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Fusarium wilt of banana (FWB), caused by Fusarium oxysporum f. sp. cubense (Foc), especially tropical race 4 (TR4), presents the foremost menace to the global banana production. Extensive efforts have been made to search for efficient biological control agents for disease management. Our previous study showed that Streptomyces sp. XY006 exhibited a strong inhibitory activity against several phytopathogenic fungi, including F. oxysporum. Here, the corresponding antifungal metabolites were purified and determined to be two cyclic lipopeptide homologs, lipopeptin A and lipopeptin B. Combined treatment with lipopeptin complex antagonized Foc TR4 by inhibiting mycelial growth and conidial sporulation, suppressing the synthesis of ergosterol and fatty acids and lowering the production of fusaric acid. Electron microscopy observation showed that lipopeptide treatment induced a severe disruption of the plasma membrane, leading to cell leakage. Lipopeptin A displayed a more pronounced antifungal activity against Foc TR4 than lipopeptin B. In pot experiments, strain XY006 successfully colonized banana plantlets and suppressed the incidence of FWB, with a biocontrol efficacy of up to 87.7%. Additionally, XY006 fermentation culture application improved plant growth parameters and induced peroxidase activity in treated plantlets, suggesting a possible role in induced resistance. Our findings highlight the potential of strain XY006 as a biological agent for FWB, and further research is needed to enhance its efficacy and mode of action in planta. [ABSTRACT FROM AUTHOR]

Carbon fibers (CFs) are normally manufactured from synthetic or biomass polymers. However, the synthesis and spinning of traditional polymer precursors inevitably requires the use of a large amount of hazardous solvents, resulting in high extra cost and pollution from the production of CFs. Herein, sugars were used as brand-new CF precursors in an eco-friendly and sustainable approach, obviating the need for hazardous solvents. This strategy involves the synergy of sugars and double-network hydrogels. The hydrogel network provided a high-stress environment to control the carbonization of the sugar, effectively inhibiting the generation of gaseous and volatile products; meanwhile the sugar prevented the deformation of the network. As a result, the carbon yield improved substantially, reaching values of ~50%, significantly reducing carbon emissions. Thus, the SBCFs have a compact and homogeneous microstructure, along with excellent mechanical properties. The tensile strength and Young's modulus of the SBCFs were found to be 960 MPa and 77 GPa, respectively. Moreover, the precursor cost of SBCFs was only 1/10 that of traditional biobased CFs, offering the opportunity to improve both the sustainability and overall economics of bio-based CF production. [ABSTRACT FROM AUTHOR]

With MEMS technology developing rapidly, the microfluidic droplet technology has been employed into many biological or chemical experiments. To satisfy the increasingly high demands in various applications of the microfluidic chips, the size of the droplet needs accurate control. We have designed and performed a threedimensional numerical simulation of a droplet generation in a double T-junction microchannel by a level-set method in COMSOL5.0 for discussing the process of the droplet formation and the influences on the size of the droplet. We have studied out that the flow rate ratio, the continuous phase viscosity, the interfacial tension, and the contact angle influence the size of the droplet. The effective droplet diameter increases when the flow rate ratio and the interfacial tension increase. It decreases when the continuous phase viscosity and the contact angle increase. [ABSTRACT FROM AUTHOR]

By using the coupled-mode theory-based transfer matrix, we analyze the optical properties of direct and indirect coupling of cascaded cavities in the resonator-waveguide system. The dispersion relation of the system, bandgap opening mechanisms, and anticrossing behavior are investigated theoretically and numerically. We also derive the transmission coefficients of the direct and indirect coupling system with multiple cavities and demonstrate the interaction between the modes, which leads to Fano resonance with an asymmetric transmission line shape. All the results obtained by the transfer matrix method are confirmed by the finite-difference time-domain method in photonic crystals. [ABSTRACT FROM PUBLISHER]

The thermal shock behavior of hot-pressed ZrB2-SiC composite containing 15vol.% graphite flake (ZrB2-SiC-G) was investigated. The thermal shock testing was carried out by means of quenching into water from high temperatures (ΔT in the range of 200-1000°C). The damage introduced by the thermal shock was characterized by the degradation of bending strength. The residual strength exhibited a complex evolution and could be divided into three zones according to the variation of the temperature difference: (i) no damage zone (200-300°C), (ii) strength degradation zone (300-400°C), and (iii) low stable strength zone (400-1000°C). The minimum residual strength of 160 MPa, higher than 40% of the initial strength of 396 MPa, was obtained in the third zone of temperature difference. The surface feature of ZrB2-SiC-G composite after the thermal shock tests was also investigated. [ABSTRACT FROM AUTHOR]

HfB2–SiC-based ultra-high-temperature ceramics with aluminum nitride (AlN) as a sintering aid were hot pressed at 1850°C. The sinterability and mechanical properties were investigated and compared with the composite without a sintering aid. It was shown that the addition of AlN greatly improved the powder sinterability and enabled the production of a nearly full-dense composite. The mechanical properties, especially the flexural strength, were enhanced remarkably through the improvement in the sinterability and microstructure. The oxidation resistance of a composite doped with 10 vol% AlN was evaluated by a plasma arc heater and the ablation mechanism was discussed. [ABSTRACT FROM AUTHOR]

HfB2-20 vol% SiC composite was hot-pressed at 1900°C with silicon nitride (Si3N4) as sintering aid. Sinterability and mechanical properties were investigated and compared to the composite without the sintering aid. It was shown that the addition of Si3N4 greatly improved the powder sinterability and enabled the production of nearly full dense composite. The flexural strength and fracture toughness were 590MPa and 5.43MPam½, respectively. The oxidation resistance of composite doped with Si3N4 was evaluated by the oxyacetylene oxidation test and the oxidation mechanism was discussed. [ABSTRACT FROM AUTHOR]

HfB2-20 vol% SiC composite was hot-pressed at 1900°C with silicon nitride (Si3N4) as sintering aid. Sinterability and mechanical properties were investigated and compared to the composite without the sintering aid. It was shown that the addition of Si3N4 greatly improved the powder sinterability and enabled the production of nearly full dense composite. The flexural strength and fracture toughness were 590MPa and 5.43MPam½, respectively. The oxidation resistance of composite doped with Si3N4 was evaluated by the oxyacetylene oxidation test and the oxidation mechanism was discussed. [ABSTRACT FROM AUTHOR]

Structural ceramics, including ultrahigh-temperature ceramics such as zirconium diboride (ZrB2) and hafnium diboride (HfB2), are brittle and sensitive to flaws. As a result, the structural integrity of this ceramic component may be affected seriously. In this paper, a novelty technique namely preoxidation was proposed to overcome this problem. A ZrB2-based composite containing 20 vol% SiC whisker was produced by hot pressing. The composite was preoxidized at temperatures of 800° and 1200°C for various times ranging from 10 to 180 min in air. The flexural strength and microstructure of specimens were investigated systematically under each preoxidation condition. The strength was improved after preoxidation, with a maximum increase of strength (15%) for samples after preoxidizing at 800°C for 180 min. Microstructure analysis suggested that the increase in strength was due to the self-crack-healing behavior of the composite by surface oxide glass, such as B2O3-, SiO2-rich liquids, and borosilicate glass. However, oxide evaporation and formation of gas (i.e., B2O3 and CO) were found to be detrimental to for the crack-healing ability. Oxidation behavior during the preoxidation process followed parabolic-law kinetics. [ABSTRACT FROM AUTHOR]

The present work reported the effect of addition of ZrO2 on the microstructure and mechanical properties of ZrB2-based ceramic composites by means of hot-pressed sintering. Observation of microstructure and systematic testing results of mechanical properties were carried out. Through X-ray diffraction analysis and calculation of the volume fraction of ZrO2 phase transformability, the toughening mechanism of the present composites was explored. The phase transformation toughening by ZrO2 additive played an important role in improving the fracture toughness of ZrB2-based composites. [ABSTRACT FROM AUTHOR]

Uniaxial tensile tests were carried out in the temperature range of 250–450°C and the strain rate range of 0.7×10−3–1.4×10−1 s−1 to evaluate the superplasticity of AZ31 Mg alloy. The threshold stress which characterizes the difficulty for grain boundary sliding was calculated at various temperatures. The surface relieves of superplastically deformed specimens were observed by using a scanning electronic microscope (SEM). Results show that, at the temperature of 400°C and strain rate of 0.7×10−3s−1, the strain rate sensitivity exponent, i e, m value reaches 0.47 and the maximum elongation of 362.5% is achieved. Grain boundary sliding (GBS) is the primary deformation mechanism and characterized by a pronounced improvement in the homogeneity with increasing temperatures. A large number of filaments were formed at the end of deformation and integranular cavities were produced with the necking and fracture of filaments. Finally, the model for the formation of intergranular cavities was proposed. [ABSTRACT FROM AUTHOR]

Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering (LPS). The Si2N2O phase was generated by an in-situ reaction 2Si3N4(s)+1.5 O2(g)=3Si2N2O(s)+N2(g). The content of Si2N2O phase up to 60% in the volume was obtained at a sintering temperature of 1650°C and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1700°C. The sintering procedure contains a complex crystallization and a phase transition: amorphous silicon nitride→equiaxial α-Si3N4→equiaxial β-Si3N4→rod-like Si2N2O→needle-like β-Si3N4. Small round-shaped β-Si3N4 particles were entrapped in the Si2N2O grains and a high density of staking faults was situated in the middle of Si2N2O grains at a sintering temperature of 1650°C. The toughness increased from 3.5 MPa·m1/2 at 1600°C to 7.2 MPa·m1/2 at 1800°C. The hardness was as high as 21.5 GPa (Vickers) at 1600°C. [ABSTRACT FROM AUTHOR]