The dynamics of ring polymer melts are studied via molecular dynamics simulations of the Kremer-Grest bead-spring model. Rouse mode analysis is performed in comparison with linear polymers by changing the chain length. Rouselike behavior is observed in ring polymers by quantifying the chain length dependence of the Rouse relaxation time, whereas a crossover from Rouse to reptation behavior is observed in linear polymers. Furthermore, the non-Gaussian parameter of the bead displacement is analyzed. It is found that the non-Gaussianity of ring polymers is remarkably suppressed, which is in contrast to the growth in linear polymers, particularly with increasing chain length.
Insufficient nutrient supply through vertebral canal structures to the intervertebral disc (IVD) has been considered as an important contributor for disc degeneration. Despite previous canal structure characterization studies using histology, scanning electron microscopy, and angiography, among others, their three-dimensional (3D) topology inside the vertebral endplate remains poorly understood. This study aims to characterize the 3D canal structure in the rabbit lumbar vertebral endplate using micro computed tomography (mCT). Vertebral endplates were imaged using high-resolution mCT with 1.4 Â 1.4 Â 1.8 mm voxel size. Diameter, length, orientation, and depth starting from the vertebral endplate surface were analyzed for each canal using individual 3D canal models from the vertebral endplate scans. In the layer underneath the vertebral endplate, at a mean depth of 76.2 mm, longitudinallyoriented relatively short-length (57.6 mm) and small diameter (45.7 mm) canals were dominant. Large-scale canals with a mean diameter of 152.1 mm running parallel to the endplate surface were isolated at the depth of 224.1 mm. These canals were connected to both IVD and bone marrow spaces through vertically oriented canals. ß
At Tokyo Electric Power Company (TEPCO) Fukushima Daiichi nuclear power plant (NPP), water contaminated with radionuclides such as Cs-137 and Sr-90 has been stored in tanks and seawaterintake area. We have prepared cobalt-ferrocyanide-impregnated fibers via four steps: the grafting of an epoxy-group-containing monomer, the conversion of the epoxy group into positively charged groups, the binding of ferrocyanide ions ([Fe(CN) 6 ] 4− ), and the precipitation of cobalt ferrocyanide (Co 2 [Fe(CN) 6 ]) by contact with cobalt ions. However, the impregnation structure of cobalt ferrocyanide microparticles onto the fiber remains unclear. Here, we describe the impregnation structure from the results of rebinding [Fe(CN) 6 ] 4− to the cobalt-ferrocyanide-impregnated fiber. The amount of [Fe(CN) 6 ] 4− re-bound onto the fiber was found to decrease with increasing amount of Co 2 [Fe(CN) 6 ] initially impregnated. This suggests that the microparticles of cobalt ferrocyanide become entangled with the grafted polymer chains via multipoint electrostatic interactions.
Amorphous materials exhibit peculiar mechanical and vibrational properties, including non-affine elastic responses and excess vibrational states, i.e., the so-called boson peak (BP). For polymer glasses, these properties are considered to be affected by the bending rigidity of the constituent polymer chains. In our recent work [Tomoshige, et al 2019, Sci. Rep.
9 19514], we have revealed simple relationships between the variations of vibrational properties and the global elastic properties: the response of the BP scales only with that of the global shear modulus. This observation suggests that the spatial heterogeneity of the local shear modulus distribution is insensitive to changes in the bending rigidity. Here, we demonstrate the insensitivity of elastic heterogeneity by directly measuring the local shear modulus distribution. We also study transverse sound wave propagation, which is also shown to scale only with the global shear modulus. Through these analyses, we conclude that the bending rigidity does not alter the spatial heterogeneity of the local shear modulus distribution, which yields vibrational and acoustic properties that are controlled solely by the global shear modulus of a polymer glass.
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