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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Carbonate radical shows moderate reactivity (k2=1.8·106 M−1 s−1) with nickelglycine complex. As an oxidizing free radical, it may attack the ligand to form Ni(II) coordinated glycine radical or oxidize the metal center to form a Ni(III) glycine transient. Continuous γ-irradiation of the complex-bicarbonate mixture yields glyoxalic acid (G=1.7) as the major product. The reaction involves an attack of the ligand and precludes the oxidation of metal center.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 27 (1992), S. 6127-6130 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The objective of this investigation was to explain the variation in dielectric constants of mullite ceramics prepared with 25% excess silica under a variety of conditions as described in an earlier study. Different starting materials, mullite-silica (M-S) and alumina-silica (A-S), different particle sizes (fine or coarse) and different firing times and temperatures were used. Dielectric constants measured for the alumina-silica system at 1550°C at different times, showed an initial reduction followed by an increase on further heating. The dielectric constants of other systems increased with increase in heat-treatment time at the different heat-treatment temperatures. From the study of microstructures using transmission electron microscopy and energy dispersive X-ray spectroscopy, it was shown that the initial decrease in dielectric constant on heating the alumina-silica system was because alumina, a phase with a higher dielectric constant was being replaced by mullite, a phase with a lower dielectric constant. On completion of this reaction, the intergranular silica was absorbed by mullite thereby leading to an increase in the dielectric constant. It was then shown that whenever phases with a lower dielectric constant exist, the dielectric constant of the system as a whole is lower.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 27 (1992), S. 2423-2428 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Unidirectional composites consisting of a borosilicate glass (Corning 7740) matrix reinforced with Nicalon (silicon carbide) fibres were fabricated and tested in monotonic tension at temperatures ranging from room temperature to 650 °C. The ultimate tensile strength showed little dependence on temperature up to about 425 °C and failed by longitudinal splitting. There was a significant increase in strength at 540 °C and a slight decrease in strength when tested above this temperature, and the failure involved extensive fibre pull-out. The elastic modulus (stiffness) was found to decrease progressively with increasing temperature. The matrix consists of borosilicate glass within the plies and very fine grains of alpha (low) cristobalite in the inter-ply regions. The behaviour of the composite as a whole was found to be dependent upon the behaviour of the matrix at the temperature of testing.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 28 (1993), S. 5580-5591 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Uniaxial fatigue damage analyses were performed on borosilicate glass-ceramic matrix, Nicalon (silicon carbide) fibre reinforced unidirectional composites. The fibre volume fraction varied from about 0.25 to 0.60. Load-controlled tension-tension fatigue tests (R ratio = 0.1) were conducted at room temperature and 540°C (1000°F). The fatigue life was found to decrease with increasing cyclic stress level and a power-law relationship of the form σapp = σuts(2N f)b was established where σapp is the applied maximum stress, σuts the monotonic tensile strength, N f is the number of cycles to failure and b is the fatigue strength exponent. The fatigue damage evolution manifested itself as a decrease in stiffness of the composite with fatigue cycles. This stiffness drop was associated with matrix cracking followed by fibre-matrix debonding and fibre sliding breakage/pull-out, and final failure, respectively at 540°C. The damage evolution at room temperature was associated with degradation of the matrix followed by steady breakage of fibres with no debonding/pull-out, leading to eventual failure of the net section of the composite. In general, quantitative microscopic observations of debonded and pulled-out fibres showed a good correlation with the observed reduction in stiffness. A predictive model to interpret the drop in stiffness is presented and validated using experimental results from the current study.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 28 (1993), S. 5592-5602 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An analysis of the fatigue-damage evolution process through prediction of stiffness drop in brittle matrix unidirectional composites reinforced with continuous stiff fibres is presented. The drop in stiffness of the composite is calculated by partitioning the total damage between the components of the composite, namely the matrix, the fibre, and the interface. Predictions of drop in stiffness are validated for different fatigue test conditions in borosilicate glass-ceramic matrix-Nicalon fibre-reinforced composites. In addition, fatigue test results from other composite systems, such as LASII-Nicalon and aluminosilicate-Nicalon, are examined in the light of this model.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 12 (1993), S. 1536-1538 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 15 (1996), S. 1921-1923 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 11 (1992), S. 252-254 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1570-7458
    Keywords: Tylophora asthmatica ; Spodoptera litura ; Tylophorine ; Tylophorinine ; Pergularinine ; Insect antifeedants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alkaloid extractables of Tylophora asthmatica (Asclepiadaceae) have been tested for the antifeedant activity against Spodoptera litura by incorporating them in semisynthetic and cellulose diets. The alkaloid extractables at 0.01% concentration inhibited feeding of the larvae. Three compounds, tylophorine, tylophorinine and pergularinine, were isolated; and their EC50 values were found to be 2.9, 8.6 and 12.00 ppm, respectively.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1980), S. 651-658 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study has been made of the fragmentation upon electron impact of thieno(2,3-b)quinoline and sixteen of its derivatives containing methoxy, methylenedioxy, chloro, bromo, iodo, nitro and methyl substituents. Besides these, the fragmentation patterns of some S-oxides, and S,S-dioxides were also investigated. The majority of the spectra contain molecular ions and the principal fragmentation routes involve loss of carbon monosulphide and hydrogen cyanide from the molecular ion. Rearrangement of the molecular ion appears to precede the fragmentation process in the case of S,S-dioxides. The fragmentation of 4-methylthieno(2,3-b)quinoline is closely analogous to that of alkylquinolines. The main features of these spectra can be predicted from the fragmentation pathways proposed for the parent thieno(2,3-b)quinoline.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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