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- Laihonen, Sari J., et al.
(författare)
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Crystal structure and morphology of melt-crystallized poly(propylene-stat-ethylene) fractions.
- 1997
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 38:2, s. 371-377
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Tidskriftsartikel (refereegranskat)abstract
- Crystallinity, crystal structure and lamellar thickness in melt-crystallized samples of poly(propylene-stat-ethylene) fractions with 2.7–11.0 mol% ethylene comonomer and of approximately constant tacticity were assessed by wide- and small-angle X-ray scattering, differential scanning calorimetry and infra-red spectroscopy. Most of the samples were crystallized under isothermal conditions at 373 K. In comparison with an isotactic homopolymer of polypropylene, the copolymers showed lower crystallinity, melting enthalpy and average length of 3/1 helices, a slightly larger unit cell, a longer long period and an invariant lamellar thickness. The X-ray crystallinity of the copolymers remained approximately constant with increasing ethylene content, whereas the γ-crystallinity increased and the heat of fusion decreased moderately. It is suggested that the ethylene units are partially included in the crystals, and that this causes the invariance in crystallinity and crystal thickness. The observed gradual decrease in average 3/1 helix length with increasing ethylene content as assessed by infra-red spectroscopy is in accordance with this suggestion.
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- Laihonen, Sari J., et al.
(författare)
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Crystallization kinetics and morphology of poly(propylene-stat-ethylene) fractions.
- 1997
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 38:2, s. 361-369
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Tidskriftsartikel (refereegranskat)abstract
- The crystallization and melting behaviour and the morphology of fractions of poly(propylene-stat-ethylene) with 2.7–11.0 mol% ethylene were studied by differential scanning calorimetry, wide-angle X-ray scattering, polarized light microscopy and transmission electron microscopy, after etching with permanganic acid. The inclusion of ethylene co-repeating units in isotactic polypropylene (0–11.0 mol% ethylene) caused approximately linear decreases in kinetic and equilibrium melting temperatures and in the glass transition temperature with increasing ethylene content. X-ray scattering showed that the content of the γ form increased with increasing ethylene content, increasing crystallization temperature and decreasing cooling rate from the molten state. It was shown for one of the copolymers (8.7 mol% ethylene) that during heating approximately 50% of the γ form was converted to the α form before the final melting of the sample. The rest of the γ crystals melted without transformation to the α form. The multimodality of the crystal melting above the crystallization temperature in the polymers with a more uniform crystal structure was caused by recrystallization during heating, whereas polymers with appreciable contents of both α and γ forms exhibited multimodal melting at all the heating rates adopted. The size of the low temperature melting peak as assessed at a heating rate of 40 K min−1 was approximately proportional to the initial content of the γ form. By comparison with the spherulitic structure of homopolymers, that of the copolymers was coarser with internal and peripheral pockets of molten material during spherulite growth. The crystal lamellae exhibited more curvature in the copolymer samples than in the homopolymer.
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- Lomniczi B., Wehmann E., Herczeg J., Ballagi-Pordany, A., Kaleta, E.F., Werner, O., Meulemans, G., Jorgensen, P.H., Mante, A.P., Gielkens, A.L., Capua, I., and Damoser, J.
(författare)
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Newcastle disease outbreaks in recent years in western Europe were caused by an old (VI) and a novel genotype (VII)
- 1998
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Ingår i: Arch Virol. ; 143:1, s. 49-64
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Tidskriftsartikel (refereegranskat)
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- Bentz, M, et al.
(författare)
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Chromosome imbalances in papillary renal cell carcinoma and first cytogenetic data of familial cases analyzed by comparative genomic hybridization
- 1996
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Ingår i: Cytogenetics and cell genetics. - : S. Karger AG. - 0301-0171. ; 75:1, s. 17-21
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Tidskriftsartikel (refereegranskat)abstract
- We used comparative genomic hybridization to analyze 17 tumor samples from 11 patients with papillary renal cell carcinoma (RCC), including three patients with hereditary papillary RCC. Whereas the most frequent aberrations confirmed data obtained by banding analyses, copy number increases on 5q, which previously were considered characteristic of nonpapillary RCC, were identified in two cases. In two complex cases belonging to the same family, a characteristic pattern of chromosomal aberrations was found: five of the six imbalances present in the less complex case were included in the karyotype of the other case, suggesting a genetically determined mechanism resulting in genomic instability of specific chromosomes or chromosomal subregions and/or selection of specific mutations.
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