This paper presents technological trials aimed at producing Ag-W, Ag-WC, Ag-W-C and Ag-WC-C composite contact materials and characterizing their properties. These materials were obtained using two methods, i.e. press-sinter-repress (PSR) at the refractory phase content of less than 30% by weight as well as press-sinter-infiltration (PSI) at the refractory phase content of ≥50% by weight). The results of research into both the physical and electrical properties of the outcome composites were shown. They include the analysis of the influence of the refractory phase content (W or WC) on arc erosion and contact resistance changes for the following current range: 6 kAmax in the case of composites with a low refractory phase content, 10 kAmax in the case of composites with the refractory phase content of ≥50% by weight.
Background: Recoarctation (reCoA) of the aorta is a common complication after the Norwood procedure. Untreated, it can lead to failure of the systemic ventricle and death. The main goal of the study is to defi ne risk factors of reCoA after the Norwood procedure in hypoplastic left heart syndrome (HLHS). Methods: We retrospectively analyzed the pre-, intra- and postoperative data of 96 successive patients who underwent the Norwood procedure between 2007 and 2011. In case of reCoA balloon angioplasty was performed. We analyzed and compared the data of the patients with reCoA and without reCoA using the StatSoft STATISTICA™ 10 soft ware. Results: ReCoA was noted in 23 patients (33.3%). Th is complication was diagnosed 95.1 days (49–156 days) on the average aft er the Norwood procedure. Balloon angioplasty successfully allowed for decreasing the mean gradient across the site of the narrowing from the average 27.5 mmHg to the average 9.7 mmHg (p = 0.008) and enlarged the neo-isthmus by the average of 2 mm (p <0.05). Th e risks factors seemed to be the diameter of the ascending aorta OR = 7.82 (p = 0.001), atresia of the mitral valve OR = 7.00 (p = 0.003) and atresia of the aortic valve — OR = 6.22 (p = 0.002). Conclusion: Balloon angioplasty seems to be an eff ective intervention in case of reCoA. A low diameter of the native ascending aorta (≤3mm) and the presence of atresia of the mitral and/or aortic valve should intensify the vigilance of a cardiologist in the search for signs of reCoA of the aorta.