Spray pyrolysis of La0.6Sr0.4Co0.2Fe0.8O3-δ thin film cathodes

Spray pyrolysis has been used to prepare La0.6 Sr0.4Co0.2Fe0.8O3-δ thin film cathodes for solid oxide fuel cell (SOFC) applications. The films are polycrystalline with nano-meter sized grains and less than 1 μm in thickness. Deposition parameters for film deposition have been established. The ratio of deposition temperature to solvent boiling point is found to be the most important processing parameter that determines whether a crack free homogeneous and coherent film is obtained. The morphology can be tailored by the deposition parameters. Annealing at 650∘C for four hours in air results in coherent films of the desired perovskite phase. The films are potential cathodes for thin film micro-solid oxide fuel cell

Spray pyrolysis of La0.6Sr0.4Co0.2Fe0.8O3-δ thin film cathodes

Spray pyrolysis has been used to prepare La0.6 Sr0.4Co0.2Fe0.8O3-δ thin film cathodes for solid oxide fuel cell (SOFC) applications. The films are polycrystalline with nano-meter sized grains and less than 1 μm in thickness. Deposition parameters for film deposition have been established. The ratio of deposition temperature to solvent boiling point is found to be the most important processing parameter that determines whether a crack free homogeneous and coherent film is obtained. The morphology can be tailored by the deposition parameters. Annealing at 650∘C for four hours in air results in coherent films of the desired perovskite phase. The films are potential cathodes for thin film micro-solid oxide fuel cell

Microsatellite analysis of raccoon (Procyon lotor) population structure across an extensive metropolitan landscape

Understanding population structure can lend insight into the spread of animal-borne disease, and the effects of anthropogenic land use on habitat. Raccoons are highly adaptive to human land development and can persist in a wide range of habitat types, making them ideal subjects for investigating the level of population structure in a highly fragmented area. A total of 323 raccoons were livetrapped from 7 locations encompassing 3 distinct habitat types (agriculture, urban forest preserves, and residential) across the Chicago metropolitan region (maximum distance between 2 sites was 128 km). Genetic analyses of 14 microsatellite loci indicate that although raccoon populations across the region share up to 50% of the allelic diversity, they segregated into at least 2 distinct subpopulations, dividing the Chicago metropolitan region into northern and southern groups with further structure occurring within these larger groups. Incorporating sample sites between the identified north- south groups may provide greater resolution as to where this split occurs. Although there is evidence of population structure between all sample sites, migrant analysis suggests there is enough gene flow to preserve genetic diversity throughout the populatio

Relativistic Treatment of Hypernuclear Decay

We compute for the first time the decay width of lambda-hypernuclei in a relativistic mean-field approximation to the Walecka model. Due to the small mass difference between the lambda-hyperon and its decay products---a nucleon and a pion---the mesonic component of the decay is strongly Pauli blocked in the nuclear medium. Thus, the in-medium decay becomes dominated by the non-mesonic, or two-body, component of the decay. For this mode, the lambda-hyperon decays into a nucleon and a spacelike nuclear excitation. In this work we concentrate exclusively on the pion-like modes. By relying on the analytic structure of the nucleon and pion propagators, we express the non-mesonic component of the decay in terms of the spin-longitudinal response function. This response has been constrained from precise quasielastic (p,n) measurements done at LAMPF. We compute the spin-longitudinal response in a relativistic random-phase-approximation model that reproduces accurately the quasielastic data. By doing so, we obtain hypernuclear decay widths that are considerably smaller---by factors of two or three---relative to existing nonrelativistic calculations.Comment: Revtex: 18 pages and 4 postscript figure

Heart valve replacement with the Björk-Shiley and St Jude Medical prostheses: A randomized comparison in 178 patients

In 178 patients, a randomized prospective comparison between the 60° spherical disc Björk-Shiley (BS) and the St Jude Medical (SJM) heart valve prostheses was performed. Four-week perioperative mortality was zero in the BS (n = 84) and 4.3% in the SJM group (n = 94). During a mean ( ± SD) follow-up of 52 ± 20 months or 778 patient-years, late cardiac mortality per year was 2.4% in the BS and 2.2% in the SJM group. The yearly thromboembolic rates were 1.4% in the BS and 2.0% in the SJM group. There was no mechanical valve failure or haemolytic anaemia. Paravalvular leaks and major bleeding complications occurred at low rates in both groups (1.1% and2.2% per year in BS; 0.7% and 1.7% per year in SJM). Functional results were similarly good with 96% of patients with BS valves and 95% of patients with SJM prostheses being in NYHA classes I and II, respectively. We conclude that heart valve replacement with mechanical prostheses can be performed with equally good results using either the Björk-Shiley spherical disc valve or the St Jude Medical bileaflet prosthesi

Novel Weak Decays in Doubly Strange Systems

The strangeness-changing ($\Delta S = 1$) weak baryon-baryon interaction is studied through the nonmesonic weak decay of double-$\Lambda$ hypernuclei. Besides the usual nucleon-induced decay $\Lambda N \to N N$ we discuss novel hyperon-induced decay modes $\Lambda \Lambda \to \Lambda N$ and $\Lambda \Lambda \to \Sigma N$. These reactions provide unique access to the exotic $\Lambda \Lambda$K and $\Lambda \Sigma$K vertices which place new constraints on Chiral Pertubation Theory ($\chi$PT) in the weak SU(3) sector. Within a meson-exchange framework, we use the pseudoscalar $\pi,\eta,K$ octet for the long-range part while parametrizing the short-range part through the vector mesons $\rho, \omega, K^*$. Realistic baryon-baryon forces for the $S=0,-1$ and -2 sectors account for the strong interaction in the initial and final states. For $^6_{\Lambda \Lambda}$He the new hyperon-induced decay modes account for up to 4% of the total nonmesonic decay rate. Predictions are made for all possible nonmesonic decay modes.Comment: 19 pages, 2 ps figures, 9 table

Optical Drug Monitoring: Photoacoustic Imaging of Nanosensors to Monitor Therapeutic Lithium in Vivo

Personalized medicine could revolutionize how primary care physicians treat chronic disease and how researchers study fundamental biological questions. To realize this goal, we need to develop more robust, modular tools and imaging approaches for in vivo monitoring of analytes. In this report, we demonstrate that synthetic nanosensors can measure physiologic parameters with photoacoustic contrast, and we apply that platform to continuously track lithium levels in vivo. Photoacoustic imaging achieves imaging depths that are unattainable with fluorescence or multiphoton microscopy. We validated the photoacoustic results that illustrate the superior imaging depth and quality of photoacoustic imaging with optical measurements. This powerful combination of techniques will unlock the ability to measure analyte changes in deep tissue and will open up photoacoustic imaging as a diagnostic tool for continuous physiological tracking of a wide range of analytes

The Axial-Vector Current in Nuclear Many-Body Physics

Weak-interaction currents are studied in a recently proposed effective field theory of the nuclear many-body problem. The Lorentz-invariant effective field theory contains nucleons, pions, isoscalar scalar ($\sigma$) and vector ($\omega$) fields, and isovector vector ($\rho$) fields. The theory exhibits a nonlinear realization of $SU(2)_L \times SU(2)_R$ chiral symmetry and has three desirable features: it uses the same degrees of freedom to describe the axial-vector current and the strong-interaction dynamics, it satisfies the symmetries of the underlying theory of quantum chromodynamics, and its parameters can be calibrated using strong-interaction phenomena, like hadron scattering or the empirical properties of finite nuclei. Moreover, it has recently been verified that for normal nuclear systems, it is possible to systematically expand the effective lagrangian in powers of the meson fields (and their derivatives) and to reliably truncate the expansion after the first few orders. Here it is shown that the expressions for the axial-vector current, evaluated through the first few orders in the field expansion, satisfy both PCAC and the Goldberger--Treiman relation, and it is verified that the corresponding vector and axial-vector charges satisfy the familiar chiral charge algebra. Explicit results are derived for the Lorentz-covariant, axial-vector, two-nucleon amplitudes, from which axial-vector meson-exchange currents can be deduced.Comment: 32 pages, REVTeX 4.0 with 12pt.rtx, aps.rtx, revsymb.sty, revtex4.cls, plus 14 figures; two sentences added in Summary; two references adde

Many-Body Currents and the Strange-Quark Content of 4he

Meson-exchange current (MEC) contributions to the parity-violating (PV) asymmetry for elastic scattering of polarized electrons from $^4$He are calculated over a range of momentum transfer using Monte Carlo methods and a variational $^4$He ground state wavefunction. The results indicate that MEC's generate a negligible contribution to the asymmetry at low-|\qv|, where a determination of the nucleon's mean square strangeness radius could be carried out at CEBAF. At larger values of momentum transfer -- beyond the first diffraction minimum -- two-body corrections from the $\rho$-$\pi$ \lq\lq strangeness charge" operator enter the asymmetry at a potentially observable level, even in the limit of vanishing strange-quark matrix elements of the nucleon. For purposes of constraining the nucleon's strangeness electric form factor, theoretical uncertainties associated with these MEC contributions do not appear to impose serious limitations.Comment: 32 TEX pages and 7 figures (not included, available from authors upon request), CEBAF Preprint #TH-94-1