Synthesis of FeSi-FeAl Composites from Separately Prepared FeSi and FeAl Alloys and Their Structure and Properties.

Composites consisting of iron aluminide and iron silicide phases were studied in this work. Powders of iron aluminide and iron silicide were prepared by mechanical alloying separately. Subsequently, they were blended in three different proportions and sintered by the SPS method under various conditions. After sintering, the composites are composed of FeAl and amounts of other silicides (Fe5Si3 and Fe3Si). Ternary Fe-Al-Si phases were not determined, even though their presence was predicted by DFT calculations. This disagreement was explained by steric factors, i.e., by differences in the space lattice of the present phases. Hardness and tribological properties were measured on composites with various weight ratios of iron aluminide and iron silicide. The results show that sintered silicides with the matrix composed of iron aluminide reach comparable hardness to tool steels. The composites with higher mass ratios of iron aluminide than silicide have higher hardness and better tribological properties.

Analysis of thrombotic complications after catheter ablation.

INTRODUCTION: Thromboembolic complications are described in about 1% of the patients undergoing radiofrequency catheter ablation (RFA). The aim of this study was to analyze thrombotic complications after RFA and to determine prothrombotic states in patients with thrombotic complications. METHODS: We analyzed data from 400 patients (212 females) who underwent 453 RFA procedures for supraventricular tachycardias. Transthoracic echocardiography was performed one day before and after RFA in all patients. We evaluated the clinical and laboratory (in patients with thrombotic complications after RFA) risk factors of thromboembolism. RESULTS: We observed thrombotic complication in 7 (1.75%) patients (6 females), thrice flail thrombus in the right atrium, flail thrombus in the inferior vena cava, femoral vein thrombosis with massive pulmonary embolism, femoral vein mural thrombus and upper extremity digital arteries embolization; four of them were asymptomatic. As a prothrombotic state we identified factor V Leiden mutation in one case and the use of oral contraceptives in two cases. Two other patients had a positive history of thromboembolic events. In a subgroup of females the use of oral contraceptives (p = 0.13) or a positive history of thromboembolism (p = 0.21) were not identified as important risk factors. CONCLUSION: Echocardiographic detection of asymptomatic thrombotic complications contributed to the higher percentage of these complications in our study. Although we can identify the risk factor (laboratory or clinical) in a majority of patients with a thromboembolic complication, occurrence of these complications is unpredictable.