Structural Studies of Lanthanide Double Perovskites

This project focuses on the examination of the structures of lanthanide containing double perovskites of the type Ba2LnB'O6-d (Ln = lanthanide or Y3+ and B' = Nb5+, Ta5+, Sb5+ and/or Sn4+) using synchrotron X-ray and neutron powder diffraction. The first part of this project examined the relative stability of R3 rhombohedral and I4/m tetragonal structures as the intermediate phase adopted by the series Ba2LnB'O6 (Ln = lanthanide (III) or Y3+ and B' = Nb5+, Ta5+ or Sb5+). It was found that I4/m tetragonal symmetry was favoured when B' was a transition metal with a small number of d electrons, such as Nb5+ or Ta5+. This is due to the presence of p-bonding in these compounds. In the Ba2LnNbO6 and Ba2LnTaO6 series R3 rhombohedral symmetry was, however, favoured over I4/m tetragonal symmetry when Ln = La3+ or Pr3+ due to the larger ionic radius of these cations. The incompatibility of the d0 and d10 B'-site cations in this family of compounds was indicated by significant regions of phase segregation in the two series Ba2Eu1-xPrxNb1-xSbxO6 and Ba2NdNb1-xSbxO6. In the second part of this project the compounds in the series Ba2LnSnxB'1-xO6-d (Ln = Pr, Nd or Tb and B' = Nb5+ or Sb5+) were examined to understand the relative stability of oxygen vacancies in these materials compared to the oxidation of the lanthanide cations and to determine if any oxygen vacancy ordering occurred. It was found, using a combination of structural characterisation, X ray Absorption Near Edge Structure and Ultra-Violet, Visible and Near Infrared spectroscopies, that with Ln = Pr or Tb increased Sn4+ doping results in a change in the oxidation state of the Ln3+ cations to Ln4+. This leads to those series containing little or no oxygen vacancies. A loss of B site cation ordering was found to accompany this oxidation state change and phase segregation was found to occur in the Ba2PrSnxSb1-xO6-d series most likely due to the Pr3+ and Pr4+ cations segregating into different phases. The Nd3+ cations in the series Ba2NdSnxSb1-xO6-d, however, can not oxidise to the tetravalent state so the number of oxygen vacancies rises with increasing x. It was found that oxygen vacancies concentrate onto the axial site of the compounds with x = 0.6 and 0.8 at ambient temperature. In Ba2Sn0.6Sb0.4O5.7 the oxygen vacancies were found to change to concentrating on the equatorial site at higher temperatures and it is suggested that this oxygen vacancy ordering plays a role in the adoption of I2/m monoclinic symmetry

The predictive value of cumulative lactate dehydrogenase release within the first 72 h of acute myocardial infarction in patients treated with primary angioplasty

Background: In patients with acute myocardial infarction, estimation of infarct size by cumulative lactate dehydrogenase release at 72 h (LDHQ72) is a simple and widely used method. Our objective was to study the value of estimating infarct size, by the cumulative release of LDH over 72, 60, 48 and 36 h in predicting left ventricular ejection fraction (LVef) and cardiac death at 1 year. Methods: In the Zwolle Infarction Study infarct size estimated as LDHQ was calculated in 1224 patients treated with primary percutaneous coronary intervention for acute myocardial infarction between December 1993 and June 2001. Patients were categorized as having small (LDHQ722500 U/L) myocardial infarction. Results: LDHQ72 was closely correlated with LDHQ60, LDHQ48 and LDHQ36 (r = 0.998, 0.993 and 0.987, respectively, P <0.0001). The relations between LDHQ infarct size classification and mean LVef (51% vs 45% vs 35%, P <0.001) or cardiac death at 1 year (0-0.3% vs 0.7-1% vs 6-8%) showed a similar pattern, irrespective of whether LDH was measured up to 36, 48, 60 or 72 h. Conclusion: Infarct size classification based on LDHQ36 is an objective and widely available method for early risk stratification in patients treated with primary angioplasty for acute ST-segment elevation myocardial infarction

Treatment assignment in young women with spontaneous coronary artery dissection

Item does not contain fulltex

Randomised comparison of drug-eluting versus bare-metal stenting in patients with non-ST elevation myocardial infarction

OBJECTIVE: The superiority of drug-eluting stents (DES) over bare-metal stents (BMS) in patients with ST elevation myocardial infarction (STEMI) is well studied; however, randomised data in patients with non-ST elevation myocardial infarction (NSTEMI) are lacking. The objective of this study was to investigate whether stenting with everolimus-eluting stents (EES) safely reduces restenosis in patients with NSTEMI as compared to BMS. METHODS: ELISA-3 patients were asked to participate in the angiographic substudy and were randomised to DE (Xience V) or BM (Vision) stenting (ELISA-3 group). The primary end point was minimal luminal diameter (MLD) at 9-month follow-up angiography. In addition, 296 patients with NSTEMI who were excluded or did not want to participate in the ELISA-3 trial (RELI group) were randomised to DE or BM stenting and underwent clinical follow-up only (major adverse cardiac events (MACE), stent thrombosis (ST)). A pooled analysis was performed to assess an effect on clinical outcome. RESULTS: 178 of 540 ELISA-3 patients participated in the angiographic substudy. MLD at 9 months angiography was 2.37+/-0.63 mm (DES) versus 1.84+/-0.62 mm (BMS), p<0.001. Binary restenosis occurred in 1.9% in the DES group versus 16.7% in the BMS group (RR 0.11, 95% CI 0.02 to 0.84, p=0.007). In the pooled analysis, the incidence of MACE, target vessel revascularisation and ST at 2 years follow-up in the DES versus BMS group was 12.5% versus 16.0% (p=0.28), 4.0% versus 10.4% (p=0.009) and 1.3% versus 3.0% (p=0.34), respectively. CONCLUSIONS: In patients with NSTEMI, use of EES is safe and decreases both angiographic and clinical restenosis as compared to BMS http://www.isrctn.com/search?q=39230163. TRIAL REGISTRATION NUMBER: 39230163; Post-results