Orientation factor of polypropylene film by infrared dischroism

The orientation factor by infrared dichroism of polypropylene film was compared with the other orientation factors. After the correction of imperfect polarization and the suitable choice of the base line, it was found that infrared dichroism is a reliable indicator of the orientation factor. Orientation factors obtained from the 998 and 842 cm.^?1 bands agreed with the x-ray orientation factor, and that from the 975 cm.^?1 band agreed with the optical orientation factor.     

Tensile and impact behavior of drawn polystyrene and high-impact polystyrene

The tensile behaviors of drawn polystyrene (PS) and high-impact polystyrene (HIPS) were examined systematically in the wide range of strain rate, 1.7 × 10^?4–13.1 m/s, without changing the mode of deformation and the shape of the test pieces. It was found for both PS and HIPS that the flexion points of birefringence with increase of draw ratio are intimately correlated with the tensile properties. Especially, the breaking strain and energy of undrawn and drawn HIPS were assigned to the contributions of the following three toughening mechanisms: (a) the generation of large numbers of microcrazes from the equatorial zone of the dispersed rubber particles; (b) the extension of interfacial rubber phase around the circumpolar zone of the dispersed rubber particles and its disintegration from the matrix component; and (c) the shear band formation of the matrix component followed by cold drawing. These mechanisms were discussed in connection with the factors of stress concentration to the rubber particles, hydrostatic pressure effect arising from the difference in Poisson's ratio of rubber and matrix components, and heat generation due to the adiabatic deformation.     

Mechanism of pole‐mounted transformer damage by backflow lightning and measures against the damage on low‐voltage distribution line

Pole‐mounted transformers are especially vulnerable to lightning damage. The progress of the information society imposes increasingly stringent requirements for the reliability of electric power supply, and this in turn necessitates a reduction in lightning damage to pole‐mounted transformers. Lightning protective devices (surge arresters) are now being installed around the primary bushing of the transformers, which has decreased the number of disconnections around the primary bushing due to lightning. But surge arresters installed on the primary side of the transformer cannot protect it against backflow lightning entering the secondary side of the transformer. The characteristic of transformer damage by backflow lightning is that the electromagnetic force produced by the current flowing into the secondary side deforms the transformer windings. This paper elucidates the mechanism of transformer damage by lightning flowing into the secondary side by comparing actual lightning damage cases with the results of verification tests using a short‐circuit generator. Effective countermeasures against transformer damage by backflow lightning are examined by EMTP calculations, which indicate that neutral grounding on the low‐voltage distribution line is the most effective way of decreasing the current flowing into the transformer. The lower the grounding resistance, the less current flows into the transformer. In addition, decreasing the voltage on the secondary side is important in order to protect the secondary‐side bushing. The calculation results indicate that surge arresters installed around the secondary side of the transformer are effective in decreasing the voltage on the secondary side. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 1–11, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20921     

Possible immunodulating activities in an extract of edible brown alga,Hijikia fusiforme (Hijiki)

A significant immunomodulating activity was found in the hot-water-soluble extract of an edible brown seaweed, Hijikia fusiforme (Hijiki in Japanese) which showed an enhancing activity for the proliferative response of spleen cells in endotoxin-nonresponder C3H/HeJ mice. This activity was separated into polysaccharide and nonpolysaccharide fractions. The former fraction exhibited a much higher activity than that of the latter fraction. The enhancing effect of the polysaccharide fraction on the proliferative response of spleen cells was associated with the response of the B cell population, but not with that of the T cell population judged by experiments using nylon wool column-purified T cells and antisera against B cell- or T-cell-specific antigens. The active component of the polysaccharide fraction was further fractionated using DEAE cellulose column chromatography which also caused enhancing effects on polyclonal antibody (IgM and IgG) production and the release of interleukin-1α or tumour necrosis factor-α from peritoneal macrophages of C3H/HeJ mice. In addition, these immunomodulating activities of the polysaccharide fraction were associated with the polysaccharides themselves, but not with the artificial activities induced by contaminated endotoxins. The biochemical and physicochemical properties of the immunoenhancing polysaccharides were partially characterised and the significance of the present finding is discussed from the viewpoint of the immunopotentiating activity of edible seaweeds against carcinogenesis. © 1998 SCI.     

Gas Heating and Formation of Single Linear Discharge Channel on Repetitive Branched Streamer Corona

Under a nonuniform field in an atmospheric short gap, a branched pulse streamer corona changes to a single filamentary discharge (SFD) for a split second just before sparkover occurs. This SFD is a pretransitional phenomenon of sparkover. Therefore, it is very important to study SFD for an understanding of the sparkover mechanism. In this work, the SFD was recreated well by applying a highly repetitive impulse voltage to a needle‐plane gap in synthetic air with dilute CO₂. The characteristics of the SFD, including the channel temperature, the propagation of the streamer head, and the formation process, were investigated by means of an intensified charge coupled‐device (ICCD) camera and a spectroscopic measurement system. It was found that the transition to SFD progresses with localized gas heating along the discharge channel. Furthermore, it was revealed that the SFD is a nonbranched positive streamer.