Mechanical properties of the hollow-wall graphene gyroid lattice

© 2020 The macroscopic elastic modulus and yield strength of solid-wall nickel gyroids and hollow-wall graphene gyroids of cell size 60 nm are deduced from indentation tests on a thin coating of the gyroids, with suitable interpretation by finite element simulations. The solid-wall nickel gyroids are fabricated by the self-assembly of a triblock copolymer, followed by the chemical vapour deposition of a graphene film onto this catalytic template. The nano-indentation response of the gyroid-based coatings was measured using a Berkovich indenter. In order to interpret the indentation response, two sets of finite element simulations were performed: periodic cell calculations in order to deduce the effective macroscopic properties in terms of the relative density and cell wall properties of the lattice, and then indentation simulations of a continuum with the effective properties of the gyroid. Despite the knockdown in modulus and strength of the graphene gyroid lattice due to waviness of the layered cell walls, the structure remains remarkably strong due to nanoscale size effects

Goat and buffalo milk fat globule membranes exhibit better effects at inducing apoptosis and reduction the viability of HT-29 cells

Bovine milk fat globule membrane (MFGM) has shown many health benefits, however, there has not been much study on non-cattle MFGMs. The purpose of this study was to compare the anti-proliferation effects and investigate the mechanisms of MFGMs from bovine, goat, buffalo, yak and camel milk in HT-29 cells. Results showed that protein content in MFGM of yak milk is the highest among five MFGM. All MFGMs inhibited cellular proliferation which was in agreement with cell morphology and apoptosis. However, the number of cells in S-phase from 24 h to 72 h was increased significantly by treatment with goat, buffalo and bovine MFGMs (100 μg/mL), but not yak and camel. All MFGMs treatment significantly reduced the mitochondrial membrane potential (with an order of goat>buffalo>bovine>camel>yak) and Bcl-2 expression, but increased the expression of both Bax and Caspase-3. Taken together, the results indicate that all MFGMs, especially goat and buffalo MFGMs, showed better effects at inducing apoptosis and inhibition of the proliferation of HT-29 cells. The mechanism might be arresting the cell cycle at S phase, depolarization of mitochondrial membrane potential, down-regulation of Bcl-2 expression and increase of Bax and Caspase-3 expression

Analysis of Thermal Stresses and Strains Developing During the Heat Treatment of Windmill Shaft

In the paper the results of evaluation of the temperature and stress fields during four cycles of the heat treatment process of the windmill shaft has been presented. The temperature field has been calculated from the solution to the heat conduction equation over the whole heat treatment cycles of the windmill shaft. To calculate the stress field an incremental method has been used. The relations between stresses and strains have been described by Prandtl-Reuss equation for the elastic-plastic body. In order to determine the changes in the temperature and stress fields during heat treatment of the windmill shaft self-developed software utilizing the Finite Element Method has been used. This software can also be used to calculate temperature changes and stress field in ingots and other axially symmetric products. In the mathematical model of heating and cooling of the shaft maximum values of the strains have been determined, which allowed to avoid the crack formation. The critical values of strains have been determined by using modified Rice and Tracy criterion

Chemical vapour deposition of freestanding sub-60 nm graphene gyroids

The direct chemical vapour deposition of freestanding graphene gyroids with controlled sub-60 nm unit cell sizes is demonstrated. Three-dimensional (3D) nickel templates were fabricated through electrodeposition into a selectively voided triblock terpolymer. The high temperature instability of sub-micron unit cell structures was effectively addressed through the early introduction of the carbon precursor, which stabilizes the metallized gyroidal templates. The as-grown graphene gyroids are self-supporting and can be transferred onto a variety of substrates. Furthermore, they represent the smallest free standing periodic graphene 3D structures yet produced with a pore size of tens of nm, as analysed by electron microscopy and optical spectroscopy. We discuss generality of our methodology for the synthesis of other types of nanoscale, 3D graphene assemblies, and the transferability of this approach to other 2D materials

Mechanical properties of the hollow-wall graphene gyroid lattice

© 2020 The macroscopic elastic modulus and yield strength of solid-wall nickel gyroids and hollow-wall graphene gyroids of cell size 60 nm are deduced from indentation tests on a thin coating of the gyroids, with suitable interpretation by finite element simulations. The solid-wall nickel gyroids are fabricated by the self-assembly of a triblock copolymer, followed by the chemical vapour deposition of a graphene film onto this catalytic template. The nano-indentation response of the gyroid-based coatings was measured using a Berkovich indenter. In order to interpret the indentation response, two sets of finite element simulations were performed: periodic cell calculations in order to deduce the effective macroscopic properties in terms of the relative density and cell wall properties of the lattice, and then indentation simulations of a continuum with the effective properties of the gyroid. Despite the knockdown in modulus and strength of the graphene gyroid lattice due to waviness of the layered cell walls, the structure remains remarkably strong due to nanoscale size effects