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Bovine isoleucyl-tRNA synthetase (IARS) disorder, a major cause of weak calf syndrome, is caused by a homozygous missense (c.235G>C) mutation in the bovine IARS gene of Japanese Black (JB) cattle, which was identified in 2013. However, the extent to which the carrier rate has changed at Kagoshima prefecture, Japan, and whether the carrier status is associated with any clinical or reproductive problems, have yet to be ascertained. In this study, using a real-time polymerase chain reaction-based genotyping assay, we determined the carrier rate in a regional JB cow population at Kagoshima prefecture. Comparative analyses were performed on the metabolic profile test (MPT) results and reproductive performance data obtained for heterozygous carrier and homozygous wild-type cows. In 2009 and 2018, DNA samples were collected from 130 and 462 clinically healthy JB cows, respectively, in Kagoshima prefecture. MPT results and reproductive performance data were evaluated for 62 cows, comprising four heterozygous carriers and 58 wild-type cows. Genotyping revealed that the carrier rate was 6.9% in 2009 and 1.5% in 2018, the difference of which was statistically significant (P

In order to improve the insulation performance of oil-immersed power transformers, the characteristics of the creeping discharge under impulse voltage have been investigated. In this work, by using streak camera, investigations of the influence of the white discharge trace on the creeping discharge characteristics were implemented. The results showed that the velocity of the discharge developing along the white trace was about a thousand times larger than that of the discharge progressing on the pressboard surface. The results also showed that the length of the discharge progressing on the pressboard surface after the white trace formation was shorter than that before the white trace formation. On the other hand, the discharge time delay became larger. These results are thought to be explained by the residual charge generated by the discharge developing along the white trace.

Oil-immersed power transformers adopt oil/pressboard (PB) composite insulation system. To downsize the equipment, further understanding about the creepage discharge phenomena is required. In this study, we have investigated the effect of white discharge trace on the creepage discharge in oil/PB composite insulation system. Experimental results show that partial discharge inception voltage (PDIV) became lower after the white trace formation. In addition to this, the formation delay time of the discharge became shorter after the white trace formation. These results can be explained by the gaseous nature of the white trace.

This paper deals with experimental characterization of creepage discharge to improve the electrical characteristics of oil/pressboard (PB) composite insulation system by solid layer coating such as epoxy resin, and nano size silica/epoxy resin composite on PB surface under positive standard lightning impulse voltage (1.2/50 µs) using a needle/bar electrode arrangement in mineral oil. Creepage discharge properties of conventional PB are compared with solid layer coated PB, in terms of discharge final propagation length (l d ) and partial discharge inception voltage (PDIV). As a result, it is found that partial discharge inception probability (P d ) of solid layer coated PB increases at all applied impulse voltage levels compared with that of conventional PB. The result is interpreted in terms of drying effect, surface modification effect and electron suppression effect by nano/epoxy composite coating on PB surface.