Study on improvement of prefolded energy absorption device to constant resistance and its mechanical properties.

When the rock burst occurs, energy absorption support is an important method to solve the impact failure. To achieve constant resistance performance of energy absorption device, as an important component of the support, the mechanical properties of one kind of prefolded tube is analyzed by quasi-static compression test. The deformation process of compression test is simulated by ABAQUS and plastic strain nephogram of the numerical model are studied. It is found that the main factors affecting the fluctuation of force-displacement curve is the stiffness of concave side wall. The original tube is improved to constant resistance by changing the side wall. The friction coefficient affects the folding order and form of the energy absorbing device. Lifting the concave side wall stiffness can improve the overall stiffness of energy absorption device and slow down the falling section of force-displacement curve. It is always squeezed by adjacent convex side wall in the process of folding, with large plastic deformation. Compared with the original one, the improved prefolded tube designed in this paper can keep the maximum bearing capacity (Pmax), increase the total energy absorption (E), improve the specific energy absorption (SEA), and decrease the variance (S2) of force-displacement curve.

Design of integrin αvß3 targeting self-assembled protein nanoparticles with RGD peptide.

Integrin αvß3 was reported as positive regulators of tumorigenesis and highly expressed in cancer stem cells and kinds of cancers, thus, it is an appealing target for cancer treatment. Nanomedicine with targeting delivery ability has developed rapidly and shown its great therapeutic potential in cancer therapy. Proteins are ideal material for nanomedicine regarding to their excellent biocompatibility, and protein-only self-assembled nanoparticles technology provides a robust method to produce protein nanoparticles. Pro-apoptotic proteins or peptides, such as BAK, have attracted increasing attention in the inhibition of tumor growth. However, the self-assembled nanoparticles of BAK targeting to integrin αvß3 over-expressed tumor cells need to be investigated. In this study, we designed recombinant proteins with BH3 BAK as active domain and RGD peptides as targeting ligands to self-assemble into protein nanoparticles (named as PN2-1 et al.), then experimentally evaluated the nanoparticle size, fluorescence feature, stability, targeting ability and cytotoxicity to tumor cells in vitro. The results showed that the protein nanoparticles containing RGD peptides had a uniform particle size with an diameter of approximately 23 nm. PN2-1 had notable inhibition to cell proliferation of C6 cells, C26 cells and MCF-7 cells, with a lower IC50 than the nanoparticles which only had BAK motif without RGD peptide. PN2-1 had higher cellular uptake into C6 cells than MCF-7 cells. Our results demonstrate that the RGD peptide could enhance the cytotoxicity of BAK nanoparticles to tumor cells and increase their tumor targeting ability. This study provides an insight into the design and development of integrin αvß3 targeting protein nanoparticle for cancer treatment.

Shear characteristics and stress-strain mathematical model of waste polyester textile reinforced clay.

Clay reinforcement through appropriate applications of waste fiber or waste fiber fabric can generate huge economic and environmental benefits. In this study, clay was reinforced using waste polyester fiber filaments and waste polyester fabric blocks, respectively. Triaxial tests (σ1 > σ2 = σ3) were carried out to examine the influence of reinforcement method and the contents (0.0%, 0.5%, 1.0%, 1.5%) on the shear behavior of clay. After reinforcement, the deformation resistance and shear strength of the clay was improved. The optimal contents of fiber filament and fabric block were both 1.0%; as the fiber filament or fabric block content increased from 0.5% to 1.5%, the stiffness of the reinforced clay decreased, while the energy absorption capacity and the cohesive strength first increased and then decreased. Under the optimal content condition, the fiber filament showed better reinforcement than the fabric block. Under the train hardening condition, a hyperbolic model can be used to quantitatively describe the stress-strain relationship of the reinforced clay, and the model parameters can also reflect the strain hardening degree.

Ageing deformation of tailings dams in seasonally frozen soil areas under freeze-thaw cycles.

The freeze-thaw cycle is one of the important factors in inducing a dam-break in the permafrost region, so it is of great practical significance to study the mechanism of the failure deformation of tailings dams under freeze-thaw cycles. In this paper, the water-heat-force coupling model of a tailings dam considering frost-thaw damage is established, and the freeze-thaw cyclic ageing deformation of a tailings dam in a seasonally frozen soil area is studied. The correctness of the model is validated by numerical calculation. The research shows under the same water content, the compressive strength and modulus of deformation decrease with an increase in the number of freeze-thaw cycles, the cohesion and internal friction angle decrease, and the amplitude gradually decreases before becoming stable. In the process of cooling, the pore water pressure first increases and then decreases, and the pore water pressure first decreases and then increases during the heating process. The research results can provide a theoretical basis and reference values for the stability analysis of tailings dams in seasonally frozen soil areas.