XAFS Analysis for Niobium Carbide Particle Growth on Silica Support During Preparation Process

SiO₂-supported NbC catalysts were prepared by using temperature-programmed reactions (TPR). XAFS analysis confirmed that Nb₂O₅ was reduced to NbO₂ in the first TPR stage and converted into NbC in the second TPR stage. Nb particles grew only in the second TPR stage. Formation of highly dispersed NbC particles on SiO₂ surfaces was achieved.     

Synthesis and properties of optically active substituted polyacetylenes having carboxyl and/or amino groups

Polyacetylenes having carboxyl and/or amino groups in the side chain were synthesized by the polymerization of N-(2-propynyloxycarbonyl)-l-alanine (1) and l-alanine N-propargylamide (2) catalyzed with a rhodium cation complex. Poly(1_0.5-co-2_0.5) exhibited a larger CD signal than the homopolymers. The polymer mixtures obtained by the polymerization of 1 in the presence of poly(2), and those obtained by the polymerization of 2 in the presence of poly(1) showed specific rotations larger than calculated. The polymerization of propargylamine in the presence of poly(1) did not exhibit significant effect, while the polymer mixtures obtained by the polymerization of propiolic acid in the presence of poly(2) exhibited [α]_D of positive sign, although poly(2) alone exhibited [α]_D of negative sign.     

Thermoelectric Properties of Reduced Polycrystalline Sr0.5Ba0.5Nb2O6 Fabricated Via Solution Combustion Synthesis

The thermoelectric properties of bulk polycrystalline Sr_0.5Ba_0.5Nb₂O₆ (SBN50) fabricated via solution combustion synthesis (SCS) and reduced at temperatures of 900°C–1150°C were explored. The Seebeck coefficient (S) of all samples increased over the entire range of testing temperatures; a peak S value of ?281 μV/K was obtained at 930 K for the sample reduced at 900°C. A metal‐insulator transition was observed in the electrical conductivity (σ) of samples reduced at 1000°C–1150°C, whereas only semiconducting electrical behavior was observed for the sample reduced at 900°C. An optimal balance between S and σ was achieved for the pellet reduced at 1000°C, which exhibited a maximum power factor of 1.78 μW/cm·K² at 930 K. Over a temperature range of 300–930 K, the thermal conductivity (κ) of as‐processed and reduced (1000°C) SBN50 was found to be 1.03–1.4 and 1.46–1.84 W/m·K, respectively. A maximum figure of merit (ZT) of 0.09 was obtained at 930 K for the 1000°C‐reduced sample. X‐ray photoelectron spectroscopy revealed that the Nb²⁺ peak intensity increased at higher reduction temperatures, which could possibly lead to a distortion of NbO₆ octahedra and a decrease in the Seebeck coefficient.     

Influence of formic acid on electrochemical properties of high‐porosity Pt/TiN nanoparticle aggregates

Platinum‐deposited titanium nitride (Pt/TiN) nanoparticle aggregates with high porosities were successfully prepared via a self‐assembly‐assisted spray pyrolysis method. The addition of formic acid (HCOOH) had a significant influence on the process, promoting the simultaneous formation of metallic Pt and reduction on the surface of the TiN support material. Complete reduction of the Pt/TiN nanoparticle aggregates improved the catalytic activity. The electrochemical surface area (ECSA) of Pt/TiN with HCOOH (Pt/TiN_w/HCOOH) was 87.15 m²/g‐Pt, which was higher than that of Pt/TiN without HCOOH (Pt/TiN_w/o‐HCOOH). The catalytic durability of Pt/TiN_w/HCOOH was twice that of Pt/TiN_w/o‐HCOOH. An effective strategy for obtaining carbon‐free catalysts with high activities and durabilities was identified. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2753–2760, 2013     

多乙烯基单体对溴化丁基胶电子束交联的敏化效应

观察到溴化丁基胶(BIIR)在加速器产生的电子束辐照下可发生交联反应,测得其凝胶化剂量为12 kGy。在剂量较低时辐照产物的凝胶含量与交联密度均随剂量增加而提高,但在80 kGy后则随剂量增加而呈下降趋势。试验了5种多乙烯基单体以敏化BIIR的交联反应,从而避免高剂量下的降解现象。结果表明TMPT(三甲基丙烯酸三羟甲基丙烷酯)是有效的敏化剂,配有TMPT的BIIR交联产物其拉伸强度随TMPT用量增大而明显提高。     

miR-29 Represses the Activities of DNA Methyltransferases and DNA Demethylases

Members of the microRNA-29 (miR-29) family directly target the DNA methyltransferases, DNMT3A and DNMT3B. Disturbances in the expression levels of miR-29 have been linked to tumorigenesis and tumor aggressiveness. Members of the miR-29 family are currently thought to repress DNA methylation and suppress tumorigenesis by protecting against de novo methylation. Here, we report that members of the miR-29 family repress the activities of DNA methyltransferases and DNA demethylases, which have opposing roles in control of DNA methylation status. Members of the miR-29 family directly inhibited DNA methyltransferases and two major factors involved in DNA demethylation, namely tet methylcytosine dioxygenase 1 (TET1) and thymine DNA glycosylase (TDG). Overexpression of miR-29 upregulated the global DNA methylation level in some cancer cells and downregulated DNA methylation in other cancer cells, suggesting that miR-29 suppresses tumorigenesis by protecting against changes in the existing DNA methylation status rather than by preventing de novo methylation of DNA.     

Correlations of Hepatic Hemodynamics,Liver Function,and Fibrosis Markers in Nonalcoholic Fatty Liver Disease: Comparison with Chronic Hepatitis Related to Hepatitis C Virus

The progression of chronic liver disease differs by etiology. The aim of this study was to elucidate the difference in disease progression between chronic hepatitis C (CHC) and nonalcoholic fatty liver disease (NAFLD) by means of fibrosis markers, liver function, and hepatic tissue blood flow (TBF). Xenon computed tomography (Xe-CT) was performed in 139 patients with NAFLD and 152 patients with CHC (including liver cirrhosis (LC)). The cutoff values for fibrosis markers were compared between NAFLD and CHC, and correlations between hepatic TBF and liver function tests were examined at each fibrosis stage. The cutoff values for detection of the advanced fibrosis stage were lower in NAFLD than in CHC. Although portal venous TBF (PVTBF) correlated with liver function tests, PVTBF in initial LC caused by nonalcoholic steatohepatitis (NASH-LC) was significantly lower than that in hepatitis C virus (C-LC) (p = 0.014). Conversely, the liver function tests in NASH-LC were higher than those in C-LC (p < 0.05). It is important to recognize the difference between NAFLD and CHC. We concluded that changes in hepatic blood flow occurred during the earliest stage of hepatic fibrosis in patients with NAFLD; therefore, patients with NAFLD need to be followed carefully.     

Elongation and Contraction of Scallop Sarcoplasmic Reticulum (SR): ATP Stabilizes Ca2+-ATPase Crystalline Array Elongation of SR Vesicles

The Ca²⁺-ATPase is an integral transmembrane Ca²⁺ pump of the sarcoplasmic reticulum (SR). Crystallization of the cytoplasmic surface ATPase molecules of isolated scallop SR vesicles was studied at various calcium concentrations by negative stain electron microscopy. In the absence of ATP, round SR vesicles displaying an assembly of small crystalline patches of ATPase molecules were observed at 18 µM [Ca²⁺]. These partly transformed into tightly elongated vesicles containing ATPase crystalline arrays at low [Ca²⁺] (≤1.3 µM). The arrays were classified as ‘’tetramer’’, “two-rail” (like a railroad) and ‘’monomer’’. Their crystallinity was low, and they were unstable. In the presence of ATP (5 mM) at a low [Ca²⁺] of ~0.002 µM, “two-rail” arrays of high crystallinity appeared more frequently in the tightly elongated vesicles and the distinct tetramer arrays disappeared. During prolonged (~2.5 h) incubation, ATP was consumed and tetramer arrays reappeared. A specific ATPase inhibitor, thapsigargin, prevented both crystal formation and vesicle elongation in the presence of ATP. Together with the second part of this study, these data suggest that the ATPase forms tetramer units and longer tetramer crystalline arrays to elongate SR vesicles, and that the arrays transform into more stable “two-rail” forms in the presence of ATP at low [Ca²⁺].     

Strengthening of Porous Alumina by Pulse Electric Current Sintering and Nanocomposite Processing

Porous Al₂O₃ and SiC–dispersed-Al₂O₃ (Al₂O₃/SiC) nanocomposites with improved mechanical properties were fabricated using pulse electric current sintering (PECS). Microstructures with fine grains and enhanced neck growth, as well as high fracture strength, could be achieved via PECS of Al₂O₃. The incorporation of fine SiC particles into an Al₂O₃ matrix significantly increased the fracture strength of porous Al₂O₃. Based on microstructural observations, it was revealed that the refinement of Al₂O₃ grains and neck growth occurred by PECS and nanocomposite processing.     

Micro machining for control of wettability with surface topography

A micro fabrication is presented to manufacture hydrophobic surfaces with micro-scale structures. Hydrophobicity is controlled with the shape and the alignment of micro pillars in the structure. The structures are manufactured in large areas at high production rates in the following processes: (1) the structure is fabricated on a tool by focused ion beam sputtering; (2) the reverse structure is formed on a metal plate by incremental stamping using the structured tool; and (3) the structure is transferred onto plastic plates by molding. A consecutive stamping is also proposed to fabricate several structures on a surface accurately with a structured tool, in which the moving pitch of the structured tool is numerically controlled. The effect of the surface topography on hydrophobicity is discussed with measuring contact angles on the structured surfaces in the water droplet tests. Hydrophobicity on the plastic plate is associated with the solid fraction on the structured surface based on the Cassie–Baxter model. A larger contact angle is observed for a smaller solid fraction of the surface.