Optimization of Cohesive Parameters in the Interfacial Transition Zone of Rubberized Concrete Based on the Response Surface Method.

Rubber concrete has been applied to a certain extent in fatigue-resistant structures due to its good durability. Based on a cohesive model of rubber composed of a five-phase material containing mortar, aggregate, rubber, aggregate-mortar interfacial transition zone (ITZ), and rubber-mortar ITZ, this paper studies the influence of the cohesive parameters in the rubber-mortar ITZ on the fatigue problem of rubber concrete on the mesoscopic scale. As the weak part of cement-based composite materials, the ITZ has a great influence on the mechanical properties and durability of concrete, but the performance of the ITZ is difficult to test in macro experiments, resulting in difficulties in determining its simulation parameters. Based on the cohesive model with a rubber content of 5%, this study uses Monofactor analysis and the Plackett-Burman test to quickly and effectively determine the primary and secondary influences of the cohesive model parameters in the rubber-mortar ITZ; further, the response surface method is used to optimize the cohesive parameters in the rubber-mortar ITZ, and the numerical simulation results after optimizing the cohesive parameters are compared and analyzed with the simulation results before optimization. The results show that, under the setting of the optimized parameters, the simulation results of each item of the optimal cohesive model parameters in the rubber-mortar ITZ are in line with the reality and closer to the experimental data, and they are also applicable to rubber concrete models with different rubber dosing.

Numerical Simulation of the Effect of Freeze-Thaw Cycles on the Axial Compression Strength of Rubber Concrete.

The incorporation of rubber can enhance concrete's durability and effectively reduce the damage caused by freeze-thaw cycling (FTC). Still, there has been only limited research on the damage mechanism of RC at the fine view level. To gain insight into the expansion process of uniaxial compression damage cracks in rubber concrete (RC) and summarize the internal temperature field distribution law during FTC, a fine RC thermodynamic model containing mortar, aggregate, rubber, water, and interfacial transition zone (ITZ) is established in this paper, and the cohesive element is selected for the ITZ part. The model can be used to study the mechanical properties of concrete before and after FTC. The validity of the calculation method was verified by comparing the calculated results of the compressive strength of concrete before and after FTC with the experimental results. On this basis, this study analyzed the compressive crack extension and internal temperature distribution of RC at 0, 5, 10, and 15% replacement rates before and after 0, 50, 100, and 150 cycles of FTC. The results showed that the fine-scale numerical simulation method can effectively reflect the mechanical properties of RC before and after FTC, and the computational results verify the applicability of the method to rubber concrete. The model can effectively reflect the uniaxial compression cracking pattern of RC before and after FTC. Incorporating rubber can impede temperature transfer and reduce the compressive strength loss caused by FTC in concrete. The FTC damage to RC can be reduced to a greater extent when the rubber incorporation is 10%.

Numerical Simulation of Fatigue Life of Rubber Concrete on the Mesoscale.

Rubber concrete (RC) exhibits high durability due to the rubber admixture. It is widely used in a large number of fatigue-resistant structures. Mesoscale studies are used to study the composition of polymers, but there is no method for fatigue simulation of RC. Therefore, this paper presents a finite element modeling approach to study the fatigue problem of RC on the mesoscale, which includes the random generation of the main components of the RC mesoscale structure. We also model the interfacial transition zone (ITZ) of aggregate mortar and the ITZ of rubber mortar. This paper combines the theory of concrete damage to plastic with the method of zero-thickness cohesive elements in the ITZ, and it is a new numerical approach. The results show that the model can simulate reasonably well the random damage pattern after RC beam load damage. The damage occurred in the middle of the beam span and tended to follow the ITZ. The model can predict the fatigue life of RC under various loads.

Bardoxolone treatment alleviates lipopolysaccharide (LPS)-induced acute lung injury through suppressing inflammation and oxidative stress regulated by Nrf2 signaling.

Nuclear factor-erythroid 2 related factor 2 (Nrf2) plays critical roles in attenuating various inflammation- and oxidative stress-induced diseases, including acute lung injury (ALI). Bardoxolone (Bard), a synthetic triterpenoid based on natural product oleanolic acid, is one of the most potent Nrf2 activator. However, if Bard could prevent lipopolysaccharide (LPS)-induced ALI by inducing Nrf2 activation and its down-streaming signals, is still poorly understood. In this study, we attempted to explore the protective effect of Bard on ALI and the underlying molecular mechanisms. The results indicated that Bard significantly attenuated ALI through reducing the lung wet/dry weight ratio and protein concentration, neutrophil infiltration, malondialdehyde (MDA) and myeloperoxidase (MPO) levels, and improving superoxide dismutase (SOD) and glutathione (GSH) activities. In addition, Bard effectively ameliorated histopathological alterations, reactive oxygen species (ROS) production, pro-inflammatory cytokines release, and the expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX2) and high mobility group box 1 (HMGB1). Moreover, the inhibitory role of Bard in inflammation was also attributed to its suppression of nuclear factor-κB (NF-κB) signaling. Furthermore, the activation of mitogen-activated protein kinases (MAPKs) signaling, including p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK), induced by LPS was substantially ameliorated by Bard. The beneficial effects of Bard on ALI were confirmed in LPS-incubated cells in vitro. Meanwhile, the in vitro studies also demonstrated that Bard-improved ALI was largely due to its role in inducing Nrf2 signaling through a dose-dependent manner. Importantly, we found that Bard-attenuated histological changes, inflammation, ROS production, NF-κB and MAPKs signaling in Nrf2+/+ mice were significantly abolished in mice with Nrf2 knockout. Therefore, our study for the first time provided evidence that Bard could effectively ameliorate LPS-induced ALI by reducing oxidative stress and inflammation mainly through the activation of Nrf2 signaling.

Edge-tailored graphene oxide nanosheet-based field effect transistors for fast and reversible electronic detection of sulfur dioxide.

Graphene oxide was tailored into GO nanosheets with periodic acid treatment. Interestingly, the latter have a superior sensing performance for the fast and reversible detection of SO(2) compared with the former at room temperature. Its sensing mechanism was proposed from the structural changes of the GO nanosheets during the sensing and recovering processes.

Spontaneous growth of free-standing polypyrrole films at an air/ionic liquid interface.

A novel strategy for the one-pot fabrication of free-standing polypyrrole films is presented in this work. The films are spontaneously formed at an air/ionic liquid interface through interface oxypolymerization. The thicknesses of the films are finely controlled from tens to hundreds of nanometers, and the films are uniform and compact. Asymmetrical films with different smoothness on the two sides of the film are also obtained and exhibit different water wettability. This method is extremely simple and does not need any equipment. It may bring about a general methodology for forming free-standing conducting polymer films.

Control the diameters of mesoporous silica nanotubes by varying stirring time.

A chiral cationic gelator derived from L-alanine was synthesized. Sol-gel transcriptions were carried out to control mesoporous silica nanostructures using the organic self-assemblies of this gelator as templates. It was found that the morphologies of the obtained mesoporous silicas were sensitive to stirring time. With increasing the stirring time, the morphologies of mesoporous silicas changed from nanotubes constructed by double twisted nanoribbons to those constructed by single-strip coiled nanoribbons. The diameters of the nanotubes increased from 80 to 400 nm. This result indicated that the formation of the nanotubes following a dynamic templating process. For a better understanding the pore architectures, the TEM images of the mesoporous silicas were simulated using the 3D studio MAX software.

Formation of hollow mesoporous silica nanoworm with two holes at the terminals.

A chiral low-molecular-weight amphiphile, L- 18Ala11PyPF(6), was synthesized from L-alanine. Hollow silica nanoworms with circular pore channels parallel to the shell surfaces and holes at the terminals were prepared using the self-assemblies of it as templates via a single-templating approach. The formation of this hierarchical structure was studied by taking TEM images after different reaction time and changing reaction conditions. It was found that the morphologies of the amphiphile-silica assemblies changed gradually during the sol-gel transcription process.

From branched self-assemblies to branched mesoporous silica nanoribbons.

Branched left-handed twisted mesoporous silica nanoribbons were prepared via a template method.

The formation of helical mesoporous silica nanotubes.

Three chiral cationic gelators were synthesized. They can form translucent hydrogels in pure water. These hydrogels become highly viscous liquids under strong stirring. Mesoporous silica nanotubes with coiled pore channels in the walls were prepared using the self-assemblies of these gelators as templates. The mechanism of the formation of this hierarchical nanostructure was studied using transmission electron microscopy at different reaction times. The results indicated that there are some interactions between the silica source and the gelator. The morphologies of the self-assemblies of gelators changed gradually during the sol-gel transcription process. It seems that the silica source directed the organic self-assemblies into helical nanostructures.

Handedness inversion in preparing mesoporous silica nanoribbons.

A new chiral cationic amphiphile has been synthesized. Sol-gel transcriptions were carried out to control mesoporous silica nanostructures using the organic self-assemblies of this amphiphile as templates. Left-handed coiled mesoporous silica nanoribbons were obtained in the mixture of 1-propanol and 2.5 wt% NH(3) aq. at the ratio of 2:8 and 0 °C. However, right-handed coiled mesoporous silica nanoribbons were prepared in 2.5 wt% NH(3) aq. at 25 °C. The organization of the low-molecular-weight gelators plays an important role in this handedness inversion.