Molecular weight determinations by light scattering and osmometry and intrinsic viscosity measurements were made in various solvents on fractions of styrene–methyl acrylate copolymers with different compositions and on acrylate homopolymers prepared by free‐radical reaction. Relations between intrinsic viscosity [η] and molecular weight M thus established are compared with those reported by other authors. 2‐Methylcyclohexanol was found to be a theta solvent for the copolymers and both parent homopolymers, and isoamyl acetate was a theta solvent for poly(methyl acrylate). From theta point viscosity data obtained with these solvents, unperturbed chain dimensions were estimated. The results are compared with the unperturbed dimensions estimated from the [η]–M relations obtained in good solvents. On the basis of the experimental data it was found that the unperturbed dimension depends linearly on the copolymer composition, in contrast to the case of styrene–methyl methacrylate copolymers. Composition dependences of the theta temperature and of the parameter describing the long‐range interactions between nonadjacent segments in polymer chains were investigated. The result implies that long‐range interactions between monomeric units never disappear even when those between the same monomeric units vanish. The Huggins constant for copolymer is discussed in terms of the excluded volume variable.
Background: Endoscopic devices often cause device-related surgical morbidities such as postoperative bleeding. Delayed bleeding due to a protruding edge of an endostapler has not been previously described in the literature. Case presentation: An 80-yr-old man with a second primary lung cancer underwent a wedge resection of the right lower lobe. He developed sudden hypotension and massive bleeding from the chest tube 4 h after the surgery and underwent an emergency reoperation. A torn parietal pleura was found to have caused a persistent bleeding. There was a sharp protruding edge created by multiple firings of the endostapler. The subsequent lung expansion would have promoted a direct contact between the edge and parietal pleura resulting in delayed bleeding. Conclusions: A protruding edge due to multiple firings of an endostapler could injure the parietal pleura and cause delayed bleeding after a lung resection. This type of injury would be more common in wedge resection cases because of the larger residual lung volume preserved, which is expected to have a better lung expansion and facilitate the direct contact of the staple line and parietal pleura.
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