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We have investigated structural, electrical, and electro-mechanical properties of lead-free piezoelectric BaTiO3 doped Na0.5K0.5NbO3 (BTO-NKN) thin films deposited by pulsed laser deposition (PLD) methods. BTO-NKN thin films have been deposited on La0.5Sr0.5CoO3 (LSCO) bottom electrodes with LaAlO3 (LAO) substrates. X-ray diffraction data have shown that all the BTO-NKN and bottom electrodes are highly oriented with their c-axes normal to the substrates. In order to improve the morphology of BTO-NKN thin films, we have located an eclipse shutter between a target and a substrate. Root-mean-square roughness was changed from 91 nm to 21 nm with eclipse shutter enhanced PLD (E-PLD) method. Furthermore, the enhanced surface morphology leads to the improvement in electrical or electro-mechanical properties mainly due to increased density. Typical capacitance and d33 values of a BTO-NKN film deposited by E-PLD method are 1000 pF and 30 pmN, respectively.
RESUMO
INTRODUCTION: Stent-assisted coil (SAC) embolization is an alternative treatment option for anterior communicating artery (AcoA) aneurysms. This study was undertaken to assess the safety and effectiveness of SAC embolization in treating AcoA aneurysms and to determine risk factors for related procedural complications or recanalization. METHODS: Between August 2008 and December 2016, 184 patients with AcoA aneurysms were treated with SAC embolization. Cumulative medical record and radiologic data were analyzed using binary logistic regression to identify factors predisposing to procedural complications or recanalization. RESULTS: Contralateral A1 segment hypoplasia was observed in 59 patients (32.1%). Three types of stents (LVIS, Enterprise, and Neuroform) were variably placed by one of two routes: (1) ipsilateral A1 to ipsilateral A2 (75.5%) or (2) ipsilateral A1 to contralateral A2 (24.5%). Procedural complications occurred in 17 patients (thromboembolism 12; procedural leakage 3; both 2), showing a significant relation to subarachnoid hemorrhage at presentation (OR 57.750; P<0.01). Occlusion was documented immediately after embolization in 130 aneurysms (70.6%) and, in 23 (13.1%) of 175 AcoA aneurysms followed by angiography (median 25.9±18.5 months), recanalization developed (minor, 15; major, 8). Stent configuration (ipsilateral A1 to contralateral A2, P=0.024), maximum aneurysm size (>7 mm, P<0.01), and A1 segment hypoplasia (P=0.039) were identified as risk factors for recanalization. CONCLUSION: SAC embolization is a safe and effective method of treating unruptured AcoA aneurysms, regardless of anatomic or clinical features. However, in the event of rupture, procedural complications are likely. Stent configuration, aneurysm size, and A1 segment hypoplasia were identified as significant risk factors for recanalization.