A consideration of potentials of low‐density polyethylene using metallocene catalyst as insulator for power cable

We investigated the high‐field conduction, DC and impulse breakdown strength, space charge distribution, and tree inception voltage for three kinds of new low‐density polyethylene (LDPE) prepared using a metallocene catalyst (mLna, mLao, mLldao), linear LDPE prepared using a Ziegler catalyst (LLao), and LDPE prepared by a high‐pressure process (LDna). The dc and impulse breakdown strengths of LDPEs prepared using a metallocene catalyst were higher than those of LLao and LDna. The high‐field currents of LDPEs prepared using a metallocene catalyst were lower than those of LLao and LDna. A homo‐space charge was accumulated near the cathode in mLna. The tree inception voltage of mLna was higher than that of LDna. From these results, it is concluded that LDPE prepared using a metallocene catalyst has electrical insulating properties superior to the conventional LDPE and that the former has potential as a power cable insulator. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(4): 17–25, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.1164     

Molecular evolution of the photolyase-blue-light photoreceptor family

The photolyase-blue-light photoreceptor family is composed of cyclobutane pyrimidine dimer (CPD) photolyases, (6-4) photolyases, and blue-light photoreceptors. CPD photolyase and (6-4) photolyase are involved in photoreactivation for CPD and (6-4) photoproducts, respectively. CPD photolyase is classified into two subclasses, class I and II, based on amino acid sequence similarity. Blue-light photoreceptors are essential light detectors for the early development of plants. The amino acid sequence of the receptor is similar to those of the photolyases, although the receptor does not show the activity of photoreactivation. To investigate the functional divergence of the family, the amino acid sequences of the proteins were aligned. The alignment suggested that the recognition mechanisms of the cofactors and the substrate of class I CPD photolyases (class I photolyases) are different from those of class II CPD photolyases (class II photolyases). We reconstructed the phylogenetic trees based on the alignment by the NJ method and the ML method. The phylogenetic analysis suggested that the ancestral gene of the family had encoded CPD photolyase and that the gene duplication of the ancestral proteins had occurred at least eight times before the divergence between eubacteria and eukaryotes.     

日本POLA艺术博物馆的隔震结构和玻璃天窗

本文具体介绍了建造在自然环境中的POLA艺术博物馆的结构设计概要。为了满足艺术珍藏品在地震时不至损坏的博物馆特有的技术要求,保护地震时人命安全,结构设计时对这座几乎建造于地下的建筑采用了基底隔震系统,而且在上部结构的底部采用了立体大跨度桁架系统,更有效合理地实现了基底隔震系统的隔震性能。隔震系统和大跨度桁架系统的结合统一,既实现了优美的建筑设计要求,又确保了结构在大地震下的高度抗震性能。     

Mechanism of puffing and the role of puffing inhibitors in the graphitization of electrodes from needle cokes

A mechanism of puffing that occurs during graphitization of needle coke in the electrode is proposed based on the experimental results in the literature. Gases may evolve from within needle coke grains via porosity, causing pore walls to expand irreversibly when they are softened during graphitization. Hence, extents of puffing are influenced by rate and temperature range of gas evolution, the nature of evolved gases, location of the evolved heteroatoms such as sulfur and nitrogen in the coke, and the structure (especially grain size), porosity (pores and cracks), and preferred orientation of the coke, because these factors are related to the pressure induced by the evolved gas, timing for the softening of the coke and gas evolution and the resistivity of the wall against the pressure. Porosity within a coke grain can be modified by the coke derived from binder and impregnation pitches that can diffuse into the porosity of filler coke in the electrode. The graphitization also leads to shrinkage of the carbon. Hence, the size of the electrode is influenced by both puffing and shrinkage, these having opposing effects. The extent of puffing can be described semi-quantitatively in terms of influential factors described above. Thus, it is understandable that the puffing increased the porosity in a certain range (0.1–1 μm) and that puffing is suppressed by the increased porosity of 1–100μm. Based on the mechanism, procedures for puffing inhibition are suggested including:

1. 1. moderate acceleration of graphitization

2. 2. capture of heteroatoms to be liberated

3. 3. controled gasification to increase porosity of the filler cokes

4. 4. removal of heteroatoms from the needle coke or its starting feedstock The roles of puffing inhibitors are discussed based on the mechanism of puffing.

Compressive mechanical properties and deformation behavior of porous polymer blends of poly(ε-caprolactone) and poly(l-lactic acid)

Porous biodegradable polymeric scaffolds are developed by physically blending two different kinds of biodegradable polymers, PCL, and PLLA, for application in tissue engineering. The main objective of the development of this material is to control the mechanical properties, such as, elastic modulus and strength. The results from mechanical testing showed that the compressive mechanical properties of PCL/PLLA scaffold can be varied by changing the blend ratio. It also showed that these properties can be well predicted by the rule of mixture. The primary deformation mechanism of the scaffolds was found to be localized buckling of struts surrounding the pores. Localized ductile failure caused by PCL phase tends to be suppressed with increasing PLLA content. The immiscibility of PCL and PLLA caused the phase-separation morphology that strongly affected the macroscopic mechanical properties and the microscopic deformation behavior.     

Hypoallergenic Characteristics of Wheat Flour Produced by Stepwise Polishing

Hypoallergenic wheat flour was produced by polished-graded method using a rice polishing machine. Eight fractions (C1–C8) of polished-graded wheat flours were obtained step wise from the outer layer of whole wheat grains by 10% of the total weight, and the distribution of allergenic protein in each fraction was determined. The salt-soluble (albumin/globulin), salt-insoluble (glutenin) and alcohol-soluble (gliadin) proteins obtained from the polished-graded wheat flours were tested for the allergen assay with immunodetection using the sera of wheat allergenic patients. Immunoblotting results confirmed that the innermost fraction (C8) contained a smaller amount of allergenic proteins. Albumin/globulin groups in all fractions (C1–C8) showed different IgE-reactivity patterns, the 60–75 kDa proteins appeared in all of fraction flours. It was higher in C3–C5 fractions. Fractions C3 and C4 contained higher amount of specific wheat allergenic protein including 60–75, 35, 22, and < 20 kDa. IgE-antibody also bound to glutenin (25–37 kDa), especially in C3 and C4, but the binding proteins showed quite faint bands. Gliadin was found in all fractions of wheat flour. We propose that polishing is an appropriate method to obtain hypoallergenic wheat flours, and the fraction C8 may be possible to be consumed by people suffering from wheat allergy.     

Properties of kenaf fiber/polylactic acid biocomposites plasticized with polyethylene glycol

Biocomposites of kenaf fiber (KF) and polylactic acid (PLA) were prepared by an internal mixer and compression molding. PLA was plasticized with polyethylene glycol (PEG) (10 wt%) and evaluated as the polymer matrix (p‐PLA). Fiber loadings were varied between 0 and 40 wt%. The tensile, dynamic mechanical, and morphological properties and water absorption behavior of these composites were studied. Reinforcing effect of KF was observed when fiber loading exceeded 10 wt% despite of the inferior fiber‐matrix adhesion observed via scanning electron microscopy (SEM). Un‐plasticized PLA/KF composite exhibited higher tensile properties than its plasticized counterpart. Fiber breakage and heavily coated short pulled‐out of fibers were observed from the SEM micrographs of the composite. The presence of PEG might have disturbed the fiber‐matrix interaction between KF and PLA in the plasticized composites. Addition of PEG slightly improved the un‐notched impact strength of the composites. Dynamic mechanical analysis showed that the storage and loss moduli of p‐PLA/KF composites increased with the increase in fiber loading due to increasing restrictions to mobility of the polymer molecules. The tan delta of the composites in contrast showed an opposite trend. p‐PLA and p‐PLA/KF composites exhibited non‐Fickian behavior of water absorption. SEM examination revealed microcracks on p‐PLA and p‐PLA/KF surfaces. POLYM. COMPOS., 31:1213–1222, 2010. © 2009 Society of Plastics Engineers     

Characterization of microstructure and mechanical properties of biodegradable polymer blends of poly(L‐lactic acid) and poly(butylene succinate‐co‐ε‐caprolactone) with lysine triisocyanate

Effect of lysine triisocyanate (LTI) as an additive on the microstructure and the mechanical properties of biodegradable polymer blends of poly(L ‐lactic acid) (PLLA) and poly(butylene succinate‐co‐ε‐caprolactone) (PBSC) were investigated by using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), field‐emission scanning electron microscope (FE‐SEM), and bending and mode I fracture testing techniques. It was found that the addition of LTI dramatically improves the phase‐separation morphology of the PLLA/PBSC blends. FTIR analysis suggested that the NCO groups of LTI were acted as compatibilizer by attributing secondary process between the two polymers PLLA and PBSC, resulting lower peak intensity of ACI samples, understood as secondary process is polar interaction and hydrophobic process. DSC and FE‐SEM results also supported such improvement of immiscibility between PLLA and PBSC. Macroscopic mechanical properties such as the bending fracture energy and the mode I fracture properties are also effectively improved by the LTI addition. Void formation is suppressed due to such morphological change in PLLA/PBSC/LTI blends, and, as a result, energy dissipation in the notch‐tip region of the blends becomes higher than in that of PLLA/PBSC where localized stress concentration due to voids tends to accelerate fracture initiation and, therefore, lowers the fracture energy. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Biomechanical evaluation of porous bioactive ceramics after implantation: micro CT-based three-dimensional finite element analysis

Hydroxyapatite ceramics have been widely investigated for bone regeneration due to their high biocompatibility. However, few studies focus on their mechanical characteristics after implantation. In this study, the finite element (FE) method was used to evaluate the mechanical properties of a fully interconnected porous hydroxyapatite (IPHA) over time of implantation. Based on the micro-CT images obtained from the experiments dealing with IPHA implanted into rabbit femoral condyles, three-dimensional FE models of IPHA (1, 5, 12, 24, and 48 weeks after implantation) were developed. FE analysis indicated that the elastic modulus gradually increased from 1 week and reached the peak value at 24 weeks, and then it kept at high level until 48 weeks postoperatively. In addition, as a local biomechanical response, strain energy density became to distribute evenly over time after the implantation. Results confirmed that the mechanical properties of IPHA are strongly correlated to bone ingrowth. The efficiency of the proposed numerical approach was validated in combination with experimental studies, and the feasibility of applying this approach to study such implanted porous bioceramics was proved.