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821.
822.
The tensile deformation behaviour of poly(1-butene) and two of its ethylene copoloymers was studied at room temperature. This was done by investigating true stress-strain curves at constant strain rates, elastic recovery and stress relaxation properties and in-situ WAXS patterns during the deformation process. As for a series of semicrystalline polymers in previous studies, a strain-controlled deformation behaviour was found. The differential compliance, the recovery properties and the stress relaxation curves changed simultaneously at well-defined points. The strains at which these points occurred along the true stress-strain remained constant for the different samples despite their different percentage crystallinities. The well-defined way in which the different samples respond to external stresses complies with the granular substructure of the crystalline lamellae in a semicrystalline polymer. 相似文献
823.
824.
This paper discusses the effect of heterogeneities in crosslink density on static properties, such as the mechanical stress-strain relation (free energy) and scattering effects as occur in small-angle neutron experiments. The second part of the paper is devoted to the segmental dynamics and the long-time relaxation of polymer networks. It is shown that the heterogeneities slow down the relaxation at long times. 相似文献
825.
Maike Lettow Kim Greis Eike Mucha Tyler R. Lambeth Murat Yaman Vasilis Kontodimas Christian Manz Waldemar Hoffmann Gerard Meijer Ryan R. Julian Gert von Helden Mateusz Marianski Kevin Pagel 《Angewandte Chemie (International ed. in English)》2023,62(24):e202302883
Fucose is a signaling carbohydrate that is attached at the end of glycan processing. It is involved in a range of processes, such as the selectin-dependent leukocyte adhesion or pathogen-receptor interactions. Mass-spectrometric techniques, which are commonly used to determine the structure of glycans, frequently show fucose-containing chimeric fragments that obfuscate the analysis. The rearrangement leading to these fragments—often referred to as fucose migration—has been known for more than 25 years, but the chemical identity of the rearrangement product remains unclear. In this work, we combine ion-mobility spectrometry, radical-directed dissociation mass spectrometry, cryogenic IR spectroscopy of ions, and density-functional theory calculations to deduce the product of the rearrangement in the model trisaccharides Lewis x and blood group H2. The structural search yields the fucose moiety attached to the galactose with an α(1→6) glycosidic bond as the most likely product. 相似文献