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on several polystyrene systems, both melts and solutions, are here successfully compared with the predictions of a recent model [Ianniruberto, Macromolecules 2015, 48, 6306] that accounts for flow-induced friction-coefficient reduction. The model is here effectively simplified without loss of accuracy. Comparison with the solution data of Huang et al. [ACS Macro Lett. 2013, 2, 741], only differing for the size of the oligomeric solvent (from nearly one Kuhn length up to a few ones), reveals that friction reduction must include oligomer-size-dependent orientational coupling between the oligomeric solvent and the polymer molecules, such interactions vanishing for the smallest oligomer. The rheological "measure" of this nematiclike interaction as a function of the oligomer size (for small oligomers) is the novel result of the present paper, together with a further confirmation of the importance of friction coefficient reduction in strongly aligning flows. The model is also used to describe the stress relaxation data following fast uniaxial extension recently reported by Huang and Rasmussen [J. Rheol. 2016, 60, 465], confirming that the short-time relaxation process occurs at a faster rate because of the friction coefficient reduction induced by the previous flow. Those data also reveal the key role of convective constraint release induced by chain retraction, similarly to what happens in relaxation experiments following a large step strain.

OBJECTIVEAlthough endoscopic procedures for lumbar disc herniation have improved greatly and offer many advantages, the indications are limited mostly to nonmigrated or low-grade migrated disc herniation. Endoscopic application in migrated disc herniation cases is still challenging and technically demanding. The goal in this study was to determine the feasibility of biportal endoscopic discectomy for removal of high-grade migrated disc herniation.METHODSA retrospective review was performed in 262 patients who had undergone biportal endoscopic discectomy after the diagnosis of lumbar herniated disc. According to preoperative MRI findings, disc herniation was classified into 5 zones based on the direction and distance from the disc space. Patients were divided into 2 groups—a high-grade migration group and a low-grade migration group. Clinical outcomes were evaluated using the Oswestry Disability Index (ODI), visual analog scale (VAS), and modified Macnab criteria, and those outcomes and operation time were compared between the 2 groups.RESULTSThere were 10 patients with “high-grade up,” 8 with “low-grade up,” 98 with disc-level, 102 with “low-grade down,” and 44 with “high-grade down” herniation, thereby yielding 54 patients in the high-grade group and 208 in the low-grade group. Demographic data for the 2 groups showed no significant difference. There was no significant difference between the 2 groups in ODI, VAS, and modified Macnab criteria. Operation time between the 2 groups was not significantly different (60.74 vs 65.63 minutes, p > 0.05).CONCLUSIONSBiportal endoscopic discectomy can be effective for high-grade migrated lumbar disc herniation with no prolonged operation time and satisfactory clinical outcomes.

ratory. About 85% of these obsidians originated from the Paektusan volcano (Korea); obsidian of Japanese origin was found only at Shinbuk. INAA analyses on 6 obsidian samples from the Hahwageri and Junghnugri sites are in good agreement with our PIXE results and those of the previous report by Popov et al. (2005).