The distinct spatial architecture of the apical actin cables (or actin cap) facilitates rapid biophysical signaling between extracellular mechanical stimuli and intracellular responses, including nuclear shaping, cytoskeletal remodeling, and the mechanotransduction of external forces into biochemical signals. These functions are abrogated in lamin A/C-deficient mouse embryonic fibroblasts that recapitulate the defective nuclear organization of laminopathies, featuring disruption of the actin cap. However, how nuclear lamin A/C mediates the ability of the actin cap to regulate nuclear morphology remains unclear. Here, we show that lamin A/C expressing cells can form an actin cap to resist nuclear deformation in response to physiological mechanical stresses. This study reveals how the nuclear lamin A/C-mediated formation of the perinuclear apical actin cables protects the nuclear structural integrity from extracellular physical disturbances. Our findings highlight the role of the physical interactions between the cytoskeletal network and the nucleus in cellular mechanical homeostasis.

In the past decade, the power output of wind turbines has increased significantly. This increase has been primarily achieved through manufacturing larger blades resulting in high blade tip velocities and increased susceptibility to rain erosion. This paper is the first part in a two-part paper that presents a framework for the analysis of rain erosion in wind turbine blades. Two ingredients of the framework are presented. A stochastic rain texture model is developed to generate three-dimensional fields of raindrops consistent with the rainfall history at the turbine location by integrating the micro-structural properties of rain, i.e. raindrops size and spatial distribution with its integral properties such as the relationship between the average volume fraction of raindrops and rain intensity. An in-house GPU-accelerated computational fluid dynamics model of free-surface flows and a multi-resolution strategy are used to calculate the drop impact pressure as a function of time and space. An interpolation scheme is finally proposed to find the time evolution of impact pressure profile for any given drop diameter using the high fidelity simulation results, significantly reducing the computational cost. Other ingredients of the framework pertaining to drop impact-induced stresses and the blade coating fatigue life are presented in part II.

Rolling resistance is one of the key factors that affect the fuel efficiency of the national pavement system. In addition to pavement texture and pavement roughness, the dissipation of mechanical work provided by the vehicle because of viscous deformation within the pavement structure has been recognized as a relevant factor contributing to the environmental footprint of pavement systems. This dissipation depends on material and structural parameters that can be optimized to increase the fuel efficiency of pavements. Identifying the key material and structural parameters that drive this dissipation is the focus of this paper. This identification is achieved by a combination of dimensional analysis and model-based simulations of the dissipation of a viscoelastic beam on an elastic foundation. For linear viscoelastic systems, the dissipation is found to scale with the square of the vehicle weight and with the inverse of the viscous relaxation time, in addition to distinct power relations of top-layer stiffness, thickness, and subgrade modulus. These scaling relations can be used by pavement engineers to reduce such pavement-inherent dissipation mechanisms and increase the fuel efficiency of a pavement design. An example shows the application of these scaling relations with data extracted from FHWA's Long-Term Pavement Performance database for seven road classes. The scaling relations provide a means for evaluating the performance of the various road classes in terms of the fuel efficiency related to dissipation.

With the current trend in wind energy production, the need to manufacture larger wind turbine blades is on the rise. The high blade tip velocities associated with large blades subject them to various damages due to high speed impact with foreign objects such as raindrops. This paper is the second part in a two-part paper that presents a framework for rain erosion prediction in wind turbine blades. In part I, a stochastic rain texture model and multi-resolution simulation of raindrop impact on solid object were discussed. In part II, the predicted impact pressure profiles are imported into a finite element model of the wind turbine blade shell to analyze the raindrop impact-induced transient stresses within the blade coating and the ensuing fatigue damage pattern. The analysis is complemented with a fatigue stress-life estimation process that integrates elements of fatigue life calculation with 3D fields of raindrops generated from the stochastic rain texture model to relate damage accumulation rates to rain intensities. These accumulation rates, together with the statistics of rainfall history, provide a means for estimating the expected fatigue life of the blade coating as an indication of the onset of surface roughening or the end of the incubation period.

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