Extensive facial damage caused by a blast injury arising from a 6 volt lead accumulator.
Low-voltage electrical injuries are relatively uncommon. Injury caused by flow of heavy current due to short-circuiting a low-voltage battery has not been described in the English literature. A 9-year-old boy connected two thin household electrical wires to the two terminals of a 6 volt (lead accumulator) battery and pressed the other two ends between his teeth. This resulted in a blast causing a compound comminuted fracture of the mandible and extensive tissue damage in the oral cavity. The low internal resistance of a lead accumulator (approximately 0.03 ohms) permits the flow of a heavy current (approximately 200 amps) when short-circuited. This instantaneously vaporises a minuscule portion of wire at approximately 2000 K resulting in a sudden rise of intraoral pressure to 30 kg cm-2 leading to tissue damage.
Electrical injury of wrist: classification and treatment--clinical analysis of 90 cases.
Between January 1980 and December 1989, a prospective study was carried out on 114 upper limbs in 90 patients, which were electrically burned with the wrist as the current entrance site. Based upon extensive clinical investigations of arterial injury and its adverse effect on hand circulation, a grading system is suggested for electrically injured wrists based on the severity of injury. The total amputation rate was 39.4 per cent in this group, which was composed of miscellaneous cases with various injuries. However, in subgroups of Type I to Type IV, the amputation rates were 0, 0, 80 and 100 per cent, respectively. A new method to repair the circumferential wound of an electrically burned wrist as well as to bypass the blood flow to the obstructed hand, using a pedicled greater omentum transfer and vascular anastomosis between gastroepiploic artery and the palmar artery, was successfully used in a Type III case.
Evaluation of Lapping Grains based on Shape Characteristics.
The shape and size of abrasive grains during lapping varies complicately and irregularly. In this study, the aspect ratio of grain size and the fractal dimension of the grain external form were used as shape characteristics of grain in order to evaluate grains with lapping time. The results obtained are summarized as follows : (1)The fractal dimension increases due to microscopic fracture and decreases due to macroscopic fracture or attritious wear. (2)The aspect ratio and the fractal dimension, which are grain shape characteristicsis of the macroscopic shape and the microscopic surface complication of grain respectively, can be used for evaluating grain shape variation during lapping.