Corrosion fatigue behavior of extruded magnesium alloy AZ80-T5 in a 5% NaCl environment

The corrosion fatigue behavior of extruded AZ80-T5 magnesium alloy has been investigated in three different environments: (1) a low humidity environment (35-40% relative humidity), (2) a high-humidity environment (80% relative humidity), and (3) a 5 wt.% NaCl environment. Fatigue tests were conducted under axial loading at a stress ratio of −1 and at a frequency of 20 Hz. It was found that in both the high-humidity environment and in the 5 wt.% NaCl environment the fatigue strength was reduced relative to the low humidity environment, especially in the NaCl environment: the reduction rates of fatigue limit under high humidity and NaCl environments were 18%, and 78%, respectively. The reduction of fatigue strength under the corrosive environments was attributed to the pit formation and growth. At low stress amplitudes, multiple pits were formed and coalesced to form a large pit under NaCl environment. A fatigue crack nucleated when the pit grew to the critical size.     

Static thrust analysis of a cylindrical moving-core linear oscillatory actuator

This paper considers materials for the movers, the volume ratio of the stator and of the mover, and the structure of the mover in a cylindrical moving iron-type linear oscillatory actuator (LOA) having a permanent magnet. As a result, we obtain the following:

• (1) the static thrust characteristics are evaluated on two movers: movers P and S are made of a permendur and a stainless steel, respectively. It is clarified that the static thrust of the mover P is 30 percent larger than that of the mover S;
• (2) it is suggested that the structure of the mover P should be improved to eliminate a “lump” in the static thrust-displacement curve due to the step on the mover, and which disturbs the smooth motion of the LOA.

     

Intramolecular electron transfer in a cytochrome P450cam system with a site-specific branched structure

Cytochrome P450 (P450) is an attractive oxygenase due to the diverse catalytic reactions and the broad substrate specificity. Class I P450s require an excess concentration (more than 10 times) of iron-sulfur proteins, which transfer electrons to P450s, to attain the maximum catalytic activity and this requirement is a critical bottleneck for practical applications. Here, we show a site-specific branched fusion protein of P450 with its electron transfer proteins using enzymatic cross-linking with transglutaminase. A branched fusion protein of P450 from Pseudomonas putida (P450cam), which was composed of one molecule each of P450cam, putidaredoxin (Pdx) and Pdx reductase, showed higher catalytic activity (306 min(-1)) and coupling efficiency (99%) than the equimolar reconstitution system due to the intramolecular electron transfer. The unique site-specific branched structure simply increased local concentration of proteins without denaturation of each protein. Therefore, enzymatic post-translational protein manipulation can be a powerful alternative to conventional strategies for the creation of multicomponent enzyme systems with novel proteinaceous architecture.     

500kV交联聚乙烯电缆附件的开发

主要介绍了所开发的500 kV交联聚乙烯(XLPE)电缆附件的结构特点,对开发过程中的材料选择、绝缘设计、机械强度设计等开发要点进行了分析。所开发的500 kV XLPE电缆附件通过了GB/T 22078.3—2008规定的型式试验及预鉴定试验。     

Simultaneous construction of polymer backbone and side chains by terpolymerization. Synthesis of polyethers with the allyl side chains from dialdehydes, alkylene bis(trimethylsilyl) ethers, and allyltrimethylsilane

Polyethers with allyl side chains were synthesized by the simultaneous acid-catalyzed reaction of dialdehydes (1), alkylene bis(trimethylsilyl) ethers (2), and allyltrimethylsilane (3). The reactions of 1, 2 and 3 were carried out in the presence of 10 mol% of triphenylmethyl (trityl) perchlorate at −55°C to yield polyethers having allyl groups in the side chains. When the dialdehyde having the ester moieties as 1, ethylene bis(trimethylsilyl) ether and 1,4-bis(trimethylsiloxy)cyclohexane as 2 were used, high molecular weight polymers were obtained. In the polymerizations at ambient temperature, the polymer was precipitated during the reaction because of crosslinking between the aromatic rings via a trityl perchlorate assisted Friedel-Crafts reaction. The soluble polyether with the allyl side chains reacted with 1,2-ethanedithiol in the presence of a radical initiator in benzene at 60°C to yield a crosslinked polymer quantitatively within 1 h. This polymer synthesis is unusual in that it concurrently constructs both the polymer backbone and the functional side chains from three monomers.     

Imide oligomers having internal acetylene units in the backbone

Imide oligomers having internal acetylene groups in the backbone were prepared utilizing bis(3-aminophenyl)acetylene as an internal acetylene source. 2,2′-Bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenontetracarboxylic dianhydride (BTDA), and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) were used as acid dianhydride monomers. Amine-terminated oligomers with average degree of polymerization (DP) of 3, 5, and I 1 were prepared by controlling the ratio of monomers, and were end-capped with phthalic anhydride. Anhydride-terminated oligomers were similarly prepared and were end-capped with aniline. Imidization was conducted by refluxing in toluene. The DSC of the oligoimides containing internal acetylene units showed exotherm due to the crosslinking reaction of acetylene units. Onset temperature of the exotherm was 300–370°C, depending on the chemical structure and DP of oligoimide. By the thermal cure at high temperatures, the amount of exotherm decreased and exotherm shifted to higher temperature. Melt-processing of the oligoimides was carried out using a hydraulic press at 400°C. Melt-processed films were dark brown, opaque, and somewhat brittle. The films became less brittle with the increase of the DP of the oligomers. The films showed excellent thermal properties; T_g's were above 375°C, and their films maintained their mechanical properties aboveT_g.     

A Potential Serum N-glycan Biomarker for Hepatitis C Virus-Related Early-Stage Hepatocellular Carcinoma with Liver Cirrhosis

Detection of early-stage hepatocellular carcinoma (HCC) is beneficial for prolonging patient survival. However, the serum markers currently used show limited ability to identify early-stage HCC. In this study, we explored human serum N-glycans as sensitive markers to diagnose HCC in patients with cirrhosis. Using a simplified fluorescence-labeled N-glycan preparation method, we examined non-sialylated and sialylated N-glycan profiles from 71 healthy controls and 111 patients with hepatitis and/or liver cirrhosis (LC) with or without HCC. We found that the level of serum N-glycan A2G1(6)FB, a biantennary N-glycan containing core fucose and bisecting GlcNAc residues, was significantly higher in hepatitis C virus (HCV)-infected cirrhotic patients with HCC than in those without HCC. In addition, A2G1(6)FB was detectable in HCV-infected patients with early-stage HCC and could be a more accurate marker than alpha-fetoprotein (AFP) or protein induced by vitamin K absence or antagonists-II (PIVKA-II). Moreover, there was no apparent correlation between the levels of A2G1(6)FB and those of AFP or PIVKA-II. Thus, simultaneous use of A2G1(6)FB and traditional biomarkers could improve the accuracy of HCC diagnosis in HCV-infected patients with LC, suggesting that A2G1(6)FB may be a reliable biomarker for early-stage HCC patients.     

Self-Emergent Protocells Generated in an Aqueous Solution with Binary Macromolecules through Liquid-Liquid Phase Separation

Recently, liquid–liquid phase separation (LLPS) has attracted considerable attention among researchers in the life sciences as a plausible mechanism for the generation of microstructures inside cells. LLPS occurs through multiple nonspecific interactions and does not always require a lock-and-key interaction with a binary macromolecular solution. The remarkable features of LLPS include the non-uniform localization and concentration of solutes, resulting in the ability to isolate certain chemical systems and thereby parallelize multiple chemical reactions within the limited space of a living cell. We report that, by using the macromolecules, poly(ethylene glycol) (PEG) and dextran, that exhibit LLPS in an aqueous solution, cell-sized liposomes are spontaneously formed therein in the presence of phospholipids. In this system, LLPS is generated through the depletion effect of macromolecules. The results showed that cell-like microdroplets entrapping DNA wrapped by a phospholipid layer emerge in a self-organized manner.     

Synthesis and polymerization of methacrylate bearing a phosphorylcholine, analogous moiety

Summary A new type of methacrylate bearing a phosphorylcholine analogous moiety, 2-[2'-(trimethylammonium)-1-methylethyl-phosphoryl]ethyl methacrylate (TMPM) was synthesized. TMPM was radically homopolymerized and copolymerized with BMA to obtain the polymers. The critical micelle concentration (CMC) of TMPM was 4.9 × 10⁻² mol/l according to the fluorescent probe method. Received: 11 June 2001/Revised version: 30 July 2001/Accepted: 31 July 2001     

Preparation of thermosensitive and superabsorbent polymer hydrogels from trialkyl‐4‐vinylbenzyl phosphonium chloride‐N‐isopropylacrylamide‐N,N′‐methylenebisacrylamide copolymers and their properties

Thermosensitive and superabsorbent polymer hydrogels were synthesized by copolymerization of three kinds of tri‐n‐alkyl vinylbenzyl phosphonium chlorides (TRVB) with different lengths of alkyl chains, N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide (MBAAm). The water‐absorption ability and antibacterial activity of the hydrogels against Staphylococcus aureus (S. aureus) were investigated. The water content of TRVB–NIPAAm–MBAAm copolymers decreased with increasing temperature and increased with increasing phosphonium groups in the copolymers, while it decreased with increasing chain length of the alkyl groups in the phosphonium groups as well as with an increasing degree of crosslinking in the copolymers. The TRVB–NIPAAm–MBAAm copolymers with a higher TRVB content in the copolymers exhibited higher antibacterial activity against S. aureus, but decreased with increasing chain length of alkyl groups in phosphonium groups. The TRVB–NIPAAm–MBAAm copolymers exhibited the highest antibacterial activity at 30°C against S. aureus in deionized water. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 115–124, 2001