Magnon Mediated Electric Current Drag Across a Ferromagnetic Insulator Layer

In a semiconductor hererostructure, the Coulomb interaction is responsible for the electric current drag between two 2D electron gases across an electron impenetrable insulator. For two metallic layers separated by a ferromagnetic insulator (FI) layer, the electric current drag can be mediated by a nonequilibrium magnon current of the FI. We determine the drag current by using the semiclassical Boltzmann approach with proper boundary conditions of electrons and magnons at the metal-FI interface.Comment: 13 pages, 2 figures: to appear in PR

Far-flung Filaments of Ejecta in the Young Supernova Remnant G292.0+1.8

New optical images of the young SNR G292.0+1.8, obtained from the 0.9-m telescope at CTIO, show a more extensive network of filaments than had been known previously. Filaments emitting in [O III] are distributed throughout much of the 8 arcmin diameter shell seen in X-ray and radio images, including a few at the very outermost shell limits. We have also detected four small complexes of filaments that show [S II] emission along with [OIII]. In a single long-slit spectrum we find variations of almost an order of magnitude in the relative strengths of oxygen and sulfur lines, which must result from abundance variations. None of the filaments, with or without [S II], shows any evidence for hydrogen, so all appear to be fragments of pure SN ejecta. The [S II] filaments provide the first evidence for undiluted products of oxygen burning in the ejecta from the supernova that gave rise to G292.0+1.8. Some oxygen burning must have occurred, but the paucity of [S II]-emitting filaments suggests that either the oxygen burning was not extensive or that most of its products have yet to be excited. Most of the outer filaments exhibit radial, pencil-like morphologies that suggest an origin as Rayleigh-Taylor fingers of ejecta, perhaps formed during the explosion. Simulations of core-collapse supernovae predict such fingers, but these have never before been so clearly observed in a young SNR. The total flux from the SNR in [OIII] 5007 is 5.4 * 10**-12 ergs/cm**2/s. Using a distance of 6 kpc and an extinction correction corresponding to E(B-V) = 0.6 (lower than previous values but more consistent both with our data and radio and X-ray estimates of NH), this leads to a luminosity of 1.6 * 10**35 ergs/s in the 5007 Ang. line.Comment: 32 pages including 10 figures, and 3 tables, accepted for publication in AJ. Vol 132, July 2006. Higher resolution versions of the figures and a pdf of the manuscript can be found at http://www-int.stsci.edu/~long/papers/g292_optical

Brief Note Bat Species Diversity Patterns in East Central Indiana

Author Institution: Aullwood Audubon Center; Department of Zoology, Miami University; Department of Biology, Earlham Colleg

Quantification of opportunities for early-stage paramedicine students to practice clinical skills during clinical placements compared with an equal dose of simulation-based workshops

Introduction A reported advantage of simulation-based learning environments (SLE) over clinical placements (CPs) is that the former can provide a greater number and breadth of opportunities to practice level-appropriate clinical skills compared with the random patient presentations provided during the latter. Although logical and widely accepted as fact, we find no published evidence to demonstrate the magnitude, nor indeed veracity, of this assumption. We therefore sought to quantify the clinical skills practiced by entry-level paramedicine students attending a well-selected CP compared with an equal dosage of SLE. Methods N=37 first-year paramedicine students completed activity diaries during 3 days of CP and 3 days of SLE. Opportunities to practice clinical skills were quantified and coded as either: level-appropriate, beyond-level or of non-discipline relevance. Results During SLE, the average student was exposed 226 times to 11 level-appropriate clinical procedures. During CP the average student was exposed 48 times to 24 clinical procedures, the majority relevant to paramedicine (63%), but a minority level-appropriate (38%). Students’ opportunities for supervised, ‘hands on’ practice represented only 10% of exposures in either SLE or CP but in terms of raw numbers of level-appropriate opportunities, SLE provided more than CP (n=23 vs 2). Discussion Our results confirm that SLE provides substantially more opportunities than CP for students to practice level-appropriate skills and is therefore more appropriate for repetitive practice. However, CP is likely to remain useful to students for practicing interpersonal skills and contextualisation of knowledge within the broader health system. Educators should therefore carefully articulate learning objectives before choosing between SLE and CP

An independent audit of the Australian food industry\u27s voluntary front-of-pack nutrition labelling scheme for energy-dense nutrition-poor foods

Background/Objective: Since 2006, the Australian food industry has promoted its front-of-pack (FOP) food labelling system-the Daily Intake Guide (DIG)-as a success story of industry self-regulation. With over 4000 products already voluntary featuring the DIG, the industry argues that government regulation of FOP nutrition labelling is simply unnecessary. However, no independent audit of the industry\u27s self-regulation has ever been undertaken and we present the first such Australian data. Subjects/Methods: Energy-dense nutrient-poor (EDNP) snacks were audited at nine Australian supermarkets, including biscuits, candy, ice creams, chocolates, crisps, sports drinks, energy drinks, flavoured milks, sweetened juices and soft drinks. In these categories nutrition labels were recorded for 728 EDNP products in various packaging sizes. Results: The DIG was displayed on 66% of audited EDNP products but most of these (75%) did not report saturated fat and sugar content. Only generic supermarket EDNP products were likely to display saturated fat and sugar content, compared with very few branded products (48% vs 4%, P\u3c0.001). Branded products not displaying fat and sugar content contained on average 10-times more saturated fat than those displaying such (10% vs 1% DI, P\u3c0.001) and nearly twice as much sugar (21 vs 13% DI, P\u3c0.05). Conclusions: Most Australian manufacturers of EDNP products have adopted the DIG; consistent with industry claims of widespread adoption, but almost all still avoid displaying the high saturated fat and sugar content of their products by opting for the \u27energy alone\u27 option, violating the industry\u27s own voluntarily guidelines and highlighting serious weaknesses with the industry\u27s self-regulation

Temperature and Magnetic Field Enhanced Hall Slope of a Dilute 2D Hole System in the Ballistic Regime

We report the temperature($T$) and perpendicular magnetic field($B$) dependence of the Hall resistivity $\rho_{xy}(B)$ of dilute metallic two-dimensional(2D) holes in GaAs over a broad range of temperature(0.02-1.25K). The low $B$ Hall coefficient, $R_H$, is found to be enhanced when $T$ decreases. Strong magnetic fields further enhance the slope of $\rho_{xy}(B)$ at all temperatures studied. Coulomb interaction corrections of a Fermi liquid(FL) in the ballistic regime can not explain the enhancement of $\rho_{xy}$ which occurs in the same regime as the anomalous metallic longitudinal conductivity. In particular, although the metallic conductivity in 2D systems has been attributed to electron interactions in a FL, these same interactions should reduce, {\it not enhance} the slope of $\rho_{xy}(B)$ as $T$ decreases and/or $B$ increases.Comment: Accepted for publication in Physical Review Letter

PKS B1400-33: an unusual radio relic in a poor cluster

We present new arcminute resolution radio images of the low surface brightness radio source PKS B1400-33 that is located in the poor cluster Abell S753. The observations consist of 330 MHz VLA, 843 MHz MOST and 1398 and 2378 MHz ATCA data. These new images, with higher surface brightness sensitivity than previous observations, reveal that the large scale structure consists of extended filamentary emission bounded by edge-brightened rims. The source is offset on one side of symmetrically distributed X-ray emission that is centered on the dominant cluster galaxy NGC 5419. PKS B1400-33 is a rare example of a relic in a poor cluster with radio properties unlike those of most relics and halos observed in cluster environments. The diffuse source appears to have had an unusual origin and we discuss possible mechanisms. We examine whether the source could be re-energized relic radio plasma or a buoyant synchrotron bubble that is a relic of activity in NGC 5419. The more exciting prospect is that the source is relic plasma preserved in the cluster gaseous environment following the chance injection of a radio lobe into the ICM as a result of activity in a galaxy at the periphery of the cluster.Comment: 26 pages, 8 figures, accepted for publication in the Astronomical Journa

The quantum metrology triangle and the re-definition of the SI ampere and kilogram; Analysis of a reduced set of observational equations

We have developed a set of seven observational equations that include all of the physics necessary to relate the most important of the fundamental constants to the definitions of the SI kilogram and ampere. We have used these to determine the influence of alternative definitions being considered for the SI kilogram and ampere on the uncertainty of three of the fundamental constants (h, e and mu). We have also reviewed the experimental evidence for the exactness of the quantum metrology triangle resulting from experiments combining the quantum Hall effect, the Josephson effects and single-electron tunnelling.Comment: 16 pages, 3 figures & 5 table