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• The meso-numerical model, corresponding to the realistic aggregate distribution, was established. • The spatial distribution of the coarse aggregate determines the meso-mechanical properties of concrete and then affects the macro-mechanical behavior. • To reduce the cracking risk of concrete, the volume fraction and gradation of aggregate should be kept within an appropriate range. In this study, the aggregate information in concrete was extracted by Digital Image Processing (DIP) technology, and the two-dimension three-phase (coarse aggregate, mortar, and interface transition zone) meso-numerical model corresponding to the realistic aggregate distribution was established. Based on the model, considering the effects of coarse aggregate distribution, volume fraction and size on the fracture behavior, the fracture test and numerical simulation of four-point shear beams with notches under mixed-mode I-II stress were carried out. The results showed that the concrete meso -numerical model based on real aggregate can accurately reflect the meso-scale fracture process of concrete, and cracks always develop along the weak interface transition zone. It is the aggregate in the fracture trend zone that makes the fracture path tortuous, and the bending and shearing stress around the aggregate will change substantially. Moreover, the external force work of numerical model increases with the increase of aggregate volume fraction and maximum aggregate size, and the dissipated energy of coarse aggregate with small particle size increases with the rise in its proportion in gradation. Especially, the spatial distribution of the coarse aggregate determines the meso-mechanical properties of concrete and then affects the macro-mechanical behavior. To reduce the cracking risk of concrete, the volume fraction and gradation of aggregate should be kept within an appropriate range. [ABSTRACT FROM AUTHOR]

Highlights • The random generation and distribution of aggregate gradation, location and shape in concrete beam were realized. • The size of the specimen has influence on the peak load value in I–II mixed-mode fracture behavior of concrete. • The propagation path has no obvious relation with the content of the aggregate, and closely related with the loading pattern in concrete. Abstract The fracture and damage behaviors of concrete under I–II mixed-mode loading are of great importance in determining the failure mode of concrete material and structure. In this paper, the four-point bending beams with different aggregate volume contents have been fabricated and tested to obtain the limited loading capacities, and the Digital Image Correlation (DIC) method was utilized for monitoring the local displacement above the notch during the loading procedure. Furthermore, based on the aggregate occupation and translation algorithm, a modified random aggregate model has been proposed for generating the four-point bending beam with precast notch, and the numerical simulations for the four-point bending beam with different aggregate volume contents and depths have been proceed. [ABSTRACT FROM AUTHOR]

A novel sensor was developed based on the combination of photonic crystal templating and molecular imprinting technique (MIT) for the detection of simetryn in tobacco samples. The molecularly imprinted photonic crystal hydrogels (MIPHs) was prepared with methacrylic acid (MAA) as monomers, ethylene glycol dimethylacrylate (EGDMA) as cross-linkers, simetryn as imprinting template molecules and polystyrene (PS) microspheres as photonic crystal template. The ordered three-dimensional macro-porous structure of MIPHs with simetryn imprinting template can generate Bragg diffraction, showing a bright structural color. The results show that the MIPHs have high selectivity and excellent sensing performance and can be used for the detection of simetryn from actual tobacco samples. Among the four triazine herbicides with similar structure, MIPHs only produced obvious Bragg diffraction peak wavelength change to simetryn, and MIPHs have good recoverability with four cycle times. When the concentration of simetryn in the actual tobacco increased from 0 to 1.0 μg/mL, the wavelength was red-shifted from 457 nm to 499 nm, which was in the blue and green visible light wavelength range. This new sensor is expected to be used to directly detect pesticide residues in tobacco. • The molecularly imprinted photonic crystal hydrogels (MIPHs) can convert molecular recognition signals into optical signals. • MIPHs recognize simetryn to produce color changes (from green to orange). • MIPHs have highly specific selectivity and recoverability. • MIPHs can identify simetryn pesticide residues in tobacco. [ABSTRACT FROM AUTHOR]

DNA damage--induced NF-kB activation and the secretion of inflammatory cytokines play crucial roles in carcinogenesis and cellular senescence. However, the underlying mechanisms, especially the initial sensors and transducers connecting the nuclear DNA damage signal with cytoplasmic NF-kB activation remain incompletely understood. Here, we report that TRAF-interacting protein with forkhead-associated domain (TIFA), an established NF-kB activator in the cytosol, unexpectedly exhibited nuclear translocation and accumulation on damaged chromatin following genotoxic stress. Accordingly, we also found that DNA damage-induced transcriptional activation and the resulting secretion of classic NF-kB targets, including interleukin (IL)-6 and IL-8, was greatly enhanced in TIFA-overexpressing cells compared with control cells. Mechanistically, DNA damage induced TIFA phosphorylation at threonine 9 (pThr-9), and this phosphorylation event, involving the pThr-binding forkhead-associated domain, was crucial for its enrichment on damaged chromatin and subsequent NF-kB activation. Moreover, in conjunction with its partner protein, the E3 ligase TNF receptor-associated factor 2 (TRAF2), TIFA relayed the DNA damage signals by stimulating ubiquitination of NF-kB essential modulator (NEMO), whose sumoylation, phosphorylation and ubiquitination were critical for NF-kB's response to DNA damage. Consistently, TRAF2 knockdown suppressed TIFA overexpression-enhanced NEMO ubiquitination under genotoxic stress, and a unphosphorylatable Thr-9-mutated TIFA variant had only minor effects on NEMO polyubiquitination. Finally, in agreement with the model of DNA damage-associated secretory senescence barrier against carcinogenesis, ectopic TIFA expression limited proliferation of multiple myeloma cancer cells. In conclusion our results indicate that TIFA functions as a key transducer in DNA damage-induced NF-kB activation. [ABSTRACT FROM AUTHOR]

In order to improve ablation resistance of carbon/carbon composites, ZrB2-SiC protective laminae were prepared on carbon/carbon composites by a novel processing approach combining pressing, pyrolysis and reactive silicon infiltration. The outer layer of the as-prepared lamina was homogeneously distributed by ZrB2 and SiC; the inner layer contained ZrB2 particles adhered by resin-derived carbon. In oxyacetylene flame tests at 2500°C for 30s, carbon/carbon composites were fully protected by ZrB2-SiC laminae without being ablated. The ablation resistance could be optimized by adjusting the C/Zr ratio in the lamina. The linear ablation rate and the mass ablation rate of the specimen with the C/Zr ratio of 0.4:1 were respectively -8.0µm/s and 1.3mg/s, the latter of which was merely 45% of that of carbon/carbon composite. After ablation, along the cross-section of the specimen, a coherent ZrO2 scale, a porous ZrO2 layer and a ZrB2 (SiC-deplete) layer formed from the outside to the inside above the unreacted structure. The oxygen diffusion was significantly reduced in the ZrB2 layer. The porous ZrO2 layer led to the negative linear ablation rate. The coherent ZrO2 layer seemed to play a vital role in improving the ablation resistance of the lamina. [ABSTRACT FROM AUTHOR]

A facile approach to synthesize reduced graphene oxide (RGO) loaded potassium niobate microspheres was reported. The composition, microstructure and electron-transfer properties of the obtained product were characterized. Compared to pure potassium niobate microspheres and commercial P25 TiO2, the as-prepared potassium niobate microspheres/RGO composite showed much higher photocatalytic activity for generating hydrogen under UV irradiation. It was ascribed to the enhanced separation efficiency of electron/hole pairs as testified by electrochemical impedance spectrum and fluorescence spectrum. Importantly, the composite photocatalyst was stable and easy to recycle, and the amount of hydrogen evolution did not decrease after six recycles. The results are potentially applicable to a range of semiconductors useful in water reduction as well as other areas of heterogeneous photocatalysis. [ABSTRACT FROM AUTHOR]

Hydrogen production from an ammonia-fuelled microchannel reactor is simulated in a three-dimensional (3D) model implemented via Comsol Multiphysics™. The work described in this paper endeavours to obtain a mathematical framework that provides an understanding of reaction-coupled transport phenomena within the microchannel reactor. The transport processes and reactor performance are elucidated in terms of velocity, temperature, and species concentration distributions, as well as local reaction rate and NH 3 conversion profiles. The baseline case is first investigated to comprehend the behaviour of the microchannel reactor, then microstructural design and operating parameters are methodically altered around the baseline conditions to explore the optimum values. The simulation results show that an optimum NH 3 space velocity (GHSV) of 65,000 Nml g cat −1 h –1 yields 99.1% NH 3 conversion and a power density of 32 kW e L –1 at the highest operating temperature of 973 K. It is also shown that a 40-μm-thick porous washcoat is most desirable at these optimum conditions. Finally, a low channel hydraulic diameter (225 μm) is observed to contribute to high NH 3 conversion. Mass transport limitations in the porous-washcoat and gas-phase are negligible as depicted by the Damköhler and Fourier numbers, respectively. The experimental microchannel reactor yields 98.2% NH 3 conversion and a power density of 30.8 kW e L –1 when tested at the optimum operating conditions established by the model. Good agreement with experimental data is observed, so the integrated experimental-modelling approach developed in this paper may well provide an incisive step toward the efficient design of ammonia-fuelled microchannel reformers. [ABSTRACT FROM AUTHOR]

The retinoblastoma (Rb) protein mediates heterochromatin formation at the promoters of E2 transcription factor 1 (E2F1) target genes, such as proliferating cell nuclear antigen and cyclin A2 (CCNA2), and represses these genes during cellular senescence. However, the selectivity of Rb recruitment is still not well understood. Here, we demonstrate that a senescence-associated gene is a direct target of E2F1 and is also repressed by heterochromatin in senescent cells. In contrast, ARF and p27KIP1, which are also E2F1 targets, are not repressed by Rb and heterochromatin formation. By comparing the promoter sequences of these genes, we found a novel TAAC element that is present in the cellular senescence-inhibited gene, proliferating cell nuclear antigen, and CCNA2 promoters but absent from the ARF and p27KIP1 promoters. This TAAC element associates with Rb and is required for Rb recruitment. We further determined that TAAC element-mediated Rb association requires the E2F1 binding site, but not E2F1 protein. These results provide a novel molecular mechanism for the different expression patterns of E2F1 targets and afford new mechanistic insight regarding the selectivity of Rb-mediated heterochromatin formation and gene repression during cellular senescence. [ABSTRACT FROM AUTHOR]