Cell adhesion with extracellular matrix depends on the collective behaviors of a large number of receptor-ligand bonds at the compliant cell-matrix interface. While most biological tissues and structures, including cells and extracellular matrices, exhibit strongly anisotropic material properties, existing studies on molecular adhesion via receptor-ligand bonds have been largely limited to isotropic materials. Here the effects of transverse isotropy, a common form of material anisotropy in biological systems, in modulating the adhesion behavior of a cluster of receptor-ligand bonds are investigated. The results provide a theoretical basis to understand cell adhesion on anisotropic extracellular matrices and to explore the possibility of controlling cell adhesion via anisotropy design in material properties. The combined analysis and simulations show that the orientation of material anisotropy strongly affects the apparent softness felt by the adhesive bonds, thereby altering their ensemble lifetime by several orders of magnitude. An implication of this study is that distinct cellular behaviors can be achieved through remodeling of material anisotropy in either extracellular matrix or cytoskeleton. Comparison between different loading conditions, together with the effects of material anisotropy, yields a rich array of out-of-equilibrium behaviors in the molecular interaction between reactant-bearing soft surfaces, with important implications on the mechanosensitivity of cells.

This paper has focused on the structural performance of recycled aggregate concrete (RAC) under both cyclic and monotonic loading. RAC specimens with different recycled coarse aggregate (RCA) replacement percentages of 0%, 25%, 50%, 75% and 100% were cast and tested. The compressive stress-strain relationship and the failure mode were investigated for each RCA replacement ratio. The effects of the RCA replacement percentage on the compressive mechanical properties of the RAC specimens including the strength, elastic modulus, peak strain, ultimate strain and Poisson's ratio were also studied. The RAC specimens have shown similar failure characteristics regardless of monotonic or cyclic loading. In addition, the compression skeleton curves of the RAC specimens under cyclic loading agree well with those under monotonic loading. Based on the experimental results, the characteristic points pertaining to the hysteresis loop were defined and their relations were established. Furthermore, the constitutive equations of the RAC as well as its simplified form were proposed and applied in numerical simulations of RAC columns and frames under cyclic loading. The proposed constitutive equations have shown promising accuracy in predicting the hysteresis performance of RAC on both component and structural levels.

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A new type of reduced graphene oxide‐encapsulated silicon nitride (Si3N4@rGO) particle was synthesized via an electrostatic interaction between amino‐functionalized Si3N4 particles and graphene oxide (GO). Subsequently, the Si3N4@rGO particles were incorporated into a Si3N4 matrix as a reinforcing phase to prepare nanocomposites, and their influence on the microstructure and mechanical properties of the Si3N4 ceramics was investigated in detail. The microstructure analysis showed that the rGO sheets were uniformly distributed throughout the matrix and firmly bonded to the Si3N4 grains to form a three‐dimensional carbon network structure. This unique structure effectively increased the contact area and load transfer efficiency between the rGO sheets and the matrix, which in turn had a significant impact on the mechanical properties of the nanocomposites. The results showed that the nanocomposites with 2.25 wt.% rGO sheets exhibited mechanical properties that were superior to monolithic Si3N4; the flexural strength increased by 83.5% and reached a maximum value of 1116.4 MPa, and the fracture toughness increased by 67.7% to 10.35 MPa·m1/2.