Oxygen permeation through oxygen ion oxide-noble metal dual phase composites

Oxygen permeation behaviour of three composites, yttria-stabilized zirconia-palladium, erbia-stabilized bismuth oxidenoble metal (silver, gold) was studied. Oxygen permeation measurements were performed under controlled oxygen pressure gradients at elevated temperatures. Air was supplied at one side of a dense sintered disk specimen, while helium was fed at the opposite side to sweep away the permeated oxygen. This research has demonstrated that in addition to the presence of percolative metal phase in the oxide matrix, a large ionic conductivity of the oxide phase and a high catalytic activity of the metal phase towards surface oxygen exchange are required for the dual phase composite to possess high oxygen permeability. The bismuth oxide-silver composite fulfils these requirements, hence showing the best oxygen permeability

Filtered density functions from direct numerical simulation of a reactive jet in cross-flow

Direct numerical simulation (DNS) with multi-step hydrogen-air chemical kinetics is used to investigate the nearfield of a flame stabilized above a reactive jet in cross-flow (JICF). JICF configurations are typically used where rapid mixing is desirable; classical applications are fuel injection nozzles and dilution holes in gas turbine combustors. Due to the computational cost of DNS, approximate solution methods such as large-eddy simulation (LES) are essential to parametrically study the effect of changing fuel jet configurations on the far field, but these methods require submodels capable of accurately capturing the near-field flame stabilization for success. By incorporating a wealth of turbulence chemistry interactions (between the flame and vorticity generated by the jet shear layer instability as well as product recirculation by a large counter-rotating vortex pair), this DNS is exceptionally well suited to exploration of unclosed terms in LES formulations such as the chemical source-term. One quantity of direct relevance to several models for stratified combustion, such as the Bray-Moss (BM) model and doubly-conditional source-term estimation (DCSE), is the filtered density function for the mixture fraction ! and partially premixed progress variable c. Empirical extraction of the filtered density functions of progress variable and mixture fraction at two representative locations demonstrates the complexity of approximating these two functions from a one- or two-parameter functional form

Characterization of Grain Boundaries in Superplastically Deformed Y-TZP Ceramics

The effects of compressive deformation on the grain boundary characteristics of fine-grained Y-TZP have been investigated using surface spectroscopy, impedance analysis, and transmission electron microscopy. After sintering at low temperature (1150°C), the grain boundaries are covered by an ultrathin (1nm) yttrium-rich amorphous film. After deformation at 1200°–1300°C under low stress, some grain boundaries are no longer covered by the amorphous film. Yttrium segregation seems to occur only at wetted grain boundaries. Evidence has been found that the extent of dewetting increases with increasing applied stress

Microstructural development, electrical properties and oxygen permeation of zirconia-palladium composites

Yttria-stabilized cubic zirconia (YSZ)-palladium dual phase composites have been investigated. The percolative composite containing 40 vol% Pd (ZYPd40) showed a much larger oxygen permeability than that of the non-percolative composite containing 30 vol% Pd (ZYPd30). For a 2.0 mm thick percolative composite, an oxygen flux of 4.3 × 10−8 mol/cm2/s was measured at 1100 °C with oxygen partial pressures at the feed and permeate sides being 0.209 and 0.014 atm, respectively. This value is two orders of magnitude larger than that observed for a 2.0 mm thick non-percolative composite at the same temperature with the oxygen partial pressures at the feed and permeate sides being 0.209 and 1.5 × 10−4 atm, respectively. From the dependence of the oxygen permeation on the temperature and on the oxygen partial pressures, it was concluded that the transport of the oxygen ions through the YSZ phase in the percolative system was the rate limiting step

Singlet-triplet transitions in highly correlated nanowire quantum dots

We consider a quantum dot embedded in a three-dimensional nanowire with tunable aspect ratio a. A configuration interaction theory is developed to calculate the energy spectra of the finite 1D quantum dot systems charged with two electrons in the presence of magnetic fields B along the wire axis. Fruitful singlet-triplet transition behaviors are revealed and explained in terms of the competing exchange interaction, correlation interaction, and spin Zeeman energy. In the high aspect ratio regime, the singlet-triplet transitions are shown designable by tuning the parameters a and B. The transitions also manifest the highly correlated nature of long nanowire quantum dots.Comment: 4 pages, 4 figure

Classification and nondegeneracy of SU(n+1)SU(n+1) Toda system with singular sources

We consider the following Toda system \Delta u_i + \D \sum_{j = 1}^n a_{ij}e^{u_j} = 4\pi\gamma_{i}\delta_{0} \text{in}\mathbb R^2, \int_{\mathbb R^2}e^{u_i} dx -1$,$\delta_0$is Dirac measure at 0, and the coefficients$a_{ij}$form the standard tri-diagonal Cartan matrix. In this paper, (i) we completely classify the solutions and obtain the quantization result:$$\sum_{j=1}^n a_{ij}\int_{\R^2}e^{u_j} dx = 4\pi (2+\gamma_i+\gamma_{n+1-i}), \;\;\forall\; 1\leq i \leq n.$$This generalizes the classification result by Jost and Wang for$\gamma_i=0$,$\forall \;1\leq i\leq n$. (ii) We prove that if$\gamma_i+\gamma_{i+1}+...+\gamma_j \notin \mathbb Z$for all$1\leq i\leq j\leq n$, then any solution$u_i$ is \textit{radially symmetric} w.r.t. 0. (iii) We prove that the linearized equation at any solution is \textit{non-degenerate}. These are fundamental results in order to understand the bubbling behavior of the Toda system.Comment: 28 page

Results of the MRI substudy of the intravenous magnesium efficacy in stroke trial

<p><b>Background and Purpose:</b>Although magnesium is neuroprotective in animal stroke models, no clinical benefit was confirmed in the Intravenous Magnesium Efficacy in Stroke (IMAGES) trial of acute stroke patients. The Magnetic Resonance in IMAGES (MR IMAGES) substudy investigated the effects of magnesium on the imaging surrogate outcome of infarct growth.</p> <p><b>Methods:</b> IMAGES trial patients in participating centers were randomized to receive either intravenous magnesium or placebo within 12 hours of stroke onset. Infarct growth was defined as volume difference between baseline diffusion-weighted imaging and day 90 fluid-attenuated inversion recovery image lesions. Patients who died were imputed the largest infarct growth observed.</p> <p><b>Results:</b> Among the 90 patients included in the primary analysis, there was no difference in infarct growth (median absolute growth, P=0.639; median percentage growth, P=0.616; proportion with any growth, P=0.212) between the 46 treated with magnesium and 44 with placebo. Infarct growth correlated with NIHSS score change from baseline to day 90. There was a trend showing baseline serum glucose correlated with infarct growth with magnesium treatment, but not in the placebo group. The mismatch frequency was reduced from 73% to 47% by increasing the mismatch threshold from >20% to >100% of core volume.</p> <p><b>Conclusions:</b> Infarct growth, confirmed here as a surrogate for clinical progression, was similar between magnesium and placebo treatment, paralleling the main IMAGES trial clinical outcomes. Glucose was a covariate for infarct growth with magnesium treatment. A more stringent mismatch threshold to define penumbra more appropriately would have excluded half of the patients in this 12-hour time window stroke study.</p&gt

Luttinger Liquid Instability in the One Dimensional t-J Model

We study the t-J model in one dimension by numerically projecting the true ground state from a Luttinger liquid trial wave function. We find the model exhibits Luttinger liquid behavior for most of the phase diagram in which interaction strength and density are varied. However at small densities and high interaction strengths a new phase with a gap to spin excitations and enhanced superconducting correlations is found. We show this phase is a Luther-Emery liquid and study its correlation functions.Comment: REVTEX, 11 pages. 4 Figures available on request from [email protected]

New improved Moser-Trudinger inequalities and singular Liouville equations on compact surfaces

We consider a singular Liouville equation on a compact surface, arising from the study of Chern-Simons vortices in a self dual regime. Using new improved versions of the Moser-Trudinger inequalities (whose main feature is to be scaling invariant) and a variational scheme, we prove new existence results.Comment: to appear in GAF

PHP61 The Financial Impacts of Pharmacist Intervention in Inpatient Department of a Local Hospital in Taiwan

Morphometric analysis of S. mortenseni. (DOC 44 kb