RESUMO
Glasses frequently reveal structural relaxation that leads to changes in their physical properties including enthalpy, specific volume, and resistivity. Analyzing the short-range order (SRO) obtained from electron diffraction by transmission electron microscopy (TEM) in combination with Reverse-Monte-Carlo (RMC) simulations is shown to provide information on the atomic arrangement. The technique elaborated here features several benefits including reliability, accessibility, and allows for obtaining detailed structural data quickly. This is demonstrated with a detailed view of the structural changes in the as-deposited amorphous phase change material (PCM) GeTe. The data show a significant increase in the average bond angle upon thermal treatment. At the same time the fraction of tetrahedrally coordinated Ge atoms decreases due to an increase in octahedrally distorted and pyramidal motifs. This finding provides further evidence for the atomic processes that govern structural relaxation in amorphous GeTe and other PCMs. A thorough literature review finally unveils possible origins of the large discrepancies reported on the structure of amorphous GeTe.
RESUMO
OBJECTIVES: To compare the video-assisted thoracoscopic surgery (VATS) with the open thoracotomy access to pulmonary segmentectomy by the clinical outcomes and long-term survival in lung carcinoma. METHODS: Non-randomized comparative intention-to-treat study of prospective institutional registry data and survival data of 100 consecutive patients undergoing segmentectomy. RESULTS: Within one decade (2002-12), 100 patients with proven or highly suspected lung carcinoma underwent 100 anatomical sub-lobar pulmonary resections (52 typical and 20 atypical segmentectomies, 28 split-lobe procedures). Fifty-six patients were operated by VATS and 44 by thoracotomy access. Comparison of demographic, medical, oncological and surgical baseline data did not provide evidence for differences between the VATS and thoracotomy groups. The surgery time for the VATS group was 225 ± 62 min and 195 ± 57 min for the thoracotomy group (P = 0.014). Postoperative hospitalization was 9 days for the VATS group and 12 days for the thoracotomy group (P = 0.034). Postoperative morbidity was 35.7% for the VATS group and 50% for the thoracotomy group (P = 0.161). Both groups had no 30-day mortality. Conversion to thoracotomy occurred in 30.4% of the VATS group. Conversion was more frequent in patients with male gender, critical and prohibitive lung function, tumours with diameters exceeding 3 cm and atypical segmentectomies. The fractions of the pathological Union international contre le cancer (UICC) stages I, II and III were 74.4, 11.6 and 14% in the VATS group, and 70, 20 and 10% in the thoracotomy group (P = 0.445), respectively. Five-year overall survival was 86% in the VATS group and 69.9% in the thoracotomy group (P = 0.047), and 5-year recurrence-free survival was 58.5 and 48.6% (P = 0.480), respectively. CONCLUSIONS: Compared with thoracotomy access, the VATS approach to segmentectomy was associated with less postoperative morbidity and a 25% decrease in median hospital stay, despite a conversion rate of 30% due to the inclusion of atypical segmentectomies, higher tumour stages and patients with critical function for single lung ventilation. Five-year survival estimates suggested a small but significant overall survival benefit and a 10% difference of recurrence-free survival in favour of VATS. Although not fully conclusive, long-term results indicate that the thoracoscopic access to segmentectomy is probably not inferior to the thoracotomy approach. Confirmation by a larger number of risk-adjusted outcome data is required.