BackgroundStruma ovarii is a rare ovarian neoplasm that often appears malignant on conventional imaging. Pseudo-Meigs’ syndrome with ascites, pleural effusion, and elevated serum CA 125 levels is much rarer and leads to misdiagnosis of ovarian cancer and unnecessary extended surgery.Case presentationA 50-year-old woman with abdominal distention and dyspnoea was referred to our hospital. Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) showed a polycystic ovarian tumor with a solid component, pleural effusion, and massive ascites with negative cytology. Her serum CA 125 level was 1237 U/ml, indicating the presence of ovarian cancer. Based on increased uptake of 131I but no uptake of 18F–FDG in the tumor, the preoperative diagnosis was struma ovarii with pseudo-Meigs’ syndrome, which was confirmed histologically. She had no evidence of ascites and pleural effusion six months after surgery.ConclusionsTo date, there have been no systematic reviews focused on preoperative diagnosis with imaging modalities. The combination of 131I scintigraphy and 18F–FDG PET/CT in addition to conventional imaging modalities can provide the precise preoperative diagnosis of struma ovarii with pseudo-Meigs’ syndrome mimicking ovarian cancer, leading to the appropriate treatment strategy.
It is well known that aluminum doping is very effective for improving the Voltage-Current (V-I) characteristics of ZnO varistor elements comprising Bismuth oxide and Antimony oxide. Although it is established that the presence of aluminum lowers the resistance of ZnO grains by valence control, in this study, it is proposed that the homogeneity of micro structure of ZnO elements is more effective for improvement of V-I characteristics. The relationship between electrical characteristics and microstructure at different aluminum doping levels and sintering temperatures is shown with V-I characteristics, SEM observation and capacitance measurement of ZnO elements. As the effect of Al doping, it was found that moderation of ZnO grain growth causes the homogeneity of microstructure of ZnO varistors. In detail, reduction of the volume ratio of high resistive parts like thicker grain boundaries and multiple point between ZnO grains leads to excellent non-ohmic V-I characteristics. In addition, it is suggested that the tunnel effect by thinner grain boundaries is important as the mechanisms of improvement of V-I characteristics.
KEY WORDSZnO varistor element, metal oxide varistor, surge arrester, non ohmic, surge protective device
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