Charge accumulation mechanism in oil/pressboard composite insulation system based on optical measurement of electric field

It is important to investigate electrostatic charging phenomena in insulating oil pressboard (PB) composite system in electrical insulation design of oil-immersed power transformers. Our research aim was to clarify the charge accumulation mechanism at the oil/PB interface under static and flowing oil. In this paper, we directly measured the time variation of the electric field in the insulation system using a Kerr electro-optic technique. Results show the time decaying characteristics of an electric field in oil by charge accumulation. The results are influenced by oil flow conditions. Based on the measurement results, we propose a theoretical model for charge accumulation to clarify the process quantitatively. In the model we took the oil volume contributing to the charge accumulation into account, and analyzed the charge behavior. Finally, we clarified the charge accumulation mechanism at the oil/PB interface under oil flow conditions both with and without charging.     

A novel tumor-related protein, C7orf24, identified by proteome differential display of bladder urothelial carcinoma

Proteome analysis of bladder cancer with narrow-range pH 2-DE has identified a novel protein on chromosome 7 encoded by ORF 24 (C7orf24) as one of the highly expressed proteins in cancer cells. C7orf24 is currently registered in the protein database as a hypothetical protein with unknown function. The homologs of C7orf24 in other animals have also been registered as putative protein genes. Western blot analysis using a mAb against C7orf24 confirmed its higher expression in bladder cancer compared with normal tissue. Several other cancer cell lines were also found to express C7orf24. However, the introduction of C7orf24 into Rat-1 or NIH3T3 cells did not cause malignant transformation. A stable transfectant of NIH3T3 cells with recombinant retrovirus vector was produced for a growth rate assay, and a higher growth rate was observed in C7orf24-expressing cells compared with the controls. Six kinds of small interfering RNAs (siRNAs) were then produced, and C7orf24-siRNA#5 showed a strong knockdown effect on protein expression and significant antiproliferative effects on cancer cell lines were demonstrated by the MTT assay. Therefore, C7orf24 may have an important role in cancer cell proliferation, and may be an appropriate therapeutic target molecule against cancer.     

Effect of substrate pretreatment on diamond deposition in a microwave plasma

The evolution of substrate surface at an early stage of diamond formation in a microwave plasma was studied with a high-resolution scanning electron microscope. Changes in the shape, size and population of diamond particles at the same points were observed at prescribed time intervals. The substrate used was a mirror-polished Si (100) plate which was ultrasonically pretreated with diamond, c-BN or -Al₂O₃ powders prior to the deposition. The pretreatment introduced fragments of the abrasives as well as many scratches on the substrate surface. When the diamond and c-BN abrasive were used, diamond was formed on the surface of abrasive residues. With -Al₂O₃ abrasive powder, on the other hand, residues vanished in the plasma and no deposition was observed. These results suggest that the deposition site of diamond from the vapour phase is dependent on the type of abrasive powder used for substrate pretreatment.     

Stereospecific analysis of glycerolipids of egg yolk of Japanese quail (Coturnix coturnix japonica)

Phosphatidylcholine, phosphatidylethanolamine and triacylglycerol were isolated from egg yolk of the Japanese quail. Fatty acid compositions at the two and three positions of glycerol in the glycerolipids were determined by stereospecific analysis employing phospholipase A₂. The distribution of the total number of carbon atoms in the fatty acid moieties of triacylglycerol was also quantitated by high temperature gas liquid chromatography. The distribution of acyl groups in each of the positions of the phosphatidylcholine, phosphatidylethanolamine and triacylglycerol was not random, and each position has a characteristic composition. The phosphatidylcholine and phosphatidylethanolamine had distinctive fatty acid distributions for positionsn-2 of the triacylglycerol had a predominance of unsaturated fatty acids of which 18∶1 (69.9%) was the major component. Positionsn-3 contained 49.3% saturated fatty acids and was more saturated than positionsn-1 by 8.1%. The experimentally determined distribution of the carbon numbers in triacyl glycerol deviated significantly from the distribution predicted by 1-random-2-random-3-random association of the fatty acids. The data suggest that in Japanese quail there is marked preferencial synthesis of some triacylglycerols.     

Controlled radical polymerization of styrene initiated by diethyldithiocarbamate‐mediated iniferters

We demonstrated that density functional theory calculations provide a prediction of the trends in C‐S bond dissociation energies and atomic spin densities for radicals using two model compounds as diethyldithiocarbamate (DC)‐mediated iniferters. On the basis of this information, we synthesized 2‐(N,N‐diethyldithiocarbamyl)isobutylic acid (DTCA) and (4‐cyano‐4‐diethyldithiocarbamyl)pentanoic acid (CDPA) as DC‐mediated iniferters. Free‐radical polymerizations of styrene (St) were carried out in benzene initiated by DTCA or CDPA under UV irradiation. The first‐order time‐conversion plots showed the straight line for the UV irradiation system initiated by CDPA indicating the first order in monomer. The number‐average molecular weight (M_n) of the polystyrene (PSt) increased in direct proportion to monomer conversion. The molecular weight distribution (M_w/M_n) of the PSt was in the range of 1.3–1.7. It was concluded this polymerization system proceeded with a controlled radical mechanism. However, photopolymerization of styrene initiated by DTCA showed nonliving polymerization consistent with UV initiation. Theoretical predictions supported these experimental results. Methacrylic acid (MA) could also be polymerized in a living fashion with such a PSt precursor as a macroinitiator because PSt exhibited a DC group at its terminal end. This system could be applied to the architecture of block copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 413–418, 2005     

ZrO2 promoted with sulfate,iron and manganese: a solid superacid catalyst capable of low temperaturen-butane isomerization

A sulfated oxide of zirconium, iron and manganese is prepared and shown to isomerizen-butane to isobutane at 35°C with rates approximately 2–3 orders of magnitude greater than sulfated zirconia as claimed by workers at Sun Refining and Marketing Company. Temperature programmed desorption of benzene is used to investigate the acidity of this remarkable catalyst. Adsorbed benzene is oxidized to CO₂ by the triply promoted oxide catalyst; CO₂, SO₂ and O₂ are found to desorb at 525, 575 and 560°C, respectively. Sulfated zirconia does not adsorb benzene in a similar manner. The results from the temperature programmed desorption of benzene cannot be correlated with then-butane isomerization activity.On leave from The University of Tokyo.     

Mutual separation of two monovalent metal ions by multistage electrodialysis

A multistage electrodialyzer having an enriching section and a stripping one has been developed to separate monovalent cation species in the aqueous solution. A feed solution containing LiCl and KCl is supplied to the middle stage of the dialyzer, and a solution of HCl is supplied to the cathode stage. Stages from cathode to feed are the enriching section and those from feed to anode are stripping section. Aqueous solution flows from the cathode stage toward the anode stage as a reflux flow. The ratio K⁺/Li⁺ in the enriching product increased with the increase in reflux flow rate and decreased with the increase in current density, while the ratio Li⁺/K⁺ in the stripping product increased with the current density and decreased with the reflux flow rate. Simulation by a stage to stage calculation was carried out by use of the operating equation based on mass balance and the relation of permselectivities alternatively. The calculated results were in good agreement with the experimental ones, and indicated that a large yield of product as well as a large concentration ratio can be achieved by increasing stage number.     

Reclamation of vulcanized rubbers by chemical degradation. V. Degradation of vulcanized synthetic isoprene rubber by the phenylhydrazine–ferrous chloride system

The changes of effective network chain density and soluble fraction were measured for gum vulcanizates of synthetic isoprene rubber (IR) during the degradation by the phenylhydrazine–ferrous chloride system. From the decrease of effective network chain density and the increase of soluble fraction, the network chain was concluded to undergo a severance reaction by the reagents in the following order of ease: polysulfide linkage > monosulfide linkage > carbon–carbon crosslink. Analysis of the relation of soluble fraction with decrease of effective network chain density according to the theory of Horikx indicated that the severance of crosslinks predominated over main-chain scission in the degradation of sulfur vulcanizate by the reagents. The experiments of the degradation of sulfur vulcanizate in sealed vessels in the absence of oxygen indicated that atmospheric oxygen is necessary for the degradation reaction.     

SEMIBATCH PRECIPITATION ACCOMPANYING GAS-LIQUID REACTION

To obtain large particles of insoluble product by precipitation accompanying a gas-liquid reaction, a sparged stirred vessel was operated continuously for the gaseous and liquid reactants but batchwise for the product particles. Except at the beginning of run, most particles formed floes. With increasing concentration of product particles, the average size of floes increased for CaC0₃ but remained unchanged or decreased slightly for SrCO₃ and BaC0₃The effect of agitation on the floc size was significant for CaC03 but scarcely observed for SrC0₃ and BaC0₃ The mass per unit volume of sedimented floes of the three species increased with increasing concentration of product particles, and under the same conditions, they decreased in the following order: CaC0₃ SrC0₃ BaC0₃     

Internal stress of epoxy resin modified with acrylic polymers produced by in situ UV radiation polymerization

A cured epoxy resin is modified with polybutyl acrylate (A) and polyethyl acrylate (B) produced by in situ ultraviolet radiation polymerizations of their corresponding monomers in the epoxy resin, respectively, to reduce the internal stress. In the A system, a heterogeneous structure with submicron domains was formed. In the B system, however, the B mixed well with the epoxy matrix. In both systems, the internal stress was decreased by the modification. The glass transition temperature of the epoxy matrix decreased in the B system more than in the A system. The A-modified resin was superior to the B-modified resin in reducing the internal stress without decreasing the thermal resistance of epoxy resin.