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  • 1970-1974  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 28 (1972), S. 470-474 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The incorporation of C14-amino acids (aspartic acid, glutamic acid, threonine and proline) and C14-nucleic acid bases (adenine, guanine, cytosine and uracil) into the seedling, reproductive stage and young ear portion of rice plant was investigated. It was found that C14-aspartic acid was incorporated into the rice seedling more rapidly than C14-threonine or C14-proline; on the other hand C14-proline was found to be more rapidly incorporated than C14-aspartic acid into reproductive stage plant and young ear portion. Similarly C14-adenine was incorporated into the rice seedling more rapidly than other C14-labelled bases. On the other hand C14-uracil was preferentially incorporated to C14-adenine or C14-guanine into the reproductive stage plant and young ear portion. It is suggested from the results obtained that proline is polymerized into polypeptide or protein in the rice plant more rapidly at the reproductive stage than at the seedling stage and that a higher proportion of pyrimidine bases might be involved into the metabolic process at the reproductive stage of rice plant.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 6 (1970), S. 139-150 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On établit une relation exprimant l'évolution de la ductilité des métaux et alliages en fonction de la pression hydrostatique. Dans l'expression: $$\left( {\frac{P}{{\sigma _n }}} \right) = \tfrac{1}{2}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{locale} (P)^{\tfrac{3}{2}} - \varepsilon _{locale} (O)^{\tfrac{3}{2}} \} + \tfrac{1}{3}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{locale} (P) - \varepsilon _{locale} (O)\} + \tfrac{1}{2}\{ \varepsilon _{locale} (P)^{\tfrac{1}{2}} - \varepsilon _{locale} (O)^{\tfrac{1}{2}} \}$$ P désigne la pression hydrostatique, ɛlocale la déformation accumulée entre le debut de la striction et la rupture, σ n la contrainte de striction et dσ-/dɛ le coefficient d'écrouissage linéaire. Cette relation est établie en se basant sur un nouveau critère de la rupture ductile, à savoir la constance des tensions hydrostatiques, qui rend compte que l'évolution de la ductilité avec la pression hydrostatique obéit à une loi de puissance trois demi. L'accroissement de ductilité que l'on a observé sur des métaux et alliages de caractéristiques très diffèrentes soumis à des pressions allant jusqu'à 10.000 kg/mm2, confirme la pertinence du critère proposé. On montre également que la ductilité de certains alliages de cuivre á faible énergie de défauts d'empilement-tels que les alliages Cu-Zn et Cu-Ge-augmente an début de la mise sous pression, mais que, á partir de pressions relativement basses, à savoir 3500 à 4000 kg/cm2, l'accroissement cesse de se manifester, et la ductilité demeure sensiblement indépendante de la pression. Pour expliquer ce comportement des alliages á faible énergie d'empilement, on suggère que la rupture ductile de ces métaux résulte d'un processus où n'interviennent pas les composantes de contraintes hydrostatique, mais uniquement les contraintes de cisaillement.
    Abstract: Zusammenfassung Es wird eine Formel aufgestellt, welche den Verlauf der Verformbarkeit von Metallen und Legierungen in Abhängigkeit des hydrostatischen Druckes angebt. In der Gleichung: $$\left( {\frac{P}{{\sigma _n }}} \right) = \tfrac{1}{2}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{local} (P)^{\tfrac{3}{2}} - \varepsilon _{local} (O)^{\tfrac{3}{2}} \} + \tfrac{1}{3}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{local} (P) - \varepsilon _{local} (O)\} + \tfrac{1}{2}\{ \varepsilon _{local} (P)^{\tfrac{1}{2}} - \varepsilon _{local} (O)^{\tfrac{1}{2}} \}$$ Bruch, σn die Einschnurungsspannung und dσ/dn den Koeffizienten der linearen Verformungshartnung. Diese Abhängigkeit wurde abgeleitet auf Grund einer neuen Kenngröße des Dehnbruchverhaltens, nähmlich der Konstanz der hydrostatischen Spannungen, welche angibt, daß der Verlauf der Dehnbarkeit mit dem hydrostatischen Druck einem Gesetz der Potenz drei halbe folgt. Der Anstieg der Verformbarkeit unter Drücken bis zu 10000 kg/cm2 welcher für zahlreiche Metalle and Legierungen mit sehr unterschiedlichen Eigenschaften beobachtet wurde bestätigt die Aussagekraft des vorgeschlagenen Kennwertes. Es wird ferner gezeigt, daß die Verformbarkeit verschiedenen Legierungen mit geringer Fehlbaustellenenergie-wie z.B. die Legierungen Cu-Zn and Cu-Ge-sich zuerst mit steigendem Druck erhöht, daß dann ober schon ob relative niedrigen Drucken d.h.: bei 3500–4000 kg/cm2 ein weiterer Ausbieg der Verformbarkeit nicht mehr auftritt und dieselbe annahernd konstant bleibt and dies unabhängig von dem aufgegebenen Druck. Um dieses Verhalten der Legierungen mit geringer Fehlbaustellenenergie zu erklären wird vermutet, daß der Verformungsbruch dieser Metalle durch einen Vorgang hervorgerufen wird bei dem die Komponenten der hydrostatischen Spannung nicht beteiligt sind sondern nur die Scherspannungen wirken.
    Notes: Abstract A law governing the change in the ductility of metals and alloys under pressure is given: $$\begin{gathered} \left( {\frac{P}{{\sigma _n }}} \right) = \tfrac{1}{2}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{local} (P)^{\tfrac{3}{2}} - \varepsilon _{local} (O)^{\tfrac{3}{2}} \} + \tfrac{1}{3}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{local} (P) - \varepsilon _{local} (O)\} + \hfill \\ {\text{ }} + \tfrac{1}{2}\{ \varepsilon _{local} (P)^{\tfrac{1}{2}} - \varepsilon _{local} (O)^{\tfrac{1}{2}} \} \hfill \\ \end{gathered}$$ where P is the hydrostatic pressure, ɛlocal is the strain accumulated from the start of necking to fracture, σ n necking stress and (dσ/dɛ) the coefficient of linear work hardening. This relation is derived from a newly proposed criterion of ductile fracture, viz. “constancy of hydrostatic tensile stress”, which indicates that the change of ductility with pressure obeys a three halves power law. The observed increase in ductility of widely differing metals and alloys under pressure up to 10,000 kg/cm4 has confirmed that the proposed criterion is acceptable. It is further shown that the ductilities of some copper alloys with low stacking fault energy, such as Cu-Zn and Cu-Ge alloys, increases with pressure at the beginning but the increase stops at fairly low pressure, i.e. 3,500 ∼ 4,000 kg/cm2, and their ductilities become almost insensitive to the pressure applied. It is suggested that ductile fracture of metals with low stacking fault energy is dominated by a process which occurs not by the hydrostatic stress component but by shear stress only.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copolymerization of vinylhydroquinone (VHQ) and vinyl monomers, e.g., methyl methacrylate (MMA), 4-vinyl-pyridine (4VP), acrylamide (AA), and vinyl acetate (VAc), by tri-n-butylborane (TBB) was investigated in cyclohexanone at 30°C under nitrogen. VHQ is assumed to copolymerize with MMA, 4VP, and AA by vinyl polymerization. The following monomer reactivity ratios were obtained (VHQ = M2): for MMA/VHQ/TBB, r1 = 0.62, r2 = 0.17; for 4VP/VHQ/TBB, r1 = 0.57, r2 = 0.05; for AA/VHQ/TBB, r1 = 0.35, r2 = 0.08. The Q and e values of VHQ were estimated on the basis of these reactivity ratios as Q = 1.4 and e = -;1.1, which are similar to those of styrene. This suggests that VHQ behaves like styrene rather than as an inhibitor in the TBB-initiated copolymerization. No homopolymerization was observed either under nitrogen or in the presence of oxygen. The reaction mechanism is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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