RESUMO
Silicon carbide (SiC) ceramics with high bending strength were prepared by hot pressing sintering (HPS) with yttrium aluminum garnet (Y3Al5O12, YAG) as sintering additive, and the effects of YAG content and sintering temperature on the sintering behavior, microstructure and mechanical properties of SiC ceramics were investigated in detail. The uniform distribution of YAG to form a liquid phase and the driving force provided by hot pressing sintering decrease the sintering temperature, improve the densification of SiC ceramics, and refine the crystal size. By means of suitable sintering conditions with the additional amount of YAG of 5 wt%, the sintering temperature of 1950 °C and a pressure of 30 MPa, the resultant SiC/YAG composite ceramics possesses high sintering and mechanical properties with the relative density of 98.53%, the bending strength of 675 MPa, the Vickers hardness of up to 17.92 GPa, and the elastic modulus of 386 GPa. The as-prepared SiC/YAG composite ceramics are promisingly used as the dry gas seal materials in the centrifugal compressors.
RESUMO
Transition metal sulphide electrocatalytic materials possess the bright overall water-splitting performance of practical electrocatalytic technologies. In this study, an amethyst-like MoS2@Ni9S8/Co3S4 rod electrocatalyst was constructed via a one-step hydrothermal method with in-situ-grown ZIF-67 nanoparticles on nickel foam (NF) as a precursor. The rational design and synthesis of MoS2@Ni9S8/Co3S4 endow the catalyst with neat nanorods morphology and high conductivity. The MoS2@Ni9S8/Co3S4/NF with the amethyst-like rod structure exposes abundant active sites and displays fast electron-transfer capability. The resultant MoS2@Ni9S8/Co3S4/NF exhibits outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic activities, with low overpotentials of 81.24 mV (HER) at 10 mA cm-2 and 159.67 mV (OER) at 50 mA cm-2 in 1.0 M KOH solution. The full-cell voltage of overall water splitting only achieves 1.45 V at 10 mA cm-2. The successful preparation of the amethyst-like MoS2@Ni9S8/Co3S4 rod electrocatalyst provides a reliable reference for obtaining efficient electrocatalysts for overall water splitting.
RESUMO
We present a Fourier finite element modeling of light emission of dipolar emitters coupled to infinitely long waveguides. Due to the translational symmetry, the three-dimensional (3D) coupled waveguide-emitter system can be decomposed into a series of independent 2D problems (2.5D), which reduces the computational cost. Moreover, the reduced 2D problems can be extremely accurate, compared to its 3D counterpart. Our method can precisely quantify the total emission rates, as well as the fraction of emission rates into different modal channels for waveguides with arbitrary cross-sections. We compare our method with dyadic Green's function for the light emission in single mode metallic nanowire, which yields an excellent agreement. This method is applied in multi-mode waveguides, as well as multi-core waveguides. We further show that our method has the full capability of including dipole orientations, as illustrated via a rotating dipole, which leads to unidirectional excitation of guide modes. The 2.5D Finite Element Method (FEM) approach proposed here can be applied for various waveguides, thus it is useful to interface single-photon single-emitter in nano-structures, as well as for other scenarios involving coupled waveguide-emitters.
RESUMO
Studies of the epigenome have attracted little interest in nephrology, especially in uremia. Several lines of evidence have suggested that there are links between genomic DNA hypomethylation and cardiovascular complications in uremia patients. However, to date, our knowledge about the alterations in histone methylation in uremia is unknown. H3K4me3 variations were analyzed in peripheral blood mononuclear cells from 20 uremia patients and 20 healthy subjects, using chromatin immunoprecipitation microarray (ChIP-chip) approach. ChIP-real-time polymerase chain reaction (PCR) was used to validate the microarray results. mRNA expression and DNA methylation status can be further analyzed by quantitative (q) reverse transcription (RT)-PCR and methyl-DNA immunoprecipitation (MeDIP)-qPCR, respectively. Seven hundred twenty-six increased and 218 decreased H3K4me3 genes displaying significant H3K4me3 differences were found in uremia patients compared with healthy subjects. The results of ChIP-real-time PCR coincided well with microarray results. Expression analysis by qRT-PCR revealed positive correlations between mRNA and H3K4me3 levels. Aberrant DNA methylation can also be found on selected positive genes (CNOT1 PLTP EDG1 TCF3 KIR3DL2). In addition, we even found that there is an inverse relationship between H3K4me3 and promoter DNA methylation in uremia patients. Our studies indicate that there are significant alterations of H3K4me3 in uremia patients; these significant H3K4me3 candidates may help to explain the immunological disturbance and high cardiovascular complications in uremia patients. Such novel findings show the significance of H3K4me3 as a potential biomarker or promising target for epigenetic-based uremia therapies.
