Search

UV ray is an unavoidable environmental factor in the operation of outdoor cable accessories, which is easy to cause the cable accessories flashover and breakdown faults. In this paper, the changes of insulation properties of silicone rubber (SiR) after UV radiation treatment were studied from the aspects of microstructure, dielectric properties, surface properties and discharge properties. Combined with the analysis of molecular chain damage and surface trap, the influence mechanism of UV radiation on the insulation properties of SiR was revealed. The experimental results show that the dielectric constant of SiR after UV radiation treatment first decreases and then increases, it decreases to 3.06 at 240 h and increases to 3.93 at 1000 h. UV radiation can reduce the surface resistance of SiR, it decreases by 48% after 1000 h radiation. With the extension of UV radiation time, the surface trap level corresponding to the peak of the trap density is about 0.95 eV, the trap density decreases to 2.32 × 1022 eV−1 m−3 at 240 h. Short-term UV radiation can promote the secondary cross-linking of SiR, resulting in the increase of flashover voltage from 6.32 to 7.64 kV. Long-term radiation can destroy the molecular chain structure, resulting in a slight decrease in the flashover voltage. With the extension of UV radiation time, the breakdown strength decreases by about 14% at 1000 h. This work has guiding significance for the radiation performance and life evaluation of cable accessories. [ABSTRACT FROM AUTHOR]

Exosomes are secreted to the extracellular milieu when multivesicular endosomes (MVEs) dock and fuse with the plasma membrane. However, MVEs are also known to fuse with lysosomes for degradation. How MVEs are directed to the plasma membrane for exosome secretion rather than to lysosomes is unclear. Here we report that a conversion of phosphatidylinositol-3-phosphate (PI(3)P) to phosphatidylinositol-4-phosphate (PI(4)P) catalyzed sequentially by Myotubularin 1 (MTM1) and phosphatidylinositol 4-kinase type IIα (PI4KIIα) on the surface of MVEs mediates the recruitment of the exocyst complex. The exocyst then targets the MVEs to the plasma membrane for exosome secretion. We further demonstrate that disrupting PI(4)P generation or exocyst function blocked exosomal secretion of Programmed death-ligand 1 (PD-L1), a key immune checkpoint protein in tumor cells, and led to its accumulation in lysosomes. Together, our study suggests that the PI(3)P to PI(4)P conversion on MVEs and the recruitment of the exocyst direct the exocytic trafficking of MVEs for exosome secretion. The molecular mechanism by which exosomes are released from cells is unclear. Here the authors report that a phosphatidylinositide conversion couples the recruitment of the octameric exocyst complex to multivesicular endosomes for exosome secretion. [ABSTRACT FROM AUTHOR]

In numerical simulations of complex flows with discontinuities, it is necessary to use nonlinear schemes. The spectrum of the scheme used has a significant impact on the resolution and stability of the computation. Based on the approximate dispersion relation method, we combine the corresponding spectral property with the dispersion relation preservation proposed by De and Eswaran (J Comput Phys 218:398–416, 2006) and propose a quasi-linear dispersion relation preservation (QL-GRP) analysis method, through which the group velocity of the nonlinear scheme can be determined. In particular, we derive the group velocity property when a high-order Runge–Kutta scheme is used and compare the performance of different time schemes with QL-GRP. The rationality of the QL-GRP method is verified by a numerical simulation and the discrete Fourier transform method. To further evaluate the performance of a nonlinear scheme in finding the group velocity, new hyperbolic equations are designed. The validity of QL-GRP and the group velocity preservation of several schemes are investigated using two examples of the equation for one-dimensional wave propagation and the new hyperbolic equations. The results show that the QL-GRP method integrated with high-order time schemes can determine the group velocity for nonlinear schemes and evaluate their performance reasonably and efficiently. [ABSTRACT FROM AUTHOR]

On the idea of mapped WENO scheme, properties of mapping methods are analyzed, uncertainties in mapping development are investigated, and new piecewise rational mappings are proposed. Based on our former understandings, i.e. the mapping at endpoints {0, 1} tending to identity mapping, a so-called Cn,m condition is summarized for function development. Uncertainties, i.e., whether the pattern at endpoints of mapping would make mapped scheme behave like WENO or ENO, whether piecewise implementation of mapping would entail numerical instability, and whether WENO3 could preserve the third-order at first-order critical points by mapping, are analyzed and clarified. A new piecewise rational mapping with sufficient regulation capability is developed afterwards, where the flatness of mapping around the linear weights and the profile at endpoint tending toward identity mapping can be coordinated explicitly and simultaneously. Hence, the increase of resolution and preservation of stability can be balanced. Especially, concrete mappings are determined for {WENO3, 5, 7}. Numerical examples are tested for the new mapped WENO, which regard preservation and convergence rate of accuracy, numerical stability including that in the long-time computation, resolution and robustness. For comparison, some recent mappings such as IM by [App. Math. Comput. 232, 2014:453–468], RM by [J. Sci. Comput. 67, 2016:540–580] and AIM by [J. Comput. Phys. 381, 2019:162–188] are tested; in addition, some recent WENO-Z type schemes are chosen as well. The results manifest that new schemes can preserve optimal orders at corresponding critical points, achieve numerical stability, and indicate overall comparative advantages regarding accuracy, resolution and robustness. [ABSTRACT FROM AUTHOR]