymer structure and the magnitude of the temperature rise. Several ways of reducing the magnitude of this temperature rise are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070240611
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  • 17
    Electronic Resource
    Electronic Resource
    A Classical Synthesis of the Collagen-like Peptides with the Sequence Z(GlyProPro)nOBut and their characterization with circular dichroism and ultracentrifugation (1975)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 1276-1287 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oligopeptides with the sequence Z(GlyProPro)nOBut (n = 3-7) were synthesized along a clasical pathway. Generally long fragments were condensed in order to allow an easy separation of the products from the reactants. It is established by molecular weight determination and measurements of circular dichroism that the peptides form the collagen-like triple helix in methanol and that they assume the random coil conformation in dilute acetic acid. The circular dichroism spectra agree reasonably well with the corresponding spectra for (ProProGly)10 which was obtained by solid phase synthesis in another laboratory.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19750580506
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  • 18
    Electronic Resource
    Electronic Resource
    Acetoxytropyliumbromid: Synthese, Strukturbeweis, Verhalten in Lösung17. Mitt. über Fulvene und Fulvalene, 16. Mitt. siehe [1]. - Mitt. Nr. 272 der Abteilung für Kristallographie und Strukturlehre, Universität Bern. (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 2344-2354 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetoxytropyliumbromide: Synthesis, Structural Evidence, Behaviour in Solution.Acetoxytropyliumbromide (9) is formed from tropone and acetylbromide. In solution the tropylium salt equilibrates with the educts, 9 being favored at low temperature in polar aprotic solvents. The structure of the title compound has been proved by X-ray analysis, as well as by investigation of the 1H-NMR. spectra of solutions of 9.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590707
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  • 19
    Electronic Resource
    Electronic Resource
    The Crystal and Molecular Structure of an Octacycloheneicosane Inert Towards Lewis Acid Isomerization (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 3566-3576 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Die Struktur eines gegenüber Umlagerungen mit Lewis-Säuren inerten OctacycloheneicosansBei der Hydrid-Transfer-Reduktion (96 proz. Schwefelsäure in Methylcyclohexan) von trimerem Norbornadien (1) entsteht exo, exo-Octacyclo[8.8.1.13,6.112,15.0 2,9.04,8.011,18.013,17]heneicosan (4). Die aus der Röntgenstrukturanalyse von 4 erhaltenen Bindungslängen und Bindungswinkel stimmen gut mit denen aus Kraftfeldrechnungen überein. Auch mit hochaktiven Lewis-Sauren als Katalysatoren erfolgt keine weitere Umlagerung von 4 zu stabileren C21H28- Isomeren wie z. B. 2 oder 3. Dies ungewöhnliche Verhalten wird mit der erforderlichen Bildung energetisch ungünstiger, hochgespannter Zwischenprodukte mit quartären Kohlenstoffatomen erklärt, die unter diesen Reaktionsbedingungen nicht entstehen können.
    Notes: Hydride transfer reduction (with 96% H2SO4 and methylcyclohexane) of norbornadiene trimer (1) gives exo, exo-octacyclo[8.8.1.13,6.112,15.0 2,9.04,8.011,18.013,17]heneicosane (4). The X-ray structural details of 4 and those calculated by force field methods are in excellent agreement. Further rearrangement of 4 to more stable C21H28 isomers (e.g., 2 or 3) does not take place even with highly active Lewis acid catalysts. This exceptional behavior is attributed mechanistically to energetically unfavorable “bottlenecks”, i. e., intermediates with quaternary carbons and highly strained structures lying along the rearrangement pathway, which cannot be achieved under the reaction conditions without decomposition taking place.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791121106
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  • 20
    Electronic Resource
    Electronic Resource
    Synthesen von Verbindungen der Corrin-Reihe, XII. Darstellung eines Tetradehydrocorrinato-platin(II)-bromids (1977)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1977 (1977), S. 767-771 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses of Corrins, XII.  -  Synthesis of a Tetradehydrocorrinatoplatinum(II) BromideIn connection with our knowledge of the cytostatic effect of platinum complexes with coordinated nitrogen, platinum was inserted into the tetradehydrocorrin chromophore for the first time. Starting from the 1,19-dideoxybilatriene salt 2 which was isolated as the first representative of this class of compounds, a variant of A. W. Johnson's oxidative cyclization reaction yields 4.
    Notes: Im Zusammenhang mit der Kenntnis der cytostatischen Wirksamkeit von über Stickstoff koordinierten Platinkomplexen wurde Platin erstmals in das chromophore System der Tetradehydrocorrine eingebaut. Ausgehend von dem zum ersten Mal isolierten 1,19-Didesoxybilatrien-Salz 2 gelang die Synthese von 4 unter Abwandlung des oxidativen Ringschlusses nach A. W. Johnson.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197719770507
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