Graded ferroelectric capacitors with robust temperature characteristics

Ferroelectric thin films offer the possibility of engineering the dielectric response for tunable components in frequency-agile rf and microwave devices. However, this approach often leads to an undesired temperature sensitivity. Compositionally graded ferroelectric films have been explored as a means of redressing this sensitivity, but experimental observations vary depending on geometry and other details. In this paper, we present a continuum model to calculate the capacitive response of graded ferroelectric films with realistic electrode geometries by accurately accounting for the polarization distribution and long-range electrostatic interactions. We show that graded c-axis poled BaxSr_(1−xT)iO_3 BST parallel plate capacitors are ineffective while graded a-axis poled BST coplanar capacitors with interdigitated electrodes are extremely effective in obtaining high and temperature-stable dielectric properties

Anatomical knowledge retention in physiotherapy students: A preliminary assessment

Introduction: Anatomical knowledge and understanding are key components of physiotherapy education and practice. Traditionally, anatomy has been taught as a foundation stream within the first year(s) of physiotherapy education. This curricular model is based on the assumption that further learning in subsequent years builds upon the knowledge gained in the early stages of the program. However, the retention rate in all basic sciences has often been called into question. In anatomy, several studies suggest that anatomy knowledge endures considerable attrition, highlighting the need for the evaluation of retention rates. This paper aimed at making a preliminary assessment of the knowledge and retention of anatomy among physiotherapy students. Materials and Methods: We used a carpal bone identification test and assessed 129 first year and 113 fourth year physiotherapy students. Results: 20% of the students managed to identify all bones while 47% were able to identify more than five bones. The best recognised bones were pisiform and scaphoid while the most difficult to identify were trapezium and trapezoid. Conclusion: Overall, first year students performed better than their fourth year counterparts which suggested attrition of anatomical knowledge. Educational strategies based on revision, integration and clinical application of anatomy could contribute towards the decrease of attrition of anatomical knowledge

Microbiological Spoilage of Aviation Turbine Fuel: Part II Evaluation of a Suitable Biocide

Addition of ethylene glycol monoethyl ether, an anti-icing fuel additive supports microbial growth when added to aviation turbine fuel in low dosages. however, increases in its concentration to certain limits effectively prevents bioactivity in the fuel. The optimum dosage of this biocide for prevention of bioactivity in aviation turbine fuel has been studied by the specified qualitative performance tests after 18 months storage of the inhibited fuel under accelerated conditions of temperature and humidity

Spatial Distributions of Multiple Dust Components in the PPN/PN Dust Shells

We investigate spatial distributions of specific dust components in the circumstellar shells of a proto-planetary nebula candidate, HD 179821, and a planetary nebula, BD$+30^{\circ}$3639, by means of spectral imaging. With high-resolution ground-based images and ISO spectra in the mid-infrared, we can derive ``dust feature only'' maps by subtracting synthesized continuum maps from the observed images at the feature wavelength. Such spatially detailed information will help to develop models for the evolution of dust grains around evolved stars.Comment: 4 pages + 7 figures, to appear in the proceedings of the conference, "Post-AGB Objects (proto-planetary nebulae) as a Phase of Stellar Evolution", Torun, Poland, July 5-7, 2000, eds. R. Szczerba, R. Tylenda, and S.K. Gorny. Figures have been degraded to minimize the total file siz

Mid-infrared imaging of the massive young star AFGL 2591: Probing the circumstellar environment of an outflow source

Most, if not all, stars are now believed to produce energetic outflows during their formation. Yet, almost 20 years after the discovery of bipolar outflows from young stars, the origins of this violent phenomenon are not well understood. One of the difficulties of probing the outflow process, particularly in the case of massive embedded stars, is a deficit of high spatial resolution observations. Here, we present sub-arcsecond-resolution mid-infrared images of one massive young stellar object, AFGL 2591, and its immediate surroundings. Our images, at 11.7, 12.5 and 18.0 microns, reveal a knot of emission ~6'' SW of the star, which may be evidence for a recent ejection event or an embedded companion star. This knot is roughly coincident with a previously seen near-infrared reflection nebula and a radio source, and lies within the known large-scale CO outflow. We also find a new faint NW source which may be another embedded lower-luminosity star. The IRAS mid-infrared spectrum of AFGL 2591 shows a large silicate absorption feature at 10 microns, implying that the primary source is surrounded by an optically thick dusty envelope. We discuss the interrelationship of these phenomena and suggest that mid-infrared imaging and spectroscopy provide powerful tools for probing massive star birth.Comment: 14 pages, 3 PostScript figures, accepted for publication in The Astrophysical Journal Letter

The ALPS project: open source software for strongly correlated systems

We present the ALPS (Algorithms and Libraries for Physics Simulations) project, an international open source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. Development is centered on common XML and binary data formats, on libraries to simplify and speed up code development, and on full-featured simulation programs. The programs enable non-experts to start carrying out numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), as well as the density matrix renormalization group (DMRG). The software is available from our web server at http://alps.comp-phys.org.Comment: For full software and introductory turorials see http://alps.comp-phys.or