FUSE Observations of the Dwarf Nova SW UMa During Quiescence

We present spectroscopic observations of the short-period cataclysmic variable SW Ursa Majoris, obtained by the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite while the system was in quiescence. The data include the resonance lines of O VI at 1031.91 and 1037.61 A. These lines are present in emission, and they exhibit both narrow (~ 150 km/s) and broad (~ 2000 km/s) components. The narrow O VI emission lines exhibit unusual double-peaked and redshifted profiles. We attribute the source of this emission to a cooling flow onto the surface of the white dwarf primary. The broad O VI emission most likely originates in a thin, photoionized surface layer on the accretion disk. We searched for emission from H_2 at 1050 and 1100 A, motivated by the expectation that the bulk of the quiescent accretion disk is in the form of cool, molecular gas. If H_2 is present, then our limits on the fluxes of the H_2 lines are consistent with the presence of a surface layer of atomic H that shields the interior of the disk. These results may indicate that accretion operates primarily in the surface layers of the disk in SW UMa. We also investigate the far-UV continuum of SW UMa and place an upper limit of 15,000 K on the effective temperature of the white dwarf.Comment: 21 Pages, 3 figures, to be published in Ap

Planar Josephson Tunnel Junctions in a Transverse Magnetic Field

Traditionally, since the discovery of the Josephson effect in 1962, the magnetic diffraction pattern of planar Josephson tunnel junctions has been recorded with the field applied in the plane of the junction. Here we discuss the static junction properties in a transverse magnetic field where demagnetization effects imposed by the junction geometry and configuration of the electrodes are important. Measurements of the critical current versus magnetic field in planar Nb-based high-quality junctions with different geometry, size and critical current density show that it is advantageous to use a transverse magnetic field rather than an in-plane field to suppress the Josephson tunnel current and Fiske resonances in practical applications.Comment: 5 pages, 2 figures, submitted to Journal of Applied Physic

A Comparison of Ultraviolet, Optical, and X-Ray Imagery of Selected Fields in the Cygnus Loop

During the Astro-1 and Astro-2 Space Shuttle missions in 1990 and 1995, far ultraviolet (FUV) images of five 40' diameter fields around the rim of the Cygnus Loop supernova remnant were observed with the Ultraviolet Imaging Telescope (UIT). These fields sampled a broad range of conditions including both radiative and nonradiative shocks in various geometries and physical scales. In these shocks, the UIT B5 band samples predominantly CIV 1550 and the hydrogen two-photon recombination continuum. Smaller contri- butions are made by emission lines of HeII 1640 and OIII] 1665. We present these new FUV images and compare them with optical Halpha and [OIII], and ROSAT HRI X-ray images. Comparing the UIT images with those from the other bands provides new insights into the spatial variations and locations of these different types of emission. By comparing against shock model calculations and published FUV spectroscopy at select locations, we surmise that resonance scattering in the strong FUV permitted lines is widespread in the Cygnus Loop, especially in the bright optical filaments typically selected for observation in most previous studies.Comment: 21 pages with 10 figures. See http://www.pha.jhu.edu/~danforth/uit/ for full-resolution figure

Universal restrictions to the conversion of heat into work derived from the analysis of the Nernst theorem as a uniform limit

We revisit the relationship between the Nernst theorem and the Kelvin-Planck statement of the second law. We propose that the exchange of entropy uniformly vanishes as the temperature goes to zero. The analysis of this assumption shows that is equivalent to the fact that the compensation of a Carnot engine scales with the absorbed heat so that the Nernst theorem should be embedded in the statement of the second law. ----- Se analiza la relaci{\'o}n entre el teorema de Nernst y el enunciado de Kelvin-Planck del segundo principio de la termodin{\'a}mica. Se{\~n}alamos el hecho de que el cambio de entrop{\'\i}a tiende uniformemente a cero cuando la temperatura tiende a cero. El an{\'a}lisis de esta hip{\'o}tesis muestra que es equivalente al hecho de que la compensaci{\'o}n de una m{\'a}quina de Carnot escala con el calor absorbido del foco caliente, de forma que el teorema de Nernst puede derivarse del enunciado del segundo principio.Comment: 8pp, 4 ff. Original in english. Also available translation into spanish. Twocolumn format. RevTe

Underground railroads: citizen entitlements and unauthorized mobility in the antebellum period and today

In recent years, some scholars and prominent political figures have advocated the deepening of North American integration on roughly the European Union model, including the creation of new political institutions and the free movement of workers across borders. The construction of such a North American Union, if it included even a very thin trans-state citizenship regime, could represent the most significant expansion of individual entitlements in the region since citizenship was extended to former slaves in the United States. With such a possibility as its starting point, this article explores some striking parallels between the mass, legally prohibited movement across boundaries by fugitive slaves in the pre-Civil War period, and that by current unauthorized migrants to the United States. Both were, or are, met on their journeys by historically parallel groups of would-be helpers and hinderers. Their unauthorized movements in both periods serve as important signals of incomplete entitlements or institutional protections. Most crucially, moral arguments for extending fuller entitlements to both groups are shown here to be less distinct than may be prima facie evident, reinforcing the case for expanding and deepening the regional membership regime

Influence of climatic variables on crown condition in pine forests of Northern Spain

Producción CientíficaThe aim of this study was to find relationships between crown condition and some climatic parameters to identify which are those having a main influence on crown condition, and how this influence is shown in the tree (crown transparency), and to contribute to the understanding of how these parameters will affect under future climate change scenarios

Highlights of the mini-symposium on extracellular vesicles in inter-organismal communication, held in Munich, Germany, August 2018

All living organisms secrete molecules for intercellular communication. Recent research has revealed that extracellular vesicles (EVs) play an important role in inter-organismal cell-to-cell communication by transporting diverse messenger molecules, including RNA, DNA, lipids and proteins. These discoveries have raised fundamental questions regarding EV biology. How are EVs biosynthesized and loaded with messenger/cargo molecules? How are EVs secreted into the extracellular matrix? What are the EV uptake mechanisms of recipient cells? As EVs are produced by all kind of organisms, from unicellular bacteria and protists, filamentous fungi and oomycetes, to complex multicellular life forms such as plants and animals, basic research in diverse model systems is urgently needed to shed light on the multifaceted biology of EVs and their role in inter-organismal communications. To help catalyse progress in this emerging field, a mini-symposium was held in Munich, Germany in August 2018. This report highlights recent progress and major questions being pursued across a very diverse group of model systems, all united by the question of how EVs contribute to inter-organismal communication

An XMM-Newton Observation of the Local Bubble Using a Shadowing Filament in the Southern Galactic Hemisphere

We present an analysis of the X-ray spectrum of the Local Bubble, obtained by simultaneously analyzing spectra from two XMM-Newton pointings on and off an absorbing filament in the Southern galactic hemisphere (b ~ -45 deg). We use the difference in the Galactic column density in these two directions to deduce the contributions of the unabsorbed foreground emission due to the Local Bubble, and the absorbed emission from the Galactic halo and the extragalactic background. We find the Local Bubble emission is consistent with emission from a plasma in collisional ionization equilibrium with a temperature $\log T_{LB} = 6.06^{+0.02}_{-0.04}$ and an emission measure of 0.018 cm^{-6} pc. Our measured temperature is in good agreement with values obtained from ROSAT All-Sky Survey data, but is lower than that measured by other recent XMM-Newton observations of the Local Bubble, which find $\log T_{LB} \approx 6.2$ (although for some of these observations it is possible that the foreground emission is contaminated by non-Local Bubble emission from Loop I). The higher temperature observed towards other directions is inconsistent with our data, when combined with a FUSE measurement of the Galactic halo O VI intensity. This therefore suggests that the Local Bubble is thermally anisotropic. Our data are unable to rule out a non-equilibrium model in which the plasma is underionized. However, an overionized recombining plasma model, while observationally acceptable for certain densities and temperatures, generally gives an implausibly young age for the Local Bubble (\la 6 \times 10^5 yr).Comment: Accepted for publication in the Astrophysical Journal. 16 pages, 9 figure

Dynamical Masses for Low-Mass Pre-Main Sequence Stars: A Preliminary Physical Orbit for HD 98800 B

We report on Keck Interferometer observations of the double-lined binary (B) component of the quadruple pre-main sequence (PMS) system HD 98800. With these interferometric observations combined with astrometric measurements made by the Hubble Space Telescope Fine Guidance Sensors (FGS), and published radial velocity observations we have estimated preliminary visual and physical orbits of the HD 98800 B subsystem. Our orbit model calls for an inclination of 66.8 $\pm$ 3.2 deg, and allows us to infer the masses and luminosities of the individual components. In particular we find component masses of 0.699 $\pm$ 0.064 and 0.582 $\pm$ 0.051 M_{\sun} for the Ba (primary) and Bb (secondary) components respectively. Modeling of the component SEDs finds temperatures and luminosities in agreement with previous studies, and coupled with the component mass estimates allows for comparison with PMS models in the low-mass regime with few empirical constraints. Solar abundance models seem to under-predict the inferred component temperatures and luminosities, while assuming slightly sub-solar abundances bring the models and observations into better agreement. The present preliminary orbit does not yet place significant constraints on existing pre-main sequence stellar models, but prospects for additional observations improving the orbit model and component parameters are very good.Comment: 20 pages, 6 figures, ApJ in press; tables 2 and 3 to be included in ApJ versio

Reassurance Policing and Signal Crimes

A reassurance function for policing was first considered by American psychologist Charles Bahn (1974: 338) as “feelings of safety that a citizen experiences when he knows that a police officer or patrol car is nearby.” This idea was taken forward in Britain by Martin Innes and colleagues in the early 2000s through the development of a signal crimes perspective. At this time, British policing implemented a National Reassurance Policing Programme (NRPP) where local policing priorities were decided through consultation with local communities. The impact of reassurance policing has since spread and the approach has also been considered in Australia, Belgium, the Netherlands, and Sweden. In this entry, the background to reassurance policing is considered with particular reference to the work of Charles Bahn and Martin Innes and colleagues. The development of a policy of reassurance policing in Britain is also examined. The successes and limitations of the approach are considered and three main issues identified: that reassurance needs to be a consideration for all policing; that increases in visible patrol need to be questioned (especially at a time of budget restraint); and that reassurance policing has the potential to be a model of democratic policing, but only if consultation is truly inclusive, for instance, including those that have been victimized and groups that have been targets of police activity such as young people, the homeless, and other minority and marginalized groups