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Although significant increase in mechanical properties has been achieved in α-SiAlON ceramics by introducing self-toughening bimodal microstructure, the bimodal microstructure may not always result in better cutting performance of α-SiAlON tool inserts. Herein Dy-α-SiAlON ceramics were prepared by hot-pressing at 1900°C under 30MPa. Diameter and aspect ratio of the large elongated α-SiAlON grains pivotal to formation of bimodal microstructures were regulated by using 0-5wt.% Dy2O3 as a sintering additive. Mechanical properties and cutting performance of α-SiAlON tool inserts were evaluated. The results showed good Vickers hardness (19.0-19.7GPa) and fracture toughness (3.61-4.18MPa•m1/2) increasing with crack propagation length. However, transverse section of the large elongated grains was revealed as critical crack to cause premature fracture of the α-SiAlON ceramics. Fracture rather than attrition wear was recognized as dominant mechanism for tool failure, indicating that for better cutting performance of the α-SiAlON tool inserts a selftoughening microstructure consisting of thinner grains with large aspect ratio is required.

Dealing with physiological stress is a necessity for all organisms, and the pathways charged with this task are highly conserved in Metazoa . Accumulating evidence highlights cell-nonautonomous activation as an important mode of integrating stress responses at the organism level. Work in Caenorhabditis elegans highlighted the importance of such regulation for the unfolded protein response (UPR) and for gene expression downstream of the longevity-associated transcription factor DAF-16 Here we describe a role for the JNK homolog KGB-1 in cell-nonautonomous regulation of these two response modules. KGB-1 protects developing larvae from heavy metals and from protein folding stress (which we found to be independent of canonical UPR pathways), but sensitizes adults to the same stress, further shortening life span under normal conditions. This switch is associated with age-dependent antagonistic regulation of DAF-16 Using transgenic tissue-specific KGB-1 expression or tissue-specific KGB-1 activation we examined the contributions of KGB-1 to gene regulation, stress resistance, and life span. While cell-autonomous contributions were observed, particularly in the epidermis, cell-nonautonomous contributions of neuronal KGB-1 (and also in muscle) were effective in driving intestinal gene induction, age-dependent regulation of intestinal DAF-16, and stress resistance, and did not require KGB-1 expression in the target tissue. Additional genetic analyses revealed requirement for UNC-13 in mediating neuronal contributions, indicating involvement of neurotransmission. Our results expand the role of KGB-1 in stress responses from providing local cellular protection to integrating stress responses at the level of the whole organism.

The mitochondrial unfolded protein response (UPRmt) can be triggered in a cell-non-autonomous fashion across multiple tissues in response to mitochondrial dysfunction. The ability to communicate information about the presence of mitochondrial stress enables a global response that can ultimately better protect an organism from local mitochondrial challenges. We find that animals use retromer-dependent Wnt signaling to propagate mitochondrial stress signals from the nervous system to peripheral tissues. Specifically, the polyQ40-triggered activation of mitochondrial stress or reduction of cco-1 (complex IV subunit) in neurons of C. elegans results in the Wnt-dependent induction of cell-non-autonomous UPRmt in peripheral cells. Loss-of-function mutations of retromer complex components that are responsible for recycling the Wnt secretion-factor/MIG-14 prevent Wnt secretion and thereby suppress cell-non-autonomous UPRmt. Neuronal expression of the Wnt ligand/EGL-20 is sufficient to induce cell-non-autonomous UPRmt in a retromer complex-, Wnt signaling-, and serotonin-dependent manner, clearly implicating Wnt signaling as a strong candidate for the "mitokine" signal.

Aflatoxin B1 (AFB1) contamination is a serious threat to nutritional safety and public health. The CotA-laccase from Bacillus licheniformis ANSB821 previously reported by our laboratory showed great potential to degrade AFB1 without redox mediators. However, the use of this CotA-laccase to remove AFB1 in animal feed is limited because of its low catalytic efficiency and low expression level. In order to make better use of this excellent enzyme to effectively degrade AFB1, twelve mutants of CotA-laccase were constructed by site-directed mutagenesis. Among these mutants, E186A and E186R showed the best degradation ability of AFB1, with degradation ratios of 82.2% and 91.8% within 12 h, which were 1.6- and 1.8-times higher than those of the wild-type CotA-laccase, respectively. The catalytic efficiencies (kcat/Km) of E186A and E186R were found to be 1.8- and 3.2-times higher, respectively, than those of the wild-type CotA-laccase. Then the expression vectors pPICZαA-N-E186A and pPICZαA-N-E186R with an optimized signal peptide were constructed and transformed into Pichia pastoris GS115. The optimized signal peptide improved the secretory expressions of E186A and E186R in P. pastoris GS115. Collectively, the current study provided ideal candidate CotA-laccase mutants for AFB1 detoxification in food and animal feed and a feasible protocol, which was desperately needed for the industrial production of CotA-laccases. [ABSTRACT FROM AUTHOR]

A new route based on HfO2 + B4C + C → HfB2 + HfC + CO reaction was developed to synthesize HfB2‐HfC hybrid powders. X‐ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and transmission electron microscopy were used to evaluate the powder products. The effects of excess additions of B4C and C on the phase constituents of the powder products were investigated. Thermodynamics of relevant reactions for the synthesis of the hybrid powders were calculated to guide the selection of compositions and processing parameters. The results indicated that HfB2‐HfC hybrid powders were obtained by reaction at 1750°C for 1 h. HfB2:HfC phase content ratios showed a dependence on B4C and C additions. The obtained hybrid powders exhibited good oxidation resistance with an oxidation activation energy of 303 kJ/mol. Good sinterability of the powder products was demonstrated by spark plasma sintering at 2100°C. The consolidated ceramics based on them measured good Vickers' hardness values (>26.0 ±.5 GPa) and fracture toughness (>3.78 ±.27 MPa·m1/2). [ABSTRACT FROM AUTHOR]