A photon-counting photodiode array detector for far ultraviolet (FUV) astronomy

A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location

HST/ACS Images of the GG Tauri Circumbinary Disk

Hubble Space Telescope Advanced Camera for Surveys images of the young binary GG Tauri and its circumbinary disk in V and I bandpasses were obtained in 2002 and are the most detailed of this system to date. The confirm features previously seen in the disk including: a "gap" apparently caused by shadowing from circumstellar material; an asymmetrical distribution of light about the line of sight on the near edge of the disk; enhanced brightness along the near edge of the disk due to forward scattering; and a compact reflection nebula near the secondary star. New features are seen in the ACS images: two short filaments along the disk; localized but strong variations in disk intensity ("gaplets"); and a "spur" or filament extending from the reflection nebulosity near the secondary. The back side of the disk is detected in the V band for the first time. The disk appears redder than the combined light from the stars, which may be explained by a varied distribution of grain sizes. The brightness asymmetries along the disk suggest that it is asymmetrically illuminated by the stars due to extinction by nonuniform circumstellar material or the illuminated surface of the disk is warped by tidal effects (or perhaps both). Localized, time-dependent brightness variations in the disk are also seen.Comment: 28 pages, 7 figures, accepted for publication in the Astronomical Journa

Rocket and FUSE Observations of IC 405: Differential Extinction and Fluorescent Molecular Hydrogen

We present far-ultraviolet spectroscopy of the emission/reflection nebula IC 405 obtained by a rocket-borne long-slit spectrograph and the Far Ultraviolet Spectroscopic Explorer. Both data sets show a rise in the ratio of the nebular surface brightness to stellar flux (S/F_*) of approximately two orders of magnitude towards the blue end of the far-UV bandpass. Scattering models using simple dust geometries fail to reproduce the observed S/F_* for realistic grain properties. The high spectral resolution of the FUSE data reveals a rich fluorescent molecular hydrogen spectrum ~1000" north of the star that is clearly distinguished from the steady blue continuum. The S/F_* remains roughly constant at all nebular pointings, showing that fluorescent molecular hydrogen is not the dominant cause for the blue rise. We discuss three possible mechanisms for the ``Blue Dust'': differential extinction of the dominant star (HD 34078), unusual dust grain properties, and emission from nebular dust. We conclude that uncertainties in the nebular geometry and the degree of dust clumping are most likely responsible for the blue rise. As an interesting consequence of this result, we consider how IC 405 would appear in a spatially unresolved observation. If IC 405 was observed with a spatial resolution of less than 0.4 pc, for example, an observer would infer a far-UV flux that was 2.5 times the true value, giving the appearance of a stellar continuum that was less extinguished than radiation from the surrounding nebula, an effect that is reminiscent of the observed ultraviolet properties of starburst galaxies.Comment: 8 pages, 9 figures, using emulateapj, ApJ - accepte

Targeted colonic release formulations of mesalazine - A clinical pharmaco-scintigraphic proof-of-concept study in healthy subjects and patients with mildly active ulcerative colitis.

Colonic targeting of orally applied therapeutic drugs remains a challenge. Tablet coatings relying on gastrointestinal pH and colonic bacterial enzymes as triggers in association with an inner alkaline layer are expected to improve targeting efficiency. Mesalazine release from three differently coated tablets labelled with 1 MBq 153Sm was characterised in a single centre, open-label, parallel group study in nineteen healthy subjects and seven patients with mildly active ulcerative colitis. Two semi-organic and one aqueous-based outer coating with different ratios of enteric polymer and resistant starch were tested. All coatings showed comparable release lagtimes in biorelevant dissolution media and were not affected by neutron-activation of the samarium tracer. Mesalazine pharmacokinetics and gamma scintigraphy were used to characterise drug release, anatomical site of tablet disintegration and gastrointestinal transit. Initial tablet disintegration occurred at the ileo-caecal junction or beyond in 92% of the subjects Time to initial tablet disintegration was inversely correlated with maximal plasma concentrations and systemic mesalazine exposure. Although high inter-subject variability precluded detection of differences between solvent types and different enteric polymer to polysaccharide ratios, the dual pH and enzymatic triggered release system in combination with an inner alkaline layer promoted mesalazine release at the target site with high accuracy

Knowledge Graph Embedding for Ecotoxicological Effect Prediction

Exploring the effects a chemical compound has on a species takes a considerable experimental effort. Appropriate methods for estimating and suggesting new effects can dramatically reduce the work needed to be done by a laboratory. In this paper we explore the suitability of using a knowledge graph embedding approach for ecotoxicological effect prediction. A knowledge graph has been constructed from publicly available data sets, including a species taxonomy and chemical classification and similarity. The publicly available effect data is integrated to the knowledge graph using ontology alignment techniques. Our experimental results show that the knowledge graph based approach improves the selected baselines

Fluorescent Molecular Hydrogen Emission in IC 63: FUSE, HUT, and Rocket Observations

We present far-ultraviolet observations of IC 63, an emission/reflection nebula illuminated by the B0.5IV star gamma Cassiopeia, located 1.3 pc from the nebula. Molecular hydrogen fluorescence was detected first in IC 63 by IUE and later at shorter wavelengths by ORFEUS. Here we present Far Ultraviolet Spectroscopic Explorer (FUSE) observations towards three locations in the nebula, complemented by Hopkins Ultraviolet Telescope (HUT) data on the central nebular position. In addition, we present a sounding rocket calibration of a FUSE spectrum of gamma Cas. Molecular hydrogen fluorescence is detected in all three FUSE pointings. The intensity of this emission as well as the contributions from other species are seen to vary with position. The absolute flux calibration of the sounding rocket data allows us to reliably predict the radiation field incident on IC 63. We use these data to test models of the fluorescent process. Our modeling resolves the perceived discrepancy between the existing ultraviolet observations and achieves a satisfactory agreement with the H_2 rotational structure observed with FUSE.Comment: 7 pages, 6 figures, using emulateapj. Accepted by Ap

GUN: An Efficient Execution Strategy for Querying the Web of Data

International audienceLocal-As-View (LAV) mediators provide a uniform interface to a federation of heterogeneous data sources, attempting to execute queries against the federation. LAV mediators rely on query rewriters to translate mediator queries into equivalent queries on the federated data sources. The query rewriting problem in LAV mediators has shown to be NP-complete, and there may be an exponential number of rewritings, making unfeasible the execution or even generation of all the rewritings for some queries. The complexity of this problem can be particularly impacted when queries and data sources are described using SPARQL conjunctive queries, for which millions of rewritings could be generated. We aim at providing an efficient solution to the problem of executing LAV SPARQL query rewritings while the gathered answer is as complete as possible. We formulate the Result-Maximal k-Execution problem (ReMakE) as the problem of maximizing the query results obtained from the execution of only k rewritings. Additionally, a novel query execution strategy called GUN is proposed to solve the ReMakE problem. Our experimental evaluation demonstrates that GUN outperforms traditional techniques in terms of answer completeness and execution time