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Many studies have examined the effects of surface topography on the settlement behaviour of marine organisms and this article reviews these investigations with more emphasis on the effects of topography scale. It has been observed that macro topographies (1-100 mm) are generally favoured by marine fouling taxa and are unsuitable for antifouling applications. This is because macro topographies are usually large enough to fit fouling organisms and provide refuge from dangers in the marine environment. Micro topographies had only limited success at reducing fouling from a wide range of marine taxa. The antifouling performance of micro topographies (1 to ≤ 1000 μm) is dependent on the properties of topography features in terms of symmetry, isotropy, width, length, height/depth, separation distance and average roughness. In terms of the antifouling performance of micro topography, topography geometry may only be of secondary importance in comparison to the size of features itself. It is also noted that hydrodynamic stresses also contribute to the settlement trends of foulers on textured surfaces. Future studies on antifouling topographies should be directed to hierarchical topographies because the mixed topography scales might potentially reduce fouling by both micro and macro organisms. Patterned nano-topographies (1- ≤ 1000 nm) should also be explored because the antifouling mechanisms of these topographies are not yet clear.

The knowledge of mechanical properties of root cell walls is vital to understand how these properties interact with relevant genetic and physiological processes to bring about growth. Expansion of cell walls is an essential component of growth, and the regulation of cell wall expansion is one of the ways in which the mechanics of growth is controlled, managed and directed. In this study, the inherent surface mechanical properties of living Arabidopsis thaliana whole-root epidermal cells were studied at the nanoscale using the technique of atomic force microscopy (AFM). A novel methodology was successfully developed to adapt AFM to live plant roots. Force-Indentation (F-I) experiments were conducted to investigate the mechanical properties along the length of the root. F-I curves for epidermal cells of roots were also generated by varying turgor pressure. The F-I curves displayed a variety of features due to the heterogeneity of the surface. Hysteresis is observed. Application of conventional models to living biological systems such as cell walls in nanometer regimes tends to increase error margins to a large extent. Hence information from the F-I curves were used in a preliminary semiquantitative analysis to infer material properties and calculate two parameters. The work done in the loading and unloading phases (hysteresis) of the force measurements were determined separately and were expressed in terms of "Index of Plasticity" (η), which characterized the elasticity properties of roots as a viscoelastic response. Scaling approaches were used to find the ratio of hardness to reduced modulus (H/E(*)).

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This paper presents a numerical technique for the analysis of the cone penetration test by means of the commercial finite element code ABAQUS. The von Mises yield criterion with its associated flow rule is assumed to model the plastic behaviour of elastoplastic undrained clays. An explicit finite element scheme is used to efficiently perform a large number of loading increments and to simplify the treatment of contact. An Arbitrary Langrangian-Eulerian (ALE) scheme is adopted to preserve the quality of mesh throughout the numerical simulation. A volumetric weighting algorithm adjusts the relative positions of nodes after each loading increment. This prevents mesh over distortion and allows the simulation to run continuously. The variation of the cone resistance is examined in relation to various parameters such as the in situ stress state, shaft and cone face roughness, and the material strength when steady state conditions have been reached. The trends of these variations are highlighted and compared with those found by other researchers. This technique can be extended to analyse the plastic behaviour of elastoplastic sands often modelled using either the Drucker-Prager yield criterion or a critical state model.