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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 18 (1994), S. 183-192 
    ISSN: 1432-0789
    Schlagwort(e): Nematodes ; Structure ; Cultivated areas Luvisols ; Non-calcic brown soils ; Multivariate analyses ; Spain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We studied the nematofauna in cultivated Euvisols in the Spanish Central Region in terms of multivariate statistical relationships between nematode groups and environmental variables (habitat, hosts, soil lexture, and quantitative edaphic variables). Three large nematode associations were recognized, one group being characteristic of the region's rotational crops (Pratylenchus, Ditylenchus, Helicotylenchus, Tylenchorhynchus, Rotylenchus, other Dorylaimidae,Plectus, andTylenchus), a second group related to cereal monoculture and wild gramineae associated with bush formations (Heterodera, Criconemoides, Discolaimus, and other Rhabditidae), and a third group characteristic of uncultivated soils (Paratylenchus, Xiphinema, Hemicycliophora, Mononchus, Tripyla, andAlaimus).Paratylenchus andTylenchus species were shown to have an indicator value for certain edaphic properties, especially soil texture, and may be regulated by the clay content of the soil.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Polymer bulletin 18 (1987), S. 59-63 
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary The crystallization from the glassy state of poly(oxetane) or poly(trimethylene oxide), after quenching the molten polymer in liquid nitrogen, has been studied by differential scanning calorimetry and X-ray diffraction analysis. The results indicate that two crystalline modifications are obtained, depending on the crystallization temperature: the orthorhombic modification is produced when the temperature is higher than −30 °C, while the trigonal form is found below −45 °C, both forms coexisting at intermediate temperatures.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 23
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary Small-angle synchrotron experiments have been performed in two samples of poly[oxybis(trimethylene) p,p′-bibenzoate], PDTMB. Owing to the very slow transformation of the mesophase of this polymer into the crystal, only the liquid crystalline phase is present in a PDTMB sample quenched from the melt, while about 30% crystallinity is found in the annealed specimen. The results indicate that the layer spacing peak for the mesophase is very close to a crystal diffraction. This seems to be a general fact in thermotropic polybibenzoates. Moreover, no long spacing has been detected in the quenched sample. On the contrary, the annealed specimen exhibits a long spacing centered at about 16 nm, corresponding to a rather small crystal thickness.
    Materialart: Digitale Medien
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  • 24
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary The ageing process of the liquid crystalline glass of poly(diethylene glycolp,p′-bibenzoate), PDEB, has been studied by differential scanning calorimetry and microhardness measurements. The experiments have been performed on a sample of PDEB aged at 36±C during different times. The process was found to be rather fast at that temperature, and the results from both techniques are compared.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Polymer bulletin 31 (1993), S. 89-95 
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary Three copolymers of ethylene and 1-decene, covering a wide range of compositions, have been synthesized with a MgCl2-supported Ziegler-Natta catalyst. The analysis by DSC and X-ray shows a great degree of heterogeneity in these copolymers and appreciable levels of crystallinity, corresponding to the orthorhombic lattice of polyethylene, are present even for very high 1-decene contents.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 262 (1984), S. 913-918 
    ISSN: 1435-1536
    Schlagwort(e): Poly(3,3-dimethyl oxetane) ; isothermal crystallization ; crystallization kinetics ; crystallization temperature coefficient
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Poly(3,3-dimethyl oxetane) fractions ranging in number average molecular weights from 18500 to 130000 have been isothermally crystallized from the relaxed melt state in the temperature range from 12 to 44 °C, where only the monoclinic modification is formed. The influence of molecular weight and undercooling in crystallization kinetics has been analyzed. The level of crystallinity is very slightly dependent on molecular weight but the influence of this parameter on the time scale of the crystallization is relatively pronounced. The crystallization temperature coefficient was determined and it was found a constant value of the product of the interfacial energies in the range of molecular weights which has been analyzed. Growth rate measurements were carried out for fraction ¯M n=130000 and it was found that the temperature coefficients for overall and growth rates are equal. Finally, the comparison of the experimental results for this polymer with those reported for poly(oxetane) shows two main differences: first, the crystallization rate is slower for poly(3,3-dimethyl oxetane) and second, the temperature coefficient is smaller for this polymer.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 262 (1984), S. 605-610 
    ISSN: 1435-1536
    Schlagwort(e): Poly(oxetane) ; poly(oxacyclobutane) ; isothermal crystallization ; bulk crystallization ; crystallization temperature coefficient
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Poly(oxetane) fractions ranging in number-average molecular weights from 7800 to 157000 have been isothermally crystallized in the temperature range from −50 to 19
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Polymer bulletin 20 (1988), S. 291-296 
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary The effect of the substituents on the glass transition temperature is analyzed for a series of polyoxetanes, with alkyl substituents in position 3. The results show a regular increase of that parameter with the Van der Waals volume of the linear substituents, although a departure from this trend seems to be observed for poly(3,3-dibutyloxetane), presumably because of the effect of internal plasticization. On the other hand, the increase of Tg for poly(3-terbutyloxetane) is specially high, as usual for branched substituents. The behaviour of the glass transition temperature along the series has been analyzed in terms of interand intramolecular interactions, concluding that the latter factor is the dominant contribution in determining the Tg in this group of polymers.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Polymer bulletin 25 (1991), S. 413-418 
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary Three polybibenzoates with two, three and four oxyethylene units in the spacer have been synthesized in order to analyze the influence of the length of the spacer on the stability of the mesophase and on the solubility behaviour. It was found that the thermal stability of the mesophase decreases as the length of the spacer increases, in such a manner that an amorphous polymer is obtained when four oxyethylene units are involved. On the other hand, although the value of the solubility parameter is little affected by the spacer, the solubility range is significantly widened by an increase in the number of oxyethylene units. Optimal characteristics are displayed by the polyester with three such units in the spacer.
    Materialart: Digitale Medien
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  • 30
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary The influence of thermal history on the mechanical properties of thermotropic poly(triethylene glycol p,p'-bibenzoate) has been studied. The mechanical parameters of three samples of this polyester with different thermal histories have been determined at two deformation rates (1 and 10 cm/min) and two drawing temperatures (23 and 50°C), showing the influence of the thermal and mechanical histories on the stress-strain plots. The phase state and the degree of crystallinity of the samples also affect the mechanical parameters (Young modulus, yield stress and deformation at break).
    Materialart: Digitale Medien
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