Interaction of two-dimensional transverse jet with a supersonic mainstream

The interaction of a two dimensional sonic jet injected transversely into a confined main flow was studied. The main flow consisted of air at a Mach number of 2.9. The effects of varying the jet parameters on the flow field were examined using surface pressure and composition data. Also, the downstream flow field was examined using static pressure, pitot pressure, and composition profile data. The jet parameters varied were gapwidth, jet static pressure, and injectant species of either helium or nitrogen. The values of the jet parameters used were 0.039, 0.056, and 0.109 cm for the gapwidth and 5, 10, and 20 for the jet to mainstream static pressure ratios. The features of the flow field produced by the mixing and interaction of the jet with the mainstream were related to the jet momentum. The data were used to demonstrate the validity of an existing two dimensional elliptic flow code

On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer IRS and Infrared Space Observatory SWS spectra of 217 oxygen-rich asymptotic giant branch stars and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally-rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 microns. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ~10^-9 solar masses/year. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-micron feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-micron band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.Comment: Accepted for publication in MNRAS, 24 pages, 16 figure

Narrow Components within the Fe Kalpha Profile of NGC 3516: Evidence for the Importance of General Relativistic Effects?

We present results from a simultaneous Chandra HETG and XMM-Newton observation of NGC 3516. We find evidence for several narrow components of Fe Kalpha along with a broad line. We consider the possibility that the lines arise in an blob of material ejected from the nucleus with velocity ~0.25c. We also consider an origin in a neutral accretion disk, suffering enhanced illumination at 35 and 175 gravitational radii, perhaps due to magnetic reconnection. The presence of these narrow features indicates there is no Comptonizing region along the line-of-sight to the nucleus. This in turn is compelling support for the hypothesis that broad Fe Kalpha components are, in general, produced by strong gravity.Comment: 12 pages, 3 color figures. LaTeX with postscript figures. Resubmitted June 7 2002, to Astrophysical Journal Letter

Heisenberg's Universal (lns)**2 Increase of Total Cross Sections

The (lns)**2 behaviour of total cross-sections, first obtained by Heisenberg 50 years ago, receives now increased interest both on phenomenological and theoretical levels. In this paper we present a modification of the Heisenberg's model in connection with the presence of glueballs and we show that it leads to a realistic description of all existing hadron total cross-section data.Comment: 6 pages, 3 figure

CASSIS: The Cornell Atlas of Spitzer/Infrared Spectrograph Sources. II. High-resolution observations

The Infrared Spectrograph (IRS) on board the Spitzer Space Telescope observed about 15,000 objects during the cryogenic mission lifetime. Observations provided low-resolution (R~60-127) spectra over ~5-38um and high-resolution (R~600) spectra over ~10-37um. The Cornell Atlas of Spitzer/IRS Sources (CASSIS) was created to provide publishable quality spectra to the community. Low-resolution spectra have been available in CASSIS since 2011, and we present here the addition of the high-resolution spectra. The high-resolution observations represent approximately one third of all staring observations performed with the IRS instrument. While low-resolution observations are adapted to faint objects and/or broad spectral features (e.g., dust continuum, molecular bands), high-resolution observations allow more accurate measurements of narrow features (e.g., ionic emission lines) as well as a better sampling of the spectral profile of various features. Given the narrow aperture of the two high-resolution modules, cosmic ray hits and spurious features usually plague the spectra. Our pipeline is designed to minimize these effects through various improvements. A super sampled point-spread function was created in order to enable the optimal extraction in addition to the full aperture extraction. The pipeline selects the best extraction method based on the spatial extent of the object. For unresolved sources, the optimal extraction provides a significant improvement in signal-to-noise ratio over a full aperture extraction. We have developed several techniques for optimal extraction, including a differential method that eliminates low-level rogue pixels (even when no dedicated background observation was performed). The updated CASSIS repository now includes all the spectra ever taken by the IRS, with the exception of mapping observations

Reddening, Emission-Line, and Intrinsic Absorption Properties in the Narrow-Line Seyfert 1 Galaxy Akn 564

We use Hubble Space Telescope UV and optical spectra of the narrow-line Seyfert 1 (NLS1) galaxy Akn 564 to investigate its internal reddening and properties of its emission-line and intrinsic UV absorption gas. We find that the extinction curve of Akn 564, derived from a comparison of its UV/optical continuum to that of an unreddened NLS1, lacks a 2200 A bump and turns up towards the UV at a longer wavelength (4000 A) than the standard Galactic, LMC, and SMC curves. However, it does not show the extremely steep rise to 1200 A that characterizes the extinction curve of the Seyfert 1 galaxy NGC 3227. The emission-lines and continuum experience the same amount of reddening, indicating the presence of a dust screen that is external to the narrow-line region (NLR). Echelle spectra from the Space Telescope Imaging Spectrograph show intrinsic UV absorption lines due to Ly-alpha, N V, C IV, Si IV, and Si III, centered at a radial velocity of -190 km/s (relative to the host galaxy). Photoionization models of the UV absorber indicate that it has a sufficient columnand is at a sufficient distance from the nucleus (D > 95 pc) to be the source of the dust screen. Thus, Akn 564 contains a dusty ``lukewarm absorber'' similar to that seen in NGC 3227.Comment: 25 pages, 4 figures. LaTeX with encapsulated postscript figures. Accepted for publication in the Astrophysical Journa

The Spectral Energy Distribution and Emission-Line properties of the NLS1 Galaxy Arakelian 564

We present the intrinsic spectral energy distribution (SED) of the NLS1 Arakelian 564, constructed with contemporaneous data obtained during a multi-wavelength, multi-satellite observing campaign in 2000 and 2001. We compare it with that of the NLS1 Ton S180 and with those obtained for BLS1s to infer how the relative accretion rates vary among the Sy1 population. Although the peak of the SED is not well constrained, most of the energy is emitted in the 10-100 eV regime, constituting roughly half of the emitted energy in the optical/X-ray ranges. This is consistent with a primary spectral component peaking in the extreme UV/soft X-ray band, and disk-corona models, hence high accretion rates. Indeed, we estimate that \dot{m}~1. We examine the emission lines in its spectrum, and we constrain the physical properties of the line-emitting gas through photoionization modeling. The line-emitting gas is characterized by log n~11 and log U~0, and is stratified around log U~0. Our estimate of the radius of the H\beta-emitting region ~10 \pm 2 lt-days is consistent with the radius-luminosity relationships found for Sy1 galaxies. We also find evidence for super-solar metallicity in this NLS1. We show that the emission lines are not good diagnostics for the underlying SEDs and that the absorption line studies offer a far more powerful tool to determine the ionizing continuum of AGNs, especially if comparing the lower- and higher-ionization lines.Comment: 15 pages, 10 figures; accepted for publication in The Astrophysical Journal, LaTeX emulateapj.st

VLTI observations of the dust geometry around R Coronae Borealis stars

We are investigating the formation and evolution of dust around the hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars. We aim to determine the connection between the probable merger past of these stars and their current dust-production activities. We carried out high-angular resolution interferometric observations of three RCB stars, namely RY Sgr, V CrA, and V854 Cen with the mid-IR interferometer, MIDI on the VLTI, using two telescope pairs. The baselines ranged from 30 to 60 m, allowing us to probe the dusty environment at very small spatial scales (~ 50 mas or 400 stellar radii). The observations of the RCB star dust environments were interpreted using both geometrical models and one-dimensional radiative transfer codes. From our analysis we find that asymmetric circumstellar material is apparent in RY Sgr, may also exist in V CrA, and is possible for V854 Cen. Overall, we find that our observations are consistent with dust forming in clumps ejected randomly around the RCB star so that over time they create a spherically symmetric distribution of dust. However, we conclude that the determination of whether there is a preferred plane of dust ejection must wait until a time series of observations are obtained.Comment: Accepted for publication in MNRAS; 14 pages, 10 figures, 6 table

SmartEx: a case study on user profiling and adaptation in exhibition booths

An investigation into user profiling and adaptation with exhibition booth as a case study is reported. First a review of the field of exhibitions and trade fairs and a summary introduction to adaptation and profiling are given. We then introduce three criteria for the evaluation of exhibition booth: effectiveness, efficiency and affect. Effectiveness is related the amount of information collected, efficiency is a measurement of the time taken to collect the information, and affect is the perception of the experience and the mood booth visitors have during and after their visit. We have selected these criteria to assess adaptive and profiled exhibition booths, we call smart exhibition (SmartEx). The assessment is performed with an experiment with three test conditions (non-profiled/non adaptive, profiled/non-adaptive and profiled adaptive presentations). Results of the experiment are presented along discussion. While there is significant improvements of effectiveness and efficiency between the two-first test conditions, the improvement is not significant for the last test condition, for reasons explained. As for the affect, the results show that it has an under-estimated importance in people minds and that it should be addressed more carefully