Effect of large dosage irradiation in air on polyethylene

The large dosage irradiation effect on polyethylene in air was examined by the method of double irradition. Polyethylene was first irradiated with γ-rays to a dosage of a few hundred Mrad in air at 298°K. The formed radicals were destroyed, and the polymer, changed chemically and morphologically, was irradiated again in vacuo at 77°K with a dose of 12.7 Mrad. The thermal decay of radicals produced in polyethylene by the second irrdiation was investigated. The results were compared with the sample not exposed to the first irradiation. The results were also compared with previous data of polyethylene irradiated in vacuo to a great extent and then treated in the same manner as that in the present experiment. The results show that scission of the polymer chain by oxidation makes the radical decay faster. Simultaneously, crosslinks formed in polyethylene irradiated in air to a great extent slow down the radical decay. Almost the same number of double bonds was formed in polyethylene irradiated in air as in polyethylene irradiated in vacuo. These double bonds react with alkyl radicals to form allyl radicals.     

Synthesis and conformational study of poly(l-β-3,4-dihydroxyphenyl-α-alanine)

High molecular weight poly(l-β-3,4-dihydroxyphenyl-α-alanine) has been synthesized. Both optical rotatory dispersion and circular dichroism spectra of the polypeptide are anomalous and give little information about its conformation. From the total results obtained by a study of the optical rotation, nuclear magnetic resonance and infra-red absorption, poly(l-β-3,4-dihydroxyphenyl-α-alanine) is most probably right-handed helical in trimethyl phosphate, methanol or water/trimethyl phosphate ($\text{1:1}\text{v}\text{v}$) mixed solvents below pH 10.4. It is in the random coil structure in dimethyl sulphoxide or water/trimethyl phosphate mixed solvents above pH 11. The transition midpoint is pH 10.6 in water/trimethyl phosphate mixed solvents. The results were compared with those of poly(l-tyrosine).     

Effect of large dosage irradiation in vacuo on polyethylene

The effect of large dosage irradiation in vacuo on polyethylene was investigated by the method of double irradiation. Polyethylene was first irradiated with γ-rays to a dosage of several hundred Mrad in vacuo at 298°K. The formed radicals were destoryed, and the polymer, changed chemically and morphologically, was irradiated again in vacuo at 77°K with a dose of 12.7 Mrad. The thermal decay of radicals produced in polyethylene by the second irradiation was investigated. The results show that many double bonds are formed in the sample irradiated to several hundred Mrad on the first irradiation. Alkyl radicals produced by the second irradiation react with these double bonds yielded by the first irradiation to form a large number of allyl radicals. These allyl radicals are much more stable than alkyl radicals radicals in vacuo at 298°K. In a sample not exposed to the first irradiation, almost all radicals formed by the second irradiation decay to form stable products. Crosslinks formed by a large amount of irradiation make the polyethylene matrix more rigid. This rigidity slows down the radical decay. These results suggest that the rate of radical accumulation in polyethylene irradiated in vacuo increases as the dosage increases.     

Novel fabrication of nano-rod array structures on titanium and in vitro cell responses

Nano-scale rod arrays of titania were fabricated on titanium surface by a glass phase topotaxy growth (GPT) method, which was featured by an interfacial reaction between sodium tetraborate coating and the preheated metallic titanium at elevated temperature. The samples were characterized by thin-film X-ray diffraction (XRD), scanning electron microscope (SEM), profilometer and contact angle measurement. Thin-film XRD analysis indicated that the nano-rod arrays were composed of pure rutile titania phase. SEM images showed that these rutile rods were 100-200 nm wide and 1-2 mum long. The nano-rod arrays had significantly higher average roughness (P < 0.05) and greater hydrophilicity (P < 0.05) compared to the control. Human embryonic palatal mesenchymal (HEPM) cells were grown to evaluate in vitro cell responses to the nano-rod array structures in terms of cell attachment and proliferation. An equivalent high attachment rate of 94% was observed after 4-h incubation, but a lower proliferation rate was observed on the nano-rod array after 12-day culture compared to the control (P < 0.05).     

Effect of thin carbonate-containing apatite (CA) coating of titanium fiber mesh on trabecular bone response

The influence of thin carbonate-containing apatite (CA) coating on trabecular bone response to cylindrical titanium fiber mesh (porosity of 85%, pore size of 200–300 μm, 2.8 mm diameter × 6 mm length) implants was investigated. Thin CA coatings were deposited by the so-called molecular precursor method. Molecular precursor solution was obtained by adding dibutylammonium diphosphate salt to Ca–EDTA/amine ethanol solution by adjusting Ca/P = 1.67. Sintered cylindrical titanium fiber mesh was immersed into molecular precursor solution and then tempered at 600 °C for 2 h. The immersion and tempering process was repeated three times. An adherent thin CA film could be deposited on the inside of titanium fiber mesh. After the immersion of a CA-coated titanium fiber mesh in simulated body fluid, apatite crystals precipitated on the titanium fiber mesh. Uncoated and CA-coated titanium fiber mesh was inserted into the trabecular bone of the left and right femoral condyles of rabbits. Histological and histomorphometrical evaluation revealed a significantly greater amount of bone formation inside the porous area of the CA-coated titanium fiber mesh after 12 weeks of implantation. The present results suggested that a thin CA-coated titanium mesh has better osteoconductivity and will be useful for a three-dimensional scaffold.     

Liquid chromatography of theta-shaped and three-armed star poly(tetrahydrofuran)s: theory and experimental evidence of topological separation

A theoretical background is provided for the methods of the analysis and topological separation of complex macrocyclic polymers by means of size exclusion chromatography (SEC), liquid adsorption chromatography, and liquid chromatography at the critical condition. We focus on a particular problem of the separation of theta-shaped polymers from its three-armed star analogues. Based on the theory, we simulate chromatograms for model mixtures of polydisperse theta- and star-polymers and analyze conditions for good separation of these polymers by topology. A theory is compared with the behavior of star- and theta-shaped poly(THF)s in size exclusion and interactive chromatography, and a good qualitative agreement between theory and experiment is observed. In particular, it is shown that in both SEC and interactive chromatography theta-polymers elute after the corresponding stars of the same molar mass. According to theory and experiment, chromatography under the critical and near-critical interaction conditions is especially promising for the separation of polydisperse macrocyclic polymers from their linear or branched analogues.     

Basic study of pole change generator for micro windmill generation system

This paper proposes a pole change generator for a windmill. Since micro windmill systems generate power from natural energy, power generation characteristics across a wide band are necessary. However, the conventional generator, in which the open voltage is simply proportional to the rotational velocity, encounters difficulty in generating power across a wide range of rotational velocities from low to high, because of the power generation characteristics. To develop a generator with a wide power band suitable for a micro windmill, this paper proposes a technique for switching the status of the generator coil connection. To demonstrate the effectiveness of pole changing, we use a pole‐changing generator with 16 coils as an example. The coils can be connected using four patterns: 16‐pole series, 8‐pole 2‐parallel, 4‐pole 4‐parallel, and 2‐pole 8‐parallel. Theoretical and experimental studies from this point of view demonstrate that this technique is effective. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(1): 28–36, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20873     

Methanol decomposition to synthesis gas at low temperature over palladium supported on ceria–zirconia solid solutions

The Ce_xZr_1−xO₂ solid solution was used as a support of a palladium catalyst for methanol decomposition to synthesis gas at low temperature. All Pd-containing catalysts tested in this study showed high selectivity to synthesis gas (over 96%). The Pd supported on the composite oxide with a Ce/Zr molar ratio of 4/1 exhibited the highest activity. Pd/Ce_0.8Zr_0.2O₂ (17 wt.%) (cop) (prepared by coprecipitation method) showed a conversion of 51.2% for the methanol decomposition at 473 K, which was higher than those over 17 wt.% Pd/CeO₂ (cop) (40.7%) and 17 wt.% Pd/ZrO₂ (cop) (24.3%) at 473 K. The 17 wt.% Pd/Ce_0.8Zr_0.2O₂ (cop) catalyst showed a higher BET surface area and smaller Pd particles than those of 17 wt.% Pd/CeO₂ (cop). Moreover, a more active Pd^σ+ state could be maintained by Zr⁴⁺ ion modification due to promotion of the oxygen mobility and enhancement of the reductibility and increase in the acid sites of the CeO₂ support. The 17 wt.% Pd/Ce_0.8Zr_0.2O₂ (cop) catalyst showed a much higher conversion (51.2%) than that over 17 wt.% Pd/Ce_0.8Zr_0.2O₂ (imp) (prepared by impregnation method) (17.2%) at 473 K. This is due to the 17 wt.% Pd/Ce_0.8Zr_0.2O₂ (cop) possessing many small Pd particles. The 17 wt.% Pd/Ce_0.8Zr_0.2O₂ (cop) catalyst showed an initial conversion of 51.2% at 473 K but the conversion decreased to 43.1% after 24 h on stream. This deactivation was attributed to carbonaceous deposit on the catalyst surface. The amounts of coke on the 17 wt.% Pd/Ce_0.8Zr_0.2O₂ (cop) catalyst were 0.9 wt.% after 24 h on stream at 473 K and 2.1 wt.% after 1 h on stream at 523 K.     

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.     

Formation of Silicalite-1 in Channels of Novel SiO2–ZrO2 Porous Glass Tubes Used as Both a Silica Source and a Substrate

Silicalite-1 has been prepared using a novel SiO₂–ZrO₂ porous glass tube as both a silica source and a substrate. The SiO₂–ZrO₂ glass tube was found to possess sufficient physical strength to enable practical use as a separation and catalytic membrane after silicate-1 deposition within its channel. This is in contrast to porous SiO₂ glass which cannot be used to synthesize a silicalite-1 deposited membrane with enough physical strength to perform gas permeance measurements.