Preparation and evaluation of PEGylated phospholipid membrane coated layered double hydroxide nanoparticles

AbstractThe aim of the present study was to develop layered double hydroxide (LDH) nanoparticles coated with PEGylated phospholipid membrane. By comparing the size distribution and zeta potential, the weight ratio of LDH to lipid materials which constitute the outside membrane was identified as 2:1. Transmission electron microscopy photographs confirmed the core-shell structure of PEGylated phospholipid membrane coated LDH (PEG-PLDH) nanoparticles, and cell cytotoxicity assay showed their good cell viability on Hela and BALB/C-3T3 cells over the concentration range from 0.5 to 50 μg/mL

Effect of 2D spatial variability on slope reliability: A simplified FORM analysis

To meet the high demand for reliability based design of slopes, we present in this paper a simplified HLRF (Hasofer–Lind–Rackwitz–Fiessler) iterative algorithm for first-order reliability method (FORM). It is simply formulated in x-space and requires neither transformation of correlated random variables nor optimization tools. The solution can be easily improved by iteratively adjusting the step length. The algorithm is particularly useful to practicing engineers for geotechnical reliability analysis where standalone (deterministic) numerical packages are used. Based on the proposed algorithm and through direct perturbation analysis of random variables, we conducted a case study of earth slope reliability with complete consideration of soil uncertainty and spatial variability. Keywords: Slope stability, Spatial variability, Random field model, Probability of failure, HLRF algorithm, First-order reliability method (FORM

Numerical investigation of the opening effect on the mechanical behaviours in rocks under uniaxial loading using hybrid continuum-discrete element method

Openings including their size, shape and distribution in rock play a significant role in the performance of rock related structures. The well-established knowledge in this area can contribute to the engineering practices, for example, underground space design, planning and optimisation in Civil and Mining Engineering and wellbore stability in Drilling Engineering, among others. Thus, understanding the failure mechanism of rock with openings is theoretically and practically meaningful. Laboratory testing on rock or rock-like materials with openings have been studied extensively in the literature, which, however, primarily focuses on the cracks/fractures. In this paper, a comprehensive numerical study on the effect of non-banded openings, i.e., circular, rectangular, and triangular opening, on the rock mechanical behaviour is performed using a hybrid continuum-discrete element method. It is revealed that the proposed simulation method can reproduce reasonably the crack initiation and propagation, and predict well the change of the mechanical behaviour due to the openings. In addition, the influence of the opening shape and opening ratio (=area of opening/specimen area) on the mechanical behaviour is also investigated

Evaluation of the performance of a breakage model for high porosity Haubourdin chalk

We examine a new continuum micromechanical approach to predicting the macroscopic mechanical responses of Haubourdin chalk under various load conditions. The approach is based on a simple breakage model that accounts for an evolving microstructural degradation through coccosphere crushing with only five physically meaningful parameters and one grading index. The model correlates the intrinsic failure mechanisms including the coccosphere crushing, pore collapse and plastic shearing that are identified by corresponding internal variables within thermodynamic framework. On this basis, numerical predictions of the stresses and strains are examined against their experimental counterparts as well as the results from an existing continuum model. Parametric studies are further conducted to investigate the effect of the model parameters. The favourable agreements in various conventional and complex compression tests indicate a satisfactory performance of the breakage model, highlighting the importance of capturing the microscopic degradation mechanisms when building a constitutive model