Fluidization of Transient Filament Networks

Stiff or semiflexible fi laments can be crosslinked to form a network structure with unusual mechanical properties, if the crosslinks at network junctions have the ability to dynamically break and re-form. The characteristic rheology, arising from the competition of plasticity from the transient crosslinks and nonlinear elasticity from the fi lament network, has been widely tested in experiments. Though the responses of a transient fi lament network under small deformations are relatively well understood by analyzing its linear viscoelasticity, a continuum theory adaptable for fi nite or large deformations is still absent. Here we develop a model for transient fi lament networks under arbitrary deformations, which is based on the crosslink dynamics and the macroscopic system tracking the continuously re-shaping reference state. We apply the theory to explain the stress relaxation, the shape recovery after instant deformation, and the necking instability under a ramp deformation. We also examine the role of polydispersity in the mesh size of the network, which leads to a stretched exponential stress relaxation and a diffuse elastic-plastic transition under a ramp deformation. Although dynamic crosslinks are taken as the source of the transient network response, the model can be easily adjusted to incorporating other factors inducing fluidization, such as fi lament breakage and active motion of motor crosslinks, opening a way to address cell and tissue activity at the microscopic level.This work is funded by the Theory of Condensed Matter Critical Mass Grant from EPSRC (EP/J017639)

Mitigating cryogenic microcracking in carbon-fibre reinforced polymer composites using negative thermal-expansion nanoparticles functionalized by a polydopamine coating

Herein, we report a new method of mitigating cryogenic microcracking in carbon-fibre reinforced-plastics (CFRPs) using a negative thermal-expansion nanomaterial, zirconium tungstate (ZrW2O8), to simultaneously reduce the thermal residual stresses and enhance the fracture energy of the epoxy matrix of CFRPs. The results show that 1 wt% of added ZrW2O8 nanoparticles functionalized by polydopamine can increase the fracture energy of the matrix material by 140%, reduce the coefficient of thermal expansion by 20% and, more importantly, enhance the interlaminar fracture energy of the resulting CFRP by about 100% at −196 °C. The ZrW2O8-modified matrix has been demonstrated to successfully prevent microcracking at −196 °C in a blocked cross-ply CFRP laminate with a [04/908/04] fibre architecture

Twin pregnancy in a liver transplant recipient with HIV infection

We are not aware of a report detailing the complex obstetrical and medical management of twin pregnancy in the context of HIV infection and early post-liver transplantation period. Here we describe the successful outcome of a twin pregnancy in a 28-year-old HIV-positive female receiving antiretroviral therapy and immunosuppressive therapy who was the recipient of a liver transplant for previous drug-induced liver failure