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Three familiar properties of a parabola are that it is the locus of points that are equidistant from the focus and the directrix, that it can be created by an intersection of a plane and a cone, and that incoming rays parallel to the axis are reflected to a single point. The first two are often used as definitions, and the third may be used as an alternative definition or characterisation.
Ever since their discovery, mirror neurons have generated much interest and debate. A commonly held view of mirror neuron function is that they transform “visual information into knowledge,” thus enabling action understanding and non-verbal social communication between con-specifics (Rizzolatti & Craighero 2004). This functionality is thought to be so important that it has been argued that mirror neurons must be a result of selective pressure.
The oxygen conductor yttria-stabilized-zirconia (YSZ) is widely used in miniaturized solid oxide fuel cells (µSOFC) and may be suitable for solid state ion emitter applications e.g. as miniaturized ion engines for electric propulsion. Since the YSZ films are not completely free of stress during the growth, cracks in fabricated free-standing membranes are often observed.
YSZ thin films were deposited on silicon substrates by radio frequency sputtering. Free-standing YSZ membranes were fabricated by partially removing the Si substrate by anisotropic wet-chemical etching using different masking patterns defined by electron beam lithography. We show how different sizes and etching conditions influence the strain in the fabricated membranes. To characterize these membranes we used optical microscopy and scanning electron microscopy.
We will briefly review in situ synchrotron x-ray investigation of model thin film cathode systems for solid oxide fuel cells. The film cathodes examined in this study are (La,Sr)MnO3_δ (LSM), (La,Sr)CoO3_δ (LSC), and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) thin films epitaxially grown on YSZ single crystal substrates by the pulse laser deposition technique. We find in all cases that Sr is enriched or segregated to the surface of the film cathodes. We concluded that the Sr enrichments or segregations are mainly the results of annealing because they do not depend on whether the cathodes are electrochemically biased or not during annealing. However, at least in the case of LSCF, we find that B-site Co segregates rather uniformly to the surface and the segregation responds sensitively and reversibly to the electrochemical bias.
A fast proton conducting glass with proton transport number tH = 1 was successfully prepared by using conventional melting method. In-situ FTIR (Fourier transform infrared) measurements under hydrogen atmosphere, temperature of 300°C and applying 1 V between Pt electrodes were carried out in order to monitor the proton concentration. The electrode reaction on Pt in these conditions is similar to that under intermediate-temperature fuel cell operation. It was found from the in-situ FTIR measurements that the absorbance around 2900 cm-1 increases clearly after applying 1 V, whereas no significant change was observed around 3400 cm-1. Proton infiltration into the glass is discussed based on the in-situ FTIR and impedance results.
Density functional theory calculations are used to study the equilibrium energetics of protons on the surface and in the bulk of Y-doped BaZrO3. It is shown that protonic species in direct contact with Y dopants have energies lower than in perfect BaZrO3 by up to 0.4 eV. This energetic stabilization is achieved when the protonic species is in direct contact with two Y dopants. On the (001) surface of BaZrO3, protonic species are found to be energetically more stable than in the bulk by 1.1 eV and 1.6 eV on the BaO and ZrO2 surface terminations, respectively. At these terminations, the energy of protons recover the bulk value after penetrating three surface layers, and the energy cost associated with bulk incorporation is larger than 1 eV.
Cardiovascular magnetic resonance assessment of adults late after an atrial redirection operation for transposition is demanding and time consuming. We hypothesised that the relatively fast and standardised 3-dimensional time-resolved contrast-enhanced magnetic resonance angiography, or dynamic angiography, would be valuable in the periodic follow-up of these patients.
We investigated prospectively 36 adults with transposition using dynamic angiography, comparing our results against a comprehensive but non-contrast cardiovascular magnetic resonance protocol. We acquired 6 dynamic angiographic datasets after injection of contrast. The primary aim was to detect significant obstruction of the pathways for venous flow.
In 4 patients (11%), we found evidence of moderate-to-severe, and thus clinically important, obstruction of systemic venous channels on standard cardiovascular magnetic resonance. All these patients were correctly identified by dynamic angiography. In 4 additional patients, we found mild and haemodynamically insignificant obstructions in the systemic venous channels. Of the 8 (22%) patients with any obstruction, 6 were detected by angiography. There were no false positives reported, giving sensitivity of 75% and specificity of 100%, a positive predictive value of 100%, and negative predictive value of 93%. In 1 patient, there was a moderate obstruction of the pulmonary venous compartment which was not readily seen by dynamic angiography.
3-dimensional dynamic angiography is a useful method for detecting anatomically moderate-to-severe, but not mild, obstructions in the systemic venous channels following Mustard repair for transposition. This technique can be used as a single imaging method and/or as complimentary to standard two dimensional cardiovascular magnetic resonance techniques for detection of clinically important obstructions in the systemic venous channels.
La0.8Sr0.2Fe0.6Ni0.4O3-x - Ce0.9Gd0.1O2-x and La0.8Sr0.2Fe0.8Co0.2O3-x - Ce0.9Gd0.1O2-x nanocomposites were synthesized via ultrasonic dispersion of nanocrystalline powders of perovskite and fluorite oxides in acetone with addition of a surfactant, followed by drying and sintering at temperatures up to 1200°C. The evolution of the structure of samples with sintering temperature was studied by XRD and TEM with EDX and compared with the data on conductivity, oxygen isotope exchange, O2 TPD, H2 and CH4 TPR. Preliminary testing of button-size cells with cathodes supported on thin YSZ layer covering Ni/YSZ cermet demonstrated a high and stable performance of LSNF–GDC composite promising for the practical application.
Colloidal crystal templating has been used to prepare three-dimensionally ordered macroporous (3DOM) films of La1-xSrxMnO3-d (LSM), yttria stabilized zirconia (YSZ) and porous composites of LSM and YSZ. These materials have direct applications as cathodes in solid oxide fuel cells (SOFCs). The 3DOM materials have been prepared by low temperature processing, which is a major step towards overcoming electrode sintering, interdiffusion and deleterious phase formation associated with conventional high temperature processing. The preparation of porous composites and the elimination of high temperature densification presents an opportunity to create SOFCs with a large number of triple phase boundaries which should be accompanied by an corresponding improvement in device performance. The microstructure of the 3DOM films was assessed using scanning electron microscopy and the crystal structure and phase purity assessed by x-ray diffraction.
The nanocrystalline samples of 10wt.%Scandia stabilized Zirconia (10ScSZ) and 1wt.%Ceria doped ScSZ (1Ce10ScSZ) prepared via co-precipitation route were characterized and compared to commercially available samples regarding their transport properties and electrical conductivity. The results of oxygen isotope experiments show that for Zirconia-based electrolytes, the rate of heteroexchange is lower than that for Samaria-doped Ceria. The results of Secondary Ions Mass Spectrometry (SIMS) indicate that all admixed components are present both in the surface layer and the bulk of the studied samples with pronounced segregation on the grain boundary. The highest total conductivity is observed for DKKK sample. In the range of 600-400°C the highest conductivity observed for synthesized nanocrystalline 1Ce10ScSZ sample is explained by the effect of segregated Scandia doped Ceria surface layers.
When Fontan and Baudet devised what has become known as the Fontan operation, they understandably assumed that inflow and outflow valves should be included to achieve a pump-like action of the subpulmonary right atrial cavity. Over the following years, however, it became apparent that valves did not function satisfactorily in this situation. Worse, the implanted valves had a tendency to become obstructive, which often lead to critical elevation of the already raised systemic venous pressure. Surgeons gradually realised that the outcomes of surgery designed to create the Fontan circulation were likely to be better without inclusion of valves in the subpulmonary right atrium, and they stopped putting them in.
Congenital anomalies of the tricuspid valve, and/or its supporting apparatus, leading to severe tricuspid regurgitation are rare. Although well tolerated in early childhood, long-standing and progressive volume loading of the right heart leads to symptoms of decreased exercise tolerance, and may predispose to arrhythmias in the long term. We report three cases of severe tricuspid regurgitation related to anomalies of the cords supporting the antero-superior leaflet of the tricuspid valve. Shortened cords leading to tethering of the leaflet were seen in two cases, and hypoplasia of the leaflet in the other. In all cases, the regurgitant jet was directed posteriorly towards the coronary sinus and atrial septum. Surgical repair was possible in one case, while it proved necessary to replace the valve in a second. The third child is asymptomatic and under regular review.
When used as ceramic membranes for the electrically driven separation of oxygen from air, BIMEVOX materials allow the production of high oxygen fluxes at moderate temperature, 300–600°C. However, 18O/16O Isotope Exchange Depth Profile Technique revealed low kinetics of oxygen transfer at the surface of these ceramics when studied under equilibrium. These kinetics were considerably enhanced when a current was applied. The same membranes were characterized under working conditions using X-ray synchrotron and neutron radiations. Their dynamical transformation under bias was confirmed and explained by a slight reduction of the BIMEVOX electrolyte under working conditions.
A patient with unrepaired complex pulmonary atresia had a normal life, achieving two successful pregnancies, until the age of 44 years. Confluent central pulmonary arteries were supplied by a fistu-lous communication from the left coronary artery, and from other collateral arteries arising from the underside of the aortic arch. Unusual aneurysms were present. Death at the age of 46 resulted from dissection and rupture of an aneurysmal dilation of the pulmonary trunk.
Gadolinia-doped ceria electrolyte is being investigated as an alternative electrolyte for solid oxide fuel cells operating at temperatures below 700°C. Measurements were made to determine the effects that small additions of Ca, Pr and Fe to gadolinia-doped ceria have on the bulk and grain boundary conductivities. These small additions (1–2%) of dopant did not alter the bulk conductivity significantly but resulted in a large increase in the grain boundary conductivity. The grain boundary conductivity was similar for all three electrolyte compositions. These results are explained by the possible formation of second phases at the grain boundary, which can incorporate impurity elements. The electronic conductivity in these electrolyte materials was also evaluated, but it was found that the Ca, Pr and Fe additions do not reduce the electronic conductivity compared to a standard Gd-doped ceria sample.
We discuss a patient with recoarctation of the aorta who, 4 weeks after reoperation, presented with fresh haemoptysis and was subsequently found at delayed emergency surgery to have a leaking false aortic aneurysm. The case emphasizes the significance of haemoptysis following repair of recoarctation, the difficulty of reoperation due to abnormalities of the aortic wall, and the value of serial magnetic resonance imaging in demonstrating regions of different signal intensity from haemorrhages of varying age around a leaking false aortic aneurysm.