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  • 1
    ISSN: 1618-2650
    Keywords: Best. von Polycyclen in Luft ; Fluorescenzspektrometrie ; selektive Anregung, Sauerstofflöschung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Anhand der substanzspezifischen absoluten Fluorescenzspektren lassen sich die chromatographisch nur schwer zu trennenden und in der Umwelt fast immer zusammen vorkommenden polycyclischen Aromaten, wie Benz(a)anthracen-Chrysen-Triphenylen, Benz(a)pyren-Benz(e)pyren-Benz(k)fluoranthen-Benz(b) fluoranthen-Perylen sowie Benz(ghi)perylen-Anthanthren mittels selektiver Anregung und/oder Sauerstofflöschung nebeneinander quantitativ bestimmen.
    Notes: Abstract By means of the selective excitation and/or oxygen quenching method a quantitative fluorescence spectroscopic determination for those mixtures of polycyclic aromatic hydrocarbons is described which are difficult to separate by conventional chromatographic methods, e.g. benz(a)anthracene-chrysene-triphenylene, benz(a)pyrene-benz(e)pyrene-benz(k fluoranthene-benz(b)fluoranthene-perylene and benz(ghi)perylene-anthanthrene.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 1 (1965), S. 75-80 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 1 (1965), S. 318-320 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1615-6102
    Keywords: Compartmentation ; Poncirus trifoliata ; Terpene biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In der Frucht vonPoncirus trifoliata liegen in der Außenschale Drüsenzellkomplexe, die ein monoterpenreiches ätherisches Öl mit geringem Anteil an Sesquiterpenen und O-haltigen Substanzen produzieren. Ähnlich aussehende Exkretzellkomplexe aus den Saftschläuchen enthalten hauptsächlich Sesquiterpenkohlenwasserstoffe (STKW) und O-haltige Komponenten und sehr wenig Monoterpenkohlenwasserstoffe (MTKW). Im Schalenöl konnten nach gaschromatographischer Trennung mit Hilfe der Massenspektrometrie 19 Komponenten identifiziert werden, im Saftschlauchöl 25. Elektronenmikroskopische Aufnahmen der jüngsten Drüsenzellen beider Drüsenkomplexe lassen erkennen, daß beide Terpenklassen wahrscheinlich hauptsächlich bzw. ausschließlich plastidär entstehen. Exogen angebotenes14CO2 wird zunächst überwiegend in die MTKW eingebaut, erst später nimmt die Markierung der STKW und O-haltigen Komponenten stark zu. Über den Ferntransportweg angebotenes14C-Leucin führt anfangs zu einer starken Markierung der STKW und O-haltigen Komponenten, erst später verschiebt sich der Einbau etwas mehr in Richtung MTKW. Als Hauptursache für den differenten Einbau wird das Vorhandensein zweier Typen von Drüsenzellkomplexen mit unterschiedlichen Syntheseleistungen angesehen. Die aus dem14CO2 in der Außenrinde gebildeten Assimilate werden zuerst in das MTKW-reiche Öl der Schalenexkretbehälter eingebaut. Die überwiegend STKW erzeugenden Saftschlauchbehälter werden erst später beliefert. Beim Leucinangebot über die Fruchtstiele scheint es gerade umgekehrt zu verlaufen. Die aufeinanderfolgenden Maxima der Ölproduktion in den beiden Drüsenzellkomplex-Typen und die Änderung des Komponentenspektrums ihres ätherischen Öls im Verlauf der Vegetationsperiode tragen ebenfalls zu einem je nach Jahreszeit unterschiedlichen Einbau in die MTKW und STKW bei.
    Notes: Summary The fruit ofPoncirus trifoliata shows glandular cell complexes in the exocarp, which produce a volatile oil rich in monoterpenes but poor in sesquiterpenes and oxigenated compounds. The juice vesicles of the endocarp possess similar cell complexes mainly containing sesquiterpenes and oxigenated compounds, whereas monoterpenes only occur in small amounts. By the use of combined gas chromatography-mass spectrometry 19 components of the rind oil and 15 compounds of the endocarp oil could be identified. As demonstrated by electron microscopy the terpenes most probably are synthesized predominantly, if not exclusively in plastids. As shown by gasradiochromatography radioactive precursors (14CO2 and14C-leucine) are incorporated into mono- and sesqui-terpenes to a different extent. This is due to two gland types producing essential oils of different composition with regard to their mono- and sesqui-terpene percentage. In fruit development the exocarp glands differentiate earlier than the endocarp glands do. The activity of exogenously applied14CO2 first reaches the peripheral glands and later on appears in the interior glands. Depending upon the growth season, labelled leucine transported by the conducting tissues from lower plant parts leads to a high specific activity of the sesqui-terpenes and oxigenated compounds. It could be argued that in this instance the glands of the pulp are better provided with precursors than the exocarp glands. The successive maxima of essential oil production in both glandular complexes, and the changes in the concentration of individual oil constituents during the ontogeny of the fruit also contribute to different incorporation ratios of radioactive precursors into mono- and sesqui-terpenes.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 331 (1964), S. 256-274 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The thermodynamics of Pyrex glass and of the crystalline Se modifications have been calorimetrically determined by the drop-method between 90 and 540°K (data see, Inhaltsübersicht”). The transformations of the Se modifications are discussed.
    Notes: Mit Hilfe der,drop “Methode wurden die Wärmeinhalte sowohl von Pyrexglas als auch von hexagonalem und monoklinem Selen im Temperaturbereich von  -  180° bis + 270°C bestimmt. Aus den Versuchsergebnissen wurden die spezifischen Wärmen und Entropien errechnet und die entsprechenden allgemeinen Gleichungen abgeleitet.Beide Kristallinen Selen-Modifikationen durchlaufen beim Erhitzen z. T. mehrere, bisher unbekannte, reversible endotherme Umwandlungen 2. Art: hexagonales Selen bei + 106 ⊥ 1°C und monoklines Selen (α  -  Se + β  - Se) bei  - 120 ± 2°C, + 15 ± 1°C und + 30° ± 1°C; die Umwandlungswärmen betragen jeweils 0 ± 20 cal/g-At.Beim Erhitzen geht die monokline Modifikation bei etwa + 110°C irreversibel exotherm in das hexagonale Selen über, das bei 221 ± 1°C schmilzt; die Schmelzwärme beträgt 1,6 ± 0,4 kcal/g-At.Unter Zugrundelegung von thermodynamischen und röntgenographischen Meßergebnissen werden die Umwandlungen der kristallinen Selen-Arten diskutiert.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We study the production of an isolated large- $p_T$ photon as well as the production of an isolated prompt photon plus a jet in $e^+e^-$ collisions. Our results are obtained by a NLO Monte Carlo program of partonic event generator type. We discuss the possibilities to constrain the parton densities in the real photon and compare to preliminary OPAL data.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 17 (1987), S. 247-253 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper presents an investigation of the dependence of harmonic-like topological constraints in entangled and moderately crosslinked polymer networks on segment and crosslink density and on the deformation of the sample. The approach is an extension of a theory developed for the highly crosslinked case and for polymer melts. The results are used to discuss the influence of topological constraints on the mechanical properties of different types of rubberelastic networks.
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  • 9
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper presents a theoretical investigation of SANS from labeled chains in polymer networks which are characterized by the topology of tube-like deformation dependent configurational constraints. The deformation dependence of the constraints is assumed to relax and to be determined by a microscopic deformation law. The results lead to the conclusion that the change of the radius of gyration of a network chain may be much less than the deformation of the macroscopic sample. It is pointed out that network defects favour the effect of constraint release.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 18 (1987), S. 53-57 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper describes the onset of the influence of entanglement effects on the mobility of polymer chains in a polydisperse melt. Extending a scaling relation between the critical molecular mass of homodisperse melts and segment number density yields in the case of polydisperse melts a functional equation for the critical chain length. The case of the normal distribution will be solved and discussed.
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