Application of a novel polypropylene to the insulation of an electric power cable

Cross‐linked polyethylene (XLPE) has been widely adopted as insulating material for high‐voltage power cables up to 500 kV. Further improvement of electrical and thermal properties on insulating material is required in order to increase cable operation efficiency. Therefore, the development of novel insulating material possessing high thermal properties will be necessary. Recent progress of catalysis technology contributes to obtain new polymeric materials which may be applied to electrical insulation. The authors investigated the basic properties of newly developed stereoregular syndiotactic polypropylene (s‐PP) which is synthesized with homogeneous metallocene catalyst. Though recycling of cross‐linked polymers such as conventionally used XLPE may be difficult because of their poor heat deformation, the s‐PP which is not cross‐linked must be suitable for recycling. A series of experiments on its physical and electrical properties gave the following results.

• (1) s‐PP has sufficient flexibility compared with isotactic polypropylene (i‐PP ).
• (2) Both AC and lightning impulse breakdown strength of s‐PP in spite of no cross‐linking are superior to those of XLPE in the temperature range from 25 to 90 °C.
• (3) Degradation by copper of s‐PP is less than that of i‐PP.
• (4) s‐PP/VLDPE blend shows sufficient brittleness temperature for use.

These results suggested that s‐PP should serve as insulating material for power cables at higher‐temperature operation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 18–26, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002//eej.10210     

Fast short-circuit protection under current imbalance condition for multi-paralleled SiC-MOSFETs

This paper proposes methodology and gate drive circuit that can immediately detect short-circuit (SC) of multiparalleled SiC-MOSFETs even under current imbalance condition. Proposed method detects SC current using an integration circuit that can sense di/dt. The detection level of SC current can be adjusted to a desired value regardless of the number of SiC-MOSFETs connected in parallel. The effectiveness of the proposed approach was experimentally validated for four-paralleled SiC-MOSFETs under extreme current imbalance in SC condition. SC was detected within 0.5 μs and all SiC-MOSFETs were protected without destruction at most 2.2 μs after the onset of SC, for all types of SC 1, 2, and 3.     

Current Control Method of Achieving Wide‐Range Power Driving for Linear Synchronous Motor with Half‐Wave‐Rectified Self‐Excitation

In a previous paper, we proposed a novel linear synchronous motor with half‐wave‐rectified self‐excitation. A long‐stator‐type linear synchronous motor was built and its performance was verified by experiments. This paper presents a new current control method for the linear synchronous motor in order to achieve a wide range of speeds and high‐power operations. First, we propose a current control method for high‐thrust operation in the constant‐thrust region. This operation is realized by using the reluctance thrust resulting from the saliency of the linear synchronous motor. We also propose a control method that maximizes the ratio of the thrust to the voltage; this method can be used to expand the operating range. Wide‐range‐speed operation can be achieved by applying this new control method along with field‐weakening control. The thrust and operating characteristics of the proposed control methods are estimated by performing experiments and coupled electric and magnetic analysis.     

Effect of heparin on high glucose induced proliferation and expression of matrix metalloproteinases in normal human mesangial cells

Background The pathogenesis of diabetic nephropathy (DN) is a complex pathophysiological process. Its precise mechanism is not fully known. In recent years it has been recognized that synthesis of various extracelluar matrix (ECM) components may increase, and that degradation of ECM may decrease in DN. It was reported heparin could inhibit mesangial cells proliferation in vitro. The main aim of this study is to explore whether heparin inhibits proliferation of mesangial cells grown in high glucose concentration and to measure the effect of heparin on matrix metalloproteinases (MMPs) expression in mesangial cells. Methods The medium contained either low glucose (5 mmol/L) or high glucose (25 mmol/L). The concentrations of heparin in the culture medium were 0, 25, 50, 100, 200 or 400 μg/mL. A metabolic (WST-1) assay was used to measure mesangial cell proliferation and Western blot analysis was used to measure MMPs expression of mesangial cells. Results Normal human mesangial cell (NHMC) proliferation was higher in high glucose (HG) medium than in low glucose (LG) medium. They showed a 1.93 fold expansion after 72 h in high glucose in contrast to a 1.63 fold expansion in low glucose. In the presence of heparin, mesangial cells proliferation was inhibited, which was more obvious at high glucose concentrations than at low glucose concentrations. In high glucose, with heparin concentration of 50, 100, 200 and 400 μg/mL, the mesangial cells showed a 0.61 fold, 0.52 fold, 0.52 fold and 0.41 fold reductions in cell number compared to cells grown without heparin. In low glucose, only concentrations of 200 μg/mL and 400 μg/mL showed reduction in cell number, namely 0.54 fold and 0.45 fold, when compared to cells grown without heparin. In Western blot analysis, MMP₁, MMP₂, MMP₃ and MMP₉ was expressed by mesangial cells expressed in both high and low glucose concentrations, which was more prominent in high glucose medium. Incubation of heparin further increased expression of MMP₁, MMP₂, MMP₃ and MMP₉. Conclusions This study suggests that glucose can accelerate mesangial cell proliferation while heparin can reduce proliferation, being more obvious at high glucose concentrations. Higher glucose concentrations led to increased MMP expression, which may take part in the regulation of mesangial matrix synthesis and degradation. Addition of heparin resulted in a corresponding increase in MMP expression, most notably at high glucose concentrations, indicating a potentially renoprotective role in DN. Foundation item: Project (30370663) supported by the National Natural Science Foundation of China     

Adhesion between polymer surface modified by graft polymerization and tissue during surgery using an ultrasonically activated scalpel device

In the field of surgery, achieving adhesion between a polymer implant and tissue poses a challenge considering that suturing is not appropriate for the stability of such implants. An ultrasonically activated scalpel that generates heat by mechanical vibration and promotes adhesion between a polymer implant and native tissue by pressing the two materials together has very good potential for application in the field. To determine the type of polymer that is suitable for the purpose, we investigated polyethylene (PE) and polystyrene (PS) films, the surfaces of which were activated by corona discharge. Graft polymerization was then performed on the corona‐treated surfaces to vary their properties. The corona‐treated PE and PS films grafted with poly(acrylic acid), poly(methacrylic acid), poly(vinyl benzylacrylic acid), and poly(hydroxylethyl acrylate), respectively, adhered to the tissue when the ultrasonically activated scalpel was applied. The heat generated by the mechanical vibration and the applied pressure enabled the carboxyl or hydroxyl groups to bond with the proteins in the extracellular matrix. We therefore concluded that it was possible to integrate this technique in the development of new types of polymer devices that could be stably implanted in a living body. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40885.     

Ethanolamine Is a New Anti-Prion Compound

Prion diseases are a group of fatal neurodegenerative disorders caused by accumulation of proteinaceous infectious particles, or prions, which mainly consist of the abnormally folded, amyloidogenic prion protein, designated PrP^Sc. PrP^Sc is produced through conformational conversion of the cellular isoform of prion protein, PrP^C, in the brain. To date, no effective therapies for prion diseases have been developed. In this study, we incidentally noticed that mouse neuroblastoma N2a cells persistently infected with 22L scrapie prions, termed N2aC24L1-3 cells, reduced PrP^Sc levels when cultured in advanced Dulbecco’s modified eagle medium (DMEM) but not in classic DMEM. PrP^C levels remained unchanged in prion-uninfected parent N2aC24 cells cultured in advanced DMEM. These results suggest that advanced DMEM may contain an anti-prion compound(s). We then successfully identified ethanolamine in advanced DMEM has an anti-prion activity. Ethanolamine reduced PrP^Sc levels in N2aC24L1-3 cells, but not PrP^C levels in N2aC24 cells. Also, oral administration of ethanolamine through drinking water delayed prion disease in mice intracerebrally inoculated with RML scrapie prions. These results suggest that ethanolamine could be a new anti-prion compound.     

Low-Speed Drive of PWM-VSI-Fed Brushless Self-Excited Synchronous Motor

The brushless self-excited synchronous motor with halfwave rectified field circuits has been invented already by Nonaka. For the low-speed drive of the motor a new method of the voltage supply which superimposes a higher-order harmonic component on sinusoidal low-frequency voltage by a pulsewidth modulated (PWM) GTO inverter is presented. The amplitude and frequency of the fundamental component and those of the harmonic component are controlled independently by a microcomputer-based PWM strategy. It is confirmed from the experimental results that controllable brushless self-excitation and smooth low-speed operation without torque pulsation are achieved by the proposed scheme.     

Metallization of cross-linked polyurethane resins by reduction of polymer-incorporated metal ion

Polyurethane (PU) resins having different degree of cross-linking were prepared by the reaction of 4,4′-methylenebis(phenyl isocyanate) (MDI) with various molar ratio of two kind of pentaerythritol ethoxylates (PEE15, ratio of ethyleneoxy (EO) unit/hydroxyl (OH) unit=15/4; PEE3, EO/OH=3/4) in the presence of cobalt(II) chloride at 100 °C for 48 h. Metallization behavior of the CoCl₂-containing PU resins by reduction with aqueous sodium tetrahydroborate solution was investigated by means of infra-red (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). It was confirmed by the measurement of degree of swelling and glass transition temperature that the PU resin having a higher molar ratio of PEE15/PEE3 has a lower degree of cross-linking. When the PU films were reduced at 20 °C, the PU resins with PEE15/PEE3=10/0, 8/2, and 6/4 afforded the films with a metallic luster, whose surface resistance increased in this order. The formation of cobalt metal on both the sides of the PU film was revealed from the results of the XPS and EPMA measurements. The PU resin having a lower degree of cross-linking could be more easily metallized by this reduction treatment.     

Pressureless all-solid-state sodium-ion battery consisting of sodium iron pyrophosphate glass-ceramic cathode and β″-alumina solid electrolyte composite

In recent years, the expansion of demand for lithium ion batteries has resulted in soaring prices of the constituent resources. From the viewpoint of safety, studies on all-solid-state batteries are actively being carried out. In this study, we succeeded in driving all-solid-state batteries derived from nontoxic oxide glasses at room temperature without requiring scarce resources such as lithium and cobalt. The main structure of the ceramic batteries with a simple structure in which Na₂FeP₂O₇ crystallized glass and β″-alumina solid solution are joined by pressureless cofiring at 550°C. During the crystallization of Na₂O-Fe₂O₃-P₂O₅ glass, fusion with the β″-alumina solid solution is achieved. Reversible charge and discharge of 80 mAh/g were achieved at room temperature. It is not necessary to apply pressure during cell preparation or the use of the batteries. Furthermore, the strong junction at the cathode and electrolyte interface does not peel off during charge and discharge over a long period of 623 cycles. Ex situ X-ray photoelectron spectroscopy revealed partial Fe⁴⁺ induction and a reversible charge and discharge reaction even after overcharging to 9 V. It was demonstrated that Na₂FeP₂O₇ is very stable against overcharging to 9 V.