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  • 1
    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: Compounds of propylene-homopolymers with SBS-, EPM- and EPDM-rubber are principally qualified to improve impact resistance esp. at low temperatures.The relationship between the improvement of impact properties and deterioration of tensile-, flexural- and torsional strength in this case is worse than for propylene-block-copolymers. The advantage of compounds is given by the simple possibility to improve the impact resistance as wanted. It has been shown by light- and electron-optical investigations that by compoundation a new phase is formed with particle sizes of 5 μm diameter.
    Notes: Die Compoundierung von Propylen-Homopolymerisat mit SBS-, EPM- und EPDM- Kautschuk ist grundsätzlich geeignet, ein verbessertes Kälteschlagverhalten zu erreichen.Die Relation zwischen Verbesserung der Schlagzähigkeitswerte und der Verschlechterung des Spannungsverformungsverhaltens ist dabei ungünstiger als bei einem Propylen-Block-Copolymerisat. Der Vorteil der Compounds liegt in der einfachen Möglichkeit, das Schlagverhalten von Polypropylen praktisch beliebig zu gestalten.Licht- und elektronenoptische Untersuchungen zeigen, daß durch Compoundierung mit Kautschuk eine neue Phase entsteht mit Teilchendurchmessern bis zu 5 μm.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 13C n.m.r. studies of a series of twelve 1,2-dithiole-3-ylidene ketones and aldehydes have shown that the geometry of the carbon backbone is the same as found in 1,6,6aλ4-trithiapentalenes. No evidence has been found which favours a bicyclic structure for the system. A linear correlation of observed 13C chemical shifts with calculated charge densities is found to be valid. The observations are in agreement with a structure which is a hybrid between a true ketonic structure and a true mesoionic structure.By using the difference in the 13C chemical shifts of ortho and meta carbon atoms in substituent phenyl groups it is possible to qualify the degree of coplanarity of the phenyl groups with the backbone of the molecule.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 6 (1977), S. 117-122 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: It is shown that application of the Compton scattering method for matrix correction in the X-ray fluorescence spectrometric determination of the trace elements Rb and Sr in rock samples can provide concentrations at a relative accuracy level of 1%. The empirical method applies to rock samples showing differences in mass absorption up to a factor of two. The accuracy of the method has been tested by analysis of 57 samples analysed for Rb and Sr by mass spectrometric isotope dilution. In addition a few of the U.S. Geological Survey (U.S.G.S.) reference rock powders, showing significantly different mass absorption, were analysed for Rb and Sr. It is demonstrated that the mica effect, if significant, is smaller than 1% relative. There is no advantage in the use of the LiF(220) analysing crystal as a substitute for the LiF(200). The method appears to be insensitive to the pellet thickness.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1977), S. 297-301 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of hexafluorobenzene, hexafluorobicyclo[2.2.0]hexa-2,5-diene (perfluoro-Dewar benzene) and 1,1,1,6,6,6-hexafluorohexa-2,4-diyne, and the fragmentation mechanisms of their parent ions are reported. The behaviour of the two cyclic isomers under electron impact is very similar; the linear one behaves quite differently. The ionization potentials of the molecules and the appearance potentials of the fragment ions (both normal and metastable) have been measured. The heats of formation of [C6F5]+ and [C5F3]+ are calculated. A value for the heat of formation of 1,1,1,6,6,6-hexafluorohexa-2,4-diyne is proposed.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1977), S. 330-333 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is reported that ions gererated in the gas phase by dissociative electron attachment to nitrous oxide react with propyne-d3 (trideuteromethyl acetylene) to yield the ions ĊD=C=CH, ĊD2—C≡C-, -CD2C≡CH and CD3C≡C-. From their differing reactivity with methyl formate it is suggested that these four ions are distinct stable species.
    Additional Material: 1 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 4 (1977), S. 310-316 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra and gas chromatographic properties of 17 synthetic fluoro-, chloro- and Bromomethoxybiphenyls and 12 dichlorodimethoxybiphenyls have been examined. From this representative series it appears that the position of the methoxy group (ortho, meta and para to the biphenyl bond) in all monomethoxy compounds examined, and the positions of the two methoxy groups in most of the dimethoxy compounds, can be assigned unambiguously by their difference in fragmentation pattern. The value of this method was shown by metabolism experiments in which 4,4′-difluoro- and 4,4′-dibromobiphenyl were fed to rats and 4,4′-dichlorobiphenyl was administered to plants. All hydroxylated metabolites found were identified by gas chromatography mass spectrometry. Relationships between structure and gas chromatographic retention time of these compounds are discussed.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1735-1745 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared spectroscopy was used for the determination of the base-pairing content of four specific tRNAs in deuterium oxide solution. Infrared spectra were obtained in the 1750-1550 cm-1 region at various temperatures ranging from about 15 to 90°C. Melting curves were constructed by plotting the molar extinction coefficient at ν = 1657 cm-1 versus temperature. These transition curves enabled us to determine the ranges of temperature which correspond to the ordered (partially double-stranded) or randomly coiled structure of the tRNA. For a set of wavenumbers the extinction coefficients at these temperatures were used for the calculation of the base-pairing content. The procedure employed here is based on a method described earlier by Thomas [(1969) Biopolymers 7, 325-334]. For the conditions selected for this investigation (Mg2+-free D2O-buffer; 0.01M tris-DCl, 0.015M NaCl, pD 7.5) the results of this determination agree within the limits of errors with the number of base pairs predicted by the cloverleaf model.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 9 (1977), S. 283-293 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal reaction of 1,3-butadiene (BD) has been studied between 464 and 557°K at pressures between 49 and 450 torr. The products are 4-vinylcyclohexene (VCH) and cis, cis-cycloocta-1,5-diene (COD), and their formations are second order. The rate constant (in 1/mol · sec) for VCH is given by \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}_{10} k_{\rm V} = - (24,530 \pm 120)/4.576T + (6.95 \pm 0.05) $$\end{document} and that for COD by \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}_{10} k_{\rm C} = - (28,440 \pm 100)/4.576T + (7.65 \pm 0.04) $$\end{document}The thermal reaction of COD has also been studied. The temperature was varied from 505 to 586°K and the pressure from 15 to 51 torr. The rate constants (in sec-1) for the formations of VCH and BD are given by \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm log}_{10} k_{{\rm VCH}} = - (51,780 \pm 120)/4.576T + (15.34 \pm 0.05) \\ {\rm log}_{10} k_{{\rm BD}} = - (56,380 \pm 100)/4.576T + (16.46 \pm 0.04) \\ \end{array} $$\end{document}A biradical mechanism seems to fit these results. The heat of formation and the entropy of COD are estimated.
    Additional Material: 4 Ill.
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